CMOS Image Sensor Pixel with Dual Photodiodes for Dynamic Range
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Solution Overview
Problem
Current imaging apparatuses face challenges in achieving high image quality due to limitations in dynamic range and noise reduction, particularly in capturing images with varying luminance levels.
Innovation Solution
The imaging apparatus employs a CMOS image sensor configuration with multiple light-receiving devices, charge accumulation sections, and switches to generate pixel values through correlated double sampling and double data sampling techniques, enhancing image quality by reducing noise and expanding dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a photodiode and storage capacitor are used to accumulate photoelectric charges, then the dynamic range is expanded, but the image quality and noise reduction remain insufficient
Solution Approach 1:
The imaging pixel is divided into multiple independent photodiodes (first photodiode, second photodiode) with different light reception regions. Each photodiode captures light in specific luminance ranges, allowing the system to segment the dynamic range into multiple zones and select the appropriate segment based on lighting conditions, thereby improving both dynamic range and image quality
Solution Approach 2:
The patent implements multiple charge accumulation sections (first charge accumulation section, second charge accumulation section) that can simultaneously accumulate photoelectric charges from different photodiodes. This partial action approach allows the system to capture both bright and dark regions separately and combine them, achieving excessive coverage of the dynamic range spectrum for superior image quality
2Measurement precision
If multiple light-receiving devices and charge accumulation sections are implemented, then image quality and noise reduction improve, but the device complexity increases
Solution Approach 1:
Multiple photodiodes and charge accumulation sections are merged into a single integrated imaging pixel structure. The control logic combines the operation of multiple switches and accumulation sections, managing them through unified control signals that coordinate charge transfer and readout, thereby reducing overall system complexity despite the increased number of components
Solution Approach 2:
The imaging pixel is designed with multi-functionality where the same structural components (photodiodes, charge accumulation sections, switches) serve multiple purposes: light reception, charge accumulation, charge transfer, and signal generation. This universal design allows a single component to perform various functions depending on the operational phase, reducing the need for dedicated components for each function
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 approach improves image quality by effectively reducing noise and expanding the dynamic range, leading to better signal-to-noise ratios and enhanced captured image quality, especially in high luminance conditions.
Implementation Method 1
a first light-receiving device and a second light-receiving device; a first charge accumulation section and a second charge accumulation section
Data Source
AI summary
An imaging apparatus of the present disclosure includes: a first switch that couples a first light-receiving device and a first charge accumulation section to each other; a second switch that couples a predetermined node and the first charge accumulation section to each other; a third switch that applies a predetermined voltage to the predetermined node; a fourth switch that couples a second light-receiving device and a second charge accumulation section to each other; a fifth switch that couples the second charge accumulation section and the predetermined node to each other; an output section that outputs a pixel voltage; a driving section; and a processor that determines first to fourth values. The driving section turns on the second and third switches and turning off the first, fourth, and fifth switches to the off state in a first period, turns off the third switch and turns on the fifth switch in a second period, turns on the fourth switch in a third period, and turns off the fourth switch in a fourth period. The processor determines the third value on the basis of the pixel voltages in the second and fourth periods.