JPH07296498A - Optical disk reproducing device - Google Patents

Abstract

PURPOSE:To discriminate a low density optical disk and a high density optical disk even if they are in the same shape from a signal detected by an optical pickup. CONSTITUTION:An optical disk D is driven to rotate at constant angular velocity at the start-up time by a constant angular velocity driving control circuit 14. Then, an optical pickup 1 is moved into a specific position in the radial direction of the optical disk D, for instance, an innermost circumferential part by a slide movement control circuit 21. A pit length of a track in the innermost circumferential part as in the specific position in the radial direction is measured by a pulse width measuring circuit 8. A max. value in pulse width measured by the pulse width measuring circuit 8, i.e., the max. pit length is held in a max. pulse width hold circuit 10. A min. value in pulse width measured by the pulse width measuring circuit 8, i.e., the min. pit length is held in a min. pulse width hold circuit 11. The kind of an optical disk is discriminated by a disk discriminating circuit 12 in accordance with the max. pit length and the min. pit length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing apparatus for irradiating an optical disk with a laser beam to reproduce an information signal recorded on the optical disk.

Conventionally, a drive system circuit of a spindle motor and an optical pickup of a CD player for reproducing a compact disc (hereinafter referred to as a CD), which is a kind of optical disc, has a structure as shown in FIG. Here, the drive system circuit of the optical pickup is a drive system circuit that combines slide motor drive, tracking coil drive, and focus coil drive.

The optical pickup 31 is composed of, for example, optical components such as a laser diode, a collimator lens, an objective lens, a beam splitter, and a cylindrical lens, and a photodetector divided into a predetermined arrangement. The laser beam is directed to the recording surface of the CD 30. Irradiation is performed, and a change in the intensity of reflected light due to pits is detected, and a focus error signal is detected by, for example, a so-called astigmatism method, and a tracking error signal is detected by, for example, a so-called push-pull method.

First, in order for the user to reproduce the CD 30,
For example, when the play button is operated, the sequencer 43, which is a control unit, controls the slide movement control circuit 47 and drives the slide motor drive circuit 48 to drive the optical pickup 31.
Is moved until the optical pickup 31 turns on the innermost circumference detection switch 32. Then, the sequencer 43
The changeover switch 41 is switched so that the initial drive control circuit 39 is connected to the spindle motor drive circuit 42 to drive the spindle motor 33 for initial rotation.

Next, the optical pickup 31 irradiates the CD 30 with, for example, a laser beam having a wavelength of 780 nm, and the CD 3
The reflected light by 0 is detected. The RF data which is the detection output is amplified by a regenerative amplifier (denoted as RFamp in the figure) 34 and used as a binarizing means.
It is binarized by 5. This binarized signal is 8-14
It is a signal modulated by modulation (Eight to Fourteen Modulation: hereinafter referred to as EFM), and has a synchronization signal at regular intervals. The sync signal of the binarized RF signal is detected by the sync signal detection circuit 36. The detected sync signal is supplied to the sync signal interval measuring circuit 38 which measures the cycle of the sync signal based on the reference clock signal from the OCR 37. The period of the synchronizing signal measured by the synchronizing signal interval measuring circuit 38 is fed back to the spindle servo circuit 40. The spindle servo circuit 40 is the sequencer 4
With the changeover switch 41 changed over by 3,
It is connected to the spindle motor drive circuit 42 and controls the drive of the spindle motor drive circuit 42 so that the linear velocity of the CD 30 becomes constant. Therefore, the spindle motor 3
3 can rotate the CD 30 so that the linear velocity is constant.

The optical pickup 31 is installed on a feed base (not shown) screwed into a feed screw (not shown) which is driven to rotate by a slide motor (not shown), and the radius of the CD 30 is rotated by the drive of the feed screw due to the rotation of the feed screw. It is designed to be moved over. The drive control of the slide motor, that is, the feed drive of the optical pickup 31 is performed by a slide motor drive circuit 48 that drives the slide motor. The slide motor drive circuit 48 drives the slide motor based on the addition signal from the adder 51 of the servo signal from the slide servo circuit 46 and the control signal from the slide movement control circuit 47. Thus, for example, immediately after the reproduction button is pressed, the slide motor is driven only in accordance with the control signal from the slide movement control circuit 47, and the optical pickup 31 is moved until the innermost circumference detection switch 32 is turned on. Move in the direction.

Further, the optical pickup 31 outputs the focus error signal and the tracking error signal to the focus servo circuit 49 and the tracking servo circuit 44.
Supply to. The focus servo circuit 49 moves the objective lens (not shown) of the optical pickup 31 to the focus coil drive circuit 50 so that the focus error signal becomes zero.
Drive in the direction of the optical axis. Further, the tracking servo circuit 44 moves the objective lens to the tracking coil drive circuit 45 so that the tracking error signal becomes zero.
Drive in the radial direction of the disk. Here, the tracking coil drive signal output from the tracking coil drive circuit 45 is a signal for moving the optical pickup 31 in the radial direction of the CD 30, and is also supplied to the slide servo circuit 46.

The sequencer 43 controls the slide movement control circuit 47 and the changeover switch 41 as described above, and also controls the spindle servo circuit 40, the tracking servo circuit 44, the slide servo circuit 46 and the focus servo circuit 49.

[0009]

By the way, in recent years, CD
Higher density and larger capacity optical discs (hereinafter referred to as high density optical discs) have been developed, a modulation method corresponding to them has been adopted, or pits have been reduced to increase the recording density. Increasing the number of people has come to be done.

Along with this, it has become necessary for the player side to distinguish between a low density optical disk such as a CD and a high density optical disk. For example, when the diameters of the discs are different, such as a conventional CD and an optical disc on which a video signal is recorded, by providing a sensor for detecting the presence or absence of the disc on the difference in diameter on the player table, the two can be distinguished. . However, when the shape of the high-density optical disk is the same as that of the low-density optical disk such as a CD, it is impossible to distinguish them mechanically.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical disk reproducing apparatus capable of distinguishing a low density optical disk and a high density optical disk from signals detected by the same optical pickup.

[0012]

An optical disk reproducing apparatus according to the present invention comprises a constant speed driving means for rotating an optical disk at a constant speed at the time of startup, and a movement control means for moving the optical pickup to a specific radial position of the optical disk. The pit length measuring means for measuring the pit length of the track at the specific radial position where the optical pickup is moved by the movement control means, and the disc type discrimination based on the pit length measured by the pit length measuring means. The above problem is solved by having a determining means for performing.

Here, it is preferable that the constant speed driving means rotationally drives the optical disk at a constant angular speed at the time of startup.

The discriminating means discriminates the type of the optical disc based on the minimum pit length measured by the pit length measuring means.

Further, the discriminating means may discriminate the type of the optical disc based on the maximum pit length measured by the pit length measuring means.

The discriminating means may discriminate the type of the optical disc based on the minimum pit length and the maximum pit length measured by the pit length measuring means. For example, the discriminating means may discriminate the type of the optical disc based on the ratio of the minimum pit length to the maximum pit length.

[0017]

When the constant speed driving means rotates the optical disk at a constant speed, the movement control means moves the optical pickup to a specific radial position of the optical disk, and the pit length measuring means causes the pit of the track at the specific radial position. Since the length is measured and the discriminating means discriminates the type of the optical disc according to the pit length, the low density optical disc and the high density optical disc can be discriminated from the signals detected by the same optical pickup.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an optical disk reproducing apparatus according to the present invention will be described below with reference to the drawings. This embodiment is an optical disc reproducing apparatus capable of discriminating a low-density optical disc and a high-density optical disc such as a CD from the pit length thereof, not from the shape thereof.

FIG. 1 shows a drive system circuit of a spindle motor and a pickup of this optical disk reproducing apparatus. In addition,
Here, the drive system circuit of the pickup is a drive system circuit that combines slide motor drive, tracking coil drive, and focus coil drive.

In FIG. 1, the optical disk D is an optical disk whose shape cannot be discriminated as to whether it is a low density optical disk or a high density optical disk.

The optical pickup 1 is composed of, for example, optical components such as a laser diode, a collimator lens, an objective lens, a beam splitter, and a cylindrical lens, and a photodetector divided into a predetermined arrangement. A laser beam is recorded on the recording surface of the optical disc D. And the change in the intensity of the reflected light due to the pits is detected, and the focus error signal is detected by, for example, the so-called astigmatism method, and the tracking error signal is detected by, for example, the so-called push-pull method.

RF data which is a detection output detected by the optical pickup 1 is amplified by a reproduction amplifier (denoted as RFamp in the drawing) 4 and binarized by a comparator 5 used as a binarizing means. . The binarized signal is a signal modulated by 8-14 modulation (Eight to Fourteen Modulation: hereinafter, referred to as EFM), and has synchronization signals at regular intervals. The sync signal of the binarized signal is detected by a sync signal (denoted as SYNK in the drawing) detection circuit 6. The detected synchronizing signal is supplied to the synchronizing signal interval measuring circuit 9 which measures the period of the synchronizing signal based on the reference clock signal from the OCR 7. The cycle of the sync signal measured by the sync signal interval measuring circuit 9 is fed back to the spindle servo circuit 15. The spindle servo circuit 15 uses the changeover switch 16 that is switched by the sequencer 13 to drive the spindle motor drive circuit 1
The connection with 7 is selectively switched to and controlled with the constant angular velocity drive control circuit 14. Spindle motor drive circuit 17
Is connected to the constant angular velocity drive control circuit 14 or the spindle servo circuit 15, drives the spindle motor 3 at a constant angular velocity or a constant linear velocity, and rotates the optical disc D so as to have a constant angular velocity or a constant linear velocity.

The optical pickup 1 is installed on a feed table (not shown) screwed into a feed screw (not shown) which is rotationally driven by a slide motor (not shown), and the optical disc D is rotated by the feed screw being rotated by the feed screw. It is designed to move on a radius. The drive control of the slide motor, that is, the feeding drive of the optical pickup 1 is performed by a slide motor drive circuit 22 that drives the slide motor. The slide motor drive circuit 22 drives the slide motor based on the addition signal of the servo signal from the slide servo circuit 20 and the control signal from the slide movement control circuit 21 by the adder 25. Immediately after is pressed, the slide motor is driven only in response to the control signal from the slide movement control circuit 21, and the optical pickup 1 is moved in the inner diameter direction of the optical disc D until the innermost circumference detection switch 2 is turned on. Let

Here, the constant angular velocity drive control circuit 14 rotationally drives the optical disc D at a constant angular velocity when the optical disc reproducing apparatus is activated. In addition, the slide movement control circuit 21
Moves the optical pickup 1 to a specific radial direction position of the optical disc D, for example, to the innermost peripheral portion.

The optical pickup 1 also supplies the focus error signal and the tracking error signal to the focus servo circuit 23 and the tracking servo circuit 18. The focus servo circuit 23 drives the objective lens (not shown) of the optical pickup 1 in the optical axis direction by the focus coil drive circuit 24 so that the focus error signal becomes zero. The tracking servo circuit 18 drives the objective lens in the disk radial direction by the tracking coil drive circuit 19 so that the tracking error signal becomes zero. Here, the tracking coil drive signal output from the tracking coil drive circuit 19 is a signal for moving the optical pickup 1 in the radial direction of the optical disc D, and is also supplied to the slide servo circuit 20.

As described above, the sequencer 13 controls the slide movement control circuit 21 according to the detection signal from the innermost circumference detection switch 2 which detects whether or not the optical pickup 1 has moved to the innermost circumference. , Changeover switch 16,
Spindle servo circuit 15, tracking servo circuit 1
8, slide servo circuit 20, focus servo circuit 2
3 and the following two hold circuits are controlled.

The two hold circuits are the spindle motor drive circuit 17 connected to the constant angular velocity drive control circuit 14.
A maximum pulse width hold (indicated as MAX HOLD in the figure) circuit for holding the maximum pulse width and the minimum pulse width of the binarized signal obtained from the detection output read from the optical disc D rotated at a constant angular velocity by 10 and a minimum pulse width hold (denoted as MIN HOLD in the figure) circuit 11. The maximum pulse width hold circuit 10 and the minimum pulse width hold circuit 11 will be described below.

The detection output from the comparator 5 which is the binarizing means is also supplied to the pulse width measuring circuit 8. The pulse width measuring circuit 8 measures the pit length of the track at the innermost peripheral portion, which is the specific radial position where the optical pickup 1 is moved by the slide movement control circuit 21.

Specifically, the pulse width measuring circuit 8 is
In synchronization with the reference clock supplied from the CR 7, the detection output from the comparator 5 which binarizes the detection signal detected by the optical pickup 1 from the innermost track, that is, the pulse of the binarized RF signal Measure the width. The maximum value of the pulse width measured by the pulse width measuring circuit 8 is held in the maximum pulse width holding circuit 10. The minimum value of the pulse width measured by the pulse width measuring circuit 8 is held in the minimum pulse width holding circuit 11. Here, since the optical disc D is rotating at a constant angular velocity, the maximum value T _MAX of the pulse width held by the maximum pulse width holding circuit 10 represents the maximum pit length on the optical disc D. Similarly, the minimum value T _MIN of the pulse width held by the minimum pulse width hold circuit 11 represents the minimum pit length on the optical disc D.

Then, the disc determining circuit 12 determines the type of the optical disc D according to the maximum pit length T _MAX and the minimum pit length T _MIN . The sequencer 13 determines whether to reproduce the optical disk D or to stop the reproduction operation according to the judgment result of the disk judgment circuit 12.

For example, this optical disc reproducing device discriminates between a CD and a high density optical disc, but is a reproducing device capable of reproducing only CD, for example, only audio data, and the operation when the optical disc D is a CD will be described below. explain.

First, when the user operates, for example, a reproduction button to reproduce the optical disc D, the sequencer 13 which is the control unit controls the slide movement control circuit 21 and drives the slide motor drive circuit 22 to drive the optical pickup. 1 is moved until the optical pickup 1 turns on the innermost circumference detection switch 2. Then, the sequencer 13 switches the changeover switch 16 so that the constant angular velocity drive control circuit 14 is connected to the spindle motor driving circuit 17 to drive the spindle motor 3 at a constant angular velocity.

In this state, that is, in a state where the optical disc D is rotating at a constant angular velocity, the optical pickup 1 irradiates a laser beam having a wavelength of 780 nm, for example, on the innermost peripheral portion of the optical disc D at a specific radial position. , The reflected light from the innermost part of the optical disc D is detected. The RF data, which is the detection output from the innermost peripheral portion, is amplified by RFamp 4 to form a waveform as shown in FIG. 2 (B), and is then binary-valued by the comparator 5 as shown in FIG. 2 (C). RF
Signaled. The binarized RF signal shown in (C) of FIG. 2 is supplied to the pulse width measurement circuit 8, and the maximum pulse width T
_MAX is held in the maximum pulse width hold circuit 10 and minimum pulse width T _MIN is held in the minimum pulse width hold circuit 11.

Since the optical disc D is rotating at a constant angular velocity, the maximum value T _MAX of the pulse width held by the maximum pulse width holding circuit 10 represents the maximum pit length on the optical disc D. Similarly, the minimum value T _MIN of the pulse width held by the minimum pulse width hold circuit 11 represents the minimum pit length on the optical disc D.

Then, the disc determination circuit 12 compares the maximum pit length T _MAX and the minimum pit length T _MIN with the respective values of the CD stored in the storage unit (not shown) in advance, and determines the maximum pit of the optical disc D. _Assuming that the length T _MAX and the minimum pit length T _MIN match those of the CD, the optical disc D
Is a CD having pits as shown in FIG. Since the optical disc D is a CD, the sequencer 13 controls the spindle servo circuit 15, the changeover switch 16, the slide servo circuit 20, and the slide movement control circuit 21 to rotate the optical disc D, which is a CD, at a constant linear velocity to make an optical pickup. 1 is moved in the outer diameter direction. Then, the sequencer 13 further controls the tracking servo circuit 18 and the focus servo circuit 23,
The laser beam emitted from the optical pickup 1 is caused to follow the pit.

Next, the operation of this optical disk reproducing apparatus when the optical disk D is not a CD will be described below.

After the reproduction button is operated, the operation until the spindle motor 3 is driven at a constant angular velocity and the reflected light from the innermost peripheral portion which is a specific portion of the optical disc D in which the optical pickup 1 is rotating at a constant angular velocity. Since the operation up to the detection of is the same as the case described above, the description thereof is omitted here.

RF which is the detection output from the innermost peripheral portion
The data is amplified by the RFamp 4 to have a waveform as shown in FIG. 3B, and then the data is amplified by the comparator 5 in FIG. 3C.
As described above, the RF signal is binarized. Figure 3 (C)
The binarized RF signal shown in (1) is supplied to the pulse width measurement circuit 8, and the maximum pulse width T _MAX is held in the maximum pulse width hold circuit 10 and the minimum pulse width T _MIN is held in the minimum pulse width hold circuit 11. .

Here, since the optical disc D is rotating at a constant angular velocity, the maximum value T _MAX of the pulse width held in the maximum pulse width holding circuit 10 represents the maximum pit length on the optical disc D. Similarly, the minimum value T _MIN of the pulse width held by the minimum pulse width hold circuit 11 represents the minimum pit length on the optical disc D.

Then, the disc determining circuit 12 compares the maximum pit length T _MAX and the minimum pit length T _MIN with the respective values of the CD stored in the storage unit (not shown) in advance, and determines the maximum pit of the optical disc D. If the length T _MAX and the minimum pit length T _MIN do not match those of the CD, it is determined that the optical disc D is not the CD. Here, if the recording unit stores each value of the high density optical disk in advance, the disk determination circuit 12 determines that the optical disk D is, for example, (A) in FIG.
It is determined that the optical disc is a high density optical disc having pits as shown in.

Since the optical disc D is not a CD but a high density optical disc, for example, the sequencer 13 controls the spindle servo circuit 15, the changeover switch 16, the slide servo circuit 20 and the slide movement control circuit 21 to stop the reproducing operation. . Further, in this case, the sequencer 13 may display that the optical disc D is a non-reproducible high density optical disc or perform an eject process.

As described above, since the optical disk reproducing apparatus discriminates the optical disk according to the maximum pit length and the maximum pit length, even if the low density optical disk and the high density optical disk have the same shape, they are detected by the same optical pickup. It can be determined from the signal.

The optical disc reproducing apparatus according to the present invention is not limited to the above-mentioned embodiment, and has a dedicated optical pickup and a signal processing system capable of reproducing a low density optical disc and a high density optical disc, respectively. The disc may be used so that the disc thus discriminated can be reproduced as it is.

Further, the optical disk reproducing apparatus according to the present invention may judge the optical disk by comparing only the minimum pit length or the maximum pit length. For example, in the case of judging the optical disk having a different modulation method. May find the ratio of the minimum pit length to the maximum pit length and compare the ratios.

[0045]

The optical disk reproducing apparatus according to the present invention comprises a constant speed driving means for rotationally driving the optical disk at a constant speed at startup, a movement control means for moving the optical pickup to a specific radial position of the optical disk, and the movement. A pit length measuring means for measuring the pit length of a track at a specific radial position where the optical pickup is moved by the control means, and a discriminating means for discriminating the type of the optical disc based on the pit length measured by the pit length measuring means. Therefore, even if the low-density optical disc and the high-density optical disc have the same shape, they can be discriminated from the signals detected by the same optical pickup.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an optical disc reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an operation of discriminating a compact disc.

FIG. 3 is a diagram for explaining an operation of discriminating a high density optical disc.

FIG. 4 is a block circuit diagram of a conventional compact disc player.

[Explanation of symbols]

 1 optical pickup 2 innermost circumference detection switch 3 spindle motor 4 reproduction amplifier 5 comparator 6 sync signal detection circuit 7 OCR 8 pulse width measurement circuit 9 sync signal interval measurement circuit 12 disk determination circuit 13 sequencer 14 constant angular velocity drive control circuit 15 spindle servo Circuit 16 Changeover switch 17 Spindle motor drive circuit 18 Tracking servo circuit 19 Tracking coil drive circuit 20 Slide servo circuit 21 Slide movement control circuit 22 Slide motor drive circuit 23 Focus servo circuit 24 Focus coil drive circuit 25 Addition circuit

Claims (4)

[Claims] 1. A constant speed driving means for driving an optical disk to rotate at a constant speed at startup, a movement control means for moving the optical pickup to a specific radial position of the optical disk, and the movement control means for moving the optical pickup. An optical disk reproduction comprising: a pit length measuring means for measuring the pit length of a track at a specific radial position; and a judging means for judging the type of the optical disk based on the pit length measured by the pit length measuring means. apparatus. 2. The optical disc reproducing apparatus according to claim 1, wherein the discriminating means discriminates the type of the optical disc based on the minimum pit length measured by the pit length measuring means. 3. The optical disc reproducing apparatus according to claim 1, wherein the discriminating means discriminates the type of the optical disc based on the maximum pit length measured by the pit length measuring means. 4. The optical disc reproducing apparatus according to claim 1, wherein the discriminating means discriminates the type of the optical disc based on the minimum pit length and the maximum pit length measured by the pit length measuring means.