Fabry-Perot Light Detector Layout for Stray Light Suppression
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Solution Overview
Problem
Light detection devices with Fabry-Perot interference filters face challenges in suppressing stray light and maintaining temperature uniformity, which affect the S/N ratio and resolution, due to variations in the distance between mirrors and environmental temperature changes.
Innovation Solution
A light detection device design with a Fabry-Perot interference filter having a variable mirror distance, where the light transmission region is aligned on a predetermined line, and a band pass filter positioned outside the filter's edge, along with a thick light transmitting member to enhance heat capacity and prevent stray light entry, ensuring accurate temperature control and improved light detection characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the light transmitting unit is positioned inside the Fabry-Perot interference filter, then the device complexity is reduced, but stray light enters the package causing degradation of light detecting characteristics
Solution Approach 1:
The light transmitting unit is repositioned from an internal location to an external location on the package, changing the spatial dimension of its placement. This dimensional shift allows the unit to filter light before it enters the package, effectively blocking stray light while maintaining structural simplicity.
Solution Approach 2:
The light transmitting unit acts as an intermediary component placed on the package opening. It serves as a mediator that selectively transmits desired light wavelengths while blocking stray light, protecting the Fabry-Perot interference filter and light detector from harmful light interference.
2Speed
If the light transmitting unit has small heat capacity, then the response speed is fast, but temperature uniformity in the package deteriorates causing stress variations
Solution Approach 1:
The heat capacity parameter of the light transmitting unit is optimized to an appropriate value that balances thermal stability and response speed. By adjusting this physical parameter, the unit can maintain temperature uniformity in the package while still responding adequately to operational changes.
Solution Approach 2:
The light transmitting unit serves a dual function: it filters light and simultaneously acts as a thermal mass to maintain temperature uniformity in the package. This self-service capability allows it to contribute to thermal stability without requiring additional dedicated temperature control components.
3Manufacturing precision
If the outer edge of the light transmitting unit is positioned inside the Fabry-Perot interference filter, then the manufacturing precision requirement is reduced, but light enters via side surfaces becoming stray light
Solution Approach 1:
The light transmitting unit is positioned outside the Fabry-Perot interference filter, changing the spatial relationship between components. This external positioning eliminates the problem of light entering through side surfaces, as the unit now filters light before it reaches the filter assembly.
Solution Approach 2:
The light transmitting unit performs preliminary light filtering before light enters the package and reaches the Fabry-Perot interference filter. By preprocessing the light in this preliminary stage, stray light is blocked before it can cause problems downstream in the optical path.
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 solution effectively suppresses stray light and maintains uniform temperature, enhancing the S/N ratio and resolution of the light detection device by positioning the band pass filter outside the Fabry-Perot interference filter and using a thick light transmitting member to increase heat capacity and prevent stray light entry.
Implementation Method 1
a band pass filter configured to transmit light incident on the light transmission region
Implementation Method 2
a Fabry-Perot interference filter having a first mirror and a second mirror, a distance therebetween is variable
Implementation Method 3
a light transmission region configured to transmit light corresponding to the distance between the first mirror and the second mirror
Implementation Method 4
the heat capacity of the light transmitting unit and a thermally connected area between the light transmitting unit and the package increases, and thus as a result the temperature in the package can be uniformized
Data Source
AI summary
A light detection device includes: a Fabry-Perot interference filter provided with a light transmission region; a light detector configured to detect light transmitted through the light transmission region; a package having an opening and accommodating the Fabry-Perot interference filter and the light detector; and a light transmitting unit arranged on an inner surface of the package so as to close an opening, the light transmitting unit including a band pass filter configured to transmit light incident on the light transmission region. When viewed from a direction parallel to the line, an outer edge of the Fabry-Pert interference filter is positioned outside an outer edge of the opening, and an outer edge of the light transmitting unit is positioned outside the outer edge of the Fabry-Perot interference filter.