JPS5842946Y2 - Device for measuring the velocity and/or length of moving materials - Google Patents

Description

[Detailed description of the invention] The present invention is a device for measuring the velocity and/or length of a material that moves almost continuously and has a large surface reflectance. A device in which a laser irradiated by a laser beam is directed toward the surface K of a material to be measured, and a laser beam spot reflected from there is detected by a light receiving device, and an evaluation is performed according to the image frequency. It is.

Generally speaking, the light beam originating from the helium-neon gas laser is reflected by the surface of the movable material in the form of a so-called beam beam, which results in statistically distributed light spots at the receiver.

This so-called light spot appears and disappears at a frequency that can be evaluated statistically as a measure of the relative velocity between the laser and the surface of the material moved with respect to the laser.

By using suitable optical systems, certain interfering effects can be significantly eliminated, so that the reflected laser light has a very high intensity for measurement, especially when there is no interference between the laser light source and the object to be measured. (German Publication No. 243)
3038, 2506539).

German Patent No. 20150 for measuring the velocity and/or length of a moving material using the previously mentioned measuring principle
In the case of the devices known from DE 24 37 511 and DE 24 37 511, the reflected laser light spot is detected by a receiver device, which is followed by an amplifier,
The modulator, filter and detection oscillator are connected,
The output of the detection oscillator is connected to a modulator and a frequency meter that indicates the moving material Q velocity.

In the last published publication of the above-mentioned specifications, the detected velocity of the moving material is used to determine the length of the workpiece or to determine the length of a sub-piece of very long material. can be derived in such a way that the sensed velocity value is integrated over a period of time.

While there is a certain time subsection that is required by the detection oscillator to find the respective measured signal frequency (measurement frequency), in the event of a disturbance in the measurement value, the time integration is carried out in an approximation to the velocity.

For this purpose, a suitable electronic integrator is connected downstream of the output of the frequency meter, which is calibrated to the material velocity.

The problem of this invention is the speed of the species mentioned at the beginning.
and the apparatus for measuring length has been significantly improved, so as to increase the accuracy of the determination, and in particular to eliminate systematic errors which are difficult to determine when making measurements. The aim is to create a device that

In order to solve this problem, according to the present invention, the device is formed as follows.

That is, a variable high-pass filter is connected between the light receiving device and the amplifier, and its limit frequency is controlled by the control voltage generated in the detection oscillator.

In the known device, a multi-part filter is provided with a low-pass filter on the input side, which keeps interference signals above the limiting frequency of the reflected laser light away from the detection oscillator.

Surprisingly, it has been found that this nevertheless results in an interference frequency in the detection oscillator, which frequency varies as a function of the material velocity, so that implausible velocities are clearly detected.

Such drawbacks can be avoided with the present invention.

It is particularly advantageous if a control voltage is derived which influences the frequency generator of the detection frequency in order to control the lower limit frequency of the high-pass filter.

For the high precision that is to be sought in this way, it is generally sufficient that the high-pass filter is designed to be automatically switchable to three limit frequencies.

Approximately (10) depending on the material velocity that can be detected
If there is a frequency range of reflected laser light (measurement frequency) from KH2 to 500KH2, the lower limit frequency should be set to 1OKH2, 60KH2 and 160KH2.
It is reasonable to use it as KH2.

In order to further support this sought result, it is more expedient to form the detection oscillator as follows.

That is, the purpose of the detection oscillator is to form the detection oscillator so that each detection operation starts at its highest detection frequency and gradually decreases to a lower frequency until it reaches a target frequency corresponding to the measurement frequency of the reflected laser light. It has come true.

In this way, the detection oscillator will always detect the correct highest measurement frequency, even for lower frequencies of the reflected laser light, and in some cases speed-dependent frequencies, although this is true in practice. This will be guaranteed as an additional matter.

Readings that temporarily do not represent the velocity sufficiently accurately have a particularly significant effect on the accuracy of the length measurement of the material.

If a certain digital display moves within predetermined limits, the corresponding exact intermediate value (average value) cannot be determined immediately upon reading.

For an integrator downstream of the output of this frequency meter, however, such deviations cannot be eliminated.

The frequency meter operates as follows.

That is, the gate circuit opens at a certain time and the number of pulses corresponding to the corrected oscillator frequency f2, ie the measuring frequency f1, is counted and displayed as a speed value at the end of the opening time.

As the moving material changes its velocity during the pulse count time, the frequency meter is forced to indicate an intermediate material velocity, but that velocity is within the limits of the actual velocity at the start of the count and at the end of the count.

This velocity value is subsequently incorporated into the connected time integrator and therefore leads to an inaccurate length measurement.

In order to eliminate this drawback, the following is proposed in the present invention.

That is, the output of the integrator of the detection oscillator is divided into two parallel circuits, each of which is divided into one analog storage device, and a frequency generator is connected after each storage device, and both of their outputs are connected to the next one. The present invention proposes a structure that can be automatically switched between two states as shown in FIG.

That is, both outputs of the frequency generator are connected to a frequency meter for velocity measurements, one output frequency to an integrator for length measurements, and also to a modulator.
The second frequency output is then blocked, or the second frequency output is connected to the modulator as a result of the detection operation of the detection oscillator being initiated, and the other frequency output is isolated from the modulator. It is possible to automatically switch between the two states to take either one of the two states.

the one connected to the frequency meter and length integrator, respectively.
For example, when the first frequency generator of the detection oscillator has a target frequency f2 corresponding to the measurement frequency f1 of the laser beam, the detection oscillator does not perform any detection operation, and the constant values on both sides, velocity and length are detected very accurately. Ru.

Subsequently, a velocity change occurs in the moving material and the measurement frequency f1
changes accordingly, the then connected e.g.
The frequency generator follows the same course with almost no inertia Kf2.

Therefore, the time integration for length measurement directly connected afterwards also has no error.

If the reflected laser light is disturbed by an external influence, the detection oscillator carries out its operation with a second frequency generator, which is now connected to the modulator, and which itself is directly connected to the corresponding target. It operates until frequency f2 is found, and then the measuring device is energized.

In the meantime, the first generator, isolated from the modulator, is maintained at its frequency f2.

It is at this frequency that velocity measurements, in particular counting for the time integration of the pulses, take place.

The frequency f2 of the second generator will therefore enter the time integral for the length measurement as an approximation.

Since the detection actuation of the detection oscillator is on the order of about 10 to 100 milliseconds, new and accurate measurements for integration are available very quickly, thereby neglecting integration errors. The more you get, the less you get.

The accuracy of the detected measurements is further improved by connecting a delay circuit between the comparator and the integrator of the detection oscillator, in particular a circuit with a delay time of approximately 5 to 10 milliseconds. It becomes.

Note that this delay circuit is designed to send out a comparator signal only after the frequency generator in the detection operating state starts operating.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

According to the drawing, the device of the present invention has a laser receiver 9 at its input, which is reflected by the surface of the object to be measured, and which is known from the publications mentioned at the beginning and is not shown here. It senses light rays that are guided through an optical system that does not have an optical system.

The light receiving device 9 is connected to an amplifier 10 via a high-pass filter 37 whose lower limit frequency can be changed, and a frequency modulator 11 is connected to it.

Its output is passed through a filter 12, after which a detection oscillator 13 is connected.

The detection oscillator has one output, the signal of which is fed to a frequency meter 14 for speed measurement and also directly to an integrator 43 for material length measurement.

A further output is now connected to the frequency modulator 11, and a third output supplies the high-pass filter 37 with its control voltage.

The filter 12 includes a 296KH2 bandpass filter 16 and a 304KH2 bandpass filter 1 parallel to it.
7, and their conduction (passage) region is partially covered by the intermediate region, so that the contact points of both passage curves are 3
It has an intermediate frequency of 00KH2.

Each filter 16,17 is followed by a rectifier 18 and 19.

Their outputs are fed in the detection oscillator to an OR element 20 and further directly or via a reversible element 23 to an integrator 22.

The OR circuit 20 includes a comparator 21 and a delay member 38
It is connected to the integrator 22 via.

Integrator 22 can be reset via a setting (adjustment) element.

The output of the integrator 22 is split into two parallel circuits, each into one analog storage 39 and 40, each followed by a frequency generator 25.25a.

The output of each frequency generator is connected to both filtration through a switch 41.
A fl instrument, a frequency meter 14 and a length integrator 43 and/or a second switch 42 can be connected to the modulator 11 .

A control line leads from the output of the integrator 22 to a high-pass filter 37 which can be switched in three stages.

The frequency meter 14 is of well-known circuit technology and includes, for example, a pulse forming stage 26, a monostable trigger 27, and a low-pass filter 28.
and a measured value indicating stage 29 for the detected speed are connected in sequence.

The individual elements of the block diagram are known per se and therefore do not need to be described in detail here.

Measurement 1 of the reflected laser light received in the illustrated embodiment
The constant frequency lies in the range from 10 KH2 to 500 KH2, to which a velocity of the moving material from 5 cm/see to 50 m/see corresponds, depending on the respective optical measurement principle and calibration.

Frequency generator 25a voltage controlled by integrator 22
.

According to the discussed characteristics of both filters 16 and 17, 18, 19 rectifier and reversible 23, integrator 22
The control voltages of the frequency generators 25a to 250 are constant, and the auxiliary frequency f2 remains unchanged.

A correct pulse train is maintained by the output of, for example, a first frequency generator 25a connected to the frequency meter 14 and the length integrator 43, respectively.

At this time, the frequency generator 25a also energizes the modulator 11.

The second frequency generator 25 is switched off at the output and is in a standby state with its memory 39 .

Lower limit frequency 1OKH2,60KIl (2,160
A three-stage switchable high-pass filter 37 called KH2 is generated by the detection oscillator 13, and a control voltage applied to the output of the integrator causes said high-pass filter to
The lf frequency is automatically switched to be located less than or equal to the frequency.

When a velocity change occurs in the moving material, the measurement frequency f changes
1 causes asymmetry in the output of the filter 12 and the output of the integrator 22, and as a result, the auxiliary frequency f2 of the connected first frequency generator 25a operates with almost no inertia, and the frequency meter 14 and The length integrator 43 will operate accurately.

When the amplitude of one of the two signals at the outputs of the rectifiers 18 and 19 is below the response threshold of the comparator 21,
The detection oscillator 13 starts its detection operation at its highest detection frequency and gradually decreases to a lower frequency.

This occurs, for example, when reflected laser beam damage occurs.

The associated analog storage device 40 will then go into a stopped state and the first frequency generator 25a will be disconnected from the modulator 11.

Instead, a second frequency generator 25 is connected to the modulator 11, with the result that one or several detection cycles are carried out with this frequency generator, corresponding to each measurement frequency f1. This continues until the auxiliary frequency f2 is reached.

The first frequency generator 25a will then be disconnected from the measuring instruments 14 and 43, and the second frequency generator 25 will be immediately connected to these measuring instruments without inertia.

First frequency generator 25a and its analog storage device 4
0 then the detection oscillator 130 is stopped until the next required detection cycle.

By directly coupling the integrator 43 for length measurement to the output of the detection oscillator 13, it is achieved that each acceleration or braking of the moving material immediately and precisely participates in the integral.

A delay circuit 38 that provides a time delay of approximately 5 to 10 milliseconds is connected to the comparator 2 of the detection oscillator 13.
1 and the integrator 22, eliminating another source of error.

During the detection operation, when the auxiliary frequency f2 approaches the target value with respect to the intermediate frequency of the filter 12, the control of the comparator 21-integrator 22 is performed by the frequency generators 25a to 2 that are being detected.
5 will be suppressed until it moves completely.

[Brief explanation of the drawing]

The drawing is a block diagram illustrating an embodiment of the invention. Next, the main items are listed as follows by comparing the reference numbers in the figures and the names in the text. 9... Light receiving device, 10... Amplifier, 1
1...Modulator, 12...Filter
13...Detection oscillator, 14...Frequency meter, 20...OR member, 21...Comparator, 22...Integrator, 25 , 25 a.
...Frequency generator, 38...Delay circuit, 39°40...Analog storage device, 43
...Integrator.

Claims (1)

[Claims for Utility Model Registration] l A device for measuring the velocity and/or length of a material that moves almost continuously and has a large surface reflectance, and that irradiates it continuously and in a focused manner. A laser beam to be measured is directed at the surface of the material to be measured, and the laser light spot reflected from there is detected by a photodetector and evaluated according to the image frequency.At that time, an amplifier, a modulator, In such a device, a variable filter is connected between the light receiver 9 and the amplifier 10, in which a detection oscillator with an output for frequency measurement and a feedback circuit to the modulator is connected. high-pass filter 3
7 is connected, and its limit frequency is detected by the detection oscillator 13.
A device characterized in that it is controlled by a control voltage generated within the device. 2 In the device described in paragraph 1 of the claims for utility model registration,
Device characterized in that the control voltage for the frequency generator 25 in the detection oscillator 13 also controls the high-pass filter 37. 3 Utility Model Registration In the device according to claim 1 or 2, the high-pass filter 37 is configured to be switchable in three stages, and in particular has a lower limit frequency of 1OKH2, 60KH2, and 160KH2. A device characterized by being formed in. 4 Utility Model Registration In the device set forth in any one of claims 1 to 3, the detection oscillator 13
is a device whose detection operation begins at the highest detection frequency and gradually decreases to lower frequencies. 5. The orer member of the oscillator connected to the two outputs of the filter with a detection oscillator in which the calibration value of the velocity measurement or, temporarily, an approximation of the velocity is integrated over a period of time to determine the length of the material. is coupled to an integrator controlling a frequency generator via a comparator, the two further inputs of which are connected to both outputs of the filter. In the device according to any one of the preceding clauses, the output of the integrator 22 is divided into two parallel circuits, namely one analog storage device 39:40 each, and a frequency generating device in each case. 25 is connected afterwards,
Both outputs are automatically switchable into two states, i.e. only one output frequency 25 or 25a is connected to the frequency meter 14 and the integrator 43 for length measurement.
It is further connected to the modulator 11, and its temperature removal 2
The second frequency output 2 must be blocked, otherwise the second frequency output 2
5a or 25 is connected to the modulator 11, and the other frequency output 25 or 25a is disconnected from the modulator. 6 In the device set forth in claim 5 of the utility model registration claim,
A delay circuit 3 is provided between the comparator 21 and the integrator 22.
8 is connected to the device, characterized in that it releases (sends out) the comparator signal only after the operation of the frequency generator 25; 25a in detection mode has taken place.