Illuminance Sensor Infrared Noise Filtering
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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, making it difficult to accurately sense ambient brightness.
Innovation Solution
The design incorporates a dual light receiving system with specific optical configurations, including linear polarization plates and quarter-wave plates, to differentiate between infrared and visible light, allowing for the elimination of infrared noise and effective illuminance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an illuminance sensor is disposed at a position separated from the display portion, then the sensor can accurately sense ambient brightness, but the device width increases and design flexibility is reduced
Solution Approach 1:
The patent combines the illuminance sensor with the display portion by integrating it into the optical stack of the display device. The sensor is positioned within the same housing structure, sharing the same space with the display panel, thereby eliminating the need for separate border space while maintaining sensing functionality.
Solution Approach 2:
The illuminance sensor is nested within the display portion's optical path structure. The sensor is positioned between the polarizing plate and the display panel, utilizing the existing optical stack space. This nesting approach allows the sensor to be housed within the display portion without increasing overall device dimensions.
2Measurement precision
If an illuminance sensor is used to sense ambient brightness, then display brightness control is improved, but infrared light causes noise that degrades sensing accuracy
Solution Approach 1:
The patent converts the harmful infrared light interference into a beneficial filtering mechanism. By positioning the illuminance sensor to receive light through the display portion, the display panel itself acts as an infrared filter, blocking infrared wavelengths while allowing visible light to pass through to the sensor. This transforms the display portion into a dual-function element: display and infrared filtering.
Solution Approach 2:
The display portion serves as an intermediary element between the ambient light and the illuminance sensor. It selectively transmits visible light to the sensor while blocking infrared light, acting as a wavelength-selective mediator that protects the sensor from 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 accurate illuminance detection by filtering out infrared light interference, enhancing the sensor's ability to measure visible light in narrow spaces and reducing noise, thus improving the accuracy of ambient brightness sensing.
Implementation Method 1
a first linear polarization plate, a first quarter-wave plate, a second quarter-wave plate and a second linear polarization plate
Implementation Method 2
The first optical region and the second optical region include a first linear polarization plate, a first quarter-wave plate, a second quarter-wave plate and a second linear polarization plate
Implementation Method 3
a first light receiving portion and a second light receiving portion; a first optical region and a second optical region, disposed corresponding to the first light receiving portion and the second light receiving portion, respectively
Data Source
AI summary
In an illuminance sensor, a slow axis of a first quarter-wave plate has a relation of +45° or −45° in regard to a polarization direction of a first linear polarization plate; a relation of a slow axis of a first portion of a second quarter-wave plate in regard to a polarization direction of a second linear polarization plate is the same with relation of the slow axis of the first quarter-wave plate in regard to the polarization direction of the first linear polarization plate, that is, +45° or −45°; and a relation of a slow axis of a second portion of the second quarter plate in regard to the polarization direction of the second linear polarization plate is −45° or +45° that is opposite in sign to the relation of the slow axis of the first quarter-plate in regard to the polarization direction of the first linear polarization plate.