CN104729420A - Device and method for measuring low-temperature deformation of infrared focal plane module - Google Patents

Abstract

The invention discloses a device and method for measuring low-temperature deformation of an infrared focal plane module. The device comprises a testing Dewar flask having a special window requirement and a laser interferometer. According to the method, a tested sample is adhered to a cold head of the vacuum Dewar flask to obtain sample surface deformation information through laser interference in a non-contact mode. The method has the advantages that the testing process is quick, the temperature of the sample is controllable, and the inherent shortcomings of unstable sample temperature, frost formation occurring on the surface and the like of a traditional testing method are overcome.

Description

A kind of device and method measuring infrared focus plane module low temperature deformation

Technical field

The present invention relates to infrared eye detection technique, specifically refer to and utilize special dewar window with the thermal mismatching deformation at low temperatures of measurements by laser interferometry infrared focus plane module, it is applicable to the detection of the surface topography of infrared focal plane device in encapsulation process.

Background technology

Under refrigeration type infrared detector assembly is generally operational in low-temperature condition, its working temperature is usually even lower at 100K, because infrared detector module is made up of various different material, the thermal expansivity of these materials is different, thermal stress will inevitably be produced when assembly changes between room temperature and working temperature, thermal stress is one of subject matter affecting infrared eye reliability at present, it can cause the inefficacy of the various modes of infrared eye, such as layering, photoelectric properties degeneration, functional material sliver etc.

Therefore the thermal stress reducing functional module is an important goal of infrared detector module package design.After component design completes and enters the trial production stage, need that test is carried out to thermal stress and characterize, generally describe by the surface deformation of sample the thermal stress that mercury cadmium telluride bears.

Step instrument is the common equipment measuring sample surfaces deformation, it utilizes probe to streak at sample surfaces, the profile of sample surfaces is obtained with this, for the distortion measurement under low temperature, its test process is generally that sample is fixed on very large heat sink of thermal capacitance, then liquid nitrogen cooling is immersed together, at the heat sink complete cold surface deformation be placed under low temperature step instrument being measured sample surfaces.But the temperature of this method controls not ideal enough, and in test process, sample surfaces has frosting, and these all have larger impact to test result, therefore need the method for new measurement low temperature pattern.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art, the invention provides a kind of device and method measuring infrared focus plane module low temperature deformation, solving the measured deviation that the unstable and surperficial frosting of the temperature residing for test of conventional test methodologies etc. brings.

The technical solution adopted in the present invention is: be different from classic method and measure the sample surfaces scanning and be directly exposed in air with step instrument, the present invention obtains sample surfaces deformation data with laser interferance method, and the low temperature environment needed for measuring is provided by vacuum dewar.As shown in Figure 1, sample is pasted on cold head typical test Dewar structure, and cold head and sample are all in vacuum, and liquid nitrogen is stored in liquid nitrogen cavity, directly freezes to cold head.Vacuum mainly plays the effect of thermal insulation and isolation steam, and make good Dewar vacuum degree very high, it is very little to the leakage heat of environment, does not also have moisture condensation at sample surfaces.Window material, to visible transparent, generally adopts diamond material.Sample is pasted on after on Dewar cold head, installs window cap, then vacuumizes, and treats that Dewar vacuum degree is better than 1X10 ^-3after Pa, in liquid nitrogen cavity, inject liquid nitrogen refrigeration cool-down, monitor cold head temperature simultaneously, treat that sample is cooled to the measurement that liquid nitrogen temperature just can carry out low temperature pattern later.

A branch of monochromatic collimated beam is successively through standard mirror, sample surfaces (see Fig. 1) is incided after dewar window, if light a appears window and again incides standard mirror after sample surfaces reflection, form light a ', light a ' meets at the reflected light b ' of the surface of standard mirror with the light beam b in parallel beam herein, form coherent light and produce interference fringe, different stripeds represents the difference of directional light optical path difference after running into testing sample surface reflection, in surface deformation and the optical path difference of sample, mapping relations are one by one formed between interference fringe, by can obtain the surface deformation of sample to the analysis of interference fringe, measure the low-temperature surface deformation of focal plane thus.

The measuring error of this method mainly comes from the change of uneven the brought optical path difference of the in uneven thickness and window material refractive index of dewar window, therefore the homogeneity of refractive index and the depth of parallelism of window upper and lower surface that control test dewar window material are the keys reducing test error, generally adopt diamond material and the depth of parallelism controlling its upper and lower surface is within 0.5um.

A kind of device measuring infrared focus plane module low temperature deformation of the present invention comprises test Dewar and laser interferometer, testing sample is pasted on the cold head of test Dewar, the material reply visible transparent of the window of described test Dewar, the depth of parallelism in window two faces is better than 0.5um, and laser interferometer obtains test sample sample surfaces deformation data non-contactly through dewar window.

Infrared focus plane module low temperature deformation measuring method step is as follows:

1) Dewar is placed on displacement platform and with the laser beam of laser interferometer aims at, the position of adjustment Dewar, pitching and inclination, make it to meet dewar window perpendicular to interference imaging requirements such as laser beam;

2) in Dewar liquid nitrogen cavity, slowly inject liquid nitrogen to lower the temperature, monitor the temperature of Dewar cold head, until Dewar cold head temperature reaches 80K simultaneously;

3) sampling of laser interference figure is carried out;

4) after having sampled, carry out data processing, obtain the surface deformation of sample.

The advantage of measuring method of the present invention is that sample is pasted on the cold head of vacuum dewar, with the mode of laser interference non-contacting acquisition sample surfaces deformation data, test process is quick, sample temperature is controlled, overcomes the intrinsic difficulties such as the unstable and surperficial frosting of the sample temperature of conventional test methodologies.

Accompanying drawing explanation

Fig. 1 is Dewar and measurements by laser interferometry principle schematic, in figure the definition of each numbering by number sequential arrangement be from small to large once:

1---vacuum;

2---liquid nitrogen;

3---cold head;

4---window;

5---the standard mirror of interferometer;

6---sample;

A, b---incident ray;

A ', b '---reflection ray;

Fig. 2 is the temperature lowering curve of Dewar cold head;

Fig. 3 is the surface deformation of sample.

Embodiment

Prepared by 1 test dewar window: dewar window material is jewel sheet, thickness window d=0.3mm, and the depth of parallelism Δ d1=0.1um in two faces of window, window diameter is 30mm.

2 preparation of samples: sample installs dewar window, then vacuumizes Dewar, make the vacuum of Dewar vacuum cavity be better than 1E after being pasted on the center of test Dewar cold head with thermally conductive grease ^-3pa.

3 Dewars to be placed on six-degree of freedom displacement platform and to aim at the laser beam of ZYGO laser interferometer, and the position of adjustment Dewar makes dewar window and standard mirror directly apart from Pass Test setting value 250mm.

The pitching of 4 adjustment displacement platforms and inclination, make it to meet dewar window perpendicular to interference imaging requirements such as laser beam.

5 slowly inject liquid nitrogen in Dewar liquid nitrogen cavity lowers the temperature, and monitors the temperature of Dewar cold head, until Dewar cold head temperature reaches 80K (see Fig. 2) simultaneously.

6 carry out the sampling of laser interference figure.

7 sampled after, the data processing software that laser interferometer carries automatically identifies conoscope image and carries out data processing, finally obtains the surface deformation (see Fig. 3) of sample.

Claims (2)

1. measure a device for infrared focus plane module low temperature deformation, it comprises the test Dewar and the laser interferometer that window are had to particular/special requirement, it is characterized in that:

Testing sample (6) is pasted on the cold head (3) of test Dewar, the material reply visible transparent of the window (4) of described test Dewar, the depth of parallelism in window two faces is better than 0.5um, and laser interferometer obtains test sample sample surfaces deformation data non-contactly through dewar window.

2., based on a kind of infrared focus plane module low temperature deformation measuring method measuring the device of infrared focus plane module low temperature deformation according to claim 1, it is characterized in that comprising the following steps:

1) Dewar is placed on displacement platform and with the laser beam of laser interferometer aims at, the position of adjustment Dewar, pitching and inclination, make it to meet dewar window perpendicular to interference imaging requirements such as laser beam;

2) in Dewar liquid nitrogen cavity, slowly inject liquid nitrogen (2) to lower the temperature, monitor the temperature of Dewar cold head (3), until Dewar cold head (3) temperature reaches treat testing temperature simultaneously;

3) sampling of laser interference figure is carried out;

4) after having sampled, carry out data processing, obtain the surface deformation of sample.