TOF Distance Sensor Flare Signal Subtraction
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Solution Overview
Problem
Time-of-flight distance image capturing devices face challenges in accurately measuring distances due to the flare phenomenon, where reflected light from nearby objects overlaps with light from distant objects, leading to increased calculation costs and errors in distance measurement.
Innovation Solution
A distance image capturing device and method that utilize a light source unit, a light receiving unit with charge storage units, and a pixel drive circuit to synchronize charge storage and emission timing, allowing for the calculation of flare light reception timing and subtraction of flare light signals to accurately determine object distances without increasing calculation costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the TOF type distance image capturing device is used to simultaneously capture images of objects at short distance and far distance, then the reflected light from short distance objects is received with higher light intensity, but the flare phenomenon occurs causing superposition on pixels receiving light from far distance objects, making it difficult to accurately measure distance
Solution Approach 1:
The pixel is divided into multiple charge storage units (first charge storage unit, second charge storage unit, third charge storage unit) that store charges generated at different time intervals. This segmentation allows separate storage and processing of light signals from different time periods, enabling the system to distinguish between flare light from short distance objects and reflected light from far distance objects, thereby resolving the superposition problem caused by the flare phenomenon
Solution Approach 2:
The light source unit emits optical pulses at periodic time intervals, and the pixel stores charges generated during each pulse emission period in separate charge storage units. By controlling the emission timing of optical pulses and storing charges at synchronized timing, the system creates distinct time windows for capturing light from different distances, allowing the flare light and reflected light to be separated and processed independently
2Object-affected harmful factors
If four equations are generated and parameters are obtained such that each equation becomes 0 to reduce the flare phenomenon, then the calculation cost increases
Solution Approach 1:
The invention extracts and separately stores the flare light signal in the first charge storage unit by controlling the emission timing of the optical pulse and the gate timing to coincide with the flare light reception timing. By extracting the flare light component into a separate storage unit, the system can subtract this component from the total signal without requiring complex equation solving, thereby reducing the calculation cost while effectively suppressing the harmful effects of the flare phenomenon
Solution Approach 2:
The system performs preliminary separation of the flare light signal by storing it in the first charge storage unit before the final distance calculation. By preliminarily identifying and isolating the flare light component through controlled emission timing and gate timing synchronization, the system prepares the data in advance for simple subtraction operations, avoiding the need for complex real-time calculations to eliminate the flare effect
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 accurate distance measurement by subtracting flare light signals, reducing errors and calculation costs, and improving the precision of distance imaging without generating additional equations or increasing computational complexity.
Implementation Method 1
a time of flight (hereinafter, referred to as 'TOF') type distance image sensor has been implemented that uses a known speed of light and measures a distance between a measuring instrument and an object based on a flight time of light in space
Implementation Method 2
a light receiving unit having a pixel including a photoelectric conversion element that generates charges according to light incident from the space to be measured
Data Source
AI summary
A distance image capturing device includes a distance image processing unit, that drives pixels with three driving patterns consisting of a first pattern, a second pattern, and a third pattern, calculates a flare light reception timing at which flare light is received in the first pattern, controls an emission timing such that the flare light reception timing and a gate opening and closing timing are the same timing, in the second pattern, controls such that an emission period is shorter than an emission period in the second pattern, in the third pattern, and calculates a flare signal amount corresponding to a light amount of the flare light received by a pixel, by using a subtraction value obtained by subtracting a storage signal in the third pattern from a storage signal in the second pattern to calculate a distance to an object by using the calculated flare signal amount.