JPS60262081A - Distance measuring apparatus by laser - Google Patents

Abstract

PURPOSE:To enable the measurement of distance accuracy within about 1mm. by counting the time length for measuring a fixed number of square waves switching ON or OFF light each time changes are detected in the quantity of light in reflected waves performed by a laser light. CONSTITUTION:A target is irradiated with a laser light 5 outputted from a laser oscillator 4 and light is switched ON or OFF with the modulation by a light modulator 3 to form a square wave of light each time the quantity of light changes in the reception of a laser light 7 reflected with a reflector 6 mounted on a target with a receiver near a light source. This generates a square wave at the cycle reflecting distance information accurately. Then, the time for counting the fixed number of waves is measured to display the distance converted from the measured value.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention can reduce the distance to an object moving at low speed from several meters to several +
The present invention provides a method for measuring with an accuracy of about 1 ma from a position of 1 mm.

(Background of the invention) □ Conventionally, there have been various methods for measuring the distance to a moving object, but there is no simple method that can measure distances from several meters to several tens of meters moment by moment with an accuracy of about 1 meter. 7 However, in ultrasonic flaw detection of large structures, when a probe is attached to a remotely controlled trackless moving body and scanned, the detected original defect position is divided by the position accuracy of 1 mwli degree / recorded. There is a need for the development of a measurement method that can satisfy this need.' [Object of the Invention] The object of the present invention is to meet these needs.

[Summary of the invention]

A functional block diagram of its configuration is shown in FIG.

Conventional methods of measuring distance using light or radio waves include:
The conventional method was to calculate the distance by measuring the time difference or phase delay angle between the time of wave transmission and the time of wave reception.
All of these methods were used to measure the time difference between when a transmitted wave is reflected by a target and when it is received.

□ Therefore, in these methods, the distance difference is 16.
Without measuring 66 PS, it was not possible to detect a distance difference of 1 m, and due to technical difficulties it was not possible to create a convenient alignment that could be used in practice.

In the present invention, a laser beam is irradiated onto a target object, reflected by a reflector attached to the target object, and the light is opened and closed each time the amount of light received by a receiver near the light source changes. By creating a rectangular wave of light, a rectangular wave with a period that accurately reflects distance information is generated, and the time it takes to count a certain number of m periods is measured.

Therefore, the optical path length 2no, which corresponds to IIIwll in the distance to the reflector, is the time during which light is transmitted -X 10-11 seconds is multiplied by m, so if m is chosen appropriately, the time difference can be easily measured. I can do it.

In addition, in the present invention, since m is a constant number, the constant time delay unrelated to distance within the time constituting one cycle is m
Within the time to count the number of waves] is also a constant time multiplied by m, so it can be easily calibrated by measuring a known distance.

- [Embodiment of the Invention] The present invention will be described in detail below with reference to FIG. 1 showing a block diagram of an embodiment of the present invention and FIGS. 2 and 3, which are time charts thereof.

In FIG. 1, 1 to FFI are RS flip-flops, whose Q output passes through 2 to amplifier 41, modulates 3 to optical modulator M, and 4 to laser beam output from laser oscillator. Open and close. When the 27~starting pulse is input to the 26~OR element, its 201 output is input to S of 1~FFI, Q becomes H, and 203 output light starts to be output from 3~M. (See Figure 2) The laser beam 5 that has passed through the modulator M is incident on the reflector 6 attached to the target device, and is sent back as a reflected light beam parallel to the direction of incidence. After a certain period of time required for the light to travel back and forth along the optical path, the light is received by the optical sensor 204 and generates an electrical signal, which signal passes through the amplifier A2 9 and then is differentiated by the differentiating circuit 206. It becomes a differential wave.The positive pulse of the differential wave passes through 24~diode, 26~OR element, and then 1~flip-flop FF.
I(7)Il, :207-FFIR input wave is input,
) By setting the Q output 208 to L, the output 209 of 2 to A1 is set to L, and the output light 210 of 3 to M is closed. 6 Therefore, after a certain period of time, the light reception 211 to decreases, and 10 to
The output 212 of the differentiator circuit - negative pulse passes through the diode 25! 1 ~ The polarity is inverted by the polarity inverter 213
This becomes a positive pulse, and the positive pulse is input to S of flip-flops 1 to FF1, and turns 214 to Q to H.

Therefore, after the output light of the 3~ modulator starts to come out.

After a certain period of time during which the light travels back and forth, the output of amplifier 9 rises, and the positive wave of its differentiation is input to R of 1 to FFI to change Q to 1, and the light is blocked by modulator 3.

After a certain period of time after the light is interrupted, the output of amplifier A2 from 9 falls, and the negative pulse of the differential wave is reversed in polarity by the polarity inverter from 11 to become a positive pulse, which is input to S of 1 to FF1. to return Q to H, and start projecting light from the 3~ modulator.

In this way, the output light of the modulators 3 to 1 becomes a rectangular wave with a constant period, and accordingly, the Q outputs of the modulators 1 to FF1 also become rectangular waves.

The period of this rectangular wave is determined by the time of aerial optical path transmission from the modulator output surface to the reflector surface, the intra-reflector transmission time, the aerial optical path transmission time from 8 to the receiver to 3 to the modulator. It consists of the delay time of the electric signal until the end of the signal and the rise time of the signal depending on the length of the modulator, but the aerial optical path transmission time is proportional to the distance, and other things are constant. , see Figures 1 and 3 below the nose.

1~The Q output of FIL 220~The rectangular wave is obtained by inputting the input wave 221 of the same waveform to 12~counter C1, changing the count number 223~ every time it falls 222~, and counting a constant number 224~ After the carry signal 225 is set to 13~
Input to D of D flip-flop FF2.

14~Digital switches DIG and SWI are 12~When the 227~LOAD signal is input to the counter C]1. C
This is to set the number position to be LO^D to 1, and is to set the required count number m.

15 - Constant frequency oscillator is an oscillator of 228 - clock signal for measuring the time for 12 - counter C1 to count m.

When the clock signal goes low after 225~ when the carry signal of 12~C, 1 rises, 13~FF2 starts at 229~.
reads the carry signal and when the clock falls 23
0~ set F, Q of F2 to H226 and both set to L.

”; After Q of 3 to 12F2 becomes H, the clock starts,
When it reaches 23■, ~, 16~D flip-flop FF3 reads the H of Q of FF2, and the clock rises F2.
When it becomes 32.~, Q227~ of FF3 is set to I-i.

At this time, 1? The L of Q of F'2 and the H of Q of FF3 are input, but the output LOA
The D signal remains at L and is not loaded.

However, at time 233 when the input of 12~counter C1 rises, -IP-YIJ- of 12~counter C1
Signal '°4~'17. )”) J, ++71 after 1′
. 7ri 235~ rises, then 236~ falls, 2
37~FF2-Q237~ falls. Then 13~
Since both F2 and F2 become H, the output of the AND element from 23 to I becomes
LOAD signal 238 ~ is input to C2, and 20
~Contents of digital switch DIG, SW2 are 18~C2
is loaded.

When Q of 13~FF2 becomes H, 17~Register RE
The L A T CH signal is input to G, the contents of 18~ distance power ureta C2 are taken to 17~ register, and 239~
The numerical value is displayed from 19 to numeric display device DISPLAY.

12 - When the carry signal of the counter C1 falls, the carry signal is inverted by the signal inverter 21 - becomes a rising signal and is input to the AND element 22 -.

15~Start outputting the oscillator clock signal 18~Power counter C1.

18~In counter C2, when the output of 22~AND element rises, the clock also rises at the same time.Read the output of 22~AND element into the first digit of 02, and when the clock falls, the first digit of C2. Change the output to H or L.

, 13-FF2. After the clock becomes (L), the clock becomes (
When the signal rises to -L and then falls, the Q of 16 to F Fi 3 changes to L.

Therefore, the LOAD signals from 18 to C2 also stop, and C2 starts running 1-. □ Since 12 to C1 are also in the counting state at this time, a carry signal is generated after multiplying the wave number of the rectangular wave of the preset wave period by m coefficients.

Therefore, 18~C2 counts 12~Counter C
] during which the carry signal becomes H and 16 to FF F3-
This is a time other than the period when Q becomes H.

The frequency of the oscillator is determined from 15 so that the number n counted during this period is 172, which is the number expressed in terms of the distance of light traveling during this period.

In other words, the clock f to identify the distance 1wn is becomes.

Then, the time Q corresponding to m times the aerial optical path 2Qnwn Therefore, the count value of n is the number expressing the distance in I units.

As mentioned above, the actual period of the preset wave includes a constant delay time in addition to the time proportional to the distance, and the count number of C2 corresponding to this constant delay time must be subtracted from the count number of C2. Must be.

20~Digital switch DIG, SW2 is for input to input the complement of the constant count number into 02, and C
The content of 2 represents the value after subtracting the constant.

Just now f. = 1.5 MHz = 1.5 x 10' Hz, and it can be seen that the distance can be counted at a frequency that can be easily counted.

Assuming that 12~C1 issues a carry with 214, the count number is 16384, so to set m = 40,000, load 6384 with 14~digital switch.
L/You should do it.

The frequency of the preset wave is 2 x 3 x 10'' when the distance is Q = 3000 mm, ignoring the constant part, and 5 M7 when Q = 30,000 m = 30 nw, both of which are easily calculated. This is the frequency that can be counted.

Therefore, when Q = 30 m, m = 10 t 000 is counted, so 0.2 sec is 1. For those that move mm, the guaranteed limit is 0.23 mm, and considering the constant delay, it will be slower than normal.

If you need to measure up to 10 times the speed in units of 1 m, set m = 1000, and! ,, = 1. j OM
It needs to be Hz.

FIG. 4 shows a diagram of the principle of the optical modulator.

100 ~ Laser light passes through 101 ~ polarizing plate 110 ~
Only the angular deviation shown in the figure is sent to 104~photoelectric crystal.

Crystal axis X1 of photoelectric crystal. X2. The direction of X3 is 11
3.

Electrodes 104 and 105 are attached to the top and bottom of 104, and voltages from 106 to modulated power source V are applied.

When a voltage is applied to the electrodes, the polarized light passing through the crystal 104 is divided into an ordinary ray and an extraordinary ray, and the difference in propagation power increases, and the light exiting the crystal changes into elliptically polarized light 107 as shown in 111 to 112. By means of an analyzer that passes only the polarized light shown in 1.09, only the components of the polarized plane are irradiated onto the target as a beam of light.

With such an optical modulator, light can be opened and closed at high speed, and the crystal size is 0.
．． When using 311III x 0.3rm x 2211II+, the wavelength
It can be modulated into a pulse of it/s and is sufficient as a modulation element of the present invention.

FIG. 4 shows the relationship between the rise and fall speeds of optical pulses and the differential output depending on the length of the optical modulator.

The rise or fall time is the time it takes for the light to pass through the length of the electrode, and its change is linear, so the gap between the times when the light crosses the same height gives the correct period.

Figure d shows the differential waveform, and shows that the rise of the differential wave coincides with the modulation start time.

□The reason for using a laser beam as the light source of the present invention is about 3.
The position of the distance measurement point is accurately determined by passing through a total of 60 m from 0 m to obtain sufficient light reflection necessary for detection, and by accurately selecting the target and obtaining reflection from a defined reflective surface. This is to define it.

However, if the reflector attached to the target is flat, when the incident direction of the beam deviates from the normal line, it will be reflected in a direction with twice the direction error relative to the normal line, and the beam will not be effectively received at the transmitting point. .

Therefore, in the present invention, a reflector as shown in FIG. 7 combined with a right-angle prism is used, so that even if there is some angular error in the direction of the reflector, the reflected wave can be correctly directed in a direction parallel to the incident direction. Use a reflector to send back.

Figure 6 shows the situation even if there is an error in the direction of incidence within the plane.

FIG. 2 is a diagram showing the principle of producing reflected light parallel to the incident direction by two plane mirrors at an angle of 90″ to each other perpendicular to the plane.

The reflector shown in FIG. 7 is a combination of mirror surfaces so that the reflection operation shown in FIG. 6 can be performed even in a perpendicular plane. Total reflection on a prism surface can be used as the reflecting surface.

This type of reflector is commonly known from the news that it was installed on the lunar surface to measure the distance to the moon using laser light.

In order to reflect a laser beam irradiated from any direction around the moving object in the irradiated direction, a reflecting prism like this is attached to the moving object with a rotating shaft, and when the laser beam irradiation is detected on the moving object, It is sufficient to rotate the reflector to the direction of the laser beam and stop it, and some error in the stopping angle is allowed.

In addition, if multiple prism reflectors like this are arranged in an annular or hemispherical shape, laser beams arriving from any direction around the circumference will be reflected as reflected light beams parallel to each other. Simultaneous distance measurement becomes possible, and coordinate positioning becomes possible in units of 11Il11.

Therefore, by combining this device with a mechanism that changes the direction of the transmitted laser beam by following the changing direction of the reflector attached to the target moving object, it is possible to change the distance to a moving object that moves arbitrarily. can be measured.

This method was invented with the main purpose of measuring the direct distance to a moving object from 3 to several tens of meters, but if the light source is strong enough, it can be measured in units of 1+nm even at distances of several kilometers. This is a method that can be measured using However, the time required for measurement increases in proportion to the distance.

-Also, in order to measure in units of 0.1 mm, the number of m should be multiplied by 10, but this also increases the measurement time by 10 times.

Such an application is also useful as a distance measuring device for geodetic surveying using poles.

〔Effect of the invention〕

According to the present invention, the instantaneous position of an ultrasonic probe attached to a trackless self-propelled vehicle can be determined from two or three fixed points by a direct distance of 1w.
Since it is possible to record in w++ units, it becomes possible to express the discovered defect position as reproducible and accurate coordinates.

Therefore, there is no need for a toothed track that was conventionally provided for position detection, and ultrasonic flaw detection using a remotely controlled trackless vehicle becomes possible, thereby saving construction costs for track installation.

Furthermore, when this is applied to geodetic applications, the accuracy can be improved compared to conventional distance measuring devices.

Therefore, by measuring the expansion and contraction of the ground over several kilometers at 0.1 shoulder height, it becomes easy to obtain data for earthquake prediction.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of one embodiment of the present invention.
The figure is a time chart showing that the laser beam becomes a rectangular wave, Figure 3 is a time chart showing the relationship between the voltage waveforms of each part in Figure 1, and Figure 4 is a time chart of the optical modulation device used in the present invention. The principle diagram, FIG. 5 is an explanatory diagram showing the detailed rise and fall of the output light of the optical modulator and the relationship between the differential wave rise time,
FIG. 6 is an explanatory diagram of the principle of the reflector used in the present invention, and FIG. 7 is an explanatory diagram of the structure of the reflector and the path of light rays used in the present apparatus. 3... Optical converter M, 4... Continuous laser beam oscillator, 5... Sending laser beam, 6... Reflector, 7...
・Reflected laser light, 8... Optical sensor - P8.9...
Increase) Heavy equipment, 10... Differential circuit, 11... Polarity inverter, 24... Diode, 25... Diode, 26
...OR element for starting. 27...Start pulse input. Agent Patent Attorney Akio Takahashi Condolences on Unsuccessful Days] Figure

Claims (1)

[Claims] ■The laser beam is reflected at the target position, and each time a photodetector detects a change in the light intensity of the reflected wave, the light is opened or closed to generate a rectangular wave signal, and it takes a certain amount of time to measure this rectangular wave at a certain number of waves. ,
A laser distance measuring device that counts using constant cycle clock pulses and expresses distance using the numerical value.