ToF Distance Sensing for Close Low-Reflectance Objects
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Solution Overview
Problem
Indirect ToF distance measurement devices struggle to accurately measure the distance to low-reflectance objects, especially at close distances, leading to focus issues in autofocus applications, such as images of low-reflectance objects shot obliquely, resulting in defocus and increased power consumption.
Innovation Solution
A distance measurement device with a light detection unit, exposure control unit, distance image calculator, and detector that dynamically adjusts exposure control and distance image parameters based on the detection of low-reflectance and close objects, using features like depth, confidence values, and histograms to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exposure control is performed using conventional indirect ToF method, then power consumption is reduced, but distance measurement accuracy deteriorates for close and low-reflectance objects
Solution Approach 1:
The patent implements dynamic exposure control by detecting close and low-reflectance objects and adjusting exposure parameters accordingly. The system switches between conventional indirect ToF mode (lower power) and enhanced exposure mode (higher accuracy) based on real-time object detection, making the system adaptive rather than static.
Solution Approach 2:
The patent changes exposure parameters (such as integration time, gain, or light emission intensity) based on detected object characteristics. When close low-reflectance objects are detected, the system modifies these parameters to improve signal strength and measurement accuracy without continuously operating at high power consumption levels.
2Measurement precision
If exposure time is increased to improve distance measurement of low-reflectance objects, then measurement accuracy is improved, but power consumption increases
Solution Approach 1:
The patent uses periodic object detection and conditional exposure adjustment. Instead of continuously increasing exposure time, the system periodically detects objects and only increases exposure parameters when close low-reflectance objects are present, thereby improving accuracy only when necessary and reducing overall power consumption.
3Measurement precision
If conventional autofocus is used for oblique shots of low-reflectance objects, then device complexity is minimized, but focus accuracy deteriorates
Solution Approach 1:
The patent implements feedback-based autofocus control where the distance measurement results are fed back to adjust focus settings. The system detects focus status and object characteristics, then adjusts exposure and focus parameters accordingly, creating a closed-loop control system that improves focus accuracy without requiring complex hardware modifications.
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 of low-reflectance objects, maintaining focus and reducing power consumption by adaptively controlling exposure and image processing parameters, thus improving autofocus performance.
Implementation Method 1
The ToF method is a method of measuring the distance to a subject (measurement target) by radiating light toward the subject from a light source and detecting the time of flight elapsed before the irradiation light is reflected and returned to the light detection unit by the subject.
Data Source
AI summary
A distance measurement device includes a light detection unit, an exposure control unit; a distance image calculator, a detector, and a control unit. The light detection unit receives light from a subject. The exposure control unit performs exposure control on the basis of a signal value outputted by the light detection unit. The distance image calculator calculates a distance image on the basis of an output of the light detection unit. The distance image includes depth and a confidence value. The detector detects, from a feature of data processed by the distance image calculator, a close and low-reflectance object whose distance is unmeasurable. The control unit dynamically controls at least one of a parameter of the exposure control unit or a parameter of the distance image calculator on the basis of a result of detection of the detector.