Ophthalmic imaging instrument and line scan alignment control therein

Abstract

The invention relates to an ophthalmic imaging instrument and line scan alignment control therein. The ophthalmic imaging instrument includes a light source emitting a light beam; a polygonal scanning mirror including a plurality of reflective facets; a driver arranged to rotate the polygon scanning mirror during operation such that each facet reflects a light beam at a varying angle; an optical element arranged to direct the light beam reflected at a varying angle towards the eye of the subject; and a detector arranged to detect light of a reflected light beam incident from a respective one of the reflective facets, and positioned in a fixed relationship with the optical element.

Description

Technical Field

[0001] This invention relates to an ophthalmic imaging instrument and line scan alignment control therein. More specifically, but not exclusively, this invention relates to controlling line scan alignment to improve image quality. background

[0002] Ophthalmic imaging instruments are widely used to image a patient's eye to assess its health. Such a system includes a light source and a controller arranged to control the light source to generate a beam with a target optical power. The beam is deflected by one or more scan relay elements to cover the imaging area by means of a parallel arrangement of multiple scan lines. The scan relay elements typically include a polygonal scanning mirror and one or more scanning galvanometers. The polygonal scanning mirror comprises multiple reflecting facets arranged along the circumference of a rotating body. A driver is arranged to rotate the body of the polygonal scanning mirror during operation, such that each facet reflects the incident beam at a varying angle. During passage through a single facet, the beam is deflected within a corresponding range of varying angles. After such a deflection cycle is completed, the next facet essentially repeats the process, and so do all other facets.

[0003] This repeated deflection of the polygonal scanning mirror forms a basis for at least one scanning direction by providing multiple parallel scan lines. Additional scanning elements, such as the galvanometer already mentioned, can then further deflect the beam in another direction to displace the scan lines relative to each other on the target and ultimately cover the two-dimensional scan area. In at least some imaging modalities, light from the scanning beam is scattered back from the target tissue, which, in the case of ophthalmic imaging, primarily comprises parts of the human eye, such as the retina. Typically, the light thus returns along the incident light path so that it is eventually detected by an imaging detector in the form of a light sensor, converted into an intensity signal, and processed to form an image. Specifically, this subsequent signal processing is achieved by means of digital processing resources that compile the individual images from the corresponding set of line scans.

[0004] When compiling an image from a set of line scans traveling in one scanning direction, their respective alignment relative to each other can affect image quality. For example, varying scan line alignment and / or varying scan line lengths can cause jitter effects in the image, and thus result in unsatisfactory low image quality. However, since scan line lengths and their relative positions to each other may depend on the characteristics of the optical elements that deflect and guide the scan beam, the corresponding tolerances in the involved elements can also affect the image quality degradation.

[0005] Therefore, there is a need for improved deflection control and scan line alignment in ophthalmic imaging instruments, which allows for the efficient combination of image data with improved image quality, including reduced image jitter levels, while keeping system complexity at an acceptable level. Overview

[0006] The subject matter of the independent claim solves the problem and achieves the objective. Further preferred embodiments are defined in the dependent claims.

[0007] According to one embodiment of the present invention, an ophthalmic imaging instrument is provided, comprising: a light source for emitting a light beam; a polygonal scanning mirror including a plurality of reflective facets; a driver arranged to rotate the polygonal scanning mirror during operation such that each facet reflects the light beam at a varying angle; an optical element arranged to guide the light beam reflected at the varying angle toward the eye of a subject; and a detector arranged to detect light of a reflected light beam incident from a corresponding reflective facet of the reflective facets, the detector being positioned in a fixed relation arrangement with the optical element.

[0008] According to another embodiment of the present invention, a method for operating an ophthalmic imaging instrument is provided, the ophthalmic imaging instrument comprising a light source for emitting a light beam, a polygonal scanning mirror comprising a plurality of reflective facets, an optical element, and a detector arranged to detect light of a reflected light beam incident from a corresponding reflective facet of the reflective facets and positioned in a fixed relationship with the optical element. The method includes rotating the polygonal scanning mirror such that each facet reflects the light beam at a varying angle, and guiding the light beam reflected at the varying angle toward a subject's eye by means of the optical element; forming an imaging signal stream by detecting light from the subject's eye; and compiling an image of the subject's eye from the imaging signal stream using signals provided by the detector, which is positioned in a fixed relationship with the optical element. Brief description of the attached diagram

[0009] Embodiments of the invention will now be described with reference to the accompanying drawings, which are presented to better understand the inventive concept but should not be construed as limiting the invention. In the drawings: Figure 1 A schematic diagram of an ophthalmic imaging instrument according to a general device embodiment of the present invention is shown; Figure 2 An optical schematic diagram of an ophthalmic imaging instrument according to an embodiment of the present invention is shown; Figure 3A and Figure 3BExamples of optical elements as part of an ophthalmic imaging instrument are shown in a more detailed embodiment of the device according to the present invention; Figure 4 A schematic diagram of an ophthalmic imaging instrument, particularly in the context of retrieving imaging signals, is shown according to an embodiment of the present invention. Figures 5A to 5C An imaging signal retrieved according to an embodiment of the present invention is illustrated schematically; and Figure 6 A flowchart illustrating a general method embodiment of the present invention is shown.

[0010] It should be understood that, unless otherwise stated, some figures are not necessarily shown to scale. In some cases, details that are not essential for understanding this disclosure or that make other details difficult to perceive may have been omitted. Of course, it should be understood that this disclosure is not necessarily limited to the specific examples or embodiments shown or depicted herein. Detailed description

[0011] Figure 1 A schematic diagram of an ophthalmic imaging instrument according to a general device embodiment of the present invention is shown. Specifically, an ophthalmic imaging system 112 is shown, which includes an ophthalmic imaging instrument 102 providing at least one imaging modality 121. For example, the ophthalmic imaging instrument 102 may take the form of a scanning laser ophthalmoscope (SLO) or an optical coherence tomography (OCT) imaging instrument. The imaging modality 121 can then be understood as an operating mode for operating the corresponding instrument. Typically, the ophthalmic imaging instrument 102 can operate in multiple modes, thereby providing multiple corresponding imaging modalities. The ophthalmic imaging system 112 may also include or have access to computing resources 106, which in turn includes a processing unit 108 and a memory unit 110. The components of the ophthalmic imaging system 112, including the ophthalmic imaging instrument 102 and the computing resources 106, may be housed within a common housing, such that the system 112 is formed as an ophthalmic imaging instrument, such as an ophthalmoscope. In some embodiments, the computing resources 106 may be located in various different housings outside the instrument 102. In some embodiments, any component may be housed in a different housing than the rest of the components.

[0012] Computational resource 106 controls ophthalmic imaging instrument 102 to operate in a selected imaging mode 121, and computational resource 106 has at least one processing unit 108 (such as a central processing unit (CPU) and / or graphics processing unit (GPU)) and a memory unit 110 storing instructions that, when executed by at least one processing unit 108, cause the processing unit 108 to perform one or more methods and functions described herein. In embodiments of local computational resources or local physical components of a computing device, the resources may include processors (such as CPUs and / or GPUs), system memory, and a system bus coupling the system memory to the CPU / GPU. System memory may include random access memory (“RAM”) and read-only memory (“ROM”). A basic input / output (“I / O”) system is stored in the ROM, which contains basic routines such as those that help transfer information between elements within the computing device during startup. The computational resource may also include a mass storage device capable of storing software instructions and data. The mass storage device may be connected to the CPU / GPU via a mass storage controller connected to the system bus. Mass storage devices and their associated computer-readable data storage media can provide non-volatile, non-transitory storage for computing resource 106. While the description of computer-readable data storage media herein refers to mass storage devices such as hard disk drives or CD-ROM drives, those skilled in the art will understand that computer-readable data storage media can be any available non-transitory physical device or article of manufacture from which a device can read data and / or instructions. Mass storage devices are examples of computer-readable storage devices.

[0013] Computer-readable data storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable software instructions, data structures, program modules or other data). Examples of computer-readable data storage media include, but are not limited to, RAM, ROM, EPROM, EEPROM, flash memory or other solid-state storage technologies, CD-ROM, digital versatile optical disc (“DVD”), other optical storage media, magnetic tape, magnetic tape, disk storage devices or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible by a computing device.

[0014] Computing resource 106 can operate in a networked environment using a logical connection to remote network devices via a network, such as a local area network, the Internet, or another type of network. Computing resource 106 can be connected to a network via a network interface unit connected to a system bus. The network interface unit can also be connected to other types of networks and remote computing systems. Computing resource 106 includes an input / output controller for receiving and processing input from multiple other devices, including a touch user interface display or another type of input device. Similarly, the input / output controller can provide one or more outputs to a touch user interface display, a printer, or other type of output device. As described above, mass storage devices and RAM can store software instructions and data. The software instructions can include an operating system suitable for controlling the operation of computing resource 106. Mass storage devices and / or RAM can also store software instructions that, when executed by a CPU / GPU, cause computing resource 106 to provide the functionality discussed in this document, including the methods described herein and shown in the accompanying drawings.

[0015] In some embodiments, imaging mode 121 can be provided as the previously mentioned SLO operating mode, which uses a confocal laser scanning microscope to perform diagnostic imaging of the retina of the eye. Imaging can be two-dimensional (2D) imaging, and a laser beam can be used to scan across the retina in a raster pattern to illuminate successive elements of the retina point-by-point. Light reflected from each retinal point can be captured by a photomultiplier tube. The output of the photomultiplier tube can be recorded and displayed in a digital format. In this way, the imaging mode in the SLO is capable of producing high-contrast, detailed images of the retina. In some embodiments, images are captured sequentially through one imaging mode and through at least one other imaging mode.

[0016] Figure 2An optical schematic diagram of an ophthalmic imaging instrument according to an embodiment of the invention is shown. As shown, the ophthalmic imaging instrument 102 includes a light source 200 that emits a beam 201 as a scanning beam. A polygonal scanning mirror 202 acts as a first scanning element (or in other words, a first scanning relay device), and includes a plurality of reflective facets 2021, 2022, ... . A driver 203 is arranged to rotate the polygonal scanning mirror 202 during operation such that each facet 2021, 2022, ... reflects the beam 201 at a varying angle. As shown, the path of the scanning beam 201 is illustrated in a 1D scan generated during the rotation of the polygonal scanning mirror 202 (indicated by the curved arrow). Path "A" is an example of the scanning beam 201 reflected from the corresponding facet 2021 of the polygonal scanning mirror 202 at the starting point during rotation (i.e., when facet 2021 moves into the path of the beam 201 from the light source 200). Path "B" is an example of a scanning beam 201 reflected from the corresponding facet 2021 of the polygonal scanning mirror 202 at a later point in time after further downward rotation. As facet 2021 moves out of the range of beam 201, the adjacent facet 2022 substantially repeats the described reflection process.

[0017] In this way, the polygonal scanning mirror 202 reflects the beam 201 at a varying angle α. This angle α varies within a range controlled by the length and rotation of the respective facets, as the respective orientation of the facets relative to the incident beam 201 determines the reflection angle. However, since the reflection process is continuously repeated with the operation and rotation of the polygonal scanning mirror 202, each facet changes for each scan line. The characteristics of the polygonal scanning mirror, and especially the characteristics of each facet, can now influence the variation in the reflection behavior of each facet during each iteration, where a facet 202... i The beam 201 is reflected into a range of varying angles. For example, manufacturing tolerances associated with the polygonal scanning mirror can lead to variations in facet length or other characteristics and properties, which can alter the reflection angle and thus change the corresponding positions of the scan lines relative to each other.

[0018] The ophthalmic imaging instrument 102 also includes an optical element 204 arranged to guide a light beam 201' reflected at varying angles toward the subject's eye E. Additional components and optical elements such as 290 may be arranged between the optical element 204 and the subject's eye E. The optical element 204 may be or include a curved mirror as shown, but may also take any other suitable form, such as a lens or lens group. An embodiment considering an anterior curved mirror is explained in more detail elsewhere in this disclosure. According to this device embodiment, the ophthalmic imaging instrument 102 includes a detector 205 arranged to detect light from a reflected light beam 201' incident from a corresponding reflecting surface (e.g., surface 2021 as shown). The detector 205 is further positioned in a fixed relationship with the optical element 204. For example, the detector 205 may be positioned in a fixed relationship with the curved mirror (as an optical element guiding the reflected light beam toward the eye), the fixed relationship corresponding to a predetermined angle αi within a range of varying angles. For example, the predetermined angle αi may correspond to the starting angle at the beginning of the reflection period, and thus assume a separate scan line. Typically, the detector may act as a line start sensor 205 and may be located close to the optical element 204, for example at the edge of the optical element 204 / near the optical element 204 or in the peripheral regions 240A, 240B of the optical element 204.

[0019] Detector 205 can be arranged to generate and output a signal S, for example, in the form of a line-start pulse signal. In the example, detector 205 provides a current and / or voltage response relative to the intensity of incident light. Therefore, signal S can include, for example... Figure 2 The illustration shows the intensity versus time distribution. I ( t The pulse-like characteristic T in the signal S. The intensity as part of the signal S. I This feature T can indicate the time ti when the beam 201' is at angle αi, which can be considered as an indication that the beam is at the starting point of the scan line. The signal S can be used to align and / or synchronize scan lines with each other, especially considering scan lines generated by different facets of the polygonal scanning mirror 202, which may have different characteristics, particularly regarding facet length. This embodiment allows for effective synchronization of scan lines and the resulting imaging signal because the detector can provide an output that at least defines or indicates a common point for each scan line, regardless of the facet acting as a reflector or the nature and characteristics of that individual facet.

[0020] Figure 3AAn example of an optical element as part of an ophthalmic imaging instrument according to a more detailed embodiment of the device according to the present invention is shown. As described elsewhere in this disclosure, a light source provides a light beam guided at a polygonal scanning mirror having multiple reflective facets. When the driver rotates the polygonal scanning mirror, each facet reflects the light beam at a varying angle into the optical element, which further guides the light beam reflected at varying angles toward the subject's eye. Typically, the optical element according to the embodiment should be able to further guide light beams incident from different directions toward an imaging target. To this end, the optical element can provide a finite input extension for capturing light beams incident from different directions due to reflection at varying angles at an upstream optical element.

[0021] therefore, Figure 3A An example of such an optical element in the form of an elongated curved mirror 204 is shown. This optical element is capable, for example, of capturing light beams incident from different directions (such as a first direction A and a second direction B). Thus, the optical element includes a curved mirror arranged to guide a light beam incident from a corresponding reflective facet towards the subject's eye by further reflecting the light beam along a reflective ray on the mirror. For this purpose, the curved mirror 204 provides an input extension IE that can cover a range of different directions and angles of the light beam 201'. Therefore, the curved mirror 204 provides an extended reflective region 2040, which in turn accommodates a reflective ray 2041 along which the incident light beam 201' is reflected when the angle of incidence changes. Assuming continuous rotation of the polygonal scanning mirror as an upstream optical element, the reflection point R will move along the reflective ray 2041 accommodated by the extended reflective region 2040. Since the repeated reflections of the polygonal scanning mirror form a scanning direction, the reflective ray 2041 provides a scan line of the light beam. If the angle of incidence varies over a wider range than can be covered by the curved mirror 204, then the curved mirror 204 effectively controls the length of the scan line. This might be the case, for example, if the extended reflection region 2040 is too short because it does not cover (and reflect) the incident beam at one or more ends 2042A, 2042B. Alternatively, for example, if the curved mirror 204 is arranged to cover the full range of varying angles and directions of incidence, the length of the scan line can certainly be controlled by any other optical element.

[0022] Figure 3B Examples of optical elements as part of an ophthalmic imaging instrument are shown in a more detailed embodiment of the device according to the invention, and again, examples of optical elements as part of an ophthalmic imaging instrument are shown, except for those combined with... Figure 3AOptical elements in the form of curved mirror 204, other than those explained (therefore the same reference numerals denote the same elements and functions). Specifically, this embodiment considers the arrangement of detectors such that the detectors detect light incident from all facets of the polygonal scanning mirror at at least one point in the reflection period. As the polygonal scanning mirror rotates, the reflection period can be defined by the light beam reflected from a single facet of the polygonal scanning mirror.

[0023] For example, a fixed arrangement of the detector and optical elements allows a beam of light reflected at varying angles to hit the detector's detection point across all facets of the polygonal scanning mirror. In this embodiment, the curved mirror 204 is shown together with the detector 205, which is arranged to detect the light of an incident beam reflected by a corresponding facet of the upstream polygonal scanning mirror. The detector 205 is positioned in a fixed relationship with the curved mirror 204 such that the position of the detector 205 can be assumed to have a well-defined and constant relationship with its position in the scan line. For example, line 2051 can represent a line in the (curved) plane of the curved mirror 204 that the incident beam 201' intersects as the upstream polygonal scanning mirror rotates. A starting direction A can mark the beginning of line 2051, and an ending direction B can mark the end of line 2051. As shown, the incident beam 201' can begin at an angle at which it neither hits the detector 205 nor the reflecting surface of the curved mirror 204. In this way, the incident beam 201' can always hit the detector 205, so that the detection of light at the detector 205 can provide reliable information about the starting point of the scan line.

[0024] Specifically, the starting direction A can vary due to the nature of any upstream optical element. For example, the facets of the upstream polygonal scanning mirror can have varying characteristics, such as varying lengths, due to manufacturing tolerances. As a result, the starting direction can vary such that for a longer facet length, the direction is A', and for a shorter facet length, the direction is A''. Preferably, the detector 205 is positioned in a fixed arrangement with the curved mirror 204 and other elements of the ophthalmic imaging instrument such that all occurring starting directions within the range of variation from A', which is a corresponding minimum, to A'', which is a corresponding maximum, are located before the position of the sensor 205. Thus, the maximum range of incident directions can be as shown in range 2051, where the lower starting point can vary as described in conjunction with directions A, A', and A'', and the upper stopping point can also vary (see B' and B''). However, the latter may only have a lower relevance, as embodiments of the invention allow determining the reproducible position of at least one point, which may in turn be sufficient to position the scan lines between each other.

[0025] Specifically, the incident beam 201' can begin its cycle in a direction varying between directions A' and A'', and continue the cycle as indicated by arrow Cy. Thus, the start of the cycle is always along the reflection line 2041 located before the position of detector 205 and the detection point P. Note that this line can actually extend beyond the end 2042A of the curved mirror 204, since reflection by the mirror naturally does not occur in that region. In this way, detector 205 is positioned in a fixed arrangement with the curved mirror 204 such that when the reflection cycle Cy begins for each facet of the polygonal scanning mirror, the incident beam 201' first hits detector 205 (e.g., specifically its detection point P), and then hits the reflection region 2040 of the curved mirror 204. A deadband 2054 can exist between the starting point or the detection point P and the start of reflection at end 2042A, which will result in a corresponding deadband in the corresponding image signal. However, such a dead zone can be acceptable because the fixed arrangement of the detector and the optical element in the form of the curved mirror 204 can be regarded as the basis for filtering out the corresponding data, as explained elsewhere in this disclosure.

[0026] Typically, ophthalmic imaging instruments may also include a carrier on which optical elements and detectors are mounted. As an example, and as... Figure 3B As shown, this carrier can be in the form of a mirror carrier 209, which may include features for mounting and stabilizing optical elements in the form of curved mirrors, and may include features for suppressing deflections caused by vibration and / or temperature. For example, the carrier may provide a fitting shape that holds and stabilizes a large portion of the corresponding relative extension of the curved mirror. In the example shown, carrier 209 provides a mounting plateau 2090 for detector 205. For example, the shape that fits to accommodate the curved mirror may extend continuously into the planar platform. The carrier may be manufactured from a single component such that it is formed as a single continuous body, for example, by die casting.

[0027] Figure 4 A schematic diagram of an ophthalmic imaging instrument according to an embodiment of the present invention, particularly in the context of retrieving imaging signals, is shown again, as in conjunction with... Figure 3A and Figure 3BThe elements are explained as such (the same reference numerals therefore denote the same elements and functions). An ophthalmic imaging instrument 120 is described in the context of an imaging modality in which a beam 201 is generated by a light source 200 and directed toward a patient's eye E, reflected at the tissue of the eye E, and directed back to a detector 218. As part of, for example, a SLO, the instrument 120 includes a light source 200 that emits the beam (i.e., the scanning beam 201) and a plurality of scanning relay elements. The scanning relay elements include a first scanning element in the form of a polygonal scanning mirror 202, a second scanning element 206, and optical elements positioned and configured to guide the scanning beam 201. In some embodiments, the optical elements may include an optical element 204 and a second optical element 208, where the optical element 204 may be a scan compensation element, such as a curved mirror or a slit mirror, and the second optical element 208 may be a scan transmission element, such as a primary mirror.

[0028] Optical elements 204 and 208 are positioned and configured to guide the scanning beam 201. The second scanning element 206 may be or include an oscillating plane scanning mirror or a plane scanning mirror coupled to a galvanometer motor. Optical element 204 may be a curved mirror, such as an ellipsoidal 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 and 206 may be referred to as a scanning device or multiple separate scanning devices. It should be understood that the functions shown are merely examples of configurations that can be used with the embodiments described herein.

[0029] Detector 205, for example having the form and function of a line-start sensor, is disposed in or along the optical path of scanning beam 201 and is positioned in a fixed relationship with optical element 204. In some embodiments, detector 205 may be positioned close to optical element 204, for example at / near the edge of optical element 204 or near the peripheral region 240A of optical element 204. Detector 205 may be configured to generate and output a signal, such as a line-start pulse signal, when scanning beam 201 passes through a detection point of detector 205. For example, such a detection point may be defined by the aperture or opening of an optical sensor, which provides a well-defined location for detecting incident light. In some examples, detector 218 may be a separate component or device operatively coupled to light source 200, such that detector 218 and light source 200 may be positioned in the same location or adjacent to each other. In some examples, the light source 200 may be implemented together with the detector 218 as a single device or a device within a common housing, such that, in addition to emitting the scanning beam 201, the device may also be able to detect or receive light, such as light reflected from the first scanning element 202 or from the optical element 204.

[0030] In an exemplary SLO operating in an exemplary imaging mode, the scanning beam 201 can be a laser with a suitable wavelength used in the SLO application. If other imaging modes are included, the scanning beam 201 can be a collimated beam, comprising, for example, a laser for the SLO application and 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 other light sources with sufficient intensity and good collimation to produce sufficient retinal illumination. In such applications, an SLD can be used due to the short coherence length required to distinguish the retinal layer from the resulting interferometric data. The SLD can be free-space coupled to the scanning system or fiber-coupled to the scanning system via a standard or polarization-maintaining fiber. A frequency-scanning laser source can also be used in other applications, thereby tuning the wavelength of the source within a given range.

[0031] In some embodiments, one or more of the 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 a polygonal 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, as long as it is suitable for providing a scan at a corresponding focal point F1 or F2 (as shown) where the scanning elements are positioned. Focal points F1 and F2 are the focal points of optical element 204, and focal points F2 and F3 are the focal points of 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 E is located at focal point F3 (also referred to as a virtual scan point). When light sweeps across the virtual scan point within the eye E (e.g., through F3), the resulting scan may be a 2D scan of the scanning beam 201 or a scan pattern.

[0032] In some embodiments, the first scanning element 202 provides a vertical scan, horizontal scan, or patterned scan incident on the optical element 204 to a point on the second scanning element 206 via the optical element 204. For example, the scan can be a one-dimensional (1D) optical scan or a two-dimensional (2D) optical scan. The axes of the first scanning element 202 and the second scanning element 206 can be arranged to create a 2D optical scan, such as in the form of a raster scan pattern of a scan beam 201. The alignment of the first scanning element 202 and the second scanning element 206 can be orthogonal, substantially orthogonal, or arranged to produce any scan geometry around the optical elements 204 and 208.

[0033] In some embodiments, the second scanning element 206 provides various scans, such as 1D or 2D optical scans, which may include horizontal scans, vertical scans, or any pattern of the scanning beam 201. The scans provided by the first scanning element 202 and the scans provided by the second scanning element 206 differ from each other, for example, with respect to the orientation of the scans. In some examples, one of the scanning elements may provide a vertical scan of the retina, and the other scanning element may provide a horizontal scan of the retina. The scanning beam 201 is guided toward the patient's eye E via scanning elements 202 and 206, and optical elements 204 and 208, thereby achieving an ultra-wide field of view scanning angle at the pupillary plane of the eye E.

[0034] A "wide field of view" scan refers to a scanning angle exceeding 50 degrees in one or two dimensions. An "ultra-wide field of view" scan refers to a scan that essentially covers the entire retina of the eye E. In some examples, multiple line scans can be generated by scanning the retina along a first direction using a first scanning element 202, and by changing the position of the multiple line scans along a second direction using a second scanning element 206, wherein the second direction is orthogonal to the first direction. Figure 4 As shown, the path of the scanning beam 201 is illustrated in a 1D scan generated by a single oscillation or rotation (indicated by the curved arrow) of the first scanning element 202. Path "A" is an example of the scanning beam 201 reflected from the polygonal scanning mirror at one orientation of the reflective facet during rotation, while paths "B" and "C" are examples of the scanning beam 201 reflected at other orientations of the facet during rotation.

[0035] The components of the ophthalmic imaging instrument 120 can be arranged such that the axis of rotation of the first scanning element 202 is substantially parallel to the line connecting the two focal points (i.e., F2 and F3) of the optical element 208, such that the scanning beam 201 scans across the secondary axis of the optical element 204. Furthermore, the first scanning element 202 can produce a 1D or 2D scan incident on the optical element 204. Therefore, the optical element 204 can also produce a 1D or 2D scan. The components of the ophthalmic imaging instrument 102 can be arranged such that the line connecting the two focal points (i.e., F2 and F3) of the optical element 208 lies substantially on the plane defined by the scan produced by the optical element 204 (e.g., a 1D vertical scan).

[0036] Therefore, the first scanning element 202 and the second scanning element 206 can work together to create an optical scan in the form of a raster scan pattern, such as a 2D scan, from a single point in space at or near the focal point F3 in the patient's eye E. The first and second scanning elements can have operating parameters including the amplitude and rotational offset of the oscillation. The operating parameters also include the oscillation speed. Both operating parameters can be selected to control the direction and pattern of the optical scan from the surface point light source. In some examples, the first and second scanning elements can be housed in a rotatable mount (not shown) that can adjust the centering (or eccentricity) of the scanning beam 201 on the retina of the eye E, providing the ability to “move” the imaging field across the retina.

[0037] Figures 5A to 5C An imaging signal retrieved according to an embodiment of the present invention is illustrated schematically. Figure 5A The diagram shows a schematic representation of signal flow 500, which represents an imaging detector (e.g., combined with...). Figure 4 The output of the detector 218 is explained. Specifically, the signal stream 500 can represent the relationship between the detector output and time t in the form of an intensity signal. For example, the intensity of the first detected light can be represented as an analog signal I1, and the intensity of the second detected light can be represented as an analog signal I2 (as shown in the case of the analog signal for the signal section 501).

[0038] Alternatively, in a digital implementation, signal stream 500 can represent a stream of numerical values, where a set of information bits can represent an intensity value. For example, the binary number 00001111 can represent an intensity value of decimal 15, which in turn can correspond to a known intensity value or the corresponding detector output voltage or current. Note that analog form 501 and digital form 502 can coexist with an ophthalmic imaging system according to an embodiment of the invention. Specifically, the signal stream can initially be provided as an analog signal (such as 501) as an immediate output of detector 218, and then converted by an analog-to-digital converter (ADC) into the form shown in digital form 502. The latter can be adapted for subsequent data processing using digital computing resources to ultimately compile the corresponding image data to be displayed to the user of the instrument.

[0039] exist Figure 5BThe diagram illustrates a schematic representation of the signal flow 500 as described above, but incorporates a schematic representation of a signal output by a detector arranged to detect light from a reflected beam incident on the reflective facets of a polygonal scanning mirror, and positioned in a fixed relationship with an optical element that directs the beam to the subject's eye. For example, signal 510 could represent the output of detector 205 as explained in connection with any embodiment of this disclosure. Signal flow 510 could represent the relationship between intensity and time t as the output of detector 205. For example, an analog signal could include a peak amplitude indicating the point of detection of the beam incident from the polygonal scanning mirror (see, for example...). Figure 3B The detection point P of the detector 205. This is shown as the peak amplitude in the signal section 511 for the case of analog signals.

[0040] Alternatively, in a digital implementation, signal stream 510 can represent a stream of numerical values, where a set of information bits can represent the intensity value detected by detector 205, wherein, for example, one or more bits "1" can indicate that the beam has passed through the detection point of the detector. Note that analog form 511 and digital form 512 can coexist with an ophthalmic imaging system according to an embodiment of the invention. Specifically, the signal stream can initially be provided as an analog signal (such as 511) as an immediate output of detector 205, and then converted by an analog-to-digital converter (ADC) into the form shown in digital form 512. The latter can be adapted for later data processing using digital computing resources to ultimately compile corresponding image data to be displayed to the user of the instrument. For this purpose, signal stream 500 and signal stream 510 are processed synchronously with each other, as described below.

[0041] Figure 5CThe processing of an imaging signal stream 500, for example, originating from an imaging sensor 218, is schematically illustrated. Specifically, the stream 500 is processed into individual scan lines represented by sections 500-1 to 500-7 of the stream 500. Note that section 500-(i+1) may begin in the original stream 500 after the end of the previous section 500-i. In embodiments of the invention, the output of detector 205 can be used to segment the signal stream 500 into individual scan lines. Specifically, the beam 201' incident from the polygonal scanning mirror can be considered as the starting position 591 of each section 500-1, ... through detector 205. Thus, any variation in length caused, for example, by the changing characteristics of the various reflective facets of the polygonal scanning mirror can be compensated for, since each scan line begins at the same clearly defined position, and any variation toward the end of the scan line can be ignored or cut off after the position indicated by line 593. Each segment may also include data representing dead zone 592, as this may be caused by a finite distance between the detection point of detector 205 and the beginning of the reflective surface of an optical element that guides a beam of light reflected at varying angles by a polygonal scanning mirror toward the subject's eye. Detector 205 can be configured to generate and output a signal, for example, in the form of a line start pulse signal. It should be noted that the starting point of a scan line is merely an example, as alignment of multiple scan lines can also be achieved by knowing the common line stop point or any other well-defined intermediate point. This signal can be formed in any way as a synchronization signal for image data processing and / or acquisition.

[0042] Figure 6 A flowchart of a general method embodiment of the present invention is shown. Specifically, the method embodiment relates to operating an ophthalmic imaging instrument including a light source, a polygonal scanning mirror, optical elements, and a detector arranged to detect light reflected from a facet of the polygonal scanning mirror and positioned in a fixed relationship with the optical elements. For example, the method may be adapted to operate an ophthalmic imaging instrument such as instrument 102 or instrument 120 disclosed and described in conjunction with embodiments of this disclosure. The method includes step S101: rotating the polygonal scanning mirror such that each facet reflects the light beam at a varying angle; step S102: guiding the light beam reflected at the varying angle toward the subject's eye by means of the optical elements; step S103: forming an imaging signal stream by detecting light from the subject's eye; and step S104: compiling an image of the subject's eye from the imaging signal stream using signals provided by a detector positioned in a fixed relationship with the optical elements. For example, signals from detector 205 can be used to process the imaging signal stream formed in step S103, as in conjunction with... Figures 5A to 5CAs described, the image is compiled in step S104. It should be noted that steps S101 to S104 may be performed simultaneously and / or at least partially sequentially, if the chosen implementation is most suitable.

[0043] In another method embodiment, step S104 of compiling the image may include detecting the start point of a scan line based on a signal provided by a detector. Furthermore, step S104 of compiling the image may include aligning adjacent scan lines based on the detected start of the corresponding scan line. For example, a detector may be used to segment the signal stream into individual scan lines, wherein a beam of light incident from a polygonal scanning mirror can be used by the detector to determine the start point of the scan line (see, for example...). Figure 5C Individual scan lines 500-1, ..., 591). Thus, adjacent scan lines can be aligned taking into account the determined corresponding starting points, so as to improve image quality while compensating for even varying lengths caused, for example, by varying characteristics of the individual reflective elements.

[0044] The foregoing has presented embodiments and details thereof as part of the present invention, which can provide one or more advantages by improving deflection control and scan line alignment in ophthalmic imaging instruments that allow for efficient combination of image data with improved image quality, including reduced image jitter levels, while keeping system complexity at an acceptable level. While various embodiments of this disclosure have been described above, it should be understood that they are presented by way of example and not limitation. It will be apparent to those skilled in the art that various changes in form and detail can be made. Therefore, the exemplary embodiments described above are not limiting.

[0045] While this specification contains numerous details of specific embodiments, these should not be construed as limiting the scope of any invention or potentially claimed content, but rather as descriptions of features specific to the particular embodiments described herein. Certain features described in this specification within the context of individual 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 individually or in any suitable sub-combination in multiple embodiments. Furthermore, although features may be described above as acting in a particular combination and even initially claimed in this way, one or more features from a claimed combination may be removed from the combination in some cases, and the claimed combination may be for a sub-combination or a variation thereof.

Claims

1. An ophthalmic imaging instrument (102), comprising: Light source (200) that emits beam (201); A polygonal scanning mirror (202) includes multiple reflective facets (2021, 2022, ...). A driver (203) is arranged to rotate the polygonal scanning mirror (202) during operation such that each facet (2021, 2022, ...) reflects the light beam at a varying angle (α); An optical element (204) is arranged to guide the light beam, reflected at varying angles, toward the subject's eye (E), and A detector (205) is arranged to detect light from a reflected beam incident from a corresponding one of the reflective facets (2021, 2022, ...), and is positioned in a fixed relationship with the optical element (204).

2. The ophthalmic imaging instrument (102) according to claim 1, wherein, The detector (205) is positioned in a fixed arrangement with the optical element (204) corresponding to a predetermined angle within the range of the changing angle (α).

3. The ophthalmic imaging instrument (102) according to claim 2, wherein, The predetermined angle corresponds to the starting point of the scan line.

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

5. The ophthalmic imaging instrument (102) according to claim 4, wherein, The fixed arrangement of the detector (205) and the optical element (204) is such that the light beam reflected at a varying angle (α) hits the detection point (P) of the detector (205) on all facets (2021, 2022, ...) of the polygonal scanning mirror (202).

6. The ophthalmic imaging instrument (102) according to any one of claims 1 to 5, wherein, The optical element (204) includes a curved mirror arranged to guide the light beam incident from a corresponding one of the reflective facets (2021, 2022, ...) toward the subject's eye (E) by further reflecting the light beam along a reflective line on the curved mirror.

7. The ophthalmic imaging instrument (102) according to claim 6, wherein, The detector (205) is positioned in a fixed arrangement with the curved mirror such that when a reflection cycle begins for each facet of the polygonal scanning mirror (202), the incident light beam first hits the detector (205) and then hits the reflection area of ​​the curved mirror.

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

9. The ophthalmic imaging instrument (102) according to claim 8, wherein, The optical element (204), which is arranged to direct the light beam (201) toward the subject's eye (E), is formed of a curved mirror, wherein the carrier (209) includes a shape adapter for accommodating the curved mirror and a mounting platform (2090) arranged for holding the detector (205).

10. The ophthalmic imaging instrument (102) according to any one of claims 1 to 9, wherein, The detector (205) is arranged to provide signals for aligning scan lines during imaging processing.

11. The ophthalmic imaging instrument (102) according to any one of claims 1 to 10 further includes processing resources arranged to compile an image of the subject's eye (E) using signals provided by the detector (205), the detector (205) being positioned in the fixed relationship with the optical element (204).

12. The ophthalmic imaging instrument (102) according to claim 11, wherein, The processing resources are arranged to use the signal provided by the detector (205) as a synchronization basis for forming segments of scan lines representing the image in one direction.

13. A method for operating an ophthalmic imaging instrument, the ophthalmic imaging instrument comprising a light source for emitting a light beam, a polygonal scanning mirror including a plurality of reflective facets, optical elements, and a detector, the detector being arranged to detect light of a reflected light beam incident from a corresponding reflective facet of the reflective facets and being positioned in a fixed relationship with the optical elements, the method comprising: Rotate the polygonal scanning mirror so that each facet reflects the light beam at a changing angle (S101). The optical element guides the light beam, which is reflected at a changing angle, toward the subject's eye (S102). An imaging signal stream is formed by detecting light from the subject's eyes (S103). The image of the subject's eye from the imaging signal stream is compiled using the signal provided by the detector, which is positioned in the fixed relationship with the optical element (S104).

14. The method according to claim 13, wherein, The step of compiling the image (S104) also includes detecting the starting point of the scan line based on the signal provided by the detector.

15. The method according to claim 13 or 14, wherein, The step of compiling the image (S104) also includes aligning adjacent scan lines based on the starting point of the detected corresponding scan line.

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