The present application claims priority under 35 U.S.C. §120 to U.S. patent application Ser. No. 14/218,607, filed Mar. 18, 2014 to Aina et al. (pending/allowed) which is herein incorporated by reference in its entirety.
Field
The example embodiments in general are directed to an automotive collision avoidance sensor system.
Related Art
Lasers or other forms of coherent electromagnetic radiation (ER) today have numerous applications, such as applications for marking and guiding munitions, vehicles, determining distance (ranging), navigating, surveying, remote sensing, highlighting an object and so on. In response, laser warning receiver (LWR) systems have become important to detect and process laser emissions. Typically, a LWR is a passive system that detects incoming laser emissions and processes the incoming laser emissions for various parameters, such as range of the origin or source of the laser emissions to the LWR system, angle of arrival of the laser emissions, spectral content, etc. For example, it is common for military vehicles, such as planes, helicopters, ships, etc., to be equipped with a LWR system. LWR systems may also be used in civilian or commercial settings, such as for vehicle safety, mass transit, etc.
Currently, the known LWR's are limited in sensitivity, range, spectral coverage (e.g., range of wavelengths detectible by the LWR system), angular coverage, operating temperature, resolution, etc. Moreover, current LWR devices are large and/or bulky and consume large amounts of power. This makes the known LWR systems unsuitable for many applications in which they would otherwise be useful. Furthermore, the known LWR's are prone to false alarms due to ambient light and/or other sources of optical emissions, which are common in the environment.
Applicant described a solution to the above limitations in their co-pending '607 application, presenting an electromagnetic or laser warning sensor of an optical detection system and system thereof. In general, the system includes a Fresnel lens coupled to an array of photodetectors having a pixel pitch which enabled an angular coverage of up to 360°.
In operation, the Fresnel lens collects incident optical signals and focuses the same onto the array, where the optical signals into electrical outputs analyzed by the optical detection system to determine, for each optical signal, an incident angle of arrival of thereof, and a range of a source of the optical signal to the sensor that is determined from the calculated angle of arrival. The electrical outputs were further analyzed to minimize a false alarm rate by discriminating each optical signal spectrally to calculate a wavelength thereof, so as to distinguish whether an incident optical signal is from a narrowband laser source operating at a single wavelength or from a broadband light source operating at a continuum of wavelengths.
Applicant has discovered that their sensor technology, with slight variations, is applicable to automotive collision avoidance technologies, for both driver and driverless cars. Currently, it has been observed that smart/intelligent cars (such as those of UBER® or GOOGLE®) are employing LiDAR. These are cumbersome and expensive ($65,000) systems, typically sitting 4 feet above the driver line of sight, and utilizing several rotating lenses in an effort to build a picture of the 3D environment around the car. The sensitivity of these sensors is also poor, particularly degrading in poor weather/visibility conditions (fog, snow, rain, etc.). Moreover, these current LiDAR systems are limiting in terms of their actual capability, and can only see a swath or narrow beam angle at a time. So instead of a complete 360 degree view, a series of cylindrical views are fed into a computation engine, thus it is a very computation-intensive system. Therefore, these system cannot provide the 3D picture at every instant as can the human brain, being limited by the frame rate (typically 10-60 Hz) which is way too slow a reaction/refresh time.
What is needed is a collision avoidance sensor system providing a lower cost, lower power and less computationally intensive solution, particularly one which is more sensitive as well as requiring less power both in normal and obscured conditions.
An example embodiment is directed to an automotive collision avoidance sensor system installed at both the fore and aft of a vehicle, which includes an output lens, an input lens, and a transmit laser. The transmit laser is adapted to transmit a pulsed beam through the output lens to impact roadway, surrounding vehicles or objects fore, aft, port and starboard of the vehicle, with return signals from the roadway, surrounding vehicles or objects reflecting off the input lens. A sensor of the system adapted collects the return signals from the input lens to convert them into output voltages and signals, and has a data processor configured to analyze the output voltages and signals so as to calculate real-time 3-dimensional situation awareness measurements and safety metrics which are constantly measured and updated to prevent possible collision.
Example embodiments will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are represented by like reference numerals, which are given by way of illustration only and thus are not limitative of the example embodiments herein.
Before delving into Applicant's novel automotive collision avoidance system, Applicants provides the background of their electromagnetic or laser warning sensor as described in the co-pending '607 application. In the following description, certain specific details are set forth in order to provide a thorough understanding of various example embodiments of the disclosure. However, one skilled in the art will understand that the disclosure may be practiced without these specific details. In other instances, well-known structures associated with manufacturing techniques have not been described in detail to avoid unnecessarily obscuring the descriptions of the example embodiments of the present disclosure.
Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.”
Reference throughout this specification to “one example embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one example embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more example embodiments.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. The term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
As used in the specification and appended claims, the terms “correspond,” “corresponds,” and “corresponding” are intended to describe a ratio of or a similarity between referenced objects. The use of “correspond” or one of its forms should not be construed to mean the exact shape or size. In the drawings, identical reference numbers identify similar elements or acts. The size and relative positions of elements in the drawings are not necessarily drawn to scale.
In Applicant's co-pending '607 application, which forms the basis for this new subject matter, there is described a laser sensing system that has high angular resolution and is sensitive to a low laser powers. The sensing system is sensitive to a wide range of wavelengths, has up to a 360° angular coverage at the aperture of the system, and has high discrimination and angular resolution (e.g., the measure (in degrees or radians) of the system's ability to detect small details of the incident optical signal with high accuracy). In one embodiment, the laser sensing system has a near-zero false alarm rate ((FAR), e.g., the rate representing the time between false alarms with the system activated), nanowatt/cm2 optical sensitivity, and high detection probability. In addition, the system has spectral discrimination (e.g., the ability to determine the actual wavelength(s) of an optical signal incoming or incident to the system so as to discriminate a laser emission (narrowband and at a single wavelength) from a light emission (broadband signal with a spread of wavelengths) and or high angular resolution.
The following
TABLE 1 shows some exemplary performance specifications that may be achieved by Applicants LWR system.
As shown, the 100 may comprise a sensor 102, which further comprises optics 104 and a detector 106, a sensor interface 108, a processor 110, and an optional output device 112. The sensor 102 receives light and laser emissions and provides an output to indicate various parameters about the light and laser emissions. As noted, the sensor may comprise optics 104 and a detector 106.
The optics 104 are responsible for collecting the light and (if present) laser emissions and focusing the light onto the detector 106. In some embodiments, the optics 104 may be an optical package that comprises a lens and/or other types of ports. In one example, the optics 104 may be an optical package that comprises comprise a Fresnel lens and an optical grating. In another example, optics 104 may be an optical package that comprises a doublet Fresnel lens for 2D angle resolving detection (EFL 2.5 mm, FOV)>100° and a transmission grating and cylindrical lens (FL 5 mm, FOV)>100° focused on a one-dimensional linear array (1D array) for optical false alarm rejection.
The detector 106 is responsible for converting the light energy and received laser emissions into an electrical output. In one embodiment, the detector 106 may comprise an array of avalanche photodiodes (APDs) that are sensitive to various forms of light and laser emissions. Detector 106 may comprise multiple arrays of detectors to discriminate laser emissions and minimize/avoid false alarms. For example, the detector 106 may comprise a two dimensional (2D) array of APDs that form individual pixels and a one dimensional array (1D) array of APDs.
The angular coverage at the aperture of the 2D array depends directly on the pixel pitch, the number of pixels of the APD arrays and the optical configuration of the sensor 102. In an embodiment, the aperture of detector 106 in sensor 102 of system 100 has up to a 360° angular coverage. In this embodiment, the APD array layout may range from about 50-um pixel diameter and a pitch that ranges from about 150-um to 210-um pitch.
The sensor interface 108 is responsible for acquiring the signals from the detector 106 and converting them into useful output voltages and signals for analysis by the processor. In some embodiments, the sensor interface 108 comprises a readout integrated circuit (ROIC).
The processor 110 is responsible for analyzing the output of the sensor interface 108 and determining various parameters, such as angle of arrival of laser emissions, spectral content, range to source of laser emissions, etc. In one embodiment, processor 110 comprises a field programmable array (FPGA) module to process the detector data. For example, the processor 110 may be implemented based on an Opal Kelly XEM6010 Spartan-6 FPGA module. Alternatively, the processor 110 may be a microprocessor, such as a Rabbit Core RCM3400 microprocessor. One skilled in the art will recognize that various types of processors may be used in the embodiments.
The processor 110 may execute various algorithms and processes using executable program code and software. Data processing algorithms for detection and false alarm rejection and angle are further described below.
The processor 110 may also execute a software interface through a communications interface, such as RS-485 connector, a wireless network, etc. In some embodiments, processor 110 may execute software for detection and alarm declaration with or without real time data storage, for example, onto a storage card or other medium. The processor 110 may also be provided with GPS connectivity.
The output device 112 is an optional device of system 100 so that a user can interface with the system 100. For example, the output device 112 may be a speaker or display, a computer, a laptop, or other form of user interface device. The output device 112 may also comprise an interface to other computing systems, such as one or more communications ports or an application programming interface.
In one embodiment, the output device 112 is adaptable to various systems. For example, the output device 112 may employ one or more standard communications protocols, such as RS-485, as an output interface. The output device 112 may thus provide information about the threat and periodic system status updates.
In
In one embodiment, the control and data processing components may employ an FPGA. For example, the Spartan-6 FPGA may be used to control the onboard chips (MUX, ADC, DAC, ROIC, RS485) and for processing the detector outputs and running the detection algorithms. Alternatively, a microprocessor may be used for onboard chip control and signal processing.
Resistors may be used in the sensor interface 108 to convert the photocurrent from the detector 104 into output voltages. This alternate approach may have better noise performance and speed. In this embodiment, all APD outputs from the detector 106 feed through a resistive load circuit (shown in
Angle of arrival detection is accomplished by using a Fresnel lens in optics 104A to focus incoming signals onto a pixel on an 8 by 8 APD detector array 106A. The angular discrimination can be determined by the pixel detecting the focused optical signal or the algorithms can be used to determine the angle of arrival.
Spectral discrimination and false alarm rejection is accomplished by using a transmission grating as part of 1D optics 104B and a cylindrical lens over a linear 1 by 16 APD detector array 106B (“1D detector array 106B”) and is used by the algorithms for false alarm rejection.
To understand the determination of angle of arrival of a laser emission,
The angle of arrival can be determined from the relative intensity of all the pixels in the detector array 106A. The technique is based on the known non-coherent Fresnel finding technique. In particular, the Fresnel lens located at the aperture of detector array 106A causes the transmittance of the radiation to vary continuously as a function of the incident angle. The intensity at each pixel in the detector array 106A is thus a function of the angle of each pixel relative to the emission source, and the range and the resolution is a function of the relative intensity distribution over the image formed by the pixels in the detector array 106A.
The measured relative intensities at each pixel provide enough information for range determine using algorithms and by electronic signal processing of the pixel photocurrent data.
The angle of arrival (Theta) can be calculated using the angle dependent Fresnel transmission curves, which can be correlated to the photocurrent signals I generated by each pixel of the detector array using the following equations:
In addition, the range of the origin or source of the laser to system 100 may be calculated based on the following equation:
Angular Determination Algorithm.
Various algorithms may be used for determining the incident angle of an optical signal, such as a laser emission. These non-linear equations can be solved using non-linear equation solvers that may be programmed into FPGAs or as a microprocessor firmware, or software as part of processor 110. In general, the angular recognition algorithm comprises: measuring photocurrents of pixels received by the sensor; calculating photocurrent ratios; solving the nonlinear equations to determine an angle of arrival of the optical signal; and using the angle of arrival to determine a distance of the optical signal.
One example is described with reference to determining the angle and distance of an optical signal, such as a laser. As shown in
In the above, θi is the angle of incidence on pixel pi, θ is the angle subtended between the source and the midpoint between pixels pi and pi+1. G is the constant in the range equation which accounts for the detector performance and other physical constants, d is the spacing between the pixels and b is the optical attenuation coefficient.
The intensity ratio at each pixel can then be expressed as:
Equation 4 can be used to generate i non-linear equations with i variables and the intensity ratios are based on the measured photocurrent data at each pixel. Any other type of non-linear equations can be formulated based on any functions or transform of the photocurrent data. The most obvious of these is the intensity ratio, which has the advantage of normalizing the data to eliminate systematic anomalies.
False Alarm Rejection.
As shown, the 1D detector array 106B receives an optical signal from 1D optics 104B, which may be configured as a transmission grating and cylindrical lens focused. As shown, the incoming threat optical signal passes through the grating, which disperses the photons spatially depending on their wavelength. Lasers operating at a single wavelength will only illuminate a small area of the 1D detector array 106B and will therefore be incident at a predetermined pixel depending on the optical design. Broadband light sources, however, have a continuum of wavelengths and thus will be split into individual wavelengths and illuminate many pixels. Using the pixel distribution of photocurrent on the linear array, the LWR electronics of system 100 can determine if the optical signal is coming from a narrowband source and at what wavelength.
The normalization of the output signals allows the range measurement to be independent of the signal level from the target. Therefore, by measuring the photocurrents of the detector array pixels the angles can be calculated.
Exemplary Software Process Flows.
Alternatively, spectral discrimination may be accomplished using a grating to spatially disperse the optical signal onto an array of pixels designed to correspond to different wavelengths. These spectral discrimination features enable false alarm rejection, threat identification, classification, as well as spectral binning to reduce false alarms and enable the capability for day/night operation.
Detection Threshold.
S
min
=Q*NEP
FAR=1/2[1−erf(Q/√2)]˜1/√(2p)[exp((−Q2/2))/Q] 3.2.2
FAR˜NEP/√(2p)[exp((−(Smin/NEP)2/2))/Smin,] 3.2.3
In the above, NEP is the noise equivalent power at which the signal-to-noise ratio (SNR) is 1, Q is the error or false alarm factor which is related to FAR by an error function for generalized noise or a Gaussian function for Gaussian noise. While NEP is the minimum noise power (sensitivity) at SNR=1, Smin is the sensitivity at an SNR designed to produce a particular FAR. These equations were used to estimate the trade-off between FAR and sensitivity. For these estimates, the threshold may be set to yield a probability of detection close to 100%.
Applicant's LWR sensor system 100 having been described in detail, the example embodiments are now directed to an automotive collision avoidance system and method that can be fabricated at lower cost, uses lower power in both normal and obscured conditions, is much less computationally intensive, and much more sensitive to thereby provide 360 degree coverage with greater accuracy then current solutions.
Referring to
In an example, the sensor system 200 is mounted in both the fore and aft of the vehicle (generally along the line of sight of the driver in the front grill and rear bumper, as an example), and is capable of detecting scattered laser signals from the nearby vehicles Similar to LWR system in
Optics 204 may be an optical package that comprises one Fresnel lens for the input and another for the output lens of optics 204, with or without an optical grating. In another example, optics 204 may be an optical package that comprises a doublet Fresnel lens (I/O lenses) and also for 2D angle resolving detection (EFL 2.5 mm, FOV)>100° and a transmission grating and cylindrical lens (FL 5 mm, FOV)>100° focused on a one-dimensional linear array (1D array) for optical false alarm rejection. Optics 204 could be a combination lens setup with transmitter lens on the output side and Fresnel on the receive/input side.
As previously described with the LWR sensor 102, CA sensor 210 is adapted to collect the incident optical signal, and includes a detector array of photodetectors (as was described for detector 106 in
In one specific configuration, and similar to as specified for LWR 102 above, the optics 204 may be embodied as a doublet Fresnel lens, and the detector array may be a two dimensional (2D) detector array of avalanche photodiodes (APDs) coupled to the Fresnel lens to convert the optical signal into a photocurrent. Output voltages and signals converted from the 2D detector array photocurrent by the sensor interface are employed with Fresnel equations in algorithms iterated by the processor to determine the range, azimuth, elevation). In an example, the 2D detector array may have a breakdown voltage of 35 volts, a dark current of less than 100 nA, and an optical gain between 10-15 A/W.
Further, and similar to as specified for LWR 102 above, here the CA sensor 210 may further includes a transmission grating with cylindrical lens attached thereto, and a linear (1D) detector array coupled to the grating and to the cylindrical lens, the incident optical signal passing through the grating, which disperses photons thereof spatially depending on wavelength, the photons collected by the cylindrical lens and directed to the 1D detector array for conversion into photocurrents, the output voltages and signals converted therefrom by the sensor interface analyzed spectrally by the processor
Sensor system 200 is designed to provide 3D situation awareness. Namely, the CA sensor 210 with its associated data processor is adapted to determine each of the range R, azimuth angle θaz and elevation angle θele of vehicle surroundings. In other words, information as to the proximity of objects fore, aft, starboard and port are constantly measured and updated. CA sensor 210 with its associated data processor then builds a point cloud of vehicle surroundings from the R, θaz and θele data, and then builds a 3D model of vehicle surroundings from the point clouds. This 3D model will be similar to, but more precise than what a human driver would see if he/she had 180° field-of-view (FOV). The CA sensor 210 then constructs a safe zone (such as a safe breaking distance zone) in the 3D model and generates alarms or takes evasive actions for any intrusion into the safe zone.
The sensor system 200 is foreseen in various operational scenarios. In one example, system 200 may include a vehicle cutting-in warning/braking system command setup; in another, a vehicle ahead sudden braking warning/braking system command setup. Sensor system 200 may also provide a side-swipe avoidance system function to the driver or car.
The sensor system 200 employs an active CA laser sensor 210, operating in wavelengths of near-uv, or blue (350-450 nm) to penetrate fog and enhance sensitivity in obscured conditions. As the transmit laser 220 emits a pulsed beam, a high frame rate is not needed.
Accordingly, the automotive collision avoidance sensor system 200 described herein provides 3-dimensional situation awareness measurements, namely real-time distance, azimuth and elevation angles of objects. Sensor system 200 offers automobiles the same 3D situation awareness capabilities as humans. The proximity of objects fore, aft, starboard & port are constantly measured and updated. Safe breaking distance may be constantly measured and updated, and an imminent collision warning may be issued for proximity less than the safe breaking distance, or outside the safe zone.
The example embodiments having been described, it is apparent that such have many varied applications. For example, the example embodiments may be applicable but not limited to connection to various devices, structures and articles.
The present invention, in its various embodiments, configurations, and aspects, includes components, systems and/or apparatuses substantially as depicted and described herein, including various embodiments, sub-combinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in its various embodiments, configurations, and aspects, includes providing devices in the absence of items not depicted and/or described herein or in various embodiments, configurations, or aspects hereof, including in the absence of such items as may have been used in previous devices, e.g., for improving performance, achieving ease and\or reducing cost of implementation.
The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the invention are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the embodiments, configurations, or aspects of the invention may be combined in alternate embodiments, configurations, or aspects other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.
Moreover, though the description of the invention has included description of one or more embodiments, configurations, or aspects and certain variations and modifications, other variations, combinations, and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments, configurations, or aspects to the extent permitted, including alternate, interchangeable and/or equivalent structures to those claimed, whether or not such alternate, interchangeable and/or equivalent structures disclosed herein, and without intending to publicly dedicate any patentable subject matter.
Number | Date | Country | |
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Parent | 14218607 | Mar 2014 | US |
Child | 15615780 | US |