JPH0573623U - Infrared optical system - Google Patents

Abstract

(57) [Summary] [Objective] To obtain an infrared optical system that can utilize a lens system of a normal optical design and a general-purpose lens system without considering the structure in the Dewar in advance. [Structure] The cold shield 7 of the infrared optical system has a box shape, and a mask plate 11 having an opening shape larger than the cold shield opening is provided between the field lens 3 and the window 5. [Effect] The ghost optical path formed by the gap between the cold shield and the window 5 is eliminated.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to the configuration of an infrared optical system that forms an infrared image.

[0002]

[Prior Art]

 FIG. 2 is a cross-sectional view showing a conventional infrared optical system. In the figure, 1 is an objective lens, 2 is a band-pass filter, 3 is a field lens, 4 is a dewar with a vacuum sealed inside, 5 is a window fixed to the dewar 4, 6 is an infrared detector, and 7 is infrared detection. A cold shield thermally attached to the device 6 is attached, 8 is a wire for electrically connecting to the infrared detector 6, 9 is a hermetic terminal, and 10 is a cooler for cooling the infrared detector 6.

The conventional infrared optical system is configured as described above and operates as follows. The objective lens 1, the bandpass filter 2, the field lens 3 and the window 5 constitute a lens system as a whole, and an infrared detector 6 is arranged on the image plane of the lens system. The infrared detector 6 is, for example, a platinum / silicon / Schottky barrier type two-dimensional solid-state image pickup device. By connecting the drive signal and the output signal to the outside through the wire 8 and the airtight terminal 9, the infrared detector 6 The infrared image formed above is output to the outside as an electric signal. The cooler 10 acts to cool the infrared detector 6 to a proper extremely low temperature (about 80 K), and the dewar 4 which holds the inside vacuum reduces the amount of heat entering the infrared detector 6, The cooling capacity of the cooler 10 is small. The cold shield 7 is made of a metal having thermal conductivity. By making this temperature extremely low, which is almost equal to that of the infrared detector 6, the infrared rays from the outside of the optical path of the lens system are shielded. The infrared detector 6 noise that would be caused by

[0004]

As shown in FIG. 2, in the conventional infrared optical system as described above, an optical path as shown in A is formed through a gap between the window 5 and the cold shield 7, and a portion B is provided. Since the optical relationship between the infrared detector 6 and the infrared detector 6 is conjugate, the image of the portion B may be formed as a ghost image on the infrared detector 6. Further, in order to avoid this in advance, a special optical design considering all the structures must be performed, so that there is an inconvenience that a general-purpose lens system cannot always be used.

The present invention has been made in order to solve such a problem, and a lens system of general optical design and a general-purpose lens system can be used without considering the structure in the dewar 4 in advance. It is intended to be available.

[0006]

[Means for Solving the Problems]

 In the infrared optical system according to the present invention, the cold shield has a box shape and a mask plate is provided between the lens system and the window.

[0007]

[Action]

 This device prevents the existence of an optical path through the gap between the windshield and the cold shield, which causes a ghost image.

[0008]

【Example】

 Example 1. FIG. 1 is a sectional view showing an embodiment of the present invention, and 1 to 6 and 8 to 10 are exactly the same as the above-mentioned conventional device. Reference numeral 7 is a box-shaped cold shield in which the size of the opening is the same as that of the conventional example, and has the same function as the conventional device. Reference numeral 11 is a mask plate having an opening larger than the size of the opening of the cold shield.

In the infrared optical system configured as described above, since the light rays incident from the outside of the window 5 do not pass through the gap between the window 5 and the cold shield 7 and enter the inside of the dewar 4, the dewar 4 No image is formed on the inside of the infrared detector 6 to cause a ghost.

[0010]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects.

By blocking the gap between the cold shield and the window, it is possible to prevent the occurrence of ghost.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional infrared optical system.

[Explanation of symbols]

 1 Objective Lens 2 Band Pass Filter 3 Field Lens 4 Dewar 5 Wind 6 Infrared Detector 7 Cold Shield 8 Wire 9 Airtight Terminal 10 Cooler 11 Mask Plate

Claims (1)

[Scope of utility model registration request] 1. In an infrared optical system for forming an infrared image on an infrared detector, a dewar having a lens system and a window for transmitting infrared rays, and a dewar disposed in the dewar at an image forming position of the lens system. An infrared detector, a box-shaped cold shield having an opening on the light incident side between the window and the infrared detector, and a light passage portion larger than the opening of the cold shield between the lens system and the window. An infrared optical system comprising a mask plate.