CMOS Image Sensor Readout for High-Sensitivity RGB and NIR Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in capturing both visible light RGB images and infrared NIR images with high sensitivity, as they either compromise on NIR sensitivity or fail to capture RGB images due to the absence of IR cut filters.
Innovation Solution
A CMOS image sensor design that includes unit RGB pixel groups with shared floating diffusion, reset, and selection transistors, allowing for concurrent photoelectric conversion of visible and infrared light, enabling the capture of RGB and NIR images while maintaining high NIR sensitivity by adding infrared signals from color pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an IR cut filter is used to eliminate infrared light, then color reproduction quality is improved, but sensitivity is reduced and image quality is degraded
Solution Approach 1:
The pixel array is divided into two distinct regions: a first pixel array for capturing visible light RGB images and a second pixel array for capturing infrared NIR images. This segmentation allows each region to be optimized for its specific function, eliminating the need for IR cut filters while maintaining both color accuracy and infrared sensitivity
Solution Approach 2:
Different regions of the pixel array are assigned different functional characteristics. The first pixel array is optimized for visible light detection with appropriate color filters, while the second pixel array is optimized for infrared detection. This local differentiation enables simultaneous optimization of color reproduction and infrared sensitivity without compromise
2Loss of energy
If a NIR dedicated pixel with larger pixel size is used, then NIR sensitivity is improved, but the ability to capture RGB images is lost
Solution Approach 1:
The imaging device divides the pixel array into separate first and second pixel arrays. The second pixel array uses larger pixel sizes optimized for NIR detection, while the first pixel array maintains standard pixel sizes for RGB capture. This segmentation allows high NIR sensitivity without sacrificing RGB imaging capability
Solution Approach 2:
The imaging device achieves multi-functionality by incorporating both visible light and infrared light capturing capabilities in a single device. The first pixel array handles RGB imaging while the second pixel array handles NIR imaging, allowing the device to perform both functions simultaneously without requiring separate sensors
3Device complexity
If four pixels in a unit pixel group share floating diffusion and transistors, then device complexity is reduced, but NIR sensitivity is compromised
Solution Approach 1:
The pixel array is segmented into first and second pixel arrays with distinct functions. The second pixel array dedicated to NIR detection uses dedicated transistors rather than shared transistors, ensuring optimal NIR sensitivity while the first pixel array can utilize shared transistor structures for RGB capture
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
Enables the simultaneous capture of high-quality RGB and NIR images with enhanced NIR sensitivity, improving image reproduction and sensitivity without the need for IR cut filters, suitable for applications like surveillance and biometric authentication.
Implementation Method 1
a photodiode (a photoelectric conversion element) and a floating diffusion (FD) amplifier
Data Source
Figure 1
Figure 2
Figure 3
AI summary
One object is to provide a solid-state imaging device (10) that can capture visible light images such as RGB images and infrared images such as NIR images and maintain a high light-receiving sensitivity for infrared light, a method of driving such a solid-state imaging device (10), and an electronic apparatus (100). The solid-state imaging device (10) includes: a pixel part (20) having unit pixel groups (200) arranged therein, the unit pixel groups (200) each including a plurality of pixels (PXL11, PXL12, PXL21, PXL22) at least for visible light that perform photoelectric conversion; and a reading part (70) for reading pixel signals from the pixel part (20), wherein the plurality of pixels for visible light have a light-receiving sensitivity for infrared light, and in an infrared reading mode, the reading part (70) is capable of adding together signals for infrared light read from the plurality of pixels for visible light.