JP3141119B2 - Pulse signal detector and light wave distance meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises conversion means for converting an input pulse signal into a damped oscillation waveform, detects cross points with respect to a threshold level of the damped oscillation waveform, and detects a plurality of detected cross points. The present invention relates to a pulse signal detection device that detects reception timing from at least two cross points among points, and more particularly to a pulse signal detection device that is optimal for detecting a reception timing signal of an optical distance meter.

[0002]

2. Description of the Related Art A pulse type light wave distance meter using a pulse laser diode (PLD), which is a semiconductor laser, as a light source obtains the center of gravity of a received light pulse by a method as shown in FIG. ing.

That is, the pulse light (a) reflected from the object to be measured is received by the light receiving element, and becomes a damped oscillation waveform (b) by the tuning amplifier. The damped oscillation waveform can be obtained by appropriately setting the Q of the tuning amplifier. In order to obtain a reception timing signal corresponding to the position of the center of gravity of the pulse light (a) from the damped oscillation waveform (b), a reception timing detection circuit including two comparators, a first comparator and a second comparator, is required. I'm using The reception timing detection circuit, a first comparator portion of b ₂ in the damped oscillation waveform (b) capturing the threshold level V _S1 to confirm the light reception for a period of time H
An output signal (c) of high is output. The second comparator determines that the first comparator is Hi.
During the period of gh, it is in an active state, the threshold level is set to V _S2 (0 V), and a portion b ₃ of the damped vibration signal (b) is captured to output an output signal (d). ing. And as the reception timing signal,
It has been adopted a rising portion or falling portion of the output signal (d), in general, in most cases to use the rising portion d ₁ of the output signal (d).

[0004] This reception timing detection circuit provides an attenuated oscillation waveform (b) even if the peak value of the pulse light (a) fluctuates due to fluctuations in the air, if the position of the center of gravity does not change.
Does not change, the timing of the waveform of the output signal (d) of the second comparator does not change.

[0005]

However, when the offset of the second comparator fluctuates due to an external factor such as a temperature change, the threshold level V _S2 also fluctuates, and the reception timing detection circuit described above has a problem in that the accuracy of the distance measurement is reduced. There was a fatal problem of adverse effects. That is, offset adjustment of the comparator is required, and this zero-point adjustment is troublesome. In addition, it is necessary to use an expensive comparator having excellent temperature characteristics, which is extremely expensive.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above problems, and has a light receiving means for converting a pulse light into a pulse signal, and a conversion means for converting the pulse signal into a damped oscillation waveform. Means and a reception timing detecting means for capturing a cross point of the damped oscillation waveform and outputting a light reception timing signal. The reception timing detection means averages the received oscillation waveform of the received one pulse light. It is characterized by outputting at least two reception timing signals forming data.

Further, a lightwave distance meter according to the present invention comprises a light source for emitting pulsed light, optical means for transmitting light from the light source to an object to be measured, and conversion of the pulsed light into a pulse signal. Light receiving means for converting the pulse signal into a damped oscillation waveform, and a receiving timing detecting means for capturing a cross point of the damped oscillation waveform and outputting a light reception timing signal, In a light wave distance meter for measuring a distance to a measurement object by a time difference from light emission of the light source unit to the light receiving timing signal, the receiving timing detecting means includes: The distance measurement is performed by outputting a light reception timing signal and averaging distance measurement data formed based on the plurality of light reception timing signals. And it has a configuration.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention constructed as described above
The light receiving means converts the pulse light into a pulse signal, the converting means converts the pulse signal into an attenuated vibration waveform, and the receiving timing detecting means captures a cross point of the attenuated vibration waveform, outputs a light receiving timing signal, and receives the receiving timing. The detection means can output at least two reception timing signals forming data to be averaged from the received decay oscillation waveform of the one-pulse light.

Further, according to the present invention, the light source unit emits pulse light,
The optical means sends light from the light source unit to the object to be measured, the light receiving means converts the pulse light into a pulse signal, the converting means converts the pulse signal into an attenuated vibration waveform, and the receiving timing detecting means Detects the cross point of the attenuated vibration waveform, outputs the light reception timing signal, and uses the time difference between the light emission timing of the light source unit and the light reception timing signal to measure the distance to the measurement object. The detecting means measures a distance by outputting a plurality of light reception timing signals from the received decay oscillation waveform of one pulse light and averaging distance measurement data formed based on the plurality of light reception timing signals. Can be.

[0010]

An embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the pulse detection device of the present invention comprises a tuning amplifier 160 and a reception timing detection circuit 17.
0 and arithmetic processing means 1000. The tuning amplifier 160 converts an input current pulse train into a voltage signal, converts it into a damped oscillation waveform, and performs inversion amplification. The reception timing detection circuit 170 includes a first comparator 171, a second comparator 172, a one-shot vibrator 173, a rising edge detector 174, and a falling edge detector 175. As shown in FIG. 2, the first comparator 171 has a threshold level V _S1 , confirms the input of an input pulse, and activates the second comparator 172 having a threshold level 0 V for a certain time. Has become. Then, the second comparator 172 captures two cross points of the damped oscillation waveform with 0 V and outputs a reception timing signal. A rising edge detector 174 and a falling edge detector 175 are connected to the output side of the second comparator 172, and the output signals of the rising edge detector 174 and the falling edge detector 175 are calculated by the arithmetic control unit 1000. It is sent to. And the arithmetic processing means 1000
Obtains the average of d ₂ detected by the edge detector 175 falling and d ₁ detected by the rising edge detector 174, which is the average value as a timing signal of a received pulse. The cross point of the damped oscillation waveform with 0 V is not limited to two points, but two or more points can be measured and their average value can be used.

Next, an embodiment of a lightwave distance meter using the pulse detection device of the present invention will be described with reference to FIGS.

As shown in FIG. 3, the optical distance meter according to the present embodiment includes a laser diode 1, a condenser lens 2, a condenser lens 3, and a pair of split prisms 41 and 42.
, Optical path switching chopper 5, internal optical path 6, APD
71, an optical fiber 8, a prism 9, and an objective lens 10. And corner cube 11
Corresponds to an object to be measured arranged at a position distant from the main unit of the electro-optical distance meter, and has a function of reflecting an optical pulse.

Laser diode 1 and condenser lens 2
1, 22, light emitting side optical fiber 81, and split prism 41
, The prism 9 and the objective lens 10 correspond to optical means.

The laser diode 1 corresponds to a light source unit. The laser diode 1 of this embodiment employs a pulse laser diode, has a relatively large peak power, and has a duty ratio of about 0.01%. Waves can be generated. The optical path switching chopper 5 divides a light beam. The APD 71 corresponds to a light receiving means, and any element capable of receiving the pulse light emitted from the laser diode 1 is sufficient.

The splitting prism 41 includes a first half mirror 411 and a second half mirror 412, and the splitting prism 42 includes a first half mirror 421 and a second half mirror 422. I have. The optical fiber 8 includes a light emitting side optical fiber 81 and a light receiving side optical fiber 82.

When a light emission pulse train is emitted from the laser diode 1, the light emission pulse train is coupled to the input end 81 a of the light emitting side optical fiber 81 by the condenser lenses 21 and 22. The light emission pulse train emitted from the output end 81 b of the light emission side optical fiber 81 is sent to the split prism 41. The pulse train transmitted through the first half mirror 411 of the split prism 41 can be emitted to the external distance measuring optical path via the optical path switching chopper 5. The light is reflected by the first half mirror 411 of the splitting prism 41 and further reflected by the second half mirror 4.
The pulse train reflected by 12 is transmitted to the optical path switching chopper 5
The light can be emitted to the internal distance measuring optical path 6 via. The optical path switching chopper 5 is for switching between the internal ranging optical path 6 and the external ranging optical path. Therefore, when the optical path switching chopper 5 selects the external distance measuring optical path, the pulse train is reflected by the prism 9 and then emitted to the outside by the objective lens 10.

The pulse train emitted from the objective lens 10 is reflected by the corner cube 11, and is again returned to the objective lens 1.
The light is received at 0 and sent to the prism 9. The received pulse train is reflected by the prism 9 and sent to the splitting prism 42, and the received pulse light transmitted through the first half mirror 421 of the splitting prism 42 is coupled to the light receiving end 82 a of the light receiving side optical fiber 82.

When the optical path switching chopper 5 selects the internal distance measuring optical path 6, the emission pulse train is sent to the split prism 42 through the internal distance measuring optical path 6. The light pulse train is reflected by the first half mirror 421 and the second half mirror 422 built in the split prism 42,
The light receiving end 82a of the light receiving side optical fiber 82 is coupled to the light receiving end 82a.

The emitting end 8 of the light receiving side optical fiber 82
The light pulse train emitted from 2b is
It is designed to bind to APD71 by 1, 32,
The APD 71 converts the current pulse into a current pulse.

Next, the configuration of the electric circuit of this embodiment will be described in detail.

(First Embodiment)

The first embodiment shown in FIG.
0, the first frequency divider 110, the synthesizer 120, and the second
Frequency divider 130, timing circuit 140, laser diode 1, laser diode driver 150, and APD 7
1, tuning amplifier 160 and reception timing detection circuit 170
, A counter 180, a peak hold circuit 190, a level determination circuit 200, a band pass filter 210, a sample / hold (S / H) 220, a switch 230, an AD converter 300, a memory 400, and a CPU 500.

The crystal oscillator 100 is one of the reference signal generating means, and generates a 15 MHz reference signal.
This reference signal is supplied to a first frequency divider 110, a synthesizer 130, a bandpass filter 210, and a counter 180. The reference signal supplied to the first frequency divider 110 is divided by the first frequency divider 110 into 1/100 to be 150 KHz and sent to the synthesizer 120. The synthesizer 120 generates 15.15 MHz from the 150 KHz supplied from the first frequency divider 110 and the 15 MHz supplied from the crystal oscillator 100, and sends the 15.15 MHz to the second frequency divider 130. Second frequency divider 13
0 is 15.15 supplied from synthesizer 120
The frequency is divided into 1/50 to produce 303 KHz, which is sent to the timing circuit 140. Note that the first frequency divider 110, the second frequency divider 130, the synthesizer 12
The output signal of 0 is a binarized signal.

The timing circuit 140 sends a pulse laser emission timing signal to the laser diode driver 150, and the timing circuit 140 sends a reset signal to the peak hold circuit 190 having a damped oscillation waveform. I have. Note that the pulse laser emission timing signal and the reset signal for the peak hold circuit 190 are both signals repeated at 3030 Hz.

Then, the laser diode driver 15
0 drives the laser diode 1 in a pulsed manner according to the pulsed laser emission timing signal of the timing circuit 140. Therefore, the laser diode 1 has a cycle of 1 /
Emit a 3030 Hz pulsed light beam.

The light pulse emitted from the laser diode 1 passes through the optical system and is received by the APD 71. The APD 71 is one of the light receiving elements 7, and is a diode that can apply a deep bias to a pn junction to induce a nasal multiplication and obtain a gain. The APD 71 receives an optical pulse that has passed through the internal reference optical path and an optical pulse that has passed through the external ranging optical path. The light pulse is converted into an electric signal of a current pulse train by the APD 71 and sent to the tuning amplifier 160.

The tuning amplifier 160 converts the current pulse train from the APD 71 into a voltage signal, converts it into a damped oscillation waveform, and performs inversion amplification. Tuning amplifier 16
The damped oscillation waveform formed at 0 is supplied to the reception timing detection circuit 170 and the peak polled circuit 190.

The reception timing detection circuit 170 includes a first comparator 171, a second comparator 172, a one-shot vibrator 173, and a rising edge detector 1.
74 and a falling edge detector 175. The first comparator 171 has a threshold level V _S1 , captures and confirms the reception of the light pulse, and activates the second comparator 172 having a threshold level of 0 V for a certain time. Then, the second comparator 172 captures two cross points of the damped oscillation waveform with 0 V and outputs a reception timing signal. The rising edge detector 174 and the falling edge detector 175 are connected to the output side of the second comparator 172, and the output signal of the rising edge detector 174 is sent to the first sample and hold circuit 221. The output signal of the falling edge detector 175 is supplied to the second sample and hold circuit 222.
To be sent out. The cross point between the damped oscillation waveform and 0 V may be detected at two or more points.

The 15 MHz transmitted from the crystal oscillator 100 to the band-pass filter 210 becomes a sine wave and is transmitted to the first sample-hold circuit 221 and the second sample-hold circuit 222. Then, the first sample and hold circuit 221 performs sample and hold based on the output signal of the rising edge detector 174, and the second sample and hold circuit 222 performs sample and hold based on the output signal of the falling edge detector 175. I have. The waveform signal sampled and held by the sample and hold circuit 221 and the second sample and hold circuit 222 is
0, and the switching unit 230 is switched according to a switching signal from the CPU 500. The waveform signal switched by the switch 230 is AD-converted by the AD converter 300, and the converted digital data is stored in a predetermined memory 400. When the AD conversion ends, a conversion end signal is output to the CPU 500.

The output signal of the rising edge detector 174 is also supplied to the counter 180. The counter 180 has 15 MHz from the crystal oscillator 100.
Is supplied, and counts until a signal from the rising edge detector 174 is input.
This count value is sent to the CPU 500 and is set as a coarse measurement distance value. The oscillation frequency of the crystal oscillator 100 is 1
Since it is 5MHz,

(C / 15 MHz) / 2 = 10 m (C = light speed)

Thus, one clock becomes 10 m.

The damped oscillation waveform sent from the tuning amplifier 160 to the peak hold circuit 190 is peak-held by the peak hold circuit 190 and becomes a DC level signal corresponding to the peak value of the damped oscillation waveform.
Sent to 0. The level determination circuit 200 receives the signal from the peak hold circuit 190, and determines that the light amount of the light receiving pulse train is A
It is determined whether or not the PD 71, the tuning amplifier 160, and the reception timing detection circuit 170 are in a proper operating range, and the result is sent to the CPU 500. CPU5
00 is a counter 18 only when the signal from the level determination circuit 200 is received and the light amount of the light receiving pulse train is an appropriate value.
The counter value from 0 and the data from the AD converter 300 are adopted.

Further, the peak hold circuit 190 is reset every time a light emission pulse train is emitted by a reset signal from the timing circuit 140, so that the amount of light can be determined each time an emission pulse is emitted. Therefore, it is possible to minimize the adverse effect due to the fluctuation of the received light amount due to the fluctuation of the air between the main body of the lightwave distance device and the object to be measured.

15 MH sent from crystal oscillator 100
The sine wave obtained by passing z through the band-pass filter 210 and the light emission frequency of 3030 Hz of the laser diode 1 are slightly shifted. For this reason, the phase relationship between the reception timing signal and the sine wave obtained through the band-pass filter 210 also slightly deviates. This phase shift amount is

(1/3030 Hz) / (1/15 MHz) = 4950 + (50/101)

And becomes "50/101".

Each light emission pulse train and the band pass filter 2
The phase relationship with the sine-wave sine-wave signal obtained through 10 is a phase relationship in which 101 cycles constitute one cycle.
The second light emission pulse train has the same phase relationship as the first light emission pulse train. Therefore, the sample hold (S /
H) The output signal of 220 is

F = 3030 Hz / 101 = 30 Hz

Thus, one cycle is completed. Since the phase shift amount between the reception timing signal and the output signal of the bandpass filter 210 is “50/101”, the output signal of the sample hold (S / H) 220 does not become a sine wave,
By performing the rearrangement at the stage of storing in the memory 400 after the A / D conversion, when the abscissa is the address on the memory 400 and the ordinate is the A / D conversion value data, the sine wave A / D conversion data can be created. . Further, the sample-and-hold data and the A / D-converted data by the light emission pulse train after the 102nd time are the data after the second cycle of 30 Hz. Therefore, if the judgment result of the level judgment circuit 200 is appropriate, the data of the previous cycle is obtained. And then averaging the data to improve the accuracy of the A / D converted data.

The first sample hold circuit 221
Using the AD conversion data obtained by the above and the AD conversion data obtained by the second sample-and-hold circuit 222, a phase is obtained by performing a Fourier transform on each data, and an operation of averaging this value is performed. It is configured to use this average value.

The laser diode 1 executed as described above
From the emission of light to the storage of the AD-converted data in the memory 400 are performed for the external distance measuring optical path and the internal reference optical path. The AD conversion data of the internal reference optical path is compared with the AD conversion data of the external distance measuring optical path, and the phase difference φ between the two waveforms corresponds to the optical path difference. Fourier transform is performed on each waveform to obtain phase information of the fundamental component wave, and a precise measurement distance of 10 m or less can be obtained from the phase difference. Note that the coarse measurement distance is also 1 from the difference between the counters of the counter 180 in the external distance measuring optical path and the internal distance measuring optical path.
It can be obtained with an accuracy of 0 m. Then, by combining the coarse measurement distance and the precision measurement distance, the actual distance from the optical distance meter to the object to be measured can be obtained.
A configuration for performing these operations corresponds to a distance measuring unit.

Note that the precise measurement distance is obtained by performing a Fourier transform on the AD-converted data value to obtain the phase of the fundamental wave component. Therefore, the waveform to be sampled and held does not necessarily have to be a sine wave. It may be a wave or a triangular wave. Similarly, a low-pass filter can be employed instead of the band-pass filter 210.

In the first embodiment configured as described above, the AD sample obtained by the first sample and hold circuit 221 is used.
The conversion data and the AD conversion data obtained by the second sample-and-hold circuit 222 are used to perform a Fourier transform on each of the data to determine the phase and average the values. There is an excellent effect that the offset of the second comparator 172 of the timing detection circuit 170 can be removed.

(Second Embodiment)

Next, a second embodiment will be described with reference to FIG. In the first embodiment, the first sample and hold circuit 2
21 and a second sample-and-hold circuit 222. The first sample-and-hold circuit 221 performs sample-and-hold by an output signal of the rising edge detector 174, and the second sample-and-hold circuit A sample and hold 222 is performed by the output signal of the falling edge detector 175.
The signal after the sample hold is switched by the switch 230.

In the second embodiment, the sample and hold circuit 22 is used.
Using only one 0, the output signal of the rising edge detector 174 and the output signal of the falling edge detector 175 are switched by the switch 230, and the switched output signal is sent to the sample and hold circuit 220. Have been.

The second embodiment has a disadvantage that the same damped oscillation waveform cannot be measured when measuring the rising edge and the falling edge. However, if the measurement is performed alternately in a short time, the first embodiment will be described. There is an effect that the same operation as can be performed. The other configuration and operation are the same as those of the first embodiment, and thus the description is omitted.

[0050]

According to the present invention having the above-described structure, a light source for emitting pulse light, optical means for transmitting light from the light source to an object to be measured, and a pulse signal Light receiving means for converting the pulse signal into a damped oscillation waveform, and reception timing detecting means for capturing a cross point of the damped oscillation waveform and outputting a light receiving timing signal. A time difference from the light emission of the light source unit to the light receiving timing signal, in a light wave distance meter for measuring the distance to the object to be measured, the receiving timing detecting means, from the attenuation oscillation waveform of the received one pulse light, The distance is measured by outputting a plurality of light reception timing signals and averaging distance measurement data formed based on the plurality of light reception timing signals. Since a configuration, when performing detection of the received timing signal, using both the rising portion and the falling portion, it is possible to use the average value,
There is an excellent effect that errors due to fluctuations in the optical distance meter can be removed.

[0051]

[0052]

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating detection of a reception timing signal according to the embodiment;

FIG. 3 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating detection of a conventional reception timing signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode 2 Condenser lens 3 Condenser lens 41 Split prism 42 Split prism 5 Optical path switching chopper 71 APD 8 Optical fiber 9 Prism 10 Objective lens 11 Corner cube 160 Tuning amplifier 170 Reception timing detection circuit 171 First comparator 172 Second comparator 173 One-shot vibrator 174 Rising edge detector 175 Falling edge detector 180 Counter 190 Peak hold circuit 220 Sample hold circuit 230 Switcher 300 AD converter 400 Memory 500 CPU 1000 Arithmetic processing means

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masaaki Yabe 75-1, Hasunuma-cho, Itabashi-ku, Tokyo Topcon Corporation (72) Inventor Yasutaka Katayama 75-1, Hasunuma-cho, Itabashi-ku Tokyo, Japan 72) Inventor Kazushige Koshikawa 75-1, Hasunuma-cho, Itabashi-ku, Tokyo Inside Topcon Corporation (56) References JP-A-57-190281 (JP, A) JP-A-2-181689 (JP, A) Hei 1-135378 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /48-7/51 G01S 17/00-17/95

Claims (2)

(57) [Claims] 1. A method for converting pulse light into a pulse signal.
Light receiving means and converting this pulse signal into a damped oscillation waveform
Conversion means and a cross point of the damped oscillation waveform.
A reception tie for capturing and outputting a light reception timing signal
Mining detecting means is provided.
The output means calculates the average from the damped oscillation waveform of the received one-pulse light.
At least two reception times forming data to be averaged
A pulse signal detection device for outputting a pulse signal. 2. A light source unit for emitting pulsed light,
Light for transmitting light from the light source unit to the measurement target
And light receiving to convert pulsed light to pulsed signal
Means for converting this pulse signal into a damped oscillation waveform
And a cross point of the damped oscillation waveform
Receiving timing for outputting a light receiving timing signal
From the light emitted from the light source unit.
Due to the time difference to the timing signal,
In a lightwave distance meter for measuring a distance, the receiver
The imming detecting means is configured to perform a damped oscillation of the received one-pulse light.
A plurality of light reception timing signals are output from the waveform,
Distance measurement based on the number of light reception timing signals
Measuring distance by averaging data
Characteristic lightwave distance meter.