Reflection Sensor Noise Reduction via Transparent Member Geometry
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Solution Overview
Problem
Reflection type sensors face noise interference from light totally reflected on transparent members, which is superimposed on sensor signal light, affecting accuracy and reliability.
Innovation Solution
The configuration of the reflection type sensor includes a light emitting element, a light receiving element, and a transparent member, where the light receivers are positioned between the light emitter and a distance R from the emitter's end, and the distance D1 from the emitter's end to the transparent member's side surface satisfies the conditional expression D1(G+J)/tan θ, minimizing internal reflection noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light receiving area is positioned closer to the light emitting element to reduce the influence of totally reflected light, then the noise light from top surface total reflection is reduced, but the light that is totally reflected by the side surface of the transparent member and enters the light receiving element still causes noise
Solution Approach 1:
The patent utilizes the law of total internal reflection to redirect harmful noise light back toward the light emitting element. By positioning the light receiving element at a specific depth and using the side surface of the transparent member as a reflective boundary, the noise light that would normally enter the receiver is instead reflected back to the emitter, converting a harmful effect into a beneficial geometric constraint that protects the receiver
Solution Approach 2:
The patent transitions from considering only horizontal positioning to incorporating vertical depth positioning as a critical dimension. By specifying that the light receiving element be positioned at a depth greater than the distance from the light emitting element to the top surface of the transparent member, the invention uses the third dimension (depth) to geometrically exclude noise light paths while maintaining signal light reception
2Measurement precision
If the light receiving element is positioned deeper to avoid noise light, then top surface reflection noise is reduced, but the overall device size increases
Solution Approach 1:
The patent optimizes the depth parameter of the light receiving element to achieve a balance between noise reduction and compactness. By setting the depth to be greater than the distance from the light emitting element to the top surface (a specific parameter relationship), the invention achieves effective noise exclusion while minimizing the required housing volume, avoiding excessive depth that would increase overall device size
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 reduces the influence of internally reflected light on the sensor signal, enhancing accuracy and allowing for a compact design by ensuring that noise light is not superimposed on the sensor signal, thereby improving the reliability of the reflection type sensor and optical encoder.
Implementation Method 1
a light emitting element configured to emit light
Implementation Method 2
the light totally reflected on the top surface of the transparent member and the light totally reflected by a side surface of the transparent member
Implementation Method 3
a light receiving element configured to receive reflected light from a scale having a pattern, and a displacement of the measurement target is detected by a change in the reflected light amount
Data Source
AI summary
A reflection type sensor includes a light emitting element configured to emit light, a light receiving element configured to receive reflected light from a scale having a pattern, and a transparent member configured to cover the light emitting element and the light receiving element. A predetermined condition is satisfied.