Prism-Grating Imaging Spectrometer for Over-Octave Spectral Separation
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Solution Overview
Problem
Conventional imaging spectrometers for medical scopes are limited to a single octave of spectral range, leading to gaps in the acquired spectrum due to the use of spectral filters or expensive color filter arrays, and are not suitable for compact medical scope applications.
Innovation Solution
An imaging spectrometer design using a prism and blazed diffraction grating that refracts and diffracts incident light to span a spectral range greater than an octave, with the second diffracted order of λS not overlapping with the first diffracted order of any wavelengths shorter than λL, allowing simultaneous detection of diffraction orders across the desired spectral range using a single focal plane array sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectral filter is placed near the image plane to filter second order diffraction, then spatial overlap is prevented, but a gap appears in the acquired spectrum due to the physical dimensions of the filter
Solution Approach 1:
The patent introduces a scanning dimension (temporal dimension) to resolve the spatial conflict. By sequentially scanning different spectral regions and combining them over time, the system achieves complete spectral coverage without spatial gaps, transforming a spatial problem into a temporal solution
Solution Approach 2:
The spectral range is divided into multiple segments (first order and second order diffraction regions) that are detected separately and then combined. The scanning system acquires different spectral segments at different times, allowing complete spectral reconstruction without overlap or gaps
2Measurement precision
If a color filter array is used to distinguish between second diffracted order and first diffracted order, then spectral overlap is resolved, but the filter construction becomes expensive and is not generally available as production components
Solution Approach 1:
The patent replaces the complex color filter array system with a simpler scanning mechanism. Instead of using expensive optical filters to distinguish spectral orders, the system uses temporal scanning to separate and identify different diffraction orders, significantly reducing manufacturing complexity and cost
Solution Approach 2:
The patent uses standard, readily available components (diffraction grating, simple sensors, scanning mechanism) rather than expensive specialized color filter arrays. The system achieves its function using inexpensive, production-ready components that are widely available
3Device complexity
If a simple diffraction grating spectrometer is constructed, then the device is small and inexpensive, but it is limited to a single octave of spectral range
Solution Approach 1:
The patent introduces dynamic scanning capability to the simple diffraction grating system. By making the system dynamic (scanning through different angular positions), the limited static spectral range of a simple grating is extended to cover more than one octave, maintaining simplicity while adding versatility
Solution Approach 2:
The patent makes the simple diffraction grating system multi-functional by enabling it to detect multiple diffraction orders (first and second order) through scanning. This allows a single, simple component to perform the work of what would traditionally require multiple specialized components for different spectral ranges
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 achieves efficient spectral analysis across a wide range without spatial overlap, reducing the need for additional filters and minimizing the size of the spectrometer, thus making it suitable for medical scopes while maintaining high detection efficiency.
Implementation Method 1
a prism that refracts incident light in at least a spectral range for spectrographic analysis
Implementation Method 2
A blazed diffraction grating is positioned in optical alignment with the prism and diffracts the incident light
Data Source
AI summary
An imaging spectrometer and camera are disclosed including a prism that refracts incident light a spectral range for spectrographic analysis with a shortest wavelength (λS) and a longest wavelength (λL). A diffraction grating is aligned with the prism and diffracts the incident light. The refraction and diffraction for a set of diffraction orders used for the spectrographic analysis both increase a deflection angle of the incident light from an original optical axis. The spectral range spans greater than an octave such that λL>2λS. The refraction and diffraction are such that a second diffracted order of λS does not overlap with a first diffracted order of wavelengths shorter than λL. The second order diffraction for wavelengths between λS and λC, and the first order diffraction for wavelengths between λC and λL, are detected in different spatial regions to perform the spectrographic analysis from λS to λL.