JP2000222829A - Frequency error detector - Google Patents

Abstract

(57) Abstract: Provided is a frequency error detection device that can always stably detect a frequency error of a wobble signal without being affected by noise or the like. SOLUTION: A counter 101 for outputting a channel clock number obtained by counting a wobble signal using a clock signal for each predetermined period, and a first register 1 for holding and outputting the channel clock number output by the counter 101
02, a second register 103 that holds and outputs the number of channel clocks output by the first register 102,
If the difference between the number of channel clocks output from the first register 102 and the number of channel clocks output from the second register 103 is equal to or greater than a predetermined threshold, the frequency error generation circuit 106 does not output a signal indicating the difference. A frequency error detection device comprising:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency error detecting circuit in a recording / reproducing apparatus for reproducing recorded information from a recordable optical disk having minute left and right undulations in a recording area. .

[0002]

2. Description of the Related Art In an optical disk capable of recording and reproducing data, in order to increase the recording capacity, lands for recording data on both groove-shaped grooves provided on the optical disk and lands between the grooves. / Group recording method is used. The land portion and the groove portion are provided with minute left and right undulations (wobbles) having a predetermined amplitude and a predetermined period. A signal based on a change in the intensity of light reflected from the land portion or the groove portion is called a wobble signal.

FIG. 4 is a view for explaining the recording area of the optical disk. Reference numeral 300 denotes the recording area of the optical disk, on the surface of which a groove-shaped groove portion 301 and a land portion 302 between the grooves are provided. ing. Groove section 301
The land portion 302 is provided with a wobble as shown in the figure.

[0004] The optical disk provided with the wobble is
Data and address information are recorded using the frequency of the wobble signal as a carrier. On the other hand, when reproducing data from the optical disk, it is determined whether or not the frequency of the detected wobble signal is a predetermined frequency in consideration of the fact that noise, an error in the rotational speed of the disk, and the like affect the frequency. After that, if it is not the predetermined frequency, control is performed such that the detection frequency is set to the predetermined frequency. However, in the area where the address information is recorded, the wobble usually does not have a constant amplitude and a fixed period. Therefore, the frequency control as described above is not performed on the area where the address information is recorded.

FIG. 3 is a block diagram for explaining a conventional frequency error detecting device, and shows the configuration of the device. In the figure, reference numeral 200 denotes a frequency error detection device that detects whether or not the frequency of a wobble signal detected from an optical disk is a predetermined frequency. The frequency error detection device 200 changes the cycle of the wobble signal every predetermined period. A counter 201 for outputting the number of channel clocks counted using the clock signal, and comparing the number of channel clocks with a fixed channel clock number representing the number of channel clocks when the wobble signal has a predetermined frequency;
When there is a difference between the two, a frequency error generation circuit 202 outputs a signal indicating the amount of the difference.

Next, the operation will be described. Counter 20
1 receives a wobble signal detected from an optical disc,
The number of channel clocks counted using the clock signal is output every predetermined period of the period of the wobble signal. The frequency error generation circuit 202 receives the number of channel clocks and compares the number with a fixed channel clock number indicating the number of channel clocks when the wobble signal has a predetermined frequency. As a result, when there is a difference between the two, a signal indicating the amount of the difference is output. As a result, the frequency error of the detected wobble signal can be detected, and by controlling the frequency of the wobble signal based on the detected frequency error, the optical disc can be reproduced accurately.

[0007]

However, the above-described conventional frequency error detecting device has a problem when the detected wobble signal has a temporary disturbance in the period due to the influence of noise or the like. FIG. 5 shows a normal detection wobble signal A (FIG. 5).
(a)) and a wobble signal B having a temporary period disorder
(FIG. 5 (b)) is a schematic diagram for explaining FIG. As shown, a wobble signal B having a temporary period disorder
Is processed by the conventional frequency error detection device, the number of channel clocks including the part b having the disorder of the cycle is
Since the value is considerably smaller than the fixed channel clock number, the frequency error detection device 200 suddenly outputs a signal indicating a large frequency error.

If the frequency control of the wobble signal is performed based on the signal indicating the large frequency error, the wobble signal cannot be set to the predetermined frequency to be controlled, and it becomes difficult to reproduce the optical disk. Further, the range in which the frequency control can be performed is specific to the device that performs the control. For a signal that shows an excessively large frequency error, the frequency control device may not function properly. .

As described above, in the conventional frequency error detecting device, when a wobble signal having a temporary period disturbance is processed, a signal showing a remarkably large frequency error is generated for a portion having the period disturbance. Since the output is performed, it is difficult to control the frequency of the wobble signal based on the output, and there has been a problem that the optical disc cannot be accurately reproduced.

The present invention has been made in view of the above-mentioned conventional problems, and detects a frequency error of a wobble signal.
An object of the present invention is to provide a frequency error detection device that can always be stably performed without being affected by noise or the like.

[0011]

According to the frequency error detecting apparatus of the present invention, a wobble signal detected from an optical disk is
What is claimed is: 1. A frequency error detection device for detecting whether or not a signal has a predetermined frequency, comprising: a counter for outputting the number of channel clocks counted by using a clock signal for the wobble signal at predetermined intervals; The first holding means for holding and outputting the number of clocks until the next channel clock number is input, and the number of channel clocks output by the first holding means for receiving the next channel clock number. A second holding unit for holding and outputting the data until the data is stored, and a difference calculating unit for calculating a difference between the number of channel clocks output by the first holding unit and the number of channel clocks output by the second holding unit. Determining means for determining whether or not the difference is equal to or greater than a predetermined threshold; and, if the determination result indicates the threshold or less, the channel clock output by the first holding means. The number is compared with the number of fixed channel clocks to be counted when the wobble signal is at the predetermined frequency, and a signal indicating the difference is output. If the determination result indicates the threshold or more, the Frequency error generating means for not outputting a signal representing the difference.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram for explaining a frequency error detecting device according to an embodiment of the present invention, and shows a configuration of the device. In the figure, reference numeral 100 denotes a frequency error detection device that detects whether the frequency of a wobble signal detected from an optical disc is a predetermined frequency,
The frequency error detection apparatus 100 includes a counter 101 that outputs the number of channel clocks counted by using a clock signal for each cycle of a wobble signal for each predetermined cycle, and a channel clock number that is output by the counter 101. A first register 102 for holding and outputting until the number of channel clocks of the first
The second register 103 holds and outputs the number of channel clocks output by the first and second channel clocks until the next channel clock number is input, and outputs the number of channel clocks output by the first register 102 and the second register 103. Subtractor 104 for calculating a difference from the number of channel clocks to be performed, a determination circuit 105 for determining whether or not the output of the subtracter 104 is equal to or greater than a predetermined threshold value; When the result indicates the threshold value or less, the output of the first register 102 is compared with the number of fixed channel clocks to be counted when the wobble signal has a predetermined frequency. A signal indicating the amount of the difference is output, and when the determination result indicates a value equal to or greater than the threshold, the frequency error generating circuit 106 does not output a signal indicating the difference.

Next, the operation will be described with reference to FIG. The counter 101 outputs the number of channel clocks obtained by counting the period of the detected wobble signal using the clock signal at predetermined intervals. The above predetermined period,
Each cycle (each of a1, a2,..., A8 shown in FIG.
Every) or every two cycles (each b1, b shown in FIG. 2 (b)).
2,..., B4). That is, in the case shown in FIG. 2A, the counter 101 starts counting the number of channel clocks at the rising edge of the wobble signal of the cycle a1, and stops counting the number of channel clocks at the rising edge of the wobble signal of the cycle a2. The count K1 at this time is output, and thereafter, the count K is reset. Similarly, the number of channel clocks is counted from the rise of the wobble signal of cycle a2 to the rise of the wobble signal of cycle a3, and the count number K2 is output. This is sequentially performed in the cycles a1, a2,..., A8.

The first register 102 stores the counter 1
01 is held and output until the next channel clock number is input. The second register 103 holds and outputs the number of channel clocks output from the first register 102 until the next channel clock number is input. That is,
The first register 102 holds and outputs the number of channel clocks in the cycle unit immediately before the cycle unit of the wobble signal currently counted by the counter 101, and outputs the second register 1
Reference numeral 03 further stores and outputs the number of channel clocks in the previous cycle unit. The subtractor 104 has the first register 10
2 and the second register 1
03 is calculated.
The determination circuit 105 determines whether the calculation result of the subtractor 104 is equal to or greater than a predetermined threshold. When the determination result indicates the threshold value or less, the frequency error generation circuit 106 determines the number of channel clocks output by the first register 102,
When the wobble signal has a predetermined frequency, the signal is compared with a fixed channel clock number indicating a count number in one cycle unit, and a signal indicating a difference between the two is output. Regardless, a signal indicating that there is no difference is output.

Since the predetermined threshold value changes depending on the n value indicating the unit of the wobble signal to be counted, an appropriate value is set in consideration of the n value so that the frequency control can be performed stably.

When a wobble signal as shown in FIG. 2B is detected, when the counter 101 is currently counting the number of channel clocks K3 within the period b3, the first register 102 , B2, and holds and outputs the number K2 of channel clocks counted during the period of b1, and the second register 103 holds and outputs the number K1 of channel clocks counted during the period of b1. In this case, since there is no difference between the number of channel clocks K1 and the number of channel clocks K2, a signal indicating the difference between the number of channel clocks K2 and the number of fixed channel clocks is output to the frequency error generation circuit 106.
Will output.

On the other hand, when a wobble signal as shown in FIG.
Is counting the number of channel clocks K3 ′ in the period of c3, the first register 102 stores
, And the second register 103 holds and outputs the number of channel clocks K1 ′ counted during the period c1. Here, since the wobble signal corresponding to the channel clock number K2 'has a temporary disturbance in the cycle,
Channel clock number K2 'and channel clock number K1'
There is a difference between In this case, the number of channel clocks K
Regardless of the comparison result between 2 'and the fixed channel clock number, the frequency error generation circuit 106 does not output a signal indicating the difference between the channel clock number K2 and the fixed channel clock number.

As described above, according to the frequency error detecting device of the present embodiment, when the wobble signal detected from the optical disc has a temporary disturbance in its cycle, the wobble signal corresponding to the cycle is added to the wobble signal. On the other hand, the frequency error is not detected, and the frequency error is detected only for the wobble signal in the other part, so that the frequency error of the wobble signal is always detected without being affected by noise or the like. It can be performed stably.

In this embodiment, the counting of the number of channel clocks is started or stopped at the rising edge of the wobble signal. The same operation as described above can be performed.

[0020]

According to the frequency error detecting device of the present invention, there is provided a frequency error detecting device for detecting whether or not a wobble signal detected from an optical disk has a predetermined frequency. For outputting the number of channel clocks counted using a clock signal at predetermined intervals, and first holding means for holding and outputting the number of channel clocks until the next number of channel clocks is input Second holding means for holding and outputting the number of channel clocks output by the first holding means until the next channel clock number is input, and channel clocks output by the first holding means. Calculating means for calculating a difference between the number and the number of channel clocks output by the second holding means, and determining whether the difference is equal to or greater than a predetermined threshold value Means for determining the number of channel clocks output by the first holding means when the determination result is equal to or less than the threshold value, and the number of fixed channel clocks to be counted when the wobble signal has the predetermined frequency. And a frequency error generating means for not outputting a signal indicating the difference when the determination result indicates the threshold value or more. When there is disturbance, a signal representing a frequency error is not output for a portion corresponding to the period, so that stable frequency error detection can always be performed without being affected by noise or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a frequency detection device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the number of channel clocks counted every predetermined period of a wobble signal.

FIG. 3 is a block diagram illustrating a configuration of a conventional frequency detection device.

FIG. 4 is a diagram showing a structure of a recording area of an optical disc.

FIG. 5 is a diagram showing a normal (normal) wobble signal and a wobble signal having a temporary period disturbance (abnormal).

[Explanation of symbols]

 100: Frequency error detection device 101: Counter 102: First register 103: Second register 104: Subtractor 105: Judgment circuit 106: Frequency error generation circuit 200: Frequency error detection device 201: Counter 202: Frequency error generation circuit 300: Recording area of optical disk 301: Groove part 302: Land part

Claims (1)

[Claims] 1. A frequency error detection device for detecting whether or not a wobble signal detected from an optical disc has a predetermined frequency, comprising the steps of: A counter for outputting the counted number of channel clocks; first holding means for holding and outputting the channel clock number until the next channel clock number is input; and a channel for outputting the first holding means. The number of clocks
A second holding unit for holding and outputting until the next channel clock number is input; a channel clock number output by the first holding unit;
Difference calculating means for calculating a difference from the number of channel clocks output by the second holding means, determining means for determining whether the difference is equal to or greater than a predetermined threshold value, and determining whether the determination result is equal to or less than the threshold value. When the wobble signal has the predetermined frequency, the number of channel clocks output by the first holding means is compared with the number of fixed channel clocks to be counted when the wobble signal has the predetermined frequency, and a signal representing the difference is output. And a frequency error generation unit that does not output a signal indicating the difference when the determination result is equal to or greater than the threshold value.