Small-sized and light-weighted optical pickup apparatus capable of eliminating the effect due to the flaring light rays and performing the signal detection of high reliability is provided.
In the apparatus, the quarter-wave (λ/4) plate and the reflection-type birefringent prime provided with the deflecting function of deflecting the reflection light rays reflected on the optical information recording medium and the light rays flux separating function of separating the reflected light rays from the outgoing light rays are disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the reflection light rays from the optical information recording medium which are defleced and separated by the reflection-type birefringent prism is disposed on a single (same) substrate together with the semiconductor laser.
|
0. 23. A method of directing incident light onto an optical recording medium and detecting reflected light therefrom, comprising:
emitting light flux from a light source along an emitting direction;
causing said light flux emitted from said light source in said emitting direction to travel along a first optical path through a uniaxial crystal plate to an objective lens in a form of a small spot to facilitate operation of recording, reproducing and/or erasing of optical information,
said uniaxial crystal plate having a discontinuous surface and being disposed in said first optical path between said light source and the objective lens;
causing light ray flux reflected from the optical recording medium to travel to at least one light-receiving element through said uniaxial crystal plate and along a second optical path that is at least partially different from said first optical path,
wherein said light source and said at least one light-receiving element are formed in a single stem, and
wherein said at least one light-receiving element formed on said stem consists of two pieces of two-divisional light-receiving elements respectively having dividing directions different from each other, and a height of one of said light-receiving elements is the same as a height of said light source, while a height of another one of said light-receiving elements is different from said height of said light source.
0. 22. An optical pickup apparatus comprising:
a light source;
an objective lens for focusing light ray flux emitted from the light source on an optical recording medium;
a quarter-wave plate located between the light source and the optical recording medium;
a flux separating element configured to separate light rays reflected on the optical recording medium from an optical axis of incident light rays, the flux separating element being disposed in a divergent optical path between the light source and the quarter-wave plate; and
a light-receiving element positioned adjacent the light source and at a front side thereof for detecting a signal from the reflection light rays, wherein the light source and the light-receiving element are formed in a single stem,
wherein two pieces of prism consisting of same sort of uniaxial crystal respectively having optical axes intersecting perpendicularly to each other are employed as the flux separating element, such that when a refractive index for ordinary light rays of the prism ηo is larger than a refractive index for extraordinary light rays ηe, an incident angle of the ordinary light rays transmitted through the first prism to the second prism is δ, and a counterclockwise angle from the optical axis of the ordinary light rays is in a plus (+) direction when the value of δ becomes larger than zero, and such that when ηo is larger than ηe, an incident angle of the extraordinary light rays transmitted through the first prism to the second prism is δ, and a counterclockwise angle from the optical axis of the extraordinary light rays is in a plus (+) direction when the value of δ becomes smaller than zero (δ<0).
0. 1. An optical pickup apparatus comprising:
a light source;
an objective lens for focusing light ray flux emitted from said light source on an optical recording medium;
a quarter-wave plate located between said light source and said optical recording medium;
a flux separating element configured to separate light rays reflected on said optical recording medium from an optical axis of incident light rays, said flux separating element being formed of a birefringent material and disposed in a divergent optical path between said light source and said quarter-wave plate; and
a light-receiving element positioned adjacent said light source and at a front side thereof for detecting a signal from said reflection light rays.
0. 2. An optical pickup apparatus as defined in
0. 3. An optical pickup apparatus as defined in
0. 4. An optical pickup apparatus as defined in
0. 5. An optical pickup apparatus as defined in
0. 6. An optical pickup apparatus as defined in
0. 7. An optical pickup apparatus as defined in
0. 8. An optical pickup apparatus as defined in
0. 9. An optical pickup apparatus as defined in
0. 10. An optical pickup apparatus as defined in
0. 11. An optical pickup apparatus, comprising:
a semiconductor laser and at least one light-receiving element formed in a single stem and positioned such that said semiconductor laser emits light ray flux along a first optical path through an objective lens onto an optical recording medium in a form of a small spot to facilitate operation of recording, reproducing and/or erasing of optical information, and such that said at least one light-receiving element receives light from a second optical path that is at least partially different from said first optical path; and
a uniaxial crystal plate having a discontinuous surface and being disposed in said first optical path between said semiconductor laser and the objective lens;
wherein said light ray flux emitted from said semiconductor laser is transmitted along said first optical path through said uniaxial crystal plate to said objective lens for focusing on the optical recording medium; and
wherein light ray flux reflected from the optical recording medium is transmitted through said uniaxial crystal plate and along said second optical path to said at least one light-receiving element.
0. 12. An optical pickup apparatus as defined in
wherein a uniaxial crystal plate is hermetically sealed unitarily in a package containing said semiconductor laser and said at least one light-receiving element therein.
13. An optical pickup apparatus as defined in
a semiconductor laser and at least one light-receiving element formed in a single stem and positioned such that said semiconductor laser emits light ray flux along a first optical path through an objective lens onto an optical recording medium in a form of a small spot to facilitate operation of recording, reproducing and/or erasing of optical information, and such that said at least one light-receiving element receives light from a second optical path that is at least partially different from said first optical path; and
a uniaxial crystal plate having a discontinuous surface and being disposed in said first optical path between said semiconductor laser and the objective lens;
wherein said at least one light-receiving element formed on said stem consists of two pieces of two-divisional light-receiving elements respectively having dividing directions different from each other, and a height of one of said light-receiving elements is the same as a height of said semiconductor laser, while a height of another one of said light-receiving elements is different from said height of said semiconductor laser.
14. An optical pickup apparatus as defined in claim 11 13, wherein a the uniaxial crystal plate is hermetically sealed unitarily in a package containing said semiconductor laser and said light-receiving element therein.
0. 15. An optical pickup apparatus as defined in
0. 16. An optical pickup apparatus as defined in
0. 17. An optical pickup apparatus as defined in
0. 18. An optical pickup apparatus as defined in
0. 19. An optical pickup apparatus as defined in
0. 20. An optical pickup apparatus as defined in
0. 21. An optical disc system comprising the optical disc apparatus as defined in
|
This is a continuation of application Ser. No. 08/311,050 filed Sep. 23, 1994 now U.S. Pat. No. 5,694,385.
1. Field of the Invention
The present invention relates to optical pickup apparatuses employed for the optical disk drive, in particular, an optical pickup apparatus capable of constructing an optical systems nearly identifying the optical path of illuminating light rays and the other optical path of detecting light rays by use of a light rays flux separating element consisting of birefringent (complex refraction) crystal, another optical pickup apparatus which is small-sized and has a small number of employed parts, and still another optical pickup apparatus executing information record and reproduction and further executing focus servo and tracking servo.
2. Description of the Related Art
Concerning the documents respectively describing the technologies in relation to the first group of the present invention, there exist some documents as listed up below:
1) Japanese Laid-open Patent Publication No. 56-61043/1981 “A FOCUS DETECTING APPARATUS”,
2) Japanese Laid-open Patent Publication No. 4-87041/1992 “AN OPTICAL DETECTOR”,
and
3) Japanese Laid-open Patent publication No. 5-120755/1993, “AN OPTICAL HEAD”.
The above-listed document 1) relates to a focus detecting apparatus and describes that, in an information reading-out apparatus which focuses the light rays spot through the objective lens onto the information track of the recording medium having the information recorded thereon spirally or in a state of concentric circles and reads out the information therefrom, the above-mentioned focus detecting apparatus detects whether the light rays spot is correctly focused by the objective lens onto the recording medium.
The document further describes that a prism made of a birefringent material such as Rochon prism is disposed between the coupling lens (CL) and the objective lens, there reflection light rays reflected on the disk are separated from the incident light rays, the light rays flux thus separated causes an astigmatism in order to obliquely enter the coupling lens as the incident light rays, and thereby the focus detection is performed.
And further, the other above-listed
document 2) describes that, in order to simplify the construction of the optical pickup apparatus for reading out the information signal written in the magneto-optic disk and in order to facilitate the assembling and manufacturing processes thereof, an inclined uniaxial crystal plate is mounted on the supporter of the light-receiving element, and thus a detection system for detecting the magneto-optic signal, the focus signal and the track signal is constructed, for the purpose of simplifying the detection system.
Furthermore, the still other above-listed
document 3) describes the optical pickup apparatus in which, in order to enable to detect the focus error signal always with high precision and in order to detect the magneto-optic signal at the same time, the semiconductor laser (LD) employing hologram and the light detector (PD) are unitarily constructed.
In
The linearly-polarized divergent light rays emitted from the semiconductor laser (LD) 21 are converted to the parallel light rays by the coupling lens 22, pass through the polarized light beam splitter (PBS) 23, and are deflected by the deflecting mirror 24.
The deflected light rays are further converted to the circularly-polarized light rays by the quarter-wave (λ/4) plate 25 and focused on the recording surface of the light recording medium 27 by the objective lens 26. The light rays flux reflected on the recording surface is made again parallel by the objective lens 26 and further converted to the linearly-polarized light rays in which the polarizing surface thereof is relatively rotated by 90° to the incident light rays. The light rays thus converted pass through the deflecting mirror 24, and the same are reflected on the PBS 23 and guided to the detection system 31. The light rays flux guided to the detection system 31 passes through the detecting lends 28 and the cylinder lens 29, and is detected by the four-divisional light-receiving element 30. On this occasion, the focus error signal is obtained by the astigmatism, the track error signal is obtained by the push-pull method, and the Rf signal is obtained by the variation of the four-divisional summed light amount (light intensity), that is, the difference of the reflection rate from the disk.
Conventionally, as mentioned heretofore, there exists some extent of limitation in small-sizing the optical system, in order to completely separating the optical path of the illuminating light rays and that of the detecting light rays by use of the PBS (polarized light beam splitter).
And further, although it has been already proposed to separate the light rays flux by utilizing the hologram, there existed some problems to be solved in the efficiency of utilizing the light rays.
Concerning the documents respectively describing the prior-art technologies in relation to the second group of the present invention, there exist some documents as listed up below;
1) Japanese Laid-open Patent Publication No. 4-87041/1992 “Light Detector”,
2) Japanese Laid-open Patent Publication No. 4-155629/1992 “Optical Pickup”
and
3) “Hologram Pickup for use in Laser Disk” (Edited by Sachio Kurata and other seven members, SHARP Technical Report Vol. 48, March 1991, P. 21-26).
The above-listed
document 1) describes that a uniaxial crystal board is mounted on the supporter for supporting a light detecting element having plural light-receiving surfaces so as to slantedly oppose to the respective light-receiving surfaces of the above light detecting element, and thereby the construction of the optical pickup device can be simplified, namely, the light-receiving element and the light detecting optical element is unitarily combined into one.
Furthermore, the above-listed
document 2) describes that the optical pickup comprises a lens member having the light-emitting element and the light-receiving element both hermetically enclosed (sealed) therein and further having a lens surface formed on one end thereof for focusing the outgoing light rays emitted from the light emitting element, and biaxial driving means for positioning the above-mentioned lens member in both of the focus direction and the radius direction of the optical disk, and further, a hologram for guiding a part of the outgoing light rays of the light-emitting element reflected on the optical disk toward the light receiving element is formed on the lens surface of the afore-mentioned lens member, so that an optical pickup can be constructed with small number of employed parts and the reproduced signal does not vary due to the time-elapsing variation by stabilizing the positional relationship between the light-emitting element and the light-receiving element. Namely, in the document 2), the light rays flux is separated into two, one for the semiconductor laser and another one for the light-receiving element by use of the hologram, and the semiconductor laser and the light-receiving element are unitarily combined into one.
Furthermore, the above-listed
document 3) describes a hologram pickup, in which plural functions for use in CD are integrated in one hologram element, and a laser diode employed as a light source and a photo diode for detecting the signal are disposed in one package.
The light rays flux emitted from the semiconductor laser 131 is converted to parallel light rays by use of the collimating lens 132 and the beam of the light rays is enlarged by the beam shaping prism 133. In such manner, a preferable spot can be obtained on an optical information recording medium 138 mentioned later.
Thereafter, the light rays flux is radiated as an extremely small spot of almost 1 μm onto the optical information recording medium 138 after passing through the beam splitter 134, the deflecting prism 135, the quarter-wave plate (λ/4 plate) 136, and the objective lens 137. In such manner, the information is recorded and reproduced. The reflection right rays reflected on the optical information recording medium 138 pass through the objective lens 137, the quarter-wave plate (λ/4 plate) 136 and the deflecting prism 135, and the same are reflected on the beam splitter 134 and directed toward the detection system which comprises the detection lens 139, the knife-edge prism 140, the light receiving element 141 for detecting the track, and the light-receiving element 142 for detecting the focus.
The amount and direction of the focus deviation is detected from the light intensity (amount) difference A−B of the light rays received by A and B, and the objective lens 137 is controlled in the direction of the arrow F shown in
The defect of the optical system in the conventional optical pickup device as mentioned before is that the number of the construction parts is large and the respective parts become large-sized. For this reason, the art shown in
document 2); Japanese Laid-open Patent Publication No. 4-87041/1992, employs a hologram and combines unitarily the semiconductor laser (LD) and the light-receiving element into one for the purpose of realizing a small-sized optical pickup.
document 2), in which a hologram is employed, and the semiconductor laser and the light-receiving element are unitarily combined into one. In
The laser diode 154 and the light-receiving element 153 are mounted on the light-receiving/emitting substrate 155. The optical disk 156 and the optical pickup are in the positional relationship at the time of ordinary recording and reproducing. On this occasion, the outgoing light rays emitted from the laser diode 154 are focused on the recording/reproducing surface of the optical disk 156 by the hologram plate 152, and further, a part of the reflection light rays from the optical disk 156 is wave-surface-divided (diffracted) by the hologram of the hologram plate 152 and guided to the side of the light-receiving element 153. A part of the reflection light rays is focused on the central portion of the light-receiving element 153. On this occasion, a part of the light rays flux directed to the hologram plate 152 from the laser diode 154 is also wave-surface-divided by the hologram. However, since the wave-surface-divided light rays flux is reflected by the optical disk 156 in a direction opposite to that of the hologram plate 152, it does not exert any influence on the reproducing signal.
Nevertheless, the light utilizing efficiency is not so well. In general, the efficiency contributing to the spot is only a little less than 50% of the reflected light rays and the efficiency contributing to the detection system is only 10%-30% of the same. The above matter is a practical problem to be solved.
document 3); Japanese Laid-open Patent Publication No. 5-120755/1993. In
The hologram optical element (HOE) 170 is made of a sheet of glass substrate. The hologram 169 is formed on the upper surface thereof, and a diffraction grating for creating the tracking beam is formed on the lower surface thereof. A plan plate beam splitter of the optical pickup, a light branch of concave lens, and a pickup control signal creating function are integrated in the hologram. The laser diode (LD) 167 and the photo-diode (FD) 168 for detecting the signal are mounted on a common stem and accommodated in one package. The hologram optical element 170 is bonded on the upper surface of the package with adhesive agents and unitarily combined with LD 167 and PD 168. In such construction, the number of the employed parts for constructing the pickup is reduced from 7 to 3. The package for LD 167 and PD 168 is hermetically sealed. In such manner, the positional relationship between the mutual elements can be kept extremely stable.
Next, the other actual examples of the conventional optical pickup device are described hereinafter.
As to the other conventional pickups, there exist four examples as mentioned below in order. Firstly, the construction of the fifth example of the conventional pickup device is explained referring to FIG. 40. The outgoing light rays emitted from a semiconductor laser 201 are converted to parallel light rays by a collimating lens 202. Thereafter, the converted light rays pass through a beam splitter 203 and the optical path of the light rays is bent by a deflecting prism 204. And further, the light rays are focused by an objective lens 205 and form a extremely small spot on the surface of an optical disk 206 employed as the optical information recording medium. Thereby, the recording, etc. of the information is done. Furthermore, the reflection light rays reflected on the optical disk 206 go forward in the direction opposite to that of the incident optical path and are reflected by the beam splitter 203. Next, the reflected light rays are focused by a detection lens 208 in a signal detecting optical system 207 and guided to a light-receiving element 209. Thereafter, the data information recorded on the surface of the optical disk 206 is reproduced, or the tracking servo control and the focusing servo control of the objective lens 205 are performed by detecting the track error signal and the focus error signal, on the basis of the distribution of the light amount (light intensity) detected by the light-receiving element 209.
Secondly, the construction of the sixth example of the conventional pickup device is explained referring to FIG. 41. The difference between the first example and the second example is that, in the second example, a magneto-optic disk 210 is employed as the optical information recording medium, and the construction in the signal detecting optical system 207 is changed. The polarizing surface of the reflection light rays reflected on the surface of the magneto-optic disk 210 is rotated by 45° by use of the half-wave (λ/2) plate 211 of the signal detecting optical system 207, and the light rays thus rotated are focused by the detection lens 208 and enter a polarizing beam splitter 212 as incident light rays. At this time, the P-polarized light rays pass through the polarizing beam splitter 212 and are guided to a light-receiving element 213. On the other hand, the S-polarized light rays are reflected on the polarizing splitter 212 and guided to the light-receiving element 214. Thereby, the data information on the surface of the magneto-optic disk 210 can be obtained as the differential signal between the signal from the light-receiving element 213 and that from the other light-receiving element 214.
Next, the construction of the seventh example of the conventional pickup device is explained referring to the disclosure in the
document, Japanese Laid-open Patent Publication No. 62-172538/1987, “Optical Head Apparatus”, and FIG. 42. In the example, a diffraction grating 215 is employed as the optical path separating measure in order to separate the foregoing light rays 216 emitted from the semiconductor laser 201 and directed to the optical disk 206 and the reflection light rays 217 reflected on the optical disk 206, from each other. Thereafter, the diffraction light rays 218 diffracted by a diffraction grating 215 among the reflection light rays 217 reflected on the optical disk 206 are guided to the light-receiving elements; 219a and 219b, which are disposed at the side of the semiconductor laser 201 and respectively have two-divisional light-receiving surfaces, and thereby the reproduction of the information signal can be done.
Finally, regarding the construction of the eighth example of the conventional pickup device, the assembling of the optical pickup apparatus construction is explained referring to FIG. 43. The semiconductor laser 201 is mounted on one end portion of an optical pickup housing 220, and an actuator base 221 is fixedly put on the bottom surface portion 220a thereof. A deflecting prism 222, an outer yoke 223, an inner yoke 224, and a magnet 225 are disposed on the actuator base 221. And further, a movable portion 226 of the actuator on which the objective lens 205 is supported is mounted on the upper portion of such actuator base 221. A focusing coil 227 and a tracking coil 228 are disposed on the side surface of the actuator's movable portion 226. On this occasion, when the electric current flows through the focusing coil 227, the actuator's movable portion 226 can be displaced in the focus direction F. On the other hand, when the electric current flows through the tracking coil 228, the actuator's movable portion 226 can be displaced in the tracking direction T.
In the fifth and sixth examples of the conventional pickup device construction (FIG. 40 and FIG. 41), the reflection light rays reflected on the optical disk 206 or the magneto-optic disk 210 are further reflected by the beam splitter 203, and thereby the reflection light rays can be separated from the outgoing light rays emitted from the semiconductor laser 201 and guided to the light-receiving elements; 209, 213, and 214 in the signal detecting optical system 207 in order to detect the signal. Since the signal detecting optical system 207 is separatedly provided in order to reproduce the signal in such manner, there arise several problems to be solved that the number of the optical parts employed is increased and that the space for the optical system is large-sized, and further, that the weight of the optical pickup portion is also increased and thereby the high-speed seeking operation cannot be performed.
In the seventh example of the conventional pickup device construction (FIG. 42), since there exists no signal detecting optical system 207 as mentioned above, it is possible to realize a small-sized and light-weight optical pickup portion. However, when the outgoing light rays emitted from the semiconductor laser 201 pass through the diffraction grating 215, diffused reflection light rays are generated on the grating surface thereof, and such diffused reflection light rays causes an undesirable phenomenon that the diffused reflection light rays enter the light-receiving elements; 219a and 219b, as flaring light rays. Since the signal level of the flaring light rays is equal to or more than the level of the signal component regularly (properly) detected by the light-receiving elements; 219a and 219b, there arises a problem to be solved that it is impossible to avoid the S/N-level-down of the properly detected signal.
In the eighth example of the conventional pickup device construction (FIG. 43), since the optical pickup portion is constructed such that the actuator base 221 is mounted on the optical pickup housing 220, and further, the actuator's movable portion 226 is mounted on the actuator base 221, the number of the assembled parts is large and therefore the number of the employed parts is increased. This is also a problem to be solved.
The present invention is made in consideration of the above-mentioned actual circumstances.
It is an object of the present invention to solve the afore-mentioned points at issue.
It is another object of the present invention to provide an optical pickup apparatus capable of improving the problems to be solved as mentioned heretofore.
It is still another object of the present invention to provide a low-cost optical pickup apparatus constructed with the decreased number of the employed parts and with the reduced assembling works, in which a birefringent crystal is employed as a separation element for separating the illuminating light rays and the detecting light rays from each other, and thereby the optical pickup system of almost one optical path decreases the light amount (light intensity) loss.
It is still another object of the present invention to provide an optical pickup apparatus which is small-sized by employing only one optical path.
It is still another object of the present invention to provide an optical pickup apparatus having a small-sized and simplified optical system of high efficiency for utilizing the light rays.
It is still another object of the present invention to provide a small-sized and light-weight optical pickup apparatus capable of performing high-speed seeking operation.
It is still another object of the present invention to provide an optical pickup apparatus capable of avoiding the decrease of S/N of the properly detected signal.
It is still another object of the present invention to realize an optical system which is extremely small-sized, easy for operating, and in which the variation of the signal due to the positional shift between the respective optical parts is very small.
and
Prior to the description concerning the embodiments of the present invention, some key optical parts in connection with the embodiments and the functions thereof are described, in brief, hereinafter.
In the case of constructing the optical system, it is on very rare occasion to construct the system only with the lens, the prism, and the reflection mirror. For instance, by employing some special parts utilizing the polarization and the diffraction of the light rays, the system can enhance its function and utilize the light rays further effectively.
In forming the optical system, the polarization (deviation of the light rays) cannot be ignored on many occasions. There are two occasions on which the polarization can be utilized positively and harmfully. At any rate, the polarization has something to do with the optical system on many occasions. For instance, when the (semiconductor) laser is employed as the light source of the optical system, since almost all of the lasers emit the linearly-polarized light rays, the starting point of the optical system may become the linear polarization.
Next, the general polarization is explained in brief. The polarization can be classified into three; those are, “linear polarization”, “circular polarization”, and “elliptical polarization”, wherein the linear polarization can be further classified into two; those are, “P-polarization” and “S-polarization”.
The technical terms of those polarizations signify the side wave of the light rays to the electromagnetic field and show the shape of the electric field's variation.
Namely, the linearly-polarized light rays represent the light rays, the electric field of which vibrates (oscillates) only in one direction, as shown in FIG. 44.
The circularly-polarized light rays represent the light rays which have a circular orbit of the electric field's vibration viewing at a surface perpendicular to the direction of the light rays' advancing as shown in FIG. 46. The elliptically-polarized light rays represent the light rays which have a elliptic orbit of the electric field's vibration viewing at a surface perpendicular to the direction of the light rays' advancing as shown in FIG. 47.
In order to obtain the linearly-polarized light rays from the difference between the advancing directions of the ordinary light rays and the extraordinary light rays, the Wollaston prism 302 and the Rochon prism 303 as shown in
Next, an example of the phase-difference plate is explained. The conversion of the linearly-polarized light rays vs. circularly-polarized light rays and the other conversion of the compass direction angle of the linearly-polarized light rays are performed by use of the phase-difference plate. A quarter-wave (λ/4) plate which is one of the representative phase-difference plates is shown in FIG. 49. As shown in
The incident linearly-polarized light rays can be thought to be divided into two linearly-polarized light rays components perpendicular to each other. However, since the compass direction angle at the time of entering the λ/4 plate 304 is 45° in the X-Z plane, the amplitude of the component vibrating in the Z axis direction (extraordinary light rays) is equal to that of the component vibrating in the X axis direction (ordinary light rays). Assuming that the refraction index ηe of the extraordinary light rays is larger than the refraction index ηo of the ordinary light rays, the optical path length of the extraordinary light rays becomes longer than that of the ordinary light rays. Namely, a phase difference may occur between the ordinary light rays and the extraordinary light rays after being transmitted through the λ/4 plate 304. The value of the phase difference turns out to be a quarter-wave (¼) [π/2]. Now, since the amplitude (intensity) of the ordinary light rays is equal to that of the extraordinary light rays, the orbit of the light rays' vibration turns out to become circular in the X-Z plane. This is the circular polarization. To take the incident direction of the light rays inversely, when the circularly-polarized light rays enter the λ/4 plate 305, the linearly-polarized light rays of the compass direction angle of 45° can be obtained, as shown in FIG. 50.
On many occasions, the quarter-wave (λ/4) plate and the half-wave (λ/2) plate are put on the market as the phase difference plate. The λ/4 plate is employed for performing the conversions of the circular polarization vs. the linear polarization and the elliptic polarization vs. the linear polarization.
Next, the method of manufacturing the phase difference plate, referring to FIG. 52. The plate is made of the crystal demonstrating the complex refraction (birefringence). In case that the higher precision is required than that of the phase difference plate made of plastic sheet, the plate is manufactured by polishing under the control of the thickness of the birefringent crystal, such as crystallized quartz or calcareous spar, etc. Two crystal plates having respectively different thicknesses are bonded to each other with adhesives as shown in FIG. 52. The phase difference δ to be obtained can be determined by the difference of two plates' thicknesses in accordance the following equality:
The fine adjustment of the phase difference is performed by changing the compass direction angle.
In order to attain the afore-mentioned objects, the first group of the present invention is characterized in;
The definition of the ordinary light rays and the extraordinary light rays is described below in brief. In case that the light rays entering the crystal are divided into two by the action of the birefringence (double or complex refraction) and the light rays having a constant transmission speed regardless of the transmitting direction, such light rays are called the “ordinary light rays”. Because the refraction law (principle) regarding the isotropic medium can be applied as it is.
On the contrary, in case that the light rays entering the crystal are also divided into two by the action of the birefringence and the light rays having a variable transmission speed in accordance with the transmitting direction, such light rays are called the “extraordinary light rays.” Because the refraction law (principle) regarding the isotropic medium cannot be applied as it is.
The technical term “Birefringence” or “Birefringent Refraction” signifies the double (complex) refraction. When the light rays enter the anisotropic medium such as crystal, there occurs a phenomenon that two refracted light rays appear. As a result, viewing through the above anisotropic medium, the image of the object turns out to be duplicated in general. The vibrating direction of the electric flux density D of the top refracted light rays are perpendicular to each other. When the light rays pass through the uniaxial crystal, the same are divided into the ordinary light rays and the extraordinary light rays. On the other hand, when the light rays pass through the biaxial crystal, both of the light rays perform the action as the extraordinary light rays.
The preferred embodiments in the first group of the invention are concretely described hereinafter, referring to
The linearly polarized divergent light rays emitted from the semiconductor laser 1 pass through the complex refraction crystal 2, and are converted to the parallel light rays by the coupling lens 3, and further are deflected by the deflecting mirror 4. The light rays deflected by the deflecting mirror 4 are converted to the circularly-polarized light rays by the quarter-wave (λ/4) plate 5 and focused on the recording surface of the optical recording medium 7 by the objective lens 6. The light rays flux reflected on the recording surface are made parallel again by the objective lens 6 and the same are converted to the linearly-polarized light rays having a polarising surface relatively rotated by 90° to the incident light rays by the quarter-wave (λ/4) plate 5. The light rays thus converted by the quarter-wave (λ/4) plate 5 are reflected on the deflecting mirror 4 and are given a a focusing tendency by the coupling lens 3, refracted by the complex refraction crystal 2 in a direction different from that of the illuminating light rays, and are guided to the light-receiving element 8.
Next, the reason why the birefringent crystal functions as the light rays flux separating element is explained. At first, when the light rays enter the parallel plain plate made of uniaxial crystal perpendicularly thereto (at this time, the optical axis [crystal axis] is not parallel with the boundary surface), the light rays are divided into two; namely, into the polarized component going forward straight and the other polarized component refracted on the boundary surface, as shown in FIG. 2. Such phenomenon occurs due to the difference of the refractive index of the medium for the respective polarizing components, and it is called “a birefringence (complex refraction)”. The former one and the latter one are respectively called “ordinary light rays” and “extraordinary light rays”. In the biaxial crystal, both of of two polarized components function as the extraordinary light rays and the phenomenon of the birefringent refraction appears also. If the birefringent refraction is utilized, it is possible to separate those two linearly-polarized light rays by directing the light rays in the different directions.
Furthermore, the boundary surface of the light rays flux separating element consisting of the birefringent crystal can be constructed and disposed not so as to be perpendicular to the optical axis.
When the outgoing light rays emitted from the semiconductor laser are P-polarized (the polarizing direction is perpendicular to the paper) and enter the uniaxial crystal having an optical axis perpendicular to the paper, the light rays function as the ordinary light rays. Namely, if the incident boundary surface is perpendicular to the optical axis (the light rays enter perpendicular thereto), the light rays proceed straight, and if the light rays enter slantedly thereto as the incident light rays, the same are refracted in a direction satisfying the Snell's Law with the refractive index ηo for the ordinary light rays. The detection light rays reflected on the optical recording medium return through the same optical path as the S-polarized light rays.
When the light rays are S-polarized and enter the uniaxial crystal as shown in
The definition of the Snell's Law is mentioned below in brief. When the light rays are refracted on the boundary surface between two isotropic non-conductive medium of different refractive index, a constant relationship is established between the incident light rays direction and the refracted light rays direction, in accordance with the Snell's Law. As shown in
sin L/sin τ=η2/η1,
wherein the ratio is constant regardless of the incident angle L.
The astigmatism method utilizing the astigmatism caused by the birefringent crystal is adopted for detecting the focus. Otherwise, as shown in
The PD 13 is accommodated in the LD package 11. The separation distance of the LD chip 12 and the PD 13 can be determined from the parameters; the refractive index and the thickness of the complex refraction crystal, and the angle of the incident light rays. For instance, in case that the parallel plain plate made of the birefringent material of the thickness d as shown in
Assuming that the incident angle to the birefringent material is α, the refractive index of the refraction line of the ordinary light rays in the birefringent material is ηo, the refraction angle thereof is a βo, the refractive index of the refraction line of the extraordinary light rays in the birefringent material is ηe, and the refraction angle thereof is βe, and when the below equality;
α=90−θ
is assumed, the following equalities are established.
βo=sin−1 [(cos θ/ηo)],
βe=sin−1 [(cos θ/ηe)] [Equalities-1]
Assuming that the variations of the height from the incident light rays axis are ho, he respectively,
ho=(d/cos βo)·sin τ=(d/cos βo)·cos (θ+βo),
τ=90−(θ+βo)
he=(dcos βe)·sin τ=(d/cos βe)·cos (θ+βe),
τ=90−(θ+βe)
Consequently, the difference h between the optical axes of the P- and S-polarizations is given by the below equality:
h=ho−he
Next, the respective P- and S-polarized light rays enter the prism 16b as the incident light rays, the P-polarized light rays behave as the ordinary light rays and the S-polarized light rays behave as the extraordinary light rays. Consequently, the entering of the incident light rays into the prisms from 16a to 16b signifies the entering of the light rays from the medium of large refractive index to that of small refractive index in the case of the P-polarization. On the contrary, the same signifies the entering of the light rays from the medium of small refractive index to that of large refractive index in the case of the S-polarization. In such situation, the angle established by the P- and S-polarizations is widened.
Next, the state of the refraction by use of those prisms is explained, referring to FIG. 9. Assuming that when the incident angle α, of the polarized component {circle around (1)} having small refractive index in the first prism 16a to the second prism 16b (α1=δ, −90<α1<90) is positive (δ>0), the refraction angle of the component {circle around (1)} to the second prism 16b is β1, and further, when the incident angle of the polarized component {circle around (2)} having large refractive index in the first prism 16a is α2 and the refraction angle of the component {circle around (2)} to the second prism 16b is β2, α1 is smaller than α2 (α1<α2), and for the component {circle around (1)}, the state of the incident light rays turns out to be “small refractive index→large refractive index”, and for the component {circle around (2)}, the same turns out to be “large refractive index→small refractive index”. In consequence, since α1>β1 and α2>β2, (α1−α2)<(β2−β1), and the separation angle turns out to be made large by the action of the prism.
As mentioned heretofore, according to the present invention, the semiconductor laser (LD) and the light-receiving element (PD) are unitarily combined into one, and both of the illuminating system from the LD to the recording medium and the detecting system from the recording medium to the PD can be disposed on almost same optical path. Thereby, it is possible to simplify and small-size the optical pickup. On that occasion, the optical element made of the birefringent material (uniaxial crystal, biaxial crystal, etc.) is employed for separating the illuminating light rays and the detecting light rays.
Finally, the functional effects of the embodiments in the first group of the invention are described hereinafter. As is apparent from the foregoing description, according to the present invention, the following effects can be expected:
In order to attain the afore-mentioned objects, the second group of the present invention is characterized in;
The embodiments in the second group of the invention are described hereinafter.
The hermetically sealed package in which the semiconductor laser 101 and the four-divisional light-receiving element 102 are unitarily mounted on a stem and the element employing the uniaxial crystal plate such as crystallized quartz plate are employed. In the embodiment, the Wollaston prism (WP) consisting of a pair of uniaxial crystal plates respectively having different crystal axes is employed as the element 104.
The light rays flux emitted from the semiconductor laser 101 is P-polarized such that the vibrating direction thereof is parallel with the paper. After bending the optical path by use of the element 104, the light rays are converted to the parallel light rays by the collimating lens 105 and the beam of the light rays is enlarged by the beam shaping prism 106. The light rays are further converted to the circularly-polarized light rays by the quarter-wave (λ/4) plate 108 through the deflecting prism 107 and focused by the objective lens 109 onto the optical information recording medium 110 in order to form an extremely small spot thereon. In such manner, the operations of recording, reproducing, and erasing the information are performed. The reflected light rays pass through the objective lens 109 and the quarter-wave (λ/4) plate 108. Thereafter, the same are converted to the S-polarized light rays, and the vibrating direction thereof is perpendicular to the paper. The light rays thus converted (S-polarized) pass through the deflecting prism 107, the beam shaping prism 106 and the collimating lens 105, and are bent in a direction different from that of the P-polarization. The focus error signal and the track error signal are detected by the four-divisional light-receiving element 102, and the information signal is detected by all of the summed signals.
In such construction, assuming that the emission pattern of the semiconductor laser 101 is wide in a direction perpendicular to the laminating direction of the light-emitting element and the same is narrow in another direction parallel therewith as shown in
In
Furthermore, in the sixth embodiment shown in
Finally, the functional effects of the embodiments in the second group of the invention are described hereinafter. As is apparent from the foregoing description, according to the present invention, the following effects can be expected:
In order to attain the afore-mentioned objects, it is necessary to consider the means for solving the subject matters. In the seventh embodiment of the present invention, in the optical pickup apparatus in which the outgoing light rays emitted from the semiconductor laser are focused by the objective lens and form an extremely small spot on the surface of the optical information recording medium, and in such manner, the operations of recording etc. of the information are performed, and further, the reflection light rays reflected on the afore-mentioned optical information recording medium are guided to the light-receiving element and thereby the reproduction of the information and the detection of the focus error signal and the track error signal both for use in the servo (mechanism) are performed, the quarter-wave (λ/4) plate and the reflection-type birefringent prism provided with the deflecting function of deflecting the reflection light rays reflected on the above optical information recording medium and the light rays flux separating function of separating the reflected light rays from the outgoing light rays are disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the reflection light rays from the above optical information recording medium which are deflected and separated by the reflection-type birefringent prism is disposed on a single (same) substrate together with the above-mentioned semiconductor laser.
In the eighth embodiment of the present invention, in the optical pickup apparatus in which the outgoing light rays emitted from the semiconductor laser are focused by the objective lens and form an extremely small spot on the surface of the optical information recording medium, and in such manner, the operations of recording, etc. of the information are performed, and further, the reflection light rays reflected on the afore-mentioned optical information recording medium are guided to the light-receiving element and thereby the reproduction of the information and the detection of the focus error signal and the track error signal both for use in the servo (mechanism) are performed, the 3-beam Wollaston prism provided with the light rays flux separating function of separating the reflection light rays from the afore-mentioned optical information recording medium into three polarized components is disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the above light-receiving element for receiving at least two polarized components among the polarized components separated by the 3-beam Wollaston prism is disposed on a single (same) substrate together with the above-mentioned semiconductor laser.
Regarding the ninth embodiment, all of the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are mounted unitarily, in the seventh or eighth embodiment.
Regarding the tenth embodiment, the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are accommodated in the movable portion of the actuator which can be moved both in the tracking direction and in the focusing direction, in the seventh, eighth, or ninth embodiment.
Finally, the functional effects of the embodiments in the third group of the invention are described hereinafter. As is apparent from the foregoing description, according to the present invention, the following effects can be expected:
“Flaring Light Rays” signifies the light rays which spread superposing on the image of the object desired to be observed when a part of the light rays are reflected and dispersed in the interior of the optical apparatus.
Since the reflection light rays reflected on the optical information recording medium enter the 3-beam Wollaston prism having the light rays flux separating function of separating the light rays into the respective polarized components as the incident light rays, and are separated into three polarized components, and two polarized components of the light rays among those three components are completely separated from the outgoing light rays emitted from the semiconductor laser, and guided to the light-receiving element, it is not necessary to provide separatedly the signal detecting optical system as in the conventional case, and thereby the number of the employed parts can be reduced. Furthermore, since the incident/outgoing surfaces of the 3-beam Wollaston prism are plain, there occurs no diffused reflection of the light rays and the prism can execute also the function of preventing the reflection of the light rays. Therefore, such construction can suppress the occurrence of the flaring light rays to the utmost and also reduce the noise occurring on the light-receiving element. Furthermore, since the light-receiving element can be disposed at the side of the semiconductor laser, the space for the optical system can be omitted.
Since all of the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are mounted unitarily, it is possible to construct the optical pickup which can be further small-sized and operated easily. Furthermore, it is possible to realize an optical system reducing or eliminating the signal variation due to the positional shift between the respective optical parts.
Since the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are accommodated in the movable portion of the actuator which can be moved both in the tracking direction and in the focusing direction, it is possible to realize the further small-sized and further light-weighted optical pickup portion.
Description of the Concrete Embodiments (Third Group of the Invention)
The seventh embodiment of the present invention is explained, referring to
As shown in
As mentioned above, the semiconductor laser 201, the objective lens 205, the reflection-type birefringent prism 230, the quarter-wave (λ/4) plate 231, and the light-receiving element 229 construct the optical pickup portion 233.
Concerning the material of the prism 230, it is made of the birefringent substance such as crystallized quartz, calcareous spar, etc. The prism 230 thus constructed has a property of refractive index which differs in accordance with the deflecting direction. When the P-polarized light rays and the S-polarized light rays, both of which are the polarized components, enter the prism 230 through one surface thereof, those light rays are reflected on the slanted surface 230a and emitted from the prism 230 through another surface being separated by the angle θ. Consequently, assuming that the outgoing light rays emitted from the semiconductor laser 201 are the S-polarized ones, the light rays are reflected on the surface of the optical disk 206 and converted to the P-polarized light rays at the time of passing through the quarter-wave (λ/4) plate 231. Since the P-polarized light rays are reflected on the surface of the prism 230, the reflected light rays are separated thereby from the outgoing light rays. At the same time, the operation of deflecting is also done because of changing the optical path by the surface of the prism 230.
Furthermore, reflection preventing films not shown in
The operation of the optical pickup portion 233 employing the reflection-type birefringent prism 230 in such construction is described hereinafter. The outgoing light rays a emitted from the semiconductor laser 201 are reflected on the slanted surface 230a of the reflection-type birefringent prism 230, pass through the quarter-wave (λ/4 ), and are converted from the linearly-polarized light rays to the circularly-polarized light rays. Thereafter, the light rays are focused by the objective lens 205 and form an extremely small spot on the surface of the optical disk 206. Thereby, the operations of recording, erasing, etc. of the information are performed.
And further, regarding the reflection light rays b reflected on the disk surface, the rotational direction of the circular polarization is inversed, and thereafter the light rays pass through the objective lens 205 once again, and the same are converted to the linearly-polarized light rays perpendicular to the direction of the polarization thereof on the forward (outgoing) optical path and enter the reflection-type birefringent prism 230 as the incident light rays. In the reflection-type birefringent prism 230, the reflected light rays b are reflected on the slanted surface 230a of the prism 230, and thereby, on the basis of the functional principle as mentioned before, the light rays are separated from the outgoing light rays a, proceed through the optical path as shown by the dotted line (FIG. 23), and enter the light-receiving element 229 as the incident light rays. The detection of the information signal I, the focus error signal Fo, and the track error signal Tr is performed at this time.
In such manner, the information can be reproduced, and the focusing servo control and the tracking servo control can be done.
I=(A+B+C)
The focus error signal Fo can be obtained by the following equality, for instance, utilizing the beam size method:
Fo=(A+C)−B
Thereby, the positional control of the objective lens 205 in the optical axis direction thereof can be performed. The track error signal Tr can be obtained by the following equality, for instance, utilizing the push-pull method:
Tr=(A−C)
Thereby, the positional control of the objective lens 205 in the radial direction thereof can be performed.
As mentioned heretofore, since the reflection light rays b reflected on the optical disk 6 are guided to the reflection-type birefringent prism 230 having both functions of separating the light rays flux and deflecting the same and reflected thereon, and further guided to the light-receiving element 229 in a state of being completely separated from the outgoing light rays a, it is not necessary to separatedly prepare the signal detecting optical system 207 as in the case of the conventional manner, and thereby the reduction of the employed parts number and the cost-down of the optical pickup can be realized.
Furthermore, both of the incident and outgoing surfaces of the reflection-type birefringent prism 230 are plain, there occurs no diffused reflection, and further it is possible to suppress the flaring light rays to the utmost and reduce the noise in the light-receiving element 229 by forming the reflection preventing film on the surfaces of the prism 230. Thereby, the signal detection can be done with good S/N. And further, by disposing the light-receiving element 229 at the side of the semiconductor laser 201, the space for the optical system can be omitted. Consequently, it is possible to provide a small-sized and light-weighted optical pickup apparatus and perform the high-speed seeking operation.
Nextg, the eighth embodiment of the present invention is explained referring to
In the optical pickup apparatus of the eighth embodiment as shown in
As mentioned above, the semiconductor laser 201, the objective lens 205, the 3-beam Wollaston prism 235, and the light-receiving elements 229a and 229b construct the optical pickup portion 233.
Furthermore, reflection preventing films not shown in
The operation of the optical pickup portion 233 employing the 3-beam Wollaston prism 235 in such construction is described hereinafter, referring to FIG. 26. The outgoing light rays a emitted from the semiconductor laser 201 pass through the 3-beam Wollaston prism 235, are focused by the objective lens 205, and form an extremely small spot on the surface of the magneto-optic disk 210 employed as the optical information recording medium. Thereby, the operations of recording and erasing the information on the disk 210 are performed.
The operation of recording is done on the magneto-optic disk 210 in accordance with the polarity of the magnetizing direction on the surface of the magneto-optic disk. The light rays reflected on the surface of the magneto-optic disk 210 pass through the objective lens 205, and are divided into three polarized components by the 3-beam Wollaston prism 235. Two polarized components b1 and b2 among those three components enter the light-receiving elements 229a and 229b as the incident light rays.
When the linearly-polarized light rays are reflected on the surface of the magneto-optic disk 210, the polarization surface there of is rotated and the direction of its rotation varies in accordance with the direction of the magnetization (Kerr Effect). At this time, the information signal (magneto-optic signal) can be reproduced, utilizing the difference of the rotational direction of the polarizing surface. And further, the focus error signal Fo and the track error signal Tr can be detected, utilizing the method as mentioned in the previous (seventh) embodiment. (Refer to
The definition of the magneto-optic Kerr effect is mentioned below in brief. When the light rays enter the optical substrate as the incident light rays, the polarizing state (condition) and the reflection factor vary in accordance with the state of magnetization. Such phenomenon is called the “Kerr effect”.
Next, the case of detecting the information signal (magneto-optic signal) is explained referring to
On the other hand, the numeral {circle around (3)} of
The P-polarized light rays pass through {circle around (2)} and {circle around (3)}, and act as follows:
Regarding the subsequent forward optical path, only the straight-going light rays are explained. The numeral {circle around (4)} of
The numeral {circle around (5)} of
The numeral {circle around (6)} of
The numeral {circle around (7)} of
The numeral {circle around (8)} of
On the other hand, the light rays refracted on the boundary surface portion between the prism 235b and the prism 235a and entering the light-receiving element 229b are the extraordinary light rays 244 and 246 in the prism 235b, and the same are the ordinary light rays 249 and 253 in the prism 235a, as shown in
The information signal can be obtained by the difference signal between the signal detected by the light-receiving element 229a and the other signal detected by the light-receiving element 229b.
In such manner, the signal detection is performed with the differential value method by use of the 3-beam Wollaston prism 235. Consequently, the noise of the same-phase components of the respective light-receiving elements 229a and 229b can be reduced, and in addition, it is possible to obtain the output signal of the value two times of the respective signals individually detected by the light-receiving elements 229a and 229b. Therefore, the reproduction of good S/N can be done.
As mentioned above, the reflection light rays reflected on the magneto-optic disk 210 enter the 3-beam Wollaston prism 235 as the incident light rays, and are separated into three poloarized components of the light rays. Two polarized components of the light rays among three polarized components are completely separated from the outgoing light rays and are guided to the light-receiving elements 229a and 229b. Since the 3-beam Wollaston prism 235 having the light rays flux separating function of separating into the polarized components in such manner is employed, it is not necessary to provided, separatedly, the signal detecting optical system as in the conventional case, and thereby the cost-down of the optical pickup apparatus can be realized by reducing the number of the employed parts. Furthermore, since the incident and outgoing surfaces of the 3-beam Wollaston prism 235 are plain, the diffused reflection does not occur. And further, by forming the reflection preventing film, the occurrence of the flaring light rays can be suppressed to the utmost, and the noise on the light-receiving elements 229a and 229b can be reduced. Thereby, the signal detection with good S/N can be done. Furthermore, since the light-receiving elements 229a and 229b can be disposed at the side of the semiconductor laser 201, the space for the optical system can be omitted and thereby the small-sized and light-weighted construction of the optical pickup can be realized and the seeking operation can be done with high speed.
Next, the ninth embodiment of the present invention is explained referring to
In the optical pickup apparatus described in the seventh and eighth embodiments, all of the optical parts constructing the optical pickup portion 233 from the semiconductor laser 201 to the objective lens 205 are unitarily mounted.
As mentioned above, the boundary portions of almost all optical parts excluding the objective lens 205 are fixed by bonding with adhesive agents and unitarily mounted by use of the lens holder 258, or those parts are unitarily mounted by use of the optical parts holders 259 and 260. In such manner, an extremely compact construction can be realized. Furthermore, it is possible to realize an optical system of small signal variation due to the slippage of respective parts which can be handled easily.
Next, the tenth embodiment of the present invention is explained referring to FIG. 39. The explanation of the same portion as that of the seventh through ninth embodiments is omitted, and same reference numeral is attached to the same portion.
The tenth embodiment is the one, to which the optical pickup apparatuses described in the seventh through ninth embodiments are applied on the basis of a part of the construction regarding the afore-mentioned eighth example of the conventional optical pickup device. (Refer to
To state more concretely, the optical pickup portion 233 in
Finally, the functional effects of the embodiments in the third group of the invention are described hereinafter. As is apparent from the foregoing description, according to the present invention, the following effects can be expected:
Regarding the seventh embodiment of the present invention, in the optical pickup apparatus in which the outgoing light rays emitted from the semiconductor laser are focused by the objective lens and form an extremely small spot on the surface of the optical information recording medium, and in such manner, the operations of recording, etc. of the information are performed, and further the reflection light rays reflected on the afore-mentioned optical information recording medium are guided to the light-receiving element and thereby the reproduction of the information and the detection of the focus error signal and the track error signal both for use in the servo (mechanism) are performed, the quarter-wave (λ/4) plate and the reflection-type birefringent prism provided with the deflecting function of deflecting the reflection light rays reflected on the above optical information recording medium and the light rays flux separating function of separating the reflected light rays from the outgoing light rays are disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the reflection light rays from the above optical information recording medium which are deflected and separated by the reflection-type birefringent prism is disposed on a single (same) substrate together with the above-mentioned semiconductor laser.
In such construction, since the reflection-type birefringent prism having both of the deflecting function and the light rays flux separating function is employed, it turns out to become unnecessary to separatedly prepare the signal detecting optical system as in the conventional case, and thereby the cost-down can be realized by reducing the number of the employed parts. And further, since the incident and outgoing surfaces of the reflection-type birefringent prism are plain, there occurs no diffused reflection of the light rays and the incident and outgoing surface serve also as the one for preventing the reflection. Consequently, the occurrence of the flaring light rays can be suppressed to the utmost and the noise on the light-receiving element can be reduced. Thereby the signal detection with good S/N can be performed. And further since the light-receiving element can be disposed at the side of the semiconductor laser, the space for the optical system can be omitted. Thereby, it is possible to realize the small-sized and light-weighted construction of the optical pickup, and further the high-speed seeking operation can be done.
Regarding the eighth embodiment of the present invention, in the optical pickup apparatus in which the outgoing light rays emitted from the semiconductor laser are focused by the objective lens and form an extremely small spot on the surface of the optical information recording medium, and in such manner, the operations of recording, etc. of the information are performed, and further the reflection light rays reflected on the afore-mentioned optical information recording medium are guided to the light-receiving element and thereby the reproduction of the information and the detection of the focus error signal and the track error signal both for use in the servo (mechanism) are performed, the 3-beam Wollaston prism provided with the light rays flux separating function of separating the reflection light rays reflected on the optical information recording medium into three polarized components is disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the at least two polarized components among the three polarized components separated by the 3-beam Wollaston prism is disposed on a single (same) substrate together with the above-mentioned semiconductor laser.
In such construction, since the 3-beam Wollaston prism having the light rays flux separating function of separating the flux into the polarized components is employed, it turns out to become unnecessary to separatedly prepare the signal detecting optical system as in the conventional case, and thereby the cost-down can be realized by reducing the number of the employed parts. And further since the incident and outgoing surfaces of the 3-beam Wollaston prism are plain, there occurs no diffused reflection of the light rays and the incident and outgoing surfaces serve also as the one for preventing the reflection. Consequently, the occurrence of the flaring light rays can be suppressed to the utmost and the noise on the light-receiving element can be reduced. Thereby the signal detection with good S/N can be performed. And further, since the light-receiving element can be disposed at the side of the semiconductor laser, the space for the optical system can be omitted. Thereby, it is possible to realize the small-sized and light-weighted construction of the optical pickup, and further, the high-speed seeking operation can be done.
Regarding the ninth embodiment, in the seventh or eighth embodiment, since all of the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are mounted unitarily, it is possible to realize the extremely small-sized construction of the optical pickup which can be handled easily. Furthermore, it is possible also to realize an optical system of small signal variation due to the slippage of respective parts.
Regarding the tenth embodiment, in the seventh, eighth or ninth embodiment, since the optical parts constructing the optical pickup portion from the semiconductor laser to the objective lens are accommodated in the actuator's movable portion which can be moved in the tracking direction and the focusing direction, it is possible to realize the small-sized and extremely light-weighted optical pickup portion, and it is also possible to realize the high-speed seeking operation.
Heretofore, the explanation is focused mainly on the optical pickup. However, the technical thoughts of the present invention can be applied also for the magneto-optic pickup. So, the present invention is not limited to the optical pickup only. Instead, it can be applied to both.
Akiyama, Hiroshi, Takahashi, Yoshitaka, Emoto, Masami
Patent | Priority | Assignee | Title |
8081291, | Jan 12 2006 | TELEDYNE SCIENTIFIC & IMAGING, LLC | Electro-optic zoom lens system |
8981279, | Dec 13 2011 | Hon Hai Precision Industry Co., Ltd. | Photoelectric converter capable of emitting stable optical signal |
Patent | Priority | Assignee | Title |
3900247, | |||
4125860, | Jun 16 1975 | Nippon Telegraph & Telephone Corporation | Reproducer for an eraseable videodisc |
4569039, | Jul 13 1981 | Canon Kabushiki Kaisha | Optical information output device |
4624526, | Dec 25 1982 | Pioneer Electronic Corporation | Optical pickup device |
4626679, | Sep 22 1982 | Canon Kabushiki Kaisha | Optical head and method of detecting the focus thereof |
4771414, | Nov 15 1986 | Sony Corporation | Optical pick-up apparatus |
4804835, | Nov 30 1985 | Kabushiki Kaisha Toshiba | Optical head having guide means with first and second polarizing surfaces |
5050155, | Nov 11 1985 | Sharp Kabushiki Kaisha | Pick-up device for use in an optical information recording system utilizing a diffraction grating with blaze characteristics |
5056080, | Sep 22 1989 | Ritek Corporation | Optical recording/reproducing system using interference techniques |
5062096, | Dec 25 1987 | Copal Company Limited | Optical head and tracking method using same |
5132950, | May 02 1989 | Pioneer Electronic Corporation | Optical head having a prism for splitting a beam of light into two polarized light beams |
5136152, | Dec 19 1990 | LEE, WAI-HON | Hybrid optical pickup with integrated power emission and reading photodetectors |
5172368, | Apr 25 1989 | Thomson-CSF | Reader for optical recording medium |
5210627, | May 31 1990 | Mitsubishi Denki Kabushiki Kaisha | Optical record and reproduction apparatus with liquid crystal panel that rotates light followed by a polarizer or birefringent plate |
5251058, | Oct 13 1989 | Xerox Corporation | Multiple beam exposure control |
5251198, | May 29 1992 | Reading device for multi-layered optical information carrier | |
5293371, | Jul 26 1990 | Canon Kabushiki Kaisha | Optical head for a magneto-optical information reproducing apparatus including a light beam splitter having a first glass, a uniaxial crystal and a second glass arranged in sequence |
5331621, | Dec 04 1991 | Sharp Kabushiki Kaisha | Optical pickup apparatus and a hologram element used for same |
5410529, | Jan 27 1989 | Sharp Kabushiki Kaisha | Optical pickup apparatus |
5631774, | Apr 28 1994 | Olympus Optical Co., Ltd. | Polarizing beam splitter and optical pick-up head comprising the same |
JP4087041, | |||
JP4155629, | |||
JP5120755, | |||
JP56061043, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
May 22 2000 | Ricoh Company, Ltd. | (assignment on the face of the patent) | / |
Date | Maintenance Fee Events |
Sep 13 2010 | REM: Maintenance Fee Reminder Mailed. |
Feb 06 2011 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
Date | Maintenance Schedule |
Jul 01 2011 | 4 years fee payment window open |
Jan 01 2012 | 6 months grace period start (w surcharge) |
Jul 01 2012 | patent expiry (for year 4) |
Jul 01 2014 | 2 years to revive unintentionally abandoned end. (for year 4) |
Jul 01 2015 | 8 years fee payment window open |
Jan 01 2016 | 6 months grace period start (w surcharge) |
Jul 01 2016 | patent expiry (for year 8) |
Jul 01 2018 | 2 years to revive unintentionally abandoned end. (for year 8) |
Jul 01 2019 | 12 years fee payment window open |
Jan 01 2020 | 6 months grace period start (w surcharge) |
Jul 01 2020 | patent expiry (for year 12) |
Jul 01 2022 | 2 years to revive unintentionally abandoned end. (for year 12) |