Abstract: A method for virtual reality-based visual field inspection according to an embodiment is a method that performs a visual field inspection on a head-mounted display. The method includes: outputting a background including a background image and a focus point image; outputting an indicator on the background; and sensing user input from an examinee according to output of the indicator.

Abstract: Various presbyopia measurement systems are presented. Solutions include a consumer friendly system using a consumer's smart phone to present a test image. The test image by be viewed through a first lens, second lens and optional added lens such that the image is perceived to be approximately eight inches to two feet away from the consumer's eye. In addition to a lens system that may be attached to a consumer's smart phone, the systems presented include a presbyopia kit that my comprise an eyeglass kit comprising near vision attachments, mid vision attachments, clip on lenses and Plano frames. Disclosed systems include the use of the use of both the eyeglass kit and lens system that attaches to the consumer's phone.

Abstract: Disclosed is a hoist apparatus including: an electric motor, and a control box that can be electrically powered by a power supply, the control box including at least an electronic control circuit, an electrical wiring and an external casing forming a box of the control box, the external casing including at least sidewalls and a removable lid closing the box, the control box controlling the operations of the electric motor thanks to the electrical wiring connected to the electronic control circuit, to the power supply and to the electric motor, and a monitoring device, wherein the monitoring device is an insert of the box, the monitoring device being arranged within an enclosure, the enclosure being an added part of the box or being an exchanged part of the box and wherein the monitoring device is connected to the electrical wiring.

Abstract: A method of verifying ophthalmic measurements includes obtaining, via an ophthalmic measurement device, a first measurement of at least one ophthalmic parameter over a first measurement area. The first measurement area corresponds to an unassisted visible area of a patient's eye. A second measurement of the at least one ophthalmic parameter over a second measurement area is obtained via the measurement device. The second measurement area corresponds to an assisted visible area of the patient's eye. The first measurement is compared to the second measurement. It is determined if the second measurement diverges from the first measurement. Responsive to a determination that the second measurement diverges from the first measurement, an alert that the second measurement is inaccurate is generated. Responsive to a determination that the second measurement does not diverge from the first measurement, the second measurement is accepted as accurate.

Abstract: The present invention contemplates an infant eye model for wide field retinal imaging by implementing nominal physical parameters and optical characteristics found in scientific literature and by simulating retinal features and details found in real eye images. The present invention also contemplates implementing a corneal model with a translucent plastic to mimic image haze and 1st Purkinje reflection. The present invention also contemplates implementing a birefringent layer to the lens posterior surface to simulate 4th Purkinje reflection and its brightness variation. The present invention further contemplates implementing a photo-realistic retinal hemisphere shell to provide retinal details and demonstrate retinopathy associated with retinal diseases.

Abstract: An ophthalmic apparatus for examining an examinee's eye, comprising a face support member to support an examinee's face, a human detection member to detect whether or not the face is supported by the face support member, a notification member to give an announcement to an examinee or an examiner, and a control member to control the notification member based on a detection result of the human detection member.

Abstract: The present invention relates to systems for low-energy (e.g., 1.0 nJ-7.0 nJ) photoacoustic microscopy and methods for employing such systems. In certain embodiments, such systems employ a low-energy nanosecond pulsed laser beam (NPLB), at least two amplifiers, and a data acquisition system with at least three channels to generate at least three digital signals (e.g., which are averaged and normalized to the energy of the NPLB). In other embodiments, provided herein are systems for combined use of photoacoustic microscopy, dye-based microscopy (e.g., with fluorescein), and optical coherence tomography.

Abstract: An ophthalmic microscope including an observation optical system having a first focal point in front of an eye; an objective auxiliary lens positionable on the eye side of an objective lens in the observation optical system or releasable therefrom, a focal point when the objective auxiliary lens is positioned to a second focal point on an anterior ocular eye position; and a front lens positionable further toward the eye side than the first focal point or releasable from the position, a focal point through the eye's crystalline lens when the front lens is set to a third focal point and a posterior ocular segment position of the eye, the objective auxiliary lens set and the front lens released during anterior ocular segment observation, the front lens set and the objective auxiliary lens released during posterior ocular segment observation, without changing a positional relationship between the objective lens and eye.

Abstract: Optical apparatuses for enhancing scotopic vision. The optical apparatuses include a lens. In some instances, the optical apparatuses include a frame. The lens has an optical power adapted to focus light specifically under scotopic vision conditions in a user's eye. In some examples, the optical apparatuses include a spectral filter adapted to allow transmission of selected wavelengths of light through the spectral filter.

Abstract: An ophthalmological device and system is described that allows the simultaneous imaging of an eye using both scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT). Further the device and system is capable of targeting and delivering a femtosecond treatment laser for treatment of an eye condition. The system further includes a machine learning algorithm to provide a suggested treatment procedure.

Abstract: An OCT system for measuring a retina as part of an eye health monitoring and diagnosis system. The OCT system includes an OCT interferometer, where the interferometer comprises a light source or measurement beam and a scanner for moving the beam on the retina of a patient's eye, and a processor configured to execute instructions to cause the scanner to move the measurement beam on the retina in a scan pattern. Measurement data may be processed using a decurving process to enhance the resolution of the ILM layer and provide improved determinations of retinal thickness.

Abstract: Provided is a colored contact lens having: a lens; and a colored region formed in the lens, at least a part of the colored region is arranged at a position overlapping an iris of a wearer when the colored contact lens is worn, and the colored region has infrared transparency.

Abstract: A neural-network-based-implemented ophthalmologic intelligent consultation method includes: performing correction filtering on a consultation voice of a patient, framing the voice into a consultation voice frame sequence, generating a consultation text corresponding to the consultation voice frame sequence based on phoneme recognition and phoneme transcoding, and extracting an ophthalmologically-described disease; performing gray-level filtering, primary picture segmentation, and size equalization operation on an eye picture set of the to-be-diagnosed patient to acquire a standard eyeball picture group; extracting eye white features, pupil features and blood vessel features from the standard eyeball picture group, performing lesion feature analysis on the eye white features, the pupil features and the blood vessel features to acquire an ophthalmologically-observed disease, and based on the ophthalmologically-observed disease and the ophthalmologically-described disease, generating a consultation result.

Abstract: A device by which the magnification stages of a magnification selector based on Galilean telescope systems can be adjusted by a motor. The magnification selector has a sensor that transmits the currently magnification stage to a control unit; in the control unit, an assignment of the magnification stages present on the magnification selector to a sequence of the magnification stages, organized based on size, is stored. For the user, there are operating elements connected to the control unit for selecting a magnification stage. In order to set the magnification stage selected by the user via the operating elements, the magnification selector has an actuator, which is connected to the control unit to receive appropriate control signals. Although provided in particular for slit lamps and surgical microscopes having eyepieces, the solution can also be applied in other ophthalmological devices or devices from other technical fields.

Abstract: Apparatuses and methods for determining a refractive error of an eye are disclosed. A series of images of light coming from an eye are captured with varying optical powers, and the refractive error is then calculated based directly on the series of images used as approximate point spread functions. The calculation includes determining a modulation transfer area as a function of meridian angle and optical power in an angle range from 0° to 180° based on the series of images, and to calculate the refractive error based on the modulation transfer area as a function of angle and optical power.

Abstract: A system and method of assessing vision quality of an eye is presented, with a controller having a processor and tangible, non-transitory memory on which instructions are recorded. The controller is configured to selectively execute at least one machine learning model. Execution of the instructions by the processor causes the controller to: receive wavefront aberration data of the eye and express the wavefront aberration data as a collection of Zernike polynomials. The controller is configured to obtain a plurality of input factors based on the collection of Zernike polynomials. The plurality of input factors is fed into the at least one machine learning model, which is trained to analyze the plurality of input factors. The machine learning model generates at least one vision correction factor based in part on the plurality of input factors.

Abstract: Systems and techniques that facilitate background monitoring of eye health are provided. In various embodiments, a system can comprise a sensor component of a device. In various aspects, the sensor component can detect one or more physical characteristics associated with an entity. In various embodiments, the system can further comprise a diagnostic component of the device. In various instances, the diagnostic component can estimate in a background of the device a health condition of an eye of the entity based on the one or more physical characteristics. In various cases, estimating the health condition in the background of the device can facilitate real-time monitoring of the eye health of the entity without interrupting the entity's normal use of the device.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for training a fundus image processing machine learning models that is configured to process one or more fundus images captured by a fundus camera to generate a predicted label. One of the methods includes generating training data, comprising: receiving sets of one or more training fundus images captured by a fundus camera; receiving, for each of the sets, a ground truth label assigned to a different image of the eye of the patient corresponding to the set that has been captured using a different imaging modality; and generating, for each set of training fundus images, a training example that includes the set of training fundus images in association with the ground truth label assigned to the different image of the patients eye; and training the machine learning model on the training examples in the training data.

Abstract: A display system can include a head-mounted display configured to project light to an eye of a user to display virtual image content at different amounts of divergence and collimation. The display system can include an inward-facing imaging system images the user's eye and processing electronics that are in communication with the inward-facing imaging system and that are configured to obtain an estimate of a center of rotation of the user's eye. The display system may render virtual image content with a render camera positioned at the determined position of the center of rotation of said eye.

Abstract: Techniques are disclosed for systems and methods to provide dry eye and/or tear film hydration monitoring in the context of ocular aberrometry. An ocular aberrometry system includes a wavefront sensor configured to provide wavefront sensor data associated with an optical target monitored by the ocular aberrometry system and a logic device configured to communicate with the wavefront sensor. The logic device is configured to receive ocular aberrometry output data including at least the wavefront sensor data provided by the wavefront sensor, determine a tear film hydration state associated with the optical target based, at least in part, on the received ocular aberrometry output data, and generate user feedback corresponding to the determined tear film hydration state based, at least in part, on the received aberrometry output data and/or the determined tear film hydration state.

Abstract: A method for determining a near point and a near point distance of a person is disclosed, as well as methods for determining a spherical refractive power. In one implementation, optotypes are displayed on a mobile terminal and the person is asked to move the mobile terminal to the near point of the person. The position of the mobile terminal is determined on the basis of images of the surroundings and measurements of an acceleration of the mobile terminal. The near point distance can then be determined from the position of the mobile terminal at the near point and a position of the eyes of the person. Corresponding computer programs and corresponding mobile terminals are also disclosed.

Abstract: A prism array light redistribution apparatus for an eye imaging system including light transmitting fibers, light receiving fibers, and a micro prism array optically coupled to bridge the light transmitting fibers and the light receiving fibers, configured to receive light having a bell-shaped angular distribution from the light transmitting fibers and refract light emitted by the light transmitting fibers to enter the light receiving fibers.

Abstract: In accordance with one aspect of the present invention, an optical coherence tomography-based ophthalmic testing center system includes an optical coherence tomography instrument comprising an eyepiece for receiving at least one eye of a user or subject; a light source that outputs light that is directed through the eyepiece into the user's or subject's eye, an interferometer configured to produce optical interference using light reflected from the user's/subject's eye, an optical detector disposed so as to detect said optical interference; and a processing unit coupled to the detector. The ophthalmic testing center system can be configured to perform a multitude of self-administered functional and/or structural ophthalmic tests and output the test data.

Abstract: A scan area setting unit of an exemplary ophthalmic apparatus sets a scan area in a region passing through an iris outer edge. A first scan controller controls an OCT optical system to apply an OCT scan to the scan area. An image quality evaluating unit calculates an image quality evaluation value of an image from the OCT scan. A corner angle image detecting unit analyzes the image to detect a corner angle image. A position judging unit judges whether the corner angle image is located within a first area in an image frame. A second scan controller controls the OCT optical system to apply an OCT scan of a predetermined pattern to the anterior segment, if the image quality evaluation value is equal to or greater than a threshold and the corner angle image is located within the first area.

Abstract: An electronic device is configured to obtain an eye image in which an eye that looks at a display is captured. The electronic device includes at least one memory storing instructions; and at least one processor which executes the stored instructions causing the at least one processor to: perform line-of-sight detection, based on the obtained eye image; and provide, based on at least one of a position of a pupil image in the eye image and a number of corneal reflection images in the eye image, a predetermined notification regarding a method of adjusting a viewing state in which the display is visually perceived.

Abstract: An ophthalmic apparatus of an exemplary aspect performs the first and second OCT scans on a subject's eye. The first OCT scan is performed on the first region including the first site of the subject's eye, and the second OCT scan is performed on the second region including the second site. The ophthalmic apparatus acquires the first deviation information of the subject's eye prior to the first OCT scan and performs alignment, and also acquires the second deviation information of the subject's eye prior to the second OCT scan and performs alignment. The ophthalmic apparatus calculates the distance between the first site and the second site based on the first data acquired through the first OCT scan and second data acquired through the second OCT scan.

Abstract: Neurological abnormalities are often discovered through observation by health care providers, and/or parent report. Many neurodevelopmental disorders such as ASD are purely identified through behavioral analysis, and cannot be screened for using a biomarker or quantitative stimulus-response test. Current screening tools contain subjective components based on parent report and clinician observation, vary in consistency of use across providers, and demands resources, knowledge, and access to skilled expertise. As a result, the only tests used today require lengthy and subjective behavioral analysis and often, miss or misidentify neurodevelopmental disorders contributing to a delayed diagnosis. The technology disclosed herein allow for a solution to this systemic problem.

Abstract: Systems and methods for initializing and calibrating an eye tracking system include an eye tracker configured to capture a first image of an eye from a first location and a second image of the eye from a second location, and a control processor configured to detect a first plurality of eye characteristics from the first image, the eye characteristics having first corresponding image coordinates, detect a second plurality of eye characteristics from the second image, the eye characteristics having second corresponding image coordinates, and determine a calibration offset and a calibration gain. The control processor may be further configured to determine an eye fixation position and orientation relative to an optical axis of the eye tracker based at least in part on the first corresponding image coordinates and/or the second corresponding image coordinates.

Abstract: Illusionary motion-in-depth for vision therapy or entertainment is provided by altering the positional disparity by relative speed of movement and/or delay of movement of images of an image pair in motion which are viewed on a digital display device by stereoscopic means.

Abstract: A binocular scanning laser ophthalmoscope (SLO) is used to track the fixational eye movement of each of the eyes of a subject. The binocular SLO may include right eye optics for imaging a portion of the retina of the right eye and left eye optics for imaging a portion of the retina of the left eye. Shifts in the imaged portion of the retina with respect to a reference image of the retina may be used to measure and track eye movement. The right eye optics and left eye optics may be separate imaging paths, each with its own bi-directional MEMS scanning mirror and Keplerian telescope. The use of the MEMS scanning mirrors minimizes the size and weight of the binocular SLO.

Abstract: In classifying images by machine learning, provided are an image classification method, device, and program for classifying the image from which the feature difference is hardly detected, in particular, classifying the interference fringe image of tear fluid layer by the dry eye types. The method includes a step of acquiring a feature value from an interference fringe image of tear fluid layer for learning, a step of constructing a model for classifying an image from the feature value acquired from the interference fringe image of tear fluid layer for learning, a step of acquiring the feature value from an interference fringe image of tear fluid layer for testing, and a step of performing classification processing for classifying the interference fringe image of tear fluid layer for testing by types of dry eye using the model and the feature value acquired from the interference fringe image of tear fluid layer.

Abstract: The exemplified systems and methods disclosed herein involve the contemporaneous and concurrent stimulation of both eyes of a patient with dissimilar visual scenes that substantially span an expected or normal visual field of both eyes. During an assessment via the exemplified system and methods, a test eye (i.e., eye being assessed) is presented a visual scene that is rich in contours (e.g., a scene with rich texture patterns) that substantially span an expected or normal visual field of a person while the non-tested eye is presented an impoverished visual scene (e.g., a contour-free or non-distinguishing-contour scene, e.g., with a homogeneous color, with respect to the contour-rich scene). Defects in the visual field can be detected by assessing for breaks or discontinuity in the observation of the contour-rich scene by the person.

Abstract: The invention relates to a method and a computer program for estimating shape parameters of an image data set (1) of a fovea (100), comprising the steps of: Acquiring an image data set (1) of a macula (50), comprising a foveal pit (101) and a foveal rim (102) at least partially, Estimating the center of the foveal pit (101) from the image data set (1), Estimating from the center of the foveal pit (101), radially extending height profiles (c) of the fovea (100), For each height profile (c), fitting a model-function to the height profile (c), Estimating for each height profile (c) a set of fit parameters from the fitted model-function, Determining from the sets of estimated fit parameters at least one shape parameter of the fovea (100), particularly of the foveal pit (101). Determining at least one shape feature of at least a part of the fovea.

Abstract: A method, a computer program and a device for evaluating a tear fluid layer non-invasively. The method, computer program, and device include a step of detecting a time when color information in a predetermined region in a tear fluid layer interference fringe image changes by a threshold value or more as an eyelid opening time, a step of extracting an image at the time when the predetermined time has passed from the eyelid opening time as an extracted image from the tear fluid interference fringe images, a determination value calculation step of calculating a determination value from the color information in a pixel in a local region by scanning a predetermined target region, a step of detecting a corresponding pixel by comparing the calculated determination value and a threshold value, and an evaluation step of evaluating tear fluid layer breakdown by comparing the detected pixel and a threshold value.

Abstract: Head pose information may be determined using information describing a fixed gaze and image data corresponding to a user's eyes. The head pose information may be determined in a manner that is disregards facial features with the exception of the user's eyes. The head pose information may be usable to interact with a user device.

Abstract: An instrument includes a housing with a lower hand-held portion having a user-input button and a display for displaying an MPOD score for the user. The instrument further includes a viewing tube coupled to the hand-held portion. The viewing tube terminates in an eye cup. The viewing tube is transverse to the lower hand-held portion and transmits light from a light source in a direction toward the macula. The light source is an LED and provides two colored lights alternating at an initial frequency that is not perceptible by the user. The frequency decreases from the initial frequency until the user activates the user-input button in response to a frequency at which the user perceives a flicker of the two colored lights. The frequency at the perceived flicker relates to the MPOD score of the user. The MPOD score correlates to the amount of macular pigment.

Abstract: Accommodating ophthalmic devices including an ambient light sensor and an accommodation sensor and related methods of use are described. In an example, the accommodation sensor is configured to measure a biological accommodation signal of an eye on or in which the accommodating ophthalmic device is mounted. In an embodiment, the accommodating ophthalmic device is configured to measure the biological accommodation signals based on ambient light, such as based on an intensity or amount of ambient light, incident on the accommodating ophthalmic device. Such ambient light may be measured with the ambient light sensor.

Abstract: In one aspect, a device includes at least one processor and storage accessible to the at least one processor. The storage includes instructions executable by the at least one processor to receive input from at least one sensor, identify a characteristic of a user based on the input from the at least one sensor, and alter at least one setting of the device based on the identification of the characteristic. The at least one setting is related to presentation of content using the device.

Abstract: A system and method for providing image guidance for placement of one or more medical devices at a target location. The system can be used to determine one or more affected regions corresponding to the operation of one or more medical devices and display at least a portion of the one or more affected regions. The affected regions can correspond to predicted affected regions and/or dynamic affected regions and can be based at least in part on a variance parameter of the medical device.

Abstract: Detecting position information related to a face, and more particularly to an eyeball in a face, using a detection and ranging system, such as a Radio Detection And Ranging (“RADAR”) system, or a Light Detection And Ranging (“LIDAR”) system. The position information may include a location of the eyeball, translational motion information related to the eyeball (e.g., displacement, velocity, acceleration, jerk, etc.), rotational motion information related to the eyeball (e.g., rotational displacement, rotational velocity, rotational acceleration, etc.) as the eyeball rotates within its socket.

Abstract: Systems and methods for auto-calibrating a virtual reality (VR) or augmented reality (AR) head-mounted display to a given user with a refractive condition without adding corrective lenses to optical elements of the head-mounted display and without requiring subjective refraction procedures. A method comprises projecting a grid onto an eye of a user using a light source of a head-mounted display worn by the user, capturing the grid as-reflected from the eye using a camera of the head-mounted display, determining a pattern of a reflection of the grid based on the grid as-reflected, generating an aberration map based on a difference between the pattern as-reflected and the grid as-projected, and determining a correction to apply to at least one viewing lens of the head-mounted display worn by the user based on the aberration map.

Abstract: An ophthalmic measurement and laser surgery system includes: a laser source; a corneal topography subsystem; an axis determining subsystem; a ranging subsystem comprising an Optical Coherence Tomographer (OCT); and a refractive index determining subsystem. All of the subsystems are under the operative control of a controller. The controller is configure to: operate the corneal topography subsystem to obtain corneal surface information; operate the axis determining subsystem to identify one or more ophthalmic axes of the eye; operate the OCT to sequentially scan the eye in a plurality of OCT scan patterns, the plurality of scan patterns configured to determine an axial length of the eye; operate the refractive index determining subsystem so to determine an index of refraction of one or more ophthalmic tissues, wherein at least one of the corneal surface information, ophthalmic axis information, and axial length is modified based on the determined index of refraction.

Abstract: Systems and methods for allowing a user with no prior training to receive automated vision measurements without assistance of another individual by using subjective inputs from a user, which may be supplemented by a predictive method. The predictive method comprising artificial intelligence, patient data, user inputs, automated inputs from cameras and the like. The system may make use of a specific algorithm, decision tree, set of instructions, programming instructions, and the like, in order to provide vision measurements. The system combines programming instructions executed by a processor, output devices, input controls, and a plurality of corrective lenses to find a patient or user's vision measurements.

Abstract: An ophthalmic laser system for generating a first beam at a first wavelength on a first beam path and a second beam at a second wavelength on a second beam path, and directing optics to selectively direct the first beam or the second beam to a treatment beam path. The ophthalmic laser system incorporates a reflex coaxial illuminator comprising a reflex mirror movable on an axis from a position out of the treatment beam path to a position in the treatment beam path to direct illumination into an illumination path coaxial with the treatment beam path. The reflex mirror is adapted to transmit a beam that follows the second beam path.

Abstract: An ophthalmic device including an illumination module which scans light across a region of the retina of an eye when the pupil is disposed at a focal point of the illumination module. The ophthalmic device further comprises components (2, 3-1, 4-1) for: aligning the pupil with the focal point; monitoring a position of the pupil relative to the focal point and maintaining the alignment based on the monitored position; aligning a scan location of the illumination module on the retina to a target scan location while the alignment of the pupil with the focal point is being maintained, wherein the illumination module performs a scan at the target scan location. The ophthalmic device further maintains the scan location at the target scan location while the alignment of the pupil with the focal point is being maintained, using scan location correction information based on retinal feature information.

Abstract: A mask for performing an eye exam of a subject includes one or more optically transparent sections for transmitting an incident light beam therethrough and incident on the subject's eye. In some embodiments, the one or more optically transparent sections are coated with an anti-reflective coating configured to reduce reflection of the incident light beam by the one or more optically transparent sections. In some embodiments, the one or more optically transparent sections may have a portion thereof that is tilted with respect to the incident light beam when the mask is optically interfaced with the docking portion of an ophthalmic instrument, such that the incident light beam forms a finite angle of incidence with respect to the corresponding portion of the optically transparent sections.

Abstract: A prism array light redistribution apparatus for an eye imaging system including light transmitting fibers, light receiving fibers, and a micro prism array optically coupled to bridge the light transmitting fibers and the light receiving fibers. The array may be further configured to receive light having a bell-shaped angular distribution from the light transmitting fibers and refract the received light to enter the light receiving fibers such that a square-shaped angular distribution of light emits from a light emitting end of the light receiving fibers.

Abstract: An ophthalmic apparatus of an exemplary aspect performs the first and second OCT scans on a subject's eye. The first OCT scan is performed on the first region including the first site of the subject's eye, and the second OCT scan is performed on the second region including the second site. The ophthalmic apparatus acquires the first deviation information of the subject's eye prior to the first OCT scan and performs alignment, and also acquires the second deviation information of the subject's eye prior to the second OCT scan and performs alignment. The ophthalmic apparatus calculates the distance between the first site and the second site based on the first data acquired through the first OCT scan and second data acquired through the second OCT scan.

Abstract: Systems and methods according to present principles use touchscreen-based devices such as tablet computers or other computers incorporating touchscreens to both run the test and to receive input/output. It will be understood that any such device may be employed, so long as a display, means for user input, and means for eye tracking, are provided, and so long as its display screen is large enough to effectively test visual field.

Abstract: During a process of refractive index modification of an intraocular lens (IOL) using an ophthalmic laser system, optical position monitoring of the IOL is performed by a video camera system viewing the top surface of the IOL. Fiducials are incorporated into the IOL at manufacture, or created in-vivo with laser. The monitoring method employs a defined area of interest (AOI) to limit the number of pixels to be analyzed, to achieve adequately high acquisition speed. In one example, the AOI contains 5 camera scan line segments, each line segment having sufficient pixels to create a stable amplitude signature. Successive frames of the AOI are analyzed to detect movement of the fiducial and/or to determine whether the fiducial has been lost.