Optical Scanning Mirror Angle Detection with Split Light Detectors
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Solution Overview
Problem
Existing optical scanning devices face errors in detecting the deflection angle of the mirror unit due to variations in the mounting position and characteristics of the light detection unit.
Innovation Solution
The optical scanning device includes a light source, a light deflector with a mirror unit having a flat reflection part and a groove-shaped reflection part, a first actuator for reciprocating rotation of the mirror unit, a light detection unit divided into first and second light detectors, and a deflection angle detection unit that compares the outputs of the first and second light detectors to detect the deflection angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light detector is used to detect the deflection angle of the mirror unit, then the device complexity is reduced, but the measurement precision deteriorates due to variations in mounting position and characteristics
Solution Approach 1:
The light detection unit is segmented into multiple light detectors (first light detector and second light detector) that are disposed at different positions. Each detector receives light at different angles, and by comparing their outputs, the system achieves accurate deflection angle detection while compensating for mounting position variations and detector characteristic differences.
2Measurement precision
If multiple light detectors are disposed at different positions to compensate for variations, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Multiple light detectors are merged into a single integrated light detection unit structure. The first and second light detectors are disposed adjacent to each other on the light receiving surface, sharing common mounting infrastructure and signal processing circuits, which reduces overall device complexity while maintaining the precision benefits of multiple detection points.
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 accurate detection of the deflection angle by compensating for variations in the mounting position and characteristics of the light detection unit, thereby improving the irradiation quality of the scanning light.
Implementation Method 1
a groove-shaped reflection part having a longitudinal groove that extends in a predetermined direction and has a pair of inclined surfaces facing each other such that a groove width decreases from the front surface side to a back surface side, and which reflects the incident light a total of twice, once on each inclined surface
Implementation Method 2
a light detection unit which is disposed on a scanning trajectory of a scanning light spot of the scanning reflection light and at a light reception position of an index light spot of the index light
Data Source
AI summary
An optical scanning device includes a control unit, a light deflector, light detection units, and a light source. A mirror unit of the light deflector has a flat reflection part for generating scanning light and a groove-shaped reflection part for generating twice reflected light, and performs reciprocating rotation about a rotation axis. The light detection units are disposed at positions on the scanning trajectory of the scanning light where the twice reflected light is received, and are each divided into light detectors in the scanning direction of the scanning light by a division line. The control unit detects the deflection angle θ of the mirror unit based on both the output of the light detector and the output of the light detector.