JP3494912B2 - Frequency error detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a recording / reproducing method for reproducing recorded information on a recordable optical disk having minute left and right undulations in a recording area. The present invention relates to a frequency error detection circuit in a device. 2. Description of the Related Art In an optical disk capable of recording and reproducing data, in order to increase the recording capacity, data is written to both a groove-like groove provided on the optical disk and a land between the grooves. A land / group recording method for recording 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 wobble as shown in FIG. [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 the detected frequency is not the predetermined frequency, control is performed such that the detected frequency is set to the predetermined frequency. However, in the area where the address information is recorded, the wobble usually does not have a fixed 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 that outputs the number of channel clocks counted using the clock signal, and compares the number of channel clocks with a fixed channel clock number that indicates the number of channel clocks when the wobble signal has a predetermined frequency;
When there is a difference between the two, the frequency error generating 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 it with the number of fixed channel clocks indicating the number of channel clocks when the wobble signal has a predetermined frequency. As a result, if 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. However, the above-described conventional frequency error detecting device has a problem when the detected wobble signal has a temporary period disorder 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 disturbance of the period
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 on the basis of the signal indicating the large frequency error, the wobble signal cannot be set to a predetermined frequency to be controlled, so that it is 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 apparatus, 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-described conventional problems, and detects a frequency error of a wobble signal.
It is an object of the present invention to provide a frequency error detection device that can always be stably performed without being affected by noise or the like. A frequency error detecting device according to the present invention is characterized in that a wobble signal detected from an optical disc is
A frequency error detection device for detecting whether or not a signal has a predetermined frequency, the frequency error detection device being proportional to a cycle of the wobble signal.
In the every predetermined period, a counter for outputting a count channels clock using the clock signal, the number of the channel clock, a first holding means for holding and outputting until the next channel number clock is input A second holding unit that holds and outputs the number of channel clocks output by the first holding unit until the next channel clock number is input, and a channel clock number that is output by the first holding unit. When, the a difference calculation means for calculating a difference between the number of the channel clock by the second holding means outputs, determining means for determining whether the difference is greater than a predetermined threshold value, the determination result is the difference solid If is to indicate that not more than the threshold value, to the number of the channel clock where the first holding means outputs the wobble signal is counted when a said predetermined frequency By comparing the number of channel clock,
Outputs a signal indicating the difference, if the determination result indicates that the difference is equal to or greater than the threshold value, regardless of the comparison result
And a frequency error generating means for outputting a signal indicating that there is no difference between the two . Embodiments of the present invention will be described below. FIG. 1 is a block diagram for explaining a frequency error detection 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 device 100 includes a counter 101 that outputs the number of channel clocks counted by using a clock signal for each cycle of the wobble signal for each predetermined cycle, and a channel clock number 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. If the result is equal to or smaller than the threshold, 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 the threshold or more, 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 detected wobble signal cycle using a clock signal for each predetermined cycle. The above predetermined period,
Each cycle (each of a1, a2,..., A8 shown in FIG.
2) or every two cycles (each of b1, b shown in FIG. 2 (b)).
2,..., B4). In other words, 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 period a1, and stops counting the number of channel clocks at the rising edge of the wobble signal of the period a2. The count number K1 at this time is output, and thereafter, the count number 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 holds and outputs the number of channel clocks output from the counter 101 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 number of channel clocks is input. In other words, 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 the second register 103 stores the number of channel clocks in the previous cycle. Holds and outputs the unit channel clock number. The subtracter 104 calculates a 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. The determination circuit 105 determines whether the calculation result of the subtractor 104 is equal to or greater than a predetermined threshold. The frequency error generation circuit 106 determines that the determination result indicates that the calculation result is equal to or greater than a threshold value.
To indicate that not has a number of channels clock first register 102 outputs wobble signal is compared with the fixed channel clock number indicating the number of counts one cycle unit of the case is a predetermined frequency, the difference between the two Is output, and if the determination result indicates that the calculation result is equal to or greater than the threshold , a signal indicating that there is no difference between the two is output regardless of the comparison result. 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 in the period b3, the first register 102 , B2, and holds and outputs the number of channel clocks K2 counted during the period of b1, and the second register 103 holds and outputs the number of channel clocks K1 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 in the portion corresponding to the channel clock number K2 'has a temporary disturbance in the cycle,
The number of channel clocks K2 'and the number of channel clocks 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 apparatus of the present embodiment, when the wobble signal detected from the optical disk has a temporary disturbance in the 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 other part of the wobble signal, 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 the present embodiment, the counting of the number of channel clocks is started or stopped at the rise of the wobble signal. The same operation as described above can be performed. 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. A counter for outputting the number of channel clocks counted using a clock signal at predetermined intervals proportional to the cycle of the wobble signal, and holding and outputting the number of channel clocks until the next channel clock number is input A first holding unit that performs the operation, a second holding unit that holds and outputs the number of channel clocks output by the first holding unit until the next channel clock number is input, and the first holding unit Means for calculating a difference between the number of channel clocks output by the means and the number of channel clocks output by the second holding means; Determining means for determining whether or not the number of channel clocks is greater than or equal to the threshold value, and if the determination result indicates that the difference is not greater than or equal to the threshold value , the number of channel clocks output by the first holding means; by comparing the fixed number of channel clocks should be counted when a frequency, and outputs a signal representative of the difference, the determination result is the difference is more than the threshold value
, Regardless of the comparison result
Since a frequency error generating means for outputting a signal indicating that there is no difference in the case where there is a temporary disturbance in the cycle of the wobble signal, a signal representing the frequency error to the portion corresponding to the period Output Can be avoided.
Ri without being affected by noise or the like, at all times, it is possible to perform stable frequency error detection.

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 the optical disc. FIG. 5 is a diagram showing a normal (normal) wobble signal and a wobble signal having a temporary period disturbance (abnormal). [Description of Signs] 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 301 of optical disk: Groove section 302: Land section

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 20/10 G11B 20/14

Claims (1)

(57) [Claim 1] A frequency error detecting device for detecting whether a wobble signal detected from an optical disc has a predetermined frequency or not, wherein the frequency of the wobble signal is A counter for outputting the number of channel clocks counted by using the clock signal at every proportional predetermined period, and first holding means for holding and outputting the number of channel clocks until the next channel clock number is input And the number of channel clocks output by the first holding means,
Second holding means for holding and outputting until the next number of channel clocks is input; number of channel clocks output by the first holding means;
Said a difference calculation means for calculating a difference between the number of the channel clock by the second holding means outputs, determining means for determining whether the difference is greater than a predetermined threshold value, the determination result is the difference is above If it indicates that the frequency is not equal to or larger than the threshold value , 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 the difference is calculated. outputs a signal representative of, indicating that the determination result is the difference <br/> the threshold or more, written on the comparison result
Warazu, and a frequency <br/> speed error generation means for outputting a signal indicating that there is no difference between the two, the frequency error detecting apparatus characterized by.