Highly-folding pendular optical cavity for compact NDIR sensors
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Solution Overview
Problem
Conventional optical cavities for spectroscopic sensors, such as NDIR sensors, face challenges in achieving compactness while maintaining high sensitivity due to the limited number of light beam paths, which increases the cavity dimensions and compromises compactness when a high interaction length is required.
Innovation Solution
The design incorporates three elliptical mirrors with a common focal point and additional reflectors to create a highly folded optical cavity, allowing a large number of light beam paths within a compact space, utilizing elliptical mirrors with specific focal axis configurations and reflectors to maximize light ray distance and folding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional optical cavities with limited light beam paths are used, then the sensor structure is simpler, but the interaction length is insufficient and compactness is compromised
Solution Approach 1:
The patent employs multiple elliptical mirrors arranged in a three-dimensional configuration to fold the optical path. The light beam undergoes successive reflections between mirrors positioned at different spatial locations, transforming a linear path into a multi-dimensional folded path. This enables the interaction length to extend significantly beyond the physical cavity dimensions, resolving the contradiction between long interaction length and compact cavity volume.
Solution Approach 2:
The optical cavity design nests multiple reflection paths within a compact mirror arrangement. The light beam traverses the cavity multiple times through successive reflections, effectively nesting the optical path within the physical boundaries of the cavity. This allows the interaction length to be multiplied while maintaining a compact overall structure.
2Measurement precision
If the number of light beam paths is increased to enhance sensitivity, then the interaction length increases, but the cavity dimensions must be increased which reduces compactness
Solution Approach 1:
By arranging elliptical mirrors in a three-dimensional configuration with specific focal point relationships, the patent creates multiple light beam paths that fold through the cavity space. The light undergoes successive reflections between mirrors positioned at different heights and lateral positions, effectively utilizing three-dimensional space to multiply the optical path length without increasing the cavity's external footprint, thereby enhancing sensitivity while maintaining compactness.
3Volume of stationary object
If a direct path cavity is used to maintain compactness, then the cavity volume is reduced, but the interaction length becomes insufficient for high sensitivity detection
Solution Approach 1:
The patent creates a dynamic optical path where the light beam undergoes multiple reflections between elliptical mirrors, effectively 'folding' the path through the cavity. The sequential reflections cause the light to traverse the cavity length multiple times in a compact arrangement, dynamically extending the interaction length within a reduced volume compared to a direct path configuration.
Solution Approach 2:
The multiple reflection paths are nested within the compact cavity structure, with the optical path folding back and forth between mirrors positioned close together. This nesting of the optical trajectory within the physical boundaries allows the interaction length to be extended significantly while maintaining a small cavity volume.
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
This configuration enables a compact and highly efficient optical cavity that increases the optical path length within the sensor, enhancing sensitivity and maintaining compactness, while also allowing for reduced thickness and improved aliasing of light rays, thereby improving the sensor's performance.
Implementation Method 1
a first elliptical mirror, having a first focal axis noted A1, and designed to reflect a light beam emitted by a light source; a second elliptical mirror, having a second focal axis noted A2; a third elliptical mirror, having a third focal axis noted A3, the light beam exiting from the third elliptical mirror being designed to be received by a detector
Data Source
AI summary
An optical cavity includes: a first elliptical mirror, having a first focal axis A1, and designed to reflect a light beam emitted by a light source; a second elliptical mirror, having a second focal axis A2; a third elliptical mirror, having a third focal axis A3, the light beam exiting from the third elliptical mirror being designed to be received by a detector; a first reflector, arranged to reflect the light beam exiting from first elliptical mirror in the direction of the second elliptical mirror, and arranged to reflect the light beam exiting from second elliptical mirror in the direction of the third elliptical mirror; the first, second and third elliptical mirrors being arranged so that A1, A2 and A3 have a point of intersection F, corresponding to a focus common to the first, second and third elliptical mirrors.