JP2003173539A - Mark length measuring device and mark length measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mark length measuring device which can measure mark length with high accuracy in order to improve the accuracy of calculation of a fundamental frequency and deal with the speedup of the rotation of a disk, and to provide a mark length measuring method. <P>SOLUTION: The mark length measuring device is provided with a measuring instrument 101 to measure the mark length of a mark read from a disk medium, registers 111 to 113 to store each mark length of three continuous marks measured by the measuring instrument 101, respectively, a maximum value register 120 to store the maximum mark length of the measured mark length, a comparator 102 to compare the sizes of the maximum mark length and the mark length stored in the register 112, an arithmetic unit 104 to determine the sum total of mark lengths stored in the registers 111 to 113, and a control part 103 to store the sum total of mark lengths determined with the arithmetic unit 104 on the basis of a comparison result obtained with the comparator 102 as the sum total of three continuous mark lengths containing the maximum mark length into a sum total register 130. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark length measuring device and a mark length measuring method for measuring the mark length of a mark recorded on a disk medium.

[0002]

2. Description of the Related Art In optical discs such as CDs and DVDs, the frequency of a signal read out fluctuates due to fluctuations in the rotational speed of the disc. Further, in these optical discs, the circumferential length (track length) becomes longer toward the outer peripheral side of the disc.
Therefore, CAV (Constant Angular V
In the case of the (elocity) method, the linear velocity becomes faster toward the outer circumference,
Even if the disk is rotated at a constant number of rotations, the frequency of the read signal becomes higher on the outer peripheral side. Taking this into consideration, in general, a frequency variation of about ± 30% to 50% is included in the operation range when reading the disk.

As a countermeasure against the above-mentioned frequency fluctuation, a method of calculating a fundamental frequency from a signal recorded on a disk and operating the PLL assuming that the fundamental frequency is the center frequency is usually used. . Then, this basic frequency is generally calculated using the maximum mark length in the sync area (frame sync area) arranged at regular intervals.

The sync area is an area used for detecting the start position of the data area by using a code which does not exist in the data area on the disc. A frame number (frame ID) and a frame sync symbol for frame synchronization are written in this sync area. This frame sync symbol contains a mark with the maximum mark length for synchronization (frame synchronization) that is longer than any of the marks in the data area. The mark with the maximum mark length is detected and the mark length is used as the basis. Seeking the fundamental frequency.

Here, in an optical disc such as a DVD, data is recorded on the disc-shaped disc surface in a spiral or concentric form. Data recording is on the circumference (track)
This is done using a mark having a length in the direction. The mark is detected by utilizing the difference in the reflection amount depending on the presence or absence of the mark (pit or land) when the laser beam or the like is irradiated. For example, a certain slice level can be set, and the mark can be detected by the intersection point interval at which the slice level and the reflection amount (output waveform) intersect.

Usually, the length of the mark (hereinafter referred to as the mark length) is expressed by using the time interval nT of this intersection. Here, T is the time per bit (basic period), n is an integer, and the mark is recorded with a length that is an integral multiple of T.
Then, the basic frequency (1 / T) can be obtained from the basic cycle T. Hereafter, a mark with a mark length of nT is
It will be referred to as mark nT.

As a conventional mark length measuring device for measuring the maximum mark length, for example, the one shown in FIG. 9 is known. In FIG. 9, a conventional mark length measuring apparatus includes a measuring device 502 for measuring the mark length, a maximum value register 504 for storing the maximum value LMAX of the mark length LK measured by the measuring device 502, and a maximum value register 504. The comparator 501 includes a comparator 501 that compares the maximum value LMAX stored in the memory with the measured mark length LK, a measuring device 502, and a controller 503 that controls the maximum value register 504. When the measured value LK is larger than the maximum value LMAX as a result of the comparison by the comparator 501, the control unit 503 determines that
The measured value LK is stored in the maximum value register 504 (LMAX).

The maximum mark length can be detected by the conventional mark length measuring apparatus having the above-mentioned structure, for example, by the procedure shown in FIG. First, the maximum mark length (LMAX1) is detected for the first time (step S50).
1), and then the second maximum mark length (LM
AX2) is detected (step S502). And
Using the comparator 501, both (LMAX1, LMAX
It is compared whether 2) are the same (step S503). Then, in step S503, both (LMAX
If 1, LMAX2) are equal, it means that the maximum mark length has been detected, so the detection ends, and conversely, both (LMAX)
If X1 and LMAX2) are different, detection is restarted from the beginning.

The reason why the maximum mark length is measured twice and the two maximum mark lengths (LMAX1, LMAX2) are obtained as described above is to confirm the validity of LMAX1. Then, based on the detected maximum mark length,
The fundamental frequency of the signal read from the disc can be determined. However, in practice, LMAX1 and LMAX2 do not completely match due to the influence of measurement error, noise, etc., so if | LMAX1-LMAX2 | ≤ ΔL (ΔL is a permissible error considering measurement error, noise, etc.) , LM
We consider that AX1 and LMAX2 are in agreement.

[0010]

In the conventional maximum mark length measuring apparatus, the maximum mark length of the sync area which is not in the data area recorded on the disc is calculated and the reference frequency is calculated by the above-mentioned procedure. is doing. The accuracy of the frequency calculation using the maximum mark length is related to the signal reading accuracy of the entire optical disc, and in order to correspond to the signal reading at a higher speed, it is necessary to increase the basic frequency calculation accuracy. There was an issue of being desirable.

Further, the mark length is measured by using a predetermined clock count, but if the measurement is performed at the same clock frequency even when the disk rotation speed is changed, the disk rotation will be performed. When the number is high, the mark length is measured shorter than when the speed is low, and when the number is high, the accuracy of the fundamental frequency is lower than when the speed is low.

In order to avoid this, if the clock frequency is increased in proportion to the rotation speed of the disk,
This leads to an increase in circuit scale and power consumption.

The present invention has been made to solve the above-mentioned problems, and can improve the accuracy of the calculation of the fundamental frequency and can also cope with the high speed rotation of the disk. , And a mark length measuring method.

[0014]

In order to solve the above-mentioned problems, the present invention (Claim 1) provides a disk medium on which data is recorded by using predetermined mark lengths having different lengths in the circumferential direction. On the other hand, in a mark length measuring device for measuring the mark length for obtaining the fundamental frequency of the signal to be read, the mark length of the mark read from the disk medium is measured and the maximum mark length among the measured mark lengths is measured. The total mark length of three consecutive marks including the mark having the maximum mark length that is the longest length is obtained.

According to the present invention (claim 2), in the mark length measuring device according to claim 1, a measuring device for measuring the mark length of the mark read from the disk medium, and the measuring device are used. Also, three registers that store the respective mark lengths of three consecutive marks, a comparator that compares the maximum mark length with the mark lengths stored in the three registers, and the three registers. The total of the mark lengths calculated by the calculator based on the comparison result by the calculator and the comparator for calculating the total of the mark lengths stored in
And a control unit for outputting as a total of one mark length.

According to the present invention (claim 3), in the mark length measuring device according to claim 1, a measuring device for measuring the mark length of the mark read from the disk medium and the measuring device are used. Further, first to third measurement value registers respectively storing the mark lengths of three consecutive marks, a maximum value register storing the maximum mark length, and three consecutive mark values including the maximum mark length. A total register for storing the total mark length, and the first to third
Of the mark value stored in the measurement value register, a comparator for comparing the maximum mark length with the mark length of a predetermined measurement value register, and the result of the comparison by the comparator, the predetermined mark When the mark length of the measurement value register is equal to or greater than the maximum mark length, the mark length of the predetermined measurement value register is stored in the maximum value register, and the total mark length obtained by the arithmetic unit is Each time the mark length is measured by the measuring device, the mark length stored in the second measurement value register is stored in the first measurement value register while being stored in the total register. A control unit that stores the mark length stored in the measurement value register in the second measurement value register and stores the mark length measured by the measuring device in the third measurement value register. , It is those with a.

According to the present invention (claim 4), in the mark length measuring device according to claim 1, a total of the mark lengths of three consecutive marks read from the disk medium is one mark. The first to third measuring devices for measuring by shifting them one by one, the fourth measuring device for measuring the mark length of the marks read from the disk medium, and the first to third measuring devices respectively have the mark lengths. The first to third registers respectively storing the mark lengths of the three consecutive marks measured by the fourth measuring device while measuring the total of the maximum mark length and the maximum mark length. A comparator for comparing the magnitudes of the mark lengths stored in the first to third registers, and one of the first to third measuring instruments based on the comparison result by the comparator. Measured mar The total length, and a control unit for outputting as the sum of the three mark lengths successive containing the maximum mark length,
It is equipped with.

According to the present invention (claim 5), in the mark length measuring device according to claim 1, the total mark length of three consecutive marks read from the disk medium is one mark. The first to third measuring devices for measuring by shifting them one by one, the fourth measuring device for measuring the mark length of the marks read from the disk medium, and the first measuring device for measuring three consecutive marks A first measurement value register for storing the mark length of the second mark of the three marks measured by the fourth measuring device while measuring the mark length; and the second measuring device. When measuring the mark length of three consecutive marks,
2 of the 3 marks measured by the
A second measurement value register in which the mark length of the th mark is stored; and the fourth measurement device when the third measurement device measures the mark length of three consecutive marks. , A third measurement value register in which the mark length of the second mark of the three marks is stored, a maximum value register in which the maximum mark length is stored, and three consecutive mark values including the maximum mark length. A total register for storing the total mark length, the maximum mark length and the first mark
From the mark lengths stored in the first to third measurement value registers, and the comparison result by the comparator, whichever of the mark lengths stored in the first to third measurement value registers If the mark length is greater than or equal to the maximum mark length, the mark length is stored in the maximum value register and measured by a measuring instrument corresponding to the mark length.
And a control unit for storing the total mark length of three consecutive marks in the total register.

Further, according to the present invention (claim 6), the fundamental frequency of a signal to be read is obtained for a disk medium on which data is recorded by using predetermined mark lengths having different lengths in the circumferential direction. In the mark length measuring method for measuring the mark length for measuring the mark length of the marks read sequentially from the disk medium, the mark length is continuously measured, and a continuous mark including the maximum mark length which is the maximum mark length among the sequentially measured mark lengths. The total of the three mark lengths is calculated.

Further, in the mark length measuring method according to the present invention (claim 7), a predetermined mark length and the maximum mark length among the mark lengths of three consecutive marks which are sequentially measured are provided. Comparing the lengths with each other, and as a result of the comparison, if the predetermined mark length is equal to or more than the maximum mark length, a step of obtaining a total mark length of the three consecutive marks is provided. is there.

According to the present invention (claim 8), in the mark length measuring method according to claim 6, the total mark lengths of three consecutive marks read from the disk medium are sequentially measured. A step of comparing the sequentially measured mark length with the maximum mark length, and as a result of the comparison, if the measured mark length is greater than or equal to the maximum mark length, the sum of the sequentially measured mark lengths. Among these, a step of outputting a total mark length of three consecutive marks including the measured mark as a total sum of three consecutive mark lengths including the maximum mark length is provided.

Further, according to the present invention (claim 9), the fundamental frequency of a signal to be read is obtained for a disk medium on which data is recorded by using predetermined mark lengths having different lengths in the circumferential direction. A mark length measuring device for measuring a mark length for measuring a mark length of a mark read from a disk medium, and including a mark having a maximum mark length which is the maximum mark length among the measured mark lengths. The total mark length of N consecutive N marks (N is an integer of 4 or more) is obtained.

The present invention (Claim 10) includes Claim 9.
In the mark length measuring device according to the description, a measuring device for measuring the mark length of the mark read from the disk medium,
Comparing the magnitudes of N registers, which respectively store the mark lengths of N consecutive marks measured by the measuring instrument, with the maximum mark length and the mark lengths stored in the N registers. A comparator for calculating the total mark lengths stored in the N registers, and a total mark length obtained by the arithmetic unit based on the comparison result by the comparator. And a control unit for outputting as a total of N consecutive mark lengths including.

The present invention (Claim 11) includes Claim 9.
In the mark length measuring device according to the description, a measuring device for measuring the mark length of the mark read from the disk medium,
First to Nth measurement value registers for storing the respective mark lengths of N consecutive marks measured by the measuring device, a maximum value register for storing the maximum mark length, and the maximum mark A total register for storing the total of consecutive N mark lengths including the length;
An arithmetic unit for obtaining the total of the mark lengths stored in the measurement value register of N, a comparator for comparing the maximum mark length and the mark length of a predetermined measurement value register, and the result of the comparison by the comparator, When the mark length of the predetermined measurement value register is greater than or equal to the maximum mark length, the mark length of the predetermined measurement value register is stored in the maximum value register, and the total mark length obtained by the calculator is calculated. The mark lengths stored in the total register and stored in the second to Nth measurement value registers each time the mark length is measured by the measuring device are set to the first to (N-1) th mark lengths. And a control unit for storing the mark length measured by the measuring device in the Nth measurement value register.

Further, according to the present invention (claim 12), the fundamental frequency of a signal to be read is obtained for a disk medium on which data is recorded using predetermined mark lengths having different lengths in the circumferential direction. In the mark length measuring method for measuring the mark length for measuring the mark length of the marks read sequentially from the disk medium, the mark length is continuously measured, and a continuous mark including the maximum mark length which is the maximum mark length among the sequentially measured mark lengths. The total of N mark lengths (N is an integer of 4 or more) is calculated.

[0026]

(First Embodiment) A mark length measuring apparatus and a mark length measuring method according to a first embodiment of the present invention will be described below with reference to the drawings. The mark length measuring device and the mark length measuring method according to the first embodiment obtain a total mark length which is the sum of three consecutive mark lengths including the maximum mark length.

FIG. 1 is a block diagram showing the configuration of the mark length measuring apparatus according to the first embodiment. In FIG.
The mark length measuring device according to the first embodiment includes a measuring device 10
1, a comparator 102, a control unit 103, and an arithmetic unit 104
, The total register 130, and the first measurement value register 11
1, a second measurement value register 112, a third measurement value register 113, and a maximum value register 120.

The total register 130 has a total mark length LS.
UM is stored, and the maximum value register 120 stores the maximum mark length LMAX. Further, the first measurement value register 111, the second measurement value register 112, and the third measurement value register 113 store mark lengths PLK1, PLK2, and PLK3, which are mark lengths of continuous marks, respectively.

The mark length newly measured by the measuring device 101 is stored in the third measurement value register 113,
The mark length previously stored in the third measurement value register 113 is moved to the second measurement value register 112, and the mark length previously stored in the second measurement value register 112 is changed to the first measurement value. After moving to the value register 111, these operations are repeated thereafter.

On the other hand, the arithmetic unit 104 measures the new mark length LK by the measuring unit 101 and stores the new mark length LK in the third measured value register 113, and then, the first measured value register 111 and the second measured value register 111. The total mark length LSUM obtained by adding the mark lengths stored in the value register 112 and the third measurement value register 113 is calculated.

In the comparator 102, every time the measuring device 101 newly measures the mark length LK and the mark length LK is stored in the third measuring register 103, it is stored in the second measuring value register 112. The mark length PLK2 is compared with the maximum mark length LMAX stored in the maximum value register 120, and the comparison result is output to the control unit 103.

The control unit 103 indicates that the comparison result received from the comparator 102 indicates that the mark length PLK2 is the maximum mark length LM.
When it is AX or more, the first measurement value register 111 and the second measurement value register 1 obtained by the arithmetic unit 104.
12, total mark length L of the mark lengths PLK1, PLK2, PLK3 stored in the third measurement value register 113
Store SUM in sum register 130 and mark length PLK
2 as the maximum mark length LMAX and the maximum value register 12
Store in 0.

In the first embodiment, the case where the mark length of a DVD is measured will be described as an example. Next, the operation of the mark length measuring device will be described using a specific example of measuring the mark length of a DVD.

DVD data is 8/16 modulated,
Marks having a mark length of 3T to 11T are recorded in the data area. Then, there is a frame sync area different from the data area at 1488T intervals, and the mark length is 4 as a frame sync signal in the frame sync area.
Three consecutive marks of T, 14T, and 4T are recorded. In the first embodiment, three consecutive mark lengths (4T, 14T, 4T) including the maximum mark length (14T) existing in the frame sync area are measured, and a total mark length that is the sum of them is obtained. Is.

FIG. 2 is a diagram showing an example of mark lengths stored in the respective measurement value registers. Note that, in FIG. 2, for the sake of convenience, the lengths of the periods A to F are the same, but strictly speaking, the lengths of the periods A to F depend on the mark length of the input mark. And different. Also,
Here, it is assumed that the mark having the mark length shown in the uppermost row of FIG. 2 is input to the mark length measuring device in each period.

In the period A, when a mark having a mark length of 8T is input to the measuring instrument 101, the measuring instrument 101 measures the mark length LK of the mark to be 8T, and at the beginning of the period B, 8T Is stored as PLK3 in the third measurement value register 113.

In the period B, the value PLK2 stored in the second measurement value register 112 is 6T and PL
Since the value of K2 is less than LMAX (10T), the process of updating the values of the sum register 130 and the maximum value register 120 is not performed.

Then, in period C, PLK3 (8T) stored in the third measurement value register 113 in period B
Is stored as PLK2 (8T) in the second measurement value register 112, and PLK2 (6T) stored in the second measurement value register 112 in the period B is stored as PLK1 in the first measurement value register 111. To be done.

As is apparent from FIG. 2, the first measurement value register 111 (PLK1) and the second measurement value register 11
2 (PLK2), third measurement value register 113 (PLK
In 3), the mark lengths of consecutive marks are stored, and the mark lengths are shifted each time the mark length is measured by the measuring instrument 101.

Then, as shown in FIG.
When a mark having a mark length of 4T, 14T, or 4T in D is input to the measuring device 101, PLK2 becomes 1 in the period E.
It becomes 4T. At this time, in the comparator 102, the PLK
2 (14T) is determined to be LMAX (10T) or more, and PLK1, PLK2, and PLK3 are determined at the end of the period E.
(22T) is stored in the total register 130 as the total mark length LSUM, and PLK2 (14T) is stored in the maximum value register 120 (LMAX). Therefore, in the period F, the total mark length LSUM is stored in the total register 130. The total mark length LSUM is 22T, and the maximum value register 120
The maximum LMAX stored in 14 is 14T. In addition,
Since this mark length 14T is the maximum mark length in DVD, a mark having a mark length exceeding 14T is measured by the measuring instrument 1.
It is not input to 01. Therefore, the total mark length LSUM stored in the total register 130 is held, and the basic frequency can be obtained using this total mark length.

Here, it is generally considered that the measurement error that occurs in the measurement of the mark length by the measuring device 101 is ± 1. However, as in the conventional mark length measuring device, one maximum mark is required for the calculation of the fundamental frequency. When only the length (14T) is used, the ratio of the measurement error to the maximum mark length is 1/14 of the maximum mark length.

However, as in the first embodiment, three consecutive mark lengths including the maximum mark length (4T, 14T,
4T) is measured and the fundamental frequency is calculated by using the total of the 4T), it is considered that the error generated between the marks is canceled by the measurement of each mark length (for example, the first mark). The error generated at the end of the mark in the measurement of the length (4T) is offset by the error generated at the start of the mark in the measurement of the second mark length (14T)), and the measurement error at this time Is considered to be the same measurement error as when the total of the three mark lengths is collectively measured, that is, the measurement error is ± 1 in the measurement of the three mark lengths. Therefore, 3
Since the total of the two mark lengths is 22T, the ratio of the measurement error to the measured mark length (22T) is 1/22, and the accuracy can be improved as compared with the conventional case.

As described above, in the mark length measuring apparatus and the mark length measuring method according to the first embodiment, three consecutive mark lengths (4T, 14T, 4T) including the maximum mark length are included.
Since T) is measured and the total is used to calculate the fundamental frequency, the ratio of the measurement error occurring when measuring the total mark length to the whole is
It can be made smaller and the accuracy of the fundamental frequency can be improved.

Therefore, it becomes possible to deal with signal reading at high speed, which requires higher calculation accuracy of the fundamental frequency. Further, in the first embodiment, the total mark length (22T) used for the calculation of the fundamental frequency is longer than the maximum mark length (14T) that has been conventionally used. Also in the above, the basic frequency can be calculated with sufficiently high accuracy without increasing the frequency of the clock in proportion to the rotation speed of the disk.

(Second Embodiment) A mark length measuring apparatus and a mark length measuring method according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the mark length measuring device according to the second embodiment. Referring to FIG. 3, the mark length measuring apparatus according to the second embodiment includes a first measuring device 201 and a second measuring device 2.
02, the third measuring device 203, the measuring device 200, the comparator 240, the control unit 250, and the first measurement value register 2
11, a second measurement value register 212, a third measurement value register 213, a maximum value register 220, and a total register 230.

The first measured value register 211, the second measured value register 212, and the third measured value register 213 are
Mark lengths PLK1 and P that are mark lengths of continuous marks
LK2 and PLK3 are stored respectively. Further, the maximum value register 220 stores the maximum mark length LMAX,
The total mark length LSUM is stored in the total register 230.

The first measuring device 201 receives the mark read from the disk medium as an input, measures the total mark length of three consecutive marks, and calculates the total LSU of the mark lengths.
It outputs M1 to the controller 250.

The second measuring instrument 202 receives the mark read from the disk medium as an input, and calculates the total mark length of three consecutive marks starting from the mark one mark later than the first measuring instrument 201. The measurement is performed, and the total LSUM2 of the mark lengths is output to the control unit 250.

The third measuring instrument 203 receives the mark read from the disk medium as an input, and calculates the total mark length of three consecutive marks starting from the mark one mark later than the second measuring instrument 202. It measures and outputs the total LSUM3 of the mark lengths to the control unit 250.

Then, the measuring device 200 receives the mark read from the disk medium as an input, measures the mark length LK for each input mark, and outputs the mark length LK to the control unit 250.

The comparator 240 has a mark length PLK stored in the first to third measurement value registers 211 to 213.
1 to PLK3 and the maximum value register 220
The maximum mark length LMAX stored in
It receives from 0, compares the magnitude, and outputs the comparison result to the control unit 250.

The control unit 250 controls the total measurement timing of the mark lengths in the first to third measuring instruments 201 to 203 according to the timing of the marks read from the disk medium. In addition, the first to third measuring devices 201
Measured by the measuring instrument 200 so that the mark length LK of the second mark in the total mark lengths measured in 203 to 203 is stored in the first to third measurement value registers 211 to 213, respectively. Mark length LK
It is stored in the first to third measurement value registers 211 to 213. That is, the first to third measurement value registers 211 to 2
The value of 13 will be updated every time the measuring device 200 measures three mark lengths.

Then, the first to third measurement value registers 2
When a new mark length LK is stored in any of 11 to 213, the new mark length LK and the maximum value register 220
The maximum mark length LMAX stored in
Pass to 0 and receive the comparison result. As a result of the comparison,
If the mark length PLKi (i is any one of 1 to 3) newly stored in any of the first to third measurement value registers 211 to 213 is equal to or larger than LMAX, the mark length PLKi is set as LMAX at the maximum. The first register which is stored in the value register 220 and corresponds to the i-th measurement value register (i is one of 1 to 3) in which the mark length PLKi is stored.
To the total mark length LSUMi (i is any one of 1 to 3) measured by the i-th measuring device (i is any one of 1 to 3) of the third measuring devices 201 to 203 It is stored in the total register 230 as a long LSUM.

Next, the operation of the mark length measuring apparatus and the mark length measuring method according to the second embodiment will be described.
Also in the second embodiment, as in the first embodiment, three consecutive data existing in the frame sync area of the DVD are used.
The case where the total mark length of one mark (4T, 14T, 4T) is measured will be described as an example.

The controller 250 controls the first to third measuring devices 2
The measurement timing of the total LSUM of the mark lengths 01 to 203 is controlled. First, when the first mark is input, the first measuring device 201 starts the measurement, and when the second mark is input, the first mark is input. The second measuring device 202 is caused to start the measurement, and when the third mark is input, the third measuring device 203 is caused to start the measurement. Then, each of the measuring devices 201 to 203 measures the total mark length, and the control unit 2
When output to 50, the measurement is started again from the next mark, and this is repeated.

FIG. 4 is a diagram showing an example of mark lengths stored in the respective measurement value registers. Note that, in FIG. 4, for convenience, the lengths of the periods A to G are the same, but strictly speaking, the lengths of the periods A to G depend on the mark length of the input mark. And different. Also,
Here, it is assumed that the mark having the mark length shown in the uppermost row of FIG. 4 is input to the mark length measuring device in each period.

As shown in FIG. 4, the control unit 250 is
The mark length LK measured by the measuring device 200 is transferred to the first to third measurement value registers 211 to 213 to the measuring device 20.
Each time the mark length LK is received from 0, it is sequentially stored, and the storage of the mark length PLK is repeated.

Since the second measuring instrument 202 measures the total mark length of the continuous marks (mark lengths are 8T, 4T, 14T) input in the periods A to C, the continuous marks 3 are measured. Of the two marks, the control unit 250 sets the mark length (4T) of the second mark at the beginning of the period C.
When it is received from 0, the control unit 250 controls the mark length LK.
Second measurement value register 212 with (4T) as PLK2
To store.

Next, the control unit 250 controls the mark length LK (14T) received from the measuring device 200 at the beginning of the period D.
It is stored in the third measurement value register 213. In this case, since PLK3 (14T) is LMAX (10T) or more, at the end of the period D, the control unit 250 causes PLK3 (14T) to
Is stored in the maximum value register 220 as LMAX. Further, the control unit 250 controls the third measuring device 20 at the beginning of the period E.
Total LSU of 3 consecutive mark lengths received from 3
The total register 230 with M3 as the total mark length LSUM
To store. Since the mark length 14T is the maximum mark length in the DVD, the mark length exceeding 14T is not output from the measuring device 200 to the control unit 250. Therefore, the total mark length LSUM stored in the total register 230 is held, and the basic frequency can be obtained using this total mark length LSUM.

In this case, it is generally considered that the measurement error that occurs in measuring the mark length in the measuring device is ± 1, but only one maximum mark length (14T) is used as in the conventional mark length measuring device. In such a case, the ratio of the measurement error to the maximum mark length is 1/14 of the maximum mark length. However, as in the second embodiment, the measurement errors of the first to third measuring devices 201 to 203 are different. When measuring the total of three consecutive mark lengths (22T), the ratio of the measurement error to the total of the mark lengths is 1/22 of the total mark lengths (22T), which is more basic than the conventional case. The frequency accuracy can be increased.

As described above, in the mark length measuring device and the mark length measuring method according to the second embodiment, three consecutive mark lengths (4T, 14T, 4T) including the maximum mark length are included.
Since T) is measured and the total is used to calculate the fundamental frequency, the ratio of the measurement error occurring when measuring the total mark length to the whole is
It can be made smaller and the accuracy of the fundamental frequency can be improved.

Therefore, it becomes possible to cope with signal reading at high speed, which requires higher calculation accuracy of the fundamental frequency. Further, in the second embodiment, the total mark length (22T) used for the calculation of the fundamental frequency is longer than the maximum mark length (14T) used conventionally, so that the rotation speed of the disk is increased. Also in the above, the basic frequency can be calculated with sufficiently high accuracy without increasing the frequency of the clock in proportion to the rotation speed of the disk.

(Third Embodiment) A mark length measuring apparatus and a mark length measuring method according to a third embodiment of the present invention will be described below with reference to the drawings. Third Embodiment
The mark length measuring apparatus and the mark length measuring method according to (1) above obtain the total mark length which is the sum of four consecutive mark lengths including the maximum mark length by the same method as in the first embodiment.

FIG. 5 is a block diagram showing the structure of the mark length measuring apparatus according to the third embodiment. In FIG.
The mark length measuring device according to the third embodiment includes a measuring device 10
1, a comparator 302, a control unit 303, and a computing unit 304
, The sum register 330, and the first measurement value register 31
1, a second measurement value register 312, a third measurement value register 313, a fourth measurement value register 314, and a maximum value register 320. The measuring instrument 101 is
This is the same as the first embodiment and the description thereof is omitted.

The total register 330 has a total mark length LS.
UM is stored, and the maximum value register 320 stores the maximum mark length LMAX. The first to fourth measurement value registers 311 to 314 store the mark lengths PLK1 to PLK4, which are the mark lengths of the continuous marks, respectively. The comparator 302 includes the mark length PLK3 stored in the third measurement value register 313 and the maximum mark length LMAX stored in the maximum value register 320 from the control unit 303.
Is received, the magnitudes of the two are compared, and the comparison result is output to the control unit 303.

The control unit 303 stores the mark length LK received from the measuring device 101 in the fourth measurement value register 314 as the mark length PLK4. If PLK3 is equal to or larger than LMAX as a result of comparison by the comparator 302, PLK1 to PLK4 are passed to the arithmetic unit 304, and the sum of them obtained by the arithmetic unit 304 is added to the total mark length L.
Stored in sum register 330 as SUM, PLK3
As the maximum mark length LMAX, the maximum value register 320
To store. Further, each time the measuring device 101 obtains a new mark length LK, the second measurement value register 31
The value of the mark length PLK2 of 2 is stored in the first measurement value register 311 as the mark length PLK1, and the value of the mark length PLK3 of the third measurement value register 313 is changed to the mark length PLK.
Stored in the second measurement value register 312 as K2,
The value of the mark length PLK4 of the measurement value register 314 is stored in the third measurement value register 313 as the mark length PLK3. The arithmetic unit 304 obtains the total of PLK1 to PLK4 received from the control unit 303 and outputs it to the control unit 303.

Next, the operation of the mark length measuring apparatus and the mark length measuring method according to the third embodiment will be described.
In the third embodiment, the case where the mark length of a predetermined optical disc is measured will be described. The data of the predetermined optical disk is 8/16 modulated, and marks having a mark length of 3T to 11T are recorded in the data area, and there are frame sync areas different from the data area at predetermined intervals. It is assumed that four consecutive marks having a mark length of 8T, 4T, 14T, and 4T are recorded as frame sync signals in the frame sync area.

In the third embodiment, there are four continuous marks including the maximum mark length (14T) existing in the frame sync area.
Measure one mark length (8T, 4T, 14T, 4T),
The total mark length, which is the sum of them, is calculated.

FIG. 6 is a diagram showing an example of the mark length stored in each register. In FIG. 6, for convenience,
Although the lengths of the periods A to G are set to be the same, strictly speaking, the lengths of the periods A to G are different depending on the mark length of the input mark. Further, here, it is assumed that the mark having the mark length shown in the uppermost row of FIG. 6 is input to the mark length measuring instrument in each period.

In the period A, a mark having a mark length of 8T is input to the measuring device 101, the mark length LK is measured by the measuring device 101 to be 8T, and at the beginning of the period B, the control unit 303 sets the mark length LK. (8T) is received from the measuring device 101, and 8T is stored as PLK4.

In period C, PLK3 becomes 8T and PLK3 becomes
K2 becomes 6T and PLK1 becomes 5T. As is apparent from FIG. 6, the first to fourth measurement value registers 311 to 311
The mark lengths of consecutive marks are stored in 314 (PLK1 to PLK4), and these mark lengths are measured each time the measuring device 101 measures the mark length (in FIG. It has been updated (although after a period of time).

As shown in FIG. 6, when marks having a mark length of 8T, 4T, 14T, 4T are input to the measuring device 101 in the periods A to D, PLK3 is set to 14 in the period E.
It becomes T. At this time, PLK3 (14T) is LMA
X (10T) or more, and at the end of the period E, the total (30T) of PLK1 to PLK4 is stored in the total register 330 as the total mark length LSUM, and PL
Since K3 (14T) is stored in the maximum value register 320 (LMAX), in the period F, LSUM becomes 30T and LMAX becomes 14T. In addition, this mark length 14
Since T is the maximum mark length on the optical disc, 14
A mark having a mark length exceeding T will not be input to the measuring device 101. Therefore, the total mark length LSUM stored in the total register 330 is held, and the basic frequency can be obtained using this total mark length.

Here, in general, it is considered that the measurement error that occurs in measuring the mark length by the measuring device 101 is ± 1, but only one maximum mark length (14T) as in the conventional mark length measuring device. When the fundamental frequency is calculated using, the ratio of the measurement error to the maximum mark length is 1/14 of the maximum mark length.

However, as in the third embodiment, four consecutive mark lengths (8T, 4T, 1) including the maximum mark length are included.
4T, 4T) is measured and the fundamental frequency is calculated using the sum thereof, it is considered that the error generated between the marks is canceled by the measurement of the respective mark lengths. The measurement error is the same as the case where the total is collectively measured, and the measurement error is considered to be ± 1. Therefore, in the third embodiment, since the total of the four mark lengths is 30T, the ratio of the measurement error to the measured mark length (30T) is 1/30.
The accuracy can be improved as compared with the conventional case.

As described above, in the mark length measuring device and the mark length measuring method according to the third embodiment, the mark lengths (8T, 4T) of four consecutive marks including the maximum mark length are measured.
T, 14T, 4T) is measured and the fundamental frequency is calculated by using the sum of the measured values. Therefore, the ratio of the measurement error generated when measuring the total mark length to the whole is , And the accuracy of the fundamental frequency can be improved. Therefore, it becomes possible to cope with signal reading at high speed, which requires higher basic frequency calculation accuracy.

Further, since the total mark length (30T) used for calculating the fundamental frequency in the third embodiment is longer than the maximum mark length (14T) used conventionally, the rotation of the disc is accelerated. Even in this case, the fundamental frequency can be calculated with sufficiently high accuracy without increasing the frequency of the clock in proportion to the rotation speed of the disk.

(Fourth Embodiment) A mark length measuring apparatus and a mark length measuring method according to a fourth embodiment of the present invention will be described below with reference to the drawings. Fourth Embodiment
The mark length measuring device and the mark length measuring method according to the above-mentioned method obtain the total mark length which is the sum of four continuous mark lengths including the maximum mark length by the same method as in the second embodiment.

FIG. 7 is a block diagram showing the structure of the mark length measuring device according to the fourth embodiment. In FIG.
The mark length measuring device according to the fourth embodiment includes a first measuring device 401, a second measuring device 402, and a third measuring device 40.
3, the fourth measuring device 404, the measuring device 400, the comparator 440, the control unit 450, and the first measurement value register 41.
1, a second measurement value register 412, a third measurement value register 413, a fourth measurement value register 414, a maximum value register 420, and a total register 430.

First to fourth measurement value registers 411 to 4
14, mark lengths PLK1 to PLK of continuous marks are shown.
4 are stored respectively. Also, the maximum value register 420
Stores the maximum mark length LMAX in the total register 4
The total mark length LSUM is stored in 30.

The first measuring device 401 receives the mark read from the disk medium as an input, measures the total mark length of four consecutive marks, and calculates the total LSU of the mark lengths.
It outputs M1 to the controller 450.

The second measuring instrument 402 receives the mark read from the disk medium as an input, and calculates the total mark length of four consecutive marks starting from the mark one mark later than the first measuring instrument 401. It measures and outputs the total LSUM2 of the mark lengths to the control unit 450.

The third measuring instrument 403 receives the mark read from the disk medium as an input, and calculates the total mark length of four consecutive marks starting from the mark one mark later than the second measuring instrument 402. It measures and outputs the total LSUM3 of the mark lengths to the control unit 450.

The fourth measuring instrument 404 receives the mark read from the disk medium as an input, and calculates the total mark length of four consecutive marks starting from the mark one mark later than the third measuring instrument 403. It measures and outputs the total LSUM4 of the mark lengths to the control unit 450.

The measuring device 400 receives the mark read from the disk medium as an input, measures the mark length LK for each input mark, and measures the mark length LK to the control unit 4
Output to 50.

The comparator 440 uses the mark length PLK stored in the first to fourth measurement value registers 411 to 414.
1 to PLK4 and the maximum mark length LMAX stored in the maximum value register 420 are received from the control unit 450, their sizes are compared, and the comparison result is compared to the control unit 45.
Output to 0.

The control unit 450 controls the total measurement timing of the mark lengths in the first to fourth measuring instruments 401 to 404 according to the timing of the marks read from the disk medium. In addition, the first to fourth measuring devices 401
To 404, the mark length of the third mark in the total mark length being measured is stored in the first to fourth measurement value registers 411 to 414, respectively.
The mark length LK measured by 00 is stored in the first to fourth measurement value registers 411 to 414. Furthermore, when a new mark length is stored in any of the first to fourth measurement value registers 411 to 414,
Maximum mark length L stored in maximum value register 420
MAX is passed to the comparator 440, and the comparison result is received. As a result of the comparison, the first to fourth measurement value registers 4
The mark length newly stored in any of 11 to 414 is L
If it is equal to or longer than MAX, the mark length is stored as LMAX in the maximum value register 420, and the total mark length measured by the measuring instruments of the first to fourth measuring instruments corresponding to the measured value register is stored. Is stored in the total register 430 as LSUM.

Next, the operation of the mark length measuring apparatus and the mark length measuring method according to the fourth embodiment will be described.
Also in the fourth embodiment, as in the third embodiment, four consecutive marks (8
The case of measuring the total mark length of (T, 4T, 14T, 4T) will be described.

The control unit 450 controls the first to fourth measuring devices 4
When the first mark is input, the first measuring device 401 is caused to start the measurement, and then the second mark is input, the second mark is input. Start the measurement with the measuring device 402 of 3 and
When the fourth mark is input, the third measuring device 403 starts measurement, and when the fourth mark is input, the fourth mark is input.
Then, the measuring device 404 is started to measure. Then, when each measuring device measures the total mark length and outputs it to the control unit 450, the measurement is started again from the next mark, and this is repeated.

Next, regarding the operation of the mark length measuring device,
A specific example will be described. FIG. 8 is a diagram showing an example of mark lengths stored in each register. Note that in FIG. 8, for convenience, the lengths of the periods A to G are the same, but strictly speaking, the lengths of the periods A to G depend on the mark length of the input mark. And different.
In addition, here, it is assumed that the mark having the mark length shown in the uppermost row of FIG. 8 is input to the mark length measuring apparatus in each period.

As shown in FIG. 8, the control unit 450
The mark length measured by the measuring instrument 400 is sequentially stored in the first to fourth measurement value registers 411 to 414 every time the mark length LK is received from the measuring instrument 400,
The storage of the mark length LK is repeated.

It is the third measuring instrument 403 that measures the total mark length of the continuous marks (mark lengths are 8T, 4T, 14T, 4T) input in the periods A to D. When the control unit 450 receives the mark length (14T) of the third mark from the measured marks from the measuring device 400 at the beginning of the period D, the control unit 450 sets the mark length LK to the third measurement value register. It is stored in 413.

At this time, PLK3 (14T) is LMAX
Since it is larger than (10T), at the end of the period D, the control unit 450 sets PLK3 to LMAX and sets the maximum value register 4 to LMAX.
It stores in 20. Further, the control unit 450 stores the total LSUM3 of four consecutive mark lengths received from the third measuring device 403 at the beginning of the period E in the total register 430 as the total mark length LSUM. The mark length is 14
Since T is the maximum mark length on this optical disc,
When the mark length exceeding 14T is measured from the measuring device 400 to the control unit 45
It is never output to 0. Therefore, the total mark length LSUM stored in the total register 430 is held, and the basic frequency can be obtained using this total mark length.

As described above, in the mark length measuring apparatus and the mark length measuring method according to the fourth embodiment, four consecutive marks read from the optical disk by the first to fourth measuring devices 401 to 404 are read. The total mark length LSUM is measured by measuring the total mark length of the four consecutive marks whose maximum mark length is the third mark length.
Therefore, it is possible to reduce the ratio of the measurement error occurring when the total mark length LSUM is measured to the whole as compared with the conventional one, and it is possible to improve the accuracy of the fundamental frequency.

Further, since the total mark length LSUM used for calculating the fundamental frequency in the fourth embodiment is longer than the maximum mark length (14T) used conventionally,
Even when the rotation speed of the disk is increased, the basic frequency can be calculated with sufficiently high accuracy without increasing the clock frequency in proportion to the rotation speed of the disk.

In each of the above-described embodiments, the case where an optical disk such as a DVD is used as the disk medium has been described. The disk medium for obtaining the total mark length of four marks is a disk medium in which data is recorded by predetermined marks having different lengths in the circumferential direction, and continuous three or four marks including the maximum mark length. Any disk medium such as an optical disk, a magnetic disk, a magneto-optical disk, etc. can be used as long as the disk medium is recorded.

Further, among the continuous three or four marks recorded on the disc medium, the position of the mark having the maximum mark length is the second (that is, the middle) position in each of the above embodiments, or Although the third case has been described, the position of the mark having the maximum mark length may be any position, for example, the first position or the fourth position.

Further, in each of the above-described embodiments, the case where the total of the mark lengths of three or four consecutive marks including the maximum mark length is obtained has been described. The total mark length of five or more consecutive marks including the maximum mark length may be calculated, and the same effect as the above description can be obtained.

Further, in each of the above-described embodiments, it is described that the total of three or four consecutive mark lengths including the maximum mark length is stored in the total register as the total mark length LSUM. The total mark length may be output from the measuring device without being stored in the register. Then, a device (not shown) for obtaining the fundamental frequency may obtain the fundamental frequency based on the last (that is, the latest) total mark length received from the mark length measuring device. Further, each component of the mark length measuring device according to each of the above embodiments may be configured by hardware,
Alternatively, the program control software may be used.

[0099]

As is apparent from the above description, according to the mark length measuring apparatus and the mark length measuring method of the present invention, a disc on which data is recorded by predetermined marks having different lengths in the circumferential direction. The mark length of the mark read from the medium is measured, and the total of N consecutive mark lengths (N is an integer of 3 or more) including the maximum mark length which is the maximum mark length among the measured mark lengths is obtained. By doing so, it is possible to reduce the proportion of the measurement error that occurs when the total of the continuous N mark lengths is obtained,
The accuracy of the fundamental frequency can be improved by obtaining the fundamental frequency based on the total of the N consecutive mark lengths.

Further, according to the mark length measuring apparatus and the mark length measuring method of the present invention, since the total of N consecutive mark lengths is obtained, the mark length of one mark is measured as in the conventional case. As compared with the case where the mark length is measured, even if the frequency of the clock for measuring the mark length is low, the same accuracy as in the conventional case can be ensured, and the speed of the disk rotation can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a mark length measuring device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of mark lengths stored in each register according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a mark length measuring device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of mark lengths stored in each register according to the second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a mark length measuring device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an example of mark lengths stored in each register according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a mark length measuring device according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing an example of mark lengths stored in each register according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional mark length measuring device.

FIG. 10 is a flowchart showing the operation of a conventional mark length measuring device.

[Explanation of symbols]

101 measuring device 102, 240, 302, 440 comparator 103, 250, 303, 450 control unit 104, 304 computing unit 130, 230, 330, 430 total register 111, 211, 311, 411 first measurement value register 112, 212, 312, 412 Second measurement value register 113, 213, 313, 413 Third measurement value register 114, 214, 314, 414 Maximum value register 200, 400 Measuring instrument 201, 401 First measuring instrument 202, 402 Second measuring device 203, 403 Third measuring device 404 Fourth measuring device 314, 414 Fourth measured value register

Claims (12)

[Claims] 1. A mark for measuring a mark length for obtaining a fundamental frequency of a signal to be read on a disk medium on which data is recorded using predetermined mark lengths having different lengths in a circumferential direction. In the length measuring device, the mark length of the mark read from the disc medium is measured, and the mark length of the three consecutive marks including the mark having the maximum mark length, which is the maximum mark length among the measured mark lengths, is measured. A mark length measuring device characterized by obtaining a total. 2. The mark length measuring device according to claim 1, wherein a measuring device for measuring the mark length of the mark read from the disk medium, and each of three consecutive marks measured by the measuring device. The three registers that store the mark lengths respectively, a comparator that compares the maximum mark length and the mark lengths stored in the three registers with each other, and the total of the mark lengths stored in the three registers An arithmetic unit for obtaining, and a control unit for outputting the total mark length obtained by the arithmetic unit as a total of three consecutive mark lengths including the maximum mark length based on the comparison result by the comparator,
A mark length measuring device comprising: 3. The mark length measuring device according to claim 1, wherein a measuring device for measuring the mark length of the mark read from the disk medium, and each of three consecutive marks measured by the measuring device. First to third measurement value registers each storing a mark length, a maximum value register storing the maximum mark length, and a total storing a total of three consecutive mark lengths including the maximum mark length A register; an arithmetic unit that obtains the total mark lengths stored in the first to third measurement value registers; a comparator that compares the maximum mark length with a mark length of a predetermined measurement value register; As a result of comparison by the comparator, if the mark length of the predetermined measurement value register is equal to or greater than the maximum mark length, the mark length of the predetermined measurement value register is set to the maximum value register. The mark stored in the second measurement value register is stored every time the mark length is measured by the measuring device while the total mark length obtained by the arithmetic unit is stored in the total register. The length is stored in the first measurement value register, the mark length stored in the third measurement value register is stored in the second measurement value register, and the mark length measured by the measuring device is stored in the first measurement value register. Third
And a control unit for storing the measured value register in the mark length measuring apparatus. 4. The mark length measuring device according to claim 1, wherein the total mark length of three consecutive marks read from the disk medium is measured by shifting the mark length by one mark. 3 measuring device, 4th measuring device for measuring the mark length of the mark read from the disk medium, and 1st to 3rd measuring device respectively measuring the total mark length First to third registers storing the respective mark lengths of three consecutive marks measured by the fourth measuring device, and stored in the maximum mark length and the first to third registers. And a comparator for comparing the magnitude of the mark length with the other, and based on the comparison result by the comparator, the total of the mark lengths measured by any one of the first to third measuring instruments, Maximum mark A control unit for outputting as the sum of three consecutive mark lengths including, with a mark length measuring device, characterized in that. 5. The mark length measuring device according to claim 1, wherein a total of mark lengths of three consecutive marks read from the disk medium is shifted by one mark and measured. 3 measuring device, a 4th measuring device for measuring the mark length of the mark read from the disk medium, and a 1st measuring device measuring the mark length of 3 consecutive marks A first measurement value register that stores the mark length of the second mark of the three marks measured by the fourth measuring device; and the mark length of three marks in which the second measuring device is continuous A second measurement value register that stores the mark length of the second mark of the three marks measured by the fourth measuring device while measuring Three A third measurement value register that stores the mark length of the second mark of the three marks measured by the fourth measuring device while measuring the mark length of the peak, and the maximum mark A maximum value register for storing a length, a total register for storing a total of mark lengths of three consecutive marks including the maximum mark length, a maximum mark length and the first to third measurement value registers A comparator that compares the stored mark length with one of the mark lengths stored in the first to third measurement value registers as a result of comparison by the comparator When the length is equal to or longer than the length, the mark length is stored in the maximum value register, and the sum of the mark lengths of three consecutive marks measured by the measuring instrument corresponding to the mark length is added to the total register. And a control unit for storing the mark length measuring device, characterized in that. 6. A mark for measuring a mark length for determining a fundamental frequency of a signal to be read on a disk medium on which data is recorded using predetermined mark lengths having different lengths in a circumferential direction. In the length measuring method, the mark lengths of the marks read from the disk medium are sequentially measured, and a total of three consecutive mark lengths including the maximum mark length which is the maximum mark length among the sequentially measured mark lengths is obtained. A mark length measuring method characterized by the following. 7. The mark length measuring method according to claim 6, wherein a step of comparing a predetermined mark length with the maximum mark length among the mark lengths of three consecutive marks that are sequentially measured, As a result of the comparison, when the predetermined mark length is equal to or longer than the maximum mark length, a step of obtaining a total mark length of the three consecutive marks is provided. 8. The mark length measuring method according to claim 6, wherein a total of mark lengths of three consecutive marks read from the disk medium is sequentially measured, and the mark lengths sequentially measured are: Comparing the maximum mark length, as a result of the comparison, if the measured mark length is greater than or equal to the maximum mark length, out of the total of the sequentially measured mark length, the measured mark Outputting the total of the mark lengths of the three consecutive marks including, as a total of the three consecutive mark lengths including the maximum mark length,
A method for measuring mark length, characterized by: 9. A mark for measuring a mark length for determining a fundamental frequency of a signal to be read on a disk medium on which data is recorded using predetermined mark lengths having different lengths in a circumferential direction. The length measuring device measures the mark lengths of the marks read from the disk medium, and N consecutive marks (N is 4 or more) including the mark having the maximum mark length which is the maximum mark length among the measured mark lengths. An integer) of the mark length of the mark is obtained. 10. The mark length measuring device according to claim 9, wherein a measuring device for measuring the mark length of the mark read from the disk medium, and N consecutive marks measured by the measuring device. N registers in which the respective mark lengths are respectively stored, a comparator for comparing the maximum mark length and the mark lengths stored in the N registers with each other, and marks stored in the N registers. An arithmetic unit for obtaining the total length, and a control for outputting the total mark length obtained by the arithmetic unit as a total of N consecutive mark lengths including the maximum mark length based on the comparison result by the comparator. Department,
A mark length measuring device comprising: 11. The mark length measuring device according to claim 9, wherein a measuring device for measuring the mark length of the mark read from the disk medium, and N consecutive marks measured by the measuring device. A first to Nth measurement value register storing each mark length, a maximum value register storing the maximum mark length, and a total of N consecutive mark lengths including the maximum mark length are stored. A total register, an arithmetic unit for obtaining the total mark lengths stored in the first to Nth measurement value registers, and a comparator for comparing the maximum mark length with a mark length of a predetermined measurement value register. When the mark length of the predetermined measurement value register is equal to or larger than the maximum mark length as a result of comparison by the comparator, the mark length of the predetermined measurement value register is set to the maximum value register. The total of the mark lengths stored by the arithmetic unit is stored in the total register, and each time the mark length is measured by the measuring unit, the mark length is stored in each of the second to Nth measurement value registers. A control unit for storing the measured mark lengths in the first to (N-1) th measurement value registers and storing the mark length measured by the measuring instrument in the Nth measurement value register. A mark length measuring device provided with the above. 12. A mark for measuring a mark length for obtaining a fundamental frequency of a signal to be read on a disk medium on which data is recorded using predetermined mark lengths having different lengths in a circumferential direction. In the length measuring method, the mark lengths of the marks read from the disk medium are sequentially measured, and N consecutive N marks (N is 4 or more) including the maximum mark length which is the maximum mark length among the sequentially measured mark lengths. A method for measuring the mark length, wherein the total of the mark lengths is calculated.