Infrared Sensor Light Guide Layout for Low-Noise Terminal Detection
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Solution Overview
Problem
Infrared sensors in terminals suffer from high background noise due to the large overlapping area between the emission and receiving windows, limiting the dynamic range of distance detection.
Innovation Solution
Incorporating first and second light guide structures between the transmitter and receiver of the infrared sensor and the glass cover plate, respectively, to redirect light away from the overlapping area, reducing background noise and increasing the field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the transmitter and receiver are placed close to each other on the PCB, then the device complexity is reduced and space is saved, but the overlapping area between emission and receive windows increases, causing large infrared background noise
Solution Approach 1:
A light guide structure is introduced as an intermediary component between the transmitter/receiver and the glass cover plate. This light guide structure redirects the light paths, allowing the transmitter and receiver to remain close together on the PCB while preventing direct light reflection from the glass cover plate into the receiver, thus reducing infrared background noise without increasing device complexity
Solution Approach 2:
The light guide structure extends the light paths in a third dimension (vertically through the glass cover plate) rather than keeping them confined to the PCB plane. This dimensional change allows the emission and receive windows to have minimal overlap when viewed from above, reducing background noise while maintaining the compact PCB layout
2Stability of the object's composition
If the transmitter and receiver are kept at a fixed distance based on stacking requirements, then the structural stability is maintained, but the overlapping area between emission and receive windows becomes large, reducing the dynamic range for distance detection
Solution Approach 1:
The light guide structure serves as a mediator that decouples the structural stacking requirements from the optical path requirements. It allows the transmitter and receiver to maintain their fixed positions for structural stability while independently redirecting light paths to minimize overlap, thereby maximizing the dynamic range for distance detection
3Use of energy by moving object
If the emission and receive windows have a large overlapping area, then the light collection efficiency is improved, but the direct reflection of light from the cover plate increases, reducing detection accuracy
Solution Approach 1:
The light guide structure creates different local optical paths for emission and reception. The emission path is directed toward the target object, while the reception path is directed away from the glass cover plate's reflective surface. This local differentiation allows efficient light collection from the target while avoiding the harmful reflective background noise
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
Reduces background noise and increases the dynamic range of infrared sensors by minimizing direct light reflection onto the receiver, enhancing detection accuracy.
Implementation Method 1
some infrared light is reflected by a surface of the glass cover plate to the receiver
Implementation Method 2
the first light guide structure obliquely extends from a light emitting surface of the transmitter toward the glass cover plate
Data Source
AI summary
A terminal includes: a glass cover plate, an infrared sensor including a transmitter and a receiver, and a first light guide structure and/or a second light guide structure. The first light guide structure is fixed between the transmitter and the glass cover plate, and the second light guide structure is fixed between the receiver and the glass cover plate. The first light guide structure extends obliquely from a light emitting surface of the transmitter toward the glass cover plate, and an oblique direction is away from an orthographic projection of the receiver on the glass cover plate. The second light guide structure extends obliquely from a light emitting surface of the receiver toward the glass cover plate, and an oblique direction is away from an orthographic projection of the transmitter on the glass cover plate.