KR100626961B1 - Holographic rom disc and holographic rom/digital data disc combo pick-up system - Google Patents

Abstract

The present invention relates to a holographic ROM / digital data disc combo pick-up apparatus capable of playing a holographic ROM disc, and a holographic ROM disc reproducing method of a recording layer, comprising: a light source unit for emitting a reference light for holographic ROM disc reproduction; A first light path for detecting hologram reproduction light from each of the multiple data recording layers diffracted by the incident reference light and then diffracted by the reference light and output from the disc surface Tracking the holographic ROM disc using a second light path for detecting a focusing error of the hologram reproduction light, and changing the angle of the reference light by moving the light source vertically, and using light detection values detected in the first and second light paths. Servo control for controlling focusing and hologram located on the opposite side of holographic ROM disk And a digital data disc pickup unit configured to perform the pick ROM disc focusing servo control and to apply the detected focusing error signal to the servo controller to control the holographic ROM focusing operation after the initial focusing.

Description

HOLOGRAPHIC ROM DISC AND HOLOGRAPHIC ROM / DIGITAL DATA DISC COMBO PICK-UP SYSTEM}

1 is a block diagram of a holographic ROM / digital data disc combo pickup device according to the prior art;

2 is a block diagram of a holographic ROM / digital data disc combo pickup device according to the present invention;

3 is a perspective view of a holographic ROM / digital data disc combo pickup device according to the present invention;

4 is a cross-sectional view of the holographic ROM disk used in the holographic ROM / digital data disk combo pickup device according to the present invention;

5 is a view showing a track structure of a holographic ROM disk according to the present invention;

6 is a view for explaining the operation of the holographic ROM / digital data disc combo pickup device according to the present invention;

7 is a view for explaining a focus and incident reference light between an objective lens and a disc in the combo pickup device according to the present invention;

8A and 8B are diagrams specifically showing the light detectors of the combo pickup device according to the present invention;

<Brief description of the major symbols in the drawings>

200: Holographic ROM Disc Pickup

250: digital data disc pickup

201: disk

204: light source

208: Beam Splitter

210: objective lens

230: servo control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic ROM / digital data disk combo pick-up device, and more particularly to holographic ROM / digital data discs. A data disc combo pickup device.

In general, two or more different devices connected to one integrated system are called a combination system or a combo-system. An example of a combination system is a VCR / TV combo system that integrates the functions of a VCR and a TV, or a DVD / VCR that integrates a player of digital data discs such as a VCR (Video Cassette Record) deck and a DVD (Digital Video Disk). There is a combo system, which provides user convenience by playing or recording a disc such as a DVD and a VCR tape in a single device.

In addition, recently, the intensity and direction of the object light are recorded by changing the angle of the reference light such as angle overlap, wavelength overlap, and phase code overlap, so that the three-dimensional image of the object can be displayed. Development of Holographic ROM Disc / Digital Data Disc Combo Pick-up Device that Plays Holographic Disc and CD, DVD Disc that Exceeds Storage Capacity of CD and DVD by Storing Data in Thousands of Hologram Formats It is also actively underway.

FIG. 1 illustrates a schematic block configuration of one of the above-described holographic ROM / digital data disc combo pickup devices, and the patent filed by the present applicant for the holographic ROM / digital data disc combo pickup device of FIG. A description of the structure and operation is disclosed on 2003-89681.

On the other hand, the conventional combo pickup device as described above has the following problems.

First, a red laser used in a DVD is used to perform a focus servo when reproducing a holographic ROM disk. In the structure of a conventionally proposed disk, a reflective layer exists in the middle of the disk. In this case, the servo position of the objective lens becomes the reflective layer, while the image formation position of the reproduced hologram is usually just above the disk. That is, the original image of the reproduced hologram is not at the focal position of the objective lens. If the position of the object is not in the focal plane of the objective lens, the image formed in the slit plane becomes blurry than in the focal plane.

Second, optical systems, which typically use lasers, usually exhibit optimal performance for specific wavelengths. Therefore, when using a laser having two or more wavelengths with a single optical system as in the prior art, the optical system design is difficult to achieve optimal performance for each wavelength and to achieve optimal performance for all wavelengths.

Third, when reading discs of multiple media with a single pickup as in the prior art, each optical system of an optimized dedicated pickup must be slightly modified, and further, designed to satisfy the characteristics of various media simultaneously. In this case, the recording and reproducing characteristics may be worse than those of using a dedicated player, and the design of the optical system becomes very difficult because all characteristics of each medium must be considered.

It is therefore an object of the present invention to provide a holographic ROM / Digital Data Disc Combo Pick-up apparatus that uses a pickup for reproduction of a digital data disc and a pickup for reproduction of a holographic ROM disc, respectively.

Another object of the present invention is to provide a combo pick-up apparatus for a holographic ROM / digital data disc which simplifies the entire system by applying a focus servo technique by DVD when playing a holographic ROM disc.                         

It is still another object of the present invention to provide a focal length different from the center portion of the lens through which the reproduction light is transmitted and the lens outer portion through which the reference light is transmitted to have a thin objective lens so that the reference light is accurately focused on the disc. The present invention provides a combo pickup device of a holographic ROM / digital data disc that can accurately reproduce holographic data.

It is still another object of the present invention to provide a holographic ROM disk having a reflective layer filling the recording medium between two substrates and reflecting only a beam of wavelengths emitted from the optical storage device below.

The present invention for achieving the above object is a holographic ROM / digital data disc combo pickup device capable of reproducing a holographic ROM disc, comprising: a light source unit for emitting a reference light for reproducing a holographic ROM disc, and a reference light from the light source unit; The first light path for detecting hologram reproduction light from each of the multiple data recording layers diffracted by the incident reference light and then the hologram reproduction outputted from the disc surface by diffraction by the reference light Tracking the holographic ROM disc using a second light path for detecting a focusing error of light, and changing the angle of the reference light by moving the light source vertically, and using light detection values detected in the first and second light paths. A servo controller for controlling focusing, and a hologram located on an opposite surface of the holographic ROM disk Perform the focusing servo control and pick-ROM disk, is applied to the detected focusing error signal to the servo control unit to be characterized in that it comprises a digital data disc pickup for controlling so that the graphic ROM focusing operation alone interlocking after the initial focusing.

The present invention also provides a holographic ROM disk, comprising: a data recording layer on which holographic data is recorded; a protective layer formed on and under each of the data recording layers; and a reflective layer formed on the lower protective layer. The reflective layer is characterized by reflecting red wavelength light.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation of the preferred embodiment according to the present invention.

2 is a holographic ROM / digital data disc combo pick-up apparatus capable of playing a holographic ROM disk having multiple data recording layers, according to an embodiment of the present invention. The block configuration of the combo pick-up apparatus is shown.

Referring to FIG. 2, a pickup 200 for reproducing a holographic-rom disc is mounted on the upper side of the disc 201, and a pickup 250 for reproducing a DVD is mounted below. . In the layer structure of the holographic ROM disk, as shown in FIG. 4, the substrate 302, 306 and the data recording layer 304 are stacked in a sandwich like a sandwich, and the reflective layer 308 reflects only the red laser light at the bottom thereof. )). Each disk recording layer consists of an area 400 for data recording and a separate reference track 402 for finding the focal plane of the initial pickup, as shown in FIG. At this time, the track for the focus servo of each data recording layer is recorded by the reference light having the same angle.

Hereinafter, the configuration of the holographic ROM / digital data disc combo pickup device of the present invention will be described in more detail. The combo pickup apparatus includes a light source unit 204 for emitting reference light for reproducing a holographic ROM disk having multiple data recording layers; A first light path S1 for injecting the reference light from the light source unit 204 into the surface of the disk 201 at a predetermined angle and then detecting hologram reproduction light from each of the multiple data recording layers diffracted by the incident reference light; And a second light path S2 for detecting a focusing error of the hologram reproduction light diffracted by the reference light and output from the surface of the disc 201 and the light source 204 vertically to change the angle of the reference light. Servo controlling the tracking and focusing of the holographic ROM disk using photodetection values detected in the first and second optical paths S1 and S2. A holographic ROM disk focusing servo is located on the opposite surface of the fisherman 230 and the holographic ROM disk 201, and the detected focusing error signal is applied to the servo controller 230 to perform holographic after initial focusing. And a DVD pickup 250 for controlling the ROM focusing operation.

The beam splitter (PBS) 208 reflects the reference light from the light source unit 204 and enters the disk 201 plane in the first optical path S1 and transmits the hologram reproduction light diffracted by the reference light from the disk plane. And a focus lens 208 positioned between the beam splitter 208 and the light source unit 204 to adjust the beam width of the reference light emitted from the light source unit 204, and the reference light reflected from the beam splitter 208. An objective lens 212 which enters into each data recording layer of the multi-layer holographic ROM disk under control, and enters the holographic reproduction light diffracted by reference light into the beam splitter 208, and the beam A quarter wave plate positioned between the splitter 208 and the objective lens 212 to transform the reference light reflected from the beam splitter 208 and the hologram reproduction light diffracted from the disk surface into λ / 4 (210), lens 2 (216) for forming hologram reproduction light on the 3-hole slit (218) plane, lens 1 (220) for equilibrating the reproduction light passing through the slit (218), The first light detector for tracking the holographic reproduction light transmitted through the beam splitter 208 through the three-hole slit 218 and applying the detection data to the servo controller 230 as a tracking error signal. (PDIC1) 222, and a second deformable plate 214 positioned between the beam splitter 208 and the three-hole slit 218 to transform the hologram reproduction light transmitted through the beam splitter 208 into λ / 4. do.

A second light detector for focusing the hologram reproduction light that is reflected by the reflective surface of the three-hole slit 218 and then transformed into λ / 4 through the second deformation plate 214 in the second optical path S2 ( A beam splitter 208 for reflecting to PDIC2) 226, astigmatism lens 224 for injecting hologram reproduction light reflected from the beam splitter 208 to enable focus servo by astigmatism, and the aberration ratio And a second photodetector (PDIC2) 226 for detecting the hologram reproduction light incident from the score difference lens 224 and applying the detection data to the servo controller 230 as a focusing error signal.

3 is a perspective view of a combo pick-up device of such a holographic ROM / digital data disc.

As shown in Fig. 3, the pickup 250 'for the digital data disc is located below the disc 201. Then, another rail 200 'is made above the disk 201 to mount the pickup 200 for the holographic disk. When the disc 201 is inserted and determined to be a digital disc, the pickup 250 for the lower digital disc is driven to read the digital data. Because it uses the existing DVD-only pickup, it can be read without any problem during playback.

Then, if the inserted disc is identified as a holographic disc, the two pickups 200 and 250 operate at the same time. The detection and tracking servo of the signal from the holographic ROM disk is performed using the holographic dedicated pickup 200 on the upper side, and the pickup 250 for the digital data disk on the lower side is used to perform the focusing servo.

The operating principle of the system is as follows. First, when the DVD is inserted, the lower pickup 250 for DVD is operated, and its structure is exactly the same as the conventional DVD player, so that the DVD can be read without any problem.

Next, when a holographic ROM disk is inserted, first, how to read data from a holographic ROM disk of a single data recording layer will be described.

In the light source unit 204 of the pickup structure for reproducing the holographic ROM disk shown in FIG. 2, a red laser light having S polarization is oscillated as a reference light. The oscillated reference light first passes through an optical system to produce a constant beam size on the holographic ROM disk 201 surface. The reference light passing through the beam is incident to the beam splitter (PBS) 208. The PBS 208 reflects the S-polarized light and transmits the P-polarized light as it is. Thus, the reference light having S polarization is reflected by the PBS 208 and directed to the first wave plate 210 (QWP). The QWP 210 is circularly polarized when S-polarized light is incident, and P-polarized light when the circularly polarized light passes through the QWP 210 once again. Therefore, the reference light passing through the QWP 210 becomes circularly polarized light and is incident to the objective lens 212. As shown in FIG. 7, the objective lens 212 simultaneously performs two roles of detecting a signal of the holographic reproduction light emitted from the holographic ROM disk 201 and injecting a reference light, and a hologram emitted from the holographic ROM disk. The focal lengths of the middle part of the lens through which the signal of the reproduction light passes and the edge part through which the reference light passes are different, and the middle part is in focus at the position on the data of the reproduced hologram and the edge part is in the middle part of the recording medium. Therefore, the reference light incident on the objective lens 700 is incident at a specific angle to each data recording layer in which data is recorded.

The reproduction light of the hologram data is reproduced toward the objective lens 212 with the same circularly polarized light as the reference light by the incident reference light. The regenerated light passing through the objective lens 212 is changed to P-polarized light while passing through the QWP 210 again, to the PBS 208, and this time it passes through the light as it is P-polarized light and enters the lens 2 216. The lens 2 216 serves to image the hologram data of various tracks reproduced from the disc 201 on the slit 218 surface including 3-HOLE. The slit 218 is used for signal detection and tracking servo of a holographic ROM disk as shown in FIG. 8A, which is described in detail in patent application No. 10-2003-0073730, filed by the applicant of the present application. Meanwhile, in the present invention, the slit 218 is reflectively coated except for the portion where 3-HOLE is bent to serve as a mirror, so that the regenerated light reflected from the slit 218 is reflected in the second light path ( Through S2) to be used for photodetection for focusing.

Now, the focusing servo part is described. When a holographic ROM disc is inserted, the DVD pickup 250 at the bottom of the holographic ROM disc is also operated. The red laser light emitted from the DVD pickup is the holographic ROM disc ( Reflected by the reflective layer 308 of 201, the DVD objective lens is brought to the position of the reflective layer by the DVD's focusing servo.

At this time, if it is assumed that the focal position of the holographic ROM objective lens 212 is on the side of the reproduced hologram data, as shown in FIG. 6, the servo controller 230 may use the holographic ROM objective as it is. Simultaneously sent to the lens 212, when the disc is lowered down by the wobble, the objective for the DVD is lowered down according to the focusing error signal, and the object 212 for the holographic ROM is also lowered as much. In the present invention, after the initial focusing control is performed in the second photodetector 226 for focusing in this manner, the focusing servo of the holographic ROM is controlled to operate in conjunction with the DVD focusing error detection method and apparatus. Done.

Now let's look at how the initial focus position of the holographic ROM objective lens 212 can also be located on the hologram data when the DVD objective is caught by the focusing servo. It will contain two tracks at the same time. Therefore, it is difficult to use astigmatism used in conventional optical storage devices. If only one track of the hologram data is played, the astigmatism method can be used. Therefore, the present invention proposed the data structure as shown in FIG. That is, only one reference track 402 is recorded which has a data area 400 for recording data on the disc and is spaced more than the size of the reference light inside the data recording area 400. Therefore, when reference light is incident on the reference track 402, only one track is reproduced, so that the focus servo can be performed using the reproduced track.

That is, when the holographic ROM disk is inserted, the holographic ROM pickup 200 and the DVD pickup 250 move to the portion where the predetermined focusing reference track 402 is recorded. When the reference light is irradiated, hologram data of one track is reproduced, and the reproduced hologram track goes to the slit 218 surface along the first optical path S1 described above. This track then bounces off the slit 218 plane. The reflected light emitted is reflected by the second deformed plate (QWP) 214 and is reflected on the PBS 208 surface. The reflected hologram reproduction light enters the second photodetector (PDIC2) 226 for focusing through the lens 224 causing astigmatism as in DVD and the initial position of the holographic ROM objective lens by the astigmatism described above. Can be placed on the reproduced hologram data plane. This is as shown in FIG. 8B.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the invention should be determined by the claims rather than by the described embodiments.

As described above, by allowing the holographic ROM / digital data disc combo pickup device to play the holographic ROM disc without additional configuration of the combo pickup device in addition to the holographic ROM disc and digital data discs such as CD and DVD, There is an advantage of greatly increasing the convenience of use by supporting the playback of a wider variety of digital data disk. In addition, since the present invention does not share optical components with beams of different wavelengths, the optical system is prevented from degrading, and the focus servo surface and the hologram data surface do not exist on the same surface, thereby reducing the quality of the detected data. prevent.

Claims (13)

Holographic ROM / Digital Data Disc Combo Pick-up Device that can play Holographic ROM Disc, A light source unit which emits reference light for holographic ROM disc reproduction; A first light path for injecting the reference light from the light source into the disk surface at a predetermined angle and then detecting hologram reproduction light from each of the multiple data recording layers diffracted by the incident reference light; A second optical path diffracted by the reference light and detecting a focusing error of the hologram reproduction light output from the disk surface; A servo controller which changes the angle of the reference light by moving the light source vertically, and controls tracking and focusing of the holographic ROM disk using light detection values detected in the first and second light paths; A digital data disk pickup positioned on an opposite surface of the holographic ROM disk to perform holographic ROM disk focusing servo control and to apply the detected focusing error signal to the servo controller to control the holographic ROM focusing operation after initial focusing. part Holographic ROM / digital data disc combo pickup device comprising a. The method of claim 1, The first optical path includes a beam splitter that reflects the reference light from the light source unit and enters the disk surface, and transmits the hologram reproduction light diffracted by the reference light from the disk surface; An objective lens for injecting the reference light reflected from the beamsplitter to each data recording layer of the multi-layer holographic ROM disk under servo control, and for injecting the hologram reproduction light diffracted by the reference light into the beamsplitter; A first modification plate positioned between the beam splitter and the objective lens to transform the reference light reflected from the beam splitter and the hologram reproduction light diffracted from the disk surface into lambda / 4; A tracking photodetector for detecting hologram reproduction light passing through the beam splitter through a three-hole slit and applying detection data as a tracking error signal to the servo controller; A second deformation plate positioned between the beam splitter and the 3-hole slit to transform the hologram reproduction light transmitted through the beam splitter into λ / 4 Holographic ROM / digital data disc combo pickup device comprising a. The method of claim 2, And the first optical path further comprises a focus lens positioned between the beam splitter and the light source unit to adjust a beam width of the reference light emitted from the light source unit. The method of claim 2, The three-hole slit, the holographic ROM / digital data disc combo pick-up device, characterized in that the front surface of the slit except for the hole is reflected coating to reflect the holographic reproduction light incident through the beam splitter. The method of claim 4, wherein The second optical path is a beam splitter for reflecting the holographic reproduction light that is reflected by the reflective surface of the three-hole slit, and then transformed to λ / 4 through the second deformation plate; An astigmatism lens for injecting the hologram reproduction light reflected from the beamsplitter to enable focus servo by astigmatism; A focusing light detection unit which detects a hologram beam incident from the astigmatism lens and applies detection data as a focusing error signal to a servo controller. Holographic ROM / digital data disc combo pickup device comprising a. The method of claim 2, And the servo controller performs tracking control of the holographic ROM disk by horizontally moving the objective lens position according to the data detected by the tracking photodetector. The method of claim 6, And the servo controller performs focusing control of the holographic ROM disk by horizontally or vertically moving the objective lens position according to the data detected by the focusing photodetector. The method of claim 1, When the initial holographic ROM disk is loaded, the servo controller moves to an on-disk focus servo track, injects reference light onto the data recording surface in the disk, scans the number of data recording layers in the disk, and then stores the reference light emitted from the light source unit. A holographic ROM / Digital data disc combo pick-up device, characterized in that it is controlled so as to form a data recording layer. The method of claim 1, The reference light of the light source unit is a green laser light of S-polarized holographic ROM / digital data disc combo pickup device. The method of claim 1, The focusing reference light of the digital data disk pick-up unit is a red laser light. The method according to claim 1 or 2, The objective lens has a thick thickness of a portion through which the reproduction light is transmitted and a thin portion of the portion through which the reference light is transmitted, the holographic ROM / digital data disc combo pickup device. delete delete

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