JP3022987U - Electronic control device for photoelectric rangefinder - Google Patents

Abstract

(57) Abstract: To manufacture a control electronic device for a rangefinder using an optical pulse delay time measuring method so as to enhance the accuracy of the measurement and at the same time make the advantages of the method effective. SOLUTION: The amplitudes of a start signal and a stop signal are directly measured. According to the measured amplitude, the control technology means can provide that the average value for the stop pulse is controlled to a target value, so that only stop pulses having an amplitude within a certain band are accepted for measurement, The amplitude of the start pulse is controlled to a constant magnitude for each measurement, so that always the same average value for the start pulse and the stop pulse is used for each distance measurement. The measurement is started according to the difference between the target value and the actual value, and individual measurement is suppressed or allowed.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 The present invention relates to an electronic control device provided in a photoelectric rangefinder in which direct measurement of the optical delay time of a short optical pulse is used for ranging.

[0002]

[Prior art]

 Traditionally, photoelectric rangefinders have been used for land surveying. The measurement principle of the photoelectric rangefinder is that the phase difference between the arriving light waves that are modulated in a sine shape, transmitted, reflected from a reflector placed at a distance, and arriving is estimated, and the distance is inferred from that. To do. With such a measurement method, an accuracy of ± 5 mm can be obtained in several kilometers. However, the drawback of this measurement method is that the measurement process is relatively complicated, and in this measurement method, the clarity of distance measurement is improved by the gradual modulation frequency change based on the periodicity of the possible phase difference. Need to get. Since this process is relatively long, the equipment used requires a maximum measurement time of 10 seconds. Moreover, such devices are only suitable for measurements on high quality reflectors at distances in excess of tens of meters. The pulse delay time measurement method is extremely suitable for a very large range and for distance measurement to a target having no reflector (passive distance measurement) for various reasons. When a laser, for example a pulsed diode laser (semiconductor laser), is used to generate the light pulses, the reach of the reflector or, in particular, the target with the function of passive reflection is greatly extended and the measuring time is Significantly reduced. However, in the past, it was not possible to obtain sufficient accuracy to use this method for land surveying.

[0003]

[Problems to be solved by the device]

 An object of the present invention is to manufacture a control electronic device for a rangefinder using an optical pulse delay time measuring method so as to enhance the accuracy of the measurement and at the same time make the advantages of the method effective.

The main reasons for hindering the above problems are that the laser light pulse is relatively high due to the high temperature dependence of the pulse-driven semiconductor laser, and the amplitude of the reflected signal is extremely high due to the influence of the atmosphere. And the final rise time of the optical pulse and the final bandwidth of the receiver cause significant error because the signal is not constant. Therefore, the emitted light pulse (start pulse) and the reflected and received light pulse (stop pulse) are always controlled to the same magnitude in a way that does not impair the measurement accuracy, and when the target value can be obtained. The premise is to confirm. In this case, the control range for the stop pulse exceeds tens of powers. This is because the near range in a high quality reflector gives a much larger reflection signal than the far range in a poor reflector or in reflection without a reflector.

The problem is solved according to the invention by the features of the characterizing part of claim 1. In the electronic control device of the present invention, it is premised that the start pulse and the stop pulse are received by the same light receiver. In this case, the receiver is essentially a highly photo-sensitive element that converts the received light into an electrical signal, such as a photodiode, control electronics for powering the photodiode, the automatic sensitivity of the photodiode or amplifier. It is composed of an interruptable circuit for control.

The light pulses emitted periodically in the measurement process are directed in the device to a small part, the diode, and the combined electrical pulse is amplified by an amplifier. Depending on the distance, the reflected signal arrives after a short delay and is also converted into an amplified electrical signal. Since the two pulses in the analog modulation range of the amplifier must always be controlled to a constant magnitude, the two pulses can be sent on separate lines and the amplitudes can be measured separately. In this case, the pulse has a pulse width of only a few nanoseconds, in order to ensure that the optical output power used does not lead to a dangerous range, despite the high pulse repetition rate, and is continuous. Since techniques such as direct analog-to-digital conversion are not suitable for the purpose, it is premised that it is because the short rise time and width of the pulse limits the blurring of the distance measurement in advance. .

[0007]

In an electronic control device for a photoelectric rangefinder using an optical pulse delay time measuring method, a small component (start signal) of short optical pulses periodically emitted at a constant time interval is used. Pulse) is directly directed to the receiver, and the light pulse (stop pulse) reflected from the object to be measured is delayed by the round-trip delay time and can be controlled by the receiver like the start pulse. Attenuated and directed two light pulses are converted by the receiver into two analog electrical pulses, namely a start pulse and a stop pulse, which are distance-dependent and closely spaced in time intervals. The amplitude of each of the start and stop pulses caused by the pulse pulses is generated before and during the actual measurement process in order to create the conditions necessary for ranging. Two pulses, which are measured directly by the sensor and, in particular, through the electrical output line from the photoreceiver, are converted by a comparator into a logic signal and sent to a time measuring device, while on the other hand another logic signal is generated. The logic signal inverts two analog switches (one of which was previously conducting and the other was blocked) immediately after the start pulse passed through the comparator, so that the comparator component The analog electrical pulse, which is sent parallel to the path either directly or via a buffer amplifier to the two analog switches and which is separated into two separate lines by the switching process, is in each case via a diode and by another analog switch. Each time it is integrated by each comparator discharged before the arrival of the pulse, it remains in the capacitor. The generated voltage represents the amplitude that is fixed by the two sample and hold circuits until the next pulse is emitted, and a new pulse is always emitted, so that a stepped voltage signal is generated at the output end of the sample and hold circuit. The amplitude of the stop pulse is controlled for the following reasons: that is, the average stop pulse signal amplitude is controlled to a constant average value for accurate distance measurement. Is provided in the optical path of the optical stop pulse, and thereby evaluated for driving a motor acting on a device that rotates or rotates an attenuation filter or a light shielding means that changes the amplitude of the optical stop pulse, And / or a comparator is used to determine the stop pulse amplitude by comparing the stepped voltage signal with a setpoint range for individual pulse emission. Stop to check if the amplitude is below a preset amplitude for distance and / or by comparing the averaged stepped voltage signal with a target value range or target value by a comparator. The amplitude of the start pulse is used to check whether the average value of the pulse amplitude is within the range required for distance measurement and to supply the start signal for the actual distance measurement process. , For receiving a control signal for controlling the sensitivity of the photoreceiver by comparing the stepped voltage signal with a preset reference value for the start pulse, by: And to control the sensitivity of the photodetector so that the target value and the actual value match within a narrow range.

[0008]

[Embodiment of device]

 Hereinafter, an embodiment of a control technology device for a photoelectric rangefinder using the optical pulse delay time measuring method of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of a control technology device for a photoelectric rangefinder.

The analog output signal 1 of the amplifier is sent via a comparator 2 and formed into a logic pulse 3, which on the one hand is sent to the actual ranging circuit 4 and on the other hand to a flip-flop. Sent to the clock input terminal 5 of 6. In the distance measuring circuit 4, the evaluation is performed for distance measurement based on the control of the start pulse and the stop pulse, but it will not be described further here. When sending a logic pulse 3, the output signal of the comparator 2, which must have an ECL compatible output stage based on a short pulse, is the flip-flop 6, which was reset beforehand, at the end of the first pulse or star. Pulse 7 is selected to be set at the trailing edge. The output signal of the flip-flop 6 is adapted in the amplifier stage 8 to control the high speed analog switches 9, 10 such that one switch opens while the other closes. After leaving the amplifier, the analog signal is sent to the two analog switches 9, 10 via the buffer amplifier 1A. For example, if one analog switch 9 is conducting and the other analog switch 10 is shut off, the start pulse will pass through the conductive analog switch 9, which will be closed immediately thereafter, At the same time, the stop pulse passes through the other analog switch 10 that is made conductive. After that, the signal is separated and further processed in two identical separated circuits. In that case, further amplification is first carried out, and then rectification is carried out in the passing direction by the diode 11. The small capacitor 12 is discharged by another analog switch 13 and then charged by the diode 11. The voltage remaining on capacitor 12 after rectifying the pulse on capacitor 12 is a measure for the pulse amplitude. This voltage is fixed in the sample-and-hold circuit 14 where it remains as a stepwise voltage signal which represents the amplitude of the pulse at each moment and which changes in synchronization with the emitted measuring pulse. After the start pulse is issued, the stop pulse must have arrived after a certain time corresponding to the maximum coverage. Otherwise, it is not possible to evaluate each individual measurement (provided that the actual measurement process has already started). The signal responsible for such monitoring can be used to control the sample-and-hold circuit 15 and subsequently to erase the capacitor 12 (at reference numeral 16) by the analog switch 13, so that the amplitude measuring circuit after any individual measurement. Is released for the next measurement, and the measured amplitude value remains until the arrival of the next pulse.

This allows a stepped voltage signal, which represents the amplitude of the individual pulses, to remain due to the start and stop pulses until the arrival of the next pulse for the next individual measurement, for control. Will be used for.

It is important to measure every pulse directly. The start pulse stepped voltage signal is sent to the operational amplifier 17 and compared with the target value 18. If, for example, an avalanche photodiode (APD) 20 is used, the thermally stabilized bias of the photodiode in circuit 22 is the output of the comparator or operational amplifier until the target value and the measured actual value match. It is changed by the signal. At the same time, the temperature change caused in the laser 19 by the ambient temperature or the leakage power and the change caused by the aging of the laser or the light receiver are adjusted. If an APD is used, the bias 21 of the APD is pre-thermally stabilized so that the internal gain of the diode remains constant with temperature in circuit 22, as is well known. By controlling the start pulse, the sensitivity can be controlled to a lower value (by temperature stabilization of the APD) from a pre-adjusted and maximally acceptable sensitivity. Since the output power of the laser decreases as the temperature rises, by increasing the component of the optical pulse emitted and guided to the photodiode as a start pulse corresponding to the temperature, when the setting of the target value is constant, Since the control is forced from the beginning to a value below the maximum sensitivity, a sufficient control range is ensured in all cases. When manufacturing a rangefinder, the components are thus adjusted once.

The start pulse stepped voltage signal is used for three control technical purposes. First, it is used to control the stop signal to a predetermined target value. Secondly, in each of the individual measurements it is determined whether the difference between the target value and the actual value does not exceed a certain magnitude. Third, the actual measurement process is initiated when the target value and the average of the actual values are the same for a given time. The variation range of the stop pulse oscillation differs significantly from the variation range of the start pulse oscillation in the above-mentioned various reflectivities of the target and the distance. Furthermore, the stop pulse is under the influence of the atmosphere, and the atmosphere may cause a vibration change of several tenth power or more due to the density change and the beam deviation. For this reason, first of all, the start pulse stepped voltage signal is compared with the target value 24 by the operational amplifier 23 and the difference is amplified and averaged by the operational amplifier 25 in order to control the motor 26 below. Used. This motor 26 puts an attenuation filter 27 or a light shielding means in and out of the optical path for the stop pulse to control the stop pulse to a target value. Since atmospheric effects are a statistical process, only the mean value is thus controlled accordingly. This is because amplitude fluctuations have frequency components that are too high to be controlled by the motor 26, as shown by studies on atmospheric effects. The averaged start pulse stepped voltage signal also conveys information by comparison with an accurately adjusted reference voltage by two comparators 28. That is, a signal 30 having an excessively large amplitude, a signal 32 having an excessively small amplitude, and a signal 31 having an appropriate amplitude. Since the information is properly displayed to the user, the user can easily aim the rangefinder at the target. If a signal of suitable amplitude has been generated for a certain time (ie, greater than the motor control time constant), the actual measurement process is automatically started at 31.

In another circuit, the window comparator 34 checks whether the start pulse stepped voltage signal is suitable for distance measurement and is within the range preset by the reference voltage 33. The evaluation signal 35 generated in this way is used by the distance measuring circuit 4 to cancel individual measurements made by amplitude values which are not adjusted sufficiently accurately. Thus, the effect on the measurement accuracy caused by terrible disturbances in pedestrians, moving cars, leaves or the atmosphere, i.e. any disturbances that prevent direct visual connection with the reflector, is measured only by the interruption time. It can be easily eliminated by extension.

Various preferred embodiments of the electronic control device according to the invention as well as the subject matter of the dependent claims are conceivable.

FIG. 2 is a schematic representation of an optical system which is suitable for control technology equipment and which is particularly suitable for measuring very short distances.

The time to connect the start pulse and the stop pulse to separate lines, and subsequently to be free to measure the amplitude, can be several centimeters to several centimeters, especially when the pulse width of the light pulse exceeds the light delay time. It is too short for measurements in the range of a few meters, so that if a separate light path is preferably provided for the sender 36 and the receiver 37, it is contactless to the light source 39 and is also formed as a roll and behind the output end. The start pulse 38 is generated by the light pulse sent through the glass fiber section 40 being delayed beyond the pure light delay time to and from the target and by the time difference available to the control technology device of the present invention. It

FIG. 3 is a circuit diagram showing a second embodiment of the present invention, which is the same as the first embodiment except that there are two light receiving elements.

FIG. 4 is a schematic view showing a second embodiment of the present invention. Since there are two light receiving elements, only one beam splitter is required, and the angle of the reflected start pulse can be made small, so the device can be downsized.

[0020]

[Effect of device]

 In summary, the following advantages arise.

The separate measurement of the pulse amplitudes of the start pulse and the stop pulse leads to the always same premise for any ranging with simple control technology means.

The processing of the start pulse and the stop pulse does not differ so that the transit delay times of both pulses passing through the light receiver are the same.

In order to prevent the measurement accuracy from deteriorating even if there are statistical fluctuations in amplitude and interference with direct visual connection with the reflector, each measurement must meet the conditions for measuring amplitude. Immediately check whether or not there is.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a control technology device for a photoelectric rangefinder.

FIG. 2 is a diagram showing a configuration of an optical system suitable for measuring a short distance.

FIG. 3 is a circuit diagram showing a second embodiment;

FIG. 4 is a configuration diagram showing a second embodiment.

[Explanation of symbols]

 2 comparator 4 time measuring device 7 start pulse 9 analog switch 10 analog switch 11 diode 12 comparator 13 analog switch 14 sample hold circuit 1A buffer amplifier

Claims (10)

[Scope of utility model registration request] 1. An electronic control device for a photoelectric rangefinder using an optical pulse delay time measuring method, wherein a small component (start pulse) of a short optical pulse periodically emitted at a fixed time interval is received. A light pulse (stop pulse), which is directed directly to the receiver and reflected from the object to be measured, is delayed by the round-trip delay time and is controllably attenuated to the receiver, just like the start pulse. A start pulse produced by the conversion of two light pulses by the receiver into two analog electrical pulses, namely a start pulse and a stop pulse, which are distance-dependent and closely continuous in time intervals; The amplitude of each stop pulse is measured directly by each pulse emission in order to create the necessary conditions for ranging before and during the actual measurement process. In particular, the two pulses sent from the photoreceiver through the electrical output line are converted into a logic signal by the comparator 2 and sent to the time measuring device 4, which on the other hand is used to generate another logic signal. The logic signal inverts the two analog switches 9 and 10 (one of which has been previously conducted and the other of which has been blocked) immediately after the start pulse has passed through the comparator, so that the comparator circuit is shunted. In parallel, the analog electrical pulse, which is sent directly or via the buffer amplifier 1A to the two analog switches 9, 10 and which is separated into two separate lines by the switching process, is in each case connected via a diode 11 to the other. The analog switches 13 integrate the respective comparators 12 discharged before the arrival of the pulse each time, and The voltage remaining in the sampler represents an amplitude that is fixed by the two sample and hold circuits 14 until the next pulse is emitted, and a new pulse is constantly emitted, so that the output terminal of the sample and hold circuit has a stepped voltage. The signal is generated, the amplitude of the stop pulse is controlled for the following reasons: the average stop pulse signal amplitude is controlled to a constant average value for accurate distance measurement, and more specifically, the corresponding step voltage. A signal is provided in the optical path of the optical stop pulse, whereby it is evaluated for driving a motor acting on a device for rotating or rotating an attenuation filter or a shading means for changing the amplitude of the optical stop pulse, And / or by means of a comparator, by comparing the stepped voltage signal with a setpoint range for individual pulse generation, the stop pulse amplitude Stop by checking if it is below a preset amplitude for ranging and / or by comparing the averaged stepped voltage signal with a target value range or value by a comparator The amplitude of the start pulse is used to check whether the average value of the pulse amplitude is within the range required for distance measurement and to supply the start signal for the actual distance measurement process. To receive a control signal for the sensitivity control of the receiver, by comparing the stepped voltage signal with a preset reference value for the start pulse by: by means of an operational amplifier or a comparator , And used for controlling the sensitivity of the photodetector so that the target value and the actual value match within a narrow range. Apparatus. 2. The photoelectric distance measuring device according to claim 1, wherein there are two light receivers, and the start pulse is directed to one of the two light receivers and the stop pulse is directed to another one of the light receivers. Electronic control device for the purpose. 3. A high speed ECL compatible comparator at the output is used as comparator 2, the inverted output of which is an ECL compatible flip-flop 6.
To the flip-flop 6, which is set at the trailing edge of the start pulse 7 converted into a logic signal, by means of a suitably adapted complementary output signal of the flip-flop 6 via a level limiter element 8. 2. The photoelectric rangefinder according to claim 1, wherein the analog switches 9 and 10 are controlled when the trailing edge of the start pulse has just passed through the analog switch 9 at that time. Electronic control unit. 4. A clock periodically causes a logic signal to be generated, which logic signal causes an optical pulse to be emitted and derived therefrom within a predetermined time which is less than the time to emit the next optical pulse. Whether the stop signal arrives and is used for the following: after this predetermined time corresponding to the maximum measuring distance, the positively remaining voltage value is integrated into the integration capacitor 1
By controlling the sample hold circuit 14 undertaken by 2,
A signal is formed to monitor whether or not a continuous stepwise voltage signal for the start pulse and the stop pulse is used for remaining at the output of the sample and hold circuit. An electronic control device for the photoelectric ranging device according to claim 1. 5. The comparator or operational amplifier 17 sets the stepped voltage signal of the start pulse to a target value 1
8 and the bias averaged by the low-pass filter for the avalanche photodiode 20 of the photodetector is the output power of the operational amplifier 17 until the target value and the actual value of the start pulse amplitude match within a narrow range. The electronic control device for a photoelectric range finder according to claim 1, wherein the electronic control device is controlled by. 6. The step voltage signal of the stop pulse is compared with a target value range by a window comparator 34, and the "amplitude too large, amplitude too small" signal 35 is generated in the ranging circuit 4 by the relevant individual 2. The electronic control device for a photoelectric rangefinder according to claim 1, wherein the measurement of is suppressed. 7. The output signal of the operational amplifier 23, which is averaged by a low-pass filter, is compared with a target value range of the stop pulse 29 by two comparators 28, and "amplitude is too large, amplitude is too small, The "appropriate in amplitude" signals 30, 31, 32 are properly displayed on the rangefinder to enable the operator to aim the rangefinder at a target. Item 2. An electronic control device for a photoelectric rangefinder according to Item 1. 8. A signal 31 in which the amplitudes of stop pulses in a target value range are averaged is integrated, and the integrated voltage is converted into a logic signal by a comparator or operational amplifier so that the integrated voltage is constant. 2. The photoelectric rangefinder according to claim 1, characterized in that it exceeds the value of, and the logic signal formed therefrom is used in the range finding circuit 4 for initiating the range finding process. Electronic control unit. 9. A glass fiber coupled, pulse driven light source, preferably a glass fiber coupled semiconductor laser diode is used as an optical transmission element,
The stop pulse is compared to the start pulse because the optical start signal 30 is split at the coupling point and sent to the receiver, while the sent optical pulse must still pass through the glass fiber portion 40. 2. The electronic control device for a photoelectric rangefinder according to claim 1, wherein the optical control device is delayed beyond the optical delay time for going back and forth. 10. The optical device part can be separated from the electronic device part by a design in which the light source and the photodiode are coupled by a glass fiber, and the glass fibers 40, 41 couple the two device parts. By being formed as an optical transmission cable,
An electronic control device for a photoelectric rangefinder according to claim 1, wherein: