RU2293959C2 - Laboratory-scale plant for temperature tests of military optoelectronic instruments - Google Patents

Abstract

FIELD: devices of experimental determination of the characteristics of optoelectronic instruments at simulation of service conditions.

SUBSTANCE: the laboratory-scale plant for temperature tests has a long-focus collimator, optical bench, place for fastening of optoelectronic instruments to be tested, source of temperature actions, temperature recording device, timer, computer.

EFFECT: experimental determination of variations of the characteristics of optoelectronic instruments at temperature actions in the process of functioning or simulation of service conditions.

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Description

The invention relates to devices for the experimental determination of the characteristics of optoelectronic devices (OED) in simulating operating conditions and can be used in military equipment.

In accordance with GOST 16504-81, tests are understood as the experimental determination of parameters and quality indicators of products during operation or when simulating operating conditions. Tests are carried out using the necessary test equipment and measuring instruments to study certain dependencies between the maximum permissible values of the design parameters of optoelectronic devices under temperature influences and the values of their functioning modes [3].

The instability of the devices is associated with the impact on the environment and with the changes occurring in the devices. The climatic factors have a significant impact on the operation of the EIA: temperature, humidity, atmospheric pressure, solar radiation, wind load. The influence of temperature changes is one of the most significant destabilizing factors of work.

Typically, EPPs are operated in the temperature range of -50 ° С ... + 50 ° С. In some cases, it is necessary to ensure the operation of devices in extreme conditions. Experience in the combat use of artillery devices shows that the temperature range in which the EIA has to work is very wide. In tropical areas, the air temperature reaches + 55 ° C, with direct exposure to the sun, the temperature of the heated surface can be significantly higher [5]. As a result of this, the characteristics of the devices may go beyond the permissible limits, which, ultimately, affects the accuracy of artillery fire.

A special place in this case belongs to the temperature effects on the devices. The experience of the combat use of artillery optoelectronic devices (OEDs) in mountainous and desert areas has shown that they have limited use in conditions of exposure to extreme temperatures. So, for example, failures of 1D13 quantum rangefinders, the frustration of DS-1 (M) stereoscopic rangefinders were observed, and the characteristics of the devices changed dramatically.

The temperature effect causes a displacement of the image plane of the optical system, a change in its focal length, and, consequently, an increase in the system or image scale, a change in aberrations.

The change in temperature of parts and devices of the device is caused by changes in the conditions surrounding the device and the electrical energy released in the device. Warming up occurs until the thermal equilibrium of the device with the environment is established. The time to establish thermal equilibrium characterizes the thermal inertia of the device.

Existing instrumentation for climate testing and determining changes in the characteristics of optoelectronic devices does not allow to establish the dependence of changes in the characteristics of the EIA on the magnitude and rate of change of temperature parameters [3, 5].

Therefore, experimental studies of the temperature effect on elements, components and, as a consequence, on the characteristics of optoelectronic devices were carried out with the aim of establishing certain relationships between the maximum allowable design parameters of optoelectronic devices and the values of their temperature functioning modes - to establish a range that allows the use of the device on the purpose and establishment of the damage threshold value for making a decision on sending the instrument to rem nt.

The test task (measuring the characteristics of optoelectronic devices) was solved in several stages [2]:

- consideration of physical models and the results of the interaction of thermal effects with optical (semiconductor) materials and elements of optoelectronic devices;

- selection of measuring equipment and the creation of a laboratory setup for measuring the characteristics of optoelectronic devices;

- conducting research and processing the results of physical modeling of the application of devices.

Laboratory installation for temperature testing of military optoelectronic devices

Purpose of the laboratory setup:

- assessment of the relationship of the main optical characteristics of devices with parameters of temperature effects;

- the establishment of certain relationships between the maximum permissible values of the design parameters of optoelectronic devices and the values of the modes of their functioning.

When selecting measuring equipment and creating a laboratory setup for measuring the characteristics of optoelectronic devices, the standard equipment of the OSK-3 optical bench, the UKNP-1 equipment kit, etc. were widely used.

To measure the general optical characteristics of the EIA, general-purpose adjustment and adjustment devices were used [2]:

- wide-angle collimator PZ ^a - to check the eccentricity of the center of the grid relative to the diaphragm and the magnitude of the field of view of the device;

- a telescope with a UNOA level with a longitudinal and transverse level (division price of a longitudinal level of 30 '') for level adjustment;

- tube-dynamometer UDT-1 - to check the diameter of the exit pupil of the device;

- a device for checking the magnetic moment of the shooter of landmark-compasses L-76;

- adjusting goniometer South - to check the dead moves of mechanisms;

- control level type submarine.

Calibration of KY devices was carried out once every 6 months. The composition of the laboratory setup (figure 1):

1 - tested optoelectronic device;

2 - telephoto collimator with a place for installing test objects (world), for checking optical instruments, mounted on the OSK bench instead of the UKNP-1 collimator;

3 - test objects (worlds);

4 - source of incoherent radiation (incoherent polychromatic emitter - type L4-A searchlight; source of coherent radiation - laser);

5 - optical bench;

6 - control equipment (block);

7 - auxiliary equipment (kilovoltmeter indicator, diopter tube, binocular tube, electric test stand, electric current source B5-47, a set of test objects in the frame, Y117 light meter, YaRM-3 photometer, autocollimation microscope, control mirror);

8 - a universal place for mounting devices, since the set of equipment UKNP-1 is designed to mount a limited number of night devices;

9 - a timer with a button for recording the time course of processes;

10 - recording equipment and computers used for data processing according to the proposed methodology.

However, not all equipment was fully suitable for the purpose of studying the influence of temperature effects on devices, therefore it was additionally manufactured or used in a new quality:

11 - a source of temperature effects - an incandescent lamp with a power of 1000 W;

12 - fan;

13 - honeycomb lattice, tightly adjacent to the perforated lattice, to create uniform velocities of the temperature medium along the cross-section (to exclude circulation), in which the device under study is installed;

14 - temperature recording device with sensors located at the output of the temperature source, on the surface and inside the instrument under study, combined with a computer.

To study the effect on sources with different wavelengths on the tested devices, a series (set) of interference filters is used, the passband of which is associated with the wavelengths of the corresponding laser.

The appearance of the laboratory for the study of the characteristics of optical and optoelectronic devices and control of measurement results is shown in figure 2 and 3, respectively.

The currently used instrumentation for climate testing allows you to measure the characteristics of optoelectronic devices after the end of temperature influences, which makes it impossible to establish the dependence of changes in the characteristics of devices on the magnitude and rate of change of temperature parameters in real time.

Work on the laboratory installation is carried out in the following sequence:

- for standard temperature conditions, the well-known methods determine the main characteristics of optoelectronic devices, first of all, the resolution (for test objects), the accuracy of leveling using bubble levels, the accuracy of measuring horizontal and vertical angles (magnitude of dead moves), the accuracy of measuring magnetic azimuths using a magnetic arrow, etc .;

- turn on the temperature source of the incandescent lamp 11. At the same time, the timer 9 is started by the button to record the time of the processes and the temperature recording device 14 with sensors located at the output of the temperature source 11, on the surface and inside the instrument 11. The timer 11 and the temperature registration device 14 are combined with recording equipment 10 and a computer used to process data in real time, according to the proposed methodology, and display data.

A comparison of the characteristics of optoelectronic devices measured under standard conditions with the characteristics obtained in the process of changes in temperature influences allows us to establish new relationships for the real time scale between the maximum allowable design parameters of optoelectronic devices and the values of the modes of their temperature functioning, for example, temperature inertia device or protective equipment (fins, thermostatic covers, ventilation, etc.). Comparison of permissible changes in the characteristics of devices with the obtained values allows us to develop requirements for the means of protection of devices and operating modes that allow the use of the device for its intended purpose and the establishment of a threshold value for temperature damage to decide on sending the device for repair.

METHOD FOR EVALUATING TEMPERATURE IMPACTS ON OPTICAL-ELECTRONIC INSTRUMENTS

Improving the effectiveness of ground artillery firing can be achieved by maintaining the characteristics of optoelectronic devices (OED) within specified limits. The analysis carried out in [1] allows one to establish the tolerance for changes in the main characteristics of optical devices, which allows for firing based on the complete preparation of the initial data (Table 1).

Table 1
Tolerance of the main characteristics of optical instruments No. Characteristics Legend Tolerance of changes one Increase R ± 5% G 2 Corner field 2ω ± 5% 2ω 3 Exit pupil diameter d _out 10% four Exit pupil removal R' 10% 5 Resolution φ ± 20% 6 Light transmittance τ 0.15

Due to direct solar radiation, temperature, humidity, atmospheric pressure, wind load, and other climatic factors, it is possible that the characteristics of devices go beyond the tolerances indicated in Table 1, which ultimately affects the accuracy of artillery fire.

In this case, a special place belongs to the temperature effects on the devices, which causes the image plane of the optical system to move, its focal length to change, and consequently, to increase the system or image scale, and change aberrations.

When the temperature changes, the refractive index of the optical medium changes according to the law:

n = n ₀ + β (tt ₀ ),

where n ₀ is the refractive index at a temperature t ₀ ;

β is the increment coefficient of the refractive index.

The linear parameters of optical parts (thickness, radius of curvature) change as:

d = d ₀ [1 + α (tt ₀ )];

τ = τ ₀ [1 + α (tt ₀ )],

where d ₀ and τ ₀ - the value of the thickness and radius of curvature at a temperature t ₀ ;

α is the coefficient of expansion of the lens material.

Changing the focal length of an infinitely thin lens

where Δt = tt ₀ is the temperature difference.

To calculate the change in df 'caused by the change in temperature Δt, one can use well-known formulas for complex, but infinitely thin optical systems that describe chromatic aberrations of position and magnification.

For an infinitely thin component in the air, the following formulas are valid:

where ΔS 'is the displacement of the image plane caused by a change in temperature Δt;

i is the lens number in the kit;

Δl 'is the displacement of the point of movement of the main beam with the image plane caused by a change in temperature;

y is the height of the intersection of the main beam with the infinitely thin component;

l 'is the height of the intersection of the main beam with the plane;

n _i is the refractive index of the material from which the lens is made;

S 'is the distance from the image to the lens;

φ _i = F · Ф _i - reduced optical power;

F is the focal length of the entire system;

F _i - the optical power of the i-th lens.

The deviation of the ray ε from the initial (before the temperature changes) direction is determined by the formula

The radius of curvature of the trajectory of the ray R is determined by the formula

The calculation results carried out according to this technique show that when the elements of the optical system are heated by 60 °, the position chromatism becomes noticeable (Table 2).

table 2
The results of calculating the change in the value of the chromaticity of the position in the optical system with temperature System Lens Specifications Temperature change Changes in the position chromatism 1. f '<500 mm; relative aperture 1:10; glass brand: K8 (f '= 210 mm); F1 (f '= - 365 mm) up to 60 ° 0.0075 mm 2. f '<500 mm; glass brand: K8 TF1 up to 60 ° 0.018 mm 3. f '= 500 mm; glass brand: TK17; TF4 up to 60 ° 0.06 mm

The decrease in image quality is associated with a temperature gradient in the volume of the part, which leads to a change in the shape of the surfaces of the parts. The most sensitive are the reflecting surfaces of mirrors and prisms and the inner surfaces of the lenses of non-glued lenses or the first components of telephoto lenses.

Finning the surface of the instrument housing

. Величина

для различных стекол имеет разный знак.The effect of temperature changes is evaluated by various indicators. In optical systems, this quantity is a change in the relative focal length

. Value

for different glasses has a different sign.

The fin surface of the housing is a system with convective heat removal. To improve heat removal from the external surface of the device to the environment, in some cases, an increase in the area of the external surface of the device due to cooling fins is used (such finning is used in the 1D13 range finder).

The processes underlying the use of this method are reflected by the Newton-Richmann formula

Q = αS (TT ₀ ),

where α is the experimental coefficient;

T, T ₀ - temperature, respectively, of the heat transfer surface of the cooling medium;

S is the heat transfer area.

It follows from the formula that the temperature difference between the cooled surface and the environment ΔT = Т-Т ₀ with a constant value of the heat flux Q is inversely proportional to the area of the cooling surface, i.e.

ΔT = Q / αS

However, in practice, the effect of an increase in the cooling surface due to the fins is less than expected. There are two reasons for this:

- the heat transfer coefficient α per unit of the fin surface turns out to be the less, the more emptiness between the ribs;

- the heat flux removed from the surface of the rib must overcome in this case the thermal resistance of the rib itself, depending on the thermal conductivity of its material.

These two reasons, as well as an increase in the mass of the device due to fins, put restrictions on the use of this method in instrumentation. But the most significant drawback of this method is the lack of protection from environmental influences.

From this analysis, we can conclude that the most appropriate way of thermal protection of regular artillery EIAs can be the use of light removable covers or additional heat-insulating plastic cases.

Information sources

1. Parkhomenko A.V. Theory and calculation of artillery optoelectronic devices: a Training manual. - Penza: PAII. 1999 .-- 256 s.

2. The basics of heat engineering. Burlov V.V., Partala S.V., Alchinov V.I. Tutorial. - Penza: PAII. 2003 - 231 s.

3. General guidance for the repair of missile and artillery weapons. Part 4. Repair of artillery optical and electron-optical devices. - M .: Military Publishing. 1982. - 144 p.

4. Reference designer of optical-mechanical devices. - M.: Mechanical Engineering, 1980. - 368 p.

5. Designing of optoelectronic devices: a Textbook. Ed. 2nd, rev. / Yu.B. Parvulyusov et al .; Ed. Yu.G. Yakushenkova. - M .: Logos, 2000 .-- 488 p.

6. Beglaryan V.Kh. Climatic tests of equipment and measuring instruments. - M.: Mechanical Engineering. 1983 .-- 160 p.

7. A.S. 371964 dated July 12, 71. Published on March 1, 73. Bulletin 13.

Claims (1)

Laboratory installation for temperature testing of military optoelectronic devices, including the tested optoelectronic device, telephoto collimator with a place for installing test objects (world), an optical bench, a universal place for attaching the tested optoelectronic devices, characterized in that it is additionally introduced a source of temperature effects, made in the form of an incandescent lamp, a fan with a honeycomb grill that fits snugly against the perforated grill, to create uniform speeds izzhizheniya temperature environment, a temperature recording device with sensors located at the output of the source of temperature exposure, on the surface and inside the tested optoelectronic device, and a timer with a button, necessary for recording the time of influence of temperature effects on the tested optoelectronic device, combined with a computer, in addition, the installation contains auxiliary equipment: an indicator - a kilovoltmeter, a diopter tube, a binocular tube, an electric current source B5-47, a test kit OBJECTS in a frame, the light meter YU117, NMR-3 photometer.

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