CN113720805B - Method for detecting dust and dirt radiation transmittance of lens of external field photoelectric detection system - Google Patents

Abstract

The invention provides a method for detecting dust and stain radiation transmittance of a lens of an external field photoelectric detection system. In order to ensure the consistency of target radiation data of the photoelectric detection system, the influence of dust and dirt on the lens on the radiation transmittance of the detection system is required to be detected. According to the invention, the sunny sky background light is used as a short-time stable surface radiation source of the external field photoelectric detection system, the photoelectric detection system is fixedly aligned to a certain direction far away from the sun, the detection system respectively performs data acquisition before and after dust and dirt removal, and the radiation difference of the detection system in the same sky area is compared, so that the influence of the dust and dirt on the radiation transmittance of the detection system of the lens is accurately calculated. According to the test method, a clear sky background is used as a short-term radiation stable light source, the requirements on using conditions of an external field are low, using equipment is simple, and the efficiency and the applicability of the external field radiation detection of the optical system are effectively improved.

Description

A method for detecting radiation transmittance of dust and stains on lens of an outdoor photoelectric detection system

Technical Field

The invention relates to the technical field of outdoor optical radiation measurement, and in particular to a method for detecting radiation transmittance of dust and stains on a lens of an outdoor photoelectric detection system.

Background technique

In the field of field optical radiation measurement technology, the long-term consistency of the state of the photoelectric detection system is the key to ensuring the accuracy of the data throughout the measurement cycle. During the transportation, installation and long-term use of optical instruments in the field, a certain amount of dust, stains and sand will adhere to the lens of the photoelectric detection system, which will inevitably affect the target detection and inversion of the system in the field. In order to ensure the consistency and accuracy of the measurement data of the photoelectric detection system, it is necessary to detect the influence of dust and stains on the lens on the radiation transmittance of the detection system.

At present, the radiation detection method mainly uses a stable surface light source system for optical radiation measurement, mainly including integrating sphere systems, standard lamp-diffuse reflection plate systems, and sun-diffuse reflection plate and other light sources, for example, a light source system with adjustable spectral distribution based on LED (patent CN100590350C). Although these measurement methods and means are relatively mature, their high requirements for the aperture, field of view and other indicators of the photoelectric detection system to be measured have great limitations on the field measurement of optical systems, making it difficult to meet the requirements of convenience and real-time performance of field radiation detection, and limiting the efficiency of radiation detection of optical systems. Therefore, based on the demand for radiation consistency detection of the state of an outdoor optical system, it is necessary to study a method with strong applicability, simple operation, and high measurement accuracy.

Summary of the invention

In order to overcome the shortcomings of the existing technology in the radiation consistency detection of the external field optical radiation measurement system, the present invention provides a method for quickly and accurately detecting the dust and stains on the lens of the external field photoelectric detection system by using the clear sky background light.

The technical solution adopted by the present invention to solve the technical problem is as follows:

The present invention discloses a method for detecting radiation transmittance of dust and stains on a lens of an outdoor photoelectric detection system. The sky background radiation measuring device used comprises: a mechanical fixing device, a photoelectric detection system to be tested and a computer control system. The working band of the photoelectric detection system to be tested covers 350nm to 1100nm. The field of view of the photoelectric detection system to be tested is less than 5 degrees. The method is characterized in that the method comprises the following steps:

Step I: Select the daytime test time, test location, optical axis pointing direction and sky selection area of the photoelectric detection system. The sky background area should be cloudless, windless and clear, and there should be no obstructions around the observation area. Use a mechanical fixture to point the photoelectric detection system to a certain sky area away from the sun. The optical axis of the photoelectric detection system should point to the side facing away from the sun. When measuring the sky radiation of the photoelectric detection system, the angle between the optical axis of the detection system and the sun should be greater than 40 degrees, the angle between the optical axis and the solar azimuth should be greater than 90 degrees, and the solar zenith angle should be less than 80 degrees.

Step II: According to the pointing position of the photoelectric detection system in step I, before removing the dust and stains, the photoelectric detection system performs dark background measurement, and then the photoelectric detection system continuously collects data from a fixed area of the sky, once every 2 minutes, for a total of 5 times, and records the corresponding data collection time. The response value C(λ,T _i ) of the photoelectric detection system is:

C(λ,T _i )＝C_信(λ,T _i )-C_暗(λ,T _i ) (1)

Where, _Ti is the time of the i-th observation, λ is the observation wavelength, _Csignal (λ, _Ti ) is the signal code value measured by the photoelectric detection system, and _Cdark (λ, _Ti ) is the dark background code value measured by the photoelectric detection system;

Step III: After the photoelectric detection system collects data in step II, remove the dust and stains on the lens immediately to make the lens clean and dry. The time interval for removing the dust and stains on the lens should be controlled within 1 minute. Then the photoelectric detection system collects data from the same sky area, once every 2 minutes, for a total of 5 times, and records the corresponding data collection time. After completing the above test content, perform dark background measurement of the photoelectric detection system. The time interval ΔT between two adjacent tests before and after the lens dust and stains are removed is:

ΔT = T ₁ ^after - T ₅ ^before (2)

^Among them, _T5before is the fifth measurement time before wiping off the dust and stains on the lens, ^and _T1after is the first measurement time after wiping off the dust and stains on the lens;

Step IV: Based on the measurement data of Step II and Step III, obtain the change of sky background radiation within 10 minutes before and after the lens dust stains are removed, calculate the time change rate of sky background radiation, and establish the linear response relationship between the photoelectric detection system response _Ci (λ, T) and time _Ti :

Where i represents the i-th sky background light measurement, It represents the response value measured at the moment T _i ^before the lens stain is wiped off, /> represents the measured response value at time _Ti ^after the lens stains are wiped off, _abefore (λ) and _aafter (λ) are the time radiation change rates before and after the lens stains are wiped off, and the average time radiation change rate a(λ) before and after the lens is wiped off is:

Step V: Based on the calculation results of step IV, calculate the relative radiation change Γ(λ,ΔT) of the sky background light in the photoelectric detection system in the same sky area before and after the dust stains are removed:

Γ(λ,ΔT)＝a(λ)ΔT (6)

Step VI: Based on the relative radiation change Γ(λ,ΔT) of the sky background light before and after the lens dust stains are removed obtained in step V, accurately calculate the radiation effect of the lens dust stains on the external field photoelectric detection system, that is, the effect of the dust stains on the spectral transmittance of the optical system for:

^Among them, _T1after is the first measurement time after the dust and stains on the lens are removed, ^and _T5before is the fifth measurement time before the dust and stains on the lens are removed.

Compared with the prior art, the beneficial effects of the present invention are as follows: the sky background radiation is the natural light source of the earth, which is the comprehensive result of the scattering and refraction of sunlight and ground reflected light by the atmosphere around the earth. The sunny background sky light is used as a short-term radiation stable surface light source, and the radiation measurement is performed before and after the dust stains are removed from the lens of the external field photoelectric detection system to solve the problem of dust stains affecting the consistency and accuracy of data in the external field long-term radiation measurement. The field use conditions and equipment of the detection method are relatively simple, suitable for optical equipment of various calibers, and can perform simple, fast, effective and high-precision measurements on the photoelectric detection system, effectively improving the efficiency and applicability of radiation transmittance detection.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a sky background radiation measurement system of the photoelectric detection system of the present invention.

FIG. 2 is a diagram showing a method for measuring sky background radiation of a photoelectric detection system in the present invention.

Detailed ways

In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to the accompanying drawings and in combination with embodiments.

The present invention discloses a method for detecting the radiation transmittance of dust and stains on the lens of an outdoor photoelectric detection system. In the method of the present invention, as shown in FIG1 , the sky background radiation measuring device used comprises: a mechanical fixing device, a photoelectric detection system to be tested, and a computer control system. The working band of the photoelectric detection system to be tested covers 350nm to 1100nm, and the field of view of the photoelectric detection system to be tested is less than 5 degrees. The specific implementation requires the following 6 steps.

Step I: Select the daytime test time, test location and sky observation area of the photoelectric detection system. The sky radiation observation time of the photoelectric detection system is around 12:00 noon. There is no obstruction around the observation area. The photoelectric detection system is pointed to a certain sky area away from the sun by a mechanical fixing device. At this time, the sky background area is cloudless, windless and clear. As shown in Figure 2, the zenith angle _β1 corresponding to the sky observation area is about 20 degrees, the azimuth angle _α1 is about 12 degrees, the zenith angle _β2 of the sun is about 51 degrees, and the azimuth angle _α2 is about 192 degrees. Relative to the ground observation point, the angle between the sky observation area and the sun is about 60 degrees, and the angle _α2 - _α1 between the sky observation area and the sun's azimuth is about 180 degrees.

Step II: According to the pointing position of the photoelectric detection system in step I, before removing the dust and stains, the photoelectric detection system performs dark background measurement and collects 50 frames. Then the photoelectric detection system continuously collects data from a fixed area of the sky, once every 2 minutes, 50 frames each time, for a total of 5 times, and records the corresponding data collection time. The response value C(λ,T _i ) of the photoelectric detection system is:

C(λ,T _i )＝C_信(λ,T _i )-C_暗(λ,T _i ) (1)

Wherein, _Ti is the time of the ith observation, λ is the observation wavelength, _Csignal (λ, _Ti ) is the average signal code value of multiple frames of data measured by the photoelectric detection system, and _Cdark (λ, _Ti ) is the dark background code value measured by the photoelectric detection system.

Step III: After the photoelectric detection system collects data in step II, remove the dust and stains on the lens immediately to make the lens clean and dry. The time interval for removing the dust and stains on the lens is controlled within 1 minute. Then the photoelectric detection system collects data from the same sky area, once every 2 minutes, 50 frames each time, a total of 5 times, and records the corresponding data collection time. After completing the above test content, perform dark background measurement of the photoelectric detection system, collect 50 frames, and the time interval ΔT between two adjacent tests before and after the lens dust and stains are removed is:

ΔT = T ₁ ^after - T ₅ ^before (2)

Among ^them , _T5before is the fifth measurement time before wiping off the dust and stains on the lens, ^and _T1after is the first measurement time after wiping off the dust and stains on the lens.

Step IV: Based on the measurement data of steps I and II, obtain the change of sky background radiation within 10 minutes before and after the lens dust stains are removed, calculate the time change rate of sky background radiation, and establish the linear response relationship between the photoelectric detection system response _Ci (λ, T) and time _Ti :

Where i represents the i-th sky background light measurement, It represents the response value measured at the moment T _i ^before the lens stain is wiped off, /> represents the measured response value at time _Ti ^after the lens stains are wiped off, _abefore (λ) and _aafter (λ) are the time radiation change rates before and after the lens stains are wiped off, respectively. The average time radiation change rate a(λ) before and after the lens is wiped off is:

Step V: Based on the calculation results of step IV, calculate the relative radiation change Γ(λ,ΔT) of the sky background light in the photoelectric detection system in the same sky area before and after the dust stains are removed:

Γ(λ,ΔT)＝a(λ)ΔT (6)

Step VI: Based on the relative radiation change Γ(λ,ΔT) of the sky background light before and after the lens dust stains are removed obtained in step V, accurately calculate the radiation effect of the lens dust stains on the external field photoelectric detection system, that is, the effect of the dust stains on the spectral transmittance of the optical system for:

^Among them, _T1after is the first measurement time after the dust and stains on the lens are removed, ^and _T5before is the fifth measurement time before the dust and stains on the lens are removed.

Obviously, the above embodiments are only examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims (1)

1. A method for detecting dust and dirt radiation transmittance of a lens of an external field photoelectric detection system comprises the following steps of: the detection method is characterized by comprising the following steps of:

Step I: selecting daytime test time, test positions, optical axis pointing directions and sky selection areas of the photoelectric detection system, wherein the sky background areas are cloud-free, wind-free and clear sky, the surroundings of the observation areas are free from shielding, the photoelectric detection system is pointed to a certain sky area far away from the sun by using a mechanical fixing device, the optical axis pointing directions of the photoelectric detection system are opposite to the sun, when sky radiation of the photoelectric detection system is measured, the included angle between the optical axis pointing directions of the detection system and the sun is larger than 40 degrees, the included angle between the optical axis pointing directions and the sun azimuth angle is larger than 90 degrees, and the solar zenith angle is smaller than 80 degrees;

Step II: according to the pointing position of the photoelectric detection system in the step I, before dust and dirt are removed, the photoelectric detection system performs dark background measurement, then the photoelectric detection system continuously collects data of a sky fixed area for 1 time every 2 minutes, the data are collected for 5 times, the corresponding collection time of the data is recorded, and the response value C (lambda, T _i) of the photoelectric detection system is as follows:

C(λ,T_i)＝C _{Letter (letter)} (λ,T_i)-C _{Dark and dark} (λ,T_i) (1)

Wherein, T _i is the time of the ith observation, lambda is the observation wavelength, C _{Letter (letter)} (λ,T_i) is the signal code value measured by the photoelectric detection system, and C _{Dark and dark} (λ,T_i) is the dark background code value measured by the photoelectric detection system;

Step III: and (2) immediately removing dust and dirt from the lens after data acquisition of the photoelectric detection system in the step (II), enabling the lens to be clean and dry, wherein the time interval for removing the dust and dirt from the lens is controlled within 1 minute, then the photoelectric detection system acquires data of the same sky area for 1 time every 2 minutes, acquires the data for 5 times in total, records corresponding data acquisition time, and performs dark background measurement of the photoelectric detection system after the test contents are finished, and the time interval delta T between two adjacent tests before and after the dust and dirt from the lens is erased is as follows:

ΔT＝T₁ ^{Rear part (S)} -T₅ ^{Front part} (2)

wherein, T ₅ ^{Front part} is the 5 th measurement time before the dust and dirt of the lens are erased, and T ₁ ^{Rear part (S)} is the 1 st measurement time after the dust and dirt of the lens are erased;

Step IV: according to the measurement data of the step II and the step III, the sky background radiation change quantity within 10 minutes before and after the removal of dust and dirt on the lens is obtained, the sky background time radiation change rate is calculated, and the linear response relation between the response C _i (lambda, T) of the photoelectric detection system and the time T _i is established:

wherein i represents the ith sky backlight measurement, The measured response value of T _i ^{Front part} before the lens stain is erased is expressed as/>The measured response values at time T _i ^{Rear part (S)} after the lens stain is erased, and a _{Front part} (λ) and a _{Rear part (S)} (λ) are the time radiation change rates before and after the lens stain is erased, respectively, and the average time radiation change rate a (λ) before and after the lens stain is erased is:

Step V: according to the calculation result of the step IV, calculating the relative radiation variation gamma (lambda, delta T) of sky backlight in delta T time before and after dust and stain removal of the photoelectric detection system in the same sky area as follows:

Γ(λ,ΔT)＝a(λ)ΔT (6)

step VI: according to the relative radiation variation gamma (lambda, delta T) of the background light of the sky before and after removing the dust and dirt of the lens obtained in the step V, accurately calculating the radiation influence of the dust and dirt of the lens on the external field photoelectric detection system, namely the spectral transmittance influence of the dust and dirt on the optical system The method comprises the following steps:

Wherein, T ₁ ^{Rear part (S)} is the 1 st measurement time after the lens dust spot is removed, and T ₅ ^{Front part} is the 5 th measurement time before the lens dust spot is removed.