Image Sensor Entrance Pupil Distance for Focus Detection
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Solution Overview
Problem
The on-imaging surface phase difference method for focus detection deteriorates when the variation range of the incident angle of light from an imaging lens on an image sensor's peripheral portion is large, leading to pupil deviation and an insecure base line length, which affects focus detection quality.
Innovation Solution
An image capturing apparatus with an image sensor where pixels have multiple photoelectric conversion units receiving light through different partial pupil regions, with an entrance pupil distance that satisfies specific conditions relative to the minimum and maximum exit pupil distances and image height, ensuring a controlled pupil deviation and secure base line length for improved focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the image sensor is positioned at a fixed distance from the imaging lens, then the structure is simple and easy to manufacture, but the focus detection quality deteriorates when the variation range of incident angle is large
Solution Approach 1:
The patent makes the entrance pupil distance adjustable rather than fixed. The image sensor can be positioned at different distances from the imaging lens depending on the specific optical conditions (minimum or maximum exit pupil distance). This dynamic adjustment allows the system to maintain optimal focus detection quality across varying incident angle ranges while keeping the overall structure relatively simple.
2Measurement precision
If the entrance pupil distance is optimized for minimum exit pupil distance, then focus detection quality improves for that condition, but performance deteriorates when the exit pupil distance varies
Solution Approach 1:
The patent changes the parameter of entrance pupil distance to accommodate different operating conditions. By providing at least two different entrance pupil distances (first distance for minimum exit pupil distance, second distance for maximum exit pupil distance), the system can adapt its optical parameters to match the specific conditions, thereby maintaining high focus detection quality across varying scenarios.
Solution Approach 2:
The system dynamically selects the appropriate entrance pupil distance based on the actual exit pupil distance conditions. When the exit pupil distance is at its minimum, the sensor uses the first entrance pupil distance; when at maximum, it uses the second entrance pupil distance. This dynamic adaptation ensures optimal performance across the full range of operating conditions.
3Measurement precision
If multiple photoelectric conversion units are arranged to receive light from different pupil regions, then focus detection capability is enhanced, but device complexity increases
Solution Approach 1:
The patent segments the pupil into multiple regions by arranging multiple photoelectric conversion units (first, second, third, and fourth units) to receive light from different partial pupil regions. Each unit is responsible for detecting light from a specific region, and the focus detection is performed by comparing signals from these segmented units. This segmentation enables robust focus detection even when the incident angle varies, as different units remain effective under different angular conditions.
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 configuration allows for reliable focus detection over a wide range of conditions, even with varying incident angles, by maintaining a secure base line length and reducing pupil deviation, thus enhancing focus detection quality.
Implementation Method 1
a plurality of pixels each having a plurality of photoelectric conversion units for receiving light fluxes that have passed through different partial pupil regions
Data Source
AI summary
An image capturing apparatus in which a plurality of pixels each having a plurality of photoelectric conversion units for receiving light fluxes that have passed through different partial pupil regions of an imaging optical system are arrayed, wherein an entrance pupil distance Zs of the image sensor with respect to a minimum exit pupil distance Lmin of the imaging optical system and the maximum exit pupil distance Lmax of the imaging optical system satisfies a condition of4LminLmaxLmin+3Lmax<ZS<4LminLmax3Lmin+Lmax.