Optical coherence tomography-guided robotic ophthalmic procedures

Abstract

The systems and methods described herein provide improved techniques for OCT-guided robotic ophthalmic procedures. The method includes receiving position data of multiple galvanometer scanners from multiple absolute and incremental encoders coupled to corresponding galvanometer scanners during an OCT scan of the eye. The method further includes receiving scan data related to one or more tissues of the eye. The method further includes determining a first set of positions of one or more tissues of the eye in a first 3D coordinate system. The method further includes determining a position in a second 3D coordinate system of a surgical instrument coupled to a robotic device based on the first set of positions and a mapping between the first 3D coordinate system and the second 3D coordinate system. The method includes causing the robotic device to move the surgical instrument to a position in the second 3D coordinate system.

Description

[Technical Field]

[0001] Embodiments of the present disclosure relate generally to methods and apparatus for ophthalmic procedures, and more particularly to methods and apparatus for optical coherence tomography (OCT)-guided robotic ophthalmic procedures. [Background technology]

[0002] OCT-guided robotic ophthalmic procedures can improve patient care. For example, OCT-guided robotic vitreoretinal surgery can result in precise incisions of the tissue of interest in the patient's eye, more consistent surgical procedures, and prevent human error during the procedure. To safely perform a true OCT-guided robotic ophthalmic procedure, precise data regarding the location of various tissues in the eye must be provided to the robotic device.

[0003] Existing OCT systems can be configured to perform OCT scans of the eye and detect various tissues of the eye. Existing OCT systems may perform OCT scans of the eye. 2 R losses can make existing OCT systems sensitive to heat generated from heating of the galvanometer scanner. Such heat can result in thermal drift of one or more components (e.g., galvanometer scanner, analog capacitive angle sensor, etc.) of the OCT system. Thermal drift can cause one or more scanning components of the OCT system to drift from their expected positions. Similarly, friction caused by bearings of some moving components of some existing OCT systems can also result in thermal drift, causing one or more components of the OCT system to drift from their expected positions.

[0004] Typically, because galvanometer scanners are rotary actuators with limited angular range, thermal drift can result in angular position errors in the galvanometer scanners of OCT systems. The angular position errors can result in translation errors that can cause the system to erroneously target intraocular tissue up to 100 microns away from the tissue plane selected by the user. Additionally, analog capacitive angle sensors coupled to galvanometer scanners cannot compensate for such thermal drift and cannot nullify errors in the 100-micron range.

[0005] Therefore, certain existing OCT systems are unable to accurately determine the spatial location and orientation of tissue within the eye being scanned by the OCT system, and as such, such existing OCT systems are unable to accurately guide robotic ophthalmic procedures. Summary of the Invention [Means for solving the problem]

[0006] The present disclosure relates generally to methods and apparatus for OCT-guided robotic ophthalmic procedures.

[0007] In certain embodiments, an optical coherence tomography (OCT) system includes a plurality of galvanometer scanners, a plurality of absolute encoders, and a plurality of incremental encoders, wherein each one of the plurality of absolute encoders and each one of the plurality of incremental encoders is coupled to at least one of the plurality of galvanometer scanners. The OCT system further includes a controller coupled to the plurality of absolute encoders and the plurality of incremental encoders. The controller includes a processor and a memory coupled to the processor and having instructions stored thereon, which, when executed by the processor, cause the controller to receive position data of the plurality of galvanometer scanners from the plurality of absolute encoders and the plurality of incremental encoders coupled to corresponding galvanometer scanners during an optical coherence tomography (OCT) scan of the eye. The processor also causes the controller to receive scan data related to one or more tissues of the eye during the OCT scan. The processor also causes the controller to determine a first set of positions of one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received position data and the scan data. The processor also causes the controller to determine a position in a second 3D coordinate system of a surgical instrument coupled to the robotic device based on the first set of positions and the mapping between the first 3D coordinate system and the second 3D coordinate system, and the processor also causes the controller to move the surgical instrument to a position in the second 3D coordinate system.

[0008] In certain embodiments, a method generally includes receiving position data of multiple galvanometer scanners from multiple absolute encoders and multiple incremental encoders coupled to corresponding galvanometer scanners during an optical coherence tomography (OCT) scan of an eye, wherein each one of the multiple absolute encoders and each one of the multiple incremental encoders is coupled to at least one of the multiple galvanometer scanners. The method further includes receiving scan data related to one or more tissues of the eye during the OCT scan. The method further includes determining a first set of positions of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received position data and the scan data. The method further includes determining a position of a surgical instrument coupled to a robotic device in a second 3D coordinate system based on the first set of positions and a mapping between the first 3D coordinate system and a second 3D coordinate system. The method further includes determining a position in the second 3D coordinate system of a surgical instrument coupled to the robotic device based on the first set of positions and the mapping between the first 3D coordinate system and the second 3D coordinate system.

[0009] Aspects of the present disclosure provide means for apparatuses, processors, and computer-readable media for performing the methods described herein.

[0010] So that the above-listed features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and should not be considered as limiting the scope thereof, as other equally effective embodiments may be recognized. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1A illustrates a block diagram of selected components of an exemplary OCT-guided robotic eye surgery system, in accordance with certain embodiments of the present disclosure. [Figure 1B] FIG. 1B illustrates a perspective view of a galvanometer scanner, in accordance with certain embodiments of the present disclosure. [Figure 2] FIG. 2 illustrates a block diagram of selected components of an OCT controller in accordance with certain embodiments of the present disclosure. [Figure 3] FIG. 3 shows a flowchart of an exemplary method for guiding a robotic device for an ophthalmic procedure, according to certain embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] For ease of understanding, where possible, the same reference numerals are used to indicate identical elements that are common to multiple figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0013] The present disclosure relates generally to methods and apparatus for OCT-guided robotic ophthalmic procedures.

[0014] As described herein, a robotic ophthalmic procedure may be an ophthalmic procedure performed by a robotic device based on user input received from a user, which may include a selection of an ophthalmic procedure, a selection of a target tissue, instructions for performing the selected procedure, etc.

[0015] Existing OCT systems can be configured to scan an eye, allowing a surgeon to identify one or more eye tissues on an image generated based on scan data from the eye scan combined with stereoscopic digital visualization. However, existing OCT systems are generally not configured to provide the precise position or location of one or more eye tissues. For example, OCT systems typically consist of a galvanometer scanner coupled to an analog capacitive angle sensor. However, heat generated from some components of the OCT system (e.g., the galvanometer scanner) and / or bearing friction from the operation of the OCT system components can result in thermal drift, which can cause angular errors when determining the angular position of the galvanometer scanner of the OCT system. Such thermal drift can result in translational errors, typically in the range of 100 microns, when determining the location of tissues within the eye. While such thermal drift may have minimal impact on OCT image generation, attempting to determine the position and / or location of various eye tissues in a coordinate system without correcting and / or removing the thermal drift can be dangerous. Therefore, existing OCT systems are unable to accurately guide robotic ophthalmic procedures.

[0016] Accordingly, some implementations of the present disclosure provide various systems and techniques that improve the accuracy of an OCT system in determining the location of one or more tissues within an eye and effectively guiding a robotic device to move a surgical instrument to the tissue within the eye. Some implementations of the present disclosure provide various systems and techniques that configure an OCT system to receive input related to one or more target tissues of a scanned eye from a user (e.g., a surgeon) and configure the OCT system to determine the location or location of the one or more target tissues of the eye in a coordinate system of the OCT system. Some embodiments of the present disclosure provide various systems and techniques that configure the OCT system to provide a robotic device with the location or location of one or more target tissues of the eye in the coordinate system of the robotic device and cause the robotic device to move a surgical instrument or another medical instrument coupled to the robotic device to the one or more target tissues based on the provided location or location.

[0017] 1A shows a block diagram of selected components of an exemplary optical coherence tomography (OCT)-guided robotic eye surgery system 10. The OCT-guided robotic eye surgery system 10 includes an OCT system 100 and a robotic device 120. The OCT system 100 includes an OCT scanner 102, an OCT controller 104, an imaging system 106, and a display 108. The OCT system 100 can be communicatively coupled to the robotic device 120 and an external display 110.

[0018] The OCT scanner 102 may include multiple OCT components and / or devices (not shown separately in FIG. 1A ). The OCT components and / or devices may be of various types, and the OCT scanner 102 may be configured differently based on the type of OCT components and / or devices. The OCT scanner 102 performs an OCT scan of a patient's eye 130. The OCT scanner 102 may perform an OCT scan by controlling the output of one or more sample beams (not shown) onto the eye 130 and receiving one or more measurement beams (not shown) reflected back from the eye 130. The one or more measurement beams may be reflected back from the eye 130 in response to photons of the sample beams interacting with tissue within the eye 130. In some implementations, the OCT scanner 102 may be configured as a time-domain OCT (TD-OCT). In some implementations, the OCT scanner 102 may be configured as a frequency-domain OCT (FD-OCT). In some implementations, the OCT scanner 102 can be configured as a swept-source OCT (SS-OCT).

[0019] The OCT scanner 102 may include multiple galvanometer scanners (not separately shown in FIG. 1A ), which can be used to control the output of one or more sample beams onto the eye 130. In some implementations, the OCT scanner 102 may include dual galvanometer scanners. Each galvanometer scanner of the OCT scanner 102 may be configured to scan in a particular direction. For example, one galvanometer scanner of the OCT scanner 102 may be configured to scan in a first direction, and another galvanometer scanner of the OCT scanner 102 may be configured to scan in a second direction. In some implementations, the first direction and the second direction may be different directions. In some implementations, the first direction may be perpendicular to the second direction. In some implementations, one galvanometer scanner of the OCT scanner 102 may scan in a first direction on a first scanning plane, and another galvanometer scanner of the OCT scanner 102 may scan in a second direction on a second scanning plane. In some implementations, the first scan plane can be perpendicular to the second scan plane.

[0020] Each galvanometer scanner may be coupled to an absolute encoder (not separately shown in FIG. 1A ) and an incremental encoder (not separately shown in FIG. 1A ). For example, if the OCT scanner 102 includes two galvanometer scanners, a first absolute encoder and a first incremental encoder may be coupled to the first galvanometer scanner, and a second absolute encoder and a second incremental encoder may be coupled to the second galvanometer scanner. In some implementations, the absolute encoder coupled to the galvanometer scanners of the OCT scanner 102 may be an optical rotary absolute encoder. In some implementations, the incremental encoder coupled to the galvanometer scanners of the OCT scanner 102 may be an optical rotary incremental encoder. In some implementations, the absolute encoder and the incremental encoder may be coupled to a shaft connected to one or more elements (e.g., a mirror) of the galvanometer scanner. An absolute encoder may be configured to measure the absolute or true angular position of a galvanometer scanner based on rotation of a shaft connected to an element (e.g., a mirror) of the galvanometer scanner. An incremental encoder may be configured to measure a change in the angular position of a galvanometer scanner based on rotation of a shaft connected to an element (e.g., a mirror) of the galvanometer scanner.

[0021] The absolute encoders coupled to the galvanometer scanners of the OCT scanner 102 can be configured to determine the absolute or true angular position of the corresponding galvanometer scanner without performing a feedback process to initialize or reinitialize after any power interruption or thermal drift. The absolute and incremental encoders coupled to the galvanometer scanners of the OCT scanner 102 can be configured to have high angular resolution. The incremental encoders coupled to the galvanometer scanners of the OCT scanner 102 can be configured to have higher angular resolution than the absolute encoders coupled to the galvanometer scanners of the OCT scanner 102. Therefore, utilizing a combination of absolute and incremental encoders is advantageous because the absolute encoders can provide the absolute or true angular position of the galvanometer scanners to a controller, such as the OCT controller 104, without performing a feedback process after any thermal drift or power interruption, and the incremental encoders, with their higher angular resolution, can accurately detect even small changes in the angular position of the galvanometer scanners and accurately track changes in the angular position of the galvanometer scanners. In some implementations, the absolute and incremental encoders coupled to the galvanometer scanners of the OCT scanner 102 can measure resolution values ​​with bit resolution, for example, typically 16-bit resolution or greater.

[0022] Each absolute encoder can be configured to generate an output including a unique configuration of bits for each position of the galvanometer scanner to which the absolute encoder is coupled. The unique configuration of bits generated by the absolute encoder indicates the position data of the corresponding galvanometer scanner to which the absolute encoder is coupled. In some implementations, the output of each incremental encoder is analog and proportional to the sine-cosine of the scan angle. The output of the incremental encoder indicates the position of the galvanometer scanner to which the incremental encoder is coupled.

[0023] Each absolute and incremental encoder included in the OCT scanner 102 can capture angular position data of the corresponding galvanometer scanner to which it is coupled and transmit the position data to the OCT controller 104. In some implementations, the absolute and incremental encoders can be configured to transmit the position data to the OCT controller 104 in real time and / or near real time. In some implementations, one absolute encoder and one incremental encoder can be integrated into a single encoder device. Additional details about absolute and incremental encoders are described below with reference to FIG. 1B.

[0024] The corresponding galvanometer scanner position data can indicate the position of the galvanometer scanner mirror during an OCT scan of a patient's eye (e.g., eye 130). For example, position data from an absolute encoder coupled to a galvanometer scanner configured to scan in a first direction on a first scan plane can indicate the position of the galvanometer scanner mirror rotating in the first direction on the first scan plane during an OCT scan of eye 130. Similarly, position data from an absolute encoder coupled to a galvanometer scanner configured to scan in a second direction on a second scan plane can indicate the position of the galvanometer scanner mirror rotating in the second direction on the second scan plane during an OCT scan of eye 130. As described above, in some implementations, the first scan plane can be perpendicular to the second scan plane. As described above, in some implementations, the first direction can be different from the second direction. As described above, in some implementations, the first and second directions can be the same direction.

[0025] An example of a galvanometer scanner is shown in FIG. 1B. The galvanometer scanner shown in FIG. 1B is a moving magnet galvanometer scanner. FIG. 1B shows a perspective view of a galvanometer scanner 150. The galvanometer scanner 150 may include a mirror 156 and one or more magnets 164. The mirror 156 and the one or more magnets 164 may be connected to each other via a shaft 162. In some implementations, the shaft 162 may be a steel shaft. The galvanometer scanner 150 may include coils 152a-152b. The coils 152a-152b may surround the one or more magnets 164, as shown in FIG. 1B.

[0026] The encoder device 160 can include an absolute encoder and an incremental encoder, and the encoder device 160 can be coupled to the galvanometer scanner 150. For example, as shown in FIG. 1B , the encoder device 160 can be connected to the mirror 156 and one or more magnets 164 via a shaft 162. During an OCT scan of a patient's eye, the mirror 156 is driven by a coil current I induced by the one or more magnets 164. c The mirror 156 can rotate in response to the Lorentz force induced by the rotation of the mirror 156. As the mirror 156 rotates, different angular positions of the mirror 156 are captured and / or measured by the encoder device 160. The angular position of the mirror 156 may be referred to herein as the mechanical angle of the mirror 156. The absolute encoder of the encoder device 160 may be configured to generate a unique configuration of bits for each angular position or mechanical angle of the mirror 156. The incremental encoder of the encoder device 160 may be configured to track changes in the angular position or mechanical angle of the mirror 156 as the mirror 156 rotates. As described above, the mechanical angle of the mirror of a galvanometer scanner during an OCT scan can indicate the position of the galvanometer scanner described herein. Thus, different captured and / or measured mechanical angles of the mirror 156 during an OCT scan indicate different positions of the galvanometer scanner during the OCT scan.

[0027] The encoder device 160 can transmit the output of the absolute and incremental encoders to the OCT controller 104 as the position of the galvanometer scanner 150. As mentioned above, in certain implementations, the outputs of the absolute and incremental encoders can indicate, or may be referred to herein as indicating, position data of the galvanometer scanner to which the absolute and incremental encoders are coupled (e.g., the galvanometer scanner 150). During an OCT scan, the encoder device 160 can transmit the outputs of the absolute and incremental encoders to the OCT controller 104.

[0028] In some implementations, the absolute encoder of encoder device 160 may be a sine-cosine encoder. In some implementations, the absolute encoder of encoder device 160 may be a holographic encoder. In some implementations, the absolute encoder of encoder device 160 may have a grating and / or a holographic optical element (not shown separately) mounted on the absolute encoder of encoder device 160. In particular implementations, the incremental encoder operating in conjunction with the absolute encoder of encoder device 160 is holographic.

[0029] During an OCT scan, one or more sample beams 154 may be directed to a mirror 156. As the mirror 156 rotates during an OCT scan, the rotation of the mirror 156 may change the deflection angle of the one or more sample beams 154. The deflection angle of the one or more sample beams 154 may be referred to herein as the optical angle of the one or more sample beams 154. In some implementations, the OCT scanner 102 may transmit the different optical angles of the one or more sample beams 154 as part of and / or along with the scan data transmitted to the OCT controller 104.

[0030] Returning to FIG. 1A , the OCT scanner 102 may be configured to scan the eye 130 at various depths within the eye 130. For example, the OCT scanner 102 may be configured to scan the entire depth of the eye 130 for a complete eye scan of the eye 130. Similarly, the OCT scanner 102 may be configured to scan any portion of the eye 130, such as the retina of the eye 130. In some implementations, the OCT scanner 102 may scan different depths of the eye 130 with different resolutions. For example, the OCT scanner 102 may scan the entire depth of the eye 130 with a lower resolution and scan a portion of the eye 130, such as the retina of the eye 130, with a higher resolution.

[0031] The OCT scanner 102 may be configured to generate scan data based on one or more measurement beams reflected back from the eye. The scan data may represent a depth profile of the scanned tissue. In some implementations, the scan data generated by the OCT scanner 102 may include two-dimensional (2D) scan data of a line scan (B-scan). In some implementations, the scan data generated by the OCT scanner 102 may include three-dimensional (3D) scan data of an area scan (C-scan, emmetropia). The OCT scanner 102 may be configured to transmit the generated scan data to the OCT controller 104. In some implementations, the OCT scanner 102 may be configured to transmit the generated scan data in real time or near real time. In some implementations, the OCT scanner 102 may be configured to transmit the generated scan data after the entire scanning operation is completed by the OCT scanner 102.

[0032] The OCT scanner 102 may be configured to initiate a scan of the eye 130 in response to receiving a command and / or instruction from the OCT controller 104. The OCT controller 104 may be configured to send a start scan command to the OCT scanner 102 in response to receiving an instruction from a user, such as a surgeon, to initiate an eye scan. The OCT controller 104 may be configured to receive instructions to initiate an eye scan via a user interface (e.g., a graphical user interface (GUI)) and / or an input device (not shown). The input device may be communicatively coupled to and / or incorporated into the imaging system 106. Examples of input devices include, but are not limited to, a keypad, a keyboard, a touchscreen device configured to receive touch input, etc.

[0033] In some implementations, instructions from a user can provide information related to the depth and / or location of the eye for scanning, and the OCT controller 104 can be configured to provide the received depth and / or location-related information of the eye to the OCT scanner 102. For example, instructions received by the OCT controller 104 can indicate an OCT scan of the complete eye, and the OCT controller 104 can send instructions to the OCT scanner 102 indicating an OCT scan of the complete eye. Similarly, instructions received by the OCT controller 104 can indicate an OCT scan of the retina of the eye, and the OCT controller 104 can send instructions to the OCT scanner 102 indicating an OCT scan of the retina of the eye.

[0034] The OCT controller 104 may be communicatively coupled to the OCT scanner 102 via one or more electrical and / or communication interfaces. In some implementations, the one or more electrical and / or communication interfaces may be configured to transmit data (e.g., scan data generated by the OCT scanner 102) from the OCT scanner 102 at a high transmission rate such that the OCT controller 104 may receive data from the OCT scanner 102 in real time or near real time.

[0035] The OCT controller 104 may be configured to generate one or more OCT images based on the generated scan data received from the OCT scanner 102. For example, the OCT controller 104 may be configured to generate a 2D image or a B-scan image based on the generated 2D scan data of a line scan. Similarly, the OCT controller 104 may be configured to generate a 3D image or a C-scan based on the generated 3D scan data of an area scan. The OCT controller 104 may be configured to perform image generation and / or image processing in real time and / or near real time.

[0036] The OCT controller 104 may be configured with one or more tissue detection and / or auto-segmentation algorithms to detect and / or auto-segment one or more tissue layers of the eye in the generated OCT images. Examples of eye tissues that the OCT controller 104 may be configured to detect and / or auto-segment include, but are not limited to, the anterior surface of the cornea, the retina, the cornea, the iris, the pupil, the anterior and posterior surfaces of the lens as well as the location of the lens, the internal limiting membrane (ILM), etc. The OCT controller 104 may be configured to apply one or more tissue detection and / or auto-segmentation algorithms to the scan data received from the OCT scanner 102 and / or the generated OCT images to detect and / or auto-segment one or more tissues of the scanned eye.

[0037] The OCT controller 104 may be configured to determine a set of locations in a three-dimensional (3D) coordinate system for each detected tissue of the eye based on galvanometer scanner position data received from absolute and incremental encoders coupled to the galvanometer scanner and scan data received when the position data is received. For example, during an OCT scan, the OCT controller 104 may receive galvanometer scanner position data and scan data including data related to the surface of the retina (e.g., the ILM), and the OCT controller 104 may detect the surface of the retina based on the received scan data and determine the location of the surface of the retina in the 3D coordinate system based on the position data received when the scan data including the data related to the surface of the retina is received.

[0038] In some implementations, the OCT controller 104 can be configured to determine a position of the detected tissue in a 3D coordinate system based on the mechanical angle of the galvanometer scanner when scan data corresponding to the detected tissue is captured and / or generated by the OCT scanner 102. In some implementations, the OCT controller 104 can be configured with a set of rules and / or instructions for converting the mechanical angle of the galvanometer scanner to a position in the 3D coordinate system. For example, for initial reception position data of the galvanometer scanner, the OCT controller 104 can associate the data with an initial coordinate or a center coordinate of the 3D coordinate system, and for second reception position data of the galvanometer scanner, the OCT controller 104 can associate the data with a second coordinate of the coordinate system. In such implementations, the OCT controller 104 can determine the second coordinate based on a difference between the initial reception position data of the galvanometer scanner and the second reception position data of the galvanometer scanner (e.g., a difference between the mechanical angle of the initial reception position data and the mechanical angle of the second reception position data).

[0039] The coordinate system in which the OCT controller 104 determines the set of locations of each detected tissue may be referred to herein as the coordinate system of the OCT system 100. An example of a location in the coordinate system of the OCT system 100 of a detected tissue, such as a target tissue on the surface of the retina (e.g., the ILM) in the eye 130, may be determined by the OCT controller 104 to be at coordinates (-3, -2, -5) in a 3D coordinate system, where the first value (-3) is the value on the x-axis, the second value (-2) is the value on the y-axis, and the third value (-5) is the value on the z-axis of the 3D coordinate system.

[0040] In some implementations, the position value determined by the OCT controller 104 may indicate an offset from a center coordinate or an initial coordinate of a 3D coordinate system. In some implementations, the OCT controller 104 may be configured to set a center coordinate of the 3D coordinate system as a location (e.g., a center point) on the surface of the eye 130, and the first received scan data may correspond to that location (e.g., a center point) on the surface of the eye 130, such that all other positions in the 3D coordinate system represent offsets from the center coordinate. The OCT controller 104 may be configured to store position data of the detected eye tissue in a data storage unit of the OCT system 100.

[0041] The OCT controller 104 can be communicatively coupled to the display 108 and the external display 110. The OCT controller 104 can cause the generated OCT image to be displayed on the display 108 and / or the external display 110. For example, the OCT controller 104 can transmit the generated OCT image to the display 108 and / or the external display 110. In some implementations, the OCT image can be displayed as an emmetropic OCT image by the display 108 and / or the external display 110. In some implementations, the OCT image can be displayed as a semi-transparent OCT image with one or more automatically segmented tissues (e.g., on the surface of the retina), and can be displayed as a dot or wireframe array.

[0042] In some implementations, the OCT controller 104 may be communicatively coupled to one or more image capture devices (not shown separately), and the OCT controller 104 may be configured to receive optical images from the one or more image capture devices communicatively coupled to the OCT controller 104. The OCT controller 104 may be configured to overlay a generated OCT image onto the received optical image. In some implementations, the OCT controller 104 can receive a three-dimensional optical image. The OCT controller 104 may be configured to overlay an OCT image (e.g., an emmetropic OCT image) onto the 3D optical image.

[0043] An example of overlaying OCT images on optical images is disclosed in U.S. Patent No. 10,398,307, entitled "CURVATURE OF FIELD TRANSFORMATION OF OCT IMAGES DURING VITREORETINAL SURGERY," the entire disclosure of which is incorporated herein by reference. An example of generating emmetropic OCT images is disclosed in U.S. Patent No. 10,064,549, entitled "BINOCULAR EN FACE OPTICAL COHERENCE TOMOGRAPHY IMAGING," the entire disclosure of which is incorporated herein by reference. An example of generating OCT images during vitreoretinal surgery is disclosed in U.S. Patent No. 9,649,021, entitled "RESOLUTION ENHANCEMENT OF OCT IMAGES DURING VITREORETINAL SURGERY," the entire disclosure of which is incorporated herein by reference. An example of generating OCT images during vitreoretinal surgery is disclosed in U.S. Patent No. 10,013,749, entitled "RESOLUTION ENHANCEMENT OF OCT IMAGES DURING VITREORTINAL SURGERY," the entire disclosure of which is incorporated herein by reference. An example of emmetropic or 3D volumetric OCT imaging during ophthalmic surgery is disclosed in U.S. Patent No. 10,285,584, entitled "SUBTRACTIVE EN FACE OPTICAL COHERENCE TOMOGRAPHY IMAGING."

[0044] Display 108 and external display 110 may be part of an ophthalmic visualization system that provides a platform for digitally assisted ophthalmic procedures, such as the NGENUITY 3D visualization system from Alcon Laboratories Inc. In some embodiments, display 108 may be a display for a user (e.g., a surgeon), and display 110 may be a standalone monitor for viewing by various personnel during an ophthalmic procedure.

[0045] In some implementations, displays 108 and / or 110 may be implemented as a 3D visualization system, a touchscreen device, a liquid crystal display screen, a computer monitor, a television, a tablet, augmented glasses, viewing glasses, etc. Displays 108 and / or 110 may be configured to conform to one or more display standards, such as Video Graphics Array (VGA), Extended Graphics Array (XGA), Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI®), etc. In a particular implementation, displays 108 and / or 110 may be organic light-emitting diode (OLED) displays used in Alcon Laboratories Inc.'s NGENUITY 3D visualization system.

[0046] In some implementations, the OCT controller 104 may be configured to transmit scan data received from the OCT scanner 102 to the imaging system 106. The imaging system 106 may be configured to receive the generated scan data and process the scan data to generate one or more OCT images for display to a user (e.g., a surgeon, clinician, etc.). The imaging system 106 may be configured with one or more tissue detection and / or auto-segmentation algorithms to detect and / or auto-segment one or more tissue layers of the eye in the generated OCT images. The imaging system 106 may be configured to support three-dimensional (3D) visualization of the images. The imaging system 106 may be configured to capture and / or generate one or more optical images of the eye 130, and the imaging system 106 may overlay the generated one or more OCT images on the captured and / or generated one or more optical images.

[0047] For example, the imaging system 106 can transmit the optical image overlaid with the OCT image to the display 108 to display the image to a user. In some implementations, the imaging system 106 can be configured to provide the OCT image, the generated OCT image, and / or the optical image overlaid with the automatically segmented tissue of the OCT image to the OCT controller 104. For example, the imaging system 106 can transmit the optical image overlaid with the OCT image to the OCT controller 104, and the OCT controller 104 can be configured to transmit the digital optical image overlaid with the OCT image to the external display 110 for display to a user and / or other personnel.

[0048] As described above, the robotic device 120 may be communicatively coupled to the OCT system 100. The robotic device 120 includes a robotic device controller 122 and a surgical instrument 124. The robotic device controller 122 may be configured to receive input from the OCT controller 104. Examples of input from the OCT controller 104 may include, but are not limited to, instructions to move the surgical instrument to a position in a 3D coordinate system of the robotic device 120. The 3D coordinate system of the robotic device 120 may differ from the 3D coordinate system in which the position of the tissue of the eye is determined (e.g., the 3D coordinate system of the OCT system). Additional details of the transformation from the 3D coordinate system of the tissue position to the 3D coordinate system of the robotic device 120 are described below. In some implementations, the robotic device 120 may be configured to move with six degrees of freedom (6-DOF).

[0049] The robotic device 120 can be configured to interact with a user (e.g., a surgeon) via an interface to move the robotic device 120, and the robotic device controller 122 can be configured to receive input from the user via the interface. For example, the robotic device 120 can be communicatively coupled to a surgeon console, and a user, such as a surgeon, can interact with a six-degrees-of-freedom (6-DOF) haptic interface of the surgeon console to move a surgical instrument 124 of the robotic device 120 to a desired position. The user (e.g., a surgeon) can use the haptic interface to position a surgical tool near a target tissue within the eye 130. The robotic device controller 122 can be configured to receive movement of the surgeon console's 6-DOF haptic interface from the surgeon console, determine the position of the robotic device in a 3D coordinate system, and move the surgical instrument 124, so that the surgical instrument 124 can be moved to the user's desired position.

[0050] For example, after observing a desired tissue of the eye 130 displayed in the OCT image on the displays 108 and / or 110, a user (e.g., a surgeon) can interact with the robotic device 120 to move a surgical instrument to a position near the eye 130. For example, the user can position the surgical instrument near the target tissue of the eye. The robotic device controller 122 can transmit the position of the surgical instrument to the OCT controller 104.

[0051] The user can select tissue on the displays 108 and / or 110 and indicate the task the user wants the robotic device 120 to perform. For example, the user can touch a target location on the surface of the retina displayed in the optical image overlaid with the OCT image on the displays 108 and / or 110 to select the target location on the surface of the retina as the target tissue to operate on, and the user can also select a task, such as removing a membrane (e.g., an ILM), for the robotic device 120 to perform. In some implementations, the user can virtually draw the movement and / or motion of the task the user wants the robotic device 120 to perform. For example, the user can virtually draw a circular motion on the displays 108 and / or 110 displaying a particular location on the surface of the retina to indicate removal of a membrane (e.g., an ILM or epiretinal membrane) from such a particular location.

[0052] The displays 108 and / or 110 may be configured to transmit tasks and / or actions received from the user to the OCT controller 104. The OCT controller 104 may be configured to transmit received tasks and / or actions from the user to the robotic device controller 122. The robotic device controller 122 may be configured to transmit the position of the surgical device 124 to the OCT controller 104. In some implementations, the robotic device controller 122 may be configured to transmit the position of the surgical device 124 to the OCT controller 104 in response to receiving the tasks and / or actions from the user. For example, in response to receiving task and / or action information from the user via the OCT controller 104, the robotic device controller 122 may transmit position information of the surgical device 124.

[0053] The robotic device controller 122 can transmit position information of the surgical instrument 124 in the coordinate system of the robotic device 120. The OCT controller 104 can be configured to convert positions and / or coordinates in the 3D coordinate system of the robotic device 120 to positions and / or coordinates in the 3D coordinate system in which the OCT controller 104 determined the location of the detected tissue (e.g., the 3D coordinate system of the OCT system 100), or vice versa. The OCT controller 104 can be configured to apply one or more transformation techniques to convert positions from one coordinate system to another. For example, the OCT controller 104 can be configured to apply a Jacobian transformation to coordinates in one coordinate system to convert them to coordinates in another coordinate system.

[0054] In some implementations, the OCT controller 104 can be configured with a mapping between coordinates of the coordinate system in which the OCT controller 104 determines the location of tissue and the coordinate system of the robotic device 120. Based on the mapping, the OCT controller 104 can be configured to transform coordinates of the first coordinate system into coordinates of the second coordinate system. For example, for a location (-3, -2, -5) in one 3D coordinate system, the mapping can indicate that the location should be transformed to (2, 1, 4) in another 3D coordinate system.

[0055] Based on the received tissue selection, the OCT controller 104 can identify the location of the tissue in the 3D coordinate system of the OCT system 100. The OCT controller can determine the location of the tissue in the 3D coordinate system of the robotic device 120 using transformation techniques and / or mapping between the coordinate system of the OCT system 100 and the robotic device 120. For example, if a user selects a target tissue (e.g., a specific location on the surface of the retina or another location within the eye) and the location of the target tissue in the 3D coordinate system of the OCT system 100 is (-3, -2, -5), the OCT controller 104 can determine the location of the target tissue in the 3D coordinate system of the robotic device 120 using transformation techniques and / or mapping between the two 3D coordinate systems to determine the location of the target tissue within the eye 130 in the 3D coordinate system of the robotic device 120. In certain embodiments, a rigid and precise mechanical attachment between the OCT system 100 and the base of the robotic device 120 is necessary, or at least advantageous.

[0056] The OCT controller 104 can transmit the determined position in the 3D coordinate system of the robotic device 120 of the user-selected target tissue to the robotic device 120, causing the robotic device 120 to move the surgical instrument to that position. For example, the OCT controller 104 can transmit the position of the target tissue in the 3D coordinate system of the robotic device 120 (e.g., a location on the surface of the retina) to the robotic device controller 122, which can then move the surgical instrument to the position received from the OCT controller 104.

[0057] After the surgical instrument is moved to the user-selected tissue location, the robotic device 120 can be configured to perform a task selected by the user. For example, if the user selects a task to remove a membrane from the target tissue, the robotic device controller 122 can cause the surgical instrument to remove the membrane. Similarly, if the user virtually depicts an action or task to be performed on the tissue, the OCT controller 104 can send information related to that action or task to the robotic device controller 122, which can then cause the surgical instrument to perform that action or task.

[0058] Figure 2 shows a block diagram of selected components of an implementation of an OCT controller, such as the OCT controller 104 described above with reference to Figure 1. As shown in Figure 2, the OCT controller 104 includes a processor 201, a bus 202, a display interface 204, a memory 210, and a communication interface 220.

[0059] The processor 201 may be communicatively coupled to the memory 210, the display interface 204, and the communication interface 220 via the bus 202. The OCT controller 104 may be configured to interface with various external components of an OCT system (e.g., the OCT system 100) (e.g., the OCT scanner 102, the imaging system 106, the display 108, the external display 110, etc.) via the processor 201 and the communication interface 220. In some implementations, the communication interface 220 may be configured to allow the OCT controller 104 to connect to a network (not shown). In some implementations, the OCT controller 104 may be connected to one or more displays, such as the display 108, the external display 110, etc., via the display interface 204.

[0060] The memory 210 may include persistent, volatile, fixed, removable, magnetic, and / or semiconductor media. The memory 210 may be configured to store one or more machine-readable commands, instructions, data, and / or the like. In some implementations, as shown in FIG. 2, the memory 210 may include one or more sets and / or sequences of instructions, such as an operating system 212, a scan control application 214, etc. Examples of the operating system 212 may include, but are not limited to, real-time operating systems such as ThreadX provided by Express Logic, VxWorks provided by WinD River, Integrity provided by Green Hills, QNX, etc.

[0061] The scan control application 214 may be configured to perform the OCT controller operations described herein, including, but not limited to, operations related to initiating a scan of an eye, generating an OCT image, OCT image processing, receiving galvanometer scanner position data from an absolute encoder, receiving scan data, determining the position of one or more tissues of the eye in a first 3D coordinate system (e.g., the 3D coordinate system of the OCT system 100), determining a position in a second 3D coordinate system (e.g., the 3D coordinate system of the robotic device 120) based on the position of the tissue in the first 3D coordinate system, causing a communicatively coupled robotic device (e.g., the robotic device 120) to move a surgical instrument to a position in the second 3D coordinate system, etc.

[0062] 3 shows a flowchart of an exemplary method for guiding a robotic device for an ophthalmic procedure, according to certain embodiments of the present disclosure. Operations 300 may be performed, for example, by an OCT controller (e.g., OCT controller 104 of OCT system 100). Operations 300 may be implemented as software components that run on and execute on one or more processors (e.g., processor 201).

[0063] The operations 300 may begin at 302, during an OCT scan of an eye, with the OCT controller 104 receiving position data of a plurality of galvanometer scanners from a plurality of absolute encoders and a plurality of incremental encoders, each absolute encoder of the plurality of absolute encoders and each incremental encoder of the plurality of incremental encoders being coupled to at least one of the plurality of galvanometer scanners.

[0064] At 304, the OCT controller 104 receives scan data associated with one or more tissues of the eye during an OCT scan. At 306, the OCT controller 104 determines a first set of positions of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received position data and the scan data.

[0065] At 308, the OCT controller 104 determines a position in the second 3D coordinate system of a surgical instrument coupled to the robotic device based on the first set of positions and the mapping between the first 3D coordinate system and the second 3D coordinate system. At 310, the OCT controller 104 causes the robotic device to move the surgical instrument to a position in the second 3D coordinate system.

[0066] In some embodiments, the OCT controller 104 initiates an OCT scan of the eye in response to receiving a message indicating the initiation of an OCT scan of the eye and generates a real-time 3D image of the eye in a first 3D coordinate system based on the OCT scan. In some implementations, to determine a position in the second 3D coordinate system, the OCT controller 104 receives (e.g., from a user) a selection of a location in the real-time 3D image corresponding to a first tissue of the one or more tissues of the eye and maps the location to a determined position in the second 3D coordinate system based on the first set of locations and a mapping between the first 3D coordinate system and the second 3D coordinate system.

[0067] In some implementations, the OCT controller 104 provides a real-time 3D image of the eye for display to a user. In some implementations, at least one absolute encoder of the plurality of absolute encoders is a sine-cosine encoder. In some implementations, at least one absolute encoder of the plurality of absolute encoders is a holographic encoder. In some implementations, at least one galvanometer scanner of the plurality of galvanometer scanners is configured to scan in a first direction and at least one other galvanometer scanner of the plurality of galvanometer scanners is configured to scan in a second direction. In some implementations, the first direction is perpendicular to the second direction. In some implementations, at least one galvanometer scanner of the plurality of galvanometer scanners is a moving magnet galvanometer scanner.

[0068] The above-described methods and apparatus provide novel systems and methods for guiding a robotic device for an ophthalmic procedure using data generated and / or captured during an OCT scan of an eye. For example, the described systems and methods determine the location of detected tissue in a coordinate system based on galvanometer scanner position data received from absolute and incremental encoders coupled to the galvanometer scanner, thereby improving the accuracy of determining the location of various detected tissues of the eye in coordinate space and improving the accuracy of moving a robotically driven surgical instrument to a user-selected tissue for an ophthalmic procedure.

[0069] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, which scope is determined by the claims that follow.

[0070] Illustrative Embodiments Embodiment 1: A method comprising: receiving position data of a plurality of galvanometer scanners from a plurality of absolute encoders and a plurality of incremental encoders during an optical coherence tomography (OCT) scan of an eye, wherein each one of the plurality of absolute encoders and each one of the plurality of incremental encoders is coupled to at least one of the plurality of galvanometer scanners; receiving scan data related to one or more tissues of the eye during the OCT scan; determining a first set of positions of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received position data and the scan data; determining a position of a surgical instrument coupled to a robotic device in a second 3D coordinate system based on the first set of positions and a mapping between the first 3D coordinate system and the second 3D coordinate system; and causing the robotic device to move the surgical instrument to a position in the second 3D coordinate system.

[0071] 2. The method of embodiment 1, wherein at least one of the plurality of galvanometer scanners is configured to scan in a first direction and at least another of the plurality of galvanometer scanners is configured to scan in a second direction.

[0072] 2. The method of embodiment 1, wherein the first direction is perpendicular to the second direction.

[0073] 2. The method of embodiment 1, wherein at least one galvanometer scanner of the plurality of galvanometer scanners is a moving magnet galvanometer scanner.

[0074] 2. The method of embodiment 1, wherein at least one galvanometer scanner of the plurality of galvanometer scanners is an optical galvanometer scanner.

[0075] 2. The method of embodiment 1, wherein multiple absolute encoders and multiple incremental encoders are integrated into a single device. According to aspect (1), there is provided an optical coherence tomography (OCT) system, comprising: a plurality of galvanometer scanners; a plurality of absolute encoders and a plurality of incremental encoders, each one of the plurality of absolute encoders and each one of the plurality of incremental encoders being coupled to at least one of the plurality of galvanometer scanners; a controller coupled to the plurality of absolute encoders and the plurality of incremental encoders, a processor; a memory coupled to the processor and having instructions stored thereon, the instructions, when executed by the processor, causing the controller to: receiving position data of the plurality of galvanometer scanners from the plurality of absolute encoders and the plurality of incremental encoders coupled to corresponding galvanometer scanners of the plurality of galvanometer scanners during an optical coherence tomography (OCT) scan of the eye; receiving scan data relating to one or more tissues of the eye during the OCT scan; determining a first set of locations of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received location data and the scan data; determining a position in the second 3D coordinate system of a surgical instrument coupled to a robotic device based on the first set of positions and a mapping between the first 3D coordinate system and a second 3D coordinate system; a controller including a memory that causes the robotic device to move the surgical instrument to the position in the second 3D coordinate system; An optical coherence tomography (OCT) system comprising: According to aspect (2), the processor further instructs the controller to: Initiating the OCT scan of the eye in response to receiving a message indicating initiation of the OCT scan of the eye; A real-time 3D image of the eye in the first 3D coordinate system is generated based on the OCT scan. According to aspect (3), determining the position includes: receiving a selection of a location in the real-time 3D image corresponding to a first tissue of the one or more tissues of the eye; and mapping the location to the determined position in the second 3D coordinate system based on the first set of positions and the mapping between the first 3D coordinate system and a second 3D coordinate system. According to aspect (4), the processor further instructs the controller to: The real-time 3D image of the eye is provided for display to a user. According to aspect (5), at least one absolute encoder of the plurality of absolute encoders is a sine-cosine encoder. According to aspect (6), at least one absolute encoder of the plurality of absolute encoders is a holographic encoder. According to aspect (7), at least one galvanometer scanner among the plurality of galvanometer scanners is configured to scan in a first direction, and at least one other galvanometer scanner among the plurality of galvanometer scanners is configured to scan in a second direction. According to aspect (8), the first direction is perpendicular to the second direction. According to aspect (9), at least one galvanometer scanner among the plurality of galvanometer scanners is a moving magnet galvanometer scanner. According to a tenth aspect, there is provided a method for guiding a robotic device, the method comprising: receiving position data of a plurality of galvanometer scanners from a plurality of absolute encoders and a plurality of incremental encoders coupled to corresponding galvanometer scanners of a plurality of galvanometer scanners during an optical coherence tomography (OCT) scan of the eye, wherein each one of the plurality of absolute encoders and each one of the plurality of incremental encoders is coupled to at least one of the plurality of galvanometer scanners; receiving scan data relating to one or more tissues of the eye during the OCT scan; determining a first set of locations of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received location data and the scan data; determining a position in the second 3D coordinate system of a surgical instrument coupled to the robotic device based on the first set of positions and a mapping between the first 3D coordinate system and a second 3D coordinate system; causing the robotic device to move the surgical instrument to the position in the second 3D coordinate system; The method includes: According to aspect (11), initiating the OCT scan of the eye in response to receiving a message indicating initiation of the OCT scan of the eye; generating a real-time 3D image of the eye in the first coordinate system based on the OCT scan. According to aspect (12), determining the position includes: receiving a selection of a location in the real-time 3D image corresponding to a first tissue of the one or more tissues of the eye; and mapping the location to the determined position in the second 3D coordinate system based on the first set of positions and the mapping between the first 3D coordinate system and a second 3D coordinate system. According to aspect (13), the method further includes providing the real-time 3D image of the eye for display to a user. According to aspect (14), at least one absolute encoder of the plurality of absolute encoders is a sine-cosine encoder. According to aspect (15), at least one absolute encoder of the plurality of absolute encoders is a holographic encoder.

Claims

1. 1. An optical coherence tomography (OCT) system, comprising: a plurality of galvanometer scanners; a plurality of absolute encoders and a plurality of incremental encoders, each one of the plurality of absolute encoders and each one of the plurality of incremental encoders being coupled to at least one of the plurality of galvanometer scanners; a controller coupled to the plurality of absolute encoders and the plurality of incremental encoders, a processor; a memory coupled to the processor and having instructions stored thereon, the instructions, when executed by the processor, causing the controller to: receiving position data of the plurality of galvanometer scanners from the plurality of absolute encoders and the plurality of incremental encoders coupled to corresponding galvanometer scanners of the plurality of galvanometer scanners during an optical coherence tomography (OCT) scan of the eye; receiving scan data relating to one or more tissues of the eye during the OCT scan; determining a first set of positions of the one or more tissues of the eye in a first three-dimensional (3D) coordinate system based on the received position data and the scan data; determining a location of the target tissue of the eye in the second 3D coordinate system of a surgical instrument coupled to a robotic device based on the first set of locations and a mapping between the first 3D coordinate system and a second 3D coordinate system; and a memory that causes the robotic device to move the surgical instrument to the location of the target tissue of the eye in the second 3D coordinate system. An optical coherence tomography (OCT) system comprising:

2. The processor further instructs the controller to: Initiating the OCT scan of the eye in response to receiving a message indicating initiation of the OCT scan of the eye; The OCT system of claim 1 , wherein the OCT system generates a real-time 3D image of the eye in the first 3D coordinate system based on the OCT scan.

3. Determining the location of the target tissue of the eye comprises: receiving a selection of a location in the real-time 3D image corresponding to a first tissue of the one or more tissues of the eye; and mapping the location to the determined position of the target tissue of the eye in the second 3D coordinate system based on the first set of positions and the mapping between the first 3D coordinate system and the second 3D coordinate system.

4. The processor further instructs the controller to: The OCT system of claim 2 , wherein the OCT system provides the real-time 3D image of the eye for display to a user.

5. The OCT system of claim 1 , wherein at least one absolute encoder of the plurality of absolute encoders is a sine-cosine encoder.

6. The OCT system of claim 1 , wherein at least one absolute encoder of the plurality of absolute encoders is a holographic encoder.

7. 2. The OCT system of claim 1, wherein at least one galvanometer scanner of the plurality of galvanometer scanners is configured to scan in a first direction and at least one other galvanometer scanner of the plurality of galvanometer scanners is configured to scan in a second direction.

8. The OCT system of claim 7 , wherein the first direction is perpendicular to the second direction.

9. The OCT system of claim 1 , wherein at least one galvanometer scanner of the plurality of galvanometer scanners is a moving magnet galvanometer scanner.

10. A method of operating the OCT system of claim 1 for guiding the robotic device, comprising: When the processor executes the instructions stored in the memory, the controller receives the position data of the plurality of galvanometer scanners from the plurality of absolute encoders and the plurality of incremental encoders coupled to corresponding galvanometer scanners of the plurality of galvanometer scanners while an OCT scanner of the OCT system is performing an optical coherence tomography (OCT) scan of the eye, wherein each one of the plurality of absolute encoders and each one of the plurality of incremental encoders is coupled to at least one of the plurality of galvanometer scanners; the controller receiving the scan data associated with the one or more tissues of the eye during the OCT scan; determining, by the controller, the first set of positions of the one or more tissues of the eye in the first 3D coordinate system based on the received position data and the scan data; the controller determining the position of the target tissue of the eye in the second 3D coordinate system of the surgical instrument coupled to the robotic device based on the first set of positions and a mapping between the first 3D coordinate system and the second 3D coordinate system; the controller causing the robotic device to move the surgical instrument to the location of the target tissue of the eye in the second 3D coordinate system; A method comprising:

11. The method of claim 10, wherein the OCT scanner initiates the OCT scan of the eye in response to receiving a message indicating the initiation of the OCT scan of the eye; The method of claim 10 , further comprising the controller generating a real-time 3D image of the eye in the first 3D coordinate system based on the OCT scan.

12. The controller determining the location of the target tissue of the eye, comprising: receiving, by the controller, a selection of a location in the real-time 3D image corresponding to a first tissue of the one or more tissues of the eye; 12. The method of claim 11, further comprising: the controller mapping the location to the determined position of the ocular target tissue in the second 3D coordinate system based on the first set of positions and the mapping between the first 3D coordinate system and the second 3D coordinate system.

13. The method of claim 11, further comprising the controller providing the real-time 3D image of the eye for display to a user.

14. The method of claim 10, wherein at least one absolute encoder of the plurality of absolute encoders is a sine-cosine encoder.

15. The method of claim 10 , wherein at least one absolute encoder of the plurality of absolute encoders is a holographic encoder.

Images