KR20000014096A - Holographic write and read method - Google Patents

Abstract

PURPOSE: A holographic write/read method is provided to increase written information reading efficiency by aligning a recording media to an optimal state while reading written information. CONSTITUTION: A holographic device writes information by dividing light radiated from a light source into reference light and object light and being incident to the recording media to write information, and reads the information utilizing the only reference light. Regular information of a bar-array type is recorded in a first track of the recording media utilizing the reference light. Normal information is recorded from a second track of the recording media utilizing the reference and the object lights. An incident angle is reset to align the recording media to an optical state. The normal information is read by scanning the reset incident angle to an incident angle of the reference light.

Description

Holographic recording / playback method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic information recording / reproducing method, and more particularly, to a holographic information recording / reproducing method for accurate reproduction when the position of a medium is slightly distorted when reproducing information recorded on a medium of a holographic storage device. It is about.

As recording and reproducing are required due to the large capacity of information, optical information using holographic technology capable of recording and reproducing information in three dimensions as well as a two-dimensional recording / reproducing apparatus using an optical disc recording medium such as a CD or a DVD. Recording / reproducing device technology is being developed.

As shown in FIG. 1, the structure of the apparatus for recording and reproducing information using a conventional holographic technique is referred to a laser light source 15 that generates a laser beam, and a laser beam 16 of the laser light source 15 as reference light ( The beam splitter 14 is separated into a reference beam 6 and an object beam 7, and is diffused by the beam diffuser 12 and the beam diffuser 12 which enlarge the beam diameter of the reference light 6. The beam deflector 11 for changing the direction of the reference light 6 and changing the angle of incidence to the subsequent device, and the reference light 6 from the beam deflector 11 are imaged on the recording medium 3 provided at the rear end. A telescope 9 having a 1: 1 magnification, a beam blocker 17 for controlling whether the object light 7 outputs from the beam splitter 14, and a beam diameter of the object light are diffused. The beam diffuser 13, the reflector 10 for changing the beam traveling direction, the SLM (Spatial Light Modulator) 1 for converting and displaying information, and the SLM A Fourier transform lens (FTL) 2 for Fourier transforming the displayed image onto a subsequent recording medium, a recording medium 3 for recording information where the reference light 6 and the material light 7 meet, and It is located on the imaging lens 4 and the imaging surface of the imaging lens 4 which are positioned at a distance from the recording medium 3 in the direction in which the object light 7 enters the recording medium 3 and proceeds. A CCD (Charge Coupled Device) 5 for converting an image of the SLM 1 into an electrical signal, and a computer 8 for controlling the SLM 1 and the CCD 5 are provided.

Reference numeral 18 is a manipulator for manipulating the mount, and 19 is a mount having a function of manipulating the shaft as a support mechanism of the recording medium 3.

The operation of the holographic recording / reproducing apparatus configured as described above will be described below.

When recording, information is converted into the SLM from the computer 8 and displayed, and when the reference light 6 and the object light 7 are simultaneously incident on the recording medium 5, the object light 7 is a Fourier transform of the SLM image. And the reference light 6 cause an interference phenomenon to generate interference, and the interference fringe is recorded on the recording medium 3.

At the time of reproduction, when the object light is blocked by the beam blocker 17 and only the reference light is incident on the recording medium 3, the reference light is diffracted by the interference pattern recorded on the recording medium 3 in the direction in which the CCD 5 is located. When the object light is reproduced and the object light is imaged on the CCD 5 by the imaging lens 4, the image displayed on the SLM 1 is imaged on the CCD 5, and then converted into an electrical signal. ) Stores and analyzes an electrical signal from the CCD 5.

The recording of another information is recorded on the recording medium 3 by converting and displaying other information on the SLM 1 and changing the deflection angle of the beam deflector 11, between the beam deflector 11 and the recording medium 3. Since the magnification of the terel scope 9 located at 1 is 1: 1, even if the deflection angle is changed by the beam deflector 11, only the incident angle of the reference light 6 incident on the recording medium 3 is changed. 3) is always imaged constantly.

Therefore, the incident angle is recorded in the reference light and the object light recording medium which are slightly different.

In this way, when the reference light is incident on the overlapped interference pattern at the same position, only the interference light created by the reference light and the object light having the same incident angle as the reference light used at the time of recording is satisfied and only one object light is satisfied. Is played.

The incident angle satisfying the Bragg condition of the interference is very sensitive, and even if the incident angle of the reference light is slightly displaced (generally 1/100 degree or more), the desired object light is not reproduced well.

Due to the sensitivity of the incident angle of the reference light, when the recording medium is separated from the system and then recombined, the position and angle when the recording medium records the interference fringe are not shifted even a little as shown in FIGS. 3A and 3B. Should be given.

3 (a) and (b), the recording medium rotates finely by θt with the Z-axis as the rotation axis. In this case, data other than the desired data is read or desired data is reproduced. Even if the incident angle of the reference light does not satisfy the Bragg condition, the rotational efficiency to be reproduced is low, resulting in inaccurate data.

When Fig. 3 (a) with reference to (b) and described in more detail, of the recording medium position is to be evenly divided by n number of SLM page image P ₁ ~ Pn in θt = 0 the condition reference light is in the θ ₁ to θn In the case of reproduction after scanning and recording, if the position of the recording medium is θt = 0 even during reproduction, when the incident angle of the reference light is changed from θ ₁ to θ n, the images of P _{1 to} Pn are reproduced and formed on the CCD 5. .

However, if the recording medium is mounted on the mount and the angle is not θt = 0 and the angle is minute, even if the incident condition of the reference light is θi for reproducing the i-th phase Pi, the Bragg condition is not satisfied and the image is not reproduced or the image is reproduced There was a problem that there is a case that blurs and other images are reproduced.

As a conventional method for solving such a problem, there is a method as shown in FIG.

That is, a precision micromanipulator member (not shown, but generally not shown) mounted on the recording medium 3 to the mount 19 capable of finely manipulating several axes 20 to 23 and attached to the mount 19. Used to control the mount controller 18 to align the recording medium 3.

However, this method requires the use of expensive, accurate mounts and mount controllers, and it is difficult not only to increase the size of the system but also to check whether the alignment of the recording medium is correct or not. There was a problem that it was difficult.

Accordingly, the present invention is to provide a holographic recording / reproducing method for aligning a recording medium in an optimal state when reproducing recorded information.

It is another object of the present invention to provide a holographic recording / reproducing method for accurately aligning the recording medium using a conventional inexpensive fixed mount without a precise and expensive mount for fixing and mounting the recording medium.

1 is a block diagram schematically showing a conventional holographic device

2 is a view showing a precision alignment device for aligning a conventional recording medium,

3 (a) and 3 (b) are diagrams schematically showing the types of irradiation of the object light and the reference light to the recording medium and when the reference light is not aligned with the recording medium.

4 (a) and (b) show the types of information recorded on the recording medium of the present invention and the CCD output when the recording medium is reproduced, respectively.

5 is a schematic representation of a holographic device for implementing the method of the present invention;

6 is a view for explaining a recording medium correction state according to the present invention.

Explanation of symbols for main parts of the drawings

1: SLM (Spatial Light Modulator)

2: FTL (Fourier transform lens)

3: recording medium 4: imaging lens

5: CCD 6: reference light

7: object light 8: computer

9: 1: 1 telescope 10: reflector

11 beam deflector 12,13 beam diffuser

14 beam splitter 15 laser light source

17: beam blocker 18: mount controller

19,19 ': mount

In the holographic recording / reproducing method for achieving the object of the present invention, a holographic recording that records information by dividing the light emitted from the light source into a reference light and an object light and recording the information and reproducing the information using only the reference light. A recording / reproducing method comprising the steps of: recording regular information in the form of a bar-array using an object light and a reference light having a predetermined angle of incidence on a first sheet of a recording medium, and dividing the data evenly based on the angle of incidence of the reference light; Recording normal information from the second chapter of the recording medium using the reference light and the object light having a plurality of incident angles, and reading and controlling the regular information recorded in the first chapter of the recording medium using the reference light. Resetting the incident angle of the reference light so that the alignment state of the first sheet of the recording medium becomes an optimum state; And reproducing the normal information recorded from the second chapter of the recording medium by scanning at the incidence angle of the set reference light by dividing it evenly at the same interval as in the normal information recording step. It features.

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described concretely based on an accompanying drawing.

FIG. 5 is a block diagram of a holographic device for implementing the holographic recording / reproducing method of the present invention, in which the mount 19 for mounting the recording medium 3 is mounted in the conventional case shown in FIG. In the case of the present invention shown in FIG. 5, the mount 19 'is a holder for simply fixing the recording medium 3 in the case of the present invention shown in FIG. The difference is that the conventional remote controller 18 is also not provided.

Other components are the same as in the prior art shown in FIG. 1, and the detailed description thereof is omitted using the same reference numerals for the same components.

The holographic recording / reproducing method according to the present invention will be described using the holographic apparatus shown in FIG. 5 configured as described above.

First, as shown in Fig. 4 (a), the angle of incidence and the predetermined angle of incidence with the object light 11 in the first chapter P ₁ of the recording medium 3, for example, as shown in Fig. 3 (b). Using the reference light with (θ ₁ ), the regular information of the bar-array type 24 is recorded.

Next, _two recording mediums 3 are formed using the reference light 6 and the object light 7 having a plurality of incidence angles θ _{2 to} θ n evenly divided based on the incident angle θ ₁ of the reference light. Record the normal information from the first chapter (P ₂ ) to the last chapter (Pn).

In reproduction, the light blocker 17 first blocks the object light 7 and then irradiates only the reference light to the recording medium 3 so that the regular recording of the first chapter P ₁ of the recording medium 3 is performed. Read the information.

At this time, if the incident angle of the reference light is set to θ ₁ , which is the incident angle of the reference light at the time of recording, an image of a bar-array image is formed on the CCD. If the recording medium 3 is slightly rotated around the Z-axis, The angle of incidence and the angle of incidence at the time of recording become different, and as a result, θt has a minute angle as shown in FIG. 3 (b), whereby the image of the bright part of the bar-array reproduced is CCD. The current Imax (at this time, the current value is maximized as shown in Fig. 4B) and the image of the dark portion of the bar-array imaged on the CCD are converted to the current Imin ( At this time, the value of Imax-Imin, which is a difference from the current value, becomes the minimum value as shown in Fig. 4B.

Therefore, the beam deflector 11 is finely adjusted by the computer 8, and the value of Imax-Imin is controlled to the maximum, and the incident angle of the reference light at this time is θ ₁ ^′ Is obtained and reset to the incident angle of the reference light for reproducing the bar-array recorded in the first chapter of reproduction.

Incident angle at the time of this reproduction θ ₁ ^′ May be the same as or different from the incident angle θ ₁ at the time of recording, which is different from the incident angle of the reference light at the time of reproduction and the reference angle at the time of recording during the micro-rotation around the Z-axis, that is, as shown in FIG. Similarly, when the incident angle of the reference light at the time of reproduction occurs by θ s with respect to the incident angles θ ₁ to θ n (dotted line) of the reference light when information is recorded on the recording medium 3, the first chapter (P) as described above. Reference light incident angle of ₁ ) θ ₁ ^′ The deviation of θ s is compensated by controlling the beam deflector 11 under the control of the computer 8 with respect to θ ₁ ^′ ) And evenly divided by the same interval as the recording time θ ₂ ^′ -θ n ^′ By setting the reference light incident angle ( θ ₂ ^′ -θ n ^′ ) To the recording medium.

The same applies if there is no microrotation around the Z-axis.

Then, the incident angle of the reference light during reproduction ( θ ₁ ^′ ) Is determined by dividing the incident angle (θ ₁ 'to θ n') of the reference light after the second chapter evenly at the same interval as the incident angle (θ ₂ to θ n) of the reference light when recording the above-mentioned normal information. The normal information recorded from the second sheet P ₂ of the recording medium is reproduced by scanning the recording medium 3 at the incident angles θ ₂ 'to θ n'.

According to the method of the present invention, when recording, a bar-array image is recorded on the first sheet of the recording medium using the reference light and the object light having a predetermined incident angle, and the incident angle of the reference light of the first chapter from the second chapter of the recording medium. Normal information is recorded by irradiating each of the plurality of reference light incident angles which are divided equally on the basis of the degree, and recorded. After reproduction, the bar-array image recorded on the first chapter of the recording medium is reproduced using only the reference light. The reference light incident angle when the difference between the maximum current corresponding to the light on the bar-array and the minimum current corresponding to the dark portion becomes maximum is reset to the incident angle of the first chapter, and reproduction of normal information recorded from the second chapter is reset. Based on the angle of incidence of the first chapter, and equal to the interval obtained by equally dividing the angle of incidence of reference light when recording normal information By dividing it evenly at intervals, the angle of incidence of the reference light is reset, and the angle of incidence of the reference light is irradiated to the recording medium for reproduction so that the alignment of the reference light to the recording medium at the time of reproduction can be optimally adjusted. It is necessary to configure the mount finely because the beam deflector is adjusted to maintain the optimal state by decoding the current value inputted and converted into the CCD corresponding to each image by a computer while fixing the mount equipped with the recording medium. Not only does it eliminate the need for a mount controller, but it also simplifies the mount structure.

As described above, the holographic recording / reproducing method of the present invention can maintain the optimal alignment of the reference light at the time of reproducing, so that the recording information reproduction efficiency is not only high, but also the mount structure is simple and the mount adjuster is not necessary. It is possible to implement a graphics device and to significantly reduce the installation space.

Claims (2)

A holographic recording / reproducing method of dividing a light emitted from a light source into a reference light and an object light to enter a recording medium to record information and to reproduce information using only the reference light. Recording regular information in the form of a bar-array using an object light and a reference light having a predetermined angle of incidence on the first chapter of the recording medium; Recording normal information from the second chapter of the recording medium by using the reference light and the object light having a plurality of incidence angles equally divided based on the incidence angle of the reference light; Resetting the incident angle of the reference light so that the alignment state of the first sheet of the recording medium is optimal while the regular information recorded on the first chapter of the recording medium is read and manipulated by the reference light; And reproducing the normal information recorded from the second chapter of the recording medium by scanning at the incident angle of the reference light set based on the reset angle of incidence and being equally divided at the same interval as in the normal information recording step. Holographic recording / reproducing method characterized in that. The method of claim 1, Resetting the alignment of the first sheet of recording medium to an optimal state may include an image current of Imax in the regular information of the bar-array type, and an image of the dark portion of the recording medium. A holographic recording / reproducing method, characterized by resetting by controlling the incident angle of the reference light so that the value of the difference Imax-Imin becomes maximum when the current is Imin.