Optical Encoder Slit Plate Phase Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical encoder devices have limited numbers of light transmissive slits in the stationary slit plate, leading to reduced utilization of the light receiving element and high distortion rates, especially when the number of slits is less than five, resulting in significant harmonic-wave component distortion.
Innovation Solution
The optical encoder device features a stationary slit plate with light transmissive slits of 180° and non-transmissive slits of (360Xk-180)° alternately formed, where k=1±(⅓n), allowing for an increased number of light transmissive slits to be maximally utilized according to the light receiving element's length, thereby reducing distortion by optimizing slit arrangement and phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of light transmissive slits in the stationary slit plate is limited to a predetermined number (less than five), then the device complexity is reduced, but the measurement precision deteriorates with distortion rates remaining as high as 1.5% or more
Solution Approach 1:
The patent applies parameter changes by optimizing the phase difference between slits in the stationary and movable slit plates. Specifically, it sets the phase difference to 1/12 of the pitch P, and divides light transmissive slits into units of four with specific phase shifts (P/12, P/6, P/4 between consecutive slits). This parameter optimization enables effective distortion cancellation with fewer slits, reducing the distortion rate below 1.5% while maintaining device simplicity.
2Manufacturing precision
If only a predetermined number of light transmissive slits are formed in the stationary slit plate, then the manufacturing precision is improved, but the light receiving element cannot be effectively utilized leading to wasted surface area
Solution Approach 1:
The patent changes the phase difference parameter to 1/12 of the pitch and structures slits in units of four with specific phase relationships. This enables achieving low distortion rates with a reduced number of slits, allowing the light receiving element's surface area to be effectively utilized without requiring excessive slits that would complicate manufacturing.
3Measurement precision
If the number of light transmissive slits is increased to reduce distortion, then the measurement precision is improved, but the device complexity increases requiring more slits to be formed in the stationary slit plate
Solution Approach 1:
The patent achieves high measurement precision with reduced device complexity by optimizing the phase difference parameter to 1/12 of the pitch and arranging slits in specific units of four. This parameter optimization enables effective distortion cancellation without requiring a large number of slits, thus maintaining simple slit plate structure while achieving low distortion rates below 1.5%.
4Object-generated harmful factors
If conventional slit patterns with phase difference of 1/6 or 1/10 are used, then specific harmonic waves are canceled, but the distortion rate remains high when fewer than five slits are available
Solution Approach 1:
The patent improves upon conventional phase differences of 1/6 or 1/10 by optimizing the phase difference to 1/12 of the pitch. Combined with dividing slits into units of four with specific phase shifts, this parameter change enables more effective cancellation of harmonic waves and achieves distortion rates below 1.5% even with fewer than five slits, significantly improving measurement precision.
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 maximizes the number of light transmissive slits on the stationary slit plate, significantly reducing distortion rates and enhancing the accuracy of the output signal, particularly by effectively canceling higher harmonic waves, thus improving the utilization of the light receiving element's surface area.
Implementation Method 1
a light emitting element (1), a light receiving element (2) disposed to face the light emitting element (1), a movable slit plate (3) disposed between the light emitting element (1) and the light receiving element (2), and a stationary slit plate (4) disposed between the light emitting element (1) and the light receiving element (2)
Data Source
AI summary
An optical encoder device is provided, in which the number of light transmissive slits of a stationary slit plate can be increased as much as possible according to the length of a light receiving surface of a light receiving element to produce an output signal with little distortion. A movable slit plate 3 includes a slit row R1 in which a plurality of light transmissive slits (light transmissive portions) S1 each having a slit width of 180° in terms of electrical angle and a plurality of light non-transmissive slits (light non-transmissive portions) S2 each having a slit width of 180° in terms of electrical angle are alternately formed. A stationary slit plate 4 includes a slit row R2 in which a plurality of light transmissive slits S3 each having a slit width of 180° in terms of electrical angle and a plurality of light non-transmissive slits S4 each having a slit width of (360Xk-180)° in terms of electrical angle are alternately formed. k is a value that satisfies k=1±(⅓n) where n denotes the number of the light transmissive slits S3.