JPH0363032B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention utilizes the Doppler effect of light to measure the rotational speed and rotational unevenness of rotating bodies such as audio equipment, information equipment, machine tools, etc. It is related to measuring instruments.

[Conventional technology]

The rotation speed and rotational unevenness of record players, tape recorders, and VTRs, which are audio equipment, are caused by recording, recording,
It is an important element that affects the sound quality and image quality during playback, and the stability of rotation speed and uneven rotation, so-called wow.
The quality of the flutter determines the commercial value of these devices.

Therefore, measurement of rotational speed and rotational unevenness in such fields has become essential for inspection of these devices.

Generally, rotational unevenness is expressed by an index called wow/flutter W/F shown in equation (1).

W/F=△V/V×100(m)... (1) Where, V: Rotational speed (m/min) △V: Rotational uneven speed (m/min) Equation (1) is for the rotational speed N. Rotation unevenness speed△
expressed as a percentage of the ratio of N, usually as a frequency component
It is evaluated for uneven rotation speed of 0.2Hz or more.

The rotational speed V (m/min) must be determined in the form of the number of revolutions per minute N (rpm), and the number of revolutions N
The relationship between (rpm) and rotational speed V (m/min) is shown by equation (2).

N=V/2πr... (2) Here, r: radius of rotation (m) Figure 3 shows the configuration of a rotational unevenness measuring device that measures rotational speed and rotational unevenness using a conventional non-contact optical speed sensor. In the figure, 1 is a motor or a rotary body that is directly connected to a motor or the like and rotates, 2 is a laser device,
3 is a beam splitter that splits the laser beam from the laser device 2 into two; 4a, 4b, and 4c are mirrors for changing the direction of the laser beam; 5 is a lens for receiving the light scattered from the rotating body 1; 6 is a photodetector that exchanges received light into an electrical signal, 7 is an AC amplifier, 8 is a frequency tracker, and 9 is a frequency-voltage converter that converts the output frequency of the frequency tracker 8 into an analog voltage proportional to this frequency. (hereinafter referred to as an F-V converter), 10 is a frequency counter that counts the output pulse frequency of the frequency tracker 8, and 11 is an F-V converter.
A variable attenuator represented by a variable resistor etc. that varies the output voltage of the V converter 9; 12 is a high-pass filter that cuts the DC component of the output signal of the variable attenuator 11; 13 is the output of the variable attenuator 11. A low-pass filter that cuts out high frequency components of the signal, 14 is F-V
This is a gain adjuster for receiving the output signal of the converter 9, adjusting the gain, and outputting the adjusted gain.

In the rotational unevenness measuring device having the above configuration, the laser beam emitted from the laser device 2 is split into two by the beam splitter 3, and one laser beam is split into two by the mirror 4.
In b and 4c, the other laser beam changes its direction with a mirror 4a and irradiates the rotating body 1 so as to intersect the radius of rotation r (m), so that the scattered light of the rotating body 1 corresponding to each irradiation beam is The wavelength undergoes a so-called positive and negative Doppler shift depending on the rotation speed V (m/min) of the rotating body 1 at the rotation radius r (m).

When the scattered light that has undergone the two positive and negative Doppler shifts is focused by a lens 5, guided to a photodetector 6, and converted into an electrical signal, this electrical signal contains a DC signal proportional to the intensity of the received light, and a DC signal proportional to the intensity of the received light. AC signal with Doppler frequency f _d shown in equation (3) (hereinafter referred to as Doppler signal)
exists.

f _d = 2V/λ・sin/2... (3) where V: Rotation speed at rotation radius r (m) of the rotating body λ: Wavelength of laser light: Intersection angle of two irradiation beams The Doppler signal converted into a signal is weak and has a low S/N, so the AC amplifier 7
When the S/N is improved by the frequency tracker 8, a Doppler frequency f _d proportional to the rotation speed V at the rotation radius r (m) of the rotating body 1 as shown in equation (3) can be detected as a pulse signal. The rotational unevenness speed ΔV in the rotational speed V is detected as the frequency modulation amount Δf _d in the Doppler frequency f _d of the frequency tracker 8 .

When the output signal of the frequency tracker 8, which is this frequency modulation signal, is input to the F-V converter 9, the output of the F-V converter 9 is a DC voltage E proportional to the Doppler frequency f _d and the DC voltage An analog signal is obtained by superimposing both the alternating current voltage ΔE which rises and falls around E in proportion to the magnitude of rotational unevenness.

On the other hand, the output signal of the frequency tracker 8 is also connected to the frequency counter 10, and is connected to the Doppler frequency
f _d can be displayed as a count and read directly.

The variable attenuator 11 connected to the output side of the F-V converter 9 has an attenuation amount scaled by a frequency value, and has the function of attenuating the conversion output in proportion to the input frequency. By adjusting the scale frequency to the display frequency measured by the frequency counter 10, the output of the variable attenuator 11 has a rotational unevenness speed ΔV regardless of the magnitude of the rotational speed V of the rotating body 1.
The components can be extracted in proportion to the rotational speed V as shown in equation (1).

The band filter 12 is for passing only wow and flutter components of 0.2 Hz or more, and the low pass filter 13 is for removing the influence of Doppler frequency components (carrier waves) from the output of the F-V converter 9. The cutoff frequency can be varied according to the rotational speed V of the rotating body 1. In this way, the rotational unevenness speed ΔV of the rotating body 1 can be determined as the wow and flutter W/F shown in equation (1).

The number of rotations per minute N (rpm) of the rotating body 1 shown in equation (2) is determined by measuring the position of the laser beam irradiated onto the rotating body 1, that is, the radius of rotation r (m), in advance. Using the measured value of the radius r (m), the gain G of the gain adjuster 14 connected to the output of the F-V converter 9 is determined by the equation (4) derived from equations (2) and (3).
By setting the value shown in the formula, it is obtained as the output of the gain adjuster 14.

G=λ/4π・sin(/2)・r… (4) [Problem to be solved by the invention] The above-mentioned conventional rotational unevenness measuring device measures the number of revolutions N of the rotating body 1 by Separately measure the radius of rotation r (m) from the rotational speed V of 1 and the position of the laser beam irradiated onto the rotating body 1, and calculate equation (2) from the measured rotational speed V and the radius of rotation r. However, there was a problem in that the rotational speed N could not be directly measured.

The present invention was made to solve such problems, and an object of the present invention is to provide a rotational unevenness measuring device that can directly and simultaneously measure the rotational speed and rotational unevenness of the rotating body 1.

[Means for solving problems]

The rotational unevenness measuring device according to the present invention is provided with a band filter, a level meter, a waveform shaper, and a pulse counter for detecting the rotational speed of the rotating body 1 from the frequency of the rotational unevenness of the rotating body 1 after outputting the rotational unevenness. be.

[Effect]

In this invention, by utilizing the fact that the fundamental wave of the rotation unevenness frequency of the rotating body 1 is equal to the rotation speed,
By extracting the fundamental frequency of the rotational unevenness signal, which is the output signal of the low-pass filter 13, with a bandpass filter and counting the pulses, the rotational speed of the rotating body 1 can be measured without measuring the rotational radius r.

〔Example〕

FIG. 1 is a block diagram of a rotational unevenness measuring device showing one embodiment of the present invention, and will be described below with reference to the drawings.

In the figure, numerals 1 to 13 are the same as those of the above-mentioned conventional device.

15 is a band filter that extracts the fundamental frequency component of the rotational unevenness output signal that is the output of the low-pass filter 13; 16 is a level meter that monitors the output level of the band filter; 17 is a waveform shaper; and 18 is the waveform shaper 17. This is a pulse counter that measures the number of pulses or pulse period of a pulse signal per unit time.

In the rotational unevenness measuring device having the above configuration, when the rotating body 1 rotates, the rotational unevenness signal which is the output of the low-pass filter 13 is transmitted to the rotating body 1 as shown in FIG. 2a.
It is obtained as an alternating current signal with a fundamental wave having a frequency equal to the period T ₀ of one revolution.

If the rotational unevenness signal is inputted to the band filter 15 and the center frequency f ₀ of the band filter 15 is adjusted so that the indicated value of the level meter 16 becomes the maximum, the center frequency f ₀ of the band filter 15 becomes the same as that of the rotating body 11. The output signal of the bandpass filter 15 is tuned to the rotation period T ₀ (f ₀ =1/T ₀ ), and the output signal of the bandpass filter 15 becomes a sinusoidal signal with a period T ₀ as shown in FIG. After shaping the waveform in step 17 and converting it into the pulse signal shown in _FIG . This is a rotational unevenness measuring device that can directly measure the rotational speed of the rotating body 1 without any trouble.

〔Effect of the invention〕

As described above, according to the present invention, by utilizing the fact that the fundamental wave of the rotational unevenness frequency of the rotating body 1 is the rotational speed of the rotating body 1, the fundamental frequency of the rotational unevenness signal that is the output of the low-pass filter 13 is By extracting and counting the period with the pulse counter 18, it is possible to provide a rotational unevenness measuring device that can also directly measure the rotational speed of the rotating body 1 without measuring the irradiation position of the laser beam, that is, the rotational radius r.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a rotational unevenness measuring device showing an embodiment of the present invention, FIG. 2 is a diagram showing the characteristics of the rotating unevenness measuring device, and FIG. 3 is a block diagram of a conventional rotational unevenness measuring device. In the figure, 15 is a band filter, 16 is a level meter, 17 is a waveform shaper, and 18 is a pulse counter. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A laser that outputs light of a specific wavelength, a beam splitter that splits the output beam of the laser into two, and a rotating body that is irradiated with the directions of the two split laser beams crossing each other. a plurality of mirrors for obtaining Doppler signals, a lens for receiving together the scattered light that has undergone a Doppler shift according to the speed of the rotating body for each of the two irradiation beams, and an electric a photodetector for converting, an AC amplifier for amplifying the output of the photodetector, a frequency tracker for detecting the Doppler frequency from the amplified signal, and a Doppler frequency that is the output signal of the frequency tracker for converting the Doppler frequency to the Doppler frequency. a frequency-voltage converter that converts the output signal into an analog voltage proportional to , a frequency counter that counts and displays the Doppler frequency, and attenuates the output signal of the frequency-voltage converter in proportion to the Doppler frequency counted by the frequency counter. In a rotational unevenness measuring device equipped with a variable attenuator that can be used as a variable attenuator, and a high-pass filter and a low-pass filter that remove DC components and high-frequency components of the variable attenuator, respectively, the output of the low-pass filter is measured after the low-pass filter. A rotational unevenness measuring device comprising a rotational speed measuring means capable of measuring the rotational speed of the rotating body from the fundamental frequency of the rotational unevenness signal. 2. A bandpass filter that inputs the rotational unevenness signal output from the low-pass filter and outputs a sinusoidal signal, a waveform shaper that shapes the waveform of the output of this bandpass filter, and a pulse obtained by this waveform shaper. 2. The rotational unevenness measuring device according to claim 1, wherein the rotational speed measuring means includes a pulse counter that counts the number of pulses or pulse period of the signal per unit time.