Focus Detection Signal Correction for Chromatic Aberration
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Solution Overview
Problem
Existing focus detection methods in on-imaging plane phase difference AF are prone to errors due to chromatic aberration of magnification, which are not accurately corrected as they are based on design values rather than actual image sensor characteristics, leading to low accuracy in focus detection.
Innovation Solution
A focus detection apparatus and method that acquires color-specific correction values based on unique color sensitivity information of the image sensor, corrects focus detection signals, and generates evaluation values for focus state detection, thereby improving accuracy by accounting for chromatic aberration effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If correction values are calculated based on design values for the image sensor, then the correction process is simple, but the accuracy of the correction value is low due to characteristic variation and manufacturing errors
Solution Approach 1:
The patent applies preliminary action by acquiring actual color sensitivity information from the image sensor before performing focus detection. The correction values are calculated in advance based on the actual characteristics of the specific image sensor unit, rather than using generic design values. This preliminary characterization of each sensor allows subsequent focus detection to be accurately corrected for chromatic aberration specific to that sensor.
Solution Approach 2:
The patent implements parameter changes by transitioning from using fixed design values to using dynamically acquired actual color sensitivity parameters. The system measures the actual chromatic aberration characteristics of each image sensor unit and adjusts the correction values accordingly. This parameter adaptation ensures that the correction matches the specific optical and sensor characteristics of each unit.
2Measurement precision
If color-specific correction is applied to each color channel, then focus detection accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent applies segmentation by separating the focus detection signals into different color channels (R, G, B) and applying individual correction values to each channel. The color sensitivity information is acquired and stored separately for each color, allowing independent correction of chromatic aberration effects for each wavelength. This segmented approach enables precise correction while maintaining organized data structures.
Solution Approach 2:
The patent implements feedback by using the acquired actual color sensitivity information to generate correction values that are then applied to the focus detection signals. The system measures the actual chromatic aberration characteristics and feeds this information back into the correction process, creating a closed-loop system that continuously compensates for sensor-specific variations.
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 effectively reduces focus detection errors caused by chromatic aberration, enhancing the accuracy of focus detection by using color-specific signal correction and other BP corrections, leading to improved focus state evaluation and control in imaging systems.
Implementation Method 1
an image sensor that includes a plurality of photoelectric conversion portions for each of a plurality of microlenses, performs photoelectric conversion on light entering via an imaging optical system to output an electric signal
Data Source
AI summary
A focus detection apparatus comprising: an acquisition unit that acquires, for each color, a correction value for correcting a pair of focus detection signals of respective colors acquired from a color image sensor based on color sensitivity information unique to the color image sensor which includes a plurality of photoelectric conversion portions for each of a plurality of microlenses, and performing photoelectric conversion on light entering via an imaging optical system to output an electric signal; a correction unit that corrects each focus detection signal by using the correction value; a generation unit that processes the pair of corrected focus detection signals of the respective colors, and generates a pair of focus detection signals; and a focus detection unit that detects an evaluation value based on the pair of focus detection signals.