Optical Encoder Stray-Light Reduction Element Design
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Solution Overview
Problem
In optical encoders, the reduction in size and thickness leads to increased stray light due to shorter distances between light emitting and receiving sections, causing noise and deteriorating signal-to-noise ratio, which existing solutions attempt to address by making the transparent optical member thicker, but this restricts design flexibility and can result in reliability issues with mold resin packaging.
Innovation Solution
An optical encoder design incorporating a stray-light reduction element between the first and second light transmitting members, which are separate components with specific optical functions, to minimize stray light without compromising signal detection, allowing for thinner designs and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the encoder head is thinned to reduce size, then the compactness is improved, but the amount of stray light entering the light receiving section increases rapidly
Solution Approach 1:
A light shielding member is introduced as an intermediary component between the light emitting section and the light receiving section. This member selectively blocks stray light paths while allowing useful light to pass through, thereby reducing stray light contamination without requiring increases in encoder head thickness
Solution Approach 2:
The optical path is segmented into multiple regions using separate light transmitting members and light shielding members. By dividing the optical system into distinct functional zones, the design can control stray light in specific areas while maintaining overall compactness
2Object-affected harmful factors
If the transparent optical member is made thicker to reduce stray light, then the stray light is reduced, but the design flexibility is restricted and reliability issues occur
Solution Approach 1:
Instead of using a single thick transparent optical member, the system is segmented into multiple thinner light transmitting members separated by light shielding members. This segmentation allows for greater design flexibility in controlling optical paths while maintaining effective stray light reduction
Solution Approach 2:
Light shielding members are positioned as intermediaries between light transmitting members to control stray light. This approach provides design flexibility by allowing adjustment of shielding member positions and configurations without compromising stray light reduction effectiveness
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
The solution effectively reduces stray light, preventing signal saturation and maintaining a high signal-to-noise ratio, enabling thinner optical encoders with enhanced reliability and design flexibility.
Implementation Method 1
a first light transmitting member which transmits light emitted from the light emitting section, and a second light transmitting member which transmits light reflected from the scale
Implementation Method 2
a stray-light reduction element which reduces stray light between the first light transmitting member and the second light transmitting member
Implementation Method 3
a light detecting section which includes a light receiving surface which receives, via the optical pattern, light irradiated on the scale from the light emitting section and which detects light distribution formed on the light receiving surface
Data Source
AI summary
An optical encoder includes a scale which is installed on one member of which, displacement is detected, and a detecting head which is installed on the other member which moves relatively with respect to the one member, and is disposed facing the scale. A predetermined optical pattern in a direction of relative movement is provided, and the detecting head includes a light emitting section which irradiates a predetermined light on the scale, a light detecting section which includes a light receiving surface which receives light through the optical pattern, which is irradiated on the scale from the light emitting section, and which detects light distribution formed on the light receiving surface, a first light transmitting member which is disposed in an optical path between the light emitting section and the scale, and a second light transmitting member which is disposed in an optical path between the scale and the light detecting section. The optical encoder further includes a stray-light reduction element which is interposed between a surface of the first light transmitting member and a surface of the second light transmitting member, and which reduces stray light which does not contribute to signal detection.