Fabry-Perot Light Detector Layout for Stray Light and Thermal Uniformity
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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 stress generated by temperature changes and the need for precise control of the mirror distance.
Innovation Solution
A light detection device design that positions the Fabry-Perot interference filter's outer edge outside the package opening and the band pass filter's outer edge outside the Fabry-Perot interference filter, with a thick light transmitting member to enhance heat capacity and reduce stray light entry, while using a band pass filter and a silicon substrate to function as a high-pass filter for wavelength selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the Fabry-Perot interference filter is positioned with its outer edge outside the package opening, then stray light is prevented from entering the light detector, but the package size increases
Solution Approach 1:
The light transmitting unit is nested within the package structure, with the band pass filter positioned inside the package body. The Fabry-Perot interference filter extends beyond the package opening to block stray light, while the light transmitting unit provides thermal mass inside the package. This nested arrangement allows the system to achieve stray light rejection without proportionally increasing the overall package footprint.
2Temperature
If the light transmitting unit's outer edge is positioned outside the Fabry-Perot interference filter, then temperature uniformity is improved, but the device complexity increases
Solution Approach 1:
The light transmitting unit serves multiple functions: it acts as a thermal mass to uniformize temperature across the package, serves as a structural element closing the package opening, and positions the band pass filter to prevent stray light. By combining these functions into a single integrated component rather than separate elements, the design achieves temperature uniformity without proportionally increasing device complexity.
3Measurement precision
If the band pass filter is included in the light transmitting unit, then light detecting characteristics are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The band pass filter is merged with the light transmitting unit as an integrated component rather than a separate element. This combination allows the filter to be positioned and secured together with the light transmitting unit, reducing the number of separate alignment and mounting operations. The integrated design maintains the optical performance benefits of the band pass filter while simplifying the manufacturing process compared to separate assembly of multiple precision components.
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 design improves light detecting characteristics by reducing stray light, enhancing temperature uniformity, and effectively suppressing noise light, leading to improved S/N ratio and resolution.
Implementation Method 1
a light transmitting unit arranged on an inner surface of the package so as to close the opening and including 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, and provided with a light transmission region on a predetermined line, the light transmission region configured to transmit light corresponding to the distance between the first mirror and the second mirror
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-Perot 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.