A method and device for protecting an optoelectronic measuring camera from strong light without loss of sensitivity

Abstract

The application provides a light protection method and device for a photoelectric measurement camera without sensitivity loss, aiming at the use requirement that the photoelectric measurement camera bears ten-minute strong light direct radiation in the state of starting, and applying a filter with a special spectrum design, while not affecting the sensitivity of the photoelectric measurement camera, the temperature of the detector is maximally reduced, the detector is protected from temporary failure and permanent damage caused by high temperature, and the service life of the photoelectric measurement camera is greatly prolonged. The method does not need to turn on and off the detector, can play a whole protection role for the photoelectric measurement camera, is suitable for most on-orbit strong light direct radiation conditions, significantly reduces the burden of orbit design, hardware design, algorithm design and the like, and has the characteristics of wide applicability, high feasibility and strong reliability.

Description

Technical Field

[0001] This invention relates to spacecraft attitude measurement technology, and in particular to a method and device for strong light protection of an optoelectronic measurement camera without sensitivity loss. Background Technology

[0002] Optoelectronic measuring cameras are a type of measuring instrument widely used in the aerospace field. They provide key information for the attitude control, orbit change, and navigation of spacecraft, and have advantages such as high precision, low cost, and strong anti-interference ability.

[0003] CMOS detectors are widely used in photoelectric measurement cameras, converting photons received by the optical lens into electrons through the photoelectric effect. When targets such as the sun, planets, or special space debris enter the camera's field of view, the strong light signal can place a great burden on the detector, potentially causing temporary malfunctions or, in severe cases, irreversible damage and permanent failure.

[0004] The apparent mechanism of detector failure due to strong light is thermal failure caused by high temperature, but the heat source can be divided into two parts. One part comes from the Joule heat generated by the photocurrent. When the number of converted electrons exceeds the full-well capacity of the pixel, the electrons cannot be bound by the potential and escape from the pixel potential well, overflowing into VDDPIX through the detector's leakage circuit, generating additional current. The other part comes from the radiant energy of the incident light. Strong light is focused by the optical lens and directly heats the detector surface.

[0005] High-light protection methods can be divided into active and passive protection. Active protection involves using orbital design or rotating mechanisms to prevent bright celestial objects from appearing in the field of view of the photoelectric measurement camera, or to shut down the detector when a bright celestial object appears in the field of view. Active protection is the most effective, but its application conditions are highly restrictive. For example, some satellite missions require the photoelectric measurement camera to withstand continuous exposure to strong light for more than ten minutes while powered on. In such cases, passive protection methods must be implemented at the hardware level.

[0006] Without altering the optical lens design, using filters to reduce the intensity of incident light is a simple and effective passive protection measure, and it's currently the mainstream approach. However, applying filters can severely impact the sensitivity of photoelectric measurement cameras. High-precision photoelectric measurement cameras have relatively small fields of view, and to ensure a sufficient number of measurement targets within the field of view, high sensitivity is typically required. Using filters necessitates extending the exposure time, sacrificing timeliness to maintain the camera's detection sensitivity. In conclusion, photoelectric measurement cameras with CMOS detectors as their core components currently lack a side-effect-free method for protecting against strong light. Summary of the Invention

[0007] The purpose of this invention is to provide a method and device for strong light protection of photoelectric measuring cameras without loss of sensitivity. The aim is to minimize the detector temperature and ensure the normal operation of the photoelectric measuring camera under strong light irradiation without affecting the detection sensitivity or timeliness.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] A method for protecting a photoelectric measuring camera from strong light without loss of sensitivity, the method comprising the following steps:

[0010] S1. Based on the quantum response efficiency curve of the detector of the photoelectric measurement camera, determine the non-zero response spectrum and the zero response spectrum of the detector;

[0011] S2, Design a target filter, wherein the transmittance of the target filter is 100% in the non-zero response spectral band and 0% in the zero response spectral band;

[0012] S3, the target filter is installed above the detector to protect the photoelectric measurement camera from strong light.

[0013] Furthermore, prior to step S1, the method further includes:

[0014] Based on the existing filter in the photoelectric measuring camera, calculate the actual temperature of the detector of the photoelectric measuring camera. If the calculated actual temperature is greater than the safe temperature of the detector, then proceed to step S1.

[0015] Furthermore, prior to step S3, the method further includes:

[0016] Based on the target filter, calculate the optimal temperature of the detector of the photoelectric measurement camera. If the optimal temperature is not greater than the detector's safe temperature, then proceed to step S3.

[0017] Furthermore, if the optimal temperature is greater than the detector's safe temperature, the target filter is redesigned so that its transmittance is also 0 in a portion of the non-zero response spectrum.

[0018] A high-light protection device for a photoelectric measuring camera without sensitivity loss, the device comprising:

[0019] A special spectral band design filter, wherein the transmittance of the special spectral band design filter is 100% in the non-zero response spectral band of the detector of the photoelectric measurement camera, and the transmittance is 0 in the zero response spectral band of the detector.

[0020] Fasteners are used to fix the specially designed spectral filter above the detector.

[0021] Furthermore, the fastener and the special spectral band design filter are fixed together by dispensing adhesive, and the special spectral band design filter is fixed together with the detector by dispensing adhesive.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] A filter with a specially designed spectral band achieves strong light protection for photoelectric measurement cameras without sensitivity loss. Based on the working principle of the photoelectric measurement camera detector, the heating effect of strong light on the detector is divided into two categories: photocurrent Joule heating and photothermal effect. For the first type of effect, photocurrent Joule heating, its essence originates from the photoelectric effect. The photocurrent originates from photons in the non-zero response spectral band of the detector and is positively correlated with sensitivity. Reducing the photocurrent inevitably leads to a decrease in sensitivity. Therefore, according to the detector's quantum response efficiency curve, the filter is designed to be fully passable in the non-zero response spectral band, i.e., with a transmittance of 100%. For the second type of effect, photothermal effect, its physical essence is radiative heat transfer and is not directly related to sensitivity. Reducing the incident light energy in some spectral bands does not affect sensitivity. Therefore, according to the detector's quantum response efficiency curve, the filter is designed to be fully filtered in the zero response spectral band, i.e., with a transmittance of 0%. By placing the filter designed above at any position in the optical path, such as in front of the detector or the optical lens, the incident strong light signal is preprocessed before reaching the detector, thereby protecting the photoelectric measuring camera from damage by strong light and ensuring that its sensitivity is not affected.

[0024] This invention addresses the need for photoelectric measuring cameras to withstand prolonged exposure to strong direct sunlight in certain tasks, proposing a protection method based on a filter designed for a specific spectral band. This method is based on physical principles, has a clear optimization direction, and possesses universality. Using this method, photothermal effects can be minimized without affecting sensitivity. Compared to active light avoidance protection methods, this method requires no power-on / off switching, offers high reliability, and has wide applicability, without limitations imposed by operating tracks or rotating mechanisms. Attached Figure Description

[0025] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the drawings described below are one embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0026] Figure 1 Schematic diagram of the principle of strong light protection method;

[0027] Figure 2a This is a schematic diagram of a high-intensity light protection device;

[0028] Figure 2bThis is a cross-sectional view of a high-intensity light protection device;

[0029] Figure 3 This is a grayscale comparison image before and after the strong light direct exposure test;

[0030] Figure 4 This is a sensitivity comparison chart after applying the present invention;

[0031] Figure 5 This is a sensitivity comparison chart before applying the present invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0033] This invention provides a method for protecting a photoelectric measurement camera from strong light without loss of sensitivity, specifically including the following steps:

[0034] S1. Based on the quantum response efficiency curve of the detector of the photoelectric measurement camera, determine the non-zero response spectrum and the zero response spectrum of the detector;

[0035] S2, Design a target filter, wherein the transmittance of the target filter is 100% in the non-zero response spectral band and 0% in the zero response spectral band;

[0036] S3, the target filter is installed above the detector to protect the photoelectric measurement camera from strong light.

[0037] like Figure 1 As shown, the principle of this invention is as follows: based on the response curves of the photoelectric measurement camera detector to photons in different spectral bands, i.e., the quantum efficiency, the incident light is divided into the detector non-zero response spectral band and the detector zero response spectral band. For the detector non-zero response spectral band, photons are converted into electrical signals by the detector through the photoelectric effect, directly determining the sensitivity of the photoelectric measurement camera. Besides the Joule heating generated by the photocurrent, photons also heat the detector through the photothermal effect. For the detector zero response spectral band, photons are not converted into electrical signals and are unrelated to the sensitivity of the photoelectric measurement camera, but they still heat the detector through the photothermal effect.

[0038] To maintain the constant sensitivity of the photoelectric measurement camera, photons in the non-zero response spectrum of the detector need to pass through the filter completely, meaning the transmittance in this spectrum should be 100%. Conversely, since photons in the zero response spectrum of the detector only provide radiant energy and are unrelated to sensitivity, these photons can be completely filtered out, meaning the transmittance of the filter in this spectrum should be 0. This maximizes the suppression of photothermal effects and reduces the detector temperature. This results in a specially designed filter for a specific spectral band, i.e., the target filter.

[0039] like Figure 2a , 2b As shown, the target filter (i.e., the special spectral design filter 2) is placed above the detector 1, and then fastened with the fastener 3 and fixed with glue.

[0040] Furthermore, prior to step S1, the method further includes:

[0041] Based on the existing filter in the photoelectric measuring camera, calculate the actual temperature of the detector of the photoelectric measuring camera. If the calculated actual temperature is greater than the safe temperature of the detector, then proceed to step S1.

[0042] That is, by calculating the detector's actual temperature based on the existing filter and comparing it with the detector's safe temperature, it can be determined whether the existing filter meets the requirements. If it does, there is no need to add a target filter. If it does not meet the requirements, then adding a target filter can be considered.

[0043] Taking the sun as a strong light source as an example, the actual temperature of the detector is calculated based on the existing filters, as follows:

[0044] Calculate the solar radiation spectrum based on the equivalent blackbody temperature of the sun;

[0045] Calculate the solar radiation power received by the detector based on the existing filter spectral characteristics;

[0046] Based on empirical relationships, the actual temperature of the photoelectric measurement camera detector is calculated.

[0047] The empirical relationship mentioned refers to the thermal model of the photoelectric measurement camera. Sometimes it is difficult to establish an accurate thermal model, but the empirical relationship between detector temperature and radiation power can be obtained through experiments.

[0048] Similarly, any other strong light source that might appear in the field of view of the photoelectric measurement camera is handled in a similar manner to the sun, and the actual temperature of the detector based on the existing filters can be calculated using the method described above. Further details will not be elaborated here.

[0049] Furthermore, prior to step S3, the method further includes:

[0050] Based on the target filter, calculate the optimal temperature of the detector of the photoelectric measurement camera. If the optimal temperature is not greater than the detector's safe temperature, then proceed to step S3.

[0051] That is, by calculating the optimal temperature of the detector after adding the target filter and comparing it with the detector's safe temperature, it is determined whether the target filter meets the requirements. If it does, the target filter is added. If it does not, that is, if the optimal temperature is greater than the detector's safe temperature, the target filter is redesigned so that its transmittance is also 0 in a portion of the non-zero response spectrum. In other words, the transmittance curve of the target filter is readjusted to filter out light in a portion of the detector's non-zero response spectrum (where quantum response efficiency is low), resulting in a slight loss of sensitivity, but ensuring that the temperature remains within the safe range.

[0052] Taking the sun as a strong light source as an example, the optimal temperature of the detector after adding a target filter is calculated as follows:

[0053] Calculate the solar radiation spectrum based on the equivalent blackbody temperature of the sun;

[0054] The spectral characteristics of the target filter are determined based on the detector's quantum efficiency, and the solar radiation power received by the detector is calculated.

[0055] The optimal temperature of the detector is calculated based on the thermal model of the photoelectric measurement camera.

[0056] Similarly, for any other strong light source that might appear in the field of view of the photoelectric measurement camera, the treatment is similar to that of the sun; the optimal temperature of the detector after adding the target filter can be calculated using the method described above. Further details will not be elaborated here.

[0057] The following is an example of applying this invention. Using the sun as a strong light source, the protective effect of this method on a certain photoelectric measurement camera is analyzed and verified.

[0058] Based on the blackbody radiation theory, the solar radiation spectrum B is:

[0059]

[0060] In formula (1), h is Planck's constant, c is the speed of light in vacuum, and k is the speed of light in a vacuum. B λ is the Boltzmann constant, λ is the photon wavelength, and T is the solar equivalent blackbody temperature.

[0061] The effective solar radiation energy flow E entering the detector is:

[0062] E(λ)=B(λ)·p(λ)·Ω (2)

[0063] In formula (2), p is the transmittance function of the filter, and Ω is the solid angle subtended by the sun to the photoelectric measuring camera.

[0064] Within the cutoff wavelength range of the filter, λ min <λ<λ max Integrating equation (2), the actual power S received by the detector per unit area is obtained as follows:

[0065]

[0066] Based on the thermal model of this photoelectric measurement camera, the detector temperature T sensor The following relationship exists between the received radiated power S and the received radiated power S:

[0067]

[0068] In formula (4), S ⊙ It is the solar constant.

[0069] Based on the above theory and combined with the detector's quantum efficiency curve, the method of this invention can reduce the solar radiation energy received by the detector by 60% and lower the detector temperature to 64°C.

[0070] A strong sunlight direct exposure test was conducted on the photoelectric measurement camera in the laboratory using a solar simulator. After applying the method of this invention, the photoelectric measurement camera maintained normal output throughout the ten-minute period of direct sunlight exposure, with the highest detector temperature reaching 62℃, consistent with the calculated height. Before and after the strong sunlight direct exposure test, the photoelectric measurement camera was used to calculate the mean and variance of grayscale values ​​for the integrated racket image obtained at different window positions, as shown below. Figure 3 As shown, the results before and after the experiment were basically consistent, indicating that the strong light did not damage the detector.

[0071] In addition, field stargazing was conducted using photoelectric measurement cameras that did not apply this invention and those that applied this invention, respectively. Figure 4 , Figure 5 As shown, with the exposure time remaining constant, the measured detection sensitivity of the photoelectric measurement camera without the present invention is 8.96 Mv, while the measured detection sensitivity of the photoelectric measurement camera with the present invention is 8.84 Mv, indicating that the sensitivity hardly decreased.

[0072] The above experiments show that, under direct strong light, the present invention can provide full protection for the photoelectric measurement camera detector throughout the entire process without any loss of sensitivity.

[0073] Based on the same inventive concept, this invention also provides a strong light protection device for a photoelectric measuring camera without sensitivity loss, such as... Figure 2a , Figure 2b As shown, it includes:

[0074] A special spectral band design filter 2 is provided, wherein the transmittance of the special spectral band design filter 2 is 100% in the non-zero response spectral band of the detector 1 of the photoelectric measurement camera, and the transmittance is 0 in the zero response spectral band of the detector 1.

[0075] The fastener 3 is used to fix the special spectral design filter 2 above the detector 1.

[0076] Furthermore, the fastener 3 is fixed to the special spectral band design filter 2 by dispensing adhesive, and the special spectral band design filter 2 is fixed to the detector 1 by dispensing adhesive.

[0077] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for strong light protection of a photoelectric measuring camera without sensitivity loss, characterized in that, The method includes the following steps: S1. Based on the existing filter in the photoelectric measuring camera, calculate the actual temperature of the detector of the photoelectric measuring camera. If the calculated actual temperature is greater than the safe temperature of the detector, determine the non-zero response spectrum and zero response spectrum of the detector according to the quantum response efficiency curve of the detector of the photoelectric measuring camera. S2, Design a target filter, wherein the transmittance of the target filter is 100% in the non-zero response spectral band and 0% in the zero response spectral band; S3. Based on the target filter, calculate the optimal temperature of the detector of the photoelectric measurement camera. If the optimal temperature is not greater than the detector's safe temperature, then install the target filter above the detector to protect the photoelectric measurement camera from strong light.

2. The method for strong light protection of a photoelectric measuring camera without sensitivity loss according to claim 1, characterized in that, If the optimal temperature is greater than the detector's safe temperature, the target filter is redesigned so that its transmittance is also 0 in a portion of the non-zero response spectrum.

3. A photoelectric measurement camera strong light protection device with no sensitivity loss using the method described in claim 1 or 2, characterized in that, The device includes: A special spectral band design filter, wherein the transmittance of the special spectral band design filter is 100% in the non-zero response spectral band of the detector of the photoelectric measurement camera, and the transmittance is 0 in the zero response spectral band of the detector; Fasteners are used to fix the specially designed spectral filter above the detector.

4. The photoelectric measuring camera strong light protection device without sensitivity loss according to claim 3, characterized in that, The fastener is fixed to the special spectral band design filter by dispensing adhesive, and the special spectral band design filter is fixed to the detector by dispensing adhesive.

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