Source: http://www.google.com/patents/US7045783?ie=ISO-8859-1
Timestamp: 2015-05-30 11:48:55
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Matched Legal Cases: ['application No. 60', 'art 200', 'art 200', 'art 200', 'APPLICATION NO. 10', 'APPLICATION NO. 10']

Patent US7045783 - Device and method for object illumination and imaging using light pulses - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA reduced glare imaging system for motor vehicles which includes at least one light source capable of modulation. The system also includes a synchronization system which has structure for obtaining a time reference, and a trigger for modulating emissions from the light source. The trigger initiates emission...http://www.google.com/patents/US7045783?utm_source=gb-gplus-sharePatent US7045783 - Device and method for object illumination and imaging using light pulsesAdvanced Patent SearchPublication numberUS7045783 B2Publication typeGrantApplication numberUS 10/448,190Publication dateMay 16, 2006Filing dateMay 28, 2003Priority dateJun 5, 2001Fee statusLapsedAlso published asUS20030193981Publication number10448190, 448190, US 7045783 B2, US 7045783B2, US-B2-7045783, US7045783 B2, US7045783B2InventorsOleg MatveevOriginal AssigneeUniversity Of Florida Research Foundation, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (14), Non-Patent Citations (28), Referenced by (7), Classifications (34), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetDevice and method for object illumination and imaging using light pulses
US 7045783 B2Abstract
A reduced glare imaging system for motor vehicles which includes at least one light source capable of modulation. The system also includes a synchronization system which has structure for obtaining a time reference, and a trigger for modulating emissions from the light source. The trigger initiates emission of periodic light pulses from the light source at fixed times relative to the time reference. The fixed times can be randomly selected. The light pulses can have a wavelength in the range of 0.19 μm to 5 μm.
1. A reduced glare imaging system for motor vehicles traveling on roadways, comprising:
a synchronization system including structure for obtaining a time reference coupled to said light source;
a trigger for initiating emission of periodic light pulses from said light source during one of a plurality of different fixed time slot intervals relative to said time reference, wherein a first vehicle or first group of vehicles on said roadway is allocated a first of said plurality of fixed time slots and at least a second vehicle or second group of vehicles on said roadway is allocated a second of said plurality of fixed time slots; and
an imaging device for receiving scattered light from objects illuminated by said periodic light pulses, wherein said imaging device is gated to receive said scattered light only during defined gating periods.
2. The system of claim 1, wherein said light pulses have a wavelength in the spectrum range of 0.19 μm to 5 μm.
3. The system of claim 1, wherein said light pulses have a wavelength in the spectrum range of 400 nm to 750 nm.
4. The system of claim 3, wherein an average power of said light pulses is less than at least one value selected from the group consisting of 10 W, 1 W, 500 mW, 100 mW, 10 mW, 1 mW and 500 μW.
5. The system of claim 1, further comprising a display for displaying images contained in said received scattered light.
6. The system of claim 1, wherein said gating periods each have a duration approximately equal to the sum of (2DS/c)+ΔTPULSE, where ΔTPULSE is a duration of at least one of said periodic light pulses, DS is a maximum desired observation range, and c is the speed of light.
7. The system of claim 1, wherein said gating periods each have a duration approximately equal to the sum of 2(DB−DL)/c+ΔTPULSE, where ΔTPULSE is a duration of at least one of said periodic light pulses, DL is a distance correlating to a desired observation range minimum, DB is a distance correlating to a desired observation range maximum, and c is the speed of light.
8. The system of claim 1, wherein each of said gating periods commences when a correlating one of said periodic light pulses begins.
9. The system of claim 1, wherein each of said gating periods commences at a time approximately equal to ti+2DL/c and finishes at a time approximately equal to 2DB/c+ΔTPULSE, where ti=a time when a correlating one of said periodic light pulses begins, DL is a distance correlating to a desired observation range minimum, DB is a distance correlating to a desired observation range maximum, and c is the speed of light.
10. The system of claim 1, wherein said imaging detector has a luminosity-resolving power product of at least 104 cm2 sr.
11. The system of claim 1, wherein said imaging detector is at least one item selected from the group consisting of an atomic vapor ultranarrowband imaging detector, a molecular vapor ultranarrowband imaging detector, an atomic magnetooptical filter, a molecular magnetooptical filter, a spectral hole burning filter, an image intensifier, an electron bombardment charged coupled device, and a resonance ionization imaging detector.
12. The system of claim 1, further comprising a light filter, wherein said light filter is at least one item selected from the group consisting of colored glass, an acousto-optic filter, a Liot type filter, an atomic resonance fluorescence imaging monochromator, a magneto-optical filter, and an interference filter.
13. The system of claim 1, wherein said fixed times are defined by time slots, each time slot having a duration equal to at least an amount of time selected from the group consisting of a gating period and a period between light pulses.
14. The system of claim 1, wherein said fixed times are a arbitrarily selected.
15. The system of claim 1, wherein said fixed times are predetermined.
16. The system of claim 1, wherein a period between said light pulses is constant for all vehicles having said system while traveling on said roadway.
17. The system of claim 1, wherein a period between said light pulses is constant for all vehicles having imaging systems which are tuned to a light frequency which is common to all of said vehicles.
18. The system of claim 1, wherein a duration of said gating period is constant for a plurality of vehicles.
19. The system of claim 1, wherein said time reference is a wirelessly transmitted timing signal.
20. The system of claim 1, wherein said time reference is a signal transmitted from at least one of a global positioning satellite system, a global navigation satellite system and an earth based time station.
21. The system of claim 1, wherein said light source is configured as at least one device selected from the group consisting of a vehicle headlight and a head-mounted pulsed illuminator.
an illumination system mounted to said vehicle, said illumination system including:
at least one light source capable of modulation;
a synchronizing system including structure for obtaining a time reference coupled to said light source;
a trigger for initiating emission of periodic light pulses from said light source during one of a plurality of different fixed time slot intervals relative to said time reference, wherein on a roadway said vehicle is allocated a first of said plurality of fixed time slots, wherein another vehicle on said roadway is allocated a second of said plurality of fixed time slots; and
23. A method of providing reduced glare imaging for motor vehicles sharing roadways, comprising the steps:
receiving a time reference;
triggering a light source to initiate emission of periodic light pulses from said light source during one of a plurality of different fixed time slot intervals relative to said time reference, wherein on a roadway a first vehicle or first group of vehicles is allocated a first of said plurality of fixed time slots and at least a second vehicle or second group of vehicles on said roadway is allocated a second of said plurality of fixed time slots;
exclusively during gating periods correlating to said light pulses, receiving light scattered from objects illuminated by said periodic light pulses; and
displaying images based on said scattered light.
24. The method of claim 23, wherein said light pulses have a wavelength in at least one of the ranges of 0.19 μm to 5 μm.
25. The method of claim 23, wherein said light pulses have a wavelength in the spectrum range of 400 nm to 750 nm.
26. The method of claim 25, wherein an average power of said light pulses is less than at least one value selected from the group consisting of 1 W, 500 mW, 100 mW, 10 mW, 1 mW and 500 μW.
27. The method of claim 23, further comprising the step of defining said gating periods to be approximately equal to the sum of (2DS/c)+ΔTPULSE, where ΔTPULSE is a duration of at least one of said periodic light pulses, DS is a desired illumination distance for the imaging system's field of observation, and c is the speed of light.
28. The method of claim 23, wherein said gating periods each have a duration approximately equal to the sum of [2(DB−DL)/c+ΔTPULSE], where ΔTPULSE is a duration of at least one of said periodic light pulses, DL is a distance correlating to a desired observation range minimum, DB is a distance correlating to a desired observation range maximum, and c is the speed of light.
29. The method of claim 23, wherein each of said gating periods commences when a correlating one of said periodic light pulses begins.
30. The method of claim 23, wherein each of said gating periods commences at a time approximately equal to ti+2DL/c and finishes at a time approximately equal to 2DB/c+ΔTPULSE, where ti=a time when a correlating one of said periodic light pulses begins, DL is a distance correlating to a desired observation range minimum, DB is a distance correlating to a desired observation range maximum, and c is the speed of light.
31. The method of claim 23, wherein said fixed times are defined by time slots, each time slot having a duration equal to at least an amount of time selected from the group consisting of a gating period and a period between light pulses.
32. The method of claim 23, wherein said fixed times are arbitrarily selected.
33. The method of claim 23, wherein said fixed times are predetermined.
34. The method of claim 23, wherein said time reference is a wirelessly transmitted timing signal.
35. The method of claim 23, wherein said time reference is a signal transmitted from at least one of a global positioning satellite system, a global navigation satellite system and an earth based time station.
The present application is a continuation-in-part of U.S. patent application Ser. No. 10/157,359 entitled Device and Method for Vehicular Invisible Road Illumination and Imaging, filed May 28, 2002, which claims the priority of U.S. provisional patent application No. 60/295,699, filed Jun. 5, 2001.
Infrared (IR) thermal imaging using light having a wavelength of approximately 9–10 μm is another illumination concept currently being developed. In fact, IR thermal imaging cameras are commercially available on certain automobiles. Thermal imaging has several drawbacks, however. Significantly, since the 9–10 μm wavelength is 20 times longer than visible radiation, the spatial resolution of an image generated by IR thermal imaging is 20 times worse than the resolution obtained using visible light. In particular, an IR thermal image has a resolution which is typically only 76800 pixels (320�240), two orders of magnitude less than the resolution of modern charged coupled device (CCD) cameras, or the human eye.
The present invention relates to a reduced glare imaging system for motor vehicles. The reduced glare imaging system includes at least one pulsed light source. For example, the pulsed light source can be a laser, such as a Q-switched laser, a light emitting diode, and/or an electrodeless radio frequency excited lamp. The pulsed light source can be configured as a vehicle headlight. In another arrangement, the pulsed light source can be configured as a head-mounded pulsed illuminator.
The system also includes a synchronization system which has structure for obtaining a time reference, and a trigger for modulating emissions from the light source. The synchronization system can utilize a suitable wirelessly transmitted timing signal, such as the time reference is a signal transmitted from at least one of a global positioning satellite system, a global navigation satellite system and an earth based time station. The trigger initiates emission of periodic light pulses from the light source in fixed time intervals relative to the time reference. The time intervals can be arbitrarily selected or have a predetermined duration.
The light pulses can have a wavelength in the range of 0.19 μm to 5 μm, or in the range of 400 nm to 750 nm. The average power of the light pulses can be less than 10 W, 1 W, 500 mW, 100 mW, 10 mW, 1 mW and/or 500 μW. In one arrangement, a period between light pulses can be constant for a plurality of vehicles. In another arrangement, the period between light pulses can be constant for all vehicles having imaging systems which are tuned to a light frequency which is common to all vehicles.
The system also can include an imaging device for receiving light scattered from objects illuminated by periodic light pulses. The imaging device can be gated to receive the scattered light for defined gating periods. Each gating period can commence when a correlating periodic light pulse begins and can have a duration approximately equal to the sum of (2DS/c)+ΔTPULSE, where ΔTPULSE is a duration of at least one of the periodic light pulses, DS is a distance correlating to a maximum desired observation range, and c is the speed of light. In another arrangement, the gating period can have a duration approximately equal to 2(DB−DL)/c+ΔTPULSE where DB is a distance correlating to a desired observation range maximum, DL is a distance correlating to a desired observation range minimum. In yet another arrangement, each gating period can commence at a time approximately equal to ti+2DL/c and finish at a time approximately equal to 2DB/c+ΔTPULSE, where ti=a time when a correlating one of said periodic light pulses begins, DL is a distance correlating to a desired observation range minimum, DB is a distance correlating to a desired observation range maximum, and c is the speed of light.
The imaging detector can have a luminosity-resolving power product of at least 104 cm2 sr. The imaging detector can be any suitable detector, such as an atomic vapor ultranarrowband imaging detector, a molecular vapor ultranarrowband imaging detector, an atomic magnetooptical filter, a molecular magnetooptical filter, a spectral hole burning filter, an image intensifier, an electron bombardment charged coupled device, or a resonance ionization imaging detector. The system also can include a display for displaying images contained in received scattered light.
Each of the gating periods can commence when a correlating one of the periodic light pulses begins. Accordingly, fixed times can be defined by time slots, each time slot having a duration equal to at least one gating period. The duration of time elapsing between a first one of the periodic light pulses and a next one of the periodic light pulses can be greater than the product of 100, 1000 or 10,000 and the duration of the time slot. The imaging device can include an imaging detector for obtaining object images, and the imaging detector can detect the object images during each of the defined gating periods.
The system of also can include a suitable light filter. The light filter can be colored glass, an acousto-optic filter, a Liot type filter, an atomic resonance fluorescence imaging monochromator, a magneto-optical filter, or an interference filter.
The imaging system can be mounted to a vehicle wherein the trigger provides a particular time interval for the fixed times, whereby the imaging system emits light pulses which are not visible by unaided human vision during the time interval to signify an emergency condition. The emission of the invisible light pulses during the particular time interval can be detectable by an emergency service and can be detectable over a distance of at least 1 km. The particular time interval for the fixed times can be provided by the trigger upon the vehicle being operated while not being supplied a predetermined item or wherein the predetermined item is a unique key or a password.
FIG. 3 is a timing diagram representing illuminating pulses and gating periods associated with an alternate embodiment of an exemplary imaging system in accordance with the present invention.
The present invention relates to an imaging system for motor vehicles. The imaging system includes a pulsed light source which emits electromagnetic pulses in one or more parts of the light spectrum. Radiation resulting from the electromagnetic pulses (light pulses) being scattered by objects can be received by the imaging system during specific light reception gating periods and processed to provide accurate images of the objects. For example, the imaging system can provide accurate images of a road and oncoming vehicles.
The amount of time that elapses during each light pulse cycle can be divided into individual time slots, and the light pulses and gating periods for each imaging system can be configured to occur in one of the timeslots. Notably, the time slots can be extremely short in duration so that a great number of time slots can be provided within a light pulse cycle. In particular, there can be significantly more than 100 time slots. For example, there can be more than 20,000 time slots in each cycle. Accordingly, a large number of imaging systems can operate in different time slots, thereby virtually eliminating glare being between oncoming vehicles. An RF timing signal can be used by the imaging systems to keep the imaging systems synchronized.
The pulsed light source 101 can be any source of pulsed light which generates light in a spectrum which is visible or invisible to the human eye. For example, the pulsed light source can generate light having a wavelength approximately in the ranges from 0.19 μm to 5 μm. An exemplary pulsed light source can be a laser, for example a Q-switched laser, a pulsed laser diode, a pulsed arc discharge xenon lamp, an electrodeless discharge lamp, an electrodeless radio frequency excited lamp, a light emitting diode, and other such sources. If a laser generator is used as a pulsed light source 101, its output may be homogenized via a fiber optic, a light pipe, or other such means as known by those skilled in the art to uniformly illuminate a target area.
The light 110 generated by the pulsed light source 101 can be pulsed at any repetition rate. In one arrangement, the light 110 can be pulsed at a repetition rate which is greater than a reciprocal time associated with eye inertia. For example, a repetition rate of 16–24 Hz can be used. Further, the duration of the pulse, or pulse width (ΔTPULSE), can be chosen to be very short, for example several femtoseconds, to rather long, for example several microseconds. In any case, ΔTPULSE should be shorter than about DS/c, where DS is a desired illumination distance in the field of observation for the imaging system 100, and c is the speed of light.
The lens assembly can be any suitable size. Nonetheless, for a given average light intensity IR, image quality improves as the size of the lens assembly 108 is increased. Accordingly, to achieve a desired image quality, the average light intensity of the pulses generated by the pulsed light source 101 can be lower when a large lens assembly, for instance having a 10–15 cm diameter, is used in the imaging device 112 as compared to a lens assembly which is smaller. For example, in the visible region of the spectrum the light intensity IR needed to achieve an image quality which is approximately equivalent to the image quality detected with a human eye receiving a light intensity Ih can be determined by the equation IR=Ih(dh/din)2(ηh/ηim)βh/βim), where ηh is the quantum efficiency of the human eye, βim is the quantum efficiency the imaging detector, βh is the ratio of the light intensity transmitted through the optical system of the human eye to the input intensity of the light, βim is the ratio of the light intensity transmitted through the optical system of the imaging detector to the input intensity of the light, dh is the input aperture to a human eye, and din is the diameter of the lens. Notably, the quantum efficiency of an imaging system can be much greater than the quantum efficiency of the human eye, especially in situations when the human eye is blinded by an oncoming vehicle. In such instances the ratio ηh/ηim can be as small as 10−3–10 −4.
If it is assumed, for example, that βh/βim≅1, and that dh/din≅0.05, the ratio IR to Ih can be as small as 10−5–10−7. Thus, object illumination using an imaging detector and a pulsed light source generating several watts or microwatts of power can provide image quality equivalent to, or better than, a light source having 5–15 watts of power when being perceived by an unaided human eye. Importantly, the light pulses can have significantly less average power than the power of average low beam headlights. For example, an average power of the light pulses can be less than 10 W, 1 W, 500 mW, 100 mW, 10 mW, 1 mW, or less than 500 μW. Hence, even if the light pulses are white light in the visible part of the light spectrum, such light pulses will not blind oncoming drivers.
Object images converted by the image converter 106 can be forwarded to a display 105 for presentation. The display 105 can be any type of display which can present object images. For example, the display can be a microdisplay, such as a plasma display, a light emitting diode (LED) display, a liquid crystal on silicone (LCOS) display, an organic light emitting diode (OLED) on silicon display, (see S. K. Jones et al., OLED/CMOS Combo Opens a New World of Microdisplay, Laser Focus World, December 2001, at 55–58), a cathode ray tube (CRT), and other suitable displays. The display also can be a display which is worn by a driver of a vehicle, such as display goggles, or the display can be a heads-up display, for instance where images are projected onto a windshield of a vehicle. If display goggles, or any other type of head-mounted display is used, a stereoscopic image of the road can be obtained by using two imaging devices, one on each side of a vehicle. Accordingly, separate images can be generated for each side of the vehicle. Accordingly, images from the left side of the vehicle can be transmitted to the left eye and images from the right side of the vehicle can be transmitted to the right eye.
A receiver/timing signal processor (receiver) 104, which is operatively connected to an antenna 114, antenna array or satellite dish, can be provided. The receiver 104 can receive radio frequency (RF) timing signals and provide these signals to the synchronizing unit 103 for use in timing the pulsed light source 101 and the gating device 115. For example, the synchronizing unit 103 and/or receiver 104 can include an internal oscillator and software algorithms that process the RF timing signals. There are a number of timing signal references from earth based time stations that can be used. In one example, the RF timing signals can be timing signals received from either of the National Institute of Standards and Technology (NIST) time stations near Fort Collins, Colo. (WWV and WWVB) or the NIST time station in Kauai, Hawaii (WWVH). The timing signals transmitted by WWV and WWVH are specified as having a tolerance which is less than one microsecond at the transmitter site with reference to Coordinated Universal Time (UTC). Over the last several years, however, the timing signals have measured to be within fifty nanoseconds of UTC. Timing signals also can be obtained from a Wide Area Augmentation System (WAAS) which is commonly used to provide precision guidance to aircraft. Further, timing signals also can be proved in desired geographic regions, such as large metropolitan areas, with the use of a local positioning system. A local positioning system can comprise three or more local transmitters which can emanate RF signals carrying timing information and data from which coordinates can be determined.
In another example, the RF timing signals can be timing signals received via a modern Global Positioning Satellite (GPS) receiver, which can provide even greater time synchronization precision. For instance, RF timing signals can be received from the United States GPS system, the Russian Global Navigation Satellite System (GLONASS), and/or any another global positioning system. Modern GPS receivers can produce time synchronization with a standard deviation of ten nanoseconds or less. Such receivers are available from a number of commercial providers, such as TrueTime, Inc. of Santa Rosa, Calif. Further, methods for using GPS or GLONASS to achieve sub-nano second precision are known, for example as disclosed by Wlodzimierz Lewandowski of Jacques Azoubib Bureau International des Poids et Mesures in an article entitled GPS+GLONASS: Toward Subnanosecond Time Transfer, GPS World, vol. 9, at 30–39 (1998). The use of GPS or GLONASS also can have the added benefit of providing vehicle location and tracking information. The use of GPS and GLONASS for providing vehicle location and tracking information is known to those skilled in the art.
A diagram representing an exemplary pulse timing chart 200 is shown in FIG. 2A. The timing chart 200 displays a plurality of light pulse streams S1, S2, S3, Sn, each of which can represent the uniquely timed light pulses 202 generated by a different imaging system. The pulse streams S1, S2, S3, Sn can be synchronized using a time reference 206, such as an RF timing signal. The pulse timing chart 200 also shows the gating period (ΔTGATE) 204 associated with each pulse 202. For instance, pulse stream S1 includes light pulses P1−s1, P2−s1, P3−s1, Pn−s1 and gating periods G1−s1, G2−s1, G3−s1, Gn−s1, pulse stream S2 includes light pulses P1−s2, P2−s2, P3−s2, Pn−s2 and gating periods G1−s2, G2−s2, G3−S2, Gn−s2, and so on. As noted, each gating period can begin when the pulse with which the gating period is associated begins.
Referring to FIGS. 2A and 2B, the time that elapses between the end of a gating period for a particular light pulse and the beginning of a next light pulse being generated, such as a light pulse generated in another light pulse stream, can be referenced as idle time (ΔTIDLE). Accordingly, the duration of one time slot (ΔTZ) can be defined as ΔTZ=ΔTGATE+ΔTIDLE. Further, the time for one complete cycle in a light pulse stream can be defined as ΔTCYCLE, where ΔTCYCLE can be measured as the time elapsing between the start time of a first light pulse and the start time of a second light pulse in the same light pulse stream. Ideally, assuming one pulse stream can operate in each time slot, the maximum number (NS) of pulse streams that can operate without an overlap of gating periods can be determined by the number of time slots available. The number of time slots available can be determined by the formula NS=ΔTCYCLE/ΔTGATE. However, this formula assumes absolutely precise synchronization of light pulses and gating of the imaging detector and/or imaging converter. Alternatively, the equation NS=ΔTCYCLE/(ΔTGATE+ΔTIDLE)=ΔTCYCLE/ΔTZ can be used to determine the maximum number of time slots, thereby allowing for variations in timing signals and synchronization among imaging systems. For example, if ΔTGATE=1−2 μs, an appropriate value for ΔTIDLE may be 100–400 ns. Nonetheless, it may be more desirable to make ΔTGATE and ΔTIDLE much shorter to maximize NS. For instance, if ΔTCYCLE is 50 ms and ΔTZ=5 μs, 1�104 time slots are provided and 1�104 pulse streams can operate without overlap of gating periods. If ΔTCYCLE is 50 ms and ΔT=2.5 μs, 2�104 time slots are provided and 2�104 pulse streams can operate without overlap of gating periods. Assuming an operational range DS of 300 m, ΔTCYCLE=50 ms, ΔTPULSE=50 ns and ΔTIDLE=10 ns, 2.42�104 time slots can be provided. Notably, ΔTPULSE can be even shorter, for example as short as 10 ns.
It may appear that a pulse width ΔTPULSE of 10 ns would not give adequate image quality because for every second of operation only 200 ns of image data for a particular point in a road is received, assuming ΔTCYCLE is 50 ms. However, the distance of effective illumination does not correlate to pulse width. Accordingly, a series of images which are received with a repetition rate of at least 16–20 images per second will appear like a continuous image stream, even if each image gating period ΔTGATE is extremely short.
As noted, the light pulses can be synchronized using the RF timing signals. For example, the light pulses emanating from an imaging system in a vehicle can be timed so that each light pulse and its associated gating period occur within a time slot ΔTZ allocated for the vehicle. This allocation of the light pulses into defined time slots prevents light pulses and gating periods from overlapping into multiple time slots. Accordingly, a pulse emanated by a first vehicle will have significantly dissipated before a gating period begins for a second vehicle, thereby significantly reducing the likelihood of the second vehicle receiving glare caused by the first vehicle. In one arrangement, time slots may be assigned for a selected groups of vehicles, for example vehicles used by the military, the government, law enforcement agencies, ambulance services, fire rescue services, tractors, and so on. Vehicles also can be grouped by the type of vehicle, for example luxury vehicles, small vehicles, large vehicles, etc. Further, the a different time slot duration can be used for different vehicle types. For instance, the duration of a time slot ΔTZ can be 2–3 times longer for emergency vehicles as compared to other types of cars. Correspondingly the distance which is illuminated and observed in front of vehicle can be 2–3 times larger. In another arrangement, the imaging systems in different groups of vehicles can be configured to emit light pulses at different wavelengths.
The Doppler effect caused by vehicles moving toward each other is preferably considered when implementing the present invention. In particular, the minimal detection bandwidth which is required for the imaging detector 107 to detect a particular frequency of light can be estimated from the amount of frequency shift that is likely to occur due to the Doppler effect (Doppler shift). The Doppler shift can be determined by the equation Δν=2ν(V/c)=2V/λ, where ν is the frequency of the light, Δν is the change in frequency of the light, V is the relative velocity of the vehicles with respect to each other, and λ is the wavelength of the light. For example, if the maximum velocity of each of two vehicles as they approach each other is 50 mph, the relative velocity between the vehicles is V=100 mph (44.7 m/s) since the cars are moving toward each other. If the wavelength (λ) of the light pulses emanated by a first vehicle are 700 nm, the Doppler shift Δv associated with those light pulses computes to be 127.7 MHz. If the wavelength (λ) of the light pulses emanated are 1500 nm, the Doppler shift Δv is 59.6 MHz. Further, the Fourier transform of short light pulses can be evaluated and taken into consideration. Accordingly, for this example, a detection bandwidth of 100 MHz–300 MHz will be adequate if pulses with duration 1–10 ns are used.
The resolution R of an imaging detector is equal to λ/Δλ, where λ is the wavelength of the light pulses being detected and Δλ is variation in wavelength due to Doppler shift. It is preferable that the imaging detector have a resolution of approximately R=c/2V or 3.35�106 in the example. Further expanding the example, if the area of the imaging detector is approximately 3–5 cm2 and the field of view is 1–2 steradians (sr), it can be estimated that the ideal luminosity-resolving power product (LRPP) for imaging a moving object using a very narrowband light pulse is approximately 107–108 8 cm2 sr. A number of imaging detectors which provide the necessary LRPP are currently known to those skilled in the art.
In one arrangement, the imaging detector can be a resonance ionization imaging detector (RIID). A suitable RIID is disclosed in U.S. Pat. No. 6,008,496 to Winefordner et al., which is incorporated herein by reference. When a RIID is used, the RIID can be activated to detect images when the atoms of an atomic vapor in an RIID cell are excited into their Rydberg states. To decrease or eliminate the RIID noises, atoms can be excited into Rydberg states with a lifetime which is more than 2DS/c. In the case, a high voltage pulse, for example 1–50 kV, can be applied when the λ2 pulse is ended. To excite the atoms into their Rydberg states, the atomic vapor can be illuminated by a trigger light source which emanates light having a wavelength of λ2. For example, if Cs is used for the atomic vapor, the wavelength λ2 can be about 535 nm–510 nm to excite one or several Rydberg states.
RIID cells are susceptible to noise caused by nonselective multiphoton ionization of atoms and molecules due to the photo electric effect from the RIID surfaces. To eliminate the noise, a first voltage pulse can be applied to electrodes of the RIID cell in order to remove all noise electrons and ions after the gate is closed. For a RIID cell without micro channel plate (MCP), the pulse duration can be about 10 ns–500 ns and this voltage may be about 10 V-1000 V. Such a voltage pulse is not high enough to ionize the atoms of the atomic vapor which have been excited into the Rydberg state. A second voltage pulse of about 1000 V up to 50 kV can be applied to ionize the atoms which have been excited into the Rydberg state. This second voltage pulse can accelerate electrons or ions toward a screen or other imaging detector which is sensitive to charged particles, thereby producing an image of detected objects. The atoms which have been excited into the Rydberg state may also be ionized after the gate is closed by applying a delayed pulsed laser radiation, for example a 1064 nm Neodymium:Yttrium/Aluminum/Garnet (Nd:YAG) laser.
The ability of the RIID to process images from light which has a very narrow frequency bandwidth provides further advantages. For example, the probability of a first vehicle having a first imaging system receiving glare from a second vehicle having a second imaging system can be reduced by operating the first and second imaging systems at different frequencies. Accordingly, the first imaging system can be configured so that light pulses emanating from the second imaging system are not detectable by the first imaging system, and vice versa. In this manner, different light pulses can be used by different groups of vehicles to expand the number of vehicles that can use the imaging systems without excess glare being generated. If, for example, the imaging device has a bandwidth approximately 300 MHz, and the center frequency has a wavelength anywhere in the spectral range 1.52 μm–1.76 μm, almost 90,000 independent spectrally separated channels may be provided to decrease the probability of the imaging system receiving glare from oncoming vehicles. Thus, combining spectral selection with time slot allocation substantially decreases the probability of an imaging system receiving glare from an imaging system in another vehicle. Combining the above spectral selection example with our previous time slot example, the total probability of encountering a vehicle operating with an imaging system operating in the same time slot and at the same wavelength will be 1/(90,000�20,000)=5.55�10−10. Notably, the reciprocal number of this probability is at least three orders of magnitude greater than total number of cars on the Earth.
At this point it should be noted that other imaging detectors can be used and the invention is not limited to a RIID. For example, the imaging detector can be an atomic and/or molecular vapor ultranarrowband imaging detector, as described in O. I. Matveev et al., Narrow-band resonance-ionization and fluourescence imaging in a mercury-vapor cell, Optics Letters, Vol. 23, no. 4, at 304–06 (1998). An atomic and/or molecular magnetooptical filter also can be used also can be used as an imaging detector. (See, e.g., B. Yin et al., Theoretical Model for a Faraday Anomalous Dispersion Optical Filter, Optics Letters, Vol. 16, no. 20 at 1617–19 (1991). See also, R. I. Billmers et al., Experimental Demonstration of an Excited-state Faraday Filter Operating at 532 nm, Optics Letters, Vol. 20, no. 1 at 106–08 (1995); E. Dressler et al., Theory and Experiment for the Anomalous Faraday Effect in Potassium, Journal Optical Society of America, Vol. 13, no. 9 at 1849–58 (1996); B. P. Williams et al., Magnetooptic Doppler Analyser: A New Instrument to Measure Mesopause Winds, Applied Optics, Vol. 35, no. 33 at 6494–6503 (1996)). Further, a spectral hole burning filter also can be used. (See, e.g., W. E. Moerner, Persistent Spectral Hole-Burning: Science and Applications, Springer Verlag, Berlin (1988); B. S. Ham et al., Enhanced Nondegenerate Four-Wave Mixing Owing to Electromagnetically Induced Transparency in a Special Hole-Burning Crystal, Optics Letter, Vol. 22, no. 15 at 1138–40 (1997); H. Hemmati, Narrow-band Optical Filters Made by Spectral Hole-Burning, NASA Tech Brief, August, 1997 at 54; A. Rebane, Femtosecond Time-And-Space-Domain Holography, Trends in Optics, Academic Press at 165–88 (1996); K. Fujita et al., Room Temperature Persistent Spectral Hole Burning of Eu 3+ in Sodium Alumosislicate Glasses, Optics Letters, Vol. 23, no. 7 at 543–45 (1998)).
Imaging System Use as Anti-Theft System
The imaging system of the present invention may also serve as an efficient emergency notification system and/or antitheft system. In particular, a vehicle can be pre-configured to emit light pulses in a specific time slot if it is detected that the vehicle has been stolen, or if there is some other emergency situation. For example, the light pulses can be emitted in the specific time slot if a unique key has not been used in the vehicle ignition to start the vehicle, if a proper password has not been entered prior to operating the vehicle, or if a hazard switch has been activated.
The specific time slot can be an emergency time slot 309 as shown in FIG. 3. Light pulses emitted during the emergency time slot 309 can be referred to as emergency pulses. To effectuate the detection of stolen vehicles, or other vehicles requiring a response by an emergency service, an emergency service vehicle, watercraft, and/or aircraft (hereinafter referred to generally as emergency response vehicle) can be pre-configured to identify vehicles generating the emergency pulses. For example, an emergency response vehicle can be fitted with a suitable light detection system that detects the emergency pulses, such as an imaging device synchronized to receive light pulses emitted during the emergency time slot 309. Notably, the light pulses can be detectable at any time of day.
The light detection system also can be configured to detect light pulses over large distances. For example, the light pulses can be detectable over a distance greater than one kilometer, five kilometers, 10 kilometers, and other distances. If the emergency time slot 309 has a duration which is relatively short in comparison to a time delay between the moment an emergency pulse is generated and the moment the emergency pulse is received by a emergency response vehicle, the light detection system should compensate for the time delay when identifying emergency pulses.
For example, a light pulse (range finding light pulse) can be emitted from the imaging system of the emergency response vehicle towards a target vehicle and the elapsed time (ΔTE) to receive scattered radiation resulting from the illuminated object can be measured. The range finding light pulse can have a different wavelength than the light pulses used for object imaging, thereby insuring that the range finding light pulses do not create glare for the imaging system.
The time delay (ΔTD) associated with the distance between the target vehicle and the emergency response vehicle can be computed by the equation ΔTD=ΔTE/2. A processor and a data storage having a software algorithm stored thereon can be provided to compute a time delay (ΔTD). For instance, the processor and the data storage of the synchronization unit can be used to compute ΔTD. Alternatively, the distance (DR) between the target vehicle and the emergency response vehicle can be determined using a range finder, which is known to those skilled in the art, and the time delay (ΔTD) can be computed by the equation ΔTD=DR/C.
Regardless of the method used to determine the time delay (ΔTD), the time value corresponding to the moment that the light pulse was transmitted (TTRAN) can be determined by subtracting the value of the time delay (ΔTD) from a time value corresponding to the moment a light pulse is received (TREC), i.e. TTRAN=TREC−ΔTD. If the moment correlating to TTRAN falls within the emergency time slot 309, then the light pulse can be identified as an emergency pulse.
In another arrangement, the light pulses can be emitted at a particular frequency (emergency frequency) to signify a vehicle has been stolen. In this arrangement, police vehicles can be equipped with a suitable light detection system which detects the emergency frequency. A light filter can be provided to block light which does not have a spectral composition of the emergency frequency. Alternatively, a RIID can be used to detect light. As noted, a light filter is not required if a RIID is used.
Lastly, it should be noted that the present invention also can include an anti-collision option to decrease the probability of vehicles colliding. For example, the present invention can include a processor which receives vehicle coordinate data from GPS, GLONASS, WAAS, or any other suitable positioning system. Vehicle coordinate data can be provided for a vehicle with which the imaging system of the present invention is associated, and for other vehicles which are proximate to the vehicle associated with the imaging system. A software algorithm can be provided for use by the processor to evaluate the vehicle coordinate data. The vehicle coordinate data can be presented on a display. Further, vehicle trajectories can be computed and a warning signal can be generated upon predefined conditions of possible danger being present. A condition of possible danger can be, for example, a vehicle stalled on a road, a vehicle driving in an incorrect lane, or any other driving condition which can represent potential danger.
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Analytical Atomic Spectroscopy, 15:1161-1189, 2000.28Yin et al., "Theoretical model for a Faraday anomalous dispersion optical filter," Optics Letters, 16:1617-1619, 1991.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7570426 *Jun 29, 2006Aug 4, 2009The Johns Hopkins UniversityApparatus and system for wide angle narrow-band optical detection in daylightUS7705879 *Feb 13, 2007Apr 27, 2010Max-Viz, Inc.System for and method of synchronous acquisition of pulsed source light in performance of monitoring aircraft flight operationUS8254638 *Feb 26, 2008Aug 28, 2012Fujifilm CorporationRanging apparatus and ranging methodUS8311286 *Feb 26, 2008Nov 13, 2012Fujifilm CorporationRanging apparatus and ranging methodUS8354944 *Aug 18, 2006Jan 15, 2013Robert Bosch GmbhNight vision deviceUSRE44604Feb 13, 2007Nov 19, 2013Max-Viz, Inc.System for and method of synchronous acquisition of pulsed source light in performance of monitoring aircraft flight operationUSRE45452 *Feb 13, 2007Apr 7, 2015Max-Viz, Inc.System for and method of synchronous acquisition of pulsed source light in performance of monitoring aircraft flight operation* Cited by examinerClassifications U.S. Classification250/330International ClassificationB60Q1/14, G01S7/484, G01S17/89, H01S3/09, G01S17/93, G01S17/02, G01S7/487, G01S17/88, G01S17/10, G01S7/51, G01S19/48, G01S5/14Cooperative ClassificationG01S7/487, G01S7/51, G01S17/023, G01S17/107, G01S17/89, G01S7/484, G01S17/88, G01S19/14, B60Q1/1415, G01S17/936, B60Q1/14European ClassificationB60Q1/14, G01S17/89, G01S17/93C, B60Q1/14C, G01S7/484, G01S7/51, G01S17/02C, G01S7/487, G01S17/10G, G01S17/88Legal EventsDateCodeEventDescriptionJul 6, 2010FPExpired due to failure to pay maintenance feeEffective date: 20100516May 16, 2010LAPSLapse for failure to pay maintenance feesDec 21, 2009REMIMaintenance fee reminder mailedJul 29, 2005ASAssignmentOwner name: UNIVERSITY OF FLORIDA RESEARCH FOUNDATION, INC., FFree format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE S ADDRESS PREVIOUSLY RECORDED ON REEL 016200 FRAME 0390;ASSIGNOR:UNIVERSITY OF FLORIDA;REEL/FRAME:016327/0857Effective date: 20040716Free format text: CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE S ADDRESS PREVIOUSLY RECORDED ON REEL 016200 FRAME 0390. 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