Pixel-Wise Signal Correction for Phase-Difference Autofocus
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Solution Overview
Problem
Existing phase difference autofocus systems struggle with precise focusing due to lens manufacturing errors and sensor attachment errors, which cause variations in phase difference amounts within the correlation calculating area, leading to insufficient correction of image distortion and reduced focusing accuracy.
Innovation Solution
A signal processing apparatus and method that uses a correction value specific to each pixel, performing weighted sums for adjacent pixels and optionally subtracting an offset amount to correct image shifts, thereby improving focusing accuracy by adjusting pixel centers of gravity or applying offset processing to minimize errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single correction value representing the correlation calculating area is used, then the device complexity is reduced, but the measurement precision of phase difference amount deteriorates due to variation within the area
Solution Approach 1:
The correction value is divided into two segments: a first correction value (offset amount) representing the overall correlation calculating area and second correction values representing individual pixels within that area. This segmentation allows the system to maintain simplicity at the area level while achieving precision at the pixel level, resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
Different correction values are applied to different regions: the first correction value applies to the entire correlation calculating area, while second correction values are applied locally to individual pixels. This local quality approach enables precise correction of phase difference amounts at each pixel position without requiring complete redesign of the overall correction system.
2Ease of manufacture
If lens manufacturing errors and sensor attachment errors are corrected with a single correction value, then the ease of manufacture is improved, but the manufacturing precision of the autofocus system deteriorates
Solution Approach 1:
The correction system is segmented into two levels: a first correction value that can be applied uniformly across the correlation calculating area (easy to manufacture), and second correction values for individual pixels (precise but computationally handled). This segmentation maintains ease of manufacture while achieving high focusing accuracy through the combination of both correction levels.
Solution Approach 2:
The correction approach changes from using a single parameter (one correction value) to using multiple parameters (first correction value plus second correction values). This parameter change enables the system to correct manufacturing errors more precisely while still being manufacturable, as the first correction value handles the bulk of the correction and the second values refine the accuracy.
Data Source
AI summary
An apparatus includes a processing unit configured to perform signal processing for a signal from a sensor using a correction value that is different for each pixel of the pair of signals, and a calculating unit configured to perform a correlation calculation for the signal output from the processing unit. The processing unit performs a weighted sum for adjacent pixels using the correction value.