FR2887342A1 - Telemetry method for motor vehicle, involves producing signals representing transmitting and reflection waves, where signals are processed to obtain another set of signals that are compared with threshold to produce measuring signal - Google Patents

Abstract

The method involves producing a transmitting wave that meets an object and is reflected on the object. A signal (SRrf) representing the transmitting wave is produced. A reflection wave produced by the reflection of the transmitting wave is received. A signal (SRr) representing the reflection wave is produced. The signals (SRrf, SRr) are processed to obtain signals (SArf, SAr) having the same amplitude. The processed signals are compared with a predetermined threshold (TH) to produce a measuring signal representing the distance between a telemetry device and the object. An independent claim is also included for a motor vehicle comprising a lighting device and/or a headlight equipped with a telemetry device.

Description

Telemetry method and device in particular

  The invention relates generally to the field of telemetry. More particularly, the invention relates to a method and a telemetry device having preferred applications, but not exclusively, in the automotive field.

  The invention also relates to a lighting and / or signaling device, such as a projector, incorporating a telemetry device 10 as indicated above.

  Telemetry devices find interesting applications in the field of assistance to driving a motor vehicle. Indeed, these devices are used in particular for assistance in the parking maneuver and the prevention of collisions.

  In the state of the art, two types of telemetry devices are known.

  A first known device is the laser range finder whose operating principle is based on measuring a flight time of a laser pulse, by observing a delay between the laser pulse emitted and the laser pulse received after reflection by an object.

  This type of rangefinder has the advantage of offering a measurement that remains independent of the reflection power of the object, insofar as the power of the transmitter is high enough to compensate for low reflectivity.

  The operating principle of the laser range finder, however, remains highly dependent on the accuracy of measurement of the time elapsed between the emission of a laser pulse and the reception of the corresponding laser pulse reflected by the target. The measurement of small distances, of the order of 10 cm, with good relative accuracy requires electronic circuits (transmitters, sensors and amplifiers) capable of discriminating times of less than 0.2 ns.

  Laser pulses with a very short rise time are required to ensure accuracy, which requires the use of electronic circuits with large bandwidths. The result is rangefinders, which certainly can be very efficient, but are expensive and therefore unsatisfactory in view of the high cost constraints present in the automotive industry.

  A second known device operates on the principle of measuring the light intensity of a wave emitted and reflected by the object. Indeed, a photoelectric or optoelectronic sensor can be used to measure a distance if it is considered that the reflected light received from the object is dependent on the distance separating the sensor from the object. However, by its operating principle, this type of device raises problems of reliability and accuracy of the measurement. Indeed, the accuracy of the measurement is strongly dependent on the power emitted by the light source and also depends on the dimensions and the reflection power of the object. Thus, for example, if the reflection power of the object changes in a ratio of 1 to 4, the distance measurement performed varies in a ratio close to 2.

  The present invention aims to overcome the disadvantages of the prior art set forth above by providing a method and a telemetry device that allows reliable distance measurement, good accuracy and reasonable cost, in a page ranging from a few centimeters to several meters.

  According to a first aspect, the present invention provides a telemetry method for measuring a distance between a telemetry device and an object, comprising the steps of: - producing an emission wave capable of meeting the object and of reflect on this one; producing a first signal representative of the emission wave; Receiving a reflection wave produced by a reflection on the object of the emission wave; - producing a second signal representative of the reflection wave; processing the first signal and / or the second signal to obtain first and second signals of the same amplitude; comparing the first and second signals of the same amplitude to a predetermined threshold to produce a measurement signal representative of the distance between the telemetry device and the object.

  Correlatively, the invention also relates to a telemetry device capable of implementing the method described briefly above, characterized in that it comprises: means for producing an emission wave capable of meeting the object and reflect on it; means for producing a first signal representative of the emission wave; means for receiving a reflection wave produced by a reflection on the object of the emission wave; means for producing a second signal representative of the reflection wave; means for processing the first signal and / or the second signal to obtain first and second signals of the same amplitude; means for comparing the first and second signals of the same amplitude with a predetermined threshold in order to produce a measurement signal representative of the distance between the telemetry device and the object.

  The method and device according to the invention are capable of operating with visible, ultraviolet or infrared light waves. The waves can come from one or more light-emitting diodes, one or more laser diodes, one or more laser beams, or one or more other visible optical sources.

  According to another particular characteristic, the first signal representative of the emission wave is produced from a part of the emission wave wave.

  Preferably, the waves involved in the method and device according to the invention are periodic waves.

  According to another particular characteristic, an integration of the measurement signal is provided in order to extract information representative of the distance between the telemetry device and the object.

  Thus, according to particular modes and embodiments, the emission wave production means may comprise at least one light-emitting diode, a laser diode, or another optical wave generator and the wave-wave reception means. reflection may comprise a sensor adapted to receive the corresponding reflection wave.

  In addition, according to another particular characteristic, the first signal processing and / or second signal processing means comprise analog type circuits and / or circuits for the implementation of digital techniques incorporating sampling, digitization and / or or digital coding.

  Preferably, the means for producing a first representative signal comprise a sensor paired with the sensor of the reflection wave reception means, the paired sensor having characteristics substantially identical to those of the sensor of the reflection wave reception means. More generally, the means for producing a first representative signal and the reflection wave reception means may also comprise paired signal processing means, the paired signal processing means having substantially identical characteristics.

  According to still other particular features: the first signal processing means and / or the second signal processing means comprise at least one variable gain amplifier and automatic gain control means.

  the comparison means comprise first and second comparators respectively receiving, at a first input, the first and second signals of the same amplitude and receiving, at a second input, the predetermined threshold.

  the telemetry device also comprises logic means receiving output signals from the first and second comparators in order to produce the measurement signal representative of the distance between the telemetry device and the object.

  According to other aspects, the invention also relates to a lighting and / or signaling device, such as a motor vehicle headlamp, and a motor vehicle equipped with at least one telemetry device according to the invention as briefly described. above.

  It will be noted that the telemetry device according to the invention is perfectly adapted to integration also into rear signaling lights of a motor vehicle.

  Other aspects and advantages of the present invention will appear more clearly on reading the description of particular embodiments and embodiments which will follow, this description being given by way of nonlimiting example and with reference to the appended drawings. , in which: Fig.1 shows a block diagram of a particular embodiment of the telemetry device according to the invention Figs.2A to 2D show waveforms of measurement signals and logic signals produced in the device according to the invention; and FIG. 3 shows telemetry devices according to the invention integrated in projectors of a motor vehicle.

  With reference to FIG. 1, a particular embodiment of the telemetry device according to the invention is now described. This embodiment is generally designated 1 and uses optoelectronic type components.

  The device 1 essentially comprises a transmission circuit 10 and a reception circuit 11.

  The transmission circuit 10 mainly comprises a signal generator 100 and an optical signal transmitter 101.

  In this particular embodiment, the signal generator 100 provides a periodic GS frequency slot signal of relatively low frequency, for example, in the range of 10 kHz to 500 kHz. Alternatively, the signal SG may not be periodic but include for example a single pulse or a burst of pulses repeating, or not, non-periodically.

  Of course, waveforms other than that in square form may be chosen by those skilled in the art according to the envisaged applications of the device according to the invention as well as according to the analog or digital embodiment which it will retain for the control of variable gain amplifier included in the receiving circuit 11, as will become more clearly apparent thereafter.

  The signal SG is supplied to the transmitter 101. The transmitter 101 receives the signal SG and outputs an emission light beam OE representative of the signal SG. For this purpose, the transmitter 101 comprises a light-emitting diode (LED) 101E and a not shown LED driver circuit.

  As shown in FIG. 1, a first part OE0 of the emission light beam is emitted towards an object 2, while a second part OErf of this latter illuminates a photodiode 110rf of the reception circuit 11.

  The receiving circuit 11 comprises two photodiodes, 110rf and 1108, at the input of two parallel signal processing paths. In other embodiments of the invention, sensors of different types can be used such as for example phototransistors or photoresistors.

  The first signal processing channel essentially comprises the 110r1 photodiode, a 111 rf receiver and a variable gain amplifier 112rf. This first processing channel is an emission reference path which produces at output a signal representative of the emitting light beam OE from the light beam OErf received by the photodiode 110rf.

  The second signal processing channel essentially comprises the photodiode 1108, a receiver 111R and a variable gain amplifier 1128. This second processing channel is the reception channel itself, that is to say, the receiving channel. a light beam OR reflected by the object 2 when the latter is illuminated by the emission light beam 0E0.

  In the first signal processing channel, the photodiode 110rf is implanted in the device according to the invention so as to receive only the emission light beam OErf, and in no case the reflected light beam OR.

  According to the invention, the first and second treatment channels may be fully or partially matched so that their respective drifts, especially temperature, are as close as possible. This pairing feature will prevent the introduction of measurement errors that would be due to differences in drift behavior and other variations. For example, the 110rf and 110R photodiodes may advantageously be made on the same substrate and with identical characteristics of bandwidth, surface area, etc. Similarly, 111 rf and 111R receptors may be constructed around active components, such as operational amplifiers, having paired characteristics.

  In this embodiment, the receivers 111 and 111R include filters (not shown) whose bandwidths are determined to allow reception of SRrf and SRR signals corresponding to the transmitted signal SG.

  The signal SRrf is supplied by the receiver 111 rf in response to the reception by the photodiode 110rf of the emission reference light beam OErf and is referred to herein as the transmission reference signal.

  The SRR signal is provided by the receiver 111R in response to the reception by the 110rf photodiode of the reflected light beam OR and is referred to herein as the reception signal.

  Examples of waveforms of signals SRrf and SRR are shown in Fig.2A for a slot CR of the transmitted signal SG.

  As shown in Fig. 2A, the reception signal SRR is delayed by a time T with respect to the transmission reference signal SRrf. The delay time i is usually called the flight time and corresponds to the path carried out by the light beams OEo and OR between the emission diode 101E and the reception photodiode 1108, in the presence of the object 2.

  The components 101E, 110rf and 1108 being arranged in close proximity, the delay time T is substantially proportional to twice the distance d between these components and the object 2. More precisely, the distance d is given by the equality: d = (TC) / 2, where C is the speed of light.

  As will be clear from reading the following paragraphs, the invention takes advantage of the fact that the waveform of the SRR receive signal remains very close, with the exception of the amplitude, of the waveform the transmission reference signal SRrf. This similarity of the waveforms of the SRI and SRR signals remains true in the distance measurement range, from a few centimeters to a few meters, for which the telemetry device according to the invention is designed.

  As shown in FIG. 2A, in accordance with the invention, the signals SRrf and SRR are adjusted in amplitude at the same level LL and are then compared at the same threshold TH in order to produce a measurement signal SM which is representative of the time As shown in FIG. 2D, the measurement signal SM has pulses whose duration is equal to T. Referring again to FIG. 1, the function of adjusting the signals SRrf and SRR to a The same amplitude level LL is satisfied by the variable gain amplifiers 112rf and 112R and an automatic gain control circuit (AGC) 113 which is also included in the reception circuit 11.

  As shown in FIG. 1, the automatic gain control circuit comprises two CAG modules 113rf and 1138.

  The CAG 113rf and 113R modules are integrated in AGC servo loops which control by signals CGrf and CGR the gains of the amplifiers 112rf and 1128, respectively. The gains of the amplifiers 112rf and 112R are controlled so as to obtain at their output signals SArf and SAR, corresponding to the signals SRrf and SRR, the amplitudes of which are equal to the level LL, respectively.

  The LL level is a set signal for the AGC servo loops. In addition to the level LL as a reference signal, the modules 113rf and 113R also receive, as counter-reaction signals, the signals SArf and SAR present at the output of the amplifiers 112rf and 1128, respectively.

  In the waveform example of FIG. 2A, the AGC modules 113rf and 1138 control the gains of the amplifiers 112rf and 112R so as to produce the signal SArf by reducing the amplitude of the signal SRrf and the SAR signal by increasing the amplitude of the SRR signal, respectively.

  Still referring to FIG. 1, the function of comparing the signals SArf and SAR at the threshold TH in order to produce the measurement signal SM mentioned above is filled by comparators 114rf and 114R included in the reception circuit 11.

  The comparators 114rf and 114R comprise inverting inputs (-) receiving the threshold TH, non-inverting inputs (+) receiving the signals SArf and SAR and outputs providing logic signals with two states SBrf and SBR, respectively.

  As shown in Figs. 2B and 2C, the signals SBrf and SBR switch to a high state when the signals SArf and SAR rise above the threshold TH and switch to a low state when the signals SArf and SAR drop below the threshold TH, respectively. The SBrf and SBR signals have similar waveforms that derive from the similar waveforms of the SArf and SAR signals, but are temporally offset from the time T. The measurement signal SM, shown in Fig.2D, is produced by a logic circuit 115 from SBrf and SBR signals. The circuit 115 is constituted for example by a simple OR-exclusive logic gate or a flip-flop.

  The measurement signal SM carries the distance information d in the duration t i of its pulses and can be exploited in various ways which are known to those skilled in the art.

  Thus, for example, it is possible to integrate the signal SM in order to obtain a mean DC voltage representative of the distance d. This integration function is fulfilled by the integrator circuit 116 in FIG. The circuit 116 outputs a continuous signal SD representative of the distance d.

  As a variant, it is also possible to count the duration of the pulses of the signal SM by means of a counter receiving a high frequency clock signal in order to obtain the distance d in the form of digital information.

  FIG. 3 shows telemetry devices 1D and 1G according to the invention which are respectively integrated in projectors 3G and 3D of a motor vehicle 4.

  In this type of application of the invention, each telemetry device 1 D, 1G must be able to discriminate among the reflected signals received that which actually corresponds to the signal that it has emitted. Different techniques can be used to achieve this discrimination. Thus, for example, the optical frequencies of the emitting diodes as well as the frequencies and shapes of the signals SG may be different for the devices 1D and 1G in order to allow the detection of the adequate reflected signal by filtering in the receiver. As another example, it is also possible to insert a digital mark in the SG signals, for example, by pulse width modulation (PWM), in order to allow in the receiver the discrimination of the received reflected signals.

  The integration of the two telemetry devices 1 D, 1G in the vehicle 4 allows an accurate measurement of the distance D between the front of the vehicle 4 and the object 2 and a location thereof on the horizontal plane of the road . Indeed, since the distance E between the devices 1D and 1G is known, it is possible from distances dD and dG provided by the devices 1D and 1G to determine by triangulation the distance D as well as a spacing distance. dX of the object 2 with respect to a longitudinal central axis X of the vehicle 4.

  As will become clear to those skilled in the art, the electronic circuits described in the context of this particular embodiment are in no way limitative of the invention. Other electronic circuits may be designed by those skilled in the art for carrying out the method according to the invention, according to the constraints specific to the application envisaged.

  Thus, the use of digital techniques incorporating sampling, digitization and digital coding, rather than a completely analog type embodiment, is entirely compatible with the invention.

  Indeed, by using in the CAG 113rf and 113R modules of the digital and analog converters suitable for association with the logic circuits and the sampling timing required, it is possible to obtain the equality of the SArf and SAR signals with a very high precision. .

  In the particular embodiment described above with reference essentially to FIGS. 1 and 2, the wave used for the measurement of the flight time is a light beam emitted in the visible spectrum by a single light-emitting diode. Of course, the invention is not limited to the use of such a wave. Thus, for example, a wavelength can be used in the non-visible spectrum, such as near-infrared or ultraviolet. In addition, the wave used may be of a different nature without departing from the scope of the invention.

  In another embodiment of the invention which will not be described here in detail, the emitted light beam is a laser beam produced using a laser diode. Optical beam splitting means are provided to deflect a part of the laser beam to the reference processing path. The directivity of the laser beam, possibly associated with a scan, allows selective detection of the objects present in predetermined angular sectors of the horizontal plane.

Claims (18)

  Telemetry method for measuring a distance between a telemetry device implementing said method and an object, comprising the steps of: producing a transmission wave capable of meeting said object and reflecting on it ; - producing a first signal (SRrf) representative of said transmission wave; receiving a reflection wave produced by a reflection on said object of said emission wave - producing a second signal (SRR) representative of said reflection wave; processing said first signal and / or said second signal to obtain first and second signals (SArf, SAR) of the same amplitude (LL); comparing said first and second signals of the same amplitude (SArf, SAR) with a predetermined threshold (TH) in order to produce a measurement signal (SD) representative of said distance between said telemetry device and said object (2).   2. Method according to claim 1, characterized in that said waves are visible, ultraviolet or infrared light waves.   3. Method according to claim 2, characterized in that said waves are derived from one or more light-emitting diodes (101 E), one or more laser diodes, one or more laser beams, or one or more other visible optical sources.   4. Method according to any one of the preceding claims, characterized in that said step of producing a first representative signal comprises a sub-step of producing said first signal representative of said transmission wave from a part of said emission wave.   5. Method according to any one of the preceding claims, characterized in that said waves are periodic waves (SG, 0E, OR).   6. Method according to any one of the preceding claims, characterized in that it also comprises a step of integrating (116) said measuring signal in order to extract the information representative of said distance (d) between said measuring device. telemetry and said object.   7. Telemetry device suitable for implementing the method according to any one of claims 1 to 6, for measuring a distance between said device and an object, characterized in that it comprises: - means (10, 101 E ) producing a transmission wave (0E) likely to meet said object (2) and reflect on it; means (110, 111, f) for producing a first signal (SR, f) representative of said transmission wave (0E); means (1108) for receiving a reflection wave (OR) produced by reflection on said object (2) of said transmission wave (0E); means (111R) for producing a second signal (SRR) representative of said reflection wave (OR); - means (112, f ;, 112R; 113) for processing said first signal and / or said second signal to obtain first and second signals (SAn, SAR) of the same amplitude (LL); means (114, f, 1148) for comparing said first and second signals of the same amplitude (SA, f, SAR) with a predetermined threshold (TH) in order to produce a measurement signal (SM) representative of said distance (d ) between said telemetry device and said object (2).   8. Device according to claim 7, characterized in that said first signal processing means and / or second signal comprises analog type circuits and / or circuits for the implementation of digital techniques incorporating the sampling, the digitization and / or digital coding.   9. Device according to claim 7 or 8, characterized in that said emission wave generating means comprise at least one light emitting diode (101 E), a laser diode, or another optical wave generator and said means reflection wave receiving means comprises a sensor (1108) adapted to receive the corresponding reflection wave.   10. Device according to any one of claims 7 to 9, characterized in that said means for producing a first representative signal comprise a paired sensor (1104) to said sensor (1108) of said reflection wave receiving means, said sensor paired having characteristics substantially identical to those of said sensor of said reflection wave receiving means.   11. Device according to any one of claims 7 to 10, characterized in that said means for producing a first representative signal and said reflection wave receiving means comprise paired signal processing means, said paired processing means signal having substantially identical characteristics.   12. Device according to any one of claims 7 to 11, characterized in that said first signal processing means and / or second signal comprises at least one variable gain amplifier (114) and control means (113). automatic gain.   13. Device according to any one of claims 7 to 12, characterized in that said comparison means (114) comprises first and second comparators respectively receiving, at a first input (+), said first and second signals of the same amplitude. (SA) and receiving, at a second input (-), said predetermined threshold (TH).   14. Device according to claim 13, characterized in that it also comprises logic means (115) receiving output signals (SB) from said first and second comparators in order to produce said measurement signal (SM) representative of said distance ( d) between said telemetry device and said object.   15. Device according to any one of claims 7 to 14, characterized in that said means for producing a first representative signal comprise means for producing said first signal representative of said emission wave from a part (OErf). of said transmission wave.   16. Lighting device and / or signaling for a motor vehicle, characterized in that it comprises at least one telemetry device according to any one of claims 7 to 15.   17. Motor vehicle characterized in that it comprises at least one telemetry device according to any one of claims 7 to 15.   18. Motor vehicle characterized in that it comprises at least one lighting and / or signaling device (3D, 3G) according to claim 16.