Optical Sensor Package Layout for Stray Light Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical sensors suffer from stray light generation due to reflections on the package, leading to a decrease in signal-to-noise ratio and false detections.
Innovation Solution
The optical sensor design includes a light projecting unit with a recessed portion having a light source mounted on its bottom surface, covered by a light-transmissive resin, and side surfaces that absorb light to reduce stray light, along with separate housings for the light projecting and receiving units to minimize stray light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a package product integrating light source and package is used, then ease of manufacture is improved, but stray light is generated due to reflections on the package
Solution Approach 1:
The patent converts the harmful reflective property of the package into a beneficial feature by deliberately designing the package inner surface with high reflectivity. This reflected light is then directed onto a light-receiving member positioned at a specific angle, transforming what would normally be stray light interference into a useful detection mechanism for determining light source orientation
Solution Approach 2:
The patent introduces a light-receiving member as an intermediary element between the package surface and the detection system. This mediator captures the reflected light from the package and converts it into detectable signals, enabling the system to utilize package reflections constructively rather than treating them as harmful interference
2Object-generated harmful factors
If light emitted from the light source is reduced to prevent stray light, then stray light is reduced, but signal-to-noise ratio decreases
Solution Approach 1:
The patent applies local quality by creating spatial differentiation between regions experiencing stray light and regions receiving useful light. The light-receiving member is positioned to selectively receive reflected light from specific package surfaces while maintaining sensitivity to the primary light beam, allowing the system to operate with normal light emission levels without compromise to signal-to-noise ratio
3Object-generated harmful factors
If the side surface of the recessed portion includes a light-absorbing material, then stray light is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes by varying the optical properties of different package surfaces. The side surfaces of the recessed portion are designed with light-absorbing characteristics (low reflectivity) to prevent stray light generation, while the bottom surface maintains high reflectivity for the intended light direction. This parameter differentiation is achieved through material selection and surface treatment during the molding process
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 design effectively reduces stray light, maintaining a high signal-to-noise ratio and minimizing false detections by absorbing stray light and improving visibility of the main light beam on the target object.
Implementation Method 1
A side surface of the recessed portion includes a material that absorbs the light emitted from the light source
Implementation Method 2
a resin that is light transmissive and covers the light source
Data Source
AI summary
An optical sensor includes a light projecting unit, a light receiving unit, and a detection unit. The light projecting unit includes a light source that emits light and the light projecting lens configured to condense the light emitted from the light source. The light receiving unit receives the light, and the detection unit detects a target object based on the received light. The light projecting unit further includes a package having a recessed portion. The light source is mounted on the bottom surface of the recessed portion. The light projecting unit also includes a resin that is light transmissive and covers the light source. A side surface of the recessed portion includes a material that absorbs the light emitted from the light source.