Optical Sensor With Segmented Photodiodes For Disturbance Light Rejection
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Solution Overview
Problem
Conventional optical sensors fail to accurately sense the direction of movement of an object in the presence of disturbance light, such as natural or illuminating light, which affects their performance and accuracy.
Innovation Solution
An optical sensor design featuring a light-emitting element and a circularly-segmented light-receiving element group at the edges of a region where reflected light is incident, allowing the sensor to accurately detect the direction of movement by comparing the positions of light-receiving elements during entry and departure, while preventing adverse effects from external disturbance light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical sensor uses light-receiving elements to detect reflected light for sensing object movement, then the sensor can detect object position and movement, but the sensor accuracy deteriorates in the presence of disturbance light such as natural or illuminating light
Solution Approach 1:
The light-receiving element is divided into multiple segments arranged in different directions. Each segment detects light from a specific direction, allowing the sensor to determine object movement direction by comparing signals from different segments. This segmentation enables the system to distinguish between reflected light from the object and disturbance light from other directions, maintaining accuracy even in the presence of ambient light.
Solution Approach 2:
Different segments of the light-receiving element are oriented with different directivity characteristics to detect light from specific directions. By assigning different functional properties to different parts of the light-receiving element, the sensor can selectively detect reflected light from the object while ignoring disturbance light from other directions, thus resolving the contradiction between detecting object movement and rejecting disturbance light.
2Measurement precision
If the optical sensor uses multiple photodiodes to sense object movement through photocurrent changes, then the sensor can detect movement direction, but the sensor becomes more susceptible to disturbance light affecting the photocurrent measurements
Solution Approach 1:
The photodiode array is segmented into multiple light-receiving elements with different spatial orientations. Each segment's photocurrent response is analyzed independently to determine the direction of reflected light. This allows the system to distinguish between photocurrent changes caused by object movement (reflected light) and those caused by disturbance light, maintaining measurement precision.
Solution Approach 2:
The sensor system processes signals from multiple segmented photodiodes to determine object movement direction. By comparing the relative intensities of light received by different segments, the system can infer the direction of reflected light and distinguish it from disturbance light, effectively using feedback from multiple measurement channels to reject interference.
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 optical sensor effectively senses the direction of movement of an object even under conditions of disturbance light, maintaining accuracy and preventing interference from external light sources.
Implementation Method 1
a light-emitting element; a plurality of first light-receiving elements, circularly provided at edges of a region on which reflected light from an object to be sensed reflecting light emitted by the light-emitting element is incident, for generating respective photocurrents upon receiving the reflected light
Data Source
AI summary
In order to provide an optical sensor that can accurately sense a direction of movement of an object to be sensed even in a case where disturbance light is present, an optical sensor of the present invention includes: a light-emitting element; a circularly-segmented light-receiving element group (RDPD), including light-receiving elements circularly provided at edges of a region on which reflected light from an object to be sensed reflecting light emitted by the light-emitting element is incident, for generating respective photocurrents upon receiving the reflected light; and a gesture circuit section for sensing a direction of movement of the object to be sensed upon receiving the photocurrents generated by the light-receiving elements included in the circularly-segmented light-receiving element group (RDPD).