Optical Scanning Apparatus Stray Light Suppression
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Solution Overview
Problem
In optical scanning apparatuses that scan light waves outside the apparatus, stray light can occur when reflected light from a transmissive member is further reflected by a rotationally moving reflection mirror, leading to erroneous detection by the light-receiving unit.
Innovation Solution
The optical scanning apparatus includes a light-emitting unit, a light-receiving unit, a transmissive member, and at least one reflection mirror with a low reflection region on the transmissive member side of the reflection surface. The low reflection region has a reflectance lower than the high reflection region, effectively suppressing stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reflection mirror has high reflectance across the entire surface, then the light waves are favorably reflected for scanning, but stray light is generated when reflected light from the transmissive member is further reflected by the rotationally moving reflection mirror
Solution Approach 1:
The reflection mirror is designed with different reflectance characteristics in different regions: a first region with high reflectance for scanning light waves and a second region with low reflectance for suppressing stray light. This local differentiation allows the mirror to perform both functions simultaneously without compromising overall performance.
Solution Approach 2:
The reflection mirror surface is segmented into distinct functional zones - a scanning region for primary light wave reflection and a stray light suppression region with different optical properties. This segmentation enables independent optimization of each region's characteristics to address the contradictory requirements.
2Object-generated harmful factors
If a low reflection region is added to the reflection mirror to suppress stray light, then stray light is reduced, but the device complexity increases
Solution Approach 1:
The reflectance parameter of the reflection mirror is changed spatially across its surface, creating regions with different reflectance values. This parameter variation is achieved through coating techniques or surface treatment methods that modify the optical properties of specific areas without adding mechanical 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
The configuration suppresses the amount of stray light, preventing it from being incident on the light-receiving unit and reducing erroneous detections, while ensuring favorable reflection of light waves and reflected light.
Implementation Method 1
The at least one reflection mirror deflects at least either of the light waves and the reflected light using the reflection surface
Implementation Method 2
The low reflection region has a reflectance of the light waves on the reflection surface that is set to be lower than a reflectance of the light waves on the other region
Implementation Method 3
The transmissive member is configured to transmit the light waves and the reflected light of the light waves
Data Source
AI summary
In an optical scanning apparatus, a light-emitting unit emits light waves. A light-receiving unit receives reflected light of the light waves. A transmissive member transmits the light waves and the reflected light of the light waves. A reflection mirror is arranged further toward the light-emitting unit side and light-receiving unit side than the transmissive member is, includes a reflection surface that rotates, and deflects at least either of the light waves and the reflected light using the reflection surface. The reflection mirror includes a low reflection region on the transmissive member side. The low reflection region has a reflectance of the light waves on the reflection surface that is set to be lower than a reflectance of the light waves on the other region other than the low reflection region, in a state in which the reflection surface is facing the light-emitting unit side or the light-receiving unit side.