Avalanche Photodiode Image Sensor Pulse Control for Cluster Defect Mitigation
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Solution Overview
Problem
Existing image capturing systems face challenges in detecting and correcting defective pixels, particularly when switching from high illuminance to low illuminance conditions, leading to image quality deterioration due to cluster-type defects.
Innovation Solution
An image capturing apparatus equipped with a photoelectric conversion element, processor, and memory that acquires signals, performs correction processing based on pixel position information, and controls pulse signals differently in first and second modes to address defective pixels, with the number of pulses being less in the second mode to mitigate cluster defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the number of drive pulse signals is kept the same when switching from high illuminance to low illuminance image capturing, then the signal acquisition process remains simple and consistent, but the occurrence of cluster defects increases and image quality deteriorates
Solution Approach 1:
The patent applies dynamics by making the number of drive pulse signals adjustable based on illuminance conditions. The control unit dynamically changes the number of pulse signals from a first number (high illuminance) to a second number (low illuminance), allowing the system to adapt to different operating conditions and prevent cluster defects while maintaining operational simplicity.
2Measurement precision
If the number of drive pulse signals is increased to improve signal acquisition in low illuminance conditions, then more photons can be detected, but the occurrence of cluster defects increases
Solution Approach 1:
The patent applies parameter changes by modifying the number of drive pulse signals based on illuminance conditions. In low illuminance conditions, the control unit sets the number of pulse signals to a second number that is smaller than the first number used in high illuminance conditions. This parameter adjustment optimizes the balance between photon detection capability and cluster defect prevention.
3Device complexity
If defect correction is performed using a fixed threshold across all illuminance conditions, then the correction process is simple, but defective pixels cannot be accurately identified in low illuminance conditions
Solution Approach 1:
The patent applies local quality by using different threshold values for defective pixel determination based on illuminance conditions. The control unit determines whether a pixel is defective by comparing its signal to a first threshold (high illuminance) or a second threshold (low illuminance). This localized approach ensures accurate defective pixel identification in each specific operating condition while maintaining a relatively simple correction process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces the occurrence of cluster-type defects and improves image quality during low illuminance conditions by adjusting pulse signal control and threshold settings, thereby maintaining image quality consistency across varying light environments.
Implementation Method 1
photoelectric conversion apparatuses have been proposed that digitally count a number of photons that reach an avalanche photodiode (APD) and output this counted value from a pixel to serve as a digital signal that has been photoelectrically converted
Implementation Method 2
pixel comprising an APD is provided with an APD, a quenching circuit connected to the APD
Data Source
AI summary
An image capturing apparatus that is able to suppress decreases in image quality even during image capturing with a low illuminance, wherein the image capturing apparatus includes a photoelectric conversion element having an avalanche photodiode; a signal processing unit configured to perform correction on a signal that has been acquired by the photoelectric conversion element based on position information for a pixel that becomes a correction target; and a control unit configured to control a number of pulses for a pulse signal during a period in which a signal is acquired for one frame; wherein a threshold for the signal processing unit to determine whether or not the correction will be performed on a signal is different in a first mode and a second mode, wherein the number of pulses for the pulse signal is less in the second mode than in the first mode.