WO2021196622A1 - Spectromètre à transformée de fourier statique compact à haut débit - Google Patents

Spectromètre à transformée de fourier statique compact à haut débit Download PDF

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Publication number
WO2021196622A1
WO2021196622A1 PCT/CN2020/127732 CN2020127732W WO2021196622A1 WO 2021196622 A1 WO2021196622 A1 WO 2021196622A1 CN 2020127732 W CN2020127732 W CN 2020127732W WO 2021196622 A1 WO2021196622 A1 WO 2021196622A1
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Prior art keywords
condenser
coupling structure
camera lens
birefringent plate
light
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PCT/CN2020/127732
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English (en)
Inventor
Jiangquan MAI
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Hong Kong Applied Science and Technology Research Institute Company Limited
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Priority claimed from US17/089,518 external-priority patent/US11215504B2/en
Application filed by Hong Kong Applied Science and Technology Research Institute Company Limited filed Critical Hong Kong Applied Science and Technology Research Institute Company Limited
Priority to CN202080003190.6A priority Critical patent/CN112752958B/zh
Publication of WO2021196622A1 publication Critical patent/WO2021196622A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0208—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0216—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using light concentrators or collectors or condensers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0218—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G01J3/0224—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using polarising or depolarising elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0256—Compact construction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry
    • G01J3/453—Interferometric spectrometry by correlation of the amplitudes
    • G01J3/4531—Devices without moving parts
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0009—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only
    • G02B19/0014—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only at least one surface having optical power
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0085—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with both a detector and a source
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry
    • G01J3/453—Interferometric spectrometry by correlation of the amplitudes
    • G01J2003/4538—Special processing

Definitions

  • the invention relates generally to optical spectrometers and, more particularly, to high-throughput compact static-Fourier-transform spectrometer configurations, such as may be suitable for use with respect to mobile and portable electronic devices.
  • a spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum.
  • a spectrometer can separate white light and measure individual narrow bands of color (i.e., spectrum) .
  • the variables measured by a spectrometer may, for example, comprise spectral intensity and/or irradiance of the light. Such light measurements made by a spectrometer are typically used to identify materials.
  • Spectrometers have traditionally been difficult to use with field work outside of a lab due to their bulky size and high cost. As such, although spectrometers are highly useful analytical instruments, they have seen limited adoption by the general public and are commonly restricted to use with respect to lab work.
  • Spectrometers have evolved from large benchtop devices (e.g., a unit size of 550mm x 420mm x 270mm having an operational wavelength range of 325-1000nm, and providing a resolution of 4nm) available in 2010, to relatively large, self-contained devices (e.g., a unit size of 175mm x 110mm x 44mm, having an operational wavelength range of 200-1100nm, and providing resolution of 0.05-20nm) and compact self-contained devices (e.g., a unit size of 40mm x 42mm x 24mm, having an operational wavelength range of 350-800nm, and providing resolution of 1-10nm) available in 2012, to more compact, mini-spectrometer configurations (e.g., a unit size of 12mm x 20mm x 10mm, having an operational wavelength range of 340-780nm, and providing resolution of 15nm) available in2013.
  • large benchtop devices e.g., a unit size of 550mm x 420mm
  • spectrometers have been implemented as smartphone external accessories (e.g., an attachable accessory size of 55mm x 20mm x 20mm, having an operational wavelength range of 380-750nm, and providing resolution of 10nm) available in 2016.
  • the spectrometers of all such form factors have generally suffered from one or more disadvantages, such as relatively large dimensions, low stability, low resolution, narrow or limited spectral range, low throughput and sensitivity, etc.
  • Configurations used in implementing smartphone spectrometer external accessories have generally been very large when compared to the size of the host smartphone and have required delicate and complicated collimators, grating, and/or filter apparatuses.
  • Existing smartphone-based spectrometers in addition to being bulky in dimension, generally provide low resolution and narrow measurement wavelength range.
  • the smartphone-based spectrometers of U.S. patent numbers 7,420,663, 8,861,086, and 9,185,200 and the smartphone-based spectrometer described in PLOS One Journal e17150, March 2, 2011 all implement complicated grating structures.
  • a configuration based on conventional Michelson interferometer in the smartphone-based spectrometer of U.S. patent number 8,086,266 comprises moving and separated mechanical parts and complicated microelectromechanical systems which requires extra power supplied from the smartphone. Configurations requiring moving and/or separated mechanical parts in their designs can greatly affect the accuracy of spectrum measurement (e.g., during operation, external vibrations influence the steadiness of the reflectors movement that limits ability of using those spectrometers under conditions of strong vibrations) . Such spectrometer configurations suffer from low vibration stability and large size.
  • the spectrometer configurations of U.S. patent publication number 20170131146, U.S. patent numbers 6,222,627 and 9,316,539, and Chinese patent number 102297722 use birefringent crystal configurations that are not well suited for use with the large field of view (e.g., 60° to 120°) of many current smartphones and/or are provide distorted/non-symmetric interference patterns which are incompatible with the use of Fourier transform processing to obtain the spectrum.
  • patent publication number 20170131146 uses a Savart plate interferometer implementation (i.e., two birefringent plates, each having optical axis at 45° to the respective plate) in providing collimated light to a micro-lens array, resulting in a relatively large and complicated collimator implementation that requires a small angle incidence and provides a small field of view (e.g., 5°) .
  • patent number 6,222,627 uses a Wollaston prism interferometer implementation (i.e., two right triangle birefringent prisms with perpendicular optic axes) in providing collimated light to an imaging lens and detector, resulting in a relatively large collimator implementation that requires normal incidence light source and provides a small field of view (e.g., 1° to 3°) .
  • the birefringent crystal configuration of Chinese patent number 102297722 uses a combination of a Wollaston prism and Savart plate interferometer implementation and suffers from disadvantages of both.
  • patent number 9,316,539 uses a birefringent plate implementation in which a focusing lens provides frontend optics relying upon a diffused light source for optimal operation and providing either a relatively small field of view or a larger field of view with very low sensitivity (e.g., most of the light is diffused/scattered and unable to be collected by the small-aperture camera.
  • U.S. patent publication number 20200025611 provides a beam-splitter cube spectrometer configuration.
  • the beam-splitter interferometer implementation of U.S. patent publication number 20200025611 facilitates relatively simple data analysis processing by a host smartphone using generally low cost materials, although potentially experiencing somewhat low throughput.
  • the present invention is directed to systems and methods which provide a high-throughput point source light coupling structure implementing a condenser configured according to one or more condenser configuration rules, such as for mobile device based spectrometer configurations.
  • Embodiments of a high-throughput point source light coupling structure utilize a birefringent plate configuration in combination with a condenser and point source to provide a light coupler structure for a birefringent-static-Fourier transform interferometer implementation, such as to provide high light collection efficiency, wide incidence angle, broad spectral range, etc. with respect to a relatively small sized, high resolution spectrometer.
  • a birefringent plate configuration of a high-throughput point source light coupling structure of embodiments may comprise one or more birefringent plates formed from birefringent material.
  • Embodiments of the invention may utilized a birefringent plate configuration including at least two birefringent plates.
  • the principal section of a first birefringent plate is perpendicular to the principal section of a second birefringent plate of a birefringent plate configuration.
  • the optical axis of the second birefringent plate of a birefringent plate configuration is parallel or vertical to the plane of the second birefringent plate.
  • the optical axis of the first birefringent plate of a birefringent plate configuration may, for example, be in the range of -90° to +90° with respect to the plane of the first birefringent plate according to some embodiments.
  • the optical axis of the first birefringent plate of a birefringent plate configuration of some examples may be rotated -45° or +45° to the plane of the first birefringent plate.
  • the optical axis of the first birefringent plate of a birefringent plate configuration of some examples may be parallel or vertical to the plane of the first birefringent plate, while being perpendicular to the optical axis of the second birefringent plate.
  • a condenser of a high-throughput point source light coupling structure of embodiments is provided in a defined (e.g., spaced, relational, etc. ) relationship with respect to the point source and a camera lens used in capturing an interference pattern generated by the light coupling structure.
  • one or more condenser configuration rules may be implemented with respect to the condenser configuration of a high-throughput point source light coupling structure implementation.
  • Condenser configuration rules defining a condenser configuration of a high-throughput point source light coupling structure of embodiments may, for example, provide defined relationships with respect to focal lengths of the condenser and the camera lens, numerical aperture of the condenser and the camera lens, distance between the condenser and the camera lens, distance between the condenser and point source, etc.
  • Light coupling structures utilizing a birefringent plate configuration in combination with a condenser and point source provides high light collection efficiency for high throughput, facilitating enhanced sensitivity of a spectrometer implementation and broad spectral range.
  • a birefringent plate configuration of a high-throughput point source light coupling structure of embodiments generates wide incident angle for the birefringent interferometer facilitating improved resolution.
  • High-throughput point source light coupling structures of embodiments are compatible to point source input and small aperture imaging systems.
  • high-throughput point source light coupling structures of embodiments are well suited for use with respect to wide field of view (FOV) and small aperture cameras, such as those of mobile device camera configurations.
  • FOV wide field of view
  • the short focal length of a mobile device camera lens and a condenser of embodiments of a high-throughput point source light coupling structure facilitates compact size spectrometer implementation.
  • high-throughput point source light coupling structures may be provided which are small enough to be used with existing imaging devices (e.g., digital cameras) , such as those incorporated into portable equipment, and which is lightweight and convenient enough for a user to carry.
  • imaging devices e.g., digital cameras
  • portable spectrometer implementations may facilitate broadened application and markets for spectroscopy from industries and labs to ordinary consumers, facilitating use in food safety, jewelry inspection, scientific research, medicine, healthcare, art and design, etc.
  • High-throughput point source light coupling structures implemented according to concepts of the present invention may be provided as external accessories for processor-based mobile devices (e.g., smartphones, tablets, personal digital assistants (PDAs) , notebook computers, etc. ) having image capturing capabilities.
  • processor-based mobile devices e.g., smartphones, tablets, personal digital assistants (PDAs) , notebook computers, etc.
  • an external spectrometer accessory comprising embodiments of a high-throughput point source light coupling structure may be used to provide a birefringent-static-Fourier transform interferometer based spectrometer, when combined with the imaging system of a host mobile device and interferogram transform processing logic executed by a processor of the mobile device.
  • Such birefringent-static-Fourier transform interferometer based spectrometers realize high throughput/sensitivity (e.g., sensitivity to weak incident light improved by 20 times as compared to prior smartphone based solutions) , high resolution (e.g., improved by 5-10 times as compared to prior smartphone based solutions) , wide spectral range (e.g., broadened from 380nm-750nm to 400nm-1100nm range as compared to prior smartphone based solutions) , and ultra-compact (e.g., size reduced to 1/5 as compared to prior smartphone based solutions) .
  • high throughput/sensitivity e.g., sensitivity to weak incident light improved by 20 times as compared to prior smartphone based solutions
  • high resolution e.g., improved by 5-10 times as compared to prior smartphone based solutions
  • wide spectral range e.g., broadened from 380nm-750nm to 400nm-1100nm range as compared to prior smartphone based solutions
  • FIGURE 1 shows a functional block diagram of a spectrometer implementing a high-throughput point source light coupling structure according to embodiments of the present invention
  • FIGURE 2 shows detail with respect to a condenser configuration of a high-throughput point source light coupling structure of embodiments of the present invention
  • FIGURE 3 shows detail with respect to a birefringent module configuration of a high-throughput point source light coupling structure of embodiments of the present invention
  • FIGURES 4A-4C shows birefringent plate configurations of a birefringent module according to embodiments of the present invention
  • FIGURES 5A and 5B illustrate interference patterns as may result from various birefringent plat configurations.
  • FIGURES 6A and 6B show experimental results for various light coupling structure implementations.
  • FIGURE 1 shows a functional block diagram of a spectrometer implemented using an embodiment of a high-throughput point source light coupling structure according to concepts of the present invention.
  • Spectrometer 100 is shown as including high-throughput point source light coupling structure 120 and mobile device 130 configured to operate in cooperation to measure properties of light (e.g., provided as incident light 111) over a portion of the electromagnetic spectrum.
  • High-throughput point source light coupling structure 120 may, for example, comprise a removable unit configured to attach (e.g., using one or more clips, adhesive, an over-case for the mobile device, one or more fasteners, etc. ) to the mobile device in juxtaposition with a lens of an image capturing system of the mobile device.
  • embodiments of high-throughput point source light coupling structure 120 and mobile device 130 may provide a very compact spectrometer configuration having a wide spectral range, high resolution, high throughput, and relatively low cost.
  • Mobile device 130 may, for example, comprise a smartphone (e.g., Apple IPHONE, Samsung GALAXY, Huawei P SMART, etc. ) , tablets (e.g., Apple IPAD, Samsung GALAXY TAB, Microsoft SURFACE, etc. ) , personal digital assistants (PDAs) (e.g., Hewlett-Packard IPAQ, Palm TUNGSTEN, etc. ) , notebook computers (e.g., portable personal computers based upon the Intel CORE, Advanced Micro Devices RYZEN, etc. families of processors) , etc. having image capturing capabilities.
  • smartphones e.g., Apple IPHONE, Samsung GALAXY, Huawei P SMART, etc.
  • tablets e.g., Apple IPAD, Samsung GALAXY TAB, Microsoft SURFACE, etc.
  • PDAs personal digital assistants
  • notebook computers e.g., portable personal computers based upon the Intel CORE, Advanced Micro Devices RYZEN, etc. families of
  • Light coupling structure of high-throughput point source light coupling structure 120 incorporating a condenser may be configured to be compatible to point source input and the small aperture imaging systems of many mobile devices (e.g., smartphone and tablet camera configurations) .
  • a short focal length e.g., a focal length in the range of 2mm-6mm
  • a short focal length camera lens e.g., the camera lens of many smartphone and tablet camera configurations
  • high-throughput point source light coupling structure 120 converts and directs incident light 111 to image capturing apparatus of mobile device 130.
  • incident light 111 passing through point source 121 may be manipulated by condenser 122, polarizer 123, optical member 124, and polarizer 125 to form an interference pattern for spectral processing by mobile device 130.
  • Mobile device 130 of embodiments may comprise various forms of processor-based systems having image capturing capabilities. The image capturing capabilities may, for example, be provided by one or more image capturing apparatuses, such as a digital camera system integrated therein or coupled thereto.
  • an image capturing apparatus of mobile device 130 may include camera lens 131 and camera sensor used to capture an interference pattern (e.g., interference pattern 141) as provided by the light output from high-throughput point source light coupling structure 120.
  • Mobile device 130 may utilize interferogram transform processing logic 133 to transform an interference pattern provided by high-throughput point source light coupling structure 120 into corresponding spectrum data (e.g., spectrum data 143) .
  • spectrometer 100 may be utilized to generate data representative of the spectrum of observed incident light emitted by and/or reflected from a sample (not shown) for which spectroscopy is to be performed, such as for analyzing light containing features of absorption or emission associated with a sample material, substance, mixture, etc.
  • incident light 111 may comprise light incident on high-throughput point source light coupling structure 120 that is emitted by and/or reflected from such a sample.
  • a light gateway is provided to introduce at least a portion of incident light 111 into high-throughput point source light coupling structure 120.
  • Point source 121 may, for example, comprise a pinhole, slit, an optical fiber connector, and/or other pinpoint light gateway structure configured for passing a portion of incident light 111 into high-throughput point source light coupling structure 120 as a point source of light.
  • Point source 121 converts incident light 111 to a point source of light according to embodiments of the invention.
  • Condenser 122 of embodiments provides an optical element (e.g., a lens, a lens group, a prism, a concave mirror, etc. comprised of optical glass, optical plastic, crystal, etc. ) configured to render a divergent beam from a point source into a converging beam.
  • high-throughput point source light coupling structure 120 is configured so that condenser 122 focuses and images point source 121 on camera lens 131.
  • high-throughput point source light coupling structure 120 utilizes a configuration of condenser 122 for facilitating efficient throughput.
  • NA numerical aperture
  • condenser 122 may be provided in a defined relationship with respect to point source 121 and/or camera lens 131.
  • a spaced, relational, etc. relationship may be defined as between condenser 122 and point source 121 and/or as between condenser 122 and camera lens 131.
  • Condenser configuration rules defining a configuration of condenser 122 may provide defined relationships with respect to focal lengths, numerical aperture, distance, etc.
  • condenser configuration rules defining a configuration of condenser 122 provide defined relationships with respect to distance between the condenser and the camera lens and distance between the condenser and the point source, defined relationships with respect to the numerical aperture of the condenser and the camera lens, and defined relationships with respect to the focal lengths of the condenser and the camera lens.
  • FIGURE 2 illustrates implementation of a configuration of condenser 122 according to condenser configuration rules of embodiments of the invention.
  • the configuration of condenser 122 of high-throughput point source light coupling structure 120 shown in FIGURE 2 may, for example, be subject to one or more defined relationship condenser configuration rules, such as may include defined numerical aperture relationship condenser configuration rules, defined focal length relationship condenser configuration rules, defined distance relationship condenser configuration rules, etc.
  • a defined numerical aperture relationship condenser configuration rule may establish a relationship between the numerical aperture of condenser 122 and the numerical aperture of camera lens 131.
  • a defined numerical aperture relationship condenser configuration rule may establish that a numerical aperture (NA 2 ) of condenser 122 is greater than a numerical aperture diameter (NA 1 ) of camera lens 131 (e.g., NA 2 >NA 1 ) , such as to provide a light coupling structure well suited for point source input and small aperture imaging apparatus (e.g., imaging apparatus of a smartphone camera) and/or to generate wide incident angle for improved resolution of the spectrometer.
  • NA 2 numerical aperture
  • NA 1 numerical aperture diameter
  • a defined focal length relationship condenser configuration rule may establish a relationship between the focal length of condenser 122 and the focal length of camera lens 131.
  • a defined focal length relationship condenser configuration rule may establish that a focal length (f 2 ) of condenser 122 is less than a focal length (f 1 ) of camera lens 131 (e.g., f 2 ⁇ f 1 ) , such as to facilitate compact size embodiments of high-throughput point source light coupling structure 120.
  • the short focal length of condenser 122 established by the condenser configuration cooperates with a short focal length implementation of camera lens 131 to facilitate a compact size of high-throughput point source light coupling structure 120.
  • high-throughput point source light coupling structure 120 operates in cooperation with an image capture apparatus of mobile device 130 to provide an interferometer implementation for measuring properties of incident light 111.
  • camera lens 131 of mobile device 130 provides an image plane of the light source (shown as image plane 231)
  • the sensor plane of camera sensor 132 provides an image plane of the interference pattern (shown as image plane 232) .
  • the distance from the center of camera lens 131 to sensor plane of camera sensor 132 is d 1
  • the distance from the center of condenser 122 to the center of camera lens 131 is d 2
  • the distance from point source 121 to the center of condenser 122 is d 3 .
  • One or more defined distance relationship condenser configuration rules may be used to establish some or all of the foregoing distances according to embodiments of the invention.
  • the focal length f 1 and/or distance d 1 may be known from a fixed or otherwise established value provided by a manufacturer or user of the image capturing apparatus.
  • a first defined distance relationship condenser configuration rule may establish a distance relationship between condenser 122 and camera lens 131.
  • distance (d 2 ) from the center of condenser 122 to the center of camera lens 131 may be selected at least in part to accommodate the thickness of the components of the interferometer (e.g., camera lens, window glass, polarizers, optical members, and/or condenser) and the gaps between those components (e.g., the distance d 2 may be selected so as to be larger than the stacked thickness of the foregoing components) .
  • a defined focal length relationship condenser configuration rule establishes a relationship between the focal length of condenser 122 and the focal length of camera lens 131
  • the distance (d 2 ) from the center of condenser 122 to the center of camera lens 131 established by a first defined distance relationship condenser configuration rule is derived or based at least in part on the focal length (f 1 ) of camera lens 131 (e.g., d 2 ⁇ f 1 ) .
  • a first defined distance relationship condenser configuration rule of embodiments of the invention may establish that the distance d 2 is to be larger than the focal length (f 2 ) of condenser 122 (e.g., d 2 >f 2 , such as (1.5*f 2 ) ⁇ d 2 ⁇ (3.0*f 2 ) , wherein f 2 ⁇ f 1 ) .
  • a first defined distance relationship condenser configuration rule may, for example, provide that the distance d 2 is ⁇ (2.0*f 2 ) .
  • a second defined distance relationship condenser configuration rule may establish a distance relationship between condenser 122 and point source 121.
  • a second defined distance relationship condenser configuration rule may establish that the distance (d 3 ) from the center of condenser 122 to point source 121 follows the condition below:
  • a 1 is the aperture diameter of point source 121 and a 2 is the aperture diameter of camera lens 131.
  • distance d 3 follows the condition of equation (1) above, the distance (d 3 ) from the center of condenser 122 to point source 121 is based on the distance (d 2 ) between condenser 122 and the center of camera lens 131 (e.g., the image plane of point source 121) , the focal length (f 2 ) of condenser 122, the aperture diameter (a 1 ) of point source 121, and the aperture diameter (a 2 ) of camera lens 131.
  • the relationship set forth in equation (1) may be utilized according to embodiments of the invention to tune the distances d 2 and d 3 to obtain the most compact size and/or highest throughput configuration for high-throughput point source light coupling structure 120.
  • High-throughput point source light coupling structure 120 implementing condenser 122 according to condenser configuration rules of embodiments of the invention provides a light coupling structure providing high light collection efficiency for enhanced sensitivity and improved resolution. Moreover, configurations of condenser 122 disposed within high-throughput point source light coupling structure 120 according to defined distance relationship condenser configuration rules of embodiments facilitates compact size spectrometer implementation.
  • Embodiments of a high-throughput point source light coupling structure utilize an optical member configuration in combination with point source 121 and condenser 122 to provide optical path differences with respect to light passed by the light coupler structure for facilitating a static-Fourier transform interferometer implementation.
  • high-throughput point source light coupling structure 120 is shown as including polarizer 123, optical member 124, and polarizer 125 of a static-Fourier transform interferometer implementation according to some embodiments of the invention.
  • an optical member comprising one or more birefringent plates may be used in combination with point source 121 and condenser 122 to provide a light coupler structure for a birefringent-static-Fourier transform interferometer implementation.
  • a birefringent plate configuration as may be utilized in a birefringent interferometer implementation of some embodiments is shown in FIGURE 3.
  • a birefringent interferometer implemented using a birefringent plate configuration of high-throughput point source light coupling structure 120 of embodiments of the invention is configured to allow large incidence angles to facilitate a high resolution spectrometer implementation.
  • birefringent plate configurations according to concepts of the invention allowing large incidence angles facilitate large optical path difference variation for providing high resolution spectroscopy.
  • birefringent plate configurations of some embodiments are designed to obtain large optical path differences within a short distance (e.g., within a distance corresponding to a short focal length of condenser 122) facilitating high resolution in a compact sized implementation (e.g., a compact mobile device spectrometer implementation) .
  • birefringent plate configurations of embodiments facilitate generation of symmetric interference patterns (e.g., example interference pattern 141 represented in FIGURES 1 and 3) , such as may enable fast Fourier transform (e.g., by interferogram transform processing logic of mobile device 130) .
  • one or more birefringent plates (e.g., planar members having parallel primary surfaces) of a birefringent module may be disposed between condenser 122 and camera lens 131 to provide optical path differences with respect to rays (e.g., ordinary rays (o-rays) and extraordinary rays (e-rays) separated by a non-cubic crystal structure of the birefringent plate material) for generating an interference pattern (e.g., interference pattern 141) .
  • the optical path differences provided with respect to o-rays and e-rays of a birefringent module may, for example, vary with the incident angle.
  • Birefringent plates 131 and 132 of embodiments of high-throughput point source light coupling structure 120 may, for example, be formed from various birefringent material, such as uniaxial or biaxial crystals having non-cubic crystal structures, plastics having molecules in a stretched conformation, etc.
  • optical member 124 of embodiments may comprise a plurality of birefringent plates, such as birefringent plate 341 and birefringent plate 342.
  • the birefringent plates may be disposed in proximity (e.g., adjacent or near) to each other having their principal sections perpendicular, or substantially perpendicular, to each other.
  • optical member 124 of the example illustrated in FIGURE 3 include birefringent plate 341 disposed in proximity to birefringent plate 342 and configured so that the principal section of birefringent plate 341 is perpendicular, or essentially perpendicular, to the principal section of birefringent plate 342.
  • a rear primary surface of birefringent plate 341 may be adjacent to, and contacting, a front primary surface of birefringent plate 342.
  • a gap e.g., an air gap, a space filled with an optical glass, optical plastic, optical adhesive, etc.
  • birefringent plates of optical member 124 of embodiments are disposed between polarizers 123 and 125 to provide birefringent module 340 of high-throughput point source light coupling structure 120.
  • polarizer 123 may be provided adjacent to, and contacting, a front primary surface of a birefringent plate of optical member 124 or may be provided with a gap (e.g., an air gap, a space filled with an optical glass, optical plastic, optical adhesive, etc. ) on the order of 1mm between the front primary surface of the birefringent plate.
  • polarizer 125 may be provided adjacent to, and contacting, a rear primary surface of a birefringent plate of optical member 124 or may be provided with a gap (e.g., an air gap, a space filled with an optical glass, optical plastic, optical adhesive, etc. ) on the order of 1mm between the rear primary surface of the birefringent plate.
  • Polarizers 123 and 125 may, for example, each comprise a polarizing sheet or film having their surfaces perpendicular, or substantially perpendicular, to an optical path (e.g., path between point source 121 and camera lens 131) of high-throughput point source light coupling structure 120.
  • polarizers 123 and 125 provide 45° polarization (e.g., 45° left or 45° right polarization) .
  • the optical axes of the birefringent plates of optical member 124 are configured in a predetermined relationship with each other.
  • Embodiments of the invention may, for example, implement configurations in which the optical axes of the birefringent plates 341 and 342 are not within the same plane.
  • the optical axis of birefringent plate 342 may be parallel or vertical to the plane of the birefringent plate while the optical axis of birefringent plate 341 is rotated 45° to the plane of the plane of the birefringent plate.
  • Configurations in which the optical axes of the birefringent plates 341 and 342 are not within the same plane may be utilized to provide implementations that are compatible with a large field of view (e.g., 60° to 120°) often provided by the imaging system of mobile devices and/or to accommodate a large incident angle from the condenser for large optical path difference variation facilitating high resolution spectroscopy by spectrometer 100.
  • a large field of view e.g. 60° to 120°
  • a large incident angle from the condenser for large optical path difference variation facilitating high resolution spectroscopy by spectrometer 100.
  • Such a symmetric interference pattern facilitates Fourier transform processing to obtain the spectrum using fast Fourier transform.
  • incident light 111 e.g., emitted by and/or reflected from a sample
  • point source 121 of high-throughput point source light coupling structure is introduced into an optical path of the light coupling structure for manipulating to form an interference pattern for spectral processing by mobile device 130.
  • Condenser 122 operates to focus and image the light provided by point source 121 on camera lens 131.
  • Optical member 124 disposed in the optical path of high-throughput point source light coupling structure 120 between condenser 122 and camera lens 131 operates to provide different optical paths with respect to rays of light passed by the high-throughput point source light coupling structure (e.g., separate the light to o-ray and e-ray components and create optical path differences with respect to these rays) .
  • Camera lens 131 provides an image plane of point source 121, as focused by condenser 122, and focuses the light (e.g., the o-rays and e-rays) on an interference plane corresponding to the sensor plane of camera sensor 132. Accordingly, camera sensor 132 captures interference pattern 141 as a digital image and provides the digital image to interferogram transform processing logic 133 to obtain the spectrum.
  • Interferogram transform processing logic 133 of embodiments comprises logic configured to transform the interference pattern provided by high-throughput point source light coupling structure 120 into the corresponding spectrum data (e.g., spectrum data 143) .
  • Interferogram transform processing logic 133 may, for example, comprise code (e.g., software, firmware, application code, computer instruction set, applet, smart device app, etc. ) stored in a computer readable memory (e.g., random access memory (RAM) , read only memory (ROM) , flash memory, magnetic memory, optical memory, etc. ) and executed by one or more processors (e.g., central processing unit (CPU) , graphics processing unit (GPU) , microprocessor (MPU) , etc.
  • CPU central processing unit
  • GPU graphics processing unit
  • MPU microprocessor
  • interferogram transform processing logic 133 may comprise hardware logic circuits (e.g., logic circuits provided by an application specific integrated circuit (ASIC) , a field programmable gate array (FPGA) , etc. ) .
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • interferogram transform processing logic 133 of embodiments of the invention is configured to generate interferograms (e.g., interferogram 142) from a captured interference pattern (e.g., interference pattern 141) provided thereto, and to transform interferograms to corresponding spectrum data (e.g., spectrum data 143) .
  • interferogram transform processing logic 133 may combine the signals for light having traveled different optical paths (e.g., the o-rays and e-rays) of interference pattern 141 focused on camera sensor 132 to generate interferogram 142. Thereafter, interferogram transform processing logic 133 may implement Fourier transform computations to transform raw interferogram data derived from the interference pattern into data representative of the actual spectrum of the observed incident light (e.g., spectrum data 143) , such as for analyzing light containing features of absorption or emission associated with a sample substance or mixture.
  • spectrum data 143 data representative of the actual spectrum of the observed incident light
  • Embodiments of high-throughput point source light coupling structure 120 implementing condenser 122 configured according to condenser configuration rules in combination with birefringent module 340 including birefringent plates 341 and 342 having their optical axes configured so as not to be within the same plane, as described above, provide high light collecting efficiency (e.g., up to 100%) , high resolution (e.g., ⁇ 2nm@400nm, ⁇ 3nm@600nm, and ⁇ 8nm@900nm) , and broad spectral range (e.g., 400nm to 1100nm) in a compact form factor (e.g., a mobile device attachment having a thickness within 10 mm) .
  • high light collecting efficiency e.g., up to 100%
  • high resolution e.g., ⁇ 2nm@400nm, ⁇ 3nm@600nm, and ⁇ 8nm@900nm
  • broad spectral range e.g., 400n
  • embodiments of spectrometer 100 comprising high-throughput point source light coupling structure 120 configured in accordance with the concepts described above provides high throughput and wide incident angle facilitating enhanced sensitivity, broad spectral range, and high resolution.
  • a Huawei P10 PLUS smartphone was used as the host mobile device of a spectrometer implementation.
  • This host mobile device provided an imaging system comprising a CMOS camera sensor providing 3840 x 5120 pixels, a camera lens having a focal length of 3.95 mm and a camera aperture of 2.19 mm.
  • An exposure time of 0.25 ms, ISO setting of 50, and a halogen lamp was used in conducting the experiments.
  • the light coupling structures utilized in the experiments included a point source comprising an optical fiber connector having a fiber with a 400 nm core and 0.39 NA.
  • FIGURE 6A shows a graph of the wavelength and intensity of light detected by the mobile device camera sensor when using a high-throughput point source light coupling structure including a condenser and birefringent plates configured in accordance with examples described above.
  • FIGURE 6B shows a graph of the wavelength and intensity of light detected by the mobile device camera sensor when using a light coupling structure including birefringent plates configured in accordance with examples described above, but without a condenser.
  • the maximum intensity increases from 0.04 to 0.8 when the high-throughput point source light coupling structure including a condenser and birefringent plates is used.
  • high-throughput point source light coupling structures including a condenser and birefringent plates configured in accordance with concepts of the present invention enhance throughput (e.g., by 20 times in this example) and largely improve the spectrometer sensitivity. It can further be appreciated that high-throughput point source light coupling structures including a condenser and birefringent plates configured in accordance with concepts of the present invention provide broad spectral range (e.g., 400nm to 1100nm in this example) .

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  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
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Abstract

L'invention concerne des systèmes et des procédés qui fournissent une structure de couplage de lumière source ponctuelle à haut débit (120) mettant en œuvre un condenseur (122) configuré selon une ou plusieurs règles de configuration de condenseur (122). Des modes de réalisation d'une structure de couplage de lumière de source ponctuelle à haut débit (120) utilisent une configuration de plaque biréfringente (341, 342) en combinaison avec un condenseur (122) et une source ponctuelle (121) pour fournir une structure de couplage de lumière (120) en vue de la mise en œuvre d'un interféromètre à transformée de Fourier biréfringent-statique. Selon certains exemples, les axes optiques d'une première et d'une seconde plaque biréfringente (341, 342) d'une configuration de plaque biréfringente (341, 342) ne sont pas dans le même plan. Le condenseur (122) de la structure de couplage de lumière de source ponctuelle à haut débit (120) des modes de réalisation est prévu dans une relation définie (p. ex., espacée, relationnelle, etc.) par rapport à la source ponctuelle (121) et/ou un objectif d'appareil photo (131) utilisé pour capturer un motif d'interférence généré par la structure de couplage de lumière (120). La structure de couplage de lumière de source ponctuelle à haut débit (120) présentée ici peut être fournie en tant qu'accessoires externes pour des dispositifs mobiles à processeur (130) dotés de capacités de capture d'images.
PCT/CN2020/127732 2020-04-01 2020-11-10 Spectromètre à transformée de fourier statique compact à haut débit WO2021196622A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101046409A (zh) * 2007-03-16 2007-10-03 西安交通大学 静态双折射偏振干涉成像光谱仪
WO2011093794A1 (fr) * 2010-01-29 2011-08-04 Dso National Laboratories Dispositif de radiométrie spectrale imageante
US20150104860A1 (en) * 2013-01-04 2015-04-16 The Board Of Trustees Of The University Of Illinois Smartphone Biosensor
CN108593105A (zh) * 2017-12-14 2018-09-28 南京理工大学 双折射偏振干涉型的高光谱成像装置及其成像方法
CN110274692A (zh) * 2018-03-14 2019-09-24 罗伯特·博世有限公司 傅立叶变换光谱仪、用于制造傅立叶变换光谱仪的方法以及用于显示电磁波谱的方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101046409A (zh) * 2007-03-16 2007-10-03 西安交通大学 静态双折射偏振干涉成像光谱仪
WO2011093794A1 (fr) * 2010-01-29 2011-08-04 Dso National Laboratories Dispositif de radiométrie spectrale imageante
US20150104860A1 (en) * 2013-01-04 2015-04-16 The Board Of Trustees Of The University Of Illinois Smartphone Biosensor
CN108593105A (zh) * 2017-12-14 2018-09-28 南京理工大学 双折射偏振干涉型的高光谱成像装置及其成像方法
CN110274692A (zh) * 2018-03-14 2019-09-24 罗伯特·博世有限公司 傅立叶变换光谱仪、用于制造傅立叶变换光谱仪的方法以及用于显示电磁波谱的方法

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