JPH0827292B2 - Optical displacement measuring device - Google Patents

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 a relative displacement amount or displacement speed of an object. Here, the amount of displacement of the object means the amount of movement or deformation of the object.

[0002]

2. Description of the Related Art As one of means for optically measuring the amount of displacement of an object, there is a speckle method. In the speckle method,
An object is irradiated with coherent light such as laser light or the like, and a spot-like pattern (hereinafter referred to as a "speckle pattern") formed by diffusing and reflecting the irradiated light on a rough surface or the like of the object is used. Japanese Patent Application Laid-Open No. Sho 59-212773 discloses an optical speed detecting device employing a speckle method. In this device, a moving measurement object is irradiated with coherent light twice at a certain time interval. Then, the speckle patterns obtained by the two irradiations are respectively received by a plurality of light receiving elements and photoelectrically converted. The correlations are calculated while shifting the sample values collected by each light receiving element. From this calculation, the movement amount of the speckle pattern is obtained, and thus the movement amount and the movement speed of the measurement object are obtained.

[0003]

However, in such an apparatus for obtaining the moving amount / moving speed by the correlation calculation as described above, it takes time to collect the sample values and the correlation calculation, which is sufficient in terms of real-time measurable property. Not. The present invention has been made in view of the above problems, and an object thereof is an optical displacement amount measuring device capable of measuring a relative displacement amount and a displacement velocity of an object to be measured in a short time and excellent in real-time measurable property. To provide. It is another object of the present invention to provide an optical displacement amount measuring device that reduces detection errors of relative displacement amount and displacement velocity, has high measurement accuracy, and has a large dynamic range.

[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. Yang and first coherent light projecting means for reading the recorded image, the read-out double recorded image by Fourier transform
First Fourier transform means for forming a first Fourier transform image composed of interference fringes, a second recording means for recording the first Fourier transform image, and the second recording means a second coherent light projecting means for reading a Fourier transform image of said first and irradiating coherent light, a first Fourier transform images read the Fourier transform to the double
Second Fourier transform means for forming a second Fourier transform image composed of a number of diffracted light spots , and detecting the position of the center of gravity of the first-order diffracted light spot in the second Fourier transform image, Between the plurality of diffracted light points, and an optical center-of-gravity position detecting means for obtaining a relative displacement amount of the object to be measured between measurement times of
By adjusting the distance of
And an adjusting means for making only the first-order diffracted light point incident . Here, it is preferable that the light irradiation means irradiates the object to be measured with coherent light to form a speckle pattern. In addition, the position of the optical center of gravity is detected.
The emitting means consists of a semiconductor position detecting element equipped with a light incident surface.
The adjusting means adjusts the distance between the plurality of diffracted light points.
As a result, only the first-order diffracted light spot is made incident on the light incident surface.
Preferably. Here, the adjusting means is
Relative adjustment of the position of the image of the measured object at a fixed time
By doing so, only the first-order diffracted light spot is
It is preferable to make the light incident on the projection surface. The adjusting means is
To deflect the image of the measured object at the measurement time of
The deflecting means at the second measuring time,
By adjusting the deflection direction of the step, the first recording means
The relative position of the image of the measured object when double-recorded on the
Adjust so that only the first-order diffracted light spot enters the light incident surface.
It is preferable to make it fire. The adjusting means further comprises:
Means for adjusting the time interval of the measurement time of
Is preferred.

[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 Fourier-transformed by the first Fourier transforming means to form a first Fourier-transformed image composed of Young's interference fringes . 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, and a plurality of diffracted light beams are obtained.
A second Fourier transform image of dots is formed. The adjusting means adjusts the distance between the plurality of diffracted light points.
Incident only the first-order diffracted light spot on the light barycentric position detecting means.
Let The optical barycentric position detecting means detects the barycentric position of the first-order diffracted light point in the second Fourier transform image, so as to detect the optical center of the object to be measured during the second measurement time. A relative displacement amount with respect to the displacement amount measuring device is obtained. Here, when the light irradiating means irradiates coherent light, as the image of the object to be measured,
A speckle pattern is obtained. The optical center of gravity position detecting means
Is a semiconductor position detector with a light incident surface,
The adjusting means adjusts the distance between the plurality of diffracted light points.
As a result, only the first-order diffracted light spot is made incident on the light incident surface.
Let Here, the adjusting means is
When adjusting the position of the image of the measured object relatively,
First order diffraction by adjusting the relative position of the image of the measured object.
Only the light spot is made incident on the light incident surface. Also, the adjusting means
Deflects the image of the measured object at the second measurement time.
If it comprises a deflection means for
By adjusting the deflection direction of the deflection means in the
Image of the object to be measured when double-recorded on the first recording means
Adjust the relative position of the
The light is incident on the light incident surface. The adjusting means further measures the second
If there is a means to adjust the time interval of fixed time
The adjusting means also adjusts the time interval between the two measurement times.
By doing so, only the first-order diffracted light spot is made incident on the light incident surface.
Let

[0006]

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. 1A is a top 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 the present embodiment. Rectangular parallelepiped object to be measured 23
Is conveyed and moved in the direction of arrow A in FIG. 1A (direction along the plane of the drawing) by the conveyor device 24 in the form of a belt conveyor. The rectangular parallelepiped object 23 has a planar rough surface 23A extending in a direction perpendicular to the plane of the drawing.

In the measuring device 1, a laser diode (hereinafter, referred to as "LD") 2 emits a spot-shaped laser pulse light twice at a predetermined time interval.
Irradiation is performed on the fixed region R above 4. As a result, the double irradiation light is applied to the planar rough surface 23A of the measured object 23. (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 “irradiation time interval Δt (= t ₂ −t ₁ ) ”. Also, the measured object 2 at the irradiation time interval Δt.
The moving distance of 3 is | S (Δt) |. ) Incidentally, the LD
2 is controlled by the LD controller 20. The two irradiation lights are scattered and reflected by the portions of the rough surface 23A of the measured object 23 located in the fixed region R at the irradiation times t ₁ and t ₂ , respectively, and the rough irradiation is performed. The reflected light having a speckle distribution unique to the shape of the surface is formed. (Hereinafter, the reflected lights formed at the first and second measurement times are referred to as "first and second reflected lights", respectively.)
The first and second reflected lights are respectively deflected by the galvanometer mirror 3, and then the imaging lens 4 causes the first ferroelectric liquid crystal spatial light modulator (hereinafter, referred to as “first spatial light modulator”). , 5) on the writing side light incident surface 5S _w . (Hereinafter, the speckle patterns formed on the light incident surface 5S _w by the first and second reflected lights are referred to as “first and second speckle patterns”, respectively.) The light incident surface The first and second speckle patterns imaged on 5S _w have the same speckle distribution as a whole in one shift direction B and one shift distance (hereinafter, referred to as “shift distance | M The pattern is shifted by (Δt) | ”. The first spatial light modulator 5 is driven by a spatial light modulator controller (hereinafter, referred to as “light modulator controller”) 19 and double-records the first and second speckle patterns.

By the way, the galvanometer mirror 3 has a rotating shaft 3A extending in a direction perpendicular to the plane of the drawing and the rotating shaft 3A.
The flat mirror 3B is rotatably provided.
The flat mirror 3B also extends perpendicularly to the plane of the drawing.
The optical axis 4A of the imaging lens 4 extends along the plane of the drawing, and the writing-side light incident surface 5S _w of the first spatial light modulator 5 is the image side of the imaging lens 4. It extends on the focal plane in a direction perpendicular to the plane of the drawing. Therefore, the shift direction B of the speckle distribution has a fixed relationship with the moving direction of the measurement object (arrow A in FIG. 1A). In the case of this embodiment, the shift direction B is also parallel to the direction along the plane of the drawing. Now, as shown in FIG. 1A, the rotation angle position of the flat mirror 3B is set to the optical axis 4 of the imaging lens 4 described later.
Consider the angle θ measured clockwise from A. The flat plate mirror 3B moves to the first rotation angular position θ ₁ at the first measurement time t ₁ and the second rotation angular position θ at the second measurement time t _2.
It is controlled by the mirror controller 21 as shown in ₂ . Therefore, the shift distance | M (Δt) |
Between the measured object moving distance | S (Δt) | and a constant relationship determined not only by the magnification of the imaging lens 4 but also by the first and second rotational angle positions θ ₁ and θ _2. Have. More specifically, even if the measured object moving distance | S (Δt) | is constant, the shift distance | M (Δt) is greater in the case of θ ₁ > θ ₂ than in the case of θ ₁ = θ _2. ) | Becomes smaller. Moreover, the angle difference θ
_The larger ₁ −θ ₂ is, the smaller the shift distance is. On the other hand, the shift distance is greater when θ ₂ > θ ₁ than when θ ₁ = θ _2.
M (Δt) | becomes large. Moreover, the larger the angle difference θ ₂ −θ ₁ , the larger the shift distance. In other words,
For the spatial light modulator 5 of the first, the movement distance as the theta ₁ is greater larger than _{θ 2 | S (△ t)} | is apparently reduced, as theta ₂ is greater larger than theta ₁ wherein The moving distance | S (Δt) | becomes apparently large. Therefore, the shift distance | M (Δt) |
(Δt) | and the relationship defined by the following mathematical formula 1.

## EQU00001 ## | M (.DELTA.t) | = .alpha. (. DELTA..theta.). Multidot. | S (.DELTA.t) | where the variable .alpha. (. DELTA..theta.) Is the difference .DELTA..theta. It is a positive variable depending on θ ₁ −θ ₂ ), and its value is determined by a constant value such as the angular difference Δθ and the focal length of the lens 4, and the smaller Δθ is, the smaller.

In the measuring apparatus 1, the linearly polarized laser beam emitted from the He-Ne laser apparatus 7 is converted by the conversion optical system 8 including the first collimator lens 8A, the spatial filter 8B and the second collimator lens 8C.
It is converted into a parallel laser beam having a desired beam diameter. The parallel laser beam is separated by the half mirror 9 into two parallel laser beams. The two parallel laser beams are guided to a first reading optical system 10 including a variable aperture 10A and a half mirror 10B and a second reading optical system 11 including a mirror 11A and a half mirror 11B. In the first reading optical system 10, the variable aperture 10A further changes the beam diameter of the guided parallel beam to a desired value and then guides it to the half mirror 10B. The half mirror 10B reflects the parallel laser beam and makes it incident on the reading side light incident surface 5S _r of the first spatial light modulator 5. The laser beam is phase-modulated in the first spatial light modulator 5 corresponding to the positions (the shift distance | M (Δt) | and the shift direction) of the first and second speckle patterns. After receiving the light, the light is emitted from the light incident surface 5S _r on the reading side. In other words, the double recorded speckle pattern is read out. The laser beam modulated and emitted by the first spatial light modulator 5 is
After passing through the half mirror 10B, it is spatially Fourier transformed by the first Fourier transform lens 12. Writing side light incident surface 13S of the second ferroelectric liquid crystal spatial light modulator (hereinafter, referred to as "second spatial light modulator") 13.
_{Since w} is located on the image-side focal plane of the lens 12, the modulated laser beam moves on the light incident surface 13S _w ,
Image Young's interference fringes. 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 B of the speckle distribution recorded in the first spatial light modulator 5, It will be parallel to the direction along the paper. Also, the fringe spacing of the Young's interference fringes | L (Δt)
| Has a fixed proportional relationship with the reciprocal of the shift distance | M (Δt) |. Here, the proportional constant that determines the constant proportional relationship is determined by the wavelength of the read light and the focal length of the Fourier transform lens 12. The second spatial light modulator 13
Is also driven by the light modulator controller 19 to record the Young's interference fringes.

The parallel beam separated by the half mirror 9 and guided to the second reading optical system 11 is reflected by the mirror 11A and then by the half mirror 11B, and the second space is reflected. The light enters the reading side light incident surface 13S _r of the optical modulator 13. The laser beam undergoes phase modulation in the second spatial light modulator 13 corresponding to the position of the Young's interference fringes (fringe direction and fringe spacing | L (Δt) |), and then the reading is performed. The light is emitted from the light incident surface 11S _r on the stock side. In other words, the recorded Young's interference fringes are read out. The laser beam modulated and emitted by the second spatial light modulator 13 passes through the half mirror 11B and is spatially Fourier transformed by the second Fourier transform lens 15. As a result, on the image-side focal plane 15F of the lens 15, a plurality of light spots (nth-order diffracted light; n = ± 1, 1) corresponding to the correlation between the 0th-order diffracted light and the first and second speckle patterns.
± 2, ...) Is imaged. Since the plurality of light spots are arranged in parallel to the direction in which the stripes of the Young's interference fringes are arranged, they are arranged in the direction (X direction) along the paper surface of FIG. 1A. Also, the distance between adjacent light spots of the plurality of light spots | N (Δt) |
Are equal to each other, and the fringe spacing of the Young's interference fringes | M (Δ
t) There is a fixed proportional relationship with the reciprocal of the value of |. Here, the proportional constant that determines the constant proportional relationship is determined by the wavelength of the read light and the focal length of the Fourier transform lens 15. Therefore, the inter-light-spot distance | N (Δt) | has a relationship with the shift distance | M (Δt) |

## EQU2 ## | N (Δt) | = β | M (Δt) | where β is a positive constant and is determined by the wavelength of the reading light and the focal lengths of the lenses 12 and 15. Therefore, if the distance | N (Δt) |
And 2, the moving distance | S (Δt) | of the measured object is obtained. Then, by calculating the following formula 3,
Moving speed of the measured object at the time interval Δt | V
(Δt) | is required.

[Equation 3] | V (Δt) | = | S (Δt) | / (Δt)

After the Fourier transform lens 15,
One-dimensional position detecting semiconductor position detecting element (hereinafter referred to as “PS
D ”) 16 is the light incident surface (detectable area) 1
6S is arranged so as to be located on the image side focal plane 15F. Here, the PSD 16 is shown in FIGS.
As shown in B, the detectable one-dimensional direction (X direction)
Are arranged so as to be parallel to the direction along the paper surface of FIG. 1A. The origin 16S of the light incident surface 16S
_x0 is the optical axis 15A of the lens 15 and the image side focal plane 15F
It is arranged so as to be separated from the center point 15O intersecting with by a predetermined distance d. Here, the 0th-order diffracted light is imaged at the center point 15O. Then, when the first-order diffracted light is imaged on the light incident surface 16S as shown in FIG. 2A, the PSD 16 detects the center of gravity (peak position) of the first-order diffracted light.
To detect the distance X from the raw point 16S _x0 of 16S _x1. Therefore, the distance between light spots | N
(Δt) | can be obtained.

[Expression 4] | N (Δt) | = X + d Therefore, based on the detected value X of the PSD,
To 4 to calculate the moving speed of the measured object | V
(Δt) | can be obtained. In addition, such Formula 1
The computation / control device 18 connected to the PSD 16 performs computations 4 to 4. That is, the arithmetic / control device 18
A signal indicating the detected value X of the PSD is received, the mathematical expressions 1 to 4 are calculated based on the signal, and the moving speed | V (Δt) | of the measured object is obtained. A speed display device 22 is connected to the arithmetic / control device 18, and the speed display device 22 displays the moving speed value | V (Δt) |. In the measuring apparatus 1 of the present invention, the speed measurement operation described above is repeatedly performed at a predetermined time interval, so that the temporal change state of the speed of the measured object 23 can be examined.

The structure of the first spatial light modulator 5 will be specifically described below. FIG. 1B is a cross-sectional view showing the configuration of the first ferroelectric liquid crystal spatial light modulator 5. A ferroelectric liquid crystal layer (hereinafter referred to as “liquid crystal layer”) 5F is provided between the pair of alignment layers 5E and 5G. A dielectric mirror 5D is provided on the side of the alignment layer 5E opposite to the liquid crystal layer 5F.
An amorphous silicon layer (hereinafter referred to as “α-Si layer”) 5C, a writing side transparent electrode (hereinafter referred to as “electrode”) 5B, and a glass layer 5A are provided. Also,
On the side of the alignment layer 5G opposite to the liquid crystal layer 5F, a read side transparent electrode (hereinafter referred to as "electrode") 5H, a glass layer 5I, and an antireflection film 5J are provided. The liquid crystal layer 5F is a chiral smectic C (S _c ^* ) liquid crystal. The α-Si layer 5C is a photoconductor layer and functions as an address material. The glass layer 5A defines the writing side light incident surface 5S _w , and the antireflection film 5J defines the reading side light incident surface 5S _r . Between the pair of electrodes 5B and 5H, as will be described later, the optical modulator controller 19 is provided.
Applies the drive voltages V _w and V _e for writing and erasing and the compensation voltages V _wc and V _ec in pulses. Further, as shown in FIG. 1A, a light emitting diode (LED) 6 is provided so as to illuminate the entire writing side light incident surface 5S _w of the first optical modulator 5, and the liquid crystal layer 5F is already provided with the light emitting diode (LED) 6. It is used to erase the recorded image. Although the configuration of the first spatial light modulator 5 has been described above, the second spatial light modulator 13 also has the same configuration as the first spatial light modulator 5,
The optical modulator controller 19 has its electrodes 13B and 13B
The applied voltage between H is controlled. Further, as shown in FIG. 1A, a light emitting diode (LED) 14 for recording / erasing is also provided.

The operations of the first and second spatial light modulators 5 and 13, the light emitting diodes 6 and 14, and the light modulator controller 19 having such a configuration will be specifically described below. FIG. 1C shows the measurement operation timing of the moving speed of the measured object 23 described above. First, the light emitting diode 6
Of the erasing compensation voltage V _ec between the electrodes 5B and 5H while illuminating the light incident surface 5S _w of the first spatial light modulator 5 with
And the erasing drive voltage V _e are applied in this order for the same time. As a result, the image recorded in the spatial light modulator 5 in the previous measurement is erased. The compensation voltage V
_ec and the driving voltage V _e is the opposite polarity to each other. next,
Between the electrodes 5B and 5H, the compensating voltage for writing V _wc and the driving voltage for writing V _w are also equal to each other,
Add in this order. The polarity of the write drive voltage V _w is opposite to that of the erase drive voltage V _e , and
The compensation voltage V _wc and the drive voltage V _w have opposite polarities. During the application of the write drive voltage V _w , the LD2
Irradiates the measured object 23 with laser light twice at the irradiation time interval Δt, thereby double recording the first and second speckle patterns on the spatial light modulator 5. More specifically, when the first and second speckle patterns are incident on the incident surface 5S _w , a region of the α-Si layer 5C on which the speckles (bright spots) of the speckle pattern are incident. , Low resistance. As a result, the liquid crystal layer 5
Since an electric field equal to or higher than the threshold electric field peculiar to the liquid crystal is applied to the region of F corresponding to the speckle, the alignment state of the liquid crystal molecules is changed and the first and second speckle patterns are recorded. It is. At the same time as applying the voltage V _wc · V _w to the first spatial light modulator 5, the second optical modulator 1
While irradiating the light of the light-emitting diode 14 to 3, the compensation voltage V _ec for erasing and the driving voltage V _e are applied to erase the image recorded in the previous measurement. At the same time when the writing of the speckle pattern to the first spatial light modulator 5 is completed,
A write compensation voltage V _wc and a write drive voltage V _w are sequentially applied between the voltages 13B and 13H of the second spatial light modulator 13 to read out a read light pattern (Young Interference fringes) are recorded in the spatial light modulator 13. Simultaneously with this recording, the Young's interference fringes are read out, and a diffracted light spot showing the correlation between the first and second speckle patterns is imaged on the PSD 16. In this way, the moving amount | S (Δt) | of the measured object 23 when the irradiation time interval Δt is taken at a certain time T is measured, and as a result, the moving speed V = | S at the time T is measured.
(Δt) | / Δt is obtained. Next, at time T ′, by performing the same operation, the irradiation time interval Δ
The amount of movement | S (Δt) |
The moving speed V ′ at is calculated. Thus, the moving speeds V, V ', at time T, T', T ", ...
As a result of sequentially obtaining V ″, ..., It is possible to check the temporal change state of the velocity of the measured object 23. In the above measurement operation, the compensation voltage V _wc · is applied to the spatial light modulator.
The reason why V _ec is applied is to prevent deterioration of the liquid crystal layer.

The ferroelectric liquid crystal spatial light modulators 5 and 13 used in this embodiment 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. Further, the semiconductor position detecting element 16 used in this embodiment can directly detect the position of the center of gravity (center of intensity) of the light flux. Therefore, when measuring the peak position of the diffracted light, the peak position can be directly measured without performing scanning of the intensity distribution, comparison calculation, or the like. Therefore, it is possible to perform an operation that follows the operation of the ferroelectric liquid crystal spatial light modulator having a high response speed.

By the way, the first and second mirror angles θ
_{When the} measurement is performed after controlling ₁ and θ ₂ at appropriate values, only the first-order diffracted light enters the light incident surface 16S of the PSD 16 as shown in FIG. 2A. Therefore, the PSD1
6 is the barycentric position S _x1 of the light spot of the first-order diffracted light (that is,
Since the distance of the peak position) from the origin S _x0 can be detected as the X value, accurate measurement can be performed. However, the moving speed of the object to be measured | V (Δt) |
(Consequently, even if the moving distance | S (Δt) |) is small, if the mirror angles θ ₁ and θ ₂ are not properly controlled, the light incident surface 16S will have a light beam as shown in FIG. 3A. Not only the first-order diffracted light but also the second-order diffracted light, the third-order diffracted light, ... This is because the inter-light spot distance | N (Δt) | becomes remarkably small, as is clear from the equations 1 and 2. In this case, the PSD 16 detects the barycentric position S _x of the positions S _x1 , S _x2 , ... Of all the incident light spots, so that accurate measurement cannot be performed. Conversely, | V (Δt) | (and thus | S (Δt) |)
However, when the measurement is performed without properly controlling the mirror angles θ ₁ and θ ₂ , the diffracted light spots are not formed on the light incident surface 16S as shown in FIG. 3B. It will not be imaged and you will not be able to make accurate measurements. ｜ N (△ t) ｜
Is significantly increased.

Therefore, in the measuring apparatus 1 of the present invention, the mirror angles θ ₁ and θ ₂ are set to the light incident surface 16S only for the first-order diffracted light.
The velocity is measured while controlling the optimum angle values (hereinafter, referred to as “mirror optimum angle value”) Θ ₁ and Θ ₂ that can be incident on. That is, in the present measuring apparatus 1, immediately before performing a series of measurements for examining the temporal change state of the velocity of the measured object 23, the mirror optimum angle determination operation shown in FIG. Mirror optimum angle value Θ ₁ ,
Determine Θ ₂ . After that, the mirror 3 is set at the angle values Θ ₁ and Θ _2.
A series of measurements is performed while controlling the, and accurate measurements are always possible.

In order to enable such a mirror optimum angle value determination operation, the measuring apparatus 1 of the present invention has a structure shown in FIGS.
As shown in B, the PSD 16 is arranged so that the predetermined distance d is sufficiently smaller than the length X _max of the light incident surface 16S of the PSD 16 in the X direction. With such an arrangement, when the PSD 16 detects the value 0 as the X value, it becomes only when no diffracted light spot is incident on the light incident surface 16S as shown in FIG. 3B. Also, the P
A comparator 17 is connected to SD16. This is because, in the main search D ^m of each time m (m = 1, 2, ...), which will be described later, the X ^m value detected at that time is detected in the main search D ^m-1 of the previous m−1. X ^m-1 value and the comparison signal R ^m indicating the comparison result is output to the arithmetic and control unit 18. That is, in the case of X ^m> X ^m-1 outputs a positive comparison signal R ^m, in the case of X ^m = X ^m-1 is
The comparison signal R ^{m of} 0 is output, and when X ^m <X ^m−1 , the negative comparison signal R ^m is output.

Hereinafter, the mirror optimum angle value determination operation performed by the measuring apparatus 1 of the present invention will be described with reference to FIG. In addition,
The operation of determining the optimum mirror angle value is performed by the calculation / control device 18
Under the control of. The determination operation is roughly divided into the preliminary search operation D ⁰ and the main search operation D ^m as described later.
Of these, the search operation is the same as the speed measurement operation of the main measurement apparatus 1 described above.

In the mirror optimum angle value determination operation, as shown in FIG. 4, first, a preliminary search D ⁰ is performed (step S).
1). In the preliminary search D ⁰ , the arithmetic / control device 18
The LD 2 is controlled via the LD controller 20 so that the laser beam is irradiated twice with a predetermined time interval Δt.
Irradiate 3 The arithmetic / control device 18 also controls the first and second rotational angular positions θ ⁰ ₁ and θ ⁰ ₂ of the flat mirror 3b to be equal to each other via the mirror controller 21 (θ ⁰ _1). = Θ ⁰ ₂ ). The arithmetic / control device 1
8 also controls the spatial light modulators 5 and 13 via the light modulator controller 19 to form diffracted light on the image-side focal plane 15F. The PSD16
Detects the barycentric position of the diffracted light and outputs the X value (X ⁰ ) indicating the barycentric position to the arithmetic and control unit 18. The calculation
The control device 18 uses the detected value X ⁰ as the rotational angular position θ ^0.
_It is stored in the storage area together with the values of ₁ and θ ⁰ ₂ (step S2).

Next, the arithmetic / control device 18 determines whether or not the detected value X ⁰ is 0 (step S3). When X ⁰ = 0, it is determined that the moving distance | S (Δt) | is too large and no diffracted light spot is incident on the light incident surface 16S. Therefore, in steps S4, S5, and S6 described later, |
S (Δt) | The main search D ^m (m = 1, while changing the mirror angle values θ ₁ and θ ₂ so as to be apparently sequentially decreased.
2, ...) are repeated to find optimum mirror angle values Θ ₁ and Θ ₂ that allow only the first-order diffracted light to be incident on the light incident surface 16S. On the other hand, in the case of X ⁰ ≠ 0, it is unknown whether only the first-order diffracted light spot is incident or other diffracted light spots are also incident. Therefore, step S described later
In 8, 9, and 10, the main search D ^m is repeated while changing the mirror angle values θ ₁ and θ ₂ so that the moving distance | S (Δt) | is apparently sequentially increased. Only the optimum mirror angle values Θ ₁ and Θ ₂ that can make only the incident light incident on the light incident surface 16S are searched.

The operation of each of X ⁰ = 0 and X ⁰ ≠ 0 will be described in more detail below. X ⁰ = 0
In the case of, the arithmetic and control unit 18 adjusts the first and second angle values θ ¹ ₁ and θ ¹ ₂ of the mirror 3 so that θ ¹ ₂ <θ ¹ _1. The first main search D ¹ is performed (step S4). That is, in the main search D ^1, an angular difference _{^{△ θ 1 = θ 1 1 -θ}} 1 2, adopted angular difference in the previous search (preliminary search ^{D 0) △ θ 0 (=} θ 0 1 -θ 0 2 = 0), and then | S (Δt) | is apparently made smaller before measurement. The main search D ¹
Also in the above, the laser light is emitted twice at the predetermined time interval Δt. The PSD 16 outputs the detection result X value (X ¹ ). Further, the comparator 17 compares the X ¹ value with the X ⁰ value and outputs a comparison signal R ¹ which is either plus, minus or 0. The arithmetic and control unit 18, the X ¹ value and the signal R ^1, the angle value theta ¹ _1, with theta ¹ _2, and stores in its storage area (step S5). Then, in the arithmetic / control device 18, the PSD 16 outputs (X _max -d) /
The main search is repeated until the output of 2 is detected (step S6). In such a repeated main search, the angle difference Δθ = θ ₁ −θ ₂ is sequentially increased,
The movement distance of the object to be measured is sequentially reduced while apparently decreasing. That is, in the m-th (m = 1, 2, ...) Main search D ^m , the angular difference Δθ ^m1 = of the first and second angular positions θ ^m ₁ and θ ^m ₂ of the mirror 3. θ ^m ₁ −θ ^m ₂ is the angular difference Δθ adopted in the previous (m-1) main search D ^m-1.
It is adjusted to be larger than ^m-1 (= θ ^m-1 ₁ −θ ^m-1 ₂ ) by the predetermined amount. The time intervals of laser light irradiation are all the predetermined time intervals Δt.

FIG. 5 is an example showing how the detected value X ^m changes as a result of the repeated main search D ^m . First, in the preliminary search D ⁰ , since the first-order diffracted light is not incident on the light incident surface 16S, X ⁰ =
0. After that, the main search is repeated while reducing the apparent movement distance of the measured object. While the first-order diffracted light is not incident on the light incident surface 16S (the period shown in the figure), the detection value X remains 0, and the comparator 17 continues to output the comparison signal R of 0. However, if the main search is further continued, a certain search (Mth main search D ^M : in the figure)
Then, since the first-order diffracted light first enters the light incident surface 16S, the detected value X has a positive value, and the comparator 17 outputs a positive comparison signal R ^M. When the main search is further continued, the position of the first-order diffracted light gradually becomes the origin 1
Since it approaches 6S _x0 (period in the figure), the detected value X
It gradually becomes smaller, and the X value (X ^N ) of (X _max −d) / 2 is detected in the N-th main search ^DN (in the figure). During this period, the comparator 17 continues to output the negative comparison signal R.

The computing / controlling device 18 thus operates in the manner of (X
Where X (X ^N ) with a value of _max −d) / 2 is detected,
The main search ends (step S6). Then, the calculation
The controller 18 determines that the value of this (X _max -d) / 2 is X.
The mirror angle values θ ^N ₁ and θ ^N ₂ used in the main search D ^N at the time when (X ^N ) is detected (N-th time) are used as mirror optimum angle values Θ.
₁ and Θ ₂ are determined (step S7). Where (X _max
-D) / 2 mirror angle values θ ^N ₁ and θ ^N ₂ when detected
The reason for selecting is for the following reasons. That is, the distance d
Is sufficiently smaller than X _max , so (X _max −d) / 2 is X
Almost equal to _max / 2. Therefore, if the mirror 3 is controlled by the angles θ ^N ₁ and θ ^N ₂ , only the primary light can be made incident on the PSD light incident surface 16S, or almost at the center thereof. This is because the PSD has high detection accuracy in the central portion of the light incident surface, and therefore high-precision detection can be realized by controlling the mirror angles θ ^N ₁ and θ ^N ₂ .

Incidentally, the main search may be repeated as it is without terminating the main search when the value of (X _max -d) / 2 is detected. In this case, as shown in FIG. 5, the main search (N + 1th main search) performed immediately after the main search (Nth main search ^DN ) when (X _max −d) / 2 is detected. D ^{N + 1} : (in the figure), the secondary light enters the light incident surface, so that the X value suddenly increases and the comparator 1
7 outputs a positive signal R ^{N + 1} . Therefore, from the main search in which the positive comparison signal is detected at the first time (main search D ^{M in the} figure), the main search in which the positive comparison signal is detected at the second time (main search D ^{N + 1 in the} figure) It can be seen that only the first-order diffracted light was incident on the light incident surface 16S until the main search (the main search D ^{N in the} figure) one time before. Therefore,
Among the X values detected in the main search (M to N main searches) during this period, the X having the smallest difference from X _max / 2 is selected, and the mirror angles θ ₁ and θ ₂ used at that time are selected. May be determined as the optimum values Θ ₁ and Θ ₂ .

On the other hand, when X ⁰ ≠ 0, the arithmetic and control unit 18 sets the angle values θ ¹ ₁ and θ ¹ ₂ of the mirror 3 to θ.
^After adjusting so that ¹ ₂ > θ ¹ ₁ , the first main search D ¹ is performed (step S8 in FIG. 4). That is, in the main search D ^1, the angular difference _{^{- △ θ 1 = θ 1 2}} -θ 1 1 ( wherein, - △
θ ¹ is a positive value) is adjusted to be larger than the angle difference −Δθ ⁰ (= θ ⁰ ₂ −θ ⁰ ₁ = 0) adopted in the previous search (preliminary search D ⁰ ) by a predetermined amount, | S (Δt) | Also in the main search D ¹ , the laser light is emitted twice at the predetermined time interval Δt. The PSD 16 outputs a detection value X (X ¹ ), and the comparator 17 compares the X ¹ value with the X ⁰ value to obtain a comparison signal R
Output ¹ The arithmetic and control unit 18, the X ¹ value and the signal R ^1, the angle value theta ¹ _1, with theta ¹ _2, and stores in its storage area (step S9). Then, the arithmetic / control device 18 performs the main search until the PSD 16 outputs the X value of (X _max -d) / 2 and the comparator 17 outputs the negative comparison signal. The main search D ^{m is} repeated (step S10). In the repetitive main search, the angular difference −Δθ = θ ₂ −θ ₁ (−Δθ is a positive value) is sequentially increased to apparently increase the moving distance of the measured object. That is, the m-th time (m = 1,
2, ...) In the main search D ^m , the angular difference between the first and second angular positions θ ^m ₁ and θ ^m ₂ of the mirror 3 −Δθ ^m = θ ^m
₂₋ θ ^m ₁ is the predetermined amount from the angle difference −Δθ ^m-1 (= θ ^m-1 ₂ −θ ^m-1 ₁ ) used in the previous (m−1) main search D ^m-1. Adjust so that it becomes larger. The time intervals of laser light irradiation are all the predetermined time intervals Δt.

FIG. 6 is an example showing how the detected value X ^m changes as a result of the repeated main search D ^m . First, in the preliminary search D ⁰ , not only the first-order diffracted light but also the second-order diffracted light and the third-order diffracted light are incident on the light incident surface 1.
Since it is incident on 6S, X ⁰ indicating the barycentric position of all of these three diffracted light spots is detected. When the actual search is started and the apparent movement distance of the object to be measured is increased (the period shown in the figure), the diffracted light spot is in the right direction as a whole (direction away from the origin 16S _x0 ). Therefore, the comparator 17 continues to output the positive comparison signal R. However, if the main search is further continued, in a certain number of main searches (M main searches D ^M : in the figure), the tertiary light deviates from the light incident surface 16S and does not enter. As a result, the detected value X ^M suddenly decreases, and the comparator 17 outputs a negative comparison signal R ^M. When the main search is further continued (in the period shown in the figure), the two diffracted light spots are sequentially shifted rightward as a whole, so that the comparator 17 continues to output the positive comparison signal R. However, if the main search is further continued, in a certain number of main searches (N times of main searches D ^N : in the figure), the secondary light does not deviate from the light incident surface 16S, and the PSD becomes the primary Center of gravity of light only (1
( _Xmax- d) / 2, which is the peak position of the next light, is detected. Further, the comparator 17 outputs a negative comparison signal R ^N. As described above, when (X _max -d) / 2 is detected as the X value and the negative comparison signal is detected, the main search is terminated (step S10). The calculation
The controller 18 determines that the value of this (X _max -d) / 2 is X.
The mirror angle values θ ^N ₁ and θ ^N ₂ used in the main search D ^N at which (X ^N ) is detected (N times) are determined as mirror optimum angle values Θ ₁ and Θ ₂ (step S11). . In addition, (X
_The main search may be repeated after the negative comparison signal of _max −d) / 2 is detected. In this case, as shown in FIG. 6, the first-order diffracted light shifts to the right, so that the comparator 17 continues to output a positive comparison signal (period in the figure). However, in a certain time (L-th) main search D ^L , the primary light also deviates from the light incident surface 16S, and the X ^L value 0 is detected, and the comparator 1
7 outputs a negative comparison signal R ^L. Therefore,
Finally, the main search (L-1th main search ^DL-1 ) before the main search (L-th main search ^DL : in the figure) in which a negative comparison signal is detected, and immediately before that It can be seen that only the first-order diffracted light was incident on the light incident surface 16S during the main search (N-th main search D ^N : in the figure) in which the comparison signal was detected. Therefore, during this period (from the Nth time, L-1
The mirror angle values θ ₁ and θ ₂ used when the value closest to X _max / 2 among the X values obtained in the second main search) are determined as the optimum mirror angle values Θ ₁ and Θ _2. You may.

In this way, the optimum angles Θ ₁ and Θ ₂ for making only the first-order diffracted light incident on the light incident surface 16S are obtained. The measuring apparatus 1 of the present invention immediately starts a series of measuring operations for investigating the temporal change state of the velocity when the mirror optimum angle value determining operation is completed. In each operation of the series of measurement operations, the mirror 3 is controlled by the optimum angle values θ ^N ₁ and θ ^N ₂ (Θ ₁ , Θ ₂ ) to perform measurement. That is, while irradiating the laser light twice with the predetermined time interval Δt, the mirror is controlled by the angle values θ ^N ₁ and θ ^N ₂ . Then, from the detected X value, the velocity V is calculated from the above-mentioned formulas 1 to 4. In each measurement operation, since the mirror is controlled by the mirror optimum angle value, it is ensured that only the first-order diffracted light is incident on the light incident surface, and accurate measurement can be performed. Further, according to the present invention, since each measurement constituting the series of measurements can be performed in an extremely short time, the state of the time change of the velocity of the measured object can be measured at an extremely short time interval. can do.

Further, in such a series of velocity measurement,
If the laser irradiation time interval Δt is changed in accordance with the change in the velocity of the object 23 to be measured, the first-order diffracted light is emitted from the light incident surface 16
It is possible to always keep the light incident near the center of S. That is, if the speed is increasing, Δt may be decreased, and conversely, if the speed is decreasing, Δt is decreased.
It is only necessary to increase t. With this adjustment, P
It is possible to maintain the detection accuracy of SD16, and thus the accuracy of the measurement device 1, at a high level. This irradiation time interval Δ
The adjustment of t will be described in detail below. In each speed measurement of the series of speed measurements, the arithmetic / control device 18
Feedback-controls the irradiation time interval Δt in the next measurement based on the result of the speed measurement performed up to that time so that the first-order diffracted light is always imaged on the central portion of the PSD light incident surface 16S. be able to. Specifically, the arithmetic / control device 18 adjusts the irradiation time interval Δt of the LD 2 via the LD controller 20. On this occasion,
The arithmetic / control device 18 obtains the state of the temporal change in speed based on the measurement result V obtained by the measurement up to this time (measurement time T), and calculates the speed V ′ at the next measurement (measurement time T ′). Predict the value of. Then, when it is predicted that this value V ′ is larger than the current speed V, the next irradiation time interval Δt ′ is reduced by an appropriate amount with respect to the previous time interval Δt. On the contrary, when V ′ is predicted to be smaller than V, Δt ′ is made larger than Δt by an appropriate amount. In this way, the distance between light spots | N (Δt ′) | The irradiation time interval Δ in the next measurement
As a method of adjusting t ′ based on the measurement results up to this time, the following method may be used in addition to the above method. That is, when the velocity of the object to be measured suddenly increases to V at the measurement at a certain time T, the velocity V ′ at the next measurement time T ′ is expected to be equal to or higher than V, and Δt ′ Is adjusted to be smaller than Δt. When the velocity of the measuring object suddenly decreases, Δt ′ is changed to Δt
You may make it adjust larger. Further, when adjusting Δt ′ in the next measurement, this may not be adjusted based on the measurement result up to this time, but may be adjusted based on the measurement result up to the previous time or the previous two times. Adjustments may be made based on the results of measurements already made. The arithmetic / control device 18 also controls the optical modulator controller 19 in addition to adjusting the irradiation time interval Δt to adjust the voltage application timing of the spatial light modulators 5 and 13.

The comparator 17 is, for example,
The comparison circuit shown in FIG. 7 may be used. Such a comparison circuit 1
Reference numeral 7 denotes a sample hold circuit 111, an operational amplifier circuit 112, fixed resistors 113 and 114 of 1 kΩ, and 10
It comprises a variable resistor 115 having a resistance of 0 kΩ. The comparator 17
Is the PS in any number ((m-1)) of main searches.
The voltage signal X ^m-1 output by D16 is sampled and held, and compared with the voltage signal X ^m output by the PSD 16 in the next (m times) main search, and a comparison signal R ^m is output. Therefore, the comparator 17 outputs a positive value signal R ^m if X ^m > X ^m−1 , and outputs a negative value signal R ^m if X ^m <X ^m−1. Then, if X ^m = X ^m-1 , the signal R ^m having a value of 0 is output. The comparator 17 may also be arranged in the arithmetic and control unit 18.

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

The method for determining the optimum mirror angle performed by the measuring apparatus of the present invention is not limited to the method shown in FIG. The measurement is repeated while changing the angle values θ ₁ and θ ₂ of the mirror, and the optimum mirror angle value Θ ₁ ,
All that is required is to determine Θ ₂ . Further, the mirror optimum angle determination operation may be treated as the first measurement operation of the series of speed measurement operations. That is, the optimum angle values Θ ₁ , Θ ₂
Based on the X value detected in the main search using
It is also possible to calculate Δt | and use this as the first measurement value of the series of speed measurements.

In the above-described embodiment, the optimum mirror angle value for making only the primary light incident on the light incident surface 16S is determined, and a series of speed measurement is performed based on this.
However, not only the angle of the mirror but also the optimum value of the laser light irradiation time interval Δt may be determined, and the speed may be measured based on the optimum values of the mirror angle and the light irradiation time interval. Further, also in the series of speed measurement operations, not only Δt but also the mirror angle value is adjusted so that the primary light always enters near the center of the light incident surface to maintain highly accurate detection. You may do it. Also, in the above embodiment,
Although the deflection angle of the galvanometer mirror 3 is adjusted to the optimum value so that only the primary light is incident on the light incident surface 16S, the present invention is not limited to this. Instead of a galvanometer mirror, an acousto-optic deflector in which the ultrasonic wave propagation direction is arranged to be parallel to the moving direction of the object to be measured 23, an electro-optic deflector, a polygon mirror, etc. are provided, and these deflection angles are optimized You may adjust to the value. Also, instead of such a deflection means,
A means for changing the image forming magnification of the speckle pattern on the first spatial light modulator 5 is provided, and only the primary light is made incident on the light incident surface by adjusting the image forming magnification to an optimum value. May be. That is, instead of the galvanometer mirror 3 and the imaging lens 4, a zoom lens system may be provided and the magnification may be adjusted to an optimum value. Even if the magnification of the zoom lens system is changed, the shift distance | M for the moving distance | S (Δt) |
This is because (Δt) | can be changed arbitrarily. Further, instead of the zoom lens system, a variable focus lens may be provided and the focal length may be adjusted to an optimum value. Further, the focal lengths of the Fourier transform lenses 12 and / or 15 may be adjusted to optimal values. By adjusting the focal length of the lenses 12 and 15, the moving distance | S (Δt) |
This is because it is possible to arbitrarily change the distance | N (Δt) | In any case,
According to the present invention, the distance | N (Δt) | between the diffracted light spots is set to an optimum value such that only the first-order light is incident on the light incident surface 16S. Is possible.

The arithmetic and control unit 18 can obtain not only the moving amount and moving speed but also the moving direction. That is, since the moving direction of the object to be measured 23 and the direction in which the diffracted light is arranged have a fixed relationship, the moving direction of the object to be measured is also changed by adopting a two-dimensional semiconductor position detecting element as the PSD 16. You can ask.

In the above-described embodiment, the measuring device is fixed and the object to be measured moves, but conversely, the measuring device may move 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 measured object and check 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 object to be measured may be irradiated with incoherent light instead of coherent light such as laser light. In this case, not the speckle pattern but the image of the measured object is recorded in the spatial light modulator. Young's interference fringes can be obtained by double recording the images of the object to be measured at the first and second irradiation times in the first spatial light modulator and reading the double recorded image and performing Fourier transform. This is because the diffracted light can be obtained by recording this in the second spatial light modulator and further 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 object to be measured 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, in the above-mentioned embodiment, the object to be measured is irradiated with light, and the displacement amount of the object is measured by the reflected light pattern, but depending on the type of the object to be measured, the transmitted light pattern may be measured. Good. That is, the image or speckle pattern formed on the transmitted light of the object to be measured may be double recorded on the spatial light modulator. 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 4 and the first spatial light modulator 5. May be provided to increase the light intensity of the pattern, and then the light may be incident on the writing incident surface S _w of the first spatial light modulator 5.

[0037]

As is clear from the above description,
In the optical displacement measuring device of the present invention, 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 unit 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 out the double-recorded image of the first recording unit. Said read Heading was double recording images, the first Fourier transform means Fourier transform, Young
Form a first Fourier transform image composed of interference fringes . 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 performs Fourier transform on the read first Fourier transform image to form a second Fourier transform image composed of a plurality of diffracted light spots . Adjusting means adjusts the distance between the plurality of diffracted light points
By doing so, only the first-order diffracted light point
It is incident on the output means . Then, the light center of gravity position detection means
By detecting the barycentric position of the first-order diffracted light point in the second Fourier transform image, the relative displacement amount of the measured object with respect to the optical displacement amount measuring device during the second measurement time is determined. Ask. As described above, according to the present invention, in order to detect the barycentric position of the second Fourier transform image, scanning and complicated correlation calculation are unnecessary, and the measurement can be performed in a short time. For this reason, it is excellent in real-time measurement. According to the present invention, the adjusting means can arbitrarily adjust the position of the second Fourier transform image. Therefore, the displacement amount can be measured regardless of the displacement amount of the object to be measured between the two measurement times, and the dynamic range can be widened. Further, since the second Fourier transform image can be positioned in a region of the optical barycentric position detecting means with high detection accuracy, the detection error can be reduced and the measurement accuracy can be improved.

[Brief description of drawings]

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

FIG. 1B is an enlarged cross-sectional view of the ferroelectric liquid crystal spatial light modulator of FIG. 1A.

FIG. 1C is an operation timing chart of a speed measurement operation of the optical moving speed measurement device of FIG. 1A.

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

FIG. 2B is a top view illustrating the positional relationship between the PSD 16 and the lens 15 in FIG. 1A.

FIG. 3A is a front explanatory view showing the position of the diffracted light with respect to the PSD 16 when the moving distance | S (Δt) | of the object to be measured is small.

FIG. 3B is a front explanatory view showing the position of the diffracted light with respect to the PSD 16 when the moving distance | S (Δt) | of the object to be measured is large.

FIG. 4 is a flowchart showing a mirror optimum angle value determination method performed in the optical movement velocity measuring apparatus according to the embodiment of the present invention.

FIG. 5 shows a case where the main search is repeatedly performed while apparently reducing the moving distance | S (Δt) |
The position of the diffracted light spot imaged on the PSD 16 and the PSD 1
6 shows a state in which the detected value X of 6 is changing.

FIG. 6 shows a case where the main search is repeatedly performed while apparently increasing the moving distance | S (Δt) | of the object to be measured,
The position of the diffracted light spot imaged on the PSD 16 and the PSD 1
6 shows a state in which the detected value X of 6 is changing.

FIG. 7 is a circuit diagram showing a specific configuration of a comparator 17.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical movement velocity measuring device 2 Laser diode 3 Galvano mirror 5 Ferroelectric liquid crystal spatial light modulator 7 He-Ne laser device 12 Fourier transform lens 13 Ferroelectric liquid crystal spatial light modulator 15 Fourier transform lens 16 Semiconductor position detecting element 18 Arithmetic / control device 21 Mirror controller

Claims (6)

[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 A first Fourier transform means for Fourier transforming the recorded image to form a first Fourier transform image composed of Young's interference fringes; and a second recording means for recording the first Fourier transform image. , Second coherent light projecting means for irradiating the second recording means with coherent light to read out the first Fourier transform image, and Fourier transforming the read first Fourier transform image Second Fourier transform image consisting of multiple diffracted light spots And a second Fourier transform means for forming the position of the center of gravity of the first-order diffracted light point in the second Fourier transform image, and the relative displacement of the measured object between the two measurement times. An optical barycentric position detecting means for determining the quantity and an adjusting means for adjusting the distance between the plurality of diffracted light points to allow only the first-order diffracted light point to enter the optical barycentric position detection means are provided. The optical displacement measuring device according to the above. 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. The optical displacement amount measuring device according to claim 1, wherein the optical displacement amount is recorded. 3. The light center of gravity position detecting means comprises a semiconductor position detecting element having a light incident surface, and the adjusting means adjusts the distance between the plurality of diffracted light points.
The optical displacement amount measuring device according to claim 1, wherein only the second-order diffracted light point is made incident on the light incident surface. 4. The adjusting means relatively adjusts the position of the image of the object to be measured at the second measurement time so that only the first-order diffracted light point is made incident on the light incident surface. The optical displacement amount measuring device according to claim 3. 5. The adjusting means comprises a deflecting means for deflecting the image of the object to be measured at the second measurement time, and by adjusting the deflection direction of the deflecting means at the second measurement time, Adjusting the relative position of the image of the object to be measured when double-recorded on the first recording means,
The optical displacement amount measuring device according to claim 4, wherein only the first-order diffracted light spot is made incident on the light incident surface. 6. The optical displacement amount measuring device according to claim 3, wherein the adjusting means further comprises means for adjusting a time interval between the second measurement times.