Image Sensor Phase Difference Pixels for Auto Focus Accuracy
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Solution Overview
Problem
Phase difference detection type AF systems in image sensors face accuracy issues due to unequal light reception by phase difference detection pixels, particularly those at the outer regions of the image sensor, leading to reduced auto focus accuracy.
Innovation Solution
The image sensor incorporates phase difference detection pixels with varying shield region ratios, arranged in a lattice pattern, where the first group pixels have a first shield region deviated on one side, the second group pixels have a second shield region deviated on the other side, and the third group pixels have a shield region ratio that either equals or differs from the second group's, ensuring balanced light reception across the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If shielded regions are arranged symmetrically in phase difference detection pixels, then manufacturing is simplified, but AF accuracy deteriorates due to uneven light distribution between outer and central regions
Solution Approach 1:
The patent applies local quality by differentiating shield region configurations based on pixel location. Central region pixels use symmetric shield regions (equal area on both sides), while outer region pixels use asymmetric shield regions (different areas on each side). This localized adaptation compensates for the varying incident light quantities across different sensor regions, maintaining equal light reception between left and right pixels regardless of position.
2Quantity of substance
If phase difference detection pixels are arranged in outer regions of the image sensor, then more detection pixels are available, but light quantity imbalance increases between left and right pixels
Solution Approach 1:
The patent implements local quality by positioning asymmetric shield region pixels specifically in outer regions of the image sensor. These asymmetric shields compensate for the increased light quantity imbalance that occurs at peripheral locations, allowing the system to utilize more detection pixels while maintaining measurement precision across the entire sensor array.
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 ensures that phase difference detection pixels receive approximately equal amounts of light, enhancing auto focus accuracy by minimizing light quantity differences and optimizing light distribution, thereby improving the overall accuracy of phase difference detection.
Implementation Method 1
light incident through a pick-up lens is pupil-divided into a pair of images, and a phase difference, which is an interval between the images, is detected to set the position of the pick-up lens, thereby detecting focus
Implementation Method 2
some regions of the phase difference detection pixels are shielded to receive a limited amount of incident light
Data Source
AI summary
An image sensor includes phase difference detection pixels including first group pixels each having a first shield region deviated at one side and second group pixels each having a second shield region deviated at the other side, and image detection pixels arranged in a lattice pattern together with the phase difference detection pixels. The phase difference detection pixels include a first pixel group configured such that an area of the first shield region is equal to that of the second shield region, a second pixel group configured such that the area of the first shield region is equal to or greater than that of the second shield region, and a third pixel group configured such that the area of the first shield region is equal to or less than that of the second shield region.