JP2003123271A - Optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid a collision of an objective lens with a disk in performing focus search and also to perform focus draw processing in a short time. SOLUTION: A servo controller 16 sets a search signal amplitude in a search signal circuit 20 in a focus servo circuit 10 to perform focus search processing in accordance with the position of an optical pickup 5 in the radial direction of a disk in performing focus search. The closer to the outer circumference side of a disk the optical pickup 5 is located, the smaller focus search signal amplitude is set. At a failure in focus drawing, the closer to the outer circumference side of the disk the optical pickup 5 is located, the larger an increasing amount of focus search amplitude is made to perform focus search again.

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, and more particularly to an optical disk reproducing apparatus for performing focus pull-in processing according to the position of an optical pickup in the radial direction of the disk when pulling in focus.

[0002]

2. Description of the Related Art In an optical disc reproducing apparatus for reproducing information recorded on an optical disc such as a CD or a DVD, an objective lens held in a movable part of an objective lens control driving device is kept at a distance from the optical disc, and an objective lens is used. Focus servo is performed to control the focused spot to be focused on the information recording surface of the optical disk. Since the focus servo pull-in range in which the focus servo can be performed is relatively narrow, approximately 10 μm to 20 μm, when starting the reproducing operation, first, the focus search operation can be performed by the focus search means to pull in the focus servo. The objective lens position is controlled to the range, and then the focus servo loop is turned on to execute the focus servo. As the start-up process for the reproduction operation, the focus search operation and the focus servo are executed, and then the spindle servo, the tracking servo, and the like are executed. When this start-up process is completed, scanning for reproduction by a focused spot focused via the objective lens becomes possible.

A conventional focus servo system will be described below with reference to the schematic block diagram of FIG. The focus servo device includes a search signal generation circuit 30, a switch 31 for switching between a focus error signal and a focus search signal, a zero cross detection circuit 32 for detecting a zero cross point of the focus error signal, a switch control circuit 33 for controlling the switch 31, and a reflection on an optical disk. The focus state detection circuit 34 detects the focus state of the laser light applied to the optical disc by comparing the sum signal detected from the generated laser light with a reference voltage.

The search signal generation circuit 30 supplies a sawtooth wave of about 1 Hz when reproduction of an optical disk is started, for example. When a switching control signal for instructing the connection between the search signal generating circuit 1 and the focus driver 35 is supplied from the switch control circuit 33 to the switch 31,
Based on this switching control signal, the switch 31 is connected to the switched terminal SW ₁ side, and the search signal generating circuit 30 is connected.
The sawtooth wave output signal from is supplied to the focus driver 35 via the switch 31. An output signal based on the sawtooth wave supplied from the search signal generation circuit 30 is supplied from the focus driver 35 to the objective lens control drive device, and based on this output signal, the objective lens held in the movable portion of the objective lens control drive device. The focus search operation is performed to approach or leave the optical disc.

The focus error signal is the focus of the objective lens.
Reflection from an optical disc that changes with the focus search operation
Astigmatism method using light, for example, a cylindrical lens
Etc. are detected. This focus error signal is
Switched terminal SW of switch 31 _TwoAnd zero-cross detection circuit
32. The zero-cross detection circuit 32 is
When the dust error signal is at zero level, the switch controller
The status signal is supplied to the rule circuit 33. focus
The state detection circuit 34 is compared with the reference voltage generation circuit 34a.
34b, and the data reflected by the optical disc.
The sum signal detected from the laser light is supplied. focus
In the comparator 34b in the state detection circuit 34, the reference
The reference voltage and the sum signal supplied from the voltage generation circuit 34a
Are compared, and if the sum signal is greater than the reference voltage,
The status signal of focus is sent to the switch control circuit 33.
Supply. The stage supplied from the zero-cross detection circuit 32
Supplied from the status signal and focus state detection circuit 32.
Any of the focus status signals
When it is supplied to the circuit 33, that is, the objective lens is
Focus search operation and irradiate the optical disc.
The focus position of the laser light is within the focus servo pull-in range.
Switch control signal is supplied to the switch 31 when
It

When the switching control signal is supplied to the switch 31, the switch 31 is operated so as to supply the focus error signal to the focus driver 35 from the state where the search signal generating circuit 30 and the focus driver 35 are connected to each other. The terminal is switched to the switched terminal SW ₂ , and the focus servo loop is turned on.

[0007]

By the way, in recent years, there has been a remarkable increase in the capacity of optical discs. With the shortening of the wavelength of the semiconductor laser used in the optical pickup device of the optical disc reproducing apparatus, the laser beam is applied to the recording surface of the optical disc. Large NA (Numerical) of the objective lens that collects light
Aperture). Objective lens N
When A becomes large, the distance in the focus direction between the objective lens and the optical disc, that is, the so-called Working Distance
e (hereinafter, simply referred to as WD) becomes small. Therefore,
For example, if an NA 0.85 objective lens is used, W
Considering that D is approximately 100 μm and the surface wobbling is approximately 300 μm when the disc having a diameter of 5 inches is rotated, the objective lens collides with the optical disc during the focus search operation performed in the focus servo-off state, and There is a possibility that any of the objective lenses will be damaged, or that either one of the optical disk and the objective lens will be damaged.

Therefore, when performing the focus search, first, the search amplitude of the objective lens is reduced to perform the focus pull-in process, that is, the amplitude of the sawtooth wave output from the search signal generating circuit 30 is reduced at first. If the focus pull-in fails, the amplitude of the search signal is increased by a predetermined amount to perform the focus pull-in, and the amplitude of the focus search signal is gradually increased until the focus pull-in succeeds. It was In this way, it is possible to prevent the collision between the objective lens and the optical disc, but it sometimes takes time until the focus pull-in ends. In particular,
The amount of surface deviation of the disc increases toward the outer circumference of the disc.Therefore, if the amplitude of the focus search signal is set to a small value in consideration of this amount of surface deviation, even in the focus search on the inner circumference of the disc, the search signal amplitude will be changed by the time the focus pull-in is completed. Also increases and the focus pull-in operation is performed, and there is a problem that it takes time.

In view of the above, an object of the present invention is to provide an optical disk reproducing apparatus capable of avoiding the collision between the objective lens and the disk when executing the focus pull-in process and performing the focus pull-in process in a short time.

Another object of the present invention is to provide an optical disk reproducing apparatus capable of changing the focus search amplitude in accordance with the position of the optical pickup in the disk radial direction.

[0011]

In order to achieve the above object, the present invention provides an optical disk reproducing apparatus which drives an objective lens provided in an optical pickup to approach and separate from a disk surface by a drawing drive signal to perform focus drawing. A position detection means for detecting the position of the optical pickup in the radial direction of the disc, and a focus pull-in control by changing the amplitude of the pull-in drive signal based on the position of the optical pickup in the radial direction of the disc detected by the position detection means. And a control means for performing. With the above configuration, it is possible to change the amplitude of the pull-in drive signal according to the position of the optical pickup in the radial direction of the disc.

Further, the control means controls the focus pull-in by reducing the amplitude of the pull-in drive signal as the optical pickup is located on the outer circumference of the disc. By doing so, it is possible to prevent the collision between the objective lens and the disc during focus search due to the warp of the disc or the like.

Further, when the focus pull-in fails, the control means changes the increase amount of the amplitude of the pull-in drive signal based on the position of the optical pickup in the radial direction of the disk to perform the focus pull-in control again. Is.

Further, when the focus pull-in fails, the control means increases the amplitude increase amount of the pull-in drive signal as the optical pickup is located closer to the outer circumference of the disc, and performs the focus pull-in control again. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of the essential parts of an optical disk reproducing apparatus of the present invention. In the figure, 1 is a disc,
Reference numeral 2 is a turntable, 3 is a spindle motor for rotating a disk, 4 is a spindle servo circuit for performing constant linear velocity control on the spindle motor, 5 is an optical pickup for emitting a laser beam to the disk and detecting a reflected beam, The objective lens 5a is provided. Further, the optical pickup 5 is provided with a four-divided photodiode 5b, which is composed of D _{A to} D _D. D _A and D _C are connected in parallel to output the (A + C) signal, and D _B and D _D are connected in parallel to output the (B + D) signal.

FIG. 7 is a diagram showing a method of detecting a focus servo error. When in the focused state, the reflected beam is D _A of the 4-division photodiode 51, as shown in FIG.
When the beam spot hits D _D evenly and the beam spot is too far from the signal surface, it hits D _A and D _C more and hits D _B and D _D less as shown in FIG. 7 (2). When the beam spot is too close to the signal surface, as shown in FIG.
Most hits _B and D _D , and less hits D _A and D _C. Therefore, (A + C)-(B + D) indicates the error between the focus of the beam spot and the signal surface.

Returning to FIG. 1, 6 is a sled motor composed of a stepping motor for sending the optical pickup 5 in the radial direction of the disk, 7 is a sled servo circuit for applying a sled servo for tracking the sled motor, and 8 is RF. The amplifier 9 is a digital signal processing circuit. The RF amplifier 8 individually changes the current-voltage of the (A + C) signal and the (B + D) signal input from the optical pickup 5 to generate a focus error signal FE, which is created from the (A + C) signal and the (B + D) signal. A + C) signal and (B
The sum signal of the + D) signal and the sum signal are output to the focus servo circuit 10 described later.

Reference numeral 10 denotes a focus servo circuit for driving a focus actuator (not shown) provided in the optical pickup on the basis of the focus error signal FE input from the RF amplifier 8 to apply focus servo. Reference numeral 11 denotes an input from the focus servo circuit. It is a servo driver that amplifies and drives the focus actuator.

Reference numeral 12 denotes a tracking servo circuit which drives a tracking actuator (not shown) provided in the optical pickup 5 based on the tracking error signal TE input from the RF amplifier 8 to apply tracking servo.
A servo driver 13 amplifies an input from the tracking servo circuit and drives a tracking actuator.

Reference numeral 14 is a detection circuit for detecting the lower envelope of the RF signal, 15 is an analog / digital converter,
16 receives a command from the system controller described later,
A servo controller for starting various servos, automatically adjusting a pickup servo system, setting a search amplitude for the focus servo circuit 10 during focus search, and the like 17,
Is a system controller that performs overall control of the system necessary for reproducing a disc, and 18 is a memory that stores the correspondence between the position of the optical pickup and the focus search amplitude.

FIG. 2 is a block diagram of the focus servo circuit of the present invention. The difference from the conventional one is the servo controller 16
The amplitude of the sawtooth wave output by the search signal generating circuit 20 is changed in accordance with the instruction of. Servo controller 1
6 sets the amplitude of the sawtooth wave generated by the search signal generating circuit 20 by reading the corresponding search signal amplitude from the memory 18 according to the position of the optical pickup 5 in the radial direction of the disk. When the optical pickup is located on the inner side of the disc, the amplitude of the sawtooth wave is increased, and when the optical pickup is located on the outer side of the disc, the amplitude is reduced.

FIG. 3 is a diagram showing the relationship between the position of the optical pickup in the radial direction of the disk and the amplitude of the search signal.
As shown in the figure, as the position of the optical pickup is closer to the outer circumference of the disc, the search amplitude is set smaller and the focus search is performed. When focus pull-in fails in the focus search operation, the servo controller 16
The search amplitude set in the search signal generation circuit 20 of the focus servo circuit 10 is increased and the focus search is executed again. At this time, the amount of increase in the search amplitude is set according to the position of the optical pickup in the radial direction of the disc.
FIG. 4 shows the relationship between the position of the optical pickup in the radial direction of the disc and the increase amount of the search amplitude. As shown in the figure, as the position of the optical pickup is located on the outer periphery of the disc, the increase amount of the search amplitude is set larger.

Since the amount of surface deviation of the disc tends to increase toward the outer periphery, the initial focus search amplitude amount can be made smaller toward the outer periphery of the disc to avoid collision between the disc and the optical pickup. At the time of retry when focus pull-in fails, the focus pull-in can be completed with a small number of times because the increase amount of the focus search amplitude is increased as the optical pickup is located on the outer circumference of the disc.

FIG. 5 shows an operation flow at the time of focus search in the disc reproducing apparatus of the present invention. When the focus pull-in is instructed by the instruction from the system controller 17, the servo controller 16 detects the position of the optical pickup 5 in the disc radial direction (step S101). The position of the optical pickup in the radial direction of the disc can be detected by counting the pulses input to the sled motor 6 formed of a stepping motor. The position of the optical pickup may be detected by another method.

The servo controller 16 executes step S1.
Based on the position of the optical pickup 5 detected in 01, the focus search amplitude is set in the search signal generation circuit 20 of the focus servo circuit 10 (step S102), and the focus pull-in process similar to the conventional one is performed (step S1).
03).

Next, the servo controller 16 determines whether or not the focus pull-in is successful (step S10).
4) If the focus pull-in fails, the focus search amplitude is increased according to the position of the optical pickup and set in the focus servo circuit 10 (step S10).
5) The focus pull-in process is executed again.

If focus pull-in is successful in step S104, the process ends. By doing so, it is possible to prevent the objective lens from colliding with the disc during the focus search, and it is possible to finish the focus search process in a short time.

The present invention has been described above with reference to the embodiments.
The present invention can be variously modified according to the gist of the present invention described in the claims, and the present invention does not exclude these.

[0029]

As described above, according to the present invention, according to the position of the optical pickup in the radial direction of the disk during focus search, the focus search signal amplitude is set smaller toward the outer circumference of the disk for focus search. Therefore, the collision between the objective lens and the disc can be surely prevented during the focus search, and the focus pull-in can be performed in a short time during the focus search on the inner circumference side of the disc.

Further, according to the present invention, since the amplitude increase amount of the re-search signal at the time of focus search failure is set to be larger as the optical pickup is located on the outer peripheral side of the disc, the focus search is performed. The number of retries in case of failure can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an optical disc reproducing apparatus of the present invention.

FIG. 2 is a diagram showing a configuration of a focus servo circuit of the present invention.

FIG. 3 is a diagram showing a relationship between a position of an optical pickup in a disc radial direction and a search signal amplitude.

FIG. 4 is a diagram showing the relationship between the position of the optical pickup in the radial direction of the disc and the increase amount of the search signal amplitude.

FIG. 5 is a diagram showing an operation flow at the time of focus search of the disc reproducing apparatus of the present invention.

FIG. 6 is a schematic configuration diagram of a conventional focus servo apparatus.

FIG. 7 is an explanatory diagram of a focus servo error detection method.

[Explanation of symbols]

1 ... Disc 3 ... Spindle motor 4 ... Spindle servo circuit 5: Optical pickup 5a ... Objective lens 6 ... Thread motor 7 ... Thread servo circuit 10: Focus servo circuit 12 ... Tracking servo circuit 16 ... Servo controller 17 ... System controller 18 ... Memory 20: Search signal generation circuit

Claims (4)

[Claims] 1. A position detecting device for detecting a position of an optical pickup in a radial direction of a disc in an optical disc reproducing device which drives an objective lens provided in the optical pickup to approach and separate from a disc surface by a pull-in drive signal to perform focus pull-in. And an optical pickup which controls the focus pull-in control by changing the amplitude of the pull-in drive signal based on the position of the optical pickup in the disc radial direction detected by the position detecting unit. apparatus. 2. The optical disc reproducing apparatus according to claim 1, wherein the control means performs focus pull-in control by decreasing the amplitude of the pull-in drive signal as the optical pickup is located on the outer periphery of the disc. 3. When the focus pull-in has failed, the control means changes the increase amount of the amplitude of the pull-in drive signal based on the position of the optical pickup in the radial direction of the disc to perform the focus pull-in control again. The optical disk reproducing apparatus according to claim 2, wherein 4. The focus control is performed again by increasing the amplitude increase amount of the pull-in drive signal as the optical pickup is located closer to the outer circumference of the disc when focus pull-in fails. The optical disk reproducing device according to claim 3.