Range Sensor Adaptive Accumulation for Background Light Saturation
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Solution Overview
Problem
Range image sensors using the Time-Of-Flight (TOF) system face accuracy reduction in range measurement due to strong background light, particularly from sources like sunlight, leading to saturation and optical shot noise, which affects the reliability of the measurement.
Innovation Solution
The range sensor dynamically adjusts the cumulative number of light reception operations based on the magnitude of received light, reducing excessive accumulation during strong background conditions to prevent saturation and maintain measurement accuracy, and employs averaging of multiple frames to enhance statistical accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cumulative number of light reception operations is increased to improve measurement accuracy, then the statistical accuracy of range measurement is improved, but the accumulated amount of received light becomes excessive under strong background light conditions, causing saturation and reducing measurement accuracy
Solution Approach 1:
The patent applies dynamics by making the cumulative number adaptive rather than fixed. The controller dynamically adjusts the cumulative number based on real-time detection of background light intensity. When background light is strong, the cumulative number is reduced to prevent saturation; when background light is weak, the cumulative number is increased to improve measurement accuracy. This dynamic adaptation resolves the contradiction between improving accuracy through accumulation and preventing saturation under strong background light.
Solution Approach 2:
The patent changes the parameter of cumulative number based on background light conditions. By detecting the intensity of background light and adjusting the cumulative number accordingly, the system optimizes the balance between accumulating sufficient light for accurate measurement and preventing excessive accumulation that leads to saturation. This parameter change strategy enables the system to maintain reliable operation across varying background light conditions.
2Reliability
If the cumulative number is reduced to prevent saturation under strong background light, then saturation is prevented, but the statistical accuracy of range measurement deteriorates due to insufficient accumulation
Solution Approach 1:
The system dynamically adjusts the cumulative number based on detected background light intensity. Under strong background light conditions, the cumulative number is reduced to prevent saturation and maintain operational reliability. Under weak background light conditions, the cumulative number is increased to ensure sufficient light accumulation for accurate measurement. This dynamic adjustment resolves the contradiction between preventing saturation and maintaining measurement accuracy.
Solution Approach 2:
The patent changes the cumulative number parameter adaptively based on background light conditions. When background light is strong, the parameter is decreased to avoid saturation; when background light is weak, the parameter is increased to improve statistical accuracy. This parameter adaptation enables the system to optimize measurement performance across different operating conditions.
3Device complexity
If a fixed cumulative number is used for all conditions, then the device complexity is reduced, but the measurement accuracy deteriorates under varying background light conditions
Solution Approach 1:
The patent implements feedback control by detecting the background light intensity and using this information to adjust the cumulative number. The controller continuously monitors the lighting conditions and adapts the accumulation parameter accordingly. This feedback mechanism enables the system to maintain high measurement accuracy across varying background light conditions without requiring excessively complex control logic, as the adjustment strategy is straightforward: increase cumulative number in low light, decrease in high light.
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 effectively reduces the impact of strong background light on range measurement accuracy, maintaining a high frame rate and preventing saturation, while ensuring reliable range data generation even under intense illumination conditions.
Implementation Method 1
a photodiode PD that receives the light and generates an electrical signal
Implementation Method 2
the illumination light is modulated by multiplying the illumination light with a modulation signal
Implementation Method 3
a range is calculated based on a time of flight of the modulated illumination light
Data Source
AI summary
A range sensor includes a light source, a light receiver, a controller, and a range information generator. The light source repeatedly emits illumination light onto a target. The light receiver receives light from the start of a time period during which the illumination light is emitted. The controller controls the light source and the light receiver so that each of the amounts of light received by the light receiver is cumulated in synchronization with emission of the illumination light. The range information generator generates range information indicating the range to the target based on the cumulative amounts of received light. The controller changes the cumulative number that is the number of cumulating operations in which the light receiver cumulates each of the amounts of received light, in accordance with the magnitudes of the cumulative amounts of received light.