CN114500994B - A test method for radiation transient response of photoelectric image sensor - Google Patents

Abstract

The invention provides a test method for the radiation transient response of a photoelectric image sensor, which solves the problems of the typical characteristic and rule experimental test of the transient response of the photoelectric image sensor under different radiation environments, realizes the rapid and accurate test and analysis of the transient response, and provides technical support for the radiation noise processing and the radiation signal identification of the photoelectric image sensor under the radiation environments. In order to avoid the influence of the background noise of the device, the method disclosed by the invention obtains the average value by collecting a plurality of frames of dark field images when the test is carried out, and then a method for subtracting the background noise is adopted in the data processing process. In order to avoid the influence of device heating on the result in the test process, when the transient response test is carried out, firstly, the test system is subjected to preheating treatment and monitoring, and the test is carried out after the temperature is stable. To avoid the effect of radiation noise on the test results, the transient response test system of the photoelectric image sensor is periodically moved out of the radiation field, or the photoelectric image sensor is replaced.

Description

A method for testing radiation transient response of photoelectric image sensor

Technical Field

The invention belongs to the field of radiation effect testing, and in particular relates to a method for testing radiation transient response of a photoelectric image sensor.

Background Art

Radiation transient response refers to the phenomenon that when radiation particles or rays pass through the sensitive area of the device, the electron-hole pairs generated are collected by the device and produce bright spots or bright lines in the output image. Compared with cumulative radiation damage, radiation transient response is a non-permanent damage. It occurs when the imaging detection system is in the radiation field environment, and it can be restored after leaving the radiation field. The transient signal appears randomly in each frame of the image.

The radiation transient response of photoelectric image sensors can be divided into the following two aspects: Photoelectric image sensors (such as charge-coupled devices, CMOS image sensors, etc.) used in radiation environments will be affected by radiation particles or rays, generating transient noise, interfering with or reducing the imaging and detection performance of the device; Photoelectric image sensors used in radiation detection environments use the transient response generated by radiation particles or rays as a signal, and then detect the radiation environment parameters. Therefore, it is of great significance to conduct research on the radiation transient response of photoelectric image sensors under different particle or ray radiation environments.

In the process of conducting research on the radiation transient response of photoelectric image sensors, it is necessary to achieve fast and accurate measurement of their transient response. In the process of conducting the transient response test of photoelectric image sensors, the background noise of the device and the thermal noise during operation will have a certain impact on the test results. In addition, the photoelectric image sensor working in a radiation environment will be damaged by the cumulative radiation of particles or rays, thereby generating radiation noise. The above noises will have a certain impact on the transient response test of the photoelectric image sensor. At present, it is necessary to achieve fast and accurate testing and analysis of the transient response of photoelectric image sensors.

Summary of the invention

In order to achieve rapid and accurate testing and analysis of transient response, the present invention provides a testing method for radiation transient response of a photoelectric image sensor. The method solves the problem of experimental testing of typical characteristics and laws of transient response of photoelectric image sensors under different radiation environments, and provides technical support for radiation noise processing and radiation signal recognition of photoelectric image sensors used in radiation environments.

To achieve the above object, the present invention adopts the following technical solutions:

A method for testing radiation transient response of a photoelectric image sensor comprises the following steps:

Step 1, selecting the type of radiation particles or rays that generate transient response, determining the incident dose rate, incident angle, integration time and data acquisition frequency of the radiation particles or rays, or determining the incident dose rate, incident angle, integration time and data acquisition frequency of the radiation particles or rays;

Step 2: Build a transient response test system for the photoelectric image sensor, perform light shielding on the photoelectric image sensor, and then, the transient response test system continuously collects image data until the average output value of the image data reaches stability;

Step 3: Collect dark field image data under non-radiation field and different integration time conditions, then place the photoelectric image sensor in the radiation field, and sequentially collect radiation image data output under different incident dose rates, different incident angles, and different integration time conditions, or sequentially collect radiation image data output under different incident dose rates, different incident angles, and different integration time conditions;

Step 4: Move the transient response test system of the photoelectric image sensor out of the radiation field within a set time, then return to step 3, move the transient response test system of the photoelectric image sensor out of the radiation field within a set time again, return to step 3, repeat the process multiple times, and obtain multiple dark field image data and radiation image data; in this process, if the radiation particles or rays cause relatively serious damage to the photoelectric image sensor, replace the photoelectric image sensor and return to step 2;

Step 5: Process the acquired dark field image data and radiation image data to obtain transient response images and transient response experimental laws;

The output values at each pixel of multiple frames of dark field image data outside the radiation field are averaged to obtain a background noise image of the photoelectric image sensor, and the transient response image can be obtained by subtracting the background noise image from the radiation image data under the radiation field;

Edge detection is performed on the transient response image to obtain the morphological features of the transient response, and the distribution curves of multi-frame transient response signals under different conditions are plotted to obtain the transient response experimental laws.

Furthermore, in step one, the integration time is determined according to the incident flux rate or the incident dose rate of the radiation particles or rays, and the maximum integration time setting judgment standard is that the proportion of pixel units of the photoelectric image sensor outputting transient response signals does not exceed 50%.

Furthermore, in step 2, the specific method for judging whether the average output value of the image data reaches stability is: after continuously collecting image data for a period of time, the internal temperature of the photoelectric image sensor changes by less than 0.1°C within 1 minute or the output average dark signal changes by less than 2%.

Furthermore, in step 2, the light-shielding process for the photoelectric image sensor is specifically performed by using a light-shielding material to completely shield the photosensitive surface of the photoelectric image sensor, and the light-shielding material is a light-opaque light-shielding paper.

Furthermore, in step three, under the same irradiation state, the number of radiation image data frames collected is not less than 20 frames, and the radiation image data is generally saved in 8-bit, 12-bit or 16-bit raw format.

Furthermore, in step three, in the non-radiation field, the number of frames of collected data of the dark field image data is not less than 50 frames.

Furthermore, in step four, the method for judging whether the radiation causes relatively serious damage to the photoelectric image sensor is: in the radiation field environment, the signal value corresponding to the highest point in the statistical distribution diagram of the output signal of the photoelectric image sensor increases; the method for judging whether the radiation particles cause relatively serious damage to the photoelectric image sensor is: in the radiation field environment, there are thermal pixels in the output image that exceed the set threshold.

Furthermore, the photoelectric image sensor is a charge coupled device or a CMOS image sensor.

Compared with the prior art, the present invention has the following beneficial effects:

1. The method of the present invention tests the transient response of the photoelectric image sensor and processes the data to obtain the typical characteristics and laws of the transient response, providing data support for the transient response evaluation, transient response noise processing, and anti-transient response reinforcement design of the photoelectric image sensor used in the radiation field environment.

2. The method of the present invention can achieve accurate measurement of transient response. In order to avoid the influence of device background noise, the present invention collects multiple frames of dark field images to obtain the average value when conducting the test, and then adopts the method of subtracting the background noise during the data processing process. In order to avoid the influence of device heating on the results during the test, when conducting the transient response test, the method of the present invention first preheats the test system and monitors it, and then conducts the test after the temperature stabilizes. In order to avoid the influence of cumulative radiation noise on the test results, the photoelectric image sensor transient response test system is regularly moved out of the radiation field, or the photoelectric image sensor is replaced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for testing radiation transient response of a photoelectric image sensor according to an embodiment of the present invention;

FIG2 is a typical output image of the transient response of Co-60 gamma rays of the CMOS image sensor in an embodiment of the present invention;

3 is a schematic diagram of the transient response output distribution of Co-60 gamma rays of a CMOS image sensor for three consecutive frames when the dose rate is 0.05 rad(Si)/s in an embodiment of the present invention;

4 is a distribution diagram of the transient response output of Co-60 gamma rays of a CMOS image sensor before and after dark field subtraction when the dose rate is 0.1 rad(Si)/s in an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

The present invention proposes a testing method for radiation transient response of a photoelectric image sensor. The photoelectric image sensor mainly includes a charge coupled device (CCD) and a CMOS image sensor. The method realizes experimental measurement of the radiation transient response of the photoelectric image sensor, and provides technical support for the research on the radiation transient response of the photoelectric image sensor.

The method for testing the radiation transient response of a photoelectric image sensor provided by the present invention specifically comprises the following steps:

Step 1: According to the test requirements, select the type of radiation particles or rays that produce transient response, and determine the incident flux rate (or incident dose rate), incident angle, integration time and data acquisition frequency of the radiation particles or rays;

In the process of selecting the integration time, it is necessary to determine it according to the incident injection rate or the incident dose rate of the radiation particles or rays. In general, the maximum integration time setting judgment standard is that the pixel units of the photoelectric image sensor outputting transient response signals account for no more than 50%;

Step 2: Build a transient response test system for the photoelectric image sensor, so that the transient response test system of the photoelectric image sensor can output images normally, and perform light shielding on the photoelectric image sensor. Then, the transient response test system continuously collects image data for a period of time until the average output value of the image data reaches stability; wherein, the specific judgment method for the average output value of the image data reaching stability is: after continuously collecting image data for a period of time, the internal temperature of the photoelectric image sensor changes by less than 0.1°C within 1 minute or the output average dark signal changes by less than 2%;

Step 3, collecting dark field image data under non-radiation field and different integration time conditions; then placing the photoelectric image sensor in the radiation field, sequentially collecting radiation image data output under different incident dose rates, different incident angles, and different integration time conditions, or sequentially collecting radiation image data output under different incident dose rates, different incident angles, and different integration time conditions;

When the photoelectric image sensor is subjected to light shielding, a light shielding material is used to completely shield the photosensitive surface of the photoelectric image sensor. The light shielding material is generally a light-proof light-shielding paper. If it is necessary to study the transient effects of radiation particles or rays in the photoelectric image sensor after passing through different materials, the material to be studied can be added between the light-shielding paper and the photoelectric image sensor.

Under the same irradiation conditions, the number of frames of radiation image data collected shall not be less than 20 frames, and the image data is generally saved in 8-bit, 12-bit or 16-bit raw format; under non-radiation field, the number of frames of dark field image data collected shall not be less than 50 frames;

Step 4: If the transient response test time in the irradiation field is long, the radiation particles or rays will cause certain damage to the photoelectric image sensor, resulting in an increase in the background noise. Therefore, it is necessary to regularly move the photoelectric image sensor transient response test system out of the radiation field, and then return to step 3, execute this process multiple times, and obtain multiple dark field image data and radiation image data. The above test time and regular removal time are determined according to factors such as the transient response test content, the radiation field intensity, and the sensitivity of the photoelectric image sensor to radiation damage; at the same time, if the time test time is too long, the cumulative irradiation causes greater damage to the photoelectric image sensor and seriously affects the transient response test results. At this time, the photoelectric image sensor needs to be replaced, and return to step 2;

The method for judging whether the radiation causes damage to the photoelectric image sensor is that in the radiation field environment, the signal value corresponding to the highest point in the statistical distribution diagram of the output signal of the photoelectric image sensor increases, that is, the background noise of the photoelectric image sensor increases;

The criterion for judging whether radiation particles cause damage to photoelectric image sensors is that in the radiation field environment, there are many thermal pixels in the output image (the output signal is much higher than before irradiation, and the output signal of multiple consecutive frames hardly changes, which appears as fixed bright spots in the image), that is, the proportion of thermal pixels in the output image exceeds the set threshold, for example, more than 20%; in addition, in order to avoid excessive irradiation injection rate and long irradiation time, which will increase the cumulative damage in the device, a low injection rate (dose rate) and long integration time mode are generally used for data acquisition;

Step 5: Process the acquired dark field image data and radiation image data to obtain transient response images and transient response experimental laws;

The background noise image of the photoelectric image sensor is obtained by averaging the output values at each pixel point of multiple frames of dark field image data outside the radiation field. The transient response image can be obtained by subtracting the background noise image from the radiation image data under the radiation field. The morphological characteristics of the transient response are obtained by performing edge detection on the transient response image. The transient response experimental law is obtained by plotting the distribution curves of multiple frames of transient response signals under different conditions.

The embodiment of the present invention provides a method for testing the transient response of a CMOS image sensor to Co-60 gamma rays. The method for testing the transient response of a CMOS image sensor to Co-60 gamma rays is described in conjunction with the experimental test method flow chart of the transient response of a photoelectric image sensor to radiation. The specific steps are as follows:

Step 1: The radiation source of this transient response experiment is Co-60 gamma ray, the dose rates are 0.05 rad (Si) / s and 0.1 rad (Si) / s, the particle incident angle is vertical (90 degrees to the detector plane), the integration time is 6.0 ms, and the data acquisition frequency is 2 (that is, two frames of images are collected per second);

Step 2: Shield the photoelectric image sensor and collect image data under non-radiation field conditions for about 30 minutes. By real-time observation of the average grayscale value of the transient response test system output image, it is preliminarily determined that the transient response test system acquisition is close to stable. Then, within 5 minutes of continuous acquisition, the output image signal average value changes by about 1%, and the output is considered to be stable at this time.

Step 3: According to the calibration value of the laboratory dose rate measurement system, the transient response test system of the CMOS image sensor is placed at a position with a dose rate of 0.05 rad(Si)/s, the CMOS image sensor is placed at an incident angle of 90 degrees with the Co-60 gamma ray, and the modules of the transient response test system except the CMOS image sensor are shielded;

According to the experimental plan, set the integration time and acquisition frequency. In this test, the integration time is set to 6.0ms, the acquisition frame number is 20 frames, and the data saving format is 16-bit unsigned raw format data;

Step 4: Take out the radiation source from the water well where it is stored, start collecting data after reaching the designated position, and immediately lower the source after data collection is completed, and stop irradiation. Place the CMOS image sensor transient response test system at a position where the dose rate is 0.1rad(Si)/s, and shield and protect all modules of the transient response test system except the CMOS image sensor; Take out the radiation source from the water well where it is stored, start collecting data after reaching the designated position, and immediately lower the source after data collection is completed, and stop irradiation.

Step 5: Import the collected data into the image data processing system for data processing to obtain the typical characteristics and experimental laws of the Co-60 γ-ray induced transient response. The typical output image is shown in Figure 2, and the distribution diagrams are shown in Figures 3 and 4.

Claims (5)

1. A method for testing radiation transient response of a photoelectric image sensor, characterized in that it comprises the following steps: Step 1, selecting the type of radiation particles or rays that generate transient response, determining the incident dose rate, incident angle, integration time and data acquisition frequency of the radiation particles or rays, or determining the incident dose rate, incident angle, integration time and data acquisition frequency of the radiation particles or rays; The integration time is determined according to the incident injection rate or the incident dose rate of the radiation particles or rays, and the maximum integration time setting judgment standard is that the proportion of pixel units of the photoelectric image sensor outputting transient response signals does not exceed 50%; Step 2: Build a transient response test system for the photoelectric image sensor, perform light shielding on the photoelectric image sensor, and then, the transient response test system continuously collects image data until the average output value of the image data reaches stability; The specific judgment method for the average output value of the image data to be stable is: after continuously collecting image data for a period of time, the internal temperature of the photoelectric image sensor changes less than 0.1°C within 1 minute or the output average dark signal changes less than 2%; Step 3: Collect dark field image data under non-radiation field and different integration time conditions, then place the photoelectric image sensor in the radiation field, and sequentially collect radiation image data output under different incident dose rates, different incident angles, and different integration time conditions, or sequentially collect radiation image data output under different incident dose rates, different incident angles, and different integration time conditions; Step 4: Move the transient response test system of the photoelectric image sensor out of the radiation field within a set time, then return to step 3, move the transient response test system of the photoelectric image sensor out of the radiation field within a set time again, return to step 3, repeat the process multiple times, and obtain multiple dark field image data and radiation image data; in this process, if the radiation particles or rays cause relatively serious damage to the photoelectric image sensor, replace the photoelectric image sensor and return to step 2; The method for judging whether the radiation has caused serious damage to the photoelectric image sensor is: in the radiation field environment, the signal value corresponding to the highest point in the statistical distribution diagram of the output signal of the photoelectric image sensor increases; the method for judging whether the radiation particles have caused serious damage to the photoelectric image sensor is: in the radiation field environment, there are thermal pixels in the output image that exceed the set threshold; Step 5: Process the acquired dark field image data and radiation image data to obtain transient response images and transient response experimental laws; The output values at each pixel of multiple frames of dark field image data outside the radiation field are averaged to obtain a background noise image of the photoelectric image sensor, and the transient response image can be obtained by subtracting the background noise image from the radiation image data under the radiation field; Edge detection is performed on the transient response image to obtain the morphological features of the transient response, and the distribution curves of multi-frame transient response signals under different conditions are plotted to obtain the transient response experimental laws. 2. The method for testing the radiation transient response of a photoelectric image sensor according to claim 1 is characterized in that: in step 2, the photoelectric image sensor is subjected to shading treatment, specifically: a shading material is used to completely block the photosensitive surface of the photoelectric image sensor, and the shading material is opaque shading paper. 3. The test method for the radiation transient response of the photoelectric image sensor according to claim 1 is characterized in that: in step three, under the same irradiation state, the number of radiation image data frames collected is not less than 20 frames, and the radiation image data is saved in 8-bit, 12-bit or 16-bit raw format. 4. The method for testing radiation transient response of a photoelectric image sensor according to claim 1, characterized in that: in step 3, in a non-radiation field, the number of frames of collected data of the dark field image data is not less than 50 frames. 5 . The method for testing radiation transient response of a photoelectric image sensor according to claim 1 , wherein the photoelectric image sensor is a charge coupled device or a CMOS image sensor.