CN114500990B - Testing method for single particle displacement damage of photoelectric image sensor - Google Patents

Abstract

The invention provides a method for testing displacement damage of single particles of a photoelectric image sensor, which mainly solves the problem that the existing testing method cannot test the displacement damage effect of the single particles of the photoelectric image sensor rapidly and accurately. In the test system, a photoelectric image sensor is arranged on an irradiation plate, and the irradiation plate is arranged on an automatic moving platform; the FPGA control module and the power supply module are arranged on the test board and are connected with the photoelectric image sensor; the beam current terminal is arranged at one side of the photoelectric image sensor; the laser positioning instrument is arranged at one side of the photoelectric image sensor; the direct current power supply is used for supplying power to the photoelectric image sensor; the lower control computer is connected with the FPGA control module and is used for processing the image data acquired by the photoelectric image sensor and transmitting the processed data to the upper control computer. The method lays a foundation for evaluating the displacement damage degree of single particles of the photoelectric image sensor and researching the damage mechanism.

Description

Testing method for single particle displacement damage of photoelectric image sensor

Technical Field

The present invention relates to the field of radiation effect testing, and in particular to a testing system and method for single particle displacement damage of a photoelectric image sensor.

Background Art

Photoelectric image sensors (such as CCD, CMOS image sensors, etc.) used in radiation environments will be affected by radiation particles, resulting in device performance degradation or even functional failure. The displacement damage defects caused by radiation particles in the radiation-sensitive area of the device will increase the leakage current of the pixel unit of the photoelectric image sensor, causing the dark signal of the pixel unit to increase sharply within a short integration time, or even reach saturation, becoming a hot pixel (or hot image element). A large number of hot pixels induced by radiation particles will cause a large number of spike signals to appear in the image of the imaging system based on the photoelectric image sensor, seriously affecting the imaging quality, especially for the photoelectric imaging system used in low-light environments and long exposure conditions.

The particles that cause the displacement damage effect of a single particle of the photoelectric image sensor mainly include protons, neutrons, heavy ions, etc. However, at present, only the overall performance of the photoelectric image sensor has been tested, and the process of causing the displacement damage of a single particle of the photoelectric image sensor has not been tested. By testing the overall performance of the photoelectric image sensor, only the final degree of irradiation damage after a certain amount of radiation is accumulated can be obtained, but the process information of the displacement damage (such as the number of collisions, the degree of damage of a single collision, etc.) cannot be obtained, which seriously affects the research on the displacement damage mechanism of the photoelectric image sensor. Therefore, it is urgent to establish a test method for the displacement damage effect of a single particle of the photoelectric image sensor to realize the test and analysis of the single particle damage of the photoelectric image sensor.

Summary of the invention

The present invention provides a testing system and method for single particle displacement damage of a photoelectric image sensor, which realizes the testing of the displacement damage effect of a single particle induced by particles such as protons, neutrons, and heavy ions in the photoelectric image sensor, solves the problem that the existing testing methods cannot quickly and accurately test the displacement damage effect of a single particle of the photoelectric image sensor, and lays a foundation for the evaluation of the displacement damage degree of a single particle of the photoelectric image sensor and the research on the damage mechanism.

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

The present invention provides a testing system and method for single particle displacement damage of a photoelectric image sensor, which can test single particle displacement damage induced by particles such as protons, neutrons, and heavy ions, and lay a foundation for the evaluation of the degree of single particle displacement damage and the study of damage mechanism of photoelectric image sensors. Photoelectric image sensors mainly include charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) image sensors, and can also be extended to indium gallium arsenide (InGaAs) focal plane detectors, mercury cadmium telluride (HgCdTe) focal plane detectors, gallium nitride (GaN) ultraviolet focal plane detectors, etc.

The test system for the displacement damage of a single particle of a photoelectric image sensor provided by the present invention comprises a beam terminal, an automatic moving platform, an irradiation plate, a test plate, a DC power supply, a laser locator, an FPGA control module, a power module, a lower control computer and an upper control computer; the photoelectric image sensor is installed on the irradiation plate, and during the irradiation process, the photosensitive surface of the photoelectric image sensor is covered with a shading paper for shading treatment, and the irradiation plate is arranged on the automatic moving platform; the FPGA control module and the power module are arranged on the test plate, and are both connected to the photoelectric image sensor; the beam terminal is arranged on one side of the photoelectric image sensor, and the photoelectric image sensor is located at the center of the beam outlet; the laser locator is arranged on the other side of the photoelectric image sensor, and is used to locate the displacement of the photoelectric image sensor; the DC power supply is connected to the power module through a cable, and is used to power the photoelectric image sensor; the lower control computer is connected to the FPGA control module, and is used to process the image data collected by the photoelectric image sensor, and transmit the processed data to the upper control computer. The lower control computer and the upper control computer are equipped with test software and a data acquisition card.

In order to avoid damage to test personnel by irradiated particles, an automatic mobile platform and a host control computer are used for remote online control. The automatic mobile platform has X and Y two-dimensional movement functions, and the movement speed is not less than 1cm/s; the laser locator can generate a cross-line laser positioning line, which can locate the displacement of the photoelectric image sensor on the X and Y axes.

For different test objects, the irradiation board and the test board are installed in different ways. One is to separate the mother and child boards, that is, the test board and the irradiation board are connected by cables, and only the photoelectric image sensor is installed on the irradiation board. The FPGA control module, power module, etc. are installed on the test board, and the test board is shielded during the irradiation process. The other is that the test board and the irradiation board are integrated without separation, that is, the photoelectric image sensor is directly installed on the test board. This setting is only used when the radiation particle beam spot is small, the irradiation cumulative injection is small, and it ensures that other radiation-sensitive devices in the test board are almost not irradiated with particles.

The testing method for single particle displacement damage of a photoelectric image sensor provided by the present invention comprises the following steps:

Step 1: Use a laser locator to locate the photoelectric image sensor at the center of the beam outlet, and record the horizontal and vertical coordinates of the automatic moving platform at this time, that is, obtain the translation coordinates of the automatic moving platform, and then move the photoelectric image sensor to the beam-free area;

When using a laser locator for positioning, first make the center of the cross-line laser positioning line generated by the laser locator located at the center of the beam outlet, then move the photoelectric image sensor so that the center of the cross-line laser positioning line generated by the laser locator is located at the center of the photoelectric image sensor, so that the photoelectric image sensor is located at the center of the beam outlet;

Step 2: Set the integration time and data acquisition frequency, and then collect image data;

When determining the integration time, try to select a high acquisition frequency to obtain more acquisition data if the test system and the upper control computer memory allow, where f satisfies:

f＝f _max f≥f _max (2)

In the formula, f _max is the maximum acquisition frequency, t' is the time for acquiring and reading each frame of the image. However, for large-array photoelectric image sensors, since the image data occupies a large amount of memory, in order to obtain the relationship between the output signal and time over a long period of time, a smaller acquisition frequency f can be selected;

Integration time t and irradiation flux rate It is closely related to the sensitivity S, which is the product of the cross section of the non-ionizing interaction between the particle and the material in the sensitive area and the volume of the sensitive area (photosensitive area) damaged by the displacement of a single pixel unit of the photoelectric image sensor. In order to avoid invalid data due to excessive irradiation dose caused by a single image acquisition, in general, the integration time t and the irradiation injection rate are And the sensitivity S must meet:

Where a and b are the length and width of the pixel unit of the photoelectric image sensor respectively;

Step 3: After the collected image data is stable, the beam terminal is turned on. After the beam is stable, the automatic moving platform is moved according to the translation coordinates in step 1, and the irradiation plate with the photoelectric image sensor installed is moved to the particle radiation environment, so that the photoelectric image sensor is irradiated by particles, and other radiation-sensitive devices in the test system are almost not irradiated by particles;

After the system is started, the dark current of the photoelectric image sensor increases sharply, causing its temperature to rise, and the collected output signal also increases continuously. Therefore, it is necessary to perform a single particle displacement damage test after the collected data is stable. The basis for judging the stability of the collected data is divided into the following two types:

a) For photoelectric image sensors equipped with temperature sensors, the temperature is collected in real time and stability is achieved when the temperature no longer changes;

b) For photoelectric image sensors that are not equipped with temperature sensors, a curve of the output signal of the photoelectric image sensor changing with the acquisition time is given in real time during the test. Stability is achieved when the output signal hardly changes with the acquisition time;

Step 4: continuously collect image data at the data collection frequency and integration time set in step 2. When the specified fluence is accumulated, the photoelectric image sensor is removed from the particle radiation environment by using an automatic moving platform, and the beam terminal is closed;

Step 5. Use image data processing software to extract the output signal of each pixel unit in the image data, and obtain the change pattern of the output signal with the irradiation time. The pixel unit whose output signal has a step-by-step change with time is the pixel unit affected by displacement damage, and the test result of single particle displacement damage can be obtained.

When extracting the output signal of each pixel unit based on the image data processing software, according to the coordinate information of the pixel unit in the output image and the time information of the image acquisition, the output signal of each pixel unit in the local area or the whole area of the photoelectric image sensor is given by batch processing method as a function of irradiation time. When analyzing the displacement damage effect data of a single particle (the output signal of the pixel unit changes with the irradiation time), the phenomenon that a signal spike is generated in the curve but quickly recovers to the original level is called transient response (one of the single particle effects); the phenomenon that a signal spike is generated in the curve and cannot be restored to the original level afterwards is called displacement damage effect. The difference between the signal value that remains unchanged with time before the spike and the signal value that remains unchanged with time after the spike is called the signal growth value caused by the displacement damage, which can be used to evaluate the damage degree of the collision.

When the acquisition frequency is high enough and a displacement damage signal is generated, the short-term annealing process of the displacement damage caused by a single particle in the photoelectric image sensor can be obtained by analyzing the relationship between the signal peak in the curve and the subsequent signal change over time in a smaller time period.

When analyzing the displacement damage effect of a single particle based on the curve of the pixel unit output signal changing with the irradiation time, methods such as median filtering, wavelet transform, Gaussian low-pass filtering or stop-band filtering can be used to remove the noise signal in the test, and then the number and amplitude of steps in the pixel unit change curve of the local area or all areas are counted to obtain the displacement damage statistical information in the pixel array of the photoelectric image sensor. The number of collisions can be approximately obtained by averaging the number of steps, and the degree of damage of a single collision can be obtained by the step amplitude.

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

1. The present invention lays a foundation for the evaluation of the degree of single particle displacement damage and the study of damage mechanism of photoelectric image sensors by testing the single particle displacement damage induced by particles such as protons, neutrons, and heavy ions.

2. To avoid the influence of temperature on the test results, the system and method of the present invention first preheats the system and monitors it when conducting a single particle displacement damage effect test, and then conducts a single particle displacement damage effect test after the temperature stabilizes. At the same time, to avoid damage to testers caused by radiation particles, the system and method of the present invention implements remote online testing. In addition, to avoid the influence of beam quality on the test results, the system and method of the present invention install a remote mobile platform, and after the beam stabilizes, the photoelectric image sensor is moved to the center of the beam and the test is conducted.

3. Compared with the existing methods, the method of the present invention can not only obtain the final radiation damage degree of the device after accumulating a certain amount of radiation, but also accurately obtain the displacement damage process information of the photoelectric image sensor. For example, by counting the number of steps and amplitude in the curve of the output signal of the pixel unit in the local area or all areas changing with the irradiation time, the number of collisions, the damage degree of a single collision, etc. can be obtained.

4. The test system construction process and test flow of the present invention are simple, and the single-particle displacement damage information of all pixel units in the photoelectric image sensor can be quickly and accurately obtained through a single test.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a testing system for single particle displacement damage of a photoelectric image sensor according to an embodiment of the present invention;

FIG2 is a flow chart of a method for testing displacement damage of a single particle of a photoelectric image sensor according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of experimental results of a single neutron displacement damage effect test on a CMOS image sensor according to an embodiment of the present invention.

Figure numerals: 1-beam terminal, 2-automatic moving platform, 3-irradiation plate, 4-test board, 5-FPGA control module, 6-power module, 7-laser locator, 8-DC power supply, 9-lower control computer, 10-upper control computer, 11-photoelectric image sensor, 12-shading paper, 13-temperature control device, 14-shielding box.

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 embodiment of the present invention provides a CMOS image sensor single neutron displacement damage effect measurement device and test method. The single neutron displacement damage effect experiment was carried out in Hall 2 of the white light neutron terminal of the Spallation Neutron Source (CSNS), with a neutron injection rate of 1.4×10 ⁶ n/cm ² /s and a beam spot of neutrons with a diameter of 6 cm. Due to the small area of the beam spot, the test plate and the irradiation plate are integrated in the test system for the convenience of conducting the experiment, and they are not separated.

As shown in FIG1 , the test system for single particle displacement damage of the photoelectric image sensor provided by the present invention comprises a beam terminal 1, an automatic moving platform 2, an irradiation plate 3, a test plate 4, a DC power supply 8, a laser locator 7, an FPGA control module 5, a power module 6, a lower control computer 9 and an upper control computer 10. The FPGA control module 5 is connected to the lower control computer 9 via a Camerlink line. During the irradiation process, the CMOS image sensor is covered with a shading paper 12 for shading treatment; in order to avoid damage to the tester by the irradiated neutrons, the automatic moving platform 2 and the control computer are controlled remotely online.

When using the above system for testing, first adjust the test system so that the system can realize image data acquisition, then set the integration time and data acquisition frequency, and perform data acquisition; after the collected data is stable, use the automatic moving platform 2 to move the test board 4 equipped with the photoelectric image sensor 11 to the particle radiation environment, so that the photoelectric image sensor 11 is irradiated by particles, and other radiation-sensitive devices are almost not irradiated by particles; then continuously collect image data, and when the specified injection amount is accumulated, use the automatic moving platform 2 to move the test board 4 away from the photoelectric image sensor 11 from the particle radiation field; use the image data processing software to extract the output signal of each pixel unit, and obtain the change law of the output signal with the irradiation time, so as to obtain the experimental results of single particle displacement damage. Specifically, as shown in Figure 2, the test method for the single neutron displacement damage effect of the CMOS image sensor is introduced, which specifically includes the following steps:

Step 1: Since the neutron beam spot is a circular spot with a diameter of 6 cm, for the convenience of conducting experiments, the test system selects the test plate 4 and the irradiation plate 3 as one piece without separation, and then fixes the CMOS image sensor on the irradiation plate 3 through a bracket, and the irradiation plate 3 is fixed on the automatic moving platform 2; before the test, the laser positioning instrument 7 is used to position the CMOS image sensor so that the CMOS image sensor is at the center of the beam outlet and the position is recorded, and then the CMOS image sensor is moved to the beam-free area;

Step 2: according to the irradiation flux rate, the data acquisition frequency is set to 1/3 (i.e., one frame is acquired every 3 seconds) and the integration time is set to 100 ms, and then the image data is acquired;

Step 3: After the collected data is stable, the beam terminal 1 is turned on. After the beam is stable, the irradiation plate 3 with the CMOS image sensor installed is moved to the neutron radiation environment using the automatic moving platform 2, so that the CMOS image sensor is irradiated by neutrons, and other radiation-sensitive devices in the test system are almost not irradiated by neutrons;

Step 4: automatically and continuously collect image data according to the set data acquisition frequency and integration time. When the specified fluence is accumulated, the CMOS image sensor is moved away from the neutron radiation field by using the automatic moving platform 2, and the beam terminal 1 is closed;

Step 5: Use image data processing software to extract the output signal of each pixel unit, obtain the change law of the output signal with irradiation time, and then obtain the experimental results of single neutron displacement damage. The change curve of the output signal of the pixel unit [26,1] with irradiation time is shown in Figure 3. The two collisions between 200s and 300s and 500s and 600s caused the output signal of the device to rise stepwise due to displacement damage. After a collision between 500s and 600s, the output of the CMOS image sensor pixel unit reached saturation due to displacement damage, and the subsequent signal oscillation was caused by random telegraph noise.

Claims (9)

1. A test method of single particle displacement damage of a photoelectric image sensor is based on a test system of single particle displacement damage of the photoelectric image sensor, and the system comprises a beam terminal (1), an automatic moving platform (2), an irradiation plate (3), a test plate (4), an FPGA control module (5), a power supply module (6), a laser positioning instrument (7), a direct current power supply (8), a lower control computer (9) and an upper control computer (10);

the photoelectric image sensor (11) is arranged on the irradiation plate (3), the light sensitive surface of the photoelectric image sensor is covered with shading paper (12), and the irradiation plate (3) is arranged on the automatic moving platform (2);

The FPGA control module (5) and the power supply module (6) are arranged on the test board (4) and are connected with the photoelectric image sensor (11);

The beam terminal (1) is arranged on one side of the photoelectric image sensor (11), and the photoelectric image sensor (11) is positioned at the center of the beam outlet;

the laser positioning instrument (7) is arranged on the other side of the photoelectric image sensor (11) and is used for positioning the photoelectric image sensor (11);

the direct current power supply (8) is connected with the power supply module (6) through a cable and is used for supplying power to the photoelectric image sensor (11);

the lower control computer (9) is connected with the FPGA control module (5) and is used for collecting the image data of the photoelectric image sensor (11) and transmitting the collected image data to the upper control computer (10);

the method is characterized by comprising the following steps of:

Step one, a laser positioning instrument (7) is adopted, a photoelectric image sensor (11) is positioned at the center of a beam outlet, the abscissa and the ordinate of an automatic moving platform (2) at the moment are recorded, the translation coordinate of the automatic moving platform (2) is obtained, and then the photoelectric image sensor (11) is moved to a beam-free area;

Setting integration time t and data acquisition frequency f, and then acquiring image data;

f＝f_max f≥f_max (2)

Wherein f _max is the maximum acquisition frequency; t' is the time for collecting and reading out each frame of image; a and b are the length and width of a pixel unit of the photoelectric image sensor (11) respectively; the irradiation fluence rate; s is sensitivity;

Step three, after the image data to be acquired is stabilized, a beam terminal (1) is opened, after the beam is stabilized, the automatic moving platform (2) is moved according to the translation coordinates in the step one, and the irradiation plate (3) provided with the photoelectric image sensor (11) is moved to a particle radiation environment, so that the photoelectric image sensor (11) is irradiated by particles;

continuously acquiring image data under the integration time t and the data acquisition frequency f set in the step two, and when the specified fluence is accumulated, removing the photoelectric image sensor (11) from the particle radiation environment by the automatic moving platform (2), and closing the beam terminal (1);

step five, extracting an output signal of each pixel unit in image data to obtain a change curve of the output signal of the pixel unit along with irradiation time, wherein the pixel unit with the output signal changing stepwise along with time is the pixel unit affected by displacement damage, then removing noise signals in the change curve, counting the number of steps and amplitude values in the change curve to obtain displacement damage statistical information in a pixel array of the photoelectric image sensor, obtaining the number of collisions through the average number of steps, and obtaining the single collision damage degree by the step amplitude value.

2. The method for testing displacement damage of single particles of an optoelectronic image sensor according to claim 1, wherein: the moving speed of the automatic moving platform (2) is not less than 1cm/s.

3. The method for testing displacement damage of single particles of an optoelectronic image sensor according to claim 1, wherein: also comprises a temperature control device (13) for controlling the ambient temperature of the test system.

4. A method for testing displacement damage of single particles of an optoelectronic image sensor according to claim 1,2 or 3, wherein: the test board (4) and the irradiation board (3) are integrally arranged.

5. The method for testing displacement damage of single particles of the photoelectric image sensor according to claim 4, wherein: the direct current power supply (8) and the lower control computer (9) are arranged in a shielding box (14), and the shielding box (14) is used for shielding the influence of the beam current terminal (1) on the direct current power supply (8) and the lower control computer (9).

6. The method for testing displacement damage of single particles of the photoelectric image sensor according to claim 5, wherein: the photoelectric image sensor (11) is a charge coupled device, a CMOS image sensor, an InGaAs focal plane detector or a tellurium cadmium mercury focal plane detector.

7. The method for testing displacement damage of single particles of the photoelectric image sensor according to claim 6, wherein: the judgment basis of the stability of the acquired image data is as follows:

a) Acquiring the temperature of the photoelectric image sensor (11) in real time, and stabilizing the temperature when the temperature is not changed any more; or b) acquiring a change curve of the output signal of the photoelectric image sensor (11) along with the acquisition time, and stabilizing the output signal when the output signal does not change along with the acquisition time.

8. The method for testing displacement damage of single particles of a photoelectric image sensor according to claim 7, wherein: in the first step, when the laser positioning instrument is used for positioning, firstly, the center of a cross line laser positioning line of the laser positioning instrument is positioned at the center of the beam outlet, and then, the photoelectric image sensor is moved, so that the center of the cross line laser positioning line of the laser positioning instrument is positioned at the center of the photoelectric image sensor, and the photoelectric image sensor is positioned at the center of the beam outlet.

9. The method for testing displacement damage of single particles of an optoelectronic image sensor according to claim 8, wherein: in the fifth step, the noise signal is removed in the variation curve, specifically, the noise is removed by a median filtering method, a wavelet transformation method, a Gaussian low-pass filtering method or a stop band filtering method.