DE2430381B1

DE2430381B1 - Arrangement for automatic object tracking by television cameras, in particular television cameras for video telephones

Info

Publication number: DE2430381B1
Application number: DE19742430381
Authority: DE
Inventors: Adolf Dipl.-Ing. 8000 Muenchen Schneider
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1974-06-25
Filing date: 1974-06-25
Publication date: 1976-01-02

Description

Im Impulsprograrnm der F i g. 2 ist in der Zeile a die Sendeimpulsfolge der SchallkeuleH1 angedeutet. Nach dem ersten Impuls in dieser Zeile erfolgt in der Zeile b mit dem Abstand t das Signal 2 der Schallkeule H 2. U 1 und U2 sind die Impulsspannungen der Schallkeulen H1, H2 bzw. V1, V 2. T ist der zeitliche Abstand zwischen dem Sendeimpuls U1 In the impulse program of FIG. 2 is the transmission pulse sequence in line a the sound cone H1 indicated. After the first pulse in this line takes place in the line b with the distance t is the signal 2 of the sound cone H 2. U 1 and U2 are the pulse voltages of the sound cones H1, H2 or V1, V 2. T is the time interval between the transmission pulse U1

und U2. In diesem zeitlichen Abstand müßte unbedingt ein Rücksignal von U1 bzw. U2 hineinfallen, so daß jeweils eine feste Zuordnung möglich ist.and U2. In this time interval, a return signal would have to be received from U1 or U2 fall in, so that a fixed assignment is possible in each case.

In der Zeile c ist die Spannung U3 der reflektierten horizontalen bzw. vertikalen Impulse angedeutet. In line c, the voltage U3 is the reflected horizontal or vertical impulses indicated.

Die Zeile d zeigt die vom Tiefpaß T in der F i g. 3 abgegebene Signalspannung U4. Mit U5 in der Zeile e ist das Ausgangssignal der Schwelle W2 in der Fig.3 dargestellt. Den Verlauf dieses Signals beim Verlassen des Differenzierers D in der Fig.3 zeigt die Zeile f mit der Spannung U6. In der Zeile ist die Spannung U7 am Ausgang des Schmitt-Triggers R angedeutet.Line d shows the low-pass filter T in FIG. 3 output signal voltage U4. With U5 in line e, the output signal of the threshold W2 is shown in FIG. The course of this signal when leaving the differentiator D is shown in FIG the line f with the voltage U6. In the line, the voltage U7 is at the output of the Schmitt trigger R indicated.

Mit U 8 in der Zeile h ist das Signal am invertierenden Eingang eines Operationsverstärkers OP und in der Zeile i das Signal am nichtvertierenden Eingang dieses Operationsverstärkers dargestellt. Die Zeile k zeigt den Spannungsverlauf U 10 am Ausgang einer monostabilen Kippstufe K3 in der Fig. 3. In der Zeile 1 ist das Rückstellsignal U11 für eine KippstufeK2 in der Fig.4 gezeichnet. Die Spannung U12 in der Zeile m veranschaulicht das Ausgangssignal der ç Ausgangskippstufe K2. With U 8 in line h, the signal at the inverting input is one Operational amplifier OP and in line i the signal at the non-converting input of this operational amplifier shown. Line k shows the voltage curve U 10 at the output of a monostable multivibrator K3 in FIG the reset signal U11 for a flip-flop K2 is shown in FIG. The voltage U12 in line m illustrates the output signal of the output flip-flop K2.

In der F i g. 3 sind am linken Rand zwei elektroakustische Wandler I und ein Empfänger II angedeutet. Der von einem Impulsgenerator IG kommende Sendeimpuls U1 (günstigerweise mit To<50 llsec) erzeugt einen Schallimpuls mit einer vom Fernsehtelefon-Benutzer nach Fig. 1 bzw. von einem anderen Objekt aus links liegenden Schallkeule H1. In FIG. 3 there are two electroacoustic transducers on the left edge I and a recipient II indicated. The transmission pulse coming from a pulse generator IG U1 (favorably with To <50 llsec) generates a sound pulse with one of the TV telephone user according to FIG. 1 or from another object on the left Sound cone H1.

Der reflektierte Strahl ruft ein Empfangssignal U3 hervor, das zur Erhöhung der Störsicherheit zunächst über einen Tiefpaß T und eine Schwelle W2 geführt wird. Die so gewonnene Spannung U5 gelangt anschließend auf einen Differenzierer D und einen Schmitt-Trigger R und erzeugt ein digitales Signal U7, dessen Länge jeweils der Dauer der Anstiegsflanken der Impulse U5 entspricht.The reflected beam causes a received signal U3, which for Increase in immunity to interference is initially carried out via a low-pass filter T and a threshold W2 will. The voltage U5 obtained in this way then passes to a differentiator D and a Schmitt trigger R and generates a digital signal U7 whose length corresponds to the duration of the rising edges of the pulses U5.

Mit dem ersten Sendeimpuls 1 nach der Zeile a in der Fig. 2 wurde der Kondensator C 8 am invertierenden Eingang des Differenzverstärkers OP über einen durch den Sendeimpuls geschalteten Analogschalteer 52 auf die Spannung »0« gelegt. Der aus dem Empfangsimpuls 1 gewonnene Tastimpuls 1", der der Spannung U7 entspricht, schaltet nun über einen zweiten Analogschalter 51 den integrierten Empfangsimpuls entsprechend Spannung US durch und lädt den Kondensator C 8 bis zum Maximalwert der Spannung U5, das entspricht der Spannung U8 in der Fig. 2, auf. Während des ersten Sendeimpulses war eine Kippstufe K1 im Zustand »1«. Der nächste um die Zeit T verzögerte Sendeimpuls der zweiten SchallkeuleH2 bringt die Kippstufe K 1 in den Zustand »0« und legt die Analogschalter S1, S2 über einen Umschalter 53 an den Kondensator C 9 des nichtinvertierenden Eingangs des Differenzverstärkers OP. Gleichzeitig wird über den Analogschalter S2 und den Umschalter S3 der Kondensator C 9 auf die Spannung 0 gebracht. With the first transmission pulse 1 after line a in FIG the capacitor C 8 at the inverting input of the differential amplifier OP via a Analog switch 52 switched by the transmission pulse is set to voltage "0". The key pulse 1 "obtained from the received pulse 1, which corresponds to the voltage U7, now switches the integrated receive pulse via a second analog switch 51 corresponding to voltage US and charges the capacitor C 8 up to the maximum value the voltage U5, which corresponds to the voltage U8 in FIG. 2. During the The first transmission pulse was a flip-flop K1 in the "1" state. The next one at the time T delayed transmission pulse of the second sound cone H2 brings the flip-flop K 1 into the State "0" and applies the analog switches S1, S2 via a changeover switch 53 to the capacitor C 9 of the non-inverting input of the differential amplifier OP. At the same time will The capacitor C 9 to the voltage via the analog switch S2 and the changeover switch S3 0 brought.

Der Empfangsimpuls 2" steuert nun den Schalterms1 zu und lädt den Kondensator C 9 auf den Maximalwert der Spannung U4 auf, was der Spannung U9 in der Fig. 2 entspricht. Übersteigt die positive oder negative um den Faktor V verstärkte Differenz U9-U8 eine gewisse Schwelle W1, dann liegt an einem Schalter S4 eine positive oder negative Spannung. Dieser Schalter 54 wird während einer bestimmten Tmpulsdauer, die durch eine von U1 getriggerte und von U7 zurückgesetzte Kippstufe K 3 vorgegeben ist, geschlossen und führt einem elektromechanischen Regelglied, z.B. einem Motor M mit Endabschaltung, für die horizontale Lageeinstellung der Fernsehkamera eine positive oder negative Spannung zu, je nach dem in welcher Richtung nachgeregelt werden soll. The receive pulse 2 "now controls the switch ms1 and loads the Capacitor C 9 to the maximum value of the voltage U4, which corresponds to the voltage U9 in corresponds to FIG. Exceeds the positive or negative amplified by a factor of V. Difference U9-U8 a certain threshold W1, then a switch S4 is positive or negative voltage. This switch 54 is activated for a certain pulse duration by one of U1 triggered flip-flop K 3 set back by U7 is closed and controls an electromechanical control element, e.g. a motor M with limit switch, one for the horizontal position adjustment of the television camera positive or negative voltage, depending on which direction is readjusted shall be.

In dem dargestellten Ausführungsbeispiel war der zweite Empfangsimpuls 2' wesentlich größer als 1', d. h. die Person saß zu weit rechts vor dem Bildschirm des Fernsehtelefons. Der Antriebsmotor muß damit das Sichtgerät weiter nach links drehen. Sobald der Kopf und Oberkörper der Person symmetrisch zur Mittelachse des Bildfernsprechers liegen, werden die Empfangsimpulse 1', 2' gleich groß und es entsteht keine Differenzspannung mehr, die den Motor betätigen würde. In the illustrated embodiment, the second received pulse was 2 'much larger than 1', i.e. H. the person was sitting too far to the right of the screen of the television phone. The drive motor has to move the display device further to the left turn. Once the head and torso of the person are symmetrical about the central axis of the Video telephone are, the received pulses 1 ', 2' are the same size and it arises no more differential voltage that would operate the motor.

Nach jedem Impulspaar der Schallkeulen H1, H2 für die horizontale Lageregelung wird ein entsprechendes Impulspaar der Schallkeulen V1, V2 für die vertikale Positionierung des Bildfernsprechers gesendet. After each pulse pair of the sound cones H1, H2 for the horizontal Position control is a corresponding pulse pair of the sound cones V1, V2 for the vertical positioning of the video phone sent.

Die Auswertung dieser Empfangsimpulse geschieht im wesentlichen völlig analog zu der oben beschriebenen horizontalen Regelung mit dem Unterschied, daß hier ein nicht dargestellter zweiter Motor für die vertikale Schwenkung der Fernsehkamera angesteuert wird. Außerdem ist bei der Vertikalregelung der Spannung U 8 eine konstante Gleichspannung überlagert. Damit stellt sich der Ruhearbeitspunkt so ein, daß die reflektierte Spannung El stets kleiner als E2 wird, d. h. die Schallkeule V1 reicht über den Kopf des Signalpartners hinaus. Bei einer gleichmäßigen symmetrischen Bewertung der reflektierten Strahlen - wie es bei der Horizontalregelung geschieht - würde die Vetikalregelung nicht in Aktion treten, wenn beispielsweise die Kamera zu tief geneigt ist und nur die Brustpartie des Sprechpartners erfaßt. The evaluation of these received pulses takes place essentially completely analogous to the horizontal regulation described above with the difference that here a second motor, not shown, for the vertical pivoting of the television camera is controlled. In addition, the voltage U 8 is constant during vertical regulation DC voltage superimposed. The rest work point is thus set in such a way that the reflected voltage El is always smaller than E2, d. H. the sound cone V1 is sufficient beyond the head of the signal partner. With an even, symmetrical assessment of the reflected rays - as it happens with the horizontal control - would the vertical control does not come into action if, for example, the camera is too low is inclined and only covers the chest of the speaking partner.

Damit nun sowohl die Horizontal- als auch die Vertikalnachsteuerung erst dann einsetzt, wenn sich eine Person in einem gewissen Mindestabstand befindet, muß eine Entfernungsmessung vorgesehen werden. Dies kann ebenfalls durch einen Ultraschallgeber- und Empfänger mit Auswerteeinrichtungen für die reflektierten Impulse so erfolgen, daß eine Regelspannung Ur zur Verfügung steht, die direkt proportional zur Entfernung ist. Überschreitet die Spannung Ur eine gewisse Größe, dann wird ein Schwellwertschalter W3/S5 ausgelöst, der dem Motor eine konstante Spannung Uo zuführt, die ihn in die Unendlich-Stellung bewegt. So now both the horizontal and the vertical readjustment only starts when a person is at a certain minimum distance, a distance measurement must be provided. This can also be done by an ultrasonic transducer and receivers with evaluation devices for the reflected pulses take place in such a way that that a control voltage Ur is available that is directly proportional to the distance is. If the voltage Ur exceeds a certain value, a threshold switch is activated W3 / S5 triggered, which supplies the motor with a constant voltage Uo, which converts it into the Infinite position moves.

Gewisse Störprobleme könnten ferner auftreten, wenn sich sehr nahe hinter einer Person eine gut schallreflektierende Wand befindet. In diesem Falle sind unter Umständen die von der Wand rücklaufenden Impulse größer als die von dem Objekt, z. B. Certain interference problems could also occur when very close behind a person there is a good sound-reflecting wall. In this case the pulses returning from the wall may be greater than those from the Object, e.g. B.

einer Person, reflektierten Impulse und machen damit eine exakte Positionssteuerung unmöglich. Zur Sicherstellung, daß jeweils nur der erste reflektierte Impuls und nicht die noch später von entfernteren Gegenstände eintreffenden Signale ausgewertet werden, ist in der Fig.4 ein entsprechendes Ausführungsbeispiel in Form eines Blockschaltbildes wiedergegeben. Über ein NAND-Gatter G2 wird eine negativ flankengetriggerte Kippstufe K2 mit den Impulsen U7 gesetzt. Als Rückstellsignal dienen die Sendeimpulse U1 und U2.a person, reflected impulses and thus make an exact position control not possible. To ensure that only the first reflected pulse and the signals arriving later from more distant objects are not evaluated 4 is a corresponding embodiment in the form of a block diagram reproduced. A negative edge-triggered multivibrator is generated via a NAND gate G2 K2 set with the pulses U7. The transmission pulses U1 and serve as the reset signal U2.

Während der Zeit A t zwischen den Rückflanken der Impulse U7 und U2 ist der Q-Ausgang der Kippstufe kr auf »0« und blockiert über eine logische NAND-Verknüpfung weitere eventuell folgende Impulse U7. Die Spannung U13, die nach Invertierung den durch den integrierten Empfangsimpuls geschalteten Analogschalter 51 steuert, enthält daher nur die jeweils zuerst reflektierten Impulse. Damit bleiben Impulse, die von weiter weg liegenden Gegenständen herrühren, unberücksichtigt. During the time A t between the trailing edges of the pulses U7 and U2 is the Q output of the multivibrator kr at "0" and blocks via a logical NAND link further possibly following impulses U7. The voltage U13, which after inversion the analog switch 51 controlled by the integrated receive pulse therefore only the first reflected impulses. This leaves the impulses from objects located further away are not taken into account.

Claims

Claims: 1. Arrangement for automatic object tracking of television cameras, especially television cameras for video telephones, since d u r c h marked that for automatically aligning the camera to one in one a certain minimum distance to the object located in the recording field, e.g. B. a person an ultrasonic transmitting and receiving device (I, II) for two sound cones each (H1, H2 / V1, V2) for position positioning in horizontal and vertical direction and Evaluation devices (FIG. 3) are provided for the received signals.

2. Arrangement according to claim 1, characterized in that of the Ultrasonic transmission device after each pulse pair of the sound coulen (H1, H2) for the horizontal position control a corresponding pulse pair of the sound cones (V1, V2) is sent for vertical positioning.

3. Arrangement according to claim 1, characterized in that as the ultrasonic transmitting device a piezoelectric transducer is used.

4. Arrangement according to claim 1, characterized in that as an evaluation device a differentiator (D), a Schmitt trigger (R), analogue and changeover switch (S1-S3), a differential amplifier (OP) each with a capacitor (C8, C9) at the inverting input and at the non-inverting input and also one Threshold (W1) are arranged.

5. Arrangement according to claims 1 and 4, characterized in that that the reflected beam causes a received signal (U3) in the receiving device, to increase the immunity to interference initially via a differentiator (D) upstream Low pass (T) and a threshold (W 2) is performed.

6. Arrangement according to claim 3, characterized in that the first Transmit pulse of the horizontal sound cone (H 1) for the horizontal storage Capacitor (C8) at the inverting input of the differential amplifier (OP) via a Analog switch (S2) switched by the transmission pulse only during the pulse duration to the voltage "0" and the reflected, arriving later beam the integrated Receive pulse (U5) via one switched by the regenerated pulse (U7) second analog switch (S1) and this capacitor (C8) up to the maximum value the voltage (U5) released by the threshold (W2).

7. Arrangement according to claim 1, characterized in that in the Ansohluß a gate (G1) and a flip-flop (K1) are provided on the ultrasonic transmission device which is in the »1« state during the transmission pulses (U1).

8. Arrangement according to claims 2 and 7, characterized in that that in each case the response to the first transmission pulse of the left sound lobe (H1 or V 1) following transmission pulse of the right sound cone (H2 or V 2) the flip-flop (K1) in brings the state »0« and the analog switches (S1, S2) via a changeover switch (p 3) to the Capacitor (C 9) of the non-inverting input of the differential amplifier lays.

9. Arrangement according to claim 8, characterized in that the capacitor (C9) at the non-inverting input of the differential amplifier (OP) via the through the transmission pulse switched analog switch (S2) and the changeover switch (S3) to voltage "0" is brought.

10. The arrangement according to claim 9, characterized in that as a function of the second receive pulse the analog switch switched by the transmit pulse (S2) closes and the capacitor (C 9) at the non-inverting input of the differential amplifier (OP) charged to the maximum value of the voltage (U5) emitted by the threshold (W2) will.

11. The arrangement according to claim 10, characterized in that when Exceeding the positive or negative amplified by the differential amplifier (OP) Difference between the voltages (U9-U8) on the capacitors (C8, C9) due to the threshold (W 1) specified value to a control switch (S 4) a corresponding positive or negative voltage is applied.

12. The arrangement according to claim 11, characterized in that the control switch (S4) during the time between a receive and the next transmit pulse a flip-flop (K3) is closed and an electromechanical control element, z. B. a motor (M) that affects the horizontal position adjustment of the television camera.

13. Arrangement according to claims 2 and 4, characterized in that that the voltage on the capacitor (C 8) at the inverting input of the differential amplifier (OP) a constant DC voltage is superimposed on the vertical control.

14. Arrangement according to claim 1, characterized in that a device is provided for distance measurement, by means of which it is determined whether the Object located in the recording field, e.g. a person, a certain minimum distance in front of the camera, so that a unique assignment of the received horizontal and vertical impulses becomes possible.

15. The arrangement according to claim 14, characterized in that about an ultrasonic transmitter and receiver for distance measurement a control voltage (Ur) is obtained, which is directly proportional to the distance of the object to be recorded is.

16. Arrangement according to claims 12 and 15, characterized in that that a threshold switch (W 3 / S 5) is provided, which when a control voltage proportional to the maximum intended distance to the electromechanical Control element (M) supplies a fixed voltage (U5) which corresponds to the infinite position.

17. The arrangement according to claim 1, characterized in that each only the first reflected pulse and not the signals arriving later be evaluated.

18. Arrangement according to claim 17, characterized in that to ensure that that only the first reflecting pulse is evaluated, a NAND normal gate (G 2) is provided, via which a negative edge-triggered flip-flop (K2) with the voltage (U7) emitted by the Schmitt trigger (R) is set, whereby the transmission pulses (U1, U2) serve as a reset signal.

19. The arrangement according to claim 18, characterized in that the output the trigger stage (K2) via a logical NAND link (G3) further possibly following Control impulses (U7) blocked, which are reflected by distant objects.

In the case of television recordings of people, it is important that the relevant Person either correctly places himself in the recording field or the camera manually or remotely tracked. While in studio recordings in general a specially trained operator ensures the optimal camera alignment, on the television telephone, the speaker must himself, generally by hand control, Swivel or turn the device sideways.

This setting is sometimes cumbersome and time consuming and requires a frequent control of the positioning on the monitor screen, in which on self-image is switched. After mostly the picture of the other partner on a television telephone is switched on and the self-image control is missing, it can easily happen that the speaker is unfavorably or even outside of the recording field. In particular, readjustment is frequent for people of different sizes necessary.

One known device (US Pat. No. 3,116,365) has a positioning aid by a light source arranged inside the device, forming a diaphragm Opening and an annular aperture arranged in the device wall is formed. Of the Participant is then in the correct position for the reception facility, when both of his eyes are in the area of the through the aperture in the wall of the device created darker, central area, that of a light ring is surrounded. If the participant leaves the mentioned position, the light source becomes visible to him while moving through an area of smaller width.

Another known device of this type (US Patent 28 95 005) has for this purpose a ring that is slidable on a rod and that of the picture tube is arranged. The ring should be adjusted so that the user of the device can is only in the correct recording position if it is the one to be received Picks up image information through the ring.

With these known devices it is possible to receive the image information to be viewed from a point where there is no recording of the user and so too his picture was not passed on. However, it is precisely this fact that applies to the practical operation of such a device turned out to be disadvantageous, since the Finding the right position as a result of also from other positions recognizable Image reproduction often takes a long time, especially when such a Device accessible to a large number of users in a public call station is what is particularly disadvantageous for the participants because of the cost of the call can affect.

The invention is based on the object of the specified disadvantages to avoid and with simple means an arrangement for automatic object tracking of television cameras, in particular television cameras for video telephones.

This object is achieved in that for automatic alignment the camera to a location at a certain minimum distance in the recording field Object, e.g. B. a person, an ultrasonic transmitting and receiving device for each two sound cones for position positioning in horizontal and vertical direction and evaluation devices are provided for the received signals. In this way object tracking is achieved without z. B. the interlocutor at television cameras for video telephones is constantly forced to look at the picture in order to be able to use it Constantly correcting the situation. The solution according to the invention also enables tracking of a television camera for moving objects in surveillance equipment, z. B. in assembly line work.

According to a further development of the invention, the ultrasonic transmission device after each pulse pair of the sound cones for the horizontal position control a corresponding one Pulse pair of sound cones sent for vertical positioning. The advantage this solution is that the positioning aid is housed in a device is and practically a continuous alignment of the camera to the object in horizontal and vertical direction takes place.

According to an expedient development of the invention, it is used as an ultrasonic transmitter preferably a piezoelectric transducer is provided. The use of such a Converter offers the advantage of a simple structure and, moreover, a good one Efficiency.

Further details of the invention emerge from the figures and the corresponding description. The invention is explained with reference to the figures. 1 shows an overview image in a schematic representation, FIG. 2 a timing diagram, 3 shows a block diagram with the evaluation devices for the reflected signals and FIG. 4 is a block diagram for an embodiment to ensure that only the first reflected pulse is evaluated.

In FIG. 1 is a camera in each case in the side and plan view shown opposite a head in profile and in plan view. With Vi, V2 are the sound cones for vertical position control and the sound cones with H1, H2 shown for the horizontal positioning of a television camera.