Laser sensor, system and method for self-mixing interferometry

Abstract

A laser sensor comprises a laser source (12) emitting a laser beam (22) and optics (20) projecting the laser beam (22) as a one- or two-dimensional patterned laser beam (26) onto an object (24) to be inspected, such that the distance of the patterned laser beam (26) from the laser source (12) varies along the patterned laser beam (26) projected on the object (24). A detector (14) determines a self-mixing interference signal generated by laser light of the patterned laser beam (26) reflected back from the object (24) to the laser source (12). A circuit (18) spectrally analyzes the self-mixing interference signal and extracts from the spectrum of the self-mixing interference signal a plurality of frequencies indicative of a plurality of distances of the patterned laser beam (26) from the laser source (12) along and / or a plurality of velocities of the patterned laser beam (26) relative to the laser source (12). Systems having such a laser sensor as well as related methods and computer program products are also disclosed.

Description

Technical Field

[0001] This invention generally relates to the field of using self-mixing interferometry to detect the position and velocity of an object. More specifically, this invention relates to a laser sensor, a system, and a method for using self-mixing interferometry to detect the position and / or velocity of an object under inspection. This invention also relates to a computer program product. Background Technology

[0002] Self-Mixing Interference (SMI) is a technique for obtaining distance and velocity information from an object. A laser emitted from a laser source, such as a laser diode, particularly a vertical-cavity surface-emitting laser (VCSEL), is directed to an object whose velocity and / or position need to be determined. The laser reflected from the object re-enters the laser source and interferes with the light waves within a laser resonator. This results in intensity changes sensed by a detector, such as a photodiode, which can be integrated into the structure of the laser source.

[0003] SMI can be applied to applications such as mouse sensors, distance sensors, ground velocity applications, particle detection, and more.

[0004] Recently, SMI (Spotlight Induction Mechanism) has been proposed for tracking human eye gaze. Tracking different eye positions could be beneficial in various applications, such as head-mounted displays, head-up displays, and data lenses. Text or images would be displayed on the screen at the location corresponding to the user's gaze. In current eye-tracking technologies, in addition to the SMI sensor, a camera system is required to obtain the precise eye position. Therefore, conventional systems are disadvantageous in terms of cost and complexity.

[0005] It should be noted that this invention is not limited to eye gaze angle detection, but can be implemented in a variety of other applications where position and / or velocity information to be obtained from an object is to be obtained. The term "object" includes not only solid objects but also fluid objects. Furthermore, the term "one object" may include multiple objects. Summary of the Invention

[0006] One object of the present invention is to provide a laser sensor capable of performing self-mixing interferometry without the need for an additional system, such that all required position / velocity information can be obtained from the self-mixing interferometry.

[0007] Another object of the present invention is to provide a system capable of detecting at least one of the position or velocity of an object with high precision without requiring an additional system such as a camera.

[0008] Another object of the present invention is to provide a related method and a computer program product.

[0009] According to a first aspect of the present invention, a laser sensor is provided, the laser sensor comprising:

[0010] A laser source configured to emit laser beams.

[0011] An optical device configured to project the laser beam as a one-dimensional or two-dimensional patterned laser beam onto an object to be inspected, such that the distance of the patterned laser beam from the laser source varies along the patterned laser beam projected onto the object.

[0012] A detector configured to determine a self-mixing interference signal generated by the laser light from a patterned laser beam reflected back to the laser source by an object, and

[0013] A circuit configured to perform spectral analysis on the self-mixing interference signal and extract multiple frequencies from the spectrum of the self-mixing interference signal, the multiple frequencies indicating multiple distances from the laser source along the patterned laser beam and / or multiple velocities along the patterned laser beam relative to the laser source.

[0014] The laser source according to the present invention can obtain more information from the self-mixing interference signal, just like a conventional SMI laser sensor. This is achieved by two differences from conventional SMI technology. The first difference is the use of a one-dimensional or two-dimensional patterned laser beam to strike the object to be inspected. In contrast, in conventional SMI technology, the laser beam is projected onto the object as a single point spot, such that the laser spot on the object is only one distance away from the laser source at a given time. By projecting the laser beam onto the object as a one-dimensional or two-dimensional patterned laser beam, the distance of the patterned laser beam from the laser source varies along the patterned laser beam projected onto the object, thus the patterned laser beam has multiple distances from the laser source at a given time. Therefore, compared to the case of an SMI signal based on a single spot projected onto the object, the back-reflected patterned laser beam generates an SMI signal containing more position and / or velocity information based on these multiple distances.

[0015] A "one-dimensional or two-dimensional patterned laser beam" refers to a projected laser beam that extends in one or two dimensions. For example, a one-dimensional patterned laser beam can be a straight line, a curve, or a strip. The line can be a continuous line, a dashed line, or a plurality of points arranged in a line. A characteristic of a one-dimensional patterned laser beam is that the beam width in a first direction is at least twice the beam width in a second direction perpendicular to the first direction. A two-dimensional patterned laser beam can have a beam profile extending over a region having at least one minimum laser intensity, where the minimum value can be zero. For example, a two-dimensional patterned laser beam can be circular, elliptical, rectangular, a grid of multiple lines, a cross shape, etc.

[0016] The emitted laser beams may include multiple laser beams emitted by a laser source. Multiple laser beams may be emitted in a time-division multiplexing manner. The laser source may include a single laser or multiple lasers. The laser source may include a single laser comprising multiple laser beam emission regions. For example, the laser may be a VCSEL array having two or more mesas, each mesa being a laser beam emission region.

[0017] The second difference between the laser sensor according to the invention and conventional SMI laser sensors lies in the fact that the laser sensor according to the invention performs spectral analysis on the self-mixing interference signal and extracts multiple frequencies from the spectrum, such as the full spectrum or at least a fundamental portion of the spectrum, which indicate multiple distances from the laser source along the patterned laser beam and / or multiple velocities relative to the laser source along the patterned laser beam. In conventional SMI laser sensors, only the peak frequencies in the SMI signal are used to obtain position and / or velocity information from the SMI signal. By utilizing spectral analysis of the SMI signal, more, and particularly more accurate, information can be obtained from the SMI signal. Spectral analysis of the SMI signal can be performed in the frequency domain or the time domain. For example, after performing a Fast Fourier Transform (FFT) on the SMI signal, information from multiple, or even all, bins can be used according to the invention.

[0018] Instead of obtaining a velocity and / or a distance as in the case of a conventional SMI sensor, it is possible to obtain the entire information spectrum of multiple distances and velocities that can be analyzed simultaneously according to the present invention.

[0019] The laser sensor according to the invention is particularly, but not exclusively, suitable for eye gaze angle detection. An additional camera is no longer required. The laser sensor according to the invention is also particularly, but not exclusively, suitable for velocity distribution detection in flowing fluids, or object tilt detection. The invention provides a very cost- and power-efficient solution that introduces a space-saving solution compared to conventional systems using arrays of numerous traditional SMI sensors.

[0020] The laser source of the laser sensor can be a laser diode, particularly a VCSEL. The detector can be configured as a photodiode integrated into the VCSEL, for example, as an in-cavity photodiode or an external photodiode.

[0021] Preferred embodiments of the invention are defined in other aspects of the invention and as further indicated herein.

[0022] In one embodiment, the laser sensor includes an electrical driver configured to provide a drive current to the laser source to cause the laser source to emit a laser beam, wherein the electrical driver may be configured to provide a modulated drive current to the laser source to cause the laser beam emitted by the laser source to have a periodically varying wavelength.

[0023] Periodically varying wavelengths affect the self-mixing interference signal. If the object being inspected is stationary, a modulated laser beam with periodically varying wavelengths is used to improve detection accuracy at multiple locations. In the case of a moving object, the triangularly modulated laser beam generates different frequencies for the rising and falling edges of the SMI signal. The average of the two frequencies is an indicator of the object distance, while the difference is related to the dual Doppler frequencies of the SMI signal.

[0024] The pattern of the patterned laser beam projected onto the object can be selected from a free combination of continuous line patterns, dotted line patterns, and multi-line patterns. For example, the patterned laser beam can be a straight line, a curve, or a strip, including closed lines such as circles, ellipses, rectangles, grids, and crosses.

[0025] In a further embodiment, the optics are also configured to focus a patterned laser beam onto the object. Focusing the patterned laser beam onto the object advantageously increases the SMI signal strength, or in other words, increases the signal-to-noise ratio (SNR). Preferably, an optimal focus position is obtained by matching the location of the object's surface as well as possible to obtain the best SMI signal. The optics can be adapted to project the laser beam such that the focus position is optimized at the surface of the object. This is particularly advantageous if the object has a non-planar surface.

[0026] The optical device can be selected from a single cylindrical lens, two or more intersecting cylindrical lenses, cylindrical lenses with cylindrical surfaces and different cylindrical axis orientations, freeform surface optical devices, meta optics, diffraction elements, such as one or more optical gratings, holographic optical devices, and a group of mirrors. The mirror can be a spherical, cylindrical, or freeform surface mirror, wherein the mirror can be partially reflective.

[0027] Depending on the object to be inspected, the optical devices can be selected accordingly, particularly optimizing the best focusing position along the patterned laser beam.

[0028] According to a second aspect, a system is provided for detecting at least one of the position or velocity of an object, the system comprising a laser sensor according to the first aspect. Because the system includes the laser sensor according to the invention, the system can measure multiple positions and / or velocities using a single laser sensor.

[0029] The system may also include at least a second laser sensor, which includes a second laser source configured to emit a second laser beam and a second optical device configured to project the second laser beam as a one-dimensional or two-dimensional patterned laser beam onto the object, wherein the patterned laser beam intersects the second patterned laser beam on the object at a non-zero angle.

[0030] The non-zero angle can be 90°, an obtuse angle, or an acute angle. If the object can move in different directions, it is advantageous to use two patterned laser beams projected onto the object.

[0031] The object to be examined can be the human eye, and the system can be configured to detect the eye's gaze angle.

[0032] The eye's gaze angle can be detected by analyzing the spectral gaps in the spectrum of the SMI signal that indicate the pupil's position, since the patterned laser beam, or a portion thereof, is primarily reflected at the pupil position onto the retina at a distance greater than the anterior surfaces of the eye (iris and sclera). Systems for eye gaze angle detection can be configured to project multiple patterned laser beams onto the eye in a time-division multiplexing manner.

[0033] The system according to the invention can also be configured to detect the tilt angle of an object. The detection of object tilt can be used in any application, such as for quality control of products in a production line. Tilt detection can also be used to detect the eye's gaze angle, since iris tilt is a measure of eye gaze angle.

[0034] The system can also be configured to detect the velocity distribution of a flowing fluid. This is one embodiment of analyzing the spectrum of the SMI signal to extract multiple velocities along the patterned laser beam relative to the laser source. For example, particles in the fluid can reflect the patterned laser beam, thereby generating a measurable SMI signal. Thus, it is preferable to have only the SMI signal from the focused position of the patterned laser beam, making it preferable to have a relatively large numerical aperture on the fluid side for optimal positional discrimination.

[0035] According to a third aspect, a method is provided, the method comprising:

[0036] A laser beam is emitted from a laser source.

[0037] The laser beam is projected onto the object to be inspected as a one-dimensional or two-dimensional patterned laser beam, such that the distance of the patterned laser beam from the laser source varies along the patterned laser beam projected onto the object.

[0038] Determine the self-mixing interference signal generated by the laser beam of the patterned laser beam reflected back from the object to the laser source.

[0039] Spectral analysis is performed on the self-mixing interference signal, and multiple frequencies are extracted from the spectrum of the self-mixing interference signal, the multiple frequencies indicating multiple distances from the laser source along the patterned laser beam and / or multiple velocities along the patterned laser beam relative to the laser source.

[0040] According to a fourth aspect, a computer program product includes program code that, when executed on a processor of a laser sensor or a processor of a system, causes a laser sensor according to the first aspect or a system according to the second aspect to perform the steps of the method according to the third aspect.

[0041] It should be understood that the claimed systems, methods and computer programs have preferred embodiments similar to and / or identical to the claimed laser sensor, particularly as defined in the dependent claims and as disclosed herein.

[0042] It should also be understood that the preferred embodiments of the present invention can be any combination of dependent claims and corresponding independent claims.

[0043] Further advantageous embodiments are defined below. Attached Figure Description

[0044] These and other aspects of the invention will become apparent from the embodiments described below and will be illustrated with reference to the embodiments described below. In the following figures:

[0045] Figure 1 A schematic diagram of a laser sensor is shown;

[0046] Figure 2 a) and b) show examples of patterned laser beams projected onto an object;

[0047] Figure 3 A schematic diagram of a laser sensor that emits a patterned laser beam projected onto an object with a non-planar surface is shown.

[0048] Figure 4 It shows the use of Figure 1 An example of the optical components of a laser sensor;

[0049] Figure 5 A schematic front view is shown, showing two orthogonal patterned linear bundles falling at an angle onto the human eye;

[0050] Figure 6 A side view of one of the patterned linear bundles falling on the eye is shown;

[0051] Figure 7 It shows the result of, as Figure 6 A schematic diagram of the spectrum produced by the projected patterned linear beam;

[0052] Figure 8 The FFT spectrum is shown as a function of relative rotation angle in an artificial eye experiment;

[0053] Figure 9 The reconstructed eye gaze angle used in experiments on an artificial eye is shown;

[0054] Figure 10 It shows something similar to Figure 6 A schematic diagram, in which a tilted cylindrical lens serves as the optical component of a laser sensor;

[0055] Figure 11 It shows Figure 10 The distance from the eye to the laser sensor varies Figure 10 A curve showing how the angle α changes for both the eye's focusing position and its anterior position;

[0056] Figure 12 Eyeglasses with an integrated laser sensor are shown;

[0057] Figure 13 A frontal view of a human eye is shown, with four laser sensors, representing a patterned laser beam projected onto the surface of the eye.

[0058] Figure 14 a) and b) show that, according to Figure 13 The spectrum of measurements taken from two sensing regions on the surface of the eye during rotational positions, wherein, Figure 14 a) shows the corresponding spectrum of the first sensing region, while Figure 14 b) shows the spectrum of another sensing region;

[0059] Figure 15 The laser beams of four laser sensors are shown, which are projected onto the surface of the eye as two-dimensional patterned laser beams after the eye rotates.

[0060] Figure 16 a) and b) show that, according to Figure 15 The measurement spectrum of two sensing regions on the surface of the eye in the rotational position, wherein, Figure 16 a) shows the spectrum of the first sensing region, while Figure 16 b) shows the spectrum of another sensing region;

[0061] Figure 17 A laser sensor used to measure the tilt of an object is shown;

[0062] Figure 18 A laser sensor for detecting velocity distribution in a fluid is shown;

[0063] Figure 19 Another embodiment of a system for detecting eye gaze angle is shown;

[0064] Figure 20 The modified patterned laser beam projected onto the eye is shown; and

[0065] Figure 21 Another modification of the patterned laser beam projected onto the eye is shown. Detailed Implementation

[0066] Before referring to the accompanying drawings, let's first explain the principle of self-mixing interference and the basic principle of laser sensors.

[0067] Lasers, such as laser diodes and vertical-cavity surface-emitting lasers (VCSELs), operate on the principle of optical resonators. Inside the resonator, electrons are excited by an external energy input. Spontaneously emitted radiation is reflected back and forth within the optical resonator, generating stimulated emission, which amplifies the resonant modes and produces coherent radiation. On one side of the laser cavity, the laser radiation can be coupled into free space through a semi-transparent mirror. In the case of a VCSEL, the mirror structure is implemented as a distributed Bragg reflector (DBR). A photodiode can be placed within the VCSEL, either integrated into the laser cavity or placed externally. Thus, a VCSEL with an integrated photodiode, abbreviated as ViP, is formed.

[0068] The fundamental physical effects of laser self-mixing will now be explained. A laser beam emitted by a laser can be reflected at an object. As used herein, “reflection” is understood not only as specular reflection but also as diffuse reflection, also known as scattering. If the externally reflected laser radiation couples back into the laser cavity, stimulated emission within the cavity will be modulated based on the phase of the backscattered photons. If twice (round trip) the distance between the laser cavity and the external scattering surface is an integer multiple of the laser wavelength, the scattered and emitted radiation within the laser resonator are in phase. This results in positive interference, thereby lowering the laser threshold and slightly increasing the laser output, which can be sensed by a photodiode integrated into the laser. With a slightly increased distance, the two emitted waves are out of phase and, at some point, negative interference occurs, thus reducing the laser output power. If the distance to the scattering surface of the object changes at a constant rate, the laser output power oscillates between a maximum value during constructive interference and a minimum value during destructive interference. The resulting oscillation is a function of the velocity of the scatterer (object) and the laser wavelength.

[0069] The same effect, i.e., oscillating laser output power, can be observed if the distance between the laser cavity and the scattering surface remains constant, but the laser wavelength changes. Laser wavelength variation can be achieved by modulating the external energy used to drive the laser, such as the drive current. Now, the radiation phase between the inner cavity within the laser and the outer cavity between the laser and the scatterer depends on how many wavelengths are "fit" in the outer cavity. However, the oscillation frequency of the output power depends on the distance between the laser and the scattering surface. Because the laser wavelength is typically in the near-infrared region, for example, around 850 nm, while the outer cavity distance is within a few centimeters, a small change in the laser wavelength can cause a complete phase shift in the outer cavity laser. The greater the distance between the laser and the scattering surface, the smaller the wavelength change required for a complete phase shift in the outer cavity laser. When evaluating laser output power variation, the greater the distance from the scatterer, the higher the frequency of power variation under a constant laser wavelength change. Therefore, mapping the power monitoring photodiode into the frequency domain, the peak frequency is related to the distance between the laser and the scatterer. Laser wavelength variation can be introduced by power modulation of the laser diode. For example, the drive current can be linearly modulated based on the triangular laser current.

[0070] If these two effects are superimposed—that is, the laser wavelength is modulated and the scatterer moves—a beat frequency, as known from frequency-modulated continuous-wave radar systems, will occur. Due to the Doppler frequency shift, the beat frequency generated by a target moving towards the laser sensor is lower during the frequency ramp (according to wavelength modulation) and higher during the frequency descent. Therefore, the beat frequencies for the ramp and descent modulation segments must be calculated separately. The average of the two frequencies is an indicator of the object distance, while the difference is related to the dual Doppler frequencies.

[0071] Next, refer to Figure 1 This will describe the laser sensor. Figure 1 A schematic diagram of a laser sensor 10 is shown. The laser sensor 10 includes a laser source 12 and a detector 14. The detector 14 may be integrated with the laser source 12. More specifically, the detector 14 may be a photodiode integrated into a layered structure of the laser source 12, wherein the photodiode may be integrated as an in-cavity photodiode or an out-of-cavity photodiode. The laser sensor 10 may also include an electrical driver 16 and a controller 18. The controller 18 is connected to the laser source 12, which includes the photodetector 14. The electrical driver 16 provides power to the laser source 12 to cause the laser source 12 to emit a laser beam 22, indicated by dashed lines. The laser source 12 may be or include a vertical-cavity surface-emitting laser (VCSEL), i.e., ViP, with an integrated photodiode. The electrical driver 16 may be configured to provide a constant drive current or a modulated drive current to the laser source 12. In the case where the electrical driver 16 provides a modulated drive current to the laser source 12, the modulated drive current may follow a triangular shape. The controller 18 is also configured to receive an electrical signal provided by the detector 14, which is caused by the self-mixing interference (SMI) of the laser re-entering the laser cavity and the laser generated in the laser cavity.

[0072] The laser sensor 10 also includes an optics device 20. The optics device 20 is configured to project the laser beam 22 as a one-dimensional or two-dimensional patterned laser beam onto the object 24 to be inspected. The object 24 is... Figure 1 The image is shown in dashed lines, which resemble the reflective (scattering) surface of object 24.

[0073] Optical device 20 is configured to project a laser beam as a one-dimensional or two-dimensional patterned laser beam 26 onto the object 24 to be inspected, such that the distance D of the patterned laser beam 26 from the laser source 12 varies along the patterned laser beam 26 projected onto the object 24. Figure 1 The example shows three distances D1, D2, and D3, where D2 and D3 are greater than D1. Figure 2 An example of a patterned laser beam 26 is shown in a). Figure 2 The patterned laser beam 26 in a) is a linear beam, serving as an example of a patterned laser beam projected in one dimension. Figure 2 b) illustrates a cross-beam as an example of a patterned laser beam projected in two dimensions. Typically, the pattern of the projected patterned laser beam can be chosen freely as follows: Figure 2 a) A group consisting of continuous line patterns, lines including discrete points, grids of continuous lines, or dotted line patterns. For example... Figure 2The pattern shown as the cross-beam 26' can be achieved using two laser sources 12 and corresponding optical devices 20, wherein the latter may include two cross cylindrical lenses, one cylindrical lens for each laser source, or a microlens array, wherein the two sub-lens sets are orthogonal to each other.

[0074] The optics can also be configured to focus the patterned laser beam 26 onto the object 25. The patterned laser beam 26 can be focused only in the first dimension, for example... Figure 2 The y-dimensional dimension in a). Figure 2 The cross bundle 26' in b) can be focused in each of the short dimensions of the two cross bundles.

[0075] Optical device 20 may also be configured to extend the laser beam 22 emitted by laser source 12 in one or two dimensions. For example, Figure 1 The patterned laser beam 26 in the image may have been extended by the optical device 20 to extend the long dimension of the patterned laser beam 26. However, the long dimension of the patterned laser beam 26 can also be achieved by the divergence of the laser beam 22 emitted by the laser source 12 without any additional extension in the long dimension, for example, if the object is sufficiently far from the laser source.

[0076] In addition, such as Figure 3 and 6 As shown, the optical device 22 can be arranged to project the laser beam 22 obliquely onto the object 24. As... Figure 3 As shown, object 24 can also have a non-planar surface. Through the oblique projection of the laser beam 22, even for a planar object surface, the variation of the distance D between the patterned laser beam 26 and the laser source 12 along the patterned laser beam 26 is greater than... Figure 1 The symmetrical transmission shown is stronger.

[0077] Optical device 22 may include one or more optical elements. Figure 4 An example of an optical device 22 is shown, wherein the optical device includes a cylindrical lens 28. Typically, the optical device 22 can be selected from a group consisting of a single cylindrical lens, two or more intersecting cylindrical lenses, cylindrical lenses having cylindrical surfaces with different cylindrical axis orientations, freeform surface optics, super-optics, one or more optical gratings, holographic optics, and mirrors. For example, when using two laser sources, intersecting cylindrical lenses can be used to achieve the following: Figure 2 b) The laser beam 22 is projected and focused in the form of the cross-line shape shown, or the line length is adjusted independently of the line width.

[0078] Return to reference Figure 1The detector 14 is configured to determine a self-mixing interference signal generated by the laser beam 26 of the patterned laser beam 26 reflected back to the laser source 14 by the object 24. The laser sensor 10 also includes a plurality of frequencies, as described herein, that are configured to perform spectral analysis on the self-mixing interference signal and extract from the spectrum of the self-mixing interference signal multiple distances (e.g., distances D1, D2, D3) along the patterned laser beam 26 from the laser source and multiple velocities along the patterned laser beam 26 relative to the laser source 12.

[0079] The aforementioned functions of this circuit can be performed by the controller 18 of the laser sensor 10.

[0080] refer to Figures 5 to 9 An embodiment of a laser sensor for eye gaze angle detection will be described.

[0081] Figure 5 A schematic front view of a human eye E is shown. P represents the pupil of eye E, I represents the iris of the eye, and S represents the sclera of eye E. The first laser sensor 101 emits light from a source similar to... Figure 1 and 4 The optical element 20 in the laser sensor 101 projects a laser beam 221, which is a linear laser beam 261, onto the surface of the eye E. The second laser sensor 102 emits a second laser beam 222, which is also projected onto the surface of the eye E by the optical element 262. The patterned laser beam 262 can be orthogonal to the patterned laser beam 261. The optical elements used to project the laser beams 221 and 222 onto the eye E can be cylindrical lenses, namely a cylindrical lens of the laser sensor 101 and a cylindrical lens of the laser sensor 102. Figure 6 A side view of eye E is shown, in which only the laser beam 221 emitted by laser sensor 101 and the patterned (linear) projected laser beam 261 are shown.

[0082] like Figure 6 As shown, in the region of the pupil P, a laser beam 221 is projected obliquely onto the eye E. The patterned laser beam 261 has an extension along its long dimension preferably larger than the pupil diameter.

[0083] Laser beams 221 and 222 are emitted as modulated laser beams, wherein the laser sources of laser sensors 101 and 102 are provided with modulation drive currents. In this embodiment, triangular modulation is used. Due to the change in wavelength, the phase of the laser reflected from the eye E will change, thereby producing a fixed frequency for a fixed distance. However, as... Figure 6 As shown, when the laser beam 261 is projected onto the eye E, multiple different frequencies will be detected in the self-mixed interference signal because the distance between the projected patterned laser beam 261 and the laser source 101 varies along the projected patterned laser beam 261.

[0084] Therefore, the laser generated by the patterned laser beam 261 of the laser source 12 reflected back to the laser sensor 101 by the eye E, and detected by the detector 14 ( Figure 1 The determined SMI signal includes multiple frequencies corresponding to multiple distances along the patterned laser beam 261 from the laser source 12 of the laser sensor 101.

[0085] The same distance change is measured by the second laser sensor 102 along the patterned laser beam 262 on the surface of the eye E, thereby measuring multiple frequencies.

[0086] When a portion of the patterned laser beam 261 enters the pupil P, the laser travels further to the retina R. Since the distance of the retina R from the laser source 12 of the laser sensor 101 is greater than the distances of the iris I and sclera S from the laser source 12 of the laser sensor 101, a gap is expected in the SMI spectrum. The location of this frequency gap is an absolute measure of the position of the pupil P. This will be referenced... Figure 7 and 8 To explain. Figure 7 It shows the result of Figure 6 The spectrum of the SMI signal generated by the patterned laser beam 261 projected in the image. Figure 7 The horizontal axis of the chart shows the SMI signal frequency. As mentioned above, the SMI signal frequency can be converted to distance. Figure 7 The vertical axis in the diagram illustrates the power or occurrence of the SMI signal in relation to its frequency. Low-frequency SMI signals belong to low-range regions, corresponding to the bottom portion B of the projected patterned laser beam 261. Figure 6 At the pupil position, corresponding to the large distance / frequency, the patterned laser beam 261 is reflected at the retina. The intermediate frequency corresponds to the upper portion U of the patterned laser beam 261. A gap exists between the low frequency corresponding to the bottom portion B and the intermediate frequency corresponding to the upper portion U, said gap corresponding to the position of the pupil P. Therefore, the teachings of the present invention can be used to accurately measure the pupil position.

[0087] If the eye E moves, i.e. rotates, thus shifting the fixation angle, then the gap position in the spectrum ( Figure 7 The value of P changes due to variations in the "missing" distance from the pupil position. Then, by averaging the gap positions in the spectrum on the rising and falling edges of the triangular wavelength modulation of the laser beam 221, the correct and accurate pupil position can be obtained.

[0088] To verify the above, experiments were conducted using an artificial eye. The artificial eye was a 3D-printed sphere with an aperture representing the pupil. A laser beam was projected onto the artificial eye as a linearly patterned laser beam using a cylindrical lens with f=20mm imaging and 2f-2f imaging. Trigonometric modulation from an external function generator was performed at a modulation frequency of 8kHz and a modulation laser current amplitude of 0.51mApp. The average laser power was 0.5mW.

[0089] Figure 8 The results of this experiment are shown. The artificial eye in... Figure 6 The diagram shows a clockwise rotation. As the pupil P passes through the projected patterned laser beam, the low-frequency ranges disappear first, and the high-frequency ranges disappear last as the artificial eye rotates further. All frequencies become visible again after the pupil P passes through the patterned laser beam. Figure 8 The FFT spectrum is shown as a function of the relative rotation angle of the artificial eye. At approximately 30 degrees, the pupil P passes through the projected laser beam, causing a decrease in power at these frequencies. Figure 8 (bin 20 in the image). The signal line at bin 14 of the FFT is an artifact caused by the reflection of some dirt on the front surface of the cylindrical lens.

[0090] This experiment demonstrates that by performing spectral analysis on the SMI signal within the angular range of a portion of the laser beam falling into the pupil, the eye's orientation or fixation angle can be reconstructed from the measured SMI signal. This reconstruction can be performed using a feedforward neural network, where the result is as follows... Figure 9 As shown. Figure 9 The reconstructed eye fixation angle from the experiment on the artificial eye is shown, illustrating how the eye angle changes over time. Line 41 represents the true value of the eye fixation angle, and curve 43 represents the eye fixation angle measurement based on SMI. Figure 9 This demonstrates that the eye's gaze angle can be correctly reconstructed within a range of unique spectral characteristics, meaning a maximum of two seconds. After two seconds, the artificial eye's pupil P rotates away from the projected linear laser beam, and the pupil position can no longer be directly reconstructed from the measured spectrum. Figure 9 As can be seen, the actual eye-tracking angle is limited to approximately + / - 20 degrees. However, Doppler velocity signals will still be present. The integral of these velocity signals can be used to derive the eye position at a larger eye-gazing angle.

[0091] In the above experiment, the spectra were obtained at 8 kHz. Sixteen spectra were analyzed for reconstruction. Figure 9 The curve in the image was filtered using another 9-point median filter. This resulted in an update rate of 18 ms, or 56 Hz.

[0092] In an improvement to the previously described embodiment, the optics 20 for projecting the laser beam 22 as a patterned laser beam onto the eye E can be optimized for a better focusing position of the patterned laser beam 26 on the eye E. In the above experiment, this focusing position was on a line 40 mm away from the laser source 12 of the laser sensor 10. Ideally, an optimal focusing position should be found that matches the position of the anterior surface of the eye as closely as possible to obtain the best SMI signal; that is, the projected patterned laser beam 26 should be focused as close as possible to the curved beam projected onto the eye.

[0093] Figure 10 The distance between the anterior position of eye E and the laser source 12 of laser sensor 10 is shown. α is the angle of the laser beam along the patterned linear beam 26 relative to the horizontal axis H. The larger the angle α, the greater the distance from the anterior part of eye E to the laser source 12. This is achieved by using a cylindrical lens 30 with f = 5 mm (e.g., ...). Figure 1 The optical component 20 is placed at a 30° tilt position, which can achieve a similar effect at the focusing position, wherein, for the central beam, the distance from the laser source to the lens 30 is 6.3 mm. Therefore, as... Figure 10 As shown, using a tilted cylindrical lens 30 allows for better matching of the focusing position to the eye position. Figure 11 The distance from the focal position to the laser source is shown as the focal position and the anterior position of the eye vary with angle α.

[0094] This is just one example of how SMI signals can be optimized through better focusing. Further optimization can be achieved by using, for example, freeform surface optics. In this way, the Gaussian intensity distribution of the projected patterned laser beam can also be transformed into a more uniform pattern.

[0095] Crossed cylindrical lenses at varying distances from the laser source and with different magnifications (optionally different focal lengths) can also be used to produce elongated focusing. This allows for optimization of the amount of laser light collected back to the laser source. This can also be an optical element in which two crossed cylindrical lenses are distributed on two surfaces. Alternatives for producing appropriate beam focal points, made of optical materials such as glass or polymers, include grating structures such as imprinted surface gratings, holographic optical elements such as photopolymer holographic layers, or superlenses. These types of structures can also be used to create, for example, dotted lines instead of continuous lines. Other shapes as lines can also be considered.

[0096] Figure 12 A system 100 utilizing the teachings of this disclosure is illustrated according to one embodiment. The system 100 is configured to detect eye gaze (…). Figure 12(Not shown in the image). System 100 is configured as eyeglasses 102, which includes a frame with a frame support 104 and lenses 106. System 100 includes laser sensors 101, 102, 103, and 104 arranged on the frame 104. It should be noted that laser sensors 101 to 104 are arranged on the inner side of the frame 104 facing the eye of the user wearing the eyeglasses. Each of laser sensors 101 to 104 can be referenced as above. Figure 1 The configuration is as described. The number of laser sensors can be less than four, with two laser sensors, such as laser sensors 101 and 102, being sufficient for eye fixation angle detection. An additional laser sensor 105 can be arranged on the frame support 104 to measure extreme eye rotations. Some or all of the laser sensors 101 to 105 can also be integrated into one or both of the lenses 106 of the eyeglasses or into the nose pads. In another possible embodiment, the laser sensors 101 to 104 can be arranged in the frame support, but a laser beam can be emitted towards the lens 106, wherein holographic optics embedded in the lens can deflect the laser beam toward the eye. In another embodiment, for example, two sensors per eye can be used to simultaneously track the left and right eyes.

[0097] System 100 can operate in different modes. In a first mode, the laser sources of laser sensors 101 to 104 can operate as a continuous wave (constant frequency). In a second mode, the frequency of the laser sources can be modulated in real time, for example, following the triangular modulation pattern described above.

[0098] refer to Figures 13 to 16 The description will be relative to the reference. Figures 5 to 9 An embodiment of a system for eye gaze angle detection modified from the above-described embodiments.

[0099] Figure 13 Similar to Figure 5 The image shows a front view of the human eye E. Figure 13Four projected patterned laser beams 261, 262, 263, and 264 emitted by laser sensors 101, 102, 103, and 104 are shown. The projected patterned laser beams 261 to 264 can be formed by optics similar to optics 20, such as cylindrical lenses or holographic optical elements, to fit the desired shape of the sensing area on the eye E. Each of the projected patterned laser beams 261, 262, 263, and 264 forms a corresponding sensing area. In this example, four laser sensors, such as ViP sensors, are used in conjunction with cylindrical lenses to form the respective sensing areas. The projected patterned laser beams 261 to 264 are stripes arranged in a two-dimensional pattern, for example, forming intersections. However, it should be understood that other possible patterns of the projected laser beams are also conceivable, such as circles, rectangles, grids, etc. Furthermore, adding more laser sensors increases the sensing surface size, thereby increasing the field of view that can be covered. Fewer laser sensors can be used to reduce overall power consumption. Due to the high temporal resolution of the sensor principle, time-division multiplexing can be used to reduce the power consumption of necessary electronic devices and the light power on the surface of the eye to meet eye safety considerations.

[0100] As described above, laser sensors 101 to 104 measure the distance and velocity relative to the eye surface in the corresponding sensing areas corresponding to patterned laser beams 261 to 264. Furthermore, the signal-to-noise ratio (SNR) can be determined from the measured data to obtain information about the parts of the eye (sclera S, iris I, pupil P) currently being illuminated by the correspondingly projected patterned laser beams 261 to 264.

[0101] Figure 14 a) and 14b) show, in a simplified manner, the work of Figure 12 The two laser sensors 104 and 102 in the middle are for example Figure 13 The spectrum of the eye position measurement is shown. Y-axis 40 shows the signal amplitude in relation to the frequency on x-axis 42. Figure 14 a) shows the spectrum in the sensing region of the projected patterned laser beam 264. Figure 14 b) shows the spectrum in the sensing region of the projected patterned laser beam 262. Because Figure 13 The eye is centered relative to the four sensing regions 261 to 264, so the amplitude distributions in the two SMI spectra are similar, indicating similar distance patterns.

[0102] like Figure 15 As shown, if the eye E rotates toward the sensing area corresponding to the projected patterned laser beam 262, the Fourier spectrum of the SMI signal changes. The corresponding amplitude distribution (Fourier spectrum) changes accordingly due to the rotation of the eye E. Figure 16a) and 16b) show the amplitude distribution of the changes in the Fourier spectra in the two sensing regions 264 and 262 after eye rotation. The spectrum can be interpreted as a depth probability distribution. If the sensor region covers only a single spot on a flat surface, the spectrum contains only a single peak at a frequency representing the optical path length between the laser sensor and the flat surface. If the laser spot is broadened, as in the case of the projected patterned laser beams 261 to 264, and aimed at a stepped surface at two different distances, the spectrum will be represented by two peaks representing the two distance levels. The amplitude relationship of the two peaks will represent the integral power relationship between the two surface regions, depending on the power distribution with respect to the two surfaces. The laser sensor covering sensing region 262 measures the higher portions of the iris and pupil regions of the eye E. As a large number of photons enter the eye E through the pupil and reach the retina, SMI data related to the increased optical path length entering the eye is generated, which causes an increase in the amplitude of higher frequencies related to the retinal distance. On the other hand, since photons are scattered by closer surface parts of the eye, such as the sclera and iris, the amplitude at high frequencies related to the retinal distance measured by the laser sensor in sensing area 264 is reduced.

[0103] To calculate pupil position and gaze direction, the differences between laser sensor signals obtained from different sensing areas can be used. Additional SMI information acquired from the laser sensor, such as SNR or velocity, can be used to improve system accuracy. Based on the time series of measurements, additional features such as pupil size can be extracted from the laser sensor signals. Using this information, further improvements in pupil position estimation accuracy can be achieved. Other features that can be used to improve system accuracy are the full width at half maximum (FWHM) or amplitude of the spectral data, or information from the time-domain signal (e.g., threshold, time difference, etc.).

[0104] In eye fixation angle detection, eyelashes may (partially) block the projected patterned laser beam, potentially degrading signal quality. Because eyelashes provide signals from closer distances, these low-frequency spurious signals appearing in the spectrum can be discarded from the real signal from the eye when examining the spectrum.

[0105] Reference Figure 19 Describe an alternative solution for eyelash problems.

[0106] Figure 19 A system for detecting eye gaze angle is shown, the system including laser sensors 101 and 102. Laser sensor 101 includes a laser source 121, which may be a VCSEL with an integrated photodiode (ViP). Laser source 121 emits two (or more) laser beams 22. 11 and 22 12When laser source 121 includes a ViP, the ViP may include two (or more) laser emitting regions, such as two (or more) platforms. Laser beam 22 11 and 22 12 Preferably, the laser beam 22 is transmitted in a time-division multiplexing manner. The optical device 201 transmits the laser beam 22. 11 and 22 12 As a patterned laser beam 24 11 The patterned laser beams 24 and 2412 are projected onto eye E as two linear beams, as shown in the diagram on the right. 11 and 24 12 The image is projected onto the surface of the eye E at a slightly offset position. As described above, the optical device 201 can be a single optical element, such as a cylindrical lens. A controller 18 (e.g., an ASIC) including a preprocessing algorithm receives an electrical signal provided by a detector integrated into the laser source 121, the electrical signal being caused by the self-mixing interference of laser light re-entering the laser cavity of the laser source 121. Preprocessing the electrical signal in controller 18a1 includes extracting velocity distribution information Vel and distance distribution information Dis from the spectrum, wherein the velocity and distance distribution information are output to controller 18b, which includes a post-processing algorithm (e.g., analysis / neural network) and outputs the eye gaze angle “ega” measured in the horizontal direction. The laser sensor 102 can have the same configuration as the laser sensor 101, except that the laser beam 22 emitted by the laser source 122 is... 21 and 22 22 Optical device 202 serves as the patterned laser beam 24 21 and 24 22 The image is projected onto the eye E to measure the eye fixation angle in the vertical direction. Again, velocity distribution information Vel and distance distribution information Dis are output from the laser sensor 102 to the controller 18b, so that by combining the velocity and distance distribution information from the laser source 101, the 2D eye fixation angle of the eye E can be accurately measured.

[0107] refer to Figure 19 The described embodiment adds a projected laser beam 24 11 and 24 12 One of the laser beams has a chance to hit eye E without being blocked by eye E's eyelashes (partially). For two projected laser beams 24 21 and 24 22 The same applies. This results in improved accuracy for eye fixation angle detection.

[0108] As referenced above Figure 12 The laser sensors 101 and 102 can be integrated into the glasses.

[0109] Further modifications to the previous embodiments may use multiple projected patterned laser beams, such as Figure 20 As shown. Figure 20 A patterned laser beam 24 projected onto the eye E is shown. 11 ,twenty four 12 ,twenty four 13 and 24 21 ,twenty four 22 and 24 23 Using multiple projected laser beams, such as those with a grid pattern as shown, is not only beneficial in the case of eyelashes, but it can also be used to cover a larger area on the eye E, giving more opportunities to see the pupil position within one of the laser beam lines. As described above, additional methods can be used... Figure 20 Patterned laser beams of shapes other than the straight lines shown.

[0110] exist Figure 20 In one embodiment, time-division multiplexing can also be used to determine which laser beamline the signal originates from, even when using only a laser source with multiple laser emission regions and a photodiode.

[0111] Projection Figure 19 and Figure 20 Another advantage of the patterned laser beam shown is that it significantly reduces the visibility of the laser, because the irradiance on the retina (W / m²) is much lower compared to systems that project a dotted spot of light onto the eye. 2 The visibility of a laser beam is reduced. It's important to note that the human eye can even see lasers with wavelengths ranging from 750 to 950 nm. Therefore, a laser beam projected onto the eye can be disruptive. Furthermore, experiments have shown that horizontal laser beams are more visible to the user than vertical ones. Therefore, to reduce the visibility of a single laser beam or multiple laser beams, it is beneficial to project them onto the eye (E) in a diagonal pattern, such as... Figure 21 The two laser beamlines 241 and 242 are shown in the diagram. In another example, Figure 20 The laser beam pattern can also be rotated 45°.

[0112] Including those utilizing the principles of this disclosure Figure 1 The laser sensor system of laser sensor 10 can also be configured for tilt detection, i.e., for detecting or measuring the tilt of an object, such as... Figure 17As shown, for an object 60 tilted relative to a reference, such as the vertical axis 62, tilt detection is achieved by a laser sensor 10 by projecting a laser beam 22 as a one-dimensional or two-dimensional patterned laser beam 26 onto the object 60, such that the distance of the patterned laser beam 26 from the laser source of the laser sensor 10 varies along the patterned laser beam 26 projected onto the object 60, and spectral analysis is performed on the SMI signal to extract multiple frequencies indicating multiple distances from the laser source along the patterned laser beam from the laser source. The laser beam 22 can be wavelength modulated as described above, for example, triangulation of the laser beam 22 can be used. When the object 60 is not tilted, the spectral width of the frequencies after the FFT is minimal. When the object is tilted, spectral broadening occurs, wherein the broadening increases with increasing tilt.

[0113] Tilt detection can also be used for eye fixation tracking. This is because the iris is a relatively flat part of the eye. Therefore, when the eye rotates away from its central position, a corresponding tilt of the iris can be observed in the SMI signal. Thus, iris tilt is a measure of the eye fixation angle. Information about the signs of tilt can be obtained from the observed Doppler frequencies.

[0114] Tilt detection and eye gaze tracking can be performed by extracting features, such as the width, from the spectrum of the SMI signal, or by fitting a function to the spectrum (template matching), or by using a neural network.

[0115] One embodiment of an algorithm for tilt / eye gaze angle detection may include the following stages:

[0116] 1) Record the time-domain SMI signal, preferably using laser beam modulation.

[0117] 2) Use the FFT algorithm to convert the time-domain signal to the frequency domain.

[0118] 3) Extract features from the spectrum (e.g., maximum half-width or transform parameters of template matching algorithms).

[0119] 4) Mapping function from feature vector to tilt angle / eye angle.

[0120] Including similar Figure 1 The laser sensor system of the laser sensor 10 can also be configured to detect the velocity distribution of the flowing fluid. Figure 18A schematic diagram of a system configured to detect the velocity distribution of a flowing fluid 80 is shown. The velocity distribution is indicated by arrow 82, where the length of the arrow indicates the local velocity along a cross-section of the flowing fluid 80. A laser sensor 10 emits a laser beam 22, as a patterned one-dimensional or two-dimensional laser beam as described above, projected into the fluid. Particles typically present in the fluid 80 scatter the laser beam back from the position of the patterned laser beam 26 projected into the fluid 80, causing the laser beam from the position of the projected patterned laser beam 26 to re-enter the laser source. In this embodiment, it is not necessary to modulate the emitted laser beam 22. Preferably, only the SMI signal from the focused position at the position of the projected patterned laser beam 26 is present, such that, for this embodiment, a relatively large numerical aperture is preferably present on the fluid side to achieve optimal position differentiation. The strongest SMI signal will originate from the focused position, which is a different location in the fluid along the patterned laser beam 26. Thus, the velocity distribution in the fluid can be determined.

[0121] Typically, the principles of this disclosure provide a series of velocities and distances, rather than providing a single velocity and distance as in the case of normal SMI. Those skilled in the art will be able to make further applications based on the same SMI measurement principles of patterned laser beams combined with spectral analysis.

[0122] As can be seen from the above description, this disclosure also includes a method for detecting multiple velocities and / or distances, wherein the method includes: emitting a laser beam 22 from a laser source 12; projecting the laser beam 22 as a one-dimensional or two-dimensional patterned laser beam 26 onto an object to be inspected, such that the distance of the patterned laser beam 26 from the laser source 12 varies along the patterned laser beam 26 projected onto the object; determining a self-mixing interference signal generated by the laser light of the patterned laser beam 26 reflected back to the laser source 12 by the object; performing spectral analysis on the self-mixing interference signal; and extracting multiple frequencies from the spectrum of the self-mixing interference signal indicating multiple distances of multiple parts of the object from the laser source 12 and / or multiple velocities of multiple parts of the object relative to the laser source 12.

[0123] The teachings herein also include a computer program product comprising program code for causing a laser sensor, such as laser sensor 10, or a system, such as system 100, to perform the steps of the methods described above when the computer program is executed on a processor of the laser sensor or a processor of the system.

[0124] While the invention has been detailed and described in the accompanying drawings and foregoing description, such description should be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments will be understood and implemented by those skilled in the art in practicing the claimed invention from a study of the drawings, the disclosure, and the appended claims.

[0125] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single element or other unit can perform the function of multiple items listed in the claims. The fact that certain measures are listed merely in mutually different claims does not mean that a combination of these measures cannot be used advantageously.

[0126] Computer programs can be stored / distributed on suitable non-transitory media, such as optical storage media or solid-state media provided together with or as part of other hardware that may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0127] Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A laser sensor, comprising: A laser source (12) configured to emit a laser beam (22). An optical device (20) is configured to project the laser beam (22) as a one-dimensional or two-dimensional patterned laser beam (26) onto the surface of the object to be inspected (24), such that the distance of the patterned laser beam (26) from the laser source (12) varies for different areas of the surface onto which the patterned laser beam (26) is projected. Detector (14), configured to determine the self-mixing interference signal generated by the laser beam (26) of the patterned laser beam (26) reflected from the object (24) back to the laser source (12), and Circuit (18) is configured to perform spectral analysis on a single spectrum of the self-mixing interference signal and extract multiple frequencies from the single spectrum of the self-mixing interference signal, the multiple frequencies indicating at least one of the following: multiple distances of different regions of the surface from the laser source (12), and multiple velocities of different regions of the surface relative to the laser source (12).

2. The laser sensor according to claim 1, wherein, The laser sensor further includes an electric driver (16) configured to provide a driving current to the laser source (12) to cause the laser source (12) to emit a laser beam (22), wherein the electric driver is configured to provide a modulation driving current to the laser source (12) so that the laser beam (22) emitted by the laser source (12) has a periodically changing wavelength.

3. The laser sensor according to claim 1 or 2, wherein, The optical device (20) is configured to project a patterned laser beam (22) onto an object (24), the pattern being selected from a group consisting of continuous line patterns, dotted line patterns, and two-dimensional area patterns.

4. The laser sensor according to any one of claims 1 to 3, wherein, The optical device (20) is also configured to focus the patterned laser beam (26) onto the object.

5. The laser sensor according to any one of claims 1 to 4, wherein, The optical device (20) is selected from the group consisting of: a single cylindrical lens, two or more intersecting cylindrical lenses.

6. The laser sensor according to claim 1 or 2, wherein, The optical device (20) is configured to project a patterned laser beam (22) onto an object (24), the pattern being a multi-line pattern.

7. The laser sensor according to any one of claims 1 to 4, wherein, The optical device (20) is a cylindrical lens with cylindrical surfaces and different cylindrical axis orientations on the cylindrical surfaces.

8. The laser sensor according to any one of claims 1 to 4, wherein, The optical device (20) is selected from the group consisting of: freeform optical devices, super-optical devices, and diffractive optical devices.

9. The laser sensor according to any one of claims 1 to 4, wherein, The optical device (20) is selected from the group consisting of: a total or partial reflection spherical mirror, a cylindrical mirror or a freeform mirror.

10. The laser sensor according to any one of claims 1 to 4, wherein, The optical device (20) is a holographic optical device.

11. A system for detecting at least one of the position or velocity of an object, comprising a laser sensor (10) according to any one of claims 1 to 10.

12. The system according to claim 11, wherein, The system further includes at least a second laser sensor (102), the second laser sensor (102) comprising: a second laser source configured to emit a second laser beam; and a second optical device configured to project the second laser beam as a one-dimensional or two-dimensional patterned laser beam onto an object, wherein the patterned laser beam intersects the second patterned laser beam on the object at a non-zero angle.

13. The system according to claim 11 or 12, wherein, The object (24) is the human eye (E), and the circuit (18) is configured to detect the eye’s gaze angle based on the self-mixing interference signal.

14. The system according to claim 13, wherein, The laser sensor (10) is placed on or integrated into the glasses to be worn in front of the eyes.

15. The system according to claim 13 or 14, wherein, The circuit (18) is configured to determine the eye's gaze angle based on the gap between low and high frequencies in the spectrum of the self-mixed interference signal.

16. The system according to claim 11 or 12, wherein, The system is configured to detect the tilt angle of the object (60) based on the self-mixing interference signal.

17. The system according to claim 16, wherein, The object is the iris of a human eye (E), wherein the circuit is configured to determine the eye's gaze angle based on the detected iris tilt angle.

18. The system according to claim 11 or 12, wherein, The object is a flowing fluid (80), and the circuit is configured to detect the velocity distribution of the flowing fluid based on the self-mixing interference signal.

19. A method for detecting multiple velocities and / or distances, comprising: A laser beam (22) is emitted from a laser source (12). The laser beam (22) is projected as a one-dimensional or two-dimensional patterned laser beam (26) onto the surface of the object to be inspected (24), such that the distance of the patterned laser beam (26) from the laser source (12) varies for different areas of the surface onto which the patterned laser beam is projected. Determine the self-mixing interference signal generated by the patterned laser beam (26) reflected back from the object (24) to the laser source, and Spectral analysis is performed on a single spectrum of the self-mixing interference signal and multiple frequencies are extracted from the single spectrum of the self-mixing interference signal, the multiple frequencies indicating at least one of the following: multiple distances of different regions of the surface from the laser source (12), and multiple velocities of different regions of the surface relative to the laser source (12).

20. A computer program product comprising program code configured to: when executed on a processor of a laser sensor according to any one of claims 1 to 10 or on a processor of a system according to any one of claims 11 to 18, cause the laser sensor or system to perform the steps of the method according to claim 19.

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