CN-115883821-B - Method for searching exposure time and quantum efficiency measuring system

CN115883821BCN 115883821 BCN115883821 BCN 115883821BCN-115883821-B

Abstract

The invention provides a method for searching exposure time and a quantum efficiency measurement system, which comprise the steps that a data processing module configures fixed parameters of an image acquisition module and configures wavelength of a wavelength configuration device, the image acquisition module is controlled to determine a set of candidate exposure time according to a searching step length and an exposure time initial value, after the wavelength of the wavelength configuration device is configured, single-band light configured by the wavelength configuration device is received through an optical fiber bundle, target exposure time is selected from the set of candidate exposure time for multiple times, an image is shot for multiple times under the environment of the current wavelength of the wavelength configuration device, the image is judged to be not cut off by light and meets the preset image saturation constraint condition, and the target exposure time is taken as a set of searched exposure time corresponding to the current wavelength until the wavelengths of the wavelength configuration devices are searched for respectively corresponding to the set of exposure time. The method is used for accurately searching the exposure time meeting the linearity requirement.

Inventors

YANG ZHIMING
WANG KAI
ZHU RUNYI
ZHANG YUEQIANG

Assignees

上海集成电路研发中心有限公司

Dates

Publication Date: 20260508
Application Date: 20221223

Claims (10)

1. A method for searching exposure time, applied to a data processing module in a quantum efficiency measurement system, wherein the quantum efficiency measurement system comprises a data processing module, an image acquisition module and a wavelength configuration device, and is characterized by comprising the following steps: Configuring fixed parameters of the image acquisition module, wherein the fixed parameters comprise minimum image mean value difference, search step length, exposure time initial value and saturation value correction coefficient, and configuring the wavelength of the wavelength configuration device; Controlling the image acquisition module to determine a set of candidate exposure times according to the search step length and the initial exposure time value, receiving single-band light configured by the wavelength configuration device through an optical fiber bundle after the wavelength of the wavelength configuration device is configured, selecting target exposure times from the set of candidate exposure times for multiple times, shooting images for multiple times under the environment of the current wavelength of the wavelength configuration device, judging that the images are not cut off by light and meet the preset image saturation constraint condition, and meeting the image linearity constraint condition, and taking the target exposure times as a group of searched exposure times corresponding to the current wavelength of the wavelength configuration device until a group of exposure times corresponding to the wavelengths of each wavelength configuration device are searched, wherein the group of exposure times comprises three target exposure times; The process of judging that the image meets the preset image saturation constraint condition comprises the steps that a data processing module configures the exposure time of an image acquisition module to be a second exposure time and a third exposure time, a second image mean value and a third image mean value are correspondingly obtained, and if the maximum value of the second image mean value and the third image mean value is larger than a set image saturation threshold value, searching of the exposure time under the single-band light is stopped.
2. The method according to claim 1, wherein controlling the image acquisition module to select a target exposure time from the set of candidate exposure times a plurality of times, capturing an image a plurality of times in an environment of a current wavelength of the wavelength configuration device, determining that the image is not light-blocked and satisfies a preset image saturation constraint, and satisfying an image linearity constraint, taking the target exposure time as the searched set of exposure times corresponding to the wavelength of the current wavelength configuration device until a set of exposure times corresponding to the wavelengths of the respective wavelength configuration devices is searched, includes: Controlling an image acquisition module to repeatedly execute a search process until a group of exposure times corresponding to the wavelength of the current wavelength configuration device is determined from the set of candidate exposure times, and then reconfiguring the wavelength of the wavelength configuration device by the data processing module, and executing the search process again until a group of exposure times respectively corresponding to the wavelengths of the respective wavelength configuration devices is searched, wherein the search process comprises: Determining a second group of target exposure time from the set of candidate exposure times, wherein the second group of target exposure time comprises a first target exposure time, a second target exposure time and a third target exposure time, the difference between the first target exposure time, the second target exposure time and the third target exposure time is the searching step length, and the first target exposure time is taken as a reference time; Acquiring a first image generated at a first target exposure time, a second image generated at a second target exposure time and a third image generated at a third exposure time, acquiring an image average value of the first image, an image average value of the second image and an image average value of the third image, acquiring an image average value at a maximum exposure time and a minimum exposure time, calculating an image average value difference between the image average value at the maximum exposure time and the image average value at the minimum exposure time, judging that the image average value difference meets a light cut-off constraint condition, judging that the image average value of the second image and the image average value of the third image meet an image saturation constraint condition, and the image average value of the first image, the image average value of the second image and the image average value of the third image meet an image linearity constraint condition, and taking the second group of target exposure times as a group of searched exposure times corresponding to the current wavelength of the wavelength configuration device.
3. The method according to claim 2, wherein controlling the image acquisition module to determine that the image mean difference satisfies a light cutoff constraint, and the image mean of the first image, the image mean of the second image, and the image mean of the third image satisfy an image saturation constraint and an image linearity constraint, using the second set of target exposure times as the set of exposure times searched for corresponding to the wavelength of the current wavelength configuration device includes: When the image average value difference between the image average values under the maximum exposure time and the minimum exposure time meets the light cut-off constraint condition, judging whether the image average values of the second image and the third image are smaller than or equal to a set image saturation threshold value, and when the image average value is smaller than or equal to the set image saturation threshold value, judging whether the linearity of the image average value of the first image, the image average value of the second image and the image average value of the third image falls into a set linear interval, if so, taking the second group of target exposure time as a group of searched exposure time corresponding to the current wavelength of the wavelength configuration device.
4. A method according to claim 3, wherein controlling the image acquisition module to determine that an image mean difference between the image mean at the maximum exposure time and the minimum exposure time satisfies a light cutoff constraint comprises: acquiring the average value of each channel under the maximum exposure time and the minimum exposure time; And calculating the image mean value difference between the image mean value under the maximum exposure time and the minimum exposure time of each channel of the image, and judging that the image mean value difference of each channel of the image does not reach the image cut-off state.
5. The method of claim 3, wherein if the linearity of the image means of the first, second and third images does not fall within the set linear interval, controlling the image acquisition module to adjust the values of the search step size and the first target exposure time before returning to perform the continued search for the target exposure time.
6. A method according to claim 3, wherein the set image saturation threshold approximates an image saturation value.
7. A method according to claim 3, wherein after the image acquisition module obtains a set of exposure times corresponding to the wavelengths of the respective wavelength allocation devices, the method further comprises: the data processing module calculates quantum efficiency from a set of exposure times corresponding to the wavelength of each of the wavelength configuration devices.
8. The quantum efficiency measurement system is characterized by comprising a data processing module, an image acquisition module and a wavelength configuration device; The data processing module is used for configuring fixed parameters of the image acquisition module, wherein the fixed parameters comprise minimum image mean value difference, search step length, exposure time initial value and saturation value correction coefficient; The data processing module is further used for configuring the wavelength of the wavelength configuration device; The image acquisition module is used for receiving a control instruction of the data processing module, determining a set of candidate exposure times according to the searching step length and the exposure time initial value, receiving single-band light configured by the wavelength configuration device through an optical fiber bundle after the wavelength of the wavelength configuration device is configured, selecting target exposure times from the set of candidate exposure times for a plurality of times, shooting images for a plurality of times under the environment of the current wavelength of the wavelength configuration device, judging that the images are not subjected to light cutoff and meet the preset image saturation constraint condition and the image linearity constraint condition, taking the target exposure times as a group of searched exposure times corresponding to the current wavelength of the wavelength configuration device until a group of exposure times corresponding to the wavelength of each wavelength configuration device is searched, wherein the process of judging that the images meet the preset image saturation constraint condition comprises the steps that the exposure time of the data processing module is a second exposure time and a third exposure time, correspondingly acquiring a second image average value and a third image, and if the second average value and the third average value of the third image are larger than the preset image saturation threshold value, setting the image average value under the single-band saturation time.
9. The system according to claim 8, wherein the image acquisition module is specifically configured to: Controlling an image acquisition module to repeatedly execute a search process until a group of exposure times corresponding to the wavelength of the current wavelength configuration device is determined from the set of candidate exposure times, and then reconfiguring the wavelength of the wavelength configuration device by the data processing module, and executing the search process again until a group of exposure times respectively corresponding to the wavelengths of the respective wavelength configuration devices is searched, wherein the search process comprises: Determining a second group of target exposure time from the set of candidate exposure times, wherein the second group of target exposure time comprises a first target exposure time, a second target exposure time and a third target exposure time, the difference between the first target exposure time, the third target exposure time and the second target exposure time is the searching step length, and the first target exposure time is taken as the reference time; Acquiring a second image generated at a second target exposure time and a third image generated at a third exposure time, acquiring an image mean value of the second image and an image mean value of the third image, acquiring an image mean value of the maximum exposure time and an image mean value of the minimum exposure time, calculating an image mean value difference between the image mean value of the maximum exposure time and the image mean value of the minimum exposure time, judging that the image mean value difference meets a light cut-off constraint condition, and taking the second group of target exposure time as a group of searched exposure time corresponding to the wavelength of the current wavelength configuration device if the image mean value of the second image and the image mean value of the third image meet an image saturation constraint condition and an image linearity constraint condition; the data processing module is further configured to calculate quantum efficiency of the image acquisition module under the wavelength of each wavelength configuration device according to the corresponding group of exposure time of the wavelength of each wavelength configuration device.
10. A computer readable storage medium having a computer program stored therein, characterized in that the computer program, when executed by a processor, implements the method of any of claims 1 to 7.

Description

Method for searching exposure time and quantum efficiency measuring system Technical Field The invention relates to the technical field of image sensor testing, in particular to a method for searching exposure time and a quantum efficiency measuring system. Background Quantum efficiency (Quantum Efficiency, QE) is a parameter describing the ability of a pixel to convert photons into electrons and is also an important parameter in evaluating the performance of an image sensor. The higher the quantum efficiency, the stronger the photoelectric conversion capability of the image sensor at the wavelength, and the stronger the weak light expression capability. Quantum efficiency (Quantum Efficiency, QE), which is an evaluation parameter of an image sensor, is used to measure the ability of a pixel to convert photons into electric charge, and reflects how weak the image sensor can respond to. The less light is required by the image sensor to collect useful imaging data, the higher the quantum efficiency. In practice, the number of photons can be calculated from the exposure time difference, the actual light power value, the pixel size, etc., while the number of electrons can be obtained from the mean difference and the conversion gain of the image DN. The other parameters can be directly measured, except for the two parameters of the exposure time difference and the mean value difference of the image DN (the output brightness value of the sensor). Considering that the mean value difference of the image DN and the exposure time difference are strongly correlated, and linearity constraint exists in the selection of the exposure time, the key point of calculating QE is to obtain the exposure time meeting the linearity requirement, but not any exposure time can meet the requirement. Specifically, due to the existence of the influence of dark current, noise interference, whether the charge reaches saturation and the like, the image sensor cannot be guaranteed to be in a linear region, and the response capability to a light field is different for different test wave bands, sensor types and processes, and the exposure time cannot be guaranteed to meet the linearity requirement, so that the quantum efficiency of the image sensor cannot be accurately measured. Accordingly, there is a need to provide a solution for measuring the quantum efficiency of an image sensor to improve the above-mentioned problems. Disclosure of Invention The invention aims to provide a method for searching exposure time and a quantum efficiency measuring system, which are used for accurately searching exposure time meeting linearity requirements, so as to accurately measure the quantum efficiency of an image sensor. The method comprises the steps of configuring fixed parameters of an image acquisition module, wherein the fixed parameters comprise minimum image mean value difference, searching step length, initial exposure time value and saturation value correction coefficient, configuring the wavelength of a wavelength configuration device, controlling the image acquisition module to determine a set of candidate exposure times according to the searching step length and the initial exposure time value, after the wavelength of the wavelength configuration device is configured, receiving single-band light configured by the wavelength configuration device through an optical fiber bundle, selecting target exposure times from the set of candidate exposure times for multiple times, shooting images for multiple times under the environment of the current wavelength of the wavelength configuration device, judging that light cut-off does not occur and a preset image saturation constraint condition is met, and meeting an image linearity constraint condition, and taking the target exposure times as a set of exposure times corresponding to the searched wavelength of the current wavelength configuration device until the searched set of exposure times respectively corresponding to the wavelengths of the wavelength configuration device is achieved, wherein the set of the exposure times comprises three target exposure times. The method for searching the exposure time has the advantages that unnecessary searching processes are avoided by adding the cut-off constraint, the saturation constraint and the linear constraint, and the searching processes are steadily performed towards the direction meeting the linearity requirement by correcting and iterating the searching step length and the exposure time, so that the searching efficiency is greatly improved. In addition, the embodiment can realize the automation of the quantum efficiency test flow by combining hardware equipment such as a related data processing module and the like. Therefore, according to the embodiment, the exposure time does not need to be manually configured, the wavelengths of the wavelength configuration devices meeting the linearity requirement are obtained to respectively correspond to one group o