JPH03157819A - Optical disk device - Google Patents

Abstract

PURPOSE:To stably perform the focus control at the time of performing this control again by resetting a register of a digital filter when interrupting the focus control. CONSTITUTION:OR between a defocus signal 7 for defocusing and a focus off signal 8 for the stop of disk reproducing is operated by an OR circuit 9. Only when the output of the OR circuit 9 is active, a shift clock 17 and a driving data latch clock 18 are stopped by a microcomputer 6 and the register of a digital filter 5 is reset by a reset signal 10. Thus, the register of the digital filter 5 is already reset at the time of performing the focus control again and this control is not affected by the preceding state, and therefore, the focus control is stably performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical disc devices such as compact discs and laser discs.

BACKGROUND OF THE INVENTION In recent years, a large number of optical disc-related products have come onto the market. In addition to the widespread use of consumer compact disc players, the decline in the price of compatible players that can play multiple discs, such as laser discs and compact discs, is spurring their widespread use. In terms of software, low-priced, high-quality software has appeared, and it is becoming the mainstay of AV (audio/visual), which is on par with video. On the other hand, taking advantage of the large capacity and high-speed accessibility of optical discs, they are also being applied in the computer field as ROM (read-only memory). It is expected that its uses will expand greatly.

Data on an optical disk is arranged as pits in a spiral from the inner circumference to the outer circumference of the disk, and the data is determined by the presence or absence of bits. The role of the optical servo is to settle the focus of the light emitted from the optical device onto a predetermined pit row when reproducing data on a disc, so that the data can be read. Optical servo includes focus control, which focuses an optical device on the disk surface, and tracking control, which focuses on pit rows on the disk surface. In the control procedure, the disk is rotated by a motor, and then the optical device is driven in a direction perpendicular to the disk surface to perform a focus pull-in operation. To explain the generation of the focus error signal, as shown in Figure 3, the focus error signal becomes zero when the focus is on the disk surface, and increases in absolute value as the focus moves away from the disk surface in the vertical direction. After reaching a peak, it decreases.

Focus pull-in drives the optical device so that the focus error signal falls within the figure 8 peak. Focus control is performed so that when the focus error signal is within the figure 8 peak, the absolute value of the focus error signal is set to zero and the focus is focused on the disk surface.

A conventional optical disc device will be described below.

FIG. 4 is a block diagram showing the configuration of a focus control section of a conventional optical disc device, in which 1 is a disk which is an information recording medium, 2 is a disk 1 that shines light, and generates a focus error signal using the reflected light. 3 is an A/D converter that inputs the focus error signal and performs A/D conversion; 4 is a sampling clock for sampling the focus error signal; 5 inputs the A/D converted data; A digital filter that performs filter processing for compensation and high-frequency compensation; 7 is an out-of-focus signal that indicates that focus control has been lost; 8 is a focus-off signal that indicates that focus control is interrupted; 9 is an out-of-focus signal 7 and a focus-off signal 11 is a clock enable signal outputted from the microcomputer 20 and stops the shift clock 17 of the digital filter 5 and the drive data latch clock 18 of the drive means 16; 12 is a shift clock of the register of the digital filter 5; , 13 is a drive data latch clock that latches the drive data input to the drive means 16, and 14 is an OR of the clock enable signal 11 and the shift clock 12.
15 is the clock enable signal 11 and the drive data latch clock 1.
19 is a motor that rotates the disk 1, 20
is a microcomputer that controls the digital filter 5 and the driving means 16 according to the state of focus control.

The operation of the conventional optical disc device configured as described above will be described below. In a normal focus control state, the focus of the light emitted from the optical device 2 is approximately on the disk, and a loop is configured such that the absolute value of the focus error signal is small. The focus error signal output from the optical device 2 is converted to A/D by the A/D converter 3.
converted. Here, we set the sampling frequency to 44.1
It is converted to 8-bit data at KHz. Next, this converted 8-bit data is input to the digital filter 5.
Filter by. The digital filter 5 performs filtering for low-frequency compensation and high-frequency compensation, and outputs it to the next driving means 16 as an 8-bit data output.

FIG. 5 is a block diagram showing the configuration of the digital filter 5. As shown in FIG. The digital filter 5 receives 8-bit data, has a low-pass filter section 26 and a bypass filter section 27 arranged in parallel, adds the outputs of both filters, multiplies the gain coefficient, and outputs the 8-bit data.Low-pass The filter section 26 is provided with a low frequency class 1 register 21 and performs a cumulative addition operation.In order to perform the addition operation, the low frequency class register 21 is set to 24 bits.This addition data is multiplied by a low frequency class coefficient 22. (by spelling 8 pips I-9'-
It becomes ta. On the other hand, the bypass filter section 27 sets the high-frequency term register 23, multiplies the data delayed by one sample by the high-frequency term coefficient 24, and outputs the difference from the current sample data. These two filter outputs are added, multiplied by a gain coefficient of 25, and output to the driving means. Note that the high-frequency term and low-frequency registers are shifted by the shift clock 17. This shift clock is also 44.1 KHz.

Next, the driving means 16 will be described. The driving means 16 receives the output data of the digital filter 5 as input, and performs pulse width modulation based on the value of 8-bit data latched by the driving data latch clock 18. In addition, the pulse width modulation frequency is also 44.1
It is KHz. For positive data, apply a positive voltage;
Continue to apply for a time proportional to the magnitude of the absolute value of the data.

When a positive voltage is applied, the optical device 2 is driven in the direction in which the A-cass error signal decreases. Further, in the case of negative data, a negative voltage is applied and continues to be applied for a time proportional to the magnitude of the absolute value of the data. When a negative voltage is applied, the optical device 2 is driven in a direction in which the nail error signal increases. In this way, focus control is performed through closed-loop operation.

Here, when considering the case where focus control is interrupted, first of all, there are cases where the focus is lost due to disturbance such as vibration, or where reproduction of the disc is stopped. In this case, an OR circuit 9 performs an OR operation between the focus off signal 7, which is used when the focus is off, and the focus off signal 8, which is used to stop playback of the disc.
Only when the output of the R circuit 9 is active, the microcomputer 6 controls the shift clock 17 and drive data latch clock 18.
Try to stop it.

17 Problems to be Solved by the Invention However, in the conventional optical disc device as described above,
When performing focus control again, the register values are saved as they were before, resulting in the problem that the control characteristics become unstable, and in some cases, focus control cannot be performed.

The present invention solves the problems of the prior art described in 1. It is an object of the present invention to provide an optical disc device with good control characteristics when focus control is performed again.

Means for Solving the Problems To achieve this object, the optical disc device of the present invention comprises:
an optical disc that is an information recording medium; an optical device that applies a light beam to the optical disc and generates a focus error signal based on the reflected light; and an A/D converter that receives the focus error signal and performs A/D conversion; Said A/D
a digital filter that receives the output of the converter and performs filter processing; a control state detection unit that resets a register of the digital filter when focus control is interrupted; and a drive unit that receives the output of the digital filter and outputs a drive signal. The digital filter register is reset when focus control is interrupted.

Effect of the Invention According to the configuration described above, when performing focus control again, the register of the digital filter is reset, so that stable focus control can be performed without being affected by the previous focus control state.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 show an embodiment of the invention.

FIG. 1 is a block diagram showing the configuration of an optical disc device according to an embodiment of the present invention, in which numeral 1 indicates a disc as an information recording medium, numeral 2 illuminates the disc 1, and generates a focus error signal using the reflected light. 3 is an A/D converter that inputs the focus error signal and performs A/D conversion; 4 is a sampling clock for sampling the lO− focus error signal; 5 is an A/D converter that inputs the A/D converted data and converts it into a digital signal; A digital filter that performs filter processing for frequency compensation and high frequency compensation; 6 a microcomputer that controls the digital filter 5 and the driving means 16 according to the focus control state; 7;
8 is a focus off signal indicating that the focus control is interrupted; 9 is an OR circuit that ORs the focus off signal 7 and the focus off signal 8; 10 is a microcomputer 6 A reset signal 11 is outputted from the microcomputer 6 and input to the digital filter 5 to reset the register of the filter.
12 is a shift clock of the register of the digital filter 5, 13 is a drive data latch clock that latches the drive data input to the drive means 16, and 14 is an OR of the clock enable signal 11 and the shift clock 12. 15 is an OR circuit that ORs the clock enable signal 11 and the drive data latch clock 13 and sets it as a drive data latch clock 18. 19 is a motor that rotates the disk 1. be.

The operation of the optical disc device of this embodiment configured as described above will be described below.

In a normal focus control state, the focus of the light emitted from the optical device 2 is approximately on the disk, and a loop is configured such that the absolute value of the focus error signal is small.

A focus error signal output from the optical device 2 is A/D converted by an A/D converter 3. Here, the sampling frequency is 44 degrees and 1 KHz, and the data is converted into 8-bit data. Next, use this converted 8-bit data as input,
Filter processing is performed using the digital filter 5. The digital filter 5 performs filtering for low frequency compensation and high frequency compensation,
It is sent to the next driving means 18 as an 8-bit data output.

FIG. 2 is a block diagram showing the configuration of the digital filter 5. As shown in FIG. The digital filter 5 takes 8-bit data as input, has a low-pass filter section 26 and a bypass filter section 27 arranged in parallel, adds the outputs of both filters, multiplies by a gain coefficient, and outputs 8-bit data. The low-pass filter section 2θ is provided with a low-pass term register 21,
A cumulative addition operation is being performed. In order to perform the addition operation, the low frequency term register 21 is set to 24 bits. This added data becomes 8-bit data by multiplying it by a low frequency term coefficient 22. On the other hand, the bypass filter section 27 includes a high-band class register 23, multiplies the data delayed by one sample by a high-band class coefficient 24, and outputs the difference from the current sample data. These two filter outputs are added, multiplied by a gain coefficient of 25, and output to the driving means. Note that the registers for the high frequency range and the low frequency term are shifted by the shift clock 17. This shift clock is also 44. It is 1KHz.

Next, the driving means 16 will be described. The driving means 16 receives the output data of the digital filter 5 as input and performs pulse width modulation based on the value of 8-bit data latched by the driving data latch crotter. Furthermore, the pulse width modulation frequency is also 44.1KH.
It is z. In the case of positive data, a positive voltage is applied and continues to be applied for a time proportional to the magnitude of the absolute value of the data. When a positive voltage is applied, the optical device 2 is driven in a direction in which the focus error signal decreases. Further, in the case of negative data, a negative voltage is applied and continues to be applied for a time proportional to the magnitude of the absolute value of the data. When a negative voltage is applied, the optical device 2 is driven in a direction in which the focus error signal increases. In this way, the nail control is performed by closed loop operation.

Here, when considering cases in which focus control may be interrupted, first, the focus may be lost due to a disturbance such as vibration, and then there may be cases in which reproduction of the disc is stopped.

In this case, an OR circuit 9 performs an OR operation between the out-of-focus signal 7 when the focus has gone out and the focus-off signal 8 when stopping playback of the disc. Next, only when the output of the OR circuit 9 is active, the microcomputer 6
Shift clock 17 and drive data latch clock 13
- 14- Set the switch 18 to l- and reset the reset signal 10.
The register of digital filter 5 is reset by

In this way, when performing focus control again, the register of the digital filter has been reset and is not affected by the previous state, so stable focus control can be performed. If the low frequency term register 21 holds the previous value, the value of the low frequency term of O1J becomes the data of the low frequency term as soon as control is started. If the difference between the previous value of the low-frequency term and the current value of the low-frequency term is large, it takes time for cumulative addition to correct the difference, and the control may go out of order before the correction can be made. . Moreover, even if it does not come off, it takes time to stabilize.

Furthermore, if the high frequency register 23 holds the previous value, the difference between the previous value and the current value by one sample becomes the high frequency data when control is started.

At this time, the previous value is completely meaningless data, and there is a possibility that focus control may be lost or become unstable due to the disturbance caused by this first sample.

In this way, by providing the reset signal 10 from the microcomputer 6 as a control state detection means for resetting the register of the digital filter 5 when focus control is interrupted, stable control is achieved when focus control is performed again. be able to.

Although this embodiment deals with focus control, the same thing can be done with tracking control by replacing the fingernail error signal of this embodiment with a tracking error signal.

As described above, the present invention provides an optical disc as an information recording medium, an optical device that applies a light beam to the optical disc and generates a focus error signal based on the reflected light, and an optical device that generates a focus error signal based on the reflected light. A/D that converts A/D as input
a converter, a digital filter that takes the output of the A/D converter as input and performs filter processing, a control state detection means that resets the register of the digital filter when focus control is interrupted, and a drive that takes the output of the digital filter as input. Since it is configured with a drive means that outputs a signal, the register of the digital filter is reset when focus control is performed again, and it is not affected by the previous state, making it possible to perform stable focus control, which is highly effective. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an optical disc device in an embodiment of the present invention, FIG. 2 is a block diagram showing the internal configuration of a digital filter of the optical disc device in the same embodiment,
Fig. 3 is a characteristic diagram showing the relationship between the focal position of the optical device and the focus error signal, Fig. 4 is a block diagram showing the configuration of a conventional optical disc device, and Fig. 5 shows the internal configuration of the digital filter of the conventional optical disc device. FIG. 1... Disk, 2... Optical device, 3...
・A/D converter, 5... digital filter,
6...Microcomputer, 9. 14. 15...OR
Circuit, 16... Drive means, 19... Motor,
21...Low frequency term register, 22...Low frequency class coefficient, 23...High frequency class register, 24...High frequency class coefficient, 25...Gain coefficient, 26...
Low-pass filter section, 27... bypass filter section.

Claims (2)

[Claims] (1) An optical disc that is an information recording medium; an optical device that applies a light beam to the optical disc and generates a focus error signal based on the reflected light; and A that receives the focus error signal and performs A/D conversion.
/D converter; a digital filter that receives and filters the output of the A/D converter; control state detection means that resets a register of the digital filter when focus control is interrupted; and inputs the output of the digital filter. 1. An optical disc device comprising: drive means for outputting a drive signal. (2) an optical disc that is an information recording medium; an optical device that applies a light beam to the optical disc and generates a tracking error signal based on the reflected light; and an A/D converter that receives the tracking error signal and performs A/D conversion. a D converter; a digital filter that receives the output of the A/D converter as an input and performs filter processing; a control state detection means that resets a register of the digital filter when tracking control is interrupted; An optical disc device comprising: a drive means for outputting a drive signal; and a drive means for outputting a drive signal.