Focus Detection Apparatus Aberration Compensation
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Solution Overview
Problem
The imaging plane phase difference method for focus adjustment in imaging apparatuses suffers from inaccuracies due to differences in light reception by focus detection pixels and image pickup pixels, leading to discrepancies between calculated in-focus positions and optimal in-focus positions, especially under aberrations like spherical aberration and astigmatism.
Innovation Solution
A focus detection apparatus that obtains and combines image signals from different pupil areas of a focusing optical system, calculates contrast evaluation values, and detects defocus amounts based on image shifts to improve focus detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If focus detection pixels receive light through different exit pupil areas compared to image pickup pixels, then focus detection can be performed at high speed with simultaneous defocus direction and amount detection, but a difference occurs between detected in-focus position and optimal in-focus position due to lens aberrations
Solution Approach 1:
The exit pupil is divided into multiple pupil areas, with different photoelectric conversion units receiving light from different pupil areas. This segmentation allows simultaneous focus detection and image pickup while addressing the aberration-induced position discrepancy by processing signals from different pupil regions.
Solution Approach 2:
The patent changes the optical path parameters by introducing a beam splitter and redirecting light paths. The beam splitter divides the light from different pupil areas to separate photoelectric conversion units, enabling the system to maintain both high-speed focus detection capability and accurate in-focus position detection by compensating for aberration effects through optical path modification.
2Measurement precision
If separate photoelectric conversion units receive light from different pupil areas, then pupil division is achieved for phase difference focus detection, but the influence of lens aberrations (spherical aberration, astigmatism, coma) on focus detection signals differs from image pickup signals
Solution Approach 1:
A beam splitter is introduced as an intermediary optical element that redirects light from different pupil areas to appropriate photoelectric conversion units. This intermediary device enables the system to maintain signal consistency by ensuring that both focus detection and image pickup signals are affected by aberrations in a controlled and comparable manner, while still achieving the necessary pupil division for phase difference detection.
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
This approach reduces the difference between calculated in-focus positions and optimal in-focus positions, enabling high-accuracy focus detection by compensating for aberrations and improving focus detection precision.
Implementation Method 1
an imaging element having a plurality of photoelectric conversion units which are divided into NH×NV (N, N are natural numbers) portions
Data Source
AI summary
A focus detection apparatus has an obtaining unit for obtaining a first image signal corresponding to object light passing through a first pupil area of a focusing optical system and a second image signal corresponding to object light passing through a pupil area different from the first pupil area of the focusing optical system, a combination unit for generating a combination signal by combining the first and second image signals at least one of which is shifted by a predetermined step, wherein the shift and the generation of the combination signal are performed for a plurality of predetermined steps and a plurality of combination signals are generated, a calculation unit for calculating a contrast evaluation value from the plurality of combination signals, and a focus detection unit for detecting a defocus amount on the basis of the contrast evaluation value and the shift amount of the shift.