Radiation clinical thermometer

Abstract

A radiation clinical thermometer includes a probe, a detection signal processing section, a body temperature operating section, and a display unit. A filter correction section for setting a correction value based on the transmission wavelength characteristics of a filter is arranged. The body temperature operating section receives infrared data, temperature-sensitive data, and the correction value from the filter correction section so as to calculate body temperature data.

Description

T_min and T_max are respectively

set to be 273 [K] and 323 [K]. Table 2 shows the calculation results of equation (16).

The values a, b, and c when equation (12) is approximated by using the data shown in Table 2 are obtained by a method of least squares:

a═4.101×10-12 [W/cm².deg⁴ ]

b═45.96[K]

c═-6.144×10⁴ [W/cm² ]

The coefficient a of a term of degree 4 and the symmetrical axis b thus obtained represent the transmission wavelength characteristics of the silicon filter. These values a and b are output from the filter correcting means 5b. The filter correcting means 5b is part of an operating program memory of the operating section 5, in which coefficient a of the term of degree 4 and the symmetrical axis temperature b are written.

TABLE 2
______________________________________
T      f(T) ×    T      f(T) ×
[K]    10-3 [W/cm2 ]
[K]    10-3 [W/cm2 ]
______________________________________
273    10.290          299    16.208
275    10.679          301    16.746
277    11.078          303    17.298
279    11.487          305    17.862
281    11.908          307    18.439
283    12.339          309    19.030
285    12.782          311    19.634
287    13.236          313    20.252
289    13.701          315    20.884
291    14.178          317    21.530
293    14.667          319    22.191
295    15.169          321    22.865
297    15.682          323    23.555
______________________________________

When a silicon filter is used as a window member for measurement of an infrared sensor, the temperature T of an object to be measured is not calculated by equation (5), but is calculated by equation (14), thereby performing temperature calculations with high precision.

As is apparent from the above description, according to this embodiment, even if a transmission member having transmission wavelength characteristics is used as a window member of an infrared sensor, temperature measurement of an object to be measured can be performed with high precision.

In addition, even if the material of the transmission member as a window member of the infrared sensor is changed, temperature measurement can be performed with high precision by updating the value of the filter correcting means 5b as part of the program memory.

In the above embodiment, an approximate expression having a term of degree 4 as represented by equation (12) is used as a new equation replacing the Stefan-Boltzmann law. However, as shown in FIG. 13, in body temperature measurement, only a portion of the temperature measurement curve is used as a measurement range such as the range from T_min ti T_max . Therefore, an approximate expression having a term of degree 4 need not be used. Satisfactory precision of a clinical thermometer can be obtained by using an approximate expression with a proper degree. For example, expression (14) can be employed as an approximate equation having a term of degree 2:

V_d ═εK₂'{(T_b -B')² -(T₀ -b')² }(14')

A detailed arraangement of a radiation clinical thermometer which is actually manufctured by using a commercially available thermopile manufactured in consideration of mass production will be described below as a second embodiment of the present invention.

FIGS. 8 and 9 are bottom and side views, respectively, showing a radiation clinical thermometer according to the second embodiment of the present invention. Reference numberal 1 denotes a radiation clinical; thermometer comprising a main body portion 10 and a head portion 11. The display unit 6 for displaying a body measurement is arranged on the lower surface of the main body portion 10. A check button 12 having a push button structure is formed on the upper surface of the portion 11. A power switch 13 having a slide structure and major buttons 14 and 15 each having a push button structure are respectively formed on the side surfaces of the portion 11.

The head portion 11 extend from the end of the main body portion 10 in the form of an L shape. The end of the head portion 11 constitutes a probe 16. The probe 16 comprises an optical system 2 and a detecting section 3 shown in FIG. 6.

The radiation clinical theremometer 1 is operated as follows. A check operation (to be described later) is performed while the power switch is ON. Thereafter, while the probe 16 is inserted in an external ear canal of a patient to be examined, either or both of the major switches 14 and 15 is/are depressed, thereby instantaneously completing body temperature measurement. The measurement result is displayed on the display unit 6 as a body temperature.

FIG. 10 is a sectional view of the head portion 11. Each of case members 17 and 18 consists of a resin molded member having a very low thermal conductivity. A portion of the case 17 covering the probe 16 constitutes a cylindrical member 17a, in which a metal housing 19 consisting of a lightweight metal having a high thermal conductivity such as aluminum is fitted. The metal housisng 19 is integrally formed and comprises a cylindrical portion 19a and a base portion 19d having a hollow portion 19b communicating with the cylindrical portion 19a and a recess 19c in which a temperature-sensitive element is embedded. In addition, a step portion 19e for attachment of a filter is formed at the distal end of the cylindrical portion 19a. An optical guide 20 consisting of a brass (Bu) pipe having an inner surface plated with gold (Au) is fitted in the cylindrical portion 19a. A filter member in the form of a dust-proof hard cap 21 selectively allowing infrared radiation to pass therethrough is fixed to the step portion 19e. In addition, a thermopile as the infrared sensor 3a and the temperature-sensitive sensor 3b are respectively embedded in the hollow portion 19b and the recess 19c of the base portion 19d by sealing resins 22 and 23. The infrared sensor 3a and the temperature-sensitive sensor 3b are respectively connected to wiring patterns of a circuit board 26 through leads 24 and 25, and are led to amplifying circuits to be described later.

According to the above-described arrangement, since the infrared sensor 3a, the optical guide 20, and the hard cap 21 are connected to each other through the metal housing 19 having a high thermal conductivity, they can always be kept in a thermal equilibrium state. This uniform-temperature is detected by the temperature-sensitive sensor 3b. Reference numeral 28 denotes a temperature measurement cover which is detachably fitted on the probe 16 and is constituted by a resin having a low thermal conductivity. A distal end portion 28a of the cover 28 consists of a material through which infrared radiation can be transmitted.

FIG. 11 is an enlarged sectional view of the distal end portion of the probe 16. The distal end portion 28a of the cover 28 covers the distal end portion of the probe 16 so as to prevent contact of the probe 16 with the inner wall of the external ear canal.

FIG. 12 is a side view showing a state wherein the radiation clinical thermometer 1 is stored in a storage case 30. The storage case 30 comprises a mounting portion 30a for mounting the main body portion 10, and a storage portion 30b for storing the probe 16. A reflecting plate 31 is fixed to a bottom surface 30c of the storage portion 30b at a position corresponding to the distal end portion of the probe 16. In addition, a button depressing portion 30d is formed on the storage case 30 at a position corresponding the check button 12. The storage case 30 is used to perform an operation check of the radiation clinical thermometer 1. When the thermometer 1 is set in the storage case 30 with the power switch 13 being turned on as shown in FIG. 12, the distal end portion of the probe 16 is set on the reflecting plate 31, and at the same time, the check buttom 12 is depressed by the button depressing portion 30d. This state is a function check state to be described later. In this state, a user can know from a display state of the display unit 6 whether body temperature measurement can be performed.

FIG. 13 is a sectional view of an ear, showing a state wherein a body temperature measurement is performed by the radiation clinical thermometer 1. Reference numeral 40 denotes a canal; 41, external ear canal; and 42, a drum membrane. A large number of downy hairs are grown from the inner wall of the external ear canal 41. Earwax is sometimes formed on the inner wall of the external ear canal 41. When the distal end portion of the probe 16 of the radiation clinical thermometer 1 is inserted in the external ear canal 41, and the major buttons 14 and 15 are depressed with the distal end portion directed to the drum membrane 42 as shown in FIG. 13, a body temperature measurement can be instantaneously performed.

FIG. 14 is a block diagram of the radiation clinical thermometer 1 in FIG. 8. The same reference numerals in FIG. 14 denote the same parts as in FIG. 6, and a description thereof will be omitted.

Portions different from FIG. 6 will be described below. Reference numeral 50 denotes a detection signal porocessing section. FIG. 14 shows a detailed arrangement of the section 50 corresponding to the amplifying section 4 shown in FIG. 6. More specifically, the section 50 comprises an infrared amplifying circuit 51 for amplifying an infrared voltage v_s output from the infrared sensor 3a, a temperature-sensitive amplifying circuit 52 for amplifying a temperatuyre-sensitive voltage v_t output from the temperature-sensitive sensor 3b, a peak hold circuit 53 for holding a peak value of an output voltage V_s from the infrared amplifying circuit 51, a switching circuit 54 for receiving the output voltage V_s from the infrared amplifying circuit 51 and an output voltage V_sp from the peak hold circuit 53 at input terminals I₁ and I₂, respectively, and selectively outputting them from an output terminal O in accodance with conditions provided from a control terminal C, an A/D converter 55 for converting the infrared voltages V_s or V_sp output from the switching circuit 54 into digital infrared date V_d, and an A/D converter 55 for converting the output voltage V_t from the temperature-sensitive amplifying circuit 52 into digital temperature-sensitive data T₀. With this arrangement, the section 50 converts the infrared voltage v_s and the temperature-sensitive voltage v_t supplied from the detecting section 3 into the digital infrared data V_d and temperature-sensitive data T₀, and outputs them.

An operating section 60 corresponds to the operating section 5 shown in FIG. 6, and comprises an emissivity input means 5a, a filter correcting means 5b, a body temperature operating circuit 61 corresponding to the operating circuit 5c, a display driver 62 for receiving a body temperature data T_b1 calculated by the operation circuit 61 and displaying it on a body temperature display portion 6a of a display unit 6, a zero detector 63 for receiving the infrared data V_d output from the detection signal processing section 50 and outputting a detection signal S₀ when the infrared data V_d is detected to be zero so as to illuminate a measurement permission mark 6b of the display unit 6, a sensitivity correcting calculator 64 for receiving the temperature-sensitive data T₀ output from the section 50, calculating a sensitivity R in accordance with equation (8) shown in FIG. 5, and outputting it, and a sensitivity data input means 65 for outputting as sensitivity data D a value which is externally input/set on the basis of the light-receiving area S of the infrared sensor 3a and the gain A of the infrared amplifying circuit 51 shown in equation (6).

Reference numeral 90 denotes a switch circuit to which a major switch SW_m operated by the major switches 14 and 15 shown in FIG. 8 and a check switch SW_c operated by the check button 12 are connected. When either of the major buttons 14 and 15 is depressed, the major switch SW_m is turned on, and a major signal S_m is output from a terminal M.

When the radiation clinical thermometer 1 is set in the storage case 30 as shown in FIG. 12, the check button 12 is depressed, and the check switch SW_e is turned on. As a result, a check signal S_c is output from a terminal C.

The major signal S_m output from the terminal M of the switch circuit 90 is supplied to enable terminals E of the body termperature operating circuit 61 and the sensitivity correcting calculator 64. As a result, both the circuit 61 and the calculator 64 are set in an operative mode, and at the same time, the zero detector 63 is reset. The check signal S_c output from the terminal C of the switch circuit 90 is supplied to an enable terminal E of the zero detector 63, the control terminal C of the switching circuit 54, and a reset terminal R of the peak hold circuit 53.

An operation of the radiation clinical thermometer 1 having the above-described arrangement will be described below.

In an initial state wherein the power switch 13 of the radiation clinical thermometer 1 shown in FIG. 8 is turned on, since both the check switch SW_c and the major switch SW_m are kept off, the check signal S_c and the major signal S_m are not output from the switch circuit 70.

Consequently, in the operation section 60, the body temperature operating circuit 61 and the sensitivity correcting calculator 64 are set in a non-calculation mode, and the zero detector 63 is set in an inoperative mode. In addition, the switching circuit 54 of the detection signal processing section 50 selectively outputs the voltage V_sp input to the terminal I₂ to the output terminal O. The reset state of the peak hold circuit 53 is released and is set in an operative state.

The initial state is established in this manner. A function check mode will be described next.

When the thermometer 1 is set in the storage case 30 as shown in FIG. 12, the check button 12 is urged against the button depressing portion 30d of the storage case 50. As a result, the check switch SW_c shown in FIG. 14 is turned on, and at the same time, the distal end portion of the probe 16 is set at the position of the reflecting plate 31.

Consequently, the switch circuit 90 outputs the check signal S_c from terminal C when the check switch SW_c is turned on, and supplies it to the peak hold circuit 53, the switching circuit 54, and the zero detector 63. Upon reception of the check signal S_c, in the detection signal processing section 50, the peak hold circuit 53 is reset, and at the same time, the switching circuit 54 is switched to a state wherein the voltage V_s supplied to the input terminal I₁ is selectively output to the output terminal O. Subsequently, the A/D converter 55 converts the infrared voltage V_s into a digital value and outputs it as the infrared data V_d. In the operation section 60, the body temperature operating circuit 61 and the sensitivity correcting calculator 64 are set in an inoperative mode, and only the zero detector 63 is set in an operative state. The state of each portion in the function check mode has been described so far. The radiation clinical thermometer 1 in this function check mode is operated as follows. The infrared data V_d obtained by converting infrared radiation reflected by the reflecting plate 31 into a digital value by using the infrared sensor 3a, the infrared amplifying circuit 51, the switching circuit 54, and the A/D converter 55 is determined by the zero detector 63. If this infrared data V_d is zero, the zero detector 63 outputs the detection signal S₀ from the output terminal O so as to illuminate the measurement permission mark 6b of the display unit 6.

The contents of the function check mode will be described below.

Referring to FIG. 10, as described above, since the infrared sensor 3a, the optical guide 20, and the hard cap 21 are connected to each other through the metal housing 19 having a high thermal conductivity, thermal equilibrium of these components can be obtained. The above-described function check mode is a mode for confirming that the thermal equilibrium is satisfactorily obtained. More specifically, infrared radiation energies emitted from the optical guide 20 and the hard cap 21 each having the temperature T are reflected by the reflecting plate 31, and are incident on the infrared sensor 3a. In addition infrared radiation energy is emitted from the infrared sensor 3a having the temperature T₀. The energy W obtained by subtracting the emitted energy from the incident energy is given by equation (5) as described above:

W═εσ(T₄ -T₀⁴)

If T═T₀, the energy W is not present. Hence, all the voltages v_s and V_s, and the infrared data V_d are set to zero, and the detection signal S₀ is output from the zero detector 63. That is, the measurement ready permission mark 6b is illuminated to confirm that the heat source causing noise is present near the optical system 2, and hence body temperature measurement can be performed. Note that the zero detector 63 determines the infrared data V_d as a digital value. A determination value need not be strictly zero. The zero detector 63 outputs the detection signal S₀ if the infrared date V_d is smaller than a predetermined determination value. In this case, even if the determined value is not zero, it is regraded as negligible. If T≠T₀ according to equation 5, i.e., if there is a temperature difference among the infrared sensor 3a, the optical guide 20, and the hard cap 21, the differential energy W is present. Therefore, the infrared data V_d becomes larger than the determination level of the zero detector 63. As a result, the detection signal S₀ is not output, and the measurement permission mark 6b is not illuminated.

In actual use of the radiation clinical thermometer 1, the state of T≠T₀ occurs as follows.

When the environmental temperature in use of the radiation clinical thermometer 1 is abruptly changed, the above state occurs. In this case, T≠T₀ occurs due to differences in heat capacity and response characteristics of the respective elements. Since a measurement error corresponding to the value of the infrared data V_d based on the differential energy W occurs, the thermometer 1 is set in a measurement disable state. In this state, if the thermometer 1 is left in a constant environmental temperature for a while, the respective elements are stabilized in a thermal equilibrium state upon thermal conduction through the metal housing 19, and the thermometer 1 is set in a measurement permission state. However, it may takes several tens of minutes to established such a stable state.

The function check mode has been described so far. A body temperature measurement mode will be described next.

The radiation clinical thermometer 1 is detached from the storage case 30 after illumination of the measurement permission mark 6b is confirmed in the above-described function check mode. When the thermometer 1 is detached from the case, depression of the check button 12 is released, so that the check switch SW_c is turned off, and output of the check signal S_c from the terminal C of the switch circuit 90 is stopped. As a result, the reset state of the peak hold circuit 53 is released. At the same time, the switching circuit 54 is returned to the selection state for the input terminal I₂, and the zero detector 63 is returned to the inoperative state.

Consequently, in the detection signal processing circuit 50, the peak voltage V_sp of the infrared voltage V_s output from the infrared amplifying section 51, which is held by the peak hold circuit 53, is supplied to the A/D converter 55 through the switching circuit 54, thereby outputting the digital infrared data V_d converted from the peak voltage V_sp.

Although the zero detector 63 of the operating section 60 is returned to the inoperative state, the measurement permission mark 6b of the display unit 6 is kept illuminated because the detection signal S₀ is held by a storage circuit arranged in the zero detector 63. Since the major signal S_m is supplied to the reset terminal R, the detection signal S₀ if the zero detector 63 is maintained until the storage circuit is reset.

In this manner, the apparatus is prepared for measurement. When the major buttons 14 and 15 are depressed after the radiation clinical thermometer 1 is inserted in the external ear canal 41 in this state as shown in FIG. 13, a body temperature measurement is performed. More specifically, when the major buttons 14 and 15 are depressed, the major switch SW_m shown in FIG. 14 is turned on, and the major signal S_m is output from the terminal M of the switch circuit 90. As a result, in the operation section 60, the body temperature operating circuit 61 and the sensitivity correcting calculator 64 are set in an operative mode, and at the same time, the zero detector 63 is reset to turn off the measurement permission mark 66 of the display unit 6. Infrared radiation energy which is emitted from the drum membrane 42 and is incident on the the probe 16 (the optical system 2 and the detection section 3 in FIG. 14) inserted in the external ear canal 41 is converted into the infrared voltage v_s by the infrared sensor 3a, and is amplified to the voltage V_s by the infrared amplifying circuit 51. Thereafter, the peak voltage V_sp is held by the peak hold circuit 53. The peak voltage V_sp is converted into the infrared data V_d by the A/D converter 55, and is supplied to the operating section 60. In addition, the temperature-sensitive sensor 36 embedded in the metal housing 19 detects the temperature of the infrared sensor 3a and converts it into the temperature-sensitive voltage v_t. The voltage is converted into the temperature-sensitive data T₀ by the A/D converter 56, and is then supplied to the operation section 60.

When the infrared data V_d and the temperature-sensitive data T₀ are supplied to the operation section 60, the sensitivity correcting calculator 64 calculates the sensitivity R by using the data T₀ on the basis of equation (8). Note that the coefficient of variation β is set to be -0.03. The body temperature operating circuit 61 then receives the sensitivity R calculated by the calculator 64, the sensitivity data D from the sensitivity data input means, and the coefficient a of a term of degree 4 from the filter correcting means 5b, and calculates a sensitivity coefficient K₃ of this system as K₃ ═aRD.

Upon reception of the calculated sensitivity coefficient K₃, the emissivity ε from the emissivity input means 5a, and the symmetrical axis temperature b from the filter correcting means 5b, the body temperature operating circuit 61 performs a calculation based on equation (17):

V_d ═εK₃ {(T_b1 -b)⁴ -(T₀-b)⁴ }(17)

Equation (17) is further rewritten to equation (18) so as to calculate the body temperature data T_b1. Since the external ear canal has a uniform temperature, and the canal is regarded as a blackbody, the emissivity ε is set set as ε═1. ##EQU11## for b═45.95[K±]. Thus, the body temperature data T_b1 is displayed on a digit display portion 6a of the display unit 6 through the display driver 62.

One body temperature measurement is performed in this manner. A procedure of this operation will be described with reference to the flow chart of FIG. 15.

When the probe 16 is inserted in the external ear canal 41 (step 1), infrared radiation energy from the drum membrane 42 is converted into the infrared voltage V_s, and its peak voltage V_sp is held by the peak hold circuit 53 (step 2). The presence/absence of the major signal S_m is then determined (step 3). If the major buttons 14 and 15 are not depressed, NO is obtained in this step, and only the peak value holding operation in step 2 is performed.

If the major buttons 14 and 15 are depressed, YES is obtaianed in step 3. As a result, the zero detector 63 is reset by the major signal S_m (step 4). At the same time the sensitivity correcting calculator 64 reads the temperature-sensitive data T₀ (step 5) and calculates the sensitivity R (step 6).

The body temperature operating circuit 61 reads the emissivity ε, the coefficient a, the sensitivity R, and the sensitivity data D (step 7), and calculates the sensitivity coefficient K₃ by using the values a, R, and D (step 8). In addition, the operating circuit 61 reads the symmetrical axis temperature b and at the peak-held infrared data V_d (step 9) and calculates the body temperature data step T_b1 (step ○ 10 ). The display driver 62 receives the body temperature data T_b1 and displays the body temperature on the display unit 6 (step ○ 11 ), thereby completing the body temperature measurement.

The function of the peak hold circuit 53 shown in FIG. 14 will be described below with reference to FIG. 16.

FIG. 16 shows a temperature measurement curve of the radiation clinical thermometer 1 of the present invention, which corresponds to the temperature measurement curve of the conventional electronic clinical thermometer shown in FIG. 1.

Temperature measurement time is plotted along the abscissa axis, and measurement temperatures are plotted along the ordinate axis. The external ear canal 41 is a portion to be measured. A temperature curve H_s of the external ear canal 41 coincides with a measurement temperature curve M_s of the radiation clinical thermometer 1. As describe above, the downy hairs 43 and the earwax 44 are present in the external ear canal 41, as shown in FIG. 13. Similar to the drum membrane 42, the downy hairs 43 and the earwax 44 are warmed to a temperature very close to a body temperature prior to the start of temperature measurement. This state is indicated at time T₁ in FIG. 16. More specifically, time t₁ is the instant when the probe 16 is inserted in the external ear canal 41. Since the temperature in the external ear canal 41 at this instant is substantially equal to the body temperature T_b1, infrared radiation energy having a body temperature level is incident on the infrared sensor 3a, and is stored in the peak hold circuit 53 as the peak voltage V_sp. However, the temperature in the external ear canal 41 is cooled by the probe 16 and quickly drops immediately after the probe 16 is inserted, as indicated by the temperature curve H_s. With this temperature drop, the infrared voltage V_s detected by the infrared sensor 3a drops to the level of the temperature measurement curve M_s, and hence cannot exceed the peak voltage V_sp. For this reason, the peak voltage V_sp at time t₁ is stored in the peak hold circuit 53. It takes about 10 minutes for the lowered temperature represented by the curve H_s to return to the origianl body temperature T_b1. The reason will be described below with reference to FIG. 13.

When the probe 16 is inserted in the external ear canal 41, all the temperatures of the drum membrane 42, each downy hair 43, and the earwax 44 are decreased. Of these portions the temperature of the drum membrane 42 can return to the level of the body temperature T_b1 relatively quickly because of the themal conduction from the body. However, since the thermal conduction from the body to each downy hair 43 and the earwax 44 having low degree of adhesion to the body is less, about 10 minutes are required for their temperatures to return to the level of the body temperature T_b1. Therefore, the temperature in the external ear canal 41 is set at the level of the body temperature T_b1 only at time T₁, i.e., the instant when the probe 16 is inserted. Since the series of operation processing of the radiation clinical thermometer 1 cannot be performed by using the infrared radiation energy in such a short period of time, the peak voltage V_sp appearing at the instant is stored in the peak hold circuit 53 as analog data, as indicated by a dotted line in FIG. 16. The A/D conversion and the series of operating processing are performed by using this stored peak voltage V_sp, thereby performing the body temperature measurement.

Thus, in a radiation clinical thermometer without a preheating unit as in the present invention, the peak hold circuit 53 is indispensable. By using the peak hold circuit 53, the body temperature T_b1 at time T₁ can be measured within a very short period of time.

FIG. 17 a detailed arrangement of the peak hold circuit 53. The peak hold circuit 53 comprises an input buffer 80, an output buffer 81, a diode 82 for preventing a reverse current flow, a signal charging capacitor 83, and a switching transistor 84 for casuing the capacitor 83 to discharge a charged voltage. The peak hold circuit 53 receives the infrared voltage V_s and outputs its peak value as the peak voltage V_sp. In addition, when the switching transistor 84 is turned on by the check signal S_c supplied to the reset terminal R, the circuit 53 causes the capacitor 83 to discharge a charged voltage.

FIG. 18 is a sectional view of a head portion 110 according to a third embodiment of the present invention. The same reference numerals in FIG. 18 denote the same parts as in FIG. 10, and a description thereof will be omitted.

The head portion in FIG. 18 differs from that in FIG. 10 in that a through hole 19f is formed in a cylindrical portion 19a of a metal housing 19 so as to expose an optical guide 20, and a temperature-sensitive sensor 3c is fixed to the exposed portion of the optical guide 20. This temperature-sensitive sensor 3c is identical to the temperature-sensitive sensor 3b, and is also fixed by a molding resin.

The third embodiment differs from the second embodiment in a system for correcting thermal equilibrium in a probe 16. The second embodiment employs the system of permitting measurement upon confirmation of thermal equilbrium by the function check mode. In this system, measurement is inhibited while thermal equilibrium is not established. In contrast to this, the third embodiment comprises the two temperature-sensitive sensors 3b and 3c to detect a temperture difference between an infrared sensor 3a and the optical guide 20. In this system, if this temperature difference is excessively large, measurement is inhibited. If it is smaller than a predetermined value, body temperature measurement is permitted even though thermal equilibrium is not established. In this case, body temperature data is calculated by adding a correction value based on the temperature difference to the measurement value, thus widening the range of measurement conditions of the radiation clinical thermometer.

The circuit arrangement and operation of the radiation clinical thermometer of the third embodiment will be described below with reference to FIG. 19. The same reference numerals in FIG. 19 denote the same parts as in FIG. 14, and a description thereof will be omitted.

As shown in FIG. 18, a detecting section 3 comprises a temperature-sensitive sensor 3c for measuring a temperature T_p of the optical guide 20. In the detection signal processing section 50, the switching circuit 54 is omitted, and an output voltage V_sp from a peak hold circuit 53 is directly supplied to an A/C converter 55. A temperature-sensitive amplifying circuit 57 and an A/D converter 58 are additionally arranged in the section 50 so as to output the temperature sensitive data T_p.

In an operating section 60, an emissivity ε_p of the optical guide 20 is set in an emissivity input means 5a, and a temperature difference detector 67 is arranged in place of the zero detector 67 shown in FIG. 1. The temperature difference detector 67 receives temperature data T₀ of the infrared sensor 3a detected by the two temperature-sensitive sensors 3b and 3c and the temperature data T_p of the optical guide 20, and performs temperature difference determination with respect to a predetermined measurement limit temperature difference T_d. If |T₀ -T_p |<T_d, i.e., the temperature difference is smaller than the limit temperature difference, the detector 67 outputs a detection signal S₀ so as to illuminate a measurement permission mark 6b of a display unit 6. This temperature difference determination is continued while the power switch 13 shown in FIG. 9 is turned on. Therefore, the operation of the check button 12 as in the second embodiment is not required.

When the measurement permission mark 66 is illuminated, a body temperature measurement mode is set in the same manner as in the second embodiment. However, the difference is that the temperature-sensitive data T_p of the optical guide 20 is supplied to a body temperature operating circuit 61 in addition to the respective data described with reference to FIG. 14. In this embodiment, the circuit 61 calculates body temperature data T_b2 in accordance with the following equation (19): ##EQU12## where b═45.95[K] and ε_p ═0.05. This body temperature data T_b2 is obtained by correcting the temperature difference by the arithmetic operations described above, and is displayed on a body temperature display portion 6a of the display unit 6. Furthermore, in this embodiment, a check signal S_c output from a switch circuit 90 resets only the peak hold circuit 53. Therefore, when re-measurement of a body temperature is to be performed, the peak hold circuit 53 must be reset first by operating the check button after illumination of the measurement permission mark 6b is confirmed.

As described above, according to this embodiment, since body temperature measurement can be performed without waiting for perfect thermal equilibrium of the respective elements of the probe 16, intervals of repetitive measurements can be reduced. In addition, since the function check using infrared radiation is not required, a switching circuit and a storage case are not required so that the arrangement can be simplified.

In this embodiment, as an optimal embodiment, the arrangement wherein the second temperature-sensitive sensor 3c is attached to the optical guide 20 is shown. However, the present invention is not limited to this. More specifically, the second temperature-sensitive sensor 3c is designed to detect the surface temperature of the optical guide 20 which responds to an ambient temperature more sensitively than the portion in which the temperature-sensitive sensor 3b is embedded. In consideration of the fact that the surface temperature of the optical guide 20 is substantially equal to the ambient temperature, the temperature-sensitive sensor 3c may be mounted on a circuit board on which a measurement IC chip is mounted as shown in FIG. 20 so as to measure an ambient temperature, so that the measured ambient temperature is used as the surface temperature of the optical guide 20. This arrangement can also be satisfactorily used in practice.

As has been described above, according to the present invention, a filter correction value and a sensitivity correction value are supplied to a body temperature operating circuit to calculate body temperature data, so that high measurement precision can be realized without using a heating unit as in the conventional thermometer, thus realizing a compact, low-cost radiation clinical thermometer which can be driven by a small battery and which can shorten a measurement time.

In addition, by employing a peak hold circuit for analog data in the radiation clinical thermometer, instantaneous measurement can be performed, thus preventing a measurement disable state due to a temperature drop of a portion to be measured upon insertion of a probe.

Moreover, by employing a temperature difference correcting system using two temperature-sensitive sensors, re-measurement intervals can be shortened, and the problem of thermal equilibrium of a probe, which narrows the range of measurement conditions of the radiation clinical thermometer, can be solved. Therefore, the present invention is very effective to widely use a radiation clinical thermometer as a home thermometer, which has been used exclusively for a medical instrument.

Claims

1. A radiation clinical thermometer comprising:

a probe including an optical system constituted by focusing means for focusing infrared radiation from an object to be measured and a filter having transmission wavelength characteristics, an infrared sensor for converting infrared radiation energy into an electrical signal, and a temperature-sensitive sensor for measuring a temperature of said infrared sensor and an ambient temperature thereof;

detection signal processing means for receiving electrical signals from said infrared sensor and said temperature-sensitive sensor and outputting the electrical signals as digital infrared data and temperature-sensitive data, respectively;

body temperature operating means for calculating body temperature data; and

a display unit for displaying a body temperature in accordance with the body temperature data, including filter correcting means for setting a correction value based on the transmission wavelength characteristics of said filter, wherein said body temperature operating means receives the infrared data, the temperature-sensitive data, and the correction value from said filter correcting means so as to calculate body temperature data.

2. A thermometer according to claim 1, further comprising sensitivity correction calculating means for receiving the temperature-sensitive data and calculating sensitivity data of said infrared sensor, and wherein said body temperature operating means calculates the body temperature data by receiving the infrared data, the temperature-sensitive data, the correction value from said filter correcting means, and the sensitivity data from said sensitivity correction calculating means.

3. A thermometer according to claim 2, wherein said sensitivity correction calculating means calculates sensitivity data R according to the following equation:

R═a{1+β (T₀ -T_m)}

where T₀ is sensitivity data of said temperature-sensitive sensor, T_m is a temperature at the time of sensitivity adjustment, α is a sensitivity at the temperature T_m, and β is a coefficient of variation of sensitivity.

4. A thermometer according to claim 1, wherein said filter correcting means outputs a symmetrical axis, temperature correction value which is used to change a symmetrical axis temperature of a temperature-radiation energy characteristic curve represented by a temperature equation of a higher degree approximated to a temperature-radiation eneregy characteristic curve based on a Stefan-Boltzmann law.

5. A thermometer according to claim 1, wherein said probe comprises an optical guide for focusing infrared radiation energy, a filter member arranged at one end of said optical guide, an infrared sensor arranged at the other end of said optical guide, and a said temperature-sensitive sensor arranged near said infrared sensor, said optical guide, said filter member, said infrared sensor, and said temperature-sensitive sensor being coupled to each other by a metal housing having a high thermal conductivity.

6. A thermometer according to claim 5, wherein said metal housing is an integrally formed housing comprising a cylindrical portion in which said optical guide is inserted and a base portion formed at one end of said cylindrical portion and having a storage recess for housing said infrared sensor and said temperature-sensitive sensor, said optical guide being inserted and fixed in said cylindricl portion, said infrared sensor and said temperature-sensitive sensor being embedded in said storage recess of said base portion with a molding sealing resin.

7. A thermometer according to claim 5, further comprising a second temperature-sensitive sensor for detecting a surface temperature of said optical guide.

8. A thermometer according to claim 7, further comprising said second temperature-sensitive sensor arranged on a surface of said optical guide in tight contact therewith.

9. A thermometer according to claim 7, wherein said detection signal processing section comprises an A/D converter for converting an electrical signal from said second temperature-sensitive sensor into second digital temperature-sensitive data, and said body temperature operating means calculates the body temperature data by using the second temperature-sensitive data as one of input signals.

10. A thermometer according to claim 9, further comprising a temperature difference detector for receiving the temperature-sensitive data from said temperature-sensitive sensor arranged at said base protion of said probe and the second temperature-sensitive data from said second temperature-sensitive sensor, and wherein said temperature difference detector outputs a detection signal when a temperature difference is determined to be smaller than a predetermined measurement limit temperature difference.

11. A thermometer according to claim 10, wherein said display unit comprises a measurement permission mark adapted to be illuminated by the detection signal output from said temperature difference detector.

12. A radiation clinical thermometer comprising:

a probe including an optical means for focusing infrared radiation from an object to be measured, an infrared sensor for converting infrared radiation energy into an electrical signal, and a temperature-sensitive sensor for measuring a temperature of said infrared sensor and an ambient temperature thereof;

detection signal processing means for receiving electrical signals from said infrared sensor and said temperature-sensitive sensor and outputting the electrical signals as digital infrared data and temperature-sensitive data, respectively;

body temperature operating means for calculating body temperature data, and

a display unit for displaying a body temperature in accordance with the body temperature data, characterized by

a zero detector for receiving the infrared data output from said detection signal processing means and determining presence/absence of the infrared data, wherein said zero detector outputs a detection signal when the infrared data is determined to be zero or a small value.

13. A thermometer according to claim 12, further comprising a storage case for storing said radiation clinical thermometer and a reflecting plate arranged in said storage case at a position corresponding to a probe end of said radiation clinical thermometer stored in said storage case.

14. A thermometer according to claim 13, wherein said display unit comprises a measurement permission mark adapted to be illuminated by the detection signal output from said zero detector.

15. A radiation clinical theremometer comprising:

a probe including an optical means for focusing infrared radiation from an object to be measured, an infrared sensor for converting infrared radiation energy into an electrical signal, and a temperature-sensitive sensor for measuring a temperature of said infrared sensor and an ambient temperature thereof;

detection signal processing means for receiving electrical signals from said infrared sensor and said temperature-sensitive sensor and outputting the electrical signals as digital infrared data and temperature-sensitive data, respectively;

body temperature operating means for calculating body temperature data; and

a display unit for displaying a body temperature in accordance with the body temperature data, wherein said detection signal processing means includes a peak holding circuit for holding a peak value of the electrical signal from said infrared sensor as analog data and an A/D converter for converting a peak value voltage held in said peak holding circuit into digital infrared data, and said body temperature operating means calculates the body temperature data by using the infrared data converted from the peak value voltage; and

wherein said probe l including includes a filter having transmission wavelength characteristics and wherein said display unit includes filter correcting means for setting a correction value based on the transmission wavelength characteristics of said filter, wherein said body temperature operating means receives the infrared data, the temperature-sensitive data, and the correction value from said filter correcting means so as to calculate body temperature data.

16. A thermometer according to claim 15 wherein said filter correcting means outputs a symmetrical axis temperature correction value which is used to change a symmetrical access temperature of a temperature-radiation energy characteristic curve represented by a temperature equation of a higher degree approximated to a temperature-radiation energy characteristic curve based on Stefan-Boltzmann law.

17. A thermometer according to claim 15 wherein said probe includes a filter having transmission wavelength characteristics and wherein said display unit includes filter correcting means for setting a correction value based on the transmission wavelength characteristics of said filter and further comprising sensitivity correction calculating means for receiving the temperature-sensitive data and calculating sensitive data of said infra-red sensor and wherein said body temperature operating means calculates the body temperature data by receiving the infra-red data, the temperature-sensitive data, the correction value from said filter correcting means, and the sensitivity data from said sensitivity correction calculating means.

18. A thermometer according to claim 17, wherein said sensitivity correction calculating means calculates sensitivity data R according to the following equation:

R═a{1+β (T₀ -T_m)}

where T₀ is sensitivity data of said temperature-sensitive sensor, T_m is the temperature at the time of sensitivity adjustment, α is a sensitivity at the temperature T_m, and β is a coefficient of variation of sensitivity.

19. A thermometer according to claim 15, wherein said optical means comprises an optical guide, a filter member arranged at one end of said optical guide, said infrared sensor arranged at the other end of said optical guide, and said a temperature-sensitive sensor arranged near said infrared sensor, said optical guide, said filter member, said infrared sensor, and said temperature-sensitive sensor being coupled to each other by a metal housing having a high thermal conductivity.

20. A thermometer according to claim 19, wherein said metal housing is an integrally formed housing comprising a cylindrical portion in which said optical guide is inserted and a base portion formed at one end of said cylindrical portion and having a storage recess for housing said infrared sensor and said temperature-sensitive sensor, said optical guide being inserted and fixed in said cylindrical portion, said infrared sensor and said temperature-sensitive sensor being embedded in said storage recess of said base portion with a molding sealing resin.

21. A thermometer according to claim 15, wherein said display unit includes a zero detector for receiving the infrared data output from said detection signal processing means and determining presence/absence of the infrared data, wherein said zero detector outputs a detection signal when the infrared data is determined to a zero of a small value.

22. A thermometer according to claim 15, further comprising a storage case for storing said radiation clinical thermometer and a reflecting plate arranged in said storage case at a position corresponding to a probe end of said radiation clinical thermometer stored in said storage case.

23. A thermometer according to claim 22, wherein said display unit comprises a zero detector and a measurement permission mark adapted to be illuminated by detection signal output from said zero detector.