Imaging Device Focus Control via Rolling Shutter Distortion Correction
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Solution Overview
Problem
Imaging devices using CMOS sensors face challenges in accurate focus control due to distortion caused by the rolling shutter method, leading to errors in phase difference detection during subject movement, and existing solutions either limit focus detection conditions or require additional costly circuits.
Innovation Solution
An imaging device with alternately arrayed phase difference detection pixels on different lines performs correlation computations and corrections to isolate and reduce rolling shutter distortion, enabling accurate focus control without additional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase difference detection is performed using pixels on different lines during subject movement, then focus control can be carried out, but rolling shutter distortion causes errors in phase difference detection
Solution Approach 1:
The patent divides phase difference detection pixels into multiple line groups (first line group, second line group, etc.) and performs separate correlation computations for each group. By segmenting the detection process across different line groups and combining results, the system can compensate for rolling shutter distortion effects that would otherwise corrupt the phase difference measurement.
Solution Approach 2:
The patent introduces an intermediary correction process that calculates distortion amounts based on pixel positions and readout timing differences. This intermediary distortion correction mechanism mediates between the raw phase difference signals affected by rolling shutter and the final focus control output, eliminating the harmful distortion effects.
2Measurement precision
If additional circuits are added to correct rolling shutter distortion, then focus detection accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex hardware correction circuits with software-based correlation computations and mathematical processing. Instead of adding physical circuits to compensate for rolling shutter distortion, the system uses digital signal processing techniques including correlation computation between pixel signals and distortion amount calculations based on pixel positions and readout timing.
Solution Approach 2:
The imaging device uses its existing pixel array and readout system to perform self-correction. By utilizing the same phase difference detection pixels and incorporating distortion correction algorithms into the existing processing pipeline, the system achieves accurate focus detection without requiring external or additional dedicated correction circuits.
3Measurement precision
If focus control is limited to specific conditions to avoid distortion errors, then detection accuracy improves, but productivity and versatility decrease
Solution Approach 1:
The patent implements a dynamic focus control system that adapts to moving subjects by continuously calculating distortion amounts based on current pixel positions and readout timing. Instead of imposing static limitations on when focus control can be performed, the system dynamically compensates for rolling shutter effects, enabling focus control to proceed at full speed under all conditions.
Solution Approach 2:
The patent changes the approach from limiting operational parameters to adjusting correction parameters. By varying distortion correction calculations based on pixel position, line group assignments, and readout timing characteristics, the system maintains high detection reliability while preserving full focus control functionality and speed across all imaging conditions.
Data Source
AI summary
Provides an imaging device including, imaging element in which plural first lines arrayed with first phase difference detection pixels, and plural second lines arrayed with second phase difference detection pixels, are arrayed alternately; reading out section read out signals of the phase difference detection pixels; first correlation computing section carry out first correlation computation on signals read out from a set of the first and the second phase difference detection pixel; second correlation computing section carry out second correlation computation on signals read out from at least one set among a set of plural first phase difference detection pixels of the first line, and a set of plural second phase difference detection pixels of the second line; correcting section corrects results of the first correlation computation, by results of the second correlation computation; and focusing section control focusing based on the corrected correlation computation.