Summarize this: LASER TRANSPONDER SYSTEMAND
METHOD FOR DISRUPTING ADVANCED
SPEED MEASURING LIDARS
CROSS REFERENCE TO RELATED
APPLICATIONS
This application is the U.S. National Phase Application of
PCT/HR2014/000010, filed Feb. 28, 2014, the contents of
Such application being incorporated by reference herein.
FIELD OF INVENTION
The invention relates to lasers, more specifically to laser
transponders capable of disrupting the operation of vehicle
speed measuring LIDARS.
PREVIOUS STATE OF ART
In the past decade vehicle speed measuring LIDARs have
become a significant portion of devices used by agencies for
road traffic speed enforcement. In some areas they have even
replaced the use of vehicle speed measuring radars.
LIDARS (Light Detection And Ranging) have many
advantages over radar for use in road traffic vehicle speed
Surveillance. Some of the main ones are the quick capture of
vehicle speed (in a fraction of a second), the ability to target
a specific vehicle even at great distances, and it is harder to
detect and harder to disrupt its signal.
Unlike speed measuring radar which transmits a continu
ous radio wave signal and monitors frequency shift of a
reflected signal (Doppler method) a LIDAR transmits short
laser pulses and measures the time of flight (TOF) of each
emitted laser pulse to its return as a reflection from the
target. TOF is converted to a distance by using the speed of
light constant. From sequentially measured distances the
target speed is calculated (d2-d1)/(t2-t1) (cf. LASER
BASED SPEED. . . , U.S. Pat. No. 5,359,404, Dunne).
As vehicle speed measuring LIDAR use became wide
spread a countermeasure to the LIDAR appeared. First in the
form of a LIDAR laser beam detector and secondly a speed
measuring LIDAR disrupting device. A detector would be
mounted on a vehicle and if the vehicle would be targeted by
a speed measuring LIDAR the detector would instantly alert
the driver. Since measurement time of speed measuring
LIDAR is less than a second even an instant detector alert
would not enable the driver to slow down quickly enough.
This made speed measurement LIDAR detectors of limited
use as a proper countermeasure.
Speed measuring LIDAR disrupting devices incorporate a
detector and add a transmitter part. Also a signal processing
part is enhanced so it does not only recognize speed mea
Surement LIDAR signal but responds to that signal accord
ingly through a transmitter sending a disrupting signal.
Many embodiments of a LIDAR disrupting device have
been suggested in the prior art. One embodiment (LASER
TRANSPONDER . . . . U.S. Pat. No. 5,793,476 LAAK
MANN) discloses a countermeasure laser transponder
which incorporates a detector, signal processing, laser trans
mitter, user interface and other parts. The description teaches
that upon detection of a speed measuring LIDAR laser beam
the alert is given and a disrupting signal is transmitted. The
disrupting signal constitutes a continuous pulse train of
frequency between 0.8 MHz and 2 MHz. It is described that
sending disrupting laser pulses with time periods between
them that is shorter than TOF of a speed measuring LIDAR
laser pulse, guarantees that the disrupting pulses will always
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arrive to the LIDAR before the arrival of the LIDAR laser
pulse reflection. The described theory Suggests that a
LIDAR will always receive a disrupting laser pulse before it
receives its own measurement laser pulse reflection and for
that reason the distance measurement based on that pulse
will fail or compute the wrong distance. Consequently the
speed calculation will fail as well.
The described method has a weakness in that it sends a
high laser energy disrupting signal that can easily be
detected by the LIDAR signal processing unit which can
then consequently initiate an alarm for the LIDAR operator.
The described method can also be defeated by a LIDAR
countermeasure detecting circuit (COUNTERMEASURE
DETECTING CIRCUIT . . . . U.S. Pat. No. 5,715,045
DUNNE) which automatically reduces the LIDAR receiver
threshold to remove disrupting signals.
Document (LASER TRANSPONDER..., U.S. Pat. No.
5,793.476 LAAKMANN) in the prior art section also
describes another more sophisticated but more difficult to
achieve (at the time) embodiment of a “LIDAR jammer.
The described LIDAR jammer would operate by transmit
ting a disrupting signal having a pulse train frequency that
matches the pulse repetition frequency of the laser signal of
the speed measuring LIDAR. “Each pulse of the pulse train
is transmitted so that it arrives at the LIDAR speed monitor
Sometime within the time period beginning when the
LIDAR speed monitor transmits a pulse and ends when the
LIDAR speed monitor receives the pulse reflected off the
vehicle'. The described speed measuring LIDAR disrupting
method is known as frequency and phase matching (FPM) in
the previous state of art. Unlike the previously described
countermeasure it does not use a high frequency high laser
energy disrupting signal. Disrupting laser pulses are only
sent so they arrive to the speed measuring LIDAR when
LIDAR is expecting to receive its own laser pulse reflection.
It is more difficult for a LIDAR to detect such countermea
Sures because disrupting pulses are not present outside a
time window of a speed measuring LIDAR pulse measure
ment. Since disrupting pulses are sent only when they can
have an effect on the LIDAR instead of continuously, a much
higher individual disrupting pulse laser energy can be used
to increase the disrupting effect and still maintain very low
average laser energy.
Prior art speed measuring LIDAR disrupting devices
based on the FPM method use a synchronization event to
maintain phase of a disrupting signal to the speed measuring
signal. A synchronization event is one pulse of a speed
measuring LIDAR signal that is used by the disrupting
device to reset its time period (frequency) matching timer. A
synchronization event is needed by Such disrupting devices
because of the differences in the stability of time base units
of the disrupting device and speed measuring LIDAR.
Differences in stability and resolution of time base clocks
will cause drift of phase of the disrupting signal over time,
as more disrupting pulses are sent in sequence the greater the
drift of phase becomes. A synchronization event is also
needed to determine whether the speed measuring LIDAR
signal has ceased and the disrupting process needs to stop.
To receive a synchronization pulse (event) prior art dis
rupting devices need to stop transmitting their disrupting
signal since their own transmissions will inherently trigger
their own receiver. Speed measuring LIDAR disrupting
devices need to have the highest possible receiver sensitivity
and a wide reception optical angle to Successfully detect a
speed measuring LIDAR signal coming from different opti
cal angles or even when not directly aimed at the disrupting
device. Such prior art disrupting devices high sensitivity
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receivers are inherently susceptible to their own disrupting
transmissions when they return as reflections of road or
roadside objects.
This deficiency of prior art frequency and phase matching
disrupting devices consequently means that some of the
speed measuring LIDAR pulses will not be disrupted.
Document (cf. PULSED LASER SIGNAL DISRUPT
ING DEVICE . . . . US 20130105670A1, BOROSAK)
describes a LIDAR disrupting device based on frequency
and phase matching method (FPM) as stated by using a prior
art method with a fixed emitted frequency identical to the
received signal frequency, which is not required to respond
to every and each received signal.
One embodiment that uses a frequency and phase match
ing method (LASERTRANSPONDER, U.S. Pat. No. 6,833,
910 BOGH-ANDERSEN) to disrupt operation of a speed
measuring LIDAR adds to the method a novelty of trans
mitting a disrupting signal with a pulse repetition frequency
different than the one of a speed measuring LIDAR signal
that is being disrupted. The described method deviates from
frequency matching as described previously but as it
describes in FIG. 4, step 51, it still uses a free of disrupting
transmissions synchronization event to calculate a proper
“time window' and discover an end of speed measuring
signal.
Document (LASER TRANSPONDER..., U.S. Pat. No.
5,793,476 LAAKMANN) also describes other deficiencies
of the frequency and phase matching speed measurement
LIDAR disrupting method. At the time the required com
ponents (high speed and precision processing units, laser
diodes and laser diode drivers, etc.) necessary for Such
embodiment were scarcely available and at great cost. At the
present time all required components for Such an embodi
ment are widely available at low cost. It is no longer a
problem for a modern processing unit to accurately measure
pulse repetition frequency of a speed measuring LIDAR
beam and to maintain phase of a disrupting signal to speed
measuring signal.
Another described deficiency of the method still valid
today is that “such LIDAR jammers can be defeated simply
by adjusting the LIDAR speed monitor to transmit a pulse
train having an unstable, random or programmed pulse
repetition rate'.
Usual speed measuring LIDARS have a known and fixed
pulse repetition frequency but there are more modern speed
measuring LIDAR types that have unstable or programmed
pulse repetition rates. Such modern LIDARs can still be
disrupted by modern disrupting devices based on frequency
and phase matching method. Such modern disrupting
devices usually have a database of pre-stored values of
modern LIDAR type frequency deviations and use those
values to track changes in LIDAR pulse repetition rate and
keep sending disrupting signal in phase with unstable speed
measuring signal. Modern disrupting devices can also have
a period pattern database of a modern LIDAR with pre
stored pulse repetition patterns and can track changes of a
speed measuring LIDAR pulse frequency according to pre
stored pattern. Recently a new type of modern speed measuring LIDAR
has appeared that transmits speed measuring laser beam with
random pulse repetition rate, a most significant deficiency of
a prior art frequency and phase matching disrupting method.
This Advanced LIDAR additionally exploits the foremost
mentioned deficiency of prior art frequency and phase
matching disrupting devices, which is that some of the speed
measuring signal pulses are not disrupted for the synchro
nization event to take place free of disrupting transmissions.
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SUMMARY OF INVENTION
The present invention overcomes the observed deficien
cies of prior art disrupting devices and describes a device
and method for disrupting operation of both advanced and
standard speed measuring LIDARS.
A laser transponder system and method for disrupting the
operation of vehicle speed measuring LIDARS. Including
advanced speed measuring LIDARS that are immune to
standard frequency and phase matching disrupting process.
Speed measuring LIDAR transmits a pulsed laser beam
towards a target vehicle which is detected by a pair of laser
transponders on the vehicle. A central processing unit that is
connected to both laser transponders processes received
signals and determines output signals. An alert is given and
a disrupting signal is sent back to the speed measuring
LIDAR by the first laser transponder becoming a transmit
ting only transponder. The second transponder becomes a
receiving only transponder and continues to receive speed
measuring LIDAR laser beam pulses. Laser transponders are
separated and the receiving only transponder sensitivity is
automatically reduced so it does not receive the disrupting
signal emanating from the transmitting only transponder.
Every pulse of the speed measuring laser beam is received
and used for frequency and phase matching. In return the
disrupting signal is able to disrupt all pulse measurements of
the speed measuring laser beam. Disrupting pulses are
correctly transmitted so at least one of them arrives at the
LIDAR during its measurement time window, consequently
disrupting the operation of vehicle speed measuring LIDAR,
including advanced LIDARs.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is best understood from the following
detailed description when read in connection with the
accompanying drawing. Included in the drawings are the
following figures:
FIGS. 1A and 1B show block diagrams of exemplary
circuits showing a microcontroller Switching from a stan
dard LIDAR disrupting method to an advanced LIDAR
disrupting method in a case when an advanced speed
LIDAR signal is detected. Two laser transponders and a user
interface are connected to the microcontroller.
FIGS. 2A and 2B show a circuit schematic of a micro
controller module and user interface module. Transmit TX
output, receive RX input and communication PROG output
signals are shown.
FIGS. 3A and 3B show a receiver circuit of a laser
transponder showing photodiodes, transistor amplifiers,
operational amplifiers, comparators, mono-stable, tempera
ture detector and gain control section with again controlling
microcontroller. Receive RX output signal and communica
tion PROG input signals are shown on circuit schematic.
FIG. 4 shows the laser transmitter circuit schematic of a
laser transponder showing the overcurrent protection circuit,
laser diode with an output transistor, driver circuit and
impulse conditioning circuit. Transmit TX input signal is
shown.
FIGS. 5A and 5B disclose the flow chart describing the
program algorithm of the microcontroller.
DETAILED DESCRIPTION OF THE
INVENTION
An aspect of the present invention enables construction of
an effective countermeasure device to the advanced speed
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measuring LIDARS. Advanced speed measuring LIDARS
are immune to standard countermeasure devices that use
standard frequency and phase matching (FPM) disrupting
method. Standard FPM disrupting methods can only be
effective if pulse periods (frequency) of a speed measuring
LIDAR signal is completely predictive. Additionally the
operation of a LIDAR will be disrupted only if the LIDAR
is not designed to purposely recognize and use every nth of
its pulse measurements that have completed during a syn
chronization event of a disrupting device.
Standard speed measuring LIDARs that have fixed pulse
periods are predictive by definition. A disrupting device
needs to measure the pulse period T and can then directly use
that period as a disrupting period D (T=D). Multiple speed
measuring pulses in a sequence can be disrupted 1D, 2D,
3D, 4D. . . . synchronizing the D period on every nth pulse
of the speed measuring signal.
Unstable pulse rate LIDARs similar to standard LIDARs
have almost fixed pulse periods that slightly vary in length
from period to period. They are predictive by learning the
way they achieve period deviations, or their instability can
be compensated by transmitting a longer disrupting pulse or
pulse train that will cover all possible deviations of period
length.
Pre-programmed pulse rate LIDARS significantly vary
their pulse periods from pulse to pulse but periods are
determined according to a pre-stored period sequence table
in a LIDAR database. If this period sequence table is known
then a disrupting device can use it to predict which period
value will be next on a given synchronization event.
In case of advanced speed measuring LIDARS that have
random pulse repetition rate a sequence of periods can’t be
predicted on a given synchronization pulse since they are
randomly chosen by the LIDAR. Even if periods could be
predicted and a disrupting signal sent in phase after Syn
chronization pulse an advanced LIDAR will recognize its
measuring pulse that was used as a synchronization event
and was not disrupted and will calculate speed based on Such
pulses.
A solution for an effective advanced LIDAR operation
disrupting device as the present invention describes is in a
device that will disrupt all measurement pulses of a LIDAR
device and will correctly transmit disrupting pulses so they
arrive during the measurement time window of a LIDAR.
The present invention solves the problem of a synchro
nization event by a novel method of sending a disrupting
signal while synchronizing a timer for the next period of a
disrupting signal. This is achieved by using a pair of laser
transponders or by having separate modules for a laser
receiver and for a laser transmitter. Laser transponders
should be separately mounted with some distance between
them to avoid cross talk of transmitting signal on the
receiver. A microcontroller is connected to both laser tran
sponders and is analysing received signals. When an
advanced LIDAR signal is detected it reconfigures inputs
and outputs so that the first transponder becomes a trans
mitting only unit and the second transponder becomes a
receiving only unit. The microcontroller then performs an
algorithm that discovers a maximum level of receiving
transponder receiver sensitivity on which there is no echo
triggering on transmissions emanating from the transmitting
transponder. The determined level of maximum allowable
sensitivity with no echo triggering depends on conditions
Such as weather (fog, Snow), obstacles in front of a vehicle
at a given moment, reflectivity of the road, etc. If maximum
allowable sensitivity is not correctly determined or condi
tions change, the disrupting transmission could, when
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reflected off of obstacles and arrives to a receiver trigger it
and cause a false synchronization event to happen possibly
resulting in an oscillating loop. For that reason the micro
controller can perform a discovering algorithm repeatedly
during a disruption process or can reduce maximum allow
able sensitivity from a determined value by a safety margin.
Every speed measuring laser pulse received by the receiv
ing only transponder is a synchronization event, but every
speed measuring laser pulse is also disrupted by a disrupting
transmission that was timed by a timer that was synchro
nized on a previous speed measuring laser pulse. Since the
receiving transponder only receives speed measuring laser
pulses and does not receive a disrupting transmission that is
emitted at the same moment it is possible to synchronize the
disrupting timer on all speed measuring pulses and at the
same time to disrupt all speed measuring laser pulses. The
timer used for timing a disrupting transmission is synchro
nized (reset) on a received speed measuring laser pulse and
when it times out it will initiate a disrupting transmission
that will arrive at speed measuring LIDAR during its next
measuring time window, during the disrupting transmission
a new speed measuring laser pulse is received and the timer
is immediately reset (synchronized) for another cycle of
operation.
In theory the sequence of periods on a given synchroni
Zation event of an advanced speed measuring LIDAR with
random pulse repetition rate can’t be predicted. In practice
it is possible to alleviate this problem by studying the
specific advanced speed measuring LIDAR type and group
its characteristic period lengths statistically. Usually Such
advanced LIDARS use specific groups of characteristic
period lengths which they randomly interchange because of
computer algorithm type reasons or interconnectivity with
other equipment reasons. Group of possible periods is then
known for Such an advanced LIDAR for a given synchro
nization event.
An aspect of the invention discloses another novelty of
timing multiple disruption signal periods in parallel on a
given synchronization event in case of Such an advanced
speed measuring LIDAR. By doing that disrupting the next
speed measuring pulse will be achieved regardless of which
speed measuring pulse period is next from the group of
periods. When the next speed measuring pulse actually
arrives and is detected by a receiver the current cycle of
disrupting all possible periods from the group is stopped so
not all periods in the group will initiate a disrupting trans
mission on every synchronisation, unless it happens to be the
longest value period of the group. The cycle is repeated
based on this new synchronization event and thus all speed
measuring pulses are disrupted. Transmitting multiple dis
rupting transmissions timed on each possible period from
the group on a given synchronization event means that in
each cycle most of the disrupting transmissions will be out
of the LIDAR time window but also that one of the trans
missions will arrive during the measurement time window of
a LIDAR.
The present invention can be used as described in defense
as a countermeasure to a distance measuring LIDAR as well
since Such devices use the same principle of operation.
Also the present invention method can be applied to
standard speed measuring LIDARS with a fixed pulse rep
etition frequency if for some reason standard FPM disrupt
ing method can’t be used. In Such a case detected speed
measuring LIDAR signal period T is measured by the
microcontroller algorithm and is used as a disrupting period
D. A database with characteristic group of periods is then not
necessary. Transmitting multiple periods of a disrupting
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signal in parallel on a given synchronization event is also not
used since there are no multiple possible periods of the speed
measuring signal but one constant period T. Such a disrupt
ing method will benefit in performance versus standard FPM
method since all speed measuring LIDAR pulse measure
ments are disrupted.
The described laser transponder system comprises at least
two laser transponders, a microcontroller connected to both
transponders and a user interface connected to the micro
controller. Laser transponders in another embodiment can be
a dedicated laser receiving unit and a dedicated laser trans
mitting unit. A set of multi-colour LEDs, a speaker and
buttons presents a user interface which displayS/sounds
system status to a user. The buttons of a user interface are
used to input user actions to the system for instance to stop
the disrupting process prematurely or to put the system to
sleep (turn off).
The purpose of a microcontroller is to analyse received
signals and to determine according output signals. It also
communicates with the user via a user interface. Its input
signals are receive signals from laser transponders and
control signals from a user interface and its output signals
are transmit and program signals to the laser transponders
and alert signals to a user interface. The microcontroller
program code executes a speed measuring LIDAR signal
detection algorithm, standard and advanced speed measur
ing LIDAR disruption algorithms, a maximum allowable
sensitivity discovering algorithm and other maintenance
algorithms (power off, power on, premature disruption end,
etc.). A pulsed-laser detector component of a presented device
will detect the arrival of laser pulses and will convert optical
signals to electrical impulses which are then sent to a
microcontroller unit. The pulsed-laser detector component
used in the presented invention is documented in my pre
vious invention (Pulsed-Laser detector with improved sun
and temperature compensation, EP2277060 BOROSAK).
Said detector circuit is enhanced in the present invention by
adding a communication line between the detectors gain
setting microcontroller and the main laser transponder sys
tem microcontroller. Over that line, the main system micro
controller commands the maximum allowable sensitivity
setting to the detectors gain setting microcontroller.
The laser transponder transmitter component converts an
electrical signal initiated by the microcontroller to an optical
signal. Conversion is performed by a pulsed laser diode
which outputs pulses of light. The laser diode output is not
fed to a collimator so the light radiation pattern is not
coherent but spreads to an optical angle of 30 degrees which
is optimal for the purpose of the present invention. The
transmitter component additionally comprises of an over
current protection circuit, driver circuit and impulse condi
tioning circuit.
Preferred Embodiment
The circuitry and the functional detail of the preferred
embodiment in accordance with the invention will be
explained in detail in the following paragraphs.
FIGS. 1A and 1B illustrate the block diagram of a laser
transponder system according to an aspect of the present
invention. Left side of the figure shows the system in
standard configuration that is used for the standard fre
quency and phase matching disrupting process and right side
of the figure shows the system has switched configuration to
an advanced frequency and phase matching disrupting pro
cess. In the advanced FPM disrupting process configuration
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first laser transponder 101 becomes a transmitting only
transponder 101B and the second transponder 102 becomes
a receiving only transponder 102B. The microcontroller 103
is connected to both transponders 101, 102 and is analysing
input from them RX, RX signal, determines their output
TX, TX signal and control their maximum receiver sen
sitivity level by P command signal. The microcontroller 103
algorithm performs reconfiguration of microcontroller 103
inputs and outputs when an advanced speed measuring
LIDAR signal is detected. Gain of the receiving only tran
sponders 102B receiver is adjustable via P signal by the
microcontroller 103B. The discovering algorithm of the
microcontroller 103 discovers maximum allowable receiver
sensitivity on which there is no echo triggering on trans
missions emanating from the transmitting only transponder
101B. User interface 104, 104B is connected to the micro
controller 103, 103B. It sounds/displays alerts to the user
and inputs user commands to the system, for instance
powering off/on or prematurely stopping the disruption
process.
With reference to FIGS. 2A and 2B the preferred embodi
ment will be disclosed in detail. Microcontroller 206, pref
erably the Microchip PIC24HJ128GP204 is used for per
forming the algorithm logic of the program and for storing
pre-stored constants and database. An instruction time of
only 20 ns results in good resolution of its timers and in the
high speed of program and algorithm execution. FIGS. 2A
and 2B show the layout of microcontroller 206 pins, the
power Supply pins are connected to power Supply and
appropriate decoupling capacitors. Microcontroller 206
external oscillator pins are connected to the crystal 207 with
a resonating frequency of preferably 12.000 MHz. High
frequency and temperature stability crystal 207 is used such
as ABM8G-12.000MHZ with less than 50 ppm tolerance. A
stable oscillator source will ensure that disrupting period
values pre-stored in the database when used for disrupting of
advanced speed measuring LIDAR will not deviate in length
and cause a shift in phase of the disrupting signal.
In preferred embodiment the Microcontroller 206 has
separate signal pins for controlling up to four laser tran
sponders. Ideally two laser transponders 101, 102 first and
second are mounted on the front of the vehicle looking ahead
of the vehicle and two transponders third and fourth are
mounted at the rear looking behind.
Microcontroller 206 has four transmit output signals TX,
TX, TX and TX from pins 2, 3, 4 and 5 respectively.
Transmit output signals are fed to the laser transmitter
sections of the laser transponders 101, 102 and they direct
the transmission of laser disruption pulses. Microcontroller
206 can activate transmit output signals TX, TX, TX and
TX individually, in groups or all at once. Said transmit
output signals are preferably first fed to a level converter 208
preferably an Onsemi 74ACT540 inverting buffer that is
converting the 3.3 V signal levels from the microcontroller
206 to a TTL 5 V signal levels. Converted transmit output
signals are then fed to the CMOS-transistor inverting drivers
204, 203, 202, 201 comprising of preferably Onsemi BSS84
P-MOS and 2N7002 N-MOS transistors. CMOS-transistor
drivers 204, 203, 202, 201 invert the transmit output signals
and amplify their current capacity so higher loads could be
driven for instance a very long connecting cable to the laser
transmitter section.
Communication PROG output signal is generated on
microcontroller 206 pin 12 and is also fed to the level
converter 208 where its signal level is changed to TTL 5 V
levels and then to the CMOS-transistor inverting driver 205.
Communication PROG output signal is fed to the laser
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transponders 101, 102 receiver sections or more accurately
to the gain controlling microcontroller of the laser receivers.
Communication PROG signal preferably comprises of com
mands sent on standard UART serial protocol where single
byte data is sent and each byte value represents a command
to the gain setting microcontroller to set the upper limit of
laser receiver sensitivity to the value same as the data byte
value.
Microcontroller 206 has four receive input signals RX,
RX, RX and RX on pins 9, 10, 11 and 14 respectively.
Receive input signals are generated by the laser receiver
sections of the laser transponders 101, 102. When an optical
laser pulse is detected by the laser receiver an electrical
receive input pulse is sent on receive input signal line. In
preferred embodiment microcontroller 206 program code
creates an interrupt event on arrival of a receive pulse on any
of the receive signal lines 209, 210, 211, 212. Interrupt
handler program of the microcontroller 206 checks on which
individual line the receive pulse has arrived and sets appro
priate flag indicator and then proceeds to the signal analysis
program. Microcontroller 206 program code in the case that
advanced speed measuring LIDAR signal is detected dis
ables the receive signal lines 209 and 211, pins 9 and 11 by
internally grounding them and thus prevents signals RX and
RX from causing an interrupt effectively turning first 101B
and third laser transponder into transmitting only transpon
ders. Also, in that case the disrupting signal will be only
generated on transmit output signals TX and TX, pins 2
and 4 of the microcontroller 206, preferably by reconfigur
ing pins 3 and 5 to inputs.
In an alternative embodiment four receive input signals
RX, RX, RX and RX are summed by a diode array
preferably an Onsemi BAT54CW pair 213, 214, and then
Sum signal RXs is fed to a single input pin 43 of the
microcontroller 206. Input signals RX and RX are first fed
to an individual two port AND gates 216, 217, such as
Fairchild 74LVC2G08 before being summed. A control
output signal from the microcontroller 206 pin 24 is fed to
second port of both AND gates 216, 217 and controls if input
signals RX and RX will be summed or not. In the case that
advanced speed measuring LIDAR signal is detected this
control signal will be set low and signals RX and RX will
not be summed. Pin 43 of the microcontroller 206 is an
INTO interrupt input that is used in the alternative embodi
ment for processing of Summed receive signal RXs.
The controlling key button pair 290 preferably TYCO
MSPS103C0 inputs user commands to the microcontroller
206. The first button is used to turn the device on/off or more
precisely put the microcontroller 206 into sleep mode. The
second button is used to prematurely stop the disrupting
process once it has started, if the user wants to do so. The
speaker 292 preferably of type SMT-1025-S-R by PUI audio
sounds the alerts to the user. LED RGB display 291 pref
erably HSMF-C 114 by Avago shows to the user the status of
the device, green light for turned on and ready and red light
for alert. Alerts are initiated by the microcontroller 206
program logic in case of a speed measuring LIDAR signal
is detected and disruption process has started. Electrical
power to the circuit is supplied over +5 V and +3.3 V power
lines.
A preferred embodiment of laser receiver part of the laser
transponders 101, 102 according to an aspect of the present
invention is shown on FIGS. 3A and 3B. The pulsed-laser
detector from my previous invention (Pulsed-Laser detector
with improved Sun and temperature compensation,
EP2277060 BOROSAK) is enhanced and used as a laser
receiver. It should be understood that other pulsed-laser
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receivers could be used as well in alternative embodiments
of the present invention. In one alternative embodiment a
pulsed laser receiver with a permanently low sensitivity is
used so the additional sensitivity limiting circuits and pro
gram algorithms described below are not necessary to
achieve no echo triggering of receiving only transponder on
transmissions emanating from transmitting only transpon
der.
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Said preferred embodiment detector circuit is enhanced in
the present invention by adding a communication line with
communication signal PROG between the detectors gain
setting microcontroller 303 and the main laser transponder
system microcontroller 206. The main system microcon
troller 206 commands the maximum allowable sensitivity
setting via PROG signal to the detectors gain setting micro
controller 303. The signal PROG preferably comprises
single byte serial commands that are sent by an UART
module on the main microcontroller 206 and are received by
an UART module on the gain setting microcontroller 303.
Gain setting microcontroller 303 is preferably a Microchip
PIC16F1503, 8-bit unit with embedded DAC peripheral.
Said DAC peripheral is used instead of the external DAC
R2R ladder used in the original Pulsed-Laser detector,
EP2277060, to generate gain setting signal G. Gain setting
signal G. current is amplified by an operational amplifier
302 preferably a Microchip MCP6001 so it could drive a
larger resistive and capacitive load without loss of accuracy
in the voltage level. Gain setting microcontroller 303 pro
gram is as described in original Pulsed-Laser detector,
EP2277060 with the addition that gain control signal level
can be limited and that ceiling value is determined by a
command received on PROG signal.
Output Q of the final stage monostable 301 is the output
of the laser receiver, the RX signal. Electrical power to the
circuit is supplied over +24V, +10 V and +5 V power lines.
FIG. 4 discloses a pulsed-laser beam transmitter circuit as
part of a laser transponder 101, 102. A transmission com
mand signal enters the circuit through the TX input and is
brought to a filtering RC combination of components 401.
Any noise accumulated over the connecting cable is filtered
out and only 5 V TTL level impulses pass to pulse condi
tioning circuit 402. Pulse conditioning circuit 402 is pref
erably realized with Fairchild NC7WZ14 inverting gates
pair connected in series through an R-C signal shortening
element combination. This way any length of signal entering
the circuit will be shortened to approximately 30 ns in length
which is an optimal length for the purpose of the present
invention. Conditioned transmission signal now enters a
driver integrated circuit 403, preferably consisting of Fair
child 74AC14 hex Schmitt inverter gates connected in
parallel. Signal current capability is now increased and is
brought to a laser diode output transistor 404, preferably
International Rectifier IRLL014N. The output transistor 404
converts the trigger signal into a high current signal through
a laser diode 405. The laser diode 405, preferably Osram
SPLPL90 3 converts a part of the electrical energy given by
a high current to optical laser energy which radiates towards
the target. High impulse current is Supplied by an array of
fast storage decoupling capacitors 406 consisting of prefer
ably Murata 470 nF capacitors.
In case of a fault and overcurrent through the laser diode
405 an overcurrent protection circuit 407 will activate and
disengage the laser diode 405 from the circuit. The over
current protection circuit is resettable by shortly removing
the power supply from the circuit. Electrical power to the
circuit is supplied over +24 V and +5 V power lines.
US 9,500,744 B2
11
The logic of the algorithm is illustrated by the flow chart
in FIGS. 5A and 5B. Said Microchip PIC24HJ128GP204
microcontroller has available 8192 16-bit registers that
represent its RAM memory and 42600 24-bit flash words
that represent its program and ROM memory.
Variables used by the program logic are located in the
RAM registers. The microcontroller ROM memory is pref
erably used for storing the Program code, Database data and
Constants and should be pre-programmed adequately.
All the Constants and the Database data used in the
program logic are located in the said ROM memory loca
tions.
The 32-bit timer counter unit TMR4/5 in the microcon
troller 206 is used for measuring and timing of both speed
LIDAR and disrupting pulse periods. The timer unit range is
from 1 up to 2° instruction cycles. Construction of the
Microchip PIC24HJ128GP204 microcontroller is such that
one instruction cycle takes two periods of the crystal oscil
lator 207 signal that is feeding the microcontroller 206
multiplied by a set PLL factor of 8.33.
Preferably, the clock frequency of the crystal oscillator
207 is selected to 12 MHZ that results in one instruction
cycle time and timer resolution of 20 ns. The 32-bit timer
unit range is then 85.899 seconds. Timer resolution of 20 ns
applies when measuring the pulse period (frequency) of a
speed measuring LIDAR signal and also when timing a
disrupting pulse period. Time window of a single pulse
measurement of a speed LIDAR targeting a vehicle at a
distance of 100 m is 600 ns (100 mx2x3 ns/m). Since timer
resolution is much lower than the average time window of
a speed LIDAR pulse measurement 20 ns.<600 ns, set timer
resolution is adequate for the disrupting process.
There are four loop areas in the program logic, the
start-up/stand-by routine 502, disrupting a standard speed
measuring LIDAR with a fixed pulse period routine 507,
disrupting an advanced speed measuring LIDAR with ran
dom pulse repetition period routine 516 and discovering
maximum allowable receiver sensitivity routine 514. A
database 505 is present in the program and is available to
blocks 504 and 510. The database is pre-stored and contains
a table of Standard speed measuring LIDAR signal periods
and a table of advanced speed measuring LIDAR groups of
characteristic periods.
On start the program enters an infinite loop of start-up?
stand-by routine consisting of blocks 501 and 502. In this
loop the program is waiting for reception of pulses on
receive RX signals, first pulse in block 501 and then second
pulse in block 502 and measures the time period T between
two received pulses 502. If measured time period T is
Smaller than 1 second the program exits the loop to block
503 and if it is longer than the loop starts over at block 501.
Continuing to block 503 the program proceeds to timing
of the Subsequent RX signal pulse periods T, T- and T
between second and third, third and fourth, fourth and fifth
pulse respectively. If any of the periods as they are measured
and evaluated, is longer than 1 second the program starts
over immediately at block 501. When final T. period is
measured and if found to be smaller than 1 second the
program proceeds to block 504. Signal periods T, T, T
and T are stored in memory for additional analysis in later
steps. Common speed measuring LIDAR both standard and
advanced have signal pulse period that is shorter than 1
second so this value is selected as a period time threshold.
Continuing with the block 504, for the program to proceed
to block 506 stored signal periods T to T are compared and
must match each other within a predetermined tolerance
window, also a database 505 is checked and must have a
10
15
25
30
35
40
45
50
55
60
65
12
match for a T=T-T =T period value in the table of
pre-stored standard speed measuring LIDAR signal periods,
otherwise the program continues to block 510. Tolerance
window in this embodiment is set at 0.01% of the period
time.
In block 510 similar to previous block 504, stored signal
periods T to T are checked in the database 505 and must
have a match in the table of pre-stored advanced speed
measuring LIDAR groups of characteristic periods for the
program to proceed to block 511, otherwise the program
Starts over at block 501.
Block 506 represents a successful detection of a standard
speed measuring LIDAR signal by the algorithm and start of
disrupting a standard speed measuring LIDAR with a fixed
pulse period routine.
The program initiates an alert to a device operator through
the user interface, warning light and Sounds are activated.
Next, the program 507 waits up to 1 second for reception of
a pulse on receive RX signals, if pulse is received during
wait the wait is aborted and disruption timer is immediately
synchronized (reset) and program proceeds to 508, if no
pulse arrives wait finishes and program goes to block 509.
In step 508 the disruption timer reach is set to value of
previously measured receive RX pulse period T=D decre
mented by 100 ns to set the phase of the disrupting trans
mission so that it arrives to LIDAR during LIDAR next time
window and before its next original speed measuring pulse
reflection arrives. Program waits for the disruption timer to
times out and then momentary initiates a disruption pulse
transmission on transmit TX signal. In preferred embodi
ment after the first disruption pulse transmission the disrup
tion timer is again reset and disruption timer reach reloaded
and procedure repeated 3 more times. This way on one speed
measuring pulse used for synchronization following four
speed measuring pulses are disrupted, n=4 periods. The
program then loops back to block 507 to wait for another
synchronization event.
In block 509 the program clears the alert to a device
operator deactivating warning light and Sounds, and starts
over at block 501.
Block 511 represents a successful detection of an
advanced speed measuring LIDAR signal by the algorithm
and start of disrupting an advanced speed measuring LIDAR
with random pulse repetition period routine.
The program initiates an alert to a device operator through
the user interface, warning light and Sounds are activated.
Next, the program 512 reconfigures microcontroller 103 by
disabling the receive signal lines 209 and 211, signals RX
and RX, and also disabling microcontroller 103 pins 3 and
5, signals TX and TX, effectively turning first 101B and
third laser transponder into transmitting only transponders
and second 102B and fourth laser transponder into receiving
only transponders.
The program 513 then starts discovering maximum allow
able receiver sensitivity routine which is incorporated in to
the disrupting an advanced speed measuring LIDAR with
random pulse repetition period routine. In this block 513 the
program initiates a pulse transmission on transmit TX signal
that is used as a ping for checking of echo triggering on
current sensitivity level of the receiving only transponders
laser receiver. Program proceeds to block 514 where it is
checked if the ping produced an echo triggering on receive
RX signals, a presence of a received pulse. If no pulse has
been received it means the current maximum receiver sen
sitivity level does not produce echo triggering on transmis
US 9,500,744 B2
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sions emanating from transmitting transponder and program
proceeds to block 516, if pulse has been received the
program proceeds to 515.
In block 515 current maximum receiver sensitivity is
decreased by one and new value of sensitivity ceiling is 5
commanded to receiving transponders laser receiver over
PROG signal, the program loops to 513.
The discovering maximum allowable receiver sensitivity
routine finishes when program reaches block 516. Here 516
the program waits up to 1 second for reception of a pulse on 10
receive RX signals, if pulse is received during wait the wait
is aborted and disruption timer is immediately synchronized
(reset) and the disruption timer reach is set to multiple values
equal to the values of periods in the found group of char
acteristic periods from the database for the detected 15
advanced LIDAR, decremented by 100 ns.
Program waits for the disruption timer to times out
multiple times and each time momentary initiates a disrup
tion pulse transmission on transmit TX signal. During one of
these disrupting transmissions or right after one a new speed 20
measuring LIDAR pulse will be received by the receiving
only transponder, at that moment the rest of disruption timer
reach values from present cycle will be cleared and block
516 will restart into a loop by synchronizing the disruption
timer and reloading disruption timer reach values again. If 25
no pulse arrives on receive RX signals for more then 1
second the program continues to 517.
In block 517 the program clears the alert to a device
operator deactivating warning light and Sounds, reconfigures
receive signal lines 209 and 211, signals RX and RX, and 30
microcontroller 103 pins 3 and 5, signals TX and TX to
previous values, resets maximum receiver sensitivity ceiling
of receiving transponders laser receiver to highest value over
the PROG signal, and starts over at block 501.
It should be understood that the invention is not limited by 35
the embodiments described above, but is defined solely by
the claims.
The invention claimed is:
1. A laser transponder system for disrupting the operation
of a distance and/or speed measuring LIDAR in response to 40
a detected LIDAR signal, the system comprising:
at least two laser transponders, a second transponder of
the at least two laser transponders is a receiving only
transponder and a first transponder of the at least two
laser transponders is a transmitting only transponder 45
and transmissions of the transmitting only transponder
are not detected by the receiving only transponder, and
a microcontroller that comprises pre-stored values in a
database, selects microcontroller disrupting signal peri
ods based on the pre-stored database according to the 50
detected LIDAR signal, and,
wherein a disrupting signal is transmitted simultaneously
with Synchronizing a disruption timer for a next period
of the disrupting signal, and a timing of multiple
disruption signal periods in parallel based on a given 55
synchronization event, and
the at least two laser transponders have a laser receiver
with an adjustable gain controlled by the microcon
troller, and the microcontroller reduces a sensitivity
level of the receiving only transponder such that there 60
is no echo triggering on transmissions emanating from
the transmitting only transponder.
2. A laser transponder system for disrupting the operation
of a distance and/or speed measuring LIDAR in response to
a detected LIDAR signal, the system comprising: 65
at least two laser transponders a second transponder of the
at least two laser transponders is a receiving only
14
transponder and a first transponder of the at least two
laser transponders is a transmitting only transponder
and transmissions of the transmitting only transponder
are not detected by the receiving only transponder, and
a microcontroller that comprises pre-stored values in a
database, selects microcontroller disrupting signal peri
ods based on the pre-stored database according to the
detected LIDAR signal, and,
wherein a disrupting signal is transmitted simultaneously
with Synchronizing a disruption timer for a next period
of the disrupting signal, and a timing of multiple
disruption signal periods in parallel based on a given
synchronization event, and
wherein a sensitivity of the receiving only transponder is
predetermined and set to a level such that there is no
echo triggering on transmissions emanating from the
transmitting only transponder.
3. A method of operation of a laser transponder system for
disrupting an operation of a distance and/or speed measuring
LIDAR based on time-of-flight measurement, that com
prises at least one laser receiving unit and at least one laser
transmitting unit physically separated on a vehicle chassis
and pointed in a direction of the LIDAR for which normal
operation should be disrupted, where the laser receiving unit
and the laser transmitting unit do not have any cross-talk, a
receiver that is converting optical signals received from a
laser receiving unit to electrical impulses which are sent to
a microcontroller, where the microcontroller has pre-stored
values in a database regarding the LIDARS and an algorithm
with decision logic for the disruption operation based on a
disruption timer D, and a user interface; wherein the method
comprises:
a) analysing, by the microcontroller, received LIDAR’s
signal from the laser receiving unit, which comprises a
series of pulses, by extracting period times T, between
observed pulses and comparing the periods T, with
pre-stored values in the database, i) if the correspond
ing period times T, are identified within the database,
the user is alerted and the system executes one of the
LIDAR’s counter measure of steps B or C depending
on the nature of received periods T.; and ii) if the
corresponding period times Ti are not identified the
system waits for the next signal or triggering event;
b) in case all periods T. between the received pulses are
equal or within a predetermined tolerance, the proce
dure for standard speed measuring LIDAR disruption is
executed by setting the disruption timer D to a single
value equal to the pulse repetition period of the LIDAR
corrected for phase shift in the way that value D is
decremented to set the phase of the disrupting signal;
and when the disruption timer D times out the disrup
tion timer D initiates disruption transmission on the
laser transmitting unit; and
c) in case periods T, between the received pulses are not
equal or not within the predetermined tolerance, the
procedure for advanced speed measuring LIDAR dis
ruption is executed by setting the disruption timer D to
multiple values corresponding to all possible advanced
LIDAR periods, wherein each value D is corrected for
the phase shift in such a way that value D is decre
mented to set the phase of the disrupting signal; and on
each of the multiple values D when disruption timer D
times out the disruption timer D initiates disruption
transmission on the laser transmitting unit,
wherein on each signal received by the laser receiving
unit in step b) or c) the disruption timer D is reset, and
US 9,500,744 B2
15
wherein the process is finished in absence of LIDAR
signals within a predetermined time window.
4. The method of operation of a laser transponder system
according to claim 3, wherein cross-talk between the laser
receiving unit and the laser transmitting unit is eliminated by
using a receiver with an adjustable gain and a method for
determination of a maximum allowable sensitivity level of
the receiver, the determination method comprising:
Setting again on the laser receiving unit to maximum; and
consecutively decreasing the receiver gain by the micro
controller, while the laser receiving unit is pinged by
the laser transmitting unit until an echo is not observed
by the laser receiving unit.
5. The method of operation of a laser transponder system
according to claim 3 wherein two laser transponders are
used, each transponder equipped with at least one laser
receiving unit and at least one laser transmitting unit, and the
laser transponders are geometrically separated on the vehicle
chassis and pointed in the direction of the LIDAR whose
normal operation is to be disrupted; wherein the laser
transponders are reconfigurable in a way that one transpon
der is reconfigured into the transmitting only transponder
and another is reconfigured into the receiving only transpon
der until the end of the disruption process defined in step C.
10
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16
6. The method of operation of a laser transponder system
according to claim 3, wherein the disrupting period D is
decremented by 100 ns to set the phase of the disrupting
signal.
7. A laser transponder system for disrupting the operation
of a distance and/or speed measuring LIDAR based on
time-of-flight measurement comprising means for carrying
out the method of claim 3.
8. The laser transponder system as in claim 7, wherein two
pairs of transponders are used, one pair mounted on the front
end and pointed in the driving direction and another pair on
the rear of the vehicle pointed opposite of the first pair.
9. The method of operation of a laser transponder system
according to claim 4 wherein two laser transponders are
used, each transponder equipped with at least one laser
receiving unit and at least one laser transmitting unit, and the
laser transponders are geometrically separated on the vehicle
chassis and pointed in the direction of the LIDAR whose
normal operation is to be disrupted; wherein the laser
transponders are reconfigurable in a way that one transpon
der is reconfigured into the transmitting only transponder
and another is reconfigured into the receiving only transpon
der until the end of the disruption process defined in step C.