Large-Spot Spectrometer Optics for Accurate Handheld NIR Sampling
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Solution Overview
Problem
Miniaturized spectrometers, such as handheld NIR devices, have limited optical spot sizes, leading to measurement errors and increased complexity due to the need for accessories like rotating sampling cups, which prolong measurement time.
Innovation Solution
A micro-electro-mechanical system (MEMS) based Fourier Transform infrared (FTIR) spectrometer with an optical head featuring miniaturized filament-based incandescent lamps and reflective optics, a plastic molded part with reflectors and an aperture, and a protective optical window, designed to increase the optical spot size to 3-20 mm and enhance coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturized spectrometers are used, then device size is reduced, but optical spot size is limited
Solution Approach 1:
The illumination system is divided into multiple independent LED light sources arranged in specific patterns, allowing each LED to contribute to different regions of the expanded spot size without increasing the overall device footprint
Solution Approach 2:
The patent transitions from a single-point illumination approach to a multi-dimensional illumination pattern using multiple LEDs positioned at different locations and angles, expanding the optical spot size in the sample plane without increasing device volume
2Measurement precision
If spot size is increased, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
Multiple functional elements (illumination LEDs, reflectors, aperture) are integrated into a single molded optical component, reducing the number of separate parts and assembly steps while achieving the desired large spot size illumination
Solution Approach 2:
The molded optical component serves multiple functions simultaneously: it houses the LEDs, provides reflective surfaces, defines the aperture, and structures the illumination geometry, eliminating the need for separate components for each function
3Measurement precision
If accessories like rotating sampling cups are added, then spatial averaging is achieved, but measurement time increases
Solution Approach 1:
The illumination geometry is pre-configured to cover the entire sample area of interest before measurement begins, eliminating the need for mechanical scanning or rotation during the measurement process
Solution Approach 2:
The patent replaces mechanical scanning systems (rotating cups, moving stages) with a static multi-LED illumination system that achieves spatial averaging through optical design rather than mechanical motion
4Power
If aperture is optimized, then coupling efficiency is maximized, but unwanted light is not filtered
Solution Approach 1:
The aperture is positioned and sized to selectively accept light from specific regions and angles where useful scattered light is concentrated, while blocking other directions where unwanted reflections occur
Solution Approach 2:
The aperture acts as an intermediary element between the sample and detector, filtering the light based on its spatial and angular characteristics to separate useful scattered light from harmful reflections
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 provides a larger spot size and improved measurement accuracy by maximizing usable light coupling while minimizing unwanted reflections and scattering, reducing alignment errors, and maintaining spectral resolution.
Implementation Method 1
miniaturized filament-based incandescent lamps
Implementation Method 2
reflective optics (e.g., reflectors) surrounding the lamps
Implementation Method 3
an aperture configured to pass scattered light from the sample into the spectrometer, while also limiting the unwanted coupled rays into the spectrometer to maximize the coupling efficiency
Implementation Method 4
Diffuse reflectance spectroscopy may be utilized to study the molecular structure of a given material based on its spectral response
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
Portable optical device (100) providing a large spot size spectrometer. The optical device includes an optical head (102), an optical window (106), and a spectrometer (104). The optical head (102) includes a plastic moulded part (105) having an aperture (115) and a plurality of reflectors (112) around the aperture (115) formed therein. Each reflector (130) may include a respective lamp (110) assembled therein. The optical window (106) is configured to receive a sample (108), to pass input light (128) from the lamps (130) to the sample (108) and to pass scattered light from the sample (108) towards the aperture (115). The aperture (115) is configured to filter a first portion of scattered light containing unusable sample information and to pass a second portion of the scattered light to the spectrometer (104).