SYSTEM AND METHOD USING SURFACE SCANNING PATTERN/PROTOCOL BASED ON MODIFIED ELECTRICAL WAVES TO PRODUCE A WIDE AND DYNAMIC TIME INTERVAL BETWEEN SCANS

Abstract

A method of data acquisition and image generation over a wide and dynamic time interval between surface scans using modified electrical waves is disclosed. It is also disclosed that generating altered electrical waveforms that drive a scanner using conventional waves such as sinusoidal or triangle or sawtooth can enhance the method. Systems for A-scan, B-scan, and C-scan imaging pp include surface scan setups using a one-dimensional and a two-dimensional scanner, respectively. Three different arrangements of conventional waves enable modified waveforms that drive scanners to produce a wide and dynamic interscans time interval on both the fast and slow scan axes. (i) At a constant peak-to-peak voltage, the instantaneous voltage of the electrical sinusoidal wave shifts in time with the amplitude of the electrical signal in the ramp waveform within a range. (ii) The frequency of a waveform continuously increases (up-chirp) as a function of time in the form of a positive ramp sawtooth or continuously decreases as a function of time in the form of a negative ramp sawtooth. (iii) The frequency of a waveform is modulated as a function of time in a 90-degree phase retarded sinusoidal form within a deviation range of the +/ peak frequency.

Claims

1. A surface scanning system to generate a wide and dynamic interval between scans to be used in the point imaging process of surface scan patterns, comprising A collimator 101 that transforms the light or the electromagnetic radiation generated from a light source 100 into collimated light or light beam 102, At least one scanning mirror 103 that moves in one or two dimensions and allows the incident collimated light or light beam 102 to be reflected, At least one electrical signal generator 106 that generates electrical signals in different waveforms calculated using numerical model, determines the rotation angle of the scanning mirror 103 with the voltage of the generated electrical signals, drives the scanning mirror 103, and performs unidirectional or bidirectional surface scans with the collimated light or light beam 102 by the scanning mirror 103 it drives, A focusing lens 104 that enables scanning the target surface 105 by focusing the collimated light or light beam 102 to different points with the scanning mirror 103 driven by the electrical signal generator 106.

2. A surface scanning system according to claim 1, wherein the electrical signal generator 106 is an RF signal generator, function generator, random bit generator, or bit pattern generator.

3. A surface scanning system according to claim 1, wherein the scanning mirror 103 is at least one of the galvo scanning mirror, resonance scanning mirror and micro-electromagnetic systems (MEMS) based scanning mirror.

4. A surface scanning system according to claim 1, wherein the focusing lens 104 is a wide-angle scanning lens.

5. A system using the scanning patterns/protocols according to claim 1, wherein the scanning mirror 103 is a two-dimensional scanning mirror 201 that enables the target surface 105 to be driven with fast electrical signals to perform surface scanning on any of its axes or the combination of the x-axis and y-axis.

6. A surface scanning system according to claim 5, comprising an electrical signal generator 202 that drives a two-dimensional scanning mirror 201 to provide scanning in the x-axis.

7. A surface scanning system according to claim 5, comprising an electrical signal generator 202 that drives a two-dimensional scanning mirror 201 to provide scanning in the y-axis.

8. A surface scanning system according to claim 1, comprising two scanning mirrors 103.

9. A surface scanning system according to claim 8, wherein one of the scanning mirrors 103 is the one-dimensional y-axis scanning mirror 301 that can scan the y-axis of the target surface 105 by being driven with the y-axis electrical signal generator 203 and reflecting the collimated light or light beam 102, and the other one is the one-dimensional x-axis scanning mirror 302 that can scan the x-axis of the target surface 105 by being driven with the x-axis electrical signal generator 202 and reflecting the collimated light or light beam 102.

10. A surface scanning system according to claim 9, comprising the x-axis electrical signal generator 202 driving the one-dimensional x-axis scanning mirror 302 and the y-axis electrical signal generator 203 driving the one-dimensional y-axis scanning mirror 301, using the phase lock or 10 MHz reference clock or a combination of the phase lock and 10 MHz reference lock to work in the same temporal space, or clock signal.

11. A surface scanning system of claim 1, wherein the voltage of the electrical signals generated by the electrical signal generator 106 is within V with respect to time.

12. A surface scanning system of claim 1, wherein the voltage of the electrical signals generated by the x-axis electrical signal generator 202 is within V with respect to time.

13. A surface scanning system of claim 1, wherein the voltage of the electrical signals generated by the y-axis electrical signal generator 203 is within V with respect to time.

14. A surface scanning system according to claim 1, comprising electrical signal generator 106 generating electrical signal in at least one of the wave forms include, but are not limited to, the electrical sinusoidal wave 501, positive ramp sawtooth wave with a single duty cycle 502, hybrid wave 503, electrical triangle wave 701, frequency increase as a function of time in the positive ramp sawtooth form 702, up-chirp triangle wave 703, frequency increase as a function of time in 90-degree phase retarded sinusoidal form 901, and frequency-modulated triangle wave 902.

15. A surface scanning system according to claim 6, comprising electrical signal generator 202 generating electrical signal in at least one of the wave forms include, but are not limited to, the electrical sinusoidal wave 501, positive ramp sawtooth wave with a single duty cycle 502, hybrid wave 503, electrical triangle wave 701, frequency increase as a function of time in the positive ramp sawtooth form 702, up-chirp triangle wave 703, frequency increase as a function of time in 90-degree phase retarded sinusoidal form 901, and frequency-modulated triangle wave 902.

16. A surface scanning system according to claim 7, comprising electrical signal generator 203 generating electrical signal in at least one of the wave forms include, but are not limited to, the electrical sinusoidal wave 501, positive ramp sawtooth wave with a single duty cycle 502, hybrid wave 503, electrical triangle wave 701, frequency increase as a function of time in the positive ramp sawtooth form 702, up-chirp triangle wave 703, frequency increase as a function of time in 90-degree phase retarded sinusoidal form 901, and frequency-modulated triangle wave 902.

17. A surface scanning system according to claim 14, wherein the electrical signal generated by the electrical signal generator 106 is in hybrid wave 503 form.

18. A surface scanning system according to claim 15, wherein the electrical signal generated by the x-axis electrical signal generator 202 is in the form of an up-chirp triangle wave 703.

19. A surface scanning system according to claim 16, wherein the electrical signal generated by the y-axis electrical signal generator 203 is in the form of a frequency-modulated triangular wave 902.

20. A surface scanning method in which a wide and dynamic interscan time interval is generated to be used in the point imaging process of surface scanning patterns, the method comprising the steps of, driving the scanning mirror 103 or two-dimensional scanning mirror 201 by the electrical signal generator 106, which provides electrical signal in the hybrid wave 503 form depending on varying the direct current (DC) offset voltage of an electrical sinusoidal wave 501 linearly in time as a function of the positive ramp sawtooth wave with a single duty cycle 502 or as a function of the electrical signal in the ramp waveform, creating bidirectional and unidirectional surface scans on any axis of the target surface 105 or a combination of the x-axis and y-axis with the light or light beam 102 directed by the scanning mirror 103 or the two-dimensional scanning mirror 201 driven by the electrical signal generator 106.

21. A surface scanning method according to claim 20, wherein the method comprises the steps of: driving the scanning mirror 103 or two-dimensional scanning mirror 201 with an electrical signal generator 106 that provides electrical signals in the form of up-chirp triangle wave 703, creating bidirectional and unidirectional surface scans on any axis of the target surface 105 or a combination of the x-axis and y-axis with the light or light beam 102 directed by the scanning mirror 103 or the two-dimensional scanning mirror 201 driven by the electrical signal generator 106.

22. A surface scanning method according to claim 20, wherein the method comprises the steps of: driving the scanning mirror 103 or the two-dimensional scanning mirror 201 with an electrical signal generator 106 that provides electrical signals in the form of a frequency-modulated triangle wave 902 obtained by frequency deviation from linear frequency increase or linear frequency decrease as a function of time, creating bidirectional and unidirectional surface scans on any axis of the target surface 105 or a combination of the x-axis and y-axis with the light or light beam 102 directed by the scanning mirror 103 or the two-dimensional scanning mirror 201 driven by the electrical signal generator 106.

23. A surface scanning method according to claim 14 or claim 15 or claim 16, wherein the electrical signals are analog or digital.

24. A method for generation wide and dynamic time intervals between surface scans: for a wide and dynamic interscan time interval generation wherein a surface scan pattern/protocol based on hybrid waveform comprising steps of, generating a hybrid wave by varying the direct current (DC) offset voltage of an electrical sinusoidal signal linearly in time as a function of the positive ramp sawtooth wave, alternatively, at a constant peak-to-peak voltage, shifting the instantaneous voltage of the electrical sinusoidal wave in time with the amplitude of the electrical signal in the ramp waveform, equalizing the varying speed of the DC voltage to the repetition rate of the electrical signal in the ramp waveform, driving a 1-dimensional scanner for B-scanning (x-axis, z-axis) consisting of a series of A-scans (z-axis or depth) and a C-scan consisting of a series of B-scans, alternatively, driving a 2-dimensional scanner for C-scanning (x-axis, y-axis, z-axis) consisting of a series of B-scans (x-axis, z-axis). or for a wide and dynamic interscan time interval generation wherein a surface scan pattern/protocol based on up-chirp or down-chirp waveform comprising steps of, generating an up-chirp triangle wave by frequency increase as a function of time in the form of a positive ramp sawtooth, or producing a down-chirp triangle wave by frequency decrease as a function of time in the form of a negative ramp sawtooth, defining the width of the time intervals between scans by the sweeping range, dynamically defining the variation of the time interval between scans by the frequency change rate, driving a 1-dimensional scanner for B-scanning (x-axis, z-axis) consisting of a series of A-scans (z-axis or depth) and a C-scan consisting of a series of B-scans, alternatively, driving a 2-dimensional scanner for C-scanning (x-axis, y-axis, z-axis) consisting of a series of B-scans (x-axis, z-axis). or for a wide and dynamic interscan time interval generation wherein a surface scan pattern/protocol based on frequency-modulated waveform comprising steps of, generating a frequency modulated triangle wave by modulating the electrical triangle wave with frequency deviation as a function of time in a 90-degree phase retarded sinusoidal form, defining the width of the time intervals between scans by the deviation range of the +/ peak frequency, dynamically defining the variation of the time interval between scans by the modulation rate, driving a 1-dimensional scanner for B-scanning (x-axis, z-axis) consisting of a series of A-scans (z-axis or depth) and a C-scan consisting of a series of B-scans, alternatively, driving a 2-dimensional scanner for C-scanning (x-axis, y-axis, z-axis) consisting of a series of B-scans (x-axis, z-axis).

25. A method according to claim 24, wherein the scan pattern/protocol comprises the step of increasing the number of duty cycles for multiple scans based on the hybrid waveform or up-chirp or down-chirp waveform or frequency-modulated waveform.

26. A method according to claim 24, wherein: surface scanning is used to acquire data and create images, alternatively, surface scanning is employed to provide therapeutic photo-thermal damage, including ablation and coagulation.

27. A method according to claim 24, wherein B-scan and C-scan comprise bidirectional scan or unidirectional scan.

28. A system which performs the method according to claim 24, wherein the two mirror configuration comprises a light source, a collimator, two one-dimensional scanning mirrors, two electrical signal generators, and a focusing lens.

29. A method according to claim 26, further comprising the process steps of, transmission of continuous-wave light or pulsed light from a light source to an optical collimator, reflecting the collimated light into a focusing lens via a two-dimensional scanning mirror, driving the two-dimensional scanning mirror with hybrid waveform or up-chirp waveform or down-chirp waveform or frequency-modulated waveform based electrical signals provided by electrical signal generators, focusing the collimated light at different spots on the target surface over a wide and dynamic time interval between surface B-scans or C-scans, transmitting the backscattered light collected from the sample through the same optical path.

30. A system which performs the method according to claim 24, wherein the single-mirror configuration comprises a light source, a collimator, a two-dimensional scanning mirror, two electrical signal generators, and a focusing lens.

31. A method for performing the system of claim 28, further comprising the process steps of, transmission of continuous-wave light or pulsed light from a light source to an optical collimator, cascading one-dimensional scanning mirrors for the x-axis and y-axis, reflecting the collimated light into a focusing lens via cascaded two one-dimensional scanning mirrors, driving one-dimensional scanning mirrors with hybrid waveform or up-chirp waveform or down-chirp waveform or frequency-modulated waveform based electrical signals provided by electrical signal generators, focusing the collimated light at different spots on the target surface over a wide and dynamic time interval between surface B-scans or C-scans, transmitting the backscattered light collected from the sample through the same optical path.

32. A system which performs the method according to claim 28 or claim 30, wherein the light source comprises a high-power monolithic diode laser with an internal grating, a high-power broadband semiconductor optical amplifier with an internal grating, a diode driver including an on-board TEC controller, a dispersion-tuned swept-wavelength laser source, or a MEMS-VCSEL swept-wavelength laser source.

33. A system which performs the method according to claim 28 or claim 30, wherein the scanning mirror comprises, but is not limited to, a galvo scanning mirror, resonance scanning mirror, micro-electromechanical systems (MEMS) based scanning mirror, or maybe any or a combination.

34. A system which performs the method according to claim 28 or claim 30, wherein the focusing lens comprises a wide optical angle scanning lens.

35. A system which performs the method according to claim 28 or claim 30, wherein the electrical signals are analog or digital.

36. A system which performs the method according to claim 28 or claim 30, wherein the electrical signal generator comprises an RF-signal generator, a function generator, a random bit generator, a bit pattern generator, or a programmable bit pattern generator.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0021] The following are descriptions of the accompanying figures showing illustrative embodiments of the present disclosure that clearly explain the objects, features, and advantages of the invention.

[0022] FIG. 1A: Block diagram of an exemplary embodiment for surface scanning.

[0023] FIG. 1B: Diagram of an exemplary conventional pattern (e.g., raster scanning pattern) with the x-axis from left to right and the y-axis from top to bottom.

[0024] FIG. 2: Block diagram of an exemplary embodiment of a surface scanning system using a two-dimensional scanning mirror.

[0025] FIG. 3: Block diagram of an exemplary embodiment of the target surface scanning system using two one-dimensional scanning mirrors.

[0026] FIG. 4A: A graph illustrating representative bidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 5.

[0027] FIG. 4B: A graph illustrating representative unidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 5.

[0028] FIG. 5: A series of graphs illustrating an exemplary embodiment of a hybrid waveform obtained by varying the direct current (DC) offset voltage of an electrical sinusoidal wave linearly in time as a function of the positive ramp sawtooth wave with a single duty cycle.

[0029] FIG. 6A: A graph illustrating representative bidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 7.

[0030] FIG. 6B: A graph illustrating representative unidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 7.

[0031] FIG. 7: A series of graphs illustrating an exemplary embodiment of the up-chirp triangle waveform obtained by continuously increasing the frequency of an electrical triangle wave as a function of time in the form of a positive ramp sawtooth.

[0032] FIG. 8A: A graph illustrating representative bidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 9.

[0033] FIG. 8B: A graph illustrating representative unidirectional scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment shown in FIG. 9.

[0034] FIG. 9: A series of graphs illustrating an exemplary embodiment of the frequency-modulated waveform obtained by modulating the electrical triangle wave with frequency deviation as a function of time in a 90-degree phase retarded sinusoidal form within a deviation range of the +/ peak frequency.

[0035] FIG. 10: A graph representing the simulated estimate of the 1-millisecond long hybrid wave calculated by linearly increasing the direct current (DC) offset voltage over time as a function of the positively ramped sawtooth wave with a single duty cycle.

[0036] FIG. 11: A graph representing the estimated time intervals of consecutive B-scans in bidirectional and unidirectional scanning modes, respectively, to illustrate better the effect of the scan pattern/protocol based on waveform shown in FIG. 10.

[0037] FIG. 12: A graph representing the numerical simulation of the up-chirp triangle wave modeled as a sawtooth triangle wave (2 au peak to peak) whose frequency increases as a function of time in the form of a positive ramp in the range of 100 Hz to 2 kHz.

[0038] FIG. 13: A graph representing the estimated time intervals of consecutive B-scans in bidirectional and unidirectional scanning modes, respectively, to illustrate better the effect of the scan pattern/protocol based on waveform shown in FIG. 12.

[0039] FIG. 14: A graph representing the numerical simulation of the frequency-modulated triangular wave modeled as the frequency modulation of a 2-au peak-to-peak triangle signal at 20 kHz (i.e., a period of 50 s) within +/10 kHz frequency deviation.

[0040] FIG. 15: A graph representing the estimated time intervals of consecutive B-scans in bidirectional and unidirectional scanning modes, respectively, to illustrate better the effect of the scan pattern/protocol based on waveform shown in FIG. 14.

DESCRIPTION OF EMBODIMENTS

[0041] In order to increase the comprehensive impact of surface scanning data acquisition and imaging techniques in diagnostic applications and preclinical studies, it is necessary to simultaneously detect/image/measure multiple time interval changes (for example, blood flow rates). The techniques include, but are not limited to, Optical Coherence Tomography (OCT), OCT-angiography, Doppler-OCT, and laser scanning confocal microscopy. This challenge can be overcome by creating a wide and dynamic range of surface scanning rates in blood flow and angiography detection/imaging/measurement.

[0042] FIG. 1A presents an exemplary embodiment for surface scanning. The exemplary embodiment includes a light source 100, a collimator 101, a scanning mirror 103, a focusing lens 104, and an electrical signal generator 106. The collimator 101 aligns and delivers the electromagnetic radiation (i.e., light beam) generated from the light source 100 to the scanning mirror 103. The scanning mirror 103 has a single-axis scanning. The scanning mirror 103 also has, for example, a biaxial scanning. The focusing lens 104, combined with the scanning mirror 103 driven by the electrical signal generator 106, focuses the collimated light 102 at different points as a waveform function to scan the target surface 105.

[0043] For example, the surface can be scanned in a conventional pattern (e.g., raster scanning pattern) with the x-axis from left to right and the y-axis from top to bottom, as shown in FIG. 1B, and the scan in the x-axis consists of the A-scan array/sequence. Scanning in the y-axis can occur in multiple B scans. Therefore, it is possible to use surface scanning to acquire data and generate images. Alternatively, surface scanning is also employed to provide therapeutic photo-thermal damage, such as ablation or coagulation. The scanning mirror 103 includes, but is not limited to, a galvo scanning mirror, resonance scanning mirror, micro-electromechanical systems (MEMS) based scanning mirror, and maybe any or a combination. The focusing lens can be customized as a wide-angle, such as 14.0, scanning lens. The electrical signal generator 106 can generate multiple and different types of waveforms, including, but are not limited to, electrical sinusoidal wave 501, positive ramp sawtooth wave with a single duty cycle 502, hybrid wave 503, electrical triangle wave 701, frequency increase as a function of time in the positive ramp sawtooth form 702, up-chirp triangle wave 703, frequency increase as a function of time in 90-degree phase retarded sinusoidal form 901, and frequency-modulated triangle wave 902.

[0044] An exemplary embodiment of a surface scanning system using a two-dimensional scanning mirror 201 is presented in FIG. 2. As shown in FIG. 2, the collimated light 102 is reflected into the focusing lens 104 via a two-dimensional scanning mirror 201. The focusing lens 104 transmitted the collimated light 102 to different spots on the target surface 105, respectively, depending on the above electrical waveform. The two-dimensional scanning mirror 201 is driven by any or by a combination of the x-axis electrical signal generator 202 and the y-axis electrical signal generator 203. An exemplary embodiment of the target surface 105 scanning system using two one-dimensional scanning mirrors is presented in FIG. 3. As shown in FIG. 3, the collimated light 102 is reflected over a one-dimensional y-axis scanning mirror 301 and a one-dimensional x-axis scanning mirror 302, respectively. The focusing lens 104 coupled with the cascaded scanning mirrors precisely focuses the collimated light 102 directed by the scanners onto the target surface 105. The one-dimensional y-axis scanning mirror 301 is driven by the y-axis electrical signal generator 203, while the one-dimensional x-axis scanning mirror 302 is driven by the x-axis electrical signal generator 202. For example, in the exemplary embodiments presented in FIG. 2 and FIG. 3, generators can be phase-locked through a 10 MHz reference clock signal to provide intrinsically stable surface scanning. These electrical signal generators include, but are not limited to, the RF signal generator, the function generator, the random bit generator, and the bit pattern generator. The amplitude of the electrical signals based on waveforms listed above can vary within the 10 V analog position signal range. The positive and negative signs of the voltage define the direction of rotation of the scanning mirror 103, namely right rotation or left rotation or vice versa. The amplitude determines the angle of rotation of the scanning mirror 103 corresponding to the position of the reflected light on the surface. Thus, the coordinate (i.e., position) of the light focused on the target surface 105 can be controlled by the amplitude of the electrical signals.

[0045] Further, the repetition rate of the electrical signal (103 to 10.sup.6 Hz) determines the rate at which the focused light returns to the same point, that is, the time it takes for it to be at the same point again. In other words, the scan rates of the system on the x-axis and y-axis can be defined by the frequency, i.e., the period of the electrical signal. Electrical signals can be analog signals and digital signals. In the exemplary surface scanning systems depicted in FIG. 2 and FIG. 3, all waveforms suggested in the present invention can drive the two-dimensional scanning mirror 201, the one-dimensional y-axis scanning mirror 301, and the one-dimensional x-axis scanning mirror 302. Besides, these waveforms, including hybrid wave 503, up-chirp triangle wave 703, and frequency-modulated triangle wave 902, generate such surface scanning patterns/protocols, providing a wide and dynamic interscan time interval. Also, all waveforms can be used for both x-axis scanning and y-axis scanning of the surface.

[0046] FIG. 4 shows a diagram of the surface scan pattern/protocol that can be configured to produce a wide and dynamic interscan time interval according to a representative waveform embodiment of the present disclosure. FIG. 4A shows the bidirectional scan pattern/protocol, and FIG. 4B shows the unidirectional scan pattern/protocol. Both scan patterns/protocols point to the sequential position index (j), i.e., the A-scan index (j), while the y-axis denotes the time. The solid arrow line represents the B scan and the direction of the scan, and each B-scan consists of a series of A-scans corresponding to the depth-resolved point scans on the target surface 105. In the case of unidirectional scanning, the dashed line after each B-scan represents the rollback required to restore the scanner to its starting position.

[0047] FIG. 5 shows an exemplary embodiment of a hybrid wave 503. Combining conventional sinusoidal and sawtooth waves, hybrid wave 503 can be used to generate the representative surface scan model/protocol of the present disclosure presented in FIG. 4. In other words, by varying the direct current (DC) offset voltage of an electrical sinusoidal wave 501 linearly in time as a function of the positive ramp sawtooth wave with a single duty cycle 502, hybrid wave 503 can be generated. Thus, at a constant peak-to-peak voltage value, the peak voltage of the electrical sinusoidal wave 501 shifts in time with the amplitude of the electrical signal in the ramp waveform. The shift rate equals the repetition rate of the electrical signal in the ramp waveform. The shift rate can be at least 100 times slower than the repetition rate of the signal based on the electrical sinusoidal wave 501.

[0048] The amplitude of the electrical sinusoidal wave 501 does not typically change linearly with time. Thus, the direct current (DC) offset voltage shift over time causes the electrical sinusoidal wave 501 to reach its instantaneous amplitude at different nonlinear time intervals, as illustrated, for example, in FIG. 5 by the dashed line in the hybrid wave 503. In other words, a wide and dynamic interscan time interval is produced depending on the amplitude and repetition rate of a hybrid wave 503 and the time shift rate of the direct current (DC) offset voltage. The peak-to-peak voltage of the electrical sinusoidal wave 501 is lower than the peak voltage of the positive ramp sawtooth wave with a single duty cycle 502. The number of duty cycles of the positive ramp sawtooth wave can be increased for multiple scans.

[0049] Another representative waveform embodiment of the present invention can configure the surface scan pattern/protocol shown in FIG. 6 to produce a wide and dynamic interscan time interval. This exemplary surface scan pattern/protocol is obtained by having the electrical signal driving the scanning mirror 103 based on the up-chirp triangle wave 703.

[0050] A bidirectional scan of the up-chirp triangle wave 703 based surface scan pattern/protocol is exemplarily shown in FIG. 6A. FIG. 6B presents an example of unidirectional scanning of the same surface scan pattern/protocol. The dashed line after each B-scan (that consists of a series of A-scans) represents the scanning mirror returning to its initial position in this scanning case. The solid line and arrowhead indicate the B-scan and the direction of the scan. The x-axis marks the position index in the graphical representation of the surface scan pattern/protocol, and the y-axis marks the return to the same position spot at different time intervals.

[0051] FIG. 7 demonstrates an exemplary embodiment of the up-chirp triangle wave 703 that can generate the surface scan pattern/protocol shown in FIG. 6. An electrical triangle wave 701 produces the up-chirp triangle wave 703 by frequency increase as a function of time in the form of a positive ramp sawtooth. As the dashed line in FIG. 7 presents, the signal's amplitude reaches the same voltage at different time intervals.

[0052] This inference ensures that the light focused on the target surface 105 visits the exact spot at different time intervals. Therefore, the time difference between the first and second scans is different from the time between the second and third scans. Scans include B-scans and C-scans, depending on the scan axes.

[0053] The sweep range defines the width of the time intervals between scans (e.g., the first scan and the last scan), while the frequency change rate dynamically defines the variation of the time interval between scans. The rate of frequency increase as a function of time in the positive ramp sawtooth form defines the frequency change rate. The instantaneous frequency varies linearly or exponentially with time.

[0054] Alternatively, or additionally, a down-chirp triangle wave can provide a similar surface scan pattern/protocol produced by an up-chirp triangle wave. Besides, an electrical sinusoidal wave 501 can be used instead of the electrical triangle wave 701 to obtain a chirp electrical signal driven surface scan pattern/protocol. The B-scan number or C-scan number can be multiplied by increasing the duty cycle number of the frequency increase as a function of time in the positive ramp sawtooth form.

[0055] FIG. 8A and FIG. 8B demonstrate the bidirectional and unidirectional surface scan pattern/protocol in time, respectively, of another representative waveform embodiment of the present invention for a wide and dynamic interscan time interval. A frequency-modulated triangle wave 902 generates the representative surface scanning pattern/protocol. As with all the exemplary surface scan model/protocols listed throughout the text, the solid line with the arrowhead represents the B-scan and scan direction, and the dashed line represents the rollback in the unidirectional scanning.

[0056] As depicted in FIG. 9, a frequency modulated triangle wave 902 can be obtained by modulating the electrical triangle wave 701 with frequency deviation as a function of time in a 90-degree phase retarded sinusoidal form 901. The frequency range of the frequency-modulated triangle wave 902 is defined by the deviation of the +/ peak frequency (i.e., instantaneous frequency). Thus, a scanning pattern consisting of nonlinear acceleration, deceleration, and acceleration in the specified modulation range is obtained by driving the scanning mirror with the frequency modulated signal. For example, as indicated by the dashed line in FIG. 9, a frequency modulated triangle wave 902 can reach the same voltage corresponding to a position at different time intervals, producing a wide and dynamic interscan time interval. The frequency modulation rate is determined by the repetition rate of the frequency deviation as a function of time in a 90-degree phase retarded sinusoidal form 901. Furthermore, the number of duty cycles can be increased for multiple scans based on the frequency-modulated triangle wave 902.

[0057] The periodicity of the presence of focused light at a location on the target surface is changed from fast to slow and from slow to fast with a scanning mirror 103 driven by the frequency-modulated triangle wave 902. Alternatively, or additionally, the surface scan pattern/protocol of the present invention presented in FIG. 8 can also be generated for an electrical sinusoidal wave 501 instead of an electrical triangle wave 701.

[0058] The present disclosure's representative surface scan model/protocol presented in FIG. 4, FIG. 6, or FIG. 8 can be used on each or a combination of the B-scan (x-axis, z-axis) consisting of a series of A-scans (z-axis or depth) and the C-scan (x-axis, y-axis, z-axis) consisting of a series of B-scans (x-axis, z-axis). a wide dynamic scan-to-scan time interval can be produced between the corresponding B-scans and between corresponding C-scans. All scans can be bidirectional or unidirectional.

[0059] Surface scan patterns/protocols of the present invention to be generated with the waveforms described in FIG. 4, FIG. 6, and FIG. 8 were simulated by developing numerical modeling with exemplary time scale arrangements (i.e., 103 seconds) capable of producing a wide and dynamic interscan time interval. The exemplary numerical model predicted simulation results of waveforms in the time domain, and some parts of the invention were realized, including hybrid wave 503, up-chirp triangle wave 703, and frequency-modulated triangle wave 902. Besides, the model included time interval calculations between consecutive B-scans and C-scans provided in the bidirectional and unidirectional modes.

[0060] FIG. 10 shows the simulated estimate of the 1-millisecond long hybrid wave calculated by linearly increasing the direct current (DC) offset voltage over time as a function of the positively ramped sawtooth wave with a single duty cycle 502. The exemplary numerical model used a sinusoidal wave with a repetition rate of 20 kHz (i.e., a period of 500 ms) and relative amplitude of 2 arbitrary units from peak to peak. A positive ramp sawtooth wave with a single duty cycle linearly increases the DC voltage at a repetition rate of 1 kHz (i.e., a period value of 1 ms) and a peak-to-peak relative amplitude of 4 arbitrary units (4 au).

[0061] FIG. 11 shows the calculated time differences between consecutive B-scans in the bidirectional and unidirectional scanning modes, respectively. Solid black circles indicate interscan time difference results in a bidirectional scan, and empty black circles indicate interscan time difference results in a unidirectional scan. Also, the fixed time interval between successive B-scans produced by sinusoidal wave-based electrical signals used in conventional surface scanning protocols could be compared on the same graph. An exemplary conventional surface scanning protocol simulation was performed for a sinusoidal wave with a repetition rate of 20 kHz (i.e., a period of 50 s) and a relative amplitude of 2 arbitrary units from peak to peak. According to the numerical model, the constant time difference between scans in bidirectional mode was calculated as 25 s, which is half of the sinusoidal wave period. Estimated results are marked with black crosses. On the other hand, the surface scanning protocol/pattern based on an exemplary hybrid wave 503 presented in FIG. 10 provided a time interval between 35.7 s and 442 s in the bidirectional scanning mode. The predicted fast and slow scan rate differences corresponded to a wide and dynamic interscan time interval of >0.406 ms.

[0062] As shown in FIG. 12, the numerical modeling simulated another representative waveform embodiment of the present invention for a wide and dynamic interscan time interval. An exemplary up-chirp triangle wave was modeled as a sawtooth triangle wave (2 au peak to peak) whose frequency increases as a function of time in the form of a positive ramp in the range of 100 Hz to 2 kHz.

[0063] FIG. 13 presents the estimated time intervals of consecutive B-scans in bidirectional and unidirectional scanning modes to illustrate better the effect of the scan pattern/protocol using the numerical model. Calculated interscan time differences are marked with solid black circles for the bidirectional scan and hollow black circles for the unidirectional scan. The sample computation model calculated that the fastest 0.253 ms and the slowest 1.59 ms time difference was produced between bidirectional B scans, while the fastest 0.516 ms and slowest 2.713 ms time difference was calculated for unidirectional B-scans. Thus, the time differences corresponded to dynamic interscan time intervals >1.3 ms and >2.1 ms wide, respectively. For a direct comparison, the black crosses indicate the constant time difference between consecutive bidirectional B-scans that the triangle wave would provide at a repeat rate of 1050 Hz (i.e., a period of 0.95 ms) and relative amplitude of 2 arbitrary units. The fixed time interval between corresponding consecutive scans was estimated as 0.48 ms.

[0064] FIG. 14 presents an exemplary numerical model of the frequency-modulated triangular wave, another representative waveform embodiment of the present invention, which can provide a bidirectional and unidirectional surface scan pattern/protocol for a wide and dynamic interscan time interval. The model computed the frequency modulation of a 2-au peak-to-peak triangle signal at 20 kHz (i.e., a period of 50 s) within +/10 kHz frequency deviation. The peak frequency numerically deviated from 10 kHz to 30 kHz as a function of time in a 90-degree phase retarded sinusoidal form.

[0065] The modulation rate was 500 Hz, the frequency of a 90-degree delayed single-cycle sinusoidal wave. FIG. 15 presents the calculations of the time difference between successive B-scans and the corresponding time intervals. Solid circles show bidirectional scan results, and hollow circles show unidirectional scan results. Within the exemplary computational model of the surface scanning model/protocol based on frequency modulation, dynamic interscan time intervals of >66 s for bidirectional scanning and >33 s for unidirectional scanning were obtained. For direct comparison with the conventional surface scan model/protocol, the estimated results of an electrical signal based on the triangular waveform at 20 kHz producing a fixed time interval of 25 s between bidirectional B-scans are presented in FIG. 15 with black crosses.

CITATION LIST

Patent Literature

[0066] TR2018/10000, U.S. Ser. No. 10/839,568B2, EP2054712A2, US20150233701A1, U.S. Ser. No. 10/136,865B2

Non-Patent Literature

[0067] 1. V. F. Duma, K. S. Lee, P. Meemon and J. P. Rolland, Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT, Appl. Opt. 50(29), 5735-5749 (2011). [0068] 2. V. F. Duma, P. Tankam, J. Huang, J. Won and J. P. Rolland, Optimization of galvanometer scanning for optical coherence tomography, Appl. Opt. 54(17), 5495-5507 (2015). [0069] 3. A. Szkulmowska, M. Szkulmowski, D. Szlag, A. Kowalczyk and M. Wojtkowski, Three-dimensional quantitative imaging of retina! and choroidal blood flow velocity using joint Spectral and Time domain Optical Coherence Tomography, Opt. Express 17(13), 10584-10598 (2009). [0070] 4. P. Meemon and J. P. Rolland, Swept-source based, single-shot, multidetectable velocity range Doppler optical coherence tomography, Biomed. Opt. Express 1(3), 955-966 (2010). [0071] 5. M. J. Ju, M. Heisler, A. Athwal, M. V. Sarunic and Y. Jian, Effective bidirectional scanning pattern for optical coherence tomography angiography, Biomed. Opt. Express 9(5), 2336-2350 (2018). [0072] 6. T. Park, S. J. Jang, M. Han, S. Ryu and W. Y. Oh High dynamic range optical coherence tomography angiography (HDR-OCTA), Opt. Express 10(7), 3560-3571 (2019). [0073] 7. L. Shi, J. Qin, R. Reif and R. K. Wang, Wide velocity range Doppler optical microangiography using optimized step-scanning protocol with phase variance mask, J Biomed Opt. 18(10), 106015 (2013). [0074] 8. 1. Grulkowski, 1. Gorczynska, M. Szkulmowski, D. Szlag, A. Szkulmowska, R. A. Leitgeb, A. Kowalczyk and M. Wojtkowski Scanning protocols dedicated to smart velocity ranging in Spectral OCT, Opt. Express 17(26), 23736-23754 (2009). [0075] 9. W. Choi, E. M. Moult, N. K. Waheed, M. Adhi, B. Lee, C. D. Lu, E. Talisa, V. Jayaraman, P. J. Rosenfeld, J. S. Duker and J. G. Fujimoto, Ultrahigh-speed, swept-source optical coherence tomography angiography in nonexudative age-related macular degeneration with geographic atrophy, Ophthalmology 122(12), 2532 (2015). [0076] 10. S. B. Ploner, E. M. Moult, W. Choi, N. K. Waheed, B. Lee, E. A. Novais, E. D. Cole, B. Potsaid, L. Husvogt, J. Schottenhamml and J. G. Fujimoto, Toward Quantitative Optica Coherence Tomography Angiography: Visualizing Blood Flow Speeds in Ocular Pathology Using Variable Interscan Time Analysis, Retina 36, S I 18-SI26 (2016). [0077] 11. F. Jaillon, S. Makita and Y. Yasuno, Variable velocity range imaging of the choroid with dual-beam optical coherence angiography, Opt. Express 20(1), 385-396 (2011). [0078] 12. S. Kim, T. Park, S. J. Jang, A. S. Nam, B. J. Vakoc and W. Y. Oh, Multi-functional angiographic OFDI using frequency-multiplexed dual-beam illumination, Opt. Express 23(7), 8939-8947 (2015). [0079] 13. T. Park, S. J. Jang, M. Han, S. Ryu, and W. Y. Oh, Wide dynamic range high-speed three-dimensional quantitative OCT angiography with a hybrid-beam scan, Optics Lett. 43(10), 2237-2240 (2018).