Image Sensor Pupil Division for Focus Detection Accuracy
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Solution Overview
Problem
Existing image sensors using the pupil division phase-difference method for focus detection face limitations in image height range due to pupil shifts caused by mass-production variations, leading to deteriorated focus detection accuracy, especially at the peripheral image height.
Innovation Solution
The image sensor incorporates a combination of image forming pixels, first focus detecting pixels with a first light-shielding layer, and second focus detecting pixels with a second light-shielding layer, where the geometric centers of the pupil areas differ, and the eccentricity of the lenses relative to the pixel centers is opposite to the eccentricity of the light-shielding openings, allowing for improved pupil division and focus detection across a broader image height range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pupil division is performed using a single configuration of light-shielding layer and photo-electric conversion portions, then focus detection can be performed at the center image height, but focus detection accuracy deteriorates at peripheral image height due to pupil shift
Solution Approach 1:
The image sensor is divided into multiple pixel regions with different configurations: first pixel regions with first light-shielding layers and first photo-electric conversion portions, and second pixel regions with second light-shielding layers and second photo-electric conversion portions. This segmentation allows different parts of the sensor to handle different pupil shift conditions, enabling accurate focus detection across the entire image height range.
Solution Approach 2:
Different pixel regions are assigned different local qualities (configurations) to suit their specific functions. The first pixel regions are optimized for certain pupil areas while the second pixel regions are optimized for other pupil areas. This local differentiation ensures that each region can accurately detect focus for its corresponding field of view, resolving the pupil shift issue at peripheral heights.
2Ease of manufacture
If the entrance pupil distance of the image sensor differs from the exit pupil distance of the imaging lens, then the image sensor can be positioned at a standard distance, but a pupil shift occurs between the exit pupil of the imaging lens and the incident pupil of the image sensor
Solution Approach 1:
The invention changes the parameters of the light-shielding layers and photo-electric conversion portions in different pixel regions to compensate for pupil shift. By adjusting the positions and configurations of these components, the system maintains accurate focus detection even when the entrance pupil distance differs from the exit pupil distance, without requiring precise positioning of the image sensor.
3Ease of manufacture
If mass-production variations cause positional shift between microlens and divided photo-electric conversion portions, then manufacturing can be simplified, but a pupil shift occurs between the exit pupil of the imaging lens and the incident pupil of the image sensor
Solution Approach 1:
The invention performs preliminary action by pre-configuring multiple pixel regions with different light-shielding layer and photo-electric conversion portion arrangements before actual use. This preliminary differentiation ensures that regardless of mass-production variations and resulting positional shifts, there will always be appropriately configured pixel regions that can accurately detect focus, thereby compensating for manufacturing tolerances.
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 enhances focus detection accuracy by enabling uniform pupil division and reducing pupil shifts, thereby enlarging the image height range for effective focus detection using the pupil division phase-difference method.
Implementation Method 1
a microlens and a photo-electric conversion portion, wherein the microlens and the photo-electric conversion portion are arranged in an optical axis direction, and the photo-electric conversion portion is arranged at a position eccentric to a geometric centre of the microlens in a direction perpendicular to the optical axis
Data Source
AI summary
An image sensor includes a plurality of image forming pixels which receive light beams passing through an imaging pupil area of an imaging optical system, a plurality of first focus detecting pixels which receive light beams passing through a first pupil area smaller than the imaging pupil area, and a plurality of second focus detecting pixels which receive light beams passing through a second pupil area smaller than the imaging pupil area. The geometric center of the first pupil area differs from the geometric center of the second pupil area. The eccentricity of the microlens of the first focus detecting pixel relative to the center of the pixel differs from the eccentricity of the first focus detecting pixel relative to the center of the pixel of the microlens of the image forming pixel adjacent to the first focus detecting pixel.