Scanning Optical System with Dual-Angle Mirror Unit for Polarization Stability
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Solution Overview
Problem
Conventional laser radars face difficulties in detecting objects behind light-absorbing or reflective surfaces due to weak reflected light intensities, which can lead to incomplete distance measurement, especially when windows or glass are present in the scanning range.
Innovation Solution
A scanning optical system with a mirror unit featuring a first and second mirror surface inclined relative to the rotation axis, where the light flux is reflected twice to maintain polarization direction and beam profile stability, ensuring sufficient light intensity is received from objects even behind glass or windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser light fluxes are used to increase unit projected light intensity, then distance measurement capability is improved, but reflected light intensity from objects behind glass or windows becomes weak
Solution Approach 1:
The patent changes the polarization parameter of the light flux by configuring the mirror unit with specific inclination angles. The first mirror surface inclines at 45 degrees to the rotation axis, and the second mirror surface inclines at an angle different from 45 degrees, which transforms the polarization direction of the reflected light to be substantially perpendicular to the main scanning plane. This parameter change enables the light to penetrate glass surfaces more effectively and receive sufficient reflected light from objects behind glass.
2Area of stationary object
If a polygon mirror with even number of reflective surfaces is used, then scanning coverage is improved, but polarization direction stability deteriorates
Solution Approach 1:
The patent applies local quality by making the two mirror surfaces have different inclination angles relative to the rotation axis. The first mirror surface has a specific inclination angle of 45 degrees, while the second mirror surface has a different inclination angle. This local differentiation in geometric parameters allows the system to maintain stable polarization direction while achieving wide scanning coverage, resolving the contradiction between scanning area and polarization stability.
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 allows for effective distance measurement by maintaining consistent light flux intensity and polarization direction, enabling accurate detection of objects regardless of their location relative to light-absorbing or reflective surfaces.
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
Implementation Method 2
the light flux reflected on the second mirror surface is polarized in a range within an angle of ±30 degrees to the main scanning plane
Data Source
AI summary
A scanning optical system, includes a mirror unit equipped with a first mirror surface and a second mirror surface each of which inclines to a rotation axis; and a light projecting system which includes at least one light source to emit a light flux toward the first mirror surface. 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, and in a case where a direction included in a main scanning plane is set to 0 degree, the light flux reflected on the second mirror surface is polarized in a range within an angle of ±30 degrees to the main scanning plane.