Patent Description:
Many of the current methods used to produce the images of the back of the eye, known as a fundus, suffer from various deficiencies, often producing imperfect images that can complicate the diagnostic procedure. Traditional imaging techniques use a Bayer-patterned color filter array imaging sensor. Such techniques have low sensitivity and the resulting image often suffers demosaic artifacts caused by low color resolution. Additionally, many of the current methods require the dilation of the patient's eyes, which is uncomfortable and inconvenient.

Document <CIT> discloses a system for use in imaging the patient's retina, the system comprising a light emitting diode arrangement comprising multiple LEDs of different wavelength ranges and a light directing optics for directing the light beam towards a region on the retina and for collecting and directing light returned from the illuminated region to a monochromatic CMOS. High-intensity flash mode operation of a LED can be achieved by applying to the LED a controllable "pumping".

A non-mydriatic fundus imaging system according to the present invention is defined by claim <NUM>.

A method for producing an image of a fundus according to the present invention is defined by claim <NUM>.

Both the system and method can be used to screen for, monitor, and diagnose eye-related diseases such as diabetic retinopathy.

<FIG> is a schematic block diagram illustrating an example system <NUM> for recording and viewing an image of a patient's fundus. In this example, the system <NUM> includes a patient P, a fundus imaging system <NUM>, a camera <NUM> in communication <NUM> with an image processor <NUM>, a display <NUM> used by clinician C with the image processor <NUM>, and a network <NUM>. In the example system, the fundus imaging system <NUM> and the display <NUM> are in communication either directly via communication path <NUM> or via the network <NUM> using wired and/or wireless communication schemes.

The fundus imaging system <NUM> functions to create a digital image of a patient's P eye fundus. As used herein, "fundus" refers to the eye fundus and includes the retina, optic nerve, macula, vitreous, choroid and posterior pole.

The patient P, in some embodiments, is being screened for an eye disease, such as diabetic retinopathy. In some embodiments, the system <NUM> can also be used to diagnose or monitor the progression of a disease such as diabetic retinopathy.

In some embodiments, the imaging system <NUM> includes a handheld housing that supports the system's components. The housing supports one or two apertures for imaging one or two eyes at a time. In some embodiments, the housing supports positional guides for the patient P, such as an adjustable chin rest. The positional guide or guides help to align the patient's P eye or eyes with the one or two apertures. In some embodiments, the housing supports means for raising and lowering the one or more apertures to align them with the patient's P eye or eyes. Once the patient's P eyes are aligned, the clinician C then initiates one or more image captures by the fundus imaging system <NUM>.

Most known techniques for fundus imaging require mydriasis, or the dilation of the patient's pupil, which can be painful and/or inconvenient to the patient P. Example system <NUM> does not require a mydriatic drug to be administered to the patient P before imaging, although the system <NUM> can image the fundus if a mydriatic drug has been administered.

In some embodiments, the system <NUM> is used to assist the clinician C in screening for, monitoring, or diagnosing various eye diseases. In some embodiments, the clinician C that operates the fundus imaging system <NUM> is different from the clinician C evaluating the resulting image.

In the example embodiment <NUM>, the fundus imaging system <NUM> includes a camera <NUM> in communication <NUM> with an image processor <NUM>. In this embodiment, the camera <NUM> is a digital camera including a lens, an aperture, processor and a sensor array. The camera <NUM> has a sensor array equipped with a global shutter. In some embodiments, the camera <NUM> is configured to record an image the fundus of one eye at a time. In other embodiments, the camera <NUM> is configured to record an image of both eyes substantially simultaneously. In those embodiments, the fundus imaging system <NUM> can include two separate cameras, one for each eye.

In example system <NUM>, the image processor <NUM> is operatively coupled to the camera <NUM> and configured to communicate with the network <NUM> and/or display <NUM>. In some embodiments, the image processor <NUM> regulates the operation of the camera <NUM>. An example image processor is shown in more detail in <FIG>, which is described further below.

In some embodiments, the fundus imaging system <NUM> is also connected to a printer, not shown in <FIG>. The printer can be used to produce a physical copy of the one or more fundus images produced by the fundus imaging system <NUM>.

In example system <NUM>, the display <NUM> is in communication with the fundus imaging system <NUM> directly <NUM> or via the network <NUM>. The display <NUM> functions to reproduce the image produced by the fundus imaging system <NUM> in a size and format readable by the clinician C.

In some embodiments, the housing supports the display <NUM>, which is embedded in the housing. In other embodiments, the display <NUM> is a separate component of example system <NUM>, and may have its own housing, such as, for example, a monitor or a display on a mobile phone or tablet computer. In another embodiment, the display <NUM> is optional and the fundus imaging system <NUM> is connected to a cloud storage through network <NUM>. In that embodiment, the fundus imaging system <NUM> transmits the one or more fundus images to the cloud storage and the images can be viewed by accessing the cloud storage.

A more detailed discussion of an example fundus imaging system is provided with respect to <FIG>, below.

In one embodiment, the fundus imaging system is connected to the network <NUM> (connection <NUM>). The network <NUM> is, in turn, connected to the display <NUM> (connection <NUM>). The connections <NUM> and <NUM> may include any type of wireless network, a wired network, or any communication network known in the art. For example, wireless connections can include cellular network connections and connections made using protocols such as <NUM>. 11a, b, and/or g. In other examples, a wireless connection can be accomplished directly between the fundus imaging system <NUM> and the display <NUM> using one or more wired or wireless protocols, such as Bluetooth, Wi-Fi Direct, radio-frequency identification (RFID), or Zigbee. Other configurations are possible.

<FIG> is a block diagram of the components in an example fundus imaging system <NUM>. The example fundus imaging system <NUM> includes an image sensor array <NUM> that comprises monochrome photodiodes <NUM>, shutter control <NUM>, and opaque shielded storage <NUM>; illumination unit <NUM> including light-emitting diode <NUM> and timing unit <NUM>; computing system <NUM> including processor <NUM> and memory <NUM>; lens <NUM>, an optional aperture <NUM>, networking unit <NUM>, and display <NUM>.

The image sensor array <NUM> in the example system <NUM> is a complementary metal-oxide semiconductor sensor array. The example sensor array <NUM> includes monochrome photodiodes <NUM>, shutter control <NUM>, and opaque shielded storage <NUM>. The example sensor array <NUM> functions to receive and process light reflected by the patient's fundus.

The image sensor array <NUM> has a plurality of rows of pixels and a plurality of columns of pixels. In some embodiments, the image sensor array has about <NUM> by <NUM> pixels, about <NUM> by <NUM> pixels, or about <NUM> by <NUM> pixels.

In some embodiments, the pixel size in the image sensor array <NUM> is from about four micrometers by about four micrometers; from about two micrometers by about two micrometers; from about six micrometers by about six micrometers; or from about one micrometer by about one micrometer.

The example monochrome photodiodes <NUM> have a light-receiving surface and have substantially uniform length and width. During exposure, the monochrome photodiodes <NUM> convert the incident light to a charge.

Shutter control <NUM> in example system <NUM> initiates the exposure of the photodiodes <NUM> and the end of the exposure of the photodiodes <NUM>. In some embodiments, after the exposure period of the photodiodes <NUM> ends, the charge is transferred to opaque shielded storage <NUM>. Shutter control <NUM> also controls the reset of the photodiodes <NUM> and the read-out of the stored charges to be processed by computing system <NUM>.

Shutter control <NUM> is configured to operate the image sensor array <NUM> as a global shutter. That is, substantially all of the photodiodes are exposed simultaneously and for substantially identical lengths of time. The global exposure effectively integrates charge substantially evenly across the image sensor array <NUM> during the exposure time.

In another embodiment, a monochrome CMOS sensor with global reset mode can also be used without opaque shielded storage.

As discussed above with reference to <FIG>, in some embodiments the clinician initiates the exposure of the photodiodes <NUM> by global reset of all the pixels. However, the shutter control <NUM> is configured to end the exposure period by global transferring all the pixels to their correspondent opaque shielded storages. For example, in some embodiments, shutter control <NUM> ends the exposure period using a predetermined time period that starts when the clinician initiates an image capture sequence. In some embodiments, an auto exposure control algorithm will determine the exposure period dynamically according to the illumination conditions and/or image contrast.

A Bayer filter, not used in example system <NUM>, essentially blocks out two-thirds of the light incident on the image sensor array. In contrast, the monochrome photodiodes <NUM> used in the example system <NUM> do not filter out light, which in turn improves the image quality. Also, because monochrome arrays do not filter light, the example fundus imaging system <NUM> advantageously requires roughly one-third of the light required by a fundus imaging system that employs a Bayer filter array.

Additionally, in contrast to a system using a Bayer color filter array, the example fundus imaging system <NUM> can improve diabetic retinopathy screening sensitivity by reducing the number of false negatives. That is, the example fundus imaging system <NUM> can detect much lower contrast, and thereby detect more abnormal features, that the Bayer array cannot because the Bayer array limits the amount of imaged contrast. Additionally, the example fundus imaging system <NUM> can also reduce diabetic retinopathy false positives because the system <NUM> can produce higher uniform image quality without the Bayer array demosaic artifacts.

The illumination unit <NUM> in example fundus imaging system <NUM> provides light to illuminate the fundus and coordinate the timing with the exposure of the image sensor array. The example illumination unit includes light-emitting diode <NUM> and timing unit <NUM>. Example light-emitting diode <NUM> is in operative communication with the computing system <NUM> and the timing unit <NUM>.

Example light-emitting diode <NUM>, in some embodiments, is a three-color light-emitting diode (LED), where the three colors are red, green, and blue. For example, the light-emitting diode <NUM> can be a three-channel RGB LED, where each die is capable of independent and tandem operation. In some embodiments, more than one LED <NUM> is used in the illumination unit <NUM>. The LEDs have a maximum standard current draw rating of, for example, <NUM> mA, but the LED can be overdriven to draw more current, for example <NUM> mA (at <NUM>% of maximum standard current), <NUM>% of maximum current, <NUM>% of maximum current, and <NUM>% of maximum current in a low duty cycle usage. Other maximum standard current draws are possible.

The one or more LEDs <NUM> are overdriven during the illumination period, which is controlled by timing unit <NUM> in the system <NUM>. In some embodiments, the combination of overdriving the LEDs with the global shutter operation results in a shorter exposure period. The shorter exposure period, in some embodiments, results in a sharper image. Additionally, in some embodiments the shorter illumination period results in less contraction of the pupil, thereby reducing the need for pupil dilation.

In order to maintain the patient's P pupil size as large as possible without dilation, dim light must be used. In the imaging systems known in the art, this dim light requirement results in poorer image quality. For example, the image quality when a <NUM> LED illumination period is used is much better than when a <NUM> LED illumination period is used in the prior art systems. In some embodiments, the LED illumination period used in example system <NUM> are <NUM>, <NUM>, or <NUM>. The example fundus imaging system <NUM> advantageously uses a dimmer LED light and produces a higher quality image than those systems known in the art.

Each die in the LED <NUM> is capable of independent and tandem operation. For example, in one embodiment, three consecutive frames are captured by the image sensor array <NUM>. The first exposure occurs when the red die is illuminated, then the second exposure occurs when the green die is illuminated, and then third exposure occurs when the blue die is illuminated. The order of die illumination is different in other embodiments.

An alternative embodiment captures three consecutive frames for the following color illuminations: red (red die on only), yellow (red and green dies on substantially simultaneously), and white (reed, green, and blue dies on substantially simultaneously). Again, the order of illumination color is different in other embodiments. In one diabetic retinopathy embodiment, the white illumination (all dies on) produces an all features detection, a red image (only red die on) assists the clinician in retinal microaneurysms and hemorrhages confirmation, and a yellow image (red and green dies on) assists the clinician in exudates confirmation.

In some embodiments, timing unit <NUM> activates the illumination timing of, and light emitted from, light-emitting diode <NUM>. Timing unit <NUM> is, in some embodiments, a separate component including a processor and memory that is operatively coupled to the computing system <NUM> and image sensor array <NUM>. In other embodiments, timing unit <NUM> is a computer program stored on the memory <NUM> and configured to be run by the processor <NUM>.

Timing unit <NUM> can be configured to illuminate the light-emitting diode <NUM> at a time just before the image sensor array <NUM> initiates a global shutter exposure and to cease illumination shortly after the global shutter exposure ends. In other embodiments, the timing unit <NUM> can be configured to illuminate the light-emitting diode <NUM> after the global shutter exposure begins and to cease illumination before the global shutter exposure ends. In another embodiment, the timing unit <NUM> can be configured to illuminate the light-emitting diode <NUM> with an overlap period of time with the global shutter exposure period of time. In some embodiments the timing unit is configured to cause the light-emitting diode <NUM> to pulse or produce a strobe-like light during the illumination period.

In the example fundus imaging system <NUM>, the computing system <NUM> includes a processor <NUM> communicatively connected to a memory <NUM> via a data bus. The processor <NUM> can be any of a variety of types of programmable circuits capable of executing computer-readable instructions to perform various tasks, such as mathematical and communication tasks. The memory <NUM> can include any of a variety of memory devices, such as using various types of computer-readable or computer storage media. A computer storage medium or computer-readable medium may be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. In the context of the present disclosure, a computer storage medium includes at least some tangible component, i.e., is not entirely consisting of transient or transitory signals.

The example system <NUM> also includes a lens <NUM> supported by the housing. Some embodiments have more than one lens supported by the housing. For example, one lens is used to focus the light incident on the image sensor array <NUM> and another lens to focuses the light from the illumination unit <NUM>. Some embodiments use more than one lens to focus the incident light. In some embodiments, the lens has mechanical power and control connections coupled to the computing system <NUM>. The computing system <NUM> may be configured to control the position of the lens or lenses to optimize lens positioning for auto focusing for the image sensor array <NUM> and illumination unit <NUM>. In some embodiments, lens focusing is required in spite of a standard positioning guide for the patient because of unique facial geometries.

The example fundus imaging system <NUM> has, optionally, one or more apertures <NUM> supported by the housing. In some embodiments, the aperture <NUM> is an annular piece that supports a lens <NUM>. The patient's eye is aligned substantially with the aperture <NUM> before the fundus is imaged. In some embodiments, the aperture is a mechanically operated cover that can be opened and closed based upon signals from the computing system <NUM>.

In some embodiments, the example fundus imaging system <NUM> has a display <NUM> for the clinician to focus and examine the patient's eye fundus.

In some embodiments, the imaging system <NUM> has a networking unit <NUM>. Networking unit operates to enable communication between the fundus imaging system <NUM> and the example display <NUM> or other networked devices. The networking unit <NUM> may be in wireless or wired communication with the display <NUM> or other networked devices.

Additionally, the networking unit <NUM> is in communication with the network <NUM>. In some embodiments, the networking unit <NUM> communicates with the display <NUM> over a wired or wireless connection.

In some embodiments, the fundus imaging system <NUM> also includes an anti-aliasing filter, not pictured in <FIG>. The optional anti-aliasing filter is in some embodiments an optical low-pass filter. This filter is a thin layer located between the monochrome photodiodes <NUM> and the direction from which the incident light emanates. The filter, in some embodiments, prevents the occurrence of a pattern (moiré or other artifacts) different from the original image.

In some embodiments, the fundus imaging system <NUM> also includes reflective mirrors, not shown in <FIG>. The optional one or more reflective mirrors are used to direct light to the image sensor array <NUM> and from the illumination unit <NUM>. In some embodiments, the one or more mirrors are supported by, and fixed to, the housing. In other embodiments, the reflective mirror or mirrors are supported by the housing but have adjustable positions, where the clinician or computing system <NUM> can adjust the positioning of the mirrors. The example system is operable without reflective mirrors.

<FIG> is a block flow diagram of an example use <NUM> by a clinician of the example fundus imaging system. Example use <NUM> is performed in some embodiments by more than one clinician. Example use <NUM> includes positioning a patient <NUM>, adjusting the focus <NUM>, initiating a retinal imaging <NUM>, and viewing the image <NUM> created by the scan. Other embodiments may omit steps or include additional steps.

Example use <NUM> begins when the clinician positions a patient <NUM>. The patient may be seated or standing. Positioning <NUM> includes aligning the patient such that one or more of the patient's eyes are aligned with the aperture or apertures of the fundus imaging system. In some embodiments, the display coupled to the imaging system shows a preview image to help guide the clinician in positioning the patient. In some embodiments, the system emits an audible sound to notify the clinician that the patient's eye is in a proper position.

In some embodiments, there is a positioning structure, such as a chin rest or head support structure, to assist in positioning the patient. In some embodiments, the positioning structure has means for adjustment that can be used by the clinician in positioning the patient's eye relative to the housing. In other embodiments, the positioning structure is fixed and the housing has adjustment means such that the clinician can reposition the housing to be in alignment with the patient's eye or eyes.

After the patient is positioned, the next step in example use <NUM> is for the clinician to adjust the focus <NUM> on the fundus imaging system. In some embodiments, the fundus imaging system has one or more adjustable foci. These foci may be manually adjusted by the clinician, electronically adjusted by the clinician, or automatically adjusted by the fundus imaging system. In some embodiments, the focus adjusts the position of the lens through which the incident light passes. In some embodiments, the focus adjusts the lens through which the light from the illumination unit passes. In some embodiments, the clinician initiates the automatic focusing by the fundus imaging system by pressing a button or selecting an icon on a graphical user interface. In some embodiments, the adjust focus step <NUM> can be replaced by auto focusing algorithms without human intervention.

Next, the clinician initiates the retinal imaging <NUM> in example use <NUM>. In some embodiments, the clinician initiates the retinal imaging <NUM> by pressing a button or selecting an icon on a graphical user interface. An example of the fundus imaging system's steps during retinal imaging <NUM> is shown in <FIG> and described in detail below. In some embodiments, the clinician may return to step <NUM> to reposition the patient's other eye for imaging and repeat steps <NUM> and <NUM>. In other embodiments, the clinician may view the image <NUM>, and may ensure that the image is of acceptable quality, before returning to step <NUM> to image the patient's other eye.

Additionally, in some embodiments, initiate retinal imaging <NUM> is replaced by passive eye tracking algorithms to automatically trigger the image capture without human intervention. Passive eye tracking is described with reference to <FIG> below.

After the fundus imaging system images the retina <NUM>, the clinician views the fundus image <NUM> in example use <NUM>. If any image is not satisfactory to the clinician, the clinician may repeat example use <NUM>. Examples of the types of displays that may be used in step <NUM> are described in more detail with reference to block <NUM> in <FIG>.

<FIG> illustrates a block flow diagram of an example method of operation <NUM> of the fundus imaging system. Example operation <NUM> includes the fundus imaging system performing the steps of open aperture <NUM>, adjust focus on retina <NUM>, illuminate light-emitting diode <NUM>, which includes illuminate red light-emitting die <NUM>, illuminate green light-emitting die <NUM>, and illuminate blue light-emitting die <NUM>, control global shutter <NUM>, which includes global reset <NUM>, global transfer <NUM>, sequential readout of photodiodes <NUM>, store image read from photodiodes <NUM>, optionally returning to the illuminate light-emitting diode step <NUM>, process image read from photodiodes <NUM>, send processed image to display <NUM>, and send initial diagnosis to display <NUM>. Alternate embodiments may have fewer or additional steps, or perform the steps in a different order.

In example operation <NUM>, the first step is to, optionally, open aperture <NUM>. As described above with reference to aperture <NUM>, in some embodiments the aperture can be a cover opened and closed through electrical or mechanical means. In some embodiments, the aperture is a frame that, in some embodiments, supports a lens but does not have an operable cover. One purpose of the open aperture step <NUM> is to enable incident light to pass through one or more lenses towards the image sensor array.

Adjust focus on the retina <NUM> is the next step in example operation <NUM>. In some embodiments, the clinician operating the fundus imaging system manually changes one or more focal lengths. Adjusting the focus can be accomplished by, for example, mechanical means such as a knob or knobs or through electrical means such as a graphical user interface displaying focus adjustment parameters, where the interface is operatively coupled to adjustment means that is coupled to the one or more lenses. Adjusting the focus can also be accomplished automatically by auto focusing algorithms controlling a mechanical means without human intervention.

The next step in example operation <NUM> is to illuminate the light-emitting diode <NUM>. The illuminate light-emitting diode step <NUM> comprises illuminating one or more of the colored dies in the red-green-blue light-emitting diode: illuminate the red die in the diode <NUM>, illuminate the green die in the diode <NUM>, and illuminate the blue die in the light-emitting diode <NUM>. Other combinations of colors are possible, including, for example, cyan-magenta-yellow, red-green only or white-red only.

As discussed above, some embodiments of the imaging system have more than one light-emitting diode. Additionally, in some embodiments of operation <NUM>, the illuminate step <NUM> occurs either after or concurrently with the global reset step <NUM>. The illuminate step <NUM> is performed multiple times, consecutively, in some embodiments.

As discussed above, in some embodiments, one image is taken with all three dies illuminated <NUM>, <NUM>, and <NUM>, producing white light. In some embodiments, the system initiates four consecutive image captures. In those embodiments, the illumination unit is configured to produce white light for the first image capture, then red, green, and blue for the subsequent image captures. Other sequences in other embodiments are described in more detail with reference to illumination unit <NUM> in <FIG>.

The light-emitting diodes are illuminated <NUM> for a short period of time. In some embodiments, the diode, or diodes, are illuminated for less than <NUM> milliseconds, for less than <NUM> milliseconds, for less than <NUM> millisecond, or for less than <NUM> milliseconds. As discussed above, the light-emitting diode may be overdriven for some or all illuminations. One of many advantages of the example embodiments is that the intensity, or the period, of the light-emitting diodes can be reduced by from about <NUM> to about <NUM> times those imaging systems in the art using a rolling shutter/reset CMOS sensor.

Control global shutter step <NUM> includes the global reset step <NUM>, the global transfer step <NUM>, and sequential readout step <NUM>. The computing system, operatively coupled to the image sensor array, controls the image sensor array's global shutter in example operation <NUM>.

Global reset step <NUM> involves, in some embodiments, resetting and exposing every pixel in the image sensor array substantially simultaneously. The exposure of the pixels is as short as possible to avoid motion blur and to limit the amount of time the patient's pupils must be illuminated. In some embodiments the exposure time is about <NUM> milliseconds.

Global transfer step <NUM> involves, in some embodiments, simultaneously ceasing the exposure of every pixel in the image sensor array and transferring the charge from each pixel into the opaque shielded storage. An example global shutter is described in more detail with reference to image sensor array <NUM> in <FIG>, above.

Sequential readout step <NUM> in example operation <NUM> involves each pixel in the image sensor array being readout sequentially (one pixel after the other). The readout step <NUM> is accomplished, in some embodiments, by the computing system sending a readout clocking signal to the image sensor array to read out pixel value one by one.

After the global transfer step <NUM>, the pixel exposure is ended in example operation <NUM> and the image readout from the photodiodes' opaque shielded storage unit is stored <NUM> in memory. In some embodiments, multiple images are captured consecutively and the example operation repeats <NUM>. Return step <NUM> is shown in <FIG> as returning to step <NUM>, but in other embodiments the return step <NUM> begins by opening the aperture <NUM> or by adjusting the focus on the retina <NUM> step.

Next, the processor processes the image readout from the photodiodes' opaque shielded storage <NUM> in example operation <NUM>. In some embodiments, processing of the image is performed in accordance with a software program stored on the memory and run in the processor.

In some embodiments, processing <NUM> includes amplifying the data generated from the incident light and converting the generated data into a digital signal. Processing <NUM> may also include storing a set of digital signal values corresponding to incident light on the plurality of pixels of image sensor array as a frame of image data. In some embodiments, the process image step <NUM> does not use color demosaic algorithms.

Process image step <NUM> includes a processor running image processing algorithms to, for example, perform image enhancement, perform features detection, and identify a classification to correct the diabetic retinopathy.

For example, the algorithm can access an evaluation database for diabetic retinopathy such as DIARETDB0 and DIARETDB1, established by Lappeenrata University of Technology and University of Kuopio Medical Faculty in Finland. Those databases consist of about <NUM> fundus images that have been evaluated and annotated by experts and doctors to establish diagnosis results for those images. An example output of an evaluation algorithm, when using a fundus image as an input, is that small red dots exist, there are hemorrhages and hard exudates are detected in the fundus. The output can identify both a list of the diagnoses and the number of observed issues. In some embodiments, the output can also identify the detected issues on the fundus image, using, for example, graphics such as circles or arrows.

In some embodiments, the clinician can select the one or more issues the algorithm running on the processor should identify during processing step <NUM>. For example, in one embodiment the clinician selects through a graphical user interface "hemorrhages" in a menu containing possible diabetic retinopathy symptoms. The processed image then will contain identifying indicia such as on-screen arrows, circles or other identifying icons. Thus, where applicable, the image in this embodiment contains indicia flagging detected hemorrhages. But because, in this example, the clinician did not select any other symptoms, such as "exudates", even if present, the image will not contain indicia flagging other symptoms.

In an alternate embodiment, the processor is configured to detect all possible symptoms and the image contains indicia flagging all detected symptoms. Then, in some embodiments, the clinician uses a menu-type filter to select one or more symptoms to be flagged on the display.

In another embodiment, the image stored from the photodiode readout is sent to a remote cloud storage and further processed, using algorithms described above, in a remote server.

In example operation <NUM>, the computing system sends the processed image to the display <NUM> and/or sends an initial diagnosis to display <NUM>. As discussed above, in some embodiments, the system produces a raw image that does not contain any diagnostic identification information <NUM>. In other embodiments, the system produces an image accompanied by diagnostic information <NUM>.

<FIG> illustrates an alternate embodiment of initiate retinal imaging step <NUM> using passive eye tracking. The initiate retinal imaging step <NUM> operates to image the fundus of the patient P using passive eye tracking. In the initiate retinal imaging step <NUM>, the fundus imaging system <NUM> monitors the pupil/fovea orientation of the patient P. Although the initiate retinal imaging step <NUM> is described with respect to fundus imaging system <NUM>, the initiate retinal imaging step <NUM> may be performed using a wearable or nonwearable fundus imaging system, such as a handheld digital fundus imaging system.

Initially, at step <NUM>, the pupil or fovea or both of the patient P are monitored. The fundus imaging system <NUM> captures images in a first image capture mode. In the first image capture mode, the fundus imaging system <NUM> captures images at a higher frame rate. In some embodiments, in the first image capture mode, the fundus imaging system <NUM> captures images with lower illumination and at lower resolutions. In some embodiments, the lower illumination is created by the illumination unit <NUM> operating to generate and direct light of a lower intensity towards the subject. In other embodiments, the lower illumination is created by an external light source or ambient light. The first image capture mode may minimize discomfort to the patient P, allow the patient P to relax, and allow for a larger pupil size without dilation (non-mydriatic).

Next, at step <NUM>, the computing system <NUM> processes at least a portion of the images captured by the fundus imaging system <NUM>. The computing system <NUM> processes the images to identify the location of the pupil or fovea or both of the patient P. Using the location of the pupil or fovea or both in one of the images, a vector corresponding to the pupil/fovea orientation is calculated. In some embodiments, the pupil/fovea orientation is approximated based on the distance between the pupil and fovea in the image. In other embodiments, the pupil/fovea orientation is calculated by approximating the position of the fovea relative to the pupil in three dimensions using estimates of the distance to the pupil and the distance between the pupil and the fovea. In other embodiments, the pupil/fovea orientation is approximated from the position of the pupil alone. In yet other embodiments, other methods of approximating the pupil/fovea orientation are used.

Next, at step <NUM>, the pupil/fovea orientation is compared to the optical axis of the fundus imaging system <NUM>. If the pupil/fovea orientation is substantially aligned with the optical axis of the fundus imaging system <NUM>, the process proceeds to step <NUM> to capture a fundus image. If not, the process returns to step <NUM> to continue to monitor the pupil or fovea. In some embodiments, the pupil/fovea orientation is substantially aligned with the optical axis when the angle between them is less than two to fifteen degrees.

Next, at step <NUM>, a fundus image is captured. In some embodiments, the fundus image is captured in a second image capture mode. In some embodiments, in the second image capture mode, the fundus imaging system <NUM> captures images with higher illumination and at higher resolutions. In some embodiments, the higher illumination is created by the illumination unit <NUM> operating to generate and direct light of a higher intensity towards the subject. In other embodiments, the higher illumination is created by an external light source or ambient light. The second image capture mode may facilitate capturing a clear, well-illuminated, and detailed fundus image.

In some embodiments, after step <NUM>, the initiate retinal imaging step <NUM> returns to step <NUM> to continue to monitor the pupil/fovea orientation. The initiate retinal imaging step <NUM> may continue to collect fundus images indefinitely or until a specified number of images have been collected. Further information regarding passive eye tracking can be found in <CIT>, attorney docket number <NUM>. 0082US01, titled Ophthalmoscope Device, filed on even date herewith, which is hereby incorporated by reference in its entirety.

The flow diagrams depicted herein are just examples. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified.

Claim 1:
A non-mydriatic fundus imaging system (<NUM>), comprising:
an image sensor array (<NUM>) including a two-dimensional monochrome complementary metal-oxide-semiconductor, wherein the image sensor array (<NUM>) has a plurality of rows of pixels, and the image sensor array (<NUM>) is capable of global reset operations wherein each pixel of the plurality of rows of pixels is exposed substantially simultaneously;
an illumination unit (<NUM>) operatively coupled to the image sensor array (<NUM>), wherein the illumination unit (<NUM>) includes a light emitting diode (<NUM>), and the illumination unit (<NUM>) being capable of overdriving the light emitting diode (<NUM>); and
a timing unit (<NUM>) operatively coupled to the image sensor array (<NUM>) and the illumination unit (<NUM>) and configured to simultaneously expose a full frame of pixels of the image sensor array (<NUM>) during an exposure period, wherein the illumination unit (<NUM>) is configured to overdrive the light emitting diode (<NUM>) during the exposure period.