Optical Sensor Dual Photodiode Noise Suppression
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Solution Overview
Problem
Conventional display devices with optical sensors suffer from noise due to unnecessary light, such as stray light or light outside the detected wavelength range, which cannot be effectively compensated by existing light detecting elements, leading to inaccurate sensor outputs.
Innovation Solution
The implementation of a dual light detecting element system, where one element receives the light to be detected and another receives unnecessary light, with their differential output providing a noise-suppressed sensor output, allowing for high accuracy in detecting the intended light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional light detecting element for reference with entire surface covered by light blocking film is used, then dark current compensation is achieved, but unnecessary light (stray light, out-of-wavelength light) cannot be compensated
Solution Approach 1:
The light blocking film is segmented into multiple regions: a first light blocking region that blocks light to be detected while allowing unnecessary light to pass, and a second light blocking region that blocks both light to be detected and unnecessary light. This segmentation enables the reference light detecting element to receive and compensate for unnecessary light while the detection element receives only the light to be detected.
Solution Approach 2:
Different regions of the light blocking film have different light blocking properties tailored to their specific functions. The first light blocking region has selective blocking characteristics (blocks desired light, allows unwanted light), while the second light blocking region has complete blocking characteristics. This local differentiation of light blocking quality enables precise control over which light components reach each detecting element.
2Reliability
If a light detecting element for reference is provided to compensate for temperature changes, then dark current compensation is achieved, but compensation for unnecessary light is not achieved
Solution Approach 1:
The light blocking film is segmented into multiple regions: a first light blocking region that blocks light to be detected while allowing unnecessary light to pass, and a second light blocking region that blocks both light to be detected and unnecessary light. This segmentation enables the reference light detecting element to receive and compensate for unnecessary light while the detection element receives only the light to be detected.
Solution Approach 2:
Different regions of the light blocking film have different light blocking properties tailored to their specific functions. The first light blocking region has selective blocking characteristics (blocks desired light, allows unwanted light), while the second light blocking region has complete blocking characteristics. This local differentiation of light blocking quality enables precise control over which light components reach each detecting element.
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 a highly accurate sensor output by effectively suppressing noise from unnecessary light, improving the precision of light detection in display devices.
Implementation Method 1
a first light detecting element receiving light in a first range including light to be detected
Implementation Method 2
a second light detecting element receiving light in a second range other than the light to be detected
Data Source
AI summary
An optical sensor is provided with a photodiode (D1) which receives light in a first range, including light to be detected, and a photodiode (D2) which receives light in a second range other than the light to be detected. For instance, the photodiode (D1) receives light at all the incident angles, and the photodiode (D2) has a light blocking film on an incident light path so as to selectively receive only the incident light from the oblique directions. The differential between the output from the photodiode (D1) and that from the photodiode (D2) is read out as sensor output.