SYSTEM AND METHOD FOR ASSISTING SUBJECT ALIGNMENT TO OPHTHALMIC DEVICE - Patent application

Abstract

A system for assisting in alignment of a subject with an ophthalmic device including a first light source and an image sensor. The system includes first and second fixation targets disposed in a first plane for transmitting light having first and second optical characteristics. Also, first and second apertures are located in the second plane and configured to spatially filter light transmitted from the first and second fixation targets. At least one lens is configured to image the first and second apertures in the second plane to a third plane that generally corresponds to a pupil of the subject, such that a retina of the subject receives an image of at least one of the first and second fixation targets based on the ophthalmic device being misaligned with the pupil of the subject in the third plane.

Description

[Technical field]

[0001] The present invention relates generally to the field of ophthalmic imaging systems, and more particularly to self-alignment techniques for facilitating user operation of ophthalmic imaging systems. [Background technology]

[0002] Alignment of the subject's pupil is necessary to obtain acceptable image quality using ophthalmic devices. The alignment process is traditionally performed by ophthalmic technicians or by automated systems, the former requiring training of the operator, the latter potentially incurring additional costs in the manufacturing process that may be passed on to the purchaser. In optical coherence tomography (OCT) devices, to obtain good images, it is desirable for the illumination strip to pass unattenuated through the pupil of the eye and reach the fundus. This requires careful alignment of the eye with the ophthalmic imaging device of the OCT device (or other ophthalmic examination system). Thus, more training of the device operator is generally required to achieve a high level of competence in using such OCT systems.

[0003] It would be desirable to reduce the cost of operating an OCT device by implementing a mechanism for self-alignment without the operator having to monitor the subject's pupil and align the fundus camera before capturing an image of the subject's retina.

[0004] It is desirable to implement an automatic feedback mechanism to allow the subject to monitor their pupils for alignment without the assistance of an operator. To enable initial alignment of the ophthalmic device to the subject's pupil, it is desirable to implement the use of a fixation target to guide the subject's gaze, which can save time and eliminate additional training of the operator to perform this step when operating specialized (e.g., OCT) equipment.

[0005] Before the device takes an OCT or fundus image, it is desirable to perform a self-alignment that allows the subject to self-align and fixate to a homecare ophthalmic device, including but not limited to an OCT device and a fundus imaging device, without the need for a clinician to be present.

[0006] In siloed or more isolated environments with respect to the imaging operation process, it is desirable to enable fully controlled OCT or semi-remote controlled OCT with self-alignment capabilities to protect subjects and clinicians from the spread of the virus. Summary of the Invention [Problem to be solved by the invention]

[0007] At least one object of the present invention is to provide a system and method that facilitates subject self-alignment and fixation of an ophthalmic system, such as an OCT system. [Means for solving the problem]

[0008] In one embodiment, a system is provided for assisting in alignment of a subject with an ophthalmic device comprising a first light source and an image sensor, the system including: first and second fixation targets located in a first plane and configured to transmit light having first and second optical properties, respectively; first and second apertures located in a second plane and configured to spatially filter light transmitted from the first and second fixation targets; and first and second filters located substantially in the second plane, the first filter configured to optically filter the spatially filtered light from the first fixation target to have the first optical property and the second filter configured to optically filter the spatially filtered light from the second fixation target to have the second optical property, the first and second filters located in the second plane being aligned with a pupil of the subject. and at least one lens configured to image onto a corresponding third plane, wherein based on the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, the subject's pupil blocks an image of at least one of the first and second apertures, such that the subject's retina receives an image of at most one of the first and second fixation targets, based on the ophthalmic device being aligned with the subject's pupil in approximately the third plane, the subject's pupil substantially transmits the images of the first and second apertures, such that the subject's retina receives images of the first and second fixation targets, and light from a first light source of the ophthalmic device enters the subject's pupil, is reflected or scattered at the subject's retina, exits the subject's pupil, and is received by the image sensor.

[0009] In various exemplary embodiments, in the third plane, the images of the first and second fixation targets form a set of endpoints for the light from the first light source. In various exemplary embodiments, the first and second optical properties include different colors.

[0010] In various exemplary embodiments, the first and second fixation targets each include a different color filter. In various exemplary embodiments, the first optical characteristic includes a red color and the second optical characteristic includes a blue color.

[0011] In various exemplary embodiments, the first and second filters each include a different color filter. In various exemplary embodiments, the first and second optical properties include different polarizations.

[0012] In various exemplary embodiments, the first and second fixation targets each include a different polarizing filter. In various exemplary embodiments, the first and second filters each include a different polarizing filter.

[0013] In various exemplary embodiments, the light from the first light source comprises a line segment in the third plane. In various exemplary embodiments, the line segment has a length approximately equal to the width of the pupil. In various exemplary embodiments, the length of the line segments ranges from about 1.8 mm to 2.0 mm.

[0014] In various exemplary embodiments, the system further includes a second light source that generates light transmitted by the first and second fixation targets. In various exemplary embodiments, the second light source generates coherent light.

[0015] In various exemplary embodiments, the second light source generates non-coherent light. In various exemplary embodiments, the system further includes an objective lens disposed between the first plane and the second plane, the objective lens configured to project the first and second fixation targets to infinity through the first and second apertures.

[0016] In various exemplary embodiments, the at least one lens includes a pupil relay lens disposed between the second plane and the third plane, the pupil relay lens configured to image the first and second apertures to the third plane.

[0017] In various exemplary embodiments, the system further includes a beam splitter configured to transmit light from the first light source, reflect light having the first optical characteristic, and reflect light having the second optical characteristic.

[0018] In various exemplary embodiments, the ophthalmic device includes an optical coherence tomography imaging device. In various exemplary embodiments, the ophthalmic device includes a fundus imaging device. In various exemplary embodiments, the system further comprises at least one additional fixation target, at least one additional aperture, and at least one additional filter.

[0019] In various exemplary embodiments, a method for assisting in alignment of a subject with an ophthalmic device is provided, the method comprising the steps of transmitting light having first and second optical characteristics from first and second fixation targets located in a first plane, respectively, spatially filtering the light transmitted from the first and second fixation targets using first and second apertures located in a second plane, optically filtering the spatially filtered light from the first fixation target to have a first optical characteristic, optically filtering the spatially filtered light from the second fixation target to have a second optical characteristic, and optically filtering the spatially filtered light from the second fixation target to have a second optical characteristic, and using at least one lens, positioning the first and second apertures in the second plane in a third plane that generally corresponds to a pupil of the subject. and forming an image based on the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, the subject's pupil blocks an image of at least one of the first and second apertures, such that the subject's retina receives an image of at most one of the first and second fixation targets, based on the ophthalmic device being aligned with the subject's pupil in approximately the third plane, the subject's pupil substantially transmits the images of the first and second apertures, such that the subject's retina receives images of the first and second fixation targets, and light from a first light source of the ophthalmic device enters the subject's pupil, is reflected or scattered at the subject's retina, exits the subject's pupil, and is received by the image sensor.

[0020] In various exemplary embodiments, a system is provided for assisting in alignment of a subject with an ophthalmic device comprising a light source and an image sensor, the system including: a coherent light source disposed in a first plane; first and second apertures disposed in a second plane and configured to spatially filter light transmitted from the coherent light source; and at least one lens configured to image the first and second apertures in the second plane onto a third plane that generally corresponds to a pupil of the subject, the system determining that the pupil of the subject is imaged by at least one of the first and second apertures based on the ophthalmic device being misaligned with the pupil of the subject in approximately the third plane. the subject's retina receives light from at most one of the first and second apertures, and the subject's pupil substantially transmits images of the first and second apertures based on the ophthalmic device being aligned with the subject's pupil approximately in the third plane, such that the subject's retina receives an interference pattern generated by light from the first and second apertures, and light from a light source of the ophthalmic device enters the subject's pupil, is reflected or scattered at the subject's retina, exits the subject's pupil and is received by the image sensor.

[0021] In various exemplary embodiments, the interference pattern includes a vertical line pattern. In various exemplary embodiments, when the subject's retina receives light from at most one of the first and second apertures, the subject's retina receives a uniform color background.

[0022] In various exemplary embodiments, a method is provided for assisting in alignment of a subject with an ophthalmic device comprising a light source and an image sensor, the method including: spatially filtering coherent light transmitted from a light source in a first plane using first and second apertures located in a second plane; imaging the first and second apertures in the second plane onto a third plane that approximately corresponds to a pupil of the subject; and determining that, based on the ophthalmic device being misaligned with the pupil of the subject approximately in the third plane, the pupil of the subject blocks an image of at least one of the first and second apertures, such that the retina of the subject is imaged. , receiving light from at most one of the first and second apertures, and based on the ophthalmic device being aligned with the subject's pupil in approximately the third plane, the subject's pupil substantially transmits images of the first and second apertures, such that the subject's retina receives an interference pattern generated by light from the first and second apertures, and light from the light source of the ophthalmic device enters the subject's pupil, is reflected or scattered at the subject's retina, exits the subject's pupil and is received by the image sensor.

[0023] The foregoing features and elements may be combined in any combination without exclusivity, unless otherwise expressly stated herein. These features and elements, as well as the operation of the disclosed embodiments, will become more apparent with reference to the following description and accompanying drawings. [Brief description of the drawings]

[0024] The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of this specification. A more complete understanding of the present disclosure, however, can best be obtained by reference to the following detailed description and claims in connection with the following drawings, in which: The drawings illustrate various embodiments that employ the principles described herein, but the drawings are not intended to limit the scope of the claims. [Figure 1] FIG. 1 illustrates an exemplary diagram of a self-aligning fixation system integrated into an OCT, fundus imaging, or other ophthalmic device, according to various embodiments. [Figure 2A]1A-1C illustrate corresponding feedback displays of a subject's pupil alignment and a fixation target displayed to the subject, according to various embodiments. [Figure 2B] 1A-1C illustrate a corresponding feedback display of a subject's pupil misalignment and a fixation target displayed to the subject, according to various embodiments. [Figure 3A] 1A-1C illustrate various approaches and states of the pupil plane using coherent light from a laser as the light source, according to various embodiments. [Figure 3B] 1A-1C illustrate various approaches and states of the pupil plane using coherent light from a laser as the light source, according to various embodiments. [Figure 3C] 1A-1C illustrate various approaches and states of the pupil plane using coherent light from a laser as the light source, according to various embodiments. [Figure 3D] 1A-1C illustrate various approaches and states of the pupil plane using coherent light from a laser as the light source, according to various embodiments. [Figure 4] 13A-13C show another approach to pupil self-alignment that provides feedback display of a vertical pattern or a uniform background when the pupil opening is aligned or misaligned to the ophthalmic device, according to various embodiments. [Diagram 5] 2 illustrates a flowchart of the operation of the fixation module of FIG. 1 incorporated into an OCT, fundus imaging, or other ophthalmic device, in accordance with various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The following detailed description of various embodiments herein refers to the accompanying drawings, which illustrate various embodiments by way of example. Although these various embodiments have been described in sufficient detail to enable one skilled in the art to practice the present disclosure, it should be understood that other embodiments may be realized and that changes may be made without departing from the scope of the present disclosure. Thus, the detailed description herein is presented for purposes of illustration only, and not limitation. Furthermore, any reference to the singular includes multiple embodiments, and any reference to two or more components or steps may include a singular embodiment or step. Also, any reference to attached, fixed, connected, etc. may include permanent, removable, temporary, partial, complete, or any other possible attachment option. In addition, any reference to no contact (or similar phrases) may also include reduced or minimal contact. It should also be understood that unless otherwise specified, references to "a," "an," or "the" may include one or more, and references to a singular item may also include a plural item. Moreover, all ranges may be inclusive of upper and lower limits, and all range and ratio limits disclosed herein may be combined.

[0026] Ophthalmic systems and devices need to be aligned with respect to the subject's eye, and in particular may require alignment of the subject's pupil. Different ophthalmic systems have different levels of alignment requirements, but all systems require a certain level of alignment, and some systems have very high alignment requirements for proper operation. Some ophthalmic systems impose alignment requirements with sub-millimeter accuracy in three spatial dimensions with respect to the subject's eye pupil. Typically, the higher the alignment requirement, the more complex / more involved the system procedures are to achieve accurate alignment. In such cases, the alignment task has traditionally been performed by an ophthalmic technician or by an automated positioning system.

[0027] Alignment of the system with the subject can be difficult to achieve, particularly when it is desirable for the system to support self-administered ophthalmic procedures, such as for home use, portable use, remote controlled use, and / or personal use. Such systems cannot rely on an operator to provide alignment of the system with the subject. Furthermore, while such systems often have low cost requirements, the automated alignment subsystems are typically complex, expensive, and subject to reliability issues, severely limiting their use.

[0028] Various types of ophthalmic systems / devices are known, which are often used for diagnostic and / or therapeutic (e.g., treatment) purposes. Examples of ophthalmic treatment systems / devices include ophthalmic drug delivery systems (manual, automatic, or semi-automatic systems), or ophthalmic treatment systems, such as systems used in ophthalmic medical procedures, e.g., ophthalmic laser surgery. Examples of ophthalmic diagnostic systems / devices may include visual field perimeters, autorefractors, pachymeters, ophthalmic ultrasound devices, slit lamps, tonometers, surgical instruments / tools, and various ophthalmic imaging systems. Ophthalmic devices require alignment of the device with the subject's eye, with some devices having more critical alignment requirements than others. Presented herein is a self-alignment system / method that is suitable for ophthalmic systems, but can also repeatably and consistently provide a high level of eye alignment for more critical applications.

[0029] The present invention is not limited to any particular type of ophthalmic system (diagnostic and / or therapeutic), however, for the sake of brevity, the present description will be directed to an ophthalmic imaging system as an exemplary system for using the present invention, it being understood that the present invention may be applied to other types of ophthalmic systems (e.g., visual field testing perimeters, etc.).

[0030] In various exemplary embodiments, the present invention may be applied to OCT imaging performed using commercially available OCT devices equipped with remote desktop access software and consumer video conferencing technology on a smartphone and table that allows separation from the patient and operator to reduce the spread of infectious viruses.

[0031] An example of an ophthalmic imaging system is a fundus imager, which is typically used to image the fundus (or retina) of the eye. The fundus is the inner surface of the eye opposite the lens (or crystalline lens) of the eye, and may include the retina, optic disc, macula, fovea, and posterior pole. Two categories of fundus imagers used to image the fundus are flood-illumination imagers and scanning imagers. Scanning imagers are further divided into confocal point-scanning fundus imagers and line-scanning imagers. Another example of an ophthalmic imaging device is an optical coherence tomography (OCT) system, which is capable of in situ real-time cross-sectional (e.g., depth) imaging of tissues, e.g., imaging the anterior or posterior of the eye. The OCT system measures the scattering profile of the OCT beam when the OCT beam is incident on a sample (e.g., fundus), and can construct one-dimensional (1D) depth information at a single point, two-dimensional (2D) cross-sectional and end-view images, and three-dimensional (3D) volume images. Multiple OCT images can be taken at the same location and processed to extract motion information such as fluid (e.g., blood) flow. An OCT system that extracts blood flow information can be called an OCT angiography (OCTA) system.

[0032] Regardless of the type of ophthalmic system, precise alignment of the human eye to the ophthalmic diagnostic system can be important for performance. For example, precise alignment of the eye's pupil to the exit pupil (or aperture) of the ophthalmic imaging system is important when imaging the human retina with a fundus camera or OCT system. In a fundus imager, this is complicated by the need to split the aperture of the imaging system into an illumination pupil, where light enters the eye, and a collection pupil, where light exiting the eye is collected for imaging (e.g., to collect image data). A typical ophthalmic imaging system is typically operated by a technician, who uses various feedback mechanisms and alignment aids to position the ophthalmic imaging system, typically mounted on an adjustable mechanical stage, relative to a subject whose head is held in a fixed position by a rigid chin rest. Although automated control systems using various feedback mechanisms for alignment have been shown, such automated systems increase the complexity and cost of the system and require regular maintenance for ideal performance.

[0033] Smaller, lower-cost, portable or handheld ophthalmic imaging systems have been proposed. However, such systems still require a trained operator and usually require the use of an eyecup and stabilization bar to achieve repeatable positioning of the imaging system relative to the subject's eye. Further complicating their use, the lower-cost portable systems provide a smaller set of alignment aids for the operator and require more skill to achieve good image data.

[0034] A large portion of the cost of an ophthalmic imaging system device is spent achieving alignment of the device with the subject, both in terms of the mechanical placement of the imaging device relative to the eye and the alignment aids that help the operator and / or automated system know how to move the device to achieve the best alignment.

[0035] In various exemplary embodiments, in a self-alignment approach, the subject moves themselves and / or the imaging device to achieve alignment between the two. In general, to facilitate self-alignment, it is desirable for the imaging system to have an alignment aid that provides feedback to the subject to make correct alignment changes with minimal effort and training and obtain good measurements with high reproducibility. Such a system requires collaboration (e.g., voluntary cooperation) from the subject, including, but not limited to, physical movements and mental processing of the feedback. Situations in which this approach is desirable include personal care, remote care, and / or home care.

[0036] Home care and / or assisted living care are expected to become an increasingly important market as the need for home solutions increases, especially as the costs of the various components of the ophthalmic diagnostic system (e.g., digital cameras and computing equipment) decrease. Home care presents a special case in which an assistant operator (e.g., technician) may be less likely to be available to assist in acquiring image data. Here, the subject and the ophthalmic diagnostic system must work together to acquire good data without significantly increasing cost or decreasing ease of use.

[0037] To aid in alignment, ophthalmic imaging systems typically provide some form of visual stimulus to the human eye whose retina is being imaged. Good alignment may require that the eye's pupil is accurately positioned in three dimensions relative to the system's illumination pupil (aperture) and collection pupil (aperture), that the eye's line of sight is in the correct angular direction, and that the retina is in focus. The imaging system may provide alignment aids (e.g., feedback mechanisms) for only the system's illumination pupil.

[0038] With the device properly aligned, this light may cover an area of ​​the retina slightly larger than the field of view of the imaging system. When the subject approaches the aperture of the system from a distance, the subject may visualize the camera's illumination pupil as an illuminated virtual object several millimeters in diameter that appears to float in space several centimeters away from the objective lens of the imaging system. When the subject approaches the correct alignment by looking into the fundus camera and moving his or her eye to overlap the illuminated virtual object, it may become impossible to focus on the virtual object, and the subject may begin to see the shadow of his or her eye's pupil illuminated by the virtual object near the eye. This may appear to the subject as a circular illuminated area that increases in size as the subject approaches the correct axial position and shifts in lateral position depending on the lateral alignment. If the subject successfully positions the eye so that the illumination reaches the maximum area size and maximum brightness, it may be assumed that the eye's pupil is aligned with respect to the illumination pupil of the imaging system and most of the light passes through unsuppressed.

[0039] Ophthalmic systems need to be aligned with sub-millimeter accuracy in three dimensions to the pupil of the subject's eye. This task is traditionally performed by trained ophthalmic technicians and / or can be facilitated by automated positioning systems. Both of these approaches introduce complexity and cost constraints, and neither is suitable for self-administered ophthalmic procedures, such as for home use (home care). Subjects at home cannot rely on an operator (e.g., a visiting technician) to provide machine alignment, and automated systems are complex, expensive, and prone to reliability issues that subjects cannot be expected to address. Previous self-alignment approaches remain complex, unreliable, and often difficult and unachievable for elderly and physically challenged individuals.

[0040] The preferred embodiments described herein focus on the field of optical coherence tomography (OCT). OCT is a non-invasive in vivo imaging technique based on the backscattering or reflectance of light in a medium. OCT is particularly useful in ophthalmic examinations, where a light beam generated by an OCT device scans the eye through the pupil, and an imaging process records the backscattering profile of light at each location. The intensity of the backscattered light indicates the scattering properties of tissues and tissue boundaries, and a grayscale cross-sectional image is formed as the light beam sweeps across the field of view (FOV). OCT imaging has dramatically improved ophthalmic diagnostic capabilities and also provided a better understanding of the anatomy of the eye, which is fundamental to routine ophthalmic practice.

[0041] In various exemplary embodiments, the present disclosure describes self-alignment systems and methods that implement a simple, easy-to-implement optical system layout that can provide immediate and intuitive feedback to a test subject to ensure that the subject's pupil is aligned with the pupil aperture.

[0042] In various exemplary embodiments, the present disclosure describes systems and methods that use spectral or polarization split-pupil imaging that is spectrally or polarization matched to the fixation target for easy setup and intuitive feedback to the subject, such that the subject will miss some of the features of the fixation target before the OCT or fundus imaging probing beam is vignetted by the subject's own pupil.

[0043] 1 illustrates an exemplary diagram of a self-aligning fixation module ("fixation module") 100 integrated into an OCT, fundus imaging, or other ophthalmic device 110, according to various embodiments. FIG 1 illustrates an exemplary implementation of the fixation module 100 integrated into the OCT / fundus imaging path or other path via a beam splitter in the OCT device.

[0044] 1, the fixation module 100 includes a light source 10, such as an LED, which may be any light source in addition to the primary light source used for imaging in an ophthalmic device. Optionally, a second light source 12 (e.g., a coherent light source or a non-coherent light source) for an alternative mode of self-alignment operation may be configured in the fixation module 100. The light source 10 is configured to at least partially follow an axial light path (i.e., a main OCT path or a fundus imaging path) along an illumination path 5 that is transmitted through various lenses to a sample or specimen to be imaged (i.e., the retina 70 of the eye 75).

[0045] The illumination path 5 sends light through a set of color filters configured with / without a mask (filter 15) that constitute a set of fixation targets including a first fixation target 35 and a second fixation target 40 that are displayed in an image plane 30 conjugate to the retina of the first plane 17 with specific optical properties (e.g., different colors or different polarities).

[0046] In various exemplary embodiments, the fixation target 35, 40 can be configured in any number of different patterns and can include at least two sections with different spectra or polarization states. In various alternative embodiments, the fixation target can be configured as a static display configured by bandpass filters or polarizers. In either case, the fixation target is generated by incorporating a pair of matching bandpass filters or polarizers at the retina conjugate 17 (first plane) and the pupil conjugate 23 (second plane) with multiple pinholes or other apertures for viewing the pupil plane (third plane) 76. The illumination footprint 77 defined by the two pinholes (end points) is slightly overstretched relative to the footprint of the illumination light at the retina 70.

[0047] In various exemplary embodiments, a set of fixation targets (35, 40) are used to direct the subject's gaze in a specific direction (with two degrees of freedom) for eye alignment. The fixation targets 35 and 40 are presented to the same eye being imaged through the optics of the ophthalmic device 110. The fixation targets 35, 40 may be moved laterally relative to the field of view of the ophthalmic device 110 to guide the subject so that different portions of the retina 70 are within the field of view of the system. The fixation targets 35 and 40 may be presented to the subject in focus and configured with at least some features that have a small angular range to allow the subject to orient his or her gaze with high precision.

[0048] In various embodiments, the ophthalmic device 110 may be relatively stationary, and the subject moves their eye to align with the pupil of the relatively stationary instrument, similar to a benchtop microscope. The device may have controls that the subject can manipulate to align the pupil of the device with the pupil of their own eye, similar to a traditional fundus camera. The device may be a handheld device that the subject moves into position and controls the position with their hands, similar to binoculars or a spyglass. The ophthalmic device 110 may include a chin rest and / or a forehead rest to support the patient against the instrument. The device may have one or more eyecups that contact the subject and surround the subject's eye. Such eyecups may be permanent or disposable parts of the ophthalmic device 110. The eyecups may have a number of sensors operably connected to the processor 95.

[0049] The ophthalmic device 110 is properly centered when both fixation targets 35 and 40 are visible to the subject. For example, light from the fixation targets 35 and 40 is transmitted through the objective lens 20, which can be any state-of-the-art lens, including but not limited to a refractive lens, a diffractive lens, a reflective lens, or a hybrid lens. The objective lens 20 is configured to project the displayed object to infinity through a pinhole in the pupil conjugate 23. And the pupil relay lens 45 is for imaging the pinhole in the pupil conjugate 23 to the subject's pupil 65 (i.e., the imaging pupil 79).

[0050] The objective lens 20 may also be responsible for various image artifacts (e.g., light reflections) when the illumination light (i.e., light having a set of properties configured by the filters 15) passes through the objective lens 20. To compensate for or reduce reflections or other aberrations caused by the objective lens 20, another set of color filters 25 with an aperture mask (pinhole mask) is placed in the illumination path 5 to further filter and limit the light rays. Thus, the illumination path 5 to effectively eliminate artifacts or interferences in the light transmission between the objective lenses 20 implements a dual configuration of filters, a first set of filters 15 and a second set of filters 25, which better eliminates out-of-focus light and allows the image sensor 85 (of the camera 90) to better capture the point positions on the retina 70 associated with a set of fixation targets 35, 40.

[0051] In this embodiment, the second set of filters 25 constitutes a second plane of the pupil conjugate 23 that spatially filters the light transmission for each fixation target 35 and 40 whose light rays were previously filtered by the first set of filters 15. The first set of filters 15 is configured to optically filter the spatially filtered light from the set fixation target with an associated first optical property (frequency, polarity, color, etc.), and the second set of filters 25 is configured to repeat the filtering process in agreement with the frequency, color, or polarity applied to the light transmission from the first set of filters 15 to provide another step of optical filtering in approximately the same plane in which the spatial filtering was performed.

[0052] The light is then received by the pupil relay lens 45 of the illumination path 5 for imaging the spatially filtered light onto a third plane that constitutes the image plane (pupil plane) of the pupil 65. If the pupil is properly aligned such that the images of the first and second apertures in the second plane (pupil conjugate 23) are not vignetted by the pupil, the fixation target 35, 40 is then imaged into a retinal plane that corresponds approximately to the field of view (FOV) of the retina 70 by redirecting the light (by the folding mirror 50) through the transmission path to the beam splitter 55 and then towards the aperture of the retina 70. The beam splitter 55 is configured to transmit light from the light source 10, reflect light having optical properties set by the filter 15, and reflect light having optical properties of the filter 25. The light from the beam splitter 55 is captured by the image sensor 85 of the camera 90, then processed by the processor 95 and sent to the display 97 via the GUI 99. Thus, image sensor 85 captures light from light source 10 that enters the pupil opening, is reflected or scattered by the subject's retina 70, and thereby exits the subject's pupil and is received by image sensor 85. The light from light source 10 defines a line segment (i.e., illumination footprint 77) in the third plane. The line segment is approximately the width of the pupil and can range from about 1.8 mm (about 0.07087 inches) to about 2.0 mm (about 0.07874 inches).

[0053] In various embodiments, each fixation target 35, 40 can be considered a light source that produces either coherent or non-coherent light. In various embodiments, objective lens 20 is positioned between the first and second planes to project first and second fixation targets through first and second apertures of filter 25 to infinity.

[0054] The display 97 may include a graphical user interface 99 that allows configuration of the operation of the camera and image sensor that captures the OCT or fundus images. When the ophthalmic device is misaligned with the subject's retina 70 , the image displayed to the subject, including any fixation target produced by light reflection, is blocked by the pupil 65 .

[0055] Additionally, in the illumination path 5, a lens system 60 is positioned close to the eye 75 between the beam splitter 55 and the pupil 65 to focus the light beam composed of properties from both filters 15 and 25 towards the eye opening.

[0056] In various embodiments, the processor 95 may comprise several processors or one processor with several processor cores may be provided. The processor 95 is connected to a memory, for example a memory with random access (RAM) or a non-volatile memory such as a flash memory, or a combination thereof. The memory may store data and programs for operating the processor 85 and the ophthalmic device 110. In particular, different application programs (apps), for example an imaging application and an evaluation application related to checking aperture alignment and setting fixation targets, may be stored in the memory.

[0057] The processor 95 is further connected to a display 97 on which information, images, graphics, etc. can be displayed for viewing by a user, and may also be connected to a network interface for data exchange, such as a cellular interface for communication over a cellular network, a Bluetooth® interface, or a Wi-Fi / WLAN interface for the transfer of one or more types of remote control and aperture alignment related information.

[0058] FIG. 2A illustrates the subject's pupil alignment and the corresponding feedback display of fixation targets displayed to the subject, according to various embodiments. In FIG. 2A, the subject's pupil alignment is shown at the pupil conjugate or third plane 200 with properties from both sets of filters 15, 25 showing a complete illumination footprint 77 with both end points and circles 205, 210 in the pupil image 79. The camera image sensor 85 captures the reflected light from the retina and the processor 95 determines that the alignment is correct (i.e., triggers a mechanism for determining acceptable alignment). For example, the processor 95 may determine that a sufficient FOV or point spread has been collected. Once this determination is made, the subject sees feedback of both fixation targets 35 and 40 displayed on the graphical user interface 99 as feedback that the alignment is correct. Each fixation target 35 and 40 constitutes part of a cross and is a different color. Although the present disclosure illustrates a cross-shaped graphic representing both fixation targets, the present disclosure is not limited to this shape or configuration and numerous other indicators are contemplated as fixation targets, including labels and audible and other notifications.

[0059] FIG. 2B illustrates a subject's pupil misalignment and the corresponding feedback display of fixation targets displayed to the subject, according to various embodiments. In FIG. 2B, only a single end point or circle 205 is captured by reflected light at the image sensor 85. The pupil image 79 of the third plane 200 shows that the illumination footprint 77 is off-center. In response, only one of the fixation targets 35, 40 is displayed. In this case, the fixation target 35 is displayed corresponding to the end point or circle 205 to inform the subject that the alignment is off-center laterally toward the left. Here, the subject is reminded, based on the displayed feedback, to adjust by moving the eye 75 laterally toward the left to allow the other fixation target to be seen. Furthermore, the intensity of each fixation target may be adjusted to instruct the subject in the direction to correct the alignment laterally.

[0060] 3A, 3B, 3C, and 3D illustrate various approaches and states of the pupil plane using coherent light from a laser as a light source according to various embodiments. In FIG. 3A, a blocking filter is configured in the illumination path 5, which includes the coherent light from the light source 10 transmitted to the retina 70 via the laser. Here, the blocking filter can be configured as filter 15 or filter 25, or both, and acts like an F-stop in a camera to block a certain bandwidth of the transmitted light so that only apertures (pinholes) containing different frequencies for different colors of the reflected dots or circles are captured by the image sensor 85. If both dots are captured by the image sensor 85, the processor 95 displays both fixation targets 35 and 40 to indicate proper alignment. In FIG. 3B, the implementation of the blocking filter for the coherent light is similar to that in FIG. 3A, except that the pupil aperture is represented as a circle 305. Now, if the subject sees both circles 205 and 210 in the circle 305, or sees both fixation targets, the alignment will be correct. In Fig. 3C, when the coherent reflected light shows only a single circle 210 within circle 305, a corresponding single fixation target 40 is shown and the subject can determine that the pupil aperture is misaligned. Here, the pupil aperture is off-center to the right. Similarly, in Fig. 3D, a single circle 205 is displayed within circle 305 and the pupil aperture can be determined by the subject to be off-center in the opposite direction to Fig. 3C, i.e., to the left. Again, the displayed circle 205 corresponds in color to the displayed fixation target 35.

[0061] FIG. 4 illustrates another approach to pupil self-alignment that performs feedback display of a vertical pattern or a uniform background when the pupil aperture is aligned or not aligned with the ophthalmic device according to various embodiments. The feedback display approach of FIG. 4 operates similarly to the approach described in FIG. 1, but does not require a filter 15 in the pupil conjugate plane. In FIG. 4, in the diagram 400, when two points (i.e., two circles) are in the pupil plane, an image of a vertical sinusoidal pattern (vertical pattern 410) is displayed. When the pupil plane covers only one of the two points, the image is a uniform background 420 without vertical lines.

[0062] In FIG. 4, the feedback display uses a second light source 12 (FIG. 1) or coherent light source, where the coherent light source is located in a first plane 17 that transmits light into the retina plane, and is similarly located in a second plane, i.e., a pupil conjugate plane (or pupil plane) 23, which is made up of a first and second aperture (filter 25) that also spatially filters the coherent light transmission to image both apertures into a third plane 76, i.e., the pupil plane, via a pupil relay lens 45. When the ophthalmic device is misaligned with the subject's pupil approximately in the third plane, the subject's pupil blocks the image of at least one of the first and second apertures transmitted through the filter 25, so that the subject's retina receives light from at most one of the first and second apertures. When the ophthalmic device is aligned with the subject's pupil approximately in the third plane (pupil plane) 76, the subject's pupil substantially transmits an image of the first and second apertures (circles 205, 210) such that the subject's retina receives an interference pattern generated by the light from the first and second apertures (circles 205, 210). This interference pattern is shown to the subject in the feedback display of FIG. 4 of a uniform background 420 by the capture of reflected light from the coherent light source 12 by the image sensor 85. When the aperture is aligned with the subject's pupil and most of the reflected light is not blocked by the subject's pupil, the amount of reflected light captured by the image sensor 85 allows the processor 95 to determine that the pupil aperture is correctly aligned. In this case, the feedback display in the image plane is configured as a vertical pattern 410. When the subject's retina receives light from at most one of the first and second apertures of the filter 25 , the subject's retina receives a uniform (color) background 420 .

[0063] The objective lens is used to project the object to infinity through a pinhole, and the pupil relay lens is used to relay the pinhole onto the subject's pupil (the system's exit pupil).

[0064] FIG. 5 illustrates a flow chart of the operation of the fixation module of FIG. 1 incorporated into an OCT, fundus imaging, or other ophthalmic device 110, according to various embodiments. Flowchart 500 shows steps for a process of assisting in alignment of a subject with an ophthalmic device. In step 510, a light source transmits light rays from first and second fixation targets located in a first plane of retinal conjugate through a first filter 15 configured with a set of first and second optical properties on illumination path 5. In step 520, a filter 25 is set in illumination path 5 to spatially filter the light transmitted from the first and second fixation targets using first and second apertures located in a second plane of pupil conjugate. In this case, the spatially filtered light from the first fixation target is configured to have a first optical property and the spatially filtered light from the second fixation target is configured to have a second optical property. Next, in step 530, imaging is performed from the first and second apertures in the second plane to a third plane that approximately corresponds to the subject's pupil through a pupil relay lens 45. When the ophthalmic device 110 is misaligned with the subject's pupil in approximately the third plane, the subject's pupil blocks the images of the first and second apertures, so that the subject's retina receives at most one image of the first and second fixation targets. Alternatively, when the ophthalmic device 110 is aligned with the subject's pupil in approximately the third plane, the subject's pupil substantially transmits the images of the first and second apertures, so that the subject's retina receives the images of the first and second fixation targets. In this case, substantially all of the light from the first light source of the ophthalmic device that enters the subject's pupil is reflected or scattered by the subject's retina and exits the subject's pupil to be received by the image sensor 85.

[0065] In step 540, an alternative embodiment is implemented using a coherent light source located in a first plane. In this case, in step 550, incoherent light is transmitted through first and second apertures located in a second plane configured to spatially filter the light transmitted from the coherent light source. In step 560, the pupil relay lens 45 is configured to image the first and second apertures in the second plane to a third plane that approximately corresponds to the subject's pupil. When the ophthalmic device 110 is misaligned with the subject's pupil approximately in the third plane, the subject's pupil blocks the image of at least one of the first and second apertures, so that the subject's retina receives light from at most one of the first and second apertures. When the ophthalmic device 110 is aligned with the subject's pupil at approximately the third plane, the subject's pupil substantially transmits an image of the first and second apertures, such that the subject's retina receives an interference pattern generated by light from the first and second apertures, and light from the light source of the ophthalmic device enters the subject's pupil, is reflected or scattered by the subject's retina, exits the subject's pupil, and is received by the image sensor. The interference pattern includes a vertical line pattern. When the subject's retina receives light from at most one of the first and second apertures, the subject's retina receives a uniform color background.

[0066] In various exemplary embodiments, the self-alignment process allows the subject to see the complete fixation target only if the pupil is well aligned in the two pinhole images. If the eye pupil is decentered to block the light from one of the pinholes, the part of the fixation target corresponding to the color or polarization will be vignetted and disappear. In various exemplary embodiments, other possible color or polarization combinations can also be implemented based on the described process flow.

[0067] While the present invention has been described in conjunction with several specific embodiments, it will be apparent to those skilled in the art that many further alternatives, modifications, and variations will be apparent in light of the foregoing description. Accordingly, the invention as described herein is intended to embrace all such alternatives, modifications, applications, and variations that may fall within the spirit and scope of the appended claims.

Claims

1. 1. A system for assisting alignment of a subject with an ophthalmic device comprising a first light source and an image sensor, the system comprising: first and second fixation targets located in a first plane and configured to transmit light having first and second optical characteristics, respectively; first and second apertures located in a second plane and configured to spatially filter light transmitted from the first and second fixation targets; first and second filters located substantially in the second plane, the first filter configured to optically filter spatially filtered light from the first fixation target to have the first optical characteristic, and the second filter configured to optically filter spatially filtered light from the second fixation target to have the second optical characteristic; at least one lens configured to image the first and second apertures in the second plane to a third plane that generally corresponds to a pupil of the subject; based on the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, the subject's pupil occluding an image of at least one of the first and second apertures, such that the subject's retina receives an image of at most one of the first and second fixation targets; based on the ophthalmic device being in alignment with the subject's pupil in approximately the third plane; the subject's pupil substantially transmits images of the first and second apertures, such that the subject's retina receives images of the first and second fixation targets; and A system in which light from the first light source of the ophthalmic device enters the subject's pupil, is reflected or scattered by the subject's retina, exits the subject's pupil, and is received by the image sensor.

2. The system of claim 1 , wherein in the third plane, the images of the first and second fixation targets form a set of endpoints for light from the first light source.

3. The system of claim 1 or 2, wherein the first and second optical properties comprise different colors.

4. 3. The system of claim 1, wherein the first and second filters comprise different color filters.

5. The system of claim 1 or 2, wherein the first and second optical properties comprise different polarizations.

6. The system of claim 1 or 2, wherein the first and second filters each comprise a different polarizing filter.

7. The system of claim 1 or 2, wherein the light from the first light source comprises a line segment in the third plane.

8. The system of claim 1 or 2, further comprising a second light source that generates light transmitted by the first and second fixation targets.

9. The system of claim 8 , wherein the second light source generates coherent or non-coherent light.

10. 3. The system of claim 1, further comprising an objective lens disposed between the first plane and the second plane, the objective lens configured to project the first and second fixation targets to infinity through the first and second apertures.

11. 3. The system of claim 1, wherein the at least one lens comprises a pupil relay lens disposed between the second plane and the third plane, the pupil relay lens configured to image the first and second apertures to the third plane.

12. 3. The system of claim 1, further comprising a beam splitter configured to transmit light from the first light source, reflect light having the first optical characteristic, and reflect light having the second optical characteristic.

13. The system of claim 1 or 2, wherein the ophthalmic device comprises an optical coherence tomography imaging device or a fundus imaging device.

14. The system of claim 1 or 2, further comprising at least one additional fixation target, at least one additional aperture, and at least one additional filter.

15. 1. A method for assisting a subject in aligning an ophthalmic device, comprising: transmitting light having first and second optical characteristics from first and second fixation targets located in a first plane, respectively; spatially filtering light transmitted from the first and second fixation targets using first and second apertures located in a second plane; optically filtering the spatially filtered light from the first fixation target to have the first optical characteristic; optically filtering the spatially filtered light from the second fixation target to have the second optical characteristic; imaging, using at least one lens, the first and second apertures in the second plane to a third plane that generally corresponds to a pupil of the subject; based on the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, the subject's pupil blocks an image of at least one of the first and second apertures, such that the subject's retina receives an image of at most one of the first and second fixation targets; based on the ophthalmic device being in alignment with the subject's pupil in approximately the third plane; the subject's pupil substantially transmits images of the first and second apertures, such that the subject's retina receives images of the first and second fixation targets; and A method in which light from a first light source of the ophthalmic device is incident on the subject's pupil, reflected or scattered by the subject's retina, exits the subject's pupil, and is received by an image sensor.

16. 1. A system for assisting alignment of a subject with an ophthalmic device comprising a light source and an image sensor, the system comprising: a coherent light source disposed in a first plane; first and second apertures disposed in a second plane and configured to spatially filter light transmitted from the coherent light source; at least one lens configured to image the first and second apertures in the second plane to a third plane that generally corresponds to a pupil of the subject; the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, such that the subject's pupil blocks an image of at least one of the first and second apertures, such that the subject's retina receives light from at most one of the first and second apertures; based on the ophthalmic device being in alignment with the subject's pupil in approximately the third plane; a pupil of the subject substantially transmits an image of the first and second apertures, such that a retina of the subject receives an interference pattern produced by light from the first and second apertures; and A system in which light from the light source of the ophthalmic device enters the subject's pupil, is reflected or scattered by the subject's retina, exits the subject's pupil, and is received by the image sensor.

17. The system for self-alignment of an ophthalmic device of claim 16 , wherein the interference pattern comprises a vertical line pattern.

18. 17. The system for self-alignment of an ophthalmic device of claim 16, wherein when the subject's retina receives light from at most one of the first and second apertures, the subject's retina receives a background of uniform color.

19. 1. A method for assisting alignment of a subject with an ophthalmic device comprising a light source and an image sensor, the method comprising: spatially filtering the coherent light transmitted from the light source in the first plane using first and second apertures located in a second plane; imaging the first and second apertures in the second plane onto a third plane that generally corresponds to a pupil of the subject; the ophthalmic device being misaligned with the subject's pupil in approximately the third plane, such that the subject's pupil blocks an image of at least one of the first and second apertures, such that the subject's retina receives light from at most one of the first and second apertures; based on the ophthalmic device being in alignment with the subject's pupil in approximately the third plane; a pupil of the subject substantially transmits an image of the first and second apertures, such that a retina of the subject receives an interference pattern produced by light from the first and second apertures; and A method in which light from the light source of the ophthalmic device enters the subject's pupil, is reflected or scattered by the subject's retina, exits the subject's pupil, and is received by the image sensor.

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