JPS584295B2 - How to do it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a frequency measurement method, in particular, a method for measuring the unknown frequency by interacting waves such as light, microwave, ultrasound, etc. of an unknown frequency and a known frequency, and measuring the Doppler frequency. The present invention relates to a frequency measurement method.

In general, measuring the frequency of waves such as light, microwaves, and ultrasonic waves is an extremely important element in fields such as communication technology and precision measurement, and various measurement methods have been proposed recently. There is.

For example, when measuring the frequency of light, the light to be measured is transmitted through a diffraction grating or prism, and the wavelength λ of the light is measured by detecting the diffraction angle or refraction angle of the light at that time. By converting this wavelength λ into a frequency, the frequency is measured and detected.

That is, by obtaining the wavelength λ of light, the frequency can be determined based on the following equation.

Here, C is the speed of light, 299790×108m/S
is given by

However, according to this measurement method, once the wavelength λ
By detecting the frequency and indirectly measuring the frequency,
Not only is the measurement operation complicated, but it also includes errors.

Further, the frequency measuring device based on the conventional method described above cannot measure waves other than the wavelength of light with the same device, and is not versatile.

Therefore, an object of the present invention is to make it possible to directly measure the frequency of light, to make the measurement accurate and simple, and to provide versatility by being able to measure at least two types of waves. This will be explained in detail below using examples.

Generally speaking, there is a speaker that emits a sound wave with a frequency of f0, and a listener approaching the speaker will hear a sound at a higher frequency than f0, and conversely, a listener moving away from the speaker will hear a sound at a frequency lower than f0. Listen.

That is, if the speed of sound is S and the approaching speed of the listener is v, then the frequency f of the sound wave received by the listener is given as follows.

This is known as the Doppler effect, and the present invention utilizes this.

This effect also occurs in waves such as light waves and microwaves.

At this time, in the above equation, the speed of light C is included instead of the speed of sound S, resulting in the following equation.

Here, v is the speed at which the measurement system approaches the light source or other electromagnetic wave source.

However, this is a non-relativistic equation, and there is a restriction that v is sufficiently small compared to the speed of light C.

Next, when a light wave is irradiated onto a mirror and reflected, if this light wave is completely coherent, this can be approximated by a plane wave, and the electric field EI is given by the following equation.

EI (incident light) = EO exp i (kOX-ωOt)
In this case, in order for the above equation to hold true, it is necessary that the luminous flux has a certain degree of spread and that ΔPy=0 and ΔPz=0.

Note that the above ΔPy indicates the fluctuation of momentum in the y direction, that is, in the direction perpendicular to the light propagation direction.

This light wave is coherent and needs to have a constant beam diameter in the propagation direction.

Such light waves can usually be obtained from laser devices and are difficult to obtain from other light sources such as lamps and light emitting diodes.

Now, this light is reflected by a mirror, but if we assume that this mirror is moving toward the light source at a speed of v, the angular frequency ω of the reflected light is determined by the following equation due to the Doppler effect mentioned earlier. can be obtained from.

Here, the coefficient 2 is because the light wave is reflected by the mirror.

When this light ER and the above-mentioned light EI are superimposed on the same optical axis, the total electric field ET is given by the following equation.

Here, Δω and Δk are expressed as follows.

That is, from the above equation, the light intensity |ET|2 with constant XO
By observing , it is possible to detect changes in the intensity of the angular frequency Δω.

On the other hand, since ΔωO can be made sufficiently smaller than the angular frequency ωO of light, there are detectors that can detect this frequency.

For example, if λ=6×10-5 cm, f0=5×1014(Hz) Therefore, there are currently no measuring instruments that can detect this.

However, if v/C=10-6, becomes.

Therefore, there are currently measuring instruments capable of detecting frequencies of this order, such as photodiodes, avalanche photodiodes, or photomultipliers.

Furthermore, by using two light waves and simultaneously measuring the beat frequencies Δω1 and Δω2, the ratio can be obtained.

In this case, if either ω01 or ω02 is known, the unknown frequency can be found.

Therefore, according to the above equation, the mirror speed v the speed of light C does not directly affect the unknown frequency.

Not being concerned with the mirror speed V corresponds to being able to eliminate errors caused by mirror speed measurement, and means that accurate measurements can be made.

The fact that the speed of light C is not involved has no positive significance.

This is because it is precisely known.

However, it is possible to measure the frequency with the method according to the invention and know the wavelength in other ways, and determine the speed of light as the ratio of the two.

If the measurement accuracy of frequency and wavelength is high, a more precise value of the speed of light C can be determined, and in this sense, it can be said to be significant.

The above principle was explained in terms of light waves, but
Of course, this principle can also be applied to sound waves.

In this case, this corresponds to removing the sound speed S from the equation, but since the sound speed S varies depending on temperature and atmospheric pressure, this can be said to have great significance as in the above case.

Next, an embodiment of the frequency measurement method according to the present invention based on the above-mentioned principle will be described.

FIG. 1 is a simplified configuration diagram showing the principle of the frequency measurement method according to the present invention. In the figure, 1 is a laser, 2 is a microwave oscillator, and these coherent lights and microwaves are emitted in the direction of the arrow in the figure. It is sent out in the direction of the vibrating movable mirror 3.

4 is a fixed mirror arranged perpendicular to the movable mirror 3; 61 and 62 are respectively laser beam optical paths; half mirror 52 arranged in the microwave propagation path is a microwave detector; and 54 is a light wave detector. It is a vessel.

In such a configuration, the laser beam emitted from the laser 1 is separated into two beams by the half mirror 61.

One of the separated light beams is emitted in the a direction, and the other light beam passes through the half mirror 61, is emitted in the b direction, is reflected from the mirror 3, and is then irradiated onto the half mirror 61 again.

Here, this reflected light beam is reflected in the d direction, reflected in the opposite direction by the mirror 4, and transmitted through the half mirror 61.

Here, the above two beams enter the detector 54 having the same optical axis.

In this case, assuming that the movable mirror 3 is vibrating left and right at a speed v, it is possible to detect fluctuations in the amount of received light at the beat frequency Δf determined by the following equation as described above.

(f01: Laser light frequency) On the other hand, the microwaves transmitted from the microwave oscillator 2 can also be detected by the detector 52 in the same process.

Here, if the microwave frequency is f02, the detector 5
2 can detect the beat given by the following equation.

Now, assuming that f02 is known, the unknown laser light frequency f01 is given by the following equation.

Therefore, the unknown frequency f01 can be known from this.

In this case, if f01 is the known frequency, the unknown frequency f0
It is also possible to know 2.

However, in the embodiment shown in FIG. 1, since the frequencies of laser light and microwave are significantly different, mirrors 3, 4
It is difficult to use the same material for the half mirrors 61 and 62, and the measuring instruments 52 and 54 are completely different.

Therefore, it is considered that there is not much feasibility.

FIG. 2 shows another embodiment of the frequency measurement method according to the present invention that solves this problem, in which 1 is a laser oscillator, 63, 64, 65, 66, 6768 are half mirrors,
3 is a movable mirror, 4 is a fixed mirror, and 55, 56, and 57 are photodetectors.

Further, 7 is a modulator, and this modulation is performed using microwaves.

91, 92, and 93 are filters.

In this case, the frequency of light is f0, and the frequency of microwave is f1.
Then, the filters 91, 92, 93 are each f0
, f0-f1, and f0+f1.

In such a configuration, the laser light emitted from the laser 1 is modulated by microwaves applied to the modulator 7.

The light emitted from the modulator 7 includes f0, f0-f1,
It contains light of three frequencies: f0+f1.

f1 is the microwave frequency.

This modulated light is reflected or transmitted by half mirrors 63, 64, and 65, and is divided into three beams, and is filtered by filters 91, 92, and 93, f0 and f0, respectively.
It is separated into frequencies of 0-f1 and f0+f.

Assuming that the movable mirror 3 is moving leftward at a speed v, the detector 55 will detect the beat vibration given by the frequency.

Similarly, detector 56 will detect beat vibrations given by frequency and detector 57 will detect beat vibrations given by frequency.

Next, after measuring these, the frequency f0 of the laser beam can be determined by calculating the frequency f0 using the following equation.

Conversely, if the frequency f0 of the laser beam is known, then
The frequency f1 of the microwave can be determined from the following equation.

As explained above, according to the present invention, there is no need for the conventional operation of determining the frequency by determining the wavelength λ and dividing the speed of light C by this, and the accurate frequency can be determined with a simple operation.

According to this embodiment, half mirrors 63 to 68,
Since the mirrors 3 and 4 and the detectors 55 to 57 may all be used for light having similar frequencies, they can be made of materials with the same properties.

FIG. 3 shows another embodiment of the frequency measuring method according to the present invention, in which 1 is a laser oscillator, 3 is a movable mirror, 4 is a fixed mirror, 66 to 68 are half mirrors, 55
~57 is a photodetector.

Further, 72 is a modulator to which ultrasonic waves are supplied, thereby modulating the laser light.

As the modulator 72, for example, a ferroelectric material exhibiting a piezoelectric effect can be used.

A lens 75 is arranged after the modulator 72.

In this case, if the frequency of the laser beam is f0 and the ultrasonic frequency is f1, when the laser beam passes through the modulator 72, the zero-order light f0, the first-order light f0+f1, and the negative first-order light f0
−f1..., etc. are separated.

The luminous fluxes indicated by W, Z, and Y are zero-order, first-order, and negative first-order light, respectively.

These lights are sent out from the modulator 72 with a constant polarization angle, and this polarization angle is zero for zero-order light and becomes larger for higher-order terms.

When a convex lens 75 is placed at a focal length distance from the modulator 72, the W, Z, and Y light beams become parallel lights when they pass through the convex lens 75.

Then, this light is transmitted to the detector 55, similar to that described above.
Detected at 56 and 57.

The detectors 55, 56, and 57 can detect beat vibrations each having a frequency expressed by the following equation.

Here, if the frequency f1 of the ultrasonic wave is known, the frequency f0 of the laser beam can be determined by the following equation.

Conversely, if the frequency f0 of the laser beam is known, the frequency f1 of the ultrasonic wave can be determined by the following equation.

Also, Because it is You can also find f0 using

According to such a method, measurement accuracy can be improved.

In other words, according to the above method, if there are two unknown and known frequencies of light, microwaves, and sound waves, and there is a modulator that allows them to interact, the unknown frequency can be easily converted by using the Doppler effect. Accurate measurements can be made manually.

Next, the details of the above-mentioned movable mirror 3 are shown in FIGS. 5 and 6.
This will be explained using FIG.

In FIG. 5, 31 is a high frequency power source, and 32 is a reflective film that reflects the aforementioned light, which is adhered to the surface of an electrode 33.

34 is a piezoelectric effect material interposed between the electrode 33 and the electrode 35.

The electrode 35 is attached to the surface of the support wall 360.

In such a configuration, when a high frequency voltage is applied from the power source 31 to the electrodes 33 and 35 and an oscillating electric field is applied to the piezoelectric material 34, the piezoelectric material 34 repeats expansion and contraction vibrations.

Then, the reflective film 32 vibrates back and forth in synchronization with the vibration, and the amplitude at this time is proportional to the high frequency output supplied from the power source 31.

In this case, if the piezoelectric material 34 is made thicker, the amplitude can be increased, but it is also necessary to increase the voltage.

In addition, in FIG. 5, C indicates a synchronization signal.

The power source 31 may be one that sends out a sine wave, and if this is done, the velocity V of the reflection plate will also be a sine wave.

With v0 as a constant, becomes.

The beat frequency Δf in this case is given by the following equation.

Therefore, it will vibrate itself.

FIG. 4a shows the output current of the photodetector, whose oscillations represent a beat signal, but whose frequency also varies sinusoidally.

Further, if the voltage sent from the power source 31 has the waveform shown in FIG. 4e, the velocity V of the reflective film 32 is given by the following equation.

however, T: Period of voltage fluctuation n: integer On the other hand, the beat frequency is given by the following equation.

Since the beat frequency is given by the absolute value of the difference between two frequencies, it takes the same value even when v=±v0.

In FIG. 6, reference numeral 37 denotes a reflecting plate that reflects light, and is supported by a support rod 41.

The support rod 41 is inserted into the hollow part of the support cylinder 42 and is given the habit of moving in the direction of the support wall 39 via a spring 40.

Reference numeral 38 denotes an elliptical cam that comes into contact with the reflecting plate 37 and is given rotational force by an electric motor (not shown).

In such a configuration, when the cam 38 rotates, the reflecting plate 37 is pushed by the cam 38 and pulled by the spring 40, so it vibrates back and forth.

Depending on the shape of the cam 38, an arbitrary speed v(t) can be applied to the reflection plate 37.
may be given to

As shown in the figure, when this cam 38 is elliptical, the speed v
(t) is given by the following equation.

q: Rotation angular frequency of the cam a: 1/2 of the major axis diameter e: Eccentricity In FIG. 6, a crank can be used instead of the cam 38 to cause back and forth movement.

In this way, the method of imparting speed to the mirror by mechanical motion has the following advantages.

That is, since the amplitude of the movement of the mirror can be sufficiently obtained, there is an advantage that v(t) is constant for a long time.

In other words, it is possible to set the mirror speed v(t) so that it does not change much during the measurement time.

In this way, the method of using a cam or crank can provide a sufficient vibration stroke of the mirror, but since the movement is mechanical, there is a problem in that the mirror is prone to lateral wobbling.

Figure 7 solves the above problem, and in the figure, 3
7 is a reflecting plate, 43 is a ferromagnetic material attached to the back surface of this reflecting plate 37, and 44 is a support rod fixed to the reflecting plate 37, which is supported by an airtight cylinder 48 together with a piston 46 fixed to the tip thereof. Ru.

49 is a magnetic core around which a coil 47 is wound.

Gas is sealed within the cylinder 48, and this serves as a spring.

When a current is passed through the coil 47, the ferromagnetic material 43 moves to the magnetic core 49.
, and is restored when the current is cut off.

When an alternating current of arbitrary amplitude is passed through the coil 47, the second
The reflection plate 37 moves back and forth at twice the frequency.

In this case, a spring may be used instead of the cylinder 48.

According to this method using magnets, the speed of the mirror v(
t) can only be obtained in the form of a sine wave.

However, since the mass of the movable part can be made sufficiently light, it is possible to produce a movable mirror with fewer failures and a large amplitude.

Note that in the figure, C indicates that a synchronization signal is obtained.

Here, the beat signal can be obtained with a photodetector, but
This includes some errors.

This error is caused by frequency fluctuations in laser oscillation and microwave oscillation, lateral vibration of the mirror, spread of the light beam, and the like.

Let the inclination of the mirror be α, the inclination of the laser beam be θ, and when the mirror approaches the laser at a speed v, the frequency of the reflected wave fR and the direction of the optical axis be θR, as is clear from Figure 18. However, .

θ′≒θ π-θR≒(θ'-2α)≒θ-2α becomes.

θ includes both the spread of the beam and the deviation of the optical axis of the laser.

According to this method, the ratio of beat frequencies Since the same laser light and the same mirror are used in the When separated from It is.

However, the break is the deviation angle of the laser optical axis.

θb is the beam spread. Since the mirrors are the same, It is.

Considering the beam spread θb, if the luminous flux is a Gaussian beam, it is given by:

λ is the wavelength and D is the beam diameter. For example, He-Ne
If the beam diameter of the laser is 1 mm, then the following is true.

Since θb is squared, it can be ignored.

Therefore, even if these errors are taken into consideration.

As described above, according to the present invention, since the beat frequency is measured under the same conditions, errors can be canceled out and accurate measurements can be made, which is a great advantage.

In addition, if microwaves are used as they are, θb is very large and will quickly diffuse, but since the present invention superimposes microwaves on laser light, it is possible to set θb≒0, which is extremely large. It becomes convenient for

Therefore, by measuring the number of beats of the detectors 55, 56, and 57, the frequency can be measured.

In this case, the count number C is is given by

However, another problem arises here. If a commercially available frequency counter is used as a measuring device, three counters with the same performance would be required.

Moreover, it is necessary to synchronize the start and stop times of counting.

Usually, only asynchronous frequency counters are commercially available, which is difficult.

Furthermore, if the mirror speed v(t) oscillates in a sinusoidal manner, the beat waveform changes in frequency from almost DC to MHz, as shown in FIG. 4a or c.

However, with commercially available counters, it is difficult to measure over such a wide range, and range switching is often required.

Next, a device for solving the above problem will be explained in detail.

FIG. 8 shows its block diagram, in which 100
200 is a counting section, 300 is a subtraction section, 400 is a division section, and 500 is a display section.

The current waveforms of the photodetectors 55, 56, and 57 are shown in Figure 4a.
The one shown in Figure 4C is ideal, but since it is difficult to exactly match the amplitudes of the electric fields of the two light waves.

FIG. 9 is a diagram showing how this waveform is input, amplified evenly from DC to MHz, and shaped into a rectangular wave as shown in FIG. 4b.

In the same circuit, 111-124 are resistors 131-138
is a capacitor, and 151 to 152 are choke coils.

The input described above is amplified by transistor 101.

This amplified signal is sent to transistor 102103, where it is shaped into a rectangular wave, resulting in the waveform shown in FIG. 4b.

In the same circuit, 190 is a monostable multivibrator, which may be composed of transistors, but TT
It is more convenient to use LIC.

Specifically, SN74121 (TI) can be used.

The waveform sent out from the monostable multivibrator 190 has a constant pulse width, as shown in FIG. 4d.

Symbol C in the circuit is a synchronization signal, which sets or resets the monostable multibiflator 190 depending on the vibration state of the mirror 3.

In this case, an analog switch is not required.

Next, details of the counting section will be explained.

This can use a hexadecimal counter Ic.

For this reason, the 4-bit binary counter SN7493N
(TI Company) can be used.

Furthermore, a decimal counter SN7490N may be used depending on the type of IC used in the subsequent stage.

The ICs listed below are just examples, and can be freely converted.

Fig. 12 shows the connection diagram.

In the figure, 211, 212, 213 are, for example, SN7
493N (TI), TD3493AP (Toshiba), M5
Use 3293 (Mitsubishi) etc.

R01 and R02 are reset terminals, which apply a one-shot pulse at the start of counting and are then held at 0V.

InB is the input B terminal and is connected to the output A terminal.

Therefore, 211 acts as a 4-bit binary counter, and the outputs A, B, C, D are 20, 21, 22, 2
Corresponds to 3.

212 and 213 are similarly configured and have output terminals A, B,
C, D; A, B, C, D are 24, 25...
・Compatible with 211.

The counting section can be constructed in this way.

Next, the subtraction unit 300 subtracts the two counts.

That is, the count number of can be obtained by the above-mentioned calculation section.

In this case, t1 and t2 are provided by setting and resetting monostable multivibrator 190 as described above.

This subtraction applies to T3026, TM4006, TM4350 (
This can be accomplished by combining addition/subtraction ICs such as Toshiba).

As a result of this, You will get .

Further, 400 is the multiplication/division unit described above.

FIG. 10 is a wiring diagram of the elements used in this calculation. Here, 6-bit multipliers SN7497N are used for 411, 412, and 413.

In this element, inputs A, B, C, D, E, F are 20
, 21, 22, 23, 24, 25, and set the input value to
A, XB, XC, XD, XE, and XF.

In the figure, fin indicates the input clock frequency.

A clock signal is supplied to clock terminal Ck.

St is a strobe terminal. ZO is the output and YO
is its inverted output.

Further, EI is an enable input, and Ca is a cascade input.

When these are set to "0" and "1" states, respectively, a pulse given at an output frequency of can be extracted from the ZO output terminal.

Since this element is 6 bits, it can be cascaded to obtain the desired number of digits.

That is, it is sufficient to connect St and EI of the next stage to EO (enable output) of the previous stage, and connect Ca to ZO.

FIG. 10 shows an example in which three stages are connected, which is expanded to 18 bits.

In other words, if the input signal from the A terminal 411 to the F terminal 413 is Xj (j = 1, ......, 18), the pulse of (Xj = 0, 1) is output from the two outputs of 413 or It can be taken out as Y output.

FIG. 11 is a connection diagram for multiplication, and in the figure, 414 and 415 are SN7497N.

St of 414 and 415 are made common and lead the clock pulse.

EI and Ca are "0" and "1" as before, but the difference is that the two outputs of 414 are led to the clock terminal of 415.

X=XA+2XB+・・・・・・・・・25YF(41
4)Y-YA+2YB+・・・・・・・・・25YF(
415), the output pulse frequency fx of 414 is as described above.

While introducing this to the clock terminal 415,
The output fy is as follows.

In other words, we have successfully multiplied X and Y.

This is a 6-bit diagram, but 414 and 41
5 can be replaced by multiple cascade connections as shown in FIG.

Thereby, a desired number of bits can be given to each of X and Y.

Next, we will configure the division circuit, but before that we will explain the connection of the up/down counter.

FIG. 13 shows a cascade connection for increasing the number of bits.

This can use SN74192, for example.

L0 is a load terminal, and Cr is a clear terminal.

When LO is set to "1" and Cr is set to "0", the element starts counting the number of pulses.

+ is a + input terminal, - is a - manual terminal.

Ca is a carry output, and Br is a borrow output.

A, B, C, and D are output terminals based on binary coded decimal system.

When a pulse with a frequency of f1 is input to the + terminal, the count increases and a carry signal is sent every 10 times.

When a pulse of f2 is applied to one terminal, the count decreases and a borrow signal is sent every 10 times.

By cascading these, you can count the difference between the + input and - input pulses using any number of bits.

However, at this time, f1 and f2 must be out of phase.

In this case, HD2541 is used instead of SN74192.
(Hitachi), M53392N (Mitsubishi), MB457 (Fujitsu), TD34192AP (Toshiba), μPB2192D (Nichiden), etc. can also be used.

Also, if you want to obtain hexadecimal power instead of decimal power, SN
74193N, HD2542, M53393P, MB456, μPB2193D can be used.

FIG. 14 is a diagram showing an example of a multiplication/division circuit. In the figure, 401 is a clock pulse generator which sends out clock signals having the same frequency but different phases.

420 is a cascade connection of several multiplier ICs as shown in FIG.

X1 is an input terminal, and in Fig. 10, A, B...
It is written as...

Ck is clock input, Si is strobe input, ZO is Z
This is the output.

This output f1 can be expressed by the following equation.

However, X1=XA+2XB+・・・・・・・・・+XN2n−
1 (420) 425, 430, 440 are also SN7
497N cascade connection is shown.

If the input of 425 is X2, the output of 425 is a pulse with a frequency given by .

Similarly, if the input of 430 is Y1 and the input of 440 is Z, the output pulse frequency of 430 is given by:

450 is a cascade connection (FIG. 11) of the above-mentioned up/down counters.

The up/down counter counts negative pulses, so 42
The outputs of 5 and 440 take pulse signals from the inverted output YO.

Outputs Z of the up-down counters are connected to inputs Z of 440, respectively.

According to this connection configuration, the up-down counter functions as follows.

In other words, the output Z of 450 functions to be constant.

This will be explained below.

For example, if f2>f4, the + count increases and the output Z of 450 increases by that amount.

Then, since this signal is introduced at 440, f4 increases, and f4 increases until f4=f2.

Conversely, if f2<f4, the - count increases, so Z decreases.

Then, f4 decreases until f4=f2.

Here, the following equation is obtained from the above equation. X1X2=ZY1 That is, the following equation is obtained.

In this case, X1, X2, and Y1 can be given arbitrarily, and multiplication and division operations can be performed here.

Here, the reference frequency f1 is input as the X1 input.

Input the beat count number as the X2 input.

If the difference in beat counts is input as Y1 input, the following equation is obtained.

Z=f0 In other words, X1 may be fixedly connected to .

The X2 input is performed by directly introducing the calculation result shown in FIG. 12 into the terminal.

The result of the subtraction unit 300 may be input as the Y1 input.

The advantage of the circuit shown in FIG. 14 is that the Z output immediately provides the multiplication/division results as X2 and Y1 change.

In other words, there is no need to repeat setting and resetting frequently.

Next, the display section 500 will be explained.

FIG. 15 is a diagram showing an example of this, and in the same figure, 53
1,532 is a display tube.

Alternatively, an LED liquid crystal or the like may be used.

521 and 522 are BCD decimal recorder driver I
It is C.

In Figure 14, the Z output is binary coded decimal (BCD)
Since it is obtained by , all you have to do is interconnect these.

In FIG. 14, if a cascade connection of 4-Bit counters is used as 450, it is necessary to convert the binary number into a binary coded decimal number.

ICs that can be used for 521 and 522 are display tubes 531 and 53.
Of course, it differs depending on the specifications of 2.

Since the display tubes 531 and 532 include 10 numbers, they may be 7-segment display tubes.

In this case, many types of selections are possible, so examples will be omitted.

Each component of the block diagram shown in FIG. 8 has been described above.

This method has a major feature in that the beat counts included in the signals received by the detectors 55, 56, and 57 are counted separately, and the difference is calculated to perform division and multiplication.

However, the three beat counts C0, C+, C- are are very close to each other.

Because, because.

Since there is a difference of about 1 after 106 counts,
The three counting circuits 200 (FIG. 8) calculate substantially the same thing.

This is a waste.

Figure 6 is a diagram showing an example of a circuit that improves this point. In the figure, 200 is a counting unit, 400 is a multiplication/division unit, 500 is a display unit, and 520 is a cascade connection of up/down counters (see Figure 13). .

Counting part 1 is reduced to one, which is Count only.

C0 and C are used for the + and – inputs of the up/down counter.
Connect + or C-.

The cascade number of 250 can then be much shorter than the 200 counters.

In other words, since 106≈220, a 6-bit counter can be reduced by 4, and a 4-bit counter can be reduced by 5.

Now, as described above, the calculation of multiplying the output of 250 and the ratio of 200 by f1 is performed using 400.

That is, It is.

Finally, an embodiment for compensating for lateral shake of the movable mirror 3 will be described.

The beat count C is It is.

S is the distance that the mirror in the area hit by the beam has moved from t1 to t2.

Even if v(t) varies, as long as S is common to the three beams, a proper ratio is maintained between beat counts.

FIG. 19 is a diagram showing the amplitude of the vibrating mirror.

When the mirror moves forward, the three beams become k and m, respectively.
, o, and when the mirror retreats, it is reflected at l, n, and p.

For example, if the count time is set to half the period of the vibration of the mirror, the moving distance S of the mirror is kl, mn, op, respectively.
equal to the length of

Therefore, the ratio of the beam counts can be appropriate for mirror blur as shown in a in the figure.

This is because in Figure a, kl=■=■.

In fact, beat vibration will not occur unless the vibration surface is perpendicular to the optical axis, but we are considering a slight angular deviation.

However, it is necessary to correct the amplitude of the mirror as shown in FIG. 19b.

However, even in this case, the intervals between the luminous fluxes are kept equal, so .

■=So ■=So−S1, ■=So+S1.

If zero-order modulated light f0 is propagated along the optical axis mn and ±first-order modulated light f± is propagated along the optical axes kl and op, a serious defect will occur.

That is, at this time, the following equation holds true.

It is.

Depending on the combination of these three numbers, f1
S0 and S1f0 cannot be separated.

What we want to find is f1S0, and f0S1 is the error due to horizontal bull.

Since f1/f0≈10-6 to 10-7, in order to eliminate this, it is necessary to suppress S1/S0≪10-6.

Therefore, the zero-order modulated light (f0) is guided to one end.

For example, it is assumed that the optical axes of the zero-order modulated light are aligned with kl, the ± modulated light is aligned with mn, and the one-modulated light is aligned with OP.

At this time, the count number is as follows.

get.

Considering this linear combination, we get the following equation.

Here, since S0≫S1, this value is approximately f1S0
It is.

Therefore, the above-mentioned problems can be solved. FIG. 17 is a block diagram of an improved circuit based on this method. In the figure, 240 is a 1/2 frequency divider circuit, which can be constructed using a flip-flop.

The upper and lower 200 give C0 and C- count pulses,
The middle 200 provides a C+ count pulse.

C0, C- undergoes a 1/2 divide and is added to C+ at 350.

As a result, we get ■d, so It is obvious that we only need to calculate .

400 and 500 are the same as before.

The block diagram of FIG. 17 corresponds to the invention of the block diagram of FIG.

In the circuit shown in Fig. 16 that uses up-down counters, the two up-down counters have C+ and C0.
The same effect can be obtained by connecting C+ and C-.

At this time, a part of the normal counter counts C0.

This will not change.

That is, the first-order modulated light (f0±f1) and the zero-order modulated light (f
0) along parallel and equally spaced optical axes included in the same plane, and the central optical axis should correspond to one of the modulated lights.

The count numbers at both ends need only be counted to 1/2 of the count number in the middle.

Division by 1/3 can be easily performed by slightly modifying the arithmetic unit 400.

For example, a 1/3 frequency divider can be inserted.

As explained above, according to the present invention, it is possible to directly and accurately know the waves of light, microwaves, sound waves, etc., and moreover, it is possible to know the frequencies of various types of waves with one device, making it possible to use a general-purpose device. It has great effects such as improving sexual performance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining the principle of the frequency measurement method according to the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG.
The figure shows another embodiment, Figure 4 shows voltage waveforms at various parts, Figure 5 is a cross-sectional view of a movable mirror using piezoelectric material, and Figure 6 is a cross-sectional view of a movable mirror using a cam. , Fig. 7 is a side view of a movable mirror using electromagnetic field, Fig. 8 is a block diagram of an electronic circuit used in the present invention, Fig. 9 is an amplification and waveform shaping circuit diagram, and Fig. 10 is a multiplication Figure 11 is a cascade connection diagram of a multiplication IC, and Figure 1 is a multiplication connection diagram of a multiplication IC.
Figure 2 is the connection diagram of a 4-bit binary counter IC, the first
Figure 3 is a cascade connection diagram of a 4-bit up/down counter, and Figure 14 is an IC for the division operation used in the present invention.
Flock diagram, Figure 15 is a diagram showing an example of the display section, Figure 16 is a diagram showing an example of the display section.
Figure 17 is a block diagram of an electronic circuit using an up/down counter, Figure 17 is a block diagram of an electronic circuit improved by the present invention, Figure 18 is a schematic diagram for considering lateral misalignment of the laser and mirror, Figure 19 The figure is a diagram for considering the amplitude deviation of the mirror. 1... Laser, 7, 72... Optical modulator,
63-68...half mirror, 3...movable mirror, 4...fixed mirror, 91-93...
... Filter, 52-57 ... Detector,
100... Width increase/waveform shaping section, 200...
- Counting section, 250... Difference frequency counting section, 300,
350...Subtraction section, 400...Multiplication/division section, 500...Display section, 411-415...
Multiplication IC, 211-213... Counting IC, 251
~252...Up-down counter IC.

Claims (1)

[Claims] 1. A coherent light beam modulated by microwaves is divided into three by half mirrors 63, 64, and 65, and separated into zero-order modulated light and first-order modulated light by filters 91, 92, and 93. After that, each light beam is further divided into two by a half mirror, reflected by a fixed mirror 4 and a movable mirror 3, and then combined again, and a beat signal generated by the Doppler effect is transmitted to photodetectors 55, 56, 57. 1. A frequency measurement method characterized in that after detecting and counting the frequency of one of the coherent light beams or microwaves as known, the frequency of the other is calculated. 2. The coherent light beam modulated by the ultrasonic wave is transmitted to the lens 7.
5, the beam is made into a parallel beam, and then divided into two by the half mirrors 66, 67, and 68 separated here, reflected by the fixed mirror 4 and the movable mirror 3, and then combined again. A frequency measuring method characterized in that after detecting and counting beat signals by photodetectors 55, 56, 57, one frequency of a coherent light beam or an ultrasonic wave is known and the frequency of the other is calculated.