WO2018211345A1 - Holographic device or imager - Google Patents

Holographic device or imager Download PDF

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Publication number
WO2018211345A1
WO2018211345A1 PCT/IB2018/053006 IB2018053006W WO2018211345A1 WO 2018211345 A1 WO2018211345 A1 WO 2018211345A1 IB 2018053006 W IB2018053006 W IB 2018053006W WO 2018211345 A1 WO2018211345 A1 WO 2018211345A1
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WO
WIPO (PCT)
Prior art keywords
previous
plane
guiding element
light beam
light
Prior art date
Application number
PCT/IB2018/053006
Other languages
French (fr)
Inventor
Manon ROSTYKUS
Christophe Moser
Original Assignee
Ecole Polytechnique Federale De Lausanne (Epfl)
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Publication of WO2018211345A1 publication Critical patent/WO2018211345A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0402—Recording geometries or arrangements
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0443—Digital holography, i.e. recording holograms with digital recording means
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0402—Recording geometries or arrangements
    • G03H2001/0434—In situ recording when the hologram is recorded within the device used for reconstruction
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0402—Recording geometries or arrangements
    • G03H2001/0439—Recording geometries or arrangements for recording Holographic Optical Element [HOE]
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0443—Digital holography, i.e. recording holograms with digital recording means
    • G03H2001/0445—Off-axis recording arrangement
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • G03H1/04—Processes or apparatus for producing holograms
    • G03H1/0443—Digital holography, i.e. recording holograms with digital recording means
    • G03H2001/0454—Arrangement for recovering hologram complex amplitude
    • G03H2001/0456—Spatial heterodyne, i.e. filtering a Fourier transform of the off-axis record
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00—Optical components
    • G03H2223/16—Optical waveguide, e.g. optical fibre, rod
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00—Optical components
    • G03H2223/18—Prism
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2223/00—Optical components
    • G03H2223/23—Diffractive element
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H2227/00—Mechanical components or mechanical aspects not otherwise provided for
    • G03H2227/02—Handheld portable device, e.g. holographic camera, mobile holographic display

Definitions

  • the present invention relates to a holographic device or system.
  • the holographic device or system may be, for example, a compact transmission lensless digital imagers, in particular, those systems that involve holography.
  • Digital holographic microscopy is a well-developed interferometric technique for 3D imaging or visualizing transparent objects [M. K. Kim, “Principles and techniques of digital holographic microscopy,” J. Photonics Energy 18005 (2010); U. Schnars and W. Jueptner, Digital Holography (Springer- Verlag, 2005)] .
  • a laser beam is separated in two beams, one called object beam and going through the object to be imaged and one called reference beam.
  • the two beams are then recombined with a slight angle to form an interferometric pattern, so-called off-axis hologram, recorded on a digital camera.
  • Magistretti "Measurement of the integral refractive index and dynamic cell morphometry of living cells with digital holographic microscopy.," Opt. Express 13, 9361— 9373 (2005); B. Kemper and G. von Bally, “Digital holographic microscopy for live cell applications and technical inspection,” Appl. Opt. 47, A52-A61 (2008); F. Dubois, C. Yourassowsky, O. Monnom, J.-C. Legros, O. Debeir, P. Van Ham, R. Kiss, and C. Decaestecker, "Digital holographic microscopy for the three-dimensional dynamic analysis of in vitro cancer cell migration.," J. Biomed. Opt. 1 1, 54032 (2014); B.
  • Rappaz, E. Cano, T. Colomb, J. Kiihn, C. Depeursinge, V. Simanis, P. J. Magistretti, and P. Marquet "Noninvasive characterization of the fission yeast cell cycle by monitoring dry mass with digital holographic microscopy.," J. Biomed. Opt. 14, 34049 (2009)] since a quantitative measurement of the phase is accessible.
  • Diverse implementations have been presented such as an add-on for a widefield microscope [B. Kemper, A. Vollmer, C. E. Rommel, J. Schnekenburger, and G. von Bally, "Simplified approach for quantitative digital holographic phase contrast imaging of living cells.," J. Biomed. Opt.
  • This invention addresses the above-mentioned inconveniences and problems and provides a holographic device or system according to claim 1.
  • the present disclosure provides a device structure and physical mechanism that provides, for example, a transmission digital holographic microscope or, for example, a compact off-axis lensless transmission digital holographic microscope using side illumination to produce two collimated illumination beams with one divergent, but not limited to, light source.
  • the device may, for example, comprise a light source emitting a single mode spatial profile and disposed to the side of a guiding structure, which maybe flat, but not limited to, such as, but not limited to, a waveguide and a holographic material into which a hologram grating or multiplexed hologram gratings are recorded and which generate the appropriate illumination angle depending on the position of the illumination laser source.
  • This system advantageously allows for weakly light absorbing samples, but not limited to, to be imaged.
  • the amplitude and phase images of a sample can be digitally retrieved.
  • the exemplary system description that immediately follows is intended to give, by way of example, physical dimensions and possible component selection. It should not be treated as being restrictive.
  • the system may, for example, include a prism as the waveguide structure, or an assembly of prisms, with, but not limited to, an entrance surface of, for example, 20mm x 10mm, a side length of, for example, 17mm and one 30° cut side.
  • a single mode spatial light source such as but not limited to, a VCSEL can be placed at for example approximately several centimeters away from the side opposite to the slanted side of the prism.
  • One VCSEL chip is a square of for example 250 ⁇ side, but not limited to.
  • the present invention relates to a compact side illumination system.
  • a photopolymer film is, for example, laminated on one side of the prism, but not limited to.
  • Several analog hologram gratings are recorded in the photopolymer.
  • the hologram grating recording process of, for example, spatially multiplexed hologram gratings follows processes known in the state of the Art.
  • holographic photopolymers such as Bayfol® HX polymer [H. Berneth, F.-K. Bruder, T. Facke, R. Hagen, D. Honel, D. Jurbergs, T. Rolle, and M.-S. Weiser, "Holographic recording aspects of high-resolution Bayfol® HX photopolymer", Proc. Of SPIE vol.
  • the light source or VCSEL positioned at the side of the prism there are corresponding two (analogic) hologram gratings each having a specific diffraction direction. The light diffracted by one of the two gratings illuminates the sample to be imaged.
  • a sample holder contains the sample and a hole made into the sample holder to let the second diffracted beam go through.
  • the holder is, for example, a glass slide with the sample situated on only one part.
  • a corresponding one (analogic) hologram grating having one specific diffraction direction.
  • the light diffracted by the grating illuminates a glass slide which contains in one part the sample to be imaged and in another part a diffraction grating.
  • the light source or VCSEL positioned at the side of the prism corresponds one (analogic) hologram grating with one specific diffraction direction.
  • the light diffracted by the grating illuminates for example a wedged holder which contains in one flat part the sample to be imaged and in another part a wedge to deviates part of the incident beam with or at a specific angle.
  • the light transmitted by the sample recombines with the beam that did not pass through the sample.
  • the interference pattern which is an off-axis hologram, is recorded on the camera.
  • the sample holder is for example a glass slide, but not limited to, which contains the sample to be analyzed and next to which the second (diffracted) beam goes through.
  • the obtained digital hologram is used in an off-axis reconstruction algorithm [U. Schnars and W. Jueptner, Digital Holography (Springer- Verlag, 2005); U. Schnars and W. Juptner, "Direct recording of holograms by a CCD target and numerical reconstruction.," Appl. Opt. 33, 179-81 (1994); E. Cuche, P. Marquet, and C.
  • the device or system of the present disclosure can be battery operated because the light source, for example, a VCSEL is a low power consumption device or laser.
  • the present disclosure permits the design and fabrication of a compact transmission digital holographic imager that can be lensless.
  • the device presented herein may comprise a low power laser, such as but not limited to, vertical cavity surface emitting laser (VCSEL), a prism, but not limited to, onto which a photopolymer film is laminated, and a camera to record the image electronically.
  • VCSEL vertical cavity surface emitting laser
  • prism a prism, but not limited to, onto which a photopolymer film is laminated, and a camera to record the image electronically.
  • Multiplexed analogic hologram gratings can be recorded in the holographic photopolymer to redirect the light with specific angles towards the camera.
  • the sample to be imaged is positioned between the prism and the camera.
  • An off-axis digital hologram of the sample is recorded.
  • the off-axis hologram is then digitally processed to obtain amplitude and phase images of the sample.
  • the system is advantageously compact in the vertical direction, thus providing for a flat compact imager that can for example be used in portable applications such as, but not limited to, in cellular phones.
  • Fig. 1 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager
  • Fig. 2 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager
  • Fig. 3 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager
  • Fig. 4 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager
  • Fig. 5 is a digital hologram taken with the device with VCSEL as light source
  • Fig. 6 is the digitally reconstructed intensity of the hologram of Fig. 5;
  • Fig. 7 is the digitally reconstructed phase of the hologram of Fig. 5;
  • Fig. 8 is a side view drawing of an embodiment of the compact side illumination part of the holographic device of the present disclosure during the multiplexing recording process of two hologram gratings;
  • Fig. 9 is a side view drawing of an embodiment of the compact side illumination part of the holographic device of the present disclosure during the multiplexing recording process of two hologram gratings;
  • Fig. 10 is a top-side perspective view of a three-dimensional drawing to scale of an embodiment of the compact lensless imager in a housing.
  • Embodiments of the holographic system or device of the present disclosure are shown, for example, in Figures 1 to 4 and 10.
  • the holographic system or device includes an optical guiding element 100 (Figure 1) configured to redirect light incident from a light source 101 to a target interference plane.
  • the target interference plane is, for example, located at a recording plane of a camera 103 or of an image sensor 103 comprising a plurality of light sensing elements for producing a digital hologram.
  • the optical guiding element 100 includes at least one diffraction grating 104.
  • the diffraction grating is configured to generate by diffraction at least one light beam from the incident light 105 and to direct at least a part of the produced light beam towards the target interference plane .
  • the diffraction grating (or gratings) is configured to produce at least one light beam propagating in a specific diffraction direction.
  • the optical guiding element 100 includes a first interface (or side or side plane) S 1 for receiving the incident light 105 and a second interface (or side or side plane) S2 through which the incident light redirected by the diffraction grating 104 passes in propagation towards the target interference plane.
  • the first and second interfaces S I, S2 extend one with respect to the other in non-parallel directions or planes.
  • the first interface S I is connected to the second interface or side S2.
  • An angle defined between the interfaces can be between 15° and 105°, or between 35° and 95°, or between 45° and 90°. The angle can be for example 45° or 90°.
  • optical guiding element 100 comprises a prism and the angle defined between the first and second sides S I and S2 is for example 60°.
  • Figure 2 shows another example where the optical guiding element 100 comprises an elongated optical waveguide and the angle defined between the first and second sides S 1 and S2 is (about) 90°.
  • the optical waveguide can, for example, be an elongated rectangular waveguide.
  • an optical fiber such as a plastic optical fiber; or defined by parallel sheets or layers within which the light is guided.
  • the optical grating 104 is located at or on at least part of the second interface or side S2.
  • the incident light 105 is incident on the first interface or side S I and at least part of the incident light contacts the optical grating 104 to be redirected by diffraction towards the target interference plane or camera 103.
  • the optical guiding element is laterally illuminated by the incident light from the light source.
  • the target interference plane or camera is located below or above the optical guiding element.
  • the optical guiding element can be additionally configured to reflect by total internal reflection incident light, that is not diffracted to the target interference plane or camera by a grating, out of the optical guiding element and away from the target interference plane or camera.
  • the diffraction grating may for example comprise a hologram grating or a transmission hologram grating, or a surface relief grating.
  • the optical guiding element can, for example, include a photopolymer layer containing at least one grating defined in the photopolymer layer.
  • the photopolymer layer can, for example, be attached or laminated on a side S2 of the optical guiding element to provide at least one diffracted light beam.
  • a plurality of gratings may be used and the plurality of gratings can, for example, be spatially multiplexed hologram gratings or spatially multiplexed transmission hologram gratings.
  • the system or device may include at least one light source.
  • the light source is, for example, a coherent light source.
  • the light source can be a single spatial mode light source.
  • the light source may, for example, comprises a VCSEL or a plurality of VCSELs; or a laser diode or a plurality of laser diodes, or a Superluminescent light emitting diode (SLED) or a plurality thereof, or a light emitting diode or a plurality thereof, or a plurality of light emitting quantum dots.
  • a VCSEL or a plurality of VCSELs or a laser diode or a plurality of laser diodes, or a Superluminescent light emitting diode (SLED) or a plurality thereof, or a light emitting diode or a plurality thereof, or a plurality of light emitting quantum dots.
  • SLED Superluminescent light emitting diode
  • the system or device may also include the camera or image sensor comprising a plurality of light sensing elements.
  • the camera or image sensor can be, for example, a CMOS device comprising a plurality of pixels each configured to individually capture incoming light or an active pixel sensor (APS) containing an array of pixel sensors each comprising for example a photodetector and amplifier.
  • CMOS device comprising a plurality of pixels each configured to individually capture incoming light
  • APS active pixel sensor
  • the system or device can also include a holder or optically transparent holder H located between the optical guiding element and the target interference plane or camera.
  • the holder is, for example, configured to receive a sample to be imaged.
  • the techniques, apparatus, materials and systems as described in this disclosure are used to implement the device or system that is, for example, a holographic imager or a transmission holographic imager.
  • the holographic imager can, for example, be lensless.
  • the device or system according to the present disclosure can, for example, advantageously provide a compact transmission lensless digital holographic imager. Described herein is an imager 1, 2, 3, 4 that is side illuminated.
  • the imager can be lensless.
  • the relative arrangement of the device components allows to provide a compact device or system.
  • a compact side illumination lensless imager can thus, for example, be provided.
  • the optical guiding element 100 includes a first diffraction grating configured to generate by diffraction a first light beam 106 from the incident light and to direct (at least part of) the first light beam to the target interference plane 103.
  • the optical guiding element 100 also includes a second diffraction grating configured to generate by diffraction a second light beam 107 from the incident light and to direct (at least part of) the second light beam to the target interference plane 103.
  • the first and second diffraction gratings are configured to generate non-collinear first and second light beams directed to interfere at the target interference plane for the formation of an off-axis hologram.
  • the light beams recombine at the target interference plane 103 in an off-axis manner in which the one beam is inclined compared to the second beam. That is, the first (object) beam and the second (reference) beam impinge upon a recording plane or medium from the same side and/or from directions which are separated by an angle, for example, a small angle.
  • the first and second diffraction gratings are, for example, located at or on the second interface or side S2 of the optical guiding element 100.
  • the optical guiding element 100 may comprise at least one prism 100 as shown in Figure 1, or at least one elongated optical waveguide (Figure 2) whose second interface or side S2 extends in a guiding direction of the optical waveguide.
  • the holder H can be located between the at least one optical guiding element 100 and the target interference plane.
  • the holder receives a sample to be imaged.
  • the second diffraction grating can be configured to direct (at least part of) the second light beam outside an area defined by the holder H or outside an area of the holder configured to receive the sample to be imaged.
  • the holder H includes an opening permitting light redirected by the optical guiding element to pass through the opening to the target interference plane.
  • An imager 1 composed of a waveguide 100, a spatially single mode VCSEL 101, but not limited to, a holographic photopolymer film 104 in which one or more hologram gratings are defined and a camera 103.
  • Figure 1 shows an exemplary depiction of a side view drawing of one embodiment of the imager and shows the light path of an emitting VCSEL 101 towards the camera 103.
  • the light path coming from the VCSEL (101) on the left side is shown with arrows (105).
  • the beam enters the prism (100) through a side opposite to the (non-perpendicular) slanted side and is diffracted by multiplexed hologram gratings recorded in a photopolymer layer (104).
  • one beam shown with arrows (106) goes through the sample ( 102) and the second diffracted beam shown with arrows (107) does not go through the sample.
  • the two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (103) to produce a digital hologram.
  • the exemplary process to record the digital hologram is as follow, but not limited to:
  • the VCSEL 101 is turned on.
  • the light it emits enters the prism 100.
  • One of the said diffracted beams (106) illuminates the sample 102, and the second one (107) does not go through the sample 102.
  • the two diffracted beams recombine in the camera plane and the hologram is recorded on the camera to produce the digital hologram.
  • the result is an off-axis digital hologram formed through interference of the beams.
  • This digital hologram is then introduced as input to a reconstruction algorithm.
  • the output of the algorithm is an amplitude image and a quantitative phase image of the sample 102.
  • An obtained digital hologram is used in an off-axis reconstruction algorithm as disclosed for example in:
  • the device or system includes, for example, a calculation unit or processor as well as software SW or a program to operate the processor.
  • the processer extracts the optical amplitude and phase information originating from the sample out of the hologram.
  • the device or system can include memory or storage to store the software and algorithm (for example, off-axis hologram reconstruction algorithm) for processing the obtained numerically recorded hologram to extract the optical amplitude and phase information.
  • the processor may have with dedicated software.
  • the computation of the amplitude and phase can, for example, be performed as described in the above-mentioned references.
  • the interference of the beams creates a hologram that is digitally recorded by the camera.
  • the image is then transferred to the processor or computer.
  • Dedicated software processes the image to retrieve the complex optical wave front in amplitude and phase, for example, as set out below.
  • the hologram is the recorded intensity (I) of a wave front resulting from the interference of both a reference (R) and an object (O) beam.
  • the intensity is composed of the following terms:
  • the process first filters the hologram to keep the spatial frequencies of interest. This is performed in the spatial frequency domain obtained by a fast Fourier transform (FFT) of the hologram.
  • FFT fast Fourier transform
  • the off-axis geometry implies the spatial separation of the different interference orders (0, -1 and 1) in this domain.
  • the filtering is performed by applying, for example, a mask to select only OR* for example.
  • the inverse FFT generates the complex optical wave front of OR* in the plane of the camera.
  • a second part of the process can comprise a numerical propagation of the wave front into focus. This is performed in the Fresnel approximation.
  • the last step is to extract the amplitude and phase measurements out of the propagated wave front by calculating the absolute value and argument.
  • Figure 2 shows an exemplary depiction of a side view drawing of another embodiment of the imager 2 and shows the light path of the light source, for example, an emitting VCSEL 201 towards the camera 203.
  • the optical guiding element 200 includes an elongated optical waveguide.
  • the light path coming from the VCSEL (201) on the left side is shown with arrows (205).
  • the beam enters the waveguide (200) through the side S I .
  • the light is guided through the waveguide 200 by total internal reflection shown with arrows (210).
  • the beam is diffracted by, for example, multiplexed hologram gratings recorded in the photopolymer layer (209).
  • one grating generated beam shown with arrows (206) goes through the sample (202) and the second diffracted beam shown with arrows (207) does not go through the sample.
  • the sample is situated, for example, on a part of a glass slide (208).
  • the two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (203).
  • the light that is not diffracted by the gratings exits the waveguide by the side opposite to the entering one as shown by arrows (204).
  • Figure 3 shows an exemplary depiction of a side view drawing of another embodiment of the imager 3.
  • the optical guiding element 300 includes at least one diffraction grating 304 configured to generate by diffraction a first light beam 309 from the incident light and to direct at least a part of the first light beam 309 to the target interference plane and camera 303.
  • the system or device 3 further includes an optical element 308 configured to form a second light beam 307 from the first light beam 309 and to direct the second light beam 307 to the target interference plane.
  • Part 306 of the first beam 309 passes through the sample and interferes with the second beam 307.
  • the diffraction grating and the optical element 308 generate non-collinear beams 306, 307 that interfere at the target interference plane for the formation an off-axis hologram.
  • the optical element 308 is located between the optical guiding element 300 and the target interference plane or camera 303.
  • the optical element 308 may, for example, comprises an optical wedge 308 orientated with respect to the first light beam 309 to redirect at least a part of the first light beam 309 to form a light beam 307 non-collinear to the first light beam 309 or part 306 of the first light beam.
  • a sloped surface of the optical wedge is arranged so as the at least a part of the first light beam 309 is incident thereon.
  • the holder (H) may, for example, include the optical element or wedge 308.
  • the holder H can include a first portion comprising the optical element 308 and a second portion configured to receive the sample to be imaged.
  • the second portion can include a parallel plate on which is or may be disposed a sample under test.
  • the optical guiding element 300 can comprises one or a plurality of prisms, or may comprise an elongated optical waveguide.
  • Figure 3 shows the light path of, for example, the emitting VCSEL 301 towards the camera 303.
  • the light path coming from the VCSEL (301) on the left side is shown with arrows (305).
  • the beam enters the waveguide structure (300) through the side S I .
  • the incident beam 305 is diffracted (shown with arrows (309)) by, for example, a hologram grating recorded in the photopolymer layer (304).
  • one part of the beam 309 shown with arrows (306) goes through the sample (302) and the second part of the diffracted beam shown with arrows (307) does not go through the sample and goes through a wedge (308).
  • the two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (303).
  • Figure 4 shows an exemplary depiction of a side view drawing of another embodiment of the imager 4.
  • the optical guiding element 400 includes at least one diffraction grating 404 configured to generate by diffraction a first light beam 409 from the incident light and to direct at least a part 406 of the first light beam to the target interference plane or camera 403.
  • the system or device 4 further includes a second diffraction grating 408 configured to generate by diffraction a second light beam 407 from the first light beam 409 and to direct the second light beam 407 to the target interference plane or camera 403.
  • the first 404 and second 408 diffraction gratings are configured to generate non-collinear light beams directed to interfere at the target interference plane or camera 403 for the formation an off-axis hologram.
  • the second diffraction grating 408 is located between the optical guiding element 400 and the target interference plane or camera 403.
  • the optical guiding element 400 can comprise one or a plurality of prisms, or may comprise an elongated optical waveguide as previously mentioned.
  • the optical guiding element 400 may include a single diffraction grating.
  • the holder (H) may for example include the second diffraction grating 408.
  • the holder H may include a first portion comprising the second diffraction grating 408 and a second portion configured to receive the sample to be imaged.
  • Figure 4 shows the light path of for example the emitting VCSEL 401 towards the camera 403.
  • the light path coming from the VCSEL (401) in the left side is shown with arrows (405).
  • the beam enters the waveguide structure (400) through the side S 1.
  • the beam 405 is diffracted (shown with arrows (409)) by for example a hologram grating recorded in the photopolymer layer (404) or for example a surface relief grating.
  • one part of the beam shown with arrows (406) goes through the sample (402) and the second part of the diffracted beam shown with arrows (407) does not go through the sample and goes through another hologram grating (408).
  • the two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (403).
  • the system or device may also include a housing ( Figure 10) comprising mounting elements configured to hold the components in predetermined relative positions.
  • the system or device may also include an attachment configured to attach the housing or system or device to an electronic device.
  • the optical guiding element can include a photopolymer layer containing at least one or more gratings defined in the photopolymer layer.
  • the photopolymer film is, for example, laminated on one side of the optical guiding element, but not limited to.
  • One or more (analog) hologram gratings can be recorded in the photopolymer.
  • the hologram grating recording process can follow processes known in the state of the Art, for example in US3658526A, US20110236803A1, US20060194120A1, or US6127066A the contents of each of which are hereby incorporated by reference.
  • holographic photopolymers such as Bayfol® HX polymer [H. Berneth, F.-K. Bruder, T. Facke, R. Hagen, D. Honel, D. Jurbergs, T. Rolle, and M.-S. Weiser, "Holographic recording aspects of high- resolution Bayfol® HX photopolymer", Proc.
  • the optical guiding element may, for example, comprise or consist of glass, for example, K9 or NBK7 material.
  • Figures 8 and 9 show side view drawings of an embodiment of the compact side illumination optical guiding element 100, 200, 300, 400 during a multiplexing recording process of two hologram gratings.
  • the beam (801) from the light source (800) interferes with a beam (803) in the photopolymer layer or film (806).
  • the interference pattern is recorded in the photopolymer.
  • This interference pattern is or defines for example an (analog) phase hologram grating.
  • the same process is done sequentially for the beam (801) from the source (800) interfering with a beam (804) to record a further interference pattern and a further (analog) phase hologram grating.
  • the two gratings can be recorded sequentially.
  • Figure 8 shows the recording process of two spatially multiplexed hologram gratings in the photopolymer film laminated on a prism 802.
  • a continuous-wave, single frequency laser is collimated and split by a beam splitter (not-illustrated) to generate, but not limited to, a plane wave signal beam and a high numerical aperture spherical reference beam.
  • the reference and the signal beams interfere in the photopolymer film or layer inducing index of refraction changes therein, which result in the creation of a phase grating.
  • the angle of the signal beam with respect to the normal to the prism is controlled with a 2D scanning system.
  • a second similar prism (805) can be put on top of the prism (802) with index matching oil between the two prisms, in order to control the angle of the signal beam which would be affected by the refraction leaving the prism (802).
  • the beam (905) from the source (901) is guided through the waveguide (900) by total internal reflection.
  • the guided beam is shown with arrows (902).
  • This beam interferes with the beam (906) in the photopolymer film or layer (903).
  • the interference pattern is recorded in the photopolymer film or layer 903.
  • This interference pattern is or defines an (analog) phase hologram grating.
  • the same process is done sequentially for the beam (901) from the source (901) interfering with the beam (907) to record a further interference pattern and a further analog phase hologram grating.
  • the two gratings can be recorded sequentially.
  • Figure 9 shows the recording process of two spatially multiplexed hologram gratings in the photopolymer film laminated on the waveguide.
  • a continuous-wave, single frequency laser is collimated and split by a beam splitter (not shown) to generate, but not limited to, a plane wave signal beam and a high numerical aperture spherical reference beam.
  • the reference and the signal beams interfere in the photopolymer film or layer inducing index of refraction changes therein, which result in the creation of a phase grating.
  • the angle of the signal beam with respect to the normal to the prism is controlled with a 2D scanning system.
  • Figure 10 is a top-side perspective view of a three-dimensional representation to scale of an exemplary embodiment of the holographic device or system according to the present disclosure .
  • The, device is, for example, a compact lensless imager connected to a camera chip 1002, for example but not limited to.
  • the prism 1001 onto which the photopolymer is laminated, the sample, one is shown with reference numeral 1000, and the light source, one is shown with reference numeral 1003, are held by the housing 1004.
  • the camera chip 1002 is used to record the off-axis holograms.
  • a continuous-wave red laser was set in a Mach-Zender interferometer configuration to record two spatially multiplexed hologram gratings in a 70 ⁇ thick photopolymer film laminated on a K9 prism with an entrance surface of 20mm x 10mm, a side length of 17 mm and one 30° cut side.
  • Each hologram grating was recorded with the same position of the reference beam along the prism entrance side.
  • the direction of the signal beam with respect to the normal to the prism longest side surface in the plane of the prism was different. -2.9° and 2.9 angles were chosen. The zero order (>99%) is reflected out of the prism by total internal reflection.
  • FIG. 5 A digital off-axis hologram of a USAF 1951 phase test target was recorded (Fig. 5) with the device with a VCSEL light source and its intensity (Fig. 6) and phase (Fig. 7) were reconstructed.
  • the distance between the sample and the camera sensor was about 4cm.

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Abstract

The present disclosure concerns a holographic system or device comprising at least one optical guiding element (100) configured to redirect light incident from a light source (101) to a target interference plane (103), wherein the optical guiding element includes at least one diffraction grating (104) configured to generate by diffraction at least one light beam from the incident light and to direct at least part of the at least one light beam towards the target interference plane.

Description

HOLOGRAPHIC DEVICE OR IMAGER
CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority to International Patent Application PCT/IB2017/052853 filed on May 15th, 2017, the entire contents thereof being herewith incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a holographic device or system. The holographic device or system may be, for example, a compact transmission lensless digital imagers, in particular, those systems that involve holography.
BACKGROUND
Digital holographic microscopy (DHM) is a well-developed interferometric technique for 3D imaging or visualizing transparent objects [M. K. Kim, "Principles and techniques of digital holographic microscopy," J. Photonics Energy 18005 (2010); U. Schnars and W. Jueptner, Digital Holography (Springer- Verlag, 2005)] . In this method, a laser beam is separated in two beams, one called object beam and going through the object to be imaged and one called reference beam. The two beams are then recombined with a slight angle to form an interferometric pattern, so-called off-axis hologram, recorded on a digital camera. The latter hologram is then processed with well-known algorithms to extract the phase and amplitude of the sample [U. Schnars and W. Jueptner, Digital Holography (Springer- Verlag, 2005); U. Schnars and W. Juptner, "Direct recording of holograms by a CCD target and numerical reconstruction.," Appl. Opt. 33, 179-81 (1994); E. Cuche, P. Marquet, and C. Depeursinge, "Simultaneous amplitude -contrast and quantitative phase-contrast microscopy by numerical reconstruction of Fresnel off-axis holograms.," Appl. Opt. 38, 6994-7001 (1999)] . When applied to microscopy, it is often used to image transparent biological material and quantify the optical thickness of cells [P. Marquet, B. Rappaz, P. J. Magistretti, E. Cuche, Y. Emery, T. Colomb, and C. Depeursinge, "Digital holographic microscopy: a noninvasive contrast imaging technique allowing quantitative visualization of living cells with subwavelength axial accuracy," Opt. Lett. 30, 468-470 (2005); B. Kemper, D. Carl, J. Schnekenburger, I. Bredebusch, M. Schafer, W. Domschke, and G. von Bally, "Investigation of living pancreas tumor cells by digital holographic microscopy," J. Biomed. Opt. 1 1, 34005 (2006); A. Anand, V. K. Chhaniwal, N. R. Patel, and B. Javidi, "Automatic identification of malaria-infected RBC with digital holographic microscopy using correlation algorithms," IEEE Photonics J. 4, 1456- 1464 (2012); Z. El-Schich, S. Kamlund, B. Janicke, K. Aim, and A. G. Wingren, "Holography: The Usefulness of Digital Holographic Microscopy for Clinical Diagnostics," in Holographic Materials and Optical Systems (InTech, 2017); B. Rappaz, P. Marquet, E. Cuche, Y. Emery, C. Depeursinge, and P. Magistretti, "Measurement of the integral refractive index and dynamic cell morphometry of living cells with digital holographic microscopy.," Opt. Express 13, 9361— 9373 (2005); B. Kemper and G. von Bally, "Digital holographic microscopy for live cell applications and technical inspection," Appl. Opt. 47, A52-A61 (2008); F. Dubois, C. Yourassowsky, O. Monnom, J.-C. Legros, O. Debeir, P. Van Ham, R. Kiss, and C. Decaestecker, "Digital holographic microscopy for the three-dimensional dynamic analysis of in vitro cancer cell migration.," J. Biomed. Opt. 1 1, 54032 (2014); B. Rappaz, E. Cano, T. Colomb, J. Kiihn, C. Depeursinge, V. Simanis, P. J. Magistretti, and P. Marquet, "Noninvasive characterization of the fission yeast cell cycle by monitoring dry mass with digital holographic microscopy.," J. Biomed. Opt. 14, 34049 (2009)], since a quantitative measurement of the phase is accessible. Diverse implementations have been presented such as an add-on for a widefield microscope [B. Kemper, A. Vollmer, C. E. Rommel, J. Schnekenburger, and G. von Bally, "Simplified approach for quantitative digital holographic phase contrast imaging of living cells.," J. Biomed. Opt. 16, 26014 (201 1); P. Girshovitz and N. T. Shaked, "Compact and portable low-coherence interferometer with off-axis geometry for quantitative phase microscopy and nanoscopy," Opt. Express 21, 5701 (2013)], a color DHM [F. Dubois and C. Yourassowsky, "Full off-axis red-green-blue digital holographic microscope with LED illumination," Opt. Lett. 37, 2190 (2012)], autofocus [P. Ferraro, G. Coppola, S. De Nicola, A. Finizio, G. Pierattini, S. De Nicola, A. Finizio, and G. Pierattini, "Digital holographic microscope with automatic focus tracking by detecting sample displacement in real time.," Opt. Lett. 28, 1257-1259 (2003)] and stand-alone DHM in transmission and reflection configuration [M. Frometa, G. Moreno, J. Ricardo, Y. Arias, M. Muramatsu, L. F. Gomes, G. Palacios, F. Palacios, H. Velazquez, J. L. Valin, and L. Ramirez Q, "Optimized setup for integral refractive index direct determination applying digital holographic microscopy by reflection and transmission," Opt. Commun. 387, 252-256 (2017)] . Reconstruction can be done in different depth planes which allows DHM to track elements in a 3D volume [F. Dubois, C. Yourassowsky, O. Monnom, J.-C. Legros, O. Debeir, P. Van Ham, R. Kiss, and C. Decaestecker, "Digital holographic microscopy for the three-dimensional dynamic analysis of in vitro cancer cell migration.," J. Biomed. Opt. 1 1, 54032 (2014); A. Anand, V. K. Chhaniwal, and B. Javidi, "Imaging embryonic stem cell dynamics using quantitative 3-D digital holographic microscopy," IEEE Photonics J. 3, 546-554 (201 1); P. Langehanenberg, L. Ivanova, I. Bernhardt, S. Ketelhut, A. Vollmer, D. Dirksen, G. Georgiev, G. von Bally, and B. Kemper, "Automated three-dimensional tracking of living cells by digital holographic microscopy.," J. Biomed. Opt. 14, 14018 (2015)] . Tomography has also been investigated by rotating the sample and recording several holograms [Y. Lin, H.-C. Chen, H.-Y. Tu, C.-Y. Liu, and C.-J. Cheng, "Optically driven full-angle sample rotation for tomographic imaging in digital holographic microscopy," Opt. Lett. 42, 1321 (2017); F. Charriere, A. Marian, F. Montfort, J. Kuehn, T. Colomb, E. Cuche, P. Marquet, and C. Depeursinge, "Cell refractive index tomography by digital holographic microscopy," Opt. Lett. 31, 178 (2006)] . Compact versions of off-axis DHMs have been implemented [W. Qu, C. O. Choo, V. R. Singh, Y. Yingjie, and A. Asundi, "Quasi-physical phase compensation in digital holographic microscopy," J. Opt. Soc. Am. A 26, 2005 (2009); J. K. Wallace, S. Rider, E. Serabyn, J. Kiihn, K. Liewer, J. Deming, G. Showalter, C. Lindensmith, and J. Nadeau, "Robust, compact implementation of an off-axis digital holographic microscope," Opt. Express 23, 17367 (2015); V. Chhaniwal, A. S. G. Singh, R. A. Leitgeb, B. Javidi, and A. Anand, "Quantitative phase- contrast imaging with compact digital holographic microscope employing Lloyd's mirror," Opt. Lett. 37, 5127 (2012)] . For example, an implementation makes use of a beam splitter to obtain two beams, object and reference, from one light source [W. Qu, C. O. Choo, V. R. Singh, Y. Yingjie, and A. Asundi, "Quasi-physical phase compensation in digital holographic microscopy," J. Opt. Soc. Am. A 26, 2005 (2009); N. Shaked, "Quantitative phase microscopy of biological samples using a portable interferometer," Opt. Lett. 37, 2016-2018 (2012)] . An objective is added in front of the sample to increase the resolution. This type of design only works in reflection. Another proposed scheme is made of a set of different lenses to image in transmission [J. K. Wallace, S. Rider, E. Serabyn, J. Kiihn, K. Liewer, J. Deming, G. Showalter, C. Lindensmith, and J. Nadeau, "Robust, compact implementation of an off-axis digital holographic microscope," Opt. Express 23, 17367 (2015)] . The two paths are created by using only a part of a collimated beam for each beam (object and reference). Finally, other holographic techniques have been utilized, such as self-interference design [V. Chhaniwal, A. S. G. Singh, R. A. Leitgeb, B. Javidi, and A. Anand, "Quantitative phase -contrast imaging with compact digital holographic microscope employing Lloyd's mirror," Opt. Lett. 37, 5127 (2012); N. Shaked, "Quantitative phase microscopy of biological samples using a portable interferometer," Opt. Lett. 37, 2016-2018 (2012)] and shearing interferometry [S. Rawat, S. Komatsu, A. Markman, A. Anand, and B. Javidi, "Compact and field-portable 3D printed shearing digital holographic microscope for automated cell identification," Appl. Opt. 56, D 127 (2017)], to achieve this goal. All those implementations either include lenses or only work in reflection.
The same kind of device using a beam splitter has been presented for lensless imaging [E. C. Shi, J. J. Ng, C. M. Lim, and W. Qu, "Compact lensless digital holographic microscopy using a curved mirror for an enlarged working distance," Appl. Opt. 55, 3771 (2016)], i.e. without an objective in front of the sample, which makes it more compact but works only in reflection. Inline digital holography is another well studied technique that allows fabrication of ultra- compact devices [W. Luo, A. Greenbaum, Y. Zhang, and A. Ozcan, "Synthetic aperture-based on-chip microscopy," Light Sci. Appl. 4, e261 (2015); M. Rostykus, F. Soulez, M. Unser, and C. Moser, "Compact lensless phase imager," 25, 241-245 (2017)] but it needs several tens of digital inline holograms obtained by either changing the illumination wavelength, the angle illumination or a combination of both. Specific algorithms which are computationally intensive [W. Luo, A. Greenbaum, Y. Zhang, and A. Ozcan, "Synthetic aperture-based on-chip microscopy," Light Sci. Appl. 4, e261 (2015)] are needed to retrieve the phase of the sample. A comparison between inline and off-axis holography algorithms is presented in [E. Cuche, P. Marquet, and C. Depeursinge, "Simultaneous amplitude -contrast and quantitative phase- contrast microscopy by numerical reconstruction of Fresnel off-axis holograms.," Appl. Opt. 38, 6994-7001 (1999)] .
The contents of each of the above-mentioned references are hereby incorporated by reference.
SUMMARY OF THE INVENTION
This invention addresses the above-mentioned inconveniences and problems and provides a holographic device or system according to claim 1.
Further advantages features are present in the dependent claims.
The present disclosure provides a device structure and physical mechanism that provides, for example, a transmission digital holographic microscope or, for example, a compact off-axis lensless transmission digital holographic microscope using side illumination to produce two collimated illumination beams with one divergent, but not limited to, light source. The device may, for example, comprise a light source emitting a single mode spatial profile and disposed to the side of a guiding structure, which maybe flat, but not limited to, such as, but not limited to, a waveguide and a holographic material into which a hologram grating or multiplexed hologram gratings are recorded and which generate the appropriate illumination angle depending on the position of the illumination laser source.
This system advantageously allows for weakly light absorbing samples, but not limited to, to be imaged. The amplitude and phase images of a sample can be digitally retrieved.
The exemplary system description that immediately follows is intended to give, by way of example, physical dimensions and possible component selection. It should not be treated as being restrictive. The system may, for example, include a prism as the waveguide structure, or an assembly of prisms, with, but not limited to, an entrance surface of, for example, 20mm x 10mm, a side length of, for example, 17mm and one 30° cut side. A single mode spatial light source, such as but not limited to, a VCSEL can be placed at for example approximately several centimeters away from the side opposite to the slanted side of the prism. One VCSEL chip is a square of for example 250 μπι side, but not limited to.
In at least one embodiment, the present invention relates to a compact side illumination system.
A photopolymer film is, for example, laminated on one side of the prism, but not limited to. Several analog hologram gratings are recorded in the photopolymer. The hologram grating recording process of, for example, spatially multiplexed hologram gratings follows processes known in the state of the Art. For example, can be used, holographic photopolymers such as Bayfol® HX polymer [H. Berneth, F.-K. Bruder, T. Facke, R. Hagen, D. Honel, D. Jurbergs, T. Rolle, and M.-S. Weiser, "Holographic recording aspects of high-resolution Bayfol® HX photopolymer", Proc. Of SPIE vol. 7957, 79570H], Dichromated gelatin [T. A. Shankoff, "Phase holograms in dichromated gelatin", Applied Optics, vol. 7, no. 10 (1968)], PQ-PMMA [Y. Luo, P. J. Gelsinger, J. K. Barton, G. Barbastathis, and R. K. Kostuk, "Optimization of multiplexed holographic gratings in PQ-PMMA for spectral-spatial imaging filters", Optics Express, vol. 33, no. 6 (2008)] or Dupont polymer [U.-S. Rhee, H. J. Caulfield, C. S. Vikram, and J. Shamir, "Dynamics of hologram recording in DuPont photopolymer", Applied Optics, vol. 34, no. 5 (1995)] .
In at least one embodiment, to the light source or VCSEL positioned at the side of the prism there are corresponding two (analogic) hologram gratings each having a specific diffraction direction. The light diffracted by one of the two gratings illuminates the sample to be imaged.
In at least one embodiment, a sample holder contains the sample and a hole made into the sample holder to let the second diffracted beam go through.
In another embodiment, the holder is, for example, a glass slide with the sample situated on only one part.
In yet another embodiment, to the light source or VCSEL positioned at the side of the prism there is a corresponding one (analogic) hologram grating having one specific diffraction direction. The light diffracted by the grating illuminates a glass slide which contains in one part the sample to be imaged and in another part a diffraction grating.
In another embodiment, to the light source or VCSEL positioned at the side of the prism corresponds one (analogic) hologram grating with one specific diffraction direction. The light diffracted by the grating illuminates for example a wedged holder which contains in one flat part the sample to be imaged and in another part a wedge to deviates part of the incident beam with or at a specific angle. The light transmitted by the sample recombines with the beam that did not pass through the sample. The interference pattern, which is an off-axis hologram, is recorded on the camera.
In another embodiment, the sample holder is for example a glass slide, but not limited to, which contains the sample to be analyzed and next to which the second (diffracted) beam goes through. Then, the obtained digital hologram is used in an off-axis reconstruction algorithm [U. Schnars and W. Jueptner, Digital Holography (Springer- Verlag, 2005); U. Schnars and W. Juptner, "Direct recording of holograms by a CCD target and numerical reconstruction.," Appl. Opt. 33, 179-81 (1994); E. Cuche, P. Marquet, and C. Depeursinge, "Simultaneous amplitude-contrast and quantitative phase-contrast microscopy by numerical reconstruction of Fresnel off-axis holograms.," Appl. Opt. 38, 6994-7001 (1999)] .
Further, in at least one embodiment, the device or system of the present disclosure can be battery operated because the light source, for example, a VCSEL is a low power consumption device or laser.
The present disclosure permits the design and fabrication of a compact transmission digital holographic imager that can be lensless. The device presented herein may comprise a low power laser, such as but not limited to, vertical cavity surface emitting laser (VCSEL), a prism, but not limited to, onto which a photopolymer film is laminated, and a camera to record the image electronically.
Multiplexed analogic hologram gratings can be recorded in the holographic photopolymer to redirect the light with specific angles towards the camera.
The sample to be imaged is positioned between the prism and the camera. An off-axis digital hologram of the sample is recorded. The off-axis hologram is then digitally processed to obtain amplitude and phase images of the sample.
The system is advantageously compact in the vertical direction, thus providing for a flat compact imager that can for example be used in portable applications such as, but not limited to, in cellular phones. BRIEF DESCRIPTION OF THE DRAWINGS
For purposes of clarity, not every component may be labeled in every drawing. The drawings are not necessarily drawn to scale, with emphasis instead being placed on illustrating various aspects of the techniques and devices described herein. The invention will be better understood through the description of preferred embodiments and in view of the drawings, wherein:
Fig. 1 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager; Fig. 2 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager;
Fig. 3 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager;
Fig. 4 is a side view drawing of an embodiment of the compact transmission lensless digital holographic imager;
Fig. 5 is a digital hologram taken with the device with VCSEL as light source;
Fig. 6 is the digitally reconstructed intensity of the hologram of Fig. 5;
Fig. 7 is the digitally reconstructed phase of the hologram of Fig. 5;
Fig. 8 is a side view drawing of an embodiment of the compact side illumination part of the holographic device of the present disclosure during the multiplexing recording process of two hologram gratings;
Fig. 9 is a side view drawing of an embodiment of the compact side illumination part of the holographic device of the present disclosure during the multiplexing recording process of two hologram gratings; and
Fig. 10 is a top-side perspective view of a three-dimensional drawing to scale of an embodiment of the compact lensless imager in a housing.
DETAILED DESCRIPTION
Embodiments of the holographic system or device of the present disclosure are shown, for example, in Figures 1 to 4 and 10.
The holographic system or device includes an optical guiding element 100 (Figure 1) configured to redirect light incident from a light source 101 to a target interference plane. The target interference plane is, for example, located at a recording plane of a camera 103 or of an image sensor 103 comprising a plurality of light sensing elements for producing a digital hologram.
The optical guiding element 100 includes at least one diffraction grating 104. The diffraction grating is configured to generate by diffraction at least one light beam from the incident light 105 and to direct at least a part of the produced light beam towards the target interference plane .
The diffraction grating (or gratings) is configured to produce at least one light beam propagating in a specific diffraction direction. The optical guiding element 100 includes a first interface (or side or side plane) S 1 for receiving the incident light 105 and a second interface (or side or side plane) S2 through which the incident light redirected by the diffraction grating 104 passes in propagation towards the target interference plane. The first and second interfaces S I, S2 extend one with respect to the other in non-parallel directions or planes.
The first interface S I is connected to the second interface or side S2. An angle defined between the interfaces can be between 15° and 105°, or between 35° and 95°, or between 45° and 90°. The angle can be for example 45° or 90°. For example, optical guiding element 100 comprises a prism and the angle defined between the first and second sides S I and S2 is for example 60°. Figure 2 shows another example where the optical guiding element 100 comprises an elongated optical waveguide and the angle defined between the first and second sides S 1 and S2 is (about) 90°. The optical waveguide can, for example, be an elongated rectangular waveguide. For example, an optical fiber such as a plastic optical fiber; or defined by parallel sheets or layers within which the light is guided.
The optical grating 104 is located at or on at least part of the second interface or side S2. The incident light 105 is incident on the first interface or side S I and at least part of the incident light contacts the optical grating 104 to be redirected by diffraction towards the target interference plane or camera 103.
The optical guiding element is laterally illuminated by the incident light from the light source. The target interference plane or camera is located below or above the optical guiding element.
The optical guiding element can be additionally configured to reflect by total internal reflection incident light, that is not diffracted to the target interference plane or camera by a grating, out of the optical guiding element and away from the target interference plane or camera.
The diffraction grating may for example comprise a hologram grating or a transmission hologram grating, or a surface relief grating. The optical guiding element can, for example, include a photopolymer layer containing at least one grating defined in the photopolymer layer. The photopolymer layer can, for example, be attached or laminated on a side S2 of the optical guiding element to provide at least one diffracted light beam.
A plurality of gratings may be used and the plurality of gratings can, for example, be spatially multiplexed hologram gratings or spatially multiplexed transmission hologram gratings.
The system or device may include at least one light source. The light source is, for example, a coherent light source.
The light source can be a single spatial mode light source.
The light source may, for example, comprises a VCSEL or a plurality of VCSELs; or a laser diode or a plurality of laser diodes, or a Superluminescent light emitting diode (SLED) or a plurality thereof, or a light emitting diode or a plurality thereof, or a plurality of light emitting quantum dots.
The system or device may also include the camera or image sensor comprising a plurality of light sensing elements.
The camera or image sensor can be, for example, a CMOS device comprising a plurality of pixels each configured to individually capture incoming light or an active pixel sensor (APS) containing an array of pixel sensors each comprising for example a photodetector and amplifier.
The system or device can also include a holder or optically transparent holder H located between the optical guiding element and the target interference plane or camera. The holder is, for example, configured to receive a sample to be imaged. The techniques, apparatus, materials and systems as described in this disclosure are used to implement the device or system that is, for example, a holographic imager or a transmission holographic imager. The holographic imager can, for example, be lensless. The device or system according to the present disclosure can, for example, advantageously provide a compact transmission lensless digital holographic imager. Described herein is an imager 1, 2, 3, 4 that is side illuminated. The imager can be lensless. The relative arrangement of the device components allows to provide a compact device or system. A compact side illumination lensless imager can thus, for example, be provided.
In the exemplary embodiment of Figure 1, the optical guiding element 100 includes a first diffraction grating configured to generate by diffraction a first light beam 106 from the incident light and to direct (at least part of) the first light beam to the target interference plane 103. The optical guiding element 100 also includes a second diffraction grating configured to generate by diffraction a second light beam 107 from the incident light and to direct (at least part of) the second light beam to the target interference plane 103.
The first and second diffraction gratings are configured to generate non-collinear first and second light beams directed to interfere at the target interference plane for the formation of an off-axis hologram.
The light beams recombine at the target interference plane 103 in an off-axis manner in which the one beam is inclined compared to the second beam. That is, the first (object) beam and the second (reference) beam impinge upon a recording plane or medium from the same side and/or from directions which are separated by an angle, for example, a small angle.
The first and second diffraction gratings are, for example, located at or on the second interface or side S2 of the optical guiding element 100. The optical guiding element 100 may comprise at least one prism 100 as shown in Figure 1, or at least one elongated optical waveguide (Figure 2) whose second interface or side S2 extends in a guiding direction of the optical waveguide.
The holder H can be located between the at least one optical guiding element 100 and the target interference plane. The holder receives a sample to be imaged.
The second diffraction grating can be configured to direct (at least part of) the second light beam outside an area defined by the holder H or outside an area of the holder configured to receive the sample to be imaged. Alternatively or additionally, the holder H includes an opening permitting light redirected by the optical guiding element to pass through the opening to the target interference plane. An imager 1 composed of a waveguide 100, a spatially single mode VCSEL 101, but not limited to, a holographic photopolymer film 104 in which one or more hologram gratings are defined and a camera 103.
Figure 1 shows an exemplary depiction of a side view drawing of one embodiment of the imager and shows the light path of an emitting VCSEL 101 towards the camera 103. The light path coming from the VCSEL (101) on the left side is shown with arrows (105). The beam enters the prism (100) through a side opposite to the (non-perpendicular) slanted side and is diffracted by multiplexed hologram gratings recorded in a photopolymer layer (104). Then one beam shown with arrows (106) goes through the sample ( 102) and the second diffracted beam shown with arrows (107) does not go through the sample. The two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (103) to produce a digital hologram. The exemplary process to record the digital hologram is as follow, but not limited to:
The VCSEL 101 is turned on.
The light it emits enters the prism 100.
It is then diffracted by the two multiplexed hologram gratings recorded in the photopolymer film 104.
- One of the said diffracted beams (106) illuminates the sample 102, and the second one (107) does not go through the sample 102.
The two diffracted beams recombine in the camera plane and the hologram is recorded on the camera to produce the digital hologram. The result is an off-axis digital hologram formed through interference of the beams. This digital hologram is then introduced as input to a reconstruction algorithm. The output of the algorithm is an amplitude image and a quantitative phase image of the sample 102. An obtained digital hologram is used in an off-axis reconstruction algorithm as disclosed for example in:
- U. Schnars and W. Jueptner, Digital Holography (Springer-Verlag, 2005);
- U. Schnars and W. Juptner, "Direct recording of holograms by a CCD target and numerical reconstruction", Appl. Opt. 33, 179-81 (1994);
- E. Cuche, P. Marquet, and C. Depeursinge, "Simultaneous amplitude-contrast and quantitative phase-contrast microscopy by numerical reconstruction of Fresnel off-axis holograms.," Appl. Opt. 38, 6994-7001 (1999);
- E. Cuche, F. Bevilacqua, and C. Depeursinge, "Digital holography for quantitative phase- contrast imaging", Opt. Lett. 24 (5), 291-293 (1999);
- EP1119798 and US6262818: METHOD AND APPARATUS FOR SIMULTANEOUS AMPLITUDE AND QUANTITATIVE PHASE CONTRAST IMAGING BY NUMERICAL RECONSTRUCTION OF DIGITAL HOLOGRAMS
- US7649160 APPARATUS AND METHOD FOR DIGITAL HOLOGRAPHIC IMAGING the content of each of which is fully incorporated herein by reference.
The device or system includes, for example, a calculation unit or processor as well as software SW or a program to operate the processor. The processer extracts the optical amplitude and phase information originating from the sample out of the hologram. The device or system can include memory or storage to store the software and algorithm (for example, off-axis hologram reconstruction algorithm) for processing the obtained numerically recorded hologram to extract the optical amplitude and phase information.
The processor may have with dedicated software. The computation of the amplitude and phase can, for example, be performed as described in the above-mentioned references.
A concise summary of an exemplary approach is given here. The interference of the beams creates a hologram that is digitally recorded by the camera. The image is then transferred to the processor or computer. Dedicated software processes the image to retrieve the complex optical wave front in amplitude and phase, for example, as set out below.
The hologram is the recorded intensity (I) of a wave front resulting from the interference of both a reference (R) and an object (O) beam. The intensity is composed of the following terms:
I = |0+R|2 = OO* + RR* + OR* + RO*, where | .| denotes the absolute value and * the complex conjugate. The two first terms are the intensity of the object, respectively reference beams and compose the 0-order. The two last terms are the interference terms (order 1 and -1).
The process first filters the hologram to keep the spatial frequencies of interest. This is performed in the spatial frequency domain obtained by a fast Fourier transform (FFT) of the hologram. The off-axis geometry implies the spatial separation of the different interference orders (0, -1 and 1) in this domain. The filtering is performed by applying, for example, a mask to select only OR* for example. The inverse FFT generates the complex optical wave front of OR* in the plane of the camera.
As the object image may not be focused, a second part of the process can comprise a numerical propagation of the wave front into focus. This is performed in the Fresnel approximation. The last step is to extract the amplitude and phase measurements out of the propagated wave front by calculating the absolute value and argument.
Figure 2 shows an exemplary depiction of a side view drawing of another embodiment of the imager 2 and shows the light path of the light source, for example, an emitting VCSEL 201 towards the camera 203.
As previously mentioned, the optical guiding element 200 includes an elongated optical waveguide. The light path coming from the VCSEL (201) on the left side is shown with arrows (205). The beam enters the waveguide (200) through the side S I . The light is guided through the waveguide 200 by total internal reflection shown with arrows (210). The beam is diffracted by, for example, multiplexed hologram gratings recorded in the photopolymer layer (209). Then one grating generated beam shown with arrows (206) goes through the sample (202) and the second diffracted beam shown with arrows (207) does not go through the sample. The sample is situated, for example, on a part of a glass slide (208). The two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (203). The light that is not diffracted by the gratings exits the waveguide by the side opposite to the entering one as shown by arrows (204).
Figure 3 shows an exemplary depiction of a side view drawing of another embodiment of the imager 3.
The optical guiding element 300 includes at least one diffraction grating 304 configured to generate by diffraction a first light beam 309 from the incident light and to direct at least a part of the first light beam 309 to the target interference plane and camera 303. The system or device 3 further includes an optical element 308 configured to form a second light beam 307 from the first light beam 309 and to direct the second light beam 307 to the target interference plane.
Part 306 of the first beam 309 passes through the sample and interferes with the second beam 307.
The diffraction grating and the optical element 308 generate non-collinear beams 306, 307 that interfere at the target interference plane for the formation an off-axis hologram.
The optical element 308 is located between the optical guiding element 300 and the target interference plane or camera 303.
The optical element 308 may, for example, comprises an optical wedge 308 orientated with respect to the first light beam 309 to redirect at least a part of the first light beam 309 to form a light beam 307 non-collinear to the first light beam 309 or part 306 of the first light beam.
A sloped surface of the optical wedge is arranged so as the at least a part of the first light beam 309 is incident thereon.
The holder (H) may, for example, include the optical element or wedge 308. The holder H can include a first portion comprising the optical element 308 and a second portion configured to receive the sample to be imaged. The second portion can include a parallel plate on which is or may be disposed a sample under test. The optical guiding element 300 can comprises one or a plurality of prisms, or may comprise an elongated optical waveguide.
Figure 3 shows the light path of, for example, the emitting VCSEL 301 towards the camera 303. The light path coming from the VCSEL (301) on the left side is shown with arrows (305). The beam enters the waveguide structure (300) through the side S I . The incident beam 305 is diffracted (shown with arrows (309)) by, for example, a hologram grating recorded in the photopolymer layer (304). Then one part of the beam 309 shown with arrows (306) goes through the sample (302) and the second part of the diffracted beam shown with arrows (307) does not go through the sample and goes through a wedge (308). The two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (303).
Figure 4 shows an exemplary depiction of a side view drawing of another embodiment of the imager 4.
The optical guiding element 400 includes at least one diffraction grating 404 configured to generate by diffraction a first light beam 409 from the incident light and to direct at least a part 406 of the first light beam to the target interference plane or camera 403. The system or device 4 further includes a second diffraction grating 408 configured to generate by diffraction a second light beam 407 from the first light beam 409 and to direct the second light beam 407 to the target interference plane or camera 403.
The first 404 and second 408 diffraction gratings are configured to generate non-collinear light beams directed to interfere at the target interference plane or camera 403 for the formation an off-axis hologram.
The second diffraction grating 408 is located between the optical guiding element 400 and the target interference plane or camera 403.
The optical guiding element 400 can comprise one or a plurality of prisms, or may comprise an elongated optical waveguide as previously mentioned.
The optical guiding element 400 may include a single diffraction grating. The holder (H) may for example include the second diffraction grating 408. The holder H may include a first portion comprising the second diffraction grating 408 and a second portion configured to receive the sample to be imaged.
Figure 4 shows the light path of for example the emitting VCSEL 401 towards the camera 403. The light path coming from the VCSEL (401) in the left side is shown with arrows (405). The beam enters the waveguide structure (400) through the side S 1. The beam 405 is diffracted (shown with arrows (409)) by for example a hologram grating recorded in the photopolymer layer (404) or for example a surface relief grating. Then one part of the beam shown with arrows (406) goes through the sample (402) and the second part of the diffracted beam shown with arrows (407) does not go through the sample and goes through another hologram grating (408). The two beams recombine to form an off-axis hologram in the camera plane and is recorded on the camera (403).
The system or device may also include a housing (Figure 10) comprising mounting elements configured to hold the components in predetermined relative positions. The system or device may also include an attachment configured to attach the housing or system or device to an electronic device.
As previously mentioned the optical guiding element can include a photopolymer layer containing at least one or more gratings defined in the photopolymer layer.
The photopolymer film is, for example, laminated on one side of the optical guiding element, but not limited to.
One or more (analog) hologram gratings can be recorded in the photopolymer. The hologram grating recording process can follow processes known in the state of the Art, for example in US3658526A, US20110236803A1, US20060194120A1, or US6127066A the contents of each of which are hereby incorporated by reference. For example, can be used, holographic photopolymers such as Bayfol® HX polymer [H. Berneth, F.-K. Bruder, T. Facke, R. Hagen, D. Honel, D. Jurbergs, T. Rolle, and M.-S. Weiser, "Holographic recording aspects of high- resolution Bayfol® HX photopolymer", Proc. Of SPIE vol. 7957, 79570H], Dichromated gelatin [T. A. Shankoff, "Phase holograms in dichromated gelatin", Applied Optics, vol. 7, no. 10 (1968)], PQ-PMMA [Y. Luo, P. J. Gelsinger, J. K. Barton, G. Barbastathis, and R. K. Kostuk, "Optimization of multiplexed holographic gratings in PQ-PMMA for spectral-spatial imaging filters", Optics Express, vol. 33, no. 6 (2008)] or Dupont polymer [U.-S. Rhee, H. J. Caulfield, C. S. Vikram, and J. Shamir, "Dynamics of hologram recording in DuPont photopolymer", Applied Optics, vol. 34, no. 5 ( 1995)] .
The contents of each of the above-mentioned references are hereby incorporated by reference.
The optical guiding element may, for example, comprise or consist of glass, for example, K9 or NBK7 material.
Figures 8 and 9 show side view drawings of an embodiment of the compact side illumination optical guiding element 100, 200, 300, 400 during a multiplexing recording process of two hologram gratings.
Reference is now made in particular to Figure 8 by the way of example. The beam (801) from the light source (800) interferes with a beam (803) in the photopolymer layer or film (806). The interference pattern is recorded in the photopolymer. This interference pattern is or defines for example an (analog) phase hologram grating. The same process is done sequentially for the beam (801) from the source (800) interfering with a beam (804) to record a further interference pattern and a further (analog) phase hologram grating. The two gratings can be recorded sequentially.
Figure 8 shows the recording process of two spatially multiplexed hologram gratings in the photopolymer film laminated on a prism 802. A continuous-wave, single frequency laser is collimated and split by a beam splitter (not-illustrated) to generate, but not limited to, a plane wave signal beam and a high numerical aperture spherical reference beam. The reference and the signal beams interfere in the photopolymer film or layer inducing index of refraction changes therein, which result in the creation of a phase grating. The angle of the signal beam with respect to the normal to the prism is controlled with a 2D scanning system.
A second similar prism (805) can be put on top of the prism (802) with index matching oil between the two prisms, in order to control the angle of the signal beam which would be affected by the refraction leaving the prism (802). Reference is now made to Figure 9 by the way of example. The beam (905) from the source (901) is guided through the waveguide (900) by total internal reflection. The guided beam is shown with arrows (902). This beam interferes with the beam (906) in the photopolymer film or layer (903). The interference pattern is recorded in the photopolymer film or layer 903. This interference pattern is or defines an (analog) phase hologram grating. The same process is done sequentially for the beam (901) from the source (901) interfering with the beam (907) to record a further interference pattern and a further analog phase hologram grating. The two gratings can be recorded sequentially.
Figure 9 shows the recording process of two spatially multiplexed hologram gratings in the photopolymer film laminated on the waveguide. A continuous-wave, single frequency laser is collimated and split by a beam splitter (not shown) to generate, but not limited to, a plane wave signal beam and a high numerical aperture spherical reference beam. The reference and the signal beams interfere in the photopolymer film or layer inducing index of refraction changes therein, which result in the creation of a phase grating. The angle of the signal beam with respect to the normal to the prism is controlled with a 2D scanning system.
Figure 10 is a top-side perspective view of a three-dimensional representation to scale of an exemplary embodiment of the holographic device or system according to the present disclosure . The, device is, for example, a compact lensless imager connected to a camera chip 1002, for example but not limited to. The prism 1001 onto which the photopolymer is laminated, the sample, one is shown with reference numeral 1000, and the light source, one is shown with reference numeral 1003, are held by the housing 1004. In this embodiment the camera chip 1002 is used to record the off-axis holograms.
As a proof of principle example, a continuous-wave red laser was set in a Mach-Zender interferometer configuration to record two spatially multiplexed hologram gratings in a 70μπι thick photopolymer film laminated on a K9 prism with an entrance surface of 20mm x 10mm, a side length of 17 mm and one 30° cut side. Each hologram grating was recorded with the same position of the reference beam along the prism entrance side. For each hologram the direction of the signal beam with respect to the normal to the prism longest side surface in the plane of the prism was different. -2.9° and 2.9 angles were chosen. The zero order (>99%) is reflected out of the prism by total internal reflection.
A digital off-axis hologram of a USAF 1951 phase test target was recorded (Fig. 5) with the device with a VCSEL light source and its intensity (Fig. 6) and phase (Fig. 7) were reconstructed. The distance between the sample and the camera sensor was about 4cm.
Various aspects of the devices, system and techniques described herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing description and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Use of ordinal terms such as "first," "second," "third," etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
While the invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments, and equivalents thereof, are possible without departing from the sphere and scope of the invention. In particular, the features of any one embodiment may be combined with the features of any other embodiment. Accordingly, it is intended that the invention not be limited to the described embodiments, and be given the broadest reasonable interpretation in accordance with the language of the appended claims.

Claims

1. Holography system or device ( 1;2;3;4) comprising:
at least one optical guiding element (100; 200; 300; 400; 1001) configured to redirect light incident from a light source (101 ; 201 ; 301 ; 401 ; 1003) to a target interference plane, wherein the optical guiding element ( 100; 200; 300; 400; 1001) includes at least one diffraction grating (104, 204, 304, 404) configured to generate by diffraction at least one light beam from the incident light and to direct at least part of the at least one light beam towards the target interference plane.
2. The system or device according to claim 1, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) includes a first interface or side or side plane (S I) for receiving the incident light and a second interface or side or side plane (S2) through which the redirected incident light passes in propagation towards the target interference plane; the first and second interfaces or sides (S I, S2) extending one with respect to the other in non-parallel directions or planes.
3. The system or device according to claim 2, wherein the first interface or side or side plane (S I) is connected to the second interface or side or side plane (S2) at an angle of between 15° and 105°, or between 35° and 95°, or between 45° and 90°, or at an angle of 45° or 90°.
4. The system or device according to claim 2 or 3, wherein the at least one optical grating (104, 204, 304, 404) is located at or on at least part of the second interface or side or side plane (S2) of the optical guiding element (100; 200; 300; 400; 1001) and the incident light is incident on the first interface or side or side plane (S I).
5. The system or device according to anyone of the previous claims, wherein the optical guiding element (100; 200; 300; 400; 1001) includes a first diffraction grating (104, 209, 304, 404) configured to generate by diffraction a first light beam ( 106; 206; 306; 406) from the incident light and to direct at least part of the first light beam to the target interference plane, and a second diffraction grating (104, 209, 408) configured to generate by diffraction a second light beam (107; 207; 407) from the incident light and to direct at least part of the second light beam to the target interference plane; the first and second diffraction gratings ( 104, 209, 304, 404, 408) being configured to generate non-collinear first and second light beams directed to interfere at the target interference plane for the formation of an off-axis hologram.
6. The system or device according to claim 5, wherein the first and second diffraction gratings are located at or on the second interface or side (S2) of the optical guiding element (100; 200; 300; 1001).
7. The system or device according to claim 5, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) comprises at least one prism, or at least one optical waveguide wherein the second interface or side (S2) extends in the guiding direction of the optical waveguide.
8. The system or device according to anyone of the previous claims, further including a holder (H) or optically transparent holder (H) located between the at least one optical guiding element (100; 200; 300; 400; 1001) and the target interference plane.
9. The system or device according to the previous claim, wherein the holder or optically transparent holder (H) is configured to receive a sample to be imaged.
10. The system or device according to the previous claim, wherein the second diffraction grating ( 104, 204, 304, 404) configured to direct at least part of the second light beam to the target interference plane and outside an area defined by the holder (H) or outside an area of the holder configured to receive the sample to be imaged.
1 1. The system or device according to the previous claim 9 or 10, wherein the holder or optically transparent holder (H) includes an opening permitting light redirected by the at least one optical guiding element ( 100; 200; 300; 400; 1001) to pass through the opening to the target interference plane.
12. The system or device according to anyone of the previous claims 1 to 4, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) includes at least one diffraction grating ( 104, 209, 304, 404) configured to generate by diffraction a first light beam from the incident light and to direct at least a part of the first light beam to the target interference plane; and the system or device further includes an optical element (308) configured to form a second light beam (307) from the first light beam and to direct the second light beam to the target interference plane; the at least one diffraction grating and the optical element (308) being configured to generate non-collinear first and second light beams directed to interfere at the target interference plane for the formation an off-axis hologram.
13. The system or device according to the previous claim, wherein the optical element (308) is located between the at least one optical guiding element (100; 200; 300; 400; 1001) and the target interference plane.
14. The system or device according to the previous claim 12 or 13, wherein the optical element (308) comprises an optical wedge (308) orientated with respect to the first light beam to redirect at least a part of the first light beam to form a light beam non-collinear to the first light beam.
15. The system or device according to the previous claim, wherein a sloped surface of the optical wedge is arranged so as the at least a part of the first light beam is incident thereon.
16. The system or device according to any one of the previous claims, wherein the optical guiding element comprises or consists of K9 or NBK7 material.
17. The system or device according to anyone of the previous claims 12 to 16, further including a holder (H) or optically transparent holder (H) located between the at least one optical guiding element (100; 200; 300; 400; 1001) and the target interference plane, wherein the holder (H) or optically transparent holder (H) includes the optical element (308).
18. The system or device according to the previous claim, wherein the holder (H) or optically transparent holder (H) includes a first portion comprising the optical element (308) and a second portion configured to receive the sample to be imaged.
19. The system or device according to any one of the previous claims 15 to 18, wherein the holder is an optically transparent sample holder consisting of or comprising at least two parts:
- a parallel plate on which is or may be disposed a sample under test,
- the wedge disposed adjacent to the parallel plate or the sample under test, permitting to produce two beams intersecting at the target interference plane or a camera plane in an off-axis manner.
20. The system or device according to any one of previous claims 12 to 19, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) comprises at least one prism.
21. The system or device according to anyone of the previous claims 1 to 4, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) includes at least one diffraction grating ( 104, 209, 304, 404) configured to generate by diffraction a first light beam from the incident light and to direct at least a part of the first light beam to the target interference plane; and the system or device further includes a second diffraction grating (408) configured to generate by diffraction a second light beam (407) from the first light beam and to direct the second light beam (407) to the target interference plane; the first and second diffraction gratings being configured to generate non-collinear first and second light beams directed to interfere at the target interference plane for the formation an off-axis hologram.
22. The system or device according to the previous claim, wherein the second diffraction grating (408) is located between the at least one optical guiding element ( 100; 200; 300; 400; 1001) and the target interference plane.
23. The system or device according to anyone of the previous claims 12 to 22, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) includes a single diffraction grating.
24. The system or device according to anyone of the previous claims 21 to 23, further including a holder (H) or optically transparent holder (H) located between the at least one optical guiding element (100; 200; 300; 400; 1001) and the target interference plane, wherein the holder (H) or optically transparent holder (H) includes the second diffraction grating (408).
25. The system or device according to the previous claim, wherein the holder (H) or optically transparent holder (H) includes a first portion comprising the second diffraction grating (408) and a second portion configured to receive the sample to be imaged.
26. The system or device according to anyone of the previous claims 21 to 25, wherein the second diffraction grating (408) is configured to direct the diffracted second light beam towards a transparent sample holder (H) consisting of or comprising at least two parts: - a parallel plate on which is or may be disposed a sample under test,
- a transmission diffraction grating (408) disposed adjacent to the parallel plate or sample under test,
permitting to produce two lights beams intersecting at the target interference plane or a camera plane in an off-axis manner.
27. The system or device according to any one of previous claims 21 to 26, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) comprises at least one prism.
28. The system or device according to any one of the previous claims, wherein the at least one diffraction grating (104, 204, 304, 404) is configured to produce at least one light beam propagating in a specific diffraction direction, or the first and second diffraction gratings are configured to produce light beams propagating in specific diffraction directions.
29. The system or device according to any one of the previous claims, wherein the diffraction grating comprises a hologram grating or a transmission hologram grating.
30. The system or device according to any one of the previous claims, wherein the first and second diffraction gratings are spatially multiplexed hologram gratings or spatially multiplexed transmission hologram gratings.
31. The system or device according to any one of the previous claims, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) includes a photopolymer layer containing a grating defined therein, the photopolymer layer being attached or laminated on a side (S2) of the at least one optical guiding element to provide at least one diffracted light beam.
32. The system or device according to any one of the previous claims, further including at least one light source.
33. The system or device according to the previous claim, wherein the at least one light source is a coherent light source.
34. The system or device according to the previous claims 32 or 33, wherein the at least one light source is a single spatial mode light source.
35. The system or device according to any one of the previous claims, wherein the at least one light source comprises a VCSEL or a plurality of VCSELs; or a laser diode or a plurality of laser diodes, or a Superlumine scent light emitting diode (SLED) or a plurality thereof, or a light emitting diode or a plurality thereof, or a plurality of light emitting quantum dots.
36. The system or device according to the previous claims 32 to 35, wherein the at least one light source is positioned on at least one side (S I) of the at least one optical guiding element (100; 200; 300; 400; 1001) to emit a light beam into said at least one side (S I).
37. The system or device according to any one of the previous claims, further including at least one camera (103, 203, 303, 403) or image sensor (103, 203, 303, 403) comprising a plurality of light sensing elements.
38. The system or device according to the previous claim, wherein the at least one camera (103, 203, 303, 403, 1002) or image sensor (103, 203, 303, 403, 1002) is located at the target interference plane for recording the hologram.
39. The system or device according to the previous claim, wherein the at least one camera or a recording plane of the camera ( 103, 203, 303, 403, 1002) or the image sensor ( 103, 203,
303, 403, 1002) or a recording plane of the image sensor is located at the target interference plane for producing a digital hologram.
40. The system or device according to any one of the previous claims, further including a processor configured to process a digitally recorded hologram and to extract intensity and/or phase information from said hologram.
41. The system or device according to any one of the previous claims, further including a housing comprising mounting elements configured to hold the system or device components in predetermined relative positions.
42. The system or device according to any one of the previous claims, further including an attachment configured to attach the housing or system or device to an electronic device.
43. The system or device according to any one of the previous claims, including a processor and memory configured to retrieve amplitude and quantitative phase images of a sample.
44. The system or device according to any one of the previous claims, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) comprises a prism or an array of prisms; or a rectangular waveguide.
45. The system or device according to any one of the previous claims, wherein the at least one optical guiding element (100; 200; 300; 400; 1001) is further configured to reflect by total internal reflection the undiffracted incident light out of the optical guiding element away from the target interference plane or camera.
46. The system or device according to any one of the previous claims, wherein the at least one optical guiding element is configured to produce a single diffracted light beam that is collimated or not and directed towards a sample and the target interference plane or camera.
47. The system or device according to the previous claim, wherein said single diffracted light beam is directed towards a transparent sample holder consisting of or comprising at least two parts:
- a parallel plate on which may be or is disposed the sample under test,
- a wedge disposed adjacent to the parallel plate or sample under test,
permitting to produce two beams intersecting at the target interference plane or camera plane in an off-axis manner.
48. The system or device according to claim 46, wherein said single diffracted second light beam is directed towards a transparent sample holder consisting of or comprising at least two parts:
- a parallel plate on which may be or is disposed the sample under test,
- a transmission grating disposed adjacent to the parallel plate or sample under test, permitting to produce two beams intersecting at the target interference plane or camera plane in an off-axis manner.
49. The system or device according to any one of the previous claims, wherein the at least one diffraction grating is or comprises a holographic photopolymer film which is single color or panchromatic.
50. The system or device according to any one of the previous claims, wherein the at least one diffraction grating is or comprises a surface relief grating.
51. The system or device according to any one of the previous claims, wherein said diffracted light beam comprises two collimated light beams having non co-linear direction generated by diffraction by two spatially multiplexed gratings whereby:
- the first of the two beams is directed towards a sample under test disposed on a sample holder,
- the second of the two beams is directed to propagate outside the area of the sample under test,
the first and second beams intersecting at the target interference plane or a camera plane in an off-axis manner.
52. The system or device according to claim 44, wherein a thin layer of photopolymer is laminated on a side of a prism or prisms to provide one or two diffracted beam, part of the diffracted beam of one of the two diffracted beams, produced by diffraction from the holographic photopolymer film, illuminating a sample.
53. The system or device according to any one of the previous claims wherein the at least one light source is positioned along one side (SI) of the at least one optical guiding element or prism.
54. The system or device according to any one of the previous claims, wherein a sample to be imaged is arranged between (i) the at least one optical guiding element or prism and (ii) a camera or image sensor.
55. The system or device according to any one of the previous claims, further comprising digital image processing means configured to digitally process images produced by a camera or image sensor, in order to retrieve an amplitude image and a quantitative phase image of a sample.
56. The system or device according to any one of the previous claims, further comprising attachment means configured to attach the system or device to a consumer electronic device.
57. The system or device according to the previous claim, wherein the consumer electronic device comprises or is a smart phone.
58. The system or device of claim 51, wherein the sample holder includes a hole to let the second of the two beams through.
59. The system or device according to any one of the previous claims, further comprising a sample holder and/or a sample under test.
60. The system or device according to any one of the previous claims, comprising at least one light source emitting a first light beam positioned on the side (S 1) of the at least one optical guiding element comprising at least a top plane and two side planes.
61. The system or device according to any one of the previous claims, wherein the the at least one includes at least a top plane and two side planes, and the grating is positioned on one plane of said at least one optical guiding element and arranged to be illuminated by the light from the at least one light source.
62. The system or device according to any one of the previous claims, wherein the system or device is a lensless system or device.
63. Electronic device or smart phone including the system or device according to any one of the previous claims.
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WO2021094536A1 (en) * 2019-11-15 2021-05-20 See-Through Scientific Limited Digital holographic microscope

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