DE3041272A1 - ELECTRONIC DISTANCE METER - Google Patents

Description

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4. Distance meter according to claim 1 or 2, characterized in that the evaluation circuit (11) has a comparison stage (12), a setpoint adjuster (13) and an ignition circuit (1 k) aufwe.

5. Distance meter according to one of the preceding claims, characterized in that the control circuit is formed by a programmable plague memory module (6) and by a digital / analog converter (7).

6. Distance meter according to one of the preceding claims, characterized in that a gate circuit (3) is provided between a generator (k) for generating the further pulse train and the pulse counter (5), which is controlled on the one hand by the transmission pulse and on the other hand by the received pulse.

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A regulation of the receiving amplifier by the received signals would be possible if the duty cycle is low were. Usually, however, the duty cycle is high in pulse-time-of-flight rangefinders, so that due to Regulation is not practically possible due to the necessary control time constants.

(DE-OS 20 55 250)

In US Pat. No. 3,725,925 / it is mentioned that the receiving amplifier can be timed so that its gain factor during the transmission pulse interval is raised.

The object of the invention is to provide a range finder To propose of the type mentioned above, with which a pulse transit time measurement for short and long transmission pulses Transmission pulse pauses in a wide range of distances is possible.

According to the invention, the above object is achieved in that Each transmission pulse switches a further pulse train to a pulse counter, the pulse train frequency of which is higher than the frequency of the transmission pulse sequence that the counter reading is passed to an evaluation circuit, that a control circuit forms a control variable from the counter reading, which is the square of the counter reading and possibly includes a correction value for the input voltage dependency of the gain factor, that the control variable is converted into a control voltage that controls the gain of the receiving amplifier, that the receiving amplifier when receiving a pulse

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the pulse counter stops and that the pulse counter is reset when a transmission pulse occurs.

The pulse counter is switched on at the same time as a transmission pulse is emitted «In the course of the As the counter runs up, the gain of the amplifier is proportional to the square of the respective Counter reading increased. If the dependence of the gain factor on the input voltage is non-linear is, this non-linearity is also taken into account when increasing the gain factor.

As soon as a receive pulse occurs, the amplifier is there set to an amplification factor that ensures the necessary amplification of the received pulse. When the receive pulse is received, the Counter stopped. The end value of the counter is a measure of the distance traveled by the pulse to and from the target.

The pulse repetition frequency of the pulse train incrementing the counter can be chosen so that the counter will ever Unit of the target distance, e.g. 1 dm each, incrementing by "1". The final counter reading is evaluated in the evaluation circuit.

If the rangefinder provide a readable display should, the pulse counter is followed by a digital display unit. If the rangefinder is in a Distance detonator is arranged, the counter reading is compared with a stored target value and if they match the ignition is triggered.

Further advantageous refinements of the invention emerge from the following description of an exemplary embodiment. In the drawing show:

Figure 1 is a circuit diagram of a range finder with a display unit as an evaluation circuit,

Figure 2 shows another evaluation circuit for the range finder and

Figure 3 is a timing diagram.

A generator 1 generates a transmission pulse sequence, the pulse duration being short, for example in the ns range, and the pulse pauses are long, for example in the s range. Such a pulse train is in Figure 3a shown. The generator 1 is followed by a transmission amplifier 2, which is an optoelectronic one

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Transmitter component charged. Instead of the optoelectronic transmission component, an electroacoustic transmission component operating in the ultrasonic range can also be provided.

The output of the generator 1 is connected to a gate circuit 3, which is located between a further pulse generator h and a digital counter 5. The generator h generates a pulse train, the frequency of which is significantly higher than that of the transmit pulse train (see FIG. Jb). When a transmission pulse occurs, this closes the gate circuit 3 so that the generator k is connected to the counter 5. - 5 -

The counter 5 is followed by a programmable fixed memory module (PROM) 6. Such a module is known, for example, under the type designation CDP 1833 C from Hughes. The PROM 6 is a digital / Analog converter 7 connected downstream, its analog output is connected to that input of a receiving amplifier 8 at which its gain factor can be adjusted. At the input of the receiving amplifier there is a receiving component 9, which is connected to the transmitting component 3 is equivalent to.

The output of the receiving amplifier is connected to the gate circuit 3 via a pulse shaper stage 10 in such a way that an output pulse from the pulse shaper stage 10 opens the gate circuit 3 and thus interrupts the connection between the generator k and the counter 5.

In the exemplary embodiment according to FIG. 1, the counter is followed by a digital display unit 11.

The programmable read-only memory module 6 is like this programmed that it forms a control variable from the respective counter reading, which is proportional to the square of the counter reading. In addition, the programming can make the gain factor dependent of the amplifier 8 can be compensated for by the receiving voltage. This dependency results from the data sheets of such a reception amplifier 8 (e.g. TBA ** 00 Siemens; MC 33 ^ 0 Motorola). The control variable that module 6 generates is a

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digital size. This is converted into a corresponding one in the converter 7 Analog value implemented.

It is therefore during the running of the counter 5 (cf. Figure 3d) i.e. during the course of the transmission pulse from the transmission component 2 'to the target and back to the receiving component 9 the gain of the receiving amplifier increases continuously. For larger distances between the rangefinder and target, the reflected pulse hits the higher gain factor set amplifier 8 than at shorter distances, with the quadratic decrease in the intensity of the pulse is taken into account with its running distance.

In order to achieve the simplest possible construction of the display unit, the frequency of the generator h is designed so that 0.5 pulses per lowest display position (dm, m) are counted, taking into account the speed of the signal pulse (speed of sound or speed of light). In the case of acoustic pulses, taking into account the speed of sound of 330 m / s and if the lowest decimeter is to be displayed, the result is a pulse repetition frequency of about 1.66 kHz for the generator 4. For light pulses, taking into account the speed of light, the result is

ability of 3. 10 m / s if the lowest point is meters should be displayed, a frequency of 150 MHz.

So that the counter starts counting again from zero with each transmission pulse, this is in the time between

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the arrival of the received pulse and the occurrence of the next transmission pulse is reset to its zero value. The falling edge of the Received pulse after the pulse shaper stage 10 is used will. In this case, the "up to then counted display" can be saved by means of a buffer memory of the next receive pulse can be maintained.

Is used to reset the counter 5, the increasing Edge of the transmission pulse at the output of generator 1 is used, then to close gate circuit 3, its falling edge is evaluated.

The circuit according to FIG. 2 can be used instead of the display unit if the target distance is not displayed, but an ignition process is to be triggered at a specific target distance. A comparison stage 12 is provided here, which is connected to the counter 5 and to which a setpoint generator 13 is arranged. The comparison stage 12 is followed by an ignition circuit Ik . If the counter reading agrees with the target value, the ignition circuit 14 is triggered.

A transmission pulse sequence is shown in FIG. 3a, the transmission pulse pause being approximately 2 s. Assuming that the pulse repetition frequency of the generator k (Figure 3b) is 1.65 kHz, then with a received pulse (Figure 3c 1) received after 1 s, 165Ο received pulses will have entered the counter 5 (cf.

Figure 3di). The display reads accordingly Display unit "165, O m". This ad is the same as that Distance of the rangefinder from the target, as the acoustic Impulse has run from the transmitter to the target and back in 1 s at a speed of 330 ms.

In Figure 3d, d1, the relationships are for themselves approaching target shown. In Figure 3c2 and 3d2 the relationships for a retreating target are shown, The upper limit of the detectable distance in the case of an acoustic pulse and the above-mentioned transmission pulse spacing is theoretically 330 m.

When using light pulses, the conditions change according to the speed of light and the then selected pulse repetition frequency of the generator h .

In the circuit described, it is also advantageous that, due to the digital counting, a time-temperature practically does not occur.

Claims (3)

Claims 1.) Electronic rangefinder for determination of a target distance, whereby a transmitter emits an optical or acoustic transmission pulse sequence, which after The reflection at the target reaches a receiving amplifier whose gain factor occurs during the transmission pulse interval is raised as a function of time, characterized in that each transmission pulse has a further pulse train activates a pulse counter (5) whose pulse frequency is higher than the frequency of the transmission pulse train that the count is passed to an evaluation circuit (11; 12) is that a control circuit (6, 7) forms a control variable from the counter reading, which is the square of the counter reading and, if necessary, a correction value for the input voltage dependency of the gain factor comprises that the control variable is converted into a control voltage the gain of the receiving amplifier (8) controls that the receiving amplifier (8) when receiving a Pulse stops the pulse counter (5) and that when a transmission pulse occurs, the pulse counter (5) is reset is. 2. Distance meter according to claim 1, characterized in that the pulse repetition frequency of the further Pulse sequence is chosen so that the pulse counter (5) advances by "1" per unit of the target distance. 3. Distance meter according to claim 1 or 2, characterized characterized in that the evaluation circuit is formed by a display unit (11). - 10 - DIEHL GMBH & CO., 85oo Nuremberg Electronic rangefinder Oils invention relates to an electronic range finder for determining a target distance at which a Transmitter an optical or acoustic transmission pulse sequence which after reflection at the target reaches a receiving amplifier, its gain factor during the transmission pulse intervals increased as a function of time will. In the case of rangefinders that detect the treadmill of a transmission pulse to and from the target, the received signals lie in a wide dynamic range. Due to the quadratic dependence takes the intensity of the received signals with the square of the distance traveled Signals from, so that when the measuring range of the rangefinder is designed for a factor of 100, the Receiving amplifier already receives signals with a k
Must handle dynamic range of 10. _ - ζ -