JPH0935327A - Cd-rom having two-layered structure and its reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for high-accuracy control of an optical pickup and to make it possible to respectively simultaneously read out the data of the two recording surfaces of two-layered structures. SOLUTION: The CD-ROM 1 having the two-layered structures is formed by superposing the first CD-ROM 11 and the second CD-ROM 12 above and below. Pit strings are formed on the first CD-ROM 11 on the upper side in the same manner as for ordinary CD-ROMs. A polarized light reflection film 11a having the characteristic to reflect an S polarized light component and to allow the transmission of a P polarized light component is deposited on the surface of these pit strings. The second CD-ROM 12 of the lower side is formed in the same manner as for the ordinary CD-ROMs. An aluminum reflection film 12a which reflects the laser beam transmitted through a disk substrate is deposited on the surface of the pit strings. The first and second CD-ROMs 11, 12 are superposed in such a manner that the positions of the pit strings thereof are aligned to each other in a vertical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-layered CD-ROM and a reproducing apparatus thereof, and more particularly to a CD-ROM having a double-layered structure and doubling the recording capacity and a reproducing apparatus thereof.

[0002]

2. Description of the Related Art As a method of doubling the recording capacity of a CD-ROM, a method of providing recording surfaces on both sides of the disk and a method of forming a recording surface on one side of the disk into a two-layer structure are considered.

A conventional CD-ROM whose recording surface is simply a two-layer structure.
When data is reproduced from the ROM, the optical pickup provided on one side is controlled to select the recording surface and reproduce the data.

[0004]

As described above, in the case of reproducing a conventional CD-ROM in which the recording surface is simply a two-layer structure, the recording surface is selected by controlling the optical pickup. High-precision control of the optical pickup is required, resulting in high cost. Further, in a reproducing apparatus in which one optical pickup is provided on one side of the disc, it is not possible to simultaneously read data from each of the two recording surfaces of the two-layer structure.

The object of the present invention does not require highly precise control of the optical pickup, and one optical pickup provided on one side can simultaneously read data from two recording surfaces having a two-layer structure. It is an object of the present invention to provide a double-layered structure CD-ROM and a reproducing device thereof.

[0006]

DISCLOSURE OF THE INVENTION The two-layer CD-of the present invention
The ROM is a first CD-ROM in which a polarized reflection film having a characteristic of reflecting an S-polarized light component and transmitting a P-polarized light component is attached to the surface of the pit row, and a metal reflective film is attached to the surface of the pit row. The formed second CD-ROM is superposed so that the positions of the pit rows are vertically aligned with each other.

A reproducing apparatus for a two-layer structure CD-ROM according to the present invention comprises a laser light generating means for generating a laser light containing an S-polarized component and a P-polarization component respectively, and the laser light for the two-layer structure CD-ROM. First optical means for irradiating the pit train and separating reflected laser light reflected from the pit train of the two-layer structure CD-ROM, and an S-polarized component and a P-polarized component contained in the reflected laser light, respectively. Second optical means for extracting, first light detecting means for detecting the S-polarized component extracted by the second optical means, and detection of the P-polarized component extracted by the second optical means Second light detecting means for

[0008]

The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of a two-layer structure CD-ROM of the present invention. Here, the two-layer structure CD-ROM 1
Is the first CD-ROM 11 and the second CD-ROM 12
Are formed by overlapping.

A second CD-ROM 12 which is overlaid on the lower side
Is formed in the same way as a normal CD-ROM,
An aluminum reflection film 12a that reflects the laser light that has passed through the disk substrate is attached to the surface of the pit row having the uneven structure.

A first CD-ROM 11 which is overlaid on the upper side
A pit row is formed in the same manner as in a normal CD-ROM, but the surface of this pit row is covered with a polarization reflection film 11a having a characteristic of reflecting an S-polarized component and transmitting a P-polarized component. It is worn. And the first and second C
The pit rows of the D-ROMs 11 and 12 are stacked so that the positions of the pit rows coincide with each other in the vertical direction.

By the way, as the laser light 20 for irradiating the two-layer structure CD-ROM 1, a laser light having an S polarization component and a P polarization component is used. Laser light 2
0 first enters the first CD-ROM 11. Then, the S-polarized component of the laser light 20 is reflected by the polarization reflection film 11a, but the P-polarized component of the laser light 20 passes through the polarization reflection film 11a and enters the second CD-ROM 12. The P-polarized component of the laser light 20 that has entered the second CD-ROM 12 is reflected by the aluminum reflection film 12a and transmitted through the first CD-ROM 11.

Therefore, by detecting the S-polarized component of the reflected laser light 21 reflected from the double-layered CD-ROM 1, the pit string information of the first CD-ROM 11, that is, the information is recorded in the first CD-ROM 11. The reproduced data can be reproduced. Further, by detecting the P-polarized component of the reflected laser light 21 reflected from the two-layer structure CD-ROM 1,
It is possible to reproduce the pit string information of the second CD-ROM 12, that is, the data recorded in the second CD-ROM 12.

FIG. 2 shows such a two-layer structure CD-ROM.
1 shows an example of a reproducing device of the laser light generator 2 for generating a laser light 20 including an S-polarized component and a P-polarized component.
, A polarizing prism 3 for separating the reflected laser light 21 reflected from the two-layer structure CD-ROM 1, an S-polarized component, and a P-polarized component.
A polarization prism 4 for separating a polarization component and an S polarization component 2
The light detector 5 detects 2 and the light detector 6 detects the P-polarized component 23.

The laser light 20 containing the S-polarized component and the P-polarized component passes through the polarizing prism 3 and has a two-layer structure CD-R.
It is incident on OM1. The reflected laser light 21 from the two-layer structure CD-ROM 1 includes the S-polarized component reflected by the polarization reflection film 11a of the first CD-ROM 11 and the second CD-R.
The P-polarized light components reflected by the luminum reflective film 12a of the OM 11 are included.

The reflected laser light 21 is separated by the polarization prism 3 and then further separated by the polarization prism 4 into an S polarization component 22 and a P polarization component 23. First CD-
The S-polarized light component 22 including the recording data of the ROM 11 is detected by the photodetector 5 and output as the reproduction data signal S1 of the first CD-ROM 11. Similarly, the second C
The P-polarized light component 23 including the recorded data of the D-ROM 12 is
The second CD-ROM 12 detected by the light detection unit 6
Is output as the reproduced data signal S2.

[0017]

As described above, according to the present invention, S
A first C in which a polarization reflection film having a polarization characteristic of reflecting a polarization component and transmitting a P polarization component is attached to the surface of the pit row.
A D-ROM and a second CD-ROM in which a metal reflection film such as aluminum is adhered to the surface of the pit row are stacked so that the positions of the pit rows are aligned with each other in the vertical direction. -ROM is formed, and this two-layer CD-RO
By irradiating M with a laser beam containing an S-polarized component and a P-polarized component and separately detecting the S-polarized component and the P-polarized component from the reflected laser light, the optical pickup does not need high-precision control. Moreover, data can be simultaneously reproduced from two recording surfaces having a two-layer structure by one optical pickup provided on one side.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a two-layer structure CD-ROM of the present invention.

FIG. 2 is a block diagram showing an embodiment of a reproducing device for a double-layered CD-ROM of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Two-layer structure CD-ROM 2 Laser light generation part 3,4 Polarization prism 5,6 Photodetection part 11 1st CD-ROM 11a Polarization reflection film 12 2nd CD-ROM 12a Aluminum reflection film 20 Laser light 21 Reflection Laser light 22 S-polarized component 23 P-polarized component S1, S2 Reproduced data signal

Claims (2)

[Claims] 1. A first CD-ROM having a polarizing reflection film having a characteristic of reflecting an S-polarized component and transmitting a P-polarized component transmitted on a surface of a pit row, and a metal reflective film on a surface of the pit row. A two-layer structure CD-ROM, which is formed by superposing a deposited second CD-ROM so that the positions of pit rows are vertically aligned with each other. 2. A laser beam generating means for generating a laser beam containing an S-polarized component and a P-polarized component, respectively, and irradiating the laser beam to a pit row of the double-layered CD-ROM and the double-layered CD- The first optical means for separating the reflected laser light reflected from the pit row of the ROM, the second optical means for extracting the S-polarized component and the P-polarized component contained in the reflected laser light, and the second optical means. First optical detecting means for detecting the S-polarized component extracted by the optical means, and second optical detecting means for detecting the P-polarized component extracted by the second optical means. Characteristic two-layer structure CD-ROM reproducing apparatus.