Matched Spectral Filters for Optical Imaging Ambient Light Suppression
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Solution Overview
Problem
Existing optical imaging systems face challenges in suppressing ambient light, particularly when using spectral filters with narrow passbands, as the transmission passband shifts with incidence angle, affecting the efficiency of light detection and contrast between dedicated light sources and ambient light.
Innovation Solution
A system comprising a light source and a light detection unit, with matched first and second spectral filters having angular-dependent transmission passbands, optimizing the suppression of ambient light by ensuring the transmission properties align at different incidence angles, thereby enhancing light detection efficiency and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spectral filters with narrow passbands are used to suppress ambient light, then ambient light suppression is improved, but light detection efficiency deteriorates due to passband shift with incidence angle
Solution Approach 1:
The patent applies parameter changes by matching the angular dependence characteristics of the first spectral filter (in illumination unit) and second spectral filter (in detection unit). This ensures that the transmission passband wavelengths remain consistent across different incidence angles, resolving the contradiction between narrow passband suppression and detection efficiency
Solution Approach 2:
The patent introduces angular dependence matching as an additional dimension of control. By considering and matching the angular characteristics of both filters, the system maintains passband alignment across different viewing and illumination angles, enabling narrow passbands to function effectively without losing detection efficiency
2Object-affected harmful factors
If spectral filters are used to match light source wavelengths to detection unit wavelengths, then ambient light suppression is improved, but device complexity increases
Solution Approach 1:
The patent optimizes filter design by focusing on matching angular dependence parameters rather than requiring complex multi-layer structures. This approach achieves effective ambient light suppression while maintaining relatively simple filter constructions
Solution Approach 2:
The patent uses identical or matching spectral filter designs for both the illumination unit and detection unit. By copying the same filter type and matching its angular characteristics, the system achieves coordinated spectral filtering without requiring complex custom-designed filters for each unit
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 system effectively suppresses ambient light, improving the intensity of light detected while maintaining cost-effectiveness by using filters with fewer layers and optimizing the arrangement of light sources and detection units, which is beneficial for applications like optical authentication and machine vision.
Implementation Method 1
in particular for spectral filters relying on interference effects such as dielectric spectral filters
Implementation Method 2
Spectral filters may be used to match the wavelengths emitted by the light source to the wavelengths detected by the detection unit
Data Source
AI summary
Systems, methods and devices are for optical imaging are described. A system includes a light source and a light detection unit. The light source includes a light-emitting device and a first spectral filter opposite the light emitting device. The first spectral filter includes at least one dielectric filter and has a first angular dependence of a transmission passband. The light source further includes at least one reflector adjacent side surfaces of the light emitting device. The light detection unit includes an optical sensor and a second spectral filter opposite the optical sensor. The second spatial filter has a second angular dependence of a transmission passband that is matched to the first angular dependence.