Systems and methods for performing photoluminescence analysis on a medium

Abstract

A system and method for performing photoluminescence analysis on a medium such as the fundus of a patient's eye are provided. An imaging device, a spectral analyzer, and an excitation light source are provided. Optical components define an imaging optical path between the patient's eye and the imaging device and a spectral analysis optical path between an analysis point on the patient's eye and the spectral analyzer. The excitation light source generates an excitation beam that includes an excitation wavelength selected to excite a component present in the patient's eye to generate fluorescence at a photoluminescence wavelength and is optically coupled to the spectral analysis optical path for projecting the excitation beam onto the analysis point. A filter is coupled to the spectral analyzer, having a low transmittance at the excitation wavelength and a high transmittance at the photoluminescence wavelength.

Description

Technical Field

[0001] This technical field generally relates to spectroscopic reflectometer systems and methods, and more particularly to devices for spectroscopic absorption analysis, fluorescence, autofluorescence, spontaneous Raman spectroscopy, coherent Raman spectroscopy, or other eye-related measurements. Background Art

[0002] The assessment of the photoluminescence of analytes (such as proteins or other compounds) naturally present in the retina, or of photoluminescence markers directly added to the retina or on the light absorption at a specific excitation wavelength, is a useful non-invasive tool with a wide range of medical and health monitoring applications. In fact, the assessment of photoluminescence can provide valuable information about metabolism, the pathophysiology of different diseases and disorders, or the efficacy of administered treatments.

[0003] In addition, the combination of photoluminescence assessment and imaging provides valuable additional information about physiological and pathophysiological phenomena.

[0004] There is still a need for an improved device that can be used to quantify fluorescence, autofluorescence, spontaneous and coherent Raman spectra, and perform analysis on other parameters in a patient's eye to provide at least some of the above advantages. Summary of the Invention

[0005] According to one aspect, a system for performing photoluminescence analysis on a medium is provided.

[0006] The system includes an imaging device configured to acquire an image of the medium including an analysis point, a spectroscopic analyzer, and an optical component. The optical component defines an imaging optical path between the medium and the imaging device and a spectroscopic analysis optical path between the analysis point on the medium and the analyzer.

[0007] The system further includes an excitation light source operable to generate an excitation beam including an excitation wavelength selected to excite a component present in the medium for generating light of photoluminescence at an emission wavelength different from the excitation wavelength. The excitation light source is optically coupled to the spectroscopic analysis optical path for projecting the excitation beam onto the analysis point.

[0008] The system further includes a filter coupled to the spectroscopic analyzer. The filter has a low transmittance at the excitation wavelength and a high transmittance at the emission wavelength.

[0009] In some embodiments, the system includes a beam splitter that is positioned and configured to direct an imaging portion of the return light from the medium traveling along the imaging optical path to an imaging device and to direct a spectral analysis portion of the return light to a spectral analysis optical path. The beam splitter can be a dichroic beam splitter. In some variations, the beam splitter is configured to divide the light traveling along the imaging optical path into an imaging portion and a spectral analysis portion based on one of an intensity ratio and a polarization direction.

[0010] In some embodiments, the system includes a first fiber optic link extending between the spectral analysis optical path and a spectral analyzer, a second fiber optic link extending between the spectral analysis optical path and an excitation light source, and a three-way coupler that optically couples the spectral analysis optical path, the first fiber optic link, and the second fiber optic link. The three-way coupler can include one of a multimode optical circulator, a double-clad fiber, and a free-space beam splitting configuration. In some variations, the filter includes a free-space optical component disposed between the first fiber optic link and the spectral analyzer. In other variations, the filter includes a thin film deposited on a fiber-based component disposed between the first fiber optic link and the spectral analyzer.

[0011] In some embodiments, the filter is a long-pass filter. In other embodiments, the filter is a band-pass filter.

[0012] In some embodiments, the system includes an illumination subassembly configured to project illumination light toward the medium. The system may further include an illumination light source that is operable to generate the illumination light and is optically coupled to the illumination subassembly.

[0013] A controller may also be provided to generate control signals for controlling the illumination light source, the imaging device, the spectral analyzer, and the excitation light source. The controller is preferably configured to operate in the following modes:

[0014] - An illumination mode, in which the controller turns on at least the illumination device and the imaging device; and

[0015] - An excitation mode, in which the controller turns on at least the excitation light source and the spectral analyzer.

[0016] In some embodiments, the system includes a controller configured to operate in the following modes:

[0017] - An illumination mode, in which the controller operates the illumination device to project illumination light toward the medium, operates the imaging device to obtain an image of the medium, and operates the spectral analyzer to obtain a spectral analysis of an analysis point on the medium; and

[0018] - An excitation mode, in which the controller operates the excitation light source to project an excitation beam onto the analysis point and the spectral analyzer to obtain a photoluminescence analysis of the analysis point on the medium.

[0019] In some embodiments, the system further includes a point moving device positioned in the spectral analysis optical path and configured to move the position of the analysis point on the medium.

[0020] According to another aspect, there is provided a system for performing photoluminescence analysis on the fundus of a patient's eye. The system includes:

[0021] - an imaging device configured to acquire a fundus image;

[0022] - a spectral analyzer;

[0023] - an optical assembly defining an imaging optical path between the patient's eye and the imaging device and a spectral analysis optical path between an analysis point on the patient's eye and the spectral analyzer;

[0024] - an excitation light source operable to generate an excitation beam, the excitation beam including an excitation wavelength selected to excite a component present in the patient's eye for generating fluorescence at a photoluminescence wavelength, the excitation light source being optically coupled to the spectral analysis optical path for projecting the excitation beam onto the analysis point; and

[0025] - a filter coupled to the spectral analyzer, the filter having a low transmittance at the excitation wavelength and a high transmittance at the photoluminescence wavelength.

[0026] In some embodiments, the system includes a beam splitter positioned and configured to direct an imaging portion of the return light from the patient's eye traveling along the imaging optical path to the imaging device and a spectral analysis portion of the return light to the spectral analysis optical path. The beam splitter can be a dichroic beam splitter. The beam splitter can be configured to divide the light traveling along the imaging optical path into an imaging portion and a spectral analysis portion based on one of an intensity ratio and a polarization direction.

[0027] In some embodiments, the system includes a first optical fiber link extending between the spectral analysis optical path and the spectral analyzer, a second optical fiber link extending between the spectral analysis optical path and the excitation light source, and a three-way coupler optically coupling the spectral analysis optical path, the first optical fiber link, and the second optical fiber link. The three-way coupler can include one of a multimode optical circulator, a double-clad optical fiber, and a free-space beam splitting configuration.

[0028] In some embodiments, the filter includes a free-space optical component disposed between the first optical fiber link and the spectral analyzer. In other embodiments, the filter can include a thin film deposited on a fiber-based component disposed between the first optical fiber link and the spectral analyzer.

[0029] In some embodiments, the filter can be a long-pass filter or a band-pass filter.

[0030] In some embodiments, the system includes an illumination subassembly configured to project illumination light toward a patient's eye. The system further includes an illumination light source operable to generate the illumination light and optically coupled to the illumination subassembly.

[0031] In some embodiments, the system may include a controller that generates control signals for controlling the illumination light source, the imaging device, the spectral analyzer, and the excitation light source. Preferably, the controller is configured to operate in the following modes:

[0032] - An illumination mode, in which the controller turns on at least the illumination device and the imaging device; and

[0033] - An excitation mode, in which the controller turns on at least the excitation light source and the spectral analyzer.

[0034] In some embodiments, the system may further include a controller configured to operate in the following modes:

[0035] - An illumination mode, in which the controller operates the illumination device to project the illumination light toward the patient's eye, operates the imaging device to obtain an image of the fundus, and operates the spectral analyzer to obtain a spectral analysis of an analysis point on the fundus; and

[0036] - An excitation mode, in which the controller operates the excitation light source to project an excitation beam onto the analysis point and the spectral analyzer to obtain a photoluminescence measurement of the analysis point on the fundus.

[0037] In some embodiments, the system further includes a point moving device positioned in the spectral analysis optical path and configured to move the position of the analysis point on the fundus.

[0038] According to another aspect, there is provided a use of the above system for performing photoluminescence analysis on the fundus of a patient's eye.

[0039] In some embodiments, the photoluminescence analysis includes one of absorbance measurement, fluorescence measurement, autofluorescence measurement, spontaneous Raman spectroscopy, and coherent Raman spectroscopy.

[0040] According to another aspect, there is provided a method for performing photoluminescence analysis on a medium. The method includes:

[0041] a) Provide an imaging device, a spectral analyzer, an optical component, an excitation light source, a filter coupled to the spectral analyzer, and an illumination light source, where the optical component defines an imaging optical path between the medium and the imaging device and a spectral analysis optical path between an analysis point on the medium and the spectral analyzer, the excitation light source is optically coupled to the spectral analysis path and is operable to generate an excitation beam that includes an excitation wavelength selected to excite a component present in the medium for generating photoluminescence light at an emission wavelength different from the excitation wavelength, and a filter coupled to the spectral analyzer, the filter having a low transmittance at the excitation wavelength and a high transmittance at the emission wavelength;

[0042] b) Operate the illumination light source to project illumination light toward the medium, and operate the imaging device to acquire an image of the medium; and

[0043] c) Operate the excitation light source to project the excitation beam onto the analysis point and the spectral analyzer to obtain a photoluminescence measurement of the analysis point on the fundus.

[0044] In some embodiments, the method further includes operating the excitation light source and the imaging device to obtain an image of the analysis point.

[0045] In some embodiments, the method further includes the step of superimposing the image of the analysis point on the image of the medium.

[0046] In some embodiments, the medium is the fundus of a patient's eye.

[0047] In some embodiments, the photoluminescence measurement includes one of absorbance measurement, fluorescence measurement, autofluorescence measurement, spontaneous Raman spectroscopy measurement, and coherent Raman spectroscopy measurement.

[0048] Other features and advantages will be better understood by reading the preferred embodiments with reference to the accompanying drawings. Description of the Drawings

[0049] Figure 1 is a schematic diagram of a system according to an embodiment.

[0050] Figure 2 is a detailed schematic diagram of a system according to an embodiment.

[0051] Figure 3A and 3B is Figure 2 a schematic diagram of a variant of the filter of

[0052] Figures 4A to 4C shows different configurations of a triple coupler for use in a system according to some embodiments.

[0053] Figure 5AShows a fundus image of a patient acquired by an imaging device; Figure 5B Shows a spectral analysis of a fundus analysis point. Figure 5C Shows the autofluorescence spectrum obtained at the analysis point; Figure 5D Shows an image of the analysis point that appears as a point in the field of view of the imaging device; and Figure 5E Shows a combined image of the fundus and the analysis point thereon.

[0054] Figure 6 Is a timing diagram of the operation of a system according to some embodiments.

[0055] Figure 7A And 7B Is a configuration example of a point moving device used in a system according to an embodiment. Detailed Description

[0056] This description generally relates to systems and methods for performing photoluminescence analysis of a medium, such as for example autofluorescence analysis of a patient's fundus. In some embodiments, the photoluminescence analysis is combined with imaging and additional spectral analysis capabilities.

[0057] In the embodiments described herein, the system has a spectroradiometer configuration for ophthalmology to study a patient's eye. In the context of this application, with respect to the technology related to a spectroradiometer, the expression "spectroreflectometric" is generally used as an abbreviation of the terms "spectral" and "reflectometer". As will be readily understood by those skilled in the art, a reflectometer refers to the use of reflected light or other electromagnetic waves to analyze the properties of a medium. Light is typically projected onto the medium, and the interaction of the light wavefront with the medium causes the returned light to have optical properties affected by the medium. In a spectroradiometer, spectral analysis of the returned light, i.e., analysis of the properties of the returned light as a function of its wavelength distribution, is used to obtain or infer information about the medium and its components.

[0058] A spectroradiometer is used, for example, in an ophthalmic environment to sense the oxygen content in a patient's fundus. For example, the oxygen content is evaluated by the presence of oxyhemoglobin having characteristic light absorption patterns. Similarly, the concentrations of deoxyhemoglobin and carboxyhemoglobin (related to the carbon dioxide content present) can be determined based on their respective light absorption patterns. These compounds and their regulation indicate metabolism, response to stress and stimuli, and potential pathophysiology.

[0059] The expression photoluminescence generally refers to the light emission after photons are absorbed by a medium. The light stimulation can be generated by one or more excitation light sources, which generate light at one or more selected wavelengths to trigger the desired conversion in the medium. In the context of ophthalmology, for example, a laser diode can be used to project light at the excitation wavelength onto the fundus of a patient's eye. The excitation wavelength is selected to interact specifically with known components of the eye to emit a photoluminescence light wavefront with less energy, which is the result of an elastic interaction with the medium. This energy exchange causes the wavelength of the resulting light to shift relative to the excitation light, usually towards longer wavelengths. It is readily understood that the expression photoluminescence encompasses a variety of techniques, such as absorbance, fluorescence, autofluorescence, spontaneous and coherent Raman spectroscopies (coherent anti-Stokes Raman scattering, stimulated Raman scattering, etc.).

[0060] In some embodiments, the systems and methods described herein can be used to perform fluorescence analysis of a patient's eye. The expression "fluorescence" is understood to refer to a specific type of photoluminescence generated by singlet-singlet electronic relaxation. In some embodiments, the systems and methods can be used in the context of analyzing autofluorescence from the fundus of a patient's eye. "Autofluorescence" is a special case of fluorescence where the light emission comes from the native molecules of the medium under study. In other applications, the fluorescence being analyzed may originate from fluorophores artificially added to the medium as markers. Fluorescence imaging is an effective procedure for ophthalmic clinicians and can be used as a tool for diagnosing various visual pathologies. For example, autofluorescence imaging of lipofuscin granules (LG) is known. LG tends to accumulate in the retinal pigment epithelium of the eyes of patients with genetic diseases, particularly in age-related macular degeneration (AMD). Quantifying LG at specific locations in the retina can provide better diagnosis and assessment of the severity of diseases such as AMD. Fluorescence analysis can be performed on different regions of the fundus of a patient's eye or other features on the fundus. In other embodiments, fluorescence analysis can be performed on other parts of the eye, such as the conjunctiva.

[0061] It will be readily appreciated that the systems and methods described herein can be used for applications different from spectral reflectometry and fluorescence analysis of the eye. More generally, the systems below can be used in any context that requires spectral information in response to light excitation from a portion of an imaging medium. Various molecules and phenomena can also be studied, such as, for example, melanin fluorescence or Raman scattering, fluorescence from fluorophore labels, etc., as they cause changes in the spectral profile of the returned light. Those skilled in the art will readily appreciate that in some applications, the system can be used to analyze light transmitted or reflected by the medium of interest. The medium under study can be other than the eye and can be, for example, skin, organ tissue, exposed muscle tissue, and other biological tissues or fluids. In some embodiments, the medium under study can be an in vitro sample, such as blood, tissue, etc., stored in a transparent container, such as a bag, vial, syringe, or cuvette, or on a suitable substrate.

[0062] Referring Figure 1 , a high-level schematic diagram of a spectral reflectometer system 20 for performing photoluminescence analysis on the fundus 30 of a patient's eye 21 according to one embodiment is shown.

[0063] The spectral reflectometer system 20 first includes an imaging device 50 and a spectral analyzer 52. The spectral reflectometer system 20 further includes an optical assembly that defines an imaging optical path 34 between the patient's eye 21 (or other medium under study) and the imaging device 50, and a spectral analysis optical path 36 between the analysis point 82 on the patient's eye 21 and the spectral analyzer 52. An illumination light source 22 that can be controlled to generate illumination light 24 can also be provided. The spectral reflectometer system 20 further includes an excitation light source 90 for generating an excitation beam whose spectral content includes one or more excitation wavelengths that are selected to excite the generation of light that photoluminesces at one or more emission wavelengths in the medium. A filter 96 having a low transmittance at one or more excitation wavelengths and a high transmittance at one or more emission wavelengths is coupled to the spectral analyzer 52. If the emission wavelength is longer than the excitation wavelength, the optical filter 96 is preferably a long-pass filter. In some embodiments where the emission wavelength is shorter than the excitation wavelength, a low-pass filter can be used. In other variants, a band-pass filter or a notch rejection filter can be used, which is configured to allow light at the emission wavelength to pass through and block light at the excitation wavelength.

[0064] In the configuration illustrated herein, the spectral reflectometer system 20 can operate in two modes: an illumination mode and an excitation mode.

[0065] In the illumination mode, illumination light 24 is projected onto the fundus 30 of the patient's eye 21 to illuminate it, thereby obtaining return light 32 that travels along the imaging optical path 34 from the fundus 30. Using a beam splitter 48, the return light 32 is preferably split into an imaging portion 54 that travels along the imaging optical path 32 and a spectral analysis portion 56 that diverts to the spectral analysis optical path 36. The imaging portion 54 is detected via an imaging device 50 to obtain an image of the fundus 30 of the patient's eye 21.

[0066] In the excitation mode, an excitation light source 90 generates an excitation beam 94. The excitation beam 94 is coupled to the spectral analysis optical path 36 to be projected onto the fundus of the patient's eye 21 at the analysis point. The excitation beam 94 can be absorbed by a fluorescent compound or the like present in the retina, exciting the singlet state of the fluorescent compound. The then-excited compound will lose energy through heat and emit light at an emission wavelength, whose energy is lower than that of the excitation photon. The emission is isotropic, and a portion of the emitted light will become part of the return light 32, pass through the imaging path 34, reach the beam splitter 48, and enter the spectral analysis path 36. The presence of a long-pass filter will block any components reflected at the excitation wavelength and allow light at the emission wavelength to pass through.

[0067] The excitation beam 94 can also be reflected by Rayleigh scattering without a change in wavelength. Thus, the return light 32 from the fundus further includes a reflected component 94' at the excitation wavelength, which travels along the imaging optical path 34 to the imaging device 50. Since both the spectral analysis portion 56 of the return light 32 and the excitation beam 94 follow the same optical path, detecting the reflected component 94' of the excitation beam using the imaging device 50 provides a visual representation of the analysis point within the fundus image obtained in the illumination mode.

[0068] It will be readily understood that in some embodiments, the excitation beam can include more than one excitation wavelength without departing from the scope of protection. By way of example, in coherent Raman spectroscopy applications, the excitation of a compound in a medium may be caused by the coherent absorption of two photons at different wavelengths, and thus the excitation beam 94 can include photons at these two wavelengths. In other embodiments, the excitation beam can have a spectral profile within a spectral band or range that includes the desired excitation wavelength or wavelengths and does not include the emission wavelength or wavelengths.

[0069] It is readily understood that the expression "analysis point" refers to an area or region on the patient's fundus or other medium being analyzed, from which the portion of the return light reaching the spectral analyzer originates. The analysis point can have different sizes and / or shapes, mainly determined by the optical design and configuration of the spectral reflectometer system.

[0070] Reference Figures 5A to 5E and 6 show examples of results obtained by implementing the methods and systems described herein. Figure 6Shows a possible timing diagram of control signals provided to a spectral analyzer 52, an imaging device 50, an illumination source 22, and an excitation source 90. According to some embodiments, a spectral reflectometer system may include a controller 80 (as Figure 1 shown), which generates control signals and is configured to operate in an illumination mode and an excitation mode. In some embodiments, the illumination mode and the excitation mode may operate alternately, while in other embodiments, they may operate simultaneously. The control signals may have various profiles, and it should be understood that Figure 6 the signals shown in Figure 6 are for illustrative purposes only. For example, while the control signal of the imaging device is shown as an AC signal in

[0071] In illumination mode I m , the illumination source 22 and the imaging device 50 are turned on, while the excitation light source 90 is turned off. As a result, an image of the fundus is acquired by the imaging device, such as for example Figure 5A shown. Optionally, the spectral analyzer 52 may also be turned on in illumination mode I m , in which case a spectral analysis of the analysis point may also be obtained, as Figure 5B shown. A spectral analysis is performed on a portion of the return light that is coupled to the spectral analysis path and reaches the spectral analyzer. It should be noted that the presence of a filter may remove spectral components from the light reaching the spectral analyzer, but in the case where the filter is designed to block external wavelengths at the spectral regions of interest for such analysis, this removal may not affect the results of the spectral analysis.

[0072] In excitation mode E m , the illumination source 22 is turned off, while the excitation light source 90 and the spectral analyzer 52 are turned on. Thus, the spectral analyzer receives the light emitted after the excitation of the fluorescent compound in the patient's fundus. As described above, the reflected light at the excitation wavelength is blocked or substantially attenuated by the filter before reaching the spectral analyzer. Figure 5C Shows an example of the light intensity versus wavelength information that can be obtained in this mode. This curve can be compared with the expected fluorescence from the reference data to diagnose the potential presence of a pathology. The imaging device 50 may also be turned on in this mode to collect an image of the analysis point, which will be displayed as a point in the field of view of the imaging device, such as Figure 5D shown. This image can be combined with or otherwise associated with the fundus image obtained in the illumination mode, so that the position of the analysis point on the fundus can be known and visualized, such as Figure 5E shown. In this way, the excitation beam also acts as an indicator beam similar to a "laser pointer" pointing to the analysis point, Figure 5B and Figure 5C the information on the two curve graphs of

[0073] In some embodiments, it may be advantageous to operate the illumination source in a continuous manner. Such operation can prevent an object from perceiving a flicker of light during acquisition.

[0074] Reference Figure 2 , shows a schematic diagram embodying the configuration of a spectral reflectometer system 20 according to an example.

[0075] As described above, the spectral reflectometer system 20 includes an imaging device 50. In some embodiments, the imaging device 50 may be embodied by a CCD or CMOS sensor or any surface that is sensitive and converts light intensity or energy into a useful signal. The imaging device 50 may include a processor, a computer, circuitry, or any other hardware component or collection of hardware components, or communicate with a processor, a computer, circuitry, or any other hardware component or collection of hardware components, which are programmed with instructions to construct, store, and display an image acquired by the imaging device 50. An integrated or separate display may be provided to allow an operator or user of the spectral reflectometer system 20 to view the resulting image.

[0076] The spectral analyzer 52 may be embodied by any suitable device or combination of devices that allows light to be analyzed as a function of wavelength. The spectral analyzer 52 may be embodied, for example, by a spectrometer. As is known to those skilled in the art, a spectrometer decomposes incident light according to its wavelength, typically using light refraction (e.g., using a prism) or light diffraction (using a diffraction grating), and includes a detector that measures the distribution intensity of the decomposed light. The spectral analyzer 52 may include a computer or processor programmed with instructions to analyze the detected spectrum according to predetermined parameters, such as those explained above. In some embodiments, the spectral analyzer 52 may be grating-based. However, it is readily understood that various other configurations and structural components may be used without departing from the scope of this specification. By way of example, the spectral analyzer 52 may include at least one dispersive element, such as a reflective or transmissive grating or prism. In other embodiments, the spectral analyzer 52 may include a plurality of individual photodetectors, each detecting a specific wavelength, for example, using an associated filter for detection. In another example, a single photodetector may be spectrally separated by another dichroic / polarizing / fiber optic circulator beam splitting device, similar to the one used to separate the imaging and spectral analysis optical paths.

[0077] The filter 96 may be embodied by any optical component having the desired light transmittance characteristics, such as low light transmittance at the excitation wavelength and high light transmittance at the emission wavelength. As described above, the filter 96 may be a long-pass filter, but in other variants, the filter 96 may be a band-pass filter, a short-pass filter, a dynamic filter, etc. Reference Figure 3A, in one embodiment, the filter 96 may include, for example, a pair of lenses, a first lens 98a coupled to the spectral analysis optical path 36 that collimates the incident light, and a second lens 98b that focuses the light into the spectral analyzer 52. The filter 99 of a possible embodiment has been described previously and is located between the two lenses. Refer to Figure 3B , in another embodiment, the filtering medium is a very thin filter directly deposited on the output surface of the optical fiber 70 that transmits light to the spectral analyzer 52. In some embodiments, the filter is a hard coating filter. In another embodiment, the filter is a stack of absorbing materials, interference coatings, and metal layers laminated together. It is readily understood that Figure 3A and Figure 3B the configurations of are provided only as examples, and other configurations that provide the desired filtering effect can be envisioned.

[0078] The excitation light source 94 may be embodied by any light source that generates a light beam 68 suitable for triggering fluorescence generation or other desired photoluminescence phenomena. In one example, the excitation light source 66 may be a laser diode. In other embodiments, the light source may be an LED with a specific filter that can be used via an optical fiber or simply at position 22. The excitation light beam 94 may have any wavelength or spectral content within the detection range of the imaging device that is safe for the patient's eyes (at least in ophthalmic applications) and is readily capable of generating fluorescence or other photoluminescence reactions from compounds present in the retina. The excitation light source may emit, for example, in the visible or near-infrared (NIR) spectral range. For example, lipofuscin present in A2E absorbs blue light, mostly between 450 and 480 nm. Using an NIR source near 787 nm will excite melanin.

[0079] The spectral reflectometer system 20 may further include an illumination light source 22 operable to generate illumination light 24, which may be projected towards the fundus 30 of the patient's eye 21 in an illumination mode. The illumination light source 22 may include one or more LED (light emitting diode) emitters. The LED emitters of a given illumination light source 22 may have selected similar optical characteristics or different complementary optical characteristics so as to obtain the desired optical characteristics of the illumination light 24 after combination. It will be readily understood that in alternative embodiments, many other variants of light sources such as lasers, OLEDs, fluorescent lamps, incandescent lamps, tungsten lamps, and other bulbs may be used. The expression "illumination light" is used herein to refer to electromagnetic radiation suitable for projection into the patient's eye 21 and used to induce, generate, or otherwise produce return light 32, which, upon appropriate analysis, can yield information of interest regarding the fundus 30 of the patient's eye 21. It will be readily understood that the term "light" is not considered limited to the visible portion of the electromagnetic spectrum. The illumination light 24 preferably has a broadband spectral profile that encompasses all wavelengths of interest for the spectral analysis that the system is configured to perform. In some variants, the illumination light may be white light. In other variants, the illumination light 24 may have a spectral profile designed in view of the field of use of the spectral reflectometer system 20. In another set of variants, the illumination light may have any other suitable spectral profile, as described by one or more factors such as the optical characteristics of the patient's eye, the availability of the light source, photoluminescence, and / or the nature and characteristics of the spectral analysis to be performed. By way of example, in some embodiments, the illumination light may have a selected spectral profile to perform autofluorescence imaging and / or mapping of the medium. For example, this can be used to locate fluorescent regions within the medium image and accordingly select the analysis points of the spectral analyzer. In some variants, autofluorescence imaging can be accomplished by using a narrowband electromagnetic source, such as an LED or laser emitting at the desired excitation wavelength as the illumination source, and providing a filter blocking at this wavelength anywhere within the imaging optical path (between the beam splitter 48 and the imaging device 50). In other variants, the illumination light source may combine broadband light with excitation light within the same light beam, providing an autofluorescence map overlaid on the medium image. This can be done, for example, by using a dichroic filter to combine light beams from multiple sources.

[0080] As described above, the spectral reflectometer system 20 may further include an optical assembly 26. The optical assembly 26 defines, on the one hand, an imaging optical path 34 between the patient's eye 21 and the imaging device 50, and on the other hand, a spectral analysis optical path 36 between the imaging optical path 34, the patient's eye 21, and the spectral analyzer 52.

[0081] It will be readily understood that the optical assembly 26 can be embodied in various configurations suitable for the purpose of illuminating the patient's eye and collecting the resulting return light. The optical assembly 26 can include one or more optical components configured to transmit an image of the fundus 30 onto the image plane 46. The optical components can include lenses, mirrors, polarizers, filters, etc. The optical components can be arranged in any suitable area generally known to those skilled in the art. The optical assembly 26 can further include other non-optical components, such as mechanical or electrical components that provide structural and / or functional support for the optical components, where the optical components are such as fixed or movable bases, screens, pinholes, stepper motors, etc.

[0082] The optical assembly 26 can include an illumination sub-assembly 28 that is optically coupled to the illumination source 22 and is configured to project the illumination light 24 from the illumination source 22 towards the fundus 30 of the patient's eye 21.

[0083] In the illustrated configuration, the illumination sub-assembly 28 includes a perforated mirror 38 positioned at an angle along the imaging optical path 34. The perforated mirror 38 has a central hole 39 that is aligned with the imaging optical path 34. Preferably, the illumination source 22 is positioned orthogonally to the eye of the patient 21, and the perforated mirror is at an angle of 45° with respect to the optical axis of the illumination light 24. In an alternative embodiment, the illumination sub-assembly 28 can include one or more optical components having variable light transmittance and reflection characteristics, such as a mirror designed to have a low reflectivity at the center and a high reflectivity around this center.

[0084] The illumination sub-assembly 28 can further include beam shaping optics that project the illumination light 24 from the illumination source 22 onto the perforated mirror 38 for reflection towards the fundus of the patient's eye. The beam shaping optics can include one or more optical components that interact with the illumination light 24.

[0085] It will be readily appreciated that the illumination sub - assembly 28 can be embodied by any suitable collection of optical components and attendant structural, mechanical, electrical, or other features that cooperate to bring illumination light from an illumination source to the patient's eye with desired optical characteristics. The components of the illumination sub - assembly can redirect, focus, collimate, filter, or otherwise act on the light in various ways. Those skilled in the art will readily appreciate that a variety of designs can provide such results. For example, in some variations, one or more optical fibers can be used to convey the illumination light 24 at least in part from the illumination source 22 to the fundus 30. It will be further appreciated that the illumination source 22 can be provided separately or integrally with the optical component 26. In one example, the optical component 26 can include a light port configured to receive the illumination light directly or indirectly from the illumination source. Those skilled in the art will readily appreciate that many optical configurations can embody the illumination sub - assembly. By way of example, one such configuration is shown in International Patent Application No. PCT / CA2018 / 051559, the contents of which are incorporated herein by reference in their entirety.

[0086] Still referring to Figure 2 as shown, the optical component 26 can further include the beam splitter 48 described above. The beam splitter 48 is positioned along the imaging optical path 34 and is configured to allow the direct imaging portion 54 of the return light 32 to travel to the imaging optical path 34 and deflect the spectral analysis portion 56 of the return light 32 to the spectral analysis optical path 36. It will be readily understood that although in the illustrated variation, the beam splitter 48 is configured and arranged to transmit the imaging portion 54 of the return light 32 and reflect the spectral analysis portion 56 of the return light 32, in other variations, it can be configured and arranged to reflect the imaging portion 54 towards the imaging device 50 and transmit through the photoluminescence analysis portion 56 to the spectral analyzer 52.

[0087] In some embodiments, the translatable focusing lens 37 can be positioned between the beam splitter 48 and the imaging device 50. In some embodiments, the translatable focusing lens 37 can be mounted on a suitable translation actuator to allow it to be displaced along the imaging optical path 34. Such movement displaces the imaging plane 46 to compensate for refractive index variations in different patient eyes. In other variations, the focusing lens 37 can have a variable focal length and can be adjusted by different means.

[0088] The imaging portion 54 of the return light 32 travels along the imaging optical path 34 until it reaches the imaging device 50 for detection. Of course, many optical components can be provided along the imaging optical path to collimate, focus, filter, redirect, or otherwise affect the imaging portion 54 before it reaches the imaging device 50. The beam - shaping optics 51 are indicated as a black - box representation of these components in Figure 2 the configuration shown.

[0089] The spectral analysis portion 56 of the return light 32 is deflected into the spectral analysis optical path 36 and is ultimately detected by the spectral analyzer 54. The spectral analysis optical path 36 is also optically coupled to the excitation light source 90 such that the excitation light beam 94 can travel in the reverse direction along the spectral analysis optical path 36 to the beam splitter 48. The operation of the excitation light source 66 and other features that can be provided along the spectral analysis optical path 36 will be further explained in detail below.

[0090] It will be readily understood that while in the illustrated variant the beam splitter 48 is configured and arranged to transmit the imaging portion 54 of the return light 32 and reflect the spectral analysis portion 56 of the return light 32, in other variants it can be configured and arranged to reflect the imaging portion 54 towards the imaging device 50 and transmit through the spectral analysis portion 56 towards the spectral analyzer 52 according to the polarization direction.

[0091] The beam splitter 48 can operate according to any of a variety of principles to separate the light incident thereon into different portions. In one embodiment, the beam splitter 48 is a dichroic beam splitter. As is well known to those skilled in the art, dichroic optical components affect light according to their spectral characteristics. The dichroic beam splitter 48 can have a spectral transmission profile suitable for the operation of the spectral reflectometer system 20.

[0092] In other embodiments, the beam splitter 48 can separate light according to other characteristics than spectral content. The beam splitter 48 can be configured, for example, to divide the return light 32 traveling along the imaging optical path 34 into an imaging portion and a spectral analysis portion according to an intensity ratio independent of the wavelength or polarization state of the light. In other variants, the beam splitter 48 can be configured to divide the return light 32 traveling along the imaging optical path 34 into an imaging portion and a spectral analysis portion.

[0093] Still referring to Figure 2 , in some embodiments, the optical assembly 26 includes first and second optical fiber links 70 and 72. The first optical fiber link 70 extends between the spectral analysis optical path 34 and the spectral analyzer 52. The second optical fiber link 72 extends between the spectral analysis optical path 34 and the excitation light source 90. The optical assembly 26 further includes a three-way coupler 74 that optically couples the spectral analysis optical path 34, the first optical fiber link 70, and the second optical fiber link 72.

[0094] The three-way coupler 74 can be embodied by various devices and / or configurations that provide an optical loop from the spectral analysis optical path 36 to the first optical fiber link 70, allowing the spectral analysis portion 56 of the return light 32 to reach the spectral analyzer 52, and from the second optical fiber link 72 to the spectral analysis path 36, allowing the excitation light beam 94 to be emitted towards the eye of the patient 21 in the system. Referring to Figures 4A to 4C , different variants of the three-way coupler 74 are shown. In the Figure 4A example, the three-way coupler 74 includes a multimode optical circulator. Figure 4BAnother variant is shown, in which the triple coupler 74 includes a double-clad optical fiber that can support the propagation of the indicator beam in the core, and the light collected by the spectral analysis region through the cladding is sent to the spectral analyzer. In this case, the core mode is optically coupled to the first optical fiber link, and the cladding mode is optically coupled to the second optical fiber link (and vice versa). In yet another variant, the triple coupler 74 can be a free-space configuration, such as a free-space beam splitting configuration 76.

[0095] Of course, many optical components can be provided along the spectral analysis optical path to collimate, focus, filter, redirect, or otherwise affect the spectral analysis section 56 before reaching the triple coupler 74. The beam shaping optics 78 are indicated as Figure 2 a black box representation of such components in the configuration shown in A. As an example, a lens 79 that focuses light onto the triple coupler 74 is also shown.

[0096] The spectral reflectometer system 20 can include additional components and functions.

[0097] In some embodiments, the spectral reflectometer system 20 can include a point moving device 86 located in the spectral analysis path 36 and configured to move the position of the analysis point above the fundus 30 of the patient's eye without affecting the imaging section 21. The point moving device 86 can include displacement optics, such as one or more steerable mirrors. The pivoting of the steerable mirror can be used to change the angle of incidence between the excitation beam 94 traveling along the spectral imaging optical path 36 and the beam splitter 48. Refer to Figure 7A and 7B , two examples of the configuration of the point moving device are shown. In Figure 7A , first and second mirrors 88a, 88b having displacements in both the phi and theta directions are used to change the angle of incidence of the excitation beam 94 onto the beam splitter 48. The displacement direction of the first mirror 88a is opposite to that of one of the second mirrors 88b, which is to keep the position of the excitation beam 94 on the beam splitter 48 and only change the angle of incidence and the position of the second mirror 88b. In Figure 7B , a gimbal mirror 89 is used instead of the second mirror 88b. This scheme, in combination with two lenses 90a and 90b used in a 4f configuration, can change the angle of incidence of the excitation beam 94 onto the beam splitter 48 without changing the position where the excitation beam 94 impinges on the beam splitter.

[0098] In some variants, a spectral reflectometer system 20 similar to the above system can be used to perform spectral analysis on a medium other than the fundus. For example, in some embodiments, the medium to be studied can be a bag of liquid, such as containing blood or plasma. In such a variant, the spectral reflectometer system can, for example, include Figure 2All of the same components of the system shown, including the optical component 26 and the illumination sub-component 28. In this variant, the illumination sub-component 28 may further include an additional output lens. The additional output lens may be added to Figure 2 the configuration of to provide focusing and form an image of the medium being detected on the imaging device 50. Those skilled in the art will readily understand that this method can provide an easy adaptation of the system originally envisioned for detecting the fundus 21, since such a concept takes into account the natural light focusing performed by the eye lens, which is essentially replaced by the additional output lens. In other variants, the output lens and the additional output lens may be replaced by a single lens or different optical arrangements.

[0099] According to another aspect, a method for photoluminescence analysis of a medium is provided.

[0100] In some embodiments of the method, the medium may be the fundus of a patient's eye, as described above. In other embodiments, the medium may not be the eye, but may be, for example, skin, organ tissue, exposed muscle tissue, and other biological tissues or fluids. In some embodiments, the medium under study may be an in vitro sample, such as blood, tissue, etc., stored in a transparent container, such as a bag, vial, syringe, or cuvette, or on a suitable substrate.

[0101] The method first includes providing an imaging device, a spectral analyzer, an optical component that defines an imaging optical path between the medium and the imaging device and a spectral analysis optical path between the analysis point on the medium and the spectral analyzer, an excitation light source optically coupled to the spectral analysis path and operable to generate an excitation beam at an excitation wavelength selected to excite components present in the medium to generate photoluminescence light at an emission wavelength different from the excitation wavelength, and a filter coupled to the spectral analyzer, a filter having a low transmittance at the excitation wavelength and a high transmittance at the emission wavelength, and an illumination light source. Of course, it is readily understood that systems such as those described above may be used.

[0102] The method further includes operating the illumination light source to project illumination light onto the medium, and operating the imaging device to obtain an image of the medium. Optionally, the excitation light source may be operated together with the imaging device to further obtain an image of the analysis point. The image of the analysis point may be superimposed on the image of the medium, as Figure 5E shown. In this way, the operator can, for example, visualize from the fundus area where the photoluminescence analysis is obtained.

[0103] The method further includes operating the excitation light source to project the excitation beam onto the analysis point and the spectral analyzer to obtain a photoluminescence measurement of the analysis point on the fundus. The photoluminescence measurement may be one of absorbance measurement, fluorescence measurement, autofluorescence measurement, spontaneous Raman spectroscopy measurement, and coherent Raman spectroscopy measurement.

[0104] Then photoluminescence measurements can be used to provide an analysis of one or more parameters from the medium. As described above, such data can be used, for example, to quantify lipofuscin granules in a patient's fundus.

[0105] Of course, various modifications can be made to the above embodiments without departing from the scope of the invention described in the appended claims.

Claims

1. A system for performing photoluminescence analysis on a medium, comprising: - An illumination subassembly configured to project illumination light towards the medium, and an illumination light source, The illumination light source being operable to generate the illumination light and optically coupled to the illumination subassembly; - An imaging device configured to acquire an image of the medium including an analysis point; - An excitation light source operable to generate an excitation beam including an excitation wavelength selected to excite a component present in the medium for generating photoluminescence light at an emission wavelength different from the excitation wavelength; - A spectral analyzer; - An optical assembly defining an imaging optical path between the medium and the imaging device and a spectral analysis optical path between the analysis point on the medium and the spectral analyzer, the excitation light source being optically coupled to the spectral analysis optical path for projecting the excitation beam onto the analysis point, the spectral analyzer being configured to analyze the light returned from the analysis point as a function of wavelength; And - A filter coupled to the spectral analyzer, the filter having a low light transmittance at the excitation wavelength and a high light transmittance at the emission wavelength.

2. The system according to claim 1, comprising a beam splitter positioned and configured to direct an imaging portion of the returned light from the medium traveling along the imaging optical path to the imaging device and a spectral analysis portion of the returned light to the spectral analysis optical path.

3. The system according to claim 2, wherein The beam splitter is a dichroic beam splitter.

4. The system according to claim 3, wherein, The beam splitter is configured to divide the light traveling along the imaging optical path into the imaging portion and the spectral analysis portion according to one of an intensity ratio and a polarization direction.

5. The system according to claim 1, comprising: a) A first optical fiber link extending between the spectral analysis optical path and the spectral analyzer; b) A second optical fiber link extending between the spectral analysis optical path and the excitation light source; And c) A three-way coupler optically coupling the spectral analysis optical path, the first optical fiber link, and the second optical fiber link.

6. The system according to claim 5, wherein, The three-way coupler includes one of a multimode optical circulator, a double-clad optical fiber, and a free-space beam splitting configuration.

7. The system according to claim 5, wherein, The filter includes a free-space optical component disposed between the first optical fiber link and the spectral analyzer.

8. The system according to claim 5, wherein, The filter includes a thin film deposited on an optical fiber-based component disposed between the first optical fiber link and the spectral analyzer.

9. The system according to claim 1, wherein The filter is a long-pass filter.

10. The system according to claim 1, wherein The filter is a band-pass filter.

11. The system according to claim 1, further comprising a controller that generates control signals for controlling the illumination light source, the imaging device, the spectral analyzer, and the excitation light source.

12. The system according to claim 11, wherein, The controller is configured to operate in the following modes: - An illumination mode, in which the controller turns on at least the illumination device and the imaging device; and - An excitation mode, in which the controller turns on at least the excitation light source and the spectral analyzer.

13. The system according to claim 1, further comprising a controller configured to operate in the following modes: - A lighting mode, wherein the controller operates the lighting device to project the lighting light towards the medium, operates the imaging device to obtain an image of the medium, and operates the spectral analyzer to obtain a spectral analysis of the analysis point on the medium; and - An excitation mode, wherein the controller operates the excitation light source to project the excitation light beam onto the analysis point, and operates the spectral analyzer to obtain a photoluminescence analysis of the analysis point on the medium.

14. The system according to claim 1, further comprising a point moving device positioned in the spectral analysis optical path and configured to move the position of the analysis point on the medium.

15. The system according to any one of claims 1 to 14, configured to perform a photoluminescence analysis on the fundus of a patient's eye as the medium.

16. Use of the system according to any one of claims 11 to 14 for performing a photoluminescence analysis on the fundus of a patient's eye.

17. The use according to claim 16, wherein, The photoluminescence analysis includes one of absorbance measurement, fluorescence measurement, autofluorescence measurement, spontaneous Raman spectroscopy, and coherent Raman spectroscopy.

18. A method for performing a photoluminescence analysis on a medium, comprising: a) providing an imaging device, a spectral analyzer, an optical component, an excitation light source, and a filter coupled to the spectral analyzer, and a lighting light source, the optical component defining an imaging optical path between the medium and the imaging device and a spectral analysis optical path between an analysis point on the medium and the spectral analyzer, the excitation light source being optically coupled to the spectral analysis path and operable to generate an excitation light beam, the excitation light beam including an excitation wavelength selected to excite components present in the medium for generating photoluminescence light at an emission wavelength different from the excitation wavelength, the filter having a low light transmittance at the excitation wavelength and a high light transmittance at the emission wavelength; b) operating the lighting light source to project lighting light towards the medium, and operating the imaging device to acquire an image of the medium; and c) operating the excitation light source to project the excitation light beam onto the analysis point, and operating the spectral analyzer to obtain a photoluminescence measurement of the analysis point on the fundus.

19. The method according to claim 18, further comprising operating the excitation light source and the imaging device to obtain an image of the analysis point.

20. The method according to claim 19, further comprising the step of superimposing the image of the analysis point on the image of the medium.

21. The method according to claim 18, wherein, The medium is the fundus of a patient's eye.

22. The method according to any one of claims 18 to 21, wherein, The photoluminescence measurement includes one of absorbance measurement, fluorescence measurement, autofluorescence measurement, spontaneous Raman spectroscopy measurement, and coherent Raman spectroscopy measurement.

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