A device and method for testing thermal stability of optical axis of infrared sight

Abstract

The present invention discloses a device and method for testing the thermal stability of the optical axis of an infrared sight, comprising an optical platform, an infrared thermal radiation target, a temperature test chamber, a tooling flange, a theodolite, an image acquisition and display device, an infrared sight, and a collimator. During the test, the temperature test chamber provides constant temperature conditions for the infrared sight, the tooling flange, and the second reference reflector in the chamber; the theodolite measures the angle change between the first reference reflector and the second reference reflector; at the same time, the infrared sight records the position change of the center position of the infrared image output under different temperature conditions relative to the infrared thermal radiation target; the optical axis thermal drift is obtained by calculating and analyzing the position change corrected by the angle change, and the thermal stability of the optical axis is evaluated. By evaluating the angle change, the present invention eliminates the test error introduced by the instability of the angle measuring device itself during long-term measurement, and reduces the stringent requirements of high-precision measurement on the stability of the test equipment.

Description

Technical Field

[0001] The invention relates to a device and method for testing the thermal stability of an infrared sight optical axis, and belongs to the field of thermal stability testing of infrared thermal imagers. Background Art

[0002] Due to the thermal expansion and contraction properties of materials, the optical axis of an infrared sight will drift relative to normal temperature when the ambient temperature changes. This optical axis drift causes the optical axis of the infrared sight to deviate from the true optical axis, resulting in a decrease in the infrared sight's aiming performance. Therefore, enhancing the thermal stability of the infrared sight's optical axis can effectively improve its aiming accuracy. Accurately measuring the changes in the infrared sight's optical axis is a prerequisite for understanding its thermal deformation, optimizing its optical system, and improving its thermal stability.

[0003] An infrared sight generally consists of an infrared optical system, an infrared detector assembly, an infrared image processing circuit, and a mechanical support structure. The infrared radiation energy from the target is transmitted through the infrared optical system to the photosensitive element of the infrared detector assembly. The infrared detector assembly, through the photoelectric conversion effect, converts the received infrared radiation energy into an electrical signal for transmission. The infrared image processing circuit processes the electrical signal and ultimately outputs an infrared thermal image visible to the human eye. The infrared optical system, infrared detector assembly, and mechanical support structure can directly affect the thermal stability of the optical axis. The infrared image processing circuit, however, generates heat during operation. The resulting temperature gradient can affect the thermal stability of the infrared optical system, infrared detector assembly, and mechanical support structure, indirectly affecting the thermal stability of the optical axis. Infrared images are output in a video format. Display images are composed of pixels, which correspond to the pixels of the core detector component in an infrared sight. The number of pixels is also a way of expressing the detector's specifications. For example, a medium-wave 640×512 infrared sight has a 640×512 pixel count. Medium wave is the detector's operating band, and 640×512 refers to the detector's specifications, with 640 pixels horizontally and 512 pixels vertically. Generally, one pixel corresponds to one pixel in the image.

[0004] The thermal stability of an infrared sight's optical axis refers to the ability of the infrared image center to withstand temperature fluctuations. It is typically measured by the offset of the infrared image center relative to the center at a reference temperature within a certain temperature range, expressed in pixels. It can also be measured by the offset angle between the optical axis and the initial optical axis at the reference temperature within a certain temperature range, expressed in arc seconds per degree. A smaller value indicates a higher thermal stability.

[0005] The thermal stability test method for the optical axis of an infrared sight generally involves attaching a plane reflector to the mounting flange of the sight. A goniometer then sends a very fine beam of light to the plane reflector and receives the reflected beam. The goniometer then measures the plane reflector's reflection angle. A temperature test chamber is then used to control the temperature of the infrared sight. The sight is then held at a fixed infrared heat radiation target before and after the temperature changes. The difference in the plane reflector's reflection angle before and after the temperature changes is the thermal drift of the infrared sight's optical axis, measured as the offset angle.

[0006] However, traditional measurement methods place very high demands on the goniometer and infrared thermal radiation target's anti-interference capabilities. They must ensure that their initial positions remain fixed despite the long-term vibrations of the temperature test chamber. Under these conditions, the difference in reflection angle before and after the temperature change is the only way to accurately represent the infrared sight's optical axis thermal drift. However, if the goniometer and infrared thermal radiation target's initial positions shift due to environmental vibrations during the test, this shift will be directly incorporated into the final measurement results and cannot be eliminated. This can lead to large, random errors between the measured results and the actual optical axis thermal drift, thus interfering with the infrared sight's optical axis thermal stability testing and optimization design. Summary of the Invention

[0007] The technical problem solved by the present invention is to overcome the above-mentioned shortcomings and provide a testing device and a testing method for the thermal stability of the optical axis of an infrared sight. Its purpose is to effectively avoid the measurement errors introduced by the traditional testing method due to the poor anti-interference ability of the goniometer and the infrared thermal radiation target, and accurately test the thermal drift of the optical axis of the infrared sight under different temperature conditions.

[0008] The technical solution of the present invention is:

[0009] A device for testing the thermal stability of an infrared sight's optical axis comprises an optical platform, a target, a temperature test chamber, a tooling flange, a theodolite, an image acquisition and display device, an infrared collimator, a first reflector and a second reflector.

[0010] The optical platform serves as a stable support device for the target and the infrared collimator, providing a stable target object; the infrared collimator is installed on the optical platform, the target is installed at the side aperture of the collimator, and the first reflector is connected to the target as a reference for the target; the temperature test chamber simulates different temperature environments of the product; the tooling flange firmly connects the temperature test chamber to the infrared sight under test; the second reflector is installed on the tooling flange as a reference for the infrared sight; the theodolite is placed between the collimator and the temperature test chamber to measure the angle between the first reflector and the second reflector, and the change in the angle is measured through a cross test before and after the temperature changes in the temperature chamber. This change is the optical axis drift of the infrared sight after the temperature change.

[0011] During the test, the temperature test chamber provides constant temperature conditions for the infrared sight, tooling flange and second reflector in the temperature chamber, so that the inside and outside of the infrared sight reach the specified temperature. The theodolite measures the angle between the first reflector and the second reflector. At the same time, the infrared sight records the position change of the center position of the infrared image output at this time relative to the infrared thermal radiation target. By calculating and analyzing the position change after the angle change is corrected, the optical axis thermal drift is obtained, and the thermal stability of the optical axis of the infrared thermal sight is evaluated.

[0012] A method for testing the optical axis stability of an infrared sight, the test steps are as follows:

[0013] Step 1: Under the initial temperature conditions, first aim the infrared sight at the center or near the infrared thermal radiation target, and use the image acquisition and display device to read the coordinate position of the center of the infrared sight relative to the infrared thermal radiation target, that is, the initial position of the optical axis, and record it as (X0, Y0) in pixels.

[0014] Step 2: Then use the TM6100A theodolite to aim and measure the angles of the first reflector and the second reflector, respectively, and record them as α0(X 反1-0 , Y 反1-0 ),β0(X 反2-0 , Y 反2-0 ), and use the formula (β0-α0)=(X 反1-0 -X 反2-0 , Y 反1-0 -Y 反2-0 ) Calculate the angle between the two space angles and record it as γ0=β0-α0, unit: arc second.

[0015] Step 3: Use a temperature test chamber to apply temperature changes to the infrared sight (including the tooling flange and the second reflector) to the test target temperature range. During this process, the infrared sight will not operate.

[0016] Step 4: Turn on the infrared sight and read the coordinate position of the center of the infrared sight relative to the target through the image acquisition and display device, that is, the total change position of the optical axis, and record it as (X i , Y i ), unit: pixel.

[0017] Step 5: Use the TM6100A theodolite to aim and measure the angles of the first reflector and the second reflector, and record them as

[0018] α i (X 反1-i , Y 反1-i ), β i (X 反2-i , Y 反2-i ), and use the formula (β i -α i )=(X 反1-i -X 反2-i , Y 反1-i -Y 反2-i ) calculate the angle between the two space angles and record γ i =β i -α i , unit: arc second.

[0019] Then, through two cross-tests, we can get the following relationship:

[0020]

[0021] Among them, A = [1 -1 -1] is the transformation matrix, For the measurement results, To be sought quantity.

[0022] Correction amount X amend 、Y amend With the measurement results γ i (α i , β i ) is related to γ0(α0, β0) and can be solved by the following relationship:

[0023]

[0024] Among them, FOV is the field of view of the infrared sight, N Upixel and N Vpixel They are the number of pixels in the horizontal and elevation directions of the infrared sight's detector respectively.

[0025] At this point, the optical axis thermal stability test of the infrared sight is completed.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The existing technology usually requires that the angle measuring equipment has the ability to maintain long-term stability. Otherwise, due to the vibration of the temperature test chamber, the instability of the angle measuring equipment itself, or environmental noise, the angle measuring equipment will be disturbed, introducing unnecessary and unpredictable test errors. The present invention separates the measurement benchmark from the measuring instrument benchmark by judging the change in the angle. The measurement benchmark is the reflector 1. The stability of the measurement result is related to the stability of the position of the reflector 1 and is no longer affected by the instability of the measuring instrument benchmark. This effectively eliminates the test error introduced by the instability of the measuring instrument benchmark during long-term measurement, and effectively reduces the stringent requirements of high-precision measurement on the stability of the test equipment.

[0028] (2) The existing technology has very high requirements for the measurement environment. It requires the temperature test chamber and the measuring instrument to have a high degree of seismic isolation to prevent the external environment or vibration from interfering with the measurement process. As a result, the construction cost of such laboratories is high, the number is small, a single project takes a long time, and the use efficiency is low. The present invention only needs to set up a reasonable optical platform to maintain a certain stability of the target. The test environment does not have too high requirements. The general temperature laboratory environment can also meet the higher precision requirements, which reduces the cost of building a laboratory. Under the same funding, the number of laboratories can be increased and the detection efficiency can be improved.

[0029] (3) The test accuracy of the present invention is based on the completion in a general temperature test inspection environment, and has good environmental adaptability and high versatility.

[0030] (4) Existing technologies are unable to separate and locate the main factors affecting the optical axis drift of the test system and the object being tested. The present invention understands and locates the main factors affecting the optical axis drift by simultaneously monitoring the changes in the angles between multiple targets and a single reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 : Schematic diagram of the composition of the optical axis thermal stability testing device of the present invention.

[0032] Figure 2 : A schematic diagram of the composition of a testing device based on a conventional infrared collimator of the present invention.

[0033] Figure 3 : A schematic diagram of the composition of the testing device based on the vibration isolation building of the present invention.

[0034] Figure 4 : Schematic diagram of the stability principle of the test method of the present invention.

[0035] Figure 5 : Schematic diagram of the measurement principle of the optical axis variation of the second reflector of the present invention.

[0036] Figure 6 : Schematic diagram of the refraction of light when it passes through a window film.

[0037] Reference numerals in the figure: optical platform 1, infrared collimator 2, target 3, temperature test chamber 4, tooling flange 5, theodolite 6, image acquisition and display equipment 7, infrared sight 8, vibration isolation building 9, first reflector 13, second reflector 25. DETAILED DESCRIPTION

[0038] Example 1

[0039] like Figure 1 As shown, a test device for thermal stability of the optical axis of an infrared sight includes an optical platform 1, an infrared collimator 2, a target 3, a temperature test chamber 4, a tooling flange 5, a TM6100A theodolite 6, an image acquisition and display device 7, an infrared sight 8, a first reflector 13, and a second reflector 25;

[0040] The optical platform 1 serves as a stable support device for the infrared collimator 2 and the target 3, providing a stable target object; the infrared collimator 2 is installed on the optical platform 1, the target 3 is installed at the side aperture of the infrared collimator 2, and the first reflector 13 is installed at the target 3 as a reference mirror representing the target 3; the temperature test chamber 4 is used to provide different temperatures for the product, the second reflector 25 and the infrared sight 8 are fixedly connected to the tooling flange 5 and placed in the temperature test chamber 4, and the second reflector 25 serves as a reference for the infrared sight 8; the TM6100A theodolite 6 is arranged between the infrared collimator 2 and the temperature test chamber 4, and is used to measure the change in the angle between the first reflector 13 and the second reflector 25 under different temperature conditions; the image acquisition and display device 7 is used to acquire and display images of the infrared sight 8.

[0041] During the test, the temperature test chamber 4 provides constant temperature conditions for the infrared sight 8, tooling flange 5, and first reflector 13 inside the temperature chamber, so that they fully reach the specified temperature. The TM6100A theodolite 6 measures the angle change between the first reflector 13 and the second reflector 25. At the same time, the infrared sight 8 records the position change of the center position of the infrared image output under different temperature conditions relative to the infrared thermal radiation target 3. By calculating and analyzing the position change after the angle change is corrected, the optical axis thermal drift is obtained, and the thermal stability of the optical axis of the infrared thermal sight is evaluated.

[0042] Based on Figure 1 The test method for the thermal stability of the infrared sight optical axis of the infrared sight optical axis test device shown in the figure has the following test steps:

[0043] Step 1: Under the initial temperature conditions, first aim the infrared sight 8 at the center or near the target 3, and use the image acquisition and display device 7 to read the coordinate position of the center position of the infrared sight 8 relative to the target 3, that is, the initial position of the optical axis, and record it as (X0, Y0), unit: pixel.

[0044] Step 2: Then use the TM6100A theodolite 6 to aim and measure the optical axis spatial angles of the first reflector 13 and the second reflector 25 respectively, and read out the angle between the two spatial angles, and record it as (α0, β0), unit: arc second.

[0045] Step 3: Apply temperature change to the infrared sight 8 (including the tooling flange 5 and the second reflector 25) to the test target temperature change range through the temperature test chamber 4. During this process, the infrared sight 8 does not work.

[0046] Step 4: Turn on the infrared sight 8, and read the coordinate position of the center of the infrared sight 8 relative to the target 3 through the image acquisition and display device 7, that is, the total change position of the optical axis, and record it as (X i , Y i ), unit: pixel.

[0047] Step 5: Use the TM6100A theodolite 6 to aim and measure the optical axis spatial angles of the first reflector 13 and the second reflector 25 respectively, and read the angle between the two spatial angles, and record it as (α i , β i ), unit: arc second.

[0048] The data recorded in steps 1 and 4 is the total optical axis drift of the thermal imager before and after the temperature change (including the position deviation caused by the thermal deformation of the tooling flange 5 and the vibration of the test environment. If the change is obvious, it is necessary to set a correction amount in this method to eliminate it from the total optical axis drift). The relationship is:

[0049]

[0050] Among them, A = [1 -1 -1] is the transformation matrix, For the measurement results, To be sought quantity.

[0051] The data obtained from steps 2 and 5 are then used to calculate the correction value X amend 、Y amend Correction amount X amend 、Y amend Compared with the measurement results (α i , β i ) is related to (α0, β0) and can be solved by the following relationship:

[0052]

[0053] Among them, FOV is the field of view of the infrared sight, N Upixel and N Vpixel are the number of pixels in the detector's horizontal and elevation directions, respectively. This formula maps the number of pixels to the field of view angle, converting the number of pixels into the number of arc seconds per pixel. By allocating the field of view angle of each pixel to the total field of view of the infrared sight, the corresponding field of view angle can be calculated. The number of pixels offset from the image center can then be converted into the number of arc seconds offset.

[0054] The testing method of this embodiment first obtains the total optical axis change of the infrared sight (including the optical axis change of the infrared sight itself and the deviation caused by the tooling flange driving the infrared sight to move due to the vibration and thermal effect of the temperature chamber) through steps one and four, then obtains the deviation caused by the tooling flange driving the infrared sight to move through steps two and five, and then subtracts the change caused by the tooling flange from the total change to obtain the optical axis change of the infrared sight itself.

[0055] The main disadvantages of this embodiment are: it is necessary to modify the conventional infrared collimator 2 and target 3 so that the target 4 can be clearly imaged while ensuring that the first reflector 13 can reflect light back to the TM6100A theodolite through the infrared collimator 2.

[0056] The advantages of this embodiment are as follows: since the first reflector 13 represents the position of the target 3, the target position deviation limit of ±3" can be eliminated, and the system accuracy can be improved from the original 6.63" to 6.32".

[0057] Example 2

[0058] like Figure 2 As shown, a test device for the thermal stability of the optical axis of an infrared sight is provided. This embodiment is based on the first embodiment. If the optical platform can stably support a conventional infrared collimator, and the test environment is independently operated without too many people entering and leaving, the first reflector 13 is attached to the chassis of the infrared collimator 2. At this time, the system accuracy needs to be calibrated in advance to determine the target position deviation limit value.

[0059] If the tooling flange 3 can accurately represent the reference of the infrared sight 8, the optical axis drift of the infrared sight 8 can be directly evaluated by the change in the angle before and after.

[0060] Based on Figure 2 The test method for the thermal stability of the infrared sight optical axis of the infrared sight optical axis test device shown in the figure has the following test steps:

[0061] Step 1: Under the initial temperature condition, first aim the infrared sight 8 at the center of the target 3.

[0062] Step 2: Then use the TM6100A theodolite 6 to aim and measure the angles of the first reflector 13 and the second reflector 25, respectively, and record them as α0(X 反1-0 , Y 反1-0 ),β0(X 反2-0 , Y 反2-0 ), and use the formula (β0-α0)=(X 反1-0 -X 反2-0 , Y 反1-0 -Y 反2-0 ) Calculate the angle between the two space angles and record it as γ0=β0-α0, unit: arc second.

[0063] Step 3: Apply temperature change to the infrared sight 8 (including the tooling flange 5 and the second reflector 25) in the temperature test chamber to the test target temperature change range. During this process, the infrared sight 8 does not work.

[0064] Step 4: Turn on the infrared sight 8 and aim the infrared sight 8 at the center of the target 3 again.

[0065] Step 5: Use the TM6100A theodolite 6 to aim and measure the angles of the first reflector 13 and the second reflector 25, respectively, and record them as α i (X 反1-i , Y 反1-i ), β i (X 反2-i , Y 反2-i ), and use the formula (β i -α i )=(X 反1-i -X 反2-i , Y 反1-i -Y 反2-i ) calculate the angle between the two space angles and record γ i =β i -α i , unit: arc second.

[0066] Step 6: Using formula γ i -γ0 calculates the angle change △, which is the optical axis drift of the infrared sight 8 before and after the temperature change.

[0067] The accuracy of this embodiment will be affected by the error introduced by the temperature effect of the tooling flange 3 itself, which is related to the design capability of the tooling flange 3 itself.

[0068] Example 3

[0069] like Figure 3The test system layout based on a vibration-isolating structure is designed for situations where the optical platform cannot stably support the target and infrared collimator. To ensure the spatial stability of first reflector 13 in a highly cluttered experimental environment with frequent personnel movement, this embodiment utilizes a load-bearing wall or a vibration-isolating structure 9 within the workshop to mount first reflector 13, ensuring absolute stability. The test procedures, data processing, and evaluation methods of either Example 1 or Example 2 can be selected based on the required measurement accuracy of the infrared sight 8.

[0070] The main factors affecting the test accuracy of the method of the present invention include the aiming accuracy of the measuring device e1, the influence of the reference plane reflector e2, the influence of atmospheric thermal effect on the optical path e3, the influence of the observation window e4, and the influence of the test environment temperature change and vibration on the target position and the measuring device e5. The total accuracy of the system is the combined result of the various influences.

[0071] The following is an analysis of the test accuracy of the method of the present invention:

[0072] a) The aiming accuracy of the device is the device's own measurement accuracy. Here, e1 = 0.5" is introduced by the TM6100A theodolite.

[0073] b) The deviation of the reference plane reflector is mainly due to the deviation of the aiming point caused by the change of the surface shape, which is calculated by the formula Calculation, d is the aiming point offset caused by vibration and temperature effects. Taking a 30mm diameter reflector as an example, referring to the measured value, the estimated maximum offset is 6mm. R is the equivalent curvature radius of the plane mirror, using the formula Calculation, D = 30mm, h is the plane mirror type deviation, use the formula Calculation, N is the aperture number, calculated according to the limit value N = 2, λ is the test wavelength, here λ = 632.8nm. The limit state deviation is Usually, during the measurement process, considering that the vibration is large and the randomness is strong in the high and low temperature box, the deviation value is considered to be uniformly distributed, and the total influence of the plane reflector used for the reference is

[0074] c) Atmospheric thermal effect is mainly caused by the temperature characteristics of the gas refractive index on the light. According to the basic principle of light refraction when it propagates in different media, when the refractive index of the gas in the high and low temperature box changes, it will inevitably cause the optical axis to shift. According to the temperature characteristics of the air refractive index, under standard atmospheric pressure, when the temperature is t, the refractive index of air n t It can be expressed as: t -1=(n 15 -1)[1.0549 / (1+0.00366t)], where n15 is the refractive index of air at 15°C, and its value is expressed as a function of wavelength λ as follows: (n 15 -1)×10 8 =8342.1+2406030 / (130-υ 2 )+15996 / (38.9-υ 2 ), where υ = 1 / λ (λ is expressed in microns). Taking the long-wave infrared band as an example, λ = 10μm, the refractive index of air at 55℃ and -40℃ is calculated as follows: n 55 =1+2.39×10 -5 , n -40 =1+3.37×10 -5 According to the law of refraction, through calculation, under the condition of uniform air, the optical axis deviation caused by the change of air refractive index is about 0.01mrad. Taking into account the influence of the unevenness and humidity of the air in the high and low temperature box, it is estimated that the maximum deviation introduced by the change of air refractive index is Δ=6". According to the uniform distribution, the influence of atmospheric thermal effect on the optical path is statistically analyzed.

[0075] d) The influence of the observation window is related to the form of the window used. The present invention uses a plastic film (polystyrene film, hereinafter referred to as plastic film) as an infrared window. Its advantage is that the plastic film is relatively thin (the original thickness is d = 0.02mm, and after improvement, the thickness has reached 0.1mm). During the high and low temperature test, the refractive index and thickness of the plastic film change due to temperature changes, which has little effect on the optical axis. The disadvantage is that the transmittance is low and it is easily affected by vibration. Considering that the transmittance requirement for the optical axis stability test is not very high, the following mainly analyzes the influence of temperature change on the optical axis and the influence of vibration on the optical axis. According to the law of refraction: n1sinθ1 = n2sinθ2, where n1, n2 are the refractive indices, θ1, θ2 are the angles between the incident light and the normal and the angles between the refracted light and the normal, respectively, such as Figure 6 As shown;

[0076] Since the optical axis and the plastic film cannot always be perpendicular, assuming that the incident light forms an angle θ1 with the normal of the plastic film, after refraction through the plastic film, the outgoing light is parallel to the incident light, but has undergone a translation shift of Δd = d(tanθ1 - tanθ2). The temperature effect of plastic film is mainly manifested in two aspects: one is the change in thickness, and the other is the change in refractive index;

[0077] According to the reference material, the thermal expansion coefficient of plastic film is α=7×10 -5 / K, assuming that the temperature change ΔT = 67K, the thickness change is: δ1 = α·d·ΔT = 9.4×10 -8m, this change is very small. Due to the small thickness of the plastic film, the uneven thermal expansion caused by the temperature gradient and the optical axis deviation caused by the gradient refractive index are also relatively small. Therefore, the uncertainty of the influence of high and low temperature environments on the plastic film window can be ignored.

[0078] The vibration of the window film caused by high and low temperature operation causes the incident angle to change, and due to the irregularity and unevenness of this change, the reflected light is offset. It is complicated to analyze the size of the offset. In this case, the uncertainty introduced by it can be analyzed through experimental methods. Test method 1: At room temperature, use a theodolite to align the cross image reflected by the reflector, and then artificially vibrate the window and apply different pressures to deform the window film, and the aligned cross image is offset (obviously, this artificial effect is much larger than the offset caused by the vibration of the high and low temperature box). Use a theodolite to test the offset. 8 tests were conducted, and the test results were: 3", 2", 4", 2", 3", 0", 3", 2", and the average deviation was: 2.37". Test method 2: Use two theodolites to conduct a sight test through the windows of the high and low temperature box, such as Figure 2 As shown, two theodolites were aligned at room temperature. The temperature of the high and low temperature box was then set to 55°C and -40°C respectively. The effect of the box vibration on the alignment of the theodolite crosshairs during the heating and cooling process was investigated. After two rounds of tests, it was found that the deviation of the theodolite crosshairs due to the vibration of the window was very small during the entire process, generally not exceeding 3". Based on the above tests and experience, it was determined that the maximum deviation caused by the vibration of the window film was △ = 5". According to the normal distribution, the effect of the film as the window on the observation is statistically analyzed.

[0079] e) The impact of test environment temperature changes and vibrations on target position and measurement equipment refers to the impact of the test environment on the test system. These factors mainly include changes in ambient temperature and humidity, environmental vibrations (mainly foundation vibration and acoustic vibration), and atmospheric disturbances caused by test personnel during activities. These factors can cause slight changes in the optical axis position of the infrared collimator and the position of the observed target, and can also affect the alignment accuracy of the TM6100A theodolite.

[0080] The Class B evaluation method is used for the slight changes in the optical axis position of the infrared collimator and the position of the observed target. Within an effective test period (here 8 hours), based on the working characteristics of the test device and system, the deviation limit of the optical axis position of the infrared collimator is estimated to be ±0.5", and the deviation limit of the observed target position is ±3". According to the normal distribution, at this time

[0081] The impact of the environment on the alignment accuracy of the TM6100A theodolite was evaluated by moving the TM6100A theodolite back and forth, cross-aligning it with a target. The results were calculated using the Class A evaluation method. Measurement method: A reference reflector 1, representing the target position, and a second reflector 25 were placed in a temperature test chamber. The TM6100A theodolite was used to measure the angle α of the first reflector 13 and the angle β of the target reflector 2, respectively. The included angle γ was calculated as β - α. The change in included angle γ was evaluated by moving the TM6100A theodolite back and forth. The measurement was repeated 10 times, and the deviation Δ was calculated.

[0082]

[0083]

[0084] Statistics -45℃ standard deviation: σ x =2.41″,σ y =1.61″, the repeated measurement deviation is:

[0085] Statistics -20℃ standard deviation: σ x =1.66″, σ y =1.43″, the repeated measurement deviation is:

[0086] Statistical standard deviation at +35℃: σ x =1.50″,σ y =1.70″, the repeated measurement deviation is:

[0087] Statistical standard deviation at +65℃: σ x =2.10″,σ y =1.12″, the repeated measurement deviation is:

[0088] According to the normal distribution,

[0089] The total impact of the test environment on the test system is:

[0090] f) The total accuracy of the system is the result of the synthesis of various influences:

[0091]

[0092] The test accuracy of the present invention is completed based on a general temperature test inspection environment, and has good environmental adaptability and high versatility.

Claims

1. A device for testing the thermal stability of the optical axis of an infrared sight, characterized by: The test device comprises an optical platform (1), an infrared collimator (2), a target (3), a temperature test chamber (4), a tooling flange (5), a theodolite (6), an image acquisition and display device (7), an infrared sight (8), a first reflector (13) and a second reflector (25); along the direction of the light, the theodolite (6) is located between the optical platform (1) and the temperature test chamber (4) and is used to measure the change in the angle between the first reflector (13) and the second reflector (25) under different temperature conditions; the infrared collimator (2) is installed on the optical platform (1), and the target (3) is installed on the side hole of the infrared collimator (2). The first reflector (13) is installed at the target (3) as a reference mirror representing the target (3), or the first reflector (13) is attached to the chassis shell of the infrared parallel light tube (2), or the first reflector (13) is installed on the wall of the vibration isolation building (9); the temperature test box (4) is used to provide different temperatures, the second reflector (25) and the infrared sight (8) are fixedly connected to the tooling flange (5) and placed in the temperature test box (4), and the second reflector (25) serves as a reference for the infrared sight (8); the image acquisition and display device (7) is used to connect to, acquire and display images of the infrared sight (8).

2. The testing device according to claim 1, wherein: The theodolite (6) adopts the TM6100A theodolite.

3. The testing device according to claim 1, wherein: The infrared window of the infrared sight is made of polystyrene film.

4. The testing device according to claim 3, wherein: The thickness of the polystyrene film is 0.1 mm.

5. A method for testing the thermal stability of the optical axis of an infrared sight, characterized in that: The method uses the testing device for thermal stability of the infrared sight optical axis as claimed in claim 1, and the testing steps include: Step 1: Under the initial temperature condition, first aim the infrared sight (8) at the center or near the target (3), and read the coordinate position of the center of the infrared sight (8) relative to the target (3) through the image acquisition and display device (7), that is, the initial position of the optical axis, and record it as (X0, Y0), unit: pixel; Step 2: Then, use the theodolite (6) to aim and measure the spatial angles of the optical axes of the first reflector (13) and the second reflector (25), and read the angle between the spatial angles of the two, and record it as (α0, β0), in units of arc seconds; Step 3: applying temperature changes to the infrared sight (8), the tooling flange (5), and the second reflector (25) to a test target temperature change range through a temperature test chamber (4), during which the infrared sight (8) does not operate; Step 4: Turn on the infrared sight (8), and read the coordinate position of the center of the infrared sight (8) relative to the target (3) through the image acquisition and display device (7), that is, the total change position of the optical axis, and record it as (X i , Y i ), unit: pixel; Step 5: Use the theodolite (6) to aim and measure the spatial angles of the optical axes of the first reflector (13) and the second reflector (25), and read out the angle between the two spatial angles, and record it as (α i , β i ), unit: arc second; Step 6: Based on the data recorded in steps 1 and 4, the relationship is as follows: ， in: is the transformation matrix, For the measurement results, For the quantity to be sought, ; The data obtained in steps 2 and 5 are then used to calculate ; Compared with the measurement results (α i , β i ) is related to (α0, β0) and can be solved by the following relationship: ， in: is the field of view of the infrared sight (8), and are the number of pixels in the horizontal and elevation directions of the detector of the infrared sight (8), respectively.

6. A method for testing the thermal stability of the optical axis of an infrared sight, characterized in that: The method uses the testing device for thermal stability of the infrared sight optical axis as claimed in claim 1, and the testing steps include: Step 1: Under the initial temperature condition, first aim the infrared sight (8) at the center of the target (3); Step 2: Then use the theodolite (6) to aim and measure the angles of the first reflector (13) and the second reflector (25), respectively, and record them as α0 (X 反1-0 , Y 反1-0 ), β0(X 反2-0 , Y 反2-0 ), and use the formula (β0-α0) = (X 反1-0 -X 反2-0 , Y 反1-0 -Y 反2-0 ) Calculate the angle γ0 between the two space angles and record it as γ0=β0-α0, unit: arc seconds; Step 3: applying temperature changes to the infrared sight (8), the tooling flange (5), and the second reflector (25) to a test target temperature change range through a temperature test chamber, during which the infrared sight (8) does not operate; Step 4: Turn on the infrared sight (8) and aim the infrared sight (8) at the center of the target (3) again; Step 5: Use the theodolite (6) to aim and measure the angles of the first reflector (13) and the second reflector (25), respectively, and record them as α i (X 反1-i , Y 反1-i ), β i (X 反2-i , Y 反2-i ), and use the formula (β i -α i ) = (X 反1-i -X 反2-i , Y 反1-i -Y 反2-i ) calculate the angle γ between the two space angles i , record γ i =β i -α i , unit: arc second; Step 6: Use the formula △=γ i -γ0 is used to calculate the angle variation △, which is the optical axis drift of the infrared sight (8) before and after the temperature change.

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