JP2708024B2 - Optical disc identification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining an optical disk on which an information signal can be recorded, reproduced or erased.

[0002]

2. Description of the Related Art In recent years, in addition to read-only optical disc devices such as CD players, optical disc devices capable of recording and reproducing signals have been actively developed. Usually, recording and reproduction of an optical disk are performed by focusing a radiation beam such as a semiconductor laser on a recording layer of the optical disk by a lens. Here, the recording layer is a layer in which a pit layer is formed in a CD and a layer formed in a recordable optical disk is deformed or forms a magnetic domain by a focused laser beam. In order to increase the recording density of the optical disk, it is necessary to reduce the spot diameter r of the focused beam, but r has the following relationship between the numerical aperture NA of the lens and the wavelength λ of the laser light.

R = λ / NA (1) The above equation (1) indicates that a large NA can reduce the spot diameter r and enable high-density recording. However, when a high NA lens is used, spot aberration due to disc tilt (tilt) or the like increases.
To suppress this, it is effective to reduce the thickness of the disk substrate of the optical disk. Therefore, in an optical disk capable of high-density recording, it is preferable that the disk substrate be thinner than a conventional optical disk.

Therefore, as a measure for increasing the recording density of an optical disk, a thinner disk substrate is used on the optical disk side, a lens with a higher NA is used on the optical disk device side, and the focusing corresponding to the thin disk substrate is performed. An optical head for an optical system is required. FIG. 9 is a diagram showing a configuration of such an optical disk device. In FIG.
Denotes an optical disk, as shown in FIG. 10, a disk substrate having a thickness d smaller than the conventional one, a recording or pit layer,
And a protective layer. An optical head 102 includes optical elements such as a high NA objective lens (not shown), a semiconductor laser, and a photodetector. Reference numeral 103 denotes a linear motor, which is installed below the optical disc 101. 104 is a drive circuit for driving the linear motor 104, 105 is a spindle motor, 106 is a servo circuit, and 107 is a controller.

The operation of the conventional optical disk device configured as described above will be described below. Servo circuit 1
06 controls the spindle motor 105 to drive the optical disc 101 at a constant linear velocity (CLV) or a constant peripheral velocity (CAV).
V). The optical head 102 is designed with an optical system that focuses a laser beam on a recording or pit layer of the optical disc 101 and also corrects aberrations caused by a substrate having a thickness of d. Play the signal on the disc. Also, the servo circuit 106
According to the servo signal output from the optical head 102, the laser beam is focused on the optical disk 101, or the linear motor 103 is controlled through the drive circuit 104 by a command from the controller 107 to move the optical head 102 in the inner circumferential direction of the disk or Move in the outer peripheral direction.

If an optical disk apparatus corresponding to such a high recording density and thin disk substrate is used to focus laser light on a conventional optical disk having a low recording density and a thick disk substrate, the thickness of the disk substrate is reduced. Due to the difference, aberration occurs in the beam spot, and it becomes difficult to record or reproduce a signal. Therefore, a device for condensing laser light with an optical system corresponding to the substrate thickness of each optical disk is considered. At this time, it is necessary to discriminate the disc substrates having different thicknesses and select an optical system corresponding to each disc. It is conceivable that the state is determined according to the type of the disk.

[0007]

However, providing such an identification hole in the cartridge increases the number of manufacturing steps of the disk cartridge. In view of the above, an object of the present invention is to provide a method of distinguishing high-density and low-density optical disks having different thicknesses of disk substrates with a simple configuration.

[0008]

In order to achieve the above object, an optical disc discriminating method according to the present invention comprises one of a plurality of transparent substrates having different thicknesses and is capable of recording, reproducing or erasing information signals. A method of discriminating, wherein a light beam is condensed through a transparent substrate by a converging optical system in which aberration is corrected for a plurality of transparent substrates having different thicknesses, and a diffracted light component included in the light beam returned from the optical disk. , The type of the optical disc is determined.

[0009]

According to the present invention, by taking the above-described procedure, the light beams are condensed by the condensing optical systems corresponding to a plurality of transparent substrates having different thicknesses on the mounted optical disk, and the light beams returned from the transparent substrate are condensed. Only when the diffracted light component can be detected
The transparent substrate having a thickness corresponding to the condensing optical system at that time is identified.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present embodiment, the following description will be made on the assumption that the disk substrate has two types of thicknesses. FIG. 1 is a configuration diagram of an optical disk apparatus according to a first embodiment using the optical disk discriminating means of the present invention, FIG. 2 is a plan view showing the arrangement of main parts of the embodiment, and FIG. It is a perspective view of a cartridge.

In the above three figures, reference numeral 1 denotes a first or second optical disk, each having a different disk substrate thickness. Reference numeral 2 denotes a cartridge for storing and protecting a disk, and is formed of a rigid material such as plastic. Reference numerals 3 and 5 denote a first optical head and a second optical head, each of which includes a focusing optical system including an objective lens (not shown), a semiconductor laser, a photodetector, a beam splitter, and the like, a base, an actuator, and the like. Reference numeral 4 denotes a first linear motor which is installed on the lower surface of the optical disk 1 and moves the first optical head 3 in the radial direction of the disk while keeping a constant distance from the disk surface. Reference numeral 6 denotes a second linear motor which is installed on the lower surface of the optical disk 1 so as to face the first linear motor 4 and moves the second optical head 5 in the same manner. As shown in FIG. Is longer than the first linear motor 4 and extends outside the outer peripheral portion of the optical disc 1. Therefore, when the second optical head 5 moves to the outside of the disk most, the second optical head 5 protrudes outside the disk surface. 7
Denotes an identification hole provided on the surface of the cartridge 2.

Referring to FIG. 3, the cartridge of this embodiment will be described.
In the case of the optical disk of, the identification hole 7 is closed,
In the case of the second optical disk, it is opened. In the same figure, reference numeral 14 denotes a slide shutter, which is provided at two locations in this embodiment in order to use two optical heads. When it is removed from the optical disk device, it is closed for dust protection. Reference numeral 8 denotes an LED installed so as to be located above the identification hole 7 when the cartridge 2 is mounted on the optical disk device of the present embodiment. Reference numeral 9 denotes an LED installed at a position facing the LED 8 and the cartridge 2 therebetween. And outputs a detection signal to a controller 13 described later. Reference numeral 10 denotes a drive circuit for driving the linear motors 4 and 6.
Reference numeral 11 denotes a servo circuit, which is the first optical head 3 or the second optical head 3.
The servo signal is input from the optical head 5 and the drive current is supplied to the actuator of the first optical head 3 or the actuator of the second optical head 5 accordingly. Further, it outputs a control signal to the drive circuit 10 and outputs a control signal to a spindle motor 12 described later. Reference numeral 13 denotes a controller that outputs a control signal to the drive circuit 10 and the servo circuit 11 according to the output of the photodiode 9.

Here, the first optical disc is a conventional CD.
Or, it has the same recording density, and the thickness of the disk substrate is d1 as shown in FIG. For example, d1 =
1.2 mm. The second optical disk is an optical disk capable of recording at a higher density than that, and the thickness of the disk substrate is d2 as shown in FIG. 4 (b). In order to reduce the aberration of the focused spot due to the tilt shift, d2
Is designed to be smaller than d1, for example, d2 = 0.3
mm.

On the other hand, the first optical head 3 uses, for example, an objective lens having an NA of 0.45 for a semiconductor laser having a wavelength of 780 nm, and the focused spot diameter on the disk at this time is about φ2.1 μm. Becomes In addition, the optical design of the objective lens is designed to correct aberrations caused by a disk substrate having a thickness of 1.2 mm. The second optical head 5 uses, for example, an objective lens having an NA of 0.7 to 0.8, and the spot diameter at this time is about φ1.4 to φ1.4.
1.2 μm. Moreover, the optical design of the objective lens
The aberration caused by the disk substrate having a thickness of 0.3 mm is corrected.

As described above, the first optical head 3 has the focusing optical system formed corresponding to the first optical disk, and the second optical head 3 has the second optical head.
The optical head 5 has a focusing optical system corresponding to the second optical disk. The operation of the optical disk device of the present embodiment configured as described above will be described below. First, when the cartridge 2 containing the first or second optical disk is mounted on the optical disk device of the present embodiment, the LED 2
8 emits light, and the photodiode 9 detects the presence or absence of transmitted light passing through the identification hole 7. If transmitted light is detected,
The controller 13 determines that the content of the mounted cartridge 2 is the second optical disk, and
And a servo circuit 11 for driving the second linear motor 6.
To output a control signal. Thereafter, the recording or reproduction of the optical disk 1 is performed by the second optical head 5 until the cartridge 2 is detached.

That is, the servo circuit 11 controls the spindle motor 12 and controls the optical disc 1 to perform CLV or CAV.
Rotate with V etc. The second optical head 5 has an optical system that focuses a laser beam on a pit layer of the optical disc 1.
It is formed in consideration of the thickness d2 of the disk substrate, and records signals on the disk and reproduces signals on the disk. The servo circuit 11 focuses the laser beam on an appropriate position on the optical disk 1 in accordance with the servo signal output from the second optical head 5, or the second linear motor through the drive circuit 10 in accordance with a command from the controller 13. 6, the second optical head 5 is moved in the inner circumferential direction or the outer circumferential direction.

On the other hand, when the photodiode 9 does not detect the transmitted light, the controller 13 determines that the contents of the cartridge 2 is the first optical disk, and drives the first optical head 3 and the first linear motor 4. A control signal is output to the servo circuit 11 so that Thereafter, recording or reproduction of the optical disc 1 is performed until the cartridge 2 is detached.
Is performed by the optical head 3.

At the same time, during operation of the first optical head 3,
The controller 13 controls the second linear motor 6 to retract the second optical head 5 to the outside of the disk surface as shown in FIG. This prevents the high NA objective lens having a short working distance of the second optical head from colliding with the surface of the disk due to the runout of the disk. As described above, according to the present embodiment, a focusing optical system corresponding to the thickness of the disk substrate of the first and second optical disks is provided.
By providing the first optical head 3 and the second optical head 5, signals can be recorded and reproduced satisfactorily with an optical head of a focusing optical system suitable for the thickness of each disk substrate. In addition, the identification hole 7 provided on the cartridge 2
And an LED 8 and a photodiode 9 for detecting the opening and closing thereof.
With the provision of the disk discriminating means, each optical head can be automatically and correctly selected only by mounting the cartridge 2.

FIG. 5 shows a configuration diagram of an optical disk apparatus according to a second embodiment using the optical disk discriminating means of the present invention. In the figure, 1 optical disk, 2 cartridge, 4 second linear motor, 7 identification hole, 8
LED, 9 photodiode, 10 drive circuit, 11 servo circuit, and 13 controller are basically the same as those in the first embodiment, and the first optical head 3 and the second optical head 5 Instead, the optical head 20 has a configuration including a third optical head.

FIG. 6 shows a third embodiment of the present invention.
1 shows a detailed configuration diagram of the optical head 20 of FIG. In the figure, 1 is a first or second optical disk, 22 is a first semiconductor laser serving as a light source, 23 is a first collimator lens for collimating light from the first semiconductor laser 22,
24 is a first beam splitter for splitting light into two, 25 is a first mirror for changing the direction of light, 26 is a first objective lens for condensing light on the optical disk 1, and 27 is a split beam splitter 24 A first sensor lens 28 for condensing the reflected light, which is a second photodetector for obtaining an information reproduction signal, a focus error signal, and a tracking error signal from the condensed reflected light, is used in the first embodiment. The first focusing optical system 21 described above is configured. Also, 32
Is a second semiconductor laser serving as a light source, 33 is a second collimator lens for collimating light from the second semiconductor laser 32, 34 is a second beam splitter for dividing light into two,
5 is a second mirror for changing the direction of light, 36 is a second objective lens for condensing light on the optical disc 1, and 37 is a second objective for condensing reflected light split by the second beam splitter 34.
Is a second photodetector for obtaining an information reproduction signal, a focus error signal and a tracking error signal from the condensed reflected light, and the second focusing optical system 31 described in the first embodiment. Is composed. The first focusing optical system 21 and the second focusing optical system 31 described above are installed on the same base member (not shown), and constitute the third optical head 20. The base member is usually formed of aluminum or the like, and supports the first focusing optical system 21 and the second focusing optical system 31 and is supported by the first linear motor 4.

Here, as described in the first embodiment of the present invention, for example, the first objective lens 26 has a NA = 0.
45, and the focused spot diameter on the disk at this time is about φ2.1 μm. In addition, it is designed to correct aberrations caused by a 1.2 mm disk substrate.
The second objective lens 36 has, for example, NA = 0.7 to 0.7.
0.8, and the spot diameter at this time is about φ1.4-
1.2 μm. Moreover, it is designed so as to correct the aberration caused by the disk substrate having a thickness of 0.3 mm.

The operation of the optical disk device of the present embodiment having the above-described configuration will be described below. First, when the cartridge 2 is mounted on the optical disk device of this embodiment, the LED 8 emits light, and the photodiode 9 detects the presence or absence of transmitted light passing through the identification hole 7. When the transmitted light is detected, the controller 13 determines that the content of the mounted cartridge 2 is the second optical disc, selects the second focusing optical system 31 of the third optical head 20, and selects the second focusing optical system. A control signal is output to the third optical head 20 and the servo circuit 11 to operate the second semiconductor laser 32 and the second photodetector 38. That is, in the second focusing optical system 31, the light emitted from the second semiconductor laser 32 is made parallel by the second collimator lens 33,
Through the beam splitter 34 and the second mirror 35
Is focused on the second optical disk by the objective lens 36. The light reflected by the disk is collimated again by the second objective lens 36, and the second mirror 3
The light is separated by a second beam splitter 34 through 5, and is condensed on a second photodetector 38 by a second sensor lens 37. Second photodetector 3
Reference numeral 8 outputs a focus error signal and a tracking error signal to the servo circuit 11 from the collected disk reflected light, and reproduces an information signal on the disk. Such an operation is performed until the cartridge 2 is detached.

The servo circuit 11 controls the spindle motor 12 to rotate the optical disk 1 at CLV, CAV, or the like. Further, the servo circuit 11 includes the third optical head 2.
The laser beam is focused on the optical disc 1 in accordance with a servo signal such as a focus error signal or a tracking error signal output from the first linear motor 4 or the first linear motor 4 through the drive circuit 10 in accordance with a command from the controller 13.
To move the third optical head 20 in the inner circumferential direction or the outer circumferential direction.

On the other hand, when the photodiode 9 does not detect the transmitted light, the controller 13 determines that the contents of the cartridge 2 are the above-mentioned first optical disk, and the first focusing optical system of the third optical head 20. 21 and the third optical head 20 and the servo circuit 11 so as to operate the first semiconductor laser 22 and the first photodetector 28.
To output a control signal. The operation of the first focusing optical system 21 is basically the same as that of the second focusing optical system 31 described above, and the recording or reproduction of the first optical disk is performed by the first focusing optical system until the cartridge 2 is detached. 21.

As described above, according to this embodiment, the identification means 7 provided on the cartridge 2, the discriminating means comprising the LED 8 and the photodiode 9 for detecting the opening and closing thereof,
A first optical disc corresponding to the thickness of the disc substrate of the first optical disc;
And a second focusing optical system 31 corresponding to the thickness of the disk substrate of the second optical disk, and a third optical head 20 provided on a common base. Signals can be recorded and reproduced satisfactorily with a focusing optical system suitable for the thickness of the disk substrate.

Further, the first focusing optical system 21 and the second focusing optical system 31 are installed on the same base to constitute the third optical head 20, so that the linear motor is shared and the number of parts is reduced. Therefore, the size of the apparatus can be reduced. FIG. 7 is a diagram showing the configuration of an optical disk apparatus according to a third embodiment using the optical disk discriminating means of the present invention. In the figure, since the configuration is the same as that of the optical disk device in the second embodiment shown in FIG. 5 except for the fourth optical head 40, detailed description of the entire optical disk device is omitted.

FIG. 8 shows a detailed configuration diagram of the fourth optical head 40 according to the third embodiment of the present invention. In the figure, reference numeral 1 denotes a first or second optical disc,
42, a third semiconductor laser serving as a light source; 43, a third collimator lens for collimating light from the third semiconductor laser 42; 44, a third beam splitter for dividing light into two; This is the third mirror that changes. 26
And 36 are the same as the first objective lens and the second objective lens described in the second embodiment of the present invention, and are respectively disposed between the third beam splitter 44 and the third mirror 45 and the optical disk 1. is set up. 46 is a first shutter provided between the third beam splitter 44 on the optical path passing through the first objective lens 26, and 47 is connected to the third mirror 45 on the optical path passing through the second objective lens 36. And a second shutter that opens and closes the optical path according to a control signal of the controller 13. Reference numeral 48 denotes a third sensor lens for collecting the reflected light split by the beam splitter 44, and reference numeral 49 denotes a third photodetector for obtaining an information reproduction signal, a focus error signal, and a tracking error signal from the collected reflected light. is there. Among the constituent elements described above, the first objective lens 26 is the third semiconductor laser 4.
2, the third collimator lens 43 and the third beam splitter 44 constitute the first focusing optical system described in the second embodiment of the present invention, and the second objective lens 36 includes the third semiconductor laser 42. , A third collimator lens 43, a third beam splitter 44, and a third mirror 45.
Of the focusing optical system. Then, both are installed on a common base (not shown) together with the first shutter 46 and the second shutter 47, and constitute a fourth optical head 40.

The operation of the fourth optical head 40 according to the present embodiment configured as described above will be described below. First, when a control signal is input from the controller 13 to the fourth optical head 40 so as to select the second focusing optical system, the first shutter 46 closes and the second shutter 47 closes.
Is open. In this state, the light emitted from the third semiconductor laser 42 is converted into parallel light by the third collimator lens 43, and is split into two parts, the transmitted light and the reflected light, by the third beam splitter 44. It is shut off by the first shutter 46. Therefore, only the transmitted light is the third
The light is focused on the optical disk 1 by the second objective lens 36 through the mirror 45 and the second shutter 47. The light reflected by the optical disk 1 is again converted into parallel light by the second objective lens 36, passes through a third shutter 47 and a third mirror 45, is reflected and separated by a third beam splitter 44, and is then subjected to a third sensor. The light is focused on the third photodetector 49 by the lens 48. The third photodetector 49 converts the collected disk reflected light into
It outputs a focus error signal and a tracking error signal to the servo circuit 11 and reproduces an information signal on a disk. Such an operation is performed until the cartridge 2 is detached.

On the other hand, when a control signal is input from the controller 13 to the fourth optical head 40 so as to select the first focusing optical system, the first shutter 46 is opened and the second shutter 47 is closed. State. In this state, of the transmitted light and the reflected light in the third beam splitter 44, the transmitted light is blocked by the second shutter 47, and only the reflected light passes through the first shutter 46 to the first objective lens. The light is condensed on the optical disk 1 by 26. Subsequent operations are the same as in the case where the above-described second focusing optical system is selected.

As described above, according to this embodiment, the identification hole 7 provided on the cartridge 2, the detecting means including the LED 8 and the photodiode 9 for detecting the opening and closing thereof, and the disc substrate of the first optical disc A fourth optical head provided with a first focusing optical system corresponding to the thickness and a second focusing optical system corresponding to the thickness of the disk substrate of the second optical disk on a common base; Thus, signals can be recorded and reproduced satisfactorily with a focusing optical system suitable for the thickness of each disk substrate. In addition, since the first shutter 46 and the second shutter 47 are provided as the light beam selecting means, a semiconductor laser, a collimator lens, a beam splitter, a sensor lens, and a photodetector can be shared among the respective focusing optical systems. The size and weight of the head can be reduced. As a result, it is possible to improve the performance such as shortening the seek time.

In the above three embodiments, the thickness of the disk substrate is described as two types, but the present invention can be applied to three or more types. In this case, if the number of identification holes in the cartridge is plural, for example, three or more types of optical discs can be identified. For example, by providing n identification holes, 2n types of optical disks can be identified.

The discrimination means uses the discrimination hole 7 provided on the cartridge 2, the LED 8 and the photodiode 9, but instead of the discrimination hole, it is colored with paint having different reflectivity, Alternatively, a mechanical switch or the like may be used. Further, the difference in the thickness of the disk substrate may be determined directly by the reflected laser light from the disk without using a cartridge.
For example, in a focusing optical system corresponding to a thin substrate thickness, an optical disk having a large substrate thickness has a spherical aberration of a focused beam.
Usually, a tracking error signal cannot be obtained. Therefore, an optical disk having two thicknesses can be determined from the presence or absence of the tracking error signal. In this case, there is an excellent effect that a detector such as an LED or a photodiode is not required, and the apparatus is simplified.

[0033]

As described above, according to the present invention,
Light fluxes are condensed by condensing optical systems in which aberrations are corrected for a plurality of transparent substrates having different thicknesses. Only when condensed by the condensing optical system corresponding to the transparent substrate of the loaded optical disk, the diffracted light component can be detected in the returned light beam. Can be identified. Therefore, the type of the optical disk can be identified without adding a new component for distinguishing the type of the disk to the cartridge, so that the manufacturing cost of the optical disk and its recording / reproducing apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical disk device in a first embodiment using an optical disk determination method of the present invention.

FIG. 2 is a plan view showing an arrangement of a main part of the optical disc device in the first embodiment.

FIG. 3 is a perspective view of an optical disk cartridge according to the first embodiment.

FIG. 4 is a schematic diagram showing a cross section of the optical disc and a state of light focusing by an objective lens in the first embodiment.

FIG. 5 is a configuration diagram of an optical disk device according to a second embodiment using the optical disk determination method of the present invention.

FIG. 6 is a detailed configuration diagram of an optical head according to the second embodiment.

FIG. 7 is a configuration diagram of an optical disk device according to a third embodiment using the optical disk determination method of the present invention.

FIG. 8 is a detailed configuration diagram of an optical head according to the third embodiment.

FIG. 9 is a configuration diagram of a conventional optical disk device.

FIG. 10 is a schematic diagram showing a cross section of an optical disk and a state of light condensing by an objective lens in a conventional optical disk device.

[Explanation of symbols]

 Reference Signs List 1 optical disk 2 cartridge 3 first optical head 5 second optical head 7 identification hole 8 LED 9 photodiode 20 third optical head 21 first focusing optical system 22 first semiconductor laser 24 first beam splitter 26 1st objective lens 28 1st photodetector 31 2nd focusing optical system 32 2nd semiconductor laser 34 2nd beam splitter 36 2nd objective lens 38 2nd photodetector 40 4th optical head 42 3rd Semiconductor laser 44 third beam splitter 46 first shutter 47 second shutter 49 third photodetector

Claims (2)

(57) [Claims] 1. A method for determining an optical disk comprising one of a plurality of transparent substrates having different thicknesses and capable of recording and / or reproducing and / or erasing information signals, wherein the thicknesses are different. Aberration correction is performed on each of the plurality of transparent substrates, and the information signal is recorded on the optical disk.
By one of the spare / or reproducing and / or erasing a plurality of focusing optical system, comprising the steps of condensing the light beam through the transparent substrate, a light detection means the return light of the light beam from the optical disk
Therefore, the step of receiving light includes the step of receiving the light detection signal,
Diffracted light component whose magnitude changes according to the degree of difference correction
Detecting the size of, the thickness of the transparent substrate according to the size of the diffracted light component
Determine the difference and use one of the plurality of focusing optics.
Recording and / or reproducing and / or reproducing the information signal.
A method for determining whether an optical disk is to be erased . 2. A tracking error indicating a shift amount between a converged light flux and an information signal track is detected.
2. The method according to claim 1 , wherein the signal is a signal .