Rough Opaque Coating for Stray Light Reduction in Active-Pixel Devices
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Solution Overview
Problem
Conventional active-pixel devices face issues with stray light due to reflected light from masks and coatings, which can contribute to noise and reduce sensitivity and spatial resolution, despite efforts to block stray light through apertures and side-wall masks.
Innovation Solution
The implementation of low-reflectivity, rough surface coatings on the cover glass and other surfaces to absorb incoming light and prevent reflections from reaching the active pixels, thereby reducing stray light signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional masks and coatings are used to block stray light, then light transmission is blocked, but light reflection occurs and continues to propagate causing stray light signal
Solution Approach 1:
The patent converts the harmful reflective property of conventional masks and coatings into a beneficial absorptive property by using rough opaque coatings. The rough surface structure transforms reflected light into absorbed light through multiple internal reflections, converting the harmful reflection effect into a beneficial light-trapping mechanism that reduces stray light signal.
Solution Approach 2:
The patent changes the surface parameter of the coating from smooth to rough. This parameter change fundamentally alters the light interaction mechanism from reflection to absorption. The rough surface creates multiple scattering events that increase the optical path length and probability of absorption, thereby changing the dominant optical property from reflective to absorptive.
2Use of energy by moving object
If polished surfaces are used on cover glass and focusing optics, then light transmission is improved, but light reflection occurs and reaches active pixels
Solution Approach 1:
The patent applies different surface qualities to different locations: polished surfaces are maintained on the cover glass and focusing optics for optimal light transmission, while rough opaque coatings are applied specifically to the mask structures. This local differentiation allows each component to optimize its primary function while the rough coating specifically addresses the reflection problem at critical locations.
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 rough opaque coatings effectively suppress reflections and absorption of light, significantly reducing stray light signals and enhancing the sensitivity and spatial resolution of active-pixel devices.
Implementation Method 1
These rough coatings are designed to have microscopic roughness that at least partially absorbs incoming light and prevents the incoming light from later reaching the active pixels
Implementation Method 2
The rough opaque coating is rough so as to suppress reflection of light incident thereon from at least one side
Data Source
AI summary
An active-pixel device assembly with stray-light reduction includes an active-pixel device including a semiconductor substrate and an array of active pixels, a light-transmissive substrate disposed on a light-receiving side of the active-pixel device, and a rough opaque coating disposed on a first surface of the light-transmissive substrate and forming an aperture aligned with the array of active pixels, wherein the rough opaque coating is rough so as to suppress reflection of light incident thereon from at least one side. A method for manufacturing a stray-light-reducing coating for an active-pixel device assembly includes depositing an opaque coating on a light-transmissive substrate such that the opaque coating forms a light-transmissive aperture, and roughening the opaque coating to form a rough opaque coating, said roughening including treating the opaque coating with an alkaline solution.