Optical coherence imaging and analysis system and method

Abstract

The invention provides a non-invasive optical scanning system and method using full field optical coherence tomography (FF-OCT) to acquire data sets related to scattering properties of a targeted three dimensional region of skin or eye tissue. The system uses image sensor arrays to acquire, in a sufficiently short period of time to avoid fringe washout, at least two data sets that have an interferometric phase relationship. Because acquisition time for the data sets is less than one millisecond and independent of the frame rate of the image sensor arrays, low cost image sensors satisfy cost requirements for consumer monitors, such as sub-dermal fingerprint imager for enhanced bio security. In some embodiments, such as home retinal scanning for monitoring macular degeneration, an artificial intelligence (Al) agent can be used to assist in system alignment and use.

Description

Title: Optical Coherence Imaging and Analysis System and MethodCROSS REFERENCES TO RELATED PATENTS OR APPLICATIONS

[0001] This patent application, titled “Optical Coherence Imaging and Analysis System”, has docket number JH260101PT and claims priority from each and all of the following provisional patent applications: 63 / 745,083 filed on 14 Jan 2025; 63 / 810,650 filed on 22 May 2025; and 63 / 957,826 filed on 10 Jan 2026, the contents of which is incorporated by reference as if fully set forth herein.FIELD OF THE INVENTION

[0002] The invention relates to non-invasive interferometric imaging and analysis systems and method for applications involving in-vivo tissue. The invention further relates to full field optical coherence tomography (FF-OCT).BACKGROUND OF THE INVENTION

[0003] Optical coherence tomography (OCT) is an optical technology for non-invasive imaging and analysis that is well suited for imaging sub-dermal regions of tissue, for example imaging the sub-dermal fingerprint, and for safely analyzing the eye, including the retina of the eye.However, current OCT imaging systems typically have at least some expensive components, such as, lateral scanning galvanometers, a swept optical source, or a spectrometer, thus making them unsuitable for low cost consumer devices. Unavailability of low cost consumer devices contributes to barriers to levels of detection, analysis and monitoring that is essential to many debilitating health conditions.

[0004] Major causes of blindness, for example, are macular degeneration and diabetic retinopathy. The onset or progression of macular degeneration and diabetic retinopathy can be monitored by imaging the retina and, for example, measuring spatial characteristics of layers of the retina including, but not limited to, the distance between layers in the retina, such as, theinner limiting membrane (ILM) and the retinal pigment epithelium (RPE) layer of the retina or changes in smoothness of such layers.

[0005] Furthermore, the vascular and central nervous systems are exposed in the retina of the eye and OCT analysis of the vascular and central nervous systems enables monitoring for the onset or progression of a myriad of conditions in addition to macular degeneration and diabetic retinopathy. Other relevant conditions include, but are not limited, to multiple sclerosis, Parkinson's disease, and Alzheimer's disease.

[0006] For eye conditions that are treatable with drugs, such as vascular endothelial growth factor (VEGF), timely intervention and monitoring are critical, because irreversible damage leading to impaired vision, and eventually blindness, can occur quickly. Current patient treatment for many of these conditions frequently involves monthly visits to a doctor's clinic to undergo scanning by a medical grade OCT system operated by a trained operator.

[0007] However, urgent conditions like leaking blood vessels can arise and cause irreversible damage between scheduled visits. Furthermore, effective treatments may stabilize conditions, enabling longer periods between clinic visits. Access to frequent OCT scanning by a home monitoring OCT system reduces the time between measurements and enables optimizing appropriate care.

[0008] Currently available OCT systems have complex and bulky alignment and scanning subsystems that result in physically large and costly systems. One approach, full field OCT (FF-OCT), eliminates the lateral scanning requirement. A typical FF-OCT system, configured as a Michelson interferometer, is described in a paper by authors Egidijus Auksorius, and A. Claude Boccara entitled “Fast subsurface fingerprint imaging with full-field optical coherence tomography equipped with a silicon camera”. However, this approach requires acquiring multiple full field data sets with different phase relationships in order to extract the interferometric signal, typically with four relative phases of 0, 180, 90, and 270 degrees.

[0009] Critically, for in vivo applications, collecting multiple data sets with different, but defined, phase relationships must occur within a time period that is sufficiently short so as to be insensitive to the normal motion of a live target, thereby avoiding “fringe wash-out” of the interferometric aspect of the signals. Typically a time period of the order of one millisecond or less is sufficient to avoid fringe wash-out in ophthalmic applications.

[0010] In conventional FF-OCT, high speed cameras or image sensor arrays are most often used, making the system expensive. Low cost consumers cameras, with frame rates of at best 120 fps, with a frame to frame time period of ~ 8 milliseconds, cannot preserve the interferometric phase relationship between image data sets, and fringe wash-out is unavoidable. Conventional FF-OCT approaches are reviewed in the paper “Methods and applications of full-field optical coherence tomography: a review” by Ling Wang, et al.

[0011] An FF-OCT approach that does not require high speed cameras is described in the paper “In-vivo retinal imaging with off-axis full-field time-domain optical coherence tomography” by Peter Koch et al, however this approach spatially separates different phases of the interferometric signal and therefore compromises the ability to separate the interferometric signal from the signals due to other scattering and reflection signals.

[0012] What is needed is a system, a method, and an apparatus for optically imaging at least one selected region of a living subject (the target) in a manner that avoids fringe wash-out while using low cost, low frame rate image sensor arrays or cameras and while fully exploiting the FF-OCT opportunity for removing unwanted scattering and reflection signals that only contribute noise, i.e. what is needed is a means to avoid fringe wash-out with high common mode noise rejection while using inexpensive low frame rate image sensor arrays or cameras.

[0013] What is also needed is a means for achieving such imaging and analysis without a dedicated system operator; and that includes a means for communicating relevant measurement data and results to the subject and / or to a designated care staff member.BRIEF SUMMARY OF THE INVENTION

[0014] The invention taught herein meets at least all of the above-mentioned unmet needs. The present invention provides an optical interferometric system using full field optical coherence tomography (FF-OCT) to acquire, or capture, data sets related to scattering properties of a selected three dimensional region of an in vivo target in a manner that is sufficiently insensitive to motion between the target and the system, so as to avoid fringe wash-out and preserve the interferometric relationship between relevant optical signals.

[0015] The optical interferometric system includes an optical source whose output is separated into an optical probe beam and an optical reference beam; and also includes at least one opticalbeam splitter that combines a portion of the optical probe beam backscattered from the target with a portion of the optical reference beam; and also includes a first image sensor array and a second image sensor array that acquire a pair of data sets simultaneously.

[0016] Because of the interferometric relationship between the pair of simultaneously acquired data sets, one data set of the pair has components that have a 180 degree phase relationship with components of the other data set of the pair where such components of both data sets of the pair are related to a selected three dimensional region of the target and are referred to herein as a pair of orthogonal data sets.

[0017] The selected three dimensional region of the target is determined by the cross-sectional extent or field of the optical probe beam, the coherence length of light output by the optical source, and the optical path length of the optical reference beam. The depth location of the selected three dimensional region of the target is referred to as the OCT window or the interferometric window.

[0018] In a preferred embodiment, the two image sensor arrays acquire two pairs of orthogonal data sets in a time period that is less than one millisecond, which is substantially less than the period of the frame rate of consumer image sensors arrays, thereby preserving the interferometric relationship between all four data sets and avoiding fringe wash-out. A phase offset of substantially 90 degrees is introduced between acquisition of the first and second pair of orthogonal data sets resulting in the four data sets having relative phase offsets of 0, 90, 180, and 270 degrees. The four data sets are processed to generate a single data set representing a scattering intensity of the selected region of the target.

[0019] In the preferred embodiment, the image sensor arrays have global shutters. Upon acquisition: the first pair of orthogonal data sets is immediately transferred to a protected region of each of the sensor arrays; the 90 degree phase offset is introduced; the active photodiode array of the sensor is reset; and the second pair of orthogonal data sets is acquired and held in the active photodiode array of the sensor; and the optical source is turned off (or the probe beam is blocked).

[0020] In alternate embodiments, the second pair of orthogonal data sets is transferred to additional sensor array memory elements, such as those used to enable high dynamic range (HDR) or custom memory elements. The time period starting with a photodiode array reset just before the global shutter and ending with the optical source being turned off is typically of theorder of one millisecond or less, which is sufficiently short to prevent fringe wash-out and thereby preserves the 0, 90, 180, and 270 degree phase relationship of the four acquired data sets.

[0021] The four data sets are processed to generate a single data set representing the scattering intensities of the selected three dimensional region of the target while suppressing common mode intensity signals emanating from regions other than the selected three dimensional region.

[0022] In the preferred embodiment, the optical source is an SLD with a coherence length of less than 10 microns, and the depth location of the OCT window is varied in depth to acquire data sets at a range of known depth locations. The data sets are combined to form a three dimensional data set similar to a conventional three dimensional OCT data set.

[0023] In an alternate embodiment, the optical source is a tunable laser with a coherence length of tens to hundreds of microns. Multiple data sets representing scattering intensities of the selected three dimensional region of the target are acquired with the tunable laser emitting different wavelengths. The resulting data sets are combined, using Fourier domain processing, to form a three dimensional data set of the target similar to a conventional three dimensional OCT data set.

[0024] In yet another alternate embodiment, the optical interferometric system is installed in a head mounted device similar to a virtual reality viewing device where the system can be readily aligned laterally and in depth to acquire three dimensional OCT data sets of the retina of a subject’s eye. In some embodiments, artificial intelligence is used to assist with aligning the system, interacting with the subject, and ensuring that the acquired retinal scans are of sufficient quality for monitoring for the progression of conditions such as age related macular degeneration (AMD) or diabetic retinopathy (DR).

[0025] Many variations of the system can address other applications. For example, a more complex embodiment using four image sensors enables acquiring signals with full polarization diversity. Such a system is suitable for non-invasive glucose level monitoring.

[0026] In a simpler embodiment, pairs of orthogonal data sets are successively acquired at a repetition rate that is synchronous with the frame rate of the image sensor arrays. In this embodiment, where the target is human skin, successively acquired pairs of orthogonal data sets have a random phase relationship or phase offset with the other pairs, where the random number of degrees in the phase offset is the result of relative motion of the target the optical interferometric system.

[0027] Applications of this embodiment include, but are not limited to, measuring blood oxygen levels, or imaging the sub-dermal capillary blood vessel network in the fingerprint region of a finger. Such an image is also referred to as a sun-dermal fingerprint. In this application, the finger or target being imaged can be placed on a platen to reduce relative motion between target and the optical interferometric system.

[0028] By acquiring a number of pairs of orthogonal data sets at the frame rate of the image sensors, data sets with a diversity of phase offsets can be acquired and processed to generate an image of the sub-dermal fingerprint. The same data sets can also be processed to generate the conventional surface fingerprint.

[0029] In this application, the optical source is typically a laser diode with a coherence length of the order of - 0.4 millimeters (40 microns). The platen can be compressible to facilitate depth alignment of the OCT window with the subdermal fingerprint. LED indicators can be used to guide the subject whose finger is being imaged to increase or decrease pressure and thereby align the OCT window with the subdermal fingerprint.

[0030] With image sensors with rolling shutters, the optical source is pulsed on (either electronically or optically by turning off the optical source or by means of an optical or mechanical shutter) for a time duration that is approximately one millisecond and typically less than one millisecond, which is sufficiently short to avoid fringe wash-out. With global shutters, the time duration of the shutter is approximately one millisecond and typically less than one millisecond, or sufficiently short to avoid fringe wash-out.

[0031] In some embodiments, at least some of the successively acquired pairs of orthogonal data sets are acquired while the optical source emits light of different wavelengths, either by using more than one optical source or a tunable laser and data sets of the selected three dimensional regions of said target are acquired multiple times and at least some of the acquired data sets are acquired while the optical source is emitting a different wavelength, enabling Fourier domain processing to yield a data set similar to a conventional three dimensional OCT data set.

[0032] The drawings to aid in understanding the invention are briefly described as follows. Figure 1 depicts an embodiment of the optical imaging and analysis system, configured with two image sensor arrays, suitable for acquiring data sets from targets such as skin tissue.Figure 2 depicts aspects of the frame and horizontal timing signals that are applied to the two image sensor arrays of Figure 1.Figure 3 depicts the embodiment of the optical imaging and analysis system suitable for acquiring fingerprint related data sets such skin tissue of a finger.Figure 4 depicts an embodiment of the optical imaging and analysis system, involving four image sensor arrays, suitable for acquiring data sets from targets such as skin tissue where in one mode the system is capable of acquiring data sets corresponding to four different phases of the phase modulator.Figure 5 depicts aspects of the frame and horizontal timing signals that are applied to the two image sensor arrays with both global shutter and global charge transfer.Figure 6 depicts an embodiment of the optical imaging and analysis system suitable for acquiring data sets from targets such as the retina of an eye.Figure 7 depicts an embodiment of the optical imaging and analysis system with an additional interleaved OCT system with a small diameter beam.Figure 8 depicts a full polarization embodiment of the optical imaging and analysis system using a Mach Zehnder interferometer configuration, configured with four image sensor arrays, suitable for acquiring data sets from targets such as skin tissue.Figure 9 depicts (in Fig. 9A) an example pixel structure of an image sensor array with separate global resets for both photodiodes and memory elements and with global charge transfer and depicts (in Fig 9B) a pixel structure with two memory elements.Figure 10 depicts aspects of the frame and horizontal timing signals that are applied to the two image sensor arrays with separate global resets for both photodiodes and memory elements and with global charge transfer.Figure 11 depicts an embodiment suitable for axial length measurement and central macular thickness measurement.Figure 12 depicts an embodiment suitable for comprehensive imaging and analysis of the retinal of an eye.Figure 13 depicts (in Fig. 13 A) the reference path and a portion of the probe path of an OCTmodule that is comprised only of low cost components and depicts (in Fig. 13B) a side view of a section of the OCT module of Fig. 13 A.Figure 14 depicts a side view of a more extensive portion of the OCT module, including fixation aspects and optics to direct the probe beam into the eye.Figure 15 depicts a side view of a more extensive portion of the OCT module, including additional depth scanning components and a display suitable for displaying optical images that include, but are not limited to, fixation by the subject whose eye is under test.Figure 16 depicts two OCT modules aligned to perform OCT scans on both eyes of a subject. Figure 17 depicts the two OCT modules mounted on rails that allow them to be aligned horizontally in order to perform OCT scans on both eyes of a subject.Figure 18 depicts two OCT modules aligned horizontally to perform OCT scans on both eyes of a subject, where the OCT modules rails are mounted in a frame.Figure 19 depicts a single OCT module that can be horizontally translated and positioned to scan either eye of a subject, where the OCT module rails are mounted in a frame.Figure 20 depicts (in Fig. 20A) a front view of an OCT module with a cut-out to allow turning mirrors to be translated vertically and (in Fig. 20B) depicts a side view of an OCT module and its relationship with other components.Figure 21 depicts a block diagram of the home retinal monitoring system.DETAILED DESCRIPTION OF THE INVENTION

[0033] This invention provides a method, apparatus and system capable of imaging and making measurements on targets such as skin tissue or the retina of an eye by acquiring, generating, or computing, one or more scattering intensity data sets from a selected three dimensional region of the target in a manner that is insensitive to relative motion between the target and the optical imaging and analysis system and that can be implemented using low cost components.

[0034] A preferred embodiment of the invention, depicted in Figure 1, is suitable for imaging and analyzing targets such as skin tissue. Applications include, but are not limited to, imaging the sub-dermal fingerprint for enhanced bio-security, measuring the concentration an analytes such as the glucose concentration of glucose in tissue fluids, or measuring blood oxygen concentration or saturation levels.

[0035] In this embodiment the optical coherence imaging system is comprised of an optical source 101 whose coherence length is selected to determine the desired depth thickness of the selected three dimensional region of the target. For example, in the sub-dermal fingerprint application, the desired depth thickness of the selected three dimensional region of the target is approximately ~ 40 microns. This is approximately the depth thickness of a typical capillary blood vessel network, an image of which constitutes a sub-dermal fingerprint.

[0036] The output of the optical source 101 is collimated and typically expanded to a substantially round optical beam (or field of light) by lenses 103, 105, 107. The expanded optical beam can have a diameter of the order of - 1cm or more for a fingerprint application. The substantially round (or oblong) beam 109 is applied to a beam splitter 111 that separates the beam into a reference beam 113 and a probe beam 115. Beams 113 and 115 are also referred to as reference light and probe light or reference radiation and probe radiation.

[0037] The reference beam 113 is directed through an optional optical attenuator 117 and through an optional phase modulator 119 to turning mirror 121 and beamsplitterl23 with a reflective coating 124 that acts as a second turning mirror and that compensates for the image inversion direct at least a portion of the reference beam to a second beam splitter 125.

[0038] The image inversion that occurs with a retro mirror is well known by persons skilled in the art, as are various arrangements to compensate for the image inversion. For example, the reflective coating 124 of beam splitter 123 could be replaced by a separate mirror, or the turning mirror 121 could be replaced by a beam splitter with a reflective coating and the element 123 could be a simple turning mirror. For simplicity of description, the turning mirror and the beam splitter with a reflective coating are sometimes referred to herein as turning mirrors 121 and 123.

[0039] The probe beam 115 is directed, through an optional additional optical component 127, such as a transparent platen, at the target 129 where the light of the probe beam is scattered within the target. Some of the probe light is back-scattered along the input path of the probe beam to the aforementioned beam splitter 111.

[0040] At the beam splitter Ill a portion of the back-scattered probe beam, also referred to as back- scattered probe light, is transmitted to the second beam splitter 125 where it can optically interfere with a portion of the reference beam.

[0041] Of the two output beams emerging from the beam splitter 125, one contains the true component and the other the complementary component of the optical interference signalresulting from combining the reference beam and scattered probe beam emanating from the selected region of the target. The selected region of the target is determined by the optical path length of the reference beam, the coherence length of the optical source, and the lateral dimensions of the optical probe beam in the target. The term “lateral dimensions” of a beam is also referred to as the field of a beam.

[0042] One output beam emerging from the beam splitter 125 is detected by a first image sensor array 131, The other output beam emerging from the beam splitter 125 is detected by a second image sensor array 133. The two image sensor arrays 131 and 133 are aligned or registered with each other such that they are both exposed to substantially the same spatially aligned image information thereby enabling high common mode noise rejection of signals that emanate from regions other than the interferometrically selected region of the target.

[0043] In some embodiments, one of the image sensor arrays could be replaced by a right angled mirror and the other image sensor array positioned to detect both output beams of the beam splitter 125. This configuration enables the use of only a single image sensor array that uses substantially half of the sensor array to detect each of the outputs of beam splitter 125.

[0044] In some embodiments, where there is some misalignment and when registration is not accurate, registration is corrected by aligning the digital images, or data sets, that are output by the two image sensor arrays. The electronic timing signals 135 (labeled TA) and 137 (labeled TB) can be common to the two image sensor arrays. These timing signals, along with the signal 149 Labeled TM) and the sync generator 151 are described later.

[0045] The optical path length of the reference beam or of the probe beam can be adjusted to locate the selected region of the target 129 at the desired depth, i.e. the OCT window can be located at the desired region of the target 129.

[0046] There are many approaches to adjusting the relative optical path length of the reference beam and the probe beam to locate the OCT window within the target. For example, the turning mirrors 121 and 123 (in the dashed box 139) could both be translated in a direction indicated by the double arrow 141, or the optical system enclosed in the dashed box 143 could be translated in a direction indicated by the double arrow 145.

[0047] In some embodiments, the translation actuator of the turning mirrors 121 and 123 could also include a piezo stage that can introduce a phase shift (e.g. of 90 degrees) in the reference beam with respect to the probe radiation.

[0048] The attenuator 117 can be selected to transmit an optimal amount of the reference beam towards the second beam splitter 125. Alternatively, or in addition, the transmission and reflection properties of the beam splitter 123 can be selected to transmit an optimal amount of the reference beam towards the second beam splitter 125.

[0049] The beam splitter 111 can be selected as either a non-polarized beam splitter or a polarized beam splitter. In the preferred embodiment, the beam splitter 111 is a non-polarized beam splitter that transmits a high percentage of the source radiation as reference radiation and reflects a small percentage as probe radiation.

[0050] For example, substantially 90% may be transmitted as reference radiation and 10% reflected as probe radiation. This has the advantage of also transmitting substantially 90% of back- scattered light from the target towards the detection system.

[0051] In such an embodiment, the probe radiation reflected by the beam splitter 111 is directed at the target, which in this embodiment is tissue 129 that is in contact with the optional platen 127. A portion of the scattered probe radiation is back- scattered through the platen 127 to the beam splitter 111 where approximately 90% of it is transmitted to the beam splitter 125.

[0052] The 90% of source light transmitted through beam splitter 111 as reference radiation passes through the optional attenuator 117, and an optional phase modulator 119.

[0053] The phase modulator 119 is not required in all embodiments as the relevant interferometrically related (true and complementary) components of the two data sets simultaneously acquired by image sensor arrays 131 and 133 are automatically 180 degrees out of phase with each other and are referred to herein as a pair of orthogonal data sets. Successively acquired pairs of orthogonal data sets typically have at least a small relative phase offset due to small relative motion between the target and the optical system, especially if the target is living tissue.

[0054] However, in some applications, it is desirable to vary the relative phase between successive pairs of orthogonal data sets, such as when there is negligible relative motion between the optical system and the target. The phase modulator enables introducing other phase changes, for example 90 degree offsets in successive pairs of orthogonal data sets. In some embodiments, the phase modulator is used to introduce pseudo random phase offsets to achieve phase diversity prior to averaging. For purposes of this invention, the term phase offset also includes a phase offset of zero degrees.

[0055] In some embodiments, such as the fingerprint application, where the platen 127 enables very small motion of the target, a phase modulator is not required and the small motion is sufficient to introduce a random phase change between successive pairs of orthogonal true and complementary acquired images. In some such embodiments, the images formed by subtracting true and complementary components are averaged, or are further processed to estimate the relative phase offset of successive images and then combined using the resulting phase information. In some embodiments each orthogonal pair is processed using processing that includes a Hilbert transform.

[0056] In the case of beam splitter 111 being a polarized beam splitter, an attenuator 117 may not be required. Only the portion of the back-scattered probe beam whose polarization has been rotated is transmitted through the beam splitter 111 to interfere with the reference beam in the beam splitter 125. In some embodiments a quarter wave plate may be inserted into the (double pass) probe path to rotate the polarization of the back- scattered probe beam.

[0057] A consequence of the combination of the automatic 180 degrees phase relationship of the components of the light corresponding to the selected region of the target reaching the two sensors 131 and 133 is that when the image data sets of the two image sensor arrays are subtracted (on a pixel by pixel basis) the light signal from all regions other than the selected region of the target (and its corresponding reference light) is substantially eliminated or cancelled, i.e. common mode noise is eliminated or canceled.

[0058] That is, subtracting the image data sets from the two sensors 131 and 133 yields a data set containing image data only from the interferometrically selected region of the target, thereby eliminating the noise due to un-useful light scattered or reflected from other surfaces or other regions of the target.

[0059] The interferometrically selected region of the target is also referred to herein as the interferometric window, the coherence window, or the OCT window. The interferometric aspect enables detecting the scattering intensity data set of the interferometric window with an enhanced signal to noise ratio and therefore enables the use of lower optical power and low cost silicon based sensor arrays.

[0060] Some aspects of the image sensor array timing signals are depicted in Figure 2 where the set of timing signals 201 are depicted that are typical of very low cost image sensor arrays with a rolling shutter. The x axis represents time increasing from left to right. The y axis showssequential horizontal video lines with labels Hl, H2, H3, etc. with Hl tagged as 203 being the first horizontal line in a frame.

[0061] At the beginning of a frame, the pixel array of the image sensor array is reset as indicated by 205. In very low cost sensors, the pixel array is always exposed and therefore it is desirable to eliminate or at least minimize ambient light. A global flash 207 follows the global reset 205. This corresponds to the optical source being pulsed on or turned on for a time duration of approximately one millisecond or less, where the time duration is short with respect to relative motion of the optical system and the target. An optical shutter could be used to block and “flash” the optical source.

[0062] Following the global flash, there is a charge transfer 209 of the first horizontal line of pixels into a line shift register. The line shift register can be comprised of analog charge coupled devices (CCD) or, in sensors with an analog to digital converter (ADC) per line pixel or per pixel, a digital shift register.

[0063] Referring again to Figure 2, following the charge transfer 209, a sequential pixel read out 211 occurs for line 1. This process is repeated for horizontal line 2, whose charge transfer 213 is followed by its line read out. The sequential read out of the depicted horizontal lines is depicted by the set of single arrow lines 215.

[0064] A timing sequence, such as is depicted in Figure 2 enables a low cost rolling shutter type image sensor arrays to be used in a configuration such as is depicted in Figure 1 to simultaneously acquire data sets whose interferometric related components from the selected region of a target to be acquired. This arrangement is power efficient in that the sensor need only be illuminated for the brief period of the flash 207. The optical source need only be pulsed for ~ 200 micro-seconds or less. This system is capable of acquiring at least a single pair of orthogonal data sets at the sensor frame rate.

[0065] Many low cost image sensor arrays now have “global shutters”. For example, in sensors with a global charge transfer, the signals in the active portion (i.e. the exposed photodiode portion) of all pixels are simultaneously transferred to protected regions (or memory elements) of each pixel in the pixel array. In Figure 2, the solid block representing the charge transfer 209 would be extended in the vertical direction so that all pixels would simultaneously have a charge transfer to the protected region (or memory) of every pixel and the charge transfers, other than 209, for lines H2, H3, etc. would not exist.

[0066] The combination of global reset and global charge transfer effectively comprises a global shutter or a global electronic shutter. Varying the time between the global reset and the global charge transfer varies the time duration of the global shutter.

[0067] The optical source may be pulsed on during this time duration to optimize optical power and to further control the acquisition time of signals. Optical filters can be used to eliminate signals from ambient light at wavelengths other than that of the optical source.

[0068] Other image sensor array types with a dedicated global shutter signal can also be used. For purposes of this specification, global shutter or electronic global shutter can refer to any combination of electronic control signals (including controlling the optical source output) that defines the time period during which a signal is acquired by the image sensor array for subsequent processing.

[0069] In some global shutter embodiments, the duration of the optical pulse (or flash) is substantially the same as the time duration between the global reset and the global charge transfer (charge transfer signal 209 would be vertically extended to apply to all horizontal lines). In some global shutter embodiments, the optical source remains on at either a constant or a reduced power level. Note the time period between the reset signal 205 and the charge transfer signal 209 is not limited to the duration depicted in Figure 2, but can be selected to be long enough to provide sufficient optical exposure and short enough to avoid fringe wash-out.

[0070] The same timing signals are applied to the two image sensor arrays 131 and 133 of Figure 1. These are indicated as 135 (labeled TA) and 137 (labeled as TB). The timing signals 135 and 137 are generated by a sync generator 151. The two sensors are spatially aligned with each other so they both acquire substantially the same surface image.

[0071] An application of this invention where the target is human skin and the selected region of the target is the sub-dermal fingerprint is illustrated and described with respect to Figure 3 of sheet 3 where the optical probe beam 301 (115 of Figure 1) of the optical imaging and analysis system 303 (i.e. the optical system of Figure 1) is applied to the skin tissue of a finger 305 resting on a transparent platen 307.

[0072] In some embodiments the platen is compressible and the subject whose finger is being imaged and analyzed is instructed (e g. by means of optical indicators (such as LEDs), or by audio means) to increase or reduce applied pressure to center the sub-dermal fingerprint in the “interferometric window” of the optical imaging and analysis system 303.

[0073] In some embodiments the platen is spring-loaded and the subject whose finger is being imaged and analyzed is instructed (e g. by means of LED indicators) to increase or reduce applied pressure to center the sub-dermal fingerprint in the “interferometric window” of the optical imaging and analysis system 303.

[0074] In some embodiments, where the two image sensor arrays are misaligned in one or both lateral directions, the image data sets (of the true and complementary pairs) are processed to align them in one or both lateral directions prior to subtraction or averaging.

[0075] In some embodiments, data sets of a selected three dimensional region of the target are acquired multiple times and at least some of the acquired data sets are averaged to form a high resolution two dimensional data set or image of the selected three dimensional region of the target.

[0076] In some embodiments, one or more of the multiple resulting image data sets are excluded from the averaging process. For example, if a single image data set differs significantly from an average of multiple other image data sets.

[0077] In some embodiments, the optional phase modulator 119 of Figure 1 is modulated to introduce a varying phase shift, for example switching between zero degrees and 90 degrees (or 45 degrees in double pass if the modulator is located in the probe path) for different frames. This enables ensuring there is phase diversity in different pairs of orthogonal data sets, especially in situations where there is very little motion, such as the case when a finger is resting stably on a platen. The control signal 149 (labeled TM) to the phase modulator 119 can also be generated by the Sync Generator 151.

[0078] Another embodiment of the invention using four image sensor arrays is depicted in Figure 4. While the version depicted in Figure 4 is suitable for imaging and analyzing targets such as skin tissue, other configurations are suitable for imaging and analyzing the retina of an eye. In such embodiment the optical source and optical beam conditioning optics are similar to that of Figure 1. The substantially round optical beam is applied to the beam splitter 111 that separates the beam into a reference beam and a probe beam.

[0079] As described with reference to Figure 1, the reference beam is directed through an optional optical attenuator 117 and through a phase modulator 119 to turning mirrors 121 and 123 and directed at beam splitter 125. For simplicity of illustration, the beam splitter and reflective coating of one of the turning mirrors is not depicted. As in Figure 1, the probe beam115 is directed, through an optional transparent platen 127 at the target 129 where the light of the beam is scattered within the target, some of which is back-scattered along the input path of the probe beam to the aforementioned beam splitter 111. At the beam splitter Ill a portion of the back- scattered probe light is transmitted to the beam splitter 125 where it can combine with the reference light.

[0080] A portion of the combined reference light and back-scattered probe light output from one port of beam splitter 125 is directed at beam splitter 427 and a portion of that light is transmitted through beam splitter 427 to the image sensor array 429.

[0081] A portion of the combined reference light and back-scattered probe light output from the other port of beam splitter 125 is directed at beam splitter 431 and a portion of that light is transmitted through beam splitter 431 to the image sensor array 433.

[0082] The interferometric components associated with the light back- scattered from the selected region of the target (the OCT window) of the data sets acquired by image sensor arrays 429 and 433 are 180 degrees out of phase with respect to each other. The light reflected by beam splitter 427 and detected by image sensor array 435 is similarly 180 degrees out of phase with the light reflected by beam splitter 431 and detected by image sensor array 437.

[0083] The four image sensor arrays 429, 433, 435, and 437 have global resets and global charge transfers. Aspects of the timing signals for the four image sensor arrays are depicted in the timing chart 501 of Figure 5. A first global reset 503 is applied to all pixels in image sensor arrays 429 and 433. This is followed by a first pulse 505 of the optical source that illuminates all image sensor arrays and this is then followed by a first global transfer 507 applied to image sensor arrays 429 and 433.

[0084] A second global reset 509 is then applied to image sensor arrays 435 and 437. This is followed by a second pulse 511 of the optical source that illuminates all image sensor arrays and this is then followed by a second global transfer 513 applied to image sensor arrays 435 and 437 of Figure 4. The phase modulator 119 of Figure 4 introduces a 90 degree phase shift in the reference path (or a 45 degree phase change in the probe path, between the two optical pulses. (Alternatively, a piezo or electro mechanical device could introduce the phase change.)

[0085] The phase modulator 119 of Figure 4 has a signal 439 (labeled TM) from the sync generator applied to it that introduces a 90 degree phase change in the reference path. The phase is stable for the duration to the first and second optical pulses 505 and 511. One phase changeshould occur between the two time periods (indicated by 517) in which the optical source is turned on and could coincide with the transition from the first charge transfer 507 to the second reset 509. The reverse phase change could occur anytime during the read out periods (indicated by 519), when the optical source is turned off.

[0086] In the embodiment depicted in Figure 4, the electronic signals applied to image sensor arrays 429 and 433 can be the same as each other (indicated by 441 and 443, labeled TAB). The electronic signals applied to image sensor arrays 435 and 437 (indicated by 445 and 447, labeled TCD), can also be the same as each other. (The read out signals can be the same for all four image sensor arrays. The electronic signals are generated by a sync generator (as shown in Figure 1).

[0087] The four data sets acquired by the four image sensor arrays 429, 435, 433, and 437 have components with phase offsets of 0, 90, 180, and 270 degrees with respect to each other. These data sets can be processed to yield a data set associated substantially only with the selected region of the target (the OCT window).

[0088] Another embodiment, uses the two image sensor array configuration of Figure 1.However, the image sensor arrays have global shutters with global resets and global charge transfers that transfer the charge accumulated in the active regions of the pixel array to a protected region, also referred to as a light shielded storage capacitor, or a Floating Diffusion (FD) node, for each pixel.

[0089] In this embodiment, the timing sequence is depicted in Figure 5 and is, in many respects the same as that depicted in Figure 2, however, the second charge transfer 513 does not occur immediately after the flash 511 at the time indicated by 513 in Figure 5.

[0090] Instead, the second charge transfer 513 does not occur until the first complete read-out of all horizontal lines has occurred (for both image sensor arrays). This effectively uses the active pixel array as storage elements for the signals acquired during the second flash 511 until the first complete readout of all horizontal lines has occurred. Implementing a 90 degree relative phase change between the first and second flashes (505 and 511) enables 4 data sets with relative phase offsets of 0, 90, 180, and 270 degrees to be acquired in a time that is significantly shorter than the time period associated with the frame rate of typical image sensor arrays. A time frame of the order of a millisecond and ideally less than one millisecond is typically sufficient to avoid fringe wash out when imaging living tissue.

[0091] The first reset 503 is applied to both image sensor arrays 131 and 133 of Figure 1, then the first flash exposure 505 occurs, then the first charge transfer signal 507 transfers the charge from the active region of all pixels to their protected regions or FD nodes. The active pixels of the image sensor arrays are then reset 509 (in sensors where such a reset does not affect the storage capacitor in the light shielded protected region) along with a 90 degree phase shift of the phase modulator, then the second global flash exposes the active pixel sections of the image sensor arrays to the phase shifted light. However, the second charge transfer does NOT occur at this time.

[0092] The signals from this second global flash are stored in the active pixels. The sequential read out of the horizontal lines (indicated by 519) then proceeds from both image sensor arrays. When this first readout of all horizontal lines from both image sensor arrays is complete, then the second charge transfer occurs to transfer the active pixel signal to the protected region of each pixel resulting in a second pair of orthogonal data sets being available for readout, after which the sequential line readout of the information from the second (phase shifted) flash exposure proceeds.

[0093] In sensors where the light shielded storage capacitor of each pixel can be reset without affecting the active pixel array, these shielded capacitors are reset just before the second charge transfer occurs. Then the second horizontal line readout from both image sensor arrays occurs.

[0094] In sensors where the light shielded storage capacitor of each pixel can NOT be reset without affecting the active pixel array, the second charge transfer occurs without a global light shielded storage capacitor reset occurring and the second horizontal line readout from both image sensor arrays proceeds. The second pair of orthogonal data sets from such image sensor arrays still contains data from the first global flash, which must be subtracted to yield the desired resulting paired data set.

[0095] The resulting two pairs of orthogonal data sets (for a total of four data sets) acquired by the two image sensor arrays 131, and 133 of Figure 1 have components with phase offsets of 0, 90, 180, and 270 degrees. These data sets can be processed to yield a data set associated substantially only with the selected region of the target. One typical processing approach is to calculate the intensities of each element of the final data set as Int = sqrt( ((Into - Intl80) / 2)**2 + ((Int90 - Int270) / 2)**2 ) where IntX is the intensity of an element of the data set at phase X, where X can be 0, 90, 180, or 270 degrees.

[0096] While it takes the time period of two image frames to read out the four data sets, fringe wash-out is avoided by having the two flash exposures (517 of Figure 5) with the 90 degree phase offset occur in a short time period typically of the order of several hundred micro-seconds as depicted, i.e. a small fraction of the image sensor array frame period. For purposes of this invention, the image sensor array frame period is the time it takes the image sensor array to read out a two dimensional image. In some more stable embodiments, the time duration encompassing the two flashes can be of longer duration, up to several milliseconds. More generally, the two pairs of orthogonal data sets are acquired in a time period that is sufficiently short to preserve the interferometric relationship between the four data sets of first and second pairs of two dimensional data sets.

[0097] Referring now to Figure 6, a configuration of the preferred embodiment, suitable for imaging and analyzing the retina of an eye, is illustrated and described with respect to Figure 6. The system is in many respects similar to the system of Figure 1 however the target is an eye 615 and the optics to direct the optical probe beam here indicated by the lens 613 (that is intended to be illustrative but not necessarily an accurate representation of the optics). In this embodiment the diameter of the optical probe beam at the retina is of the order of 2mm.

[0098] The optical probe beam 617 is directed through the pupil of the eye 615 to the retina 619 of the eye. The reference path includes at least one dispersion compensating element 623.

[0099] In some embodiments where the target is the retina, the selected region of the retina is the front region of the retina that includes the inner limiting membrane (ILM), but not the highly reflective retinal pigment epithelium (RPE).

[0100] In some embodiments the target is the retina and selected region of the retina includes the ILM, and the retinal pigment epithelium (RPE). In some embodiments the selected region of the retina includes the ILM, the retinal pigment epithelium (RPE), and the region behind the RPE also referred to as the choroid. Embodiments are not limited to these described regions.

[0101] The region of the retina that is selected by the interferometric window is determined by (a) appropriately selecting the coherence length of the optical source to determine the range of the interferometric window and (b) by adjusting the relative distance of the probe path and the reference path.

[0102] A portion of the back-scattered probe beam is transmitted through the beam splitter 111 to the beam splitter 621 where it can combine with the reference beam. The beam splitter 111can be selected so it transmits a large percentage of the back-scattered probe beam, e g. 90%, thereby optimizing use of the back-scattered probe beam.

[0103] The reference beam is directed through a dispersion compensating element 623, an optional optical attenuator 625 and through an optional phase modulator 627, and by way of turning mirror 629 and beam splitter with reflective coating 631 (also referred to as turning mirrors 629 and 631 ) to the beam splitter 621.

[0104] Typically, the dispersion compensating element 623 matches the dispersion of the eye 615. In a Mach Zehnder configuration where the reference beam does not undergo a double pass of the optics (as it does in a Michelson configuration) the dispersion compensating element 623 must have significantly higher dispersion than the eye has, or be of greater length, or have more than one element, as indicated by a second dispersion compensating element (dashed box) 624 and should include the beam splitter 631.

[0105] At the beam splitter 621 a portion of the back-scattered probe light and a portion of the reference light are combined such that the image sensor arrays 633 and 635 can simultaneously acquire a pair of orthogonal data sets that have components that are 0 and 180 degrees out of phase or two pairs of orthogonal data sets whose four data sets that have 0, 90, 180, and 270 degree phase offsets with the use of the phase modulator switching between 0 and 90 degree relative phase shifts.

[0106] The one or two pairs of orthogonal data sets (for a total of two or four data sets) embodiments depend on the choice of image sensor array and having the appropriate timing signals 637 and 639 as described earlier.

[0107] In the preferred embodiment, the four data sets of the two pairs of orthogonal data sets are combined (on a pixel by pixel basis) to substantially eliminate or cancel the light signal from all regions other than the selected region of the target (and its corresponding reference light). That is, processing the image data from the four data sets yields a data set containing image data only from the interferometrically selected region of the target (i.e. the OCT window, also referred to as the interferometric window), thereby eliminating to common mode noise due to un-useful light scattered or reflected from other surfaces or other regions of the target.

[0108] One technique for processing the four data sets includes subtracting data sets with 0 and 180 phase offsets, and also subtracting data sets with 90 and 270 degree offsets, and combining the resulting data sets (as described earlier). The fact that these data sets are being acquired at arate close to the high horizontal line rate (~ 200 micro-seconds) and ideally less than one millisecond renders this optical imaging and analysis system insensitive to relative motion between the optical system and the target, where such motion is typically due to the normal unavoidable motion of a human subject. Acquiring all the data sets and generating the phase changes in such a short time period avoids fringe wash-out.

[0109] The location of the OCT window within the target can be modified in many ways including, but not limited to, (a) adjusting the position of the optical system, indicated by the dashed box 641, in the depth direction indicated by 643, (b) adjusting the location of the pair of turning mirrors 629 and 631, indicated by the dashed box 645 in the direction indicated by 647, (c) inserting an optical flat in the reference beam as indicated by the dashed box 649, where such an optical flat is one of many selectable flats of differing thickness on, for example, a rotatable wheel, (d) in embodiments where the reflective coating of a beamsplitter (such as, 124 of Figure 1) is replaced by a separate mirror, translating the separate mirror for depth scanning or alignment. In some embodiments, the rotatable wheel can contain one or more (highly attenuating) stops capable of blocking the optical beam for reasons, such as safety reasons.

[0110] Instead of a phase modulator 627, a piezo device or electro-mechanical actuator could be included in the translation actuator that adjusts the position of the optical system or the pair of turning mirrors 629 and 631, where the piezo device can introduce a translation of an eight or a quarter of a wavelength which is equivalent to introducing a relative phase change of 90 degrees.

[0111] In some applications, such as generating an image of the sub-dermal fingerprint of a finger, an optical source with a coherence length of the order of 0.5mm enables selectively detecting intensity data related to the sub-dermal fingerprint and substantially eliminating light reflected or scattered from other regions and surfaces.

[0112] In some applications, such as generating a fundus image of the retina of an eye, an optical source with a coherence length of the order of 0.5mm enables selectively detecting intensity data related to the retina and substantially eliminating light reflected or scattered from other regions and surfaces.

[0113] In the sub-dermal fingerprint application, a compressible platen with a thickness monitor could enable a method of changing the relative optical path length.

[0114] Platen thickness can be measured by capacitance monitoring or other known monitoring technology.

[0115] Embodiments with an optical source with a coherence length of the order of 0.01mm or 10 microns enables acquiring a three dimensional data set of the target, by acquiring and combining multiple three dimensional “slices” (or cross sections) of the target at different and known depth locations, thereby effectively acquiring an optical coherence tomographic data set of the target. In such cases the optical source 101 of Figure 1 could be other than a laser diode, such as a superluminescent (SLD) diode or a light emitting diode (LED).

[0116] The multiple slices can be selected or scanned through by techniques that include, but are not limited to: (a) a stepping actuator adjusting the position of dashed box 641, in the depth direction indicated by 643; (b) a stepping actuator adjusting the location of the pair of turning mirrors 629 and 631, indicated by the dashed box 645 in the direction indicated by 647; (c) rotating the wheel containing different thickness flats, indicated by the dashed box 649, synchronously with the frame rate of the image sensor arrays 633 and 635 or a multiple of the frame rate of the image sensor arrays 633 and 635.

[0117] In some embodiments, the same electro mechanical actuator that adjusts the depth location of the OCT window could have its scan speed and the time interval between the two optical pulses selected such that the motion of the electro mechanical actuator also introduces the required 90 or 45 degree phase offset between the two optical pulses. In such embodiments, the optical pulses would be sufficiently short to have negligible phase change over each of their duration.

[0118] Another embodiment that acquires an optical coherence tomographic data set of the target is depicted in Figure 7. This embodiment includes the optical system of Figure 1 with an SLD as the pulsed field optical source 101. Interleaved with the optical system of Figure 1 is a conventional OCT system with a small diameter optical beam that makes a single point depth scan with sufficient depth resolution to distinguish layers in the depth scan.

[0119] In some embodiments the conventional small diameter OCT system, is a SS-OCT system and the optical source 745 of Figure 7 is a swept source (or tunable laser) that is collimated to a small diameter beam by optics represented by the light collimator lens 747.

[0120] The collimated OCT beam 749 is interleaved with the broad area pulsed field light of the optical system of Figure 1 by turning mirror 751 and dichroic mirror 753. The back-scattered swept source OCT probe beam is partially separated from the pulsed field optical back-scatteredprobe beam by the dichroic mirror 755. The swept source OCT reference beam is substantially separated from the pulsed field optical reference beam by the dichroic mirror 757.

[0121] The separated back-scattered swept source OCT probe beam is directed by a turning mirror 759 to a beam splitter 761, where it is combined with the separated swept source OCT reference beam. A small portion of the back-scattered swept source OCT probe beam is transmitted to the beam splitter 125 and hence the image sensor arrays 131 and 133.

[0122] The true and complementary optical signal outputs of the beam splitter 761 are focused by first and second lenses 763 and 765 and detected by first and second photo-detectors 767 and 769. The electronic signals from the photo-detectors are processed (by conventional processing) to yield a depth scan of the target 129.

[0123] The depth locations of specific characteristics of the target, such as layers of tissue, are used to correctly depth align multiple two dimensional data sets acquired by the pulsed field optical system, so they can be combined to yield a three dimensional data set that represents a tomographic representation of the target, similar to a conventional OCT three dimensional data set.

[0124] In this embodiment the turning mirror 121 of Figure 1 is replaced by a beam splitter 771 with a reflective coating 773 on one side and the beam splitter 123 with reflective coating 124 of Figure 1 is replaced by turning mirror 773.

[0125] In some embodiments, the optical source 101 of Figure 7 and Figure 6 is a tunable laser (or swept source). This enables acquiring multiple data sets at least some of which are acquired at different wavelengths by changing the wavelength of the optical source substantially synchronous with the frame rate or multiples of the frame rate of the image sensor arrays.

[0126] An advantage of the tunable laser Full Field OCT embodiments is that the wavelength scanning speed of the tunable laser (or swept source) can be at the relatively low speed of the frame rate of the array sensors or a sub-multiple of the frame rate, (unlike the typical high speed of swept sources scanning speed used with galvo scanning SS-OCT systems). This enables using tunable laser sources such as “slotted surface grating lasers” as the optical source that have relatively slow tuning speeds.

[0127] The multiple two dimensional data sets at least some of which are acquired at different wavelengths can be combined using Fourier transform processing to yield a three dimensionaldata set that represents a tomographic representation of the target, similar to a conventional OCT 3D data set.

[0128] In some embodiments two or four data sets (i.e. one or two pairs of orthogonal data sets) are acquired with the same wavelength with relative phase offsets of 0 and 180 degrees, or of 0, 90, 180, and 270 degrees. This is done for each of the multiple wavelengths emitted from the optical source. In some embodiments, depth alignment of the multiple data sets can be maintained or corrected for using the narrow beam OCT system.

[0129] Lateral alignment of the multiple data sets can be maintained or corrected for by processing the two or four data sets (i.e. one or two pairs of orthogonal data sets) to yield at least one full field data set for each wavelength. Data points at common topographical structural details are identified. One or more data points in one data set, resulting from processing four data sets with 0, 90, 180, and 270 degree phases, are selected to be a reference data set. Other data sets are compared with the reference data set. If there is misalignment, the data set, or sets, are digitally shifted to achieve alignment, using interpolation if required for optimum alignment.

[0130] In some embodiments, angular rotation can be included to achieve optimum alignment. Aligned data sets at different wavelengths are combined using Fourier transform based processing to yield a single data set that is a tomographic representation of the target, similar to a conventional OCT 3D data set.

[0131] In some embodiments the relative phase information of at least one common topographical detail in data sets of different wavelengths is included in the Fourier transform based processing. Such relative phase information can be determined by calculating the phase offset for the at least one common topographical detail by calculating the phase offset from having two corresponding data points in the 0 degree and 180 degree data sets, of a paired data set, equal to each other and the corresponding data points of the 90 degree and 270 degree data sets having a maximum difference.

[0132] In some embodiments, where such phase information for spatially different data points of common topographical detail do have different phase offsets, a smooth phase correction contour map is generated and applied to the complete data set. Such a smooth phase correction contour map is generated and applied for the data sets of each wavelength.

[0133] In some embodiments, a previously acquired high resolution conventional OCT 3D data set is processed to generate an assemblage of reference data sets that is comprised of multiple 2Ddata sets, similar to the 2D data sets that could be acquired by the optical system of this invention at depth offsets spanning the desired depth range to be imaged or analyzed within the target.

[0134] In embodiments involving a multi-wavelength optical source and Fourier domain based processing, the generated assemblage of reference data sets includes an assemblage of 2D reference data sets for each wavelength that the multi-wavelength optical source is centered on when acquiring the 2D data sets by the optical system of this invention.

[0135] In some embodiments, a previously acquired high resolution conventional OCT 3D data set is processed to generate a modified OCT 3D data set that is similar to a 3D data set that would be obtained if no correction elements were included when acquiring the OCT 3D data set. Correction elements include, but are not limited to, aberration correction worn by the target subject. The resulting 3D data set would be then further processed to generate an assemblage of 2D reference data sets for the target subject being imaged or analyzed.

[0136] In some embodiments, a previously acquired high resolution conventional OCT 3D data set is processed to modify the OCT 3D data set to be similar to a 3D data set that would be obtained if the actual correction elements were worn by the target subject. The resulting 3D data set would be then further processed to generate an assemblage of 2D reference data sets for the target subject being imaged or analyzed and the target subject would wear the same corrective elements while the multiple 2D data sets are being acquired by the inventive optical system.

[0137] Such correction elements include, but are not limited to: one or more contact lens; spectacles; one or more custom lens.

[0138] In some embodiments the conventional narrow beam OCT system is an SD-OCT system and the optical source 745 of Figure 7 is an SLD. In such embodiments, the lenses 763 and 765 and photo-detectors 767 and 769 are replaced by, at least one, spectral domain detection system, that typically includes a diffraction grating and detector array.

[0139] In some embodiments, such as a configuration similar to the system depicted in Figure 7 but with additional optical elements (such as 613, 623, and 624 of Figure 6) making it suitable for retinal imaging, the optical source 745 is an SLD, LD, or LED used (a) for the subject to fixate on, (b) to make a spot on the cornea for two or more cameras to provide distance to eye (and hence depth) measurement and alignment assistance, (c) provide a spot to be acquired by the sensor arrays and used for lateral alignment.

[0140] In some retinal imaging embodiments with a narrow beam OCT system, the narrow beam OCT system has its OCT window depth aligned with the front surface of the eye.

[0141] In some retinal imaging embodiments with a narrow beam OCT system, the narrow beam OCT system with its OCT window depth aligned with the front surface of the eye and where its spot on the cornea is monitored by two or more cameras to provide distance to eye information, the axial length of the eye can be measured and monitored for changes over time. If the subject’s axial length is known, this information can be used to assist in depth alignment.

[0142] The broad spot on the cornea due to the optical probe beam 617 of Figure 6 as it is diverging may also be acquired by the one or more cameras and used for lateral and depth alignment. The depth location of the selected three dimensional region of said target is measured by processing the image of the broad spot on the cornea due to the diverging optical probe beam. A narrow beam spot may be distinguished by pulsing the narrow beam source, ideally synchronously with camera and image sensor array frame rates. The diverging broad spot will change in lateral size with a change in depth and thereby its image can be used by one or more cameras for depth alignment.

[0143] In some such retinal imaging embodiments, the components 755, 757, 759, 761, 763, 765, 767, and 769 are not required.

[0144] In some embodiments, there is an additional array of LEDs, LDs, or SLDs one or more of which are selected at a time to be used for the subject to fixate on and thereby target different regions of the retina for imaging.

[0145] In some embodiments, the optical source 745 is replaced by an array of LEDs, LDs, or SLDs one or more of which is selected at a time to be used for the subject to fixate on and thereby target different regions of the retina for imaging.

[0146] Referring now to Figure 8, an optical system enabling the acquisition of data sets with full polarization diversity from a selected region of a target is depicted, well suited for targets such as skin tissue.

[0147] In some embodiments of Figure 8, the optical source outputs a source beam a polarized beam whose polarization vector is at 45 degrees with respect to the polarized beam splitters 845 and 849. In some embodiments, the optical source outputs a circularly polarized beam.

[0148] The system depicted in Figure 8 is in some respects the same as the system depicted in Figure 1, however the portion of the back-scattered probe radiation that propagates through thenon-polarized beam splitter 111 to the polarized beam splitter 845 contains all polarization components. The transmission output of the polarized beam splitter 845 is directed at nonpolarized beam splitter 847.

[0149] The reference beam is directed by beam splitter 871 with reflective coating 873 to the polarized beam splitter 849, one output of which is directed by turning mirror 823 at the second input to non-polarized beam splitter 847 where it is combined with a portion of the back-scattered probe radiation.

[0150] As both beams being input to beam splitter 847 have the same polarization, they can form interference signals. With the appropriate reference optical path length, true and complementary interferometric components related to the selected region of the target emerge from the beam splitter 847. The output beams of beam splitter 847 are detected and acquired by image sensor arrays 851 and 853 to yield a pair of orthogonal data sets.

[0151] The reflected output of the polarized beam splitter 849 is directed at the non-polarized beam splitter 855, while the reflected output of the polarized beam splitter 845 is directed by the turning mirror 857 to the other input of the non-polarized beam splitter 855. The output beams of beam splitter 855 are detected by first and second image sensor arrays 859 and 861.

[0152] The timing signals 863, to 865, 867, and 869 to the image sensor arrays 851, 853, 859, and 861 can be configured (as described earlier) to acquire one pair of orthogonal data sets for each of the two polarization components with 0 and 180 degrees offsets with respect to each other.

[0153] Alternatively, the timing signals 863, to 865, 867, and 869 to the image sensor arrays can be configured (as described earlier) to acquire two pairs of orthogonal data sets, totaling four data sets, for each of the two polarization components with 0, 90, 180, and 270 degrees offsets with respect to each other.

[0154] The two above configurations have the advantage (as discussed before) that the multiple data sets are acquired in a time period of the order of milliseconds or less, or sufficiently short to avoid fringe wash-out, (significantly less than the period of the image sensor frame rate).

[0155] Another configuration of the full polarization diversity system of Figure 8 uses an optical source that can be switched between two or more wavelengths and acquires a pair of data sets for each of the two polarization components with 0 and 180 degrees offsets with respect to each other, for each wavelength.

[0156] Such a configuration would, for example, be suitable for measuring the concentration an analytes such as the concentration of glucose in tissue fluids. The combination of a full field OCT system with polarization diversity, the acquisition of four data sets at 0, 90, 180, and 270 degrees with low cost components for both polarization components, and the availability of a skin surface image (e.g. the surface fingerprint, enables accurately targeting and analyzing a specific 3D volume to determine glucose concentration, or the concentration of other analytes. Artificial intelligence can be used to assist in alignment and analysis.

[0157] In some embodiments, the optical source 101 is a tunable laser (or swept source) and Fourier domain processing of multiple data sets can yield a three dimensional (3D) data set with full polarization diversity.

[0158] In some embodiments, the optical source 101 is switchable between two or more optical sources, each of which could be a tunable laser (or swept source) and Fourier domain processing could yield multiple full polarization diversity three dimensional (3D) data sets, with the two or more optical sources having different wavelength ranges from each other.

[0159] A full diversity configuration is, for example, suitable for measuring the concentration an analytes such as the concentration of glucose in tissue fluids. The combination of a three dimensional (3D) OCT data set with full polarization diversity and the lateral and depth alignment or location capability, for example using a surface fingerprint as well as a capillary structure, provides rich data sets suitable for analysis for the concentration of glucose or the measurement of blood oxygen levels, or the concentration of other analytes.

[0160] Figures 9 and 10 illustrate details of the electronic circuit structure and the timing of the electronic signals of image sensor arrays of alternate embodiments, such as that depicted in Figure 1. Fig. 9A of Figure 9 depicts an example of the structure (Yang Liu Thesis Page 20, 2017, Delft University) of a single pixel and associated electronics of the pixel array of an image sensor array with a separate global photodiode reset 901 and global memory element reset 903, where the term memory element includes, but is not limited to, a light shielded storage capacitor, or a Floating Diffusion (FD) node. The signal 905, labeled TX is the global charge transfer signal that transfers charge from the photodiode to the memory element 907 labeled M.

[0161] A typical timing sequence 1001 for image sensor arrays with a separate global photodiode reset, a global charge transfer, and a global memory element reset of embodiments, such as that depicted in Figure 1, is depicted in Figure 10. At the beginning of a frame, whichmay be initiated by a trigger signal (not shown), there is a first global photodiode reset 1003 labeled Reset PD1, followed by (or coincident with) a first global memory element reset 1005 labeled Reset memory elment 1, followed by the first global flash labeled Flash 1 indicated by the arrow line 1007, followed by the first global charge transfer 1009 labeled charge transfer 1, followed by the second global photodiode reset 1011 labeled Reset PD2, followed by the second global flash labeled Flash 2 indicated by the arrow line 1013, followed by the sequential readout of the horizontal lines with 1015 indicating the first horizontal line.

[0162] When the first complete set of horizontal lines is read out, the second global memory element reset 1017 labeled Reset memory element2, followed by the second global charge transfer labeled Charge transfer 2, after which occurs the second sequential readout of the horizontal lines with 1021 indicating the first horizontal line.

[0163] A timing sequence such as depicted in Figure 10 and implemented using image sensor arrays with a pixel structure such as that depicted in Fig. 9A of Figure 9 in preferred embodiments such as those depicted in Figures 1 and 6 enable two pairs of orthogonal data sets to be acquired in a time period of the order or less than one millisecond (significantly shorter than the period of the frame rate of the image sensor arrays) thereby avoiding fringe wash-out. In some embodiments, a relative phase change of 90 degrees between the reference and backscattered probe beams is introduced between the first and second flashes to yield four data sets with relative phase offsets of 0, 90, 180 and 270 degrees.

[0164] Some embodiments, exploit existing sensor array memories, such as those used for high dynamic range HDR capability. Some embodiments have custom sensor arrays that (a) have two or more memory elements associated with each pixel in the sensor array, (b) have an independent global reset signal for the active pixel array, (c) have independent global reset signals for each set of protected memory elements, (d) have global charge transfer signals for each set of memory elements, and (e) have signals to select which set or sub-set of memory elements to enable for horizontal readout thereby enabling sequential or interleaved readout.

[0165] Fig 9B of Figure 9 depicts details of a custom sensor array having at least two memory elements (labeled MA and MB) associated with each pixel in the sensor array. In embodiments using such custom arrays, a global reset of the pixel array 911, labeled RPD (for reset photodiodes) prepares the sensor array for illumination by a first (global) flash. A first global reset 915 labeled RMA of memory element MA clears one set of memory elements. The first(global) flash then occurs followed by the first global charge transfer 917 labeled TXA that transfers the charge in each pixel to its corresponding protected memory element MA 913.

[0166] A second global reset of the pixel array 911 labeled RPD prepares the sensor array for illumination by a second (global) flash. A second global reset 919 labeled RMB of memory element MB clears a second set of memory elements. The second (global) flash then occurs followed by the second global charge transfer 921 labeled TXB that transfers the charge in each pixel to its corresponding protected memory element 923.

[0167] In OCT system configurations using a phase modulator, or equivalent, a phase shift of substantially 90 degrees is introduced between the two global flashes, keeping the time between the start of the first flash and the end of the second flash sufficiently short to preserve their interferometric relationship (and avoid fringe wash-out).

[0168] At the appropriate read out time signal 925 labeled RS A selects the signal in MA to be output, while at the appropriate read out time signal 927 labeled RSB selects the signal in MB to be output.

[0169] The signals in memory set A 913 (labeled MA and set B 923 (labeled MB) can be interleaved on a pixel by pixel basis so both corresponding pixel signals are available for processing. In configurations with a paired sensor arrays (such as that depicted in Figure 1), interleaving on a pixel by pixel basis enables four data sets to be acquired with relative phase offsets of 0, 90, 180, and 270 degrees.

[0170] In embodiments with two sets of protected memory elements per pixel, the active pixel array could also be used to store a third pair of data sets to provide six data sets with relative phase offsets of 0, 60, 120, 180, 240, and 300 degrees from three optical pulses that are sufficiently short to avoid fringe wash-out. More generally, the phase offset between corresponding data sets in said pairs of orthogonal data sets is a fixed number of degrees (which can include zero degrees).

[0171] In some embodiments, the analog (or digital) signals in corresponding memory elements of two or more memory element sets, can be combined (or processed) prior to horizontal readout. In some embodiments, additional horizontal line memories facilitate combining the analog (or digital) signals in corresponding memory elements thereby minimizing the number of processing circuits. Combining or processing circuitry includes, but is not limited to, subtracting signals of corresponding memory elements. Such processing can occur before or after digitization.

[0172] Many other configurations and combinations of configurations are possible. For example, an embodiment with a narrow beam OCT system, where the narrow beam OCT system has its OCT window depth aligned with the retina of the eye and where its spot on the cornea is monitored by two or more cameras to provide distance to eye information, could be a stand-alone axial length monitor (with or without the full field imaging system). It could also be integrated into an ophthalmoscope. It could be combined with a conventional fundus imaging camera.

[0173] Figure 11 depicts such a stand-alone axial length monitor (without a full field imaging system) where an OCT system with a small diameter probe beam 1101 is mounted on a frame 1103 and the subject whose eye is being scanned fixates on the optical probe beam. The frame 1103 has at least a first and a second camera 1105 and 1107 that are each used to image subject’s the eye 1109 under test. Additional optics may be used to enable the cameras to image the eye 1109 , such as mirrors 1111 and 1113.

[0174] The cameras 1105 and 1107 are selected to be sensitive to the wavelength of the OCT beam in addition to being sensitive to visible light. For example, cameras with a silicon based image sensor array (and without an IR filter) are available as low cost web-cams. An image 1115 acquired by such a camera is depicted in Figure 11, where the OCT probe beam 1117 is visible as a white spot in the pupil of the eye 1109.

[0175] The cameras 1105 and 1107 and associated optics are aligned such that when frame 1103 is at a particular and known distance from the eye under test, the two acquired images (one from each camera) will substantially overlap, as will the two OCT spots.

[0176] A calibration process could also enable knowing the distance from the eye for situations where the pupils and OCT spots of the two images are not overlapping as depicted in the picture 1119, where a composite of the images from the two cameras is depicted. This enables knowing the distance from the eye based on the distance between the two OCT spots. More generally, the depth location of the selected three dimensional region of said target is measured by processing the degree of overlap of aspects of images acquired by the at least two cameras acquiring images of the front surface of said target. The relationship of the images and the OCT spots also enables knowing wether the frame 1103 is too close or too far from the eye, i.e. the direction to move the frame to bring the spots into coincidence (or to a predetermined separation).

[0177] When the frame 1103 is at a desired distance from the eye (achieved by moving the frame, in depth as indicated by the double arrow 1121), the OCT system 1101 is moved in depth with respect to the frame 1103, as indicated by the double arrow 1123.

[0178] The relative position of the OCT system 1101 and the frame 1103 is measured and monitored by conventional methods (described later).

[0179] If the nominal axial length of the subject is known, this can be used to determine a starting value for the relative (calibrated) distance between the front of the cornea and the retina, otherwise systematic scanning could locate a positional configuration of the frame and the OCT system that enable a processing algorithm to detect both the cornea front (by the relative overlap of the camera images) and the retina 1125 of the eye 1109 (by being depth aligned with the OCT window).

[0180] Once both the cornea and the retina are detected, processing the camera images and the OCT signals can provide feedback to keep the OCT system 1101 and the frame 1103 depth aligned by tracking and predicting relative motion of the subject until sufficient high quality scans are acquired to determine the axial length with the required accuracy.

[0181] In some embodiments, the OCT system includes additional optical elements that enable a second OCT window to be aligned with the front surface of the eye. Light from the optical probe beam is also back-scattered from the front surface of the eye, indicated by the arrow head 1127.

[0182] While OCT signals from both the retina and the front surface of the eye will be present in the detected data sets, they can be distinguished from each other by the fact that they will move with respect to each other if the reference path of the one OCT window is moved with respect to the other OCT window by changing the reference path length for one of the OCT windows, while the reference path length for the other OCT window remains unchanged (or is changed by a different amount).

[0183] Using OCT signals to determine the location of both the retina 1125 and the front surface 1127 enables the axial length to be measured to a resolution determined by the OCT signals, which can be increased by increasing the bandwidth of the optical source. The actual axial length of the eye can be determined by measuring the distance that one OCT window is moved with respect to the other OCT window.

[0184] As discussed later, this can be determined by conventional methods, for example, using a fine pitch screw in the translational stage and monitoring the rotary position and number of turns of the screw, in conjunction with known calibrated end positions.

[0185] The images from the two cameras also provide useful feedback for alignment in depth and in the lateral directions. The location of the OCT spot with respect to the pupil provides lateral alignment feedback. The degree to which the two images overlap can provide depth alignment feedback, including depth change direction alignment information.

[0186] As mentioned before, a broad spot on the cornea due to the source 101 of Figure 6 may also be acquired by the two or more cameras and used for lateral and depth alignment. The narrow beam spot may be distinguished by pulsing the narrow beam source, ideally synchronously with camera and image sensor array frame rates.

[0187] Figure 12 illustrates a comprehensive retinal monitoring system. The output of the first optical source 1201, typically an SLD, LED, tunable laser, or swept source is collimated and typically expanded to a substantially round broad optical beam (or field of light) by a combination of lenses exemplified as first, second, and third lenses 1203, 1205, 1207.

[0188] A second optical source 1209, such as an SLD, tunable laser, or a swept source laser, is the optical source for a small diameter (or narrow) beam OCT system. The optical source 1209 has its output collimated to a small diameter beam by a fourth lens 1211 or lens combination and combined with the broad optical beam by a first turning mirror 1213 and a first dichroic mirror 1215.

[0189] The combined broad optical beam and small diameter beam is applied to a beam splitter 1217 where it is split into combined probe beams and combined reference beams.

[0190] The combined probe beams are focused be a lens 1219 or lens combination and directed at the target 1221 where (in some embodiments) a substantially collimated combined beam reaches the retina 1223 where some of the combined probe beams are back-scattered through the beam splitter 1217.

[0191] Portions of the combined reference beam pass through an attenuator 1225, which can be one of several attenuators in various arms of the reference paths, to a dichroic partial mirror 1227 that directs a portion of the small diameter reference beam towards a second partial mirror 1229. Both mirrors 1227 and 1229 attenuate the small diameter reference beam.

[0192] The portions of the combined reference beams that are transmitted through the partial mirror 1227 to a dispersion compensation optic 1231 which can include a turning mirror 1233 which directs the combined reference beams to a dichroic mirror 1235 that directs the small diameter reference beam through another optional dispersion compensation optic 1237 to the partial mirror 1229.

[0193] Portions of the small diameter reference beams that are recombined by the partial mirror 1229 are directed at another beam splitter 1239.

[0194] A portion of the broad optical reference beam is transmitted through the dichroic mirror 1235 to a beam splitter with reflective element 1241 (acting as a turning mirror), through an optional dispersion compensation optic 1243, through an optional phase modulator 1245, and through an optional attenuator 1247 to a beam splitter 1249 where it is combined with a portion of the back-scattered broad optical probe beam that has been transmitted through the beam splitter 1217 and a dichroic mirror 1251 that reflects at least a substantial portion of the back-scattered small diameter probe beam.

[0195] In some embodiments, a small portion of the back- scattered small diameter probe beam is transmitted through the dichroic mirror 1251.

[0196] The two outputs of the beam splitter 1249 are detected by two image sensor array detectors 1253 and 1255 as data sets that contain true and complementary scattering intensity maps (i.e. a simultaneously acquired pair of orthogonal data sets) substantially from the region of the target defined by the OCT window.

[0197] A portion of the small diameter back-scattered probe beam that is transmitted through the dichroic mirror 1251 is also detected by the first and second image sensor array detectors 1253 and 1255. These signals do not have a true and complementary relationship but can be extracted by processing the data sets of the image sensor array detectors separately, typically by adding or averaging them. These small diameter back- scattered probe beam signals enable accurately locating the small diameter probe beam with respect to the broad optical probe beam on the retina in the two lateral directions.

[0198] The portion of the small diameter back-scattered probe beam reflected by the dichroic mirror 1251 is directed by a turning mirror 1257 to a beam splitter 1239 where it is combined with a portion of the small diameter reference beam reflected by mirrors 1235 and 1229.

[0199] In embodiments where the optical source 1209 is a swept source, the two outputs of beam splitter 1239 are detected by photo-diodes, typically after being focused by lenses 1265 and 1267. The detected true and complementary small diameter signals are processed to provide a depth scan of a spot on the cornea and, with appropriate alignment of the reference path length, a depth scan of a spot on the retina.

[0200] The reference path length can be modified by translating the components in the dashed box 1269 in a direction indicated by the double arrow 1271. Signals associated with the depth scan of the cornea can be distinguished from signals associated with the depth scan of the retina by the relative movement of signals with adjustment of the reference path length.

[0201] Alignment of the system with respect to the cornea can be accomplished by one or more conventional cameras. Two cameras 1273 and 1275 acquire images of the front of the eye.Examples of additional optional optics to direct light for the images are depicted as mirrors 1277 and 1279.

[0202] Suitable cameras do not contain infra-red filters and can detect the small diameter beam, as depicted in the eye image 1115 of Figure 11 which can be detected by both cameras when the small diameter beam is centered on the pupil. Using images from either or both cameras to center the spot from the small diameter beam on the pupil of the eye enables lateral alignment.

[0203] Combining the images from the two cameras enables system depth alignment. When the system, enclosed in the dashed box 1281 is translated in the direction indicated by the double arrow 1283 the images from the two cameras overlap to a greater or lesser amount.

[0204] When the system is at one particular distance from the eye (or a test target), the spot and the pupil images can overlap to a maximum amount, thereby providing a useful reference point. The deviation from maximum overlap with direction and magnitude of change in depth can be calibrated, thereby enabling the degree of overlap to be a measurement of the distance from the cornea of an eye.

[0205] In some embodiments, the locations of the components 1227 and 1229 are selected so the OCT window, of this arm of small diameter reference beam, is centered on the cornea when the maximum overlap of the camera images occurs (or has a known offset from this condition). This enables depth alignment of the front surface (the cornea) to interferometric accuracy.

[0206] The components in the dashed box 1269 are translated in the direction indicated by the double arrow 1271 to align the longer reference path of the small diameter beam and thereference path of the of the broad optical reference beam such that their OCT windows are aligned with the retina. In some embodiments, the optical element 1241 is a simple turning mirror (like 823 of Figure 8) and optical element 1233 includes a beam splitter with a reflective side (similar to 871 and 873 of Figure 8) to compensate for the image inversion.

[0207] In some embodiments, where the nominal axial length of the eye is known, the components in the dashed box 1269 are preset to use this information to facilitate alignment.

[0208] The fixed optical distances can be calibrated and known. At least some locations of the module containing the components in the dashed box 1269 can have known positions, e.g. using LEDs and photo-diodes or arrays of photo-detectors. Distances traveled by the module from one of these known locations can be monitored by means, such as known screw pitch or more light detection systems, e.g. a tilted surface moving relative to a two dimensional array.

[0209] Since the optical path length of the various components are known (or can be measured) and the locations of the movable reflective elements 1233, 1235, and 1241 can be known, the ability to monitor changes in axial length is enabled by calculating the current axial length and comparing it to a previously acquired axial length measurement.

[0210] Other embodiments of this comprehensive eye monitoring system are possible. For example, the optical source 1209 of the small diameter beam is an SLD and the components 1261, 1263, 1265, and 1267 of dashed box 1287 are replaced by one or two diffractive gratings and detector arrays of an SD-OCT system. Such an embodiment avails of the superior signal to noise ratio (SNR) of an SD-OCT system.

[0211] Many other configurations and combinations are possible. For example, a simpler system could have no components associated with the small diameter OCT system (i.e. 1209, 1211, 1213, 1215, 1227,1229, 1285, 1251, 1257, and all the components in dashed box 1287) and would use the images from the two cameras 1273 and 1275 to determine relative offsets in depth due either to translation of components of dashed box 1269.

[0212] In some embodiments, different regions of the retina are targeted for depth scanning by means of fixation. In one such embodiment a one or two dimension array of LEDs or other optical sources can have one or more LEDs illuminated at one or more different wavelengths.

[0213] In an example of one possible embodiment, a two dimensional array of LEDs 1289 that can be turned off or turned on to illuminate at one of two different wavelengths, such as red and green, fixation is enabled. The light output by the array of LEDs 1289 is directed at the retinaunder test by means of the dichroic mirror 1291 making multiple possible light paths to the retina, one of which is labeled 1293.

[0214] In some embodiments, the LED array 1289 is replaced by a visual display. There are many other configurations by which the fixation array or display can be made visible to the subject whose retina is under test.

[0215] A configuration of the preferred embodiment suitable deployment in a virtual reality type headset or as a tabletop device, and suitable for home monitoring aspects of the retina of an eye by measuring characteristics of the retina is disclosed. Such characteristics include but are not limited to, the distance between layers in the retina at one or more locations, the local variation in the distance between layers in the retina at one or more locations, the local smoothness of layers in the retina at one or more locations.

[0216] Relevant layers of the retina include, but are not limited to, the inner limiting membrane (ILM) and the retinal pigment epithelium (RPE) layer of the retina.

[0217] The measured characteristics of the retina are typically compared with previously acquired similar measurements of the same characteristics at substantially the same location or set of locations. Changes in such measurements are assessed against one or more pre-defined criteria and if appropriate a pre-determined course of action, such as a clinical office visit, is initiated.

[0218] Referring now to Figures 13 through 15, a configuration of the preferred embodiment of Figure 6 suitable for a home retinal monitor is depicted. This embodiment makes a targeted set of depth measurements by means of a full field optical coherence tomography (FF-OCT) system at one or more broad area regions of the retina, where the subject, whose eye is being monitored, fixates on a fixation target and thereby the retina is targeted.

[0219] Fixation is accomplished by any of a variety of approaches, including, but not limited to: (a) fixating on the OCT probe beam; (b) fixating on at least one illuminated LED of an array of LEDs; (c) fixating on a video display whose content is dynamically varied to induce the subject to fixate at either selected orientations (by displaying content of interest to the viewer) or random orientations.

[0220] In some embodiments, fixation is achieved by the fellow eye of the eye on which OCT measurements are being performed.

[0221] In some embodiments, correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by correlating the acquired image with a previously acquired image (or images) of the retina.

[0222] In some embodiments, correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by correlating the acquired data set with a previously acquired data set of the retina.

[0223] In some embodiments correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by acquiring at least two images of the front surface of the eye. In some preferred embodiments, correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by using eye tracking techniques to determine the orientation of eye with respect to the OCT beam.

[0224] Having the subject fixate on optical signals at different locations enables different regions of the retina to be targeted for imaging by the OCT module.

[0225] In other embodiments correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by using eye orientation detection techniques such as foveated imaging to determine the orientation of eye with respect to the OCT beam.

[0226] In some embodiments correct targeting of the location on the retina that is being depth scanned, or measured, by the OCT beam is confirmed by acquiring one or more fundus images retina of the of the eye.

[0227] In some embodiments use is made of artificial intelligence to assist in alignment of the optical system with respect to the eye under test and to assist with acquiring appropriate depth scans of the eye.

[0228] The low cost compact OCT system (also referred to as the OCT module) of the preferred embodiment is illustrated in and described with respect to Figures 13 A and 13B of sheet 13, Figure 14 of sheet 14, and Figure 15 of sheet 15. Embodiments suitable for a head-mounted or table top device are further illustrated in and described with respect to Figures 16, 17, 18, 19, and 20.

[0229] Figure 13 A of sheet 13 depicts the reference path and a portion of the probe path of the OCT module, that is comprised of off the shelf components. The optical source 1301 is a superluminescent diode (SLD) that directs a collimated optical beam to a first beam splitter 1303that separates the optical beam into a probe and reference beam 1309. The collimated optical beam is a broad area beam with lateral dimensions of the order of two or more millimeters.

[0230] A portion of the probe beam that is directed through the beam splitter 1303 proceeds to a turning mirror 1305 that directs the probe beam through some additional optical elements and through the pupil of the eye to the retina of the eye (not shown). A portion of the probe beam, scattered in the retina, returns substantially along the path of the probe beam back to the first beam splitter 1303 where a portion of it is directed to a second beam splitter 1307.

[0231] The first beam splitter 1303 can be selected to reflect a substantial portion, of the order of 90%, of the returned scattered probe beam to the second beam splitter 1307, thereby maximizing the use of the information carrying returned (or back-scattered) probe beam.

[0232] The reference beam 1309 is directed via multiple turning mirrors, such as 1311, 1313, other turning mirrors, through a first dispersion compensation element 1315, through a beam splitter 1316 to a mirror 1318 that reflects the beam back to the beam splitter 1318 (thereby compensating for beam inversion), through an optional second dispersion compensation element 1317, to the second beam splitter 1307.

[0233] The second beam splitter 1307, interferometrically combines the reference beam with the returned scattered probe beam and directs portions of these combined broad area beams to first and second image detectors 1323 and 1325, also referred to as image sensors or image sensor arrays 1323 and 1325. The interferometrically related portion of the light detected by the first image sensor array 1323 is 180 degrees out of phase with the corresponding portion detected by the second image sensor array 1325 and are referred to as true and complementary interference signals or data sets.

[0234] The true and complementary components of these data sets are related to scattering intensities of a depth region of the retina (the target) determined by the magnitude of the reference optical path length. The targeted region of the retina is centered on the location where the optical path lengths of the probe and reference beams are equal. The thickness of the depth slice is determined by the bandwidth of the SLD.

[0235] When true and complementary data sets are subtracted, common mode noise cancels and the resulting data set is a noise reduced data set of scattering intensities.

[0236] The use of the broad area beams of FF-OCT removes the requirement of (expensive) lateral scanning devices (such as galvanometers). The use of the double beam splitterarchitecture (as opposed to the more conventional Michaelson interferometer architecture), enables the simultaneous detection of pairs of true and complementary data sets, referred to herein as a pair of orthogonal data sets.

[0237] A single pair of orthogonal data sets (consisting of a true and a complementary data set), or multiple consecutive pairs of orthogonal data sets, with inevitable random phase offsets, can be combined to yield a noise reduced data set. Signal to noise ratio is further enhanced by the high reflection (-90%) of beam splitter 1303.

[0238] The first dispersion compensation element 1315, in some embodiments, is a reflective dispersive element (as is depicted) and can have its length, indicated by the dashed double arrow line 1319, selected in conjunction with other optical components to substantially match the dispersion of the eye under test. This length selection may be based on the known axial length of the subject eye.

[0239] The reflective dispersion compensation element 1315 can have its location in the reference path, indicated by the double arrow line 1321, selected in conjunction with other optical components to substantially match the optical distance to the of the eye under test. This location selection may be based on the known axial length of the subject eye and other physical considerations.

[0240] The optional transmissive dispersion compensation element 1317, may also include or be replaced by attenuation elements to optimize the intensity of the reference radiation that reaches the beam splitter 1307, to achieve an optimum signal to noise ratio. An attenuator may be placed elsewhere in the reference path and the transmission / reflection ratio of the beam splitter 1316 can be selected to optimize the intensity of the reference radiation.

[0241] The combination of the reflective and transmissive dispersion elements can be optimized to match the dispersion of the eye under test and any additional optics in the probe path. Having two dispersive elements enables using elements with different dispersive properties and thereby achieving a more accurate match between the reference path and the probe path.

[0242] The location of the depth region from where these true and complementary components emanate within the target may be varied by modifying the relative magnitude of the probe and reference path lengths, as described later.

[0243] The inventive system provides one or more pairs of orthogonal data sets are processed to yield a scattering intensity map of the retina at the depth location determined by the relativemagnitude of the probe and reference path lengths. This process is repeated for different depth locations and the resultant data sets are combined to yield a three dimensional data set of the targeted region of the retina.

[0244] Figure 13B, within the dashed box 1337 of sheet 13, depicts a side view of that depicted in Figure 13 A. The substrate 1327 is a side view of a section of the substrate 1329 of Figure 13A. The components 1301, 1303 and 1305 of Figure 13B correspond to the same components 1301, 1303 and 1305 of Figure 13A. Components 1333 and 1335 correspond to turning mirrors of Figure 13 A.

[0245] The Figure 13B (labeled side view), depicts the probe beam 1331 that has been directed by the turning mirror 1305 through a hole (not shown) in the substrate 1327 of Figure 13B and 1329 of Figure 13 A.

[0246] Figure 14 of sheet 14 again depicts the probe beam 1431 (corresponding to 1331 of Figure 13B) emerging through the hole (not shown) in substrate 1427 (corresponding to 1327 of Figure 13B).

[0247] The probe beam 1431 is directed by a turning mirror 1433 that directs the probe beam through a focusing lens 1435 to a reflective element 1437 that directs the probe beam through an optional optic 1439 to the front of the eye 1441. The beam is substantially collimated by the cornea and the lens of the eye and the collimated beam 1449 is directed at the retina 1443 where some of the beam is scattered. Some of the scattered beam returns along the input probe beam to eventually generate the true and complementary interference signals that are detected by the image sensor arrays 1323 and 1325 of Figure 13.

[0248] The optional optic 1439 is an optic to substantially correct for refractive error of the eye under test. The optic 1439 may be convex or concave or a custom optic selected for individual subjects.

[0249] Also depicted in Figure 14 is fixation array 1451 of optical sources. In some embodiments the fixation array 1451 is a one or two dimensional array of LEDs any of which can be either off, emitting (for example) red light, or (for example) emitting green light.Selecting one or more LEDs to emit green or red light is used to cause the subject to orient an eye under test in a particular direction, i.e. to fixate on one or more of the illuminated LEDs. Many other LED arrays are possible capable of emitting single or multiple wavelengths.

[0250] In this preferred embodiment the reflective element 1437 is highly reflective at the OCT wavelength and is transmissive at the wavelengths of the LEDs

[0251] Figure 15 of sheet 15 depicts a video display 1553 that replaces the fixation array 1451 of Figure 14. The video display 1553 provides a more flexible fixation capability and can also be used to communicate other information to the subject. The display can be visually similar to an LED array, but with more positional variability.

[0252] The video display 1553 can also display images (such as those of a game) specifically designed to cause a subject to fixate in a particular direction, or can display live TV, or in some embodiments can display the output of on-board cameras that provide the subject with a view similar to normal vision.

[0253] In some embodiments the display 1553 can display the output of on-board cameras that provide the subject with a view of the front surface of an eye. Such a view of the front surface of the eye, that includes an image of the OCT spot, can assist in alignment.

[0254] For purposes of this invention a fixation module refers to either a fixation array of optical sources or a video display capable displaying video or still images.

[0255] In some embodiments the turning mirror 1533 and the lens 1535 are an integrated unit that can be translated horizontally to adjust the vertical height of the probe beam into the eye or to adjust the optical path length of the probe beam.

[0256] The composite optical element 1561 on which the TV display is mounted and which contains the reflective element 1537 can be an integrated optical element that facilitates a clear view of the TV display (or LEDs). The reflective element 1537 is highly reflective at the OCT wavelength and transmissive at shorter (visible) wavelengths.

[0257] The optional optical element 1539 can again be selected for enhancing collimation for an individual eye 1541 such that the collimated beam 1549 optimally probes the retina 1543.

[0258] Two or more cameras 1557 and 1559 provide feedback to assist in aligning the probe beam with the eye in the lateral directions and aligning the OCT module in depth with respect to the eye. A single camera could also be used and the size of the diverging beam on the cornea used for depth alignment.

[0259] The component 1555 is a rotating disc containing a set of optical flats each of different thickness that can be inserted into the path of the probe beam, thereby modifying the location of the OCT window. This provides a mechanism for scanning the retina in depth. The disc is rotatedsynchronously with the frame rate or a multiple of the frame rate (fps) of the image sensor arrays.

[0260] For example, if the frame rate were 60 fps, and the disc had 60 different flats that differed in optical thickness from each other by 12 microns, then rotating the disc at 20 Hz (1200 rpm) would enable acquiring 3 pairs of orthogonal data sets for each 12 micron step in depth over a total depth of 0.72 mm in one second. Rotating the disc at 30 Hz would enable acquiring 2 pairs of orthogonal data sets for each 12 micron step in depth. In embodiments that included a phase modulator (for example included in the element 1317 of Figure 13) the 2 pairs of orthogonal data sets could be comprised of 4 data sets with relative phase offsets of 0, 90, 180, and 270 degrees. The readout of the 2 pairs of orthogonal data sets would take two image sensor array frame periods.

[0261] Many variations and combinations of disc structure and rotational speed are possible. For example, more than 60 flats of differing optical thickness could be used to extend the range of the depth scan. The phase of the rotating disc could be controlled to ensure transitions from one flat to another (intersecting the probe beam) would occur at times when data sets are not being acquired by the image sensor arrays.

[0262] The data sets from multiple depth locations within the target are combined to form a three dimensional OCT data set.

[0263] In an alternate embodiment, the optical source 1301 of Figure 13 is a tunable laser (or a swept source). The optical source 1301 directs a collimated optical beam to a beam splitter 1303 of Figure 13 that separates the optical beam into a probe and reference beam. The collimated optical beam is a broad area beam with lateral dimensions of the order of two or more millimeters. The optical reference and probe beam paths are substantially as described above. For purposes of this invention a tunable laser includes a swept source laser.

[0264] In the preferred tunable laser embodiment, the coherence length of the laser beam is at least sufficiently long to acquire interferometric signals over the range of the desired depth scan of the target. As before the path length of the reference beam determines the location of the OCT window (or the interferometric depth scan of the target).

[0265] As before at least one pair of orthogonal data sets are simultaneously acquired by image sensor arrays 1323 and 1325 of Figure 13. The wavelength of the tunable laser (or swept source)is substantially constant over the time duration during which the pair of data sets is being acquired by image sensor arrays 1323 and 1325.

[0266] Pairs of orthogonal data sets data sets are acquired over a range of different wavelengths by tuning the laser to different wavelengths (or sweeping the optical source). The resulting collection of data sets are processed to yield a three dimensional data set of the selected region of the target.

[0267] Typical processing can include: calculating a difference data set for each true and complementary pair by subtraction to form a noise reduced data set; spatially realigning the date sets with each other if required; Fourier processing the data sets or the noise reduced data sets to generate a three dimensional data set of the selected region of the target.

[0268] In the Fourier domain tunable laser embodiment, the disc 1555 is not required for (relatively) high speed depth scanning by rotation. In some embodiments the disc 1555 is not included. In some embodiments it is included and used for depth alignment of the OCT window with the region of the target to be analyzed, such as the layers or regions of the retina that are to be measured or analyzed.

[0269] In such embodiments, the optical flats can consist of a set that have optical distances that are multiples of a substantial fraction of the optical thickness of the region of the target to be analyzed. For example, the flats could have an optical distance equal to an integer times one quarter the optical thickness of the region of the target to be analyzed. Many other sets of optical flats could be chosen to facilitate depth alignment of the OCT window.

[0270] In some embodiments the disc 1555 could be rotated for depth alignment under the local control of the subject, or be under automatic local control, or remotely by an operator. In some embodiments rotation and positioning of particular optical flats could be either under local Artificial Intelligence (Al) based control or remote Al control.

[0271] Figure 15 of sheet 15 also depicts cameras 1557 and 1559 that image the front surface of the eye. The cameras do not have an infra-red filter and therefore can readily image the OCT probe beam scattered on the surface of the eye. Images of the probe beam on the eye provide feedback for spatially aligning the OCT module in the horizontal and vertical directions with respect to the pupil of the eye. Note these cameras are mounted on what is referred to herein as the “eye-side” of the OCT module.

[0272] Having at least two cameras enables aligning them so that at a specific distance from the eye, the two images of the pupil accurately overlap. The degree to which the two images of the pupil do not overlap provides feedback for spatially aligning the OCT module in depth with respect to the front surface of the eye. This feedback can be included in aligning the OCT module with respect to the OCT window and the retina.

[0273] Also depicted in Figure 15 of sheet 15 are holes 1565 and 1567 in the substrate 1527. These holes through the length of the substrate are to accommodate rails that enable moving the OCT module horizontally in order to align it horizontally with respect to the pupil of the eye. In some embodiments, a number of holes other than two could be used.

[0274] Figure 16 depicts two OCT modules overlaid on a partial image of a face with the modules oriented and positioned to perform depth scans on both eyes of the subject. The geometry of the OCT module is such that two OCT modules can be positioned and aligned, each with one eye, without interfering with each other, while still enabling an appropriate reference path length to have the OCT window in the regions of the retinas of the eyes.

[0275] In Figure 16, one OCT module 1601 is aligned such that the probe beam of this OCT module is centered on the pupil 1603 of one eye. The module depicted in Figure 16 (and subsequent Figures) the reflective dispersion element (1315 of Figure 13) is replaced by two conventional turning mirrors 1609 and 1611 and the dispersive element 1617 (1317 of Figure 13) is longer. Furthermore, the mirror 1618 (1318 of Figure 13) can be positioned at different distances from beam splitter 1616 in the direction indicated by the double arrow 1620.Repositioning can be static and selected for an individual eye, or dynamic to adjust for depth. In some embodiments, an attenuator 1622 can be placed in the reference path (preferably ahead of the beam splitter 1616). Many such system variations are possible.

[0276] The second OCT module 1605 is oriented and aligned such that the probe beam of this second OCT module is centered on the pupil 1607 of the second eye of the subject. Note: the face is actually on the eye-side of the OCT modules, and although it would not be visible, it is depicted here for clarity of illustration. Also, the pupils of the eyes are accentuated for clarity.

[0277] Figure 17 depicts two rails 1701 and 1705 suitable for enabling horizontal translation of the OCT modules. (Note, each rail is labeled at both ends with the same label). In some embodiments, a number of rails other than two could be used.

[0278] Both the first OCT module 1707 and the second OCT module 1709 are mounted on the rails 1701 and 1705. The two modules are depicted overlaid on a partial image of a face and showing the probe beam of each aligned with the pupil of each eye.

[0279] In some embodiments, the holes through the substrates of the OCT modules are larger than the rails by an amount such that the rails do not touch the substrate and small tubular low friction bushings are inserted in the substrates at least at some of the locations 1711, 1715, 1717, 1721, 1723, 1727, 1729, and 1733 thereby locating the OCT modules and providing stable positioning and smooth motion. In some embodiments, fewer bushings would be installed for each OCT module.

[0280] Figure 18 depicts the two rails 1801 and 1803 on which the two OCT modules 1807 and 1809 are mounted. Note, for illustration clarity the optional bushings of Figure 17 are not shown in Figure 18.

[0281] The two rails are fixed in a frame 1811, as indicated by the example 1813. This facilitates horizontally aligning each OCT module to an eye. The interpupillary distance is indicated by the double arrow 1815.

[0282] The invention provides for the two OCT modules to be aligned to perform OCT scans on both eyes of subjects or to perform an OCT scan of one eye with one OCT module, while using the other OCT module to assist with alignment.

[0283] In some embodiments, the frame 1811 contains a set of holes, one of which is labeled 1817. These holes can accommodate another set of rails that enable the frame 1811 to be translated closer or further from the eyes, i.e. to be aligned in the depth direction. While eight such holes are depicted in Figure 18, the number of such holes could be other than eight.

[0284] The ability to translate the frame 1811 in the depth direction provides another opportunity to align the OCT windows of the OCT modules. As before, the OCT modules 1807 and 1809 can be independently translated along the rails 1801 and 1803 to align the probe beams with the pupils of the eyes, as depicted by the double sided arrow line 1815 that also points to the locations of the eyes which are not actually visible through OCT modules as they are on the “eye-side”.

[0285] It can be appreciated that, as drawn, the translation of OCT modules 1807 and 1809 along line 1815 corresponds to inter-pupillary distance.

[0286] Figure 18 also depicts three cameras associated with each OCT module. One such camera is labeled 1819 is associated with OCT module 1807. The other two are not labeled, but have the same square icon. Similarly, camera 1821 is one of the three cameras associated with OCT module 1809.

[0287] The cameras provide feedback to align an OCT probe beam with respect to a pupil of an eye in the horizontal and vertical direction. Cameras also provide feedback to align an OCT module in depth with respect to the front surface of the eye and thereby facilitate aligning the OCT window with the retina of the eye.

[0288] Embodiments with two OCT modules can be used to acquire depth scans of both retinas at the same time. Other embodiments with two OCT modules can be used to acquire depth scans of one eye, while the OCT module, aligned with the fellow eye, can be used to assist in correct alignment of the eye being depth scanned. The OCT module of the fellow eye could provide a fundus image to assist in alignment of the eye being depth scanned.

[0289] The cameras targeting the fellow eye of the eye being scanned by the OCT probe beam also provide feedback for correctly aligning the OCT probe beam with respect to the retina of the eye being scanned. Camera feedback relating to depth, i.e. the distance of the OCT module to the front surface of the fellow eye provides horizontal angular information regarding the OCT probe beam with respect to the retina of the eye being scanned, thus facilitating angular alignment in the horizontal plane.

[0290] Camera feedback relating to depth, i.e. the distance of the OCT module to the front surface of the fellow eye in combination with the location of the pupil of the fellow eye in the camera images provides angular information regarding angular alignment of the OCT probe beam with respect to the retina, thus facilitating angular alignment in the vertical plane.

[0291] Note, any vertical offset in the relative height of the two eyes can be accommodated by having the cameras of the fellow eye ensure that a selected portion is consistently centered in the camera images that is not necessarily the center of the pupil.

[0292] This removes the requirement of having independent control over the height of two OCT modules and facilitates the more stable and more accurate arrangement of having both OCT modules independently horizontally positioned along the set of rails.

[0293] In some embodiments, element 1561 containing the reflective element 1537, the lens 1539 of Figure 15, and the cameras, two of which are 1819 and 1821 of Figure 18 are fixed to the OCT module and move in unison when the OCT module is translated.

[0294] In some embodiments, at least some of the cameras are fixed to the frame 1811 of Figure 18. For example, cameras 1819 and 1821 could be fixed to the frame at the nominal interpupillary distance of the subject. In some embodiments, two lenses 1539 of Figure 15 (which may be different from each other) are fixed to the frame at the nominal interpupillary distance of the subject.

[0295] Figure 19 depicts a preferred embodiment in which a single OCT module can be translated horizontally along rails 1903 and 1907 to perform an OCT scan of either eye of a subject. The range for horizontal motion is indicated by the double arrow 1909.

[0296] In this embodiment the optic 1561 of Figure 15 that contains the reflective element 1537 extends a substantial portion of the length of the rails 1903 and 1907, thereby enabling the subject to have a clear view of the fixation LEDs or TV screen 1553 of Figure 15.

[0297] In some embodiments, the two optional lenses (1539 of Figure 15), which may be different from each other, and one of which is labeled 1911, are fixed to the optic 1561 of Figure 15 that contains the reflective element 1537.

[0298] In some embodiments, the two optional lenses (1539 of Figure 15), which may be different from each other, and one of which is labeled 1911, are fixed to a separate optic that is mounted in front of the optic 1561 of Figure 15 that contains the reflective element 1537. This facilitates having a simple custom optic that has custom refractive correction optics at the appropriate interpupillary distance for each subject.

[0299] In some embodiments, the cameras used to assist with alignment are mounted on the OCT module; or some are mounted on the OCT module and some on the simple custom optic; or on the optic 1561 of Figure 15 that contains the reflective element 1537.

[0300] For example, the cameras 1913 and 1915 could be mounted on the simple custom optic, or on the optic 1561 of Figure 15 that contains the reflective element 1537. The other two cameras depicted in Figure 19, but not labeled, could be mounted on the OCT module.

[0301] As before, the rails 1903 and 1907 could be fixed in a frame 1917 with holes for depth alignment rails, one of which holes is labeled 1919.

[0302] Figure 20A depicts an embodiment of the OCT module 2001 that has a cut-out 2003 that enables the two probe beam turning mirrors, 2005 of Figure 20A and 20B and 2007 of Figure 20B to be translated vertically with respect to the OCT module 2001, thereby enabling the relative length of the probe and reference paths to be modified.

[0303] The turning mirrors 2005 and 2007 are fixed on a carrier (or bridge) 2009 of Figures 20A and 20B that can be translated vertically, as indicated by the double arrow line 2011 of Figures 20A and 20B, to accomplish either depth alignment of the OCT window or depth scanning. In such embodiments the through-hole (not shown) is enlarged to allow the probe beam to be translated vertically without obstruction.

[0304] In some embodiments the carrier or bridge 2009 is linked to the OCT module 2001 by means of a ball bearing slide to ensure smooth translation (with the top of the substrate 2013 extended vertically if necessary). The carrier or bridge 2009 may be translated by mechanical, electro-mechanical, or magnetic means.

[0305] In some embodiments, a stepper motor is used to translate the carrier or bridge 2009 and the step size selected to systematically scan the target region of interest in depth. For example, the step size could be a less than the coherence length of an SLD optical source. In such a case the rotating wheel 2015 (if required) could be used for coarse depth alignment.

[0306] In some embodiments, a stepper motor could be used for coarse depth alignment and the step size selected accordingly. For example, the step size could be a fraction, such as a quarter or a third, of the size of the region to be depth scanned. In such embodiments the rotating wheel 2015 would be used for depth scanning.

[0307] In embodiments where the optical source is a tunable laser (or swept source), only one of either the rotating wheel 815 or the vertical moving carrier (or bridge) 2009 are required and the selected one would be used for coarse depth alignment. In some embodiments, both could be used, with control of one being manual. Many other combinations are possible.

[0308] The lens 2017 could also be fixed to the substrate 2013 of the OCT module 2001 by means of a bridge 2019 that did not obstruct the wheel 2015. The optical flats of the wheel 2015 would also be large enough to present substantially the same optical delay when the bridge 2009 is moved vertically so the probe beam is not interfered with.

[0309] The bridge 2019 could also be extended to have at least one camera 2021 fixed to it and thereby fixed to the OCT module 2001 (and physically offset from the optic element 2027). Thelower camera 2023 and the two custom lens, one of which is labeled 2025, could be fixed to a transparent plate (not depicted) that has the appropriate custom lenses at the correct interpupillary distance from each other.

[0310] In some embodiments, the optic 2027 containing the reflective element 2029, also contains the two custom lenses, one of which is 2025, at a particular interpupillary distance and is a custom element for each individual, or set of individuals.

[0311] In some embodiments, at least some of the cameras are fixed to the custom optic 2027 in a removable manner, as is the fixation module or display 2031 fixed to the custom optic 2027 in a removable manner (e g. with screws).

[0312] The rails may also be repositioned to avoid obstruction. For example, an embodiment with two rails (one of which is 2033) is depicted in Figure 20B. The vertical locations of the rails could be changed to accommodate avoiding obstruction or for other reasons. Mechanisms other than rails (such as sliding tongue in groove) or various combinations of mechanisms could be used on the rails to facilitate optimum smooth motion.

[0313] The frame 1811 of Figure 18 and 1917 of Figure 19 containing the OCT modules can a housed in a virtual reality type headset. Many conventional mechanisms are possible to allow alignment of the frame and of the OCT module or modules. These mechanisms can be configured to provide vertical and horizontal adjustment, and if necessary angular adjustment in addition to the relative horizontal positioning of two OCT modules within the frame.

[0314] In some embodiments, a minimum of electronics is on board the headset containing the OCT modules. Such minimum electronics include, but are not limited to, a sync generator to coordinate the devices, optional data serializer or serializers to serialize data from image sensors and / or cameras, amplifiers for drive signals for the actuators and the various motors, preprocessing of the video signals from the various cameras, decoders for LEDs, and incoming video display signal processing.

[0315] Many mechanisms for achieving depth, vertical, and horizontal alignment of the OCT modules, including having rail and motor systems within the headset, while independent horizontal alignment of the one or two OCT modules is achieved by the rail system within the frame as described above.

[0316] In some embodiments, control over the alignment motors, including that of the depth aligning disc, is electronic. The alignment electronic control signals are determined usingfeedback from the eye-side mounted cameras, and by analyzing the data generated by the OCT depth scan.

[0317] The feedback data to determine the alignment electronic control signals are processed using a processing module that is either local or a combination of local and remote processing and can include, but is not limited to, predetermined algorithms or artificial intelligence, or a combination of predetermined algorithms and artificial intelligence.

[0318] In some embodiments the role of artificial intelligence includes an Al agent. The Al agent communicates with the subject whose eye is under test. Such communication can include audio, video, or text communication or any combination thereof.

[0319] Figure 21 depicts a block diagram of an embodiment of the OCT based retinal scanning system. The retinal scanning home monitor 2101 includes: a sync generator 2103 that generates the electronic timing signals for the system; multiple conventional cameras 2105 that provide at least images of the front surface of the eye; a video display module 2107 that can display images, including but not limited to, fixation images and other useful visual information and in some cases receives audio; the retinal scanning OCT module 2109; and a processing module 2111.

[0320] In some embodiments, the processing module 2111 includes an Al agent that interacts with the subject, assists in system alignment, and has a secure communication link 2113 with an internet portal 2115. In some embodiments, the Al agent is remote and controls a more conventional algorithm based processing module 2111.

[0321] The Al agent initiates a retinal scanning session by communicating with the subject by conventional means, including but not limited to, a phone call, text, or e-mail.

[0322] The Al agent assists in aligning the OCT depth scanning system with the targeted region of the retina. Such assistance can include, but is not limited to, communicating with the subject to have the subject, for example, manually adjust aspects of the OCT depth scanning system, such as its vertical positioning or to adjust the gaze direction of the subject by loading an appropriate fixation pattern on the display (2031 of Figure 20).

[0323] The Al agent uses images acquired by cameras (such as 2021 and 2023 of Figure 20) as feedback to control electronic actuators that can electronically re-position components of the OCT scanning system. Such electronically controlled aspects include, but are not limited to: lateral (or horizontal) positioning of an OCT module (such as 2001 of Figure 20); the rotatingdisc 2015 and the carrier or bridge 2009, both of which can modify the optical length and thereby depth align the OCT window.

[0324] The electrically controlled actuators or motors capable of aligning the OCT module with respect to the retina of eye are referred to as alignment motors.

[0325] In some embodiments the Al agent has access to other bio-metrics including, but not limited to, temperature, blood pressure, pulse rate, electrocardiogram, blood oxygenation levels. In some embodiments, the Al agent communicates with care-givers or authorized medical personnel.

[0326] In some embodiments, the Al agent has access to at least some medical records of the subject and uses historical and current retinal scans and other bio-metrics to provide information and guidance to relevant parties, such as the subject under test, care-givers, and authorized medical personnel.

[0327] In some embodiments, the 3D data sets of the retinal scans and optionally other biometrics of the subject under test are combined with those of other subjects to be data mined with the goals that include, but are not limited to, identifying other conditions whose status can be determined from OCT depth scans of the retina.

[0328] In some embodiments, control over at least some of the alignment motors, is mechanical. For example, depth alignment of the frame (or frames) housing the OCT modules could be controlled manually with feedback and direction provided by means of LEDs or by audio.

[0329] In some embodiments the feedback to determine the alignment electronic control signals is processed locally using predetermined algorithms.

[0330] In some embodiments the feedback data to determine the alignment electronic control signals are processed locally using at least some predetermined algorithms with assistance from an operator at a remote location.

[0331] In some embodiments the feedback data to determine the alignment electronic control signals are processed locally using at least some predetermined algorithms with assistance from an operator and an artificial intelligence agent or module, both at a remote location.

[0332] In some embodiments the feedback data to determine the alignment electronic control signals are processed locally using at least some predetermined algorithms with assistance an artificial intelligence agent or module at a remote location.

[0333] In some embodiments the feedback data to determine the alignment electronic control signals are processed locally using at least some predetermined algorithms in conjunction with a local artificial intelligence agent or module and, if required, assistance from a remote operator.

[0334] In some embodiments the feedback data to determine the alignment electronic control signals are processed locally using at least some predetermined algorithms in conjunction with a local artificial intelligence agent module.

[0335] In some embodiments, communication to and from a remote location is by means of the Internet and a web-site portal. In some embodiments, communication to and from a remote location includes securely encrypted communication.

[0336] In some embodiments, the web-site portal has access to historical information about the subject whose eye is being measured. Such information can include, but is not limited to, medical and social information useful in relaxing subject or directing performance of measurements.

[0337] In some embodiments, there is also communication to and from a medical facility or caregiver with whom the subject whose eye is under test has a relationship.

[0338] In some embodiments, the video display 1553 of Figure 15 displays images (such as those of a game) specifically designed to cause a subject to fixate in a particular direction, the game may be configured to have a red color coincident with the OCT beam to reduce its likelihood of causing the viewer a disturbance.

[0339] In some embodiments, the display images have a flickering red background to reduce the OCT beam’s likelihood of causing the viewer a disturbance.

[0340] In some embodiments, the video display 1553 of Figure 15 can display live video input from a remote operator, e.g. over Zoom (or equivalent), assisting with a retinal exam and thereby enabling the operator to assist the subject with aspects including, but not limited to, alignment of the OCT module or modules and achieving appropriate fixation.

[0341] There are many possible configurations of the video display 1553 of Figure 15 and the transparent optical element 1561. In some embodiments, the display 1553 is secured to the optical element 1561, or the video display 1553 is secured to the headset, while the optical element 1561 is secured to the OCT module; or both the display 1553 and the optical element 1561 are secured to the headset.

[0342] The reflective element 1573 of Figure 15 can extend substantially along the length of the optical element 1561 by bonding two optic elements where the bond is the reflective element. The optional element 1539 could be secured to the OCT module and could be selected to be optimal for individual subjects. The one or two OCT modules could move with respect to the optic element 1561, as described earlier.

[0343] In the case of a remote operator assisting with a retinal exam over Zoom, in some embodiments, the display 1553 is the subject’s computer screen and the remote operator is a caregiver, or a technician, or a medical professional, or an artificial intelligence agent.

[0344] In the case of an artificial intelligence agent, the Al agent has access to at least some historical medical records of the subject and is HIPA compliant.

[0345] In some embodiments, the optical source 1301 of Figure 13 A sheet 13 of an OCT module are replaced by fibers whose outputs are collimated and whose optical input is one or two SLDs or one or two swept source lasers or tunable lasers. The fiber (or fibers) is included in a cable providing communication, control signals, power to the OCT modules.

[0346] In some embodiments, the headset is battery powered with control signals, etc. generated on-board the headset.

[0347] While in some embodiments, the OCT module frame is housed in a virtual reality type headset, in other embodiments the OCT modules is housed in a table top device where the subject looks into the device and the OCT modules are aligned with the eyes of the subject.

[0348] While depicted or described configurations of the full field imaging systems (the broad optical beam OCT system) have substantially round optical beams, beams with geometries other than round are included in this invention.

[0349] The phase modulator 1245 of Figure 12 enables introducing a 90 degree phase offset between illuminating flashes of the optical source 1201, however in some embodiments it is not necessary. For example, in embodiments where the location of the cornea or retina can be very accurately measured, the second illuminating flash is triggered when an offset corresponding to 90 degrees is determined.

[0350] This offset determination could be based on prediction, using previous smooth relative motion to predict the timing of a 90 degree phase change. Accurate determination of the actual phase offset is calculated by processing the acquired data sets to determine that actual phase offset and the magnitude of any angular deviation that had also occurred.

[0351] In some depicted embodiments, some conventional optical elements, such as lenses, diaphragms and apertures are not shown. Many different configurations of optical attenuators and dispersion compensation elements are possible. In embodiments where depth aligning disc is under local control, the user is informed to increment or decrement the probe optical path length by means of illuminating red or green LEDs.

[0352] Some dispersion compensation elements exploit having significantly different dispersion at different wavelengths ranges to more accurately match dispersion in the eye.

[0353] While configurations of the systems depicted in Figures 1, 4, 6, 7, 8, 11 and 12 are free space embodiments, equivalent fiber embodiments are included in this invention.

[0354] Various combinations and equivalents of elements depicted or described in these embodiments are included in this invention. Other examples will be apparent to persons skilled in the art. The scope of this invention is determined by reference to the specification, claims and drawings, along with the full scope of equivalents as applied thereto.

Claims

What is claimed is:

1. An optical interferometric system (143) that generates one or more two dimensional data sets related to a selected three dimensional region of a target (129);where said optical interferometric system includes an optical source (101) that is separated into an optical probe beam (115) and an optical reference beam (113); and includes at least one optical beam splitter (125) that combines a portion of said optical probe beam backscattered from said target with a portion of said optical reference beam; and includes a first and a second image sensor array (131, 133) that simultaneously acquire a pair of orthogonal data sets;andwhere one data set of said pair of orthogonal data sets has components that have a 180 degree phase relationship with components of the second data set of said pair of orthogonal data sets, where said components of both said data sets are related to said selected three dimensional region of said target;andwhere, said pair of image sensor arrays (131, 133) acquire at least one second pair of orthogonal data sets where components of one data set of said second pair have a 180 degree phase relationship with components of the other data set of said second pair of orthogonal data sets and where said components are related to said selected three dimensional region of said target;andwhere said first and second pairs of orthogonal data sets are acquired in a time period that is sufficiently short to preserve the interferometric relationship between the four data sets of said first and second pairs of two dimensional data sets;andwhere said second pair of orthogonal data sets have a phase offset from corresponding data sets in said first pair of orthogonal data sets;andwhere said first and said second pair of orthogonal data sets are processed to generate a two dimensional data set related to said selected three dimensional region of said target.

2. The system of claim 1, wherein said selected three dimensional region of said target is determined by the lateral dimensions of said optical probe beam, the coherence length of light output by said optical source, and the optical path length of said optical reference beam.

3. The system of claim 1, wherein said optical source is one of a superluminescent diode, a laser diode, a tunable laser, a swept source laser.

4. The system of claim 1, where said optical source is pulsed on one or more times for a time duration that is approximately 1 millisecond or less.

5. The system of claim 1, wherein said image sensor arrays are operated in a global shutter mode.

6. The system of claim 5, where said global shutter mode includes electronic control of at least some functions of said image sensor arrays.

7. The system of claim 1, wherein said image sensor arrays have a global charge transfer that transfers signals acquired by the active sensor array to an array of protected regions for each pixel of the pixel array.

8. The system of claim 1, wherein said image sensor arrays have a global charge transfer that transfers signals acquired by the active sensor array to an array of memory elements for each pixel of the pixel array.

9. The system of claim 1, wherein said time period in which said first and second pairs of orthogonal data sets are acquired is less than one millisecond.

10. The system of claim 1, wherein said time period in which said first and second pairs of orthogonal data sets are acquired is approximately one millisecond.

11. The system of claim 1, wherein said phase offset between corresponding data sets in said first and said second pair of orthogonal data sets is a fixed number of degrees.

12. The system of claim 1, wherein said phase offset between corresponding data sets in said first and said second pair of orthogonal data sets is approximately 90 degrees.

13. The system of claim 11, wherein said phase offset between corresponding data sets in said first and said second pair of orthogonal data sets of a fixed number degrees is generated by one of a phase modulator, a piezo device, an electro-mechanical actuator.

14. The system of claim 1, wherein said phase offset between said first and second pair of data sets is a random number of degrees.

15. The system of claim 14, wherein said phase offset of a random number of degrees is the result of relative motion of said target with respect to said optical interferometric system.

16. The system of claim 1, further including at least one camera, wherein the depth location of said selected three dimensional region of said target is measured by processing the image of the broad spot on the cornea due to the diverging optical probe beam.

17. The system of claim 1, further including at least two cameras, wherein the depth location of said selected three dimensional region of said target is measured by processing the degree of overlap of aspects of images acquired by said at least two cameras acquiring images of the front surface of said target.

18. The system of claim 1, wherein the depth location of said selected three dimensional region of said target is measured by processing the signals of a narrow beam OCT system that is interleaved with said optical interferometric system.

19. The system of claim 1, wherein the depth location of said selected three dimensional region of said target is determined by correlating said generated two dimensional data set with previously acquired or generated reference data sets.

20. The system of claim 1, wherein the processed data sets of multiple selected three dimensional regions of said target that are acquired at different known depth locations are combined to form a three dimensional data set of said target.

21. The system of claim 1, wherein said optical source is a tunable laser and wherein data sets of a selected three dimensional regions of said target are acquired multiple times and where at least some of said acquired data sets are acquired while said tunable laser optical source is emitting a different wavelength and where data sets that are acquired at different wavelengths are combined using Fourier domain processing to form a three dimensional data set of said target.

22. The system of claim 1, wherein data sets of a selected three dimensional region of said target are acquired multiple times and where at least some of the acquired data sets are averaged to form a high resolution two dimensional data set or image of said selected three dimensional region of said target.

23. The system of claim 1, further including a sync generator (1 1) electrically connected so as to control said system.

24. The system of claim 23, wherein said sync generator controls pulsing of said optical source and includes electronic control of at least some functions of said first and second image sensor arrays.

25. The system of claim 1, wherein said pair of image sensor arrays are two sections of the same device.

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