Absolute Encoder Inclined Irradiation Axis Reduces Reflection
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Solution Overview
Problem
Absolute encoders in surveying devices face accuracy issues in detecting angles due to reflection of detection light between the light-receiving area and the scale plate, leading to increased manufacturing costs when anti-reflection films are used to mitigate this problem.
Innovation Solution
The absolute encoder is designed with a light-emitting mechanism and a light-receiving mechanism positioned such that the irradiation axis is inclined relative to the rotation axis direction, preventing reflection detection light from reaching the light-receiving area without the need for anti-reflection films, thus reducing manufacturing costs and maintaining detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an anti-reflection film is provided on the back surface of the scale plate, then the reflected detection light is prevented from reaching the light-receiving area, but the manufacturing cost increases due to additional manufacturing processes and parts
Solution Approach 1:
The harmful reflected light is extracted and redirected away from the light-receiving area by inclining the irradiation axis, eliminating the need for anti-reflection films and reducing manufacturing complexity
Solution Approach 2:
The irradiation axis inclination angle is changed from 0 degrees (parallel to rotation axis) to a specific inclined angle, which fundamentally alters the light path geometry and prevents reflected light from reaching the light-receiving area
2Measurement precision
If the light-emitting mechanism and light-receiving mechanism are positioned with an inclined irradiation axis, then reflected detection light is directed away from the light-receiving area, but the device complexity increases due to precise positioning requirements
Solution Approach 1:
The symmetric arrangement of light-emitting and light-receiving mechanisms is broken by introducing an inclined irradiation axis, creating an asymmetric configuration that inherently redirects reflected light away from the light-receiving area
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 effectively prevents accuracy reduction in angle detection caused by light reflection, while avoiding the increased costs associated with anti-reflection film application, by ensuring the reflection detection light is directed away from the light-receiving area.
Implementation Method 1
there is a case that a part of the detection light that irradiates the light-receiving area is reflected on the light-receiving area toward the scale plate and the reflected detection light is reflected again on the scale plate
Data Source
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AI summary
An absolute encoder includes a light-emitting mechanism including a light-emitting surface and emitting detection light from the light-emitting surface. A light-receiving mechanism including a scale plate having a scale area and receiving at a light-receiving area the detection light emitted from the light-emitting surface and passing through the scale area of the scale plate. The light-emitting mechanism and the light-receiving mechanism are set to a positional relationship that inclines an irradiation axis extending from the light-emitting surface through the scale area to the light-receiving area relative to a rotation axis direction of the scale plate.