JPH0678940B2 - Infrared optics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an infrared optical device that splits the power of incident infrared rays and detects the split powers with different detectors.

[Conventional technology]

Fig. 4 is a conventional example shown in "Outline of Visible Thermal Infrared Radiometer (VTIR) for Ocean Observation Satellite 1 (MOS-1)", IEICE Technical Report, SANE86-29, pp17-24. 3 is a cross-sectional view showing the infrared optical device of FIG. In the figure, 1 is an incident infrared ray, 2 is a telescopic optical system, 3 is a scanning mirror for changing the direction of the incident infrared ray 1 incident on the telescopic optical system 2, 4 is a driving device for rotating the scanning mirror, and 5 is a driving device. A semi-transparent mirror that is installed so as to be inclined with respect to the optical path in order to split the incident infrared light emitted from the telescopic optical system 2 into two optical paths, and 6 is a first part for detecting a reflection component of the incident infrared light reflected by the semi-transparent mirror 5. 1
Is a second detector for detecting the transmitted component of the incident infrared ray 1 transmitted through the semi-transparent mirror 5, and 8 is an incident infrared ray incident on the first detector 6 and the second detector 7. A filter for limiting the wavelength range, 9 is an imaging optical system for condensing the incident infrared ray 1 emitted from the filter 8 on the first detector 6 and the second detector 7, and 10 is the first detector 6 And 11 is a diaphragm for limiting the field of view of the second detector 7, and 11 is a part of the housing which the first detector 6 and the second detector 7 see by the transmission and reflection of the semi-transparent mirror 5, respectively.

The semi-transparent mirror 5 is an optical component that reflects a part of the incident light amount and transmits the other part, and is made by, for example, depositing a metal thin film or a dielectric multilayer film on a substrate that transmits the incident infrared ray 1. The diaphragm 10 has an opening for taking the incident infrared ray 1 into the detector, and is a metal cover having a blackened surface. As a detector, for example, when using a high-sensitivity quantum detector used by cooling to liquid nitrogen temperature, the aperture 10 is used to prevent infrared rays emitted from the aperture 10 itself from entering the detector and increasing shot noise. Is cooled to a low temperature like the detector, and its infrared radiation amount is suppressed. Therefore, this diaphragm 10 is called a cold shield.

In the figure, 12 is the first detector 6 and the second detector 7.
Is an infrared radiator for calibrating the output of, and is composed of an object whose emissivity in the detection wavelength range of at least the two detectors 6 and 7 is extremely close to 1. As such an object, for example, a special paint has been developed and put on the market. The infrared radiator 12 does not completely satisfy the condition of a black body that the emissivity is 1 for all wavelengths, but it is usually called a black body for convenience. Reference numeral 14 is a metal substrate having good thermal conductivity, and the infrared radiator 12 is formed on the surface thereof. Reference numeral 13 is a temperature setting device for setting the temperature of the infrared radiator 12, 15 is a Peltier element attached to the back surface of the metal substrate 14, and 16 is an adjuster for adjusting the current input to the Peltier element 15. The operation of the temperature setting device 13 will be described below. A thermocouple, for example, is attached to the metal substrate 14 as a means for detecting its temperature. The output of the thermocouple is input to the regulator 16 and compared with the voltage corresponding to the preset temperature. As a result, when it is determined that the temperature of the metal substrate 14 is lower than the set temperature, a current is passed from the regulator 16 to the Peltier element 15, and the metal substrate 14 is heated.
On the contrary, when the temperature of the metal substrate 14 is higher than the installed temperature, a current is passed from the regulator 16 to the Peltier element 15 in the opposite direction to the above, and the metal substrate 14 is cooled. By the above operation, the temperature of the metal substrate 14 is set constant, and therefore the temperature of the infrared radiator 12 formed on the surface thereof is also set constant. Since the emissivity of the infrared radiator 12 in the detection wavelength region is extremely close to 1, the amount of infrared radiation emitted from the infrared radiator 12 in the detection wavelength region is a function of temperature only, which is close to Planck's radiation law. Since the temperature of the infrared radiator 12 is set constant as described above, the infrared radiation amount is kept constant.

Next, the operation of the conventional device will be described.

The conventional infrared optical device is configured as described above, and the incident infrared ray 1 is split into two by the semitransparent mirror 5 after passing through the scanning mirror 3 and the telescopic optical system 2. The wavelength range of each of the two divided incident infrared rays 1 is limited by a filter 8, and the infrared rays are focused on detectors 6 and 7 by an imaging optical system 9 and detected. By rotating the scanning mirror 3 by the driving device 4, the arrival direction of the incident infrared rays 1 incident on the detectors 6 and 7 is changed, and a predetermined wide field of view can be scanned. Although not shown, the outputs of the detectors 6 and 7 are AC amplified and become video signals. Since the video signal is amplified here, it has only information about the spatial variation of the infrared radiation amount of the measuring object. Therefore, in order to obtain the absolute infrared radiation amount, it is necessary to calibrate the video signal with reference to a light source having a known infrared radiation amount. The infrared radiator 12 is used as the reference light source, and the infrared radiation emitted from the infrared radiator 12 enters the detectors 6 and 7 every time the scanning mirror 3 makes one rotation.

The first detector 6 is transmitted through the semi-transparent mirror 5 and a part of the housing
Looking at 11. Similarly, the second detector 7 looks at the part 11 of the housing by the reflection of the semi-transparent mirror 5. Therefore part of the housing 11
The infrared rays emitted from the detector always enter detectors 6 and 7. However, if the amount of infrared light emitted from the part 11 of the housing is constant, or if its fluctuating frequency is outside the frequency band of the amplifier for AC amplification, the infrared light is converted into the signal component of the video signal. The influence exerted is suppressed by the frequency characteristic of the amplifier.

[Problems to be solved by the invention]

The conventional infrared optical device is configured as described above,
Infrared rays emitted from a part of the housing are incident on the detector, so when the temperature of the housing rises due to sunlight irradiation or heat generation of the drive device, the amount of infrared light incident on the detector increases There was a problem that instrument noise increased and measurement accuracy deteriorated.

In addition, if a part of the housing has a certain degree of reflectance, the detector sees the other part of the housing due to the reflection of a part of the housing. If there is a device that generates stray light with varying light quantity within the frequency band of the amplifier, such as a scanning mirror or a mechanical chopper for interrupting the incident infrared light, these stray light are detected by the detector and the fluctuation component of the stray light is converted into a video signal. There is a problem that the detection accuracy of the incident infrared rays is deteriorated due to the overlapping.

In addition, for example, when a solid-state image sensor that accumulates the charge generated by the detector due to the incidence of infrared rays for a certain period of time and reads it out with a CCD (charge-coupled device) is used as a detector, the solid-state image sensor has a charge corresponding to the absolute amount of incident infrared rays. In order to output, the video signal includes a component due to infrared rays emitted from a part of the housing. Therefore, if the amount of infrared light emitted from a part of the housing changes faster than the calibration period by the reference light source, sufficient calibration cannot be performed, and the detection accuracy of incident infrared light deteriorates. Furthermore, if the temperature of the case rises and the amount of infrared light emitted from a part of the case increases, the dynamic range of the detector output decreases, or the detector output saturates, and the detection accuracy of the incident infrared light is reduced. There was a problem of getting worse.

The present invention has been made to solve such a problem, and an object thereof is to obtain an infrared optical device capable of detecting incident infrared rays with high accuracy even when the temperature inside the housing changes.

[Means for solving problems]

The infrared optical device according to the present invention is constructed such that a detector looking at the inside of the housing by reflection or transmission of the semi-transparent mirror is covered with an infrared radiator having a high emissivity and a constant temperature.

[Action]

In the present invention, since the infrared radiation emitted from the infrared radiator whose infrared radiation amount is controlled to be constant enters the detector, the temperature inside the housing can be reduced by setting the infrared radiation amount of the infrared radiator small in advance. Even if it increases, it is possible to suppress the increase of detector shot noise, the fluctuation of video signal output, the saturation of detector output, etc.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an infrared optical device according to an embodiment of the present invention. In the drawing, 1,5,6,7,9,10,12 to 16 are the same as the above conventional device. Reference numeral 17 is a field of view through which the first detector 6 transmits the semi-transparent mirror 5 and the second detector 7 reflects the semi-transparent mirror 5 to see the inside of the housing. The infrared radiator 12 is installed so as to cover the visual field 17. Reference numeral 18 denotes an optical section, which has a semi-transparent mirror 5 and an imaging optical system 9. The incident infrared ray 1 becomes a convergent light by the image forming optical system 9, is divided into two by a semi-transparent mirror 5 installed at an inclination in this optical path, and then enters a detector 6, 7 to be detected.

In the infrared optical device configured as described above, the infrared light emitted from the infrared radiator 12 passes through the visual field 17 and
Will be incident on the detector 6 and the second detector 7.
The emissivity of the infrared radiator 12 has a value extremely close to 1, and its temperature is controlled to a constant value, so that its infrared radiation amount is constant. Therefore, the infrared radiator 12
Even if the temperature of the housing rises, the amount of infrared light incident on the first detector 6 and the second detector 7 can be suppressed to a low level by setting the temperature of 2 to a low value. Incident infrared ray 1 can be detected with high accuracy by suppressing an increase in detector shot noise, saturation of detector output, and fluctuation of detector output.

Further, since the infrared radiator 12 has an extremely high emissivity, its reflectance is low. Therefore, although not shown, there is a device such as a scanning mirror or a mechanical chopper that generates stray light with a variable light amount provided in the housing, and an infrared radiator for these stray lights is provided.
The component reflected by 12 and incident on the detectors 6, 7 can be suppressed, and incident infrared rays can be detected with high accuracy.

FIG. 2 is a sectional view showing another embodiment of the present invention. In the figure, 19 is a condensing optical system installed in the optical path between the semi-transparent mirror 5 and the infrared radiator 12. The optical section 18 is a semi-transparent mirror 5.
And a focusing optical system 19 and imaging optical systems 9a and 9b respectively installed in the optical paths between the detectors 6 and 7 and the semi-transparent mirror 5. The incident infrared ray 1 is divided into two by the semi-transparent mirror 5, and then focused and detected by the imaging optical system 9 on the detector 6 or the detector 7, respectively. The field of view 17 seen by the detectors 6, 7 through the semi-transparent mirror 5 is covered by the aperture of the collection optics 19.

In the infrared optical device configured as described above, the infrared light emitted from the infrared radiator 12 passes through the condensing optical system 19 and is divided into two by the semi-transparent mirror 5, and then condensed by the imaging optical system 9 respectively. Since it enters the detectors 6 and 7, even if the temperature inside the housing rises, it is possible to suppress an increase in detector shot noise, saturation of the detector output, and fluctuations in the detector output. Since the field of view 17 seen through the transparent mirror is narrowed down by the condensing optical system 19, the area of the infrared radiator 12 can be reduced,
This has the effects of downsizing the device and facilitating temperature control of the infrared radiator 12. Although a lens is shown as the focusing optical system 19 in FIG. 2, the focusing optical system 19 may be a reflecting mirror. Another embodiment of the present invention using a reflecting mirror is shown in FIG.

Although the number of detector elements is not described in the above description, it is needless to say that the present invention can be applied to any detector of single element, one-dimensional array element and two-dimensional array element. Therefore, the present invention can be applied to an image pickup apparatus for obtaining a target thermal image and a spectroscopic apparatus for obtaining a target spectral characteristic.

〔The invention's effect〕

As described above, according to the present invention, in the infrared optical device, the field of view of the detector looking inside the housing by the reflection or transmission of the semi-transparent mirror is covered with the infrared radiator having a high emissivity and a constant temperature. Therefore, with a simple structure, there is an effect that incident infrared rays can be detected with high accuracy without being affected by a temperature change inside the housing.

[Brief description of drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing another embodiment of the present invention, FIG. 3 is a sectional view showing another embodiment of the present invention, and FIG. FIG. 6 is a cross-sectional view showing a conventional infrared optical device. 5 is a semi-transparent mirror, 6 is a first detector, 7 is a second detector, 9
Is an imaging optical system, 12 is an infrared radiator, 13 is a temperature setting device,
Reference numeral 17 is the field of view of the detectors 6, 7 looking inside the housing by the reflection and transmission of the semi-transparent mirror 5. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. An optical unit having a semi-transparent mirror installed on an optical path of incident infrared rays and inclined with respect to the optical path, and at least one imaging optical system for first and second detectors described later. An infrared optical device having first and second detectors for detecting reflected and transmitted components of the incident infrared light reflected or transmitted by the semi-transparent mirror, respectively, wherein the first detector is the The field of view seen through the semi-transparent mirror,
Radiation close to 1 in the detection wavelength range of the first and second detectors installed so that the second detector covers the field of view seen by the reflection of the semi-transparent mirror and has a constant temperature. An infrared optical device comprising an infrared radiator having a rate. 2. The optical section has a condensing optical system between the semi-transparent mirror and the infrared radiator, and the aperture of the condensing optical system is such that the first detector transmits the semi-transparent mirror. 2. The infrared optical device according to claim 1, wherein the field of view to be viewed and the field of view to be viewed by the second detector are reflected by the semitransparent mirror.