Image Pickup Apparatus Vignetting Correction via Pixel Gain
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Solution Overview
Problem
Conventional image pickup apparatuses face challenges in maintaining image quality due to vignetting effects caused by the image pickup optical system, particularly as focus detection pixels receive less light than image formation pixels, leading to varying gain requirements based on pixel position and incident light angles.
Innovation Solution
An image pickup apparatus that includes an optical influence estimation unit and an optical influence correction unit, using output signals from both image formation and focus detection pixels, along with two-dimensional pixel position information, to estimate and correct for vignetting effects by executing image processing with varying details based on the estimated influence, thereby improving image quality across different image heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If focus detection pixels are physically shielded from light to enable phase difference detection, then focus detection capability is improved, but light acquisition amount deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the treatment of focus detection pixels based on their position. Screen center region pixels (with small incident angles) receive one level of gain correction, while screen peripheral region pixels (with large incident angles) receive different gain correction. This localized differentiation resolves the contradiction by optimizing light compensation for each region's specific characteristics.
Solution Approach 2:
The patent changes the gain parameter dynamically based on pixel position and incident angle. By calculating different gain values for screen center and peripheral regions, the system compensates for the reduced light acquisition of shielded focus detection pixels, thereby maintaining both detection capability and adequate signal strength.
2Illumination intensity
If gain correction is applied to focus detection pixels to compensate for reduced light, then light acquisition compensation is improved, but image quality deteriorates due to vignetting effects
Solution Approach 1:
The patent applies local quality by implementing region-specific gain correction. Screen center region pixels and screen peripheral region pixels are treated differently, with the peripheral region receiving adjusted gain values that account for vignetting effects. This localized approach prevents uniform over-correction that would degrade overall image quality.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and storing gain values in a lookup table before image processing. The gain correction values are determined in advance based on incident angle and pixel position, preventing vignetting-induced image quality deterioration while compensating for reduced light acquisition in focus detection pixels.
3Illumination intensity
If gain values are calculated for each pixel position to compensate for incident angle variations, then light acquisition compensation is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating gain values for all possible pixel positions and incident angles, then storing them in a lookup table. During actual image processing, the system simply retrieves pre-computed values based on pixel position, avoiding complex real-time calculations and reducing processing complexity while maintaining high correction precision.
Solution Approach 2:
The patent uses a lookup table as a simplified copy of the complex gain calculation relationships. Instead of performing complex trigonometric calculations for each pixel, the system copies pre-stored gain values from the lookup table, significantly reducing computational complexity while preserving the precision of position-dependent gain correction.
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 solution effectively prevents image quality deterioration caused by vignetting, ensuring high-quality image data acquisition regardless of the image pickup optical system used, even with manufacturing variations or lack of optical information from the system.
Implementation Method 1
an image pickup device configured to photoelectrically convert the subject image formed by the image pickup optical system
Data Source
AI summary
An image pickup apparatus of the present invention includes: an image pickup optical system configured to form a subject image; an image pickup device configured to photoelectrically convert the subject image formed by the image pickup optical system, wherein part of pixels in a region provided with image formation pixels arranged in a matrix are arranged as focus detection pixels; an optical influence estimation unit configured to use output signals from the image formation pixels, output signals from the focus detection pixels, and two-dimensional pixel position information of the focus detection pixels to estimate a level of influence of vignetting caused by the image optical system according to an image height; and an optical influence correction unit configured to execute image processing with different details that vary according to an estimation result of the optical influence estimation unit.