Laser Array Unit

Abstract

A light source unit comprising: an array of single-mode vertical cavity surface-emitting lasers (VCSELs) having a selected arrangement; and an array of lenses comprising a plurality of lens units each associated with a respective single-mode VCSEL, the plurality of lenses having selected focal lengths and positioned at selected distances from the plurality of VCSELs to provide a plurality of substantially collimated output beams, the plurality of substantially collimated output beams being non-parallel therebetween.

Description

[Technical Field]

[0001] The present disclosure relates to arrays of Vertical Cavity Surface Emitting Lasers (VCSELs) and devices utilizing such arrays for use in conjunction with driving monitoring systems (DMS). [Background technology]

[0002] A driver monitoring system (DMS) is a vehicle safety system used to analyze and monitor the driver's condition and to warn or take action to reduce the risk of a vehicle collision. A typical DMS utilizes one or more camera units and a control system operable to collect and analyze data regarding the driver's attention, alertness, and possibly other biomedical conditions.

[0003] DMS systems are considered high-level safety systems for road vehicles. Such systems are among the list of safety systems required to provide reliable monitoring of driver attention and awareness. This is particularly important in vehicles that utilize assisted driving functions.

[0004] VCSEL technology is becoming an increasingly popular choice for implementation in automotive production due to the technology's high power, robustness, and cost-effectiveness. Furthermore, the VCSEL structure results in a narrow bandwidth compared to LEDs, providing improved temporal coherence and signal-to-noise ratios when needed. In recent years, driver monitoring systems (DMS) have been developed to provide real-time assessment of driver presence and status. These DMS include camera-based systems aimed at the driver's face to provide warnings to the driver and initiate intervention to manage vehicle control when necessary. This technology helps improve safety on the roads and provides better control over the vehicle.

[0005] Speckle patterns are patterns of bright and dark areas formed within an illuminated area due to the coherence of light. Although speckle is typically considered noise, various techniques are known that utilize speckle analysis for remote monitoring of selected parameters. Laser speckle contrast analysis (LASCA) is a technique that enables monitoring and analysis of blood perfusion and blood flow in tissue based on variations in the contrast of the speckle pattern. This technique allows for the determination of data such as heart rate, heart rate variability, and possibly blood pressure and respiratory rate.

[0006] For example, AFFercher et al., "Flow visualization by means of single-exposure speckle photography," Opt. Commun., 37(5), 326-330 (1981), describe the use of LASCA, in which a photograph of a flow field is taken under laser illumination. If the exposure is sufficiently short, the velocity distribution within the field is mapped onto the photograph as variations in speckle contrast. These contrast variations can be converted to intensity variations by simple spatial filtering techniques, yielding a direct image of the velocity distribution in the flow field. The potential application of this technique to mapping retinal blood flow is discussed.

[0007] P. Vaz et al., "Laser speckle contrast analysis for pulse waveform extraction," in Novel Biophotonics Techniques and Applications III, A. Amelink and I. Vitkin, eds., Vol. 9540 of SPIE Proceedings (Optica Publishing Group, 2015), paper 954007, presents a method for pulse waveform extraction using laser speckle contrast analysis. An experimental setup was assembled using a coherent light source and a digital video camera to record the time-varying speckle pattern emitted from the radial artery. The speckle data were analyzed by calculating the speckle pattern contrast on a sequence of video frames. The speckle pulse wave signal was compared with the photoplethysmography signal in both the time and frequency domains. A total of 30 data sets were acquired from 10 individuals. The subjects' heart rates were identified with a root-mean-square error of 1.3 beats per minute. Signal similarity was assessed using spectral coherence with an overall average coherence of 0.63. Speckle contrast analysis is a newly commercialized technique for monitoring microvascular blood flow. However, these results demonstrate the ability of the same technique to extract pulse waveform information. The inclusion of this feature in current speckle devices would involve only minor modifications of signal processing techniques and video acquisition parameters, but could be very useful in a clinical setting. Summary of the Invention

[0008] Driver monitoring systems are becoming an increasingly important safety element in vehicles. Typical driver monitoring systems often utilize image processing to determine the driver's state and alertness level to improve road safety.

[0009] Monitoring a driver's biomedical and physiological parameters can provide valuable data regarding the driver's condition. Speckle analysis, particularly the laser speckle contrast analysis (LASCA) technique, allows for the remote and non-contact collection of biomedical and physiological parameters such as heart rate, heart rate variability (HRV), respiratory rate, and blood perfusion level.

[0010] Determining such parameters using spackle analysis generally requires coherent illumination, resulting in spackle patterns due to self-interference between light components. The present disclosure provides a light source unit configured to provide an illumination pattern that includes coherent illumination, while being adapted for use in a typical vehicle space and for integration with existing typical driver monitoring systems (DMS).

[0011] To this end, the present disclosure provides a light source unit comprising an array of multiple single-mode vertical-cavity surface-emitting lasers (VCSELs). The multiple VCSEL units are configured in a selected arrangement and associated with selected optical elements that provide a pattern of output beams that are approximately collimated and non-parallel. The divergence angles of the approximately collimated beams and the angular relationships between the beams are selected to provide an illumination pattern in the form of multiple illumination spots at a selected range from the system. In this context, as used herein, the term "approximately collimated" may refer to an output illumination beam having a divergence angle within a selected range of 0.1 to 3 degrees, preferably 0.5 to 2 degrees.

[0012] Generally, such a light source may be installed within a vehicle, and the driver's headbox may be located a selected distance from the location of the light source, and the arrangement of the output beams may be configured to generate a selected pattern of illumination spots that enables the collection of image data, with many well-separated illumination spots falling within the driver's headbox.

[0013] Additionally, the light sources of the present disclosure may also be used in a variety of other environments, for example, incorporated into electronic devices such as laptops, smartphones, display screens, or other devices to provide selected monitoring functions.

[0014] The light source unit may comprise one or more additional arrangements of VCSEL units, typically comprising multi-mode VCSEL units that emit illumination of increased intensity and reduced coherence that can be used for flood illumination and / or illumination patterns that enable depth detection.

[0015] The light source units may be formed on a common substrate forming a single VCSEL chip carrying one or more arrays of VCSEL units, allowing for relatively low cost manufacturing and integration with conventional DMS systems.

[0016] Therefore, according to a broad aspect, the present disclosure provides a light source unit comprising an array of single-mode vertical-cavity surface-emitting lasers (VCSELs) having a selected arrangement; and an array of lenses comprising a plurality of lens units each associated with a respective single-mode VCSEL, the plurality of lenses having selected focal lengths and positioned at selected distances from the plurality of VCSELs to provide a plurality of substantially collimated output beams, the plurality of substantially collimated output beams being non-parallel therebetween.

[0017] The output beams of the multiple single mode VCSELs may have a divergence angle of 0.1 to 4 degrees, or 0.1 to 2 degrees, or 0.5 to 2 degrees.

[0018] According to some embodiments, the light source unit may include an additional lens located downstream of the plurality of lens units and having an effective area covering a first of the plurality of VCSELs, the additional lens thereby providing an angular variation between the plurality of approximately collimated output beams such that the plurality of approximately collimated output beams are non-parallel.

[0019] According to some embodiments, the plurality of lens units comprises lens units having shifted positions relative to the emission apertures of the respective VCSEL units, thereby shifting the angular direction of the respective substantially collimated output beams.

[0020] According to some embodiments, the lens units may have shifted positions, each shifted by a different amount in at least one of direction and length, to provide a non-parallel, approximately collimated output beam.

[0021] According to some embodiments, the light source unit may further comprise a second array of multi-mode VCSELs positioned to the side of the array of single-mode VCSELs.

[0022] According to some embodiments, the array of single-mode VCSELs and the second array of multi-mode VCSELs are formed on a common substrate.

[0023] According to some embodiments, the second array is configured to provide flood lighting within a selected range.

[0024] According to some embodiments, the second array is configured to provide patterned illumination formed from a plurality of spatially separated illumination spots having a predetermined arrangement.

[0025] According to some embodiments, the multiple non-parallel, substantially collimated output beams are configured to form a predetermined pattern of non-overlapping illumination spots at a selected range from the light source unit.

[0026] According to some embodiments, the predetermined pattern includes illumination spots with spatial interfaces between the illumination spots.

[0027] According to some embodiments, the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern of overlapping illumination spots at selected ranges from the light source unit.

[0028] According to some embodiments, the selected range from the light source unit may be determined based on the typical distance between the dashboard and the driver's head in a vehicle.

[0029] According to some embodiments, the selected range from the light source unit is between 40 cm and 120 cm.

[0030] According to some embodiments, the multiple non-parallel, substantially collimated output beams are configured to form a predetermined pattern of non-overlapping illumination spots covering an area with dimensions between 40 cm x 40 cm and 100 cm x 100 cm.

[0031] According to some embodiments, the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern comprising a selected number of sub-patterns configured to illuminate a selected number of regions within the illumination space.

[0032] According to some embodiments, the VCSEL is configured to emit substantially monochromatic electromagnetic radiation within the wavelength range of 800 nm to 1100 nm.

[0033] According to some embodiments, an array of a plurality of single-mode VCSELs is operable to emit a selected temporal pattern of illumination pulses of selected duration.

[0034] According to another broad aspect, the present disclosure provides a light source unit comprising an array of single-mode vertical-cavity surface-emitting lasers (VCSELs) having a selected arrangement, and an optical unit configured to apply selected optical power to output illumination from the VCSELs to provide a plurality of substantially collimated output beams, the plurality of substantially collimated output beams being non-parallel therebetween. The optical elements may include lenslet arrays, diffraction grating arrays, fabricated optical elements determined by freeform optical planning, etc.

[0035] According to another broad aspect, the present disclosure provides a driver monitoring system comprising at least one light source unit and at least one camera, the at least one light source unit comprising a light source unit described herein.

[0036] According to some embodiments, a driver monitoring system may be configured to utilize the coherent illumination emitted by the array of single-mode VCSELs to determine one or more driver biomedical parameters through analysis of a speckle pattern produced by the coherent illumination.

[0037] According to some embodiments, analyzing the speckle pattern includes analyzing contrast variations in the speckle pattern. [Brief explanation of the drawings]

[0038] In order to better understand the subject matter disclosed herein, and to illustrate how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: [Figure 1] 1A and 1B schematically illustrate a light source unit formed from multiple single-mode VCSELs, according to some embodiments of the present disclosure. [Figure 2] The following shows an example of a typical layer structure of a VCSEL. [Figure 3A]3A illustrates an optical arrangement including a lens array used with a VCSEL array, according to some embodiments of the present disclosure. Figure 3A illustrates the VCSEL and lens array, and Figure 3B illustrates the geometry and positioning of the lens array. [Figure 3B] 3A illustrates an optical arrangement including a lens array used with a VCSEL array, according to some embodiments of the present disclosure. Figure 3A illustrates the VCSEL and lens array, and Figure 3B illustrates the geometry and positioning of the lens array. [Figure 4] 10 illustrates additional lens configurations according to some embodiments of the present disclosure. [Figure 5] 1 illustrates a light source unit and a generated illumination pattern according to some embodiments of the present disclosure. [Figure 6A] 6A and 6B illustrate spatial relationships between illumination spots according to some embodiments of the present disclosure: FIG. 6A shows well-separated illumination spots, FIG. 6B shows interfacing illumination spots, FIG. 6C illustrates illumination spots with little overlap, and FIG. 6D illustrates illumination spots with increased overlap. [Figure 6B] 6A and 6B illustrate spatial relationships between illumination spots according to some embodiments of the present disclosure: FIG. 6A shows well-separated illumination spots, FIG. 6B shows interfacing illumination spots, FIG. 6C illustrates illumination spots with little overlap, and FIG. 6D illustrates illumination spots with increased overlap. [Figure 6C] 6A and 6B illustrate spatial relationships between illumination spots according to some embodiments of the present disclosure: FIG. 6A shows well-separated illumination spots, FIG. 6B shows interfacing illumination spots, FIG. 6C illustrates illumination spots with little overlap, and FIG. 6D illustrates illumination spots with increased overlap. [Figure 6D] 6A and 6B illustrate spatial relationships between illumination spots according to some embodiments of the present disclosure: FIG. 6A shows well-separated illumination spots, FIG. 6B shows interfacing illumination spots, FIG. 6C illustrates illumination spots with little overlap, and FIG. 6D illustrates illumination spots with increased overlap. [Figure 7] 10 illustrates a light source unit including an additional multi-mode VCSEL array, according to some embodiments of the present disclosure. [Figure 8] 1 illustrates a single-mode VCSEL array according to some embodiments of the present disclosure formed with two or more separately operating regions. DETAILED DESCRIPTION OF THE INVENTION

[0039] As indicated above, the present disclosure provides a light source unit including multiple single-mode vertical-cavity surface-emitting lasers (VCSELs). See FIG. 1 , which schematically illustrates a light source unit 100 according to some embodiments of the present disclosure. The light source unit 100 includes a substrate 110, typically fabricated as a multi-layer substrate having a layered arrangement that forms a vertical cavity. The substrate carries multiple single-mode VCSELs 130 operable to emit optical radiation in a selected wavelength range. The light source unit 100 also includes an optical element 120, such as a lens array, a diffractive optical element, or the like, configured to manipulate output beams 132 of the single-mode VCSELs to provide an arrangement of substantially collimated beams propagating in a non-parallel relationship toward a selected region, thereby generating a selected illumination pattern in the selected region.

[0040] In this regard, Figure 2 illustrates a schematic diagram of a VCSEL unit 130. The VCSEL unit 130 is based on a layered substrate 110 including a top electrical contact 210 with an opening 212. The electrical contacts may be disposed on a top Bragg reflector 220 and a bottom Bragg reflector 240, with a quantum well layer 230 located between the top 220 and bottom 240 Bragg reflectors. The bottom Bragg reflector 240 is located on a substrate 250, which is typically a semiconductor substrate, and a bottom electrical contact 260.

[0041] The layered structure of the substrate 110 provides a vertical cavity, allowing light emission through the aperture 212 in response to sufficient power provided between the top electrical contact 210 and the bottom electrical contact 260. VCSEL units typically have a relatively short optical cavity, leading to a high free spectral range (FSR) and a high distance between longitudinal modes. VCSEL characteristics often provide a narrow wavelength range and a low longitudinal mode count. Therefore, VCSEL lasing modes typically relate to spatial (transverse) modes, which are determined by the VCSEL diameter. The diameter of the aperture 212 thus defines the transverse spatial modes supported by the VCSEL unit 130. Larger apertures generally support several transverse spatial modes and allow for higher power output, while smaller apertures may support a single mode and provide limited power output. Such single-mode VCSELs generally support a single Gaussian-shaped spatial mode, and therefore can provide illumination with increased coherence relative to multimode VCSELs. Light source unit 100 utilizes an array of single-mode VCSELs to overcome the power limitations associated with the small diameter of single-mode VCSELs and to provide a selected illumination pattern formed from multiple illumination spots.

[0042] It should also be noted that the high FSR typical of VCSELs effectively provides a laser source that is generally insensitive to temperature fluctuations relative to edge-emitter laser types. This reduces wavelength drift, increases the contrast of the speckle pattern produced by single-mode VCSEL illumination, and eliminates the need for thermal stabilization.

[0043] Furthermore, VCSEL laser units can generally be mass-produced at relatively low cost and provide a reliable production line. A single chip can include multiple VCSEL emitters with selected characteristics, which may be similar or different, as described in further detail below. Additionally, the light source unit 100 of the present disclosure can be configured for use with a driver monitoring system (DMS). Such DMSs are typically configured to monitor one or more parameters of a driver to detect fluctuations in the driver's level of attention and issue a warning if the driver appears distracted, and the light source unit 100 of the present disclosure typically provides a coherent illumination pattern directed toward the driver but which may also be directed toward one or more other individuals within the vehicle. The coherent illumination from the light source unit of the present disclosure can be used to determine one or more biomedical and / or physiological parameters of the driver (or other persons) using speckle analysis.

[0044] Laser speckle contrast analysis (LASCA) is a generally known technique that utilizes variations in the contrast of speckle patterns to determine one or more parameters of a person. The speckle pattern is formed due to specific self-interference between coherent light components of a light beam illuminating an area of ​​the body. Variations in the body surface can cause shifts in the speckle pattern, which can typically be acquired as reduced contrast due to smearing of the pattern during the exposure time of image acquisition. Monitoring such variations over time can be used to determine parameters such as heart rate, heart rate variability, perfusion level, and respiratory rate.

[0045] A DMS may also utilize a light source to generate selected illumination to enhance image processing capabilities. Such selected illumination patterns may include flood illumination and / or patterned illumination formed by spatially separated illumination spots. As discussed further below, the use of a VCSEL unit as the light source allows for simple and straightforward integration with such a DMS; a single chip may include multiple VCSEL emitters that may have similar or different light-emitting characteristics.

[0046] Generally, the light source units may be formed on chips having selected dimensions ranging from a few millimeters to one or two centimeters. Furthermore, to provide an efficient illumination pattern in the driver's headbox area, the illumination pattern may be expanded in both a selected divergence angle of each of the output beams and the relative propagation paths of the output beams. In this regard, reference is made to FIGS. 3A-3B and 4, which illustrate selected configurations of light source units 100 according to some embodiments of the present disclosure.

[0047] FIG. 3A illustrates a light source unit 100 including an array of single-mode VCSELs 130 and a respective array of lenses 120. The array of lenses 120 can be constructed using various techniques, such as a microlens array, a lenslet array, or an array of diffractive lenses, and effectively includes multiple lens regions 122, each associated with a respective one of the single-mode VCSELs 130. Typically, single-mode VCSELs have a relatively small output aperture, resulting in a relatively large divergence angle. The array of lenses 120 includes lens regions 122 with selected optical powers and are positioned at a selected distance to condition the output beam and provide a substantially collimated output beam 132. In this context, the term “substantially collimated” should be understood broadly and refers to a beam having a selectively low divergence angle. More specifically, the substantially collimated output beam 132 has a divergence angle selected to generate an illumination spot 136 of a selected spot area at a selected distance. For example, for a headbox distance of 40 cm to 120 cm from the light source unit (typical for operating conditions), a divergence angle of the output beam of 0.1 to 4 degrees can be selected to provide an illumination spot having an area of ​​a few square millimeters to a few square centimeters. In some configurations, the divergence angle of the output beam can be selected between 0.5 degrees and 2 degrees.

[0048] Additionally, the pattern created by the multiple lighting spots is preferably arranged in space to cover the driver's headbox area. For example, the total coverage of the lighting pattern may be 40x40cm. 2 ~100×100cm 2To this end, multiple output beams are directed in non-parallel paths, with each output beam propagating at a slightly different angle than the other beams to generate a resulting illumination pattern such as that illustrated in FIG. 3A . To this end, the lens array 120 is configured to apply a selected spatial phase shift or spatial chirp to direct the output beams in a selected non-parallel pattern. For example, the lens array 120 may include lens units 122 that are shifted in position relative to the emission aperture of each VCSEL unit 130. Such position shifts introduce angular variations in the propagation paths of the output beams; alternatively, different lenses 122 may have selected phase variations provided to change the angular direction of propagation of the output beams. In some configurations, the lens array may have a tailored design, determined by freeform optical design, to provide coherent output beams having a selected divergence angle and propagating in a selected non-parallel angular relationship.

[0049] FIG. 3B illustrates a spatial shift in the optical axis of the lens relative to the optical axis of each VCSEL unit and the resulting variation in the propagation path. As shown in FIG. 3B, lens 122a is positioned so that its optical axis OAa coincides with the optical axis of VCSEL 130a. As a result, output beam 132a is approximately parallel to optical axis OAa. Alternatively, lens 122b is installed at a location shifted upward relative to the optical axis of each VCSEL 130b. The spatial shift in lens location results in a spatial phase shift of the output beam, which results in the output beam being directed at an angle relative to the optical axis, with the angle of propagation depending on the direction and size of the spatial shift.

[0050] To provide a selected pattern, the output beams 132 of each of the VCSELs 130 are non-parallel to one another. To this end, in some embodiments, each of the lenses 122 or arrays 120 may apply a selected phase shift (e.g., by spatial shifting) that is determined according to the location of the lens 122 within the array 120. For example, the center point of the VCSEL array may be determined, and each lens 122 may be shifted away from (or toward) the center point by a factor of its distance from the center point. This spatial shift pattern may provide a phalanx-like arrangement of different output beams to cover a selected area.

[0051] An alternative configuration is illustrated in FIG. 4 . In this configuration, the light source unit includes an array of single-mode VCSELs 130, each associated with a lens 122 of the lens array 120 to provide a selected level of collimation of the output beam, as described above. In addition, the light source unit of this embodiment includes an additional optical element 140 located downstream of the lens array 120. The optical element 140 may be a lens unit, a diffractive element, or the like, and is configured to cover multiple lens units 122 that cover the surface area of ​​the array of single-mode VCSELs. The optical element 140 is defined by a selected optical axis and changes the angular direction of the output beam according to the location of the beam source relative to that optical axis. More specifically, the optical element 140 may be represented by a lens unit having an optical axis aligned with the center point of the array 130. An output beam 132 emitted at a location other than the center point is shifted from the optical axis, resulting in an angular shift in the beam propagation direction.

[0052] Reference is now made to FIG. 5 , which illustrates a schematic configuration of a light source unit and its illumination pattern. As shown, the light source unit 100 is configured to be positioned at a selected location and to generate an illumination pattern formed from multiple coherent illumination spots 136 at a selected distance (e.g., 40-120 cm). The illumination spot arrangement can be any arrangement with limited or no overlap between adjacent spots 136, thereby allowing the illumination spots 136 to include specific regions of coherent illumination and enable speckle analysis based on light collection of the illumination spots. The spatial arrangement of the illumination pattern can be any arrangement, including a rectangular array as illustrated in FIG. 5 , a hexagonal array, a triangular array, or any other selected spatial arrangement. The spatial arrangement of the array can also include one or more, or two or more, separate regions with separated and / or different illumination pattern arrangements. For example, light source unit 100 may be configured to direct a portion of its output beam to form an illumination pattern where a driver's headbox may be located, and an additional, secondary portion of the output beam may be directed toward an area where a passenger's headbox may be located, thereby enabling a single light source unit to be used to monitor one or more individuals within a common vehicle.

[0053] 6A-6D illustrate various spatial relationships between illumination spots. FIG. 6A illustrates spatially separated illumination spots 136, FIG. 6B shows interfacing illumination spots, FIG. 6C shows illumination spots with low overlap (e.g., less than 10% surface area overlap), and FIG. 6D shows illumination spots with increased overlap (e.g., greater than 10% surface area overlap). The arrangement of illumination spots 136 in a selected pattern can be used to provide selected and / or additional functions supported by light source unit 100.

[0054] To obtain image data suitable for spackle analysis, a sufficient portion of the illumination spot 136 is preferably non-overlapping, which places a portion of the illumination spot under coherent illumination, resulting in a speckle pattern within the illumination spot 136.

[0055] Furthermore, a typical DMS can often be used to provide additional monitoring techniques. To this end, the light source unit 100 can be configured to provide an illumination pattern that supports further image processing functions. For example, spatially separated light spots on the illumination pattern can be used for depth perception and three-dimensional mapping using variations in spot size in the resulting image. In addition, partial overlap between light spots can provide field illumination suitable for various image processing techniques and provide relatively uniform illumination of the driver's headbox area. Thus, a typical illumination pattern produced by an array of single-mode VCSELs, such as those illustrated in FIGS. 6A-6C, may be suitable for speckle analysis according to embodiments of the present disclosure. However, an illumination pattern such as that illustrated in FIG. 6D, i.e., with large overlap between light spots, may be less suitable for spackle analysis. Generally, the contrast of a speckle pattern is reduced by 1 / sqrt(n) when the pattern is formed by illumination from two or more light sources (or n light sources); therefore, overlap between illumination spots produced by different VCSELs 130 in the array reduces speckle contrast in the overlapping areas. However, the light source unit 100 of the present disclosure can still provide a lighting pattern such as that illustrated in FIG. 7 below, typically for flood lighting purposes.

[0056] FIG. 7 illustrates a combined light source unit 100 according to some further embodiments of the present disclosure. In this example, a common chip 110 carries an array 130 of single-mode VCSELs and an additional array 150 of multimode VCSELs. The single-mode VCSELs are associated with optical elements 120, as described above, to provide an array of non-parallel, nearly collimated output beams 132. The array of multimode VCSELs may also be associated with optical elements 124, such as a diffuser, pumped diffuser, or homogenizer, or configured to generate output light in the form of multiple output beams 152. The illumination pattern of the multimode VCSEL array 150 may be selected to provide spatially separated light spots, as illustrated in FIG. 6A, to support three-dimensional analysis of the illuminated area. Alternatively, as illustrated in FIG. 7, the illumination pattern may include overlapping output beams, generating field illumination suitable for general image processing performed by a typical DMS system.

[0057] The light source unit 100 may be operable in a selected illumination sequence to enable multiplexing between two or more DMS functions. For example, the illumination sequence may include coherent illumination using a single-mode VCSEL array for a first duration, followed by incoherent field illumination using a multimode VCSEL array for a second duration, and / or spatially separated patterned illumination for three-dimensional spatial perception. Image collection by the DMS may be coordinated with the illumination sequence to utilize coherent illumination for speckle analysis and to determine biomedical parameters of the driver or other people in the vehicle. Incoherent field illumination may also be used for image processing, such as gaze detection, head orientation, and eye movement.

[0058] Additionally, FIG. 8 illustrates another example of the light source unit 100. While only the single-mode VCSEL array 130 is illustrated, the light source in this embodiment can be formed according to the embodiment of FIG. 7, including additional VCSEL arrays. Furthermore, the single-mode VCSEL array 130 can be separated into two or more regions, e.g., three or more regions or subarrays of single-mode VCSELs, e.g., subarrays 112, 114, and 116, as illustrated in FIG. 8. The different subarrays 112-114 and 116 can be independently operable and configured to direct an illumination pattern formed by multiple substantially collimated, non-overlapping output beams toward different sections of the illumination area. The different subarrays can be selectively operated to enable energy savings and reduce heat dissipation in the VCSEL chip. For example, a DMS system can be mounted and aligned to cover various driver headboxes. During operation, the DMS can identify that the driver's head is actually in the upper portion of the illumination area (or the lower portion of the illumination area, or the central portion of the illumination area). In response, the DMS may proceed by operating only a sub-array of single-mode VCSELs that directs the output beam in a relevant portion of the illumination area, reducing the energy demand and heat generated by the system.

[0059] Therefore, the present disclosure provides a light source unit comprising an array of single-mode VCSELs and respective optical elements for providing output illumination in the form of a substantially collimated, non-parallel output beam. The light source unit may be an integrated light source unit formed on a single common chip and may include one or more additional VCSEL arrays, typically multimode arrays. The light source unit may provide a total output power in the range of 2 W to 10 W and may include an arrangement of 100 to 10,000 single-mode VCSELs, or 1,000 to 6,000 single-mode VCSELs, or 1,500 to 4,000 single-mode VCSELs to provide a desired illumination pattern as described herein. The light source unit and / or its respective array of single-mode VCSELs may be operable for pulsed illumination, including pulses with durations of 30 milliseconds to 30 microseconds, enabling time multiplexing of illumination conditions and image collection for selected processing applications. The light source unit may be operable to emit substantially monochromatic illumination in one or more wavelength ranges from 800 nm to 1100 nm. For example, the output wavelengths may include 850 nm and / or 940 nm. In this context, the term substantially monochromatic relates to continuous wave (CW) illumination having a narrow illumination bandwidth, for example, of at most 50 nm, or at most 20 nm, or at most 10 nm, or at most 5 nm.

[0060] It should be noted that the various features described in the different embodiments can be combined according to all possible technical combinations.

[0061] It is to be understood that the present invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways. Accordingly, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will readily appreciate that they may readily utilize the conception upon which the present disclosure is based as a basis for the designing of other structures, methods and systems for carrying out some of the purposes of the subject matter of the present disclosure.

[0062] Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the present invention as hereinbefore described without departing from the scope thereof as defined in and by the appended claims.

Claims

1. 1. A light source unit comprising: an array of a plurality of single-mode vertical-cavity surface-emitting lasers (VCSELs) having a selected arrangement; and an array of lenses comprising a plurality of lens units each associated with a respective single-mode VCSEL, the plurality of lenses having selected focal lengths and positioned at selected distances from the plurality of VCSELs to provide a plurality of substantially collimated output beams, the plurality of substantially collimated output beams being non-parallel among the substantially collimated output beams.

2. 10. The light source unit of claim 1, further comprising an additional lens located downstream of the plurality of lens units and having an effective area covering a first plurality of VCSELs of the plurality of VCSELs, the additional lens thereby providing a variation in angular orientation between the plurality of substantially collimated output beams such that the plurality of substantially collimated output beams are non-parallel.

3. 3. The light source unit of claim 1, wherein the plurality of lens units comprises lens units having shifted positions relative to the emission aperture of the respective VCSEL units, thereby shifting the angular direction of the respective substantially collimated output beams.

4. 4. The light source unit of claim 3, wherein the lens units having shifted positions are each shifted by a different amount in at least one of direction and length to provide a non-parallel, approximately collimated output beam.

5. 5. A light source unit according to any preceding claim, further comprising a second array of multi-mode VCSELs positioned to the side of the array of single-mode VCSELs.

6. The light source unit of claim 5 , wherein the array of single-mode VCSELs and the second array of multi-mode VCSELs are formed on a common substrate.

7. 7. A light source unit according to claim 5 or 6, wherein the second array is configured to provide flood illumination within a selected range.

8. 7. The light source unit of claim 5, wherein the second array is configured to provide patterned illumination formed from a plurality of spatially separated illumination spots having a predetermined arrangement.

9. 9. A light source unit according to any one of claims 1 to 8, wherein the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern of non-overlapping illumination spots at selected ranges from the light source unit.

10. The light source unit of claim 9 , wherein the predetermined pattern comprises illumination spots with spatial interfaces between the illumination spots.

11. 9. A light source unit as claimed in any one of claims 1 to 8, wherein the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern of overlapping illumination spots at selected ranges from the light source unit.

12. The light source unit according to any one of claims 9 to 11, wherein the selected range from the light source unit is determined based on a typical distance between a dashboard and a driver's head in a vehicle.

13. The light source unit according to any one of claims 9 to 12, wherein the selected range from the light source unit is between 40 cm and 120 cm.

14. 14. The light source unit of claim 9, wherein the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern of non-overlapping illumination spots covering an area with dimensions between 40 cm x 40 cm and 100 cm x 100 cm.

15. 15. The light source unit of claim 9, wherein the plurality of non-parallel, substantially collimated output beams are configured to form a predetermined pattern comprising a selected number of sub-patterns configured to illuminate a selected number of regions in an illumination space.

16. 16. A light source unit according to any one of the preceding claims, wherein the VCSEL is configured to emit substantially monochromatic electromagnetic radiation in the wavelength range of 800 nm to 1100 nm.

17. A light source according to any preceding claim, wherein the array of a plurality of single-mode VCSELs is operable to emit a selected temporal pattern of illumination pulses of a selected duration.

18. A driver monitoring system comprising at least one light source unit and at least one camera, wherein the at least one light source unit comprises a light source unit according to any one of claims 1 to 17.

19. 20. The driver monitoring system of claim 18, configured to utilize the coherent illumination emitted by the array of single-mode VCSELs to determine one or more biomedical parameters of the driver by analysis of a speckle pattern produced by the coherent illumination.

20. 20. The driver monitoring system of claim 19, wherein analyzing the speckle pattern includes analyzing contrast variations in the speckle pattern.

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