JP3375413B2 - 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 a displacement amount measuring device for optically measuring the displacement amount of an object to be measured.

[0002]

2. Description of the Related Art A technique for optically measuring a displacement amount of an object to be measured has been studied so far in the form of double exposure image and its fringe analysis. The measurement principle is, for example, that a double exposure image of a fluid to be measured is taken, and how much the same pattern stored in the image moves is processed at high speed by a fringe analysis method (Fourier transform). To do.

For example, Japanese Patent Application Laid-Open No. 4-204312 proposes an optical displacement amount measuring device using two spatial light modulators in order to increase the speed by using optical calculation.
The proposed mechanism uses an optical modulator (FLC) with recording characteristics.
-SLM: Ferroelectric liquid crystal spatial light modulator) is used to realize double exposure, and fringe analysis of the obtained double-exposure image is performed using optical Fourier transform. .

[0004]

In order to realize such an apparatus, conventionally, in order to doubly expose an input image, the multiple memory function of the spatial light modulator is used. However, the spatial light modulator having such a function is extremely expensive, and the number of spatial light modulators having this function is small, which is not practical.

On the other hand, the measurement range of such a displacement amount measuring device is determined by the exposure time and the double exposure interval. That is, in the conventional measuring device, the shutter time of the SLM (the response time of the SLM = about 100 μsec) determines the upper limit of the measurement range.

[0006] For example, when measuring the blood flow velocity using a microscope, if the magnification of the microscope is set to about 40 times for proper observation, the blood flow velocity in the vicinity of the heart is 5 m / s. The blood flow velocity is 200 m / s on the image picked up by, and it moves at an extremely high velocity.

Therefore, the response time of the SLM is 100 μsec.
In this case, the shutter interval needs to be set to 200 μsec or more. An object moving at 200 m / s is
When double exposure is performed for sec, the amount of movement of the image is 200 (m / s) × 0.2 × 10 ⁻³ (s) = 40 (m
m). In other words, the two images have a positional relationship of 40 mm apart, but the size of the input surface of the SLM is 18 mm x 18 mm.
Therefore, this double exposure image cannot be obtained in the input screen of the SLM. Therefore, it is impossible to measure the velocity of this blood flow. In other words, the range that can be measured under this condition is a moving speed of about 9 mm (half the effective area) during 200 μsec, and V (speed) = 9 mm × 40 (magnification) / 200 (μse
c) = 1.8 m / s. The measurement range can be expanded by lowering the magnification,
The particle size of the target becomes smaller than the resolution of the SLM and the measurement area is widened, so that the shape of the correlation peak is widened when the velocity distribution has a distribution, which causes a problem that the detection accuracy is lowered.

The present invention has been made to solve such a problem, and its purpose is to set the range of the light intensity of the object to be measured and the allowable range of the measured displacement amount and speed of the object to be measured.
An object of the present invention is to provide a displacement amount measuring device which is larger than a conventional device.

[0009]

Therefore, a displacement amount measuring apparatus according to a first aspect of the present invention comprises a double exposure section having a photocathode and a fluorescent surface, and a control section for controlling a time interval of the double exposure. The double exposure image is optically Fourier-transformed to obtain a correlation peak image, and a correlation amount calculation unit for detecting the correlation peak image to obtain a displacement amount of the double exposure image is configured. . The control unit controls the voltage applied to the photocathode to control the time interval of double exposure on the phosphor screen and the exposure time of each exposure. Under the control of this control unit, the double exposure unit accumulates the image of the moving object on the phosphor screen to form a double exposure image of the moving object.

A displacement amount measuring apparatus according to a third aspect of the present invention is a double exposure unit having a photocathode, a microchannel plate and a fluorescent screen, a time interval of double exposure in the double exposure unit and an exposure time of each exposure. A control unit for controlling, a correlation calculation unit for optically Fourier transforming the obtained double exposure image to obtain a correlation peak image, and a displacement amount calculation unit for obtaining the displacement amount of the double exposure image from this correlation peak image. And is configured. The control unit controls at least one of the voltage applied to the photocathode and the voltage applied to the microchannel plate to control the double exposure time interval and the exposure time of each exposure on the phosphor screen. Under the control of this control unit, the double exposure unit accumulates the image of the moving object on the phosphor screen to form a double exposure image of the moving object.

The correlation calculation unit of the displacement amount measuring device according to the first and third aspects includes a first light modulating unit for converting a double exposure image obtained from the double exposure unit into a coherent image, and the first light modulating unit. A first Fourier transform optical system that performs a Fourier transform on a coherent image obtained from the modulator, a second light modulator that converts an intensity image Fourier-transformed by the first Fourier transform optical system into a coherent image, and the second light The second coherent image obtained from the modulation means may be Fourier-transformed to obtain a correlation peak image by the second Fourier-transform optical system.

A displacement amount measuring device according to a fifth aspect of the present invention includes a double exposure unit having a photocathode, a fluorescent screen and an image pickup means, and a control unit for controlling a time interval of the double exposure and an exposure time of each exposure. A display unit for displaying the double-exposure image captured by the image-capturing unit, a correlation calculation unit for optically Fourier transforming the double-exposure image displayed by the display unit to obtain a correlation peak image, and the correlation peak image And a displacement amount calculation unit that detects the displacement amount of the double-exposure image and detects the displacement amount. Under the control of the control unit, the double exposure unit inputs the images of the moving object before and after the displacement within the time of one frame rate of the image pickup unit, and forms the double exposure image of the moving object.

Further, a displacement amount measuring apparatus according to a seventh aspect of the present invention controls a double exposure unit having a photocathode, a microchannel plate, a fluorescent screen and an image pickup means, a time interval of double exposure and an exposure time of each exposure. A control unit, a display unit that displays the double-exposure image captured by the image-capturing unit, a Fourier transform of the double-exposure image displayed by the display unit, and a correlation calculation unit that obtains a correlation peak image; And a displacement amount calculation unit that detects the correlation peak image and obtains the displacement amount of the double exposure image. Under the control of the control unit, the double exposure unit inputs the images of the moving object before and after the displacement within the time of one frame rate of the image pickup means, and forms the double exposure image of the moving object.

The correlation calculation unit of the displacement amount measuring device according to the fifth and seventh aspects includes a first light modulating unit for converting the double exposure image displayed on the display unit into a coherent image, and the first light modulating unit.
A first Fourier transform optical system that performs a Fourier transform on a coherent image obtained from the light modulator, a second light modulator that converts an intensity image Fourier-transformed by the first Fourier transform optical system into a coherent image, and a second light modulator. A second Fourier transform optical system that obtains a correlation peak image by performing Fourier transform on the coherent image obtained from the light modulation means can be configured.

[0015]

In the displacement amount measuring device according to the present invention, the photoelectrons reaching the fluorescent screen are controlled under the control of the control unit. An image intensifier having a so-called shutter function (gate function) can be used for the double exposure section, and the shutter time is about 3 × 10 ⁻⁹ seconds at minimum.
Compared to conventional SLM shutter speeds, 3 digits to 4
It will be improved by several orders of magnitude, and the measurement range will be expanded proportionally.

Further, the fluorescence lifetime of the fluorescent screen or the one frame rate of the image pickup means is utilized to store the image when forming the double exposure.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 conceptually shows the configuration of a displacement amount measuring device according to the present invention. This apparatus is a double exposure apparatus 10,
It is composed of a correlation calculation device 20 and a control device 30. The double exposure apparatus 10 is given an input image 40 of a moving object, accumulates images before and after the moving object is displaced, and forms a double exposure image of the moving object. The correlation calculation device 20 optically Fourier transforms the double exposure image obtained from the double exposure device 10 to obtain a correlation peak image. The image correlation calculation at this time is performed by repeating the Fourier transform twice. The same result can be obtained by performing two Fourier transforms of the image by the computer. The control device 30 obtains the displacement amount of the double exposure image based on the correlation peak position of the correlation image obtained by the correlation calculation device 20, and outputs it as an output signal 50 to the outside. In addition, the double exposure apparatus 1
A control signal for controlling exposure conditions such as exposure time is given to 0.

FIG. 3 shows a specific example of the configuration of the displacement amount measuring device. In this configuration example, the double exposure apparatus 10 is configured by an image intensifier as an electron tube, and the photocathode 11 and the photocathode 11 on which an image of a moving object is incident.
Microchannel plate 12 that multiplies the photoelectrons emitted from the phosphor, and a fluorescent screen 13 that converts the photoelectron image multiplied by the microchannel plate 12 into a visible light image.
Is equipped with. Not limited to visible light, but by selecting the phosphor screen,
It is possible to form an image having a wavelength that matches the input sensitivity of the subsequent processing system.

The correlation calculation device 20 has two spatial light modulators (PAL-SLM) 21 and 22. The PAL-SLM that constitutes the spatial light modulators 21 and 22 is configured by combining liquid crystal and amorphous Si, and has no image storage function (memory function), and has a simple configuration. Therefore, it is available at a relatively low cost. The response speed is about 30 msec.

Further, half mirrors 23a and 23b are provided as a reading optical system for irradiating the spatial light modulator 21 in the preceding stage with the reading light, and the reading light is directed to the spatial light modulator 22 in the succeeding stage. Half mirrors 24a and 24b are provided as a reading optical system for irradiation. In addition, the Fourier transform lenses 25 and 26 for optically Fourier transforming the read signal are provided to the respective spatial light modulators 21,
22 are arranged on the output side, respectively. Note that reference numerals 14 and 27 indicate image forming lenses, and reference numeral 28 indicates a filter.

The control device 30 is provided with a photoelectric conversion device 31 such as a photodiode for detecting a correlation peak position of a correlation image obtained by performing two Fourier transforms. Since the image is formed on the conversion device 31, the position of this bright spot is detected. Based on the detected correlation peak position, the displacement amount calculation device 31 calculates and obtains the displacement amount, speed, etc. of the double exposure image, and outputs the result to the outside. The exposure time control device 33 changes the voltage applied to the photocathode 11 to control the double exposure time interval and the exposure time in the double exposure device 10. The control of the applied voltage may be performed on the microchannel plate 12.

The operation of the displacement amount measuring device thus constructed will be described. First, in the state where the image of the moving object is formed on the photocathode 11 via the imaging lens 14,
Under the control of the exposure time controller 33, the voltage pulse applied to the photocathode 11 is applied twice. From the photocathode 11, photoelectrons are emitted twice from the part corresponding to the image of the moving object at the timing when the applied voltage pulse is applied. Photocathode 1
The two images of the moving object converted into photoelectrons in 1 are sequentially multiplied by the microchannel plate 12 and reach the phosphor screen 13. At this time, the double exposure time interval is set shorter than the fluorescent life of the fluorescent screen 13, so that two images overlap each other on the fluorescent screen 11, and a double image is obtained.
The normal fluorescence lifetime is about 0.1 msec to 10 msec, and can be arbitrarily selected. Thus, FIG.
A double exposure image as shown in (a) is obtained.

The double-exposure image formed on the photocathode 11 of the double-exposure device 10 is formed on the input surface of the spatial light modulator 21 at the preceding stage via the imaging lens 27. Here, the laser light as the reading light is incident on the output surface of the spatial light modulator 21 via the half mirrors 23a and 23b. By thus entering the laser beam, the coherent image of the double exposure image is read out. The read coherent image is sequentially transmitted through the half mirror 23b and the Fourier transform lens 25 to be subjected to Fourier transform, and the Fourier transform image is passed through the filter 28 and the spatial light modulator 22 at the subsequent stage.
Is imaged on the input surface of. The filter 28 is for removing the 0th order light. By writing the Fourier transform image in the spatial light modulator 22 in this way, it is converted into an intensity image.

Further, similarly to the former stage, the laser light as the reading light is incident on the output surface of the latter spatial light modulator 22 via the half mirrors 24a and 24b. By thus entering the laser light, the coherent image of the intensity image is read out. The read coherent image is
The light is sequentially transmitted through the half mirror 24b and the Fourier transform lens 25, and is again Fourier transformed. The result becomes a bright spot and appears on its focal plane, and a correlation peak signal as shown in FIG. 2B is obtained. In this figure, the central portion is due to the 0th order light (70), and symmetrical positions on both sides of the center part are ± 1st order light (71) detected as a correlation signal.
Is. The array interval and array direction of the bright spots to be detected have a constant relationship with the displacement amount (velocity) of the moving object and the displacement direction, as is already known. Therefore, by detecting the position of the bright spot appearing as the correlation peak signal by the photoelectric conversion device 31 and performing a predetermined calculation process, the displacement amount, displacement velocity, and displacement direction of the moving object can be detected.

FIG. 4 shows another embodiment of the displacement amount measuring device. In this configuration, the image obtained from the fluorescent screen 13 in the double exposure apparatus 10 is captured by the CCD camera 15. The image obtained by the CCD camera 15 is converted into an electric signal and then displayed on the CRT 16. The image displayed on the CRT 16 is used as the input image of the correlation calculation device 20 including the Fourier transform optical system. Other configurations are the same as those of the displacement amount measuring device shown in FIG. 3, and the same components are designated by the same reference numerals.

With this configuration, the CCD camera 1
When capturing an image of a moving object obtained from the fluorescent screen 13, the reference numeral 5 integrates the time of one frame rate and captures it as one image, and thus performs an image storage function during this period.
By utilizing this function, a double exposure image can be obtained by the CCD camera 15.

As shown in FIG. 5, the CCD camera 1
A binarization circuit 17 for binarizing the output signal of 5;
The output of the binarization circuit 17 may be used as the input signal of the CRT 16. By thus disposing the binarization circuit 17, even if the contrast of the image pattern obtained from the phosphor screen 13 is not clear, the binarization processing is performed on the video signal output from the CCD camera 15. S of the correlation output obtained by the correlation calculation device 20 in the subsequent stage is possible.
It is possible to improve the / N ratio. In this way, since the video signal binarization can be directly processed, the calculation speed is not delayed, and the CCD camera 15
By processing the video signal that is the output of, the noise can be removed and the image for each wavelength can be extracted.

In each of the embodiments described above, the double exposure apparatus 10 is illustrated as including the photocathode 11, the microchannel plate 12, and the fluorescent screen 13, but the photocathode 11 is not included. And the fluorescent screen 13 may be used. In this case, the double exposure image can be similarly obtained by controlling the voltage applied to the photocathode 11 by the exposure time control device 33. Besides using the shutter function of such an image intensifier, it is also possible to obtain a double exposure image by using a pulse light source. further,
It is also possible to use a two-dimensional spatial light modulator such as FLC-SLM (ferroelectric liquid crystal SLH) as the spatial light modulators 21 and 22.

The displacement amount measuring device having such a configuration can be used as a velocity measuring system because the displacement amount of the moving object and the time interval of double exposure can be easily converted into velocity.

The greatest feature of this construction is that
The output light quantity obtained from the phosphor screen is amplified several thousand times compared to the input light quantity, so a moving object (target object) with a weak light quantity
The point is that a clear image can be obtained even with a minute exposure time. This makes it possible to measure the displacement of a weak light region such as light emission, fluorescence, and phosphorescence under a microscope.

For example, it is possible to measure the effect of the drug in real time by measuring the change in blood flow when the drug is administered. In addition, by selectively staining potassium or calcium, the migration speed and activity of each ion can be observed. In addition, it becomes possible to monitor the activity of sperm in real time.

Since the photocathode has a shutter speed of 3 nsec at the maximum, a double-exposure image of the object to be measured can be easily obtained when measuring the speed of a high-speed phenomenon. For example, pulse width 100 nsec, pulse interval 200 nse
When double exposure of c is performed, the speed is 25,000 m / s (90,000 k / h).
m) can be measured. This measurement speed is based on the case where the displacement of the double exposure image on the spatial light modulator 21 in the preceding stage is 5 mm, and the imaging magnification is assumed to be 1: 1. The speed measurement range is
It depends on the imaging magnification. For example, when an objective lens of 100 times is used, the apparent speed is 10
Since it becomes 0 times, 250 m / s can be measured under the above conditions. By improving the drive circuit system, the shutter speed can be further increased by about 100 times, and the measurement range is similarly expanded by 100 times.

[0034]

According to the displacement amount measuring apparatus of the present invention, since the so-called high-speed shutter function (gate function) for controlling the applied voltage of the photocathode of the double exposure section by the control section is utilized, the speed is extremely high. It is possible to measure the displacement amount of a moving object, and the measurement displacement amount of the measurement target and the allowable range of speed are improved as compared with the conventional measuring device.

Further, since the image is stored when the double exposure is formed by utilizing the fluorescent life of the fluorescent screen or the one frame rate of the image pickup means, the memory function is provided as in the conventional case. It is not necessary to use the expensive FLC-SLM, which is provided, the measuring device can be manufactured at low cost, and the selection range of available spatial light modulators is widened.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing the structure of a displacement amount measuring apparatus according to the present embodiment.

FIG. 2A is a diagram showing a double exposure image of a moving object obtained by the double exposure device, and FIG. 2B is a diagram showing a correlation peak image of the double exposure image obtained by a correlation calculation device. Is.

FIG. 3 is a configuration diagram showing a configuration example of a displacement amount measuring device.

FIG. 4 is a configuration diagram showing a configuration example of a displacement amount measuring device.

FIG. 5 is a configuration diagram showing a configuration example of a displacement amount measuring device.

[Explanation of symbols]

10 ... Double exposure device, 11 ... Photoelectric surface, 12 ... Micro channel plate, 13 ... Phosphor screen, 20 ... Correlation calculation device, 21 ... Spatial light modulator (first light modulating means), 23a,
23b ... Half mirror (first light modulating means), 25 ... Fourier transform lens, 22 ... Spatial light modulator (second light modulating means), 23a, 23b ... Half mirror (second light modulating means), 26 ... Fourier transform Lens, 30 ... Control device, 3
DESCRIPTION OF SYMBOLS 1 ... Optical position detection device (displacement amount calculation part), 32 ... Displacement amount calculation device (displacement amount calculation part), 33 ... Exposure time control device.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuji Kobayashi 1 1126, Nomachi, Hamamatsu, Shizuoka Prefecture 1126 Hamamatsu Photonics Co., Ltd. (72) Inventor Tsutomu Hara 1126, 1126 Nomachi, Hamamatsu, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. (72) Inventor Takeshi Ohno 1 1126 Ichino-cho, Hamamatsu-shi, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. (56) Reference JP-A-4-204312 (JP, A) JP-A-5-296720 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00-11/30

Claims (8)

(57) [Claims] 1. A displacement amount measuring device for measuring a displacement amount of a moving object, wherein a photoelectric surface on which light from the moving object is incident and a photoelectron image emitted from the photoelectric surface are converted into a light image. A fluorescent screen, the image of the moving object is accumulated on the fluorescent screen for a certain period of time, a double-exposure unit that forms a double-exposure image of the moving object, and the voltage applied to the photocathode is controlled, A controller that controls the time interval of double exposure on the fluorescent screen and the exposure time of each exposure, and the double exposure image of the moving object output from the double exposure unit is Fourier transformed to obtain a correlation peak image. A displacement amount measuring device comprising: a correlation calculation unit; and a displacement amount calculation unit that detects a correlation peak image obtained from the correlation calculation unit and obtains a displacement amount of the double exposure image. 2. The correlation calculation unit converts the double-exposure image obtained from the double-exposure unit into a coherent image, and a coherent image obtained from the first light-modulating unit by Fourier transform. A first Fourier transform optical system for converting, a second light modulating means for converting an intensity image Fourier-transformed by the first Fourier transform optical system into a coherent image, and a coherent image obtained from the second light modulating means by Fourier transform. The displacement amount measuring device according to claim 1, which is configured to include a second Fourier transform optical system for converting and obtaining a correlation peak image, and performing Fourier transform optically. 3. A displacement amount measuring device for measuring a displacement amount of a moving object, comprising a photoelectric surface on which light from the moving object is incident, and a microchannel plate for multiplying photoelectrons emitted from the photoelectric surface. A fluorescent screen for converting the photoelectron image multiplied by the microchannel plate into a light image, and the image of the moving object is accumulated on the fluorescent screen to form a double-exposure image of the moving object. Double exposure unit, controlling the applied voltage of at least one of the applied voltage to the photocathode and the applied voltage of the microchannel plate, the time interval of the double exposure on the phosphor screen and the exposure time of each exposure. A control unit that controls, a double-exposure image of the moving object that is output from the double-exposure unit, a correlation calculation unit that performs Fourier transform to obtain a correlation peak image, and a correlation obtained from the correlation calculation unit. A displacement amount measuring device comprising: a displacement amount calculation unit that detects a peak image and obtains a displacement amount of the double-exposure image. 4. The correlation calculation section converts the double exposure image obtained from the double exposure section into a coherent image, and a first coherent image obtained from the first light modulating section by Fourier transform. A first Fourier transform optical system for converting, a second light modulating means for converting an intensity image Fourier-transformed by the first Fourier transform optical system into a coherent image, and a coherent image obtained from the second light modulating means by Fourier transform. The displacement amount measuring device according to claim 3, which is configured to include a second Fourier transform optical system for converting and obtaining a correlation peak image, and performing Fourier transform optically. 5. A displacement amount measuring device for measuring a displacement amount of a moving object, wherein a photoelectric surface on which light from the moving object is incident and a photoelectron image emitted from this photoelectric surface are converted into a light image. An image of the moving object before and after displacement is input within a time period of one frame rate of the image pickup means, and a double exposure image of the moving object is formed. And a control unit that controls the applied voltage to the photocathode and controls the time interval of double exposure and the exposure time of each exposure on the fluorescent screen, and image by the imaging unit of the double exposure unit. A display unit that displays the double-exposure image that has been formed, a double-exposure image of the moving object that is displayed on the display unit, and a correlation calculation unit that performs a Fourier transform to obtain a correlation peak image; The obtained correlation peak image is detected and Displacement measuring device and a displacement calculating unit for obtaining the displacement amount of the exposure image. 6. The correlation calculation unit converts the double exposure image displayed on the display unit into a coherent image, and a Fourier transform of the coherent image obtained from the first light modulating unit. A first Fourier transform optical system, a second light modulating means for converting an intensity image Fourier transformed by the first Fourier transform optical system into a coherent image, and a coherent image obtained from the second light modulating means by Fourier transform And a second Fourier transform optical system for obtaining a correlation peak image, the displacement amount measuring apparatus according to claim 5 configured to optically perform a Fourier transform. 7. A displacement amount measuring device for measuring a displacement amount of a moving object, comprising a photocathode on which light from the moving object is incident, and a microchannel plate for multiplying photoelectrons emitted from the photocathode. The image pickup device includes a fluorescent screen for converting the photoelectron image multiplied by the microchannel plate into an image, and an image pickup device for picking up the image converted by the fluorescent screen.
A double exposure unit that inputs an image of the moving object before and after displacement and forms a double exposure image of the moving object within a frame rate time; an applied voltage to the photocathode and an application of the microchannel plate. Of the voltage, at least one of the applied voltage is controlled to control the double exposure time interval and the exposure time of each exposure on the phosphor screen, and the image capturing means imaged in the double exposure unit. A display unit that displays a double exposure image, a correlation calculation unit that obtains a correlation peak image by performing a Fourier transform on the double exposure image of the moving object displayed on the display unit, and a correlation obtained by the correlation calculation unit. A displacement amount measuring device comprising: a displacement amount calculation unit that detects a peak image and obtains a displacement amount of the double-exposure image. 8. The correlation calculation unit converts the double-exposure image displayed by the display unit into a coherent image, and a Fourier transform of the coherent image obtained from the first light modulating unit. A first Fourier transform optical system, a second light modulating means for converting an intensity image Fourier transformed by the first Fourier transform optical system into a coherent image, and a coherent image obtained from the second light modulating means by Fourier transform And a second Fourier transform optical system for obtaining a correlation peak image, the displacement amount measuring apparatus according to claim 7 configured to optically perform a Fourier transform.