JPH06241725A - Optical displacement quantity measuring device - Google Patents

Abstract

PURPOSE:To provide an optical displacement quantity measuring device capable of measuring a displacement quantity of a measuring object in a short time and excellent in real time measurement. CONSTITUTION:An object 30 for measurement is irradiated with laser beam twice at a certain time interval, and the obtained two speckle patterns are recorded in superposition two speckle patterns are recorded in superposition are read out. And the Young's interference fringe obtained by Fourier transform with a Fourier transform lens 12 is recorded in FLCSLM13. The Young's interference fringe is read out and Fourier transformed with a Fourier transform lens, so that a diffraction light point is formed according to the correlation between the superposition recorded speckle patterns. A photodiode 116 measures light intensity of the O-order diffraction light, and a DSS16 measures the position of the center of gravity in the +1st-order diffraction light. A calculation/ control device 17 feedback controls the time interval on the basis of the O-order light intensity. And thus, with the +1st-order diffraction light incident on the PSD15, the move speed of an object for measurement is calculated on the basis of the detection result of the PSD16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement amount measuring device for optically measuring the displacement amount of an object. Here, the amount of displacement of the object refers to the amount of movement, the amount of deformation, etc. of the object, and includes the movement speed, the deformation 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 irradiated light on a rough surface of the object is used. Third
Proceedings of the 9th Joint Lecture on Applied Physics 28a-A-
3 proposes an optical displacement measuring device using the speckle method as shown in FIG. This optical displacement measuring device has a high-speed operation, high resolution, a memory function, and
A ferroelectric liquid crystal spatial light modulator having binary recording characteristics (hereinafter referred to as "FLC-SLM") and a barycentric position of incident light can be detected at high speed and high resolution regardless of the spot shape. Semiconductor position detection element (Position Sensitive Light Detector:
"PSD") is adopted. In this optical displacement amount measuring device, the speckle pattern generated from the rough object 330 is double-written on the first FLC-SLM 307, and then Fourier-transformed by the lens 312 to perform the second FLC.
-Record on SLM 313. FLC-SLM3
The pattern recorded on 13 is again Fourier-transformed by the lens 315, and autocorrelation signal light that is first-order diffracted light is formed on the PSD 316. The arithmetic and control unit 317 is
The signal from SD316 is fed back to the double write system to control the double write time interval. For example, when the velocity of the measured object increases, the position of the autocorrelation signal light is separated from the 0th order light, and the position output from the PSD 316 changes. Therefore, the double write interval is controlled so that the position of the autocorrelation signal light is moved to the 0th-order light side and the central portion where the PSD position detection error is small. In this way, after controlling the position of the autocorrelation signal light to be substantially at the center of the PSD 316, the velocity of the measured object is obtained based on the detection result of the PSD 316. According to such an optical displacement measuring device,
A wide range of speeds can be measured with high accuracy.

[0003]

In such a conventional optical displacement amount measuring device, the PSD is irradiated with the first-order diffracted light and P
Feedback control of the double write interval is performed based on the SD detection result. Then, after irradiating the substantially central region of the PSD with the first-order diffracted light, the moving speed of the measured object is obtained based on the detection result of the PSD. Therefore, it is necessary to irradiate the PSD with the first-order diffracted light. Here, when the approximate moving speed of the object to be measured is known in advance, the PSD can be immediately irradiated with the first-order diffracted light, so that the feedback control can be immediately started. Even when the moving speed of the measured object is unknown, the approximate displacement speed can be found by sweeping the double writing interval and changing the moving amount of the measured object in various ways. Therefore, the feedback control can be started relatively quickly.
However, when the measured object undergoes a rapid speed change and the first-order diffracted light deviates from the PSD entrance window, the measurement can be performed in a shorter time if the approximate moving speed can be determined more easily. be able to. The present invention has been made in view of the above points, and an object thereof is to provide an optical displacement amount measuring device that can measure a displacement amount of an object to be measured in a shorter time and is extremely excellent in terms of real-time measurable property. To do.

[0004]

In order to achieve the above object, an optical displacement measuring device of the present invention irradiates a measuring object with light to form an image of the measuring object at two measurement times. And a first recording means for double-recording the image of the object to be measured at the second measurement time, and a coherent light for irradiating the first recording means. First coherent light projecting means for reading a recorded image, first Fourier transform means for Fourier transforming the read double recorded image to form a first Fourier transform image, and Second recording means for recording one Fourier transform image, and second coherent light projecting means for irradiating the second recording means with coherent light to read out the first Fourier transform image And the read first Fourier transform image In other words, the second Fourier transform means for forming the second Fourier transform image having the 0th-order diffracted light point image and the light intensity of the 0th-order diffracted light point image of the second Fourier transform image are A light intensity detecting unit for detecting, and a displacement for obtaining a relative displacement amount of the object to be measured with respect to the first recording unit between the two measurement times based on a detection result of the light intensity detecting unit. Equipped with quantity specifying means. Here, the displacement amount specifying means calculates a detection result of the light intensity detecting means to obtain a relative displacement amount of the measured object with respect to the first recording means between the two measurement times. It is preferably composed of a calculation means. The optical displacement measuring device of the present invention may further include adjusting means for adjusting the second Fourier transform image. In this case, the light intensity detecting means detects the light intensity of the 0th-order diffracted light point image of the adjusted second Fourier transform image. Here, the displacement amount identifying means includes a control means for controlling the adjustment state of the adjusting means based on the detection result of the light intensity detecting means, and a primary order of the adjusted second Fourier transform image. Light center of gravity position detecting means for detecting the position of the center of gravity of the diffracted light point image, and the object to be measured between the two measurement times based on the detection result of the light center of gravity position detecting means and the adjustment state of the adjusting means. And a displacement amount calculation unit for calculating a relative displacement amount between the first recording unit and the first recording unit.
Here, it is preferable that the optical center-of-gravity position detecting means is composed of a semiconductor position detecting element. The adjusting means is preferably means for adjusting the time interval between the second measurement times. The adjusting means may be position adjusting means for relatively adjusting the position of the image of the measurement target at the second measurement time. The position adjusting means is, for example, a deflecting means for deflecting an image of the object to be measured formed at the second measuring time, and a deflecting means for relatively adjusting the deflection amount of the image at the second measuring time by the deflecting means. It is preferably composed of an amount adjusting means. The first and second recording means are preferably ferroelectric liquid crystal spatial light modulators. It is preferable that the light irradiation means irradiates the object to be measured with coherent light to form a speckle pattern.

[0005]

In the optical displacement measuring device of the present invention having the above structure, 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 of 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 of the first recording unit. The second Fourier transform means Fourier-transforms the read first Fourier transform image to form a second Fourier transform image having a 0th-order diffracted light point image. The light intensity detecting means detects the light intensity of the 0th-order diffracted light point image of the second Fourier transform image. The displacement amount specifying means, based on the detection result of the light intensity detecting means, the first recording means (that is, the optical displacement amount measuring device) of the measured object between the two measurement times.
Calculate the relative displacement with respect to.

Here, the light intensity of the 0th-order diffracted light point image of the second Fourier transform image is the correlation of the image of the object to be measured at the second measurement time, in other words, at the second measurement time. It corresponds to the relative displacement amount of the object to be measured with respect to the first recording means (that is, the optical displacement amount measuring device). Therefore, when the displacement amount specifying means is the calculating means,
The detection result of the light intensity detecting means is calculated to obtain the relative displacement amount of the object to be measured with respect to the first recording means (that is, the optical displacement amount measuring device) between the two measurement times.

The barycentric position of the first-order diffracted light point image included in the second Fourier transform image is also the correlation of the image of the object to be measured at the second measurement time, in other words, the object to be measured at the second measurement time. Of the first recording means (that is, the optical displacement amount measuring device). Therefore, when the optical displacement amount measuring device of the present invention is provided with the adjusting means for adjusting the second Fourier transform image, the light intensity detecting means is provided with the adjusted second Fourier transform image. The light intensity of the 0th-order diffracted light point image is detected. The control means of the displacement amount specifying means controls the adjustment state of the adjustment means based on the detection result of the light intensity detection means. The optical center-of-gravity position detecting means of the displacement amount specifying means detects the position of the center of gravity of the first-order diffracted light point image of the adjusted second Fourier transform image. The displacement amount calculating means of the displacement amount specifying means is configured to detect the object to be measured and the first recording means between the two measurement times based on the detection result of the optical center-of-gravity position detecting means and the adjustment state of the adjusting means. A relative displacement amount (that is, an optical displacement amount measuring device) is calculated. Here, when the adjusting means comprises means for adjusting the time interval between the second measurement times, the adjusting means adjusts the time interval between the second measurement times to adjust the second Fourier transform image. Adjust. Further, when the adjusting means comprises a position adjusting means for relatively adjusting the position of the image of the measured object at the second measurement time, the second position is adjusted by the relative position adjustment of the image of the measured object. Adjust the Fourier transform image. In particular, when the position adjusting means comprises the deflecting means and the deflection amount adjusting means, the deflecting means deflects the image obtained at the second measurement time, and the deflection amount adjusting means causes the second image to be deflected. The second Fourier transform image is adjusted by relatively adjusting the deflection angle of the second image to adjust the relative positional relationship between the two images.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment 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 an optical system plan view showing a schematic configuration of an optical moving speed measuring apparatus (hereinafter referred to as “measuring apparatus”) 1 according to this embodiment. The measuring apparatus 1 irradiates the measured object 30 twice with laser light from the laser diode 3 at a predetermined time interval, and a speckle pattern forming unit 1A for forming two speckle patterns. A first ferroelectric liquid crystal spatial light modulator (hereinafter, referred to as "first FL") for double recording the formed two speckle patterns.
C-SLM ”) 7 ;; phase-modulates the laser light from the He-Ne laser device 2 by the first FLC-SLM 7 in which the speckle pattern is double recorded, and further spatially performs Fourier transform. 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- 13);
A plurality of diffracted light light spots are formed by phase-modulating the laser light from the He-Ne laser device 2 by the second FLC-SLM 13 in which Young's interference fringes are recorded, and further spatially performing Fourier transform. A diffracted light forming portion 1C for
Of the formed diffracted light spots, the light intensity of the 0th-order diffracted light is measured, the value at the predetermined time interval is feedback-controlled, and then the center of gravity of the + 1st-order diffracted light is measured to measure the object 30 to be measured.
And a measuring / controlling unit 1D for calculating the moving amount and thus the moving speed in the predetermined time interval. That is, in the measuring apparatus 1, the FLC-SLM 7 and the interference fringe formation units 1B and 1F are used for the two speckle patterns having the same pattern obtained by the speckle pattern formation unit 1A.
The LC-SLM 13 and the diffracted light forming unit 1C perform the same process as the joint conversion correlation process, and the 0th-order diffracted light point image and the autocorrelation signal light of the speckle pattern (±
A first-order diffracted light point image) is formed. The measurement / control unit 1D measures the light intensity of the 0th-order diffracted light point image, and feedback-controls the predetermined time interval based on the measurement result. After such feedback control, the measurement / control unit 1D also measures the barycentric position of the + 1st-order diffracted light point image, and calculates the distance between the two speckle patterns based on the measurement result. The moving speed of the measuring object is calculated.

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

A rectangular parallelepiped object 30 to be measured 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. In the speckle pattern forming unit 1A, the laser diode (LD) 3 irradiates the laser beam twice in a specific one direction with a predetermined time interval under the control of the LD controller 4. 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 ”, respectively, and the predetermined time interval is “double writing interval Δt (= t ₂ − t ₁ ) ”, and the moving distance of the measured object 30 in the 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, The first and second speckle patterns "). The imaging lens 5 images 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 formed on the light incident surface 7S _w have the same speckle distribution as a whole in one shift direction X ′ by 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. Also, the shift distance | M (Δt) | has a relationship with the measured object moving distance | S (Δt) | expressed by the following formula 1 determined by the imaging magnification m of the imaging lens 5. Have.

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

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

On the other hand, in the interference fringe forming section 1B, He-Ne
The laser device 2 continuously emits a linearly polarized parallel laser beam. The He-Ne laser beam is converted into a parallel laser beam having a desired beam diameter by the beam diameter conversion optical system 8 including the first collimator lens 8A, the spatial filter 8B, and the second collimator lens 8C. 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 reading side light incident surface 7 of the first FLC-SLM 7.
Guided by S _r . 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 corresponds to the positions (the shift distance | M (Δt) | and the shift direction) of the first and second speckle patterns in the FLC-SLM 7. After undergoing the phase modulation described above, the light is emitted from the light incident surface 7S _r . In this way, the reading of the double recorded speckle pattern is performed. The FLC-S
The laser beam emitted from the LM7 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. . Direction in which the stripes of the Young's interference fringes are arranged (direction perpendicular to the extending direction of each stripe)
Is parallel to the shift direction X'of the speckle distribution recorded on the first FLC-SLM 7, and therefore is parallel to the direction along the plane of the drawing. The fringe spacing of the Young's interference fringes (hereinafter referred to as “| K (Δt) |”) and the reciprocal of the shift distance | M (Δt) | There is a proportional relationship determined by the wavelength λ of the reading light (He-Ne laser light) applied to the reading side surface 7S _r of the SLM 7 and the focal length f ₁₂ of the Fourier transform lens 12.

| K (Δt) | = λf ₁₂ / | M (Δt) | Therefore, the spatial frequency U (Δt) of the Young's interference fringes
Is determined by the following mathematical formula.

## EQU3 ## U (Δt) = 1 / | K (Δt) | = | M (Δt) | / λf ₁₂

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 comprising 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 zero-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 Young's interference fringes are arranged, the direction (X direction) along the paper surface of FIG.
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 lights are arranged at positions symmetrical with respect to the center point 15O. Here, the ± first-order diffracted light is the autocorrelation of the speckle pattern obtained as a result of performing the same processing as the joint transform correlation processing on the first and second speckle patterns having the same pattern. It is a signal light. The distances between the adjacent light points of the diffracted light spots of the 0th order, the ± 1st order, ... (Hereinafter, referred to as “| N (Δt) |”) are equal to each other, and their values are given by As shown in FIG. 4, the reciprocal of the value of the fringe spacing | K (Δt) | of the Young's interference fringes and the reading light (He-Ne laser light) irradiated on the reading side surface 13S _r of the FLC-SLM 13 There is a constant proportional relationship determined by the wavelength λ and the focal length f ₁₅ of the Fourier transform lens 15.

## EQU4 ## | N (Δt) | = λf ₁₅ / | K (Δt) |

Therefore, from the above formulas 1 to 4, the distance between diffracted light spots | N (Δt) | and the shift distance | M (Δt)
| Has the relationship of Equation 5 below.

[Formula 5] | N (Δt) | = λf ₁₅ / | K (Δt) | = λf ₁₅ · U (Δt) = | M (Δt) | · (λf ₁₅ / λf ₁₂ ) = | M (△ t) ｜ ・ (f ₁₅ / f ₁₂ )

By the way, the present inventor has studied and studied the relationship between the diffracted light spot and the fringe spacing | K (Δt) | of the Young's interference fringes (that is, the spatial frequency U (Δt)). As a result, the distance between light spots | N (Δt) |
Not only the light intensity of 0th-order diffracted light (hereinafter referred to as "I")
Also experimentally found that they have a certain relationship with Young's interference fringe spacing | K (Δt) |. That is, the light intensity I of the 0th-order diffracted light is the spatial frequency U of Young's interference fringes.
(Δt) and the one-to-one relationship as shown in FIG.
It was experimentally discovered that there is a monotonically increasing relationship in which I increases as U (Δt) increases. According to this characteristic, as shown in FIG. 2, it can be seen that I and the moving distance | S (Δt) | of the measured object also have a fixed relationship, that is, a one-to-one correspondence relationship. Specifically, I
Has a monotonically increasing relationship that increases as | S (Δt) | increases. According to Equations 1 to 3, | S (Δt) | and U
This is because (Δt) has a proportional relationship. Furthermore, it can be seen that I and the distance | N (Δt) | between the diffracted light spots also have a one-to-one correspondence relationship (monotonically increasing relationship). This is because according to Equation 5, | N (Δt) | and U (Δt) are also in a proportional relationship. In addition, the present inventor further
The light intensity of the second-order diffracted light (hereinafter referred to as “first-order diffracted light”)
As shown in FIG. 2, there is a one-to-one correspondence relationship between | K (Δt) |, U (Δt), and | S (Δt) |
It was discovered experimentally that there is a monotonically decreasing relationship.

Therefore, in the measurement / control unit 1D of the present invention,
The semiconductor position detecting element (PSD) 16 for one-dimensional position measurement and the photodiode 116 are arranged so that their incident windows 16S and 116S are located on the image side focal plane 15F. More specifically, as shown in FIGS. 3A and 3B, the circular entrance window 116S of the photodiode 116 is used.
Is arranged at the center point 15O of the image-side focal plane 15F so that the 0th-order diffracted light spot can enter it. The photodiode 116 outputs a signal corresponding to the light intensity value I of the incident 0th-order diffracted light spot. Incidentally, the entrance window 116S
Must be larger than the spot size of the 0th-order diffracted light spot so that the entire area of the 0th-order diffracted light spot is incident on the entrance window 116S. The area of the entrance window 116S also needs to be limited to a size such that the + 1st-order and -1st-order diffracted light spots do not enter the entrance window 116S. These +
This is because it is necessary to remove the influence of the 1st-order and -1st-order diffracted light and accurately measure the light intensity of the 0th-order diffracted light. on the other hand,
The PSD 16 is arranged so that the one-dimensional direction that can be detected extends parallel to the X direction. PSD16 also
The origin 16S _x0 of the entrance window 16S is arranged so as to be separated from the center point 15O by a predetermined distance d in the X direction. The length of the entrance window 16S in the X direction is L. P
When the + 1st-order diffracted light spot is incident on the incident window 16S, the SD 16 outputs a signal indicating the distance X from the origin 16S _{x0 of the} center of gravity position (that is, the peak position). Therefore, the detection result X of the PSD 116 and the diffracted light light spot distance | N (Δt) | have the relationship of the following expression 6.

[Expression 6] | N (Δt) | = X + d Therefore, the following Expression 7 is obtained from the above Expressions 1 to 6.

Equation 7] | S (△ t) | = The (1 / m) · (f 12 / f 15) · (X + d), the moving velocity V of the object to be measured 30 are obtained by the following equation 8.

[Formula 8] V = | S (Δt) | / Δt

As shown in FIG. 1, the measurement / control unit 1D is provided with an arithmetic / control device 17 connected to the PSD 16 and the photodiode 116. A signal indicating the 0th-order diffracted light intensity I is input from the photodiode 116 to the calculation / control device 17, and the PSD 16 outputs +1.
A signal indicating the barycentric position (peak position) of the next-order diffracted light is input. The arithmetic and control unit 17 stores the above-mentioned formulas 7 and 8, and the formulas 7 and 8 are stored based on the signal from the PSD.
Is calculated. The arithmetic and control unit 17 is also connected to the laser diode 3 via the LD controller 4,
The laser diode 3 controls the irradiation of the laser light to the object 30 to be measured. Here, the arithmetic / control device 17 is L
The value of the double write interval Δt is also adjusted via the D controller 4. The arithmetic and control unit 17 is also FLC-SL.
First and second FLC-S via M controller 19
It is connected to the LMs 7 and 13 and drives and controls them. In other words, the arithmetic / control device 17 executes a diffracted light forming operation F described later via the LD controller 4 and the FLC-SLM controller 19 to form a diffracted light spot on the image side focal plane 15F of the lens 15. Form an image. More specifically, the arithmetic / control device 17 adjusts the double write interval Δt via the LD controller 4 based on the signal from the photodiode 116, and the diffracted light described later via the controllers 4 and 19. The forming operation F is executed. The diffracted light forming operation F is repeatedly executed until it is determined by the signal from the photodiode 116 that the + 1st order diffracted light spot has entered the entrance window 16S of the PSD 16. +
When it is determined that the first-order diffracted light spot has entered the entrance window 16S of the PSD 16, the arithmetic / control unit 17 uses the above-described expressions 7 and 8 based on the X value indicated by the signal output by the PSD 16 at that time. Is calculated to obtain the moving distance | S (Δt) | and the moving speed V of the measured object. A speed display device 18 is connected to the arithmetic / control device 17. The speed display device 18 determines the moving speed V of the measured object obtained.
The value of is displayed on the display surface.

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. 4, 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”)
7B and the 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.
And a glass layer 7I and an antireflection film 7J. 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 7
As will be described later, the FLC-SLM controller 19 receives the drive voltage V _w for writing and erasing between H and H.
V _e and the compensation voltages V _wc and V _ec are applied in pulses. The compensation voltages V _wc and V _ec are applied to prevent deterioration of the liquid crystal layer 7F. Also, as shown in FIG.
The light emitting diode (LED) 6 has a writing side light incident surface 7S.
It is provided so as to irradiate the entire surface of _w , and the liquid crystal layer 7F
It is used to erase the image already recorded on the.

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 voltage applied 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 M13 have extremely fast writing speed and are extremely excellent in real-time measurement property. Since it is a binary recording device, it is suitable for recording speckle patterns and Young's interference fringes. The details of the structure and operation of the FLC-SLM are described in JP-A-2-289827.

The measuring device 1 having the above configuration is the arithmetic / control device 1
The diffracted light forming operation F executed under the control of 7 will be described with reference to FIG. 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 / control unit 17 operates the FLC-S.
Via the LM controller 19, the first FLC-SL
The erasing compensation voltage V _ec and the erasing drive voltage V _e are applied in this order between the electrodes 7B and 7H of the M7 for the same time.
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 write compensation voltage V _wc and the write drive 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 laser diode 3 via the LD controller 4 while applying the write drive voltage V _w , and the laser light is irradiated twice with a double write interval Δt. Measuring object 3
0 is irradiated. In this way, the FLC-SLM7
Double-record the first and second speckle patterns. On the other hand, the laser light from the He-Ne laser device 2 is
The reading side surface 7S _r of the FLC-SLM 7 is always illuminated. Therefore, the speckle pattern double-recorded on the FLC-SLM 7 is immediately read and Young's interference fringes are formed. The arithmetic / control device 17 applies the voltages V _wc and V _w to the first FLC-SLM 7, and at the same time, supplies the compensation voltage V _ec for erasing and the driving voltage V _e to the second FLC-SLM 13. Add. At the same time, the light emitting diode 14 irradiates the FLC-SLM 13 with uniform light to erase the image recorded in the previous measurement. The arithmetic / control device 17 terminates the writing of the speckle pattern to the FLC-SLM 7 and at the same time
The write compensation voltage V _wc and the write drive voltage V _w are sequentially applied between the voltages 13B and 13H of the SLM 13 to record Young's interference fringes on the FLC-SLM 13. He-Ne
The laser light from the laser device 2 is always applied to the reading side surface 13S _r of the FLC-SLM 13. Therefore, the Young's interference fringes recorded on the FLC-SLM 13 are immediately read, and a diffracted light spot showing the correlation between the first and second speckle patterns is formed.

In the measuring apparatus 1 of the present invention, the double write interval Δ is determined based on the output signal of the photodiode 116.
The diffracted light forming operation F is repeatedly performed while adjusting t. The output signal of the photodiode 116 is +1.
When it is shown that the next-order diffracted light spot has entered the entrance window 16S of the PSD 16, the arithmetic / control unit 17 determines that the PSD
Equations 7 and 8 are calculated based on the 16 output signals to obtain the moving distance and moving speed of the measured object 30.

The measurement operation will be described below.

The inter-spot distance | N (Δt) | of the diffracted light obtained in the diffracted light forming operation F and the zero-order light intensity I have the relationship shown in FIG. 2 as described above. Therefore, from Expression 6, the 0th-order light intensity I has a monotonically increasing relationship with the detection result X of the PSD 16. Here, when X = 0 (| N (Δt) | =
In the case of d), the 0th-order light intensity is Ia, and when X = L (| N
If the 0th-order light intensity of (Δt) | = L + d) is Ib, the + 1st-order diffracted light spot becomes P only when the photodiode 116 detects the 0th-order light intensity I satisfying Ia ≦ I ≦ Ib.
It can be seen that the light is incident on the incident window 16S of SD16. Therefore, in the measuring apparatus 1 of the present embodiment, the double writing interval Δt is adjusted via the LD controller 4 until the photodiode 116 detects the 0th order light intensity I that satisfies Ia ≦ I ≦ Ib. When the 0th-order light intensity I that satisfies Ia ≦ I ≦ Ib is obtained, the arithmetic / control unit 17 causes the PSD 16 in that case.
Equations 7 and 8 are calculated on the basis of the output result X of ## EQU1 ## to obtain the moving distance | S (Δt) | and the moving speed V.

The measurement operation will be described with reference to the flow chart shown in FIG. First, the arithmetic / control device 17
The double writing interval Δt is set to a predetermined value T _i (i = 1) via the LD controller 4, and the i-th (i = 1) diffracted light forming operation F _i is set via the FLC-SLM controller 19. (I = 1) is executed (step S1). Calculation·
Next, the controller 17 receives the 0th-order light intensity I (I _i : i = 1) which is the detection result of the photodiode 116, and determines whether or not this satisfies the relation of Ia ≦ I _i (step S2). When Ia> I _i , the moving speed V of the object to be measured is relatively small, and thus the double writing interval T _i (i =
1) the moving distance of the measured object during | S (Δt) |
Is small, and the distance | N (Δt) | between the diffracted light spots is smaller than d. In this case, the + 1st order diffracted light spot does not enter the entrance window 16S of the PSD 16. Therefore, the arithmetic / control device 17 resets the double writing interval Δt to a value T _{i + 1} larger than the predetermined value T _i adopted in the diffracted light forming operation F _i of this time (the i-th time). (Steps S3 and S4), the i + 1-th diffracted light forming operation F _{i + 1} is executed via the FLC-SLM controller 19 (step S1). When the 0th-order light intensity I _i obtained by the diffracted light forming operation satisfies the relation of Ia ≦ I _i (step S2: Yes), the arithmetic / control device 17 further
It is determined whether or not the light intensity I _i satisfies the relationship of I _i ≤Ib (step S5). If I _i > Ib, the moving speed V of the object to be measured is relatively high, and thus the moving distance | S (Δt) of the object to be measured during the double writing interval T _i.
Is large, and the distance between diffracted light spots | N (Δt) | is d + L
You can see that it is larger. Also in this case, +
The first-order diffracted light spot does not enter the entrance window 16S of the PSD 16. Therefore, the arithmetic / control device 17 sets the double writing interval Δt to the diffracted light forming operation F of this time (the i-th time).
_The value T _{i + 1} smaller than the predetermined value T _i adopted in _i is reset (steps S6 and S7), and the i + 1-th diffracted light forming operation F is performed via the FLC-SLM controller 19.
_{i + 1} is executed (step S1). On the other hand, when it is determined that the 0th-order light intensity I _n obtained in the diffracted light forming operation F _i (i = n) at a certain time (n-th time: i = n) satisfies Ia ≦ I _n ≦ Ib To (Yes in steps S2 and S5), +
It is determined that the first-order diffracted light has entered the entrance window 16S of the PSD 16. Therefore, the arithmetic / control device 17
Equations 7 and 8 are calculated based on the X value detected by the PSD 16 when the diffracted light forming operation F _n of that time (the n-th time) is executed, and the moving distance | S (Δt) | The moving speed V is obtained (step S8).

As described above, according to the measuring apparatus 1 of the present embodiment, even if the + 1st order diffracted light deviates from the incident window 16S of the PSD 16, the + 1st order diffracted light is obtained by the 0th order light intensity obtained by the photodiode 116. You can know the position of. Therefore, by adjusting the double writing interval Δt based on the detected value of the 0th-order light intensity, the + 1st-order diffracted light can be returned extremely quickly into the entrance window 16S of the PSD 16. Further, as described above, since the intensity of the 0th-order diffracted light can be detected and the position of the + 1st-order diffracted light can be roughly known from the result, the apparent movement amount of the measured object can be changed variously to obtain the + 1st-order diffracted light. There is no need to search the position. Therefore, it is possible to perform the measurement in a shorter time than the conventional case. Furthermore, according to the present invention, it is possible to measure the velocity change of a wide range of the object to be measured. Moreover, since the position of the + 1st-order diffracted light can be roughly known from the intensity of the 0th-order diffracted light, the area of the entrance window 16S of the PSD 16 can be further reduced. That is, it becomes possible to measure with a small position measuring device.

In the above embodiment, the light intensity I of the 0th-order diffracted light spot is detected by the photodiode. However, instead of the photodiode 116, another PSD
116 'may be newly provided. That is, the center point 15
It is also possible to dispose the PSD 116 ′ in O and make the 0th-order diffracted light spot enter the incident window 116 ′S. In this case, P
The zero-order light intensity I can be obtained by detecting the total amount of current obtained at the plurality of output electrodes of SD116 '. Further, the position of the center of gravity of the 0th-order light spot can also be detected. Therefore, even when the image forming position of the 0th-order light spot fluctuates and deviates from the center point 15O, the distance between diffracted light spots | N
(Δt) | can be accurately detected, and the amount of movement | S (Δt) | of the object to be measured can be measured with high accuracy.

Further, in the above embodiment, the + 1st order diffracted light is PSD based on the detection result of the photodiode 16.
After controlling the light to enter the 16 incident windows 16S, P
Moving distance of the measured object based on the detection result of SD16 |
S (Δt) | However, as described below, the + 1st-order diffracted light is controlled to enter the center of the entrance window 16S of the PSD 16 based on the detection result of the photodiode 16, and then the moving distance is obtained based on the detection result of the PSD 16. Is also good. That is, in the graph of FIG. 2, when X = L / 2 (| N (Δt) | = d + (L
/ 2)) and the 0th-order light intensity is Ic, the photodiode 16 causes the 0th-order light intensity Ic-dIc ≦ I ≦ Ic + d.
When Ic (here, dIc is a predetermined minute value) is detected, it can be seen that the + 1st-order light spot is incident on the central region of the incident window 16S of the PSD 16. Therefore, the 0th-order light intensity I obtained by the photodiode 116 is expressed by the relational expression Ic-
Until dIc ≦ I ≦ Ic + dIc is satisfied, the diffracted light forming operation F is repeatedly executed while adjusting the double writing interval Δt, and when the 0th-order light intensity I satisfying the relational expression is obtained, the PSD 16 is detected. You may perform the calculation of Numerical formula 7 and 8 based on a result. Since the PSD generally has high accuracy in its central region, such a method can obtain the moving distance and moving speed of the measured object with higher accuracy.

In the above embodiment, the object to be measured is irradiated with laser light to form a speckle pattern on the reflected light, and the amount of movement 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-mentioned embodiment, the laser diode 3 is set to the predetermined time interval Δ.
The object to be measured 30 is irradiated with the laser light twice after the time t. However, as shown in FIG. 6, the laser diode 3 may always irradiate the measured object 30 with laser light. In this case, FLC-S
The LM controller 19 pulse-writes the write drive voltage V _w to the first FLC-SLM 7 at the first and second times t ₁ and t ₂ (that is, twice at the 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 recording may be performed in the 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. 5 and 6, He-Ne laser light is always applied to the reading side light incident surfaces 7S _r and 13S _r of the first and second FLC-SLMs 7 and 13. Is being irradiated. However, the irradiation may be performed at the timing shown by the dotted line in the figure. That is,
The reading side light incident surface 7S _r of the first FLC-SLM 7 is irradiated with He—Ne laser light for a certain period of time after the application of the write drive voltage V _w to the FLC-SLM 7, and then the Young's Form interference fringes. At the same time, the voltages V _wc and V _w are applied to the second FLC-SLM 13 to record the formed Young's interference fringes. Similarly,
Light-incident surface 13S on the reading side of the second FLC-SLM 13
After the application of the write drive voltage V _w to the FLC-SLM 13 is finished, the _r is irradiated with the He—Ne laser light for a certain period of time to form a diffracted light spot. Note that H
E-Ne laser light is selectively read out and the side light incident surface 7
S _r, in order to irradiate the 13S _r, for example, as indicated by a dotted line in FIG. 1, the first and second readout optical system 1
Optical shutters 21 and 22 may be provided at 0 and 11, respectively.

The inventor of the present invention has found that the 0th-order diffracted light intensity I and the moving distance of the object to be measured | S (Δt) in the measuring apparatus 1 of the present invention.
The following experiment was conducted in order to investigate the relationship of |.

In this experiment, as shown in FIG.
The He—Ne laser light was continuously applied to the ground glass plate as the measured object 30 without using the laser diode 3. The ground glass plate, which is the object to be measured 30, is 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, the moving stage 31 was moved in the direction of arrow V by the DC servo motor belt. In this experiment, He-Ne laser light (λ = 0.632 × 10 ⁻³⁾ transmitted through the ground glass plate which is the object to be measured 30.
[Mm]) was formed with a speckle pattern, and this was used for measurement. Further, the imaging lens 5 was not used. Therefore, the imaging magnification m = 1 in the mathematical formula 1. Also, the first and second Fourier transform lenses 12, 1
As No. 5, a Fourier transform lens having focal lengths f ₁₂ = 150 [mm] and f ₁₅ = 1000 [mm] was used. PSD 11 instead of photodiode 116
6 ′ was provided, and the 0th-order diffracted light intensity I indicated by the total amount of output currents of the PSD 116 ′ 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
I didn't use it either.

In this experiment, the arithmetic / 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. 6, He
The Ne glass light was continuously applied to the ground glass plate, which is the object to be measured. Erasing voltage V _ec of the first FLC-SLM 7, 1000, respectively application time of V _e [μs], the application time of the write compensation voltage V _wc 300 [μs], and the application of the write driving voltage V _w Set the time to 150 [μ
s]. The write drive voltage V _w is set twice for the FLC-SL with a double write interval Δt = 1 [ms].
It was applied to M7. On the other hand, the second FLC-SL
The application time of the erase voltages V _ec and V _e of M13 is 1
000 [μs], and the application time of the write voltages V _wc and V _w was set to 500 [μs], respectively. In addition, in this experiment,
After writing the write voltage V _wc and V _w to the FLC-SLM 7 to record the speckle pattern, the He-Ne laser light is irradiated to the reading side surface 7S _r of the FLC-SLM 7,
Young's interference fringes were formed. At the same time, FLC-
Writing voltages V _wc and V _w were applied to the SLM 13 to record Young's interference fringes. Then, by irradiating a He-Ne laser beam on the side surface 13S _r read the FLC-SLM 13, to form a diffracted beam spot. In addition, reading side 13
Irradiation time of He-Ne laser light to S _r is 1950 [μ
s]. The measurement performed at the above timing was repeatedly performed at a time interval of 4000 + Δt [μs]. When performing each measurement, the speed V of the ground glass plate (that is, the moving stage) was set to various values of 300 [mm / s] or more. In every measurement, set the double write interval Δt to 1
Since it is fixed to [ms], | S (Δt) | = V · 1 [m
[s] is changed to various values, and the measurement is executed each time.

By the way, in this experiment, the speed V was restricted to 300 [mm / s] or more and the double writing interval Δt was fixed to 1 [ms] as described above. Therefore, according to the following formula 9, the distance | N (Δt) | between the diffracted light spots is 2 [mm].
It can be seen that the above is restricted.

[Equation 9] | N (Δt) | = (f ₁₅ / f ₁₂ ) · | M (Δt) | = (1000/150) × (300 × 1 × 10 ⁻³ ) = 2 [ms] In this experiment, The diameter of He-Ne laser light (reading light) with which the surface 13S _r of the FLC-SLM 13 is irradiated is 1
It was set to 0 [mm]. Therefore, from Equation 10 below,
The spot diameter R of the obtained 0th-order diffracted light spot is 80 × 1.
It turns out that it becomes 0 ^-3 [mm].

R = 1.22x (0.632x10 ^-3 x1000) / 10 = 80x10 ^-3 Considering the above points, in this experiment, PSD116 ′ was used.
The length of the incident window 116S 'in the X direction is 1 [mm]
The incident window 116S ′ captures the entire 0th-order light spot, but does not capture the + 1st-order and −1st-order diffracted light.

From the above experiment, the results shown in the graph of FIG. 10 were obtained. That is, the moving distance of the measured object | S
It was experimentally confirmed that the relationship shown in the graph of FIG. 10 exists between (Δt) | and the 0th-order light intensity I. In addition, in this figure, the moving distance | S (Δt) |
Spatial frequency U (△ of Young's interference fringes recorded in LM
The values of t) and the distance between diffracted light spots | N (Δt) | are also shown. (The values of U (Δt) and | N (Δt) |
It is obtained from (Δt) | by Equations 1 and 5. ) As is apparent from FIG. 10, the 0th-order diffracted light intensity I is | S (Δt) |, U (Δt) and | N (Δt) |
It has been found that there is a one-to-one correspondence with. More specifically, the 0th-order diffracted light intensity I is | S (Δt)
It was found that the function was a monotonically increasing function for |, U (Δt) and | N (Δt) |. In addition, in this experiment, the light intensity of the + 1st order diffracted light was also measured. The results are also shown in FIG. As is clear from this figure, +
The light intensity of the first-order diffracted light is also | S (Δt) |, U (Δ
It was found that there is a one-to-one correspondence with t) and | N (Δt) |. More specifically, the + 1st order diffracted light intensity is | S (Δt) |, U (Δt) and | N (Δ
It was found that there was a monotonically decreasing function for t) |.

A second embodiment of the present invention will be described below with reference to FIG. The optical moving speed measuring apparatus 100 of this embodiment is the same as the optical moving speed measuring apparatus 1 of the first embodiment except that a deflector 101 such as a galvanometer mirror and a mirror controller 102 are provided. . The deflector 101 is for deflecting the first and second reflected lights from the measured object 30. Here, the deflector 101
Shifts the deflection direction by the deflection angle θ during the double writing interval Δt. Therefore, the first and second speckle patterns imaged on the FLC-SLM 7 are separated by an apparent shift distance | M ′ (Δt) |. This apparent shift distance | M '(Δt) |
Satisfies the following formula 11 instead of the above-mentioned formula 1,
Further, it satisfies | M (Δt) |

| M ′ (Δt) | = α (θ, m) · | S (Δt) | where α (θ, m) is the deflection angle θ and the imaging magnification m of the lens 5. It is a dependent variable. On the other hand, the mirror controller 102 is for adjusting the deflection angle θ of the deflector 101 and adjusting the apparent shift distance | M ′ (Δt) | to an arbitrary value.

The measuring apparatus 1 of the present embodiment having the above configuration
In 00, the calculation / control device 17 observes the detection result of the photodiode 116 and feedback-adjusts the deflection angle θ instead of the double writing interval Δt, and repeatedly executes the diffracted light forming operation F. The 0th-order light intensity I, which is the detection result of the photodiode 116, indicates that the + 1st-order diffracted light is imaged in the incident window 16S of the PSD 16 or in the central region thereof. Is calculated to obtain the moving distance and speed of the object to be measured. In addition, in the present embodiment, not only the deflection angle θ but also the measurement time interval Δt may be adjusted together.

As described above, the measuring apparatus 100 of this embodiment
Also, the + 1st-order diffracted light is incident on the incident window 16S of the PSD 16.
If it deviates further, the position of the + 1st order diffracted light can be known from the 0th order light intensity obtained by the photodiode 116. Therefore, by adjusting the deflection angle (and double writing interval) based on the detected value of the 0th-order light intensity,
Extremely promptly adds + 1st order diffracted light to the incident window 16S of the PSD 16.
Can be put back in. Further, since the position of the + 1st-order diffracted light can be roughly known from the detection result of the intensity of the 0th-order diffracted light, it is possible to change the apparent movement amount of the measured object in various ways to search the position of the + 1st-order diffracted light. Since it is unnecessary, the measurement can be performed in a short time. Further, it is possible to measure the speed change of the object to be measured over a wide range. Further, since the position of the + 1st order diffracted light can be roughly known from the intensity of the 0th order diffracted light, the area of the entrance window 16S of the PSD 16 can be reduced.

In the first and second embodiments, the photodiode 116 and the PSD 16 are arranged in parallel on the image side focal plane 15F of the lens 15.
However, the photodiode 116 and the PSD 16 do not have to be arranged in parallel. For example, as shown in FIG. 12, a condensing unit 115 such as another lens is provided at the rear stage of the image-side focal plane 15F of the lens 15, and a 0th-order diffracted light point image is formed at the rear stage of the condensing unit 115. The photodiode 116 may be arranged there. In this case, the area of the incident window 116S of the photodiode 116 is determined only by the spot size of the 0th-order light spot condensed by the new condenser means 115, and the position of the + 1st-order diffracted light spot obtained is determined. Has the advantage that it does not need to be considered. However, it goes without saying that the PSD 16 must be arranged so as not to block the transmission of the 0th-order light.

The third embodiment of the present invention will be described below with reference to FIG. Like the first and second embodiments, this embodiment also relates to an optical moving speed measuring device for measuring the moving speed of a moving object to be measured.

As shown in FIG. 13, unlike the first embodiment, the measurement / control unit 1D of the optical movement velocity measuring apparatus 200 of this embodiment does not have the PSD 16 and the photodiode 1 does not.
Only 16 are provided. In this embodiment, the arithmetic / control device 17 measures the moving distance and moving speed of the measured object based only on the 0th-order diffracted light intensity detection result by the photodiode 116. That is, as described above, the 0th-order diffracted light intensity I has a monotonically increasing function as shown in FIGS. 2 and 10 with respect to the moving distance | S (Δt) | of the object to be measured. Therefore, the 0th-order light intensity value I obtained for various moving distances | S (Δt) |
If a graph or a mathematical formula showing the relationship with (Δt) | is obtained, the moving distance, and thus the moving distance, of the object to be measured whose moving distance is unknown can be measured by measuring the detection result of the photodiode. The moving speed can be calculated. Therefore, in the measuring device 200 of the present embodiment, the arithmetic / control device 1
In FIG. 7, a graph, a mathematical expression or the like showing the relationship between I and | S (Δt) | obtained in advance is stored. The calculation / control device 17 obtains the moving distance | S (Δt) | of the object to be measured from the 0th-order light intensity value I input from the photodiode 116 by using such graphs and mathematical formulas, and further calculates the speed from the mathematical formula 8. Calculate V.

Since the photodiode 116 can detect the light amount extremely fast, the FLC having a fast response speed.
-The operation following the operation of the SLMs 7 and 13 can be performed. Therefore, the measuring apparatus 200 of the present embodiment, which is configured by combining the FLC-SLMs 7 and 13 and the photodiode 116, can also perform the measurement in a short time and is extremely excellent in the real-time measurement property.

Instead of the photodiode 116, other light intensity detecting means such as a photomultiplier tube may be used. Alternatively, PSD may be used.

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.

Means 7 for double recording of speckle pattern
Is not limited to the ferroelectric liquid crystal spatial light modulator, the light receiving pattern of the measured object at the first measurement time can be accumulated until at least the second measurement time, and the image (speckle pattern) of the measured object can be stored. Any spatial light modulator capable of double recording can be used. For example, MSLM may be used.

A means 13 for recording Young's interference fringes
Is not limited to the ferroelectric liquid crystal spatial light modulator, but T
NLC-SLM (twisted nematic liquid crystal SLM)
Alternatively, a phase modulation type SLM (for example, a homogeneous nematic SLM) may be used. Further, an SLM (for example, MSLM) using an EO crystal for the modulator may be used. However, an SLM using a material having a peak value in the diffraction efficiency and giving a high diffraction efficiency at a specific spatial frequency (for example, a thermoplastic photosensitive material having the diffraction efficiency as shown in FIG. 14) is not suitable as the modulator. Because S
This is because in the LM, there is no one-to-one correspondence (monotonic increase or monotonic decrease relationship) between the spatial frequency U (Δt) of Young's interference fringes and the obtained 0th-order diffracted light intensity I. However, an SLM using such a material can also be adopted by using only a range where a one-to-one correspondence relationship (monotonic increase or monotonic decrease relationship) is obtained in the measurement. Similarly, an analog phase modulation type SLM can also be adopted as the means 13 by using a range in which a one-to-one correspondence relationship (monotonic increase or monotonic decrease relationship) is obtained. In other words, as means for recording the Young's interference fringes to be adopted in the measuring device of the present invention, the spatial frequency U (Δt) of the recorded interference fringes and the read light are recorded by the interference fringes. It is sufficient that the light intensity I of the 0th-order diffracted light obtained by performing the optical Fourier transform after being modulated by the means described above has a one-to-one correspondence (monotonically decreasing or monotonically increasing).

In the above-mentioned embodiment, the measuring device is fixed and the object to be measured is moving. However, conversely, the measuring device may be moving and the object to be measured is fixed. In this case, by measuring the amount of movement and the speed of the fixed measured object relative to the measuring device,
The absolute movement amount and speed of the speed measuring device can be obtained. 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 is only necessary to be able to measure the amount of displacement of the object, such as the amount of movement or distortion of the object. Furthermore, the measured object has
Instead of coherent light such as laser light, incoherent light may be emitted. In this case, the image of the measured object is displayed instead of the speckle pattern in the first FLC-SLM.
To record. 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 are obtained. This is because the diffracted light can be obtained by recording this on the second FLC-SLM and then reading out the recorded Young's interference fringes and performing Fourier transform.

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 intensity is formed between the imaging lens 5 and the first FLC-SLM 7. A fire may be provided to increase the light intensity of the pattern, and then the light may be incident on the writing incident surface 7S _w of the first FLC-SLM 7.

[0050]

As is clear from the above description, in the optical displacement amount measuring device of the present invention, the light irradiating means is displaced relative to the optical displacement amount measuring device. The measurement target 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 second measurement times. The first coherent light projecting unit irradiates the first recording unit with coherent light to read the double-recorded image of 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 of the first recording unit. The second Fourier transform means Fourier-transforms the read first Fourier transform image to form a second Fourier transform image having a 0th-order diffracted light point image. The light intensity detecting means detects the light intensity of the 0th-order diffracted light point image of the second Fourier transform image. The displacement amount specifying means obtains a relative displacement amount of the object to be measured with respect to the optical displacement amount measuring device between the two measurement times based on the detection result of the light intensity detecting means. Therefore, according to the optical displacement amount measuring device of the present invention, the displacement amount of the object to be measured can be measured in a short time, and the real-time measurable property is extremely excellent.

[Brief description of drawings]

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

FIG. 2 shows the light intensity of the 0th-order diffracted light and the 1st-order diffracted light obtained on the image-side focal plane 15F of the Fourier transform lens 15, the spatial frequency U (Δt) of Young's interference fringes, and the moving distance of the measured object | S (Δt) |, distance between diffracted light spots | N (Δt)
It is a graph which shows the qualitative relationship of | and the output value X of PSD.

3A is a front explanatory view illustrating an arrangement state when the PSD 16 and the photodiode 116 of FIG. 1 are viewed from the lens 15 side, and FIG. 3B is a PSD 16 of FIG.
FIG. 7 is a plan view illustrating the positional relationship between the photodiode 116 and the lens 15.

FIG. 4 is an enlarged sectional view showing the ferroelectric liquid crystal spatial light modulator of FIG.

5 is an operation timing chart of a diffracted light forming operation F executed by the optical moving speed measuring apparatus of FIG.

6 is an operation timing chart of another example of the diffracted light forming operation F executed by the optical moving speed measurement apparatus of FIG.

FIG. 7 is a flowchart showing an operation in which the optical moving speed measuring apparatus of FIG. 1 repeatedly performs a diffracted light forming operation F to obtain a moving distance / moving speed of an object to be measured.

FIG. 8 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. 9 is an operation timing chart of the measurement operation of the measuring apparatus 1 of the present invention adopted in the experiment.

FIG. 10 shows the light intensities of the 0th-order diffracted light and the 1st-order diffracted light, the spatial frequency U (Δt) of Young's interference fringes, the diffracted light light point distance | N (Δt) | Distance | S (△
t) is an experimental result showing a qualitative relationship of |.

FIG. 11 is a plan view of an optical system showing an optical moving speed measuring apparatus according to a second embodiment of the present invention.

FIG. 12 is a plan view illustrating another arrangement state of photodiodes.

FIG. 13 is an optical system plan view showing an optical moving speed measuring apparatus according to a third embodiment of the present invention.

FIG. 14 is a graph showing the diffraction efficiency of a thermoplastic thermosensitive material.

FIG. 15 is an optical system plan view showing a conventional optical displacement amount measuring device.

[Explanation of symbols]

 1 Optical Moving Speed Measuring Device 2 He-Ne Laser Device 3 Laser Diode 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 PSD 116 Photodiode 17 Calculation / Operation Control device

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 out the first Fourier transform image, and Fourier transform of the read first Fourier transform image to form a 0th-order diffracted light spot Second for forming a second Fourier transform image with the image Fourier transform means, a light intensity detecting means for detecting the light intensity of the 0th-order diffracted light point image of the second Fourier transform image, and the second measurement based on the detection result of the light intensity detecting means. An optical displacement amount measuring device comprising a displacement amount specifying means for determining a relative displacement amount of the object to be measured with respect to the first recording means during a time. 2. The displacement amount specifying means calculates a detection result of the light intensity detecting means to obtain a relative displacement amount of the object to be measured with respect to the first recording means between the two measurement times. The optical displacement amount measuring device according to claim 1, characterized in that it comprises a calculating means for 3. The adjusting means for adjusting the second Fourier transform image, further comprising: the light intensity detecting means, wherein the adjusted zero-order diffracted light point image light of the second Fourier transform image is adjusted. The displacement amount identifying means has a control means for controlling the adjustment state of the adjusting means based on a detection result of the light intensity detecting means, and the adjusted second Fourier transform image. An optical center-of-gravity position detection means for detecting the position of the center of gravity of the first-order diffracted light point image, and the object to be detected between the two measurement times based on the detection result of the optical center-of-gravity position detection means and the adjustment state of the adjustment means. The optical displacement amount measuring device according to claim 1, further comprising a displacement amount calculation unit for calculating a relative displacement amount between the measurement target and the first recording unit.