Optical Encoder Light Receiving Part Geometry for Crosstalk Prevention
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Solution Overview
Problem
Conventional optical encoders suffer from light crosstalk due to light beams passing through neighboring slits being detected by adjacent light receiving parts, which degrades detection accuracy.
Innovation Solution
The optical encoder design includes light receiving parts positioned with at least one inner edge on the inner side and one outer edge on the outer side of the optical axis, with these edges being farther from the axis than the corresponding slit array edges, and optionally within a range defined by light blocking parts, to prevent crosstalk by ensuring light is detected only by the intended slit array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If light receiving parts are arranged in alignment with slit arrays to increase output level, then detection signal output increases, but light crosstalk occurs between neighboring slits and adjacent light receiving parts
Solution Approach 1:
The light receiving part is designed with non-uniform width along the optical axis direction, creating different local properties. The first light receiving part has a greater width than the second light receiving part, allowing each part to be optimized for its specific position and function in preventing crosstalk while maintaining detection sensitivity.
Solution Approach 2:
The light receiving part employs an asymmetric width configuration where the first light receiving part (corresponding to the first slit array) has a greater width than the second light receiving part (corresponding to the second slit array). This asymmetric design creates different light blocking characteristics for different slit arrays, effectively preventing crosstalk from asymmetrically directed light beams while maintaining alignment for maximum signal output.
2Area of stationary object
If light emitting part emits light in all directions, then light coverage is maximized, but light beams directed at angles reach wrong light receiving parts causing crosstalk
Solution Approach 1:
Different portions of the light receiving part have different widths to address the local quality of light beams at different positions. The first light receiving part has greater width to handle light beams from the first slit array, while the second light receiving part has smaller width for the second slit array, creating localized optimization for each light path.
Solution Approach 2:
The width parameter of the light receiving part is changed along the optical axis direction, creating a gradient or stepped configuration where the first light receiving part has a greater width than the second light receiving part. This parameter change allows the system to maintain broad light coverage while preventing angled light beams from causing crosstalk by ensuring only the intended light receiving part detects each slit array's light.
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 light crosstalk, enhancing detection accuracy and increasing the output level of the detection signal without the need for additional optical elements, thus improving the reliability and efficiency of the encoder.
Implementation Method 1
a light emitting part configured to emit light toward the plurality of slit arrays; and, a plurality of light receiving parts arranged so as to correspond to the plurality of slit arrays and to detect light which is emitted from the light emitting part and passes through the plurality of slit arrays
Data Source
AI summary
In an optical encoder which includes a rotary plate formed with a plurality of slit arrays and a plurality of light receiving parts corresponding to the slit arrays, at least one of the outer edge of a light receiving part located on the outer side of the optical axis X of light emitted from a light emitting part and the inner edge of the light receiving part located on the inner side of the optical axis X is positioned at a greater distance from the optical axis than the edge of the slit array corresponding to the light receiving part.