JPS6143648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detector, particularly an infrared detector of the type that can derive a gigahertz band high frequency signal from an internal infrared detection element.

Generally, infrared detectors having an infrared detection element made of a multicomponent semiconductor such as mercury cadmium tellurium (HgCdTe) or lead tin tellurium (PbSnTe) are used by cooling the infrared detection element to, for example, near the temperature of liquid nitrogen. . For this reason, the above-mentioned infrared detecting element is attached to a copper block inside a vacuum-evacuated metal dewar, for example, so as to have good thermal conductivity.

Therefore, when taking out the high-frequency electric signal obtained by photoelectric conversion with the infrared detection element installed inside the metal dewar to the outside of the metal dewar, the characteristic impedance of all intermediate signal transmission systems must be set to a constant value of, for example, 50Ω. It must be made up of

However, conventionally, a single conductor 4 was used as one conductor to connect the infrared detector inside the dewar to the lead-out pin 3 provided on the top cover 2 of the dewar outer cylinder 1 as shown in FIG. The other conductor used was an outer cylinder 1 of the metal dewar and an upper cover 2 which was attached to the outer cylinder 1 in close contact with screws 7. However, in Fig. 1, 6 is an O-ring to prevent vacuum leakage, 8 is a glass tablet, and 5 is, for example, a BNC type connector that is integrated with the top lid 1, and the connection from the dewar to an external amplifier is, for example, RG-58/U etc.
This is done using a 50Ω coaxial cable.

However, even if a connection with a characteristic impedance of 50 Ω is made outside the dewar, conventional connections were made inside the dewar that were haphazard in terms of characteristic impedance as described above. The output high frequency signal was reflected. For this reason, the operating frequency of the above infrared detector is low, and at most
The frequency was about 10MHz, and the value varied depending on the infrared detector. In addition, vacuum sealing using an O-ring as described above is accompanied by slow leakage, making it difficult to maintain a high vacuum inside the dewar for a long period of time.

The present invention has been made in view of these drawbacks, and provides a cooled infrared detector in which an infrared detecting element is housed in a vacuum chamber of the metal dewar, which has a double tube structure consisting of an inner cylinder and an outer cylinder, and has a vacuum inside. A connector is provided that penetrates the outer cylinder of the metal dewar and electrically connects the inside and outside of the outer cylinder, and both the connector and the connection line from the connector to the infrared detection element are coaxial types,
It is an object of the present invention to provide an infrared detector characterized in that a flange provided on the outer conductor of the coaxial type connector is directly brazed to the outer cylinder of the metal dewar. Describe.

FIG. 2 is a sectional view showing in particular the signal deriving part of the infrared detector according to the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. In FIG. 2, 10 first passes through the outer cylinder 1 of the dewar,
The connector is equipped with SMA-type receptacle parts 13a and 13b having a characteristic impedance of 50Ω, for example, with female threads 21 cut at the upper and lower ends thereof, and a flange 12 is integrally attached to the outer conductor 11 of the connector 10. It is being
14 in this connector 10 is a glass tablet 1
5 is a metal conductor, and 22 is a top connected to the metal conductor.
The lower receiving pin constitutes the internal conductor of the connector together with the metal conductor 15, and the connector 1
The characteristic impedance at zero is 50Ω, but since it is made of Kovar together with the outer conductor 11, it is a hermetic seal. A flange 12 made of Kovar is integrally attached around the outer conductor 11 of the connector 10, and the flange is brazed to the dewar sleeves 1 and 20 as shown. Therefore, the vacuum sealing of the dewar is complete and no slow leaks occur.

Moreover, the receptacle part 13b at the lower end of the connector 10, which has the female thread 21 cut therein, has a male thread cut inside and has a protruding pin (not shown).
A plug 17 of an SMA type connector is connected. This SMA type plug 17 is a dewar internal plug, and the dewar internal plug 1
7 and an infrared detection element (not shown) is a fine-core coaxial cable 19 with a characteristic impedance of, for example, 50Ω.
connected by.

On the other hand, the receptacle portion 13a at the upper end of the connector 10 having the female thread 21 cut therein also has a male thread cut inside and has a protruding pin (not shown).
A plug 16 of an SMA connector is connected, and this SMA type plug 16 is a dewar external plug, and a coaxial cable 18 is used to connect the dewar external plug 16 and an amplifier (not shown).

In this way, from the infrared sensing element to the receptacle 1
3b, from receptacle 13b to receptacle 13a, and from receptacle 13
Since the signal transmission system between a and the amplifier has a characteristic impedance of 50Ω, there is no reflection of the high frequency signal to be transmitted at any part from the infrared detection element to the amplifier. Therefore, the operating frequency of the infrared detector reaches the gigahertz order, making it possible to operate at high speed.

In addition, the connector itself, which guides the signal inside the infrared detector to the outside, and the surrounding area are hermetically sealed or brazed, so even if used for a long period of time, there will be no vacuum due to slow leaks. There is no fear of leaks.

In the infrared detector according to the present invention described above, the signal transmission system is consistently set at a constant impedance and at the same time the vacuum sealing is perfect, so that great practical effects can be expected.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a conventional infrared detector, and FIG. 2 is a sectional view of a main part of an infrared detector according to the present invention. 1: Dewar outer cylinder, 2: Upper cover, 3: Lead-out pin,
4: Conductor, 5: Connector integrated with top cover 2, 6: O-ring, 7: Screw, 8: Glass tablet, 10: Connector with hermetic seal structure, 11: Outer conductor of connector 10, 12 : flange, 13a, 13b: receptacle part, 1
4: Glass tablet, 15: Metal conductor, 16,
17: Connector plug, 18, 19: Co-rotating cable, 20: Brazing part.

Claims (1)

[Claims] 1. In a cooled infrared detector in which an infrared detection element is housed in a vacuum chamber of a metal dewar that has a double tube structure consisting of an inner cylinder and an outer cylinder, the inside of the metal dewar is evacuated. A connector is provided to electrically connect the inside and outside of the connector, and both the connector and the connecting wire from the connector to the infrared sensing element are coaxial type, and the flange provided on the outer conductor of the coaxial type connector is An infrared detector characterized by being brazed to the outer cylinder of a metal dewar.