Optical Encoder Unit Light Intensity Signal-to-Noise Ratio
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Solution Overview
Problem
Optical encoders face challenges in reducing the influence of light intensity fluctuations and require accurate optical axis adjustment, which affects their performance and reliability, especially in environments with foreign substances and varying light conditions.
Innovation Solution
An optical encoder unit with a light source and optical sensor arrangement that receives light intensity greater than the dark current of the sensor, combined with a polarizer on the optical scale and multiple photoreceivers to enhance signal-to-noise ratio and facilitate accurate angle measurement, along with a cylindrical cover to suppress external noise, allowing for miniaturization and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical encoder uses conventional light source and sensor arrangement, then the structure is compact, but the signal-to-noise ratio is low and measurement accuracy is poor
Solution Approach 1:
The patent changes the key parameter of light intensity by positioning the optical sensor unit to receive light intensity that is 100 times or more greater than the dark current of the sensor. This parameter change directly improves the signal-to-noise ratio and measurement accuracy without requiring complex optical components or precise optical axis adjustment mechanisms
2Measurement precision
If the optical encoder requires accurate optical axis adjustment, then the measurement precision can be improved, but the ease of operation and manufacturing complexity increase
Solution Approach 1:
The patent implements a self-aligning optical system where the light source and optical sensor unit are positioned to automatically receive sufficient light intensity (100 times or more greater than dark current) without requiring manual optical axis adjustment. The system serves itself by design, eliminating the need for complex adjustment procedures and specialized manufacturing processes
3Measurement precision
If the optical encoder increases light intensity to improve signal-to-noise ratio, then the measurement accuracy improves, but the energy consumption increases
Solution Approach 1:
The patent introduces the optical scale with polarizer as an intermediary element that modulates light intensity according to the rotational position. This allows the system to achieve high signal-to-noise ratio through optical modulation rather than simply increasing light source intensity, thereby improving measurement accuracy without proportionally increasing energy consumption
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 light intensity fluctuations, enhances measurement accuracy, and simplifies optical axis adjustment, leading to improved performance and reliability of the optical encoder unit.
Implementation Method 1
a light source (41) having a predetermined light distribution; an optical scale (11) having a polarizer whose polarization direction on a plane is along a predetermined direction, and whose polarization direction is changed according to rotation
Implementation Method 2
an optical scale (11) having a polarizer whose polarization direction on a plane is along a predetermined direction, and whose polarization direction is changed according to rotation
Implementation Method 3
an optical sensor unit (35) including a first photoreceiver (PD1), a second photoreceiver (PD2), a third photoreceiver (PD3), and a fourth photoreceiver (PD4) for receiving incident light
Data Source
AI summary
An optical encoder unit includes: a light source having a predetermined light distribution; an optical scale having a polarizer whose polarization direction on a plane is along a predetermined direction, and whose polarization direction is changed according to rotation; and an optical sensor unit including a first photoreceiver, a second photoreceiver, a third photoreceiver, and a fourth photoreceiver for receiving incident light that is light source light from the light source made incident on the respective photoreceivers by passing through or being reflected by the optical scale. An emitting surface of the light source and the optical sensor unit are arranged at positions so as to receive a light intensity that is predetermined times greater or more than that corresponding to dark current of the optical sensor.