Eye-safe scanning LIDAR system

Abstract

To provide an eye-safe scanning LIDAR system.SOLUTION: An LIDAR illuminator includes a plurality of laser sources, each including an electric input for receiving a modulation drive signal that causes each of the plurality of laser sources to generate an optical beam. A controller including a plurality of electric outputs, each being connected to each of the plurality of laser sources generates a plurality of modulation drive signals that causes the plurality of laser sources to generate a plurality of optical beams that form a combined optical beam. A peak optical energy of the combined optical beam in a measuring opening at a measuring distance is less than a desired value.SELECTED DRAWING: None

Description

[Technical field]

[0001] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described in this application in any way.

[0002] (CROSS REFERENCE TO RELATED APPLICATIONS) This application is a non-provisional application of U.S. Provisional Patent Application No. 62 / 470,827, entitled “Eye-Safe Scanning LIDAR System,” filed March 13, 2017. The entire contents of U.S. Provisional Patent Application No. 62 / 470,827 are incorporated herein by reference. [Background technology]

[0003] Light detection and ranging (LIDAR) systems are one of the most important sensors that enable real-time measurement of object distances. LIDAR systems measure the distance to objects by illuminating those objects with laser light. In some cases, LIDAR systems are used to sense the surroundings of a vehicle. In these and other applications, the illuminated objects may be people. Thus, opportunities exist where the laser light from a LIDAR system will illuminate the human eye.

[0004] Laser light can be very dangerous to the human eye. The coherence and small beam divergence angle of laser light, when combined with the eye's crystalline lens, results in the laser light being focused to an extremely small spot size on the retina. This small spot size, along with a sufficiently high laser light power, can result in retinal burns and permanent damage to the eye. Therefore, a LIDAR system is needed that can operate at eye-safe levels of laser light energy. Summary of the Invention [Means for solving the problem]

[0005] The present teachings relate to light detection and ranging systems (LIDAR) that measure distances to various objects or targets that reflect and / or scatter light. In particular, the present teachings relate to a LIDAR system capable of providing LIDAR measurements over long distances of over 70 m and with high refresh rates up to 1 KHz, ensuring system operation consistent with Class 1 eye safety standards.

[0006] The systems of the present teachings may use laser light sources including single emitters and / or multiple emitters. For example, a light source using a single element VCSEL or a single edge-emitting laser device would be considered a single emitter. A light source using multiple VCSEL elements or multiple edge-emitting laser sources arranged on one or more substrates would be considered a multiple emitter source. Multi-element emitters may be configured in various array configurations, including one-dimensional and two-dimensional arrays. Those skilled in the art will understand that the following description of the present teachings refers to various embodiments of eye-safe scanning LIDAR systems with single emitter sources and / or multiple emitter laser sources. It will be apparent to those skilled in the art that features of certain embodiments of LIDAR systems of the present teachings should not be considered limited to either single emitter and / or multiple emitter laser sources, but rather should be more broadly construed as applying to both single emitter and / or multiple emitter laser sources. The present invention provides, for example, the following: (Item 1) 1. A LIDAR illuminator comprising: a) a plurality of laser sources, each of the plurality of laser sources having an electrical input for receiving a modulated drive signal causing each of the plurality of laser sources to generate an optical beam; b) a controller having a plurality of electrical outputs, each of the plurality of electrical outputs connected to an electrical input of a respective one of the plurality of laser sources, the controller generating a plurality of modulated drive signals that cause the plurality of laser sources to generate a plurality of optical beams that form a combined optical beam, wherein a peak optical energy of the combined optical beams within a measurement aperture at a measurement distance is less than a desired value; and A LIDAR illuminator comprising: (Item 2) Item 2. The LIDAR illuminator of item 1, wherein the multiple laser sources comprise multiple vertical cavity surface emitting lasers. (Item 3) 2. The LIDAR illuminator of claim 1, wherein the multiple laser sources are positioned such that a combined optical beam within the measurement aperture at the measurement distance comprises only one of the multiple optical beams. (Item 4) 4. The LIDAR illuminator of claim 3, wherein the controller is configured to generate the multiple modulated drive signals to excite the multiple laser sources at pseudo-random times. (Item 5) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate the multiple modulated drive signals to excite the multiple laser sources such that none of the multiple optical beams overlap within the measurement aperture at the measurement distance at any particular time. (Item 6) 6. The LIDAR illuminator of claim 5, wherein the controller is configured to generate the multiple modulated drive signals to excite the multiple laser sources such that more than one optical beam illuminates the measurement aperture at the measurement distance for at least a portion of the time. (Item 7) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate the multiple modulated drive signals to excite the multiple laser sources such that a combined optical beam within the measurement aperture at the measurement distance has a peak optical energy that is less than or equal to a peak optical energy within the measurement aperture at the measurement distance of one of the multiple optical beams. (Item 8) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate the multiple modulated drive signals to excite the multiple laser sources such that only one of the multiple optical beams illuminates the measurement aperture at the measurement distance at any particular time. (Item 9) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals to excite the plurality of laser sources such that at any given time there are no overlapping optical beams in time within the measurement aperture at the measurement distance. (Item 10) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals to excite the plurality of laser sources such that at least two of the plurality of optical beams simultaneously overlap in time within the measurement aperture at the measurement distance. (Item 11) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals to excite the plurality of laser sources such that at least two of the plurality of optical beams simultaneously partially overlap in time within the measurement aperture at the measurement distance. (Item 12) 2. The LIDAR illuminator of claim 1, wherein the measurement aperture is about 7 mm and the measurement distance is about 100 mm. (Item 13) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals such that the plurality of laser sources generate pulsed optical beams with desired pulse widths, peak powers, and repetition rates such that each beam does not exceed maximum permissible exposure (MPE) limits within the measurement aperture at the measurement distance. (Item 14) 2. The LIDAR illuminator of claim 1, wherein the multiple optical beams produce a combined optical beam with a peak optical energy within the measurement aperture at the measurement distance that is Class 1 eye-safe. (Item 15) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals to maximize a refresh rate of the LIDAR illuminator. (Item 16) 2. The LIDAR illuminator of claim 1, wherein the controller further comprises a memory electrically connected to the controller, the memory storing data representing the plurality of modulated drive signals that cause the LIDAR illuminator to generate a particular desired pattern of light. (Item 17) Item 1. The LIDAR illuminator of item 1, further comprising an optical sensor for measuring energy density, the optical sensor having an output electrically connected to the controller. (Item 18) 2. The LIDAR illuminator of claim 1, wherein the controller is configured to generate a plurality of modulated drive signals such that the plurality of modulated drive signals generate a plurality of optical beams that form a combined optical beam that varies as a function of time. (Item 19) 1. A method of LIDAR illumination comprising: a) providing a plurality of laser sources; b) generating a plurality of modulated drive signals for each of the plurality of laser sources that cause the plurality of laser sources to generate a plurality of optical beams forming a combined optical beam, wherein a peak optical energy of the combined optical beams within a measurement aperture at a measurement distance is less than a desired value; A method comprising: (Item 20) 20. The method of claim 19, wherein providing the plurality of laser sources comprises providing a plurality of vertical cavity surface emitting lasers. (Item 21) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources at pseudo-random times. (Item 22) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that none of the multiple optical beams overlap at any particular time within the measurement aperture at the measurement distance. (Item 23) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that more than one optical beam illuminates the measurement aperture at the measurement distance for at least a portion of the time. (Item 24) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that a combined optical beam within the measurement aperture at the measurement distance has a peak optical energy that is less than or equal to a peak optical energy of one of the multiple optical beams within the measurement aperture at the measurement distance. (Item 25) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that only one of the multiple optical beams illuminates the measurement aperture at the measurement distance at any particular time. (Item 26) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that at any given time there are no overlapping optical beams in time within the measurement aperture at the measurement distance. (Item 27) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that at least two of the multiple optical beams simultaneously overlap in time within the measurement aperture at the measurement distance. (Item 28) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to excite the multiple laser sources such that at least two of the multiple optical beams simultaneously overlap in time within the measurement aperture at the measurement distance. (Item 29) 20. The method of claim 19, wherein the measurement aperture is about 7 mm and the measurement distance is about 100 mm. (Item 30) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals such that the multiple laser sources generate pulsed optical beams with desired pulse widths, peak powers, and repetition rates such that each beam does not exceed maximum permissible exposure (MPE) limits within the measurement aperture at the measurement distance. (Item 31) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to generate a combined optical beam with a peak optical energy within the measurement aperture at the measurement distance that is Class 1 eye-safe. (Item 32) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating the multiple modulated drive signals to generate multiple modulated drive signals that maximize a refresh rate of the LIDAR illuminator. (Item 33) 20. The method of claim 19, further comprising accessing a memory to obtain the plurality of modulated drive signals. (Item 34) 20. The method of claim 19, further comprising measuring an energy density within the measurement aperture at the measurement distance. (Item 35) 20. The method of claim 19, wherein generating the multiple modulated drive signals for each of the multiple laser sources includes generating a plurality of modulated drive signals such that the multiple modulated drive signals generate a plurality of optical beams that form a combined optical beam that varies as a function of time. [Brief description of the drawings]

[0007] The present teachings, together with further advantages thereof, according to preferred exemplary embodiments, are more particularly described in the following detailed description with reference to the accompanying drawings. Those skilled in the art will appreciate that the drawings described below are for illustrative purposes only. The drawings are not necessarily to scale, with emphasis instead generally being placed on illustrating the principles of the present teachings. The drawings are not intended to limit the scope of the applicant's teachings in any respect.

[0008] [Figure 1] FIG. 1 illustrates a LIDAR system of the present teachings implemented on a vehicle.

[0009] [Diagram 2] FIG. 2 illustrates a diagram for determining maximum permissible exposure (MPE) limits for a LIDAR system of the present teachings.

[0010] [Diagram 3] FIG. 3 illustrates an embodiment of a laser array for a LIDAR system illuminator of the present teachings.

[0011] [Figure 4A] FIG. 4A illustrates a chip comprising a number of clustered VCSEL devices arranged individually.

[0012] [Figure 4B] FIG. 4B illustrates a chip with multiple clustered VCSEL devices arranged in a bar.

[0013] [Figure 4C] FIG. 4C illustrates a top view of the anode metal contact pads of a chip comprising multiple clustered VCSEL devices of the present teachings.

[0014] [Figure 4D] FIG. 4D illustrates a bottom view of the cathode metal contact pads of a chip comprising multiple clustered VCSEL devices as illustrated in FIG. 4C.

[0015] [Diagram 5] FIG. 5 illustrates a system block diagram of an embodiment of a compact VCSEL laser driver assembly for an eye-safe LIDAR system in accordance with the present teachings.

[0016] [Figure 6A] FIG. 6A illustrates a schematic diagram of an embodiment of a LIDAR illuminator of the present teachings using two arrays of different wavelength VCSELs with a first lens system.

[0017] [Figure 6B]FIG. 6B illustrates a schematic diagram of an embodiment of a LIDAR illuminator of the present teachings using two arrays of different wavelength VCSELs with a second lens system.

[0018] [Figure 6C] FIG. 6C illustrates a schematic diagram of an embodiment of a LIDAR illuminator of the present teachings using two arrays of different wavelength VCSELs with a third lens system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present teachings will now be described in more detail with reference to exemplary embodiments thereof as illustrated in the accompanying drawings. Although the present teachings are described in connection with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. Instead, the present teachings extend to various alternatives, modifications and equivalents as will be understood by those skilled in the art. Those skilled in the art with access to the present teachings herein will recognize additional implementations, modifications and embodiments, and other fields of use, that are within the scope of the present disclosure described herein.

[0020] As used herein, reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present teachings. The appearances of the phrase "in one embodiment" in various places in the specification do not necessarily all refer to the same embodiment.

[0021] It should be understood that the individual steps of the methods of the present teachings can be performed in any order and / or simultaneously so long as the present teachings remain operable. Further, it should be understood that the apparatus and methods of the present teachings can include any number or all of the described embodiments so long as the present teachings remain operable.

[0022] FIG. 1 illustrates the operation of a LIDAR system 100 of the present teachings implemented on a vehicle. The LIDAR system 100 includes a laser projector, sometimes referred to as an illuminator, that projects a light beam 102 generated by a light source toward a target scene. The LIDAR system 100 also includes a receiver that receives light 104 that reflects off an object, shown as a human 106, in the target scene. The LIDAR system 100 can also include a controller that calculates the distance from the reflected light to the object 106. In various embodiments, the controller can be a simple electrical circuit or a more complex processor, depending on the specific LIDAR requirements. In addition, the LIDAR system 100 also includes elements that can scan or provide a specific pattern of light, which can be a static pattern, across a desired range and field of view (FOV). The receiver and controller are used to convert the received signal light into measurements that represent a point-by-point three-dimensional (3D) map of the surrounding environment that is within the LIDAR system range and FOV.

[0023] An illuminator, including a laser source and optical beam projector and receiver, is sometimes located on the front side of the vehicle 108. A person 106 and / or another object, such as a car or utility pole, will provide light that is reflected from the source to the receiver. The range or distance to the object is determined from the reflected light by the LIDAR receiver. The LIDAR receiver calculates range information based on time-of-flight measurements of light pulses emitted from the light source.

[0024] In addition, information about the optical beam profile illuminating the scene in a target plane associated with a particular range, for example known from a particular design of the source and projector system, is used to determine location information about reflective surfaces to generate a complete x, y, z or 3D picture of the scene. In other words, a point-by-point 3D map of the surrounding environment represents a collection of measurement data indicating position information from all surfaces that reflect illumination from a source within the field of view of the LIDAR system to a receiver. In this way, a 3D representation of objects within the field of view of the LIDAR system is obtained. The point-by-point 3D data map may also be referred to as a measurement point cloud.

[0025] Various embodiments of the LIDAR system of the present teachings operate with different laser pulse durations and laser pulse repetition rates depending on the desired performance. One example is the sampling rate required for one embodiment of an automotive LIDAR system. A car moving at 100 kilometers per hour (kph) travels at approximately 28 millimeters per millisecond (mm / msec). If two cars approach each other, the relative distance will decrease at twice that rate, or 56 mm / msec. For the system to be accurate across the entire field of view with a distance accuracy of 50 mm (about 2 inches) per measurement point, it needs to be able to scan the full FOV for that time. The eye-safe LIDAR system of the present teachings may be applied to other types of LIDAR sensing applications and is not limited to sensing for vehicles or automobiles.

[0026] A multi-source and multi-wavelength LIDAR system has been proposed by the assignee of the present application. See U.S. Patent Application No. 15 / 456,789, filed March 13, 2017, entitled "Multi-Wavelenght LIDAR System." The entire contents of U.S. Patent Application No. 15 / 456,789 are incorporated herein by reference. For illustrative purposes, assume a multi-source LIDAR system using 1,000 laser clusters corresponding to specific desired 3D point-by-point measurement locations. As explained above, to achieve position accuracy across the full FOV, it would be necessary to scan through all 1,000 lasers every millisecond. For a single-wavelength system, only one laser can be operated and detected at a time, which means that you have 1 microsecond per laser to obtain position information for that measurement point.

[0027] One feature of the multi-wavelength LIDAR system of the present teachings is that it provides a relatively high refresh rate. The refresh rate is sometimes also referred to as the frame rate. The refresh rate is directly proportional to how often the distance measurement of the 3D or 2D scene being sensed by the LIDAR is updated. Some embodiments of the present teachings provide a system refresh rate that is at least the same as current low-cost CMOS camera systems, which typically have a refresh rate of 30 Hz. However, the refresh rate can be 1 kHz or higher. To understand why a high refresh rate is important, consider a car traveling at 100 km / hour. Under these conditions, the car will move about 3 meters within 0.1 seconds. Thus, if the refresh rate is only 10 Hz, an object in front of the car will move significantly within that time, causing a significant loss of resolution.

[0028] For example, in a LIDAR system of the present teachings using four wavelengths with 4,096 lasers being measured in one frame and a pulse duration of 1 microsecond, the refresh rate would be 1 kHz for a single system. If multiple systems were used to cover a full 360 degree field of view, the refresh rate would still need to be 1 kHz. This assumes a single pulse per measurement. However, if multiple pulses per measurement were used, the refresh rate would be lower.

[0029] Laser eye safety regulations have been established to set standards for the amount of laser radiation that can enter the eye without causing eye damage. The standards ensure that products that emit laser light are labeled in a manner that consumers understand the safety risks associated with a particular product. The most commonly referenced standard in the world is IEC 60825-1 published by the International Electrotechnical Commission (IEC), which has been adopted in Europe as EN 60825-1. In the United States, laser products are covered by CDRH21 CFR 1040.10. Compliance with EN 60825-1 has been established as acceptable to meet the US Federal Standard.

[0030] Laser eye safety standards have different safety categories classified by wavelength and maximum output power. The standard defines the Maximum Permissible Exposure (MPE), which is defined as the optical power or energy that can pass through a fully open pupil without causing any damage. The MPE is a function of energy and therefore related to the laser pulse duration and repetition rate in systems where the laser is pulsed (i.e., not operating continuously).

[0031] Class 1 lasers are safe under all conditions of normal use. The Maximum Permissible Exposure (MPE) cannot be exceeded in Class 1 products. It is highly desirable for automotive LIDAR systems to be Class 1 eye safe. In a Class 1 rated LIDAR system, the laser light produced by the LIDAR system will not exceed the MPE in all cases where exposure to the human eye is possible.

[0032] Steps must be taken in a LIDAR system to provide the highest system performance while also ensuring class 1 eye safety. System performance may include parameters such as angular resolution, refresh rate, field of view, and range. Many of these performance parameters are directly linked to the laser power and / or intensity of the optical beam produced at the target plane of the LIDAR system. For example, it is desirable to have the highest peak optical power for the transmitted laser pulses in order to have the best possible signal-to-noise ratio in the receiver and also to provide long-distance maximum range. However, class 1 eye safety limits the maximum peak optical power of each pulse.

[0033] For example, from the International Electrotechnical Commission (IEC) standard IEC 60825-1, it is calculated that the allowable exposure energy for a 903-nm laser over an exposure duration of 10 psec to 5 μsec would be 0.392 μJoules. For a single laser pulse of 5 nsec duration delivered every 5 μsec, assuming a square pulse shape with zero rise and fall times, the maximum peak power of this pulse would be 78.4 W. For a square pulse with a 50-nsec duration delivered every 5 μsec, the maximum peak power would be one tenth that, or 7.84 W.

[0034] The exposure energy is the energy calculated to pass through the eye's fully open pupil. The International Electrotechnical Commission (IEC) standard includes instructions on how it should be measured, and for systems with wavelengths between 400 nm and 1,400 nm wavelength, there are two conditions that apply. Condition 1 applies to beams collimated by telescopes or binoculars, where the danger is increased if the aperture stop is equal to 50 mm at 2,000 mm. Condition 3 applies to the determination of the exposure for the naked eye for scanning beams that define an aperture stop / limiting aperture of 7 mm at 100 mm. The reference point for the scanned emission is the scanning apex (pivot point of the scanning beam). A LIDAR system according to the present teachings with a 100 meter range would nominally fire a pulse every 1 microsecond to maximize the refresh rate. In this example, the optical peak power is constrained such that a pulse every 1 microsecond would need to be one-fifth as large as if a pulse was fired every 5 microseconds.

[0035] One aspect of the present teachings is that a LIDAR system using multiple lasers can be operated such that the lasers are excited to reduce or substantially eliminate overlap in the optical power of the multiple optical beams to create an eye-safe system. As described herein, the MPE provides the maximum energy measured at any fixed 7-mm aperture at a distance of 100 mm from the laser array and at 50 mm at a distance of 2,000 mm. The power added at a particular measurement point from the overlap of multiple optical beams will affect the maximum power allowed per optical beam. However, the performance per measurement point, e.g., signal-to-noise ratio, will be limited by this maximum power. Figure 2 illustrates this concept.

[0036] FIG. 2 illustrates a schematic diagram for determining the MPE limit for a LIDAR system illuminator 200 of the present teachings. Some applications may be desirable to operate with each beam generated by a particular laser at the MPE limit for Class 1 standards. In these embodiments, if the two beams were operated simultaneously and overlapped, the energy would exceed the MPE limit in the area of ​​the optical beam overlap. In these embodiments, one solution according to the present teachings to the problem of overlapping optical beams is to excite or fire the laser to generate overlapping optical beams at separate times. In this way, the energy of both beams is not provided simultaneously to the overlapping section of the two optical beams. This allows both beams to operate at the full energy level allowed by the MPE without the chance that the system would exceed eye safety limits in the overlapping beam area.

[0037] The LIDAR system illuminator 200 is designed such that at a distance 202 of 100 mm from the laser array 204, the four beams 206 corresponding to the discrete lasers 208 are spaced further apart than 7 mm. In other words, none of the optical beams 206 are closer than 7 mm at a distance of 100 mm, and therefore they do not overlap at 100 mm. In this optical configuration, all four lasers 206 can be fired simultaneously without forming a combined beam that has more optical power than any of the individual optical beams such that any two of the optical beams combined would affect eye safety. This is true regardless of whether each laser emits an optical beam with a unique wavelength or whether at least two of the optical beams emit optical beams with the same wavelength. Various embodiments of the scanning LIDAR system of the present teachings utilize illuminators that include lasers or laser arrays operating at a single wavelength and illuminators that include lasers or laser arrays operating at multiple wavelengths.

[0038] In some embodiments of the LIDAR system illuminators of the present teachings that utilize a large number of lasers, such as hundreds of lasers, it is likely that the optical beams from some of the lasers will overlap in the eye-safety measurement aperture and some will not. In such systems, the sequence of firing of the lasers cannot be totally random to prevent overlapping beams that may present an eye safety hazard. Thus, one aspect of the present teachings uses a pseudo-random sequence of firing of the lasers. The pattern of firing satisfies a set of mathematical rules that result in an allowable sequence of firings that meets eye safety limits.

[0039] Another aspect of the present teachings is to select a preferred firing sequence that will maximize the refresh rate of the system while maintaining an eye-safe environment. For example, a non-random firing pattern can be determined that will maximize the overall pulse rate while maintaining an eye-safe environment. Such a firing pattern can be implemented, for example, through a set of rules for firing the laser that are established in the firmware of the controller.

[0040] In different embodiments of the LIDAR illuminator of the present teachings, each laser source generates an optical beam with a specific energy based on the pulse width, repetition rate, and peak power of the optical pulse. It is understood by those skilled in the art that the optical beam generated by each laser source has a specific energy density as a function of position in a plane located at the measurement distance. The energy density of the light produced from the multiple laser sources in a plane located at the measurement distance is the sum of the individual energy densities as a function of position in the plane resulting from the combination of the optical beams. The eye safety classification is met, for example, if the combined energy density of the combined optical beams as a function of position results in a peak energy sampled within a 7-mm aperture diameter across a plane at a 100-mm measurement distance that does not exceed the MPE.

[0041] By controlling the pattern of electrical signals firing the multiple laser sources, it is possible to control the energy density produced at a plane by the combined optical beams of the multiple lasers. In particular, it is possible to produce a combined optical beam from the multiple laser sources where the peak optical energy of the combined optical beam within a measurement aperture at a particular measurement distance is less than a desired value. In some embodiments, the measurement aperture is a 7-mm aperture as defined by the International Electrotechnical Commission, the measurement distance is 100 mm, and the peak optical energy is the MPE based on the particular laser wavelength as defined by the International Electrotechnical Commission.

[0042] 3 illustrates an embodiment of a laser array 300 for a LIDAR system illuminator of the present teachings. The laser array 300 consists of 30 individual laser emitters 302 in a configuration of three bars 304, each with two different wavelengths 306. In this configuration, laser emitters 302 that are immediately adjacent to one another will generate optical beams that overlap within a particular eye-safety measurement aperture. Optical beams generated by laser emitters 302 that are not immediately adjacent will not overlap. The refresh rate can be maximized without affecting eye safety by using the rule that adjacent lasers cannot be fired at the same time, but non-adjacent lasers of different wavelengths can be fired at the same time.

[0043] In this firing rule, the laser 302 on the bar 304 labeled B1 in FIG. 3 cannot be operated when the lasers 302 on the bars 304 labeled A1 and A2 in FIG. 3 are operated. In addition, the laser 302 on the bar 304 labeled A2 cannot be operated when the lasers 302 on the bars 304 labeled B1 and B2 are operated. Also, the laser 302 on the bar 304 labeled A1 may be operated simultaneously with the laser 302 on the bar 304 labeled B2. In this way, the system of firing rules allows simultaneous operation of non-adjacent bars at the maximum pulse rate of the system, but ensures that the resulting energy in the optical beam within the eye-safety measurement aperture is below the maximum permissible exposure (MPE) limit. This ensures class 1 eye safety of the overall LIDAR system.

[0044] In some embodiments of the scanning LIDAR system of the present teachings, rules regarding the firing pattern for the lasers would be generated based on monitoring the illumination pattern emitted from the illuminator. That is, the monitor would determine the peak energy in a particular aperture at a particular distance, and a firing pattern would be determined to ensure that the peak energy in a particular aperture at a particular distance is less than a particular value. In some embodiments, the rule for the firing pattern of the lasers would be that any lasers that produce two or more optical beams that overlap within any eye-safety measurement aperture associated with the illuminator would not be operated simultaneously. This rule would apply to a system in which each laser produced an optical beam that produced the maximum energy allowed within the eye-safety measurement aperture.

[0045] Another aspect of the present teachings is that various operating specifications, such as laser power operating variations and mechanical tolerances for positioning the optical beam within the illuminator, can be achieved by appropriate selection of rules regarding the firing (excitation or activation) pattern for the laser.

[0046] Various embodiments of the LIDAR system of the present teachings utilize multiple cluster VCSEL devices on a single chip. Figure 4A illustrates an array 400 comprising multiple cluster VCSEL devices 402. In particular, Figure 4A illustrates 25 cluster VCSEL devices 402 in a two-dimensional array. The array is formed with contacts 404 for the 25 individual cluster VCSEL devices 402, which can be individually biased.

[0047] Figure 4B illustrates an array 450 comprising a plurality of cluster VCSEL devices 452. Figure 4B illustrates that the array is arranged to include five cluster VCSEL devices 452 connected with contacts 454 to form five bars, with each bar including five cluster VCSEL devices 452. It will be apparent to one skilled in the art that a single monolithic 2D VCSEL array can be produced as well.

[0048] Figure 4C illustrates a top view of the anode metal contact pad 470 of a chip 472 that comprises multiple clustered VCSEL devices 474 in a 2D monolithic VCSEL array. The chip shown in Figure 4C is the top side that illuminates the VCSEL array. All the anodes of all the VCSELs in a single row are connected together with a single metal contact.

[0049] FIG. 4D illustrates a bottom view of the cathode metal contact pads 476 of a chip 472 with multiple clustered VCSEL devices as illustrated in FIG. 4C. All the cathodes in a single row are connected together with a single metal contact to reduce the number of electrical connections. With this pattern of metallization, individual VCSEL devices 474 (FIG. 4C) can be operated by biasing each row and column contact at a desired bias level. In general, when the anodes of one group of laser emitters are connected to one contact and the cathodes of a second group of laser emitters are connected to a second contact, only those individual lasers belonging to both the first and second groups of laser emitters, i.e., those with connected anodes and cathodes, will be excited when the first and second contacts are appropriately biased.

[0050] For the particular configuration shown in Figure 4D with 5 rows and 5 columns, only 10 electrical connections are required versus 25 if the VCSEL devices 474 were individually connected. Those skilled in the art will appreciate that the configuration shown in Figure 12D is one of many possible electrical addressing configurations, and that the present teachings are not limited to any particular row and column configuration or geometry of emitters. It is important to note that this advantage of reducing the number of electrical connections becomes greater as the size of the 2D VCSEL array increases.

[0051] The use of one contact connected to the anode of one group of laser emitters and a second contact connected to the cathode of a second group of laser emitters can be used to excite one laser emitter or a group of laser emitters for a particular bias condition depending on the configuration of the connections. The anode connections of the various lasers to the various contacts and the cathode connections of the various lasers connected to the various contacts determine the rules for the firing pattern. For example, the known patterns of individual laser emitters or groups of laser emitters excited together, and the energy of the optical beams these lasers generate at a particular eye-safe measurement aperture, are all taken into account in the firing control scheme when determining which individual lasers or groups are allowed to fire simultaneously.

[0052] FIG. 5 illustrates a system block diagram of an embodiment of a compact VCSEL laser driver assembly 500 for multi-wavelength LIDAR of the present teachings. In this embodiment, a pulse generation chain 502 is generated locally on the same carrier as the VCSEL assembly 504. The pulse generation chain 502 includes a pulse controller 506, a memory 508, a pulse pattern generator 510, and a laser driver 512. The laser driver 512 is connected to a VCSEL laser 514 as shown. In some embodiments, the laser driver is connected to a common contact that is used to drive multiple VCSEL lasers. In some embodiments, the pulse shapes may be stored in local memory or may be generated by a combination of a controller and pattern generator.

[0053] A system processor 516 is connected via digital input / output connections 518. The system processor 516 generates a set of instructions that instruct the laser to fire and for how long. These instructions will determine the firing pattern type. However, the firing pattern generation and biasing of the laser is done locally on the VCSEL assembly. Generating the laser driver pulse patterns locally on the VCSEL assembly greatly simplifies the interface required to the overall LIDAR system. In some embodiments, the pulse controller 506, memory 508, pulse pattern generator 510, and laser driver 512 functions are all contained within a single IC package. In various embodiments, the VCSEL device can be hermetically packaged or non-hermetically packaged.

[0054] The rules for firing the laser can be stored in various places in the scanning LIDAR system. In some embodiments, the rules for firing the laser are stored in memory 508. In some embodiments, the rules for firing the laser are input via digital I / O 518. In yet other embodiments, the rules for firing the laser are generated in a system processor based on the operating parameters of the LIDAR system. In yet other embodiments, the rules for firing the laser are generated in a controller based on the operating parameters of the LIDAR system. In yet other embodiments, the rules for firing the laser change over time based on changes in the output power, pulse width, and repetition rate provided by the laser driver assembly 500.

[0055] One feature of the present teachings is that the combination of the spacing of the transmitter elements and / or transmitter arrays, the emission pattern of the transmitter elements, and the optics used for projection and / or collimation determine whether and where the laser beams will overlap in space. In addition, separate arrays with separate wavelengths may be used. FIG. 6A illustrates a schematic diagram of an embodiment of a LIDAR illuminator 600 of the present teachings using two arrays of VCSELs of different wavelengths with a first lens system. The two VCSEL arrays 602, 604 are offset by a distance 606 of about 8 mm. It can be seen that in some cases, the individual laser beams 608, 610 from each array of VCSELs will combine in space, while in other cases, the laser beams 612, 614 will not combine. There are geometric relationships that determine the criteria for whether the beams 608, 610, 612, 614 will combine. For example, with an 8 mm offset distance 606 between arrays 602, 604, beams projected at the same nominal angle (i.e., beams 608, 614 and beams 612, 610 from two separate arrays) would not spatially combine to exceed eye-safety limits at a 7 mm aperture 616 positioned at a distance 618 of 100 mm. If one only considers the 7 mm aperture 616, a simple rule that would allow simultaneous firing of VCSELs from both arrays 602, 604 would be to choose the same location within each array under the assumption that the lens systems per array are nominally the same.

[0056] However, if the beams are highly collimated, other eye safety criteria corresponding to the use of binoculars must be considered. FIG. 6B illustrates a schematic diagram of an embodiment of a LIDAR illuminator 630 of the present teachings using two arrays 632, 634 of different wavelengths of VCSELs with a second lens system that produces a highly collimated beam. When highly collimated, two beams with the same projection angle will combine within a 50 mm aperture at 2,000 mm. The beams must differ by about 1.4° relative to each other so that the beams do not combine within a 50 mm aperture at 2,000 mm. Thus, in the embodiment shown in FIG. 6B, the laser beams 636, 638 from the two arrays 632, 634 are projected at an angle of 1.4° relative to each other so that the laser eye safety rules will be met for the conditions of binocular use. The laser beams 636, 638 do not overlap within a 50 mm aperture 642 at a distance 644 of 2,000 mm. In some embodiments, the lens system of FIG. 6B is the same as the lens system in the embodiment described in connection with FIG. 6A, and the projection angle that determines whether the beams are combined is based on the emission pattern of the laser elements in the VCSEL array. In some embodiments, the projection angle is also influenced by the configuration of the lens system. Regardless of the mechanism by which the projection angle is determined, the condition for non-overlapping beams that meet laser eye safety rules is projection at an angle 640 of 1.4° relative to each other.

[0057] FIG. 6C illustrates a schematic diagram of an embodiment of a LIDAR illuminator 660 of the present teachings that uses two arrays 662, 664 of different wavelengths of VCSELs with a third lens system 666. The two arrays 662, 664 are separated by a distance 668 of about 8 mm. The range of angles excluded from a 7 mm aperture 670 at a distance 672 of 100 mm is shown in FIG. 6C. Here, it can be seen that the range of 0° to −9.5° needs to be avoided for the upper array laser beam relative to the lower array laser beam. Thus, in some embodiments, when combining the two safety conditions, the system utilizes relative projection angles between the upper and lower beams outside the range of 1.4° to −9.5° to implement simultaneous firing of the lasers.

[0058] (Equivalent) While the applicant's teachings are described in conjunction with various embodiments, it is not intended that the applicant's teachings be limited to such embodiments. Rather, the applicant's teachings extend to various alternatives, modifications, and equivalents, which can be made therein without departing from the spirit and scope of the present teachings, as will be appreciated by those skilled in the art.

Claims

1. A LIDAR illuminator, a) a laser array comprising a plurality of laser sources, each of the plurality of laser sources generating an optical beam when excited at an electrical input, the plurality of laser sources being arranged such that the generated optical beams from at least some of the plurality of laser sources are in an eye-safe measurement aperture and at least some other of the generated optical beams are not in the eye-safe measurement aperture; b) a controller having an output electrically connected to an input of a laser driver, the laser driver comprising a plurality of electrical outputs, one of the plurality of electrical outputs being electrically connected to one of the plurality of laser sources, the controller being configured to excite the plurality of laser sources based on firing pattern rules such that the generated optical beams from at least some of the plurality of laser sources in the eye-safety measurement aperture are not excited during the same period of time that at least some other laser sources of the plurality of laser sources in the eye-safety measurement aperture are excited, and configured to excite the plurality of laser sources such that optical power generated by the laser array in the eye-safety measurement aperture does not exceed a maximum permissible exposure (MPE) limit; and 1. A LIDAR illuminator comprising:

2. A LIDAR illuminator as described in claim 1, wherein each electrical output of the plurality of electrical outputs of the laser driver is connected to an electrical input of a respective laser source of the plurality of laser sources.

3. The LIDAR illuminator of claim 1, wherein one of the multiple electrical outputs of the laser driver is electrically connected to a common contact used to drive multiple VCSEL lasers.

4. A LIDAR illuminator as described in claim 1, wherein the controller is further configured to excite the multiple laser sources based on a firing pattern rule such that at least some of the other optical beams of the generated optical beams that are not in the eye-safety measurement aperture are excited simultaneously.

5. A LIDAR illuminator as described in claim 1, wherein the firing pattern rules are selected to result in an acceptable sequence of firings that meets eye safety limits.

6. The LIDAR illuminator of claim 1, wherein the firing pattern rule includes a pseudo-random sequence.

7. The LIDAR illuminator of claim 1, wherein the laser array includes a vertical cavity surface emitting laser (VCSEL) array.

8. The LIDAR illuminator of claim 7, wherein at least one VCSEL in the VCSEL array includes a cluster VCSEL.

9. The LIDAR illuminator of claim 1, wherein the eye-safe measurement aperture has a diameter of 7 mm and a measurement distance is 100 mm.

10. The LIDAR illuminator of claim 1, wherein the eye-safe measurement aperture has a diameter of 50 mm and a measurement distance is 2000 mm.

11. A LIDAR illuminator as described in claim 1 having a range of at least 100 meters.

12. The LIDAR illuminator of claim 1, wherein the multiple laser sources in the laser array are positioned in multiple rows.

13. A LIDAR illuminator as described in claim 12, wherein at least some of the generated optical beams from at least one of the plurality of laser sources in adjacent rows of the plurality of rows are in the eye-safety measurement aperture, and at least one other of the generated optical beams from the plurality of laser sources in non-adjacent rows of the plurality of rows are not in the eye-safety measurement aperture.

14. The LIDAR illuminator of claim 13, wherein the firing pattern rules include firing pattern rules that enable excitation of at least one of the laser sources in non-adjacent rows during the same time period.

15. The LIDAR illuminator of claim 13, wherein the firing pattern rules include firing pattern rules that prevent excitation of at least one of the laser sources in adjacent rows during the same time period.

16. The LIDAR illuminator of claim 1, wherein the laser array further comprises at least one single metal contact connecting the electrical inputs of multiple laser sources in the laser array positioned in a row.

17. A LIDAR illuminator as described in claim 1, wherein the laser array further comprises at least one single metal contact connecting the electrical inputs of multiple laser sources in the laser array positioned in a row.

18. A LIDAR illuminator, comprising: a) a laser array comprising a plurality of laser sources, each of the plurality of laser sources generating an optical beam when excited at an electrical input, the plurality of laser sources being arranged such that the generated optical beams from at least some of the plurality of laser sources are in an eye-safe measurement aperture and at least some other of the generated optical beams are not in the eye-safe measurement aperture; b) a processor having a digital output; c) a controller having a digital input and an output electrically connected to the digital output of the processor; d) a laser driver having an input electrically connected to the output of the controller and a plurality of electrical outputs, each of the plurality of electrical outputs being electrically connected to one of the plurality of laser sources, the controller being configured to excite the plurality of laser sources based on firing pattern rules such that the generated optical beams from at least some of the plurality of laser sources in the eye-safety measurement aperture are not excited during the same period of time that at least some other laser sources of the plurality of laser sources in the eye-safety measurement aperture are excited, and configured to excite the plurality of laser sources such that optical power generated by the laser array in the eye-safety measurement aperture does not exceed a maximum permissible exposure (MPE) limit; 1. A LIDAR illuminator comprising:

19. The LIDAR illuminator of claim 18, wherein the processor includes the controller.

20. The LIDAR illuminator of claim 18, further comprising a pattern generator.

21. A LIDAR illuminator as described in claim 20, wherein the pattern generator and the laser driver are formed within a single integrated circuit.

22. The LIDAR illuminator of claim 18, further comprising a memory electrically connected to the controller, the memory storing a pulse shape.

23. A LIDAR illuminator as described in claim 22, wherein the memory and the laser driver are formed within a single integrated circuit.

24. The LIDAR illuminator of claim 18, wherein each electrical output of the plurality of electrical outputs of the laser driver is connected to an electrical input of a respective laser source of the plurality of laser sources.

25. The LIDAR illuminator of claim 18, wherein the controller is further configured to excite the multiple laser sources based on a firing pattern rule such that at least some of the other optical beams of the generated optical beams that are not in the eye-safety measurement aperture are excited during the same time period.

26. The LIDAR illuminator of claim 18, wherein the firing pattern rules are selected to result in an acceptable sequence of firings that meets eye safety limits.

27. ​​A LIDAR illuminator as described in claim 18, wherein the multiple laser sources in the laser array are positioned in multiple rows, and at least some of the generated optical beams from at least some of the multiple laser sources in adjacent rows of the multiple rows are in the eye-safety measurement aperture, and at least some other of the generated optical beams from the multiple laser sources in non-adjacent rows of the multiple rows are not in the eye-safety measurement aperture.

28. The LIDAR illuminator of claim 27, wherein the firing pattern rules include firing pattern rules that enable excitation of at least one of the laser sources in non-adjacent rows during the same time period.

29. The LIDAR illuminator of claim 27, wherein the firing pattern rules include a firing rule that prevents excitation of at least one of the laser sources in adjacent rows during the same time period.

30. The LIDAR illuminator of claim 18, wherein the laser array includes a vertical cavity surface emitting laser (VCSEL) array.

31. The LIDAR illuminator of claim 30, wherein at least one VCSEL in the VCSEL array includes a cluster VCSEL.

32. The LIDAR illuminator of claim 18, wherein the eye-safe measurement aperture has a diameter of 7 mm and a measurement distance is 100 mm.

33. The LIDAR illuminator of claim 18, wherein the eye-safe measurement aperture has a diameter of 50 mm and a measurement distance is 2000 mm.

34. A LIDAR illuminator as described in claim 18, having a range of at least 100 meters.

35. A LIDAR illuminator comprising: a) a laser array comprising a plurality of laser sources positioned in a plurality of rows, each of the plurality of laser sources adapted to generate an optical beam when excited at an electrical input, the plurality of laser sources being arranged such that the generated optical beams from at least some of the plurality of laser sources are in an eye-safe measurement aperture and at least some other of the generated optical beams are not in the eye-safe measurement aperture; b) a controller having an output electrically connected to an input of a laser driver, the laser driver comprising a plurality of electrical outputs, one of the plurality of electrical outputs electrically connected to one of the plurality of laser sources, the controller being configured to excite the plurality of laser sources based on a firing pattern rule such that at least some of the generated optical beams from at least some of the plurality of laser sources in adjacent ones of the plurality of rows are in the eye-safe measurement aperture and at least some other of the generated optical beams from the plurality of laser sources in non-adjacent ones of the plurality of rows are not in the eye-safe measurement aperture; and 1. A LIDAR illuminator comprising:

36. The LIDAR illuminator of claim 35, wherein the controller is further configured to prevent the generated optical beams from at least some of the multiple laser sources that spatially overlap at a target from being excited during the same period of time.

37. The LIDAR illuminator of claim 35, wherein the firing pattern rules include a firing rule that enables excitation of at least one of the laser sources in non-adjacent rows during the same time period.

38. The LIDAR illuminator of claim 35, wherein the firing pattern rules include a firing rule that prevents excitation of at least one of the laser sources in adjacent rows during the same time period.

39. The LIDAR illuminator of claim 35, wherein the laser array includes a vertical cavity surface emitting laser (VCSEL) array.

40. The LIDAR illuminator of claim 39, wherein at least one VCSEL in the VCSEL array includes a cluster VCSEL.

41. The LIDAR illuminator of claim 35, wherein the eye-safe measurement aperture has a diameter of 7 mm and a measurement distance is 100 mm.

42. The LIDAR illuminator of claim 35, wherein the eye-safe measurement aperture has a diameter of 50 mm and a measurement distance is 2000 mm.

43. A LIDAR illuminator as described in claim 35, having a range of at least 100 meters.

44. A LIDAR illuminator comprising: a) a laser array comprising a plurality of laser sources positioned in a plurality of rows, each of the plurality of laser sources adapted to generate an optical beam when excited at an electrical input, the plurality of laser sources being arranged such that at least some of the generated optical beams from at least some of the plurality of laser sources in adjacent rows of the plurality of rows are in an eye-safe measurement aperture, and at least some other of the generated optical beams from the plurality of laser sources in non-adjacent rows of the plurality of rows are not in the eye-safe measurement aperture at a target; b) a processor having a digital output; c) a controller having a digital input electrically connected to the digital output of the processor and having an output; d) a laser driver having an input electrically connected to the output of the controller and a plurality of electrical outputs, each of the plurality of electrical outputs being electrically connected to one of the plurality of laser sources, the controller being configured to excite the plurality of laser sources based on firing pattern rules such that the generated optical beams from at least some of the plurality of laser sources in the eye-safe measurement aperture at the target are not excited during the same period of time as at least some other laser sources of the plurality of laser sources in the eye-safe measurement aperture are excited; 1. A LIDAR illuminator comprising:

45. The LIDAR illuminator of claim 44, wherein the firing pattern rules include a firing rule that enables excitation of at least one of the laser sources in non-adjacent rows during the same time period.

46. ​​The LIDAR illuminator of claim 44, wherein the firing pattern rules include a firing rule that prevents excitation of at least one of the laser sources in adjacent rows during the same time period.

47. The LIDAR illuminator of claim 44, wherein the laser array includes a vertical cavity surface emitting laser (VCSEL) array.

48. The LIDAR illuminator of claim 47, wherein at least one VCSEL in the VCSEL array includes a cluster VCSEL.

49. The LIDAR illuminator of claim 44, wherein the eye-safe measurement aperture has a diameter of 7 mm and a measurement distance is 100 mm.

50. The LIDAR illuminator of claim 44, wherein the eye-safe measurement aperture has a diameter of 50 mm and a measurement distance is 2000 mm.

51. A LIDAR illuminator as described in claim 44, having a range of at least 100 meters.

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