JPS6015144Y2 - Electronically cooled radiation detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an improved construction of an electronically cooled radiation detection device that operates at temperatures much lower than the outside world.

To detect long-wavelength radiation using a photon-type infrared sensing element, the S/N ratio is improved by cooling the element to a temperature much lower than room temperature to sufficiently reduce the effects of thermal noise. This is already well known.

FIG. 1 shows the structure of a radiation detector that uses a liquid refrigerant such as liquid nitrogen as a cooling means.

In FIG. 1, a radiation detection element 1 made of a semiconductor and a cold aperture 2 are installed on the inner wall surface of the bottom of an open thermos flask-shaped refrigerant container 6 having a transmission window 5 that transmits long wavelength radiation, that is, infrared rays. There is.

Similar to a so-called thermos flask, the space between the double walls of the refrigerant container 6 is vacuumed to prevent heat conduction from the outside.

As is well known, the role of the cold aperture 2 is to shield the radiation detection element 1 from heat radiation from the inner wall surface of the refrigerant container 6, particularly from the transmission window 5 and its vicinity.

The cold aperture 2 is painted black so as to absorb radiation well.

On the other hand, recently, a radiation detection device has been proposed that performs cooling using an electronic cooling element instead of a liquid refrigerant such as liquid nitrogen.

FIG. 2 shows the structure of such a thermoelectrically cooled radiation detection device. , a lead wire 27 for the sensing element, and a lead wire 28 for the electronic cooling element.

However, the conventional electronically cooled radiation detection device was not provided with anything equivalent to the cold aperture 2 shown in FIG.

The reason for this is that the heat absorption ability of the electronic cooling element was weak, and
This is because the wavelength used by this type of radiation detection device was in a relatively short wavelength region, so there was little need for a cold aperture.

However, recently there has been a tendency for the usable wavelengths of radiation detection devices to extend into the far-infrared region, and it has become necessary to use electronically cooled detection devices in the far-infrared region in order to avoid the hassle of using liquid refrigerants. It's here.

In order to meet this requirement, even in an electronically cooled radiation detection device, the detection element must be shielded from radiation from the container wall in order to obtain a good signal-to-noise ratio.

In view of the above-mentioned points, the present invention aims to provide a structure of a new electronically cooled radiation detection device that shields the sensing element from the thermal radiation of the container wall without overcharging the load on the electronic cooling element. .

An embodiment of the present invention will be described in detail below.

FIG. 3 is a sectional view showing the structure of an embodiment of the radiation detection device according to the present invention, and the same parts as in FIG. 2 are given the same reference numerals.

In FIG. 3, a small cold aperture 29 is attached to the radiation detection element 21, and the cold aperture structure has features.

The reason why the cold aperture does not cause an overload to the electronic cooling element will be explained below.

Here, the heat exchange between the cold aperture and the container outer cylinder can be expressed as follows.

Qr=5-67X10-'2A1, +AI(1,), (T'j TD2 T1 and T2 indicate the absolute temperatures on the low-temperature side and high-temperature side, respectively.

Qr is the amount of heat load due to radiation (W) A,: Side area of cold aperture (cm) A2 = Side area of container (self) El: Cold aperture emissivity E2: Container outer cylinder emissivity Here is an example. Let's make the following assumptions.

A, = 0,4 cyfl A2 = 5c4 T1 = 223'K T2 = 323'K t2 = 0.9 t, = 0.95 (conventional) 0.1 (this invention) As a result of the assumption, the conventional In this case, Qr = 17 mW, but in the configuration of the present invention, Qr = 21 TIW.

If the cold aperture is made of a material with a very low emissivity in this way, it becomes possible to install the cold aperture with a very small increase in heat load.

A specific example of the configuration of the cold aperture is shown in FIG.
As shown in by c.

Figure 4a shows a cold aperture 34 made of copper, kovar, etc.
A metal coating 31 of Al, Au, or the like is applied to the outer surface to reduce the radiation of the outer surface.

Also, instead of coating with AI, Au, etc., the cold aperture shown in Figure b uses a material 32 such as Imphal or titanium, and the entire outer surface is mirror-polished to increase the reflectance and therefore reduce the emissivity. This is what I did.

In addition, Figure 0 shows that a material with high emissivity is used near the hole of the cold aperture in Figure A or on the entire upper surface 33 (excluding the side surfaces) coated with metal coating 31 to prevent diffuse reflection of thermal radiation, and that surface This is a configuration in which the image is colored black.

In addition, the inner surface 34 can be constructed in various ways, such as by using a material with a high emissivity to prevent diffused reflection, so that a structure can be constructed in which the thermal load on the electronic cooler due to thermal radiation is reduced.

The thermoelectrically cooled radiation detection device according to the present invention can be cooled by attaching a cold aperture with a small heat load to a part of the thermoelectric cooler, which allows shielding to be far removed without impairing the cooling characteristics of the thermoelectric cooler. The effect is good.

When a thermoelectrically cooled radiation detector is used in a high-temperature environment such as industrial use, the heat generating side of the thermoelectrically cooled element reaches a temperature higher than the ambient temperature, so there is some concern about conduction from the outer cylinder. Attaching this is effective in reducing background noise caused by conduction from the outer casing.

Also, if the background noise is large and fluctuates in a high temperature environment,
Since the resistance value of the sensing element changes with background noise, the signal level changes with the element resistance value.

In the device to which the present invention is applied, the above-mentioned drawbacks are prevented, and fluctuations in signal level are significantly reduced.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the structure of an example of a conventional liquid-cooled infrared detection device, Fig. 2 is a sectional view showing an example structure of a conventional electro-cooled infrared detection device, and Fig. 3 is a sectional view showing the structure of an example of a conventional electro-cooled infrared detection device. Cross-sectional view showing an example structure of a line detection device, Figures 4a and b
, c are cross-sectional views showing the structure of a cold aperture. 1 and 21: infrared sensing element, 2 and 29: cold aperture, 6 and 24: container outer cylinder, 5 and 25
: Infrared transmitting window, 22: Electronic cooling element.

Claims (1)

[Scope of utility model registration request] An electronic cooler is installed inside an airtight container that partially has a radiation-transmitting window, a radiation detection device is fixed to the cooling surface of the electronic cooler, and the sensing element is surrounded by the cooling part near the sensing element. An electronically cooled radiation detection device characterized by having a cold aperture whose outer surface is treated with low emissivity.