Solid-State Imaging Device Pixel Segmentation for Distance Measurement
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Solution Overview
Problem
Conventional solid-state imaging devices for distance measurement face challenges in achieving high accuracy and wide distance measurement ranges due to limitations in pixel size, resolution, and sensitivity, particularly in miniaturized TOF sensors, where increased pulse width for range extension compromises accuracy and introduces variations from background light and production tolerances.
Innovation Solution
The method involves a solid-state imaging device configuration with two unit pixels per distance measurement pixel, utilizing enhanced transistor structures and drive timing to efficiently accumulate and differentiate signals for distance calculation, allowing for reduced optical size and increased unit pixel size while maintaining high sensitivity and accuracy across a wider distance range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the pulse width of the light source is increased to widen the distance measurement range, then the distance measurement range is improved, but the distance measurement accuracy is decreased
Solution Approach 1:
The patent divides one distance measurement pixel into multiple unit pixels (first, second, third, and fourth unit pixels), each capturing signals during different exposure periods. This segmentation allows the system to obtain multiple signal components (A0, A1, A2, A3) from a single distance measurement pixel, enabling accurate distance calculation across extended ranges without sacrificing precision.
2Reliability
If three pixels are used as one distance measurement unit to account for background light, then background light removal is achieved, but the distance measurement unit size is large making downsizing difficult
Solution Approach 1:
The patent merges multiple exposure periods and their corresponding signals within a single distance measurement pixel by dividing it into multiple unit pixels. This allows background light removal to be achieved through signal processing (combining signals from different unit pixels) rather than requiring separate physical pixels, thereby reducing the overall unit size while maintaining reliability.
3Device complexity
If each pixel includes only one charge accumulator, then the device structure is simple, but increasing the pulse width leads to decreased distance resolution
Solution Approach 1:
The patent segments the distance measurement pixel into multiple unit pixels, each with its own charge accumulator. This segmentation allows each accumulator to capture signals from specific exposure periods, enabling the system to maintain high distance resolution even with increased pulse widths by properly timing and combining the accumulated charges from multiple unit pixels.
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 configuration enables a small solid-state imaging device to achieve high distance measurement accuracy and a wide range, reducing variations and improving sensitivity, allowing seamless distance measurement from short to long distances with reduced pixel size and increased unit pixel size.
Implementation Method 1
a distance is measured using flight time that light takes to travel to and return from a measurement object
Data Source
Figure 1~2
Figure 3
Figure 4A
AI summary
Provided is a method for driving a solid-state imaging device (1000) including a unit pixel which includes: a photoelectric converter which receives reflected light from an object (600) and converts the reflected light into charge; a charge discharger which discharges the charge of the photoelectric converter; an exposure resetter which switches timing for accumulating the charge in the photoelectric converter and timing for discharging the charge from the photoelectric converter to the charge discharger; n charge accumulators which accumulate the charge where n is a natural number; and n readers which read the charge where n is a natural number. The method includes performing an exposure sequence including: an exposure start step of starting exposure of the photoelectric converter by placing the exposure resetter in a non-conducting state after the lapse of a predetermined period of time starting from the readers are placed in a conducting state; and an exposure stop step of stopping the exposure of the photoelectric converter by placing the exposure resetter in the conducting state a predetermined period of time before placing the readers in the non-conducting state after the exposure is started.