LIDAR data acquisition and control

Abstract

To provide methods and systems for performing three-dimensional LIDAR measurements by using an integrated LIDAR measurement device.SOLUTION: In one aspect, a return signal receiver generates a pulse trigger signal that triggers generation of a pulse of illumination light and data acquisition of a return signal, and also triggers time of flight calculation by time to digital conversion. In addition, the return signal receiver also estimates width and peak amplitude of each return pulse, and samples each return pulse waveform individually over a sampling window that includes the peak amplitude of each return pulse waveform. In a further aspect, the time of flight associated with each return pulse is estimated based on a coarse timing estimate and a fine timing estimate. In another aspect, the time of flight is measured from the measured pulse due to internal optical crosstalk and a valid return pulse.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This patent application claims priority to U.S. Provisional Patent Application No. 62 / 503,237, entitled "LIDAR Data Acquisition and Control," filed May 8, 2017, which in turn claims priority to U.S. Provisional Patent Application No. 15 / 974,527, entitled "LIDAR Data Acquisition and Control," filed May 8, 2018, the entire contents of which are incorporated herein by reference.

[0002] The disclosed embodiments relate to a LIDAR-based 3D point cloud measurement system. [Background technology]

[0003] LIDAR systems use pulses of light to measure distance to objects based on the time of flight (TOF) of each light pulse. Light pulses emitted from a light source in a LIDAR system interact with distant objects. Some of the light reflects off the object and returns to the LIDAR system's detector. Distance is estimated based on the time elapsed between the emission of the light pulse and the detection of the returning light pulse. In some examples, pulses of light are generated by a laser emitter. The light pulses are focused through a lens or lens assembly. The time it takes for the laser light pulse to return to a detector mounted near the emitter is measured. Distance is derived with high precision from the time measurement.

[0004] Some LIDAR systems use a single laser emitter / detector combination in combination with a rotating mirror to effectively scan a plane. The range measurements performed by such systems are two-dimensional (i.e., planar) in nature, and the range points captured are presented as a two-dimensional (i.e., single-plane) point cloud. In some instances, the rotating mirror rotates at very high speeds (e.g., thousands of revolutions per minute).

[0005] Many operational scenarios require 3D point clouds. Many schemes are employed to survey the surrounding environment in three dimensions. In some instances, 2D equipment moves up and down and / or back and forth, often on a gimbal. This is commonly known to those skilled in the art as a sensor "wink" or "nod." A single-beam LIDAR unit can thus be used to capture an entire 3D array of distance points, albeit one point at a time. A related example uses a prism to "split" a laser pulse into multiple layers, each with a slightly different vertical angle. This simulates the nodding effect described above, but the sensor itself does not operate.

[0006] In all of the above examples, the optical path of a single laser emitter / detector combination is modified in some way to obtain a wider field of view than a single sensor. The number of pixels such a device can produce per unit time is inherently limited by the pulse repetition rate of the single laser. Modifying the beam path by actuating mirrors, prisms, or other devices that expand the coverage area results in a decrease in point cloud density.

[0007] As mentioned above, there are several configurations for 3D point cloud systems. However, many applications require a wide field of view. For example, in autonomous vehicle applications, the vertical field of view must extend as far downward as possible to view the ground in front of the vehicle. Additionally, the vertical field of view must extend above the horizon in case the vehicle enters a pothole. Furthermore, the delay between real-world motion and the imaging of that motion must be minimized. In some instances, complete image updates at least five times per second are desirable. To address these requirements, a 3D-LIDAR system has been developed that includes an array of multiple laser emitters and detectors. This system is described in U.S. Patent No. 7,969,558, issued June 28, 2011, the contents of which are incorporated herein by reference in their entirety.

[0008] In many applications, a series of pulses are emitted, with the direction of each pulse changing rapidly in succession. In these examples, the distance measurements associated with each pulse consider pixels, and the collection of pixels emitted and captured in rapid succession (i.e., a "point cloud") can be obtained as an image or analyzed for other reasons (such as obstacle detection). In some examples, display software is used to obtain the resulting point cloud as an image that is displayed to the user in three dimensions. Various schemes can be used to represent the distance measurements as a 3D image that appears as if it were taken with a real-life camera.

[0009] Some existing LIDAR systems employ illumination sources and detectors that are not integrated on a common substrate (e.g., electrical mounting board). Furthermore, the illumination and collection beam paths are separated within the LIDAR device. This makes the optomechanics design complex and difficult to align.

[0010] Additionally, the mechanical devices used to scan the illumination beam in different directions are sensitive to mechanical vibrations, inertial forces, and general environmental conditions, and if not properly designed, these mechanical devices can deteriorate, leading to poor performance or failure.

[0011] To measure a 3D environment with high resolution and high throughput, measurement pulses must be very short. Current systems suffer from low resolution due to their limited ability to generate short-duration pulses and resolve short-duration return pulses.

[0012] In realistic operating environments, target reflectivity and proximity vary greatly, limiting measurement capabilities due to detector saturation. Additionally, power consumption can cause LIDAR systems to overheat.

[0013] Illuminators, targets, circuits, and temperatures vary in every system. Variations in all of these factors can limit system performance unless the signals detected by each LIDAR device are properly calibrated.

[0014] To improve image resolution and image range, improvements to the illumination drive electronics and receiver electronics of LIDAR systems are desired. Summary of the Invention

[0015] SUMMARY OF THE INVENTION A method and system for performing three-dimensional LIDAR measurements using an integrated LIDAR measurement device is described herein.

[0016] In one embodiment, the return signal receiver of the LIDAR measurement device generates a pulse trigger signal that causes an illumination driver to supply power to the illumination source, causing the illumination source to generate pulses of illumination light. Additionally, the pulse trigger signal initiates data acquisition of the return signal and associated time-of-flight calculations. In this manner, the pulse trigger signal is used to initiate both pulse generation and return pulse data acquisition. This ensures precise synchronization of pulse generation and return pulse acquisition, enabling accurate time-of-flight calculations through time-to-digital conversion.

[0017] In another aspect, the return signal receiver identifies one or more return pulses of light reflected from one or more objects in the surrounding environment in response to the pulse of illumination light and determines the time of flight associated with each of the return pulses. The return signal receiver also estimates the width of each return pulse, the peak amplitude of each return pulse, and samples each return pulse waveform individually over a sampling window that includes the peak amplitude of each return pulse waveform. Information about the characteristics and timing of these signals is communicated from the integrated LIDAR measurement device to a master controller.

[0018] In a further aspect, the time of flight associated with each return pulse is estimated by the return signal receiver based on the coarse timing module and the fine timing module. In a further aspect, when the hit signal arrives at a clock transition, a metastable bit is used to determine the correct count of the coarse timing module. The value of the metastable bit determines whether the hit signal arrives at a high-to-low transition of the counter signal or a low-to-high transition of the counter signal, resulting in the correct count value.

[0019] In another further aspect, the return pulse receiver IC measures the time of flight based on the time spent between the detection of a pulse due to internal crosstalk between the illumination source and the photodetector of the integrated LIDAR measurement device and a valid return pulse, thus eliminating system-induced delays from the time of flight estimate.

[0020] In another aspect, the master controller is configured to generate a plurality of pulse command signals that are respectively transmitted to separate integrated LIDAR measurement devices, each of which generates a corresponding pulse trigger signal based on the received pulse command signal.

[0021] The foregoing description is a summary and, as such, necessarily contains simplifications, generalizations, and omissions of detail; therefore, those skilled in the art will appreciate that this summary is merely illustrative and is in no way limiting. Other aspects, innovative features, and advantages of the devices and / or processes described herein will become apparent in the non-limiting detailed description set forth herein. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a simplified diagram illustrating one embodiment of a LIDAR measurement system including at least one integrated LIDAR measurement device in accordance with at least one novel aspect.

[0023] [Figure 2]1 illustrates the timing associated with emitting a measurement pulse from an integrated LIDAR measurement device 130 and capturing a returning measurement pulse.

[0024] [Figure 3] 1 shows a simplified diagram illustrating one embodiment showing a portion of a return signal receiver IC including a return signal analysis module 160 in one embodiment.

[0025] [Figure 4] 1 shows a simplified diagram illustrating one embodiment of a portion of a return signal receiver IC including a constant fraction discriminator module 170 in one embodiment.

[0026] [Figure 5] 1 shows a simplified diagram illustrating one embodiment of a portion of a return signal receiver IC including a coarse timing module in one embodiment.

[0027] [Figure 6] 1 shows a simplified diagram illustrating one embodiment of a portion of a return signal receiver IC including a precision timing module in one embodiment.

[0028] [Figure 7] 1 shows a simplified diagram illustrating one embodiment of a portion of a return signal receiver IC including a pulse width detection module in one embodiment.

[0029] [Figure 8] FIG. 1 illustrates an embodiment of a 3D-LIDAR system 100 in one exemplary operating scenario.

[0030] [Figure 9] FIG. 1 illustrates another embodiment of the 3D-LIDAR system 10 in one exemplary operating scenario.

[0031] [Figure 10] 1 illustrates an exploded view of a 3D-LIDAR system 100 in one exemplary embodiment.

[0032] [Figure 11] FIG. 2 is a diagram showing details of an optical element 116.

[0033] [Figure 12] 1 is a cross-sectional view of optical system 116 showing the shaping of each beam of collected light 118. FIG.

[0034] [Figure 13] 3 shows a flowchart illustrating a method 300 for performing LIDAR measurements with an integrated LIDAR measurement device in accordance with at least one novel aspect. DETAILED DESCRIPTION OF THE INVENTION

[0035] Reference will now be made in detail to background and certain embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0036] 1 illustrates a LIDAR measurement system 120 in one embodiment. The LIDAR measurement system 120 includes a main controller 190 and one or more integrated LIDAR measurement devices 130. The integrated LIDAR measurement device 130 includes a return signal receiver integrated circuit (IC) 150, a gallium nitride-based illumination driver integrated circuit (IC) 140, an illumination source 132, a photodetector 138, and a transimpedance amplifier (TIA) 141. Each of these elements is mounted on a common substrate 144 (e.g., a printed circuit board) that provides mechanical support and electrical connectivity between the elements.

[0037] Additionally, in some embodiments, the integrated LIDAR measurement device includes one or more power supplies that power the electronic elements mounted on the substrate 144 and that power the illumination device 132. The power supplies may be configured to provide a suitable voltage or current. In some embodiments, one or more power supplies are mounted on the substrate 144. In general, however, any of the power supplies described herein may be mounted on a separate substrate and electrically connected to the various elements mounted on the substrate 144 in any suitable manner.

[0038] Master controller 190 is configured to generate pulse command signals 191 that are communicated to receiver ICs 150 of the integrated LIDAR measurement devices 130. Typically, a LIDAR measurement system includes several different integrated LIDAR measurement devices 130. In these embodiments, master controller 190 communicates pulse command signals 191 to each of the different integrated LIDAR measurement devices. In this manner, master controller 190 coordinates the timing of LIDAR measurements performed by any number of integrated LIDAR measurement devices.

[0039] Pulse command signal 191 is a digital signal generated by master controller 190. As such, the timing of pulse command signal 191 is determined by a clock associated with master controller 190. In some embodiments, pulse command signal 191 is used directly to initiate pulse generation by light driver IC 140 and data acquisition by receiver IC 150. However, light driver IC 140 and receiver IC 150 do not share the same clock as master controller 190. As such, accurate estimation of time-of-flight becomes much more computationally cumbersome when pulse command signal 191 is used directly to initiate pulse generation and data collection.

[0040] In one embodiment, receiver IC 150 receives pulse command signal 191 and, in response to pulse command signal 191, generates pulse trigger signal V TRGThe receiver IC 150 generates a pulse trigger signal 143. The pulse trigger signal 143 is communicated to the illumination driver IC 140 and directly operates the illumination driver IC 140 to provide electrical pulses 131 to the illumination source 132, which causes the illumination source 132 to generate pulses of illumination light 134. In addition, the pulse trigger signal 143 directly initiates data acquisition of the return signal 142 and associated time-of-flight calculation. In this manner, the pulse trigger signal 143, generated based on the internal clock of the receiver IC 150, is used to initiate both pulse generation and return pulse data acquisition. This ensures synchronization between pulse generation and return pulse acquisition, which allows for accurate time-of-flight calculation through time-to-digital conversion.

[0041] Illumination source 132 emits a measurement pulse of illumination light 134 in response to the pulse of electrical energy 131. Illumination light 134 is focused and projected onto a specific location in the surrounding environment by one or more optical elements of the LIDAR system.

[0042] In some embodiments, the illumination source 132 is laser-based (e.g., a laser diode). In some embodiments, the illumination source is based on one or more light-emitting diodes. In general, any suitable pulsed illumination source is contemplated.

[0043] As shown in FIG. 1, illumination light 134 emitted from an integrated LIDAR measurement device 130 and corresponding return measurement light 135 reflected back toward the integrated LIDAR measurement device 130 share a common optical path. The integrated LIDAR measurement device 130 includes a photodetector 138 having an active sensor area 137. As shown in FIG. 1, the illumination source 132 is located outside the field of view of the photodetector's active area 137. As shown in FIG. 1, an overmolded lens 136 is attached to the photodetector 138. The overmolded lens 136 includes a conical cavity that corresponds to the ray acceptance cone of the return light 135. Illumination light 134 from the illumination source 132 is coupled to the detector acceptance cone by a fiber waveguide. An optical coupler optically couples the illumination source 132 to the fiber waveguide. At the end of the fiber waveguide, a mirror element 133 is tilted at an angle (e.g., 45 degrees) relative to the waveguide to direct illumination light 134 into the cone of return light 135. In one embodiment, the end face of the fiber waveguide is cut at a 45-degree angle, and the end face is coated with a highly reflective dielectric coating to provide a mirrored surface. In some embodiments, the waveguide includes a rectangular glass core and a polymer cladding with a lower refractive index. In some embodiments, the entire optical assembly is encapsulated in a material with a refractive index that closely matches the refractive index of the polymer cladding. In this way, the waveguide directs illumination light 134 into the acceptance cone of return light 135 with minimal occlusion.

[0044] The placement of the waveguide within the acceptance cone of the return light 135 projected onto the active sensing area 137 of the detector 138 is chosen to ensure maximum overlap in the far field between the illumination spot and the field of view of the detector.

[0045] 1, the return light 135 reflected from the surrounding environment is detected by a photodetector 138. In some embodiments, the photodetector 138 is an avalanche photodiode. The photodetector 138 generates an output signal 139, which is communicated to a return signal receiver IC 150.

[0046] The output signal 139 is received and amplified by the TIA 141. The amplified signal 142 is transmitted to the return signal analysis module 160. Generally, the amplification of the output signal 139 can include multiple amplifier stages. In this sense, an analog transimpedance amplifier is presented as a non-limiting example, as many other analog signal amplification schemes are contemplated within the scope of this patent document. As shown in FIG. 1 , the TIA 141 is integrated with the return signal receiver IC 150, although in general, the TIA 141 can be implemented as a separate device separate from the receiver IC 150. In some embodiments, integrating the TIA 141 with the receiver IC 150 is preferred to save space and reduce signal pickup.

[0047] The return signal receiver IC 150 performs several functions. In one embodiment, the receiver IC 150 identifies one or more return pulses of light reflected from one or more objects in the surrounding environment in response to the pulse of illumination light 134 and determines the time of flight associated with each of these return pulses. Generally, the output signal 139 is processed by the return signal receiver IC 150 for a period corresponding to the time of flight of light from the LIDAR measurement device 130 to a distance equal to the maximum range of the device 130 and back to the device 130. During this period, the illumination pulse 134 may encounter several objects at different distances from the integrated LIDAR measurement device 130. Thus, the output signal 139 may include several pulses, each corresponding to a portion of the illumination beam 134 reflected from different reflective surfaces located at different distances from the device 130. In another embodiment, the receiver IC 150 determines various characteristics of each return pulse. 1, receiver IC 150 determines an indication of the width of each return pulse, determines the peak amplitude of each return pulse, and individually samples each return pulse waveform over a sampling window that includes the peak amplitude of each return pulse waveform. These signal characteristics and timing information are communicated from integrated LIDAR measurement device 130 to master controller 190. Master controller 190 can further process this data or communicate this data directly to an external computing device (e.g., by a user of LIDAR measurement system 120) for further image processing.

[0048] FIG. 2 illustrates the timing associated with emitting measurement pulses and capturing return measurement pulses from the integrated LIDAR measurement device 130. As shown in FIG. 2, measurements are initiated by the rising edge of a pulse trigger signal 143 generated by the receiver IC 150. As shown in FIGS. 1 and 2, an amplified return signal 142 is generated by the TIA 141. As previously described, a measurement window (i.e., the period of time during which collected return signal data is associated with a particular measurement pulse) is initiated by enabling data acquisition on the rising edge of the pulse trigger signal 143. In response to emitting a sequence of measurement pulses, the receiver IC 150 time-scales the duration of the measurement window, T, to correspond to the window of time during which a return signal is expected. measurement In some examples, the measurement window is enabled at the rising edge of the pulse trigger signal 143 and disabled at a time corresponding to the time of flight of light over a distance approximately twice the range of the LIDAR system. In this way, the measurement window is open to collect return light from objects adjacent to the LIDAR system (i.e., with negligible time of flight) up to the maximum range of the LIDAR system. In this way, all other light that may not contribute to a useful return signal is filtered out.

[0049] 2, the return signal 142 includes three return measurement pulses corresponding to the emitted measurement pulses. Typically, signal detection is performed for all detected measurement pulses. Further, signal analysis can be performed to identify the closest valid signal 142B (i.e., the first valid event of the return measurement pulses), the strongest signal, and the furthest valid signal 142C (i.e., the last valid event of the return measurement pulses in the measurement window). Any of these events can be reported by a LIDAR system as potentially useful distance measurements.

[0050] Internal system delays associated with emitting light from a LIDAR system (e.g., signaling delays and latencies associated with switching elements, energy storage elements, and pulse emitters) and delays associated with collecting light and generating signals indicative of the collected light (e.g., amplifier latencies, analog-to-digital conversion delays, etc.) contribute to errors in estimating the time-of-flight of a measured pulse of light. Therefore, measuring time-of-flight based on the elapsed time between the rising edge of pulse trigger signal 143 and each valid return pulse (i.e., 142B and 142C) introduces undesirable measurement errors. In some embodiments, a calibrated, predetermined delay is employed to compensate for the electronic delay to obtain a corrected estimate of the actual time-of-flight of light. However, static corrections for dynamically changing electronic delays have limited accuracy. Frequent recalibration is possible, but this adds computational complexity and negatively impacts system uptime.

[0051] In another embodiment, receiver IC 150 measures the time of flight based on the elapsed time between the detection of detected pulse 142A due to internal crosstalk between illumination source 132 and photodetector 138 and valid return pulses (e.g., 142B and 142C). In this way, system-induced delays are eliminated from the time of flight estimate. Pulse 142A is generated by internal crosstalk, which effectively eliminates the propagation distance of light. Therefore, the time delay from the rising edge of the pulse trigger signal to the event of detection of pulse 142A captures all system-induced delays associated with illumination and signal detection. By measuring the time of flight of valid return pulses (e.g., return pulses 142B and 142C) relative to detected pulse 142A, all system-induced delays associated with illumination and signal detection due to internal crosstalk are eliminated. As shown in FIG. 2, receiver IC 150 estimates a time of flight TOF1 associated with return pulse 142B and a time of flight TOF2 associated with return pulse 142C relative to return pulse 142A.

[0052] In some embodiments, the signal analysis is performed entirely by the receiver IC 150. In these embodiments, the time-of-flight signal 192 communicated from the integrated LIDAR measurement device 130 includes an indication of the time-of-flight of each return pulse as determined by the receiver IC 150. In some embodiments, the signals 155-157 include waveform information associated with the return pulses generated by the receiver IC 150. This waveform information is further processed by one or more processors onboard the 3D LIDAR system or external to the 3D LIDAR system to obtain another estimate of the distance, an estimate of one or more physical properties of the detected object, or a combination thereof.

[0053] Return signal receiver IC 150 is a mixed analog / digital signal processing IC. In the embodiment shown in Figure 1, return signal receiver IC 150 includes TIA 141, return signal analysis module 160, time-of-flight calculation module 159, and analog-to-digital conversion module 158.

[0054] Figure 3 illustrates one embodiment of the return signal analysis module 160. In the embodiment illustrated in Figure 3, the return signal analysis module 160 includes a constant fraction discriminator (CFD) circuit 170, a coarse timing module 180, a fine timing module 190, a pulse width detection module 200, and a return pulse sample and hold module 210.

[0055] Amplified return signal, V TIA 142, and a threshold signal, V THLD 145 is received by the CFD 170. When the return signal 142 exceeds a threshold (i.e., the value of the threshold signal 145), the CFD 170 identifies a valid return pulse. Additionally, the CFD 170 repeatedly determines when a valid return pulse has been detected and generates a rapidly changing hit signal V HIT 178. Hit signal 178 indicates the detection of a valid return pulse and initiates the timing and waveform acquisition and analysis functions of return signal analysis module 160, respectively.

[0056] For example, the coarse timing module 180 determines a digital signal (i.e., RANGE 151) that indicates the number of digital clock cycles that have elapsed since the transition of the pulse trigger signal 143 that initiated the illumination pulse 134 and the transition of the hit signal 178 associated with a particular valid return pulse. The coarse timing module 180 generates a digital signal (i.e., MS 152) that is the digital clock signal shifted in time by half a period of the digital clock signal.

[0057] Additionally, the precision timing module 190 generates an analog signal (i.e., V ) having a voltage value indicative of the elapsed time between the transition of the hit signal 178 associated with a particular valid return pulse and the next transition of the digital clock signal CLK. CLK 153). Similarly, precision timing module 190 determines an analog signal (i.e., V 153 ) having a voltage value indicative of the elapsed time between the transition of hit signal 178 associated with a particular valid return pulse and the next transition of inverted digital clock signal CLKB. CLKB 154). The time-of-flight module 159 determines the RANGE 151, MS 152, and V CLK 153, and V CLKB 154 is used to determine the time of flight associated with each detected return pulse.

[0058] The return pulse sample and hold module 210 generates an analog signal (i.e., V) having a signal value (e.g., voltage) indicative of the peak amplitude of each valid return pulse. PEAK In addition, the return pulse sample and hold module 210 generates a set of analog signals (i.e., V WIND 155). In some embodiments, the number of sampling points before and after the peak amplitude of the waveform is programmable.

[0059] The pulse width detection module 200 detects an analog signal (i.e., V WIDTH 157). In the illustrated embodiment, V WIDTH The value of 157 is the return pulse signal 142 V THLD 145 and the transition of the hit signal 178 associated with a particular valid return pulse. WIND 155, V PEAK 156, and V WIDTH 157 are each converted to a digital signal by an analog-to-digital converter (ADC) 158 in the return signal receiver IC 150 before transmission from the return signal receiver IC to the main controller 190.

[0060] 4 illustrates a constant fraction discriminator 170 in one embodiment. As shown in FIG. 4, the constant fraction discriminator 170 includes a signal delay module 171, a signal splitting module 172, an enable module 173, and a comparator module 174. The analog output signal 142 generated by the TIA 141 is communicated to the signal delay module 171, the signal splitting module 172, and the enable module 173. The signal delay module 171 introduces a fixed delay into the signal 142, and V DELAY At the same time, the signal division module 172 generates V TIA Divide 142 by a certain ratio (for example, by 2) to get V FRACT 176 includes a voltage divider circuit to generate V DELAY 175 and V FRACT The value of 176 is compared by comparator 174. In one example, the hit signal V HIT 178 is V DELAY 175 is V FRACT When it is greater than 176, it goes high and V DELAY 175 is V FRACT When it is less than 176, V HIT 178 goes low. Thus, V HIT178 indicates when a return pulse arrives and when it passes in a consistent manner. If an arbitrary threshold were employed to determine the arrival of a return pulse, the timing of the arrival would be inconsistent because different return pulses would not be similarly shaped. However, by using a constant fraction discriminator, the timing of return pulse arrival and passage is consistently identified across multiple return pulses. Enable module 173 controls the voltage threshold V THLD 145 and receives the return signal V TIA The value of 142 is V THLD When it exceeds 145, the enable signal V ENABLE 177. In this way, the comparator module 174 is only enabled when the return signal 142 exceeds the threshold. This allows spurious spikes in the return signal 142 to be ignored and valid return pulses to be processed by the comparator module 174. In general, the CFD 170 is configured to generate a hit signal 178 associated with each valid return pulse that arrives during the measurement window. Thus, V HIT 178 includes multiple hit signals, each associated with a separate return pulse.

[0061] FIG. 5 illustrates one embodiment of coarse timing module 180. As shown in FIG. 5, coarse timing module 180 includes a binary counter module 181, a binary-to-Gray code converter 182, a metastable bit generator 183, and one or more latch modules 184A-N. As shown in FIG. 5, a digital clock signal CLK and an inverted digital clock signal CLKB are received by the coarse timing module 180. In one embodiment, the digital clock signal is generated by a phase-locked loop (PLL) attached to the on-board return signal receiver IC 150. In one embodiment, the digital clock signal has a frequency of 1 gigahertz. Thus, in this particular embodiment, coarse timing module 180 can determine the time-of-flight associated with a particular return pulse to the nearest 1 nanosecond.

[0062] Binary counter module 181 receives pulse trigger signal 143 and begins counting in response to the pulse trigger. A digital signal BIN[0:10] 186 representing the running count is communicated to binary to Gray code converter 182. Binary to Gray code converter 182 converts binary count signal BIN[0:10] 186 into a digital signal COUNT[0:10] that corresponds to Gray code. COUNT[0:10] is communicated to each of latch modules 184A-N. In addition, the first bit of the running binary count BIN[0] is communicated to metastable bit generator 183. Metastable bit generator 183 generates metastable bit MS 188 by introducing a half-period shift into BIN[0]. MS 188 is also communicated to each of latch modules 184A-N.

[0063] Additionally, each hit signal 178 associated with a separate return pulse is communicated to a separate latch module (i.e., one of latch modules 184A-N). Each of latch modules 184A-N latches the last known values ​​of COUNT[0:10] and MS upon the transition of the corresponding hit signal indicating the identity of the return pulse. The resulting latched values, RANGE[0:10] 151 and MS 152, respectively, are communicated to time-of-flight module 159 shown in FIG. 1.

[0064] 6 illustrates one embodiment of a precision timing module 190. The precision timing module 190 includes two pulse width generators 191 and 193 and two time-to-voltage converters 192 and 194. The pulse width generator 191 receives each hit signal 178 and a clock signal CLK. Similarly, the pulse width generator 193 receives each hit signal 178 and a clock signal CLKB. The pulse width generator 191 generates a pulse having a duration that corresponds to the time between the rising edge of the hit signal 178 and the next rising edge of the clock signal CLK. This pulse signal V PULSE 195 is transmitted to the time-to-voltage converter 192. VPULSE In response to 195, time-to-voltage converter 192 generates a current ramp through a capacitor for the duration of the pulse. The voltage across the capacitor indicates the duration of the pulse. This voltage signal V CLK 153 is transmitted to ADC 158 for conversion to a digital signal and transmitted to time-of-flight module 159. Similarly, pulse width generator 193 generates a pulse having a duration corresponding to the time between the rising edge of hit signal 178 and the next rising edge of clock signal CLKB. This pulse signal V PULSE-B 196 is transmitted to the time-to-voltage converter 194. V PULSE-B In response to 196, a time-to-voltage converter 194 generates a current ramp through a capacitor for the duration of the pulse. The voltage across the capacitor indicates the duration of the pulse. This voltage signal V CLKB Because the ADC1, pulse width generators 191 and 193, and time-to-voltage converters 192 and 194 are analog modules, the uncertainty associated with estimating the time elapsed from the rising edge of the hit signal to the next clock signal is less than 10 picoseconds. Thus, the precision timing modules allow for highly accurate estimation of the time-of-flight associated with a particular return pulse.

[0065] In another aspect, the determination of the time of flight associated with each return pulse is made based on the outputs of both the coarse timing module and the fine timing module. In the embodiment shown in FIG. 1, the time of flight module 159 is implemented digitally. The time of flight module 159 determines the time of flight associated with a particular return pulse based on the coarse time estimate RANGE[0:10] and the fine time estimate associated with the return pulse. The time of flight module 159 determines the V CLK or V CLKB Determines whether to use V as a fine time estimate. For example, if the hit signal comes close to a transition of the CLK signal, the CLKB signal was stable at that time, so V CLKBis used as the basis for the precise time estimation. Similarly, if the hit signal occurs near a transition of the CLKB signal, the CLK signal was stable at that time, so VCLK is used as the basis for the fine time estimate. In one example, the estimated time of flight is the sum of the coarse time estimate and the selected fine time estimate.

[0066] In a further aspect, when a hit signal occurs near a clock transition, i.e., near a transition of the counter module 181, the metastable bit MS[0] is employed to determine the correct count of RANGE[0:10]. For example, if the hit signal 178 transitions near a transition of the counter 181, it is unclear which count is associated with the hit signal. For a 1 gigahertz clock, the error would be one count, or one nanosecond. In this situation, the value of the metastable bit is used to determine which count is associated with a particular hit. The value of the metastable bit determines whether the hit signal occurred near a high-to-low transition of the counter signal or a low-to-high transition of the counter signal, i.e., the correct count value.

[0067] 7 shows one embodiment of a pulse width detection module 200. The pulse width detection module 200 includes a pulse width generator 201 and a time-to-voltage converter 202. The pulse width generator 201 generates an enable signal V ENABLE 177 and the falling edge of the hit signal 178. This pulse signal V PULSE 203 is transmitted to the time-to-voltage converter 202. V PULSE In response to 203, time-to-voltage converter 202 generates a current ramp through a capacitor for the duration of the pulse. The voltage across the capacitor indicates the duration of the pulse. This voltage signal V WIDTH 155 is transmitted to an ADC 158 for conversion to a digital signal.

[0068] The pulse width detection module 200 is shown as a non-limiting example. In general, the pulse width detection module 200 operates with different input signals to detect V PULSE 203 and V WIDTH 155. In one example, the pulse width generator 201 may be configured to generate a pulse width signal 155 between the rising edge of the hit signal 178 and V TIA 142 is V THLD Generate a pulse with a duration that matches the time between the moment V falls below 145. TIA 142 is T HLD The moment when the voltage drops below 145 is determined by another comparator or by V HIT In another example, the pulse width generator 201 may be determined by the output of the comparator module 174 without latching the output, as in V TIA 142 is V THLD Above 145 and then V TIA 142 is V THLD 145. In one example, instead of pulse width generator 201, V ENABLE 177 is used, V ENABLE 177 is provided as an input to a time-to-voltage converter 202, which generates a current ramp through the capacitor for the duration of the pulse. The voltage across the capacitor is V ENABLE The pulse duration is indicated.

[0069] In another aspect, the master controller is configured to generate a plurality of pulse command signals, each of which is communicated to a separate integrated LIDAR measurement device, and each return pulse receiver IC generates a corresponding pulse control signal based on the received pulse command signal.

[0070] 8-10 illustrate 3D-LIDAR systems with multiple integrated LIDAR measurement devices. In some embodiments, a delay is established between the activation of each integrated LIDAR measurement device. In some examples, the delay is longer than the flight time of the measurement pulse sequence between an object at the maximum range of the LIDAR device. In this manner, crosstalk is eliminated for any of the integrated LIDAR measurement devices. In some other examples, a measurement pulse is emitted from one integrated LIDAR measurement device before a measurement pulse emitted from another integrated LIDAR measurement device returns to the LIDAR device. In these embodiments, care is taken to ensure sufficient spatial separation between the regions of the environment surveyed by each beam to avoid crosstalk.

[0071] 8 illustrates an embodiment of a 3D-LIDAR system 100 in one exemplary operating scenario. The 3D-LIDAR system 100 includes a lower housing 101 and an upper housing 102 having a dome-shaped shell element 103 constructed from a material transparent to infrared light (e.g., light having wavelengths in the spectral range of 700 to 1,700 nanometers). In one example, the dome-shaped shell element 103 is transparent to light having wavelengths centered at 905 nanometers.

[0072] As shown in Figure 8, multiple light beams 105 are emitted from 3D LIDAR system 100 through dome-shaped shell element 103 over an angular range α measured from central axis 104. In the embodiment shown in Figure 8, each light beam is projected onto a plane defined by the x- and y-axes at multiple different, spaced apart locations. For example, beam 106 is projected onto the xy plane at location 107.

[0073] 8, the 3D-LIDAR system 100 is configured to scan each of a plurality of light beams 105 around a central axis 104. Each light beam projected onto the xy plane follows a circular pattern centered at the intersection of the central axis 104 and the xy plane. For example, over time, a beam 106 projected onto the xy plane follows a circular trajectory 108 centered on the central axis 104.

[0074] 9 illustrates another embodiment of a 3D-LIDAR system 10 in one exemplary operating scenario. The 3D-LIDAR system 10 includes a lower housing 11 and an upper housing 12 having a cylindrical shell element 13 constructed of a material that is transparent to infrared light (e.g., light having wavelengths in the spectral range of 700 to 1,700 nanometers). In one example, the cylindrical shell element 13 is transparent to light having wavelengths centered at 905 nanometers.

[0075] As shown in FIG. 9 , multiple light beams 15 are emitted from the 3D LIDAR system 10 through the cylindrical shell element 13 over an angular range β. In the embodiment shown in FIG. 9 , the chief ray of each light beam is shown. Each light beam is projected outward into the surrounding environment in multiple different directions. For example, beam 16 is projected toward location 17 in the surrounding environment. In some embodiments, each beam of light emitted from the system 10 diverges slightly. In one example, the light beam emitted from the system 10 illuminates a spot size with a diameter of 20 centimeters at a distance of 100 meters from the system 10. As such, each beam of illumination light contributes to a cone of illumination light emitted from the system 10.

[0076] 9, the 3D LIDAR system 10 is configured to scan with each of multiple light beams 15 about a central axis 14. For illustrative purposes, the light beams 15 are shown at one angular orientation relative to a non-rotating coordinate frame of the 3D LIDAR system 10, and the light rays 15′ are shown at another angular orientation relative to the non-rotating coordinate frame. As light beam 15 rotates about central axis 14, each light beam (e.g., each cone of illumination light associated with each beam) projected onto the surrounding environment illuminates a corresponding environment as the illumination beam sweeps around central axis 14.

[0077] 10 illustrates an exploded view of a 3D LIDAR system 100 in one exemplary embodiment. The 3D LIDAR system 100 further includes a light emission / collection engine 112 that rotates about a central axis 104. In the embodiment illustrated in FIG. 10, a central optical axis 117 of the light emission / collection engine 112 is tilted at an angle θ relative to the central axis 104. 10 , the 3D-LIDAR system 100 includes a stationary electronics board 110 mounted in a fixed position on a lower housing 101. A rotating electronics board 111 is disposed above the stationary electronics board 110 and configured to rotate relative to the stationary electronics board 110 at a predetermined rotational speed (e.g., 200 revolutions per minute or greater). Power and electronic signals are transmitted between the electronics board 110 and the rotating electronics board 111 through one or more transformers, capacitor elements, or optical elements, resulting in contactless transmission of these signals. An optical emission / collection engine 112 is fixedly mounted to the rotating electronics board 111 and therefore rotates about a central axis 104 at a predetermined angular velocity ω.

[0078] 10, the optical emission / collection engine 112 includes an array of integrated LIDAR measurement devices 113. In one embodiment, each integrated LIDAR measurement device includes an optical emission element, an optical detection element, and associated control and signal conditioning electronics integrated onto a common substrate (e.g., a printed circuit board or other electrical circuit board).

[0079] Light emitted from each integrated LIDAR measurement device passes through a series of optical elements 116, which collimate the emitted light to generate a beam of illumination light that is projected from the 3D LIDAR system onto the environment. In this manner, an array of light beams 105 emitted from separate LIDAR measurement devices is emitted from the 3D LIDAR system 100, as shown in FIG. 11 . In general, any number of LIDAR measurement devices can be arranged to simultaneously emit any number of light beams from the 3D LIDAR system 100. Light reflected from objects in the environment due to illumination by a particular LIDAR measurement device is collected by the optical elements 116. The collected light passes through the optical elements 116, where it is focused onto the detector elements of the same particular LIDAR measurement device. In this manner, collected light associated with illumination of different portions of the environment due to illumination generated by different LIDAR measurement devices is separately focused onto the detectors of each corresponding LIDAR measurement device.

[0080] FIG. 11 shows details of the optical element 116. As shown in FIG. 11, the optical element 116 includes four lens elements 116A-D arranged to focus collected light 118 onto each detector in the array of integrated LIDAR measurement devices 113. In the embodiment shown in FIG. 11, light passing through the optical system 116 is reflected by a mirror 124 and directed toward each detector in the array of integrated LIDAR measurement devices 113. In some embodiments, one or more of the optical elements 116 are composed of one or more materials that absorb light outside a predetermined wavelength range. The predetermined wavelength range includes the wavelengths of light emitted by the array of integrated LIDAR measurement devices 113. In one example, one or more of the lens elements are composed of a plastic material containing a colorant additive that absorbs light having a wavelength shorter than the infrared light generated by each of the array of integrated LIDAR measurement devices 113. In one example, the colorant is Epolight 7276A available from Aako BV (The Netherlands). In general, any number of different colorants can be added to any of the plastic lens elements of optical system 116 to filter out undesired spectra.

[0081] FIG. 12 shows a cross-sectional view of the optical system 116 depicting the shaping of each beam of collected light 118.

[0082] Thus, a LIDAR system such as the 3D-LIDAR system 10 shown in FIG. 9 and the system 100 shown in FIG. 8 includes multiple integrated LIDAR measurement devices, each of which emits a pulsed beam of illumination light from the LIDAR device into the surrounding environment and measures the return light reflected from objects in the surrounding environment.

[0083] In some embodiments, such as those described with reference to Figures 8 and 9, the integrated LIDAR measurement array is mounted to a rotating frame of the LIDAR device, which rotates relative to the base frame of the LIDAR device. In general, however, the integrated LIDAR measurement array can be movable in any suitable manner (e.g., gimbaled, pan / tilt, etc.) or fixed to the base frame of the LIDAR device.

[0084] In some other embodiments, each integrated LIDAR measurement device includes a beam directing element (e.g., a scanning mirror, a MEMS mirror, etc.) that scans the illumination beam generated by the integrated LIDAR measurement device.

[0085] In some other embodiments, each of the two or more integrated LIDAR measurement devices emits a beam of illumination light toward a scanning mirror device (e.g., a MEMS mirror) that reflects the beam of illumination light in different directions into the surrounding environment.

[0086] In a further embodiment, one or more integrated LIDAR measurement devices are in optical communication with an optical phase modulator, which directs the illumination beams generated by the one or more integrated LIDAR measurement devices in different directions. The optical phase modulator is an active device that receives a control signal to change the state of the optical phase modulator, thereby changing the direction of the light diffracted from the optical phase modulator. In this manner, the illumination beams generated by the one or more integrated LIDAR devices are scanned in various orientations, effectively interrogating the surrounding 3D environment being measured. The diffracted beams projected into the surrounding environment interact with the environment. Each integrated LIDAR measurement device measures the distance between the LIDAR measurement system and the detected object based on the return light collected from the object. The optical phase modulator is positioned in the optical path between the integrated LIDAR measurement device and the object being measured in the surrounding environment. Thus, both the illumination light and the corresponding return light pass through the optical phase modulator.

[0087] Figure 13 illustrates a flowchart of a method 300 suitable for implementation by the integrated LIDAR measurement device described herein. In some embodiments, the integrated LIDAR measurement device 130 is operable according to the method 300 illustrated in Figure 13. However, in general, implementation of the method 300 is not limited to the embodiment of the integrated LIDAR measurement device 130 described with reference to Figure 1. These illustrations and their corresponding descriptions are provided by way of example, as many other embodiments and operational examples are possible.

[0088] In block 301, a pulse trigger signal is generated in response to a pulse command signal received at a return signal receiver IC mounted on a printed circuit board.

[0089] In block 302, an illumination source is selectively electrically connected to a power source in response to a pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light.

[0090] Return light received by a photodetector in response to a measurement pulse of illumination light is detected in block 303. The illumination source and photodetector are mounted on a printed circuit board.

[0091] At block 304, an output signal is generated indicative of the detected returned light.

[0092] In block 305, the output signal is received at the return signal receiver IC for the duration of the measurement window.

[0093] At block 306, one or more return pulses of the detected return light are identified.

[0094] In block 307, the time of flight associated with each of the identified return pulses is determined.

[0095] At block 308, one or more characteristics of each segment of the identified return pulse are determined.

[0096] A computing system as described herein may include, but is not limited to, a personal computer system, a mainframe, a computer system, a workstation, a graphics computer, a parallel processor, or other devices known in the art. In general, the term "computing system" may be broadly defined to encompass any device having one or more processors, which executes instructions from a storage medium.

[0097] The program instructions for performing the methods as described herein may be transmitted over a transmission medium such as a wire, cable, or wireless transmission link. The program instructions are stored on a computer-readable medium. Exemplary computer-readable media include read-only memory, random-access memory, a magnetic or optical disk, or a magnetic tape.

[0098] In general, power sources described herein can be configured to provide power defined as a voltage or a current. Accordingly, power sources described herein as voltage sources or current sources can also be considered equivalent current sources or voltage sources, respectively. Similarly, electrical signals described herein can also be defined as voltage signals or current signals. Accordingly, electrical signals described herein as voltage signals or current signals can also be considered equivalent current signals or voltage signals, respectively.

[0099] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Storage media may be any available medium accessible by a general-purpose or special-purpose computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage, or other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Furthermore, any connection may be properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio waves, or microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio waves, or microwaves are included within the definition of media. As used herein, disks and magnetic disks include compact disks (CDs), laser disks, optical disks, digital versatile disks (DVDs), floppy disks, and Blu-ray disks, where magnetic disks typically reproduce data magnetically and disks typically reproduce data optically with a laser. Combinations of these are also included within the scope of computer-readable media.

[0100] While specific embodiments have been described above for illustrative purposes, the teachings of this patent document are of general applicability and are not meant to be limited to the specific embodiments described above. Accordingly, various modifications, alterations, and combinations of the various features of the described embodiments may be made without departing from the scope of the invention as set forth in the claims.

Claims

1. an illumination source mounted on a printed circuit board; an illumination driver integrated circuit (IC) mounted on the printed circuit board, the illumination driver IC configured to selectively connect the illumination source to a power source in response to a pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light; a photodetector mounted on the printed circuit board, the photodetector configured to detect returned light received by the photodetector in response to a measurement pulse of the illumination light and to generate an output signal indicative of the detected returned light; an optical element positioned to receive the returning light along a common optical path shared with the illumination light and direct the returning light to a photodetector, the optical element comprising an overmolded lens attached to the photodetector, the overmolded lens including a conical cavity, the illumination light being incident on a receiving cone of the optical element and the returning light passing through the conical cavity; a return signal receiver IC mounted on the printed circuit board, the return signal receiver IC and the lighting driver IC being separate components, the return signal receiver IC comprising: receiving the output signal during a measurement window; identifying one or more return pulses of the detected return light; determining a time of flight associated with each of the identified return pulses; a return signal receiver IC configured to determine one or more characteristics of each identified segment of the return pulse; An integrated LIDAR measurement device comprising:

2. 2. The integrated LIDAR measurement device of claim 1, wherein the return signal receiver IC generates the pulse trigger signal in response to a pulse command signal received by the return signal receiver IC.

3. The return signal receiver IC includes a return signal analysis module, the return signal analysis module comprising:

10. The integrated LIDAR measurement device of claim 1, comprising: a constant fraction discriminator module having a first input node, a second input node, and an output node, the first input node coupled to receive the output signal, and the return signal analysis module configured to switch the hit signal at the output node to a different value when the output signal exceeds a threshold voltage value at the second input node.

4. The return signal analysis module:

4. The integrated LIDAR measurement device of claim 3, further comprising: a coarse timing module having a first input node connected to the output node of the constant fraction discriminator, a second input node, and an output node, the second input node connected to receive the pulse trigger signal, the coarse timing module configured to generate a digital value at the output node indicative of the time spent between a transition of the pulse trigger signal and a transition of the hit signal.

5. 5. The integrated LIDAR measurement device of claim 4, wherein the digital value is a count of the number of transitions of a digital clock signal occurring between the transition of the pulse trigger signal and the transition of the hit signal.

6. The return signal analysis module:

6. The integrated LIDAR measurement apparatus of claim 5, further comprising a precision timing module having a first input node, a first output node, and a second output node, the first input node coupled to receive the hit signal, the precision timing module configured to generate a first electrical signal at the first output node indicative of a time difference between the transition of the hit signal and a subsequent transition of the digital clock signal, and to generate a second electrical signal at the second output node indicative of a time difference between the transition of the hit signal and a subsequent transition of the inverted digital clock signal.

7. 6. The integrated LIDAR measurement device of claim 5, wherein the coarse timing module is configured to generate a metastable signal, the metastable signal being a digital clock signal shifted in time by half a period of the digital clock signal.

8. 8. The integrated LIDAR measurement apparatus of claim 7, further comprising a time-of-flight module configured to estimate a value of a time-of-flight of the measurement pulse of illumination light based at least in part on a digital value indicative of the metastable signal, the digital value indicative of the time spent between the transition of the pulse trigger signal and the transition of the hit signal, the time difference between the transition of the hit signal and a subsequent transition of the digital clock signal, the time difference between the transition of the hit signal and a subsequent transition of the inverted digital clock signal, and the metastable signal.

9. The return signal analysis module: a first input node connected to receive the hit signal; a second input node connected to receive an enable signal; an output node; a pulse width detection module having 4. The integrated LIDAR measurement device of claim 3, wherein the pulse width detection module is configured to produce an electrical signal at the output node indicative of the time difference between a transition of the enable signal and when the amplitude of the hit signal falls below a threshold.

10. The return signal analysis module:

4. The integrated LIDAR measurement device of claim 3, further comprising a return pulse sample and hold module configured to generate an output signal indicative of a peak amplitude of the output signal after a transition of the hit signal.

11. 11. The integrated LIDAR measurement device of claim 10, wherein the return pulse sample and hold module is further configured to generate a plurality of output signal values, each value representing an amplitude of the output signal before and after the peak amplitude.

12. 12. The integrated LIDAR measurement device of claim 11, wherein the number of output signal samples before and after the peak amplitude is programmable.

13. 2. The integrated LIDAR measurement device of claim 1, wherein a first return pulse of the one or more return pulses of the detected return light is due to optical crosstalk between the illumination source and the photodetector, and a time of flight associated with each subsequent return pulse of the one or more return pulses is determined with reference to the first return pulse.

14. 2. The integrated LIDAR measurement device of claim 1, wherein the duration of the measurement window is approximately the time of flight of light from the integrated LIDAR measurement device to a maximum range of the integrated LIDAR measurement device and back to the integrated LIDAR measurement device.

15. generating a pulse trigger signal in response to the pulse command signal received by a return signal receiver IC mounted on a printed circuit board; selectively connecting an illumination source to a power source with an illumination driver IC in response to the pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light, the illumination source and the illumination driver IC being mounted on the printed circuit board; receiving, by the return signal receiver IC during a measurement window, from a photodetector mounted on the printed circuit board an output signal indicative of detection of returned light received by the photodetector in response to a measurement pulse of the illumination light, wherein an optical element is positioned to receive the returned light on a common optical path shared with the illumination light and direct the returned light to the photodetector, the optical element comprising an overmolded lens mounted on the photodetector, the overmolded lens including a conical cavity, the illumination light being incident on a reception cone of the optical element and the returned light passing through the conical cavity; identifying one or more return pulses of the detected return light by the return signal receiver IC; determining, by the return signal receiver IC, a time of flight associated with each of the detected returned lights; determining, with the return signal receiver IC, one or more characteristics of each identified segment of the return pulse; A method comprising:

16. generating a hit signal that switches to another value when the output signal exceeds a voltage threshold; generating a digital value indicative of the time spent between a transition of the pulse trigger signal and a transition of the hit signal, the digital value being the total number of transitions of the digital clock signal that occurred between the transition of the pulse trigger signal and the transition of the hit signal; 16. The method of claim 15 further comprising:

17. generating a first electrical signal indicative of the time difference between the transition of the hit signal and a subsequent transition of the digital clock signal and a second electrical signal indicative of the time difference between the hit signal and a subsequent transition of the inverted digital clock signal; generating a metastable signal, said metastable signal being a digital clock signal time-shifted by half a period of said digital clock signal; 17. The method of claim 16, further comprising:

18. 18. The method of claim 17, further comprising estimating a time-of-flight value of the measurement pulse of illumination light based at least in part on the digital value indicating the time spent between the transition of the pulse trigger signal and the transition of the hit signal, the time difference between the transition of the hit signal and a subsequent transition of the digital clock signal, the time difference between the transition of the hit signal and a subsequent transition of the inverted digital clock signal, and the metastable signal.

19. 17. The method of claim 16, further comprising generating an electrical signal indicative of the time difference between a transition of an enable signal and the moment the amplitude of the hit signal falls below a threshold.

20. 17. The method of claim 16, further comprising generating an output signal indicative of the peak amplitude of the output signal after the transition of the hit signal.

21. 21. The method of claim 20, further comprising generating a plurality of output signals respectively indicative of the amplitude of the output signal before and after the peak amplitude, wherein the number of output signal samples before and after the peak amplitude is programmable.

22. 1. An integrated LIDAR measurement system, comprising: an integrated LIDAR measurement device; The integrated LIDAR measurement device includes: an illumination source mounted on a printed circuit board; an illumination driver integrated circuit (IC) mounted on the printed circuit board, the illumination driver IC configured to selectively connect the illumination source to a power source in response to a pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light; a photodetector mounted on the printed circuit board, the photodetector configured to detect a measurement pulse of first illumination light due to crosstalk between the illumination source and the photodetector and a valid return pulse of light reflected from a location in the environment illuminated by the second measurement pulse; an optical element positioned to receive the return pulses on a common optical path shared with the illumination light and direct the return pulses to a photodetector, the optical element comprising an overmolded lens attached to the photodetector, the overmolded lens including a conical cavity, the illumination light being incident on a receiving cone of the optical element and the return light passing through the conical cavity; a return signal receiver IC mounted on the printed circuit board, the return signal receiver IC comprising: a return signal receiver IC configured to estimate the time between detecting a measurement pulse of the first illumination light due to crosstalk and detecting a valid return pulse of the light; 1. An integrated LIDAR measurement system comprising:

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