Systems and methods for miniature spatial heterodyne spectrometry
Systems and methods for miniature spatial heterodyne spectrometer (SHS) systems are described. Methods for optimizing the miniature SHS systems can reduce the sizes and format while achieving high sensitivity and detection quality. The miniature SHS systems can be deployed for handheld use in real-world or remote activities outside of research or diagnostic facilities.
1 . A device for performing spectroscopy, comprising:
a spatial heterodyne spectrometer (SHS) core comprising a beam-splitter, a first grating, and a second grating; wherein the beam-splitter, the first grating, and the second grating form a 90° angle with the beam-splitter at the vertex of the angle; and wherein the beam-splitter is configured to split the incoming light to the first grating and the second grating;
fore-optics aligned with the SHS core and configured to direct incoming light into the SHS core, wherein the fore-optics comprises a light collection lens and a collimating lens, wherein the light collection lens produces a minimum root mean square spot size at a field stop plane, and wherein an aperture stop is controlled at a position before the first power element in the fore-optics;
aft-optics aligned with the SHS core, such that light exiting the SHS core passes into the aft optics; and
a detector to image a fringe pattern generated by the SHS core.
2 . The device for performing spectroscopy of claim 1 , wherein the SHS core further comprises a first field widening prism and a second field widening prism, wherein the first field widening prism is located between the beam splitter and the first grating and the second field widening prism is located between the beam splitter and the second grating.
3 . The device for performing spectroscopy of claim 2 , wherein the first and second field widening prisms possess an angle for field widening based on a desired heterodyne wavelength, index of refraction of a construction material, and frequency of the first and second gratings.
4 . The device for performing spectroscopy of claim 2 , wherein: the first and second grating and the first and second field widening prisms are tilted to a position where a heterodyne wavelength gut ray angle of incidence from the first field widening prism and the first grating and a heterodyne wavelength gut ray angle of incidence from the second field widening prism and the second grating are zero at the detector.
5 . The device for performing spectroscopy of claim 2 , wherein the first field widened prism forms a first angle α with an edge of the beam-splitter and an edge of the first field widened prism proximal to the beam-splitter; wherein the second field widened prism forms a second angle α with an edge of the beam-splitter and an edge of the second field widened prism proximal to the beam-splitter, and wherein the first angle α and the second angle α are configured such that the fringe localization pattern is located at the detector.
6 . The device for performing spectroscopy of claim 2 , wherein the first grating is tilted to form a first angle β between the first grating and a path of light directed toward the first grating; wherein the second grating is tilted to form a second angle β between the second grating and a path of light directed toward the second grating; and wherein the first angle β and the second angle β are configured such that the fringe localization pattern is located at the detector.
7 . The device for performing spectroscopy of claim 1 , further comprising a filter located prior to the fore-optics such that incoming light passes through the filter into the fore-optics, wherein the filter is selected from a long pass filter, a short pass filter, and a band pass filter.
8 . The device for performing spectroscopy of claim 1 , wherein the fore-optics, the beam-splitter, and the first grating form an afocal system, wherein an exit pupil of the afocal system is located at the first grating and the detector is positioned so that the image at the exit pupil of the afocal system is re-imaged on to the detector.
9 . The device for performing spectroscopy of claim 1 , wherein:
the collimating lens is at least two lenses;
the light collection lens is an asphere lens; or
the collimating lens is at least two lenses and the light collection lens is an asphere lens.
10 . The device for performing spectroscopy of claim 1 , wherein the fore-optics comprises a light collection lens and a collimating lens wherein the collimating lens forms an optimized collimated beam at the grating.
11 . The device for performing spectroscopy of claim 1 , wherein the aft-optics, the beam-splitter, and the second grating form a double-gauss re-imager.
12 . The device for performing spectroscopy of claim 1 , wherein each optical component in the aft-optics has a diameter sufficient to allow a full field of view to pass through the aft-optics un-vignetted.
13 . The device for performing spectroscopy of claim 1 , further comprising a frame and barrel assembly housing the detector, the SHS core, the fore optics, and the aft optics;
optionally, wherein the frame and barrel assembly is 3D printed.
14 . The device for performing spectroscopy of claim 1 , wherein:
the SHS core, the fore optics, and the aft optics have a combined mass of less than 1000 grams;
the SHS core, the fore optics, the aft optics, and the detector have combined dimensions of less than or equal to 15 cm×15 cm×15 cm; or
the SHS core, the fore optics, and the aft optics have a combined mass of less than 1000 grams and the SHS core, the fore optics, the aft optics, and the detector have combined dimensions of less than or equal to 15 cm×15 cm×15 cm.
15 . The device for performing spectroscopy of claim 1 , wherein the device for performing spectroscopy has a mass of less than 2000 grams.
16 . The device for performing spectroscopy of claim 1 , wherein all optical components are constructed of the same material.
17 . The device for performing spectroscopy of claim 16 , wherein all optical components are constructed of fused silica, quartz, fused quartz, borosilicate glass, aluminosilicate glass, sapphire, calcium fluoride, alkali-aluminosilicate glass, or a glass ceramic.
18 . A method of using a spectroscopy device, comprising:
obtaining a light from a sample into a spectroscopy device, wherein the spectroscopy device comprises:
a spatial heterodyne spectrometer (SHS) core comprising a beam-splitter, a first grating, and a second grating; wherein the beam-splitter, the first grating, and the second grating form a 90° angle with the beam-splitter at the vertex of the angle; and wherein the beam-splitter is configured to split the incoming light to the first grating and the second grating;
fore-optics aligned with the SHS core and configured to direct incoming light into the SHS core, wherein the fore-optics comprises a light collection lens and a collimating lens, wherein the light collection lens produces a minimum root mean square spot size at a field stop plane;
aft-optics aligned with the SHS core, such that light exiting the SHS core passes into the aft optics; and
a detector to image a fringe pattern generated by the SHS core;
wherein an aperture stop is controlled at a position before the first power element in the fore-optics
wherein the light passes through the fore-optics into the SHS core to image a fringe pattern on the detector; and
analyzing the fringe pattern to identify a component within the sample.
19 . The method of claim 18 , wherein the sample is selected from one or more of a biological sample, an agricultural sample, an environmental sample, and a pharmaceutical sample; and wherein the light from the sample is selected from emission, reflection, absorption, fluorescence, and Rahman.
20 . A method for making a spectroscopy device, comprising:
identifying an angle α for a field widening prism based on a desired heterodyne wavelength, index of refraction of a construction material, and frequency of a grating;
optimizing fore-optics as an afocal system, wherein the afocal system comprises a light collection lens, a collimating lens, a beam splitter, a first field widening prism, and a first grating and produces a minimum root mean square spot size at a field stop plane, and wherein an aperture stop is controlled at a position before the first power element;
optimizing aft optics as a re-imaging system, wherein the re-imaging system comprises at least one lens, the beam splitter, a second field widening prism, and a second grating; and
optimizing a detector position, such that an image at a pupil of the fore-optics is re-imaged on the detector.
21 . The method of claim 20 , further comprising locating a filter located forward of the fore optics, such that incoming light passes through the filter then into the fore optics; and
wherein optimizing the fore optics comprises:
locating an aperture stop between the filter and the fore optics;
locating an exit pupil of the fore optics to be located at the grating;
optimizing the light collection lens to produce a minimum root mean square spot size at a field stop plane; and
optimizing the collimating lens to form an optimized collimated beam at the first grating.
22 . The method of claim 20 , wherein optimizing the aft optics comprises:
optimizing generalized distortion to zero; and
minimizing a spot size at the detector.