Image Sensor Row-Defect Detection With Clock-Timing Comparison
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Solution Overview
Problem
Image sensors may malfunction due to errors in driving signal output or signal transfer lines, leading to defective pixel rows that affect normal operation.
Innovation Solution
An image sensor with a detection circuit that counts cycles of a clock signal during a time interval for delayed row output signals, generates difference values, and compares these with reference values to determine faulty rows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detection circuit is added to detect defective rows, then reliability is improved, but device complexity increases
Solution Approach 1:
The detection circuit merges multiple functional components (counter circuit, difference circuit, comparison circuit, signal selection circuit) into an integrated unit that shares common signal lines and control mechanisms with the pixel array and row driver, thereby improving reliability through comprehensive defect detection while limiting the increase in overall device complexity
Solution Approach 2:
The detection circuit serves multiple functions: it counts clock cycles to measure timing delays, identifies defective rows through comparison with reference values, and provides feedback signals for defect notification. This multi-functionality allows a single added component to address multiple reliability concerns without proportionally increasing complexity
2Measurement precision
If timing detection and comparison operations are performed for each row, then measurement precision is improved, but processing time increases
Solution Approach 1:
The system performs preliminary timing measurements by counting clock cycles during the normal operation of row output signals. The counter circuit continuously monitors and records timing information without requiring additional processing time during actual image capture operations, thereby achieving precise measurement while minimizing time loss
Solution Approach 2:
The comparison circuit receives real-time timing data from the counter circuit and immediately compares it against reference values stored in memory. This feedback mechanism allows for rapid identification of defective rows without requiring extensive processing time, as the comparison operation is performed continuously during signal transmission
Data Source
AI summary
An image sensor is provided. The image sensor includes: a pixel array with a pixel area and a dummy area; a row driver configured to sequentially output driving signals to the pixel array; a detection circuit configured to receive a row output signals generated based on the driving signals from the dummy area, and receive the driving signals; and a timing controller configured to provide the driving signals to the row driver, and the driving signals and a clock signal to the detection circuit. The detection circuit is further configured to identify difference values between delay times corresponding to adjacent rows of the rows, determine whether the rows are defective by comparing the difference values with a reference value, and output result values indicating whether the rows are defective.