JPH0666940A - Laser length measuring apparatus - Google Patents

Abstract

PURPOSE: To realize a highly accurate measurement of length by performing precise correction and measurement of time difference using a plurality of digital programmable signal delay generators. CONSTITUTION: The laser length measuring system comprises a laser signal driver 1, a light emitter 2, a light receiver 3, and a flight time processing unit 4. The laser signal driver 1 trigers the light emitter 2 to output a laser pulse and to provide the flight time processing unit 4 with a trigger signal. The light receiver 3 receives a laser signal reflected from an object and delivers a trigger signal simultaneously to the flight time processing unit 4. The flight time processing unit 4 comprises at least two digital programmable signal delay generators and a data flip-flop which is fed with two trigger signals subjected to appropriate time difference correction. Based on the output state, a microprocessor determines the flight time of laser signal by binary search method and calculates the distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser length measuring apparatus, which has a plurality of "digital programmable
The signal delay generator is used to perform precise correction and measurement of the time difference to realize a simpler and more effective length measuring circuit than the laser length measuring circuit of the known technology, and a digital programmable signal By connecting a delay generator in series, the length measurement accuracy is further improved.

[0002]

2. Description of the Related Art The basic principle of laser length measurement is to calculate a laser signal emitted from a length measuring instrument to irradiate an object, and then reflected by an optical sensor of the length measuring instrument to return. And the required flight time (time-of-fly) is ΔT,
Using this flight time ΔT, the distance D between the length measuring device and the object
Can be calculated approximately directly (if the refractive index of air is not taken into account, the time of flight ΔT is approximately twice the distance 2D that the laser signal travels back and forth divided by the speed of light). However, since the laser signal travels at the speed of light and the speed of light is extremely large, when the accuracy of the distance D is desired to be up to 15 cm, the measurement accuracy of the flight time ΔT is 1 nanosecond (ns = 10 ⁻⁹ seconds). ) Will be required. Therefore, how to measure the flight time ΔT accurately and quickly is a key point of the laser measuring technique.

The conventional length measuring method utilizes an electronic circuit to
By extending the signal width of the measured flight time ΔT to make it easier to measure, or by converting the signal of the flight time ΔT into another electric value (for example, voltage) that can be easily measured and used as a change in the electric value. On the contrary, there have been attempts to estimate the magnitude of the flight time ΔT, but whichever method is used, the electronic circuit is complicated and the number of precision electronic components is increased. It was supposed to be easily affected. Of course, it is possible to measure the time of flight ΔT using the phase change of the laser signal, but with such a measurement method, the electronic circuit becomes more and more complicated,
Furthermore, the calculation speed was reduced.

A general laser length measuring device uses two optical sensors to detect a laser signal for light emission and a laser signal for light reception, respectively, and serves as a base for calculating a flight time ΔT of the laser signal. However, the use of two photosensors doubles the amount of signal processing, and thus relatively increases the complexity of the electric circuit. Therefore, a relatively new laser length measuring device processes a laser signal emitted and received by the length measuring device by a single optical sensor, thereby simplifying an electric circuit, but a laser beam fed back by using an optical fiber. The optical fiber partially blocks the light emitting area of the laser light source, which leads to attenuation of the laser signal, which makes optical design difficult and at the same time reduces the reception efficiency of the optical sensor. descend. Further, since the laser signal emitted and received by the length measuring device is processed by one optical sensor, the configuration of the signal processing circuit becomes difficult.

Further, in general laser length measuring devices, it is required that the accuracy in the length measuring range be set differently depending on the purpose, and in any laser length measuring method, all the length measuring accuracy is required. Resolution of the length measurement method (resolution)
It depends on the
If it is desired to change the accuracy, the design must be changed according to the requirements, and the required labor and cost are equivalent to newly developing the laser length measuring device.

[0006]

SUMMARY OF THE INVENTION Under the circumstances described above, the present invention intends to provide a laser length measuring device, and a plurality of digital programmable delay generators (DPDGs hereinafter) are provided. (Abbreviated as) is an important component, and a length measurement circuit that is significantly simplified as compared with a known length measurement circuit is configured. Further, a main object of the present invention is to use a characteristic of DPDG to provide a digital program type control method,
The rising edge of one pulse signal is delayed by an appropriate time to construct a simplified length measuring circuit, and it is not necessary to extend the width of the time signal or convert the signal form.

Another object of the present invention is to use a DPDG circuit in a laser length measuring device to perform precise correction and measurement of a time difference, so that an accurate and effective length measuring function can be exerted and a laser signal of a laser signal can be displayed. Since the firing time is directly determined by the trigger edge signal of the laser driving circuit, the length measuring circuit only needs to detect and measure the returning laser signal, and the feedback by the optical fiber is unnecessary, and the The function of the sensor is improved, the optical design is facilitated, and the signal processing circuit is easily configured. Furthermore, since it is digital signal processing, it is not easily affected by temperature.

The second object of the present invention is to measure the time difference D
Since the PDG circuits can be arranged in series and the length measurement range accuracy can be easily increased from several times to several tens of times, different accuracy requirements can be met.

[0009]

The laser length measuring apparatus of the present invention comprises a laser driver, a light emitter, a light receiver, a time-of-flight processing unit, and a microprocessor. 1 or 2 DPDs
By using G to correct the time difference between the light emission and light reception signals, and by combining at least one DPDG with a data flip-flop to measure the time difference, the microprocessor can accurately and quickly measure the time of flight of the laser signal. ΔT
It is possible to calculate and realize an effective length measurement function.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Other objects and functions of the present invention will be described in the following with reference to the accompanying drawings in the structure and effects thereof. FIG. 1 is a block diagram showing a system configuration diagram of the present invention. The present invention includes a laser signal driver 1 to drive the light emitter 2 to generate a tuned laser pulse signal, as well as a transmit time (transmit).
(Ting time) trigger edge signal Tt to the time-of-flight processing unit 4 to immediately respond to the emission time of the laser signal, and the light emitter 2 is provided with a laser diode 21 to emit a laser signal, and the laser signal is emitted from the optical fiber The light is guided to a lens 23 via 22 and is irradiated onto an object (not shown). The light receiver 3 transmits the laser signal reflected by the object via the lens 31 and the optical fiber 32. While being guided to the sensor 33, separately from this, the backscatter time (Backscatter ti) corresponding to the flight time ΔT of the laser signal is obtained.
The trigger edge signal T _b of (me) is sent to the flight time processing unit 4. The flight time processing unit 4 has two trigger edge signals Tt, T
b under the control of the microprocessor 5,
By precisely correcting and measuring the time difference, the flight time ΔT of the laser signal can be calculated (details will be described later), and the length measuring function is completed.

FIG. 2 is a time-of-flight processing unit 4 of the present invention.
3 is a block diagram showing a configuration example of and a signal flow. FIG. In the present embodiment, the time-of-flight processing unit 4 includes three digital programmable delay generators DPD.
It has G411, 412, 413 and one data flip-flop 42. First, two trigger edge signals Tt, T for emitting and receiving a laser signal
b is generated as shown in FIG. 1 and is input to the DPDG 411 and DPDG 413 as shown in the figure. Correct the delay signals T and R appropriately.
(Shown in FIG. 2) to generate these delay signals T, R
The time difference between them is exactly equal to the flight time ΔT (detailed in FIG. 3). The microprocessor 5 further controls the DPDG 412 to delay the delay time T once again to generate the variable delay signal TT. The variable delay signal TT and the delay signal R are respectively data flip
By inputting to the flop 42 and changing its output state, the microprocessor 5 can obtain the time of flight ΔT of the laser signal accurately and quickly.
This procedure is detailed in FIG. By the way, delayed signal R
The signal pulse width W of the signal is adjusted to an appropriate value by a delay line (not shown) attached to the DPDG.
(The G circuit is a known technology), and the flight time ΔT is easily calculated, and the delay signals T and TT use only the rising edge signal thereof (these operations are described in detail in FIG. 4).

The DPDG used in the present invention is a well-known component, and basically includes a linear ramp generator, a digital / analog converter (D / A converter) and a voltage comparator. In preparation, the rising edge of the external input signal first triggers the ramp generator, and the voltage comparator immediately monitors the ramping ramp voltage, which becomes the reference voltage value set by the digital / analog converter. Sometimes it outputs a delayed signal.

The reference voltage value can be adjusted programmably by inputting a digital signal with an external microprocessor or the like. The length of the Lamb wave is determined based on the maximum distance range that can be measured by the present invention by the electric resistance and the capacitor attached to the maximum possible delay width. Below, the maximum possible delay width is FS (full scale range). ), Which allows the DPDG to divide this FS into 2 ⁿ intervals by utilizing the n-bit input of the microprocessor in the FS. For example, if n is an 8-bit input, the FS can be divided into 256 sections, so the corresponding measurement distance is also 25.
It is considered that the data is divided into 6 sections, and if the microprocessor inputs data to the DPDG as "11111111".
Then, the delayed signal (its rising edge) occurs at the furthest point in the FS. For example if the microprocessor D
If the input to the PDG is "11111000", the delayed signal is generated in the 248th section of FS. Therefore, all delay points can be arbitrarily designated by the program operation by the n-bit input of the microprocessor.
It is possible to generate the correct delayed signal in G.

The data flip-flop 42 used in the present invention has a digital input terminal D and a clock input terminal C.
LK and output terminal Q, the operating state is CL
When the trigger signal is input to the K terminal, if the D terminal is high level input, the Q terminal becomes high level output,
If the D terminal is low level input, the Q terminal is also low level output. In other words, data flip
Whether the level of the output terminal Q of the flop 42 is high or low is determined by the level of the delayed signal R of the D terminal being high or low when the trigger edge signal TT is input to the CLK terminal.

FIG. 3 is a timing chart showing clock pulses for which the present invention delays a signal to correct the flight time. In this length measurement system, the reaction time is delayed due to the components such as the electronic device, the electric circuit, the optical fiber, etc., so that the calculation of the flight time ΔT is likely to be inaccurate. Therefore, in all of the known laser length measurement techniques, the length measurement circuit is complicated because the time must be corrected. In the present invention, DPD
By using G to control the delay signal in a programmable manner, a predetermined delay time Δt ₁ Δt ₃ is designated and output at the rising edges of the input pulse signals Tt and Tb, and the delay signals T and R are output. That is, according to the present invention, the DPDG 411 and DPDG4
By correcting the delay times Δt ₁ and Δt ₃ of 13 so that the time difference between the delay signals T and R is just the flight time ΔT, the delay of the reaction time of the system is changed in the DPDG 41.
1 and the DPDG 413 make a total correction at one time (note that the signal T must lead the signal R). In this way, the delay in the reaction time of the system can be easily solved without changing the length measuring circuit. Further, if the place where the present invention is used is fixed, the signal delay situation of the trigger edge signals Tt and Tb can utilize the relatively stable result obtained by testing many times. Since a predetermined delay time can be set for the signal correction that is suitable for the entire measuring distance, the DPDG4
11 or DPDG413 can be selected, and one D
Just use PDG to make the above-mentioned comprehensive correction,
To achieve the purpose of simplifying the configuration.

FIG. 4 is a timing chart showing the signal pulses by which the time-of-flight processing unit calculates the time-of-flight of the laser signal in the present invention. In this embodiment, the microprocessor 5 adjusts the delay time between the DPDG 411 and the DPDG 413 based on the above-mentioned correction purpose, and outputs two trigger edge signals Tt and Tb for emitting and receiving a laser signal to appropriate delay signals. Since T and R are delayed, the time difference is set as the flight time ΔT to be measured. Next, the microprocessor 5 follows a binary search method described below.
Each time the subsequent laser signal is emitted or received, a control command is continuously issued to change the delay time C value of the DPDG 412 (see FIG. 4).
C _1, C ₂ ...) in, so DPDG412 is within FS range of FIG. 4, the attempt number of times of different delay processing for the delay signal T, corresponding respectively to the TT _1, TT ₂ ... etc. Generate a delayed signal. The data flip-flop 42 provides its output based on the signals R and TT at its input and CLK inputs, allowing the microprocessor 5 to find the correct C value and calculate the corresponding measured distance. The operation is as follows.

In FIG. 4, if the DPDG 412 has already set its proper maximum range FS, then the DPDG
The signal pulse range W of the delayed signal R output from 413 is also adjusted to about half FS to perform the analysis procedure described below. If the DPDG 412 partitions the FS into 16 (= 2 ⁴ ), and the rising edge of the signal R (ie, the terminal at ΔT) is between the fifth and sixth partitions of the FS, then the microprocessor 5 The binary search method is used to obtain an appropriate delay time value c after the search is performed n (here, 4) times according to the signal state indicated by the output terminal Q of the flip-flop 42, and it is extremely close to the flight time ΔT. , Calculate the corresponding measurement distance. That is, first, the microprocessor 5 causes the first-order delay time C
₁ is C ₁ = Fs / 2 (that is, C ₁ = 8), and DPD
When the delay signal TT ₁ as shown in the figure is generated in G412, its rising edge comes after the delay signal R, so that the output terminal Q of the data flip-flop 42 becomes high level, which is defined as Q ₁ = 1. it can. Then, the microprocessor 5 sets the second-order delay time C ₂ to C ₂ = C ₁ −
When the delay signal TT ₂ as shown in the figure is generated in the DPDG 412 with FS / 4 (that is, C ₂ = 4), its rising edge comes before the delay signal R, so that the output terminal Q of the flip-flop 42 becomes low. Level, Q ₂ = -1
It is defined as Therefore, the microprocessor 5 outputs the third delay signal C ₃ to C ₃ = C ₂ + FS / 8 (that is, C ₃ = 6).
As a delay signal TT ₃ as shown in the figure.
Is generated, its rising edge comes after the delayed signal R, so that the output of the flip-flop 42 becomes Q ₃ = 1 and the microprocessor 5 causes the fourth delay time C ₄ = C.
Similarly, we obtain Q ₄ = −1 for _3- FS / 16. Thereby, the delay signal R can be obtained, and the flight time ΔT is between the delay times C ₃ (5) and C ₄ (6) and can be represented by the intermediate value 5.5. calculate. Of course, if the DPDG 412 raises the numerical value for partitioning the FS to 2 ⁸ (that is, n = 8), the unit accuracy of measurement is also raised, and the number of searches in the binary search at this time is 8. Such a procedure can be roughly expressed by the following mathematical formula.

[0018]

[Equation 1]

Further, the n-bit digital input method of the microprocessor as described above is determined by adopting the DPDG hardware. The larger n is, the larger the number of sections is, which is a plus for the unit accuracy of measurement. . Further, since the distance range to be measured corresponds to the size of the FS range, this determines the unit accuracy of the laser length measuring device. That is, the larger the FS is, the naturally divided 2 ⁿ divisions become sparse, and the unit accuracy thereof is relatively lowered. On the contrary, if the FS is smaller, the division 2 ⁿ is divided. ^{The n} divisions are becoming more dense,
The unit accuracy is relatively improved. Therefore, if at least two DPDGs are connected in series (ie, DPDG4
If another DPDG is added after 12), the former has a lower unit accuracy and the latter has a higher unit accuracy. ) Comprehensively in a relatively narrow time range, and then with a higher unit accuracy DPDG, the narrow time segment is divided into dense time segments for precise approach, and two or more DPDGs are combined. Therefore, the measurement accuracy can be easily increased from several times to several tens of times.

[0020]

Since the length measuring apparatus of the present invention has a simple circuit configuration, its accuracy characteristic can be easily set elastically, and the system in which the microprocessor controls the length measuring circuit by a digital method can reduce the influence of environmental temperature. I don't receive much, so
For example, the relative movement speed and the like can be quickly read by applying it to the dynamic measurement of an obstacle of a vehicle.

Although the embodiments have been described so clearly, the scope of the present invention is not limited thereto, and modifications made by those skilled in the art based on the technical idea of the present invention belong to the scope of the claims of the present invention. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration diagram of the present invention.

FIG. 2 is a block diagram showing a configuration of a flight time processing unit of the present invention and a signal flow.

FIG. 3 is a timing chart showing a time-of-flight correcting signal clock pulse of the present invention.

FIG. 4 is a timing chart showing signal clock pulses by which the time-of-flight processing unit of the present invention calculates the time-of-flight of a laser signal.

[Explanation of symbols]

1 laser signal driver 2 light emitter 3 light receiver 4 time-of-flight processing unit 5 microprocessor 21 laser diode 22, 32 optical fiber 23, 31 lens 33 optical sensor 42 data flip-flop 411, 412, 413 digital programmable
Delay generator

Claims (4)

[Claims] 1. A laser length measuring device comprising a laser signal driver, a light emitter, a light receiver, and a time-of-flight processing unit controlled by a microprocessor, wherein the laser signal driver drives the light emitter to emit a laser beam. At the same time as outputting the pulse, it provides a time-of-flight trigger signal to the time-of-flight processing unit, and the light receiver receives the time-of-flight backscatter time trigger signal corresponding to the laser signal based on the laser signal reflected by the object. To the time-of-flight processing unit, the time-of-flight processing unit having at least two digital programmable signal delay generators and a data flip-flop to provide the above-mentioned firing time and Under the control of the above microprocessor, two trigger signals called backscattering time In addition to performing the appropriate correction of the time difference, the microprocessor inputs the data flip-flop, and the microprocessor controls the correction of the time difference described above, and based on the output state of the data flip-flop, Laser length measuring device characterized by determining flight time. 2. At least one digital programmable signal delay generator in said time-of-flight processing unit first delays at least one of said reflection and backscatter time trigger signals, and 2. The device according to claim 1, wherein the time difference between the signals is made equal to the exact flight time, and the delay of the reaction time as the system is comprehensively corrected at one time based on the known distance. 3. At least one digital programmable signal delay generator in the time-of-flight processing unit further prior to the two signals of time-of-flight difference under control of the microprocessor, The delay time is changed so as to gradually approach the latter one of the two signals, and the microprocessor determines the delay time closest to the flight time based on the output state of the data flip-flop. 3. The device according to claim 2, wherein the device is discriminated to represent the flight time. 4. The time-of-flight processing unit is modified to provide two digital programmable signal delay generators to delay in time, one of which is in a relatively large time range. , While roughly classifying the delay time and searching the range of flight time,
4. The apparatus according to claim 3, wherein the accuracy of length measurement is improved by relatively finely dividing the delay within this rough division range and making a precise approach.