JP2000111312A - Optical frequency linear sweeping device and modulated correction data recorder for optical frequency sweeping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a function of correcting nonlinear light FM wave to linear light FM sweep for improving the measuring accuracy of a light frequency linear sweeping device and reduce the cost. SOLUTION: This sweeping device 81 is constituted by providing a light source (a variable wavelength type light source) 87 capable of outputting light FM signal of which light wavelength varies with time in a specific period, and correcting modulation of light FM signal based on external correction signal, a reference signal generator 83 generating reference signal necessary for the wavelength variation control of the light source 87, a correction signal generator 84 preparing in advance a correction signal for correcting to make a modulation characteristic specific to the light source 87 and outputting the prepared correction signal, and an adder 86 adding the reference signal and the correction signal and supplying the added output to the light source 87.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical frequency linear sweep device and an optical frequency linear sweep device suitable for distance or multiple position measurement based on a measurement principle using a light source capable of continuous optical frequency sweep. And a modulation correction data recording device.

[0002]

2. Description of the Related Art In recent years, technical developments using high-performance light sources have been made, and their applications have been made in various fields. Considerations are being made. In the field of optical measurement, optical frequency domain reflection measurement (FMCW method: Freq
uency Modulated Continuous Wave, OFDR method: Opti
cal Frequency Domain Reflectometry, collectively
The technique using the optical frequency domain reflection measurement method is applied to measurement in an optical fiber sensor or an optical fiber flaw detection inspection.

This optical frequency domain reflection measurement method is a method of measuring a distance or a multiplex position based on a measurement principle using a light source capable of continuous optical frequency sweep. A light source with FM (Frequency Modu
lation: frequency modulation), the optical FM wave (hereinafter, sometimes referred to as optical FM output light) is transmitted from the measurement location to the target object, and the light reflected by the target object is received. In this method, a beat (beat) frequency between the reference light and the reflected light is observed.

That is, in this measurement method, an optical FM wave repeatedly output from a light source capable of temporally linear sweep is input to an interferometer, where it is converted into reference light and object light (measurement light). The optical path difference (beat frequency) caused by the optical path difference time τ between the reference light and the object light generated when the light is reflected and fed back again, overlapped, and interfered with each other is obtained, whereby the optical path difference 2ΔL = τc (c: speed of light)
That is, it calculates the spatial distance. Here,
Temporal linear sweep means that the frequency is changed at regular intervals with respect to the time axis.

FIG. 5 is a block diagram showing a conventional optical frequency domain reflection measuring device. The optical frequency domain reflection measurement device 20 shown in FIG. 5 is a light reflection measurement device using a semiconductor laser as a light source, and includes a light source unit 13 and a main measurement interference system unit 14. Here, the light source unit 13 outputs an optical frequency modulation signal whose optical wavelength changes with time in a required cycle, and includes an oscillator 1 and a semiconductor laser 2.

The oscillator 1 outputs a modulation signal, and the semiconductor laser 2 is a wavelength-tunable light source that outputs laser light linearly modulated by the modulation signal from the oscillator 1. That is, the optical FM wave 3 whose optical frequency changes with time is output from the semiconductor laser 2.
Note that this light source need only be tunable in wavelength, and is not limited to a semiconductor laser.

[0007] The main measurement interference system section 14 includes a light source section 13.
The optical FM wave 3 output from is split inside, and one is irradiated to the measurement object, and the other is reflected by the reference mirror, and the reflected light interferes to measure the spatial distance of the measurement object. A beam splitter 4, a reference mirror 6, a measurement target 8, a photodetector 10, an A / D converter 1
1, the arithmetic unit 12 is provided.

[0008] Here, the beam splitter 4 includes the light source unit 1.
The light FM wave 3 output from the semiconductor laser 2 in the reference light 3 is divided into a reference light 5 and an object light 7 and reflected light is superimposed to generate interference light.
The beam splitter 4 reflects the reference light 5 branched and output. The measurement object 8 is irradiated with the object light 7 branched and output from the beam splitter 4, and the photodetector 10 square-detects the interference light output from the beam splitter 4 to perform electric signal waveform. Is detected.

Further, the A / D converter 11 includes the photodetector 1
The arithmetic unit 12 performs analog-to-digital conversion of an electric signal waveform output from the A / D converter 1.
1 is a computer which takes in the output signal of No. 1. With such a configuration, in the optical frequency domain reflection measurement device 20, the optical FM
Wave 3 is generated to detect a beat signal and perform distance measurement. That is, the semiconductor laser 2 is linearly modulated by the modulation signal from the oscillator 1 in the light source unit 13 shown in FIG. 5 to output the optical FM wave 3 whose optical frequency changes with time, and the beam splitter in the main measurement interference system unit 14 is output. 4, the light F
The M wave 3 is distributed to the reference light 5 and the object light 7.

The reference light 5 is reflected by a reference mirror 6 which is separated from the beam splitter 4 by a distance L1 and is turned back again to become a light FM wave (reference light) 21. On the other hand, the object light 7 is also reflected by the measurement object 8 separated by the distance L2 and turned back again to become the light FM wave (reference light) 22.
These light FM waves 21 and 22 are superposed in the beam splitter 4 to become interference light 9. In this case, the difference ΔL in distance is | L1−L2 |.

Next, a method (principle) for detecting a beat signal will be described with reference to FIGS. 6 (a) to 6 (d). FIG. 6A is a diagram showing a change of the optical FM wave, and shows the behavior of the optical FM waves 21 and 22 which are the reflected lights. Here, the horizontal axis is time, and the vertical axis is the frequency of the output optical FM wave. As shown in FIG. 6A, each of the optical FM waves 21 and 22 is swept in a value between the optical modulation frequency ν0 and ν0 + Δν (Δν: optical modulation bandwidth). They are superimposed with a shift of an optical delay time (optical path time difference) τ corresponding to the reciprocation 2ΔL of the optical path difference with the measurement target 8. Here, the frequency difference fb occurs over almost the entire interval between the modulation periods 1 / fm (where fm is the modulation frequency). This is the beat frequency. In this case, a sawtooth wave is taken as an example, but the same can be said for a triangular wave.

FIG. 6B is a diagram showing a change in beat frequency, and shows a time change of the frequency difference fb. As shown in FIG. 6B, the low-frequency beat 27
And the high frequency beat 28 appear, but the high frequency beat 28 occurs only at a time interval of τ, and can be almost ignored because of the relationship τ << 1 / fm. Here, what is called a beat frequency is the low-frequency beat 27.

FIG. 6C shows the beat signal intensity waveform. As shown in FIG. 6C, two signal waveforms 29 corresponding to the low-frequency beat 27 and the signal waveform 30 corresponding to the high-frequency beat 28 appear. These are the results of the square detection performed by the photodetector 10 in FIG. 5 and detection as an electric signal waveform. FIG. 6 (d)
Shows the beat frequency components. As shown in FIG. 6D, the beat signal spectrum 31 having the frequency fb
Is appearing.

Thus, the interference light 9 output from the beam splitter 4 in FIG. 5 is square-detected by the photodetector 10 and detected as an electric signal waveform. The signal waveform passes through the A / D converter 11 and is calculated by the computer. Computing device 1 such as a machine
2 and a beat frequency component is obtained. Here, the frequency analysis algorithm is DFT, FFT,
There are various types such as MEM and wavelet transform, and they can be used properly according to their properties.

Also, the beat frequency fb obtained in this way is
And the known parameter, the distance ΔL is calculated from equation (1). ΔL = (c / 2Δν) * (fb / fm) (1)

[0016]

However, in the conventional optical frequency domain reflection measurement apparatus, in order to improve the measurement accuracy of the optical frequency domain reflection measurement method, the temporal non-linearity inherent in the optical FM wave is corrected. It is necessary to perform a linear sweep operation. That is, in order to generate and detect an ideal unique beat frequency with respect to the measurement distance ΔL, it is necessary to sweep the optical frequency as linearly as possible, and the optical FM waves 21 and 22 for causing interference (FIG. 6).
(A)) requires that the frequency fluctuate at regular intervals with respect to the time axis. However, due to various factors of the light source itself, the light source actually has some nonlinearity.
The cause depends on the type of the light source. For example, in the case of a semiconductor laser, the cause is largely due to a thermal effect in the element resonator. For this reason, the beat frequency value supposed to be unique to the distance fluctuates, and the measurement accuracy deteriorates with ambiguity. The beat signal generates various frequency components, and it is difficult to specify a specific beat frequency component.

Therefore, in order to improve the accuracy of the optical frequency domain reflection measurement method, the temporally non-linear (non-linear) sweep of the optical FM is corrected to a linear (linear) sweep, or the optical FM is measured in advance. It must be generated and performed. Therefore, a method for solving this will be described with reference to FIG. 7 and the accompanying problem will be described. FIG. 7 shows a block diagram of an optical frequency domain reflection measurement device having a function of linearly correcting an optical frequency. The optical frequency domain reflection measurement device 72 shown in FIG. 7 performs a nonlinear optical FM sweep by using a linear optical FM
This is a reflection measuring device having a function of correcting for sweeping, and includes an optical frequency linear sweeping device 71 and a main measurement interference system section 14.

This optical frequency linear sweep device 71 has a function of correcting a nonlinear optical FM sweep to a linear one.
This is an M output device including a wavelength variable light source unit 70, a beam splitter 41, a correction interference system unit 42, a photodetector 43, a frequency discriminator 44, a reference beat signal source 45, and a comparator 46. . Here, the tunable light source unit 70
Outputs an optical frequency modulation signal whose optical wavelength changes with time in a required period, and can correct and modulate the optical frequency modulation signal based on an external control signal. It has a laser 70-2 and an adder 47.

The adder 47 corrects and modulates the optical FM wave based on an external control signal. Note that the oscillator 70-1 and the semiconductor laser 70-2 are
Since the oscillator 1 and the semiconductor laser 2 have the same functions as those described above, the duplicate description will be omitted. Further, the beam splitter 41 outputs the optical FM wave 73 output from the semiconductor laser 70-2 in the wavelength-variable light source unit 70.
With the optical FM wave (measurement wave) 74 and the optical FM wave (correction wave) 75
And a half mirror can be used for the same purpose.

Further, the correction interference system section 42 causes one of the correction waves 75 branched by the beam splitter 41 to interfere internally, and outputs beat light corresponding to the optical path difference. -1 and reference mirror 4
2-2 and 42-3 are configured as an optical system. Here, the beam splitter 42-1 is an optical distributor that distributes the correction wave 75 from the beam splitter 41 in two directions, and the reference mirrors 42-2 and 42-3 are mutually reciprocated from the beam splitter 42-1. Light beams distributed in these two directions which are arranged at different fixed distances are reflected and interfere with each other in the beam splitter 42-1 so that beat light is produced.

The photodetector 43 is provided with a correction interference system section 42.
The beat discriminator 44 receives the beat light input from the controller, and outputs the detected beat signal by photoelectrically converting the beat light.
Performs frequency-to-voltage (FV) conversion on a signal having a frequency in the electric domain output from the photodetector 43,
The signal is output as a voltage corresponding to the magnitude of the signal. Further, the reference beat signal source 45 outputs a voltage corresponding to a temporally constant beat frequency signal, and the comparator 46 generates a voltage difference between each output of the frequency discriminator 44 and the reference beat signal source 45. Is to be detected.

The photodetector 43, the frequency discriminator 44, the reference beat signal source 45, and the comparator 46 each constitute an electric system. The low-frequency error signal from the comparator 46 is input to the wavelength-variable light source unit 70 and is subjected to negative feedback so as to control the frequency. This is similar to a PLL (Phase Locked Loop). As for the function, a technique cultivated in the past electronic circuit technology is used.

Further, the measurement interference system section 14 is the same as that described with reference to FIG. 5, and a duplicate description thereof will be omitted. With such a configuration, one of the light FM waves (the correction wave 7) split by the beam splitter 41 is formed.
5) is the correction interference system unit 4 in the optical frequency linear sweep device 71.
2, the correction interference system section 42 generates beat light corresponding to the optical path difference in the interference system section. Then, in the photodetector 43, the beat light is photoelectrically converted into a detected beat signal, and in the frequency discriminator 44, the instantaneous beat frequency component of the detected beat signal is converted into a voltage signal.

Further, an error signal corresponding to the difference between the output voltage of the frequency discriminator 44 and the output voltage of the reference beat signal source 45 is output from the comparator 46, and the error signal is output from the adder 47 in the tunable light source 70. This error signal is input as a negative feedback and added to the output of the oscillator 70-1, so that the correction modulation to the semiconductor laser 70-2 can be performed.

Thus, the nonlinearity of the optical FM wave can be corrected through the instantaneous beat frequency, the spread of the beat frequency can be suppressed, a unique beat frequency can be obtained, and the measurement accuracy can be improved. Further, as described above, the light FM can be linearly swept in the optical frequency domain reflection measurement method. However, in the device as shown in FIG. 7, the nonlinearity of the optical FM wave can be corrected. However, in order to generate a negative feedback signal to the wavelength variable light source unit 70, the correction interference system unit 42, the frequency discriminator 44, The system must be configured such that the reference beat signal source 45 and the comparator 46 are always attached to the main measurement interference system unit 14 in the optical frequency domain reflection measuring device 72, and the entire optical frequency domain reflection measuring device 72 is constructed. This poses problems such as complexity and high cost. At the same time, there is a limit to the improvement of the linear accuracy of the optical FM, which is governed by the influence of the drift of the error signal itself due to instability depending on the hardware properties of the optical frequency linear sweep device 71 itself.

The present invention has been made in view of such a problem, and contributes to simplification and cost reduction of the entire optical frequency domain reflection measurement apparatus, and to the conventional hardware of the negative feedback system. A highly accurate non-linear optical FM sweep that can eliminate dependent instability
It is an object of the present invention to provide an optical frequency linear sweep device and a modulation correction data recording device for the optical frequency linear sweep device that can be corrected for sweep.

[0027]

For this reason, the optical frequency linear sweeping device of the present invention can output an optical frequency modulation signal whose optical wavelength changes with time in a required period, and can output an optical frequency modulation signal based on a correction signal from the outside. A wavelength-variable light source unit capable of correcting and modulating the frequency-modulated signal, an optical distributor for distributing the optical frequency-modulated signal from the wavelength-variable light source unit in at least two directions, and distributed by the optical distributor. A correction interference system for receiving a light frequency modulation signal on one side and outputting a beat light corresponding to an optical path difference set therein, and a detection interference system for detecting the beat light from the correction interference system as an electric signal. A photodetector, a frequency discriminator for detecting a time-varying signal of the instantaneous frequency with respect to the electric signal detected by the photodetector, and cutting a DC component from the time-varying signal detected by the frequency discriminator, Force is characterized by being configured to include a DC cut filter that is used as a correction signal for the modulation correction to the wavelength-variable light source unit (claim 1).

Also, the optical frequency linear sweeping device of the present invention
A wavelength tunable light source capable of outputting an optical frequency modulation signal whose optical wavelength changes with time in a required cycle and capable of performing correction modulation on the optical frequency modulation signal based on an external correction signal; and A reference signal generating unit capable of generating a reference signal required for wavelength tunable control and a correction signal for performing correction such that modulation characteristics specific to the wavelength tunable light source are prepared are prepared in advance. A correction signal generation unit that can output the set correction signal, and an adder that can add the reference signal from the reference signal generation unit and the correction signal from the correction signal generation unit and supply an addition output to the wavelength variable light source. (Claim 2).

Further, the modulation correction data recording device for an optical frequency linear sweep device according to the present invention provides an optical frequency modulation signal output from a variable wavelength light source as a component of the optical frequency linear sweep device based on a reference signal. Receiving the light, a correction interference system for outputting a beat light corresponding to an optical path difference set inside, a light detector for detecting the beat light from the correction interference system as an electric signal, and detection by the light detector A frequency discriminator for detecting a time-varying signal of the instantaneous frequency of the electric signal, and a DC component is cut from the time-varying signal detected by the frequency discriminator to correct the modulation to the wavelength variable light source. And a correction signal information recording unit that can record waveform information on the correction signal from the DC cut filter as recording medium data. It is characterized in that Ete constructed (claim 3).

[0030]

Embodiments of the present invention will be described below with reference to the drawings. (A) Description of First Embodiment of the Present Invention An optical frequency reflection region measuring apparatus to which the present invention is applied includes a main measurement interference system unit for performing light reflection measurement,
An optical frequency linear sweep device for correcting a nonlinear optical FM sweep into a linear optical FM sweep is provided.

FIG. 1 shows a configuration of an optical frequency domain reflection measuring apparatus according to a first embodiment of the present invention. The optical frequency domain reflection measurement device 17 shown in FIG. 1 is a reflection measurement device having a function of correcting a non-linear optical FM sweep into a linear optical FM sweep, and includes a main measurement interference system unit 14 and an optical frequency linear sweep. It is configured with the device 15. The main measurement interference system section 14 divides the input optical FM wave into two parts, irradiates one part to the measurement target, reflects the other part by the reference mirror, and causes both reflected lights to interfere with each other. The beam splitter 4, the reference mirror 6, the object to be measured 8, the photodetector 10, the A / D converter 1
1, is configured to include an arithmetic unit 12, and as the main measurement interference system unit 14, one having the same function as that shown in the conventional example is used.

That is, the optical FM wave 60b output from the optical frequency linear sweep device 15 is
In the beam splitter 4 inside, the reference light 5 and the object light (reference light) 7 are distributed. Then, the reference light 5 is reflected by the reference mirror 6 to become the reference light 21, and the object light 7 is irradiated onto the measurement target 8 and reflected to become the object light 22, and these reflected lights are respectively beam-shaped. The light is superimposed on the splitter 4 and input to the photodetector 10 as interference light 9.

In the photodetector 10, the interference light 9 is square-detected and detected as an electric signal waveform. In the A / D converter 11, the electric signal waveform output from the photodetector 10 is analog. The digital signal is converted, and the output signal of the A / D converter 11 is input to the computer or the like in the arithmetic unit 12. Further, the beat frequency fb is obtained from the captured data by using a frequency analysis algorithm such as FFT, and the distance ΔL is calculated from the equation (2) using this and a known parameter.

ΔL = (c / 2Δν) * (fb / fm) (2) Next, the optical frequency linear sweep device 15 corrects the nonlinear optical FM sweep into a linear optical FM sweep. The output device includes a variable wavelength light source unit 16, a beam splitter 51, a correction interference system unit 52, a photodetector 53, a frequency discriminator 54, and a DC cut filter 56.

Here, the variable wavelength light source unit 16 can output an optical frequency modulation signal whose optical wavelength changes with time in a required cycle, and based on a correction signal (control signal) from the outside, the optical frequency modulation signal is output. , And includes an oscillator 16-1 and a semiconductor laser 16-2 and an adder 55.

The oscillator 16-1 outputs a modulation signal in accordance with a current value.
Reference numeral -2 denotes a wavelength-tunable light source that outputs an optical FM wave 3 linearly modulated by an injection current from the oscillator 16-1.
Note that this light source is only required to be able to change the wavelength, and is not limited to a semiconductor laser. Further, the adder 55
The correction modulation is performed on the optical FM wave 3 based on a correction signal from the outside.

Further, the beam splitter 51 is an optical splitter for splitting the optical frequency modulation signal from the semiconductor laser 16-2 in the wavelength tunable light source section 16 in at least two directions. , Reference light 60a and object light 6
0b. Half mirrors can be used for similar applications. The reference light 60a is input to the correction interference system 52, and the object light 60b is input to the main measurement interference system 14 as described above. Note that the number of distributions may be increased and used for monitoring.

The correction interference system 52 uses the reference light 60a input from the beam splitter 51 for correction, and outputs beat light corresponding to an optical path difference set therein. It comprises a splitter 52-1 and reference mirrors 52-2 and 52-3. Here, the beam splitter 52-1 is a light splitter that splits the reference light 60a from the beam splitter 51 in two directions, and the reference mirrors 52-2 and 52-3 are mutually separated from the beam splitter 52-1. The half mirrors are arranged at different fixed distances, and reflect the light distributed in these two directions so that the beam splitter 52-1 generates beat light. These beam splitters 52-
1, the correction interference system section 52 including the reference mirrors 52-2 and 52-3 forms an optical system.

The photodetector 53 includes a correction interference system 52
Is detected as an electric signal (instantaneous beat frequency signal 61), and the frequency discriminator 54 detects the electric signal (instantaneous beat frequency signal 61) detected by the photodetector 53. This is for detecting a time-varying signal of the instantaneous frequency. Specifically, the frequency signal is converted into a voltage signal and output.

The DC cut filter 56 cuts a DC component from the time-varying signal detected by the frequency discriminator 54, and its output is used as a correction signal for modulation correction to the wavelength-variable light source unit 16. Things. The components of the photodetector 53, the frequency discriminator 54, and the DC cut filter 56 form an electric system, and a negative feedback loop in the optical frequency linear sweeping device 15 includes an optical system and an electric system. It can be said that.

Further, the correction signal (AC signal) obtained by the DC cut filter 56 is subjected to negative feedback addition to the modulation signal output from the oscillator 16-1 by the adder 55 in the wavelength tunable light source unit 16, Modulation signal correction is performed. With such a configuration, the semiconductor laser 16-2 is linearly modulated by the injection current from the oscillator 16-1 in the wavelength tunable light source unit 16, and the optical FM wave 3
Is output, and this light F
The M wave 3 is split into a reference beam 60a and an object beam 60b, and the object beam 60b is guided to the main measurement interference system unit 14, while the reference beam 60a is guided to the optical frequency linear sweep device 15.

The measurement principle of the optical FM linear correction will be described with reference to FIGS. FIG. 2A is a diagram showing a change in the optical FM wave, and shows the behavior of the reference light 60a and the object light 60b. As shown in FIG. 2A, the reference light 60a and the object light 60b are superimposed with a shift of the optical delay time. However, these waveforms are non-linear and are not swept linearly with respect to the time axis. Then, beat light having an appropriate value is generated from the reference light 60 a in the correction interference system section 52, and the beat light is photoelectrically converted into an instantaneous beat frequency signal 61 in the photodetector 53.

FIG. 2B is a diagram showing changes in the beat frequency and the voltage signal, and shows the behavior of the instant beat frequency signal 61. FIG. 2B shows that the instantaneous beat frequency signal 61 is also nonlinear in time.
Then, the instant beat frequency signal 61 is subjected to signal conversion (FV conversion) from frequency to voltage in the frequency discriminator 54, and is converted from the beat signal to a voltage signal. As the electric method, a method cultivated in other electronic circuit technologies can be used, and for example, a slope detection method using a resonator circuit can be used. The method of FV conversion in the present invention is not limited to this, and another method may be used.

The voltage signal at the output of the frequency discriminator 54 is input to a DC cut filter 56 so that only an AC signal can pass. Hereinafter, the reason for removing the DC signal by passing only the AC signal will be described. First, in the optical frequency domain reflection measurement method,
It is based on the use of repeated linear light FM waves. That is, in the case of an ideal repetitive linear light FM, the time behavior of the instantaneous frequency component is direct current (DC) and has no alternating current (AC) component. This means that, as shown in FIG. 6B, the time behavior of the low-frequency beat 27 is DC-like and has no AC component during the period of the normal repetition modulation period 1 / fm (sec). Equivalent to.

Here, even if the reference on the correction interference system section 52 side fluctuates not due to the nonlinearity factor on the optical FM wave side,
The fluctuation of the interference condition is usually the repetition modulation period 1 / fm
Since it is much slower than (sec), it can be said that it is DC-like. Thus, the variation of the beat frequency appears only in the variation of the AC component within a period in which the variation range is only within the repetition modulation period 1 / fm (sec). Minutes are not affected.

As described above, the correction information for the non-linear sweep of the optical FM wave generated purely on the light source side includes the DC / AC mixed signal obtained by the frequency discriminator 54.
It is only necessary to take out the AC component. Then, in order to extract this AC component, a DC cut filter 56
Is provided in the next stage of the frequency discriminator 54, and the correction signal obtained here is added to the modulation signal in the adder 55 in the wavelength tunable light source unit 16 by negative feedback, so that the modulation signal is corrected. . As a result, the optical FM wave 3 which was originally a nonlinear sweep is linearly corrected, and a time sweep with good linearity is realized.

FIG. 2 (c) is a diagram showing beat frequency components, and shows beat frequency spectra of a corrected optical FM wave and a non-corrected optical FM wave. From FIG. 2C, it is understood that the spread of the beat frequency spectrum 63 is suppressed, and the beat frequency spectrum 64 is easily specified. Thus, the present invention focuses on the fundamental use of a repetitive linear optical FM wave in the optical frequency domain reflection measurement method. If an ideal repetitive linear optical FM wave is used, the time behavior of the instantaneous frequency component is It takes full advantage of the characteristics of being DC and having no AC component. That is, with the DC cut filter 56,
By cutting the DC component from the time-varying signal detected by the frequency discriminator 44 and using the output as a correction signal for modulation correction to the wavelength-variable light source unit 16,
A linear optical FM wave can be generated, and measurement can be performed using the corrected optical FM wave in the main measurement interference system unit 14.

Thus, the correction interference system 52, the photodetector 53, the frequency discriminator 54, the DC cut filter 56
The optical frequency linear sweeping device 15 provided with the optical frequency correction device 15 can correct the nonlinearity of the optical FM wave which was originally a nonlinear sweep through the instantaneous beat frequency, and linearly sweep the optical FM wave. The optical frequency domain reflection measurement method can be performed according to the above. Furthermore, in the measurement based on the optical frequency domain reflection measurement method, the frequency spread of the beat signal measured by the main measurement interference system unit 14 is suppressed, and the unique beat signal is easily specified. That is,
The spread of the frequency spectrum 63 is suppressed, the beat frequency spectrum 64 is easily specified, and the measurement accuracy of the optical frequency domain reflection measurement method can be improved. In this case, the light source is not limited to the semiconductor laser, but may be another light source that can change the wavelength.

Therefore, according to the present invention, a method as shown in FIG. 7, that is, a reference beat frequency signal source 45 is separately prepared, and this reference beat frequency signal (6 in FIG.
2) is not compared with the instantaneous beat frequency signal (61 in FIG. 2 (b)) to obtain an error signal (65 in FIG. 2 (b)). In addition, it is necessary to calculate an ideal beat frequency value in advance in accordance with the conditions of the correction interference unit 52, a change in conditions such as an optical path difference and a change in ambient temperature, and a reference beat frequency signal source. The point that the accuracy of the correction signal deteriorates due to the addition of the fluctuation component from itself is improved.

According to the present invention, the means shown in FIG.
By replacing the reference beat signal source 45 and the comparator 46 with the DC cut filter 56 instead of the reference beat signal source 45, the effect that the device configuration can be simplified and the cost of the entire measurement system can be reduced can be expected. (B) Description of Second Embodiment of the Present Invention FIG. 3 is a diagram showing a configuration of an optical frequency domain reflection measuring device according to a second embodiment of the present invention. The optical frequency domain reflection measuring device 80 shown in FIG. 3 is a reflection measuring device having a function of correcting a non-linear optical FM sweep into a linear optical FM sweep. And an optical frequency linear sweep device 81 for correcting a nonlinear optical FM sweep into a linear optical FM sweep.

The main measurement interference system 82 divides the input FM wave into two parts, irradiates one part to the object to be measured, and reflects the other part by the reference mirror to cause the two reflected lights to interfere with each other. A beam splitter 93, a reference mirror 90, a measurement target 92, a photodetector 95, an A / D converter 96, and a calculation device 97.
It is configured with. Since these have the same functions as those described above, further description will be omitted.

Next, the optical frequency linear sweep device 81 is an optical FM output device having a function of correcting a non-linear optical FM sweep into a linear optical FM sweep, and includes a light source (variable wavelength light source).
87, a reference signal generator (reference signal generator) 83, a correction signal generator (correction signal generator) 84, and an adder 86. The reference signal generator 83, the adder 86, and the light source 87 correspond to the variable wavelength light source unit 16 (see FIG. 1) in the first embodiment.

Here, the light source 87 (denoted as a semiconductor laser in FIG. 3) can output an optical frequency modulation signal whose optical wavelength changes with time in a required period, and can output an optical frequency modulation signal based on an external correction signal. Correction modulation of a frequency modulation signal is possible, and a semiconductor laser is used. Then, an optical FM wave (optical FM output light) 88 is output to the main measurement interference system unit 82. Further, the reference signal generator 83 can generate a reference signal necessary for the variable wavelength control of the light source 87. Further, the correction signal generator 84 is capable of preparing a correction signal for performing correction so as to have a modulation characteristic unique to the light source 87 in advance, and outputting the prepared correction signal. Note that a synchronization signal line 98 for synchronizing with the reference signal generator 83 is input from the correction signal generator 84 to the reference signal generator 83.

The correction signal generator 84 receives the correction signal waveform data 85. The correction signal waveform data 85 is in a form that can be supplied to a recording medium, a network, or the like. The correction signal waveform data 85 is data unique to each semiconductor laser, and Modulation and characteristics are measured,
It is generated based on them. The generation method is described in a correction signal waveform generation device 12 described later.
Performed by 0. Further, the adder 86 can add the reference signal from the reference signal generator 83 and the correction signal from the correction signal generator 84 to supply an addition output to the light source 87.

Therefore, this optical frequency linear sweeping device 81
Can output an optical frequency modulation signal (optical FM wave 88) whose optical wavelength changes with time in a required period, and corrects and modulates the optical frequency modulation signal based on an external correction signal (correction signal waveform data 85). Tunable light source (light source 87), a reference signal generator (reference signal generator 83) capable of generating a reference signal necessary for tunable control of the tunable light source, and a tunable light source A correction signal for performing correction so as to have a unique modulation characteristic is prepared in advance, a correction signal generator (correction signal generator 84) capable of outputting the prepared correction signal, and a reference signal It comprises an adder 86 that can add the reference signal from the generation unit and the correction signal from the correction signal generation unit and supply an addition output to the variable wavelength light source.

As a result, in the optical frequency linear sweep device 81, the correction signal waveform data 85 is input to the correction signal generator 84, and the output from the reference signal generator 83 and the correction signal from the correction signal generator 84 are output. Are added in an adder 86, and the added output is supplied to a light source 87.
Then, the optical FM wave 88 is input to the main measurement interference system unit 82.

Next, a method of generating the correction signal waveform data 85 will be described with reference to FIG. FIG. 4 is a diagram illustrating a configuration of a correction signal waveform generation device according to the second embodiment of the present invention. The correction signal waveform generator 1 shown in FIG.
20 generates correction signal waveform data 85, and includes a reference signal generator 83, a light source 87 (denoted as a semiconductor laser in FIG. 4), and a modulation correction data recording device 100. It is configured.

This modulation correction data recording device 100 is for recording correction signal waveform data 85 on a predetermined medium, and includes a correction interference system section 121, a photodetector 104, a frequency discriminator 110, a DC cutoff It comprises a filter 111 and a waveform recording device 112. The correction interference system section 121 receives an optical frequency modulation signal output from a wavelength variable light source as a component of the optical frequency linear sweep device based on a reference signal, and receives beat light corresponding to an optical path difference set therein. And comprises a coupling lens 102, a 2 × 2 optical fiber coupler (directional coupler) 101, and reference mirrors 105 and 107. Here, the coupling lens 102 is a light FM wave (light FM output light) 1 from the light source 87.
The 2 × 2 optical fiber coupler (directional coupler) 101 is an optical element for generating beat light. The reference mirrors 105 and 107 are the same as those described above, and further description will be omitted. The photodetector 104 detects the beat light from the correction interference system section 121 as an electric signal, and the frequency discriminator 110 detects the instantaneous frequency of the electric signal detected by the photodetector 104. In order to detect the time-varying signal. Further, the DC cut filter 111 can cut a DC component from the time-varying signal detected by the frequency discriminator 110 and output a correction signal to the light source 87 for modulation correction. Further, the waveform recording device 112 can record waveform information on the correction signal from the DC cut filter 111 as recording medium data.

With this configuration, the light source 87 is modulated by the reference signal from the reference signal
The M-wave 113 is output. Then, this optical FM wave 113
Is the coupling lens 1 in the correction interference system section 121.
02, the fiber input light 1 propagating in the fiber
03, which is guided to the 2 × 2 optical fiber coupler 101. The fiber input light 103 is converted into a reference light 10 in the fiber by a 2 × 2 optical fiber coupler 101.
6,108. Here, these reference beams 1
The optical path differences 06 and 108 are always kept constant. These reference beams 106 and 108 are respectively applied to reference mirrors 105 and 107 on the fiber end surface.
After that, the light propagates through the fiber as reflected reference light, is combined again by the 2 × 2 optical fiber coupler 101, and interference light (beat light) 109 is generated. Further, the interference light 109 propagates through the fiber, is square-detected by the photodetector 104 at the terminal, and is converted into a beat electric signal. Thereafter, the beat discriminator 110 detects a time-varying signal of the instantaneous frequency component of the beat electric signal. Specifically, the beat electric signal is converted from a frequency signal to a voltage signal and output. Then, the DC signal of the voltage signal is removed by the DC cut filter 111, and the correction signal waveform is input to the waveform recording device 112. In the waveform recording device 112, a desired correction signal waveform is processed and recorded as correction signal waveform data 85. Thereafter, the correction signal waveform data 85 obtained from the modulation correction data recording device 100 is copied to a recording medium such as a floppy disk, and the data is stored in an optical frequency domain reflection measuring device 80 (see FIG. 3). The correction signal waveform data 85 of the correction signal generator 84 in the frequency linear sweep device 81 is input and used.

Further, in FIG. 3, the light F which is originally a nonlinear sweep and whose optical frequency characteristic is corrected to a linear sweep is shown.
The M wave 88 is guided to the main measurement interference system section 82 and is used as output light in the optical frequency domain reflection measurement method. The object light 91 obtained by splitting the output light is converted into a beam splitter 93.
The interference light 94 is generated from the object light 91 reflected by the object 92 and the reference light 89 reflected by the reference mirror 90, and is input to the photodetector 95. Then, in the photodetector 95, the interference light 94 is detected as an electric signal waveform, and in an A / D converter 96, the electric signal waveform output from the photodetector 95 is subjected to analog-to-digital conversion. In, the output signal is taken into a computer or the like. Further, the captured data is used to calculate a distance using a frequency analysis algorithm such as FFT.

Next, FIG. 2 (a) shows a case where the measurement principle is considered.
This will be described with reference to FIG. Note that, specifically, a flow until the correction signal waveform data 85 is generated will be described. As shown in FIG. 2A, the reference light 106 and the object light 108 are superimposed on each other with a shift of the optical delay time τ, but their waveforms are nonlinear and linear with respect to the time axis. The frequency has not been swept. The reference light 106 and the object light 108 are transmitted to the correction interference system 1 shown in FIG.
In the 2 × 2 optical fiber coupler 101 in FIG. 21, beat light is generated by causing interference, and
At 04, the beat light is the instant beat frequency signal 6
Converted to 1. The temporally non-linear instantaneous beat frequency signal 61 shown in FIG.
At 10 (see FIG. 4), signal conversion (FV conversion) from frequency to voltage is performed, and the beat signal is converted to a voltage signal. As the electric method, a method cultivated in other electronic circuit technologies can be used, and for example, a slope detection method using a resonator circuit can be used.
The method of FV conversion in the present invention is not limited to this, and another method may be used. Furthermore, frequency discriminator 1
The voltage signal at the output of the DC cut filter 1
11 and only the AC signal is passed. The reason is the same as that described above. That is, if it is an ideal repetitive linear light FM, the time behavior of its instantaneous frequency component is direct current (DC) and alternating current (AC)
Has no components. This means that, as shown in FIG. 6B, the time behavior of the low-frequency beat 27 is DC-like and has no AC component during the period of the normal repetition modulation period 1 / fm (sec). Is equivalent to Even if the reference on the 2 × 2 optical fiber coupler 101 side fluctuates not due to the nonlinearity factor on the optical FM wave side, the fluctuation of the interference condition is usually sufficiently slower than the repetition modulation period 1 / fm (sec). It can be called DC. Thus, the variation of the beat frequency repeats the range of the variation, and the modulation period is 1 / fm (s
It appears only in the change of the AC component within the period set only in ec), and is not affected by the DC fluctuation of the interference condition. Other points are the same as those described in the first embodiment, and further description will be omitted. FIG.
(C) is a diagram showing a beat frequency component, and shows a beat frequency spectrum of a corrected optical FM wave and a non-corrected optical FM wave. From FIG. 2C, it can be seen that the spread of the beat frequency spectrum 63 is suppressed, and a narrowed unique frequency component like the beat frequency spectrum 64 is easily identified.

Therefore, as the correction information for the non-linear sweep of the optical FM wave generated purely by the light source 87, only the AC signal of the DC / AC mixed signal obtained by the frequency discriminator 110 may be used. In order to extract this AC component, a DC cut filter 111 is provided at the next stage of the frequency discriminator 110. Then, a waveform recording device 11 capable of recording the obtained correction signal as waveform data
2 is processed and saved. As a result, the correction signal waveform data 85 is generated, and at the same time, duplication is possible.
The correction signal waveform data 85 is used as signal output data of the correction signal generator 84 of the optical frequency linear sweep device 81, and the correction signal and the reference signal from the reference signal generator 83 are synchronized by the synchronization signal line 98. , And the adder 86
And can be applied to the light source (semiconductor laser) 87 in advance as a final correction modulation signal. Thus, the optical FM wave 113, which was originally a non-linear sweep, is a light that is subjected to time sweep with good linearity. It is corrected to the FM wave 88.

Returning to FIG. 7, the correction interference system 42
Photodetector 43, frequency discriminator 44, reference beat signal source 4
5, the part of the feedback loop including the comparator 46 can be replaced with the modulation correction data recording device 100. That is, the correction signal from the output side of the comparator 46 shown in FIG. 7 corresponds to the correction signal waveform data 85 output from the waveform recording device 112 of the modulation correction data recording device 100 in FIG.

Further, in FIG. 3, it is possible to provide a modulation correction data recording device 100 shown in FIG. 4 instead of the optical frequency linear sweeping device 81 in the optical frequency domain reflection measuring device 80. As described above, the present invention pays attention to the fact that it is fundamental to use a repetitive linear optical FM wave in the optical frequency domain reflection measurement method. It takes full advantage of the feature that the behavior is DC and has no AC component. That is, the DC cut filter 111
The DC component is removed from the time-varying signal detected by the frequency discriminator 110, and the output of the time-varying signal is converted into the correction signal waveform data 8.
It becomes 5. The correction signal waveform data 85 is used as a correction signal for the linear light FM wave of the light source 87 to generate a linear light FM wave 88. By using this, highly accurate optical frequency domain reflection measurement can be performed.

In the measurement based on the optical frequency domain reflection measurement method, the spread of the frequency of the beat signal measured by the main measurement interference system section 82 is suppressed, the unique beat signal is easily specified, and the optical frequency domain reflection measurement is performed. The measurement accuracy of the method can be improved. In this case, the light source is not limited to the semiconductor laser, but may be another light source that can change the wavelength.

Further, by preparing waveform data necessary for correction in advance, the device configuration can be simplified as compared with the correction method using negative feedback, and at the same time, the correction signal waveform is Any number of copies can be made as data. By simply supplying this to a plurality of optical frequency linear sweep devices by software, linear sweep of an optical FM wave can be easily realized. This can be realized at a lower cost than the conventional hardware-based correction method for individual devices, and can contribute to a reduction in the overall cost of the measurement system. Then, it is possible to eliminate the degradation of the linearity of the optical frequency due to the influence of the drift of the correction signal itself due to the instability of the hardware itself, and the degradation of the precision of the present measurement method resulting therefrom. as a result,
There is an effect that contributes to the improvement of the accuracy of the present measurement method as compared with the related art.

(C) Others The optical frequency linear sweeping apparatus shown in FIGS. 1 to 4 has only a basic configuration. For example, the frequency shift rate of the optical FM per unit modulation signal level and the direction of the shift are described. The frequency discriminator 54 (112) may be configured to include a gain amplifier, a polarity converter, and the like in accordance with the specifications of various light sources.

Further, since these device systems are very simple, even if they are added, they do not affect the effects of the present invention, and do not hinder the superiority of the present invention. Furthermore, the present invention is not limited to the optical frequency domain measuring device described above, and can be implemented with various modifications without departing from the spirit of the present invention. Specifically, it is a device used for three-dimensional shape measurement, non-contact vibrometer and blood flow meter, particle (particle) counter, measurement using laser radar, spectroscopic analysis, pollution analysis. The present invention can be variously modified and implemented in the art.

In addition, a medium for storing the data of the correction signal waveform data 85 may be an optical disk medium or a paper medium in addition to the magnetic disk medium, and may take various forms. Needless to say.

[0070]

As described above in detail, according to the optical frequency linear sweeping device of the present invention, the wavelength variable type light source unit can output an optical frequency modulation signal whose optical wavelength changes with time in a required cycle. The optical modulator modulates the optical frequency modulation signal based on an external correction signal, distributes the optical frequency modulation signal from the wavelength variable light source section in at least two directions in an optical distributor, The optical frequency modulation signal on one side distributed by the distributor is received, and a beat light corresponding to an optical path difference set inside is output, and in the photodetector, the beat light from the correction interference system is converted into an electric signal. When the frequency discriminator detects the time-varying signal of the instantaneous frequency of the electrical signal detected by the photodetector, and the DC cut filter detects the time-varying signal. Since the DC component is cut from the fluctuation signal, and the output is used as a correction signal for the modulation correction to the wavelength variable type light source unit, the frequency spread of the beat signal is suppressed, and the unique beat signal Can be easily identified, thereby improving the measurement accuracy of the optical frequency domain reflection measurement method, and using a DC cut filter can simplify the device configuration and contribute to reducing the cost of the entire measurement system. (Claim 1).

According to the optical frequency linear sweeping device of the present invention, the wavelength variable light source can output an optical frequency modulation signal whose optical wavelength changes with time in a required cycle, and
Correction modulation of the optical frequency modulation signal is enabled based on a correction signal from the outside, and a reference signal generation unit generates a reference signal necessary for tunable control of the wavelength tunable light source, and a correction signal generation unit In advance, a correction signal for performing a correction such that the modulation characteristic is unique to the wavelength-variable light source is prepared in advance, and the prepared correction signal is output. In the adder, the reference signal from the reference signal generator is output. And the correction signal from the correction signal generator are added to supply the added output to the wavelength-variable light source. This simplifies the device configuration compared to the conventional correction method using negative feedback. At the same time, this correction signal waveform can be copied several times as data, and this can be supplied to a plurality of optical frequency linear sweep devices by software. To just simply linear sweep of the light FM wave can be realized. Therefore, compared to the conventional hardware correction method for each individual device, it can be realized at a lower cost, can contribute to a reduction in the overall cost of the measurement system, and can cause drift of the correction signal itself due to instability of the hardware itself. As a result, it is possible to eliminate the deterioration of the accuracy of the present measurement method due to the deterioration of the linearity of the optical frequency. As a result, there is an effect that contributes to the improvement of the accuracy of the present measurement method as compared with the related art (claim 2).

Further, according to the modulation correction data recording device for an optical frequency linear sweep device of the present invention, in a correction interference system, an output is performed based on a reference signal from a wavelength variable light source as a component of the optical frequency linear sweep device. Receiving the optical frequency modulation signal, outputs a beat light corresponding to the optical path difference set therein, and in a photodetector, detects the beat light from the correction interference system as an electric signal, and in a frequency discriminator, A time-varying signal of the instantaneous frequency of the electric signal detected by the photodetector is detected, and a DC cut filter cuts a direct-current component from the time-varying signal detected by the frequency discriminator, and transmits the signal to a wavelength-variable light source. A correction signal for modulation correction is output, and in the correction signal information recording unit, waveform information about the correction signal from the DC cut filter is recorded as recording medium data. It is also possible to simplify the device configuration, and it is also possible to simply copy a number of correction signal waveforms as data and supply this to a plurality of optical frequency linear sweep devices in software. Easy light F
A linear sweep of M waves can be realized. Also, it can be realized at a lower cost than the hardware correction method for each device,
This method can contribute to the overall cost reduction of the measurement system, and also reduces the accuracy degradation of the measurement method due to the degradation of the linearity of the optical frequency due to the drift of the correction signal itself due to the instability of the hardware itself. It can be eliminated (claim 3).

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical frequency domain reflection measurement device having an optical frequency linear sweep device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an optical frequency domain reflection measurement device according to a first embodiment and a second embodiment of the present invention;
(A) is a diagram illustrating a change in an optical FM wave, (b) is a diagram illustrating changes in a beat frequency and a voltage signal, and (c) is a diagram illustrating a component of a beat frequency.

FIG. 3 is a diagram illustrating a configuration of an optical frequency domain reflection measurement device according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a configuration of a correction signal waveform generation device according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a conventional optical frequency domain reflection measurement device.

6A and 6B are diagrams showing a conventional optical frequency domain reflection measuring device, and FIG. 6A is a diagram showing a change of an optical FM wave;
(B) is a diagram illustrating a change in beat frequency, (c) is a diagram illustrating an intensity waveform of the beat signal, and (d) is a diagram illustrating a component of the beat frequency.

FIG. 7 is a block diagram of another conventional optical frequency domain reflection measurement device.

[Explanation of symbols]

1, 16-1, 70-1 Oscillator 2, 16-2, 70-2 Semiconductor laser 3, 21, 22, 60a, 60b, 73, 74, 75,
88,113 Optical FM wave (optical FM output light) 4,41,42-1,52-1,51,93 Beam splitter 5,89,106,108 Reference light 6,42-2,42-3,52- 2,52-3,90,
105, 107 Reference mirror 7, 91 Object light 8, 92 Measurement object 9, 94, 109 Interference light 10, 43, 53, 95, 104 Photodetector 11, 96 A / D converter 12, 97 Arithmetic unit 13 Light source unit 14,82 Measurement interference system unit 15,71,81 Optical frequency linear sweep unit 16,70 Variable wavelength light source unit 17,20,72,80 Optical frequency domain reflection measurement device 27 Low frequency beat 28 High frequency beat 29,30 Signal Waveform 31 Beat signal spectrum 42, 52, 121 Correction interference system section 44, 54, 110 Frequency discriminator 45 Reference beat signal source 46 Comparator 47, 55, 86 Adder 56, 111 DC cut filter 61 Instantaneous beat frequency signal 62 Reference Beat frequency signal 63 Beat frequency spectrum by non-linear light FM 64 By corrected linear light FM Frequency spectrum 65 Error signal 83 Reference signal generator 84 Correction signal generator 85 Correction signal waveform data 87 Light source 98 Synchronization signal line 100 Modulation correction data recording device 101 2 × 2 optical fiber coupler 102 Coupling lens 103 Fiber input light 112 Waveform recording device 120 Correction signal waveform generation device

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2F064 AA01 CC04 DD02 EE10 FF02 GG00 GG22 GG24 HH01 HH05 JJ04 JJ05 2F065 AA02 AA06 DD03 EE01 FF13 FF51 GG06 GG25 HH13 JJ01 KK01 LL02 Q25QQQ

Claims (3)

[Claims] 1. A wavelength-variable light source unit capable of outputting an optical frequency modulation signal whose optical wavelength changes with time in a required period and capable of performing correction modulation on the optical frequency modulation signal based on an external correction signal. An optical distributor for distributing the optical frequency modulation signal from the wavelength tunable light source unit in at least two directions; receiving the optical frequency modulation signal on one side distributed by the optical distributor, and internally receiving the optical frequency modulation signal; A correction interference system for outputting a beat light corresponding to the set optical path difference, a photodetector for detecting the beat light from the correction interference system as an electric signal, and an electric detector detected by the photodetector. A frequency discriminator for detecting a time-varying signal of the instantaneous frequency of the signal; a DC component cut from the time-varying signal detected by the frequency discriminator; The for Characterized in that it is configured to include a DC cut filter that is used as a positive signal, the optical frequency linear sweep device. 2. A wavelength tunable light source capable of outputting an optical frequency modulation signal whose optical wavelength changes with time in a required period and capable of performing correction modulation on the optical frequency modulation signal based on an external correction signal; A reference signal generating unit capable of generating a reference signal required for tunable control of the tunable light source, and a correction signal for performing a correction to provide a modulation characteristic unique to the tunable light source are prepared in advance. In addition, the correction signal generation unit capable of outputting the prepared correction signal, the reference signal from the reference signal generation unit and the correction signal from the correction signal generation unit are added and output. And an adder that can supply the wavelength-variable light source to the variable-wavelength light source. 3. An optical frequency modulation signal output from a variable wavelength light source as a component of the optical frequency linear sweep device based on a reference signal, and outputs beat light corresponding to an optical path difference set inside. Interferometer for detecting a beat light from the interferometer as an electric signal, and detecting a time-varying signal of the instantaneous frequency of the electric signal detected by the photodetector. A frequency discriminator; a DC cut filter capable of cutting a DC component from the time-varying signal detected by the frequency discriminator and outputting a correction signal for modulation correction to the wavelength-variable light source; An optical frequency linear sweep device, comprising: a correction signal information recording unit capable of recording waveform information on the correction signal from the cut filter as recording medium data. Modulation data recording device.