Tilted Optical Filter Elements Reduce Multiple-Reflection Interference
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Solution Overview
Problem
Spectroscopic devices using filters with varying transmission wavelengths experience multiple-reflection issues, leading to light components from other wavelength bands being received by light-receiving elements, which affects measurement accuracy.
Innovation Solution
The spectroscopic unit incorporates a filter with multiple optical filter elements arranged sequentially, where a first optical filter element is rotated by a given angle about a rotational axis orthogonal to the direction of incident light, thereby reducing multiple-reflection by being inclined relative to adjacent elements and the light-receiving section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple optical filter elements are combined to create a filter with varying transmission wavelength, then the filter can achieve wavelength separation functionality, but multiple-reflection occurs between the filter elements causing light components from other wavelength bands to be received by light-receiving elements
Solution Approach 1:
The patent applies asymmetry by tilting the first optical filter element at a specific angle (e.g., 5-15 degrees) relative to the second optical filter element. This asymmetric arrangement breaks the parallel alignment between filter elements, causing reflected light to diverge at different angles and preventing it from reaching the light-receiving section, thereby eliminating multiple-reflection interference while maintaining wavelength separation functionality
Solution Approach 2:
The patent introduces a new dimensional parameter - the tilt angle of the first optical filter element - to solve the multiple-reflection problem. By adding this angular dimension to the otherwise planar arrangement of filter elements, the reflected light is redirected into a different spatial dimension, preventing it from interfering with the intended light path to the light-receiving section
2Object-generated harmful factors
If the filter and light-receiving section are disposed with one inclined relative to the other, then multiple-reflection between them is reduced, but multiple-reflection within the filter itself still occurs
Solution Approach 1:
The patent applies asymmetry by tilting the first optical filter element at a specific angle (e.g., 5-15 degrees) relative to the second optical filter element. This asymmetric arrangement breaks the parallel alignment between filter elements, causing reflected light to diverge at different angles and preventing it from reaching the light-receiving section, thereby eliminating multiple-reflection interference while maintaining wavelength separation functionality
Solution Approach 2:
The patent introduces a new dimensional parameter - the tilt angle of the first optical filter element - to solve the multiple-reflection problem. By adding this angular dimension to the otherwise planar arrangement of filter elements, the reflected light is redirected into a different spatial dimension, preventing it from interfering with the intended light path to the light-receiving section
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 effectively minimizes the reception of light components outside the specific wavelength band by each light-receiving element, enhancing spectroscopic accuracy and measurement precision.
Implementation Method 1
a filter for spectrally dispersing target light to be measured, on a wavelength-by-wavelength (wavenumber-by-wavenumber) basis, wherein the filter has a transmission wavelength which varies depending on an incident position along a first direction
Implementation Method 2
a first optical filter element as one of the plurality of optical filter elements is rotated, by a given angle, about a rotational axis defined along a third direction orthogonal to each of the first direction and a second direction extending from the incident side toward the output side of the target light, or rotated, by a given angle, about a rotational axis defined along the first direction, and thereby disposed inclinedly with respect to a second optical filter element disposed in adjacent relation to the first optical filter element
Data Source
Figure 1A~1C
Figure 2A~2D
Figure 3A~3B
AI summary
A spectroscopic unit and spectroscopic device according to the present invention are provided with a filter that is provided with a plurality of optical filter elements disposed in order from the entrance side to the exit side of light under measurement and has different transmission wavelengths corresponding to entrance positions along a first direction. A first optical filter element from among the plurality of optical filter elements is tilted with respect to a second optical filter element disposed adjacently to the first optical filter element as a result of the first optical filter element being rotated by a prescribed angle with a third direction that is perpendicular to both the first direction and s second direction from the entrance side to the exit side as the axis of rotation thereof or being rotated by a prescribed angle with the first direction as the axis of rotation thereof.