Dual-Mirror Scanning Optical System for Laser Radar
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Solution Overview
Problem
Existing laser radar systems face a trade-off between increasing the density of laser light fluxes for accurate object measurement and maintaining a wide measurement range, as higher density leads to narrower irradiated spots and reduced efficiency, while conventional polygon mirrors are not optimized for radar applications.
Innovation Solution
A scanning optical system with a mirror unit featuring a first and second mirror surface inclined to the rotation axis, where the light flux is reflected twice to maintain a stable cross-sectional shape orthogonal to the scanning direction, allowing for wider sub-scanning ranges with fewer scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the density of laser light fluxes is increased to improve measurement accuracy, then the light amount of reflected light fluxes increases, but the irradiated spot diameter becomes smaller and the measurement range narrows
Solution Approach 1:
The patent transforms the conventional single-mirror scanning approach into a dual-mirror configuration where the first mirror surface reflects light in the main scanning direction and the second mirror surface reflects light in the sub-scanning direction. This dimensional separation allows the light flux to maintain high density while expanding the overall measurement range by utilizing both main scanning and sub-scanning dimensions simultaneously.
Solution Approach 2:
The scanning function is segmented into two independent mirror surfaces with distinct orientations. The first mirror surface (inclined at angle α) handles main scanning, while the second mirror surface (inclined at angle β) handles sub-scanning. This segmentation allows each mirror to be optimized for its specific scanning direction, maintaining light flux density in the main scanning direction while expanding coverage in the sub-scanning direction.
2Device complexity
If a conventional polygon mirror is used for scanning, then the device complexity is reduced, but the cross-sectional shape of the light flux changes significantly during scanning
Solution Approach 1:
The patent employs asymmetric mirror configurations where the first mirror surface is inclined at a specific angle α to the rotation axis and the second mirror surface is inclined at a different angle β. This asymmetric arrangement is specifically designed to compensate for the natural rotation of the light flux cross-section during scanning, maintaining shape stability without requiring complex additional components.
Solution Approach 2:
The patent optimizes the inclination angles of the two mirror surfaces as key parameters. By carefully selecting angle α for the first mirror and angle β for the second mirror, the system achieves cross-sectional shape stability throughout the scanning range. This parameter optimization allows the use of simple rotating mirror mechanisms while maintaining stable light flux characteristics.
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 enables the projection of a light flux with sufficient intensity over a wide range, maintaining cross-sectional shape stability and reducing longitudinal distortion, thus enhancing measurement efficiency and accuracy.
Implementation Method 1
a light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, thereafter, reflected on the second mirror surface, and then, projected so as to scan in a main scanning direction
Data Source
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AI summary
A scanning optical system, includes a mirror unit having a first mirror surface and a second mirror surface which incline to a rotation axis; and a light projecting system having a light source. A light flux emitted from the light source is reflected on the first mirror surface of the mirror unit, thereafter, reflected on the second mirror surface, and then, projected so as to scan in a main scanning direction onto an object in accordance with rotation of the mirror unit. In the case where a virtual plane is set in a range including the object, a light flux reflected on the second mirror surface has, upon entering the virtual plane, a cross sectional shape in which a length in a direction orthogonal to the main scanning direction is longer than a length in the main scanning direction.