Time-of-Flight Sensor Dynamic Range via Pixel Segmentation
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Solution Overview
Problem
Time-of-flight distance measuring devices face challenges in achieving a large dynamic range and high frame rate, especially when mounted on vehicles, due to limitations in receiving reflected light intensity and pixel arrangement, which affects their ability to accurately measure distances in varying environments.
Innovation Solution
The device divides the base exposure period into sub-exposure periods, allowing for simultaneous acquisition of both short and long time exposure values from the same pixel, and groups pixels into different exposure groups to perform multiple short exposures within the time of a single long exposure, thereby expanding the dynamic range and increasing frame rate without complex optical designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple exposure is performed in series to achieve large dynamic range, then dynamic range is improved, but exposure time becomes longer and tracking performance against moving target is deteriorated
Solution Approach 1:
The pixel array is divided into multiple pixel groups, where each group performs exposure for a different duration. Specifically, first pixel groups perform exposure for a first period while second pixel groups perform exposure for a second period that is longer than the first period. This segmentation allows simultaneous capture of both short-exposure and long-exposure data, achieving high dynamic range while maintaining high frame rate for tracking moving targets.
2Adaptability or versatility
If multiple exposure is performed in series to achieve large dynamic range, then dynamic range is improved, but device complexity is increased due to pixel grouping requirements
Solution Approach 1:
The pixel array is divided into multiple pixel groups, where each group performs exposure for a different duration. Specifically, first pixel groups perform exposure for a first period while second pixel groups perform exposure for a second period that is longer than the first period. This segmentation allows simultaneous capture of both short-exposure and long-exposure data, achieving high dynamic range while maintaining high frame rate for tracking moving targets.
3Productivity
If frame rate is increased to track moving targets, then tracking performance is improved, but dynamic range is reduced due to shorter exposure time
Solution Approach 1:
The pixel array is divided into multiple pixel groups, where each group performs exposure for a different duration. Specifically, first pixel groups perform exposure for a first period while second pixel groups perform exposure for a second period that is longer than the first period. This segmentation allows simultaneous capture of both short-exposure and long-exposure data, achieving high dynamic range while maintaining high frame rate for tracking moving targets.
Solution Approach 2:
While first pixel groups are performing exposure for the first period, second pixel groups simultaneously perform exposure for the second period. This continuous parallel operation ensures that both short-exposure and long-exposure measurements are obtained within the same frame time, maintaining high frame rate while achieving high dynamic range.
4Adaptability or versatility
If pixel grouping is implemented to achieve different exposure times, then dynamic range is improved, but ease of manufacture is reduced
Solution Approach 1:
The pixel array is divided into multiple pixel groups, where each group performs exposure for a different duration. Specifically, first pixel groups perform exposure for a first period while second pixel groups perform exposure for a second period that is longer than the first period. This segmentation allows simultaneous capture of both short-exposure and long-exposure data, achieving high dynamic range while maintaining high frame rate for tracking moving targets.
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 the device to effectively measure distances with a wider dynamic range and higher frame rate, suitable for on-vehicle applications where targets are moving, by optimizing the exposure periods and pixel grouping.
Implementation Method 1
a light emitting element emits modulated light modulated by a pattern having a repeating period to a space
Implementation Method 2
A light receiving element distributes an electric charge according to incident light including reflected light of the modulated light reflected by a target
Data Source
AI summary
A time-of-flight distance measuring device divides a base exposure period into a plurality of sub exposure periods and holds without resetting an electric charge stored in the sub exposure period for a one round period which is one round of the plurality of sub exposure periods. The distance measurement value of short time exposure is acquired during the one round period and the distance measurement value of long time exposure is acquired during a plurality of the one round periods. Both of the distance measurement value of the long time exposure and the distance measurement value of the short time exposure can be acquired from the same pixel. With this, a dynamic range is expanded without being restricted by a receiving state of reflected light, optical design of received light, and an arrangement of pixels.