JPH0440327A - Cold shield - Google Patents

Abstract

PURPOSE:To well prevent stray light by integrally forming the cold shield of a material having the absorption end wavelength longer than the absorption end wavelength of a detecting element. CONSTITUTION:The cold shield 10 is fixed at both ends of a photodetector 6 via a mounting board 34 and is integrally formed of an IR absorbing material, such as HgCdTe or HgTe, and the absorption end wavelength thereof is set at the wavelength longer than the absorption end wavelength of the element 6. Plural apertures 36 are formed in the positions respectively opposite to the photodetecting part 6a of the element 6 of this shield 10. The visual field angle of the photodetecting part 6a is limited by this apertures 36. The entire part of the shield 10 is formed of the IR absorbing material if the shield is constituted in such a manner and, therefore, the possibility in the detection sensitivity by the generation of stray light in the apertures 36, etc., is eliminated.

Description

Detailed Description of the Invention Overview Regarding a cold shield for an infrared detection device, the objective is to provide a cold shield that can effectively prevent stray light. The detection element is integrally formed from a material having an absorption edge wavelength longer than that of the detection element.

Industrial applications The present invention relates to a cold shield for an infrared detection device.

An infrared detection device is a device that converts the intensity of infrared rays incident on an infrared detection element into an electrical signal and outputs the electrical signal. In order to increase the detection sensitivity of an infrared detector, it is necessary to narrow the viewing angle of the infrared rays that enter the receiver from the detection target as much as possible.
It is desirable to eliminate extraneous radiation coming from the background other than the object to be detected. For this reason, a shielding member that limits the viewing angle is arranged on the infrared incident side of the light receiving section to exclude radiation from the background. In this case, if the temperature of the shielding member is high, radiation from the shielding member deteriorates the detection sensitivity, so the shielding member is used after being cooled to a low temperature like the detection element, and the shielding member is called a cold shield. If the cold shield has a high reflectance for infrared rays to be detected, stray light will occur and detection sensitivity will deteriorate, so there is a need for a cold shield that can effectively prevent stray light.

BACKGROUND OF THE INVENTION FIG. 4 is a diagram showing an example of a cross-sectional configuration of an infrared detection device. This device includes a dual-structure vacuum insulation container consisting of an inner tube 2 and an outer tube 4, an infrared detection element 6 provided on the vacuum space side of the inner tube 2, and an infrared detection element 6 installed in the outer tube 4 opposite to the infrared detection element 6. The provided infrared transmitting window 8 and the infrared detecting element 6
A cold shield 10 is provided to limit the viewing angle of infrared rays incident on the light receiving section. The output signal of the sensing element 6 is taken out from the terminal 14 via the signal line 12.

A cross-sectional configuration of a conventional cold shield is shown in FIG. In the configuration shown in FIG. 3A, in order from the infrared incident side, a metal aperture 16 having an opening 16a, an antireflection film 18, an infrared transmitting layer 20 made of ZnS, etc., a semitransparent metal layer 22, and a dielectric material. A layer 24 and a metal layer 26 are provided. By arranging the light receiving section of the infrared sensing element to face the interrupted portion of the metal layer 26, the viewing angle of the light receiving section can be limited. The thickness of the dielectric layer 24 is such that the infrared rays reflected on the infrared transmitting layer 20 side of the semi-transparent metal layer 22 are transmitted through the semi-transparent metal layer 22, reflected by the metal layer 26, and transmitted through the semi-transparent metal layer 22 again. The phase relationship is set such that the infrared rays generated by the infrared rays cancel each other out.

In the configuration shown in FIG. 5, a cold shield body 28 of a specific shape is formed by selectively etching Si, and the cold shield body 28 is reflective except for the surface facing the sensing element. A prevention film 30 is formed. The cold shield 28 has an infrared transmitting window 3
2 is provided, and the viewing angle of the light receiving section is limited by this transmission window. The anti-reflection film 30 is
It is formed by oxidizing or nitriding the surface of the cold shield body 28.

Problem to be Solved by the Invention In the configuration shown in FIG. 5(a), the surface reflectance is 5 to 20%, but the reflectance has wavelength dependence due to the above-mentioned operating principle. Therefore, it is not always possible to effectively prevent stray light. On the other hand, in the configuration shown in FIG.
The antireflection effect of the monooxide film or S]nitride film is incomplete, and the surface reflectance is 10% or more. Further, since Si transmits infrared rays, the transmittance is actually 10% or more. As described above, with the conventional configuration, stray light could not be effectively prevented, and there was a limit to the improvement in detection sensitivity.

The present invention was created in view of the above circumstances, and an object of the present invention is to provide a cold shield that can effectively prevent stray light.

Means for Solving the Problem The above-mentioned technical problem is solved by the first or second configuration shown below.

The first configuration is a cold shield that blocks infrared rays incident on the infrared sensing element from outside its viewing angle, and is integrally formed from a material having an absorption edge wavelength longer than the absorption edge wavelength of the sensing element. .

The second configuration is that in a cold shield that blocks infrared rays incident on the infrared sensing element from outside its viewing angle, the absorption edge is longer than the absorption edge wavelength of the sensing element, except for the surface facing the sensing element. An infrared absorbing film made of a material having a wavelength is formed.

Effect: According to the first or second configuration above, the entire cold shield or the surface layer of the cold shield is made of a material (infrared absorbing material) having an absorption edge wavelength longer than the absorption edge wavelength of the sensing element. Therefore, the infrared rays irradiated to the cold shield are absorbed by the infrared absorbing material. Therefore, the reflectance and transmittance of the cold shield for the infrared wavelength are reduced, and stray light is effectively prevented.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a cutaway side view of a cold shield showing an embodiment of the first configuration of the present invention. In this embodiment, 6 is a multi-element type light receiving element, 6a is a light receiving part of the light receiving element, and the cold shield 10 is fixed to both ends of the light receiving element 6 via a mounting base 34.

The cold shield 10 is integrally formed from an infrared absorbing material such as HgCdTe or HgTe, and its absorption edge wavelength is set to be longer than the absorption edge wavelength of the light receiving element 6.

A plurality of openings 36 are formed in the cold shield 10 at positions facing the light receiving portions 6a of the light receiving elements, respectively.
This aperture 36 limits the viewing angle of the light receiving section 6a.

According to this configuration, since the entire cold shield is made of an infrared absorbing material, there is no possibility that stray light will occur inside the opening 36 and the detection sensitivity will deteriorate.

FIG. 2 is a sectional view of a cold shield showing an embodiment of the second configuration of the present invention. In this embodiment, the cold shield main body 38 is formed from a material that can be normally etched selectively, such as Si, and an infrared absorbing film 40 is formed on the main body 38 except for the surface of the main body 38 on the side facing the detection element. Then, an antireflection film 42 is formed on the infrared absorbing film 40.

The infrared absorbing film 40 can be formed to a thickness of approximately 5 μm or more by epitaxial crystal growth using a solution containing HgCdTe as a solute. When the light reception band of the detection element is, for example, 3 to 5 μm, the absorption edge wavelength of the infrared absorption film 40 is set to be 5 μm or more, and when the light reception band of the detection element is, for example, 8 to 12 μm, the infrared absorption The absorption edge wavelength of the film 40 is set to 12 μm or more.

The absorption edge wavelength of the infrared absorbing film 40 can be adjusted by changing the composition of the infrared absorbing material. When the infrared absorbing material is HgCdTe, as shown in Figure 3, the absorption edge wavelength shifts to the longer wavelength side as the Cd concentration decreases, so by adjusting the solution concentration during epitaxial crystal growth, , it is possible to set a desired absorption edge wavelength of the infrared absorbing film. In FIG. 3, the vertical axis represents transmittance, and the horizontal axis represents wavelength.

When the infrared absorbing film 40 is formed from HgTe, the composition can be controlled relatively easily, so the film can be formed not only by epitaxial crystal growth but also by vapor deposition.

As described in detail, according to the present invention, it is possible to prevent stray light by reducing the reflectance and transmittance of the cold shield for received infrared rays. It will be possible to significantly improve detection sensitivity and resolution.

[Brief explanation of the drawing]

FIG. 1 is a cutaway side view of a cold shield showing an embodiment of the first configuration of the present invention, FIG. 2 is a sectional view of the cold shield showing an embodiment of the second configuration of the present invention, and FIG. 3 is an infrared ray FIG. 4 is a cross-sectional view of an infrared detection device, and FIG. 5 is a cross-sectional view of a conventional cold shield. 6... Infrared detection element, 6a... Light receiving part of the infrared detection element, 10... Cold shield, 40... Infrared absorption film.

Claims (1)

[Claims] 1. In the cold shield (10) that blocks infrared rays incident on the infrared detection element (6) from outside its viewing angle, an absorption edge wavelength longer than the absorption edge wavelength of the detection element (6) is provided. A cold shield characterized in that it is integrally formed from a material that has 2. In the cold shield (10) that blocks infrared rays incident on the infrared sensing element (6) from outside its viewing angle, the area of the sensing element (6), excluding the surface facing the sensing element (6), is A cold shield characterized in that an infrared absorbing film (40) made of a material having an absorption edge wavelength longer than an absorption edge wavelength is formed. 3. The cold shield according to claim 2, wherein the infrared absorbing film (40) is formed by epitaxially growing mercury, cadmium, and tellurium. 4. The cold shield according to claim 2, wherein the infrared absorbing film (40) is formed by vapor depositing mercury and tellurium.