Lens Shading Compensation Coefficient Compression via DPCM
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Solution Overview
Problem
As CMOS Image Sensors transition from lower to higher resolutions, the increased data requirements for two-dimensional lens shading compensation coefficients lead to higher storage needs and chip area occupation, with existing methods lacking effective data compression solutions.
Innovation Solution
A lens shading compensation coefficient compression/decompression device and method utilizing differential blocks to calculate differentials between and within color channels, followed by entropy coding to reduce data redundancy, specifically employing Differential Pulse Code Modulation (DPCM) and distance-weighted values for further reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-dimensional lens shading compensation coefficients are used for higher resolution CIS, then lens shading compensation accuracy is improved, but non-volatile memory capacity and chip area increase
Solution Approach 1:
The patent segments the lens shading compensation coefficient data into different color channels (R, G, B) and applies different compression strategies to each channel. The differential blocks separately process inter-channel and intra-channel differences, allowing targeted compression that maintains accuracy while reducing overall data volume.
Solution Approach 2:
The patent transforms the lens shading compensation coefficients from their original form into differential values through mathematical operations. By changing the representation parameters from absolute coefficients to relative differences, the data redundancy is reduced while preserving the essential information needed for accurate compensation.
2Measurement precision
If two-dimensional lens shading compensation coefficients are used for higher resolution CIS, then lens shading compensation accuracy is improved, but chip area occupation increases
Solution Approach 1:
The patent divides the storage requirement into multiple compressed color channel components. By segmenting the data storage into separate R, G, and B channel differential values, the total storage area is reduced while maintaining the two-dimensional structure needed for accurate compensation.
Solution Approach 2:
The patent changes the data representation parameters to differential forms, which require fewer bits per pixel for storage. This parameter transformation reduces the chip area needed for storing the lens shading compensation coefficients while preserving the accuracy required for high-resolution sensors.
3Quantity of substance
If data compression is applied to lens shading compensation coefficients, then storage requirements are reduced, but data processing complexity increases
Solution Approach 1:
The patent performs differential calculations and compression operations on the lens shading compensation coefficients during the manufacturing or calibration phase, before the actual image sensing operation. This preliminary processing reduces the data to its compressed form, so that during normal operation, only simple decompression and application are needed, minimizing real-time processing complexity.
Data Source
AI summary
A lens shading compensation coefficient compression device includes: a first differential block suitable for calculating a lens shading compensation coefficient between color channels and removing redundancy between the color channels; a second differential block suitable for calculating a lens shading compensation coefficient within color channels and removing redundancy within the color channels; and an entropy coding block suitable for performing entropy coding on remaining lens shading compensation coefficients and compressing the lens shading compensation coefficients.