Solid-State Image Capture Device Pixel Mismatch Resolution
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Solution Overview
Problem
Existing image capture devices for distance measurement using infrared light suffer from reduced resolution and sensitivity due to pixel mismatch and inefficient charge usage when subtracting signal charge obtained with and without infrared illumination, leading to errors in capturing fast-moving objects.
Innovation Solution
An image capture device with a solid-state image capture system that includes first and second pixels arranged in a matrix, where signal charge from adjacent pixels is added together during exposure periods to eliminate pixel mismatch and maximize charge usage, allowing for simultaneous reading of signal charge caused by infrared light and ambient light components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal charge obtained without infrared light illumination is subtracted from signal charge obtained by infrared light illumination, then the distance image can be obtained with infrared component removal, but the resolution is reduced by half due to one-pixel position difference
Solution Approach 1:
The image sensor divides pixels into two independent sets: first pixels for capturing infrared light and second pixels for capturing ambient light. This segmentation allows simultaneous capture of both light components without pixel position mismatch, resolving the contradiction between distance measurement precision and image resolution.
Solution Approach 2:
The patent extracts the function of capturing ambient light from the same pixel used for infrared light capture. By assigning dedicated second pixels for ambient light capture, the system eliminates the pixel position difference problem that occurs when using the same pixels for both purposes, thereby maintaining full resolution while enabling accurate distance measurement.
2Ease of operation
If signal charge is drained from photodiodes to substrate during ambient light capture, then charge from odd and even rows can be separately processed, but the charge usage rate drops to 50% reducing sensitivity
Solution Approach 1:
The photodiodes are segmented into two independent groups: first photodiodes connected to first read electrodes for infrared light capture, and second photodiodes connected to second read electrodes for ambient light capture. This segmentation eliminates the need to drain charge to substrate, allowing all photodiodes to contribute usefully to the measurement, thereby maintaining 100% charge usage rate and high sensitivity.
Solution Approach 2:
The vertical transfer unit serves multiple functions: it transfers charge from both first and second photodiodes, accumulates charge from both odd and even rows, and enables simultaneous processing of infrared and ambient light signals. This multi-functionality eliminates the need for charge drainage while maintaining efficient charge processing.
3Measurement precision
If alternating row charge reading is used (odd rows with infrared, even rows without), then infrared and ambient light charges can be separately captured, but exposure timing differences cause errors in fast-moving object measurement
Solution Approach 1:
The image sensor is segmented into first pixels for infrared light capture and second pixels for ambient light capture, with each pixel type having dedicated read electrodes. This segmentation enables simultaneous exposure and readout of both light components, eliminating exposure timing differences and allowing accurate distance measurement of fast-moving objects.
Solution Approach 2:
The patent implements periodic switching between reading charge from first photodiodes and second photodiodes within the same frame period. This periodic action allows both infrared and ambient light charges to be captured simultaneously with synchronized timing, eliminating measurement errors in fast-moving objects while maintaining the ability to separate infrared components.
4Productivity
If all pixels are read simultaneously using vertical transfer unit, then reading efficiency is improved, but the structure becomes more complex with additional electrodes
Solution Approach 1:
The vertical transfer unit is designed to handle charge from both first and second photodiodes simultaneously. It performs multiple functions: transferring charge from odd and even rows, accumulating charge from different photodiode groups, and enabling simultaneous readout of all pixels. This multi-functionality achieves high reading efficiency without requiring separate transfer units for each pixel group, thereby limiting the increase in structural complexity.
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 enables higher-precision distance imaging with reduced power consumption and heat generation by eliminating pixel mismatch and optimizing charge usage, effectively capturing fast-moving objects without errors.
Implementation Method 1
a photoelectric conversion unit configured to convert incident light from the object into signal charge
Implementation Method 2
an infrared light source configured to illuminate an object with infrared light
Data Source
AI summary
Read electrodes are provided to drain signal charge of pixels from photoelectric conversion units provided in the pixels separately to a vertical transfer unit. During a first exposure period during which an object is illuminated with infrared light, signal charge obtained from a first pixel, and signal charge obtained from a second pixel adjacent to the first pixel, are added together in the vertical transfer unit to produce first signal charge. During a second exposure period during which the object is not illuminated with infrared light, signal charge obtained from the first pixel, and signal charge obtained from the second pixel adjacent to the first pixel, are transferred without being added to the first signal charge in the vertical transfer unit, and are added together in another packet to produce second signal charge.