Image Pixel Control Method for Dynamic Range Enhancement
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Solution Overview
Problem
Image sensors in compact devices face reduced dynamic range due to smaller photodiodes, leading to decreased light reception and increased noise in multi-exposure methods, and difficulties in processing digital signals from logarithmic responses.
Innovation Solution
An image pixel control method that includes initialization, excess value sampling, initialization level sampling, and data level sampling processes, utilizing a light receiving unit and a buffer unit with transistors to manage photoelectrons and enhance dynamic range by transferring excess photoelectrons through a pre-set current path and sampling voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of photodiode is reduced to make image sensor compact, then the integration density is improved, but the dynamic range decreases due to reduced light reception
Solution Approach 1:
The patent divides the photoelectron accommodation into two separate units: a first photoelectric conversion unit and a second photoelectric conversion unit. Each unit has its own photoelectron accommodation capacity, allowing the system to capture both weak signals (in the first unit) and strong signals (in the second unit) simultaneously, thus resolving the contradiction between compact size and dynamic range.
Solution Approach 2:
The patent introduces a temporal dimension by sequentially sampling photoelectrons from the two photoelectric conversion units at different time points. The controller samples photoelectrons from the first unit, then from the second unit, combining information from both temporal samples to reconstruct the complete signal, effectively expanding the dynamic range without increasing spatial footprint.
2Illumination intensity
If multi-exposure method is used to enhance dynamic range, then the light reception is improved, but noise increases due to signal to noise ratio differences
Solution Approach 1:
The patent applies preliminary action by initializing both photoelectric conversion units to the same initial voltage level before exposure. This ensures that both units start from a known, equal baseline state, allowing accurate comparison and combination of signals without noise artifacts introduced by different initialization conditions.
Solution Approach 2:
The patent creates a copy of the photoelectric conversion process by using two parallel photoelectric conversion units with identical structures and initialization. Both units process the same light signal independently, and their outputs are combined to enhance the signal while maintaining consistent noise characteristics, thereby improving reliability.
3Illumination intensity
If logarithmic response is used to enhance dynamic range, then the light reception is improved, but digital signal processing becomes difficult
Solution Approach 1:
The patent changes the response parameter from logarithmic to linear by using two photoelectric conversion units with identical linear characteristics. Both units respond linearly to the input light signal, and the controller combines their outputs through linear addition, maintaining linear response characteristics throughout the process. This preserves ease of digital signal processing while achieving enhanced dynamic range.
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
The method effectively enhances the dynamic range of image pixels by separately reading and correcting data beyond the existing range, improving light detection and reducing noise, thereby increasing the sensitivity of image sensors.
Implementation Method 1
a light receiving unit that generates and accommodates photocharges upon receiving light
Data Source
AI summary
An image pixel control method includes: performing an initialization process comprising initializing the light receiving unit; performing an excess value sampling process comprising sampling a voltage level corresponding to a quantity of photoelectrons in excess of a photoelectron accommodation capacity of the light receiving unit; performing an initialization level comprising sampling process sampling a voltage level applied to the light receiving unit when the light receiving unit is initialized; and performing a data level sampling process comprising sampling a voltage level corresponding to a quantity of photoelectrons accommodated in the light receiving unit.