JPH05332722A - Optical displacement measuring device - Google Patents

Abstract

PURPOSE:To provide an optical displacement measuring device capable of detecting the displaced state of a measurement target within a short time and excellent in real-time measuring property. CONSTITUTION:A laser beam is emitted to an object 30 to be measured twice at a certain time interval to provide two speckle, patterns. The two speckle patterns are double recorded in a FLCSLM 7. The double recorded speckle patterns are read, and Fourier-transformed by a Fourier transforming lens 12 to form a Young's interference fringe. This is recorded in a FLCSLM 12. The Young's interference fringe is read, and Fourier-transformed by a Fourier transforming lens 15, whereby the (+) primary diffracted light according to the correlation of the double recorded speckle patterns is formed. The optical intensity of the (+) primary diffracted light is measured by a photomultiplier 16. An arithmetic control device 17 determines the moving distance and thus the moving speed in the time interval of the object 30 to be measured on the basis of the optical intensity, and a speed display device 18 displays the moving speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement measuring device for optically measuring the displacement state of an object. Here, the displacement state of the object refers to a moving state or a deforming state of the object, and includes a displacement amount (moving amount, displacement amount, etc.) and a displacement speed (moving speed, displacement speed, etc.).

[0002]

2. Description of the Related Art The speckle method is one of the means for optically measuring the amount of displacement of an object. In the speckle method,
A speckle pattern (hereinafter referred to as a "speckle pattern") formed by irradiating an object with coherent light such as a laser beam and diffusing and reflecting the irradiation light on a rough surface of the object is used. Japanese Unexamined Patent Publication No. 59-212773 discloses an optical velocity detecting device adopting the speckle method. In this device, a moving object to be measured is irradiated with coherent light twice at a certain time interval. The speckle patterns obtained by the two irradiations are respectively received by a plurality of light receiving elements and photoelectrically converted. The sample values collected by each light receiving element are shifted from each other, and the correlation is calculated. From this calculation, the amount of movement of the speckle pattern is obtained, and thus the amount of movement and the moving speed of the measured object are obtained.

[0003]

As described above, in the apparatus for obtaining the moving amount / moving speed by the correlation calculation, it takes time to collect the sample values and the correlation calculation, and it is not sufficient in terms of real-time measurable property. The present invention has been made in view of the above problems, and an object thereof is to provide an optical displacement measuring device capable of measuring a displacement state of an object to be measured in a short time and having excellent real-time measurable property. ..

[0004]

In order to achieve the above object, the optical displacement measuring apparatus of the present invention irradiates light on an object to be measured to form an image of the object to be measured at two measurement times. For irradiating the image of the object to be measured at the second measurement time, and the double recording by irradiating the first recording means with coherent light. First coherent light projecting means for reading out an image, first Fourier transforming means for performing Fourier transform on the read double recording image to form a first Fourier transform image, and Second recording means for recording the Fourier transform image of the second, and second coherent light projecting means for irradiating the second recording means with coherent light to read out the first Fourier transform image , A Fourier transform of the read first Fourier transform image To a second Fourier transform means for forming a second Fourier transform image, composed of a 0-dimensional light detection means for detecting the state of the Fourier transformed image of said second,. Here, it is preferable that the 0-dimensional light detecting means is a 0-dimensional light intensity detecting means for detecting the light intensity of the second Fourier transform image. The 0-dimensional light intensity detecting means is particularly preferably a photomultiplier tube. The second Fourier transform image is composed of two diffracted light point images corresponding to the correlation of the images of the measurement target at the two measurement times. Therefore, the 0-dimensional light intensity detecting means is
It is provided to detect at least one light intensity of the second diffracted light point image. The optical displacement measuring device further comprises
And a calculation means for calculating a relative displacement amount of the object to be measured with respect to the optical displacement measurement device between the two measurement times based on the detection result of the zero-dimensional light detection means. preferable. Further, it is preferable that the light irradiation means irradiates the object to be measured with coherent light to form a speckle pattern. The first and second recording means are preferably ferroelectric liquid crystal spatial light modulators.

[0005]

In the optical displacement measuring device of the present invention having the above construction, the light irradiating means irradiates the object to be measured which is relatively displaced with respect to the optical displacement measuring device with light.
With the irradiation light, images of the object to be measured at the two measurement times are obtained, respectively. The first recording means double-records the images at the second measurement times. The first coherent light projecting unit irradiates the first recording unit with coherent light to read the double-recorded image recorded in the first recording unit. The read double recorded image is subjected to Fourier transform by the first Fourier transform means to form a first Fourier transform image. The second recording means records the first Fourier transform image. The second coherent light projecting unit irradiates the second recording unit with coherent light to read out the first Fourier transform image recorded in the second recording unit. The second Fourier transform means Fourier transforms the read first Fourier transform image to form a second Fourier transform image. The 0-dimensional light detecting means detects the state of the second Fourier transform image. The 0-dimensional light detecting means detects the state of the second Fourier transform image and outputs information indicating the state. Here, the state of the second Fourier transform image is a relative displacement state of the measured object with respect to the first recording means during the second measurement time (that is,
It has a fixed relationship with the relative displacement state with respect to the optical displacement measuring device. Therefore, the 0-dimensional light detection means outputs information indicating the relative displacement state as the detection result. For example, the light intensity of the second Fourier transform image is constant with the relative displacement state between the object to be measured and the first recording means (that is, the optical displacement measuring device) between the two measurement times. Have a relationship. Therefore, when the 0-dimensional light detecting means is a 0-dimensional light intensity detecting means for measuring the light intensity of the second Fourier transform image, the 0-dimensional light detecting means outputs a detection result. , Information indicating the relative displacement state will be output. Further, when the optical displacement measuring device is provided with the calculating means, the calculating means is based on the detection result of the 0-dimensional light detecting means, and the object to be measured between the two measurement times. The relative displacement amount of the optical displacement measuring device is calculated. In particular, when the 0-dimensional light detecting means is the 0-dimensional light intensity detecting means, the calculating means calculates the light intensity of the second Fourier transform image detected by the 0-dimensional light intensity detecting means. Based on, the relative displacement amount of the object to be measured with respect to the optical displacement measuring device between the two measurement times is calculated. When the light irradiating means irradiates coherent light, a speckle pattern is obtained as an image of the object to be measured.

Embodiments of the present invention will be described below with reference to the drawings. The embodiment relates to an optical moving speed measuring device for measuring the moving speed of a moving object to be measured.

FIG. 1 is a plan view of an optical system showing a schematic configuration of an optical moving speed measuring apparatus (hereinafter referred to as “measuring apparatus”) 1 according to this embodiment. The measuring device 1 includes a He-Ne laser device 2 as a light source; and a laser beam from the He-Ne laser device 2 that irradiates the measured object 30 twice at a predetermined time interval to obtain a second spec. A speckle pattern forming portion 1A for forming a speckle pattern; a first ferroelectric liquid crystal spatial light modulator (hereinafter, referred to as "first FLC- S
7); and the laser light from the He-Ne laser device 2 is phase-modulated by the first FLC-SLM 7 in which the speckle pattern is double recorded, and further spatially Fourier transformed. An interference fringe forming portion 1B for forming Young's interference fringes; and a second ferroelectric liquid crystal spatial light modulator for recording the formed Young's interference fringes (hereinafter, referred to as "second FLC-SLM"). 13); and the laser light from the He-Ne laser device 2 is phase-modulated by the second FLC-SLM 13 in which Young's interference fringes are recorded, and further spatially Fourier-transformed to obtain a plurality of laser light. Diffracted light forming portion 1C for forming diffracted light spots of
A measurement / calculation unit 1D for measuring the light intensity of the + 1st order diffracted light of the formed diffracted light spots and calculating the movement amount and thus the movement speed of the measured object 30 in the predetermined time interval.
It has and. That is, in the measuring apparatus 1, the FLC-SLM 7, the two speckle patterns having the same patterns obtained by the speckle pattern forming unit 1A,
The interference fringe formation unit 1B, the FLC-SLM 13, and the diffracted light formation unit 1C perform the same process as the joint conversion correlation process to form the autocorrelation signal light of the speckle pattern. The measurement / calculation unit 1D measures the light intensity of the autocorrelation signal light, calculates the distance between the two speckle patterns based on the measurement result, and thus calculates the moving speed of the measured object. Of.

The configuration of the measuring device 1 will be described below.
The details will be described.

A rectangular parallelepiped object 30 is conveyed and moved by a conveyor device 31 in the form of a belt conveyor on a conveying path extending in the direction of arrow V in FIG. 1 (the direction along the plane of the drawing). The rectangular parallelepiped object 30 has a planar rough surface 30A extending in a direction perpendicular to the plane of the drawing. The He-Ne laser device 2 continuously emits parallel light in a linearly polarized state. In the speckle pattern forming unit 1A, the half mirror 3 reflects a part of the laser light from the He—Ne laser device and guides it to an acousto-optic deflector (hereinafter referred to as “AOD”) 4. AOD4 is AOD
The laser light is deflected under the control of the controller 20. More specifically, the AOD 4 deflects the laser light and irradiates the laser light twice in a specific direction at predetermined time intervals. As a result, the laser spot light is applied to one fixed region R on the conveyance path of the measured object 30 twice in a pulse form at the predetermined time interval. (Hereinafter, the two irradiation times are referred to as “first irradiation time t ₁ and second irradiation time t ₂ ”, and the predetermined time interval is “irradiation time interval Δt (= t ₂ −t ₁ ) ”. Also, the moving distance of the measured object 30 at the irradiation time interval Δt is | S.
(Δt) | ) The irradiation light at the two times is irradiated at the irradiation times t ₁ and t _{2 on} the rough surface 30A of the measured object 30, respectively.
In the areas 30R ₁ and 30R ₂ which have reached the fixed area R, they are scattered and reflected to form two reflected lights. (Hereinafter, referred to as “first and second reflected lights”, respectively.) The first and second reflected lights have speckle patterns unique to the rough surface shapes of the regions 30R ₁ and 30R ₂ . That is, the first and second reflected lights have a pattern in which the same speckle distributions are entirely displaced in the moving direction V by the moving distance | S (Δt) | (hereinafter, respectively, First and second speckle patterns "). The image forming lens 5 forms an image of the first and second speckle patterns on the writing side light incident surface 7S _{w of} the first FLC-SLM 7. Therefore, the first and second speckle patterns imaged on the light incident surface 7S _w have the same speckle distribution as a whole in one shift direction X ′ and one shift distance (hereinafter , "Shift distance | M (△
The pattern is shifted by (t) | Here, the shift direction X ′ has a fixed relationship with the moving direction of the measured object (arrow V in FIG. 1). In the case of this embodiment, since the optical axis 5A of the imaging lens 5 extends along the plane of the drawing, the shift direction X'also extends in the direction along the plane of the drawing. Further, the shift distance | M (Δt) | has the relationship of the following equation 1 determined by the imaging magnification m of the imaging lens 5 with the object moving distance | S (Δt) | Have.

[Equation 1] | M (Δt) | = m · | S (Δt) |

The first FLC-SLM 7 is driven by the FLC-SLM controller 19 so as to double-record the first and second speckle patterns imaged on the writing side light incident surface 7S _w . It

On the other hand, the parallel laser beam transmitted through the half mirror 3 is a beam diameter conversion optical system 8 including a first collimator lens 8A, a spatial filter 8B and a second collimator lens 8C in the interference fringe formation section 1B.
Is converted into a parallel laser beam having a desired beam diameter. A part of the parallel laser beam is reflected by the half mirror 9, and the first reading optical system 10 including the variable aperture 10A and the half mirror 10B causes the first FL to be reflected.
It is guided to the reading side light incident surface 7S _r of the C-SLM 7.
The variable aperture 10A is for converting the laser beam into a desired beam diameter. The laser beam applied to the light incident surface 7S _r is FLC-S.
In the LM 7, after undergoing phase modulation corresponding to the positions (the shift distance | M (Δt) | and the shift direction) of the first and second speckle patterns, the light is emitted from the light incident surface 7S _r. To do. In this way, the reading of the double recorded speckle pattern is performed. The laser beam emitted from the FLC-SLM 7 is spatially Fourier transformed by the first Fourier transform lens 12 after passing through the half mirror 10B, and Young's interference fringes are formed on the image side focal plane of the lens 12. Form an image. Since the direction in which the fringes of the Young's interference fringes are arranged (the direction perpendicular to the extending direction of each fringe) is parallel to the shift direction X ′ of the speckle distribution recorded in the first FLC-SLM 7, It is parallel to the direction along the paper surface of. In addition, the fringe spacing of the Young's interference fringes (hereinafter, “|
K (Δt) | ”) and the shift distance | M (Δt)
The reciprocal of | means FLC-S as shown in the following Equation 2.
The reading light (H that illuminates the reading side surface 7S _r of LM7
e-Ne laser light) wavelength λ and the Fourier transform lens 1
There is a proportional relationship determined by the focal length f of 2.

## EQU2 ## | K (Δt) | = λf / | M (Δt) |

The second FLC-SLM 13 is arranged such that the writing side light incident surface 13S _w is located on the image side focal plane of the lens 12, so that the Young's interference fringes are incident on the light. An image is formed on the surface 13S _w . The second FLC
-The SLM 13 records the Young's interference fringes,
It is driven by the FLC-SLM controller 19.

The diffracted light forming section 1C is provided with a second reading optical system 11 including a mirror 11A and a half mirror 11B, and the He-Ne transmitted through the half mirror 9 is provided.
The laser light is guided to the reading side light incident surface 13S _r of the second FLC-SLM 13. The laser beam applied to the light incident surface 13S _r was subjected to phase modulation in the FLC-SLM 13 corresponding to the position of the Young's interference fringes (fringe direction and fringe spacing | K (Δt) |). After that, the light is emitted from the light incident surface 13S _r . Thus, the recorded Young's interference fringes are read out. The laser beam emitted from the second FLC-SLM 13 passes through the half mirror 11B,
The second Fourier transform lens 15 spatially performs a Fourier transform. As a result, the image-side focal plane 15 of the lens 15
On F, a 0th-order diffracted light spot and a plurality of diffracted light spots (n-order diffracted light; n = ± 1, ± 2, ...) Depending on the correlation between the first and second speckle patterns. Is imaged. Since the plurality of diffracted light spots are arranged in parallel to the direction in which the fringes of the Young's interference fringes are arranged, a direction along the plane of FIG. 1 (X direction).
Will be lined up. More specifically, the 0th-order diffracted light is imaged on a center point 15O where the optical axis 15A of the lens 15 intersects the image-side focal plane 15F. The + first-order, + second-order, ... Diffracted lights are arranged in this order from the center point 15O in the X direction. -1
The diffracted light of the second order, the second order, ...
The second-order diffracted light is arranged at a position symmetrical with respect to the center point 15O. Here, the ± 1st-order diffracted light is obtained by subjecting the first and second speckle patterns having the same pattern to the same process as the joint transform correlation process, and Correlated signal light. The distances between the adjacent light points of these diffracted light points (hereinafter referred to as “| N (Δt) |”) are equal to each other,
The value is the reciprocal of the fringe spacing | M (Δt) | of the Young's interference fringes and the reading side surface 13S of the FLC-SLM 13.
There is a fixed proportional relationship determined by the wavelength of the reading light (He-Ne laser light) irradiated on _r and the focal length of the Fourier transform lens 15.

By the way, the present inventors have studied and studied the relationship between the diffracted light spot and the fringe spacing | M (Δt) | of the Young's interference fringes. N (△
t) |, as well as the light intensity of + 1st-order diffracted light or −1st-order diffracted light (that is, autocorrelation signal light) (hereinafter, “I”).
Also has a constant relationship with Young's interference fringe spacing | M (Δt) |. For more details,
The light intensity I of the + 1st order or −1st order diffracted light is equal to the fringe spacing | M
The larger (Δt) |, the larger the stripe interval | M (Δt) |
It was discovered that the smaller is, the smaller is. According to this characteristic, the light intensity I of the autocorrelation signal light and the moving distance | S (Δt) |
It can be seen that (that is, the moving speed V) also has a fixed relationship. Specifically, it can be seen that there is a relationship that I becomes larger as | S (Δt) | becomes smaller and I becomes smaller as | S (Δt) | becomes larger. According to Equations 1 and 2, the smaller | S (Δt) |, the more | M (Δt)
| Becomes larger, and as | S (Δt) | becomes larger, | M (Δ
This is because t) | becomes small.

Therefore, in the measurement / calculation unit 1D of the present invention,
The photomultiplier tube 16 is arranged so that its photocathode 16S is located on the image side focal plane 15F. More specifically, as shown in FIGS. 2A and 2B, the circular photocathode 16S of the photomultiplier tube 16 has a center point 15O of the image-side focal plane 15F.
Is arranged at a position slightly deviated in the X direction so that the + 1st-order diffracted light spot can enter. Therefore,
The photomultiplier tube 16 outputs a current of an amount C corresponding to the light intensity value I of the incident + 1st order diffracted light spot.
The photocathode 16S is arranged at a position deviated from the center point 16O because the 0th-order diffracted light is prevented from entering the photocathode 16S and the influence of the 0th-order diffracted light having an extremely large light intensity is removed. This is for accurately measuring the light intensity of the + 1st order diffracted light. Further, when the moving speed V of the object to be measured is small and the moving distance | S (Δt) | at the irradiation time interval Δt is small, the diffracted light light point distance | N (Δt) | also becomes small. Therefore, not only the + 1st order diffracted light, but also the + 2nd order, the + 3rd order,
.., etc., and diffracted light spots of higher orders also enter the photocathode 16S. However, the light intensity of the high-order diffracted light spot is +
Since the light intensity of the first-order diffracted light spot is extremely small, even if such a higher-order diffracted light spot is incident on the photocathode 16S, its influence can be ignored.

In the arithmetic and control unit 17 connected to the photomultiplier tube 16 shown in FIG. 1, the output current value C of the photomultiplier tube 16 (that is, the + 1st order diffracted light intensity value I) and the object to be measured. Numerical expressions, tables, and the like representing the relationship with the movement distance | S (Δt) | of 30 are stored. Therefore, the calculation / control device 17 calculates the moving distance | S (Δt) | of the measured object 30 based on the output current value C of the photomultiplier tube 16. The AOD controller 20 is also connected to the arithmetic / control unit 17, and the irradiation time interval value Δt
Information is entered. The calculation / control device 17 also calculates the moving speed V = | S (Δt) | / Δt based on the input information. A speed display device 18 connected to the arithmetic / control device 17 displays the obtained value of the moving speed V of the measured object on its display surface. The arithmetic / control unit 17
Adjusts the irradiation timing of the He-Ne laser light to the object to be measured by the AOD 4 via the AOD controller 20, and drives the first and second FLC-SLMs 7 and 13 via the FLC-SLM controller 19. By doing so, it also has a function of controlling the operation of the entire measuring apparatus 1.

The first FLC-SLM 7 used in the measuring device 1 having the above-mentioned structure will be described in detail below. In the first FLC-SLM 7, as shown in FIG. 3, a ferroelectric liquid crystal layer (hereinafter, referred to as “liquid crystal layer”) 7F.
Are provided between the pair of alignment layers 7E and 7G.
On the side of the alignment layer 7E opposite to the liquid crystal layer 7F, a dielectric mirror 7D and an amorphous silicon layer (hereinafter referred to as "α-S
7C) and a writing-side transparent electrode (hereinafter referred to as “i layer”)
An “electrode” 7B and a glass layer 7A are provided. On the side of the alignment layer 7G opposite to the liquid crystal layer 7F, a readout side transparent electrode (hereinafter referred to as "electrode") 7H.
The glass layer 7I and the antireflection film 7J are provided. The liquid crystal layer 7F is a chiral smectic C (S _c ^* ) liquid crystal. The α-Si layer 7C is a photoconductor layer and functions as an address material. The glass layer 7A defines the write side light incident surface 7S _w , and the antireflection film 7J defines the read side light incident surface 7S _r . The pair of electrodes 7B
And 7H, the FLC-SLM controller 19 drives the write and erase drive voltages V as described later.
_w, is applied V _e and the compensation voltage V _wc, a V _ec pulsed. The compensation voltages V _wc and V _ec are applied to prevent the deterioration of the liquid crystal layer 7F. Further, as shown in FIG. 1, a light emitting diode (LED) 6 is provided so as to illuminate the entire light incident surface 7S _w on the writing side, and is used for erasing an image already recorded on the liquid crystal layer 7F. Used.

Although the configuration of the first FLC-SLM 7 has been described above, the second FLC-SLM 13 also has the same configuration as the first FLC-SLM 7, and the FLC-SLM 7 has the same configuration.
The SLM controller 19 controls the applied voltage between the electrodes 13B and 13H. Further, as shown in FIG. 1, the second FLC-SLM 13 is provided with a light emitting diode (LED) 14 for recording and erasing. FLC-SL
M7 and 13 are extremely fast in writing speed and extremely excellent in real-time measurable property. Since it is a binary recording device, it is suitable for recording speckle patterns and Young's interference fringes. Details of the structure and operation of the FLC-SLM are described in JP-A-2-289827.

The operation of the measuring apparatus 1 having the above structure will be described with reference to FIG. 4A. First, while the light emitting diode 6 irradiates the light incident surface 7S _w of the first FLC-SLM 7 with uniform light, the arithmetic and control unit 17 operates the FLC-SLM.
Via the controller 19, the first FLC-SLM 7
An erasing compensation voltage V _ec and an erasing driving voltage V _e are applied in this order between the electrodes 7B and 7H of the
The image recorded on the FLC-SLM 7 during the previous measurement is erased. The compensation voltage V _ec and the driving voltage V _e have opposite polarities and their absolute values are equal. Arithmetic / control device 1
Next, 7 applies the writing compensating voltage V _wc and the writing driving voltage V _w between the electrodes 7B and 7H in this order for the same time. (Note that the polarity of the write drive voltage V _w is opposite to that of the erase drive voltage V _e . Further, the compensation voltage V _wc and the drive voltage V _w have opposite polarities to each other. The absolute values are the same.) The arithmetic / control device 17 controls the AOD 4 via the AOD controller 20 during the application of the write drive voltage V _w , and the laser light is measured twice with the irradiation time interval Δt at the measured object 30. To irradiate. In this way, the first and second speckle patterns are double recorded on the FLC-SLM 7. As a result, the double-recorded speckle pattern is read by the interference fringe forming unit 1B, and Young's interference fringes are formed. The arithmetic / control unit 17 uses the first FLC-SLM 7
At the same time that the voltage V _wc · V _w is applied to the second F
The LC-SLM 13 has a compensation voltage V _ec for erasing and a driving voltage V
Add _e . At the same time, the light emitting diode 14
By irradiating the LC-SLM 13 with uniform light, the image recorded in the previous measurement is erased. The arithmetic / control unit 17 ends the voltage 1 of the FLC-SLM 13 at the same time as the writing of the speckle pattern to the FLC-SLM 7 is completed.
The write compensation voltage V _wc and the write drive voltage V _w are applied in order between 3B and 13H to generate Young's interference fringes FLC-.
Record on SLM 13. As a result, the diffracted light forming unit 1C reads the Young's interference fringes, and forms diffracted light spots indicating the correlation between the first and second speckle patterns. The calculation / control device 17 calculates the moving distance and the moving speed of the object to be measured from the output current value of the photomultiplier tube 16, and the speed display device 18 displays the moving speed. In addition, when investigating the temporal change state of the speed,
Under the control of the control device 17, the series of operations described above are repeatedly executed at measurement time intervals ΔT.

The photomultiplier tube 16 used in the measuring apparatus 1 of the present invention is a zero-dimensional photodetector that does not detect the amount of light up to its positional state but simply measures its value.
Therefore, the photomultiplier tube 16 can perform the measurement at an extremely high speed and has a fast response speed in the FLC-SL.
Operations following the operations of M7 and M13 can be performed.
Therefore, the measuring apparatus 1 of the present invention including the FLC-SLMs 7 and 13 and the photomultiplier tube 16 is extremely excellent in real-time measurement property. Moreover, such a measuring device 1
Thus, when the speed measurement is repeatedly performed in order to check the state of the time change of the speed of the measured object, each measurement can be performed in an extremely short time, and thus the time change of the speed of the measured object is extremely short. It can be measured at time intervals ΔT. Furthermore, since the photomultiplier tube 16 which is such a zero-dimensional photodetector can perform its measurement with high accuracy, the measurement accuracy of the measuring apparatus 1 can be increased. Further, since the photomultiplier tube 16 has high sensitivity, it can detect even weak signal light. That is, even when the moving distance | S (Δt) | of the object to be measured is large and the + 1st order diffracted light intensity is small, the measurement can be performed. Since the measurement range of the photomultiplier tube 16 is wide in this way, the measurable range of the moving speed v of the measuring apparatus 1, that is, the dynamic range can be increased.

In the above-described embodiment, the object to be measured is irradiated with laser light, a speckle pattern is formed on the reflected light, and the amount of displacement of the object to be measured is measured. However, depending on the type of the object to be measured and the like, a speckle pattern may be formed on the transmitted light to perform the measurement. Further, in the above-described embodiment, the AOD 4 irradiates the measured object 30 with the laser light twice with a predetermined time interval Δt. However, the AOD 4 may not be provided. In this case, as shown in FIG. 4B, the He-Ne laser beam is constantly applied to the measured object 30. FLC-S
The LM controller 19 pulse-writes the write drive voltage V _w with respect to the first FLC-SLM 7 at the first and second times t ₁ and t ₂ (that is, twice with a time interval Δt). Apply. In this way, the speckle patterns 1 and 2 obtained at the times t ₁ and t ₂ are set to FLC-S.
Double record on LM7. The application time of the write drive voltage V _{w at} the irradiation times t ₁ and t ₂ is controlled so that the sum thereof is equal to the application time of the write compensation voltage V _wc applied immediately before. Further, in the above-described embodiment, as shown in FIGS. 4A and 4B, the reading side light incident surface 7S _{r of} the first and second FLC-SLMs 7 and 13,
He-Ne laser light is constantly applied to 13S _r . However, the irradiation may be performed at the timing shown by the dotted line in the figure. That is, the first FLC-SL
FLC-SLM is provided on the light-incident surface 7S _r on the reading side of M7.
After the application of the write drive voltage V _w to 7 is finished, He—Ne laser light is irradiated for a certain period of time to form Young's interference fringes. At the same time, the second FLC-SLM
The voltages V _wc and V _w are applied to 13 to record the formed Young's interference fringes. Similarly, the second FLC-SL
FLC-S is provided on the light-incident surface 13S _r on the reading side of M13.
After the application of the write drive voltage V _w to the LM 13 is finished, the He—Ne laser light is irradiated for a certain period of time to form a diffracted light spot. In order to selectively irradiate the He-Ne laser light to the side light incident surfaces 7S _r and 13S _r in this way, for example, as shown by a dotted line in FIG. The reading optical systems 10 and 11 may be provided with optical shutters 21 and 22, respectively.

The inventors have found that the output current value C of the photomultiplier tube 16 in the measuring apparatus 1 of the present invention (that is, the + 1st order diffracted light intensity I) and the moving distance | S (Δt) of the object to be measured.
The following experiment was conducted in order to investigate the relationship with | (moving speed V).

In this experiment, as shown in FIG.
Without using AOD4, the ground glass plate as the measured object 30 was continuously irradiated with the laser light from the He-Ne laser device. In addition, the spot diameter of the laser beam is set to the aperture 1
00, the diameter was adjusted to 17 [mm]. The ground glass plate, which is the object to be measured 30, was conveyed and moved by the moving stage, which is the conveying device 31, along the conveying path extending in the arrow V direction. More specifically, this moving stage 31
Use the C servo motor belt to move 2 in the direction of arrow V.
It was moved by 50 [mm]. In this experiment, a speckle pattern was formed on the He—Ne laser light that passed through the ground glass plate that was the object to be measured 30, and measurement was performed using this. Further, the imaging lens 5 was not used, and the distance from the moving stage to the FLC-SLM 7 was set to 170 [mm]. As the first and second Fourier transform lenses 12 and 15, focal lengths of 150 [mm] and 2000, respectively.
A [mm] Fourier transform lens was used. Further, as the reading light for reading the Young's interference fringes recorded in the second FLC-SLM 13, not the He-Ne laser light but the argon laser (wavelength 515 [nm]) light was used. The storage oscilloscope 101 was connected to the photomultiplier tube 16 and the output current value of the photomultiplier tube 16 was observed. The arithmetic / control device 17 was made to perform only the control operation of the measuring device 1 and not the arithmetic operation. Therefore, the speed display device 18 was not used either.

In this experiment, the arithmetic and control unit 17
However, the entire measuring apparatus 1 was operated at the operation timing as shown in FIG. That is, as in the case of FIG. 4B, H
The e-Ne laser light was continuously applied to the ground glass plate as the object to be measured. Erase voltage V of the first FLC-SLM 7
The application time of each of _ec and V _e is 1000 [μs], the application time of the write compensation voltage V _wc is 300 [μs], and the application time of the write drive voltage V _w is 150 [μ].
s]. The write drive voltage V _{w is set} to the time interval Δ
After t = 1000 [μs], twice FLC-SLM
The voltage was applied to No. 7. On the other hand, the second FLC-SLM
13 erase voltages V _ec and V _e are applied for 10 times each.
00 [μs] and the application time of the write voltages V _wc and V _w were set to 500 [μs], respectively. In this experiment, F
After writing the speckle pattern by applying the write voltages V _wc and V _w to the LC-SLM 7, the He-Ne laser light is irradiated to the reading side surface 7S _r of the FLC-SLM 7 to form Young's interference fringes. It was At the same time, FLC-S
Writing voltages V _wc and V _w were applied to the LM 13 to record Young's interference fringes. After that, the argon laser light is FL.
The reading side surface 13S _r of the C-SLM 13 was irradiated to form a diffracted light spot. The irradiation time of the argon laser light was 1950 [μs]. The measurement performed at the above timing was repeatedly performed at the measurement time interval ΔT = 5000 [μs].

Ground glass plate (that is, moving stage)
7A, as shown in FIG. 7A, the velocity V = 0 [mm / s] is accelerated at an acceleration a = 1960 [mm / s ² ] and the velocity becomes V = 500 [mm / s]. Then, the speed was decelerated at an acceleration a = -1960 [mm / s ² ] until the speed V = 0 [mm / s]. As a result,
The output current value of the photomultiplier tube 16 showed a temporal change state as shown in FIG. 7B. As is clear from FIG. 7B, the moving speed of the measured object is fast, and the irradiation time interval Δt (= 10
00 [μs]) moving distance of the measured object | S
It can be seen that the larger the (Δt) |, the smaller the output current value of the photomultiplier tube 16. If the moving speed of the object to be measured increases at constant acceleration, the output current value monotonously decreases, if the moving speed becomes constant, the output current value also becomes constant, and if the moving speed decreases at constant acceleration, the output current value decreases. It can also be seen that it increases monotonically. Therefore, by observing the temporal change state of the output current value of the photomultiplier tube 16, it can be understood that the temporal change state of the moving speed of the measured object 30 can be roughly determined. Further, as is clear by comparing FIGS. 7A and 7B, the output current value of the photomultiplier tube 16 is relative to the moving speed (moving distance | S (Δt) |) of the measured object 30.
It can be seen that they are obtained in a one-to-one correspondence. Therefore, if the output current value of the photomultiplier tube obtained for various values of speed is measured in advance and a mathematical formula or table showing the relationship between the output current value and the moving speed is obtained, the moving speed is unknown. It can be seen that the moving speed of any object to be measured can be obtained by measuring the output current value of the photomultiplier tube. In FIG. 7B, the photomultiplier tube 1
It is the storage oscilloscope 10 that the output current value of 6 has a discontinuous and curved characteristic curve.
The sampling frequency of 1 is the frequency of the signal light waveform (+1
This is because the generation frequency of the second-order diffracted light: in this experiment, it is coarser than 200 [kHz] because the + 1st-order diffracted light is formed every 5 [ms].

The present inventors further conducted similar experiments by changing the moving speed of the ground glass plate variously. Figure 8
As shown in A, the ground glass plate is moved at a speed V = 0 [mm /
[s] and acceleration a = 1470 [mm / s ² ]
When the velocity is V = 500 [mm / s], a constant velocity is set, and then the velocity is decelerated by acceleration a = −1470 [mm / s ² ] until the velocity V = 0 [mm / s]. The output current value of the photomultiplier tube 16 showed a temporal change state as shown in FIG. 8B. Further, as shown in FIG. 9A, the ground glass plate is accelerated from the speed V = 0 [mm / s] to the acceleration a =
Accelerate at 1470 [mm / s ² ] and speed V = 250 [m
m / s], the speed is made constant, and then the acceleration a
= -1470 [mm / s ² ] and speed V = 0 [mm / s]
When it was decelerated until, the output current value of the photomultiplier tube 16 showed a state of time change as shown in FIG. 9B. Further, as shown in FIG. 10A, the ground glass plate is
From speed V = 0 [mm / s] to acceleration a = 490 [mm /
s ² ] and the velocity becomes V = 250 [mm / s], then the velocity becomes constant, and then the acceleration a = −490 [mm]
/ S ² ], when the speed is reduced to V = 0 [mm / s], the output current value of the photomultiplier tube 16 is as shown in FIG.
The time-varying state shown in B is shown.

The present invention is not limited to the optical movement velocity measuring apparatus of the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

In the above-described embodiment, the arithmetic / control unit 17 stores the mathematical formula and the like showing the relationship between the output current value of the photomultiplier tube 16 and the moving speed value of the object to be measured. The calculation / control device 17 calculates the moving speed value of the object to be measured from the photomultiplier tube output current value based on the mathematical formula and the like, and the display device 18 displays the calculation result. However, the arithmetic / control device 17 does not need to store the mathematical formulas and the like, and may not perform the arithmetic operation. That is, the arithmetic / control unit 17 may be made to perform only the control operation. In this case, for example, as shown in FIG.
If a device (for example, an oscilloscope) that displays the state of the output current value (for example, a temporal change state) is connected to the device, it is possible to roughly indicate the temporal change state of the moving speed of the measured object. good.

In the above embodiment, the photocathode 16S of the photomultiplier tube 16 is arranged at a position deviated from the center point 16O to eliminate the influence of the 0th order diffracted light. However, instead, as shown in FIGS. 11A and 11B, the photomultiplier tube 16 has its photocathode 16S at the center point 16O.
May be arranged at a position including. In this case, the influence of the 0th-order diffracted light may be removed by covering the central point 16O and its vicinity in the photocathode 16S with a shielding film.

In the above embodiment, the light intensity of the + 1st order diffracted light was measured. However, the light intensity of the −1st order diffracted light may be measured. Alternatively, both the + 1st-order diffracted light and the -1st-order diffracted light may be incident on the photocathode 16S, and the sum of both light intensities may be measured. Further, in this example, the photomultiplier tube 16 was used to measure the light intensity. This is because the light intensity of the + 1st-order diffracted light is not very high, and therefore such a photomultiplier tube is most preferable for measuring this. However, instead of the photomultiplier tube, another 0-dimensional light intensity detection device can be used. This is because the 0-dimensional light intensity detection device is generally highly sensitive and can detect weak signal light. By adopting such a 0-dimensional light intensity detection device, even if the moving distance | S (Δt) | of the object to be measured is large and the + 1st order diffracted light intensity is small, the measurement can be performed. Therefore, the dynamic range of the measuring device 1 can be increased.

In the above-mentioned embodiment, the photomultiplier tube 16 which is a zero-dimensional light intensity detecting means is provided.
The light intensity of the diffracted light spot is measured. However,
Instead of the photomultiplier tube 16, other 0-dimensional photodetection means may be provided. That is, when the characteristics other than the light intensity of the diffracted light spot have a fixed relationship with the moving distance of the object to be measured, a zero-dimensional light detecting means for detecting such characteristics is provided. May be. The 0-dimensional light detecting means does not detect the characteristic up to its positional state, but simply measures the characteristic itself. Then, information that does not include position information is output for the characteristic. Therefore, the 0-dimensional light detecting means can detect the characteristic at an extremely high speed. Therefore, the optical displacement measuring device provided with such a zero-dimensional light detecting means is excellent in real-time measurement property. Moreover, such 0-dimensional light detection means is generally highly sensitive. Therefore, the characteristic of the diffracted light spot is
Even if the movement distance of the object to be measured | S (Δt) | changes, the measurement can be performed. Therefore, if such a zero-dimensional photodetector is adopted, the measurable range of moving distance (speed) of the measuring apparatus, that is, the dynamic range can be increased.

In the above-described embodiment, the measuring device is fixed and the object to be measured is moving, but conversely, the measuring device may be moving and the object to be measured may be fixed. In this case, the absolute movement amount and speed of the speed measuring device are obtained by measuring the relative movement amount and speed of the fixed object to be measured with respect to the measuring device. For example, by mounting the measuring device on a moving object such as an automobile, the moving amount and speed of this moving object can be obtained. Although the above-described embodiments relate to the optical movement velocity measuring device, the present invention is not limited to this. It is also possible to measure the strain state of the object to be measured and examine the stress distribution. It suffices if the displacement state of the object, such as the amount of movement or the amount of distortion of the object, can be measured. Further, the object to be measured may be irradiated with incoherent light instead of coherent light such as laser light. In this case, instead of the speckle pattern, the image of the measured object is displayed on the first FLC-S.
Record in LM. If the images of the object to be measured at the first and second irradiation times are double-recorded on the first FLC-SLM and the double-recorded image is read out and Fourier-transformed, Young's interference fringes can be obtained. Record this on the second FLC-SLM,
This is because the diffracted light can be obtained by reading out the recorded Young's interference fringes and performing Fourier transform.

The means for double recording the speckle pattern is not limited to the ferroelectric liquid crystal spatial light modulator, and the light receiving pattern of the measured object at the first measurement time can be accumulated at least until the second measurement time. Any spatial light modulator capable of double recording the image of the object to be measured may be used. Further, when the light intensity of the pattern formed in the transmitted light or the reflected light from the object to be measured is small, a known image intensifier is provided between the imaging lens 5 and the first FLC-SLM 7. After increasing the light intensity of the pattern, the light may be incident on the writing incident surface 7S _w of the first FLC-SLM 7.

[0033]

As is clear from the above description,
According to the optical displacement measuring device of the present invention, the light irradiation means,
The object to be measured which is relatively displaced with respect to the optical displacement measuring device is irradiated with light. With the irradiation light, images of the object to be measured at the two measurement times are obtained, respectively. The first recording means double-records the images at the two measurement times. The first coherent light projecting unit irradiates the first recording unit with coherent light to read the double-recorded image recorded in the first recording unit. The read double recorded image is subjected to Fourier transform by the first Fourier transform means to form a first Fourier transform image. The second recording means records the first Fourier transform image. The second coherent light projecting unit irradiates the second recording unit with coherent light to read out the first Fourier transform image recorded in the second recording unit. The second Fourier transform means Fourier transforms the read first Fourier transform image to form a second Fourier transform image. The 0-dimensional light detecting means detects the state of the second Fourier transform image. The 0-dimensional light detecting means does not detect the state of the second Fourier transform image up to its positional distribution, but simply detects the state itself,
As the detection result, information indicating the state is output. Here, the state of the second Fourier transform image corresponds to the relative displacement state of the measured object with respect to the optical displacement measuring device between the two measurement times. Therefore, the 0
The dimensional light detecting means will output information indicating the relative displacement state. As described above, according to the present invention, since the state of the second Fourier transform image is detected by the 0-dimensional light detecting means, the detection can be performed in a short time without complicated scanning or correlation calculation. .. Therefore, the optical displacement measuring device provided with the 0-dimensional light detecting means is extremely excellent in real-time measuring property.

[Brief description of drawings]

FIG. 1 is a plan view of an optical system showing an optical moving speed measuring device according to an embodiment of the present invention.

FIG. 2A is a front explanatory view illustrating an arrangement state when the photomultiplier tube 16 of FIG. 1 is viewed from the lens 15 side.

2B is an explanatory plan view for explaining the positional relationship between the photomultiplier tube 16 and the lens 15 in FIG. 1. FIG.

3 is an enlarged cross-sectional view of the ferroelectric liquid crystal spatial light modulator of FIG.

FIG. 4A is an operation timing chart of a measurement operation executed by the optical moving speed measurement apparatus of FIG.

FIG. 4B is an operation timing chart of another measurement operation executed by the optical moving speed measurement apparatus of FIG.

FIG. 5 is a plan view of an optical system showing a main part of the measuring apparatus 1 of the present invention used in an experiment.

FIG. 6 is an operation timing chart of the measurement operation of the measuring apparatus 1 of the present invention adopted in the experiment.

FIG. 7A is a velocity diagram showing a temporal change state of the moving velocity of the measured object in the experiment.

7B is a measurement result diagram of the oscilloscope showing a temporal change state of the output current value of the photomultiplier tube when the measured object moves at the moving speed shown in FIG. 7A.

FIG. 8A is a velocity diagram showing another temporal change state of the moving velocity of the measured object in the experiment.

FIG. 8B is a measurement result diagram of the oscilloscope showing a temporal change state of the output current value of the photomultiplier tube when the measured object moves at the moving speed shown in FIG. 8A.

FIG. 9A is a velocity diagram showing another temporal change state of the moving velocity of the measured object in the experiment.

9B is a measurement result diagram of the oscilloscope showing a temporal change state of the output current value of the photomultiplier tube when the measured object moves at the moving speed shown in FIG. 9A.

FIG. 10A is a velocity diagram showing another temporal change state of the moving velocity of the measured object in the experiment.

10B is a measurement result diagram of the oscilloscope showing a temporal change state of the output current value of the photomultiplier tube when the measured object moves at the moving speed shown in FIG. 10A.

FIG. 11A is a front explanatory view illustrating another arrangement state of the photomultiplier tube 16.

11B is an explanatory plan view illustrating the positional relationship between the photomultiplier tube 16 and the lens 15 in the arrangement state of FIG. 11A.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical movement velocity measuring device 2 He-Ne laser device 7 Ferroelectric liquid crystal spatial light modulation element 12 Fourier transform lens 13 Ferroelectric liquid crystal spatial light modulation element 15 Fourier transform lens 16 Photomultiplier tube

Claims (3)

[Claims] 1. A light irradiating means for irradiating light to the object to be measured to form an image of the object to be measured at the second measurement time, and an image of the object to be measured at the second measurement time. First recording means for double recording, first coherent light projecting means for irradiating the first recording means with coherent light to read out the double recorded image, and the read dual First Fourier transforming means for Fourier transforming the recorded image to form a first Fourier transform image, second recording means for recording the first Fourier transform image, and the second recording Second coherent light projecting means for irradiating the means with coherent light to read the first Fourier transform image, and second Fourier transform image by Fourier transforming the read first Fourier transform image A second Fourier transform means for forming An optical displacement measuring device comprising: a zero-dimensional light detecting means for detecting a state of a second Fourier transform image. 2. The light irradiating means irradiates the object to be measured with coherent light to form a speckle pattern at the second measurement time, and the speckle pattern is duplicated on the first recording means. 2. The optical displacement measuring device according to claim 1, wherein the optical displacement is recorded. 3. The optical device according to claim 1, wherein the 0-dimensional light detecting means is a 0-dimensional light intensity detecting means for detecting the light intensity of the second Fourier transform image. Displacement measuring device.