Distance image acquisition device and distance image acquisition method
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Solution Overview
Problem
Distance measurement sensors using the indirect Time of Flight method face limitations in extending measurement distance due to decreased light reflection and accuracy issues when widening pulse width to increase range.
Innovation Solution
A distance image acquisition device with a charge generation region including an avalanche multiplication region, dividing the measurement distance into sections and varying the time difference between light emission and charge transfer to maintain accuracy and sensitivity, allowing for extended measurement distances while suppressing pulse width widening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the pulse width of the measurement light is widened to extend the measurement distance, then the measurement distance can be extended, but the distance accuracy is degraded
Solution Approach 1:
The patent divides the charge accumulation region into multiple regions (first charge accumulation region and second charge accumulation region) that accumulate charges generated at different time periods. By separating the accumulation of charges from different time windows, the system can use a longer total measurement period without degrading distance accuracy, as each region independently processes charges from its designated time window.
Solution Approach 2:
The patent applies a preliminary gate voltage to the transfer gate electrode before the measurement light is emitted, creating a potential well in advance. This preliminary action prepares the charge accumulation regions to receive and separate charges at different time periods, enabling the system to handle extended measurement distances while maintaining accuracy through pre-configured charge separation pathways.
2Length of stationary object
If the measurement distance is extended without avalanche multiplication, then the measurement distance can be extended, but the sensitivity of the distance measurement sensor is insufficient
Solution Approach 1:
The patent introduces an avalanche multiplication region as an intermediary between the charge generation region and the charge accumulation region. This intermediary component amplifies the weak signals from reflected light through avalanche multiplication, thereby maintaining high sensitivity even when measuring distant targets where reflected light intensity is low.
Solution Approach 2:
The patent segments the sensor structure into distinct functional regions: charge generation region, avalanche multiplication region, and multiple charge accumulation regions. This segmentation allows each region to perform its specialized function optimally, with the avalanche multiplication region specifically dedicated to signal amplification, thereby maintaining sensitivity while extending measurement distance.
3Length of stationary object
If transparent objects or semi-transparent objects are present in the measurement path, then the measurement distance can be extended, but the measurement accuracy deteriorates due to multi-echo
Solution Approach 1:
The patent divides the charge accumulation into multiple regions that correspond to different time periods of charge generation. By separating charges from different time windows into different accumulation regions, the system can identify and exclude multi-echo signals from transparent or semi-transparent objects, thereby maintaining measurement accuracy while extending the measurable distance range.
Solution Approach 2:
The patent applies preliminary gate voltages to configure the transfer gate electrode before charge generation occurs, establishing predetermined charge accumulation pathways for different time periods. This preliminary configuration enables the system to pre-sort charges by their generation time, making it easier to identify and eliminate multi-echo interference from transparent objects.
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
The solution enables extended measurement distances with maintained accuracy by using avalanche multiplication and section-based timing control, reducing the impact of pulse width widening and transparent objects on measurement accuracy.
Implementation Method 1
the charge generation region includes an avalanche multiplication region that causes avalanche multiplication
Data Source
AI summary
A distance image acquisition device includes a distance measurement sensor that detects a measurement light by transferring charges generated in a charge generation region in response to incidence of a measurement light reflected by a target object, to a charge accumulation region by using a transfer gate electrode. The charge generation region includes an avalanche multiplication region that causes avalanche multiplication. The control unit divides an entire distance range of a measurement target into the plurality of sections, controls the distance measurement sensor so as to perform measurements about a plurality of sections while varying a time difference between an emission timing of the measurement light by the light source and a transferring timing of the charges by the transfer gate electrode among the plurality of sections, and generates a distance image of the entire distance range based on the results of the measurements about the plurality of sections.