JP2919632B2 - Recording and / or reproducing apparatus for optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the recording of optical recording media and / or
And a playback device .

[0002]

2. Description of the Related Art In recent years, research on using a photochromic material for a recording layer of an optical recording medium has been actively conducted.

A photochromic material has such a property that when irradiated with light of a predetermined wavelength, the structure of a molecule changes due to a photochemical reaction, and the optical characteristics of the molecule change. Further, when a molecule having the above structure is irradiated with light having another predetermined wavelength, the molecule has a property of returning to the original structure.

Therefore, when a photochromic material is used for a recording layer of an optical recording medium, information is recorded by changing the absorbance by irradiating light of a predetermined wavelength, and a change in absorbance for light of a specific wavelength is detected. There is known a recording / reproducing method for reproducing information by using the method.

However, in the above-mentioned reproducing method, there is a problem that even if the light for reproducing the information is weak, a photochemical reaction occurs in the molecule and the recorded information is destroyed.

As a recording / reproducing method other than the above, for example, Japanese Patent Application Laid-Open No. 63-259850 (G11B 7/2)
4) A publication discloses a method for recording an optical recording medium using a photochromic material having optical rotation.

According to this method, in the state before and after the reversible chemical reaction, the molecule of the photochromic material has optical rotation since one state has an asymmetric carbon atom and has an asymmetric carbon atom in the other state. Since there is no optical rotation, it is possible to use the fact that it has no optical rotation, for example, to discriminate whether information is recorded or not by the presence or absence of optical rotation.

However, when the above-mentioned method using optical rotation is used for a reflection type optical recording medium, incident linearly polarized light for reproduction passes through a recording layer having optical rotation and the polarization plane rotates by an angle δ. However, when reflected by the reflective layer and transmitted again through the recording layer, the polarization plane rotates the angle δ in the opposite direction to the above,
As a result, rotation of the plane of polarization does not occur between the reflected light and the incident light, and information cannot be reproduced.

Therefore, the above-mentioned method utilizing optical rotation is used for a transmission type optical recording medium. However, in a transmission type optical recording medium, focus servo such as that used for a normal reflection type optical recording medium is used. There was a problem that the system could not be used.

The reason is that the reflection type optical recording medium shown in FIG.
In the case of 101, when a focus shift (indicated by a broken line in the figure) occurs due to the warp or the like of the optical recording medium 101, focus servo is performed by utilizing that reflected light does not return to parallel light after passing through the objective lens 102. Although the transmission type optical recording medium 10
For 1 ', in focus deviation (Figure 6,
(Indicated by a broken line), the focus servo could not be performed because the light remained parallel after passing through the objective lens 102 '.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and has been made in consideration of the above points, and is directed to a transmission type optical recording device capable of performing servo such as focus servo.
It is an object to realize a recording and / or reproducing apparatus for a recording medium .

[0012]

SUMMARY OF THE INVENTION The optical recording medium of the present invention is described below.
The recording / reproducing device has at least a recording layer and a semi-reflective layer.
From a light source to a transmission-type optical recording medium laminated on a substrate
A first objective lens for condensing and emitting the emitted light,
A second means for converting light transmitted through the optical recording medium into desired light;
And the light reflected by the semi-reflective layer.
The first objective lens and the second
A servo circuit for driving the objective lens .

Also, in the recording and / or reproducing apparatus for an optical recording medium according to the present invention, the first and second objective lenses may be arranged such that a distance between them is set.
It is characterized in that it is adjusted and driven so that the separation is constant .

[0014]

Since the optical recording medium has the semi-reflective layer, a part of the recording light or the reproducing light is reflected, and the first light disposed on both sides of the optical recording medium based on the reflected light . The second
Servo can be performed by driving the objective lens , and recording or reproduction can be performed by another part of the recording light or the reproduction light.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of an optical recording medium 1 used in the first embodiment of the present invention. This optical recording medium 1
Is glass, PMMA (polymethyl methacrylate),
On a substrate (substrate) 2 made of a material such as PC (polycarbonate), a semi-reflective layer 3 having a property of partially transmitting reproduction light and / or recording light and partially reflecting light is formed by vapor deposition or the like. Have been.

On the semi-reflective layer 3, a recording layer 4 containing a material whose optical rotation is changed by light irradiation or heating is formed by a spin coating method, a vapor deposition method, an LB method or the like.

Further, on the recording layer 4, a protective layer 5 made of an ultraviolet curable resin or the like which transmits reproduction light and / or recording light is formed.

The semi-reflective layer 3 is made of, for example, an Al thin film having a thickness of about 300 angstroms, various metal thin films such as Au, Ag, and Cu, alloy thin films, or a film corresponding to the wavelength of light for recording and / or reproduction. A dielectric multilayer film can be used. In particular, the dielectric multilayer film is desirable because it has almost no light absorption and can be designed to efficiently reflect and transmit light. The reflectivity of the semi-reflective layer 3 can be appropriately set by changing the layer thickness or the like. If the reflectivity is about 20%, the servo described below can be executed.

The recording layer 4 has the property that the optical rotation is changed by light irradiation or heating as described above, for example, as disclosed in JP-A-63-259850 (G11B7 / 24). Various photochromic materials such as spiropyran-based photochromic materials, and further, azobenzene-based and diarylethene-based photochromic materials can be appropriately used.

The optical recording medium 1 used in the first embodiment
May have a configuration as shown in FIGS. Note that the same portions are denoted by the same reference numerals and description thereof will be omitted. In particular, the protective layer 5 made of the above-described ultraviolet curable resin can protect the recording layer 4 and the like. However, since the protective layer 5 itself is easily scratched and adhered, the semi-reflective layer 3 and the recording layer 4 as shown in FIG. 4 to substrate 2
It is desirable that the optical recording medium 1 has such a structure as to be sandwiched between them.

In the optical recording medium shown in FIGS. 1 to 3, the incident light (reproduction light and / or recording light) may be incident from either the upper or lower surface of the optical recording medium 1.

The optical recording medium 1 described above can record information by a change in the optical rotation generated in the recording layer 4 and can perform reproduction by detecting the change in the optical rotation with, for example, a polarizer.

Next, FIG. 4 shows a schematic diagram of an example of a reproducing apparatus for reproducing the above-mentioned optical recording medium 1 based on this principle. Note that a medium driving device and the like are not shown.

Reference numeral 6 denotes a reproducing light source such as a semiconductor laser which outputs linearly polarized laser light having a wavelength of 0.78 μm. Reference numeral 7 denotes a drive circuit for driving the reproduction light source 6. The laser light output from the reproduction light source 6 is collimated by the lens 8, passes through the beam splitter 9, and enters the objective lens 10.

Part of the laser light incident on the objective lens 10 passes through the semi-reflective layer 3 of the optical recording medium 1 (see FIG. 1) and is condensed on the recording layer 4, and part of the laser light is It is reflected at 3.

The laser beam condensed on the recording layer 4 rotates its polarization plane according to the optical rotation based on the information recorded on the recording layer 4, so that it is converted into parallel light by the objective lens 20. A difference occurs in the amount of light passing through the polarizer 25 and the lens 26, and a reproduced signal based on a change in the output of the photodetector 27 is obtained.

The laser light reflected by the semi-reflective layer 3 passes through the objective lens 10 again, and a part thereof is reflected by the beam splitter 9 and passes through the focus error detecting optical system 30 to the photo sensor 31. To reach.

The error signal obtained from the photo sensor 31 passes through the focus servo circuit 32 and the actuators 33 and 33 '.
Then, the objective lenses 10 and 20 are driven so as to reduce the focus error due to the above-described warpage of the optical recording medium 1 and other causes.

Various methods such as a conventional astigmatism method and a knife edge method are used for focus error detection by the focus error detection optical system 30 and the photosensor 31. At this time, the objective lenses 10 and 20 are adjusted and driven so that the distance between them is always constant.

As described above, by providing the transflective optical recording medium 1 utilizing optical rotation with the semi-reflective layer 3, of the light incident on the optical recording medium 1, the light is reflected by the semi-reflective layer 3. Focus servo can be performed using light.

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

As described above, the optical recording medium used in the present invention is:
Since optical rotation occurs in a wavelength region where the absorbance of the photochromic material is small and a wavelength region where there is no absorbance, nondestructive reading is possible by reproducing information using light in these wavelength regions. Further, the polarization state of light used in the recording and / or reproducing apparatus of the present invention is not limited to linear polarization, but other polarization states such as elliptically polarized light can be used.

A focus servo system having a function of converging a diffraction limited light spot on the optical recording medium 1 is indispensable for the reflected light detection system, but the transmitted light detection system can obtain a good reproduction signal. Auxiliary focus servo to be performed is sufficient. Therefore, in each of the first and second embodiments, a focus servo system for driving the objective lens 20 is provided, but this servo system may be omitted and the objective lens 20 may be fixed.

In this embodiment , the focus servo is used for the reproducing apparatus. However, the present invention can be used for a recording apparatus and a recording / reproducing apparatus as appropriate. Similarly, it can be performed based on the light reflected by the semi-reflective layer.

The optical recording medium of the present invention may be a disk or a tape. Further, the optical recording medium of the present invention is not limited to the embodiments, and it is sufficient that the optical recording medium has at least a semi-reflective layer and a recording layer. For example, the semi-reflective layer and the recording layer need not be in contact with each other. Further, the optical recording material used for the recording layer of the optical recording medium of the present invention may be one that utilizes optical characteristics such as absorbance other than optical rotation and birefringence. Servo can be performed. In this case, it is necessary to appropriately change the optical system of the recording and / or reproducing apparatus of the optical recording medium, the wavelength (light source or the like) of the light to be used, and the polarization state.

[0045]

Since the optical recording medium has the semi-reflective layer, a part of the recording light or the reproducing light is reflected, and the optical recording medium is arranged on both sides of the optical recording medium based on the reflected light. first, the servo by driving the second objective lens row Utame one
When the other objective lens is driven, the other objective lens
Between the optical disc and the optical recording medium
Such recording is prevented, and good recording or reproduction can be performed with the light transmitted through the optical recording medium, out of the recording light or the reproduction light.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of an optical recording medium used in a first embodiment according to the present invention.

FIG. 2 is a sectional view of another optical recording medium used in the embodiment.

FIG. 3 is a sectional view of still another optical recording medium used in the above embodiment.

FIG. 4 is a schematic diagram showing a reproducing apparatus according to a first embodiment of the present invention.

FIG. 5 shows a conventional focus servo for a reflective optical recording medium.
FIG.

FIG. 6 shows a conventional focus servo of a transmission type optical recording medium.
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Substrate 3 Semi-reflective layer 4 Recording layer

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/24 538 G11B 7/24 516 G11B 7/24 522 G11B 7/09

Claims (2)

(57) [Claims] At least a recording layer and a semi-reflective layer are formed on a substrate.
From the light source to the transmission type optical recording medium
A first objective lens for condensing and irradiating the collected light;
Second objective for converting light transmitted through the recording medium into desired light
Obtained by a lens and light reflected by the semi-reflective layer
The first objective lens and the second objective lens based on a signal.
And a servo circuit for driving the lens.
Recording and / or reproducing apparatus for an optical recording medium. 2. The method according to claim 1, wherein the first and second objective lenses are located between the first and second objective lenses.
It is characterized by being driven so that the distance is adjusted to be constant.
The recording and / or reproduction of the optical recording medium according to claim 1,
Raw equipment.