JPH06318323A - Track pitch discriminating device for optical disk - Google Patents

Abstract

PURPOSE:To obtain the track pitch discriminating device of an optical disk which is a small-sized and whose adjustment of irradiation angles is simple by irradiating two optical disks whose recording track pitches are different with irradiating lights having the same wave length in prescribed irradiation angles. CONSTITUTION:The optical disk 1 is an optical disk capable of double-side reproducing and mounted in a stational state capable of being rotated by a spindle motor 2. A track pitch discriminating device 3 is inclined so that the irradiating light 8 of a semiconductor layer 4 is cast on an irradiating part 13, where pitches of the optical disk 1 are recorded, in the direction at theta0 angular degrees from a vertical axis 7 perpendicular to the disk plane. The irradiating light 8 generates a reflected light 9. When the optical disk 1 is made to have first and second track pitches, first + or -1st order diffracted light beams 10, 10' and second + or -1st order diffracted light beams 11, 11' are generated with first and second diffraction angles thetap1, thetap2 respectively. Further, the irradiation angles theta0 of the irradiating light to the optical disk 1 is arranged so as to be approximately a quarter of the sum of diffraction angles thetap1, thetap2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for discriminating the track pitch of an optical disc, and more particularly to an apparatus for discriminating two track pitches of an optical disc having pits recorded in tracks.

[0002]

2. Description of the Related Art LDs (laser disks) on which video signals are recorded and CDs (compact disks) on which audio signals are recorded have become widespread, and there is a growing demand for optical disks for high density recording. As a means for increasing the recording density of the optical disc, there is a shortening of the wavelength of the laser light source. LD and CD
Although a semiconductor laser having a wavelength of 780 nm is used for a player for reproducing, a semiconductor laser having a shorter wavelength has been developed and put into practical use in recent years. For example, for a high-definition MUSE disc, a disc standard using a semiconductor laser having a wavelength of 670 nm is under consideration. Considering a video disc, the conventional LD having a diameter of 30 cm is considered to be applied to a MUSE disc as it is.

[0003]

As described above, since the reproduction light beam wavelength of the optical disc is different, the track pitch of the recording pit is different, but the optical disc having the same appearance except that the labels such as the outer diameter dimension, the thickness and the material are different. It will coexist. As a result, an error occurs in which the MUSE disc player attempts to reproduce the LD, and conversely the LD player attempts to reproduce the MUSE disc. Also LD and M
The appearance of compatible players capable of reproducing both USE discs is also conceivable. In such a case, the track pitch of the optical disk is discriminated, and an incorrectly mounted optical disk having a different track pitch is ejected before the reproduction is started. Especially, in the case of a MUSE disk, the CLV recorded at a constant linear velocity is recorded.
With a CAV disc recorded at a constant angular velocity with the disc,
CAV discs are CLV due to the size of the recording pits
The recording start position is closer to the outer circumference than the disc, and CL
It is necessary to discriminate between V and CAV discs and to smoothly enter into a reproducing operation suitable for a mounted optical disc before starting reproduction.

[0004]

In order to solve the above-mentioned problems, laser means for irradiating an irradiation light onto an optical disk in which pits are recorded in a track shape, and reflection diffraction by the diffraction effect of the irradiation light on the recording track pitch. In a track pitch discriminating apparatus for an optical disc having a light receiving means for receiving light and outputting a corresponding electric signal, when the optical disc has a first recording track pitch, it receives diffracted light of a first -1st diffraction angle. The first light receiving means and the second light receiving means for receiving the diffracted light of the second minus first-order diffraction angle when the optical disc has the second recording track pitch, and are arranged with respect to the vertical axis of the surface of the optical disc. An optical disc track pitch determining apparatus is provided, wherein an irradiation angle of a light beam is approximately 1/4 of a sum of the first first-order diffraction angle and the second diffraction angle.

[0005]

When laser light is irradiated onto the optical disk surface in which pits are recorded in a track shape, the diffraction grating has a track pitch P, a wavelength λ of light, a light irradiation angle θ 0 with respect to the vertical axis of the optical disk surface, and the 0th time of the first-order diffracted light. There is a relation of P = λ / Cos θ0 × Sin θp between the diffraction angle θp with respect to the folded light (reflected light). The recording track acts as a diffraction grating to obtain reflected diffracted light. When the irradiation angle θ0 of the irradiation light applied to the optical disk is changed, the 0th-order diffracted light (reflected light)
Shows a reflection angle θ0 at a contrast position of the irradiation angle θ0 with respect to an axis perpendicular to the optical disk surface at the optical disk irradiation point, and the first-order diffracted light continues to maintain the diffraction angle θp between the first-order diffracted light and the zero-order diffracted light.

As described above, by irradiating the two optical discs having different recording track pitches with the irradiation light of the same wavelength at the selected constant irradiation angle, the above-mentioned light is emitted between the two first-order diffracted lights having different diffraction angles. You can place a beam. That is, by placing light receiving elements at predetermined positions on both sides of the semiconductor laser and irradiating the optical disk with the irradiation light of the semiconductor laser at a predetermined angle, it is possible to distinguish between optical disks having two different recording track pitches. The semiconductor laser can be integrated into a small size by placing it between two light receiving elements, and by adjusting the irradiation angle of the semiconductor laser onto the optical disk,
A device for discriminating the recording track pitch of the optical disc can be configured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the configuration of an embodiment in which the optical disk recording track pitch determining apparatus of the present invention is used in an optical disk player. In the figure, an optical disc 1 is a double-sided reproducible optical disc, and is mounted in a stationary state that can be rotated by a spindle motor 2. The track pitch determination device 3 is tilted so as to irradiate the irradiation light 8 of the semiconductor laser 4 at the irradiation point 13 where the pits of the optical disk 1 are recorded with respect to the vertical axis 7 perpendicular to the disk surface at an angle of θ 0. . The irradiation light 8 produces reflected light (0th-order diffracted light) 9 at a symmetrical position on the vertical axis 7. When the optical disc 1 has the first track pitch, the reflected light 9 has a first diffraction angle θp1 of the first ± 1.
When the optical disc 1 has the second track pitch and the second diffracted light 10 and 10 'is generated, the reflected light 9 causes the second first-order diffracted angle θp2.
Since the second ± 1st-order diffracted lights 11 and 11 ′ are generated by the above, the track pitch determination device 3 is provided with the first light-receiving element 5 and the second light-receiving element 6 which respectively receive the diffracted light on the irradiation light side of ± 2 diffracted lights. .

FIG. 2 is a diagram showing the structure of the track pitch determination device 3, in which a semiconductor laser 4 is provided between the first light receiving element 5 and the second light receiving element 6 in a substantially straight line. FIG. 3 shows that the irradiation angle θ0 of the irradiation light is 17 °, 18 °, 19 with respect to the track pitch P of the optical disk when the wavelength of the irradiation light is λ = 780 nm.
The relationship between the -1st-order diffraction angle with respect to the irradiation light 8 in place of 0 ° and 20 ° is calculated from the above relational expression and shown. For example, assuming that the irradiation angle θ 0 = 20 °, the track pitch is 1.1.
In the MUSE disc of nm, the diffraction angle θ for the reflected light 9
A -1st-order diffracted light 10 of p1 = 49 ° is generated, an angle θx1 = 9 ° with the irradiation light 8, and an LD with a track pitch of 1.6 nm.
Then, the second minus first-order diffracted light 11 is generated inside the irradiation light 8 at the diffraction angle θp2 = 31.3 ° with respect to the reflected light 9 and at the angle θx2 = 8.7 °. First and second -1st-order diffracted lights 10 and 1
In order to place the irradiation light 8 in the middle of 1, the irradiation angle θ0 = 20.
You can see that it will be about 9 degrees.

That is, there is provided a track pitch discriminating apparatus 3 in which a first light receiving element 5 and a second light receiving element 6 are respectively provided at positions for receiving the first and second -1st-order diffracted lights, and a semiconductor laser 4 is provided between them. The MUSE with a track pitch of 1.1 μm can be obtained by irradiating the irradiation light 8 at an irradiation angle θ0 = 19.8 °.
In the disc, the detection voltage can be obtained from the first light receiving element 5, and in the LD having the track pitch of 1.6 μm, the detection voltage can be obtained from the second light receiving element 6. These detection voltages are applied to the control circuit 1
In addition to 2, necessary control can be performed. Since the actual track pitches have their respective allowable ranges, the light receiving elements are required to have a size capable of receiving light. Further, the semiconductor laser 4 does not necessarily have to be in the middle of the two light receiving elements 5 and 6, and may be offset to either one. Even if the light-receiving surfaces of the first and second light-receiving elements 5 and 6 are parallel to each other, there is no practical problem because the angle of inclination of the diffracted light with respect to the vertical of the light-receiving surface is small.

An example of using the track pitch discriminating apparatus 3 is shown in FIG.
Will be explained. Due to the relationship between the linear velocity and the light beam spot diameter, the MUSE CAV disc has a recording radius of the innermost pit of about 73 mm, and no pit is recorded within the radius of about 70 mm, but since it has a reflective film, it is merely a mirror surface. The MUSE CLV disc has an innermost pit recording radius of 53.5 mm like the LD. Therefore, the irradiation point 13 of the irradiation light 8 on the optical disk 1 is set to have a radius of 53.5 mm to 70 mm.
With the range of mm, the MUSE CAV disc has no pits recorded during this period, and diffracted light cannot be obtained. However, the MUSE CLV disc has pits recorded, so diffracted light can be obtained. Can be identified. The track pitch determination device 3 has a structure in which first and second light receiving elements 5 and 6 are arranged at intervals in the radial direction of the optical disc 1, and a semiconductor laser 4 having a wavelength of 780 nm is attached in the middle thereof.

Two light receiving elements 5 and 6 and a semiconductor laser 4
Is arranged at a position calculated in advance, and when the irradiation angle θ 0 to the optical disc 1 is adjusted to a predetermined value, a detection voltage is obtained at the light receiving element 5 or 6 corresponding to the track pitch of each optical disc. MUSE as optical disc 1
Equipped with a CLV disk, the irradiation light from the semiconductor laser 4 is 8
Is irradiated, the track pitch determination device 3 is tilted inward in the radial direction of the optical disc 1, and the angle is adjusted so that a detection voltage can be obtained at the light receiving element 5. If the optical disc 1 is an LD, a detection voltage is obtained at the light receiving element 6. The detection voltage of the light receiving elements 5 and 6 is applied to the control circuit 12. When the MUSE CAV disc is loaded in the optical disc player, no detection voltage can be obtained in any of the light receiving elements 5 and 6, so the control circuit 12 determines that it is a CAV disc by the separately obtained disc loading completion signal (not shown). Then, a signal for moving the optical head 14 to the reproduction start position of the MUSE CAV disc having an optical disc radius of 73 mm is output.

When the MUSE CLV disk is mounted, the detection voltage from the light receiving element 5 is obtained, so the control circuit 1
2 is an optical head 14 which is an MU having an optical disc radius of 53.5 mm.
The signal for moving to the SECLV disc playback start position is output. When the LD disk is accidentally loaded, the detection voltage of the light receiving element 6 is obtained, so the control circuit 12 controls the optical disk 1
To the mounting device 15. The track pitch discriminator 3 can reproduce MUSE discs and LDs,
A case where the player is used as a compatible player will be described.
The relationship between the installation position of the track pitch determination device 3 and the irradiation angle θ0 of the light beam is the same as that of the MUSE disc player. MUSE CAV disc and MUSE CL
The correspondence of the optical head 14 to the V disk is the same, but the corresponding optical head and signal processing circuit are switched depending on the difference between the MUSE disk (CAV and CLV) and the LD.

In the case of the LD, the optical head 14 is the MU.
Move to the same radius 53.5 mm as the SE CLV disc. Next, an optical head 14 'in which the track pitch determining device 3 shown in FIG. 4 is integrally attached to the optical head will be described. FIG. 4 is a top view of the optical head 14 '.
Two light receiving elements 5 and 6 and a semiconductor laser 4 are arranged in the radial direction of the optical disc 1 for the laser beam 16 for reading the recording pits of the optical disc 1. FIG. 5 shows the relationship between the irradiation light 8 of the track pitch determination device 3 and the laser light 16 of the optical head 14 'in the actual operating state. The irradiation light 8 is irradiated at a predetermined irradiation angle θ 0 with respect to the optical axis of the laser light 16. This irradiation angle .theta..sub.0 is set to the track pitch discriminating device 3 and the optical head 14 before being incorporated in the disc player.
There is an advantage that it can be adjusted in an integrated state. Further, when the optical head is moved to the innermost circumference of the optical disc during the operation incorporated in the disc player, the irradiation point 13 of the irradiation light 8 of the track pitch determination device 3 is at a predetermined position, for example, within the optical disc radius of 70 mm described above. If so, the track pitch determination operation of the optical disk can be performed.

[0014]

As in the above embodiment, by arranging two light receiving elements at a predetermined interval, and by arranging a semiconductor laser between them, and irradiating at a predetermined inclination angle which is not 0 ° with respect to the vertical axis of the optical disk, It is possible to configure a track pitch determination device for an optical disc that is compact and has a simple irradiation angle adjustment.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation principle of an optical disc track pitch determination device of the present invention.

FIG. 2 is a diagram showing a configuration of a track pitch determination device for an optical disc of the present invention.

FIG. 3 is a diagram showing an angle of the reflected first-order diffracted light from the optical disc with respect to the emitted light with respect to the track pitch of the optical disc when the optical beam is irradiated with a light beam of wavelength λ = 780 nm and the irradiation angle is changed.

FIG. 4 is a top view of an optical head integrally mounted with a track pitch determination device for an optical disk according to an embodiment of the present invention.

5 is a diagram for explaining the operation of an optical head integrally mounted with the track pitch determination device of FIG.

[Explanation of symbols]

 1 Optical Disc 2 Spindle Motor 3 Track Pitch Discrimination Device 4 Semiconductor Laser 5 First Light-Receiving Element 6 Second Light-Receiving Element 7 Vertical Axis 8 Irradiation Light 9 Reflected Light (0th-Order Diffracted Light) 10 First-First-Order Diffracted Light 10 'First + 1st-order diffracted light 11 2nd -1st-order diffracted light 11 '2nd + 1st-order diffracted light 12 Control circuit 13 Irradiation point 14 Optical head 14' Optical head 15 Optical disk mounting device 16 Laser light θ0 Irradiation angle and reflection angle θp1 First 1 Secondary diffraction angle θp2 Second primary diffraction angle θx1 Angle between first -1st-order diffracted light and irradiation light θx2 Angle between second -1st-order diffraction light and irradiation light

Claims (3)

[Claims] 1. A laser means for irradiating an optical disk having pits recorded in a track shape with light, and a light receiving means for receiving reflected diffracted light due to the diffraction effect of the irradiation light on the recording track and outputting a corresponding electric signal. And a first light receiving means for receiving diffracted light of a first -1st diffraction angle when the optical disk has a first recording track pitch, and a second recording track pitch. At this time, the second light receiving means receives the diffracted light of the second minus first diffraction angle, and the irradiation angle of the irradiation light with respect to the vertical axis of the surface of the optical disc is the first diffraction angle and the second diffraction angle.
The optical disk track pitch determination device is characterized in that it is approximately ¼ of the sum of the diffraction angles. 2. The laser means is on substantially the same straight line as the first and second light receiving means.
The track pitch discriminating apparatus for the optical disc described. 3. The irradiation light is on the control axis of the pit track of an optical head for reproducing the recording pits of the optical disk, and the irradiation light is irradiated on the optical axis of the reproduction light beam of the optical head. The angle is approximately 1/4 of the sum of the first diffraction angle and the second diffraction angle,
The track pitch discriminating apparatus for an optical disc according to claim 1, which is integrated with the optical head.