CMOS Pixel Charge Transfer Control for Flash Image Quality
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image capturing apparatuses with CMOS sensors face challenges in achieving high frame rates and maintaining color balance, especially when capturing bright subjects or flashes, due to the small photoelectric conversion portion area caused by the arrangement of a charge holding portion, which leads to image degradation.
Innovation Solution
The apparatus includes a controller that manages the number of times and duration the first transfer switch is activated relative to the second transfer switch, allowing for optimized charge transfer between the photoelectric conversion and holding portions, thereby preventing image degradation during flash events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a charge holding portion is arranged on each pixel to enable global shutter method, then rolling shutter distortion is eliminated and moving bodies are captured without distortion, but the area of the photoelectric conversion portion becomes relatively smaller and the saturated charge amount becomes small
Solution Approach 1:
The patent implements a nested structure where the holding portion is positioned beneath the photoelectric conversion portion within each pixel unit. This vertical nesting allows the holding portion to be integrated into the pixel structure without increasing the horizontal footprint, thereby maintaining photoelectric conversion area while providing charge storage capability for global shutter operation.
Solution Approach 2:
The patent transitions from a horizontal arrangement where charge storage would increase pixel area to a vertical arrangement where the holding portion is positioned in the depth dimension beneath the photoelectric conversion portion. This dimensional change enables charge storage without sacrificing photoelectric conversion area.
2Quantity of substance
If charges are transferred multiple times from the photoelectric conversion portion to the charge holding portion to magnify the saturated charge amount, then the saturated charge amount increases, but the read out speed (frame rate) is reduced and color balance is ruined in cases of bright subjects or flash
Solution Approach 1:
The patent performs preliminary charge transfer from the photoelectric conversion portion to the holding portion before the flash or bright subject exposure occurs. By pre-positioning charges in the holding portion, the system avoids the need for multiple transfers during flash events, thereby maintaining high frame rate and preventing color balance degradation while still achieving magnified saturated charge amount.
Solution Approach 2:
The patent dynamically controls the transfer timing between photoelectric conversion portion and holding portion based on scene conditions. The system adapts the charge transfer strategy to match the temporal characteristics of the scene, performing transfers during periods when frame rate and color balance are not compromised, thereby optimizing both charge amount and imaging performance.
3Quantity of substance
If charges are transferred multiple times from the photoelectric conversion portion to the charge holding portion to magnify the saturated charge amount, then the saturated charge amount increases, but color balance of the image is ruined in cases of bright subjects or flash
Solution Approach 1:
The patent performs preliminary charge transfer from the photoelectric conversion portion to the holding portion before the flash or bright subject exposure occurs. By pre-positioning charges in the holding portion, the system avoids the need for multiple transfers during flash events, thereby maintaining high frame rate and preventing color balance degradation while still achieving magnified saturated charge amount.
Solution Approach 2:
The patent applies partial charge transfer rather than complete multiple transfers during flash events. By transferring only the necessary amount of charge in advance and avoiding excessive transfers during critical imaging moments, the system achieves sufficient saturated charge amount while preserving color balance accuracy.
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 enables the apparatus to maintain image quality by controlling charge transfer based on capturing conditions, preventing frame rate reduction and color balance issues, even under bright or flash-lit conditions.
Implementation Method 1
a photoelectric conversion portion that converts incident light into a charge
Data Source
AI summary
An image capturing apparatus comprises an image sensor in which a plurality of pixels are arranged two-dimensionally, wherein each of the pixels have a photoelectric conversion portion, a holding portion that holds a charge obtained by the photoelectric conversion portion, an amplification portion that outputs a signal based on a charge outputted from the holding portion, a first transfer switch that transfers the charge from the photoelectric conversion portion to the holding portion, and a second transfer switch that transfers the charge from the holding portion to the amplification portion; and a controller that controls a number of times that the first transfer switch is turned on in relation to the second transfer switch being turned on one time.