JP2020046368A - Distance measurement method and distance measurement device - Google Patents

Abstract

To provide a distance measurement method and a distance measurement device, capable of measuring the distance to an object to be measured with higher accuracy than before.SOLUTION: In a distance measurement device 1, measurement distance from a reference position to the measurement surface of steel plate P is corrected on the basis of a frequency shift amount f, thereby capable of measuring the distance to the steel plate P based on the corrected measured distance. Accordingly, since the distance measurement device 1 can correct deviation of the distance to the steel plate P occurring when speed V is different, the distance to the steel plate P can be measured with higher accuracy than before.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a distance measuring method and a distance measuring device.

  Steel products are manufactured at high accuracy under the conditions where dust is drifting in the factory, the temperature of the object to be measured is high, or the temperature of the object to be measured or the atmosphere fluctuates greatly. It is necessary to measure the distance to and calculate its size and shape. As a distance measuring device for measuring the distance to the object under measurement in such a bad environment and measuring the distance to the object to be measured, for example, as shown in Patent Document 1, an FSF laser (frequency shift feedback type) 2. Description of the Related Art A distance measuring device using a laser (Frequency-Shifted Feedback Laser) light source is known.

  Generally, in a distance measuring apparatus using laser light whose frequency is modulated with respect to time, a frequency-modulated light emitted from a laser oscillator is branched into a reference light and a measuring light, and the measurement is performed. The object to be measured is irradiated with light, and the reflected light that is reflected on the surface (measurement surface) of the object to be measured and returned is incident on the light detection unit. On the other hand, the reference light is incident on the light detection unit via a path having a predetermined optical path length in the distance measuring device.

  The path from the light exiting the laser oscillator to the light detection section as reflected light through the reflection of the object to be measured on the measurement surface, and the light detection section as the reference light after the light exits the laser oscillator. The optical path length is usually different from the path leading up to the path. Therefore, the time required for the light to leave the laser oscillator and reach the light detection unit also differs between the reflected light and the reference light.

  Since the frequency of the light emitted from the laser oscillator constantly changes with time based on a predetermined rule (a triangular wave, a comb wave, a sine wave, etc.) which is grasped in advance by the operator, the light enters the light detection unit. The reflected light and the reference light have different frequencies. Therefore, in the light detection unit, a beat signal having a frequency equal to the frequency difference between the reflected light and the reference light is detected due to the interference between the reflected light and the reference light.

  The frequency of the beat signal (beat frequency) is defined as the time required for the measurement light to exit the laser oscillator and reach the light detection unit as reflected light, and the time required for the reference light to exit the laser oscillator and reach the light detection unit. It is equal to the amount of change in the oscillation frequency of the laser oscillator during the difference from the required time. Therefore, the distance measuring apparatus using the laser light whose frequency is modulated with respect to time can convert the beat frequency into a difference in optical path length, thereby measuring the distance to the object to be measured.

  By knowing the distance to the object to be measured, the shape of the object to be measured can also be known from position information, speed information, and the like on the measurement surface. Therefore, the distance measuring device can be used as a shape measuring device.

  Here, for example, an example in which a distance measuring device is used at a steel product manufacturing site will be described. As shown in FIG. 5, a steel sheet P to be measured is moved in a predetermined moving direction X ( In this case, when the sheet P is conveyed in one direction along the surface direction of the measuring surface of the steel sheet P, a distance measuring device is attached to the measuring surface of the steel sheet P moving at a predetermined speed (also referred to as a passing speed) V. Measurement light is emitted vertically from the measurement head 5. The reflected light reflected back from the measurement surface of the steel plate P is received by the measurement head 5 and sent to a light detection unit (not shown).

  The distance measuring device detects a beat (beat) signal having a frequency equal to the frequency difference between the reflected light and the reference light, and converts the beat frequency into a difference in optical path length, thereby measuring the surface of the moving steel plate P. The distance to is measured in real time.

JP-A-2006-80409

  However, the speed V at which the steel sheet P moves along the moving direction X is changed to 50 mpm, 100 mpm, and 150 mpm by using a distance measuring device using laser light whose frequency is modulated with respect to time as described above. When the distance to the measurement surface of the steel plate P was measured, the distance to the steel plate P (plate height from a predetermined position), which should be the same value, was different as a value depending on the speed V as shown in FIG. It was confirmed that it was detected.

  Here, the vertical axis in FIG. 6 is based on the distance from a predetermined position of the distance measuring device to the measurement surface of the steel plate P when the speed V is 0 mpm. For example, if the speed V is 50 mpm, the plate height is Was shifted by about 1 mm from the reference, and when the speed V was 100 mpm, the plate height was shifted by about 2 mm from the reference, and when the speed V was 150 mpm, the plate height was confirmed to be a value shifted by about 3 mm from the reference. .

  Therefore, in a steel product manufacturing site, various steel plates P are conveyed, and since the speed V at that time may be different, the measured value of the distance to the steel plate P is different each time. If detected, the shape of the steel sheet P cannot be measured with high accuracy.

  Therefore, the present invention has been made in view of the above-described problems, and has as its object to provide a distance measuring method and a distance measuring device capable of measuring a distance to an object to be measured with higher accuracy than before. And

The distance measuring method of the present invention is a distance measuring method for measuring a distance to an object to be measured, and a laser oscillation step of oscillating and emitting a laser light whose frequency is modulated with respect to time by a laser oscillator. Irradiating the object to be measured, which relatively moves, with laser light emitted from the laser oscillator from a measurement head, and receiving reflected light reflected by the object to be measured by the measurement head; A frequency analysis step of obtaining a beat frequency based on the reflected light received by the measurement head and the reference light emitted from the laser oscillator; and a distance calculation step of calculating a distance from the beat frequency to the object to be measured. And a calculation processing step of calculating a frequency shift amount for correcting the distance calculated in the distance calculation step. A wavelength obtaining step of obtaining the wavelength of the laser light, a speed obtaining step of obtaining the speed of the object to be measured with respect to the measuring head, and performing measurement while changing the speed, and determining the speed difference by the speed Calculating in the acquisition step as a calibration speed, and calculating the difference in beat frequency as a calibration frequency shift amount, a calibration data calculation step,
Using the wavelength acquired in the wavelength acquisition step, the calibration speed, and the calibration frequency shift amount, the moving direction of the object to be measured and the optical axis of the laser beam emitted from the measurement head are formed. Surface, a direction perpendicular to the moving direction, an optical axis angle calculating step of calculating an optical axis angle formed by the optical axis of the laser light emitted from the measurement head, and the wavelength obtained in the wavelength obtaining step A speed shift amount calculating step of calculating the frequency shift amount from the speed obtained in the speed obtaining step and the optical axis angle obtained in the optical axis angle calculating step; and the distance calculating step Is for measuring the distance to the object to be measured by correcting the beat frequency acquired in the frequency analysis step using the frequency shift amount.

  The distance measuring device of the present invention is a distance measuring device that measures a distance to an object to be measured, and moves relatively to a laser oscillator that oscillates and emits laser light whose frequency is modulated with respect to time. A measuring head for irradiating the object to be measured with laser light emitted from the laser oscillator to receive reflected light reflected by the object to be measured, a reflected light received by the measuring head, and the laser oscillator A frequency analysis unit that obtains a beat frequency based on the reference light emitted from the light source, a distance calculation unit that calculates a distance to the object to be measured from the beat frequency, and corrects a distance calculated by the distance calculation unit. And an arithmetic processing unit for calculating a frequency shift amount for performing the measurement, wherein the arithmetic processing unit performs measurement while changing the speed of the object to be measured with respect to the measurement head, and obtains the speed difference. A calibration data calculation unit, and also calculates the difference between the beat frequencies as a calibration frequency shift amount, a calibration data calculation unit, the wavelength of the laser beam, the calibration speed, and the calibration frequency shift. Using a quantity, a speed acquisition unit that acquires the speed of the object to be measured with respect to the measurement head, and in the plane formed by the moving direction of the object to be measured and the optical axis of the laser light emitted from the measurement head. An optical axis angle calculation unit that calculates an optical axis angle between a direction perpendicular to the moving direction and an optical axis of the laser light emitted from the measurement head, and a wavelength of the laser light and a speed difference. The speed, and the optical axis angle obtained by the optical axis angle calculation unit, from the frequency shift amount calculation unit to calculate the frequency shift amount, the distance calculation unit, the frequency analysis unit Acquired by The over preparative frequency, said by correcting using the frequency shift amount, wherein for measuring a distance to the object to be measured, is intended.

  According to the present invention, the deviation of the measured value of the distance to the object to be measured, which occurs when the speed is different, can be corrected based on the speed of the object to be measured. It can measure with higher accuracy than that.

FIG. 4 is a schematic diagram for explaining an optical axis angle of measurement light. FIG. 1 is a block diagram illustrating an overall configuration of a distance measuring device according to the present invention. FIG. 4 is a schematic diagram schematically showing a chirp frequency comb output of an FSF laser beam. 7 is a graph showing the result of correcting the plate height shown in FIG. 6 based on the frequency shift amount. It is the schematic which showed the measuring head which irradiates a measuring light with respect to the steel plate currently conveyed. It is a graph which shows the variation | change_quantity of the board | plate height produced by the difference in speed.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

<Consideration of change in measurement distance caused by different speed>
The present inventors have used a distance measuring device including a laser oscillator that oscillates FSF (Frequency-Shifted Feedback) laser light whose frequency is modulated with respect to time (that is, an FSF laser distance meter), When the distance to the measurement surface of the steel plate P moving in the vertical direction was measured, it was confirmed that the measurement distance (measurement result; apparent distance) changed depending on the speed. Therefore, the present inventors have intensively studied the cause of such a change in the measurement distance.

As a result, when measuring the shape of the moving steel sheet P using the FSF laser range finder, the present inventors have found that the measurement distance is shifted by the FSF laser beam (hereinafter simply referred to as laser beam). (Also referred to as), is thought to be affected by the Doppler shift. More specifically, as the cause of the measurement distance is shifted, as shown in FIG. 1, the optical axis a _x of the measurement light to the measurement surface of the steel plate P, that there is an unintended slight inclination of the operator , Speculated that it was affected by the Doppler shift.

Here, the inclination of the optical axis a _x of the laser beam emitted from the measuring head 5 (measurement light) (hereinafter, referred to as the optical axis angle theta) is the direction in which the steel plate P is moved (the moving direction X) and irradiated in plane formed optical axis of that laser beam, and the direction Z perpendicular to the moving direction X, and the optical axis a _x of the laser beam irradiated, the angle formed by.

If the optical axis a _x of the measuring light is inclination, the reflected light frequency f ₀ is shifted by the Doppler shift reflected from the steel plate P. Therefore, in the distance measuring apparatus using the FSF laser light, the distance is calculated based on the frequency difference between the reference light and the reflected light. As a result, as shown in FIG. 6, the distance may have changed. It is speculated that there is.

  Therefore, when the object to be measured (steel plate P) is in a stationary state, if the measurement distance changes by 1 mm in the Z direction (that is, the optical path of the reflected light changes by 2 mm), the frequency of the reflected light changes to about 0 in response. The optical axis angle θ (rad) was examined based on the following equation (1) shown in FIG. 1 using an FSF laser distance meter having a characteristic of shifting by 0.044 MHz.

f _D = 2V · sin θ / λ (1)
Note that f _D (Hz) indicates a frequency shift amount per unit distance in the Z direction, V (m / s) indicates a relative speed of the object to be measured with respect to the measurement head 5, and λ (m) indicates a laser beam. Indicates the wavelength.

Here, the frequency shift amount f _D is set to 0.044 MHz (4.4 × 10 ⁴ Hz), the speed V at which the steel sheet P moves in the moving direction X is set to 50 mpm (= 0.83 m / s), and the FSF of the laser oscillator is set. When the wavelength λ of the laser beam was 1550 nm (= 1.550 × 10 ⁻⁶ m) and the optical axis angle θ was calculated based on the above equation (1), the optical axis angle θ was 2.4 degrees. . In other words, this is, when the optical axis _{a x} is inclined 2.4 °, indicating that the measuring distance is about ^{1mm (= 1.0 × 10 -3 m} ) shift.

Here, in a steel product manufacturing site, when using a distance measuring device using an FSF laser beam, the optical axis angle θ of the measuring light applied to the measuring surface of the steel sheet P is usually 0 degrees (ie, , such that the optical axis a _x with respect to the moving direction X of the steel plate P is vertical), it has been made the installation work by the operator. However, from the results of the above considerations, in actuality, at a steel product manufacturing site, even if the worker adjusts the optical axis angle θ of the measurement light to 0 °, a slight inclination that the worker cannot confirm is small. It is presumed that it will be difficult to make accurate installation work.

Therefore, in the above example, the mounting accuracy, the optical axis a _x of the measuring light, it is considered that they've tilted about 2.4 degrees.

Therefore, in a distance measuring device using laser light whose frequency is modulated with respect to time, the laser light is considered to be affected by the Doppler shift without any intention of the operator. to measure accurately the inclination of the optical axis a _x of the measuring light be strictly considered, it is necessary to correct the measured distance.

<About the distance measuring device of the present invention>
Next, a distance measuring device capable of measuring the distance to the steel sheet P with high accuracy by correcting the influence of the Doppler shift based on the above-described consideration results will be described below. FIG. 2 shows the overall configuration of the distance measuring device 1 of the present invention. The distance measuring device 1 includes a laser oscillator 2 that oscillates FSF laser light, a branching device 3, a circulator 4, a measuring head 5, a coupler 6, a light detecting unit 7, a frequency analyzing unit 9, an arithmetic processing unit 10, and a distance calculating unit. 20.

  The laser oscillator 2 is a laser oscillator that emits FSF laser light. Here, the FSF laser light is a laser light that oscillates by feeding back the frequency-shifted light using a resonator (not shown) including an element (frequency shift element) that changes the frequency of the light. Means

  FIG. 3 is a diagram schematically illustrating the output of the FSF laser light. As shown in FIG. 3, the FSF laser light is amplified and attenuated according to the gain curve (frequency-amplitude curve) of the resonator while the light wave in the resonator undergoes a frequency shift for each rotation, and is finally attenuated. Disappear. In the oscillation output of the FSF laser light, a plurality of such instantaneous frequency components are present in a comb shape at a constant frequency interval.

In FIG. 3, τ _RT represents the orbiting time of the resonator, and ν _FS represents the amount of frequency shift per orbit. 1 / tau _RT showed longitudinal mode frequency interval of the resonator (chirped frequency comb interval), r _s is the amount of change per unit time of the instantaneous frequency of the FSF laser light, that is, the frequency modulation rate.

  The laser light (FSF laser light) output from the laser oscillator 2 is incident on the splitter 3 via an optical fiber. The splitter 3 splits the laser light incident from the laser oscillator 2 into measurement light and reference light. The measuring light branched in the branching device 3 is guided to the measuring head 5 via the first optical fiber optical path 8a. The first optical fiber optical path 8a has a circulator 4 between the time when the measuring light exits the splitter 3 and reaches the measuring head 5. The circulator 4 emits the measurement light from the splitter 3 to the measurement head 5, and emits the reflected light incident from the measurement head 5 to the coupler 6.

  The measuring head 5 has an end 5b of a first optical fiber optical path 8a and a condenser lens 5a inside. The measurement head 5 emits the measurement light transmitted from the laser oscillator 2 via the first optical fiber optical path 8a from the end 5b of the first optical fiber optical path 8a and collects the measurement light by the condenser lens 5a. Irradiates the measurement surface of the steel sheet P. The steel sheet P is conveyed by a conveying roller (not shown) in the movement direction X (one direction along the plane direction of the flat measurement surface of the steel sheet P), and the measuring head 5 moves the steel sheet P moving at a predetermined speed V. The measurement light is emitted toward the measurement surface.

  The reflected light obtained by reflecting the measurement light on the measurement surface of the steel plate P is condensed by the condenser lens 5a, and then received by the end 5b of the first optical fiber optical path 8a. The light enters the coupler 6 via the fiber optical path 8a. Specifically, the reflected light received by the measurement head 5 is guided to the circulator 4 through the same optical fiber as the optical fiber through which the measurement light has passed, and is guided from the circulator 4 to the coupler 6 through the optical fiber.

  On the other hand, the reference light split by the splitter 3 is guided to the light detection unit 7 through the second optical fiber optical path 8b. Specifically, the reference light emitted from the splitter 3 is guided to the coupler 6 through an optical fiber having a predetermined optical path length. The coupler 6 causes the reference light and the reflected light to enter the light detection unit 7 through the optical fiber.

  The light detection unit 7 receives the reflected light and the reference light, converts the light into an electric signal, and sends the electric signal to the frequency analysis unit 9. Since the reflected light and the reference light that are simultaneously incident on the light detection unit 7 have a frequency difference corresponding to the difference in the optical path length that the laser light passes from when the laser light exits the laser oscillator 2 to when the laser light enters the light detection unit 7. A beat signal is generated due to optical interference between the reflected light and the reference light.

  The frequency analysis unit 9 analyzes the electric signal sent from the light detection unit 7 to detect a beat signal generated by optical interference between the reflected light and the reference light in the group of lights detected by the light detection unit 7. Are detected within a predetermined detection frequency range. Note that a spectrum analyzer or the like can be used as the frequency analysis unit 9.

  The distance calculator 20 converts the frequency (beat frequency) of the beat signal detected by the frequency analyzer 9 into a distance. This distance is calculated based on the distance from a preset reference position (for example, a position where the optical path difference between the measurement light and the reference light on the first optical fiber optical path 8a does not occur) to the measurement surface of the steel plate P. Therefore, for example, when calculating the distance D1 from the measuring head 5 to the measuring surface of the steel plate P, the optical distance from the reference position to the measuring head 5 in consideration of the refractive index of the optical fiber and the like is calculated as described above. It can be obtained by subtracting from the distance.

In addition to such a configuration, the distance measuring device 1 of the present invention is provided with an arithmetic processing unit 10. Arithmetic processing unit 10 is for calculating the frequency shift amount f _D used for the measurement distance to shift by the speed V of the steel sheet P is different, corrected. Here, in the present embodiment the measuring head 5 is fixed to the steel plate P is moved, from the above equation (1), in order to determine the frequency shift amount f _D for shifting the frequency of the reflected light, the formula (1 ), The speed V of the steel sheet P, the optical axis angle θ, and the wavelength λ of the laser beam are required.

  The wavelength λ of the laser light can be obtained by measuring in advance with a spectroscope or the like. The speed V can be obtained by using the set speed of the transport roller that transports the steel sheet P, or by measuring the actual speed V of the steel sheet P using a laser Doppler speedometer or the like.

The optical axis angle θ of the measuring light emitted from the measuring head 5 is determined by the angle between the moving direction X of the steel sheet P, the direction Z perpendicular to the moving direction X of the steel sheet P, and the optical axis a _x of the measuring light. Therefore, it is difficult to measure directly. Further, although the optical axis angle θ of the measurement light applied to the measurement surface of the steel sheet P is originally set by an operator to be 0 °, actually, the optical axis angle is set at the manufacturing site of the steel product. It is presumed that it is difficult to accurately set the measuring head 5 so that the angle θ becomes 0 degree.

Therefore, for example, a steel plate P (test piece) serving as a test sample of the object to be measured is moved in advance in the moving direction X at a plurality of speeds V ₁ and V ₂ , and at these speeds V ₁ and V ₂ . the difference in the frequencies of the reflected light detected respectively, calculated as the frequency shift amount f _D1. Further, a speed difference between the speeds V ₁ and V ₂ is calculated as a speed V _D1 for calibration.

Thus, the optical axis angle θ of the measurement light is calculated by using the wavelength λ of the laser light, the speed V _D1 for calibration, and the frequency shift amount f _D1 at the speed V _D1 for calibration, using the above equation (1). (That is, f _D1 = 2V _D1 · Sin _θ / λ). Here, the frequency shift amount f _D1 is used for calculating the optical axis angle θ, and is hereinafter referred to as a calibration frequency shift amount f _D1 . The speed V _D1 is used for calculating the optical axis angle θ, and is hereinafter referred to as a calibration speed V _D1 .

Here, the speeds V ₁ and V ₂ for calculating the calibration speed V _D1 are 0 mpm and 50 mpm (= 0.83 m / s), 50 mpm (= 0.83 m / s) and 100 mpm (= 1.67 m / s). Various speeds can be applied, such as s). In addition, the plurality of speeds used for calculating the optical axis angle θ are _two speeds V ₁ and V _2. However, the present invention is not limited to this, and various speeds V may be used if they are two or more. ₁ , V ₂ ,... May be used.

After calculating the optical axis angle θ as described above, when newly starting to measure the shape of the steel sheet P actually moving at the speed V along the moving direction X, the speed V of the steel sheet P is measured. If acquired, the frequency shift amount f _D used to correct the measurement distance is obtained from the above equation (1) using the optical axis angle θ of the measurement light and the wavelength λ of the laser light calculated in advance by the above method. Can be calculated.

Arithmetic processing unit 10 shown in FIG. 2, and calculates the velocity V of the steel sheet P, a light axis angle theta, acquires the wavelength of the laser beam lambda, the frequency shift amount f _D from the above equation (1) is there. In this case, the arithmetic processing unit 10 includes an optical axis angle acquisition unit 11, a speed acquisition unit 12, a wavelength acquisition unit 13, and a frequency shift amount calculation unit 18. The optical axis angle acquisition unit 11, the speed acquisition unit 12, and the wavelength acquisition unit 13 constitute an acquisition unit.

In the case of this embodiment, the optical axis angle acquisition unit 11 has a calibration data calculation unit 15 and an optical axis angle calculation unit 16, and calculates the optical axis angle θ of the measurement light by calculation. For example, when the steel sheet P is moved along the moving direction X at a plurality of speeds V ₁ and V ₂ , the calibration data calculation unit 15 calculates each of the reflected light and the reference light received by the light detection unit 7. The beat frequency generated by the interference is detected. The calibration data calculation unit 15 calculates the frequency difference between the two beat frequencies detected by the light detection unit 7 at the speeds V ₁ and V ₂ as the calibration frequency shift amount f _D1 .

Further, the calibration data calculation unit 15 acquires data on the speeds V ₁ and V ₂ from the speed acquisition unit 12 and calculates the difference between the speeds V ₁ and V ₂ as the calibration speed V _D1 . The speed acquiring unit 12 acquires, for example, the set speed of the transport roller that transports the steel sheet P as the speed V (speeds V ₁ , V ₂ ), or obtains the speed V (by a laser Doppler speedometer or the like). The speeds V ₁ and V ₂ ) are actually measured and obtained.

The optical axis angle calculation unit 16 receives the data on the calibration frequency shift amount f _D1 and the calibration speed V _D1 acquired by the calibration data calculation unit 15, and calculates the wavelength λ of the laser light acquired by the wavelength acquisition unit 13. receive. Note that the wavelength acquisition unit 13 is, for example, a spectroscope or the like, and acquires the wavelength λ by measuring the wavelength λ of the laser light oscillated by the laser oscillator 2.

The optical axis angle calculation unit 16 calculates the optical axis angle θ of the measurement light from the above equation (1) using the calibration frequency shift amount f _D1 , the calibration speed V _D1 , and the wavelength λ of the laser beam, The obtained optical axis angle θ is stored in a storage unit (not shown).

Then, when actually measuring the shape of the steel plate P moving at velocity V along the direction of movement X, determine the frequency shift amount f _D uses the optical axis angle θ, which is calculated as described above , The measurement distance to the steel plate P is corrected. Hereinafter, a correction process for correcting the measurement distance to the steel plate P after calculating the optical axis angle θ will be described.

  In this case, the frequency shift amount calculation unit 18 receives the speed V of the steel sheet P moving along the movement direction X from the speed acquisition unit 12, and calculates the wavelength λ of the laser light radiated toward the steel sheet P. Received from the acquisition unit 13. Further, the frequency shift amount calculation unit 18 receives the optical axis angle θ of the measurement light, which is obtained in advance by calculation, from the optical axis angle acquisition unit 11.

Frequency shift amount calculation unit 18 uses these velocity V, the wavelength λ and the optical axis angle theta, calculates the frequency shift amount f _D from the above equation (1), and sends it to the distance calculating unit 20.

The distance calculator 20 converts the frequency (beat frequency) of the beat signal, which is sent from the frequency analyzer 9 and is generated by the optical interference between the reflected light and the reference light, into a difference in optical path length, thereby setting the distance in advance. The distance from the reference position thus determined to the measurement surface of the steel sheet P is calculated. At this time, when the steel plate P is moving, the beat frequency is subjected to frequency shift of the frequency shift amount f _D. Therefore, the distance calculation unit 20 uses the value of the frequency shift amount f _D obtained by the operation processing unit 10, that the velocity V is corrected to the effect of frequency shift that occurs by different, correct the measured distance (leaf Height). Here, FIG. 4 shows, as an example, the results obtained when the measurement distances (plate heights) shown in FIG. 6 are corrected using the frequency shift amount f _D obtained for each speed by the arithmetic processing unit 10. Show.

In this embodiment, the optical axis angle θ is 2.4 degrees of the measuring light, the wavelength of the laser beam λ is 1550 nm, the speed V is 50Mpm, 100 mpm, the frequency shift amount _{f D} of when the 150mpm was calculated. Then, the frequency of the reflected light is detected at each speed was only the value shifted in the corresponding frequency shift amount f _D. Then, the frequency of the beat signal generated by optical interference between the reference light and the reflected light whose frequency was shifted was converted into a difference in optical path length to obtain a measurement distance.

As shown in FIG. 4, the velocity V is 50Mpm, 100 mpm, even when different from the 150Mpm, by correcting the frequency of the reflected light based on the frequency shift amount _{f D} calculated respectively, the measured distance is near 0mm any results (Near the conveyance path line of the steel sheet P), it was confirmed that they substantially coincided. The distance measuring device 1 can measure the shape of the steel plate P, which is the object to be measured, from the unevenness of the measured distance (corrected measured distance) corrected in this manner.

<Action and effect>
In the above configuration, in the distance measuring device 1, the steel plate P is moved, the measuring head 5 irradiates the measuring surface of the steel plate P with measuring light, and the reflected light is received by the measuring head 5 (irradiation / light receiving step). Further, the distance measuring device 1 acquires the speed V of the steel sheet P with respect to the measuring head 5 and the wavelength λ of the laser light (speed acquiring step and wavelength acquiring step). Furthermore, the distance measuring device 1, the moving direction X of the steel plate P, and, in the optical axis a _x plane formed of the laser beam emitted from the measuring head 5, and the direction Z perpendicular to the moving direction X, the measuring head 5 for obtaining an optical axis angle θ which forms with the optical axis a _x of the irradiated laser light (optical axis angle acquisition step). And these speed V, and calculates the frequency shift amount f _D from the optical axis angle θ and the wavelength lambda (calculation step).

Thus, in the distance measuring device 1, measuring the distance from the reference position to the measuring surface of the steel plate P, it is corrected based on the frequency shift amount f _D, to measure the shape of the steel plate P based on the corrected measured distance (Measurement step). Therefore, the distance measuring device 1 can correct the deviation of the distance to the steel plate P, which occurs when the speed V is different, so that the shape of the steel plate P can be measured with higher accuracy than before.

In the distance measuring device 1, the speeds V ₁ and V ₂ of the steel sheet P are changed, and the difference between the frequencies of the reflected lights detected at the respective speeds V ₁ and V ₂ is used as a calibration frequency shift amount f _D1. Calculation (calibration data calculation step). Further, the distance measuring device 1 calculates a calibration speed V _D1 from the speed difference between the speeds V ₁ and V ₂ (calibration speed calculation step).

Thereby, the optical axis angle θ of the measurement light can be calculated from the calibration frequency shift amount f _D1 , the calibration speed V _D1 , and the wavelength λ based on the above equation (1) (optical axis angle calculation step). ). Therefore, even when it is difficult to directly measure the optical axis angle θ of the measurement light, the distance measuring device 1 can obtain the accurate optical axis angle θ, and the frequency shift is performed using the optical axis angle θ. possible to calculate the amount _{f D.}

<Other embodiments>
The present invention is not limited to the present embodiment, and various modifications can be made within the scope of the present invention. For example, although the plate-shaped steel plate P is applied as the object to be measured, the present invention is not limited to this, and the object to be measured having various shapes such as a steel plate having a rectangular parallelepiped shape or a steel material having a cylindrical or columnar shape is used. An object may be applied. Further, an object to be measured made of other materials than the steel plate may be applied.

  In the above-described embodiment, the case where the measuring head 5 is fixed and the steel plate P is moved as a state in which the measuring head is relatively moved with respect to the object to be measured has been described. Not limited to this, the steel plate P may be fixed, and the measuring head 5 may be moved in one direction along the surface direction of the measurement surface of the steel plate P.

  Further, in the above-described embodiment, the FSF laser light is applied as the laser light whose frequency is modulated with respect to time. However, the present invention is not limited to this, and the laser light whose various frequencies are modulated with respect to time. For example, a frequency modulation (FMCW: Frequency Modulated Continuous Wave) method or the like may be applied.

Further, in the above-described embodiment, the frequency shift amount f _D is obtained, and the measured beat frequency is shifted based on the frequency shift amount f _D to correct the deviation of the distance to the steel sheet P (that is, , The frequency is shifted at the stage of the frequency calculation), but the value of how far the distance shifts is measured in accordance with the speed V of the steel sheet P, and the distance to be shifted is calculated from the apparent measured distance. (That is, shifting is performed at the stage of distance calculation).

In this case, an arithmetic processing step of calculating a distance shift amount for correcting a distance is executed in the following order. For example, the wavelength λ of the laser beam is obtained in advance (wavelength obtaining step), and the speed V of the steel plate P (measurement target) with respect to the measuring head 5 is obtained (speed obtaining step). In addition, measurement is performed while changing the speed of the steel sheet P serving as a sample, and the speed difference is obtained by the speed obtaining unit 12 and calculated as the correction speed _VD1 (calibration data calculation step). Moreover this time, calculates the difference between the beat frequency as the calibration frequency shift amount f _D1 (correction data calculating step). Then, using the wavelength λ acquired by the wavelength acquisition unit 13, the calibration speed V _D1, and the calibration frequency shift amount f _D1 , irradiation is performed from the moving direction X of the steel sheet P and the measurement head 5. in plane formed optical axis a _x is a laser beam, wherein the moving direction X perpendicular to direction Z, to obtain the optical axis angle θ formed by the optical axis a _x of the laser beam emitted from the measuring head 5 (Optical axis angle acquisition step).

  Then, the arithmetic processing unit 10 calculates the wavelength λ obtained in the wavelength obtaining step, the speed V obtained in the speed obtaining step, and the optical axis angle obtaining step by a distance shift amount calculating unit (not shown). From the obtained optical axis angle θ, a distance shift amount that defines how much the apparent distance obtained as a measurement result shifts is calculated according to the speed V of the steel sheet P (distance shift amount calculation step).

  After that, the distance shift amount corresponding to the speed V is transmitted to the distance calculation unit 20. Thus, the distance calculation unit 20 can measure the distance to the measured object by correcting the measured distance from the reference position to the measured object using the correction amount (correction in the distance calculation step). And distance measurement).

  In the above-described embodiment, the speed (moving speed) V at which the steel sheet P moves is obtained by the speed acquiring unit 12 provided in the distance measuring device 1 (in particular, in the arithmetic processing unit 11). If the moving speed V of the steel plate P can be measured, the moving speed V is measured by using a known measuring device separate from the distance measuring device 1, and only the value is used by the distance measuring device 1. It is also possible.

  Further, the wavelength of the laser beam is obtained by the wavelength acquisition unit 13 provided in the distance measuring device 1 (particularly, in the arithmetic processing unit 11). It is also possible to measure the wavelength λ of the laser beam using a separate known measuring device and use only that value in the distance measuring device 1.

  In the above-described embodiment, the case where the optical axis angle acquisition unit 11 that calculates the optical axis angle θ by calculation has been described. However, the present invention is not limited to this, and the optical axis angle θ is measured by the measuring unit. An optical axis angle acquisition unit that acquires an actual measurement value may be applied, or an optical axis angle acquisition unit that simply stores the optical axis angle θ in advance may be used.

In the above-described embodiment, the distance to the steel plate P is measured by detecting a beat signal having a frequency equal to the frequency difference between the reflected light and the reference light, and converting the beat frequency into a difference in optical path length. However, the present invention is not limited to this. For example, as disclosed in JP-A-2006-80409, a reflection source is provided in the measurement head 5, reflection light is reflected by the reflection source to generate return light, and reflected light, reference light, and return light are generated. The distance to the steel plate P may be measured by using. In this case, when generating a beat signal by using the reflected light, by using a reflected light obtained by shifting the frequency by the frequency shift amount f _D, it is possible to obtain the same effect as the above-described embodiment.

DESCRIPTION OF SYMBOLS 1 Distance measuring device 2 Laser oscillator 5 Measuring head 9 Frequency analysis unit 11 Optical axis angle acquisition unit (acquisition unit)
12 Speed acquisition unit (acquisition unit)
13 Wavelength acquisition unit (acquisition unit)
18 Frequency shift amount calculation unit 20 Distance calculation unit

Claims (4)

A distance measuring method for measuring a distance to an object to be measured,
A laser oscillation step of oscillating and emitting laser light whose frequency is modulated with respect to time by a laser oscillator,
Irradiating a laser beam emitted from the laser oscillator to the object to be measured, which relatively moves, from a measurement head, and irradiating and receiving the reflected light reflected by the object to be measured by the measurement head. ,
A frequency analysis step of acquiring a beat frequency based on the reflected light received by the measurement head and the reference light emitted from the laser oscillator,
A distance calculation step of calculating a distance from the beat frequency to the object to be measured,
An arithmetic processing step of calculating a frequency shift amount for correcting the distance calculated in the distance calculation step;
Has,
The arithmetic processing step includes:
A wavelength obtaining step of obtaining a wavelength of the laser light,
Speed acquisition step of acquiring the speed of the measured object with respect to the measurement head,
Performing the measurement while changing the speed, obtaining the speed difference in the speed obtaining step, calculating the speed for calibration, and calculating the difference between the beat frequencies as the frequency shift amount for calibration, a calibration data calculating step. When,
Using the wavelength acquired in the wavelength acquisition step, the calibration speed, and the calibration frequency shift amount, the moving direction of the object to be measured and the optical axis of the laser beam emitted from the measurement head are formed. Surface, a direction perpendicular to the moving direction, and an optical axis angle calculating step of calculating an optical axis angle formed by the optical axis of the laser light emitted from the measurement head,
The wavelength obtained in the wavelength obtaining step, the speed obtained in the speed obtaining step, and the optical axis angle obtained in the optical axis angle calculating step, a frequency shift amount calculating step of calculating the frequency shift amount When,
Has,
The distance calculating step includes:
A distance measuring method for measuring a distance to the object to be measured by correcting the beat frequency acquired in the frequency analysis step using the frequency shift amount. A distance measuring method for measuring a distance to an object to be measured,
A laser oscillation step of oscillating and emitting laser light whose frequency is modulated with respect to time by a laser oscillator,
Irradiating a laser beam emitted from the laser oscillator to the object to be measured, which relatively moves, from a measurement head, and irradiating and receiving the reflected light reflected by the object to be measured by the measurement head. ,
A frequency analysis step of acquiring a beat frequency based on the reflected light received by the measurement head and the reference light emitted from the laser oscillator,
From the beat frequency, a distance calculation step of calculating a distance to the measured object,
An arithmetic processing step of calculating a distance shift amount for correcting the distance calculated in the distance calculation step;
Has,
The arithmetic processing step includes:
A wavelength obtaining step of obtaining a wavelength of the laser light,
Speed acquisition step of acquiring the speed of the measured object with respect to the measurement head,
Performing the measurement while changing the speed, obtaining the speed difference in the speed obtaining step, calculating the speed for calibration, and calculating the difference between the beat frequencies as the frequency shift amount for calibration, a calibration data calculating step. When,
Using the wavelength acquired in the wavelength acquiring step, the calibration speed, and the calibration frequency shift amount, the moving direction of the object to be measured and the optical axis of the laser beam emitted from the measurement head are formed. Surface, a direction perpendicular to the moving direction, and an optical axis angle calculating step of calculating an optical axis angle formed by the optical axis of the laser light emitted from the measurement head,
A distance shift amount calculating step of calculating the distance shift amount from the wavelength obtained in the wavelength obtaining step, the speed obtained in the speed obtaining step, and the optical axis angle obtained in the optical axis angle calculating step; When,
Has,
The distance calculating step includes:
A distance measurement method for measuring a distance to the object to be measured by correcting a distance calculated from the beat frequency acquired in the frequency analysis step using the distance shift amount. A distance measuring device that measures a distance to an object to be measured,
A laser oscillator that oscillates and emits laser light whose frequency is modulated with respect to time,
A measurement head that irradiates a laser light emitted from the laser oscillator to the object to be measured that relatively moves, and receives light reflected by the object to be measured,
A frequency analysis unit that acquires a beat frequency based on the reflected light received by the measurement head and the reference light emitted from the laser oscillator,
From the beat frequency, a distance calculation unit that calculates the distance to the measured object,
An arithmetic processing unit that calculates a frequency shift amount for correcting the distance calculated by the distance calculation unit,
Has,
The arithmetic processing unit,
The measurement is performed by changing the speed of the object to be measured with respect to the measurement head, the speed difference is obtained and calculated as a calibration speed, and the beat frequency difference is calculated as a calibration frequency shift amount. Data calculation unit,
Using the wavelength of the laser light, the calibration speed, and the calibration frequency shift amount, on a plane formed by the moving direction of the object to be measured and the optical axis of the laser light emitted from the measurement head, An optical axis angle calculation unit that calculates an optical axis angle between a direction perpendicular to the moving direction and the optical axis of the laser light emitted from the measurement head,
The wavelength of the laser light, the speed at which the speed difference was obtained, and the optical axis angle determined by the optical axis angle calculation unit, a frequency shift amount calculation unit that calculates the frequency shift amount,
Has,
The distance calculation unit,
A distance measuring device for measuring a distance to the object to be measured by correcting a beat frequency acquired by the frequency analysis unit using the frequency shift amount. A distance measuring device that measures a distance to an object to be measured,
A laser oscillator that oscillates and emits laser light whose frequency is modulated with respect to time,
A measurement head that irradiates a laser light emitted from the laser oscillator to the object to be measured that relatively moves, and receives light reflected by the object to be measured,
A frequency analysis unit that acquires a beat frequency based on the reflected light received by the measurement head and the reference light emitted from the laser oscillator,
From the beat frequency, a distance calculation unit that calculates the distance to the measured object,
An arithmetic processing unit that calculates a distance shift amount for correcting the distance calculated by the distance calculation unit,
Has,
The arithmetic processing unit,
The measurement is performed while changing the speed of the object to be measured with respect to the measurement head, the speed difference is obtained and calculated as a calibration speed, and the beat frequency difference is calculated as a calibration frequency shift amount. Data calculation unit,
Using the wavelength of the laser light, the calibration speed, and the calibration frequency shift amount, on a plane formed by the moving direction of the object to be measured and the optical axis of the laser light emitted from the measurement head, An optical axis angle calculation unit that calculates an optical axis angle between a direction perpendicular to the moving direction and the optical axis of the laser light emitted from the measurement head,
The wavelength of the laser light, the speed at which the speed difference was obtained, and the optical axis angle obtained by the optical axis angle calculation unit, a distance shift amount calculation unit that calculates the distance shift amount,
Has,
The distance calculation unit,
A distance measuring device that measures a distance to the object to be measured by correcting a distance calculated from a beat frequency acquired by the frequency analysis unit using the distance shift amount.

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