Patent Description:
LIDAR systems employ pulses of light to measure distance to an object based on the time of flight (TOF) of each pulse of light. A pulse of light emitted from a light source of a LIDAR system interacts with a distal object. A portion of the light reflects from the object and returns to a detector of the LIDAR system. Based on the time elapsed between emission of the pulse of light and detection of the returned pulse of light, a distance is estimated. 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 a pulse of laser light to return to a detector mounted near the emitter is measured. A distance is derived from the time measurement with high accuracy.

Some LIDAR systems employ a single laser emitter/detector combination combined with a rotating mirror to effectively scan across a plane. Distance measurements performed by such a system are effectively two dimensional (i.e., planar), and the captured distance points are rendered as a <NUM>-D (i.e. single plane) point cloud. In some examples, rotating mirrors are rotated at very fast speeds (e.g., thousands of revolutions per minute).

In many operational scenarios, a <NUM>-D point cloud is required. A number of schemes have been employed to interrogate the surrounding environment in three dimensions. In some examples, a <NUM>-D instrument is actuated up and down and/or back and forth, often on a gimbal. This is commonly known within the art as "winking" or "nodding" the sensor. Thus, a single beam LIDAR unit can be employed to capture an entire <NUM>-D array of distance points, albeit one point at a time. In a related example, a prism is employed to "divide" the laser pulse into multiple layers, each having a slightly different vertical angle. This simulates the nodding effect described above, but without actuation of the sensor itself.

In all the above examples, the light path of a single laser emitter/detector combination is somehow altered to achieve a broader field of view than a single sensor. The number of pixels such devices can generate per unit time is inherently limited due limitations on the pulse repetition rate of a single laser. Any alteration of the beam path, whether it is by mirror, prism, or actuation of the device that achieves a larger coverage area comes at a cost of decreased point cloud density.

As noted above, <NUM>-D point cloud systems exist in several configurations. However, in many applications it is necessary to see over a broad field of view. For example, in an autonomous vehicle application, the vertical field of view should extend down as close as possible to see the ground in front of the vehicle. In addition, the vertical field of view should extend above the horizon, in the event the car enters a dip in the road. In addition, it is necessary to have a minimum of delay between the actions happening in the real world and the imaging of those actions. In some examples, it is desirable to provide a complete image update at least five times per second. To address these requirements, a <NUM>-D LIDAR system has been developed that includes an array of multiple laser emitters and detectors.

In many applications, a sequence of pulses is emitted. The direction of each pulse is sequentially varied in rapid succession. In these examples, a distance measurement associated with each individual pulse can be considered a pixel, and a collection of pixels emitted and captured in rapid succession (i.e., "point cloud") can be rendered as an image or analyzed for other reasons (e.g., detecting obstacles). In some examples, viewing software is employed to render the resulting point clouds as images that appear three dimensional to a user. Different schemes can be used to depict the distance measurements as <NUM>-D images that appear as if they were captured by a live action camera.

Some existing LIDAR systems employ an illumination source and a detector that are not integrated together onto a common substrate (e.g., electrical mounting board). Furthermore, the illumination beam path and the collection beam path are separated within the LIDAR device. This leads to opto-mechanical design complexity and alignment difficulty.

Improvements in the opto-mechanical design of LIDAR systems are desired, while maintaining high levels of imaging resolution and range.

patent application <CIT> discloses a compact LADAR for incorporation in a personal electronic appliance or head gear as a helmet. patent application <CIT>discloses a LIDAR system for detecting airborne agents. The <CIT> discloses an active reflected energy optical transducer system of improved sensitivity wherein the light source and the detector share a single optical system. US patent application <CIT> discloses a monostatic lidar system having a scanning capability.

Methods and systems for performing three dimensional LIDAR measurements with a highly integrated LIDAR measurement device are described herein. There is provided in one aspect, an integrated light detection and ranging (LIDAR) device, according to any of claims <NUM>-<NUM>. In another aspect there is provided a method for performing three dimensional LIDAR measurements with a highly integrated LIDAR measurement device, according to claims <NUM>-<NUM>. In one aspect, the illumination source, detector, and illumination drive and a beam splitter are integrated onto a single printed circuit board. In addition, in some arrangements, the associated control and signal conditioning electronics are also integrated onto the common printed circuit board. Furthermore, in some arrangements, the illumination driver and the illumination source are integrated onto a common Gallium Nitride substrate that is independently packaged and attached to the printed circuit board.

In some arrangements a <NUM>-D LIDAR system includes multiple integrated LIDAR measurement devices. In some arrangements, a delay time is set between the firing of each integrated LIDAR measurement device. In some examples, the delay time is greater than the time of flight of the measurement pulse sequence to and from an object located at the maximum range of the LIDAR device. In this manner, there is no cross-talk among 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 has had time to return to the LIDAR device. In these arrangements, care is taken to ensure that there is sufficient spatial separation between the areas of the surrounding environment interrogated by each beam to avoid cross-talk.

According to the invention, the illumination light emitted from the illumination source and the return light directed toward the detector share a common optical path within the integrated LIDAR measurement device, wherein the return light is separated from the illumination light by a beam splitter. In general, when the polarization of the return light is completely mixed and a single polarizing beam splitter is employed, half of the return light will be directed toward detector and the other half will be directed toward the illumination source. In some other arrangements, these losses are avoided by employing one or more polarization control elements to alter the polarization state of light passing through the polarization control element in coordination with the firing of the illumination source and the timing of the measurement time window to minimize losses of return light.

In some other arrangements, that are not part of the invention, the return light is separated from the illumination light by optical design to avoid losses associated with a beam splitter.

In some arrangements, a detector includes a slot through the detector including the active sensing area. The illumination source is fixed to the back of the detector and is configured to emit illumination light through the slot in the detector. In this manner, both the detector and illumination source are located in the beam path of light emitted from an integrated LIDAR measurement device and returned to the integrated LIDAR measurement device. Although a certain amount of return light will be directed toward the slot and not detected, the relatively small area of the slot compared to the active area of the detector ensures that the majority of the return light is detected.

In some arrangements, the illumination source is located outside the field of view of the detector. In some arrangements, the index of refraction of an active optical element is controlled to pass return light and refract illumination light toward the common optical path shared by both the illumination light and the return light. The illumination light is not initially aligned with the optical axis of the optical system. However, during periods of time when light is emitted from the illumination source, the active optical element changes its state such that the illumination light is aligned with the optical axis of the optical system.

In some arrangements, a concentric focusing optic focuses return light onto the detector and a passive optical element located in the middle of the concentric focusing optic refracts the illumination light toward the common optical path shared by both the illumination light and the return light.

In some arrangements, the return light reflects from a mirror element and propagates toward the detector. In one aspect, the mirror includes a slot through which the illumination light is passed. This effectively injects the illumination light into the common optical path shared by both the illumination light and the return light.

In some arrangements, the illumination source is located in the optical path of the return light in front of the detector.

In some other arrangements, the illumination source is embedded in an optical element that is located in the optical path of the return light in front of the detector.

In another aspect, illumination light is injected into the detector reception cone by a waveguide. An optical coupler optically couples an illumination source to the waveguide. At the end of the waveguide, a mirror element is oriented at a <NUM> degree angle with respect to the waveguide to inject the illumination light into the cone of return light. In some arrangements, the waveguide includes a rectangular- shaped glass core and a polymer cladding of lower index of refraction. In some arrangements, the entire assembly is encapsulated with a material having an index of refraction that closely matches the index of refraction of the polymer cladding. In this manner, the waveguide injects the illumination light into the acceptance cone of return light with minimal occlusion.

In some arrangements, an array of integrated LIDAR measurement devices is mounted to a rotating frame of the LIDAR device. This rotating frame rotates with respect to a base frame of the LIDAR device. However, in general, an array of integrated LIDAR measurement devices may be movable in any suitable manner (e.g., gimbal, pan/tilt, etc.) or fixed with respect to a base frame of the LIDAR device.

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

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

The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is not limiting in any way. Other aspects, inventive features, and advantages of the devices and/or processes described herein will become apparent in the non-limiting detailed description set forth herein.

Reference will now be made in detail to background examples and some arrangements of the invention, examples of which are illustrated in the accompanying drawings.

<FIG> is a diagram illustrative of an arrangement of a <NUM>-D LIDAR system <NUM> in one exemplary operational scenario. <NUM>-D LIDAR system <NUM> includes a lower housing <NUM> and an upper housing <NUM> that includes a domed shell element <NUM> constructed from a material that is transparent to infrared light (e.g., light having a wavelength within the spectral range of <NUM> to <NUM>,<NUM> nanometers). In one example, domed shell element <NUM> is transparent to light having a wavelengths centered at <NUM> nanometers.

As depicted in <FIG>, a plurality of beams of light <NUM> are emitted from <NUM>-D LIDAR system <NUM> through domed shell element <NUM> over an angular range, α, measured from a central axis <NUM>. In the arrangement depicted in <FIG>, each beam of light is projected onto a plane defined by the x and y axes at a plurality of different locations spaced apart from one another. For example, beam <NUM> is projected onto the xy plane at location <NUM>.

In the arrangement depicted in <FIG>, <NUM>-D LIDAR system <NUM> is configured to scan each of the plurality of beams of light <NUM> about central axis <NUM>. Each beam of light projected onto the xy plane traces a circular pattern centered about the intersection point of the central axis <NUM> and the xy plane. For example, over time, beam <NUM> projected onto the xy plane traces out a circular trajectory <NUM> centered about central axis <NUM>.

<FIG> is a diagram illustrative of another arrangement of a <NUM>-D LIDAR system <NUM> in one exemplary operational scenario. <NUM>-D LIDAR system <NUM> includes a lower housing <NUM> and an upper housing <NUM> that includes a cylindrical shell element <NUM> constructed from a material that is transparent to infrared light (e.g., light having a wavelength within the spectral range of <NUM> to <NUM>,<NUM> nanometers). In one example, cylindrical shell element <NUM> is transparent to light having a wavelengths centered at <NUM> nanometers.

As depicted in <FIG>, a plurality of beams of light <NUM> are emitted from <NUM>-D LIDAR system <NUM> through cylindrical shell element <NUM> over an angular range,. In the arrangement depicted in <FIG>, the chief ray of each beam of light is illustrated. Each beam of light is projected outward into the surrounding environment in a plurality of different directions. For example, beam <NUM> is projected onto location <NUM> in the surrounding environment. In some arrangements, each beam of light emitted from system <NUM> diverges slightly. In one example, a beam of light emitted from system <NUM> illuminates a spot size of <NUM> centimeters in diameter at a distance of <NUM> meters from system <NUM>. In this manner, each beam of illumination light is a cone of illumination light emitted from system <NUM>.

In the arrangement depicted in <FIG>, <NUM>-D LIDAR system <NUM> is configured to scan each of the plurality of beams of light <NUM> about central axis <NUM>. For purposes of illustration, beams of light <NUM> are illustrated in one angular orientation relative to a non-rotating coordinate frame of <NUM>-D LIDAR system <NUM> and beams of light <NUM>' are illustrated in another angular orientation relative to the non-rotating coordinate frame. As the beams of light <NUM> rotate about central axis <NUM>, each beam of light projected into the surrounding environment (e.g., each cone of illumination light associated with each beam) illuminates a volume of the environment corresponding the cone shaped illumination beam as it is swept around central axis <NUM>.

<FIG> depicts an exploded view of <NUM>-D LIDAR system <NUM> in one exemplary arrangement. <NUM>-D LIDAR system <NUM> further includes a light emission/collection engine <NUM> that rotates about central axis <NUM>. In the arrangement depicted in <FIG>, a central optical axis <NUM> of light emission/collection engine <NUM> is tilted at an angle, θ, with respect to central axis <NUM>. As depicted in <FIG>, <NUM>-D LIDAR system <NUM> includes a stationary electronics board <NUM> mounted in a fixed position with respect to lower housing <NUM>. Rotating electronics board <NUM> is disposed above stationary electronics board <NUM> and is configured to rotate with respect to stationary electronics board <NUM> at a predetermined rotational velocity (e.g., more than <NUM> revolutions per minute). Electrical power signals and electronic signals are communicated between stationary electronics board <NUM> and rotating electronics board <NUM> over one or more transformer, capacitive, or optical elements, resulting in a contactless transmission of these signals. Light emission/collection engine <NUM> is fixedly positioned with respect to the rotating electronics board <NUM>, and thus rotates about central axis <NUM> at the predetermined angular velocity, ω.

As depicted in <FIG>, light emission/collection engine <NUM> includes an array of integrated LIDAR measurement devices <NUM>. In one aspect, each integrated LIDAR measurement device includes a light emitting element, a light detecting element, and associated control and signal conditioning electronics integrated onto a common substrate (e.g., printed circuit board or other electrical circuit board).

Light emitted from each integrated LIDAR measurement device passes through a series of optical elements <NUM> that collimate the emitted light to generate a beam of illumination light projected from the <NUM>-D LIDAR system into the environment. In this manner, an array of beams of light <NUM>, each emitted from a different LIDAR measurement device are emitted from <NUM>-D LIDAR system <NUM> as depicted in <FIG>. In general, any number of LIDAR measurement devices can be arranged to simultaneously emit any number of light beams from <NUM>-D LIDAR system <NUM>. Light reflected from an object in the environment due to its illumination by a particular LIDAR measurement device is collected by optical elements <NUM>. The collected light passes through optical elements <NUM> where it is focused onto the detecting element of the same, particular LIDAR measurement device. In this manner, collected light associated with the illumination of different portions of the environment by illumination generated by different LIDAR measurement devices is separately focused onto the detector of each corresponding LIDAR measurement device.

<FIG> depicts a view of optical elements <NUM> in greater detail. As depicted in <FIG>, optical elements <NUM> include four lens elements 116A-D arranged to focus collected light <NUM> onto each detector of the array of integrated LIDAR measurement devices <NUM>. In the arrangement depicted in <FIG>, light passing through optics <NUM> is reflected from mirror <NUM> and is directed onto each detector of the array of integrated LIDAR measurement devices <NUM>. In some arrangements, one or more of the optical elements <NUM> is constructed from one or more materials that absorb light outside of a predetermined wavelength range. The predetermined wavelength range includes the wavelengths of light emitted by the array of integrated LIDAR measurement devices <NUM>. In one example, one or more of the lens elements are constructed from a plastic material that includes a colorant additive to absorb light having wavelengths less than infrared light generated by each of the array of integrated LIDAR measurement devices <NUM>. 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 optics <NUM> to filter out undesired spectra.

<FIG> depicts a cutaway view of optics <NUM> to illustrate the shaping of each beam of collected light <NUM>.

A LIDAR system, such as <NUM>-D LIDAR system <NUM> depicted in <FIG>, and system <NUM>, depicted in <FIG>, includes a plurality of integrated LIDAR measurement devices each emitting a pulsed beam of illumination light from the LIDAR device into the surrounding environment and measuring return light reflected from objects in the surrounding environment.

<FIG> depicts an integrated LIDAR measurement device <NUM> in one arrangement. Integrated LIDAR measurement device <NUM> includes a pulsed light emitting device <NUM>, a light detecting element <NUM>, associated control and signal conditioning electronics integrated onto a common substrate <NUM> (e.g., electrical board), and connector <NUM>. Pulsed emitting device <NUM> generates pulses of illumination light <NUM> and detector <NUM> detects collected light <NUM>. Integrated LIDAR measurement device <NUM> generates digital signals indicative of the distance between the <NUM>-D LIDAR system and an object in the surrounding environment based on a time of flight of light emitted from the integrated LIDAR measurement device <NUM> and detected by the integrated LIDAR measurement device <NUM>. Integrated LIDAR measurement device <NUM> is electrically coupled to the <NUM>-D LIDAR system via connector <NUM>. Integrated LIDAR measurement device <NUM> receives control signals from the <NUM>-D LIDAR system and communicates measurement results to the <NUM>-D LIDAR system over connector <NUM>.

<FIG> depicts a schematic view of an integrated LIDAR measurement device <NUM> in another arrangement. Integrated LIDAR measurement device <NUM> includes a pulsed light emitting device <NUM>, a light detecting element <NUM>, a beam splitter <NUM> (e.g., polarizing beam splitter, non-polarizing beam splitter, dielectric film, etc.), an illumination driver <NUM>, signal conditioning electronics <NUM>, analog to digital (A/D) conversion electronics <NUM>, controller <NUM>, and digital input/output (I/O) electronics <NUM> integrated onto a common substrate <NUM>. In some arrangements, these elements are individually mounted to a common substrate (e.g., printed circuit board). In some arrangements, groups of these elements are packaged together and the integrated package is mounted to a common substrate. In general and according to the invention, each of the elements are mounted to a common substrate to create an integrated device, whether they are individually mounted or mounted as part of an integrated package.

<FIG> depicts an illustration of the timing associated with the emission of a measurement pulse from an integrated LIDAR measurement device <NUM> and capture of the returning measurement pulse. As depicted in <FIG> and <FIG>, the measurement begins with a pulse firing signal <NUM> generated by controller <NUM>. Due to internal system delay, a pulse index signal <NUM> is determined by controller <NUM> that is shifted from the pulse firing signal <NUM> by a time delay, TD. The time delay includes the known delays associated with emitting light from the LIDAR system (e.g., signal communication delays and latency associated with the switching elements, energy storage elements, and pulsed light emitting device) and known delays associated with collecting light and generating signals indicative of the collected light (e.g., amplifier latency, analog-digital conversion delay, etc.).

As depicted in <FIG> and <FIG>, a return signal <NUM> is detected by the LIDAR system in response to the illumination of a particular location. A measurement window (i.e., a period of time over which collected return signal data is associated with a particular measurement pulse) is initiated by enabling data acquisition from detector <NUM>. Controller <NUM> controls the timing of the measurement window to correspond with the window of time when a return signal is expected in response to the emission of a measurement pulse sequence. In some examples, the measurement window is enabled at the point in time when the measurement pulse sequence is emitted and is disabled at a time corresponding to the time of flight of light over a distance that is substantially twice the range of the LIDAR system. In this manner, the measurement window is open to collect return light from objects adjacent to the LIDAR system (i.e., negligible time of flight) to objects that are located at the maximum range of the LIDAR system. In this manner, all other light that cannot possibly contribute to useful return signal is rejected.

As depicted in <FIG>, return signal <NUM> includes two return measurement pulses that correspond with the emitted measurement pulse. In general, signal detection is performed on all detected measurement pulses. Further signal analysis may be performed to identify the closest signal (i.e., first instance of the return measurement pulse), the strongest signal, and the furthest signal (i.e., last instance of the return measurement pulse in the measurement window). Any of these instances may be reported as potentially valid distance measurements by the LIDAR system. For example, a time of flight, TOF<NUM>, may be calculated from the closest (i.e., earliest) return measurement pulse that corresponds with the emitted measurement pulse as depicted in <FIG>.

In some arrangements, the signal analysis is performed by controller <NUM>, entirely. In these arrangements, signals <NUM> communicated from integrated LIDAR measurement device <NUM> include an indication of the distances determined by controller <NUM>. In some arrangements, signals <NUM> include the digital signals <NUM> generated by A/D converter <NUM>. These raw measurement signals are processed further by one or more processors located on board the <NUM>-D LIDAR system, or external to the <NUM>-D LIDAR system to arrive at a measurement of distance. In some arrangements, controller <NUM> performs preliminary signal processing steps on signals <NUM> and signals <NUM> include processed data that is further processed by one or more processors located on board the <NUM>-D LIDAR system, or external to the <NUM>-D LIDAR system to arrive at a measurement of distance.

In some arrangements a <NUM>-D LIDAR system includes multiple integrated LIDAR measurement devices, such as the LIDAR systems illustrated in <FIG>. In some arrangements, a delay time is set between the firing of each integrated LIDAR measurement device. Signal <NUM> includes an indication of the delay time associated with the firing of integrated LIDAR measurement device <NUM>. In some examples, the delay time is greater than the time of flight of the measurement pulse sequence to and from an object located at the maximum range of the LIDAR device. In this manner, there is no cross-talk among 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 has had time to return to the LIDAR device. In these arrangements, care is taken to ensure that there is sufficient spatial separation between the areas of the surrounding environment interrogated by each beam to avoid cross-talk.

Illumination driver <NUM> generates a pulse electrical current signal <NUM> in response to pulse firing signal <NUM>. Pulsed light emitting device <NUM> generates pulsed light emission <NUM> in response to pulsed electrical current signal <NUM>. The illumination light <NUM> is focused and projected onto a particular location in the surrounding environment by one or more optical elements of the LIDAR system (not shown).

In some arrangements, the pulsed light emitting device is laser-based (e.g., laser diode). In some arrangements, the pulsed illumination sources are based on one or more light emitting diodes. In general, any suitable pulsed illumination source may be contemplated.

In some arrangements, digital I/O <NUM>, timing logic <NUM>, A/D conversion electronics <NUM>, and signal conditioning electronics <NUM> are integrated onto a single, silicon-based microelectronic chip. In another arrangement, these same elements are integrated into a single gallium-nitride or silicon based circuit that also includes the illumination driver. In some arrangements, the A/D conversion electronics and controller <NUM> are combined as a time-to-digital converter.

As depicted in <FIG>, return light <NUM> reflected from the surrounding environment is detected by light detector <NUM>. In some arrangements, light detector <NUM> is an avalanche photodiode. Light detector <NUM> generates an output signal <NUM> that is amplified by signal conditioning electronics <NUM>. In some arrangements, signal conditioning electronics <NUM> includes an analog trans-impedance amplifier. However, in general, the amplification of output signal <NUM> may include multiple, amplifier stages. In this sense, an analog transimpedance amplifier is provided by way of non-limiting example, as many other analog signal amplification schemes may be contemplated within the scope of this patent document.

The amplified signal is communicated to A/D converter <NUM>. The digital signals are communicated to controller <NUM>. Controller <NUM> generates an enable/disable signal employed to control the timing of data acquisition by ADC <NUM> in concert with pulse firing signal <NUM>.

As depicted in <FIG>, the illumination light <NUM> emitted from integrated LIDAR measurement device <NUM> and the return light <NUM> directed toward integrated LIDAR measurement device share a common path. In the arrangement depicted in <FIG>, the return light <NUM> is separated from the illumination light <NUM> by a polarizing beam splitter (PBS) <NUM>. PBS <NUM> could also be a non-polarizing beam splitter, but this generally would result in an additional loss of light. In this arrangement, the light emitted from pulsed light emitting device <NUM> is polarized such that the illumination light passes through PBS <NUM>. However, return light <NUM> generally includes a mix of polarizations. Thus, PBS <NUM> directs a portion of the return light toward detector <NUM> and a portion of the return light toward pulsed light emitting device <NUM>. In some arrangements, it is desirable to include a quarter waveplate after PBS <NUM>. This is advantageous in situations when the polarization of the return light is not significantly changed by its interaction with the environment. Without the quarter waveplate, the majority of the return light would pass through PBS <NUM> and be directed toward the pulsed light emitting device <NUM>, which is undesireable. However, with the quarter waveplate, the majority of the return light will pass through PBS <NUM> and be directed toward detector <NUM>.

However, in general, when the polarization of the return light is completely mixed and a single PBS is employed as depicted in <FIG>, half of the return light will be directed toward detector <NUM>, and the other half will be directed toward pulse light emitting device <NUM>, regardless of whether a quarter waveplate is used.

<FIG> depict various arrangements to avoid these losses.

<FIG> depicts a front view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> (e.g., an avalanche photodiode) having a circular shaped active area <NUM> with a diameter, D. In one example, the diameter of the active area <NUM> is approximately <NUM> micrometers. In one aspect, detector <NUM> includes a slot <NUM> all the way through the detector. In one example, the slot has a height, Hs, of approximately <NUM> micrometers and a width, W, of approximately <NUM> micrometers.

<FIG> depicts a side view of arrangement <NUM> depicted in <FIG>. As depicted in <FIG>, arrangement <NUM> also includes pulsed light emitting device <NUM> fixed to the back of avalanche photodiode detector <NUM> and configured to emit illumination light <NUM> through slot <NUM> in detector <NUM>. In one example, pulse light emitting device <NUM> includes three laser diodes packaged together to create an emission area having a height, HE, of <NUM> micrometers with a divergence angle of approximately <NUM> degrees. In this example, the thickness, S, of the detector <NUM> is approximately <NUM> micrometers.

In this manner, detector <NUM> and pulsed light emitting device <NUM> are located in the beam path of light emitted from an integrated LIDAR measurement device and returned to the integrated LIDAR measurement device. Although a certain amount of return light will be directed toward slot <NUM> and not detected, the relatively small area of slot <NUM> compared to the active area <NUM> of detector <NUM> ensures that the majority of the return light will be detected.

<FIG> depicts a side view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> having an active area <NUM>, a pulsed light emitting device <NUM> located outside of the active area <NUM>, a focusing optic <NUM> and an active optical element <NUM>. Active optical element <NUM> is coupled to a controller of the integrated LIDAR measurement device. The controller communicates control signal <NUM> to active element <NUM> that causes the active optical element to change states.

In a first state, depicted in <FIG>, the active optical element changes its effective index of refraction and causes the light <NUM> emitted from pulsed light emitting device <NUM> to refract toward optical axis, OA.

In a second state, depicted in <FIG>, the active optical element changes its effective index of refraction such that return light <NUM> passes through active optical element <NUM> and focusing optic <NUM> toward the active area <NUM> of detector <NUM>. During this state, the controller controls pulsed light emitting device <NUM> such that it does not emit light.

In this arrangement, the light emitted by pulsed light emitting device <NUM> is not initially aligned with the optical axis of the optical system. However, during periods of time when light is emitted from the pulsed light emitting device <NUM>, active optical element changes its state such that the illumination light is aligned with the optical axis of the optical system. In some arrangements, the active optical element is a phase array. In some arrangements, the active optical element is an acousto-optical modulator. In some arrangements, the active optical element is a surface acoustic wave modulator. In general, many active devices capable of altering their effective index of refraction may be contemplated.

<FIG> depicts a side view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> having an active area <NUM>, a pulsed light emitting device <NUM> located outside of the active area <NUM>, concentric focusing optics <NUM> and focusing optics <NUM> centered along the optical axis of the integrated LIDAR measurement device. As depicted in <FIG>, the return light <NUM> is focused onto the active area <NUM> of detector <NUM> by concentric focusing optics <NUM>. In addition, light <NUM> emitted from pulsed light emitting device <NUM> is refracted toward optical axis, OA, and collimated by focusing optics <NUM>. As depicted in <FIG>, focusing optics <NUM> occupy a relatively small area immediately centered about the optical axis. Concentric focusing optics are also centered about the optical axis, but are spaced apart from the optical axis.

<FIG> depicts a top view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> having an active area <NUM>, a pulsed light emitting device <NUM> located outside of the active area <NUM>, concentric focusing optics <NUM>, and mirror <NUM>. As depicted in <FIG>, return light <NUM> is focused by focusing optics <NUM> and reflects from mirror <NUM> toward the active area <NUM> of detector <NUM>. In one aspect, mirror <NUM> includes a slot through which light emitted from pulsed light emitting device <NUM> is passed. Illumination light <NUM> is emitted from pulsed light emitting device <NUM>, passes through the slot in mirror <NUM>, is collimated by focusing optics <NUM>, and exits the integrated LIDAR measurement device.

<FIG> depict three different light paths through an arrangement <NUM> of an integrated LIDAR measurement device. This arrangement includes a pulsed light emitting device <NUM>, a PBS <NUM>, a polarization control element <NUM> (e.g., Pockels cell), a PBS <NUM>, a quarter waveplate <NUM>, mirror element <NUM> (e.g., a PBS, a half cube with total internal reflection, etc.), delay element <NUM>, polarizing beam combiner <NUM>, half waveplate <NUM>, and detector <NUM>. Polarization control element <NUM> is coupled to a controller of the integrated LIDAR measurement device. The controller communicates control signal <NUM> to polarization control element <NUM> that causes the polarization control element to alter the polarization state of light passing through the polarization control element in accordance with control signal <NUM>.

In a first state, depicted in <FIG>, polarization control element <NUM> is configured not to change the polarization of light passing through when illumination light <NUM> is emitted from pulsed light emitting device <NUM>. <FIG> depicts the path of illumination light <NUM> through arrangement <NUM>. Illumination light <NUM> passes through PBS <NUM>, polarization control element <NUM>, PBS <NUM>, and quarter waveplate <NUM>. In the examples depicted in <FIG>, the pulsed light emitting device <NUM> emits p-polarized light, and the PBS elements <NUM> and <NUM> are configured to directly transmit p-polarized light. However, in general, different polarizations may be utilized to achieve the same result.

In a second state, depicted in <FIG>, polarization control element <NUM> is configured to change the polarization of light passing through when return light <NUM> is detected by detector <NUM>, and light is not emitted from pulsed light emitting device <NUM>.

<FIG> depicts the path of a portion 202A of return light <NUM> that is p-polarized after passing through quarter waveplate <NUM>. The p-polarized return light passes through PBS <NUM> and polarization control element <NUM>. In this state, polarization control element <NUM> switches the polarization of the return light from p- polarization to s-polarization. The s-polarized return light is reflected from PBS <NUM> toward half waveplate <NUM>. Half waveplate <NUM> switches the polarization again from s-polarization back to p-polarization. Polarizing beam combiner <NUM> reflects the p-polarized light toward detector <NUM>.

<FIG> depicts the path 202B of the portion of return light <NUM> that is s-polarized after passing through quarter waveplate <NUM>. The s-polarized return light is reflected from beam splitter <NUM> to mirror element <NUM>, through beam delay element <NUM>, through polarizing beam combiner <NUM>, which directly transmits the s-polarized light onto detector <NUM>.

Beam delay element <NUM> is introduced to balance the optical path lengths of the s and p polarized return light. Beam delay element may be simply a piece of optical glass of appropriate length.

Arrangement <NUM> also includes a beam path extension element <NUM> located in the illumination beam path between the pulsed light emitting device <NUM> and polarizing beam splitter <NUM>. In some arrangements, beam path extension element <NUM> is simply a piece of optical glass of appropriate length. Beam path extension element <NUM> is configured to equalize the illumination path length and the length of the return paths 202A and 202B. Note that the return path lengths 202A and 202B are equalized by beam delay element <NUM>. Since the return paths 202A and 202B pass through additional elements, their effective optical path is longer. By equalizing the illumination path length with the length of the return paths, the return beam is focused to a spot size that approaches the size of the illumination output aperture. This enables the use of the smallest sized detector with the least amount of noise and sensitivity to sun noise and highest bandwidth.

Arrangement <NUM> also includes a beam delay element <NUM> in return path 202B to match the effect of half waveplate <NUM> in return path 202A.

Due to the finite amount of time required to switch the state of the polarization control element, the LIDAR based measurement of relatively short distances is based on light collected by the return path 202B depicted in <FIG>. While the polarization control element is changing state, return light propagating along the path 202A depicted in <FIG> will not necessarily be subject to a change in polarization. Thus, this light has a high probability of propagating through PBS <NUM> to pulsed light emitting device <NUM>, and thus, will not be detected. This situation is acceptable because signal strength is typically not a significant issue for relatively short range measurements.

However, for relatively long range measurements, after a sufficient period of time to ensure that the state of the polarization state switching element has changed, return light propagating down both paths described in <FIG> is available for detection and distance estimation.

As discussed hereinbefore, quarter waveplate <NUM> is desirable. When performing relatively short range measurements, only light passing though the return path 202B described in <FIG> is available. When the polarization of the return light is completely mixed, half of the light will pass through the path described in <FIG>. However, when the return light has reflected from a specular target, the polarization remains unchanged. Without introducing the quarter waveplate <NUM>, light reflected from specular targets would propagate through the path described in <FIG>, and would be undetected or significantly weakened for short range measurements when the polarization control element is changing states.

<FIG> depicts an arrangement <NUM> of an integrated LIDAR measurement device that includes an additional polarization control element <NUM> in return path 202B. Arrangement <NUM> includes like numbered elements described with reference to arrangement <NUM>. Polarization control elements <NUM> and <NUM> effectively control the amount of return light that reaches detector <NUM>. As discussed with reference to <FIG>, if polarization control element <NUM> does not change the polarization state of return light 202A, the light is directed to pulsed light emitting device <NUM>, not detector <NUM>. Conversely, if polarization control element <NUM> changes the polarization state of return light 202A, the light is directed to detector <NUM>. Similarly, if polarization control element <NUM> changes the polarization state of return light 202B from s-polarization to p-polarization, the light is directed away from detector <NUM>, and ultimately dumped (i.e., absorbed elsewhere). Conversely, if polarization control element <NUM> does not change the polarization state of return light 202B, the light is directed toward detector <NUM>. Since the degree of polarization change imparted by polarization control elements <NUM> and <NUM> is variably controlled(e.g., Pockels Cells), it follows that the amount of return light that reaches detector <NUM> is controlled by a controller of the integrated LIDAR measurement device(e.g., controller <NUM>) via control signals <NUM> and <NUM>.

For example, as discussed hereinbefore, when performing relatively short range measurements, only light passing though the return path 202B described in <FIG> and <FIG> is available for detection as polarizer control element <NUM> is transitioned from its state depicted in <FIG>. During this period of time, there is a risk that detector <NUM> saturates. In this scenario, it is desirable to control polarization control element <NUM> such that the polarization of a portion of return light <NUM> is partially changed from s-polarization to p-polarization and that the p-polarized light component is dumped before it reaches detector <NUM>.

In general, the timing and profiles of control signals <NUM> and <NUM> can be tuned to maximize the dynamic range of detector <NUM> for different environmental conditions. For example, previously detected signals, signals from other integrated LIDAR measurement devices, images of the surrounding environment, or any combination thereof could be utilized to adjust the dynamic range of detector <NUM> by changing the timing and profiles of control signals <NUM> and <NUM> during operation of an integrated LIDAR measurement device. In one example, the timing and profiles of control signals <NUM> and <NUM> are programmed as a function of pulse travel distance. This can be used to avoid detector saturation caused by objects that are close to the sensor. For larger distances, measurement sensitivity is maximized and polarization control element <NUM> is programmed to pass return light 202B without changing its polarization. In this manner, the maximum amount of return light reaches detector <NUM>. Multiple profiles could be used depending on illumination pulse power, features detected in the sensed environment from data collected in a previous return, etc..

<FIG> depicts an arrangement <NUM> of an integrated LIDAR measurement device that includes additional, optional elements that may be added individually, or in any combination, to arrangement <NUM> described with reference to <FIG>. Arrangement <NUM> includes like numbered elements described with reference to arrangement <NUM>. As depicted in <FIG>, collimating optics <NUM> are located in the optical path between pulsed light emitting device <NUM> and beam splitter <NUM>. Typically, a pulsed light emitting device based on laser diode technology or light emitting diode technology generates a divergent beam of light. By collimating the illumination light emitted from the pulsed light emitting device, a small beam size is maintained throughout the illumination path. This allows the optical elements in the illumination path to remain small.

Also, arrangement <NUM> includes a focusing lens <NUM> after quarter waveplate <NUM>. By refocusing the collomated light transported through the integrated LIDAR measurement device, the output aperture of the illuminating device <NUM> is re-imaged just outside of the integrated LIDAR measurement device, keeping both the cross section of the integrated LIDAR measurement device and the effective exit and entrance aperture of the integrated measurement device small. This increases possible pixel packaging density and pixel resolution. Since focusing lens <NUM> is located in the optical path shared by the illumination light and the return light, and the illumination and return paths are balanced, an image point <NUM> is generated at the output of the integrated LIDAR measurement device. This imaging point <NUM> is imaged back to both the detector <NUM> and the pulsed light emitting device <NUM>. Various optical elements such as apertures, field stops, pinhole filters, etc. may be located at image point <NUM> to shape and filter the images projected onto detector <NUM>. In addition, arrangement <NUM> includes a focusing optic <NUM> located in the optical path between the detector <NUM> and beam combiner <NUM> to focus the return light onto detector <NUM>.

Also, arrangement <NUM> includes a spectral filter <NUM> located in the return beam path between the focusing optic <NUM> and beam combiner <NUM>. In some arrangements, spectral filter <NUM> is a bandpass filter that passes light in the spectral band of the illumination beam and absorbs light outside of this spectral band. In many arrangements, spectral filters operate most effectively when incident light is normal to the surface of the spectral filter. Thus, ideally, spectral filter <NUM> is located in any location in the return beam path where the light is collimated, or closely collimated.

<FIG> depicts a side view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM>, a pulsed light emitting device <NUM> located in front of detector <NUM> within a lens element <NUM>. <FIG> depicts a front view of arrangement <NUM>. As depicted in <FIG>, return light <NUM> is collected and focused by lens element <NUM> (e.g., a compound parabolic concentrator) onto detector <NUM>. Although the input port <NUM> of lens element <NUM> is depicted as planar in <FIG>, in general, the input port <NUM> may be shaped to focus return light <NUM> onto detector <NUM> in any suitable manner. Pulsed light emitting device <NUM> is located within the envelope of lens element <NUM> (e.g., molded within lens element <NUM>). Although pulsed light emitting device <NUM> blocks a certain amount of return light, its small size relative to the collection area of lens element <NUM> mitigates the negative impact. Conductive elements <NUM> provide electrical connectivity between pulsed light emitting device <NUM> and other elements of the integrated LIDAR measurement device (e.g., illumination driver <NUM>) via conductive leads <NUM>. In some arrangements, conductive elements <NUM> also provide structural support to locate pulsed light emitting device <NUM> within the envelope of lens element <NUM>.

<FIG> depicts a side view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> and a pulsed light emitting device <NUM> located in front of detector <NUM>. As depicted in <FIG>, return light <NUM> is collected and focused by focusing optics <NUM> onto detector <NUM>. Pulsed light emitting device <NUM> is located within focusing optics <NUM> (e.g., molded with focusing optics <NUM>). Although pulsed light emitting device <NUM> blocks a certain amount of return light, its small size relative to the collection area of focusing optics <NUM> mitigates the negative impact. Conductive elements (not shown) provide electical connectivity between pulsed light emitting device <NUM> and other elements of the integrated LIDAR measurement device (e.g., illumination driver <NUM>). In some arrangements, the conductive elements also provide structural support to locate pulsed light emitting device <NUM> within focusing optics <NUM>.

<FIG> depicts a side view of an arrangement <NUM> of an integrated LIDAR measurement device including a detector <NUM> having an active area <NUM> and a pulsed light emitting device <NUM> located outside the field of view of the active area <NUM> of the detector. As depicted in <FIG>, an overmold <NUM> is mounted over the detector. The overmold <NUM> includes a conical cavity that corresponds with the ray acceptance cone of return light <NUM>. In one aspect, illumination light <NUM> from illumination source <NUM> is injected into the detector reception cone by a fiber waveguide <NUM>. An optical coupler <NUM> optically couples illumination source <NUM> (e.g., array of laser diodes) with fiber waveguide <NUM>. At the end of the fiber waveguide <NUM>, a mirror element <NUM> is oriented at a <NUM> degree angle with respect to the waveguide to inject the illumination light <NUM> into the cone of return light <NUM>. In one arrangement, the end faces of fiber waveguide <NUM> are cut at a <NUM> degree angle and the end faces are coated with a highly reflective dielectric coating to provide a mirror surface. In some arrangements, waveguide <NUM> includes a rectangular-shaped glass core and a polymer cladding of lower index of refraction. In some arrangements, the entire assembly <NUM> is encapsulated with a material having an index of refraction that closely matches the index of refraction of the polymer cladding. In this manner, the waveguide injects the illumination light <NUM> into the acceptance cone of return light <NUM> with minimal occlusion.

The placement of the waveguide <NUM> within the acceptance cone of the return light projected onto the active sensing area <NUM> of detector <NUM> is selected to ensure that the illumination spot and the detector field of view have maximum overlap in the far field.

In some arrangements, such as the arrangements described with reference to <FIG> and <FIG>, an array of integrated LIDAR measurement devices is mounted to a rotating frame of the LIDAR device. This rotating frame rotates with respect to a base frame of the LIDAR device. However, in general, an array of integrated LIDAR measurement devices may be movable in any suitable manner (e.g., gimbal, pan/tilt, etc.) or fixed with respect to a base frame of the LIDAR device.

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

<FIG> illustrates a method <NUM> of performing LIDAR measurements in at least one novel aspect. Method <NUM> is suitable for implementation by a LIDAR system such as LIDAR systems <NUM> illustrated in <FIG> and LIDAR system <NUM> illustrated in <FIG> of the present invention. In one aspect, it is recognized that data processing blocks of method <NUM> may be carried out via a preprogrammed algorithm executed by one or more processors of controller <NUM>, or any other general purpose computing system. It is recognized herein that the particular structural aspects of LIDAR system <NUM> do not represent limitations and should be interpreted as illustrative only.

In block <NUM>, a measurement pulse of illumination light is generated by an illumination source mounted to a printed circuit board.

In block <NUM>, a return pulse of light is detected by a detector mounted to the printed circuit board. The return pulse is an amount of the measurement pulse reflected from a location in a three dimensional environment illuminated by the corresponding measurement pulse. The measurement pulse of illumination light and the return pulse share a common optical path over a distance within the integrated LIDAR device.

In block <NUM>, an output signal is generated that is indicative of the detected return pulse.

In block <NUM>, an amount of electrical power is provided to the illumination source by an illumination driver mounted to the printed circuit board. The provided electrical power causes the illumination source to emit the measurement pulse of illumination light.

In block <NUM>, the output signal is amplified by an amount of analog signal conditioning electronics mounted to the printed circuit board.

In block <NUM>, the amplified output signal is converted to a digital signal by an analog to digital converter mounted to the printed circuit board.

In block <NUM>, a time of flight of the measurement pulse from the LIDAR device to the measured location in the three dimensional environment and back to the LIDAR device is determined based on the digital signal.

Claim 1:
An integrated light detection and ranging (LIDAR) device, comprising:
an illumination source (<NUM>) mounted to a substrate (<NUM>), the illumination source (<NUM>) configured to generate a measurement pulse of illumination light;
a detector (<NUM>) mounted to the substrate (<NUM>), the detector (<NUM>) configured to detect a return pulse of light and generate an output signal indicative of the detected return pulse, wherein the return pulse is an amount of the measurement pulse reflected from a location in a three dimensional environment illuminated by a corresponding measurement pulse, wherein the measurement pulse of illumination light and the return pulse share a common optical path over a distance within the integrated LIDAR device;
an illumination driver mounted to the substrate (<NUM>), the illumination driver electrically coupled to the illumination source (<NUM>) and configured to provide an amount of electrical power to the illumination source (<NUM>) that causes the illumination source (<NUM>) to emit the measurement pulse of illumination light;
a beam splitter mounted to the substrate, the beam splitter configured to separate the return pulse of light and the illumination pulse from the common optical path; and
a computing system configured to determine a time of flight of the measurement pulse from the LIDAR device to the measured location in the three dimensional environment and back to the LIDAR device based at least in part on output signal.