Image sensor and method of detecting defective pixel

Abstract

The invention relates to an image sensor and a method for detecting defective pixels. An image sensor includes: a pixel array including pixels; and a controller configured to control the pixels to generate a plurality of images. The image sensor also includes a defect detector configured to determine, among the images, a target image based on an average green pixel value and a gain value related to an exposure time, and detect an adaptive static defective pixel as a defective pixel having a fixed position based on a pixel value included in the target image.

Description

Technical Field

[0001] Various embodiments of the present disclosure relate generally to image sensors, and more particularly, to an image sensor and a method of detecting defective pixels. Background Art

[0002] Image sensors can be roughly classified into charge coupled device (CCD) image sensors or complementary metal oxide semiconductor (CMOS) image sensors. CMOS image sensors, which have low manufacturing costs, low power consumption, and are easily integrated with peripheral circuits, are recently attracting attention.

[0003] The wafer test may detect defective pixels included in the manufactured image sensor. The defective pixel may refer to a pixel whose pixel value differs from that of an adjacent pixel by a preset value or more among pixels included in the image sensor.

[0004] Defective pixels may be included in image sensors for various reasons during the manufacturing process, or may even appear after wafer testing due to pixel failure or degradation. When an image sensor includes information about defective pixels, the accuracy of image data generated from the image sensor may be enhanced. Summary of the invention

[0005] According to an embodiment of the present disclosure, an image sensor may include: a pixel array including a plurality of pixels; and a controller configured to control the pixels to generate a plurality of images. The image sensor may also include a defect detector configured to determine at least one target image among the images based on an average green pixel value and a gain value related to an exposure time, and to detect an adaptive static defective pixel as a defective pixel at a fixed position based on a pixel value included in the target image.

[0006] According to an embodiment of the present disclosure, a method may include the following steps: generating multiple images; determining a target image among the images based on an average green pixel value and a gain value related to an exposure time; and detecting adaptive static defective pixels as defective pixels at fixed positions based on pixel values ​​included in the target image.

[0007] According to an embodiment of the present disclosure, an image sensor may include: a pixel array including pixels; and a controller configured to control the pixels to generate a plurality of images. The image sensor may also include a defect detector configured to determine a target image satisfying a preset test condition based on an average pixel value and a gain value determined based on an exposure time among the images, and to detect an adaptive static defective pixel as a defective pixel having a fixed position based on a pixel value included in the target image.

[0008] According to an embodiment of the present disclosure, an image sensor may include a pixel array including a plurality of pixels configured to output a plurality of images for setting a frame. The image sensor may also include a defect detector configured to determine at least one target image among the plurality of images, detect at least one pixel among the plurality of pixels of the target image in which a defect at a fixed position occurs more than a set number of times as an adaptive static defect pixel, and correct the adaptive static defect pixel based on the pixel values ​​of the neighboring pixels of the adaptive static defect pixel. The target image is determined based on at least one of an average output signal of the plurality of pixels, an analog gain for determining the magnitude of the output signals of the plurality of pixels, and a light receiving time of the pixel array. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram illustrating an image sensor according to an embodiment of the present disclosure.

[0010] Figure 2 is a diagram illustrating a defective pixel detection operation performed by a defect detector according to an embodiment of the present disclosure.

[0011] Figure 3 is a diagram illustrating adaptive static defective pixels included in a target image.

[0012] Figure 4 is a flowchart for describing a defective pixel detection operation of an image sensor according to an embodiment of the present disclosure.

[0013] Figure 5 is a diagram showing a stacked image sensor according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0014] Throughout this specification, specific structural or functional descriptions are provided only to illustrate the embodiments of the present disclosure, which may be practiced in various forms and should not be interpreted as being limited to the embodiments of the present disclosure.

[0015] Some embodiments of the present disclosure will now be described with reference to the accompanying drawings to describe the technical ideas of the present disclosure so that those skilled in the art can practice them.

[0016] Some embodiments of the present disclosure relate to an image sensor and a method for detecting defective pixels, by which static defective pixels at fixed positions can be adaptively detected.

[0017] Figure 1 is a diagram illustrating an image sensor according to an embodiment of the present disclosure.

[0018] Reference Figure 1, the image sensor 100 may include a pixel array 110, a controller 120, a pixel driver 130, a signal converter 140, and a defect detector 150. The image sensor 100 may generate image data based on the received optical signal and send the image data to an image signal processor for performing an operation to enhance image quality.

[0019] The pixel array 110 may include a plurality of pixels arranged in an array in rows and columns. Each pixel may include a microlens for collecting light, a color filter determined based on a pattern type, and a photoelectric element for converting an optical signal into an electrical signal. For example, the electrical signal generated from the pixel may be an analog signal. The size of the analog signal may be adjusted based on an analog gain value. As the analog gain value increases, the size of the analog signal may increase. As the size of the analog signal increases, the percentage of noise included in the signal may increase. The pixel array 110 may send the analog electrical signal to the signal converter 140.

[0020] The controller 120 may control the general operation of the image sensor 100. The controller 120 may generate a control signal to control the operation timing of the image sensor 100 or adjust the analog gain value through the pixel driver 130. The controller 120 may generate a control signal to control the operation of the signal converter 140. The controller 120 may generate a clock signal or a ramp signal and apply it to the signal converter 140. The controller 120 may generate a control signal to control the detection operation and the correction operation of the defect detector 150.

[0021] The pixel driver 130 may output a control signal for controlling the pixels of the pixel array 110. The pixels may generate an electrical signal having an analog type (hereinafter, an analog electrical signal) in response to the control signal generated from the pixel driver 130.

[0022] The signal converter 140 may convert the electrical signal output from the pixel array 110 into a digital signal. The signal converter 140 may perform correlated double sampling to eliminate noise included in the analog electrical signal. The signal converter 140 may generate a digital signal by comparing the ramp signal with the analog electrical signal. In an embodiment of the present disclosure, the digital signal may be referred to as image data. For example, the image data may include pixel values ​​corresponding to each pixel. For example, the pixel value may be an output signal of each pixel. In addition, the output signal of the pixel driver 130 may include an analog type. The size of the output signal of the pixel driver 130 may be determined based on the analog gain value. The output signal of the signal converter 140 may include a digital type. The image data may be sent to the defect detector 150.

[0023] In an embodiment of the present disclosure, the controller 120 may control the pixel array 110, the pixel driver 130, the signal converter 140, etc., so that the image sensor 100 generates a plurality of images. Each of the plurality of images may be generated based on image data corresponding to a single frame. For example, when the frame rate of the image sensor 100 is 60 frames per second (fps), the image sensor 100 may generate and output 60 images per second.

[0024] The defect detector 150 may adaptively detect at least one static defective pixel at at least one fixed position after wafer testing. In an embodiment of the present disclosure, wafer testing may refer to a test for detecting defects of the image sensor 100 in a manufacturing process. For example, defective pixels may be detected by comparing a test image generated by performing an image sensing operation under preset conditions with an ideal image corresponding to the preset conditions. Defective pixels generated in a manufacturing process may be detected by wafer testing. Based on the results of the detection operation performed multiple times, defective pixels detected at the same position on the pixel array 110 may be static defective pixels.

[0025] As described above, static defective pixels at fixed positions may be detected in wafer testing of the image sensor 100. In an embodiment of the present disclosure, after wafer testing, the image sensor 100 may further detect adaptive static defective pixels based on the sensing results of the image sensor 100. In other words, during the operation of the image sensor 100, pixels that are continuously found to be defective at the same position may be referred to as adaptive static defective pixels. Adaptive static defective pixels are in addition to static defective pixels detected as part of the manufacturing process during wafer testing. The defect detector 150 may receive image data corresponding to each of a plurality of images generated from the image sensor 100 from the signal converter 140. The defect detector 150 may determine an image similar to a test image generated at the time of wafer testing among the plurality of images generated from the image sensor 100 as a target image. The defect detector 150 may determine at least one target image for detecting static defective pixels after wafer testing even without performing additional testing.

[0026] The defect detector 150 may determine a plurality of target images among a plurality of images. The defect detector 150 may detect at least one defective pixel from each target image. In addition, the defect detector 150 may determine an adaptive static defective pixel by excluding a static defective pixel detected in a wafer test from pixels detected as defective at least a preset number of times at the same position. The defect detector 150 may store information about the detected adaptive static defective pixel in a memory. For example, the memory storing information about the adaptive static defective pixel may be a read-only memory (ROM). The defect detector 150 may send a trigger signal to the controller 120 to store information about the adaptive static defective pixel in response to the detection of the adaptive static defective pixel. The trigger signal may be sent to the controller 120 according to the interrupt signal. When the controller 120 receives the trigger signal, the controller 120 may generate a control signal to control the position information of the defective pixel detected by the defect detector 150 and the information indicating whether the defective pixel is an adaptive static defective pixel to be stored in the memory.

[0027] The image sensor 100 may generate a plurality of images. Each of the plurality of images may be image data corresponding to a single frame. The plurality of images generated by the image sensor 100 may be continuous images. The target image determined by the defect detector 150 may not be continuous.

[0028] Information about static defective pixels detected by wafer testing may also be stored in the memory. In an embodiment of the present disclosure, static defective pixels that are not detected by wafer testing but based on the result of the sensing operation of the image sensor 100 may be referred to as adaptive static defective pixels. Information about static defective pixels detected by wafer testing may have been stored in the memory. The defect detector 150 may include a pixel corrector 151 for correcting the pixel value of the defective pixel based on the information stored in the memory.

[0029] The pixel corrector 151 may correct the pixel value of the defective pixel by using the neighboring pixel values ​​of the defective pixel. How to correct the pixel value of the defective pixel using the neighboring pixel values ​​is already well known, so a detailed description will be omitted.

[0030] Figure 2 is a diagram illustrating a defective pixel detection operation of a defect detector according to an embodiment of the present disclosure.

[0031] Reference Figure 2 , the defect detector 150 can adaptively detect static defective pixels at fixed positions even after wafer testing, and correct the detected defective pixels. In other words, the image sensor 100 including the defect detector 150 can adaptively detect static defective pixels.

[0032] The image sensor 100 may generate a plurality of images. The defect detector 150 may determine a target image for detecting adaptive static defective pixels among the generated plurality of images. The defect detector 150 may determine the target image based on an average pixel value of pixels included in the image, an analog gain value for adjusting the magnitude of the pixel value, and a light receiving time for image generation. In an embodiment of the present disclosure, the defect detector 150 may determine the target image based on an average green pixel value, an analog gain value of the image sensor 100, and a light receiving time indicating a time when the image sensor 100 is exposed to light. In another embodiment of the present disclosure, the target image may be determined using an average pixel value of another color pixel other than the green pixel. The average green pixel value may refer to an average pixel value of green pixels among the pixels included in the image.

[0033] The defect detector 150 may determine a black scene image or a white scene image similar to an image generated during the wafer test among images generated after the wafer test as a target image. The image sensor 100 may generate a test image that meets a preset condition during the wafer test. The black scene image may be an image corresponding to a test image generated under dark conditions of the wafer test. In the black scene image, a pixel whose pixel value differs from an adjacent pixel by more than a preset threshold may be a defective pixel. Similarly, the white scene image may be an image corresponding to a test image generated under bright conditions of the wafer test. Dark conditions and bright conditions may change according to the wafer test.

[0034] In an embodiment of the present disclosure, the defect detector 150 may determine the target image as an image in which the average green pixel value among the images generated when the analog gain value of the image sensor 100 exceeds the first reference value and the light receiving time of the image sensor 100 exceeds the first time is less than the first threshold value. The determined target image may correspond to a black scene image. The first reference image and the first time may be set to correspond to the dark conditions of the wafer test. The average green pixel value may indicate the brightness of the generated image. The first threshold may correspond to the brightness reference of the dark conditions of the wafer test. When the average green pixel value of the generated image is equal to or greater than the first threshold value, it may indicate that the generated image is not an image corresponding to the black scene image.

[0035] The defect detector 150 may determine the target image as an image whose average green pixel value exceeds the second threshold value among images generated when the analog gain value of the image sensor 100 is less than the second reference value and the light receiving time of the image sensor 100 is less than the first time. The determined target image may correspond to a white scene image. The second threshold value may correspond to a brightness reference of a bright condition of a wafer test. The second reference image and the second time may be set to correspond to a bright condition of a wafer test. The defect detector 150 may exclude a saturated image whose average green pixel value exceeds a third threshold value from the target image, even if the image is generated when the analog gain value of the image sensor 100 is less than the second reference value and the light receiving time of the image sensor 100 is less than the first time. As a criterion for determining a saturated image, the third threshold value is greater than the second threshold value.

[0036] In an embodiment of the present disclosure, the first reference value may be greater than the second reference value, and the first time may be longer than the second time. The analog gain value and the light receiving time of the image sensor 100 may indicate the validity of the target image. For example, even if the image generated when the analog gain value of the image sensor 100 is less than or equal to the first reference value and the light receiving time of the image sensor 100 is less than or equal to the first time has an average green pixel value of the generated image less than the first threshold, the generated image may not be determined as the target image. Because the size of the pixel signal or the light receiving time is not large enough or long enough, the generated image may not be used to detect defective pixels. Similarly, even when the analog gain value of the image sensor 100 exceeds the second reference value or the light receiving time of the image sensor 100 exceeds the second time, the generated image may not be determined as a valid image for detecting defective pixels.

[0037] In another embodiment of the present disclosure, the defect detector 150 may use an average pixel value of another color other than green or an average pixel value of the entire pixel regardless of any color.

[0038] The defect detector 150 may exclude abnormal images without vertical synchronization or horizontal synchronization from the target image. Since the abnormal images without vertical synchronization or horizontal synchronization are more likely to be invalid images generated by erroneous operations, they may be excluded from the target images for defect detection.

[0039] The defect detector 150 may detect a defective pixel whose pixel value differs from that of an adjacent pixel by a preset value or more among pixels included in the target image, and count the number of times the defective pixel is detected during a period of generating a plurality of images. The defect detector 150 may count how many times each pixel position is detected as a defective pixel. For example, the defect detector 150 may count the number of defective pixels by position of the pixel array 110. The pixel position may be determined using a vertical synchronization or horizontal synchronization signal. How to determine the pixel position based on the vertical synchronization or horizontal synchronization signal is already known, so a detailed description will be omitted.

[0040] The defect detector 150 may determine a sufficient number of target images among the plurality of images to determine the adaptive static defective pixels. The defect detector 150 may repeat the target image determination operation until there are a sufficient number of target images to determine the adaptive static defective pixels.

[0041] For example, the image sensor 100 may generate 125 images, and the defect detector 150 may determine 60 of the 125 images as target images. In the case where a pixel detected as a defective pixel 100 times or more at the same position is determined as a static defective pixel, the defect detector 150 may determine an additional target image among images newly generated by the image sensor 100 until the defective pixel is detected 100 times at the same position.

[0042] The defect detector 150 may determine a defective pixel detected at the same position a preset number of times or more as an adaptive static defective pixel, i.e., a defective pixel at a fixed position, among the defective pixels. The defect detector 150 may exclude pixels detected as defective due to, for example, a temporary error or a flicker phenomenon from the adaptive static defective pixels by determining the defective pixel detected at the same position a preset number of times or more as an adaptive static defective pixel.

[0043] The defect detector 150 may exclude defective pixels at the same position as the static defective pixels stored in the memory from the detected defective pixels from the adaptive static defective pixels. In an embodiment of the present disclosure, the memory storing information about the static defective pixels may be a ROM. In the ROM, information about static defective pixels detected as defective pixels at fixed positions in wafer testing may be pre-stored. The defect detector 150 may distinguish between already detected static defective pixels and adaptive static defective pixels detected after wafer testing based on the information stored in the ROM. The defect detector 150 may perform an operation of classifying static defective pixels and adaptive static defective pixels. The defect detector 150 may determine that the defective pixels corresponding to the static defective pixels already stored in the ROM among the defective pixels detected by the detection operation of the present disclosure are not adaptive static defective pixels.

[0044] The defect detector 150 may store information about the adaptive static defective pixels in a memory. In an embodiment of the present disclosure, the memory storing the information about the adaptive static defective pixels may be a ROM. The controller 120 may send a control signal to the ROM to store the information about the adaptive static defective pixels in the ROM. In the ROM, information about the static defective pixels detected in the wafer test and the adaptive static defective pixels detected after the wafer test may be stored. The technology of storing information in the ROM is already known, so a detailed description will be omitted from this specification.

[0045] Figure 3 is a diagram illustrating adaptive static defective pixels included in a target image.

[0046] Reference Figure 3 , target images 310 to 360 each having a size of 5*5 are shown. Pixels indicated by hatching in the target images 310 to 360 may indicate pixels detected as defective pixels. Figure 3 It can be assumed that a pixel detected as defective at least 6 times at the same position can be determined as an adaptive static defective pixel.

[0047] Pixels (0, 1), (2, 2), (4, 1), and (4, 4) are shown to be detected as defective pixels in a first target image 310. Pixels (2, 0), (2, 2), (2, 3), (4, 2), and (4, 4) are shown to be detected as defective pixels in a second target image 320. Pixels (0, 0), (2, 2), (3, 1), and (4, 4) are shown to be detected as defective pixels in a third target image 330. Pixels (0, 4), (2, 2), and (4, 4) are shown to be detected as defective pixels in a fourth target image 340. Pixels (0, 4), (1, 0), (2, 0), (2, 2), (3, 0), and (4, 4) are shown to be detected as defective pixels in a fifth target image 350. Pixels (1, 2), (2, 2), (3, 2), and (4, 4) are shown to be detected as defective pixels in a sixth target image 360.

[0048] In the target images 310 to 360, the positions where pixels are detected as defective at least 6 times are (2, 2) and (4, 4). All pixels except the pixels at the positions (2, 2) and (4, 4) may not be defective pixels or may be temporarily defective pixels. The defect detector 150 may store only information about static defective pixels at fixed positions in the memory. In an embodiment of the present disclosure, the memory storing information about static defective pixels may be a ROM.

[0049] It may be assumed that the pixel at position (4, 4) is stored in the ROM as a static defect pixel detected in the wafer test. The defect detector 150 may determine only the pixel at position (2, 2) as an adaptive static defect pixel by excluding the pixel at position (4, 4) from the adaptive static defect pixel. The defect detector 150 may store information about the pixel at position (2, 2) in the memory. In an embodiment of the present disclosure, the memory storing information about the adaptive static defect pixel may be a ROM.

[0050] Figure 4 is a flowchart for describing a defective pixel detection operation of an image sensor according to an embodiment of the present disclosure.

[0051] Reference Figures 1 to 4 , the image sensor 100 may adaptively detect static defective pixels and store them in a memory even after wafer testing. Adaptive static defective pixels may refer to defective pixels at fixed positions detected after wafer testing. The image sensor 100 may correct the pixel values ​​of the defective pixels stored in the memory. In an embodiment of the present disclosure, the memory storing information about static defective pixels and adaptive static defective pixels may be a ROM.

[0052] In step S140 , the image sensor may generate a plurality of images. Each of the plurality of images may be image data corresponding to a single frame. The plurality of images may be transmitted to the defect detector 150 .

[0053] In step S420, the defect detector 150 may determine at least one target image among the plurality of images based on the average pixel value, the analog gain value, and the light receiving time. The defect detector 150 may determine the target image by using the average green pixel value or the average pixel value. The analog gain value and the light receiving time may indicate whether the target image is a valid image to be used for detecting defective pixels. The defect detector 150 may determine the black scene image as an image in which the average pixel value among the images generated when the analog gain value of the image sensor exceeds the first reference value and the light receiving time of the image sensor exceeds the first time is less than the first threshold. Similarly, the defect detector 150 may determine the white scene image as an image in which the average pixel value among the images generated when the analog gain value of the image sensor is less than the second reference value and the light receiving time of the image sensor is less than the second time exceeds the second threshold. The defect detector 150 may determine the black scene image and the white scene image as the target images to be used for detecting defective pixels. The defect detector 150 may exclude abnormal images that are not vertically synchronized or horizontally synchronized from the target image to enhance the accuracy of the detection operation. The defect detector 150 may determine a sufficient number of target images to determine the adaptive static defective pixels.

[0054] In step S430, the defect detector 150 may detect an adaptive static defective pixel among pixels included in the target image. The defect detector 150 may detect a defective pixel whose pixel value differs from an adjacent pixel value by at least a preset value among pixels included in the target image, and count the number of times the defective pixel is detected during a period of generating a plurality of images. The defect detector 150 may count the number of times the defective pixel is detected at each position. The defect detector 150 may determine a pixel that is detected as a defective pixel at least a certain number of times at the same position as an adaptive static defective pixel. The defect detector 150 may exclude pixels that are the same as pixels that have been stored in the memory as static defective pixels from among pixels that have each been detected as defective pixels at least a certain number of times at the same position, from the adaptive static defective pixels. For example, a defective pixel that has been identified as a static defective pixel during wafer testing is also not identified as an adaptive static defective pixel by the defect detector 150.

[0055] In step S440, the defect detector 150 may store information about the detected adaptive static defective pixel in a memory. The defect detector 150 may send a trigger signal to the controller in response to detecting the adaptive static defective pixel. The controller 120 may generate a control signal to store information about the adaptive static defective pixel in the memory. Upon receiving the control signal, the defect detector 150 may store position information of the adaptive static defective pixel and index information indicating the adaptive static defective pixel that is additionally detected based on an image generated from the defective pixel through an image sensing operation after the wafer test.

[0056] In step S450, the pixel corrector may correct the pixel value of the defective pixel based on the information stored in the memory.The pixel corrector may correct the defective pixel value by using pixel values ​​of neighboring pixels of the defective pixel.

[0057] Figure 5 is a diagram showing a stacked image sensor according to an embodiment of the present disclosure.

[0058] Reference Figure 5 , a cross-sectional view of an image sensor having a stacked structure of an upper element 510 and a lower element 520 connected by a through silicon via 530 is shown. The upper element 510 may include an upper substrate 511 and an upper interlayer insulating layer 512. The lower element 520 may include a lower substrate 521 and a lower interlayer insulating layer 522. The upper element 510 may be stacked on the lower element 520 so that active surfaces of the upper element 510 and the lower element 520 face each other. The active surface may refer to a side where a gate 514 or 523 is formed.

[0059] The upper substrate 511 may include a photodiode 515. A color filter 516 and a microlens 517 may be formed on top of the photodiode 515. The color filter 516 and the microlens 517 may each include an organic substance. The upper substrate 511 may include a silicon wafer and another semiconductor substrate. In an embodiment of the present disclosure, the upper substrate 511 may be referred to as a device substrate.

[0060] The upper interlayer insulating layer 512 may have a form surrounding the transfer gate 514 and the upper metal line 513. The upper interlayer insulating layer 512 may include at least one of silicon oxide, silicon nitride, or silicon oxynitride. The transfer gate 514 may be arranged to partially overlap with the photodiode 515. The transfer gate 514 may transfer electrons generated from the photodiode 515 to the floating diffusion region.

[0061] The lower substrate 521 may include a silicon wafer. The logic gate 523 may be formed on the lower substrate 521. The logic gate 523 may be an electronic circuit implemented as a digital circuit that executes firmware or a specific algorithm to perform a specific operation.

[0062] The lower interlayer insulating layer 522 may have a form of surrounding the logic gate 523 and the lower metal line 524. Similar to the upper interlayer insulating layer 512, the lower interlayer insulating layer 522 may include at least one of silicon oxide, silicon nitride, or silicon oxynitride. The lower metal line 524 and the upper metal line 513 may transmit various electrical signals and include metal or conductor.

[0063] The through silicon via 530 may penetrate the upper substrate 511 and the upper interlayer insulating layer 512, and partially penetrate the lower interlayer insulating layer 522. The through silicon via 530 may include a barrier layer on its surface. The through silicon via 530 may be electrically connected to the upper metal line 513, the transmission gate 514, the logic gate 523, and the lower metal line 524.

[0064] Reference Figure 5 as well as Figure 1, the pixel array 110 may be included in the upper substrate 511, and the controller 120, the pixel driver 130, the signal converter 140, and the defect detector 150 except the pixel array 110 may all be implemented using the lower substrate 521 and the logic gate 523. The defect detector 150 may determine the target image among the images generated by the sensing operation of the image sensor based on the brightness level and validity. The defect detector 150 may detect an image satisfying a bright condition or a dark condition among the images based on the average pixel value of the pixels. The defect detector 150 may determine whether one of the images is valid for detecting a defective pixel based on the light receiving gain value. The defect detector 150 may perform a defective pixel detection operation on the target image. The defect detector 150 may detect an adaptive static defective pixel newly generated by using the image sensor among defective pixels each detected at least a preset number of times at the same position on the pixel array 110. The controller 120 may generate a control signal to store information about the adaptive static defective pixel in the ROM in response to the detection of the adaptive static defective pixel, and the defect detector 150 may store information about the adaptive static defective pixel in the ROM in response to the reception of the control signal.

[0065] The stacked structure of the image sensor may be a structure that satisfies the performance required of the image sensor. In the case where the area of ​​the image sensor is limited, the stacked structure may allow a space for a circuit for performing operations required by the image sensor to be secured while allowing the area of ​​the pixel array to be secured as much as possible. With this stacked structure, an electronic circuit that performs more advanced functions than before may be included in the image sensor.

[0066] The stacked image sensor can perform part of the image processing operation within the image sensor itself to improve the quality of the generated image data. Since the defect detector 150 is implemented using the lower substrate 521 and the logic gate 523, the defect detection operation can be performed faster than in the image signal processor. In addition, since part of the image processing operation is performed by the image sensor, the image signal processor can perform the image processing operation with better performance. As a result, the quality of the output image can be improved.

[0067] While the present disclosure has been shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

[0068] CROSS-REFERENCE TO RELATED APPLICATIONS

[0069] This application claims the priority of Korean Patent Application No. 10-2023-0102807 filed on August 7, 2023 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

Claims

1. An image sensor, comprising: A pixel array, the pixel array comprising a plurality of pixels; a controller that controls the pixels to generate a plurality of images; as well as A defect detector that determines at least one target image among the multiple images based on an average green pixel value, an analog gain value for adjusting the size of a pixel signal, and a light receiving time indicating an exposure time, and detects an adaptive static defective pixel as a defective pixel at a fixed position based on a pixel value included in the at least one target image.

2. The image sensor according to claim 1, wherein: The defect detector determines the at least one target image as a black scene image in which the average green pixel value among the multiple images generated when the analog gain value of the image sensor exceeds a first reference value and the light receiving time of the pixel array exceeds a first time is less than a first threshold.

3. The image sensor according to claim 1, wherein: The defect detector determines the at least one target image as a white scene image in which the average green pixel value among the multiple images generated when the analog gain value of the image sensor is less than a second reference value and the light receiving time of the pixel array is less than a second time exceeds a second threshold.

4. The image sensor according to claim 3, wherein: The defect detector excludes saturated images whose average green pixel value exceeds a preset third threshold from the at least one target image, and The preset third threshold is greater than the second threshold.

5. The image sensor according to claim 1, wherein: The defect detector excludes abnormal images that are not vertically synchronized or horizontally synchronized from the at least one target image.

6. The image sensor according to claim 1, wherein: The defect detector: Detecting defective pixels, among pixels included in the at least one target image, whose pixel values ​​differ from neighboring pixels by a preset value or more; counting the number of times the defective pixel is detected during a period of generating the plurality of images; as well as Defective pixels detected at least a preset number of times at the same position among the defective pixels are determined as the adaptive static defective pixels.

7. The image sensor according to claim 6, wherein: The defect detector excludes defective pixels at the same position as that of the static defective pixels stored in the memory among the defective pixels from the adaptive static defective pixels.

8. The image sensor according to claim 7, wherein: The static defective pixels are detected as defective pixels at fixed positions during wafer testing.

9. The image sensor according to claim 7, wherein: The defect detector stores information about the adaptive static defective pixels in the memory.

10. The image sensor according to claim 9, further comprising: A pixel corrector corrects the defective pixel stored in the memory based on neighboring pixel values ​​of the defective pixel.

11. A method for detecting defective pixels in an image sensor, the method comprising the following steps: Generate multiple images; determining a target image among the images based on a brightness level of the images, a light receiving time indicating a time when the images are exposed to light, and an analog gain value for adjusting a signal size of the images; detecting an adaptive static defective pixel as a defective pixel having a fixed position based on pixel values ​​included in the target image; generating a trigger signal in response to detection of the adaptive static defective pixel to store information about the adaptive static defective pixel; as well as The information about the adaptive static defective pixels is stored in a memory in response to the trigger signal.

12. The method according to claim 11, wherein: The step of determining the target image comprises the following steps: Determine the target image as an image with a brightness level lower than a first threshold corresponding to a dark condition or higher than a second threshold corresponding to a bright condition; excluding, from the target image, a first invalid image whose light receiving time is less than or equal to a first time and whose analog gain value is less than or equal to a first reference value indicating validity of the image corresponding to the dark condition; and excluding from the target image a second invalid image whose light receiving time is equal to or greater than a second time and whose analog gain value is equal to or greater than a second reference value indicating validity of the image corresponding to the bright condition, The first time is greater than the second time, and the first reference value is greater than the second reference value.

13. The method according to claim 11, wherein: The step of detecting the adaptive static defective pixel comprises the following steps: Detecting defective pixels, among pixels included in the target image, whose pixel values ​​differ from those of adjacent pixels by a preset value or more; counting the number of times the defective pixel is detected during a period of generating the plurality of images; and Defective pixels detected at least a preset number of times at the same position among the defective pixels are determined as the adaptive static defective pixels.

14. The method according to claim 11, further comprising the steps of: The defective pixel stored in the memory is corrected based on neighboring pixel values ​​of the defective pixel.

15. An image sensor, comprising: a pixel array, the pixel array comprising pixels; a controller that controls the pixels to generate a plurality of images; as well as A defect detector that determines a target image that meets a preset test condition among the multiple images based on an average pixel value, an analog gain value for adjusting the size of an analog pixel signal, and a light receiving time indicating an exposure time, and detects an adaptive static defective pixel as a defective pixel at a fixed position based on a pixel value included in the target image.

16. The image sensor according to claim 15, wherein: The test condition corresponds to a dark condition in which the analog gain value exceeds a first reference value and the light receiving time exceeds a first time or a bright condition in which the analog gain value is less than a second reference value and the light receiving time is less than a second time, The first reference value is greater than the second reference value, The first time is longer than the second time, and The defect detector determines the target image as an image whose average pixel value is less than a first threshold corresponding to the dark condition or whose average pixel value is greater than a second threshold corresponding to the bright condition, wherein the average pixel value indicates a brightness level of the generated image.

17. The image sensor according to claim 16, wherein: The defect detector excludes, from the target image, a saturated image in which the average pixel value exceeds a saturation reference value indicating whether pixel values ​​of the image are saturated.

18. The image sensor according to claim 15, wherein: The defect detector counts the number of times a defective pixel whose pixel value differs from that of an adjacent pixel by a preset value or more is detected among pixels included in the target image during a period of generating the multiple images, and determines the defective pixel detected at least the preset number of times at the same position as the adaptive static defective pixel.

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