Stray Light Blocking Structures in Transparent Members
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Solution Overview
Problem
Incorporating optical sensors into electronic devices is challenging due to stray light interference from light-emitting components, which affects the accuracy of light-detecting components, particularly in head-mounted devices where accurate environmental measurements are crucial.
Innovation Solution
A transparent member with a stray light blocking structure, such as a polymer layer featuring protrusions and recesses or light-absorbing coatings, is used to prevent lateral propagation of stray light within the device, thereby isolating light-emitting and light-detecting components and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical sensors are incorporated into electronic devices, then sensing functionality is added, but stray light from light-emitting components creates noise that reduces measurement accuracy
Solution Approach 1:
The transparent member is divided into multiple functional layers: a first transparent layer allowing light transmission, and a second transparent layer with integrated stray light blocking structures. This segmentation allows each layer to perform its specific function - the first layer maintains optical clarity while the second layer addresses stray light interference, thereby resolving the contradiction between adding sensing functionality and maintaining measurement precision.
Solution Approach 2:
The second transparent layer acts as an intermediary element positioned between the light-emitting components and the light-detecting components. It selectively blocks harmful stray light while allowing useful light signals to pass through, thereby protecting the optical sensor from noise without interfering with its sensing capability.
2Device complexity
If light-emitting and light-detecting components are placed close together, then device compactness is improved, but stray light interference increases
Solution Approach 1:
The stray light blocking structures are nested within the second transparent layer itself, forming an integrated multi-functional component. The blocking structures are positioned within the thickness of the layer, allowing compact device design while effectively preventing stray light from reaching the light-detecting components, thus resolving the contradiction between compactness and interference reduction.
Solution Approach 2:
Instead of increasing the lateral distance between light-emitting and light-detecting components (which would compromise compactness), the solution addresses stray light interference in the vertical dimension by introducing a second transparent layer with blocking structures positioned at different depths, thereby maintaining compact device geometry while eliminating harmful interference.
3Illumination intensity
If a transparent member without blocking structures is used, then optical clarity and image visibility are maintained, but stray light propagates laterally through the polymer layer creating noise
Solution Approach 1:
The second transparent layer is designed with spatially varying properties: regions containing stray light blocking structures where needed, and transparent regions where light transmission is required. This local differentiation allows the member to simultaneously maintain optical clarity in appropriate regions while blocking stray light in specific areas, resolving the contradiction between clarity and interference prevention.
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 implementation of stray light blocking structures enhances the accuracy of optical sensors by minimizing noise from stray light, improving the signal-to-noise ratio and maintaining clear real-world image visibility.
Implementation Method 1
Light-absorbing coatings and/or patterned surfaces such as textured surfaces may be incorporated into the stray light blocking structure
Implementation Method 2
Light redirecting structures such as protrusions and/or recesses may be formed in the transparent member
Data Source
AI summary
An electronic device such as a head-mounted device may have a transparent member supported by head-mounted support structures. Optical sensors such as time-of-flight sensors and other optical sensors may have light-emitting components and light-detecting components. A stray light blocking structure may be formed in the transparent member. The stray light blocking structure may be configured to block stray light that is traveling laterally through an interior portion of the polymer layer. This prevents the stray light from being received by the light-detecting detecting device. The stray light blocking structure may formed by providing the polymer layer with light redirecting structures such as protrusions and/or recesses. Light-absorbing coatings and/or patterned surfaces such as textured surfaces may be incorporated into the stray light blocking structure.