Image Signal Processor PSF Selection for Phase-Difference Auto Focus
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Solution Overview
Problem
Conventional phase-difference auto focus systems in DSLR cameras using shielded and unshielded pixels deteriorate the quality of color images due to irregular operation of these pixels, leading to suboptimal performance.
Innovation Solution
An image signal processor that includes a memory storing point spread functions (PSFs), a PSF selection circuit, a disparity extractor, and a deconvolution circuit, which generates output image data with higher resolution by selecting appropriate PSFs based on selection information including disparity values, pixel location information, and lens position information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If shielded and unshielded pixels are used for phase-difference auto focus detection, then auto focus function is enabled, but color image quality deteriorates due to irregular operation of these pixels
Solution Approach 1:
The pixel array is segmented into multiple types: shielded pixels for phase difference detection, unshielded pixels for color image capture, and additional unshielded pixels for compensation. This segmentation allows each pixel type to perform its specialized function without interfering with others, resolving the contradiction between auto focus capability and color image quality.
Solution Approach 2:
An intermediary processing circuit is introduced that receives signals from both shielded and unshielded pixels, performs disparity calculation for phase difference detection, and generates compensation signals. This intermediary processing layer enables the system to maintain color image quality by compensating for the irregular operation of shielded pixels while preserving auto focus functionality.
2Reliability
If multiple pixel types are used for phase difference detection, then auto focus performance is improved, but image resolution and quality are compromised
Solution Approach 1:
The system changes the operational parameters of different pixel types dynamically. Shielded pixels operate for phase difference detection while unshielded pixels operate for color capture. The processing circuit adjusts disparity calculation parameters based on pixel type, enabling reliable auto focus performance while maintaining high image resolution through selective parameter optimization for each pixel category.
Solution Approach 2:
The patent employs excessive action by providing more unshielded pixels than strictly necessary for color capture alone. These additional unshielded pixels are specifically allocated for compensation purposes, allowing the system to over-compensate for the loss of regular pixel functionality in shielded regions, thereby maintaining both auto focus reliability and image resolution.
3Ease of operation
If conventional shielded pixel method is used, then phase difference detection is achieved, but optical blur and noise compensation is insufficient
Solution Approach 1:
A feedback mechanism is implemented where the processing circuit continuously monitors signals from both shielded and unshielded pixels, calculates disparities, and generates compensation signals that are fed back to enhance the final image output. This feedback loop enables effective optical blur and noise compensation while maintaining the simplicity of phase difference detection operation.
Solution Approach 2:
The system uses a composite approach by combining signals from multiple pixel types (shielded and unshielded) with different operational characteristics. The processing circuit integrates these diverse signals, applying appropriate weighting and compensation algorithms to create a composite output that effectively compensates for optical blur and noise while preserving the operational simplicity of the phase difference detection method.
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 enhances image resolution and maintains image quality by effectively utilizing PSFs to compensate for optical blur and noise, improving the performance of phase-difference auto focus systems.
Implementation Method 1
a deconvolution circuit configured to generate output image data having a higher resolution than the image data using the at least one PSF output by the PSF selection circuit and the image data
Data Source
AI summary
An image signal processor includes a memory configured to store a table, the table including a plurality of point spread functions (PSFs), a PSF selection circuit configured to output at least one of the plurality of PSFs stored in the table based on selection information, a disparity extractor configured to extract a disparity value from image data corresponding to pixel signals output from at least one pixel of a plurality of pixels included in an image sensor, and a processing circuit configured to generate pixel location information for the at least one pixel. Each of the pixels of the plurality of pixels includes a plurality of photoelectric conversion elements. The selection information includes the disparity value and the pixel location information.