Front-Lit Photodiode Detection Layout for Stray Light Blocking
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Solution Overview
Problem
Optical sensors with front lights face reduced detection accuracy due to light emitted in the opposite direction directly entering photodiodes, which reduces contrast and affects detection performance.
Innovation Solution
A detection device is designed with a light guide plate and scattering portions on the front light, an optical filter layer with light guide paths overlapping photodiodes, and a light-blocking portion with higher absorbance, where scattering portions are placed in the area overlapping the light-blocking portion to block unwanted light and enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a front light is provided between the object to be detected and photodiodes, then the object can be illuminated for detection, but light emitted in the opposite direction directly enters the photodiodes and reduces detection accuracy
Solution Approach 1:
The optical filter layer is segmented into multiple functional regions: light guide paths that allow useful light to pass through to photodiodes, and light-blocking portions that prevent unwanted direct light from reaching photodiodes. This segmentation enables selective transmission and blocking of light in different areas.
Solution Approach 2:
Different regions of the optical filter layer have different optical properties. The light guide paths have high light transmission in specific directions, while the light-blocking portions have high absorbance. The scattering portions are strategically placed in areas overlapping with light-blocking portions to scatter unwanted light. This local differentiation of optical properties resolves the contradiction between illumination and detection accuracy.
2Measurement precision
If light-blocking portions with higher absorbance are added to block unwanted light, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The optical filter layer integrates multiple functions into a single component: light guiding, light blocking, and optical filtering. The light guide paths and light-blocking portions are formed in the same layer, eliminating the need for separate components and reducing overall device complexity while maintaining detection accuracy.
Solution Approach 2:
The optical filter layer serves multiple purposes simultaneously: it guides light from the light source to the object, blocks unwanted direct light from reaching photodiodes, and works with scattering portions to redirect light. This multi-functionality reduces the need for additional separate components.
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 solution improves detection accuracy by reducing external light entry into photodiodes, enhancing signal-to-noise ratio and sensitivity, and improving the overall performance of the detection device.
Implementation Method 1
a plurality of scattering portions that are provided on the light guide plate and configured to scatter light from the light source
Implementation Method 2
a light-blocking portion having higher absorbance of the light than the light guide paths
Implementation Method 3
a plurality of photodiodes arranged on a substrate
Data Source
AI summary
According to an aspect, a detection device includes: a plurality of photodiodes arranged on a substrate; a front light including a light guide plate disposed so as to overlap the photodiodes, a light source configured to emit light to a first side surface of the light guide plate, and a plurality of scattering portions provided on the light guide plate and configured to scatter light from the light source; and an optical filter layer provided between the photodiodes and the light guide plate of the front light. The optical filter layer includes a plurality of light guide paths that at least partially overlap the photodiodes, and a light-blocking portion having higher absorbance of the light than the light guide paths. The scattering portions are provided in an area overlapping the light-blocking portion of the optical filter layer on a surface of the light guide plate facing the optical filter layer.