Ophthalmic imaging apparatus and line scan alignment control thereof

Abstract

Improving deflection control and scan line alignment of an ophthalmic imaging device SOLUTION: An ophthalmic imaging device includes a light source that emits a light beam, a polygon scanning mirror including a plurality of reflective facets, a drive configured to rotate the polygon scanning mirror such that, in operation, each facet reflects the light beam at a varying angle (α), an optical element configured to direct the reflected beam at the varying angle toward an eye of a subject, and a detector configured to detect reflected beam light incident from a respective one of the reflective facets and arranged in a fixed positional relationship with the optical element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to ophthalmic imaging devices and line scan alignment control therefor, and more particularly, but not exclusively, to line scan alignment control for improving image quality. [Background technology]

[0002] Ophthalmic imaging devices are widely used to image patients' eyes to assess ocular health. Such systems include a light source and a controller configured to control the light source to generate a light beam having a predetermined optical power. The light beam is deflected by one or more scanning relay elements to cover the imaging area with multiple parallel scan lines. The scanning relay elements typically include a polygonal scanning mirror and one or more scanning galvanometer mirrors. The polygonal scanning mirror has multiple reflective facets arranged around the circumference of a rotating body. A driver is configured to rotate the polygonal scanning mirror body during operation, thereby reflecting the incident light beam at varying angles. During each individual facet, the light beam is deflected through a corresponding range of angular changes. After such a deflection cycle is completed, the next facet essentially repeats the process, and so on through all other facets.

[0003] This repeated deflection by the polygonal scanning mirror provides multiple parallel scan lines, thereby forming the basis for at least one scanning direction. Additional scanning elements, such as the aforementioned galvanometer mirrors, can further deflect the beam in other directions, offsetting the scan lines on the target to ultimately cover a two-dimensional scan area. In at least some imaging modes, light from the scanning beam is backscattered from the target tissue. In the case of ophthalmic imaging, this includes key areas of the human eye, such as the retina. Typically, this light returns along the incident light path and is ultimately detected by an image detector in the form of a photosensor, converted to an intensity signal, and processed to form an image. This latter signal processing, in particular, is performed by a digital processing device that generates individual images from the corresponding sets of line scans.

[0004] Since an image is generated by a set of line scans, each scanning in one direction, their alignment with one another affects image quality. For example, variations in the alignment of the scan lines and / or variations in the length of the scan lines can cause a jitter effect on the image, resulting in unsatisfactory image quality. However, since the length of the scan lines and their relative positions depend on the characteristics of the optical elements that deflect and guide the scanning light beam, the corresponding tolerances of the elements involved can affect the aforementioned image quality degradation. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need for improved deflection control and scan line alignment that allows for efficient combination of image data with improved image quality and low levels of image jitter while keeping system complexity to an acceptable level. [Means for solving the problem]

[0006] The problem is solved and the object is achieved by the subject matter of the independent claims. Further preferred embodiments are defined in the dependent claims.

[0007] According to one embodiment of the present invention, there is provided an ophthalmic imaging device comprising: a light source that emits a light beam; a polygonal scanning mirror including a plurality of reflective facets; a driver configured to rotate the polygonal scanning mirror during operation such that each facet reflects the light beam at varying angles; an optical element configured to direct the beam reflected at varying angles toward a subject's eye; and a detector configured to detect the reflected beam of light incident from each one of the reflective facets, the detector positioned in a fixed relationship to the optical element.

[0008] According to a further embodiment of the present invention, there is provided a method of operating an ophthalmic imaging device comprising a light source emitting a light beam, a polygonal scanning mirror including a plurality of reflective facets, an optical element, and a detector configured to detect a reflected beam of light incident from each one of the reflective facets and disposed in a fixed relationship to the optical element, the method including rotating the polygonal scanning mirror so that each facet reflects the light beam at varying angles, directing the beam reflected at varying angles toward a subject's eye with the optical element, detecting light from the subject's eye to form a sequence of imaging signals, and generating an image of the subject's eye from the sequence of imaging signals using signals provided by the detector disposed in a fixed relationship to the optical element.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention, which are presented for a better understanding of the concept of the present invention and should not be considered as limiting the present invention, will now be described with reference to the following drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a schematic diagram of an ophthalmic imaging device according to a general apparatus embodiment of the present invention. [Figure 2] FIG. 2 shows an optical schematic of an ophthalmic imaging device according to one device embodiment of the present invention. [Figure 3A]FIG. 3A shows an example of an optical element as part of an ophthalmic imaging device according to a more detailed device embodiment of the present invention. [Figure 3B] FIG. 3B shows an example of an optical element as part of an ophthalmic imaging device according to a more detailed device embodiment of the present invention. [Figure 4] FIG. 4 shows a schematic diagram of an ophthalmic imaging device according to an embodiment of the present invention, particularly in the context of retrieving imaging signals. [Figure 5A] FIG. 5A shows a schematic imaging signal extracted according to one embodiment of the present invention. [Figure 5B] FIG. 5B shows a schematic imaging signal extracted according to one embodiment of the present invention. [Figure 5C] FIG. 5C shows a schematic imaging signal extracted according to one embodiment of the present invention. [Figure 6] FIG. 6 shows a flow diagram of a general method embodiment of the present invention.

[0011] It should be understood that, unless otherwise noted, some of the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the present disclosure or that obscure other details have been omitted. Of course, it should be understood that the present invention is not necessarily limited to the specific examples or embodiments shown and described herein. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 shows a schematic diagram of an ophthalmic imaging device according to a general apparatus embodiment of the present invention. Specifically, an ophthalmic imaging system 112 is shown that includes an ophthalmic imaging device 102 that provides at least one imaging mode 121. For example, the ophthalmic imaging device 102 may take the form of a scanning laser ophthalmoscope (SLO) or an optical coherence tomography (OCT) imaging device. The imaging mode 121 is understood to refer to the operating mode in which the respective device is operated. Generally, the ophthalmic imaging device 102 can be operated in multiple modes to provide multiple corresponding imaging modes. The ophthalmic imaging system 112 also includes or has access to a computing device 106, which includes a processing unit 108 and a memory unit 110. The components of the ophthalmic imaging system 112, including the ophthalmic imaging device 102 and the computing device 106, are housed within a common housing, such that the system 112 constitutes an ophthalmic imaging device, such as an ophthalmoscope. In some embodiments, computing device 106 may be located in a separate housing external to device 102. In some embodiments, any component may be located in a separate housing from other components.

[0013] The computing device 106 controls the ophthalmic imaging device 102 to operate in a selected imaging mode 121. The computing device 106 also includes at least one processing unit 108, such as a central processing unit (CPU) and / or a graphics processing unit (GPU), and a memory unit 110 that stores instructions that, when executed by the at least one processing unit 108, cause the processing unit 108 to perform one or more of the methods and functions described herein. In a local computing device or local physical component embodiment of the computing device, the device may include a processor, such as a CPU and / or GPU, a system memory, and a system bus connecting the system memory to the CPU / GPU. The system memory may include random access memory (“RAM”) and read-only memory (“ROM”). A basic input / output (“I / O”) system, including basic routines that help transfer information between elements within the computing device, such as during start-up, is stored in the ROM. The computing device may also include mass storage, capable of storing software instructions and data. The mass storage may be connected to the CPU / GPU via a mass storage controller connected to the system bus. Mass storage devices and associated computer-readable data storage media can provide non-volatile, non-transitory storage for computing device 106. While computer-readable data storage media as used herein refers to mass storage devices such as hard disk drives or CD-ROM drives, those skilled in the art will appreciate that a computer-readable data storage medium can be any available non-transitory, physical device or product from which a device can read data and / or instructions. Mass storage devices are one example of a computer-readable storage device.

[0014] Computer-readable data storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable software instructions, data structures, program modules, or other data. Exemplary types of computer-readable data storage media include, but are not limited to, RAM, ROM, EPROM, EEPROM, flash memory or other solid-state memory technology, CD-ROM, digital versatile disks ("DVDs"), other optical storage media, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by a computing device.

[0015] The computing device 106 can operate in a networked environment using logical connections to remote network devices through a network, such as a local network, the Internet, or other types of networks. The computing device 106 can connect to a network through a network interface unit connected to a system bus. The network interface unit can also connect to other types of networks and remote computing systems. The computing device 106 can include an input / output controller for receiving and processing input from many other devices, including a touch-sensitive user interface display screen or another type of input device. Similarly, the input / output controller can provide one or more outputs to a touch-sensitive user interface display screen, a printer, or other types of output devices. As previously mentioned, the mass storage device and RAM can store software instructions and data. The software instructions can include a suitable operating system for controlling the operation of the computing device 106. The mass storage device and / or RAM can also store software instructions that, when executed by the CPU / GPU, cause the computing device 106 to provide the functionality described herein, illustrated in the figures, and set forth herein.

[0016] In some embodiments, an imaging mode 121 can be provided as an operating mode of the previously described SLO that can use confocal laser scanning microscopy for diagnostic imaging of the retina of the eye. The imaging can be two-dimensional (2D) imaging, in which a laser light beam is used to scan the retina in a raster pattern, illuminating successive elements of the retina point-by-point. Light reflected from each point on the retina is captured by a photomultiplier tube. The output between photomultipliers can be recorded and displayed in digital form. Thus, the imaging mode of the SLO can produce high-contrast, detailed images of the retina. In some embodiments, images are captured sequentially by one imaging mode and by at least one additional imaging mode.

[0017] FIG. 2 shows an optical schematic of an ophthalmic imaging device in accordance with one apparatus embodiment of the present invention. As shown, the ophthalmic imaging device 102 includes a light source 200 that emits a light beam 201 as a scanning beam. A polygonal scanning mirror 202 acts as a first scanning element (or, alternatively, a first scanning relay) and includes a plurality of reflective facets 2021, 2022,.... A driver 203 is configured to rotate the polygonal scanning mirror 202 during operation, such that each facet 2021, 2022,... reflects the light beam 201 at a varying angle. As shown, the path of the scanning beam 201 is represented by a one-dimensional scan generated during the rotation of the polygonal scanning mirror 202 (indicated by the curved arrow). Path "A" is an example of scanning beam 201 reflecting off each facet 2021 of polygonal scan mirror 202 at the beginning of the rotation, i.e., when facet 2021 enters the path of beam 201 from light source 200. Path "B" is an example of scanning beam 201 reflecting off each facet 2021 of polygonal scan mirror 202 at a later point in time, after further rotation. As facet 2021 moves out of the reach of beam 201, an adjacent facet 2022 essentially repeats the same reflection process described above.

[0018] Thus, polygon scan mirror 202 reflects beam 201 at a varying angle α. This angle α varies over a range determined by the length and rotation of each facet, since their respective orientations relative to incident beam 201 determine the angle of reflection. However, because this reflection process is continuously repeated as polygon scan mirror 202 moves and rotates, the individual facets change from scan line to scan line. Note that the properties of the polygon scan mirror in general, and the properties of each facet in particular, can affect the changes in each facet's reflective behavior between each iteration in which a facet 202i reflects beam 201 into a range of varying angles. For example, manufacturing tolerances associated with polygon scan mirrors can result in variations in facet length or other characteristics and properties that can change the angle of reflection. This, in turn, can result in variations in the position of each scan line from one to the other.

[0019] The ophthalmic imaging device 102 further comprises an optical element 204 configured to guide the reflected beam 201′ at varying angles toward the subject's eye. Additional components and optical elements 290,..., can be disposed between the optical element 204 and the subject's eye E. The optical element 204 can be or include a curved mirror, as already indicated, but may also take any other suitable form, such as a lens or lens group. An embodiment contemplated for the former curved mirror is described in detail elsewhere in this disclosure. According to this device embodiment, the ophthalmic imaging device 102 comprises a detector 205 configured to detect the reflected beam of light 201′ incident from each of the aforementioned reflective facets, such as the facet 2021 shown in the figure. The detector 205 is further disposed in a fixed positional relationship with the optical element 204. For example, the detector 205 can be disposed in a fixed positional relationship with the curved mirror (as one form of optical element that guides the reflected beam toward the eye), which corresponds to a predetermined angle αi within a range of varying angles. For example, the predetermined angle αi can correspond to a start angle at the beginning of a reflection cycle, whereby a distinct scan line is assumed. In general, a detector can function as the scan line start sensor 205 and can be located near the optical element 204, for example, at and / or near the ends of the optical element 204, i.e., in the peripheral regions 240A, 240B.

[0020] The detector 205 can generate and output a signal S, for example, in the form of a pulsed signal at the start of a scan line. In one embodiment, the detector 205 provides a current and / or voltage response related to the intensity of the incident light. Thus, the signal S can have a pulse-like feature T in the intensity versus time profile I(t), as shown in the inset of FIG. 2 . This feature T in the intensity I as part of the signal S indicates that the time ti is when the beam 201′ is at angle αi. This can also be considered to indicate that the beam is at the beginning of a scan line. This signal S can be used to align and / or synchronize the scan lines with each other, taking into account scan lines generated by different facets of the polygonal scan mirror 202 that may have different characteristics, particularly with respect to facet length. This embodiment enables efficient synchronization of the scan lines, and the resulting imaging signal from the detector can provide an output that defines and represents a common point for each scan line, regardless of the facet acting as a reflector and regardless of the nature and characteristics of the individual facets.

[0021] FIG. 3A illustrates an example optical element as part of an ophthalmic imaging device according to a more detailed device embodiment of the present invention. As described elsewhere in this disclosure, a light source provides a light beam that is directed toward a polygonal scanning mirror having multiple reflective facets. A driver rotates the polygonal scanning mirror, with each facet reflecting the light beam at varying angles toward the optical element. The optical element further directs the reflected beam at varying angles toward the subject's eye. In general, the optical element according to this embodiment is capable of directing light beams incident from different directions toward an imaging target. To this end, the optical element can provide a finite input width for capturing light beams incident from different directions as a result of being reflected at varying angles by upstream optical elements.

[0022] FIG. 3A thus shows an example of such an optical element in the form of an elongated curved mirror 204 capable of capturing light beams incident from different directions, such as a first direction A and a second direction B. The optical element thus comprises a curved mirror configured to guide the incident beams from each of the aforementioned reflective facets toward the subject's eye by further reflecting them along reflection lines on the curved mirror. To this end, the curved mirror 204 provides an input width IE capable of covering a range of different directions and angles of the light beam 201′. The curved mirror 204 thus provides an extended reflection area 2040, which includes a reflection line 2041 along which the incident light beam 201′ is reflected as the angle of incidence changes. Assuming continuous rotation of the upstream optical element, the polygon scanning mirror, the reflection point R moves along the reflection line 2041 included in the extended reflection area 2040. Since repeated reflections by the polygon scanning mirror form a scanning direction, the reflection line 2041 provides a scanning line of the light beam. If the angle of incidence varies over a larger area than curved mirror 204 covers, then it is curved mirror 204 that effectively defines the length of the scan line. This may be the case, for example, if extended reflective area 2040 is too short to cover (reflect) the incident light beam at one or more of ends 2042A, 2042B. Alternatively, of course, the length of the scan line may be defined by any other optical element, even if curved mirror 204 is configured to cover the full range of varying angles and directions of incidence.

[0023] Figure 3B shows an example of an optical element as part of an ophthalmic imaging device in accordance with a more detailed apparatus embodiment of the present invention. Again, an optical element in the form of a curved mirror 204, as specifically described in conjunction with Figure 3A, is shown (thus, like reference symbols indicate like elements and functions). Specifically, this embodiment contemplates a detector configuration that detects light from a reflected beam incident on all facets of the polygonal scanning mirror at at least one point in a reflection cycle. A reflection cycle can be defined by the reflection of a light beam by a single facet as the polygonal scanning mirror rotates.

[0024] For example, the fixed positional relationship between the detector and the optical element may be such that a beam reflected at varying angles strikes a detection point on the detector for every facet of the polygonal scanning mirror. In this embodiment, curved mirror 204 is shown with detector 205 positioned to detect light from the incident beam reflected from each one of the reflective facets of the upstream polygonal scanning mirror. Detector 205 is positioned in a fixed positional relationship with respect to curved mirror 204, and the position of detector 205 can be considered to have a well-defined, constant relationship to the position of the scan line. For example, line 2051 represents the line where incident light beam 201′ intersects with the (curved) surface of curved mirror 204 as the upstream polygonal scanning mirror rotates. Starting direction A can represent the start point of this line 2051, and ending direction B can represent the end point of this line 2051. As shown, incident light beam 201′ may start at an angle where it does not strike either detector 205 or the reflective surface of curved mirror 204. In this way, the incident light beam 201' always strikes the detector 205, and light detection at this detector 205 can provide reliable information about the starting point of a scan line.

[0025] Specifically, the starting direction A may vary depending on the properties of any upstream optical elements. For example, the facets of the upstream polygonal scanning mirror may have varying characteristics, such as different lengths, due to manufacturing tolerances. Consequently, the starting direction may vary to direction A' for longer facet lengths and direction A" for shorter facet lengths. Preferably, the detector 205 is in a fixed positional relationship with the curved mirror 204 and other elements of the ophthalmic imaging device such that all occurring starting directions, ranging from A' as the respective minimum of variation to A" as the respective maximum of variation, are in front of the position of the sensor 205. Thus, the maximum range of incident directions is as shown in range 2051, with the lower starting point varying as described in relation to directions A, A', and A", and the upper stopping point also varying (see B', B"). However, the latter may only be of low relevance. Therefore, embodiments of the present invention contemplate determining the repeatable position of at least one point, as this may be sufficient for positioning the scan lines relative to one another.

[0026] Specifically, incident light beam 201' begins its cycle in a direction between directions A' and A" and progresses through the cycle as shown by arrow Cy. The start of the cycle is therefore always prior to the location of detector 205 and the detector's detection point P, along reflection line 2041. Note that this line extends beyond end 2042A of curved mirror 204, since of course no reflection by the mirror occurs beyond this region. Thus, detector 205 is in a fixed position relative to curved mirror 204, and therefore a reflection cycle Cy begins for each facet of the polygon scanning mirror. When initiated, incident beam 201′ first strikes detector 205 (e.g., specifically at its detection point P) and then strikes reflective area 2040 of curved mirror 204. There may be a dead zone 2054 between the initiation point, i.e., detection point P, and the beginning of reflection at end 2042, which may result in a corresponding dead zone in each corresponding imaging signal. However, as explained elsewhere in this disclosure, such a dead zone is acceptable because a fixed positional relationship between an optical element in the form of curved mirror 204 and the detector is the basis for filtering the respective data.

[0027] In general, an ophthalmic imaging device may further include a carrier to which the optical elements and detector are mounted. As an example, as shown in FIG. 3B , such a carrier may be in the form of a mirror carrier 209, which includes mounting and stabilizing features for the optical element in the form of a curved mirror, including components to dampen vibrations and temperature-induced deflection. For example, the carrier may provide a mating shape that holds and stabilizes the curved mirror over most of its extension. In the example shown, the carrier 206 provides a mount 2090 for the detector 205. For example, the shape that fits and accommodates the curved mirror may extend continuously to a flat mount. The carrier may be manufactured in one piece, for example, molded into a single continuous piece by die casting.

[0028] FIG. 4 is a schematic diagram of an ophthalmic imaging device according to one embodiment of the present invention, particularly with regard to retrieving an imaging signal, and re-illustrates elements described in connection with FIGS. 3A and 3B (whereby like reference numerals represent like elements or functions). The ophthalmic imaging device 120 will be described in connection with an imaging mode in which a light beam 201 is generated by a light source 200, directed toward a patient's eye E, reflected by the tissue therein, and directed back to a detector 218. For example, as part of an SLO, the device 120 includes a light source 200 that emits a light beam, i.e., a scanning beam 201, and multiple scanning relay elements. The scanning relay elements include a first scanning element in the form of a polygon scanning mirror 202, a second scanning element 206, and optical elements positioned and configured to direct the scanning beam 201. In some embodiments, the optical elements may include an optical element 204, which may be a scanning compensation element such as a curved mirror or a slit mirror, and a second optical element 208, which may be a scanning transfer element such as a primary mirror.

[0029] Optical elements 204, 208 are positioned and configured to direct the scanning beam 201. The second scanning element 206 may be or include an oscillating planar scanning mirror or a planar scanning mirror coupled to a galvanometer motor. Optical element 204 may be a curved mirror, such as an elliptical mirror. The second optical element 208 may be an aspherical mirror. It should be understood that the first and second optical elements may have alternative forms. Scanning elements 202, 206 may be referred to as a scanning device or multiple individual scanning devices. It should be understood that the functionality illustrated here is merely an example of configurations that may be used in the embodiments described herein.

[0030] A detector 205, e.g., having the form and function of a line start sensor, is positioned within or along the optical path of the scanning beam 201 and in a fixed positional relationship to the optical element 204. In some embodiments, the detector 205 can be positioned near the optical element 204, e.g., at or near an edge of the optical element 204 or near a peripheral region 240A of the optical element 204. The detector 205 can be configured to generate and output a signal, e.g., a line start pulse signal, when the scanning beam 201 crosses a detection point on the detector 205. For example, such a detection point can be defined by an aperture or iris of an optical sensor, providing a distinct location where incident light is detected. In some examples, the detector 218 is a separate component or device operatively coupled to the light source 200, with the detector 218 and the light source 200 being co-located or adjacent to one another. In some examples, the light source 200 can be implemented with the detector 218 as a single device or can be multiple devices within a common housing. Thus, in addition to emitting the scanning beam 201 , it may also be possible to detect or receive light, such as light reflected back from the first scanning element 202 or the optical element 204 .

[0031] In an exemplary SLO operating in an exemplary imaging mode, the scanning beam 201 may be a laser of a wavelength appropriate for use in SLO applications. When other imaging modes are included, the scanning beam 201 may be a collimated light source, including, for example, a laser for SLO applications and, for example, a superluminescent diode (SLD) for other applications. It should be understood that any suitable collimated light source can be used, such as a single-frequency laser diode, a vertical-cavity surface-emitting laser, a wavelength-scanning laser source, a pulsed laser source, or any other light source that has sufficient intensity, is sufficiently collimable, and can generate appropriate retinal illumination. In such applications, an SLD may be used due to the short coherence length required for identifying retinal layers from the resulting interferometric data. The SLD can be coupled into the scanning system by free-space coupling or by standard or polarization-maintaining fiber coupling. Wavelength-swept lasers can also be used in other applications, where the wavelength of the light source is tuned over a given range.

[0032] In some embodiments, the one or more scanning elements may include, for example, one or more of an oscillating plane mirror, a galvanometer mirror, a MEMS mirror, a rotating mirror, a prism or polygon scanner, and / or a resonant mirror. In some embodiments, each of the first scanning element 202 or the second scanning element 206 may be a single element or an arrangement of two or more elements suitable for providing a scan at each focal point F1, F2 at which the scanning element is located, as shown. Focus F1 or F2 is the focal point of the optical element 204, and focus F2 or F3 is the focal point of the optical element 208. The first scanning element 202 is located at focal point F1, the second scanning element 206 is located at focal point F2, and the eye 210 is located at focal point F3 (also referred to as a virtual scanning point). The resulting scan may be a 2D scan, or scan pattern, of the scanning beam 201 as light is swept through the virtual scanning point (e.g., through F3) within the eye 210.

[0033] In some embodiments, the first scanning element 202 provides either a vertical scan, a horizontal scan, or a pattern scan that is incident on the optical element 204 and, through the optical element 204, to a point on the scanning element 206. The scan may be, for example, a one-dimensional (1D) or two-dimensional (2D) optical scan. The axes of the first scanning element 202 and the second scanning element 206 can be arranged to generate a 2D optical scan, such as in the form of a raster scan pattern of the scanned beam 201. The alignment of the first and second scanning elements 202, 206 can be arranged to generate orthogonal, substantially orthogonal, or any arbitrary scan shape with respect to the optical elements 204 and 208.

[0034] In some embodiments, the second scanning element 206 provides multiple scans, such as 1D or 2D optical scans, which may include horizontal scans, vertical scans, or arbitrary patterns of the scanned beam 201. The scans provided by the first scanning element 202 and the second scanning element 206 may differ from each other, for example, in the direction of the scan. In some examples, one scanning element may provide a vertical scan of the retina and another scanning element may provide a horizontal scan of the retina. The scanned beam 201 is directed to the patient's eye E via scanning elements 202 and 206 and optical elements 204 and 208, achieving an ultra-wide field of view scan angle at the pupil plane of the eye E.

[0035] "Wide field" scanning refers to a scan angle greater than 50 degrees in one or two dimensions. "Ultra-wide field" scanning refers to a scan that covers substantially the entire retina of eye E. In some embodiments, the first scanning element 202 can be used to scan the retina in a first direction to generate multiple line scans, and the multiple line scans can be repositioned in a second direction using a second scanning element 206, which is orthogonal to the first direction. As shown in FIG. 4 , the path of the scanning beam 201 is depicted as a 1D scan generated by the oscillation or rotation (indicated by the curved arrow) of the first scanning element 202. Path "A" is an example of the scanning beam 201 reflecting off the polygonal scanning mirror when the reflective facets are oriented in one direction during rotation, while paths "b" and "c" are examples of the scanning beam 201 reflecting off different orientations of the facets during rotation.

[0036] The components of the ophthalmic imaging device 120 may be arranged such that the rotation axis of the first scanning element 202 is substantially parallel to a line connecting the two focal points (i.e., F2 and F3) of the optical element 208, allowing the scanning beam 201 to scan across the second axis of the optical element 204. Furthermore, the first scanning element 202 may generate a 1D or 2D scan, which is incident on the optical element 204. The optical element 204 may therefore also generate a 1D or 2D scan. The components of the ophthalmic imaging device 102 may be arranged such that the line connecting the two focal points (i.e., F2 and F3) of the optical element 208 substantially lies on a plane defined by the scan (e.g., a 1D vertical scan) generated by the optical element 204.

[0037] The first and second scanning elements are thus capable of together generating an optical scan in the form of a raster scan pattern, e.g., a 2D scan, from a point in space at or near a focal point F3 on or in the patient's eye E. The first and second scanning elements 202, 206 can have operating parameters including oscillation amplitude and oscillation rotational offset. The operating parameters can also include oscillation speed. Any of these operating parameters can be selected to control the direction and pattern of the optical scan from the apparent point source. In some embodiments, the first and second scanning elements can be accommodated on a rotation stage (not shown) that is adjustable to center (or decenter) the scanning beam 201 on the retina of the eye E, thereby allowing the imaging field of view to be "moved" across the retina.

[0038] 5A, 5B, and 5C are schematic illustrations of raw imaging signals obtained in accordance with an embodiment of the present invention. In FIG. 5A, a schematic representation of a signal sequence 500 representing the output of an imaging detector, such as detector 218, as described in connection with FIG. 4, is shown. Specifically, signal sequence 500 may represent the detector output versus time in the form of an intensity signal. For example, a first detected light intensity may be represented as analog signal I1, and a second detected light intensity may be represented as analog signal I2 (as shown for the analog signal in signal portion 501).

[0039] Alternatively, in a digital implementation, the signal sequence 500 may represent a sequence of numerical digital values, with each set of information bits representing an intensity value. For example, the binary number 00001111 represents a decimal intensity value of 15, which may correspond to a known intensity value or a corresponding detector output voltage or current. It should be noted that analog formats 501 and digital formats 502 may coexist in an ophthalmic imaging system according to an embodiment of the present invention. Specifically, the signal sequence may first be provided as, for example, an analog signal 501 as a direct output of the detector 218, and then undergo analog-to-digital conversion (ADC) to form the digital format 502 as shown. The latter is suitable for subsequent data processing in a digital computing device, ultimately generating respective image data that can be displayed to a user of the device.

[0040] In FIG. 5B, a schematic representation of the signal sequence 500 described previously is shown along with a schematic representation of a signal output by a detector positioned to detect a reflected beam of light incident from a reflective facet of the polygon scanning mirror and in a fixed relationship to the optical elements that direct the light beam toward the patient's eye. For example, signal 510 may represent the output of detector 205 described in conjunction with any embodiment of the present invention. Signal sequence 510 may represent the intensity versus time as the output of detector 205. For example, an analog signal may include a peak amplitude indicating that the light beam incident from the polygon scanning mirror passes through a detection point on the detector (e.g., see detection point P of detector 205 in FIG. 3B). This is shown in the case of an analog signal as a peak amplitude in signal portion 511.

[0041] Alternatively, in a digital implementation, the signal sequence 500 represents a sequence of digital numbers, with a set of information bits representing intensity values ​​detected by the detector 205, where, for example, one or more "1" bits can indicate that the light beam passes through the detection point of the detector. It should be noted that in an ophthalmic imaging system according to an embodiment of the present invention, the analog format 511 and the digital format 512 can coexist. Specifically, the signal sequence can first be provided as, for example, an analog signal 511 as a direct output of the detector 205, and then undergo analog-to-digital conversion (ADC) to form the digital format 512 as shown in the figure. The latter is suitable for subsequent data processing in a digital computing device, ultimately generating respective image data that can be displayed to a user of the device. For this purpose, the signal sequences 500 and 510 are processed synchronously with each other, as described below.

[0042] FIG. 5C schematically illustrates the processing of an image sequence 500, e.g., from the imaging sensor 218. Specifically, the sequence 500 is processed into individual scan lines, represented by segments 500-1 through 500-7 of the sequence. A segment 500-(i+1) can begin in the original sequence 500 after the previous segment 500-i has ended. In an embodiment of the present invention, the output of the detector 205 can be used to divide the sequence 500 into individual scan lines. Specifically, the passage of the light beam 201' incident on the polygonal scanning mirror through the detector 205 can indicate the starting position 591 of each segment 500-1, .... This allows compensation for any length variations caused by, for example, differences in the characteristics of the individual reflective facets of the polygonal reflecting mirror. This is because each scan line begins at the same, well-defined position, and any variations toward the end of the scan line can be ignored or truncated after the position indicated by line 593. Each segment can also include data representing a dead zone 592. This may occur due to a finite distance between the detection point of the detector 205 and the reflective surface of the optical element that directs the beam reflected by the polygon scanning mirror to the subject's eye at varying angles. The detector 205 may be configured to generate and output a signal, for example, in the form of a line start pulse signal. Note that the start of a scan line is merely an example, and alignment of multiple scan lines may be obtained by knowing a common line stop point or any other well-defined intermediate point. This signal may in any event form a synchronization signal for the processing and / or acquisition of imaging data.

[0043] 6 shows a flow diagram of a general method embodiment of the present invention. Specifically, the method embodiment relates to the operation of an ophthalmic imaging device that includes a light source, a polygon scanning mirror, an optical element, and a detector configured to detect a reflected beam of light incident from the polygon scanning mirror and positioned in a fixed relationship to the optical element. For example, the method may be suitable for operation of an ophthalmic imaging device such as device 102 or 120 disclosed and described in conjunction with embodiments of the present disclosure. The method includes step S101 of rotating the polygon scanning mirror so that each facet reflects a beam of light at varying angles, step S102 of directing the beam reflected at varying angles toward a subject's eye with the optical element, step S103 of forming an imaging signal sequence by detecting light from the subject's eye, and step S104 of generating an image of the subject's eye from the imaging signal sequence using signals provided by the detector positioned in a fixed relationship to the optical element. For example, the imaging signal sequence formed in step S103 can be processed using signals from detector 205 as described in connection with Figures 5A-5C to generate an image in step S104. It should be noted that steps S101-S104 can be performed simultaneously and / or at least partially sequentially, as most appropriate for the chosen implementation.

[0044] In a further embodiment of the method, the step S104 of generating an image further includes detecting the start points of the scan lines based on the signals provided by the detector. Furthermore, the step S104 of generating an image further includes aligning adjacent scan lines based on the detected start points of each scan line. For example, a detector can be used to split the signal sequence into individual scan lines, and the start points of the scan lines can be determined by the light beam incident from the polygonal scanning mirror passing through the detector (see, for example, positions 591 of individual scan lines 500-1, ... in FIG. 5C). This allows adjacent scan lines to be aligned by considering their respective start points as determined. As a result, for example, even length variations caused by variations in the characteristics of individual reflective elements can be compensated for, thereby improving image quality.

[0045] The foregoing has described certain embodiments and details of the present invention, which may provide one or more advantages by providing an ophthalmic imaging device that can efficiently assemble image data at improved image quality with reduced image jitter while maintaining acceptable system complexity by improving deflection control and scan line alignment in the ophthalmic imaging device. While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only and are not intended to be limiting. Various changes in form and detail will be apparent to those skilled in the relevant art. Accordingly, the exemplary embodiments set forth above are not intended to be limiting.

[0046] While this specification contains details of many specific embodiments, these should not be construed as limiting the scope of any invention or claimed subject matter, but rather as descriptions of features unique to the specific embodiments described herein. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, even if features are described above as acting in a particular combination and initially claimed as such, one or more features from a claimed combination may, in some cases, be deleted from that combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

Claims

1. An ophthalmic imaging device (102), comprising: a light source (200) emitting a light beam (201); a polygonal scanning mirror (202) including a plurality of reflective facets (2021, 2022, ...); a drive (203) configured to rotate the polygonal scanning mirror (202) such that, during operation, each facet (2021, 2022, ...) reflects the light beam at a varying angle (α); an optical element (204) configured to direct the reflected light beam at varying angles towards the subject's eye (E); a detector (205) configured to detect a reflected beam of light incident from each of the reflective facets (2021, 2022, ...) and disposed in a fixed positional relationship with the optical element (204); An ophthalmic imaging device (102) comprising:

2. 2. The ophthalmic imaging device (102) of claim 1, wherein the detector (205) is positioned in the fixed positional relationship with the optical element (204) and corresponds to a predetermined angle in the varying angular range (α).

3. The ophthalmic imaging device (102) of claim 2, wherein the predetermined angle corresponds to the start of a scan line.

4. The ophthalmic imaging device (102) of any one of claims 1 to 3, wherein the detector (205) is configured to detect reflected beams of light incident from all facets of the polygon scanning mirror (202).

5. 5. An ophthalmic imaging device (102) as described in claim 4, wherein the fixed positional relationship between the detector (205) and the optical element (204) is such that the reflected beam light reflected at varying angles (α) for all facets (2021, 2022, ...) of the polygon scanning mirror (202) hits the detection point (P) of the detector (205).

6. An ophthalmic imaging device (102) as described in any one of claims 1 to 5, wherein the optical element (204) comprises a curved mirror and is configured to further reflect the reflected beam light incident from each of the reflective facets (2021, 2022, ...) along a reflection line on the curved mirror and guide it toward the subject's eye (E).

7. 7. The ophthalmic imaging device (102) of claim 6, wherein the detector (205) is positioned in a fixed position relative to the curved mirror, and when a reflection cycle for each facet of the polygon scanning mirror (202) begins, the incident reflected beam light first hits the detector (205) and then hits the reflective area of ​​the curved mirror.

8. The ophthalmic imaging device (102) of any one of claims 1 to 7, further comprising a carrier (209) on which the optical element (204) and the detector (205) are mounted.

9. 9. The ophthalmic imaging device (102) of claim 8, wherein the optical element (204) configured to guide the light beam (201) to the subject's eye (E) comprises a curved mirror, and the carrier (209) comprises a fitting shape to accommodate the curved mirror and a mounting base for holding the detector (205).

10. The ophthalmic imaging device (102) of any one of claims 1 to 9, wherein the detector (205) is configured to provide a signal used for alignment of scan lines during the imaging process.

11. The ophthalmic imaging device (102) of any one of claims 1 to 10, further comprising a processing device configured to generate an image of the subject's eye (E) using a signal provided by the detector (205) arranged in the fixed positional relationship with the optical element (204).

12. 12. The ophthalmic imaging device (102) of claim 11, wherein the processing unit is configured to use the signal provided by the detector (205) as a synchronization basis for forming portions of the image representing multiple scan lines in one direction.

13. a light source emitting a light beam (201); a polygonal scanning mirror including a plurality of reflective facets; an optical element; a detector configured to detect a reflected beam of light incident from each one of the reflective facets and disposed in a fixed positional relationship with the optical element; 1. A method of operating an ophthalmic imaging device comprising: rotating the polygon scanning mirror so that each facet reflects the light beam at a varying angle (S101); directing the light beam, reflected at varying angles by the optical element, toward the subject's eye (S102); generating an imaging signal sequence by detecting light from the eye of the subject (S103); generating an image of the subject's eye from the sequence of imaging signals using signals provided by the detector disposed in the fixed positional relationship with respect to the optical element (S104); A method comprising:

14. The method of claim 13 , wherein generating the image (S104) further comprises detecting a start of a scan line based on the signal provided by the detector.

15. 15. The method of claim 13 or claim 14, wherein generating the image (S104) further comprises aligning adjacent scan lines based on the detected starting points of each scan line.

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