Rotating Mirror Optical Detection Asymmetry Vignetting
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Solution Overview
Problem
Object detection devices with rotating mirrors suffer from beam vignetting at the circumferential ends of the scanning range, leading to reduced detection performance due to inefficient use of the projected/received beam.
Innovation Solution
The device incorporates a mirror unit with inclined mirror surfaces, where the light projecting and receiving systems are positioned such that the area occupied by the emitted beam differs from the area occupied by the incident beam, with the larger area having a longer movement length on the mirror surface during rotation, preventing beam vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rotating mirror is used to scan and project light in an object detection device, then two-dimensional wide measurement of objects is achieved, but beam vignetting occurs at both circumferential ends of the scanning range leading to reduced detection performance
Solution Approach 1:
The patent applies asymmetry by positioning the light projecting system and light receiving system at different locations relative to the rotating mirror, creating asymmetric optical paths. The light projecting system is positioned on one side of the rotation axis while the light receiving system is positioned on the other side, which allows the emitted beam and received beam to occupy different areas on the mirror surface. This asymmetric arrangement prevents both beams from being affected by vignetting at the same circumferential ends of the scanning range, thereby maintaining detection performance across the full scanning range.
2Device complexity
If the light projecting system and light receiving system share the same mirror surface area, then device complexity is reduced, but beam vignetting occurs at scanning range ends due to overlapping beam paths
Solution Approach 1:
The patent resolves the contradiction by transitioning from a one-dimensional consideration (shared mirror area) to a two-dimensional spatial arrangement. By positioning the light projecting system and light receiving system at different lateral positions relative to the rotation axis, the patent creates separate spatial zones on the mirror surface for emitted and received beams. This dimensional separation ensures that even though both systems use the same mirror, their beam paths occupy different areas, preventing vignetting and improving beam use efficiency without increasing device complexity.
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 enhances the use efficiency of the projected/received beam across the entire scanning range, ensuring robust object detection performance by minimizing vignetting and maintaining detection efficiency at both ends.
Implementation Method 1
a beam emitted from the light source is reflected on the mirror surface and scanned and projected by the rotation of the mirror unit
Implementation Method 2
part of a beam scattered from the object, of the scanned and projected beam, is reflected on the mirror surface and received by the light reception element
Data Source
AI summary
Provided is an object detection device which unlikely causes vignetting of a beam reflected from a mirror surface during rotation, and fully ensures object detection performance A light projecting system and a light receiving system are disposed so that a larger one of the area of a region on a mirror surface occupied by a beam emitted from a semiconductor laser and the area of a region on the mirror surface occupied by a beam incident on a photodiode has a longer movement length on the mirror surface during rotation than a smaller one.