Optical Encoder Light Source Driver Crosstalk Mitigation
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Solution Overview
Problem
Signal interference, known as crosstalk, occurs between adjacent light receiving elements in optical encoders, degrading the accuracy of Automatic Power Control (APC) in light source units.
Innovation Solution
A semiconductor device with a light source unit driver that utilizes both signals from a photoelectric conversion element receiving incident light and a shielded element to improve APC accuracy, where the shielded element helps correct for crosstalk by generating a reference signal to set the desired light emission amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple light receiving elements are arrayed to enable APC control, then light emission amount can be maintained constant, but signal interference (crosstalk) occurs between adjacent elements degrading measurement precision
Solution Approach 1:
The light receiving elements are divided into distinct functional groups: first light receiving elements that receive incident light for APC control, and second light receiving elements that are shielded from incident light to provide reference signals. This segmentation isolates the crosstalk effect to specific elements while preserving the overall APC functionality, allowing accurate measurement of crosstalk for correction purposes.
Solution Approach 2:
The second light receiving elements (shielded from incident light) act as intermediaries that measure only the crosstalk signal without being affected by the actual light intensity variations. These reference signals serve as a baseline to quantify and correct the crosstalk interference in the signals from the first light receiving elements, thereby restoring measurement precision.
2Area of stationary object
If light receiving elements are placed close together to improve device compactness, then device area is reduced, but crosstalk between adjacent elements increases
Solution Approach 1:
Shielded light receiving elements are positioned adjacent to the light-receiving elements to serve as reference sensors that capture only the crosstalk component. These intermediary reference elements enable the system to compensate for crosstalk interference even when elements are densely packed, allowing compact device design without sacrificing signal accuracy.
Solution Approach 2:
The system uses feedback from the shielded light receiving elements to continuously monitor and quantify crosstalk levels. This feedback signal is then used to correct the measurements from the light-receiving elements, enabling the device to maintain accuracy despite the close spacing of components that necessitates compact design.
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
Enhances the accuracy of APC by effectively mitigating crosstalk, allowing for precise control of the light source unit's emission, thereby improving the overall performance of the optical encoder.
Implementation Method 1
a plurality of photoelectric conversion elements arrayed on a substrate
Data Source
AI summary
A semiconductor device comprising a plurality of photoelectric conversion elements arrayed on a substrate, a readout unit configured to read out signals from the plurality of photoelectric conversion elements, and a light source unit driver configured to drive a light source unit, wherein the plurality of photoelectric conversion elements include a first element configured to receive incident light and a second element configured to be shielded from the incident light, and the light source unit driver drives the light source based on both a signal from the first element and a signal from the second element read out by the readout unit.