Home OCT with Automatic Focus Adjustment

Abstract

An optical coherence tomography (OCT) system for imaging the retina applies a user-specific focus correction to focus a sample arm beam on the user's retina. An OCT image detector generates an OCT signal. A control unit monitors the OCT signal, controls a reference arm optical path length adjustment mechanism to identify the length of the reference arm optical path when the OCT signal corresponds to an OCT image of the retina, and changes operating parameters of the sample arm beam focusing mechanism within a range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina, thereby identifying a user-specific focus correction to be applied to the sample arm beam based on the OCT signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Application No. 16 / 439,587, filed June 12, 2019, the entire contents of which are hereby incorporated herein in their entirety for all purposes. Background Art

[0003] Macular degeneration is the leading cause of vision loss in the United States. In macular degeneration, the central part of the retina, also known as the macula, deteriorates. When healthy, the macula collects and sends highly detailed images to the brain via the optic nerve. In the early stages, macular degeneration usually does not significantly affect vision. If macular degeneration progresses beyond the early stages, vision will become choppy and / or blurry. If macular degeneration continues to progress to the later stages, central vision may be lost.

[0004] Although macular degeneration is currently considered incurable, there are treatments that can slow the progression of the disease to prevent severe vision loss. Treatment options include: injection of anti-angiogenic drugs into the eye, laser therapy to destroy actively growing (multiple) abnormal blood vessels, and photodynamic laser therapy using light-sensitive drugs to destroy (multiple) abnormal blood vessels. Early detection of macular degeneration is crucial to preventing the late progression of macular degeneration before treatment to inhibit disease progression. Timely treatment of late-stage AMD is important to maintain patient vision.

[0005] Early detection of macular degeneration and timely treatment decisions can be accomplished using appropriate retinal imaging systems. For example, optical coherence tomography (OCT) is a non-invasive imaging technique that relies on low-coherence interferometry that can be used to generate cross-sectional images of the macula. A cross-sectional view of the macula shows whether the macular layer is deformed and can be used to monitor whether the macular layer deformation has increased or decreased relative to an earlier cross-sectional image to assess the impact of macular degeneration treatment. However, existing OCT imaging systems are generally expensive and may have to be operated by trained technicians. Summary of the Invention

[0006] The following presents a simplified overview of some embodiments of the present invention in order to provide a basic understanding of the present invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key / critical elements of the present invention or to delineate the scope of the present invention. Its sole purpose is to present some embodiments of the present invention in a simplified form as a prelude to the detailed description presented later.

[0007] An optical coherence tomography (OCT) system and related methods for imaging a user's retina employ a coupling optical assembly with no moving parts, a viewer assembly, a sample arm beam focusing mechanism, an OCT image detector, and a control unit. The viewer assembly is configured to constrain the user's head to maintain a fixed distance between the user's retina and the coupling optical assembly. The sample arm beam focusing mechanism is separate from the coupling optical assembly. The sample arm beam focusing mechanism provides focusing of the sample arm beam on the user's retina to account for the specific focusing characteristics of the user's eye. The control unit monitors OCT signals generated by the OCT image detector while controlling variations in operating parameters of the sample arm beam focusing mechanism within a range to identify user-specific focus corrections to be applied to the sample arm beam based on the OCT signals. Because the coupling optical assembly has no moving parts, the cost of the OCT system is reduced relative to OCT systems employing coupling optical assemblies with moving parts. Furthermore, because the OCT system is configured to image the retina while maintaining a fixed distance between the coupling optical assembly and the retina, the user can operate the OCT system without the assistance of a trained technician, making the OCT system suitable for home-based imaging of the user's retina to monitor the onset and / or progression of macular degeneration.

[0008] Therefore, in one aspect, an optical coherence tomography (OCT) system for imaging the retina of a user is configured to be operated by the user and has coupling optical devices with no moving parts. The OCT system includes a wide-bandwidth light source, a beam splitter, a reference arm optical path, a reference arm optical path length adjustment mechanism, a sample arm optical path, an objective lens, an observer assembly, a scanning unit, a sample arm beam focusing mechanism, an OCT image detector, and a control unit. The wide-bandwidth light source emits a light beam. The beam splitter splits the light beam into a sample arm beam and a reference arm beam, and recombine the return portion of the sample arm beam with the reference arm beam to form a recombined light beam. The reference arm beam propagates on the reference arm optical path. The sample arm beam and the return portion of the sample arm beam propagate on the sample arm optical path. The objective lens is disposed on the sample arm optical path. The observer assembly is configured to constrain the user's head so that the sample arm optical path extends to the retina. The scanning unit scans the sample arm beam in two dimensions transverse to the propagation direction of the sample arm beam. The sample arm beam focusing mechanism can be controlled to change the focus of the sample arm beam on the retina. The OCT image detector generates an OCT signal of the recombined light beam. The control unit is operatively connected to the OCT image detector, the reference arm optical path length adjustment module, and the sample arm beam focusing mechanism. The control unit is configured to: (a) monitor the OCT signal, (b) control the reference arm optical path length adjustment mechanism to change the reference arm optical path length to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina, and (c) change an operating parameter of the sample arm beam focusing mechanism within a range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina to identify a user-specific focus correction to be applied to the sample arm beam based on the OCT signal.

[0009] In many embodiments, an OCT system includes a display device and a display device focus mechanism. A fixation target is displayed to a user via the display device. The display device focus mechanism is controllable to change the focus of an image of the fixation target on the retina. In many embodiments, a control unit is operably connected to the display device focus mechanism. In many embodiments, the control unit is configured to: (a) determine a focus setting for the display device focus mechanism based on a focus correction applied by the sample arm beam focus mechanism for user identification, and (b) control the display device focus mechanism to operate at the focus setting of the display device focus mechanism. In some embodiments, the control unit uses a lookup data table to determine the focus setting of the display device focus mechanism corresponding to the focus correction applied by the sample arm beam focus mechanism for user identification. In some embodiments, the display device focus mechanism includes a display device focus lens that is repositionable relative to the display device, and the focus setting of the display device focus mechanism corresponds to a corresponding position of the display device focus lens relative to the display device. In some embodiments, the display device focus mechanism is operable to change the focus of the image of the fixation target on the retina over a range of at least 15 diopters. In some embodiments, the sample arm beam focus mechanism is operable to change the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0010] In many embodiments, the OCT system is configured to constrain the user's head to maintain the retina in a fixed position on the optical path of the sample arm. For example, in many embodiments, the viewer assembly is configured to engage the user's facial features to constrain the user's head and define the distance between the eye and the objective lens. The distance between the objective lens and the eye is not controllable by the OCT system or the operator of the OCT system.

[0011] Any suitable method can be used to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina. For example, the control unit can process the OCT signal to generate an OCT image, and the OCT image is processed by the control unit using an image processing method to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina.

[0012] Any suitable method may be used to identify the focus correction for the user. For example, the control unit may process the OCT signal to generate an OCT image, which is processed by the control unit using an image processing method to identify the focus correction for the user.

[0013] In many embodiments of the OCT system, the sample arm beam focusing mechanism is disposed in the sample arm optical path between the beam splitter and the scanning unit. In some embodiments, the sample arm beam focusing mechanism comprises a controllable liquid lens.

[0014] In some embodiments, the control unit: (a) controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within a range that encompasses all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism, (b) determines candidate lengths for the reference arm optical path length, wherein each of the candidate lengths is determined based on a corresponding intensity of an OCT signal, and (c) selects the candidate length having the highest corresponding intensity of the OCT signal as the length of the reference arm optical path when the OCT signal corresponds to the retinal OCT image. In some embodiments, the range encompassing all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism covers no more than 50 mm.

[0015] In many embodiments, the OCT system is configured to monitor the alignment of a user's pupil with a sample arm optical path. For example, in many embodiments, the OCT system includes a pupil camera, a pupil imaging optical path, a pupil illumination light source, and a dichroic mirror that couples the pupil imaging optical path with the sample arm optical path. In many embodiments, a control unit is operatively coupled to the pupil camera and processes the output of the pupil camera to detect whether the pupil is open and aligned with the sample arm optical path. In some embodiments, the length of the reference arm optical path is changed only when the pupil is open and aligned with the sample arm optical path.

[0016] In many embodiments of the OCT system, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina within a suitable range to accommodate optical differences in the target user population. For example, in some embodiments, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina within a range of at least 15 diopters. In some embodiments, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina within a maximum range of no more than 25 diopters.

[0017] In many embodiments, the OCT system is configured to produce retinal images with a suitable level of resolution. For example, in some embodiments, the integration time of the a-scan is greater than 50 microseconds.

[0018] In many embodiments, the OCT system includes a telescope assembly having no moving parts. For example, in many embodiments, the OCT system includes a telescope assembly comprising an objective lens and a second lens, wherein each of the objective lens and the second lens has a fixed position in the sample arm optical path.

[0019] In another aspect, a method for imaging a user's retina using an OCT system is provided. The method includes emitting a light beam from a broadband light source. The light beam is split into a sample arm beam and a reference arm beam. The sample arm beam propagates through a sample arm beam focusing mechanism to apply focus correction to the sample arm beam. The focus-corrected sample arm beam is scanned by a scanning unit in two dimensions transverse to the propagation direction of the sample arm beam to generate a scanned sample arm beam. The scanned sample arm beam propagates through an objective lens. The user's head is constrained by an observer assembly so that the scanned sample arm beam is incident on the retina. The reference arm beam propagates along the reference arm beam optical path. A return portion of the scanned sample arm beam is recombined with the reference arm beam to generate a recombined beam. The recombined beam propagates to an OCT image detector 62. The OCT image detector generates an OCT signal for the recombined beam. A control unit monitors the OCT signal. The control unit controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path to identify the length of the reference arm optical path when the OCT signal corresponds to an OCT image of the retina. The control unit changes an operating parameter of a sample arm beam focusing mechanism within a range while maintaining a length of a reference arm optical path when the OCT signal corresponds to an OCT image of the retina, so as to identify a user-specific focus correction to be applied to the sample arm beam based on the OCT signal. In some embodiments, the sample arm beam focusing mechanism includes a controllable liquid lens.

[0020] In many embodiments, the method includes operating a display device focus mechanism at a setting corresponding to a focus correction applied by the sample arm beam focus mechanism for a user-identified focus correction. For example, in many embodiments, the method includes: (a) causing light from the display device to propagate through the display device focus mechanism to the retina, (b) determining, by a control unit, a focus setting for the display device focus mechanism based on the focus correction applied by the sample arm beam focus mechanism for the user-identified focus correction, and (c) controlling, by the control unit, the display device focus mechanism to operate at the focus setting for the display device focus mechanism. In many embodiments of the method, the control unit accesses a lookup data table to determine the focus setting for the display device focus mechanism. In some embodiments of the method, the display device focus mechanism includes a display device focus lens that is repositionable relative to the display device, and the focus setting for the display device focus mechanism corresponds to a corresponding position of the display device focus lens relative to the display device. In some embodiments of the method, the display device focus mechanism is operable to change the focus of an image of a fixation target on the retina over a range of at least 15 diopters. In some embodiments of the method, the display device focus mechanism is operable to change the focus of an image of a fixation target on the retina over a maximum range of no more than 25 diopters. In some embodiments of the method, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters. In some embodiments of the method, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a maximum range of no more than 25 diopters.

[0021] In many embodiments of the method, the viewer assembly engages facial features of the user to constrain the user's head and define a distance between the eyes and the objective lens. In many embodiments of the method, the distance between the objective lens and the eyes is set by the user's facial features and is not controlled by the OCT system or an operator of the OCT system.

[0022] In many embodiments of the method, a control unit: (a) controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within a range that encompasses all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism, (b) determines candidate lengths for the reference arm optical path length, wherein each of the candidate lengths is determined based on a corresponding intensity of an OCT signal, and (c) selects the candidate length having the highest corresponding intensity of the OCT signal as the length of the reference arm optical path when the OCT signal corresponds to the retinal OCT image. In some embodiments of the method, the range encompassing all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism does not exceed 50 mm.

[0023] In many embodiments, the method includes processing, by a control unit, an output of the pupil camera to detect whether the pupil is open and aligned with the sample arm optical path. In some embodiments of the method, the length of the reference arm optical path is changed only when the pupil is open and aligned with the sample arm optical path.

[0024] In many embodiments of the method, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina within a suitable range to accommodate optical differences among a target user population. For example, in some embodiments, the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina within a range of at least 15 diopters.

[0025] In many embodiments of the method, an image of the retina is generated with a suitable level of resolution. For example, in some embodiments of the method, the integration time of the a-scan is greater than 50 microseconds.

[0026] In many embodiments of the method, a telescope assembly with no moving parts is employed. For example, in many embodiments of the method, the sample arm beam propagates through a telescope assembly comprising an objective lens and a second lens, wherein each of the objective lens and the second lens has a fixed position in the sample arm optical path.

[0027] Any suitable method can be used to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina. For example, in some embodiments, the method includes processing the OCT signal by a control unit to generate an OCT image; and processing the OCT image by the control unit using an image processing method to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina.

[0028] Any suitable method can be used to identify the focus correction for the user. For example, in some embodiments, the method includes processing, by a control unit, an OCT signal to generate an OCT image; and processing, by the control unit, the OCT image using an image processing method to identify the focus correction for the user.

[0029] For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A user is shown looking into a viewing port of an optical coherence tomography (OCT) system for imaging the retina, in accordance with some embodiments.

[0032] Figure 2 yes Figure 1 Simplified schematic diagram of an OCT system showing the components of the OCT imaging device and the associated optical pathways.

[0033] Figure 3 yes Figure 1 Simplified schematic diagram of the components of an OCT system.

[0034] Figure 4a and Figure 4b A simplified schematic block diagram illustrating acts of a method of imaging a user's retina according to an embodiment is shown.

[0035] Figures 5a to 5h OCT images generated during the search for the reference arm path length when the OCT signal corresponds to the OCT image of the strong eye retina are shown.

[0036] Figure 6 Example OCT images showing the reference arm path length when the OCT signal corresponds to an OCT image of the strong eye retina after applying a user-specific focus correction to the sample arm beam.

[0037] Figures 7a to 7c An OCT image during the reference arm path length when searching for an OCT signal corresponding to an OCT image of the retina of the amblyopic eye is shown.

[0038] Figure 8 Example OCT images showing the reference arm path length after applying a user-specific focus correction to the sample arm beam, when the OCT signal corresponds to an OCT image of the retina of an amblyopic eye.

[0039] Figure 9 Shows that it can be Figure 4a and Figure 4b A simplified schematic block diagram of the actions of a process used in the method for identifying a reference arm optical path length when an OCT signal corresponds to an OCT image of the retina.

[0040] Figure 10 Shown in Figure 9 A fast Fourier transform is performed on it during the process to generate an example spectrum of the corresponding A-scan.

[0041] Figure 11 Shown in Figure 10 Example OCT images during the process of fine-tuning the reference arm optical path length.

[0042] Figure 12 Shows that it can be Figure 4a and Figure 4b A simplified schematic block diagram of the actions used in the method for identifying a user-specific focus correction process is shown.

[0043] Figure 13 Shows that it can be combined Figure 4a and Figure 4bThe method shown is a simplified schematic block diagram of the acts of completing a process. DETAILED DESCRIPTION

[0044] In the following description, various embodiments of the present invention will be described. For illustrative purposes, specific configurations and details are set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the present invention can be practiced without these specific details. Furthermore, well-known features may be omitted or simplified to avoid obscuring the described embodiments.

[0045] introduce

[0046] Many patients with retinal diseases are treated with intraocular injections according to general guidelines based on the average patient. However, the progression of retinal disease in any particular patient may progress in a different manner than in the average patient. In addition, a particular patient may respond differently to treatment than the average patient. Therefore, there is a strong clinical need to monitor the progression of retinal disease in some patients on an ongoing basis so that patients can receive treatment based on their own disease progression. Ophthalmic imaging devices such as optical coherence tomography (OCT) imaging are commonly used in ophthalmology clinics to image the patient's retina to monitor the progression of retinal disease. However, having to travel to an ophthalmology clinic may hinder adequate ongoing monitoring of some patients. Therefore, there is a need for an affordable OCT-based ophthalmic imaging device that can be used by patients at home to continuously monitor the progression of their retinal disease. The retinal disease may be a chorioretinal eye disease such as AMD, ocular histoplasmosis, myopia, central serous retinopathy, central serous choroidopathy, glaucoma, diabetic retinopathy, retinitis pigmentosa, optic neuritis, epiretinal membranes, vascular abnormalities and / or occlusions, choroidal dystrophy, retinal dystrophy, macular hole, or choroidal or retinal degeneration.

[0047] OCT imaging of the retina typically involves focusing the sample arm beam onto the retina to improve the resolution of the OCT images of the retina. Typically, OCT imaging of the retina is performed without the subject wearing glasses or contact lenses. Differences in the optical properties of different eyes result in different amounts of focus correction being applied to the sample arm beam for different subjects. Additionally, OCT imaging of the retina typically involves the subject gazing at a fixation target to control eye orientation and alignment during the imaging session. Focus correction is typically applied to also focus the fixation target for the subject.

[0048] Many existing OCT systems apply focus correction to the sample arm beam using methods that increase system complexity and / or require highly trained technicians to operate the OCT system. For example, some existing OCT systems employ movement of an objective lens (i.e., a coupling optical lens located closest to the subject's eye) relative to the eye to apply focus correction. In some existing OCT systems, movement of the objective lens relative to the eye is accomplished by the technician moving the OCT system relative to the eye. In some existing OCT systems, the OCT system moves the objective lens relative to the eye. Some existing OCT systems employ a focus detector, such as a fundus camera, that generates an output indicating how the sample arm beam is currently focused on the retina for use in controlling the amount of focus correction applied to the sample arm beam. Some existing OCT systems employ a coupling optical assembly, such as a telescope assembly, that includes two lenses, and the amount of focus correction applied to the sample arm beam is varied by varying the distance between the two lenses of the telescope assembly. A significant advantage of the methods of applying focus correction to the sample arm beam used in many existing OCT systems is that the same focusing mechanism focuses both the sample arm beam onto the retina and the subject's gaze target. In many existing systems, once focus correction is applied, the length of the reference arm optical path is changed to search for the length of the reference arm optical path at which the OCT detector generates a signal based on which an OCT image of the retina can be generated.

[0049] However, the increased system complexity and / or the need for trained technicians to operate the OCT system are undesirable in a home OCT system. For example, moving the objective lens relative to the retina may require movement of the OCT system relative to the retina, which complicates the operation of the OCT system. As another example, the use of a focus detector increases system complexity and cost.

[0050] Retinal imaging OCT system for non-clinical settings

[0051] Affordable retinal imaging OCT systems and related methods suitable for use in non-clinical settings (e.g., in a patient's home) are described herein, thereby reducing the costs associated with monitoring the progression of retinal disease in patients. Referring now to the drawings, in which like reference numerals represent like parts throughout the several views, Figure 1 The user 12 is shown looking into the viewing port 14 of the viewing assembly 16 of the retinal imaging OCT system 10, according to many embodiments. In many embodiments, the viewing assembly 16 is configured to position one eye of the user 12 approximately on the optical axis 20 of the OCT system 10. For example, Figure 1, viewing assembly 16 is configured to position the right eye of user 12 approximately on optical axis 20. In many embodiments, viewing assembly 16 is repositionable relative to optical axis 20 so as to reconfigure viewing assembly 16 to position the left eye of user 12 approximately on optical axis 20. Accordingly, each of the right and left eyes of user 12 can be selectively positioned approximately on optical axis 20 of OCT system 10 for imaging of the respective eye by retinal imaging OCT system 10. In the embodiments described herein, the final positioning and alignment of the optical axis of the respective eye of user 12 with the optical axis 20 of imaging system 10 is accomplished by user 12 adjusting the user's position relative to viewing port 14 in response to feedback provided to user 12 by OCT system 10.

[0052] Figure 2 FIG1 is a simplified schematic diagram of the components and associated optical paths of the OCT imaging device 30 of the OCT system 10. The OCT imaging device 30 includes a broadband light source 32, a beam splitter 34, a reference arm optical path 36, a reference arm optical path length adjustment mechanism 38, a sample arm beam focusing mechanism 40, a scanning unit 42, a first dichroic mirror 44, a coupling optical assembly 46 including a fixed-position objective lens 48 and a fixed-position rear lens 50, a second dichroic mirror 52, a display device 54, a display device focusing mechanism 56, a pupil camera 58, an eye illuminator 60, and an OCT image detector 62. In the illustrated embodiment, the OCT imaging device 30 is a spectral domain OCT imaging device operating in the wavelength range of 800 nm to 900 nm. The eye illuminator 60 illuminates the eye 64 of the user 12 using a suitable wavelength of light (e.g., above 920 nm). The display device 54 can project light at any suitable wavelength (e.g., from 400 nm to 700 nm). The first dichroic mirror 44 transmits the display device wavelength range and reflects the OCT wavelength. The second dichroic mirror 52 transmits the OCT wavelength and the display wavelength range (400 nm to 900 nm) and reflects the illumination wavelength (eg, greater than 920 nm) to the pupil camera 58 .

[0053] In operation, a broadband light source 32 emits a beam of light having an OCT wavelength. The beam of light propagates from the light source 32 to a beam splitter 34. The beam splitter splits the beam of light into a sample arm beam and a reference arm beam.

[0054] The reference arm beam propagates on the reference arm optical path 36 and then returns to the beam splitter 34. The reference arm optical path 36 includes a reference arm optical path length adjustment module 38, which is controlled by the control unit 64 (see Figure 3 ) is operable under the control of a motorized movable mirror 32 that selectively changes the length of the reference arm optical path 36. The reference arm optical path length adjustment module 38 may have any suitable configuration. For example, the reference arm optical path length adjustment module 38 may include a motorized movable mirror that is controllably displaceable.

[0055] The sample arm beam propagates from the beam splitter 34 to a sample arm beam focusing mechanism 40. The sample arm beam focusing mechanism 40, under the control of a control unit 64, is operable to selectively apply a focus correction to the sample arm beam to focus the sample arm beam onto the retina of the eye 64. The sample arm beam focusing mechanism 40 provides for focusing of the sample arm beam on the retina of the user so as to account for the specific focusing characteristics of the user's eye 64.

[0056] The sample arm beam, to which the focus correction is applied, propagates from the sample arm beam focusing mechanism 40 to the scanning unit 42. The scanning unit 42 is operable, under the control of the control unit 64, to scan the sample arm beam in two dimensions transverse to the propagation direction of the sample arm beam. The scanning unit 42 can have any suitable configuration. For example, in many embodiments, the scanning unit 42 includes a dual-axis scanning mirror.

[0057] The scanned sample arm beam propagates from the scanning unit 42 to the first dichroic mirror 44 .

[0058] The scanned sample arm beam is reflected by first dichroic mirror 44 so as to propagate through coupling optics 46 by propagating through fixed-position rear lens 50, second dichroic mirror 52, and fixed-position objective lens 48. From fixed-position objective lens 48, the scanned sample arm beam propagates into eye 64 and onto the retina of eye 64.

[0059] The return portion of the scanned sample arm beam returns from the retina and passes through the fixed objective lens 48, the second dichroic mirror 52, and the fixed rear lens 50. The return portion of the sample arm beam is reflected back to the scanning unit 42 by the first dichroic mirror 44. The return portion of the sample arm beam is redirected by the scanning unit 42 and returns to the beam splitter 34 through the sample arm beam focusing mechanism 40. The return portions of the sample arm beam and the reference arm beam are recombined by the beam splitter 34 to form a recombined beam. The recombined beam is transmitted to the OCT image detector 62.

[0060] The OCT image detector 62 generates and outputs OCT image signals that are processed using known techniques to construct a three-dimensional OCT image of the various layers of the retina. In many embodiments, the OCT image detector 62 detects interference between the reference arm light and the returning sample arm light only when the travel time of the light in the reference arm and sample arms is approximately equal. In many embodiments, the reference arm optical path length adjustment module 38 includes a mirror mounted to a motorized mechanism that is controllable to change the position of the mirror, thereby controllably changing the length of the reference arm optical path 36. The ability to change the length of the reference arm optical path 36 enables the OCT imaging device 30 to be used to generate OCT images of the retina of any user from a desired user population, even if each user's retina may be at a different distance from the fixed objective lens 48 when the user's head is engaged with the viewer assembly 16 due to corresponding anatomical variations between the users' heads and variations in the relative position of the user's head and the viewer assembly 16.

[0061] In many embodiments, the eye illuminator 60, pupil camera 58, and display device 54 are used to provide feedback to the user 12 by which the user 12 self-aligns the eye 64 with the optical axis of the OCT imaging device 30. The display device 54 displays a fixation target for the user to view to align the eye 64 with the fixation target. The display device focusing mechanism 56, under the control of the control unit 64, is operable to selectively apply focus correction light emitted by the display device 54 so that the fixation target displayed by the display device 54 is in focus for the user 12 even when imaging of the user's retina is performed without the user 12 wearing glasses or contact lenses. Similar to the sample arm beam focusing mechanism 40, the display device focusing mechanism 56 provides for focusing an item displayed by the display device 54 (e.g., a fixation target) onto the user's retina to account for the specific focusing characteristics of the user's eye 64.

[0062] In many embodiments, the OCT imaging device 30 is configured to automatically control the components / modules of the OCT imaging device 30 during an imaging session (generating an OCT image of the user's retina during the imaging session). In many embodiments, the OCT imaging device 30 includes a suitable control unit that is operably connected to the components / modules of the OCT imaging device 30 and is configured to communicate with and / or control the components / modules. For example, Figure 3is a simplified schematic diagram illustrating the components / modules of an embodiment of an OCT imaging device 30, which includes a control unit 64 operatively coupled to the components / modules. The control unit 64 includes a processor 66 and a data storage device 68. The data storage device 68 stores program instructions that are executable by the processor 66 to perform the actions described herein. The data storage device 68 may also store user-specific data that the processor 66 may use to customize its control of the operation of the OCT imaging device 30 to a specific user, as described.

[0063] The control unit 64 is operatively connected to a user interface 70 to receive input from the user 12 via the user interface 70 and / or to display output to the user 12 via the user interface 70. Any suitable user interface 70 may be employed, including, but not limited to, one or more buttons, a display, a touch display, one or more indicator lights, and / or a speaker. The user interface 70 may be configured to enable a user to input a user's identification for an imaging session, such that the control unit 30 may use parameters stored in the data storage device 68 when controlling the components / modules of the OCT imaging device 30 during the imaging session of the retina of the user 12.

[0064] The control unit 64 is operably connected to the eye illuminator 60, the pupil camera 58, and the display device 54. The control unit 64 can turn on the eye illuminator 60 at the beginning of an imaging session and turn off the eye illuminator 60 at the end of the imaging session. In many embodiments, the control unit 64 turns on the pupil camera 58 at the beginning of the imaging session, receives image data from the pupil camera 58, processes the image data to track the position of the optical axis of the eye 64 relative to the optical axis of the OCT imaging device 30, and turns off the pupil camera 58 at the end of the imaging session. In many embodiments, the control unit 64 turns on the display device 54 at the beginning of the imaging session, generates feedback on the display device 54 and displays the feedback (e.g., a gaze target) to the user 12 to enable the user 12 to reposition the user's head relative to the viewer assembly 16 to align the user's eye 64 sufficiently with the optical axis of the OCT imaging device 30 for generating an OCT image of the user's retina, and turns off the display device 54 at the end of the imaging session.

[0065] The control unit 64 is operatively connected to the broadband light source 32, the reference arm optical path length adjustment module 38, the sample arm beam focusing mechanism 40, the scanning unit 42, the display device focusing mechanism 56, and the OCT image detector 62 to control the operation of these components / modules and / or receive input from these components / modules during an OCT imaging session of the retina of the user 12. The control unit 64 can turn on the broadband light source 32 at the beginning of the OCT scanning portion of the imaging session to begin transmitting an OCT wavelength beam on the sample arm and the reference arm, and can turn off the light source 32 at the end of the imaging session. The control unit 64 can control the reference arm optical path length adjustment module 38 to change the length of the reference arm optical path to search for a reference arm optical path length at which the OCT image detector 62 generates a suitable OCT signal for generating an OCT image of the user's retina. For example, the control unit 64 can receive and process the OCT signal generated by the OCT image detector 62 to monitor the suitability of the OCT signal for generating an OCT image of the user's retina while the control unit 64 controls the reference arm optical path length adjustment module 38 to change the length of the reference arm optical path.

[0066] After identifying a suitable reference arm optical path length for generating an OCT image of the retina, control unit 64 can control sample arm beam focusing mechanism 40 to vary the amount of focus correction applied to the sample arm beam to search for a suitable focus correction for user 12. In many embodiments, control unit 64 monitors the intensity of the OCT image signal generated by OCT image detector 62 while varying the amount of focus correction applied to the sample beam to identify a focus correction that maximizes the monitored intensity of the OCT image signal, thereby identifying a focus correction that causes the sample arm beam to focus on the retina of user 12. In some embodiments, operating parameters of sample arm beam focusing mechanism 40 are varied by control unit 64, resulting in corresponding changes in the applied focus correction. In some embodiments, data storage device 68 stores a data lookup table that provides a correspondence between varying operating parameters of the sample arm beam focusing mechanism and corresponding diopter corrections for the focus corrections. Sample arm beam focusing mechanism 40 is operable to vary the amount of applied focus correction within a suitable range to accommodate any user within a target user population. For example, sample arm beam focusing mechanism 40 can be configured to vary the amount of applied focus correction within a range of at least 15 diopters. The sample arm beam focusing mechanism 40 can have any suitable configuration. For example, in some embodiments, the sample arm beam focusing mechanism 40 includes a liquid lens that can be controlled by the control unit 64 to change the applied focus correction to identify the optimal focus correction to use during the OCT imaging session of the retina of the user 12. In some embodiments, the control unit 64 monitors the output of the pupil camera 58 to monitor the alignment of the user's pupil with the optical axis of the OCT imaging device 30. In some embodiments, the control unit 64 monitors the output of the pupil camera 58 to monitor whether the user's eyelid is sufficiently open to allow the sample arm beam to reach the retina. In some embodiments, the control unit 64 suspends the search for the focus correction applied by the sample arm beam focusing mechanism 40 when the alignment of the user's eye with the optical axis of the OCT imaging device 30 is insufficient, or if the user's eyelid is not sufficiently open such that the sample arm beam cannot reach the retina.

[0067] After identifying a focus correction to be applied by the sample arm beam focusing mechanism 40 for the user 12, the control unit 64 may control the operation of the display device focus mechanism 56 to apply the corresponding focus correction so that an item displayed by the display device (e.g., a gaze target) is in focus for the user 12. For example, if a 2.5 diopter focus correction is identified as the focus correction to be applied by the sample arm beam focusing mechanism 40, the control unit 64 may control the operation of the display device focus mechanism 56 to also apply the 2.5 diopter focus correction.

[0068] 4A and 4B show simplified schematic block diagrams of the acts of a method 100 of imaging the retina by an OCT system, according to an embodiment. Any suitable OCT imaging system, such as the OCT system 10 described herein, can be used to practice the method 100.

[0069] In act 102, a light beam is emitted from a broadband light source. For example, in the OCT imaging device 30 of the OCT system 10, the control unit 64 may control the operation of the broadband light source 32 to emit the light beam.

[0070] In act 104, the light beam is split into a sample arm beam and a reference arm beam. For example, in the OCT imaging device 30, the beam splitter 34 splits the light beam into a sample arm beam and a reference arm beam.

[0071] In act 106, the sample arm beam propagates through a sample arm beam focusing mechanism to apply focus correction to the sample arm beam. For example, in the OCT imaging device 30, the sample arm beam propagates through the sample arm beam focusing mechanism 40, which applies focus correction to the sample arm beam.

[0072] In act 108, the sample arm beam is scanned by a scanning unit in two dimensions transverse to the propagation direction of the sample arm beam (with focus correction applied thereto) to produce a scanned sample arm beam. For example, in the OCT imaging apparatus 30, the scanning unit 42 scans the sample arm beam in two dimensions transverse to the propagation direction of the sample arm beam (with focus correction applied by the sample arm beam focusing mechanism 40).

[0073] In act 110, the user's head is constrained by the viewer assembly so that the scanned sample arm beam is incident on the retina. For example, in OCT system 10, the user's head is constrained by viewer assembly 16 so that the scanned sample arm beam is incident on the retina. In many embodiments, the user's head is constrained by viewer assembly 16 so that eye 64 is maintained at a fixed distance from fixed-position objective lens 48.

[0074] In act 112 , the reference arm beam propagates along the reference arm beam optical path. For example, in the OCT imaging device 30 , the reference arm beam propagates from the beam splitter 34 to the reference arm optical path length adjustment mechanism 38 and returns to the beam splitter 34 .

[0075] In act 114, the return portion of the scanned sample arm beam and the reference arm beam are recombined to produce a recombined beam. For example, in the OCT imaging device 30, the beam splitter 34 recombines the return portion of the scanned sample arm beam and the reference arm beam to produce a recombined beam.

[0076] In act 116 , the recombined light beam propagates to the OCT image detector. For example, in the OCT imaging device 30 , the recombined light beam propagates from the beam splitter 34 to the OCT image detector 62 .

[0077] In act 118, the OCT image detector generates an OCT signal of the recombined light beam. For example, in the OCT imaging device 30, the OCT image detector 62 generates an OCT signal of the recombined light beam.

[0078] In act 120, the OCT signal is monitored by the control unit. For example, in the OCT imaging device 30, the control unit 64 monitors the OCT signal.

[0079] In Act 122, the control unit controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina. For example, in the OCT imaging device 30, the control unit 64 controls the reference arm optical path length adjustment mechanism 38 to change the length of the reference arm optical path 36 to identify the length of the reference arm optical path 36 when the OCT signal corresponds to the OCT image of the retina of the eye 64.

[0080] In act 124, the control unit changes the operating parameters of the sample arm beam focusing mechanism within a range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina, so as to identify the user-specific focus correction to be applied to the sample arm beam based on the OCT signal. For example, in the OCT imaging apparatus 30, the control unit 64 changes the operating parameters of the sample arm beam focusing mechanism 38 within a range while maintaining the length of the reference arm optical path 36 when the OCT signal corresponds to the OCT image of the retina of the eye 64, so as to identify the user-specific focus correction to be applied to the sample arm beam based on the OCT signal.

[0081] Figures 5a to 5h A sequence of example OCT images generated during a search for a reference arm path length when an OCT signal corresponds to an OCT image of the retina of a strong eye is shown. The sequence of example OCT images shown illustrates aspects of an OCT image that can be identified using any suitable image processing method to identify the reference arm path length when the OCT signal corresponds to the OCT image of the retina of the strong eye.

[0082] Figure 5a An example OCT image 126 is shown at time (0) (arbitrary units (AU)) and a reference arm adjustable mirror position equal to 100 AU. The OCT image 126 includes an autocorrelation signal 128 from the retina which can be ignored.

[0083] Figure 5bAn example OCT image 130 is shown at time (1) AU and a reference arm adjustable mirror position equal to 90 AU. The OCT image 130 includes a cross-correlation signal 132 from the retina. The cross-correlation signal 132 is a negligible ghost or artifact.

[0084] Figure 5c An example OCT image 134 is shown at time (2) AU and a reference arm adjustable mirror position equal to 80 AU. The OCT image 134 includes a cross-correlation signal 136 from the retina. The cross-correlation signal 136 is a negligible ghost or artifact.

[0085] Figure 5d An example OCT image 138 is shown at time (3) AU and a reference arm adjustable mirror position equal to 70 AU. The OCT image 138 includes a cross-correlation signal 140 from the retina. The cross-correlation signal 140 is a negligible ghost or artifact.

[0086] Figure 5e An example OCT image 142 is shown at time (4) AU and a reference arm adjustable mirror position equal to 60 AU. The OCT image 142 includes a cross-correlation signal 144 from the retina. The cross-correlation signal 144 is the "true" signal from the retina and can store the corresponding reference arm optical path length and / or the position of the reference arm adjustable mirror position.

[0087] Figure 5f An example OCT image 146 is shown at time (5) AU and a reference arm adjustable mirror position equal to 50 AU. The OCT image 146 includes a cross-correlation signal 148 from the retina. The cross-correlation signal 148 is the "true" signal from the retina and can store the corresponding reference arm optical path length and / or the position of the reference arm adjustable mirror position.

[0088] Figure 5g An example OCT image 150 is shown at time (6) AU and a reference arm adjustable mirror position equal to 53 AU. The OCT image 150 includes a cross-correlation signal 152 from the retina. The cross-correlation signal 152 is the "true" signal from the retina and can store the corresponding reference arm optical path length and / or the position of the reference arm adjustable mirror position.

[0089] Figure 5h An example OCT image 154 is shown at time (7) AU and a reference arm adjustable mirror position equal to 58 AU. The OCT image 154 includes a cross-correlation signal 156 from the retina. The cross-correlation signal 156 is the "true" signal from the retina and can store the corresponding reference arm optical path length and / or reference arm adjustable mirror position.

[0090] Figure 6An example OCT image 158 is shown at time (20) AU and a reference arm adjustable mirror position equal to 53 AU. The OCT image 158 is generated by applying a user-specific focus correction to the sample arm beam. The OCT image 158 includes a cross-correlation signal 160 from the retina. The cross-correlation signal 160 is the "true" signal from the retina. The reference arm adjustable mirror position and the user-specific focus correction applied to the sample arm beam used to generate the OCT image 158 can be used to generate an OCT image of the retina of the eye.

[0091] Figures 7a to 7c Example OCT images generated during a search for a reference arm path length when an OCT signal corresponds to an OCT image of the retina of an amblyopic eye are shown. The sequence of example OCT images shown illustrates aspects of the OCT images that can be identified using any suitable image processing method to identify the reference arm path length when the OCT signal corresponds to the OCT image of the retina of the amblyopic eye. Figure 7a An example OCT image 162 is shown that does not include cross-correlation signals. Figure 7b An example OCT image 164 is shown that includes a cross-correlation signal 166 from the retina. The cross-correlation signal 166 is the "true" signal from the retina and may store the position of the corresponding reference arm optical path length and / or reference arm adjustable mirror position. Figure 7c An example OCT image 168 is shown that includes a cross-correlation signal 170 from the retina. The cross-correlation signal 170 is the "true" signal from the retina and may store the position of the corresponding reference arm optical path length and / or reference arm adjustable mirror position.

[0092] Figure 8 An example OCT image 172 is shown, generated by applying a user-specific focus correction to the sample arm beam. OCT image 172 includes a cross-correlation signal 174 from the retina. Cross-correlation signal 174 is the "true" signal from the retina. The reference arm adjustable mirror position and the user-specific focus correction applied to the sample arm beam used to generate OCT image 172 can be used to generate an OCT image of the retina of the eye.

[0093] Figure 9 A simplified schematic block diagram of a process 200 that can be used to identify the reference arm optical path length when an OCT image corresponds to an OCT image of the retina is shown. The process 200 can be used to perform act 122 of the method 100.

[0094] In act 202, when a default focus correction (e.g., 0 diopters) is applied to the sample arm beam, the reference arm optical path length adjustment mechanism is controlled to change the reference arm optical path length. For example, in the OCT imaging apparatus 30, the control unit 64 controls the sample arm beam focusing mechanism 40 to apply the default focus correction to the sample arm path beam. When the default focus correction is applied to the sample arm path beam, the control unit 64 controls the reference arm optical path length adjustment mechanism 38 to change the length of the reference arm optical path 36.

[0095] In act 204, a reference arm search B-scan (also called a cross-sectional tomographic scan) is generated and stored for each of the selections of the reference arm optical path length. The reference arm search B-scan can have any suitable number of reference arm search A-scans (also called axial depth scans). For example, in some embodiments, the reference arm search B-scan includes 500 reference arm search A-scans. In contrast, an imaging B-scan can be formed from the same number of A-scans as there are pixels in an OCT image detector, e.g., the OCT image detector can have 1024 pixels. For example, in the OCT imaging device 30, the control unit 64 processes the OCT signal generated by the OCT image detector 62 to generate a reference arm search B-scan for each of the selections of the length of the reference arm optical path 36. The control unit 64 generates the reference arm search B-scan by laterally combining a series of reference arm search A-scans. The control unit 64 controls the reference arm optical path length adjustment mechanism 38 to vary the reference arm optical path length around the corresponding selected reference arm optical path length, causing the OCT image detector 62 to generate an OCT signal, which is processed by the control unit 64 to generate each of the reference arm search A-scans. Each reference arm search A-scan indicates the amount of the sample arm beam reflected back from a position along the sample arm optical path corresponding to the corresponding reference arm optical path length. Thus, each reference arm search A-scan indicates the reflection profile of each position on the sample arm beam corresponding to the reference arm search A-scan.

[0096] Each of the reference arm search A-scans may be generated using any suitable method.

[0097] For example, in the OCT imaging device 30, each spectrum output by the OCT image detector 62 may be processed by the control unit 64 using a fast Fourier transform (FFT) to form a corresponding reference arm search A-scan. Figure 10 An example spectrum is shown on which an FFT is performed to generate a corresponding reference arm search A-scan.In some embodiments, computation time is reduced during the generation of the reference arm search A-scan by not including linearization and dispersion compensation.

[0098] In act 206, an intensity number is determined for each reference arm search B-scan by summing the gray levels of each of the reference arm search A-scans in the corresponding reference arm search B-scan. For example, in the OCT imaging device 30, the control unit 64 determines the intensity number for each reference arm search B-scan by summing the gray levels of each of the reference arm search A-scans in the corresponding reference arm search B-scan. In some embodiments, the intensity number has arbitrary units (AU).

[0099] In act 208, the reference arm optical path length is set to match the reference arm optical path length of the reference arm search B-scan having the highest intensity number. For example, in the OCT imaging apparatus 30, the control unit 64 controls the reference arm optical path length adjustment mechanism 38 to set the reference arm optical path length to match the reference arm optical path length of the reference arm search B-scan having the highest intensity number.

[0100] In act 210 , the reference arm optical path length is adjusted to fine-tune the position of the retinal image within predetermined boundaries. For example, in the OCT imaging device 30 , the control unit 64 controls the reference arm optical path length adjustment mechanism 38 to fine-tune the position of the retinal image within predetermined boundaries. Figure 11 Example OCT images are shown during fine-tuning of the reference arm optical path length to fine-tune the position of the retinal image within predetermined boundaries 212, 214. Any suitable method can be used to detect the position of the retinal image within predetermined boundaries 212, 214. For example, a suitable image processing method can be used that employs edge detection applied to a set of A-scans to detect the position of the retinal image relative to predetermined boundaries 212, 214. The set of A-scans can include any suitable selection of A-scans. For example, in some embodiments, A-scans covering 10 different sections 216 are averaged to increase the reliability of edge detection based on the averaged A-scans. Any suitable number of A-scans can be included in each of sections 216. For example, in some embodiments, 50 A-scans can be included in each of sections 216, and these 50 A-scans can be averaged to detect the edges of the retinal image. Sections 216 can be positioned relative to predetermined boundaries 212, 214 such that when a corresponding edge of the retinal image is located on section 216, the retinal image is appropriately located between predetermined boundaries 212, 214. The direction of movement of the retinal image with respect to changes in the optical path length of the reference arm can be used to assess whether the retinal image is a mirror image.

[0101] Figure 12 A simplified schematic block diagram illustrates acts of a process that may be used in method 100 for identifying user-specific focus corrections. Process 220 may be used to accomplish act 124 of method 100.

[0102] In act 222, using the finely adjusted reference arm optical path length, the sample arm beam focusing mechanism is controlled to change the applied focus correction by selecting the focus correction. For example, in the OCT imaging device 30, the control unit 64 controls the sample arm beam focusing mechanism 40 to change the focus correction applied to the sample arm beam by selecting the focus correction.

[0103] In act 224, a focus search B-scan is generated and stored for each of the selected focus corrections applied. The focus search B-scan can have any suitable number of focus search A-scans (also called axial depth scans). For example, in some embodiments, the focus search B-scan includes 500 focus search A-scans. For example, in the OCT imaging device 30, the control unit 64 processes the OCT signals generated by the OCT image detector 62 to generate a focus search B-scan for each of the selected lengths of the reference arm optical path 36. The control unit 64 generates the focus search B-scan by laterally combining a series of focus search A-scans.

[0104] Each of the focus search A-scans can be generated using any suitable method. For example, in the OCT imaging device 30, each spectrum output by the OCT image detector 62 can be processed by the control unit 64 using a fast Fourier transform (FFT) to form a corresponding focus search A-scan. In some embodiments, the computational time for generating each focus search A-scan is reduced by not including linearization and dispersion compensation.

[0105] In act 226, an intensity score is determined for each focus search B-scan by summing the gray levels of each of the focus search A-scans in the corresponding focus search B-scan. For example, in the OCT imaging device 30, the control unit 64 determines the intensity score for each focus search B-scan by summing the gray levels of each of the focus search A-scans in the corresponding focus search B-scan. In some embodiments, the intensity score for each focus search B-scan has arbitrary units (AU).

[0106] In act 228, the sample arm beam focusing mechanism is controlled to apply the focus correction corresponding to the focus search B-scan having the highest intensity number. In some embodiments, when the amount of change in intensity numbers between consecutive focus B-scans indicates that the best focus correction is between adjacent evaluated focus corrections, interpolation using any suitable method is employed to identify the best focus correction to apply.

[0107] Figure 13A simplified schematic block diagram illustrates the acts of process 300 that may be performed in conjunction with method 100. Process 300 may be used to operate a display device focus mechanism based on a user-identified focus correction applied by the sample arm beam focus mechanism to optimally focus the sample arm beam onto the retina.

[0108] In act 302 , light is transmitted from the display device through the display device focusing mechanism to the retina. For example, in the OCT imaging device 30 , light is transmitted from the display device 54 through the display device focusing mechanism 56 .

[0109] In act 304, a control unit determines a focus setting of the display device focus mechanism based on the focus correction for user identification applied by the sample arm beam focus mechanism. For example, in the OCT imaging device 30, the control unit 64 determines a focus setting of the display device focus mechanism 56 based on the focus correction for user identification applied by the sample arm beam focus mechanism 40.

[0110] In action 306 , the control unit controls the display device focus mechanism to operate with the focus setting of the display device focus mechanism. For example, in the OCT imaging device 30 , the control unit 64 controls the display device focus mechanism 56 to operate with the focus setting of the display device focus mechanism 56 .

[0111] Many of the features and methods employed in the OCT imaging systems and related processes described herein provide benefits such as reduced cost and / or ease of operation. For example, the use of the sample arm beam focusing mechanisms and motions described herein can be used in conjunction with coupling optical components that have no moving parts (e.g., a telescope). In addition, the distance between the eye and the objective lens of the OCT imaging system can be fixed. For example, the distance between the eye and the objective lens can be defined by facial features (e.g., forehead-eye distance) that engage with the observer assembly. In addition, the use of the sample arm beam focusing mechanisms and motions described herein can be used without the use of an additional detector that serves as a focus detector. The use of two separate focusing mechanisms (i.e., a sample arm beam focusing mechanism and a display device focusing mechanism) described in conjunction with the OCT imaging systems and related processes described herein is considered counterintuitive because of the use of a single focusing mechanism (e.g., each coupling optical device that can be controlled to change the focus) in many existing OCT imaging systems.

[0112] Many of the features and methods employed in the OCT imaging systems and related processes described herein can be used in conjunction with the storage and reuse of user-specific imaging parameters. For example, the reference arm optical path length and the focus correction applied that are identified and used during initial imaging of a particular user's retina can be stored and used during subsequent imaging of the particular user's retina to reduce the range of reference arm optical path lengths searched and the range of focus corrections applied during subsequent imaging, thereby reducing the time required to conduct subsequent imaging sessions. Any suitable method can be used to store and reuse user-specific imaging parameters, such as the method described in U.S. patent application serial number 16 / 424,246, filed on May 28, 2019, entitled AUTOMATIC OPTICAL PATH ADJUSTMENT IN HOME OCT, the entire contents of which are hereby incorporated by reference herein.

[0113] Other variations are also within the spirit of the invention. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and described above in detail. However, it should be understood that this is not intended to limit the invention to the specific form or forms disclosed, but on the contrary, is intended to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined by the appended claims.

[0114] The use of the terms "a", "an" and "the" and similar designations in the context of describing the present invention (especially in the context of the following claims) is intended to cover both the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. The terms "include", "have", "comprise" and "cover" should be interpreted as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The term "connected" should be interpreted as being partially or completely contained within, attached, or combined together, even if there are some intermediaries. The recording of value ranges herein is intended only to be used as a shorthand method of individually referencing each individual value falling within the range, unless otherwise stated herein, and each individual value is incorporated into this specification as if it were individually recorded herein. All methods described herein can be performed in any suitable order, unless otherwise stated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended only to better illustrate embodiments of the present invention and does not constitute a limitation on the scope of the present invention, unless otherwise required. The language in this specification should not be interpreted as indicating that any unclaimed element is necessary for practicing the present invention.

[0115] Preferred embodiments of the present invention are described herein, including the best mode known to the inventor for implementing the present invention. Variants of these preferred embodiments become apparent to those of ordinary skill in the art after reading the foregoing description. The inventor and those skilled in the art adopt these variations as appropriate, and the inventor intends that the present invention be practiced in other forms beyond the specific description herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter described in the claims appended hereto, as permitted by applicable laws and regulations. In addition, any combination of the above-mentioned elements in all their possible variations is encompassed by the present invention, unless otherwise stated herein or clearly contradictory to the context.

[0116] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0117] Examples of embodiments of the present disclosure may be described in terms of the following:

[0118] Item 1. An optical coherence tomography (OCT) system for imaging the retina of a user, the OCT system comprising: a wide-bandwidth light source that emits a light beam; a beam splitter that splits the light beam into a sample arm beam and a reference arm beam and recombines a return portion of the sample arm beam with the reference arm beam to form a recombined light beam; a reference arm optical path on which the reference arm beam propagates; a reference arm optical path length adjustment mechanism that is operable to change the length of the reference arm optical path; a sample arm optical path on which the sample arm beam and the return portion of the sample arm beam propagate; an objective lens disposed on the sample arm optical path; an observer assembly configured to constrain the user's head so that the sample arm optical path extends to the retina; a scanning unit that scans the sample arm beam in two dimensions transverse to a propagation direction of the sample arm beam; a sample arm beam focusing mechanism that is controllable to change the focus of the sample arm beam on the retina; an OCT image detector that generates an OCT signal of the recombined light beam; and a display device that displays a user's image. a fixation target seen through the retina; a display device focusing mechanism that can be controlled to change the focus of the image of the fixation target on the retina; and a control unit that is operably connected to the OCT image detector, the display device focusing mechanism, the reference arm optical path length adjustment mechanism, and the sample arm beam focusing mechanism, wherein the control unit is configured to: monitor the OCT signal; control the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path to identify the reference arm optical path length when the OCT signal corresponds to the OCT image of the retina; change the operating parameters of the sample arm beam focusing mechanism within a range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina to identify a focus correction for the user applied to the sample arm beam based on the OCT signal; determine a focus setting of the display device focusing mechanism based on the focus correction for the user applied by the sample arm beam focusing mechanism; and control the display device focusing mechanism to operate with the focus setting of the display device focusing mechanism.

[0119] Clause 2. The OCT system of clause 1, wherein the control unit uses a lookup data table to determine a focus setting of the display device focus mechanism corresponding to the focus correction applied by the sample arm beam focus mechanism for the user identified focus correction.

[0120] Item 3. The OCT system of Item 1, wherein: the display device focusing mechanism includes a display device focusing lens that is repositionable relative to the display device; and the focus setting of the display device focusing mechanism corresponds to a corresponding position of the display device focusing lens relative to the display device.

[0121] Clause 4. The OCT system of clause 1, wherein the display device focus mechanism is operable to vary the focus of the image of the fixation target on the retina over a range of at least 15 diopters.

[0122] Clause 5. The OCT system of clause 4, wherein the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0123] Clause 6. An OCT system of any one of clauses 1 to 5, wherein: the viewer assembly engages facial features of the user to constrain the user's head and define the distance between the retina and the objective lens; and the distance between the objective lens and the retina is not controllable by the OCT system or an operator of the OCT system.

[0124] Item 7. An OCT system of any one of Items 1 to 5, wherein the control unit processes the OCT signal to generate an OCT image, which is processed using an image processing method to accomplish at least one of: identification of the reference arm optical path length when the OCT signal corresponds to the OCT image of the retina; and identification of focus correction for the user.

[0125] Item 8. The OCT system of any one of Items 1 to 5, wherein the sample arm beam focusing mechanism is disposed on the sample arm optical path between the beam splitter and the scanning unit.

[0126] Item 9. The OCT system of Item 8, wherein the sample arm beam focusing mechanism comprises a controllable liquid lens.

[0127] Item 10. An OCT system according to any one of items 1 to 5, wherein the control unit: controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within a range, which covers all lengths of the reference arm optical path length that can be achieved by controlling the reference arm optical path length adjustment mechanism; determines candidate lengths of the reference arm optical path length, wherein each candidate length is determined based on the corresponding intensity of the OCT signal; and selects the candidate length with the highest corresponding intensity of the OCT signal among the candidate lengths as the reference arm optical path length when the OCT signal corresponds to the retinal OCT image.

[0128] Clause 11. The OCT system of clause 10, wherein the range encompassing all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism covers no more than 50 mm.

[0129] Item 12. The OCT system of Item 11, comprising: a pupil camera; a pupil imaging optical path; a pupil illumination light source; and a dichroic mirror coupling the pupil imaging optical path with the sample arm optical path, and wherein: a control unit is operably coupled to the pupil camera; the control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm optical path; and changes the length of the reference arm optical path only when the user's pupil is open and aligned with the sample arm optical path.

[0130] Item 13. The OCT system of Item 10, comprising: a pupil camera; a pupil imaging optical path; a pupil illumination light source; and a dichroic mirror coupling the pupil imaging optical path with the sample arm optical path, and wherein: a control unit is operably coupled to the pupil camera; the control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm optical path; and changes the length of the reference arm optical path only when the user's pupil is open and aligned with the sample arm optical path.

[0131] Clause 14. The OCT system of any one of clauses 1 to 5, wherein the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0132] Clause 15. The OCT system of any one of clauses 1 to 5, wherein the integration time of the a-scan exceeds 50 microseconds.

[0133] Clause 16. The OCT system of any one of clauses 1 to 5, comprising a telescope assembly comprising an objective lens and a second lens, each of the objective lens and the second lens having a fixed position in the sample arm optical path.

[0134] Item 17. An optical coherence tomography (OCT) system for imaging the retina of a user, the OCT system comprising: a light source that emits a light beam; a beam splitter that splits the light beam into a sample arm beam and a reference arm beam; a reference arm optical path on which the reference arm beam propagates; a reference arm optical path length adjustment mechanism that is operable to change the length of the reference arm optical path; a scanning unit that scans the sample arm beam in two dimensions transverse to a propagation direction of the sample arm beam; a sample arm beam focusing mechanism that is controllable to change the focus of the sample arm beam on the retina; an OCT image detector that generates an OCT signal; and a control unit that is operably connected to the OCT image detector and the sample arm beam focusing mechanism , wherein the control unit is configured to: monitor the OCT signal; change the operating parameters of the sample arm beam focusing mechanism within a range to identify a focus correction for the user applied to the sample arm beam based on the OCT signal; control the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within the following range: the range covers all lengths of the reference arm optical path length that can be achieved by controlling the reference arm optical path length adjustment mechanism; determine candidate lengths of the reference arm optical path length, wherein each candidate length is determined based on the corresponding intensity of the OCT signal; and select the candidate length with the highest corresponding intensity of the OCT signal among the candidate lengths as the reference arm optical path length when the OCT signal corresponds to the retinal OCT image.

[0135] Item 18. The OCT system of Item 17, wherein the sample arm beam focusing mechanism is disposed between the beam splitter and the scanning unit.

[0136] Item 19. The OCT system of Item 18, wherein the sample arm beam focusing mechanism comprises a controllable liquid lens.

[0137] Clause 20. The OCT system of any one of clauses 17 to 19, wherein the sample arm beam focusing mechanism comprises a controllable liquid lens.

[0138] Clause 21. The OCT system of any one of clauses 17 to 19, wherein the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0139] Item 22. A method for imaging a user's retina using an OCT system, the method comprising: emitting a light beam from a broadband light source; splitting the light beam into a sample arm beam and a reference arm beam; causing the sample arm beam to propagate through a sample arm beam focusing mechanism to perform focus correction on the sample arm beam; scanning the sample arm beam in two dimensions transverse to a propagation direction of the sample arm beam by a scanning unit to generate a scanned sample arm beam; causing the scanned sample arm beam to propagate through an objective lens; constraining the user's head by an observer assembly so that the scanned sample arm beam is incident on the retina; propagating the reference arm beam in an optical path of the reference arm beam; and aligning a return portion of the scanned sample arm beam with the reference arm beam. The light beams are recombined to produce a recombined light beam; the recombined light beam is propagated to an OCT image detector; an OCT signal of the recombined light beam is generated by the OCT image detector; the OCT signal is monitored by a control unit; the reference arm optical path length adjustment mechanism is controlled by the control unit to change the reference arm optical path length to identify the reference arm optical path length when the OCT signal corresponds to the OCT image of the retina; and the operating parameters of the sample arm beam focusing mechanism are changed by the control unit within a range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina to identify a focus correction for the user to be applied to the sample arm beam based on the OCT signal.

[0140] Item 23. The method of Item 22, comprising: causing light from a display device displaying a gaze target to propagate to a retina through a display device focusing mechanism; determining, by a control unit, a focus setting of the display device focusing mechanism based on a focus correction applied by a sample arm beam focusing mechanism for a user identification; and controlling, by the control unit, the display device focusing mechanism to operate with the focus setting of the display device focusing mechanism.

[0141] Clause 24. The method of clause 23, wherein the control unit accesses a lookup data table to determine a focus setting for the display device based on a focus correction applied by the sample arm beam focusing mechanism for the user identification.

[0142] Clause 25. The method of clause 23, wherein: the display device focusing mechanism includes a display device focusing lens that is repositionable relative to the display device; and the focus setting of the display device focusing mechanism corresponds to a corresponding position of the display device focusing lens relative to the display device.

[0143] Clause 26. The method of clause 23, wherein the display device focus mechanism is operable to vary the focus of the image of the fixation target on the retina over a range of at least 15 diopters.

[0144] Clause 27. The method of clause 26, wherein the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0145] Clause 28. A method as described in any of Examples 22 to 27, wherein: the viewer assembly engages facial features of the user to constrain the user's head and define the distance between the eyes and the objective lens; and the distance between the objective lens and the eyes is not controlled by the OCT system or an operator of the OCT system.

[0146] Clause 29. The method of any one of clauses 22 to 27, wherein the sample arm beam focusing mechanism comprises a controllable liquid lens.

[0147] Clause 30. The method of any one of clauses 22 to 27, wherein the control unit: controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within a range, which covers all lengths of the reference arm optical path length that can be achieved by controlling the reference arm optical path length adjustment mechanism; determines candidate lengths of the reference arm optical path length, wherein each candidate length is determined based on the corresponding intensity of the OCT signal; and selects the candidate length with the highest corresponding intensity of the OCT signal among the candidate lengths as the reference arm optical path length when the OCT signal corresponds to the retinal OCT image.

[0148] Clause 31. The method of clause 30, wherein the range encompassing all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism covers no more than 50 mm.

[0149] Item 32. The method of Item 30, comprising processing the output of the pupil camera by a control unit to detect whether the user's pupil is open and aligned with the sample arm beam, and wherein the length of the reference arm optical path changes only when the user's pupil is open and aligned with the sample arm beam.

[0150] Item 33. The method of Item 30, comprising processing the output of the pupil camera by a control unit to detect whether the user's pupil is open and aligned with the sample arm beam, and wherein the length of the reference arm optical path changes only when the user's pupil is open and aligned with the sample arm beam.

[0151] Clause 34. The method of any one of clauses 22 to 27, wherein the sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

[0152] Clause 35. The method of any one of clauses 22 to 27, wherein the integration time of the a-scan exceeds 50 microseconds.

[0153] Clause 36. The method of any one of clauses 22 to 27, wherein the sample arm beam propagates through a telescope assembly comprising an objective lens and a second lens, each of the objective lens and the second lens having a fixed position within the telescope assembly.

[0154] Clause 37. The method of any one of clauses 22 to 27 further includes: processing the OCT signal by the control unit to generate an OCT image; processing the OCT image by the control unit using an image processing method to complete at least one of the following: identification of the reference arm optical path length when the OCT signal corresponds to the OCT image of the retina; and identification of focus correction for the user.

Claims

1. An optical coherence tomography (OCT) system for imaging a user's retina, the OCT system comprising: a wide bandwidth light source emitting a light beam; a beam splitter that splits the light beam into a sample arm beam and a reference arm beam, and recombine a returning portion of the sample arm beam with the reference arm beam to form a recombined light beam; a reference arm optical path, wherein the reference arm light beam propagates along the reference arm optical path; a reference arm optical path length adjustment mechanism, the reference arm optical path length adjustment mechanism being operable to change the length of the reference arm optical path; a sample arm optical path, the sample arm light beam and the returned portion of the sample arm light beam propagating along the sample arm optical path; A coupling optical assembly without moving parts, wherein the coupling optical assembly includes an objective lens disposed in the optical path of the sample arm; a viewer assembly configured to constrain the user's head so that the sample arm optical path extends to the retina; a scanning unit configured to scan the sample arm beam in two dimensions transverse to a propagation direction of the sample arm beam; a sample arm beam focusing mechanism, the sample arm beam focusing mechanism being controllable for changing the focus of the sample arm beam on the retina; an OCT image detector that generates an OCT signal of the recombined light beam; a display device, the display device displaying a gaze target visible to the user through the retina; a display device focus mechanism, the display device focus mechanism being controllable for changing the focus of the image of the gaze target on the retina so that the gaze target is in focus for the user; as well as a control unit operatively connected to the OCT image detector, the display device focusing mechanism, the reference arm optical path length adjustment mechanism, and the sample arm beam focusing mechanism, wherein the control unit is configured to: monitoring the OCT signal; controlling the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina; varying an operating parameter of the sample arm beam focusing mechanism within a range while maintaining a length of the reference arm optical path when the OCT signal corresponds to an OCT image of the retina, to identify a focus correction for the user to be applied to the sample arm beam based on the OCT signal; determining a focus setting of the display device focus mechanism corresponding to the focus correction applied by the sample arm beam focus mechanism identified for the user so that the fixation target is in focus for the user; as well as The display device focus mechanism is controlled to operate with the focus setting of the display device focus mechanism.

2. The OCT system according to claim 1, wherein: The control unit uses a lookup data table to determine the focus setting of the display device focus mechanism that corresponds to the focus correction applied by the sample arm beam focus mechanism for the user identified focus correction.

3. The OCT system according to claim 1, wherein: The display device focusing mechanism includes a display device focusing lens that is repositionable relative to the display device; and The focus settings of the display device focus mechanism correspond to respective positions of the display device focus lens relative to the display device.

4. The OCT system according to claim 1, wherein: The display device focus mechanism is operable to vary the focus of the image of the fixation target on the retina over a range of at least 15 diopters.

5. The OCT system according to claim 4, wherein: The sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

6. The OCT system according to any one of claims 1 to 5, wherein: The viewer assembly engages facial features of the user to constrain the user's head and define a distance between the retina and the objective lens; and The distance between the objective lens and the retina is not controllable by the OCT system or an operator of the OCT system.

7. The OCT system according to any one of claims 1 to 5, wherein: The control unit processes the OCT signal to generate an OCT image, wherein the OCT image is processed using an image processing method to accomplish at least one of the following: identifying a length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina; and The focus correction for the user is identified.

8. The OCT system according to any one of claims 1 to 5, wherein: The sample arm beam focusing mechanism is arranged on the sample arm optical path between the beam splitter and the scanning unit.

9. The OCT system according to claim 8, wherein: The sample arm beam focusing mechanism includes a controllable liquid lens.

10. The OCT system according to any one of claims 1 to 5, wherein: The control unit: controlling the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within the following range: the range covers all lengths of the reference arm optical path that can be achieved by controlling the reference arm optical path length adjustment mechanism; determining candidate lengths for the reference arm optical path length, wherein each of the candidate lengths is determined based on a respective intensity of the OCT signal; and The candidate length having the highest corresponding intensity of the OCT signal among the candidate lengths is selected as the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina.

11. The OCT system according to claim 10, wherein: The range covering all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism does not exceed 50 mm.

12. The OCT system according to claim 11, wherein: include: pupil camera; pupil imaging optical path; pupil illumination light source; as well as a dichroic mirror coupling the pupil imaging optical path with the sample arm optical path, and wherein: The control unit is operatively coupled to the pupil camera; The control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm optical path; and The length of the reference arm optical path is changed only when the user's pupil is open and aligned with the sample arm optical path.

13. The OCT system according to claim 10, wherein: include: pupil camera; pupil imaging optical path; pupil illumination light source; as well as a dichroic mirror coupling the pupil imaging optical path with the sample arm optical path, and wherein: The control unit is operatively coupled to the pupil camera; The control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm optical path; and The length of the reference arm optical path is changed only when the user's pupil is open and aligned with the sample arm optical path.

14. The OCT system according to any one of claims 1 to 5, wherein: The sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

15. The OCT system according to any one of claims 1 to 5, wherein: The integration time of the a-scan exceeds 50 microseconds.

16. The OCT system according to any one of claims 1 to 5, wherein: The coupling optical assembly includes a telescope assembly, which includes an objective lens and a second lens.

17. A method for imaging a user's retina using an OCT system, the method comprising: emitting a light beam from a broadband light source; splitting the light beam into a sample arm beam and a reference arm beam; passing the sample arm beam through a sample arm beam focusing mechanism to apply a focus correction to the sample arm beam; scanning the sample arm beam in two dimensions transverse to a propagation direction of the sample arm beam by a scanning unit to generate a scanned sample arm beam; propagating the scanned sample arm beam through an objective lens; constraining the user's head with a viewer assembly so that the scanned sample arm beam is incident on the retina; Propagating the reference arm beam on the reference arm beam optical path; recombining a return portion of the scanned sample arm beam with the reference arm beam to produce a recombined beam; Propagating the reintegrated beam to an OCT image detector; generating an OCT signal of the recombined light beam by the OCT image detector; monitoring the OCT signal by a control unit; The control unit controls the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path, so as to identify the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina; by changing, by the control unit, an operating parameter of the sample arm beam focusing mechanism within a certain range while maintaining the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina, so that the control unit identifies, by the control unit, a focus correction for the user to be applied to the sample arm beam based on the OCT signal; causing light from a display device displaying a fixation target to propagate to the retina through a focusing mechanism of the display device; determining, by the control unit, a focus setting of the display device focus mechanism corresponding to the focus correction applied by the sample arm beam focus mechanism for the user identified focus correction; as well as The display device focus mechanism is controlled by the control unit to operate with the focus setting of the display device focus mechanism.

18. The method according to claim 17, wherein The control unit accesses a lookup data table to determine the focus setting of the display device based on a focus correction applied by the sample arm beam focusing mechanism for the user identified focus correction.

19. The method according to claim 17, wherein: The display device focusing mechanism includes a display device focusing lens that is repositionable relative to the display device; and The focus settings of the display device focus mechanism correspond to respective positions of the display device focus lens relative to the display device.

20. The method of claim 17, wherein: The display device focus mechanism is operable to vary the focus of the image of the fixation target on the retina over a range of at least 15 diopters.

21. The method according to claim 20, wherein The sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

22. The method according to any one of claims 17 to 21, characterized in that: The viewer assembly engages facial features of the user to constrain the user's head and define a distance between the eyes and the objective lens; and The distance between the objective lens and the eye is not controllable by the OCT system or an operator of the OCT system.

23. The method according to any one of claims 17 to 21, characterized in that The sample arm beam focusing mechanism includes a controllable liquid lens.

24. The method according to any one of claims 17 to 21, wherein The control unit: controlling the reference arm optical path length adjustment mechanism to change the length of the reference arm optical path within the following range: the range covers all lengths of the reference arm optical path that can be achieved by controlling the reference arm optical path length adjustment mechanism; determining candidate lengths for the reference arm optical path length, wherein each of the candidate lengths is determined based on a respective intensity of the OCT signal; and The candidate length having the highest corresponding intensity of the OCT signal among the candidate lengths is selected as the length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina.

25. The method of claim 24, wherein: The range covering all lengths of the reference arm optical path length achievable by controlling the reference arm optical path length adjustment mechanism does not exceed 50 mm.

26. The method of claim 24, wherein: The control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm beam, and the length of the reference arm optical path is changed only when the user's pupil is open and aligned with the sample arm beam.

27. The method of claim 24, wherein: The control unit processes the output of the pupil camera to detect whether the user's pupil is open and aligned with the sample arm beam, and the length of the reference arm optical path is changed only when the user's pupil is open and aligned with the sample arm beam.

28. The method according to any one of claims 17 to 21, characterized in that The sample arm beam focusing mechanism is operable to vary the focus of the sample arm beam on the retina over a range of at least 15 diopters.

29. The method according to any one of claims 17 to 21, characterized in that The integration time of the a-scan exceeds 50 microseconds.

30. The method according to any one of claims 17 to 21, wherein The sample arm beam propagates through a telescope assembly including an objective lens and a second lens, each of the objective lens and the second lens having a fixed position within the telescope assembly.

31. The method according to any one of claims 17 to 21, wherein Further including: Processing the OCT signal by the control unit to generate an OCT image; as well as The control unit processes the OCT image using an image processing method to perform at least one of the following: identifying a length of the reference arm optical path when the OCT signal corresponds to the OCT image of the retina; and The focus correction for the user is identified.

Images