U.S. patent application number 14/869491 was filed with the patent office on 2016-01-21 for lidar measurement device for vehicular traffic surveillance and method for use of same.
The applicant listed for this patent is Applied Concepts, Inc.. Invention is credited to Robert S. Gammenthaler.
Application Number | 20160018523 14/869491 |
Document ID | / |
Family ID | 43526706 |
Filed Date | 2016-01-21 |
United States Patent
Application |
20160018523 |
Kind Code |
A1 |
Gammenthaler; Robert S. |
January 21, 2016 |
Lidar Measurement Device for Vehicular Traffic Surveillance and
Method for Use of Same
Abstract
A Lidar measurement device for vehicular traffic surveillance
and method for use of same are disclosed. In one embodiment, video
circuitry acquires video of a field of view having a target
therein. A steerable laser progressively transmits laser
range-finding signals to the field of view in a horizontal and
vertical step-wise manner and receives reflected laser
range-finding signals from the target. A processing circuit portion
determines target data of the target based upon range and time
measurements associated with the reflected laser range-finding
signals. The processing circuit then integrates the target data
into the video such that the video may displayed with an image of
the target and speed measurement associated therewith.
Inventors: |
Gammenthaler; Robert S.;
(Plano, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Concepts, Inc. |
Plano |
TX |
US |
|
|
Family ID: |
43526706 |
Appl. No.: |
14/869491 |
Filed: |
September 29, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13894103 |
May 14, 2013 |
9146316 |
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14869491 |
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12510876 |
Jul 28, 2009 |
8441622 |
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13894103 |
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Current U.S.
Class: |
356/28 |
Current CPC
Class: |
G01S 17/89 20130101;
G01S 17/86 20200101; G01S 17/88 20130101; G01S 17/42 20130101; G01S
17/58 20130101 |
International
Class: |
G01S 17/58 20060101
G01S017/58; G01S 17/89 20060101 G01S017/89; G01S 17/02 20060101
G01S017/02 |
Claims
1. A police speed detection Lidar measurement device for vehicular
traffic surveillance in environments having multiple target
vehicles, the device comprising: a video circuitry portion for
acquiring video of a field of view having a target vehicle therein,
the video including an image of the target vehicle; a laser
configured to perform first and second scans on the field of view,
data collected from the first and second scans being stored in
first and second target data buffers, wherein reflected laser
range-finding signals from the target vehicle are received at the
device; a processing circuit portion configured to identify target
data by performing a best fit analysis comparison on the first and
second target data buffers to identify reflected laser
range-finding signals belonging to the target vehicle in each of
the first and second target data buffers, the target data being
data selected from the group consisting of speed measurement of the
target vehicle, range measurement of the target vehicle, and
heading of the target vehicle; the processing circuit portion
executing the best fit analysis comparison utilizing a range
measurement, a time measurement, and position in the field of view
of the reflected laser range-finding signal; the target data being
determined based upon the range and time measurements associated
with the reflected laser range-finding signals of the first and
second target data buffers; the processing circuit portion
integrating the target data into the video such that the target
data is associated with the image of the target vehicle; and a
display in communication with the processing circuit portion, the
display for displaying the video including the image of the target
vehicle having the target data associated therewith.
2. The device for vehicular traffic surveillance as recited in
claim 1, wherein the field of view further comprises a plurality of
targets and the display displays the video including an image of
the plurality of targets having respective plurality of target data
associated therewith.
3. The device for vehicular traffic surveillance as recited in
claim 1, wherein the processing circuit portion further comprises
image stabilization capabilities.
4. The device for vehicular traffic surveillance as recited in
claim 1, wherein the processing circuit portion comprises
speed-measurement capabilities to determine a speed measurement of
the target vehicle based upon the range and time measurements
associated with the reflected laser range-finding signals.
5. The device for vehicular traffic surveillance as recited in
claim 1, wherein the processing circuit portion comprises
range-finding capabilities to determine a range measurement of the
target vehicle based upon the range and time measurements
associated with the reflected laser range-finding signals.
6. The device for vehicular traffic surveillance as recited in
claim 1, wherein the processing circuit portion comprises
direction-sensing capabilities to determine a heading of the target
vehicle with respect to the Lidar measurement device based upon the
range and time measurements associated with the reflected laser
range-finding signals.
7. The device for vehicular traffic surveillance as recited in
claim 1, further comprising a synchronizer circuit portion for
synchronizing the field of view between the video circuitry portion
and steerable laser.
8. The device for vehicular traffic surveillance as recited in
claim 1, wherein the steerable laser and processing circuit portion
comprise identical aspect ratios.
9. A police speed detection Lidar measurement device for vehicular
traffic surveillance in environments having multiple target
vehicles, the device comprising: a video circuitry portion for
acquiring video of a field of view having a target vehicle therein,
the video including an image of the target vehicle; a laser
configured to perform first and second scans on the field of view,
data collected from the first and second scans being stored in
first and second target data buffers, wherein reflected laser
range-finding signals from the target vehicle are received at the
device; a processing circuit portion configured to identify target
data by performing a best fit analysis comparison on the first and
second target data buffers to identify reflected laser
range-finding signals belonging to the target vehicle in each of
the first and second target data buffers, the target data being
data selected from the group consisting of speed measurement of the
target vehicle, range measurement of the target vehicle, and
heading of the target vehicle; the processing circuit portion
executing the best fit analysis comparison utilizing a range
measurement, a time measurement, and position in the field of view
of the reflected laser range-finding signal; the target data being
determined based upon the range and time measurements associated
with the reflected laser range-finding signals of the first and
second target data buffers; and the processing circuit portion
integrating the target data into the video such that the target
data is associated with the image of the target vehicle.
10. The device for vehicular traffic surveillance as recited in
claim 9, wherein the field of view further comprises a plurality of
targets and the display displays the video including an image of
the plurality of targets having respective plurality of target data
associated therewith.
11. The device for vehicular traffic surveillance as recited in
claim 9, wherein the processing circuit portion further comprises
image stabilization capabilities.
12. The device for vehicular traffic surveillance as recited in
claim 9, wherein the processing circuit portion comprises
speed-measurement capabilities to determine a speed measurement of
the target vehicle based upon the range and time measurements
associated with the reflected laser range-finding signals.
13. The device for vehicular traffic surveillance as recited in
claim 9, wherein the processing circuit portion comprises
range-finding capabilities to determine a range measurement of the
target vehicle based upon the range and time measurements
associated with the reflected laser range-finding signals.
14. The device for vehicular traffic surveillance as recited in
claim 9, wherein the processing circuit portion comprises
direction-sensing capabilities to determine a heading of the target
vehicle with respect to the Lidar measurement device based upon the
range and time measurements associated with the reflected laser
range-finding signals.
15. The device for vehicular traffic surveillance as recited in
claim 9, further comprising a synchronizer circuit portion for
synchronizing the field of view between the video circuitry portion
and steerable laser.
16. The device for vehicular traffic surveillance as recited in
claim 9, wherein the steerable laser and processing circuit portion
comprise identical aspect ratios.
17. A police speed detection Lidar measurement device for vehicular
traffic surveillance in environments having multiple target
vehicles, the device comprising: a video circuitry portion for
acquiring video of a field of view having a target vehicle therein,
the video including an image of the target vehicle; a laser
configured to perform first and second scans on the field of view,
data collected from the first and second scans being stored in a
buffer, wherein reflected laser range-finding signals from the
target vehicle are received at the device; a processing circuit
portion configured to identify target data by performing a best fit
analysis comparison on the buffer to identify reflected laser
range-finding signals belonging to the target vehicle in the data
buffer, the target data being data selected from the group
consisting of speed measurement of the target vehicle, range
measurement of the target vehicle, and heading of the target
vehicle; the processing circuit portion executing the best fit
analysis comparison utilizing a range measurement, a time
measurement, and position in the field of view of the reflected
laser range-finding signal; the target data being determined based
upon the range and time measurements associated with the reflected
laser range-finding signals of the data buffer; and the processing
circuit portion integrating the target data into the video.
18. The device for vehicular traffic surveillance as recited in
claim 17, wherein the field of view further comprises a plurality
of targets and the display displays the video including an image of
the plurality of targets having respective plurality of target data
associated therewith.
19. The device for vehicular traffic surveillance as recited in
claim 17, wherein the processing circuit portion further comprises
image stabilization capabilities.
Description
PRIORITY STATEMENT & CROSS-REFERENCE TO RELATED
APPLICATIONS
[0001] This application claims priority from and is a continuation
of U.S. patent application Ser. No. 13/894,103, entitled "Lidar
Measurement Device for Vehicular Traffic Surveillance and Method
for Use of Same" filed on May 14, 2013 in the name of Robert S.
Gammenthaler, and which issued on Sep. 29, 2015 as U.S. Pat. No.
9,146,316; which is a continuation of U.S. patent application Ser.
No. 12/510,876, entitled "Lidar Measurement Device for Vehicular
Traffic Surveillance and Method for Use of Same" filed on Jul. 28,
2009 in the name of Robert S. Gammenthaler, and which issued on May
14, 2013 as U.S. Pat. No. 8,441,622. This application discloses
subject matter related to the subject matter disclosed in the
following commonly owned patent application: "Lidar Measurement
Device with Target Tracking and Method for Use of Same," filed on
Jul. 28, 2009, application Ser. No. 12/510,915, in the name of
Robert S. Gammenthaler, and which issued on Feb. 28, 2012 as U.S.
Pat. No. 8,125,622; all of which are hereby incorporated by
reference for all purposes.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates, in general, to police speed
detection systems and, in particular, to a light detection and
ranging (Lidar) measurement device for vehicular traffic
surveillance in environments having multiple target vehicles and a
method for use of the same.
BACKGROUND OF THE INVENTION
[0003] The role of speed detection in traffic safety enforcement is
widespread throughout the United States and the principal tool for
police traffic surveillance is Doppler radar. In a police Doppler
radar system, an emitted microwave frequency signal is reflected
from a target vehicle, causing a change in the frequency of the
signal in proportion to a component of the velocity of the target
vehicle. The Doppler radar system measures the frequency
differential and scales the measurement to miles per hour, for
example, in order to display the velocity of the target vehicle to
a policeman or other Doppler radar system operator. Using the
existing frequency differential scheme, conventional police Doppler
radar systems are capable of a high degree of accuracy with regard
to vehicle speed measurements in environments having one target
vehicle.
[0004] Limitations, however, have led to restricting its
effectiveness and use in highway-safety programs. Traditional radar
devices are not target selective since a beam width of
approximately 15.degree. is emitted. As a result, positive operator
target identification is perceived as challenging. Alternative
technologies, including Lidar, have been developed and deployed to
overcome these limitations. Lidar speed-measuring devices do not
operate on Doppler radar principles. Rather, Lidar speed-measuring
devices use laser pulses and time-distance principles to measure
vehicle speed. The narrow beamwidth, laser pulses of Lidar enable
the operator to select individual vehicles and positively identify
the target vehicle. But, while Lidar overcomes certain specific
limitations associated with radar speed-measurement devices, it
introduces challenges of its own. Existing Lidar speed-measuring
devices are designed to be aimed and operated from a shoulder, with
the butt end of the stock of the device firmly set against the
shoulder, or a fixed tripod mount. Both methods make use more
cumbersome than that of Doppler radar speed-measuring devices.
SUMMARY OF THE INVENTION
[0005] A Lidar measurement device and method for use of the same
are disclosed for vehicular traffic surveillance in environments
having one or multiple target vehicles. In one embodiment, video
circuitry acquires video of a field of view having a target
therein. A steerable laser progressively transmits laser
range-finding signals to the field of view in a horizontal and
vertical step-wise manner and receives reflected laser
range-finding signals from the target. A processing circuit portion
determines target data of the target based upon range and time
measurements associated with the reflected laser range-finding
signals. The processing circuit then integrates the target data
into the video such that the video may displayed with an image of
the target and speed measurement associated therewith. The target
data may include a speed measurement of the target, a range
measurement of the target, or a heading of the target, for
example.
[0006] The teachings presented herein address the aforementioned
limitations by providing precise aiming of the Lidar to track
moving vehicles in a multiple vehicle environment without the need
for existing awkward accessories or positions causing human
fatigue. In particular, tripods are avoided and it is not necessary
to maintain the butt end of the stock of the Lidar against the
shoulder. Rather, by using a steerable laser, which may, for
example, be mounted to a police vehicle, the laser beam may be
scanned horizontally and vertically in a step-wise manner to paint
a picture of the targets present within the field of view being
captured by the video circuitry. The processing capabilities of the
Lidar measurement device correlate the target data, such as range,
direction of heading, and speed, to the video image for positive
target identification by law enforcement or another user of the
Lidar measurement device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the features and
advantages of the present invention, reference is now made to the
detailed description of the invention along with the accompanying
figures in which corresponding numerals in the different figures
refer to corresponding parts and in which:
[0008] FIG. 1 depicts a schematic illustration of a multiple
vehicle environment wherein one embodiment of a Lidar measurement
device is being utilized;
[0009] FIG. 2 depicts a schematic diagram of the Lidar measurement
device of FIG. 1;
[0010] FIG. 3 depicts a schematic diagram of one embodiment of a
steerable laser for the Lidar measurement device of FIG. 1;
[0011] FIG. 4 depicts a flow chart of one embodiment of a method
for measuring speed;
[0012] FIGS. 5A and 5B together depict a flow chart of another
embodiment of a method for measuring speed; and
[0013] FIGS. 6A, 6B, and 6C together depict a flow chart of a
further embodiment of a method for measuring speed.
DETAILED DESCRIPTION OF THE INVENTION
[0014] While the making and using of various embodiments of the
present invention are discussed in detail below, it should be
appreciated that the present invention provides many applicable
inventive concepts which can be embodied in a wide variety of
specific contexts. The specific embodiments discussed herein are
merely illustrative of specific ways to make and use the invention,
and do not delimit the scope of the present invention.
[0015] Referring initially to FIG. 1, therein is depicted one
embodiment of a Lidar measurement device, which is schematically
illustrated and generally designated 10, being utilized in a
multiple vehicle environment 12. A highway 14 includes a northbound
lane 16 having a speed limit of 55 mph as depicted by speed limit
sign 18 and a southbound lane 20 having a speed limit of 55 mph as
depicted by speed limit sign 22. A vehicle 24 is traveling in the
northbound lane 16 at a speed of 50 mph as indicated by the
northbound arrow and number "50" proximate to the front portion of
the vehicle 24. The range of the vehicle 24 is displayed as
R.sub.24. Vehicles 26 and 28 are traveling in the southbound lane
20 at speeds of 75 mph (Range=R.sub.26) and 55 mph
(Range=R.sub.28), respectively. A patrol vehicle 30 equipped with
the Lidar measurement device 10 is stationary and facing north in a
location that is proximate to the northbound lane 14 in order to
conduct vehicular traffic surveillance. The patrol vehicle 10 has a
field of view 32 that includes the vehicles 24, 26, 28.
Additionally, the vehicles 24, 26, 28, are positioned such that
conditions are present that make the tracking of moving vehicles in
a multiple vehicle environment difficult with existing Lidar
measurement devices because of the need for awkward accessories or
requirement for an operator position that induces human
fatigue.
[0016] A display 34 is associated with the patrol vehicle 10 and
preferably secured to the dashboard in the interior of patrol
vehicle 10. The Lidar measurement device 10 acquires an image 36 of
the field of view 32 which includes vehicles 24, 26, and 28. The
display 34 presents the image 36 of the field of view 32 to the
operator with the vehicles 24, 26, 28 and associated target data
such as speed, range, and heading relative to the Lidar measurement
device 10. The target data is presented in target data boxes 38,
40, and 42. It should be appreciated, however, that other methods
of graphical user interface are within the teachings presented
herein. The display image 36, which includes both the video and
associated target data, furnishes positive target identification by
law enforcement or other user of the Lidar measurement device 10.
For example, by viewing display 34, the operator can positively
identify that the vehicle 24 is traveling at 50 mph away from the
patrol vehicle 30 at a distance of 2,470 feet. Similarly, the
vehicle 26 can be positively identified as traveling at 75 mph
towards the patrol vehicle 30 at a distance of 2,446 feet and the
vehicle 28 can be identified as traveling at 55 mph towards patrol
vehicle at a distance of 1,630 feet. As shown, it should be
appreciated that the display may be dedicated to displaying one or
more aspects of the target data discussed above or configurable to
provide other types of indications. For example, the display of the
Lidar measurement device 10 may be programmed to provide a history
of the speed of a particular targeted vehicle.
[0017] More particularly, as illustrated, an officer is operating
the Lidar measurement device 10 for vehicular traffic surveillance.
The Lidar measurement device 10 captures frame-by-frame video
having an aspect ratio of x' to y' as represented by video frame
44. Substantially simultaneously, the Lidar measurement device 10
captures frame-by-frame laser having an aspect ratio of x'' to y''
as represented by laser frame 46. In one embodiment, the aspect
ratios x' to y' for the video frame 44 and x'' to y'' for the laser
frame 46 are substantially the same. In another embodiment, the
aspect ratios of the video frame 44 and the laser frame 46 comprise
identical aspect ratios.
[0018] Beginning at a time t.sub.1, as part of the acquisition of
the laser frame 46, the Lidar measurement device 10 progressively
transmits short pulses of infrared light, which may be laser
range-finding signals, directed in a narrow beam towards the field
of view 32 having the target vehicles 24, 26, 28 therein. These
signals are transmitted to the field of view in a horizontal and
vertical step-wise manner. By way of example, the Lidar measurement
device 10 may begin sending signals at the upper left hand corner
of the field of view 32 and progress in a horizontal and vertical
step-wise manner through the field of view 32 by sending a laser
range-finding signal, pausing to receive a reflected laser
range-finding signal, repositioning, and sending another laser
range-finding signal.
[0019] When the light pulse strikes a target, such as the license
plate of a vehicle, a portion of the light pulse is reflected in
all directions and a small portion of this light pulse is reflected
back towards the Lidar measurement device 10. This return energy is
collected and focused on a sensitive detector that then converts
the light pulse energy to an electrical pulse. As will be discussed
in further detail hereinbelow, a high speed clock counts as the
light pulse travels from the Lidar measurement device 10 to the
target and back to determine total trip time. Using the known speed
of light, an onboard processor determines the ranges as the time of
flight is known.
[0020] With respect to the laser frame 46, the hits and misses may
be recorded in a laser frame data array 48 which is represented as
receiving reflected laser range-finding signals during the first
scan at pixels P.sub.1-1, P.sub.1-2, and P.sub.1-3. These reflected
laser-range finding signals and pixels P.sub.1-1, P.sub.1-2, and
P.sub.1-3 correspond to target vehicles 26, 24, and 28,
respectively. It should be appreciated that an indication that a
reflected laser range-finding signal was not received may also be
recorded in the laser frame data array 48. By way of example, the
laser frame data array may store the following data as shown in
Table I. It should be appreciated that although certain accuracies
and precisions are indicated in the range and time, the teachings
presented herein include instruments having different accuracies
and precisions than those presented.
TABLE-US-00001 TABLE I Exemplary Data Populating First Laser Frame
Data Array .DELTA.(x'', y'') Range Time Vehicle Pixel (x'', y'')
(pixels) (feet) (sec.) 26 P.sub.1-1 (45, 27) 5 2,460.002 0.02 24
P.sub.1-2 (109, 20) 5 2,460.833 0.03 28 P.sub.1-3 (9, 61) 5
1,640.083 0.04
[0021] With respect to the reflected laser range-finding signal
received for vehicle 26, the exemplary data presented in Table I
indicates that a reflected laser range-finding signal was received
for pixel P.sub.11 having a pixel location of (45, 27) within the
x'', y'' laser frame 46, which by way of example may have a field
of view of 128 pixels wide by 96 pixels high. Additionally, the
reflected laser-finding signal had a time of flight (not shown)
indicating a range of 2,460.002 feet for the laser range-finding
signal having a time stamp of 0.02 seconds. Based on this range and
time of flight, the .DELTA. pixel position is set at a 5 pixel
radius for finding this same target in another laser frame. Table I
includes similar data for vehicles 24, 28.
[0022] Following the first scan of the field of view 32, the Lidar
measurement device 10, performs additional scans. At a time
t.sub.n, which may be the initialization of a second scan, a laser
frame is acquired and laser frame data array 52 is built which
reflects the receiving reflected laser range-finding signals at
pixels P.sub.2-1, P.sub.2-2, and P.sub.2-3. The laser frame data
array 52 may include the information shown in the following table,
Table II.
TABLE-US-00002 TABLE II Exemplary Data Populating Second Laser
Frame Data Array .DELTA.(x'', y'') Range Time Vehicle Pixel (x'',
y'') (pixels) (feet) (sec.) 26 P.sub.1-1 (46, 26) 5 2,432.502 0.27
24 P.sub.1-2 (110, 19) 5 2,479.166 0.28 28 P.sub.1-3 (8, 62) 5
1,619.917 0.29
[0023] Following the acquisition of the laser frames 46, 50 and
laser frame data arrays 48, 52, the Lidar measurement device 10
performs a best fit analysis comparison on the laser frame data
arrays 48, 52, which each may be considered target data buffers, to
identify reflected laser range-finding signals belonging to
particular targets. The Lidar measurement device 10 may execute the
best fit analysis comparison utilizing the range measurement, a
time measurement, and position in the field of view of the
reflected laser range-finding signal.
[0024] In particular, the best fit analysis compares the pixel
positions of the reflected laser range-finding signals and verifies
that the range and time measurements are valid. By way of example,
there is a pixel position of (46, 26) at time t.sub.1 at 0.02
seconds and there is a pixel position of (45,27) at time t.sub.n at
0.27 seconds. These pixel positions are within the .DELTA.(x'',y'')
of 5 pixels and 0.25 seconds apart. This analysis suggests a
target. The presence of the target is then verified by noting that
the range in feet closed from 2,60.002 feet 2,432.502 feet in 0.25
seconds. Accordingly, the target is added to the target list 54 as
target T.sub.1 with the appropriate target data 56 including the
speed, following the calculation thereof. Similar analysis
identifies targets T.sub.2, which is the vehicle 24, and T.sub.3,
which is the vehicle 28. Exemplary target data 56 is presented in
Table III.
TABLE-US-00003 TABLE III Exemplary Target Data in Target List
Target Pixel Speed Range (Vehicle) Data f(x'', y'') (mph) (feet)
Heading T.sub.1 (26) P.sub.1-1, P.sub.n-1 f(46, 26) 75 2,466
Closing T.sub.2 (24) P.sub.1-1, P.sub.n-1 f(110, 19) 50 2,470
Opening T.sub.3 (28) P.sub.1-1, P.sub.n-1 f(8, 62) 55 1,630
Closing
[0025] As mentioned, the Lidar measurement device 10 determines the
speed, range, and heading of a particular target based upon range
and time measurements associated with the reflected laser
range-finding signals. More specifically, target speed is
calculated from the change in distance across an interval of time
by the following velocity equation:
v=(.DELTA.R)/(.DELTA.t), Equation I,
wherein [0026] .DELTA.R=R.sub.2-R.sub.1 for the range measurements
in the first and second sets of data at times t.sub.2 and t.sub.1,
respectively (Range may be expressed in feet and, in this example
t.sub.2=t.sub.n) [0027] .DELTA.t=t.sub.2-t.sub.1 for times t.sub.2
and t.sub.1 The range for a target may be an average of the range
values at times t.sub.1 . . . t.sub.n or the range value at time
t.sub.n, for example. Additionally, the heading relative to the
Lidar measurement device 10 is calculated from the change, i.e.
increase or decrease, in distance over time.
[0028] By way of example, with respect to the vehicle 26, at time
t.sub.1, 0.02 seconds, the range R.sub.26=2,460.002 feet (0.466
miles) and at time t.sub.2, 0.27 seconds, the range
R.sub.26=2,432.502 feet (0.461 miles). Accordingly, the data is
plugged into Equation I as follows with the scaling of speed as
appropriate:
v=(2,432.502 feet-2,460.002 feet)/(0.27 seconds-0.02 seconds)
v=-110 feet/second
v=-75 mph=75 mph (closing)
In this operational embodiment, the range, R.sub.26, of the vehicle
is set at the range at time t.sub.n. Similar calculations fill the
other speed and heading data presented in Table III.
[0029] Following this creation of the target list 54 having the
target data 56, the Lidar measurement device 10 integrates the
target data 56, or a portion thereof, into the video such that the
target data 56 is associated with the image of the appropriate
targets. In one implementation, to accomplish this integration, the
Lidar measurement device 10 utilizes a function, f(x'', y''), to
map the (x'', y'') coordinates of the reflected laser range-finding
signals to an aspect ratio of (x, y), which may be substantially
similar or identical to the video frame 44 aspect ratio of (x',
y'). It should be understood that if the video frame 44 aspect
ratio of (x', y') is different from the display aspect ratio of (x,
y), a similar mapping may occur. The target boxes 38, 40, 42, which
respectively include target data 56 (T.sub.2, T.sub.1, T.sub.3),
are inserted at the respective pixel locations f(x'', y''); namely,
f(110, 19), f(46, 26), and f(8, 62) in the above example. Then, as
mentioned, the display image 36, which includes both the video and
associated target data, furnishes positive target identification by
law enforcement or other user of the Lidar measurement device
10.
[0030] In one embodiment, the Lidar measurement device 10, either
automatically or by manual intervention, may furnish target-tacking
capabilities whereby a subset of the targets within the field of
view 32 are examined more frequently to reduce measurement error.
Further information regarding the target-tracking capabilities of
the Lidar measurement device 10 may be found in the following
commonly owned, co-pending patent application: "Lidar Measurement
Device with Target Tracking and Method for Use of Same," filed on
Jul. 28, 2009, application Ser. No. 12/510,915, in the name of
Robert S. Gammenthaler; which is hereby incorporated by reference
for all purposes.
[0031] FIG. 2 shows the Lidar measurement device 10 in further
detail. Interconnected are a video circuitry portion 80, a
processing circuit portion 82, a synchronizer circuit portion 84,
and a steerable laser 86. The video circuitry portion 80 includes
video equipment 88, video circuitry 90, and a video digitizer 92.
In one embodiment, the video equipment 88, video circuitry 90, and
video digitizer 92 capture frame-by-frame video at 60 fields per
seconds interlaced, for example. A representative value for the
field of view is 0.24 radians wide by 0.18 radians high (13.75
degrees wide by 10.31 degrees high) providing conventional 4:3
aspect ratio of a standard definition video. As discussed, the
video equipment 88 may be adjusted to obtain the same field of view
as the laser scanning. With respect to the video digitizer 92, in
one implementation, a resolution of 640.times.480 is used to merge
to successive fields of interlaced video to form complete frames at
a rate of 30 frames per second. It should be appreciated that other
resolutions are within the teachings of the present invention and
the selection of a resolution represents a compromise between video
quality and processing load. In the embodiment presented, however,
the video resolution will be 5 times higher than the laser
resolution, so one laser pixel will cover a 5.times.5 area of video
pixels or 1 laser pixel will be 25 total video pixels.
[0032] The processing circuit portion 82 may include a processor
and a database 96 that provide a combination of hardware, software,
and firmware for determining and handling target data. For example,
a speed measurement of the target may be determined based upon
range and time measurements associated with the reflected laser
range-finding signals. Additionally, the processor 94 and the
database 96 are able to determine range measurements and target
heading based upon the range and time measurements associated with
the reflected laser range-finding signals by utilizing
range-finding and direction-sensing capabilities. The
direction-sensing capabilities determine direction by comparing the
change in distance to the change in time to determine if, over a
period of time, the distance is decreasing (i.e., closing) or
increasing (i.e., opening). The processing circuit portion 82
integrates the target data into the video received from the video
digitizer such that the target data, such as speed, range, and
direction of heading, are associated with the image of the target
presented on the display 34.
[0033] The synchronizer circuit portion 84 includes the field of
view synchronizer 98 that communicates with the video circuitry
portion 80, processing circuit portion 82, and the steerable laser
86 to coordinate the field of views of an optical transceiver 100
and the video equipment 88. Additionally, the field of view
synchronizer 98 may coordinate the aspect ratios of the processes
of the video circuitry portion 80, processing circuit portion 82,
and the steerable laser 86. The steerable laser 86 includes the
aforementioned optical transceiver 100 which is supported by Lidar
optics and electronics 102.
[0034] Audio output 104, the display 34, an operator interface 106,
and vehicle inputs 108 are also connected to the processor 94. The
Lidar measurement device 10 may provide audio indications of
various functions through the audio output 104. The operator
interface 106 may include any type of keyboard, control panel, or
touchscreen, for example, that permits the user to interface with
the Lidar measurement device 10. Vehicle inputs 108 may include an
indication from the vehicle to the Lidar measurement device 10 of
the speed of the patrol vehicle 30. In making the various range,
speed, and heading calculations of target vehicles, the Lidar
measurement device 10 may take into account the speed of the patrol
vehicle 30.
[0035] FIG. 3 illustrates one embodiment of the steerable laser 86
for the Lidar measurement device 10. The steerable laser 86
transmits laser range-finding signals 112 and receives reflected
laser range-finding signals 114. With respect to the transmission,
a laser 110, which is supported by electronics 116, generates a
laser range-finding signal and transmits the laser range-finding
signal through transmission optics 118, which is depicted as a
collimating lens, and forms a portion of the optical transceiver
100. By way of the steering unit 130, the laser range-finding
signal is directed to a particular location in the field of view of
the steerable laser 86 and this particular location may be recorded
in terms of (x'',y'') coordinates or other coordinate systems, for
example. Following transmission, the steerable laser 86 pauses to
wait for reception of a reflected laser range-finding signal. In
this implementation, the steerable laser 86 has only one pulse
in-flight at a time. If a reflected laser range-finding signal 114
is received, the reflected laser range-finding signal is received
by the optical transceiver 100 and routed by receiving optics 120
through a filer 132 to a photodetector 134, which provides signal
detection and may include an avalanche photodiode (APD), in one
embodiment. If a reflected laser range-finding signal 114 is not
received after a sufficient pause, then the steerable laser 86 is
repositioned within the field of view and another laser
range-finding signal 112 is transmitted. The detection of reflected
laser-range finding signal and/or the absence of such a detection
may be appropriately recorded in the data storage 124.
[0036] In one embodiment, these sending and receiving events are
controlled by the dedicated hardware, which handles the high speeds
and load. In one implementation, this hardware includes fast
counting multiscaler counters 122 with access to data storage 124.
These components work with a timing unit 126, trigger circuit 128,
and a steering unit 130 to control the positioning, firing, and
waiting operations that are repeated numerous times. More
particularly, the steering unit 130 communicates with various
portions of optical transceiver assembly 136, which includes the
optical transceiver 100 and the other Lidar optics and electronics
102. As depicted, the steerable laser 86 includes a bistatic design
for the optical transceiver 100 wherein the transmission and
reception paths are kept separate. In one embodiment, the
components of the transmission and reception paths may be rigidly
mounted together within the steerable laser 86 to aim at the same
point in space. In this configuration, the steering unit 30 aims
the entire optical transceiver assembly 136 to scan the beam.
[0037] With respect to detection, the counters 122 may include
vertical and horizontal counters that are phase locked to the field
of view synchronizer signals received from the field of view
synchronizer 98, which is coordinating both the fields of view for
the video equipment 88 and the steerable laser 86. These
synchronizer signals may be received by the steering unit 130,
which coordinates the aiming and positioning of the optical
transceiver 100 and, through communication with the timing unit
126, the detection at the counters 122. In one implementation,
under the control of the synchronizer signals, the counters 122
produce 128 counts while scanning across a horizontal line and 96
counts while scanning vertically, where counts of 0 correspond to
the left and top edges respectively of the field of view, i.e.,
(x'', y'').epsilon.(0 . . . 128, 0 . . . 96).
[0038] That is, at each scan position, the optical transceiver 100
aims the laser 110 at the required point within the field of view,
fires the laser 110, and the timing unit 126 measures the time of
flight of any return signals or reflected laser range-finding
signals. The first return signal may be processed or, in another
system, multiple return signals are processed. The time of flight
of each signal is stored in a 128 by 96 memory array where the
position in the array corresponds to the position of the laser 110
and optical transceiver 100 in the field of view. As mentioned, if
no return signal is received, a status bit is set in the stored
data to so indicate. It should be appreciated that other
conditions, such as errors, may also be recorded. Storage of this
data may be handled by a directed memory access interface or DMA
which forms a portion of the data storage 124. The DMA may be
responsible for creating a status signal or interrupt that provides
an indication of a memory array being completed and the
repositioning of the optical transceiver 100.
[0039] In one embodiment, laser spot size 154 and scan step size
156 are selected to produce scanning overlap of adjacent pixels. By
way of example, a laser spot size of 3 milliradians may be used for
vehicle surveillance. A scan step size of 2 milliradians between
adjacent pixels, which produces a 33% scanning overlap of adjacent
pixels, may be utilized to insure that a target vehicle does not
fall between successive pixels. In one implementation, the field of
view of the Lidar has an aspect ratio of 4:3, which is the same as
standard video resolution. In particular, the field of view may be
128 pixels wide by 96 pixels high for a total image size of 12,288
pixels. In this embodiment, the resulting angular field of view is
0.256 radians (14.67 degrees) wide by 0.192 radians (11.00 degrees)
high, and the Lidar frame rate may be limited to 4.00 frames per
second with a laser firing rate of 49.164 KHz. Sensitivity may be
such that no target returns are expected for targets at distances
greater than 10,000 feet, and for this maximum distance, the total
round-trip time of flight is 20.34 .mu.s. The laser firing rate is
therefore limited to the aforementioned 49.164 KHz in this
embodiment. It should be understood that the schematic depicts a
layout of the Lidar optical and electronic components. It should be
appreciated that the illustrated and described embodiment
represents only one embodiment and other embodiments are within the
teachings presented herein. By way of example, the optical
transceiver 100 is depicted as having a bistatic design including
transmitting optics 118 and receiving optics 120. A monostatic
approach is possible as well.
[0040] FIG. 4 shows one embodiment of a method for measuring target
data, such as speed, range, and heading, for example. At block 170,
video is acquired with the Lidar measurement device 10 of a first
field of view having a first aspect ratio. The first field of view
includes a target therein and the video includes an image of the
target. At block 172, the Lidar measurement device progressively
repeatedly scans a second field of view having a second aspect
ratio with laser range-finding signals. The second field of view
has the target therein and is substantially similar, which includes
being identical, to the first field of view. The second aspect
ratio is substantially similar to the first aspect ratio, wherein
substantially similar includes being identical. In one embodiment,
progressively repeatedly scanning the second field of view further
comprises horizontal and vertical step size scanning of the second
field of view.
[0041] At block 172, during the progressive repeated scanning of
the second field of view, reflected range-finding signals are
received from the target at the Lidar measurement device. At block
174, a measurement of the target, such as speed, range (or
distance), or heading, is determined based upon range and time
measurements associated with the reflected laser range-finding
signals. Moreover, at this operational stage, a speed, range, or
distance measurement of the target may be determined based upon the
range and time measurements associated with the reflected laser
range-finding signals. Additionally, a direction of heading of the
target may be determined using direction-sensing capabilities of
the processor of the Lidar measurement device that monitor the
change in distance over a period of time to determine if the target
is opening or closing. Then, at block 176, the speed measurement is
integrated into the video such that the speed measurement is
associated with the image of the target on the display.
[0042] FIGS. 5A and 5B illustrate another embodiment of a method
for measuring speed. The methodology starts at block 190 and then a
user/operator target criteria may be established for the Lidar
measurement device at block 192. By way of example, the following
table, Table IV, provides a non-exhaustive matrix of the more
common operator selectable modes and preferences of the Lidar
system disclosed herein. Additional modes of operation and
user/operator target criteria may include moving modes of operation
and modes of operation limiting the number of target data boxes
displayed and prioritizing the target vehicles on a criteria based
upon the following as well as other applications of the operator
adjusted range gate criteria where a selectable interval of range
of interest is provided.
TABLE-US-00004 TABLE IV Common Operator Selectable Modes Patrol
Vehicle Type of Signal(s) Receding/Approaching Stationary Closest
and Faster Approaching Stationary Closest and Faster Receding or
Approaching Stationary Closest and Faster Receding Stationary
Closest Approaching Stationary Closest Receding or Approaching
Stationary Closest Receding Stationary Faster and Range gate
Receding or Approaching Moving Closest and Faster Approaching
Moving Closest and Faster Receding or Approaching Moving Closest
and Faster Receding Moving Closest Approaching Moving Closest
Receding or Approaching Moving Closest Receding Moving Faster and
Range gate Receding or Approaching
[0043] At block 194, video frame and laser frame acquisition are
set to substantially the same field of view and then, at block 196,
the video frame and laser frame acquisition are set to
substantially the same aspect ratios. It should be appreciated that
in one embodiment, the fields of view and/or the aspect ratios may
be pre-set. Following block 196, operations at blocks 198 and 200
occur substantially simultaneously. More particularly, at block
198, the Lidar measurement device acquires video frames before
digitizing the video frames at block 202.
[0044] Returning to block 200, the Lidar measurement device
acquires the laser frame. At block 204, target identification is
initialized at the first pixel in the laser frame. At decision
block 206, for the pixel under examination, if there is a reflected
laser range-finding signal, then the methodology advances to block
208 wherein adjacent pixels are searched for target hits and the
associated target centroid is calculated. Once the target centroid
is defined, then the reflected laser range-finding signal data is
entered into the laser frame data array at block 210 and the
methodology advances to decision block 212. If there are additional
pixels then the methodology continues to block 214 where the target
identification methodology advances to the next pixel before
returning to decision block 206. Otherwise, once all of the pixels
have been examined, the target identification methodology advances
from decision block 212 to block 216.
[0045] Returning to decision block 206, if there is not a reflected
laser range-finding signal, then the methodology advances to block
219, wherein in the laser frame data array a notation is entered
that for the particular pixel under examination there is no target.
The methodology advances to decision block 221, wherein if there
are additional pixels, then at block 214, the target identification
process advances to the next pixel before returning to decision
block 206. At decision block 220, if the target identification has
exhaustively examined all of the pixels, then the methodology
continues to block 216.
[0046] Once all of the pixels have been examined and the laser
frame data array constructed, for each target centroid, a delta
projected pixel position is calculated at block 216 and, at block
218, expiration counters are set for each target centroid. Next, at
blocks 220 and 222, respectively, for each laser frame data array,
the expiration counter is advanced and the expired target centroids
and/or expired laser frame data arrays are removed. At decision
block 224, if there is more than one laser frame data array for
comparison, then the methodology continues to block 226. Otherwise,
the process returns to block 200 in order to acquire another laser
frame.
[0047] With multiple laser frame data arrays available for
analysis, at block 226, target data determination is initialized
and continues at block 228, where a best fit analysis comparison is
executed. As previously discussed, to identify targets, the best
fit analysis compares the pixel positions of the reflected laser
range-finding signals and verifies that the range and time
measurements are valid. At block 230, specific targets and
associated target centroids are identified. At block 232, target
data is determined. Additionally, at block 232, image stabilization
may occur. Any one or more of a family of techniques may be
utilized to increase video frame-to-video frame continuity.
Non-limiting examples of stabilization techniques include
gyro-based stabilization or camera-body stabilization techniques
and electronic video stabilization techniques involving making the
optimized match between successive video frames or digital image
stabilization techniques using pixels outside the border of the
visible frame to provide a buffer for the motion, for example. It
should be understood that the image stabilization may occur as
shown at block 232 or at one or more other blocks during the
methodology. At block 234, a target list is generated.
[0048] At block 236, target history is updated so that the target
is aged. The target is then prioritized at block 238. A prioritized
target list is then generated at block 240. At block 242, once the
prioritized target list is generated at block 240 and the digitized
video frame is prepared at block 202, then the target data is
generated into the video image. At block 242, the video including
the target data appropriately associated with the targets is
displayed. The methodology then returns to blocks 198 and 200.
[0049] FIGS. 6A, 6B, and 6C together illustrate a further
embodiment of one embodiment of a method for measuring speed. The
following glossary in Table V enumerates the variables utilized in
this embodiment of the methodology. It should be appreciated that
these are non-limiting working examples of variables wherein the
functions, values, and relationships are solely representative of
those which can be employed, and are not exhaustive of those
available and operative.
TABLE-US-00005 TABLE V Variables and Definitions Variable
Definition number_of_targets number of target vehicles
best_fit_distance validity of the range measurements from different
laser frames best_fit_speed validity of the speed measurements from
different laser frames hit_flag hit flag for particular signal
target_distance Range of particular target x_position x'' position
in (x'', y'') of target y_position y'' position in (x'', y'') of
target distance_window correlation between field of view and pixels
projected_distance projected (x'', y'') for target x_window
correlation between field of view and x'' pixels y_window
correlation between field of view and y'' pixels
projected_x_position projected x'' position in (x'', y'') of target
projected_y_position projected y'' position in (x'', y'') of target
delta_distance projected .DELTA.(x'', y'') for target
last_target_distance last (x'', y'') for target delta_x .DELTA.x''
for target delta_y .DELTA.y'' for target miss_counter counter for
target misses max_targets criteria for maximum number of
targets
[0050] At block 260, the methodology begins with a power-on reset.
At blocks 262 and 264, the Lidar measurement device respectively
proceeds through a system self-test and a hardware initialization.
At blocks 266 and 268, video frame acquisition and laser frame
acquisition are started. At decision block 270, if laser frame
acquisition is complete then the process continues onto decision
block 272. Otherwise, the methodology advances to for-each block
274.
[0051] At decision block 272, if video frame acquisition is
complete, then this embodiment of the technique moves to for-each
block 276. On the other hand, if the video frame acquisition is not
yet complete, then this embodiment of the technique returns to
decision block 270. It should be appreciated that in one
implementation that the video frame acquisition will be faster than
the laser frame acquisition and this timing differential will play
a role in the methodology.
[0052] Returning to for-each block 276, the process advances to
block 280 and a best fit analysis. At decision block 282, if the
best fit analysis is valid, then the process advances to block 284,
where a target data box is added to the video image with the target
data. The best fit analysis is valid if the following are true:
[0053] best_fit_distance and best_fit_speed are valid
On the other hand, if the best fit analysis is not valid, the
methodology advances to decision block 286. Similarly, following
the addition of the target data box at block 284, the methodology
advances to decision block 286.
[0054] At decision block 286, as a part of the for-each loop
initiated at block 276, if there are additional targets then the
process returns to for-each block 276. Otherwise, the output video
frame with the target data box or target data boxes is output and
displayed to the operator at block 288. In one implementation, the
operations of blocks 270-288 update the video image for each new
video frame received, while waiting for a new laser frame.
Following block 288, the process returns to decision block 270 in
one implementation.
[0055] Returning to decision block 270, in instances where the
laser frame acquisition is not complete, the process continues to
for-each block 274, wherein the target hit flag is reset (e.g.,
reset hit-flag) for a particular target at block 290 before
continuing to decision block 292, where if the there are additional
targets requiring reset hit flags, the methodology loops back
through the for-each block 274 and block 290 until all target hit
flags are reset.
[0056] Then, for-each block 294 initiates another for-each
sequence; this for-each sequence being for each laser pixel. At
decision block 296, if the particular pixel under examination is
not used and a target return received, such as a reflected laser
range-finding signal, then a search is made for the target presence
at block 298 and at block 300, the target centroid is computed. At
block 302, delta distance measurements are recorded.
[0057] Following block 302 and a "NO" at decision block 296, the
process continues to another for-each sequence for each target
being tracked beginning with for-each block 304. At decision block
306, if the target position and (x, y) pixel position are valid,
then the process advances to blocks 307 and 308. In one embodiment,
the validity logic at block 306 is performed by the following coded
operations: [0058] If target_distance within +/- distance_window
from projected_distance and x_position within +/- x_window from
projected_x_position and y_position within +/- y_window from
projected_y_position
[0059] At block 307, image stabilization may occur to eliminate
visible frame-to-frame jitter in the video. The updating
methodology may be executed by one of the following coded
operations on successive pixels in one embodiment: [0060]
(x_position, y_position)=image_stabilization(x_position,
y_position) [0061] OR [0062] (projected_x_position,
projected_y_position)=image stabilization(projected_x_position,
projected_y_position) As described, in one embodiment, the (x, y)
positions of particular pixels or the projected (x, y) positions
may be adjusted. At block 308, the target data is updated. The
updating methodology may be executed by the following coded
operations in one embodiment:
[0063] delta_distance=target_distance-last_target_distance
[0064] last_target_distance=target_distance
[0065] delta_x=x_position--last_x_position
[0066] last_x_position=x_position
[0067] delta_y=y_position-last_y_position
[0068] last_y_position=y_position
[0069] projected_distance=target_distance+delta_distance
[0070] projected_x_position=x_position+delta_x
[0071] projected_y_position=y_position+delta_y
[0072] set hit_flag
[0073] miss_counter=3
[0074] distance_window=5 feet
[0075] x_window=2 pixels
[0076] y_window=2 pixels
[0077] Following both the update of the target data at block 308
and the a "NO" at decision block 306, the methodology advances to
decision block 310, where if the maximum number of targets has been
exceeded, then at block 312, the targets are ranked by a default or
operator criteria. This methodology may be executed by the
following coded operations in one embodiment:
[0078] If number_of_targets>max_targets
[0079] Then at block 314, the less or least target or targets are
discarded so that the maximum number of targets is not exceeded. At
decision block 316, if the target was not discarded then the number
of targets is modified at block 318. This methodology may be
executed by the following coded operations in one embodiment:
[0080] number_of_targets=number_of_targets-1 Otherwise or, if the
target was discarded, then the process advances to decision block
320. Also, as is shown on FIG. 6B, following a "NO" decision at
decision block 316, the methodology also advances to decision block
320, where if the target was not discarded then new target data is
created at block 322 before advancing to decision block 324, which
closes up the for-each loop begun at block 304 and indicates that
if there are additional targets, then the methodology returns to
for-each block 304. Otherwise, the process advances to decision
block 326, which terminates the for-each loop started at block 294.
If additional laser pixels require processing, then the methodology
returns to for-each block 294.
[0081] Continuing onto the for-each loop initiated at block 328, at
decision block 330, if the hit flag is not set, then the miss
counter is advanced at block 332 where following the advance of the
counter, if the counter has expired, then at decision block 334,
the process proceeds to block 336 where the target is discarded and
then onto block 338 so that the number of targets may be modified
by decrementing the number of targets. Returning briefly to blocks
336 and 338, the following methodology may be utilized to implement
these operations in one embodiment: [0082] Create new target:
[0083] number_of_targets=number_of_targets+1 [0084]
last_target_distance=target_distance [0085]
last_x_position=x_position [0086] last_y_postion=y_position [0087]
projected_distance=target_distance [0088]
projected_x_position=x_position [0089]
projected_y_position=y_position [0090] set hit_flag [0091]
miss_counter=3 [0092] distance_window=100 feet [0093] x_window=5
pixels [0094] y_window=5 pixels [0095]
best_fit_distance=last_target_distance [0096]
best_fit_speed=invalid [0097] If hit_flag not set then
miss_counter=miss_counter-1 [0098] If miss_counter=0, then
discard(target) and number_of_targets=number_of_targets-1 With
respect to a "NO" decision at decision block 330, a "NO" decision
at decision block 334, and following the processing at block 338,
the method continues onto decision block 340, where if there are
additional targets to process, then the for-each loop initiated at
block 328 continues; else the process returns to decision block
268.
[0099] While this invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to the description. It is, therefore,
intended that the appended claims encompass any such modifications
or embodiments.
* * * * *