Light-to-light conversion element provided with wavelength selecting reflection layer and imaging device provided with the light-to-light conversion element

Abstract

A light-to-light conversion element which includes at least a photoconductive layer and a photo-modulation layer and in which light incident on these layers is reflected by a reflection layer and in which a selective reflection characteristic corresponding to color separation is given to the reflection layer. Thereby, among the light incident on the photoconductive layer and the photo-modulation layer, light having wavelength of the specific region is selectively reflected by the reflection layer, so that the write and read operation of information is performed on the selected light.

Description

is performed by effecting the scan by deflecting write laser light, which is outputted from laser light sources or light sources such as light emitting diodes (LEDs) 72R, 72G and 72B, by using deflecting devices 74R, 74G and 74B. The information is included in the red, green blue laser light R, G and B in the time series manner. Further, a read operation of reading the information from the light-to-light conversion elements 40R, 40G and 40B of this embodiment is effected similarly as in case of the first embodiment.

Next, a third embodiment of the present invention will be described in detail hereinbelow by referring to FIG. 5. This embodiment is adapted to project the read light R, G and B on a screen and effect the color synthesis on the screen.

In this figure, the incidence of the write light on the light-to-light conversion elements 40R, 40G and 40B is preformed similarly as in case of the first embodiment. In contrast with this, the incidence of the read light on the light-to-light conversion elements 40R, 40G and 40B is effected by reflecting the read light R, G and B outputted from the light sources 76R, 76G and 76B by the semi-transparent mirrors 78R, 78G and 78B, respectively. Incidentally, it goes without saying that each of the semi-transparent mirrors 76R, 76G and 76B can be replaced with a polarization beam splitter.

Further, the rays of the read light R, G and B reflected by the light-to-light elements 40R, 40G and 40B and outputted therefrom respectively pass through the semi-transparent mirrors 78R, 78G and 78B and are respectively incident on the projecting optical systems 80R, 80G and 80B, thereby projecting the read light on a screen (not shown). Further, the color synthesis is effected on the screen.

Next, a fourth embodiment of the present invention will be described in detail hereunder by referring to FIG. 6. Although the light-to-light conversion elements are provided with respect to each of the separated light components R, G and B in the above described first, second and third embodiments, such light-to-light elements for the light components R, G and B are constructed as one unit in the fourth embodiment.

As shown in FIG. 6, a light-to-light element 82 is formed like a rectangular parallelepiped. Further, in the light-to-light element 82, a photoconductive layer 84, a photo-modulation layer 86, a dielectric mirror 88 and electrodes 90 and 92 are laminated. Incidentally, the photo-modulation layer 86 and the electrode 92 are indicated by dashed lines in this figure, for convenience of description.

Further, a basic operation of each of these composing portions is effected similarly as in case of the corresponding portion of the embodiment of FIG. 1. The dielectric mirror 88 has three division regions 88R, 88G and 88B of which wavelength selection characteristics are preliminarily established such that these regions 88R, 88G and 88B respectively reflect the rays of separated light R, G and B.

Moreover, the incidence of write light R, that of write light G and that of write light B on the light-to-light element 82 are respectively effected for the division regions 88R, 88G and 88B as indicated by arrows F20R, F20G and F20B in FIG. 6. On the other hand, the incidence of the read light R, G and B thereon is performed from the direction as indicated by an arrow F21. Further, the rays of the read light R, G and B are selectively reflected by the division regions 88R, 88G and 88B of the dielectric mirror 88 and are outputted therefrom as indicated by arrows F22R, F22G and F22B, respectively.

Next, a fifth embodiment of the present invention will be detailedly described hereinbelow by referring to FIG. 7. First, as shown in FIG. 7 (A), an example of the construction of the fifth embodiment is provided with a light-to-light conversion element which has a dielectric mirror 94 made up of stripe-like division regions which selectively reflect separated light components R, G and B. Further, as shown in FIG. 7 (B), another example of the construction of the fifth embodiment is provided with a light-to-light conversion element which has a dielectric mirror 96 composed of matrix-like division regions which selectively reflect separated light components R, G and B.

In accordance with this embodiment, white light or light obtained by mixing red, green and blue light components together is incident on the whole dielectric mirror of which each division region reflects the light having a corresponding wavelength. Thereby, operations of writing information into and reading information from the device is effected. Incidentally, in case of this embodiment, it is unnecessary to perform color synthesis.

Further, it is to be understood that the present invention is not limited to the above described embodiments. For example, the polarizing plate 32 is not necessarily provided in the device and may be provided in the device if necessary. Further, the fifth embodiment may be used as a displaying device by looking straight on the light-to-light element or device. Moreover, it is to be understood that other modifications may be made by variously altering the design of the device by combining the above described embodiments with each other.

Furthermore, although the above described embodiments are obtained by applying the present invention to a displaying apparatus, the present invention may be applied to an image sensing device. For example, the light-to-light conversion device of the present invention may be used as an image sensing device by being provided with a photoelectric conversion element and performing the scan by deflecting a pencil beam. Further, although the above described embodiments are used for displaying a color image, it is possible to make the embodiment process information on electro-magnetic radiation flux having other wavelengths by appropriately establishing the wavelength to be selected by the dielectric mirror.

Next, another preferred embodiment of the present invention will be described in detail by referring to FIG. 9 which is a schematic block diagram for showing the construction of a light-to-light conversion element embodying the present invention.

In FIG. 9, reference character PPC denotes a light-to-light conversion element (hereunder sometimes referred to as a wavelength conversion element); Et1 and Et2 electrodes; PCL a photoconductive material layer member sensitive to at least an invisible electro-magnetic radiation beam; DML a dielectric mirror reflecting an electro-magnetic radiation beam having wavelength of a predetermined region or range (the dielectric mirror DML is assumed to reflect a visible electro-magnetic radiation beam in the following description); PML a photo-modulation material layer member (for example, a photo-modulation material layer such as a single crystal of lithium niobate or a nematic liquid crystal layer) capable of changing the state of at least a visible electro-magnetic radiation beam; WL a invisible electro-magnetic radiation beam to be converted by the conversion element PPC; and RL a visible electro-magnetic radiation beam. Further, the electrode Et1 is constructed as "transparent" for at least the invisible electro-magnetic radiation beam to be converted (that is, the electrode Et1 is constructed in such a manner to transmit at least the invisible electro-magnetic radiation beam to be converted). On the other hand, the electrode Et2 is constructed as "transparent" for at least the visible electro-magnetic radiation beam (that is, the electrode Et2 is constructed in such a manner to transmit at least the visible electro-magnetic radiation beam).

As shown in FIG. 9, a circuit consisting of a power source 104 and a switch SW is connected to the electrodes Et1 and Et2 of the light-to-light conversion element PPC. Further, a movable contact of the switch SW is placed in the position of a fixed contact WR in accordance with a switch control signal supplied at an input terminal 115 of the switch SW. Then, a voltage from the power source 104 is applied across the electrodes Et1 and Et2 such that an electric field be applied across the photoconductive material layer PCL. Hereupon, when the invisible electro-magnetic radiation beam WL to be converted is incident on the electrode Et1 of the conversion element PPC, the invisible electro-magnetic radiation beam WL passes through the electrodes Et1 and reaches the photoconductive layer material member PCL.

The electric resistance of the photoconductive material layer member PCL changes correspondingly to intensity distribution of the invisible electro-magnetic radiation beam WL, which is to be converted and has reached thereto, so that electric charges having intensity distribution (that is, a charge image) corresponding to the intensity distribution of the invisible electro-magnetic radiation beam WL are generated on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML.

Thereafter, in the above described state in which the movable contact of the switch SW is placed in the position of the fixed contact WR thereof and the voltage from the power source 104 is applied across the electrodes Et1 and Et2, the visible electro-magnetic radiation beam RL having uniform intensity and coming from an electro-magnetic radiation beam source (not shown) is incident on the electrode Et2, and is reflected by the dielectric mirror DML after passing through the photo-modulation material layer member PML (for instance, the single crystal of lithium niobate PML). Then, the visible electro-magnetic radiation beam RL passes through the photo-modulation material layer member PML again and is further outputted or issued from the electrode Et2 of the conversion element PPC. At that time, the state of the visible electro-magnetic radiation beam RL is changed or modulated correspondingly to the charge distribution of the charge image generated on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML.

Namely, in the above described state in which the invisible electro-magnetic radiation beam WL is incident on the conversion element PPC and the charge image corresponding to the intensity distribution of the invisible electro-magnetic radiation beam WL is generated on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML, an electric field having strength distribution corresponding to the charge distribution of the charge image is applied to the photo-modulation material layer member PML (for example, the single crystal of lithium niobate PML) which is connected in series to the photoconductive material layer member PCL along with the dielectric mirror DML.

Further, in case where the photo-modulation material layer member PML is, for instance, the single crystal of lithium niobate, the refractive index of the photo-modulation material layer member PML changes due to electrooptic effects correspondingly to an electric field. Therefore, when the electric field having intensity distribution corresponding to the charge image is applied to the single crystal of lithium niobate, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes correspondingly to the charge distribution of the charge image.

Moreover, in case where the visible electro-magnetic radiation beam RL is projected on the electrodes Et2, the visible electro-magnetic radiation beam RL propagates through the electrode Et2 and the single crystal of lithium niobate PML used as the photo-modulation material layer member in this order. Subsequently, the visible electro-magnetic radiation beam RL is reflected by the dielectric mirror DML and then returns to the electrode Et2. However, as above described, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes due to the electrooptic effects correspondingly to the electric field. Thus, the visible electro-magnetic radiation beam RL reflected by the dielectric mirror DML comes to include information corresponding to the strength distribution of an electric field applied to the single crystal of lithium niobate PML used as the photo-modulation material layer member by the electrooptic effects of the single crystal of lithium niobate PML and is further outputted from the electrode Et2. Namely, the conversion element PPC of FIG. 9 performs the wavelength conversion of the invisible electro-magnetic radiation beam, which is incident thereon, into the visible electro-magnetic radiation beam and further issues the converted visible electro-magnetic radiation beam.

Furthermore, erasure of the charge image thus formed by the invisible electro-magnetic radiation beam WL to be converted is effected by supplying a switch control signal to the input terminal 115 of the switch SW to place the movable contact of the switch SW in the fixed contact thereof, then equalizing electric potentials of the electrodes Et1 and Et2 of the conversion element and further making an electro-magnetic radiation beam having uniform intensity distribution be incident thereon and then letting the incident electro-magnetic radiation beam pass the photoconductive material layer member PCL.

Next, other preferred embodiments of the present invention will be further described hereinbelow by referring to FIGS. 10 and 11 which are schematic block diagrams for showing the construction of each of different light-to-light conversion devices using the light-to-light conversion element of FIG. 9 embodying the present invention in case where these light-to-light conversion devices are employed as imaging devices. In FIGS. 10 and 11, reference character 0 denotes an object; 1 an imaging lens; and PPC the conversion element of FIG. 9, that is, the conversion element wherein the photoconductive material layer member sensitive to at least an invisible electro-magnetic radiation beam and the photo-modulation material layer member capable of changing the state of at least a visible electro-magnetic radiation beam in accordance with the field strength distribution are provided between two electrodes.

Further, in these figures, reference character 102 denotes an electro-magnetic radiation beam source for issuing an electro-magnetic radiation beam to be used for erasing a charge image; 103 and 108 collimator lenses; 104 a power source; 105 a visible electro-magnetic radiation beam source; 106 a polarizer provided if necessary; 109 an analyzer; BS1 and BS2 beam splitters; 115 an input terminal for inputting switching signals therefrom; and SW a switch.

Furthermore, in FIG. 10, reference character BS3 denotes a beam splitter; 107 a deflection device for deflecting an electro-magnetic radiation beam; 110 a projecting lens; 111 a screen; 112 a condenser lens; and 113 a photoelectric conversion device. Moreover, in FIG. 11, reference numeral 114 denotes an image processing unit.

In the conversion devices each constructed by using the light-to-light conversion elements of the present invention as shown in FIGS. 10 and 11, an invisible electro-magnetic radiation beam, which is to be converted, issued from the object 0 is supplied through the imaging lens 101 to the conversion element PPC, to which erasing light EL can be supplied through a path consisting of the electro-magnetic radiation beam source 102 for erasure of a charge image, the collimator lens 103 and the beam splitter BS1.

Further, in the conversion devices of the present invention of FIG. 10, a visible electro-magnetic radiation beam RL, which is deflected in a predetermined two-dimensional deflection manner, is supplied to the conversion element PPC through a path composed of the visible electro-magnetic radiation beam source 105, the polarizer 106 provided if necessary, the deflection device 107 for deflecting an electro-magnetic radiation beam, the collimator lens 108 and the beam splitter BS2. On the other hand, in the conversion devices of the present invention of FIG. 11, a visible electro-magnetic radiation beam flux RL, which has an effective section area nearly equal to or larger than the area of the electrode of the conversion element PPC, is supplied to the conversion element PPC through a path comprised of the visible electro-magnetic radiation beam source 105, the polarizer 106 provided if necessary, the collimator lens 108 and the beam splitter BS2.

Moreover, in the conversion devices of the present invention of FIGS. 10 and 11, under the conditions that the movable contact of the switch SW of the circuit, which comprises the power source 104 and the switch SW, connected to the electrodes Et1 and Et2 of the conversion element PPC is placed in the fixed contact WR in accordance with the switching signal supplied to the input terminal 115 thereof and that the voltage from the power source 104 is applied across the electrodes Et1 and Et2 so that an electric field is applied across the both ends of the photoconductive material layer member PCL, when the invisible electro-magnetic radiation beam WL, which is to be converted, coming from the object O is incident on the electrode Et1 of the conversion element PPC through the imaging lens 101, the invisible electro-magnetic radiation beam WL passes through the electrode Et1 and further reaches the photoconductive material layer member PCL.

Furthermore, as described above, the electric resistance of the photoconductive material layer member PCL changes correspondingly to intensity distribution of the invisible electro-magnetic radiation beam WL, which is to be converted and has reached thereto. Thus, a charge image having intensity distribution corresponding to the intensity distribution of the invisible electro-magnetic radiation beam WL is formed on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML.

Then, in the above described state in which the movable contact of the switch SW is placed in the position of the fixed contact WR thereof and the voltage from the power source 104 is applied across the electrodes Et1 and Et2, the visible electro-magnetic radiation beam RL having uniform intensity is supplied in a predetermined two-dimensional deflection manner through the path composed of the visible electro-magnetic radiation beam source 105, the polarizer 106 provided if necessary, the deflection device 107 for deflecting an electro-magnetic radiation beam, the collimator lens 108 and the beam splitter BS2 in the conversion devices of the present invention of FIG. 10. Further, in the conversion devices of the present invention of FIG. 11, the visible electro-magnetic radiation beam flux RL, which has an effective section area nearly equal to or larger than the area of the electrode of the conversion element PPC, is incident on the electrode Et2 through the path comprised of the visible electro-magnetic radiation beam source 105, the polarizer 106 provided if necessary, the collimator lens 108 and the beam splitter BS2.

Furthermore, in the embodiments of FIGS. 10 and 11, the visible electro-magnetic radiation beam RL, which is incident on the electrode Et2, is reflected by the dielectric mirror DML after passing through the photo-modulation material layer member PML (for instance, the single crystal of lithium niobate PML). Thereafter, the visible electro-magnetic radiation beam RL passes through the photo-modulation material layer member PML again and is further issued from the electrode Et2 of the conversion element PPC. At that time, the state of the visible electro-magnetic radiation beam RL is changed or modulated correspondingly to the charge distribution of the charge image generated on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML.

Namely, in case where the visible electro-magnetic radiation beam RL is projected on the electrodes Et2, the visible electro-magnetic radiation beam RL propagates through the electrodes Et2 and the single crystal of lithium niobate PML used as the photo-modulation material layer member in this order. Subsequently, the visible electro-magnetic radiation beam RL is reflected by the dielectric mirror DML and then returns to the electrode Et2. However, as above described, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes due to the electrooptic effects correspondingly to the electric field. Thus, the visible electro-magnetic radiation beam RL reflected by the dielectric mirror DML comes to include information corresponding to the strength distribution of an electric field applied to the single crystal of lithium niobate PML used as the photo-modulation material layer member by the electrooptic effects of the single crystal of lithium niobate PML and is further issued from the electrode Et2. Further, the issued visible electro-magnetic radiation beam is supplied to the analyzer 109 after passing through the beam splitter BS2.

The intensity of the visible electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, changes correspondingly to the charge distribution of the charge image generated on the boundary surface between the photoconductive material layer member PCL and the dielectric mirror DML of the conversion element PPC.

Further, in the conversion device of the present invention of FIG. 10, the visible electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, is reflected by the beam splitter BS3 and then a visible optical image is formed on the screen through the projecting lens 110. Moreover, the visible electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, is fed to the photoelectric conversion device 113 through the beam splitter BS3 and the condenser lens 112 and is then outputted from the device 113 as an electric signal.

In the conversion device of the present invention of FIG. 11, the visible electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, is supplied to the image processing unit 114 for effecting various optical image processing (for example, matrix processing such as matrix multiplication, non-linear processing, contour enhancement processing and gain regulating processing) whereupon predetermined image processing is effected. Then, the result of the image processing is outputted by using visible light. Incidentally, the optical image processing unit may be constructed by using a light-to-light conversion element, a polarizer, a light source capable of regulating quantity of light, a beam splitter and an optical low-pass filter as components thereof.

Further, in case of the conversion device of FIG. 10 according to the present invention, a visible electro-magnetic radiation beam is obtained as a result of the wavelength conversion from the conversion element PPC by using the visible electro-magnetic radiation beam RL deflected by the deflection device 107 in the two-dimensional manner. In contrast, in case of the conversion device of FIG. 11 according to the present invention, a visible electro-magnetic radiation beam is obtained as a result of the wavelength conversion from the conversion element PPC by using the visible electro-magnetic radiation beam RL having a large section. However, in these embodiments, the deflection device 107 of FIG. 10 may be removed therefrom and the photoelectric conversion device 113 of FIG. 10 may be replaced with a two-dimensional image sensor. Further, the deflection device 107 may be provided just prior to the collimator lens 108 of FIG. 11.

Moreover, it is to be understood that various other modifications and changes may be made therein.

Next, in the conversion devices each constructed by using the light-to-light conversion elements of the present invention as shown in FIGS. 10 and 11, erasure of the charge image thus formed by the invisible electro-magnetic radiation beam WL to be converted can be effected by supplying a switch control signal to the input terminal 15 of the switch SW to place the movable contact of the switch SW in the fixed contact E thereof, then equalizing electric potentials of the electrodes Et1 and Et2 of the conversion element and further making an electro-magnetic radiation beam having uniform intensity distribution be incident thereon through a path composed of the electro-magnetic radiation beam source 102 for the erasure of the charge image, the collimator lens 103 and the beam splitter BS1 and thereafter letting the incident electro-magnetic radiation beam pass the photoconductive material layer member PCL.

Incidentally, in case where a dielectric mirror DML having a wavelength selection characteristic by which a visible electro-magnetic radiation beam is reflected and the electro-magnetic radiation beam for the erasure is made to pass therethrough, the conversion device is constructed by making the direction of the electro-magnetic radiation beam same with that of the incidence of the visible electro-magnetic radiation beam for the erasure. Further, the conversion device of the present invention may be used as an image sensing device by being provided with a photoelectric conversion element and performing the scan by deflecting a pencil beam.

Next, still another light-to-light conversion element embodying the present invention will be described in detail by referring to FIG. 12.

In this figure, reference character PPC denotes a light-to-light conversion element; Et1 and Et2 electrodes; PCL a photoconductive material layer member sensitive to at least an electro-magnetic radiation beam to be used for writing information and practically insensitive to an electro-magnetic radiation beam to be used for reading information; PML a photo-modulation material layer member (for example, a photo-modulation material layer such as a single crystal of lithium niobate or a nematic liquid crystal layer) capable of changing the state of at least the electro-magnetic radiation beam to be used for reading the information; WL the electro-magnetic radiation beam to be used for writing the information; and RL the electro-magnetic radiation beam to be used for reading the information. Further, the electrode Et1 is constructed as "transparent" for at least the electro-magnetic radiation beam to be used for writing the information (hereunder sometimes referred to simply as the write electro-magnetic radiation beam). On the other hand, the electrode Et2 is constructed as "transparent" for at least the electro-magnetic radiation beam to be used for reading the information (hereunder sometimes referred to simply as the read electro-magnetic radiation beam).

As shown in FIG. 12, a circuit consists of a power source 210 and a switch SW is connected to the electrodes Et1 and Et2 of the light-to-light conversion element PPC. Further, a movable contact of the switch SW is placed in the position of a fixed contact WR in accordance with a switch control signal supplied at an input terminal 211 of the switch SW. Then, a voltage from the power source 210 is applied across the electrodes Et1 and Et2 such that an electric field be applied across the photoconductive material layer PCL. Hereupon, when the write electro-magnetic radiation beam WL is made to be incident on the electrode Et1 of the conversion element PPC, the write electro-magnetic radiation beam WL passes through the electrodes Et1 and reaches the photoconductive layer material member PCL.

Further, the electric resistance of the photoconductive material layer member PCL changes correspondingly to intensity distribution of the write electro-magnetic radiation beam WL reached thereto, so that a charge image having intensity distribution corresponding to the intensity distribution of the write electro-magnetic radiation beam WL having reached to the photoconductive material layer member PCL is generated on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML.

Then, under the above described condition that the movable contact of the switch SW is placed in the position of the fixed contact WR thereof and the voltage from the power source 210 is applied across the electrodes Et1 and Et2, the read electro-magnetic radiation beam RL having constant intensity and coming from an electro-magnetic radiation beam source (not shown) is made to be incident on the electrode Et2. The read electro-magnetic radiation beam RL passes through the photoconductive material layer member PCL and the photo-modulation material layer member PML (for instance, the single crystal of lithium niobate PML). Thereafter, the read electro-magnetic radiation beam RL is outputted or issued from the electrode Et2 of the conversion element PPC. At that time, the state of the read electro-magnetic radiation beam RL is changed correspondingly to the charge distribution of the charge image generated on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML (for instance, the single crystal of lithium niobate PML).

Namely, under the above described condition that the write electro-magnetic radiation beam WL is incident on the conversion element PPC and the charge image corresponding to the intensity distribution of the write electro-magnetic radiation beam WL is generated on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML (for example, the single crystal of lithium niobate PML), an electric field having strength distribution corresponding to the charge distribution of the charge image is applied to the photo-modulation material layer member PML (for example, the single crystal of lithium niobate PML) which is connected in series to the photoconductive material layer member PCL along with the dielectric mirror DML.

Further, in case where the photo-modulation material layer member PML is, for instance, the single crystal of lithium niobate, the refractive index of the photo-modulation material layer member PML changes due to electrooptic effects correspondingly to an electric field. Thus, when the electric field having strength distribution corresponding to the charge image is applied to the single crystal of lithium niobate, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes correspondingly to the charge distribution of the charge image.

Moreover, in case where the read electro-magnetic radiation beam RL is incident on the electrodes Et1, the read electro-magnetic radiation beam RL propagates through the electrode Et1, the photoconductive material layer member PCL, the single crystal of lithium niobate PML and the electrode Et2 in this order. However, as above described, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes due to the electrooptic effects correspondingly to the electric field. Thus, the read electro-magnetic radiation beam RL comes to include information, which corresponds to the strength distribution of an electric field applied to the single crystal of lithium niobate PML used as the photo-modulation material layer member, by the electrooptic effects of the single crystal of lithium niobate PML and is further issued from the electrode Et2.

Further, in the conversion element PPC of FIG. 12, the photoconductive material layer member PCL thereof is practically insensitive to the read electro-magnetic radiation beam RL. Therefore, even when the read electro-magnetic radiation beam RL passes through the photoconductive material layer member PCL, there occur no photoconductive effects. Thus, even when the read electro-magnetic radiation beam RL passes through the photoconductive material layer member PCL, the charge image present on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML is never disturbed.

Furthermore, erasure of the charge image thus formed by the write electro-magnetic radiation beam WL is effected by supplying a switch control signal to the input terminal 211 of the switch SW to place the movable contact of the switch SW in the fixed contact E thereof, then equalizing electric potentials of the electrodes Et1 and Et2 of the conversion element and further making an electro-magnetic radiation beam, to which the photoconductive material layer member PCL is sensitive, having uniform intensity distribution be incident thereon and then letting the incident electro-magnetic radiation beam pass the photoconductive material layer member PCL.

Moreover, in case of the light-to-light conversion element in which a liquid crystal is used as material of the photoconductive material layer member, the erasure of the charge image is performed by supplying an a. c. voltage to the electrodes Et1 and Et2.

Incidentally, the conversion element of FIG. 12 may be used as an image sensing device by being provided with a photoelectric conversion element and performing the scan by deflecting a pencil beam.

Furthermore, as material of the photoconductive material layer member, for example, cadmium sulfide (CdS) and a bismuth silicon oxide (Bi₁2 SiO₂0) may be employed.

For instance, CdS has sensitivity characteristics as shown in FIG. 16 and thus is sensitive to visible light and is practically insensitive to infrared light of which the wavelength is larger than or equal to 750 nano-meters (nm). FIG. 17 shows the construction of a light-to-light conversion element using CdS as material of the photoconductive material layer member PML. In case of this conversion element, visible light is used as a write electro-magnetic radiation beam WL and on the other hand infrared light, of which the wavelength is larger than or equal to 750 nm, is used as a read electro-magnetic radiation beam RL. Further, the information written into the conversion element PPC is read by making the read electro-magnetic radiation beam RL pass through the electrode Et1 and the photoconductive material layer member PCL. Moreover, the information written into the conversion element PPC can be read from the side of the photo-modulation material layer member PML by using the difference in refractive index between the photoconductive material layer member PCL and the photo-modulation material layer member PML and using the reflection of the read electro-magnetic radiation beam RL on the boundary surface therebetween.

On the other hand, FIG. 18 shows the relation between the photoconductive effect of Bi₁2 SiO₂0 (hereunder abbreviated as BSO) and the wavelength. As shown in this figure, BSO has an especially dramatic photoconductive effect in the range of the wavelength of near-ultraviolet light and blue light but very little photoconductive effect in the range of the wavelength of red light. The ratio of the magnitude of the photoconductive effect at the wavelength of 370 nm to that of the photoconductive effect at the wavelength of 630 nm is about 10³ to 10⁴. Thus, in this case, light having a wavelength in the range from near-ultraviolet light to blue light is used as a write electro-magnetic radiation beam WL and on the other hand, light, of which the wavelength is larger than or equal to 600 nm, is used as a read electro-magnetic radiation beam RL. Thereby, a high resolution image can be written or read by the conversion device using such a conversion element.

Next, an imaging device constructed by using the light-to-light conversion element of FIG. 12 embodying the present invention will be further described hereinbelow by referring to FIG. 13 which is a schematic block diagram for showing the construction of the imaging device using the light-to-light conversion element of FIG. 12. In FIG. 13, reference character O denotes an object; 212 an imaging lens; and PPC the conversion element of FIG. 12, that is, the conversion element wherein the photoconductive material layer member sensitive to at least the write electro-magnetic radiation beam and practically insensitive to the read electro-magnetic radiation beam and the photo-modulation material layer member capable of changing the state of at least read electro-magnetic radiation beam in accordance with the field strength distribution are provided between two electrodes.

Further, in this figure, reference character 217 denotes an electro-magnetic radiation beam source for issuing an electro-magnetic radiation beam (hereunder sometimes referred to as an erasure electromagnetic radiation beam) to be used for erasing a charge image; 216 and 218 collimator lenses; 210 a power source; 213 a read electro-magnetic radiation beam source; 214 a polarizer provided if necessary; 219 an analyzer; BS1 and BS2 beam splitters; 211 an input terminal for inputting switching signals therefrom; SW a switch; 220 a condenser lens; and 221 an electric conversion device.

In the imaging device of FIG. 13 constructed by using the light-to-light conversion elements of the present invention, an electro-magnetic radiation beam issued from the object O is supplied through the imaging lens 212 and the beam splitter BS1 to the conversion element PPC.

Further, a read electro-magnetic radiation beam RL, which is deflected in a predetermined two-dimensional deflection manner, is supplied to the conversion element PPC through a path composed of the read electro-magnetic radiation beam source 213, the polarizer 214 provided if necessary, the deflection device 215 for deflecting an electro-magnetic radiation beam, the collimator lens 216 and the beam splitter BS1.

Moreover, an erasure light or electro-magnetic radiation beam EL is supplied to the conversion element PPC through a path composed of the erasure electro-magnetic radiation beam source 217, the collimator lens 218 and the beam splitter BS2.

Furthermore, in the imaging device of the present invention of FIG. 13, under the conditions that the movable contact of the switch SW of the circuit, which comprises the power source 210 and the switch SW, connected to the electrodes Et1 and Et2 of the conversion element PPC is placed in the fixed contact WR in accordance with the switching signal supplied to the input terminal 211 thereof and that the voltage from the power source 210 is applied across the electrodes Et1 and Et2 so that an electric field is applied across the both ends of the photoconductive material layer member PCL, the write electro-magnetic radiation beam WL coming from the object O is made to be incident on the electrode Et1 of the conversion element PPC through the imaging lens 212 and the beam splitter BS1. The write electro-magnetic radiation beam WL passes through the electrode Et1 and further reaches the photoconductive material layer member PCL as above described.

Further, the photoconductive material layer member PCL is sensitive to the write electro-magnetic radiation beam and thus, when the write electro-magnetic radiation beam WL passes through the electrode Et1 and further reaches the photoconductive material layer member PCL, the electric resistance of the photoconductive material layer member PCL changes correspondingly to intensity distribution of the write electro-magnetic radiation beam WL having reached thereto. Thus, a charge image having intensity distribution corresponding to the intensity distribution of the write electro-magnetic radiation beam WL having reached to the photoconductive material layer member PCL is formed on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML.

Then, under the above described condition that the movable contact of the switch SW is placed in the position of the fixed contact WR thereof and the voltage from the power source 210 is applied across the electrodes Et1 and Et2, when the read electro-magnetic radiation beam RL, which has constant intensity and coming from an electro-magnetic radiation beam source 213, is made to be incident on the electrode Et1, in a predetermined two-dimensional deflection manner, through the path composed of the polarizer 214 provided if necessary, the deflection device 215 for deflecting an electro-magnetic radiation beam, the collimator lens 216 and the beam splitter BS1.

Moreover, the read electro-magnetic radiation beam RL, which has been incident on the electrodes Et1, propagates through the electrode Et1, the photoconductive material layer member PCL, the single crystal of lithium niobate used as the photoconductive material layer member PML and the electrode Et2 in this order. However, as above described, the refractive index of the single crystal of lithium niobate used as the photo-modulation material layer member PML changes due to the electrooptic effects correspondingly to the electric field. Thus, the read electro-magnetic radiation beam RL comes to include information, which corresponds to the strength distribution of an electric field applied to the single crystal of lithium niobate PML used as the photo-modulation material layer member, by the electrooptic effects of the single crystal of lithium niobate PML and is further issued from the electrode Et2. Then, the thus issued beam RL passes through the beam splitter BS2 and is thereafter supplied to the analyzer 219.

Furthermore, the intensity of the read electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, changes correspondingly to the charge distribution of the charge image generated on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML of the conversion element PPC.

Further, the read electro-magnetic radiation beam RL, which has passed through the analyzer 109 as above described, is condensed by condenser lens 220 and as a result is fed to the photoelectric conversion device 221 whereupon the condensed electro-magnetic radiation beam is converted into an electric signal. Further, the electrical signal is outputted from the photoelectric conversion device 221.

Then, the erasure of the charge image thus formed by the write electro-magnetic radiation beam WL is effected by supplying a switch control signal to the input terminal 211 of the switch SW to place the movable contact of the switch SW in the fixed contact E thereof, then equalizing electric potentials of the electrodes Et1 and Et2 of the conversion element and further making an erasure electro-magnetic radiation beam EL, to which the photoconductive material layer member PCL is sensitive, generated by the erasure electro-magnetic radiation beam source 217 and having uniform intensity distribution be incident on the electrode Et2 of the light-to-light conversion element PPC and then letting the incident electro-magnetic radiation beam pass the photo-modulation material layer member PML and the photoconductive material layer member PCL.

As stated above, in case of the light-to-light conversion imaging device in which a liquid crystal is used as material of the photoconductive material layer member, the erasure of the charge image is performed by supplying an a. c. voltage to the electrodes Et1 and Et2 of the conversion device.

Further, the imaging device described by referring to FIG. 13 is constructed such that the read electro-magnetic radiation beam RL is made to be incident on the electrode Et1 of the light-to-light conversion element PPC and is further issued from the electrode Et2 through a path comprised of the electrode Et1, the photoconductive material layer member PCL, the photo-modulation material layer member PML and the electrode Et2. However, the imaging device of the present invention may be constructed in the manner that the light-to-light conversion element provided with a photoconductive material layer member sensitive to at least the write electro-magnetic radiation beam and insensitive to the read electro-magnetic radiation beam and capable of reflecting the read electro-magnetic is employed and that the read electro-magnetic material layer member RL is made to be incident on the electrode Et2 of the light-to-light conversion element PPC and to pass the photo-modulation material layer member and thereafter the read electro-magnetic radiation beam RL is made to reflect on the boundary surface between the photoconductive material layer member PCL and the photo-modulation material layer member PML and then the read electro-magnetic radiation beam RL is made to pass the photo-modulation material layer member PML and is further issued from the electrode Et2.

Incidentally, it is apparent that the imaging device of the present invention may be constructed such that operations of writing and reading information can be performed by using light in a broad sense, namely, electro-magnetic radiation beams of all or part of spectra (thus including radiowaves from short waves such as γ rays and X rays to long waves).

While preferred embodiments of the present invention has been described above, it is to be understood that the present invention is not limited thereto and that other modifications will be apparent to those skilled in the art without departing from the spirit of the invention. The scope of the present invention, therefore, is to be determined solely by the appended claims.

Claims

1. A light-to-light conversion element for use in an image displaying or sensing device, comprising:

a photoconductive layer responsive to a first incident light, which includes image information to be written thereinto, thereon for generating electric charge corresponding to the quantity of the incident light;

a photo-modulation layer for modulating a second incident light thereon, which is used for reading written image information, by using electrooptic effects corresponding to influence of an electric field caused by the electric charge generated in said photoconductive layer; and

a light reflecting layer interposed between said photoconductive and photo-modulation layers and having a predetermined selective reflection characteristic corresponding to color separation of the second incident light for reflecting the second incident light, wherein

each of said photoconductive layer and said photo-modulation layer has a transmission characteristic by which each of said photoconductive layer and said photo-modulation layer can transmit light of wavelength of a range being broader than a range of wavelength of light reflected by said light reflecting layer.

2. An image displaying apparatus including:

first, second and third light-to-light conversion elements each having a photoconductive layer responsive to light for generating an electric charge corresponding to quantity of the light, a photo-modulation layer for modulating received light by using electrooptic effects corresponding to influence of an electric field caused by the electric charge generated in said photoconductive layer and a light reflecting layer integrated between said photoconductive and photo-modulation layers and having a predetermined selective reflection characteristic for selectively reflecting light, said reflecting layer of said first light-to-light conversion element having a selective reflection characteristic to reflect red light, said reflecting layer of said second light-to-light conversion element having a selective reflection characteristic to reflect green light, said reflecting layer of said second light-to-light conversion element having a selective reflection characteristic to reflect blue light; and

color separation means for effecting the color separation of first incident light, which includes image information to be written into said first, second and third light-to-light conversion elements, and second incident light used for reading the written image information to obtain red, green and blue composing light, for introducing the red, green and blue composing light to said photo-modulation layers of said first, second and third light-to-light conversion elements, respectively, and for receiving and transmitting light reflected by said photo-modulation layers of said first, second and third light-to-light conversion elements.

3. The image displaying apparatus as set forth in claim 2, wherein said color separation means comprises:

a first separation means for effecting the color separation of the first incident light to obtain red, green and blue composing light and introducing the red, green and blue composing light to said first, second and third light-to-light conversion elements, respectively; and

a second separation means for effecting the color separation of the second incident light to obtain red, green and blue composing light and introducing the red, green and blue composing light to said first, second and third light-to-light conversion elements, respectively.

4. The image displaying apparatus as set forth in claim 3, wherein said first separation means includes:

a first dichroic mirror for separating composing light of a predetermined color selected from red, green and blue from the first incident light; and

a second dichroic mirror for separating composing light of the other colors of red, green and blue.

5. The image displaying apparatus as set forth in claim 3, wherein said second separation means includes:

a first dichroic mirror for separating composing light of a predetermined color, which is selected from red, green and blue, from the second incident light;

a second dichroic mirror for separating composing light of the other colors of red, green and blue from each other; and

a first semi-transparent mirror for introducing the composing light of one of the other colors separated by said second dichroic mirror to a corresponding light-to-light conversion element.

6. An image displaying apparatus including:

a first, second and third light-to-light conversion element each having a photoconductive layer responsive to light for generating an electric charge corresponding to the quantity of the light, a photo-modulation layer for modulating received light by using electrooptic effects corresponding to influence of an electric field caused by the electric charge generated in said photoconductive layer and a light reflecting layer interposed between said photoconductive and photo-modulation layers and having a predetermined selective reflection characteristic for selectively reflecting the light, said reflecting layer of said first light-to-light conversion element having a selective reflection characteristic to reflect red light, said reflecting layer of said second light-to-light conversion element having a selective reflection characteristic to reflect green light, said reflecting layer of said second light-to-light conversion element having a selective reflection characteristic to reflect blue light;

image information input means for introducing red, green and blue write light, each of which includes image information to be written into said first, second and third conversion means element, to said first, second and third conversion means elements, respectively; and

color separation means for effecting the color separation of first incident light used for reading the written image information to obtain red, green and blue read light and introducing the red, green and blue read light to said first, second and third light-to-light conversion elements, respectively, and for receiving and transmitting light reflected by said photo-modulation layers of said first, second and third light-to-light conversion elements.

7. The image displaying apparatus as set forth in claim 6, wherein each of the red, green and blue write light is issued from a corresponding laser light source, and wherein said image information input means comprises:

a first input means for introducing the red write light to said first light-to-light conversion means by deflecting the red write light;

a second input means for introducing the green write light to said first light-to-light conversion means by deflecting the green write light; and

a third input means for introducing the blue write light to said first light-to-light conversion means by deflecting the blue write light.

8. The image displaying apparatus as set forth in claim 6, wherein said color separation means includes:

a first dichroic mirror for separating read light of a predetermined color selected from red, green and blue from the first incident light;

a second dichroic mirror for separating the read light of the other colors of red, green and blue from each other; and

a first semi-transparent mirror for introducing the read light of one of the other colors separated by said second dichroic mirror to a corresponding light-to-light conversion element.

9. The image displaying apparatus as set forth in claim 3, wherein said second separation means includes:

first, second and third semi-transparent mirrors which introduce the red, green and blue composing light to corresponding light-to-light conversion elements, respectively.

10. The image displaying apparatus as set forth in claim 2, wherein said first, second and third light-to-light conversion elements are combined in a single unit.

11. The image displaying apparatus as set forth in claim 10, wherein the reflecting layers of said first, second and third light-to-light conversion elements combined in a single unit are arranged in a one-dimensional arrangement.

12. The image displaying apparatus as set forth in claim 10, wherein the reflecting layers of said first, second and third light-to-light conversion elements combined in a single unit are arranged in two-dimensional arrangement. 13. The light-to-light conversion element according to claim 1, wherein said light reflecting layer is a dielectric mirror having the predetermined selective reflection characteristic.