Common Path Spectrometer Spatial Split Dichroic Assembly
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Solution Overview
Problem
Conventional hyperspectral dispersive spectrometers face challenges in manufacturing due to the need for large focal plane arrays and are prone to distortion and calibration issues, especially with multiple optical paths, which are expensive and difficult to maintain.
Innovation Solution
A dual order, common path spectrometer with a spatial split dichroic assembly that separates light into multiple bands by wavelength and a dispersive element for spectral dispersion, focusing the light onto a detector array, allowing for precise co-registration and reduced manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single optical path with a single focal plane array is used, then precise co-registration between colors is achieved, but the FPA must be very large in one dimension making manufacturing difficult
Solution Approach 1:
The spectrum is segmented into multiple orders using a diffraction grating, with each order detected by a separate region of the FPA. This divides the spectral sampling task across multiple smaller segments rather than requiring one large continuous spectral field, making the FPA more manufacturable while maintaining precise co-registration within each order.
Solution Approach 2:
The patent utilizes the spatial dimension of the FPA to detect multiple spectral orders simultaneously. By arranging detector elements to receive light at different angles corresponding to different diffraction orders, the system packs more spectral information into the same physical detector area, reducing the overall FPA size requirements.
2Area of stationary object
If multiple optical paths with multiple FPAs are used, then the spectral field is accommodated, but co-registration is difficult to achieve and maintain due to thermal expansion and vibration
Solution Approach 1:
Multiple spectral orders that would traditionally require separate optical paths and FPAs are merged into a single optical path. The diffraction grating directs different orders to different regions of one FPA, combining what would have been multiple independent detection systems into one unified instrument, thereby eliminating co-registration issues between separate paths.
Solution Approach 2:
A single FPA performs multiple functions by detecting multiple diffraction orders simultaneously. Each region of the FPA is configured to receive a specific spectral order, making the single detector array universally capable of sampling the entire spectrum across multiple orders without requiring separate specialized detectors for each order.
3Device complexity
If dual band detector arrays are used, then different wavelengths are detected at a single pixel, but the detectors are difficult and expensive to manufacture with poor signal to noise characteristics
Solution Approach 1:
The detector array is segmented into multiple regions, with each region dedicated to detecting a specific diffraction order. This spatial segmentation replaces the need for complex dual-band detector structures, using standard detector technology arranged to receive light at different angles, thereby simplifying manufacturing while maintaining the ability to detect multiple wavelength bands.
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 enables precise co-registration of spectral channels, reduces manufacturing costs, and maintains alignment despite thermal and vibrational effects, providing efficient spectral sampling and improved signal-to-noise characteristics.
Implementation Method 1
a spatial split dichroic assembly that performs spatial separation of received light into at least two bands according to wavelength. The spatially separated and spectrally dispersed light is passed through a focusing assembly and is focused onto a detector array.
Implementation Method 2
The spatial split dichroic assembly reflects light in at least a first band of wavelengths from a first surface, and reflects light in at least a second band of wavelengths from a second surface.
Implementation Method 3
The dispersive element can therefore comprise a diffractive element, such as a grating or a group of slits.
Implementation Method 4
a dispersive element that performs spectral dispersion of received light
Implementation Method 5
The spatially separated and spectrally dispersed light is passed through a focusing assembly and is focused onto a detector array.
Data Source
AI summary
The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.