Two-Stage Calibration for Image Sensor Compression
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Solution Overview
Problem
Existing image processing systems face challenges in achieving high image quality and compression rates due to fixed pattern noise and the high computational power required for calibration, leading to energy consumption and performance issues, especially in portable cameras.
Innovation Solution
A two-stage calibration method where partial calibration is performed before compression using first calibration values and full calibration after decompression using second calibration values, reducing computational effort and minimizing compression artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full calibration is performed before compression, then image quality is improved, but computational power requirements and energy consumption increase
Solution Approach 1:
The calibration process is segmented into two distinct stages: a first calibration stage performed before compression using first calibration values, and a second calibration stage performed after decompression using second calibration values. This segmentation allows the computationally intensive full calibration to be distributed, with the preliminary calibration reducing data for compression while the final calibration restores complete accuracy, thereby resolving the contradiction between image quality and energy consumption.
Solution Approach 2:
A preliminary calibration is performed before compression using reduced calibration data, which sufficiently reduces fixed pattern noise to enable effective compression. This preliminary action prepares the data in advance for compression without requiring the full computational power of complete calibration, thus reducing energy consumption while maintaining compression effectiveness.
2Measurement precision
If full calibration is performed before compression, then image quality is improved, but device complexity increases
Solution Approach 1:
The calibration functionality is segmented across two processing stages and can be distributed between different devices (camera and external processing unit). The first calibration values are used in the camera for preliminary calibration, while second calibration values are applied externally for final calibration, reducing the computational burden on any single device.
Solution Approach 2:
Compressed image data serves as an intermediary format that preserves sufficient calibration information from the first calibration stage while reducing data volume. This intermediary representation allows the calibration process to be continued after decompression without requiring all calibration computations to occur before compression, thereby reducing device complexity.
3Productivity
If calibration is performed after decompression, then compression rates are improved, but image quality may deteriorate
Solution Approach 1:
A preliminary calibration using first calibration values is performed before compression to sufficiently reduce fixed pattern noise, enabling effective compression. This preliminary action ensures that the compression process works with pre-calibrated data, maintaining compression effectiveness while allowing final quality enhancement through second calibration values applied after decompression.
Solution Approach 2:
The calibration parameters are changed between two stages: first calibration values are applied before compression with appropriate precision for compression purposes, and second calibration values are applied after decompression with full precision for final image quality. This parameter change strategy allows optimization for both compression rate and image quality at different stages.
Data Source
AI summary
A method of calibrating, compressing and decompressing image signal values of an image sensor which has a plurality of light sensitive pixels arranged in rows and columns comprises the steps of: reading out the image signal values; compressing the image signal values; and decompressing the compressed image signal values, wherein the image signal values are calibrated while using calibration data sets which include a number of calibration values for each pixel. The method is characterized in that each calibration data set includes at least one first calibration value and at least one second calibration value, wherein the calibration of the image signal values includes a first calculation step which is carried out by the compression of the image signal values in order to calculate partly corrected image signal values while using the at least one first calibration value, and wherein the calibration of the image signal values includes a second calculation step which is carried out after decompressing the image signal values in order to calculate fully corrected image signal values while using the at least one second calibration value. An image recording system uses a corresponding method.