Telecentric TOF Distance Sensing With Afocal Blur Control
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Solution Overview
Problem
Existing distance measuring apparatuses suffer from reduced accuracy due to image blurring and light reception across multiple elements, which is exacerbated by variations in object distance, leading to decreased precision.
Innovation Solution
The apparatus employs a light source unit with a microlens array and an image-side telecentric lens forming an afocal system, where the light receiving element array is positioned farther than the focal length of the telecentric lens, ensuring consistent image size and one-to-one correspondence between light emitting and receiving elements, thereby reducing image blurring and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional light receiving optical system is used without adjusting imaging position, then the device complexity is reduced, but the distance measuring accuracy deteriorates due to image blurring and light reception across multiple elements when object distance varies
Solution Approach 1:
The patent applies the dynamics principle by making the imaging position adjustable rather than fixed. The light receiving optical system can dynamically change its imaging position according to the object distance, allowing the system to maintain optimal focus conditions across varying measurement distances. This dynamic adjustment capability resolves the contradiction by enabling accurate distance measurement without requiring a completely complex optical system for each specific distance.
Solution Approach 2:
The patent employs parameter changes by varying the imaging position parameter of the light receiving optical system based on object distance. By changing this key parameter, the system adapts to different measurement scenarios, maintaining image sharpness and preventing light from spreading across multiple receiving elements. This parameter adjustment approach improves measurement accuracy without fundamentally redesigning the entire optical system.
2Reliability
If the imaging position is fixed, then the ease of manufacture is improved, but the reliability of distance measurement deteriorates due to sensitivity to object distance variations
Solution Approach 1:
The light receiving optical system is designed with dynamic imaging position adjustment capability, allowing it to adapt to different object distances. This dynamic feature enhances measurement reliability by ensuring consistent focus conditions regardless of distance variations, while the adjustment mechanism is designed to be manufacturable with standard precision requirements.
Solution Approach 2:
The system incorporates automatic imaging position adjustment that responds to object distance variations. This self-adjusting capability improves measurement reliability without requiring manual intervention or extremely tight manufacturing tolerances, as the system autonomously compensates for distance changes to maintain optimal imaging conditions.
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 configuration maintains accurate distance measurements by minimizing image size variations and blurring across different object distances, improving precision and robustness against manufacturing deviations.
Implementation Method 1
The microlens array and the image-side telecentric lens form an afocal system
Implementation Method 2
an optical system including an image-side telecentric lens, and configured to project light from the light source unit onto an object via the image-side telecentric lens
Implementation Method 3
A time-of-flight (TOF) distance measuring method is known, which measures a distance to an object (object distance) by measuring a time difference between irradiating light and detecting reflected light
Data Source
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AI summary
[PROBLEMS] To provide a distance measuring apparatus capable of reducing the degradation of distance measuring accuracy according to an object distance. [SOLUTION MEANS] A distance measuring apparatus 1 includes a light source unit 113 including a light emitting element array 210 in which a plurality of light emitting elements are arranged, and a microlens array 230 in which a plurality of microlenses are arranged, a light receiving unit 120 including a light receiving element array 310 in which a plurality of light receiving elements are arranged, and an optical system 160 including an image-side telecentric lens 130, and configured to project light from the light source unit onto an object via the image-side telecentric lens, and to cause the light receiving unit to receive reflected light from the object via the image-side telecentric lens. The microlens array and the image-side telecentric lens form an afocal system. An offset amount is set such that a distance between the light receiving element array and an image-side principal point of the image-side telecentric lens is longer than a focal length of the image-side telecentric lens.