JP3447064B2 - Real-time holography 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 real-time holography device for reproducing a three-dimensional image in real time.

[0002]

As is well known, in holography using photographic technology, object light and reference light obtained from coherent light such as laser light interfere with each other, and their interference fringes are recorded on a photographic film. By irradiating the developed photographic film, that is, the hologram with the reference light again, such object light is reproduced as diffracted light, and thus a three-dimensional image is observed. Of course,
In holography using such photographic technology, a hologram is obtained by developing and fixing a photographic film, and therefore a three-dimensional image cannot be reproduced in real time.

APPLIED OPT
ICS), May 1972, Volume 11, No. 5, pages 1261 to 12
Page 64 discloses a real-time holographic device proposed by RJ Doyle and WEGlenn. In this real-time holographic device, the interference fringes obtained by the object light and the reference light are read by the image pickup means and converted into a video signal, and the interference fringes are immediately recorded on a transparent thermoplastic recording medium based on the video signal. Has been adopted. In detail, Thermo Plus chip click recording material is configured as one coated with thermoplastic transparent electrode plate, according to the coating surface by scanning with an electron beam based on the video signal to the coated surface of the thermoplastic interference A charge distribution corresponding to the stripes is formed and the thermoplastic is electrically heated. As a result, an electrostatic force corresponding to the charge distribution acts on the thermoplastic, which deforms the thermoplastic to form irregularities corresponding to the interference fringes on the surface thereof, and thus the thermoplastic fringes on the recording medium. Will be recorded as a phase hologram. By irradiating such a phase hologram with coherent light, it is possible to immediately reproduce a three-dimensional image.

[0004]

By the way, in the conventional real-time holography device as described above, it takes some time until the coated surface of the thermoplastic is transformed into the uneven surface corresponding to the interference fringes. However, it is difficult to say that a three-dimensional image is reproduced in real time in a strict sense, because the immediacy of reproducing the three-dimensional image is poor. Further, in order to continuously reproduce a moving three-dimensional image, a plurality of thermoplastic recording bodies are prepared, and the interference fringes read by the image pickup means are sequentially recorded on these thermoplastic recording bodies, and at the same time, the thermoplastics are recorded. Since it is necessary to sequentially move the recording body to the three-dimensional image reproduction position, the entire structure is extremely complicated. Further, it is pointed out that the practical problem is inferior as the biggest problem of the conventional real-time holography device. That is, the deterioration of the thermoplastic recording material is rapid, and the number of times of writing interference fringes on the recording material is limited to several thousand. Therefore, it is an object of the present invention to provide a real-time holography device for reproducing a three-dimensional image in real time, which can reproduce a moving three-dimensional image immediately and continuously and maintain the reproduction for a long time. It is to provide a real-time holography device capable of doing.

[0005]

According to the present invention, there is provided an image pickup means for picking up an image of an interference fringe generated by causing an object light and a reference light to interfere with each other, and converting it into a video signal. In a real-time holography device comprising spatial light modulating means for reproducing the interference fringes based on a video signal, the spatial light modulating means being composed of a matrix pixel arrangement type liquid crystal element, and being diffracted by the matrix pixel arrangement type liquid crystal element. a condenser lens for the diffracted beam was focused were, installed in a substantially focal point of the condenser lens, comprising a spatial filter for removing 0-order light component of the diffraction light condensed by the condenser lens , The spatial filter is the matrix pixel
In a state where the interference fringes are not reproduced on the arrangement type liquid crystal element,
The matrix pixel arrangement type liquid crystal element through a condenser lens
Real time holography device is provided, which comprises closed the image information of the photosensitive recording photosensitive material. Said mat
Liquid crystal element with lix pixel arrangement forms a phase hologram
It can be configured to. The interference angles for causing the object light and the reference light to interfere with each other are 2θ _x and 2θ _{y in} the X direction and the Y direction, respectively, and the X direction and the Y direction of the matrix pixel arrangement type liquid crystal element are set.
If the resolving powers in the directions are N _x and N _y , respectively, and the wavelengths of the light of the light source of the object light and the reference light are λ, then θ _x =
sin ⁻¹ [(N _x / 4) λ] and θ _y = sin
_{^{-1 [(N y / 4)}} λ] of the configuration given by expression 2
It is Ru can be.

[0006]

[Action] As apparent from the above configuration, the real-time holography device according to the present invention, since a matrix pixel arrangement type liquid crystal element is used as the spatial light modulating means, immediately and sequentially performing that reproduction of the interference fringes not only is Ru is <br/> Ah possible regeneration of stable interference fringes for a long period of time can be guaranteed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the real-time holography device according to the present invention will be described below with reference to the accompanying drawings. First, in order to understand the real-time holography device according to the present invention, the principle of holography using photographic technology will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, a coherent light source, for example, a laser light L obtained from a gas laser tube 10 is magnified by a magnifying lens 12 and then collimated by a collimating lens 14. The collimated light is collimated by a half mirror 16. It is divided into two by. One of the split lights travels to the object O, and its reflected light is directed to the photographic film F as the object light L ₁ , and the other split light is reflected by the mirror 18 and directed to the photographic film F as the reference light L _2. To be Object light L ₁ and reference light L ₂
Interfere with each other on the recording surface of the photographic film F, and the interference fringes are recorded on the photographic film F as a latent image. When the photographic film F is developed and fixed, a negative film in which interference fringes are recorded as a visible image, that is, a hologram is formed.

[0009] Referring to FIG. 2, such a hologram beam F '
Are shown arranged in the reproduction optical system. That is,
The laser beam L ′ obtained from the gas laser tube 20 is magnified by the magnifying lens 22 and then converted into parallel light by the collimator lens 24. This parallel light is reflected by the mirror 26 and is applied to the hologram F ′ as reference light. At this time, the reference light is the 0th-order diffracted light L ₁ ′ that goes straight through the hologram F ′ and the 1st-order diffracted light L 1 diffracted at a predetermined diffraction angle.
'Is divided into a, this latter first-order diffracted light L _{2' 2} in FIG. 1
The object light shown in (1) is reproduced, so that a virtual image O ′ of the object O is observed. In this case, the angle 2θ (FIG. 1) formed by the object light L ₁ and the reference light L ₂ is equal to the angle between the 0th-order diffracted light L ₁ ′ and the 1st-order diffracted light L ₂ ′,
In order to clearly observe the virtual image O ′, the angle 2θ formed by the object light and the reference light is increased and the 0th-order diffracted light L ₁ ′ is converted into the virtual image O ′.
It is preferable to remove it from the observation field of view.

Referring to FIG. 3, an embodiment of a real-time holography device according to the present invention is shown schematically. In addition,
In FIG. 3, the same reference numerals are used for the same elements as those shown in FIGS. 1 and 2. As described with reference to FIG. 1, the laser light L obtained from the gas laser tube 10 is expanded by the magnifying lens 12 and then converted into parallel light by the collimator lens 14, and the parallel light is divided into two by the half mirror 16. One of the split lights travels to the object O, and the reflected light thereof becomes the object light L _1, and the other of the split lights is reflected by the mirror 18 to be the reference light L 1.
It is considered to be ₂ . The object light L ₁ is directed to an image pickup means, for example, a CCD camera 28 via an image formation lens 24 and a half mirror 26, and at this time, a real image of the object O is formed by the image formation lens 24 in the vicinity of the image pickup surface of the CCD camera 28. (Note that the imaging lens of the CCD camera 28 itself is removed). The reference light L ₂ is reflected by the half mirror 26 and then directed toward the image pickup surface of the CCD camera 28. In FIG. 3, the object light L ₁ and the reference light L ₂ are illustrated as being directed toward the image pickup surface of the CCD camera 28 in a state of being overlapped with each other, but actually, as shown in FIG.
The object light L ₁ and the reference light L ₂ are directed toward the image pickup surface of the CCD camera 28 so as to form a fine angle 2θ, and the angle 2θ is set to, for example, about 0.3 to about 0.4 degree in this embodiment. With such a fine angle, the CCD camera 28
Object light L ₁ and reference light L ₂ incident on the imaging surface of
Are interfered with each other, and the interference fringes are reflected by the CCD camera 28.
Is converted into a video signal. The object light L
_The reason why the ₁ and the reference light L ₂ interfere with each other at such a minute angle will be described in detail later.

As described above, in this embodiment, the real image of the object O is formed in the vicinity of the image pickup surface of the CCD camera 28, which is known as an optical system for forming a one-step image type hologram. In this case, it is possible to use white light when reproducing the three-dimensional image. Of course,
It is possible to record a hologram without using the imaging lens 24, which is more common as an optical system for creating a Fresnel hologram, and in this case also, the imaging lens of the CCD camera 28 itself is removed. . In this embodiment, as the CCD camera 28, KV-26 / 26L available from Hitachi Electronics Co., Ltd. is used, and its imaging area is 1 /
2 inches, the number of pixels is 768 (H) × 490 (V),
The pixel pitch is 11.4 μm × 13.3 μm.

The interference fringes between the object light L ₁ and the reference light L ₂ are CC
Based on the video signal obtained from the D camera 28, the spatial light modulating means, that is, the matrix pixel arrangement type liquid crystal element 30.
Played in real time by. The matrix pixel arrangement type liquid crystal element 30 used in this embodiment is MIM (Me
tal-Insulated-Metal) -TN type, its panel size is 0.96 inch, and its pixel number is 648 (H) × 240 (V).
And each pixel size is 30 μm (V) × 60 μm (H). Referring to FIG. 5, a block diagram for reproducing interference fringes on the matrix pixel arrangement type liquid crystal device 30 based on a video signal obtained from the CCD camera 28 is schematically shown. In the block diagram, reference numeral 32 denotes a control signal generation circuits for outputting various control signals based on the vertical and horizontal synchronizing signals included in the video signal, reference numeral 3
4 is for converting the video signal into 16-level grayscale image data 4
Reference numeral 36 denotes a signal electrode drive circuit of the matrix pixel arrangement type liquid crystal element 30, and reference numeral 38 denotes a scan electrode drive circuit of the matrix pixel arrangement type liquid crystal element 30. Video signal is CCD camera 2
8 is output from the control signal generating circuit 32 based on the horizontal synchronizing signal,
It is output to the D converter 34, whereby 4-bit grayscale image data is obtained from the A / D converter 34, and the number of these 4-bit grayscale image data is in the horizontal direction of the matrix pixel arrangement type liquid crystal element 30. Corresponds to 648 pixels. Next, the 4-bit image data is written into the 4-bit shift register 36a of the signal electrode drive circuit 36 by the shift clock signal S2 from the control signal generating circuit 32, and these image data are written into the 4-bit line memory 3.
6b is moved in parallel. When the latch clock signal S3 is output from the control signal generation circuit 32 to the line memory 36b, a pulse voltage having a time length corresponding to the 4-bit grayscale image data is output from the line memory 36b in the vertical direction of the matrix pixel arrangement type liquid crystal element 30. Output to the electrodes (in FIG. 5). On the other hand, the signal voltage S4 is output from the control signal generating circuit 32 to the gate circuit 38a of the scan electrode driving circuit 38, and the scan start signal S5 is output from the control signal generating circuit 32 to the shift register 38b of the scan electrode driving circuit 38. And the shift clock signal 6 is output, whereby the rising pulse of the scan start signal S5 is sequentially moved along the shift register 38b to open the individual gate circuit elements of the gate circuit 38a. Thus, the driving voltage is sequentially output to the row electrodes (in FIG. 5) of the matrix pixel arrangement type liquid crystal element 30,
As a result, a voltage corresponding to 4-bit grayscale image data is applied to each of the row electrodes, and the object light L ₁ and the reference light L
The interference fringe with ₂ is reproduced on the matrix pixel arrangement type liquid crystal element 30. It is already well known in liquid crystal televisions to reproduce an image on a matrix pixel arrangement type liquid crystal element based on a video signal.

By the way, the object light L₁And reference light L₂Dried with
The basic pitch P of the fringes is determined by the angle 2θ between them.
Is expressed by the following formula. 2 · SIN (θ) = Nλ N = P^-1 Where λ is the wavelength of the laser light and N is the spatial frequency.
It As is clear from the above equation, the object light L₁And reference light L₂
When the angle 2θ between and becomes large, the basic pitch P becomes small.
Object light L on the contrary₁And reference light L₂Between
As the angle 2θ becomes smaller, the basic pitch P becomes larger.
For example, the object light L₁And reference light L₂Angle 2θ between and is 30
In the case of degrees, P is about 1.2 μm.
Body light L₁And reference light L₂The interference fringes with
It is impossible to reproduce on the stationary liquid crystal element 30. When
It means the pixels of the matrix pixel arrangement type liquid crystal element 30.
Since the size is 30 μm (V) × 60 μm (H) as described above
Is. However, the object light L₁And reference light L₂Between
If the angle 2θ of is about 0.3 to about 0.4 degrees, P is about 10
Approximately 0 μm, in this case matrix pixel arrangement
Object light L on the liquid crystal element 30₁And reference light L₂Interference fringes with
It is possible to reproduce. Generally, the object light L₁When
Reference light L₂Angle 2θ between and is a matrix pixel arrangement type
It should be determined based on the resolution of the liquid crystal element 30.
Solution in X direction (horizontal direction) and Y direction (vertical direction)
Image power is N_x(lp / mm) and N_y(lp / mm)
When the optimum angle 2θ_xAnd 2θ_yCan be expressed by the following formula
Be done. θ_x= SIN^-1[(N_x/ 4) λ] θ_y= SIN^-1[(N_y/ 4) λ] λ: wavelength of laser light Matrix pixel arrangement type liquid crystal element used in this embodiment
30, the pixel density in the horizontal direction is about 33 / mm (N_x=
33/2) and the vertical pixel density is about 17 / mm (N
_y= 17/2), and based on this, the object light L₁And reference light
L₂The angle 2θ between and is about 0.
It is in the range of 3 to about 0.4 degrees. In this case, the value of θ is
If it is larger than this range, the image quality of the reproduced three-dimensional image
Decreases and the value of θ becomes smaller than the range,
The image quality of the reproduced three-dimensional image does not deteriorate so much, but 0
It becomes difficult to separate the first-order diffracted light and the first-order diffracted light. In the future
A matrix pixel arrangement type liquid crystal device with higher pixel density was opened.
If emitted, the object light L ₁And reference light L₂Corner between
It is possible to set the degree 2θ larger than the above range.
is there.

As shown in FIG. 3, the matrix pixel arrangement type liquid crystal element 30 is arranged in a reproducing optical system. That is,
The laser beam L ′ obtained from the gas laser tube 20 is magnified by the magnifying lens 22 and then converted into parallel light by the collimator lens 24, and this parallel light is made incident on the matrix pixel arrangement type liquid crystal element 30 as reference light L ₂ ′. As described above, the object light L ₁ and the reference light L ₂ are about 0.3
Or the reference beam L
The angle of incidence matrix pixel arrangement type ₂ 'liquid crystal element 30
Is almost perpendicular to the display surface of. The light transmitted through the matrix pixel arrangement type liquid crystal element 30 is condensed by the condensing lens 40, and the spatial filter 42 is arranged at the condensing position, and thus the object O can be observed as a three-dimensional image. The spatial filter 42 is provided to eliminate the 0th-order diffracted light. That is, since the 0-order diffracted light to the object beam L ₁ and the reference light L ₂ to be made to interfere at an angle of about 0.3 to about 0.4 degrees comes into the inevitable observation field, in order to block the zero-order diffracted light it is mean that spatial filter 42 is disposed. An example of producing the spatial filter 42 will be described. The spatial filter 42 is obtained by placing a photographic film at the installation location of the spatial filter 42, illuminating the laser beam L ', and developing the photographic film. At this time, the interference fringes are not reproduced in the matrix pixel arrangement type liquid crystal element 30. The spatial filter 42 thus obtained is shown in FIG. 6, and as is apparent from FIG.
Since the condensing point C where the 0th-order diffracted light is condensed by the condensing lens 40 is developed as a black spot, the spatial filter 4
By arranging the 2 at the focal point of the condenser lens 40 as it is shown in Fig 3, 0 3D image of the diffracted light is blocked by the object O can be clearly observed. As shown in FIG. 6, a large number of black spots regularly appear in addition to the condensing spot C, but these black spots are those where the condensing spot C is diffracted by the electrode plate array of the matrix pixel arrangement type liquid crystal element 30. is there.

When polarizing plates are arranged on both sides of the liquid crystal display surface of the matrix pixel arrangement type liquid crystal element 30 to reproduce the interference fringes, the matrix pixel arrangement type liquid crystal element 30 functions as an amplitude hologram. When the refractive index of the liquid crystal molecules changes depending on the orientation of the liquid crystal molecules, it is preferable that the matrix pixel arrangement type liquid crystal element 30 is made to function as a phase hologram except for the polarizing plate. This is because the latter case can reproduce a brighter three-dimensional image. In the above-described embodiment, the matrix pixel arrangement type liquid crystal element 30 is configured to function as a transmission hologram, but a mirror is arranged on one side of the liquid crystal display surface of the matrix pixel arrangement type liquid crystal element 30 to form a reflection hologram. It is also possible to function as.
Further, in the above-mentioned embodiment, the CCD camera is used for reading the interference fringes, but it goes without saying that other image pickup means may be used. Further, although the gas laser tube is used as the coherent light source in the above-mentioned embodiments, it goes without saying that a visible semiconductor laser, which has made remarkable progress in recent years, can be used.

[0016]

As apparent from the above description, according to the present invention, according to this embodiment, by use of a matrix pixel arrangement type liquid crystal element, since the playback of the interference fringes immediately and can be performed sequentially, It becomes possible to continuously reproduce a moving three-dimensional image in substantially real time. In addition, as has been proved in liquid crystal televisions and the like, the life of the matrix pixel arrangement type liquid crystal element is long, so that the reproduction of a three-dimensional image over a long period can be stably guaranteed.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating the creation of a hologram using photographic technology.

FIG. 2 is a schematic diagram illustrating reproduction of a three-dimensional image on the hologram obtained in FIG.

FIG. 3 is a schematic diagram showing a real-time holography device according to the present invention.

FIG. 4 is an enlarged view showing a part of FIG. 3 in an enlarged manner.

5 is a block diagram of a control circuit for reproducing interference fringes read by the CCD camera of FIG. 3 on a matrix pixel arrangement type liquid crystal element.

FIG. 6 is a plan view showing a spatial filter.

[Explanation of symbols]

10 ... gas laser tube 12 ... magnifying lens 14 ... co Increment Torenzu 16 ... half mirror 18 ... mirror 20 ... gas laser tube 22 ... magnifying lens 24 ... co Increment Torenzu 26 ... half mirror 28 ... CCD camera 30 ... matrix pixel arrangement type liquid crystal device 32 Control signal generation circuit 34 A / D converter 36 Signal electrode drive circuit 38 Scan electrode drive circuit 40 Condenser lens 42 Spatial filter

Claims (3)

(57) [Claims] 1. An image pickup means for picking up an image of an interference fringe generated by causing an object light and a reference light to interfere with each other and converting the imaged interference fringe into a video signal.
A real-time holography device comprising a spatial light modulating means for reproducing the interference fringes based on a video signal obtained by the imaging means, wherein the spatial light modulating means comprises a matrix pixel arrangement type liquid crystal element, A condenser lens for condensing the diffracted light diffracted by the disposition type liquid crystal element, and a zero-order light component of the diffracted light condensed by the condenser lens, which is installed at a substantially focal position of the condenser lens. And a spatial filter , wherein the spatial filter is the matrix pixel arrangement type liquid crystal.
The condenser lens without reproducing the interference fringes on the element
Through the matrix pixel arrangement type liquid crystal element image information
To have a photosensitive recording photosensitive material, real-time holography device according to claim. 2. The matrix pixel arrangement type liquid crystal element
The real-time holography device according to claim 1, which forms a phase hologram . 3. The object light and the reference light are caused to interfere with each other.
The interference angle is the interference angle in the X direction and the interference angle in the Y direction, respectively.
Re and 2 [Theta] _x and 2 [Theta] _y, said matrix pixel arrangement
The resolving power of the liquid crystal element in the X direction and the Y direction, respectively.
Let N _x and N _y be the light sources of the object light and the reference light.
When the wavelength of the light was ^{_{λ, θ x = sin -1 [}} (N x / 4) λ] and ^{_{θ y = sin -1 [(N}} y / 4) λ] of claim 1 that is given by the expression 2 Or the real-time holography device according to 2.