KR20140077276A - Apparatus and method for holographic printing - Google Patents

Abstract

Disclosed is a holographic recording apparatus. The holographic recording apparatus includes a light source unit which emits a light source, a light source separating unit which separates an object beam and a reference beam from the light source and emits the separated beams to a light refraction medium, an image obtaining unit which obtains an image of the object beam based on the object beam reflected and emitted to the light refraction medium and obtains an image of an interference pattern formed by emitting the object beam and the reference beam to the light refraction medium, and a detecting unit which detects whether the object beam is matched with the reference beam based on the image of the interference pattern and the image of the object beam.

Description

[0001] APPARATUS AND METHOD FOR HOLOGRAPHIC PRINTING [0002]

The present invention relates to holographic recording, and more particularly, to a holographic recording apparatus and method capable of detecting diffraction efficiency by detecting whether an object beam and a reference beam are matched.

Recently, studies on three-dimensional (3D) image and image reproduction technology have been actively carried out. Stereoscopic media is expected to lead the next generation imaging device as a new realistic image media that elevates the level of visual information to a new level. The conventional 2D image system provides the plane image, but the 3D image system is the ultimate image realization technology in terms of showing the actual image information of the object to the observer.

Among the methods for reproducing the stereoscopic image, the holographic method is a method of observing the hologram produced by using the laser, so that the same stereoscopic image as the real object can be felt without attaching special glasses. Therefore, the holographic method is known to be an ideal method for viewing stereoscopic images without fatigue because the stereoscopic effect is excellent.

The holographic system is based on the principle of recording and reproducing an interference signal generated by interference between an object beam reflected from an object and a reference wave (or reference beam). (Or a recording medium, a photorefractive medium) formed by causing an object beam, which is scattered by colliding with an object, to be incident on a reference beam incident from another direction by using a laser beam having high coherence, Is called a hologram. The reconstruction of a recorded hologram using the interference fringes thus recorded into a stereoscopic image is referred to as holography.

A conventional digital holographic recording method forms a hologram element (or an interference fringe pattern or a fringe pattern) by simultaneously entering an object beam and a reference beam at a small size such as 1 mm X 1 mm. At this time, the degree of matching between the object beam and the reference beam is measured mechanically, directly by an operator's eye, or measured by an image acquisition device such as a camera.

If the matching of the object beam and the reference beam is not performed accurately, the diffraction efficiency is lowered, and as a result, a good quality hologram image can not be reproduced. If the degree of matching between the object beam and the reference beam is not good, an interference fringe at a specific time point is not formed and an image having a viewing angle corresponding to this portion can not be reconstructed, or the brightness is lowered , The reproduction image may be distorted. In order to improve this, it is necessary to precisely measure and correct whether or not the object beam and the reference beam coincide with each other.

The present invention provides a holographic recording apparatus and method for detecting the matching of an object beam and a reference beam incident on a photorefractive medium to improve the diffraction efficiency.

According to one aspect of the present invention, there is provided a holographic recording apparatus. The apparatus includes a light source section for irradiating a light source, a light source separating section for separating an object beam and a reference beam from the light source and irradiating the light beam onto a photorefractive medium, a light source separation section for irradiating the light source, An image acquiring unit acquiring an image of the object beam and an interference fringe formed by irradiating the object beam and the reference beam onto the light refraction medium; and an image acquiring unit acquiring an image of the object beam and an image of the interference fringe, And a detector for detecting whether or not the object beam and the reference beam are matched.

An image of the object beam and an image of the interference fringe recorded on the photorefractive medium through the exposure of the object beam and the reference beam can be obtained to detect the degree of matching between the object beam and the reference beam, The degree of matching between the object beam and the reference beam can be adjusted to a desired degree. Therefore, the hologram reproduction quality can be improved by improving the diffraction efficiency.

1 is a block diagram schematically illustrating a holographic recording apparatus according to an embodiment of the present invention.
2 is a view showing an example where an object beam and a reference beam are incident on a photorefractive medium and are matched.
3 is a diagram showing an example of an exposed interference fringe according to the degree of matching between an object beam and a reference beam.
4 is a flowchart illustrating a method of detecting whether an object beam and a reference beam are matched using the holographic recording apparatus according to an embodiment of the present invention.
5 is a view for explaining a method of detecting whether or not an object beam and a reference beam are matched according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. Further, the present invention is not limited to the embodiments described below, but can be applied in various different forms within the scope of the technical idea of the present invention.

The components described in this specification may include components other than those described below as needed, and a detailed description of parts that are not directly related to the present invention will be omitted. In addition, the arrangement of each component described in this specification can be adjusted as necessary, and one component may be included in another component, and one component may be divided into two or more components.

The hologram can be fabricated by using an optical method using a laser, a method using a computer, a method using a wave such as an ultrasonic wave or a microwave, and an optical method is generally applied in many cases.

The optical method can be divided into an analog method and a digital method. In the case of an analog method, an object wave generation method, a light refraction medium (or a recording medium, a holographic film), a wet processing Can be classified in various ways. In the recording method, generally, a transmission type and a reflection type are distinguished. In a transmission type and a reflection type, there is a difference in an incidence method of an object beam and a reference beam. In the case of the transmission type, the object beam and the reference beam are incident on the photorefractive medium in the same direction. In the case of the reflection type, the object beam and the reference beam are incident on the photorefractive medium from different directions. The transmission type can be divided into an on-axis type and an off-axis type according to the incident angle of the object beam and the reference beam. On-axis type is a mode in which the object beam and the reference beam are in the same direction The off-axis method is a method in which the angle between the two beams is made close to zero degree, whereas the off-axis method is a method in which an object beam And the reference beam is incident on the photorefractive medium at a certain angle.

Unlike the analog method, the digital method is a method of reproducing a hologram image by recording an object beam in a discrete type in a photorefractive medium. In the case of the analog system, the size of the lens and the medium of the optical system is determined according to the size of the subject, which limits the application. In the case of the digital system, the object image to be recorded is generally generated using a computer, Since the pattern can be calculated and recorded in the photorefractive medium, it can be applied more easily than the analog method.

In addition, the digital holographic recording method is recorded in a photorefractive medium in a recording unit called hogel (hologram element). Hogel is a concept similar to a pixel, which is a unit used to represent a digital image. It has a resolution of each hogel (which means a resolution of a conventional 2D orthogonal image, for example, 1280x720 pixels) The resolution is then determined. That is, as the resolution of each hue gel is large and the size of the hue gel is small and a large number of hue gels are recorded in the photorefractive medium per unit area, the resolving power at the time of reproduction becomes large. In general, when the hologram is very small and is recorded very closely to the photorefractive medium, a natural hologram image with few discontinuities at the time point can be restored.

Hereinafter, a method and an apparatus for optically recording the gel into the optical refraction medium using the digital holographic recording method will be described. The present invention also provides a method for detecting the matching of an object beam and a reference beam incident on a photorefractive medium to improve the diffraction efficiency.

1 is a block diagram schematically illustrating a holographic recording apparatus according to an embodiment of the present invention.

1, the holographic recording apparatus 100 includes a light source 110, a light source separation unit 120, an optical header unit 130, an image acquisition unit 140, a UV irradiation unit 150, and a detection unit 160. .

The light source unit 110 radiates light (or a beam). At this time, the light may be light having coherence characteristics, for example, a laser in a single longitudinal mode (SLM). An SLM laser is a laser in which light with a short wavelength is generated in the vertical axis, and has coherence.

The light source separation unit 120 receives light emitted by the light source unit 110 and separates the light into an object beam and a reference beam. At this time, the object beam or the reference beam may be formed as a collimated beam having a property of going parallel.

The light source separation unit 120 may include a spatial light modulator (SLM), and the spatial light modulator generates an object beam from the light emitted by the light source unit 110 to project an image of the object, can do.

The object beam separated by the light source separation unit 120 is incident on the optical header unit 130 and the optical header unit 130 condenses the object beam to be incident on the optical refraction medium 170. For example, the optical header section 130 may use a condenser lens. Also, the reference beam separated by the light source separation unit 120 is incident on the photorefractive medium 170 in a parallel light form, and is combined with the object beam to generate an interference fringe.

In order to cause 100% diffraction by interference between the object beam and the reference beam incident on the photorefractive medium 170, the object beam and the reference beam are accurately aligned as shown in FIG. 2, .

FIG. 2 is a view showing an example where an object beam and a reference beam are incident on a photorefractive medium to be matched. FIG. 3 is a view showing an example of an exposed interference pattern according to the degree of matching between an object beam and a reference beam.

Referring to FIG. 2, the object beam is condensed through a condenser lens, and then enters a corresponding photo-refractive medium, that is, a corresponding gel to form an interference pattern in the photo-refractive medium. The reference beam is also incident on the corresponding gel, .

As shown in FIG. 3A, when the object beam and the reference beam are incident and correctly matched (310), the two beams are exposed in the corresponding homogeneous gel in the photorefractive medium to form a circular interference fringe 315 Can be generated.

3B, when the object beam and the reference beam are incident and not correctly matched (320), when the two beams are exposed in the corresponding gel in the photorefractive medium, the upper portion of the object beam It is possible to generate an elliptical interference fringe 325 because the interference fringe is not formed. If the object beam and the reference beam can not be precisely matched, a part of the object beam may not be coupled, resulting in distortion in reproduction of the hologram or failure to reproduce an image at a specific point in time.

Therefore, the holographic recording apparatus 100 according to the embodiment of the present invention can detect whether or not the object beam and the reference beam are matched.

Referring back to FIG. 1, the image acquisition unit 140 acquires an image using an object beam reflected from the photorefractive medium 170. For example, the image acquisition unit 140 may be a camera, and may capture an image using an object beam positioned at an upper end of the optical header unit 130 and reflected through the optical refraction medium 170. Or an object beam that is positioned at the lower end of the photorefractive medium 170 and passes through the photorefractive medium 170.

The image acquisition unit 140 acquires an interference fringe formed by exposing the object beam and the reference beam in the photorefractive medium 170. For example, a camera can be used to photograph a portion exposed in the photorefractive medium 170, that is, a corresponding gel having interference fringes recorded thereon, and acquire images therefrom.

As described above, it is one example that the image acquisition unit 140 is located at the upper end of the optical header unit 130 or the lower end of the optical refraction medium 170, and the position of the image acquisition unit 140 is limited thereto It is not. Also, in the embodiment of the present invention, the image acquisition unit 140 acquires the image signal from the object beam. However, the present invention is not limited to the image signal.

The UV irradiating unit 150 exposes the object beam and the reference beam in the photorefractive medium 170 and then irradiates ultraviolet light to the photorefractive medium 170 for fixing. For example, the UV irradiating unit 150 may be a UV lamp, and may be positioned at the top of the photorefractive medium 170 to irradiate UV light to the gel region of the photorefractive medium 170 for a predetermined period of time.

When the UV light is irradiated through the UV irradiating unit 150, the photorefractive medium 170 may change color or a specific pattern may be formed on the photosensitive layer portion of the medium.

The holographic recording apparatus 100 according to an embodiment of the present invention may further include a heating apparatus (not shown) that generates a constant temperature as required. The holographic recording apparatus 100 may include a heating apparatus (not shown) .

The detection unit 160 detects whether the object beam and the reference beam are matched based on the image of the object beam acquired by the image acquisition unit 140 and the image of the interference fringe exposed to the optical refraction medium 170. At this time, whether or not the object beam and the reference beam are matched can be determined based on a preset matching reference value. If the degree of matching between the object beam and the reference beam does not satisfy the matching reference value, the object beam and the reference beam may be readjusted to be incident on the photorefractive medium 170.

4 is a flowchart illustrating a method of detecting whether an object beam and a reference beam are matched using the holographic recording apparatus according to an embodiment of the present invention. This method can be performed in the holographic recording apparatus of FIG.

Referring to FIG. 4, the holographic recording apparatus irradiates an object beam (S400). More specifically, a holographic recording apparatus radiates a light source such as a laser to an optical system, and separates it into an object beam and a reference beam. At this time, the object beam or the reference beam may be formed as parallel light. The holographic recording apparatus forms the actual object beam including the image of the object through the spatial light modulator or through the reflection process so that the separated object beam is directly incident on the condenser lens without the image of the object, Let it enter.

The holographic recording apparatus acquires the profile of the object beam based on the beam from which the irradiated object beam is reflected in the photorefractive medium (or recording medium) (S410). In step S400, the object beam incident on the condensing lens is irradiated on the photorefractive medium and is reflected. At this time, the profile of the object beam, that is, the object beam, can be acquired from the object beam reflected by the photorefractive medium using a camera or the like . The profile of the object beam refers to the shape of the object beam, that is, the shape of the object beam. The profile of such an object beam may be a still image of one frame, or a moving image composed of a plurality of frames, and may be stored in the holographic recording apparatus. Step S410 may be performed by the image acquisition unit 140 of FIG. Also, step S410 can be performed without irradiating the reference beam.

The holographic recording apparatus simultaneously irradiates the object beam and the reference beam to the photorefractive medium (S420). That is, the object beam and the reference beam are irradiated to the photorefractive medium to expose the interference fringes by interference of the two beams. At this time, when the interference fringes are acquired through a camera or the like, the exposure time and the intensity of the light source can be adjusted so that they can be identified.

The holographic recording apparatus fixes and post-processes the exposed interference fringes (S430). That is, the holographic recording apparatus cuts off the object beam and the reference beam, and then irradiates the UV light to fix the exposed interference fringe. At this time, instead of UV light, the refractive index modulation may be enhanced by using a beam of an object beam or a reference beam for a predetermined time or by using a heat treatment apparatus which generates a constant temperature if necessary.

The holographic recording apparatus acquires the fixed beam profile from the photorefractive medium (S440). The fixed beam profile refers to an interference fringe recorded on a photorefractive medium, which is irradiated with an object beam and a reference beam to fix the interference fringe formed in the photorefractive medium by irradiating UV light again. Step S440 may be performed by the image obtaining unit 140 of FIG. 1, and the image obtaining unit 140 may obtain the image of the portion exposed from the photorefractive medium, that is, the corresponding hologram portion in which the interference fringes are recorded .

The holographic recording apparatus detects whether the object beam and the reference beam are matched based on the profile of the object beam and the fixed beam profile (S450). Step S450 may be performed by the detection unit 160 of FIG. 1 and will be described in detail with reference to FIG.

5 is a view for explaining a method of detecting whether or not an object beam and a reference beam are matched according to an embodiment of the present invention.

The profile 510 of the object beam shown in FIG. 5A is the image obtained by the step S410, and is the shape of the actual object beam to be recorded on the optical refraction medium. The obtained beam shape 515 is the shape of the object beam obtained by the ambient light generated from the photorefractive medium.

The fixed beam profile 520 shown in FIG. 5 (b) is an image obtained by step S440, which is an interference fringe that is exposed and fixed to a photorefractive medium.

The holographic recording apparatus compares and analyzes the object beam profile 510 and the fixed beam profile 520 as shown in FIG. 5 (c), and based on the result of the comparative analysis, the object beam and the reference beam The degree of matching can be judged.

Referring again to FIG. 4, in step S450, if the degree of matching between the object beam and the reference beam satisfies a predetermined matching reference value, the holographic recording apparatus ends the process of detecting whether the object beam and the reference beam are matched. If the degree of matching between the object beam and the reference beam does not satisfy the preset reference value, the holographic recording apparatus re-adjusts the object beam and the reference beam (S460) and repeats the process from step S400.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive, that other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the claims, and all technical ideas within the scope of the claims should be construed as being included in the scope of the present invention.

Claims (1)

A light source unit for irradiating a light source;
A light source separation unit for separating the object beam and the reference beam from the light source and irradiating the object beam and the reference beam;
An image obtaining unit that obtains an image of the object beam based on the object beam reflected and reflected by the photorefractive medium and acquires an image of the interference fringe formed by irradiating the object beam and the reference beam to the optical refraction medium An acquisition unit; And
And a detector for detecting whether the object beam and the reference beam are matched based on an image of the object beam and an image of the interference fringe.

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