Polarized Illuminance Sensor Layout for Infrared Noise Rejection
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Solution Overview
Problem
Existing illuminance sensors face challenges in narrow spaces and are prone to noise from infrared light, particularly in thin display devices and portable electronics like smartphones, where space constraints and infrared interference hinder effective ambient brightness sensing.
Innovation Solution
The design incorporates a dual light receiving system with specific optical configurations, including linear and quarter-wave plates, to differentiate between infrared and visible light, allowing for the elimination of infrared noise and accurate illuminance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If an illuminance sensor is disposed in a narrow border portion of a display device, then the device can be made thinner and design flexibility is improved, but the sensor may be difficult to separate from the display portion and installation becomes difficult
Solution Approach 1:
The illuminance sensor is integrated within the display device structure by nesting it in the border portion, allowing the sensor to be housed within the existing device architecture without requiring additional external space, thus achieving thinness while maintaining functionality
2Length of moving object
If an illuminance sensor is disposed close to the display portion to save space, then device thickness is reduced, but the sensor becomes more susceptible to infrared light noise
Solution Approach 1:
An infrared cut filter is introduced as an intermediary component between the display portion and the illuminance sensor. This filter selectively blocks infrared light while allowing visible light to pass through, thereby eliminating infrared noise interference and enabling accurate illuminance detection even when the sensor is positioned close to the display
3Adaptability or versatility
If an illuminance sensor is used in smartphones and tablet terminals for outdoor use, then ambient brightness sensing is enabled, but infrared light noise becomes a significant obstacle to accurate sensing
Solution Approach 1:
An infrared cut filter is positioned in the optical path between the external environment and the illuminance sensor. This filter acts as a selective mediator that transmits visible light for illuminance measurement while blocking infrared radiation, thereby enabling accurate ambient brightness sensing in outdoor conditions without infrared 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
This configuration enables effective illuminance sensing in narrow spaces by filtering out infrared interference, improving the accuracy of ambient brightness detection in devices with limited space and reducing noise from infrared light.
Implementation Method 1
The first optical region and the second optical region comprise a first linear polarization plate, a first quarter-wave plate, a second quarter-wave plate and a second linear polarization plate
Data Source
AI summary
In an illuminance sensor, a slow axis of a first portion comprises a relation of +45° or −45° in regard to a first polarization direction that is a polarization direction of the a linear polarization plate, a relation of a slow axis of a second portion in regard to the first polarization direction is −45° or +45° that is opposite in sign to the relation of the slow axis of the first portion in regard to the first polarization direction, and a slow axis of a second quarter-wave plate comprises a relation of +45° or −45° in regard to a second polarization direction that is a polarization direction of a second linear polarization plate, wherein the relation of the slow axis of the second quarter-wave plate in regard to the second polarization direction is the same with the relation of the slow axis of the first portion in regard to the first polarization direction.