JP3592277B2 - Method and apparatus for measuring track pitch of optical disk - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a track pitch measuring method and a measuring device for measuring a track pitch of an optical disc.
[0002]
[Prior art]
Measuring the track pitch P of the optical disk is necessary for evaluating the optical disk and accurately accessing the target address of the optical disk. Then, a distance (radius) r from the center of the optical disk to an appropriate first position in the radial direction₁And a distance (radius) r from the center to a second position outside the first position.₂And the track length L between the first position and the second position is measured, and these measurement results r₁, R₂, L and calculating the track pitch P by executing the operation of the following Expression 4 is conventionally known.
[0003]
(Equation 4)
P = π · (r₂ ²-R₁ ²) / L
[0004]
In this case, as a first method for measuring the track length L of the formula 4, for example, Japanese Patent Application Laid-Open Nos. 3-142747, 11-273110 and 2000-298848 disclose a laser spot. It is introduced that the track is tracked from the first position to the second position, and the track time is multiplied by the linear velocity of the optical disk at the laser spot position to calculate the track length L. As a second method, for example, JP-A-10-162525 and JP-A-2001-43601 disclose an address at a first position and a second position, respectively, and read the difference between the two addresses and the laser spot. Calculating the track length L based on the linear velocity of the optical disk at the position is introduced.
[0005]
[Problems to be solved by the invention]
However, in the first method in the above-described conventional apparatus, it is necessary to make the laser spot follow the track from the first position to the second position in order to measure the track length L, and it takes a lot of time to follow this. Therefore, there is a problem that it takes too much time to measure the track pitch P. On the other hand, the second method has an advantage that the track pitch P can be measured in a short time because the laser spot can be shifted from the first position to the second position in an instant. However, in the second method, since the method of calculating the track pitch is limited to one type of optical disk in which the recording condition of the address of the optical disk is determined, these calculation methods are applied to an optical disk having different recording conditions. There is a problem that it cannot be applied. In addition, there is a problem that the process until the track pitch calculation is complicated because the track shift is performed twice and the radius of the address start position needs to be known.
[0006]
Summary of the Invention
SUMMARY OF THE INVENTION The present invention has been made to address the above problems, and has as its object to be applied to any optical disk on which addresses are recorded, and to provide a track pitch measuring method and measuring apparatus for an optical disk capable of measuring a track pitch P in a short time. Is to provide.
[0007]
In order to achieve the above object, a feature of the present invention is a track pitch measuring method for measuring a track pitch of an optical disc on which an address is recorded, wherein a laser spot is formed on the optical disc and a laser beam reflected from the optical disc is received. A pickup device capable of reading an address recorded on the optical disk; and a rotation device for rotating the optical disk around its central axis so that the laser spot formation position on the optical disk has a constant linear velocity with respect to the pickup device. A mechanism, a radial position changing mechanism capable of changing a radial relative position of the pickup device with respect to the optical disk, a distance detecting means for detecting a distance from a center of the optical disk to a radial position at which the laser spot is formed, and an optical disk. Speed detecting means for detecting the speed of rotation And the first and second distances, which are distances detected by the distance detecting means and at which two different first and second positions at which laser spots are formed, and the first and second addresses which are read by the pickup device. The first and second addresses recorded at the second position, the distance detected by the distance detecting means, the distance relating to an arbitrary position including the first or second position where the laser spot is formed, and the rotational speed The track pitch of the optical disk is calculated based on the rotational speed detected by the detecting means and the rotational speed of the optical disk when the laser spot is at an arbitrary position.
[0008]
In this case, it is preferable to move the laser spot from the first position to the second position by using the radial position changing mechanism. Further, the detected first and second distances are represented by r₁, R₂And the read first and second addresses are represented by n₁, N₂When the distance with respect to the detected arbitrary position is r, the detected rotation speed is sp, and the track pitch is P, and a predetermined constant is K, the calculation of the track pitch P is performed. May be performed according to the following equation (5). The constant K is a constant defined by the recording condition of the address of the optical disk. In an optical disk on which an address whose number increases by "1" is recorded, the channel bit per unit of the address defined by the standard is used. Using the number B and the channel bit rate F, it is a value defined by K = 30 · F / B. In the optical disk on which the time address is recorded, the constant K is “30”.
[0009]
(Equation 5)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R ・ sp｝
[0010]
Further, the first position or the second position may be adopted as the arbitrary position.
[0011]
According to the present invention as described above, the first and second distances, the first and second addresses, the distance for any position (or the first or second distance), and the arbitrary The track pitch of the optical disk is calculated using the rotational speed of the optical disk with respect to the position. The basis of Equation 5 will be described later in detail. In this case, it is only necessary to change the radial position of the laser spot from the first position to the second position in a short time, and it is not necessary to make the laser spot follow the track unlike the conventional method. In addition, by using the above equation (5), it is possible to easily and quickly detect the track pitch on any optical disc on which an address is recorded.
[0012]
From another point of view, the features of the present invention are applied to an optical disc having an address recorded thereon, and form a laser spot on the optical disc and receive laser light reflected from the optical disc. A pickup device capable of reading an address recorded on the optical disc, and a rotation mechanism for rotating the optical disc around its central axis so that the position at which the laser spot is formed on the optical disc has a constant linear velocity with respect to the pickup device. An optical disc track pitch measuring device provided with a radial position changing mechanism capable of changing a radial relative position of a pickup device with respect to an optical disc, wherein a distance from a center of the optical disc to a radial position at which a laser spot is formed is detected. Distance detecting means and rotational speed for detecting the rotational speed of the optical disk By controlling the detection means and the position changing mechanism, the state where the laser spot is at the first radial position of the optical disk is shifted to the state where the laser spot is at the second radial position different from the first radial position of the optical disk. State changing control means for inputting a distance detected by the distance detecting means and an address read by the pickup device in a state where the laser spot is at the first position in the radial direction of the optical disk, and setting the laser spot to the second position in the radial direction of the optical disk. Input the distance detected by the distance detecting means and the address read by the pickup device in a state where the laser spot is at the first or second position in the radial direction of the optical disk, and Enter the speed and enter these entered distances, addresses and rotational speeds. There is also the provision of the calculation means for calculating a track pitch of the optical disc.
[0013]
In this case, the detection distance and the read address in a state where the laser spot is at the first position in the radial direction of the optical disc are represented by r.₁, N₁In the state where the laser spot is at the second radial position of the optical disc, the detection distance and the read address are r₂, N₂Assuming that the input detected rotation speed is sp, the track pitch is P, and a predetermined constant is K, the calculating means calculates the track pitch P according to the following equation (6) or (7). It may be configured to calculate. Also in this case, the constant K is a constant defined by the recording condition of the address of the optical disk. In an optical disk on which an address whose number increases by "1" is recorded, one unit of the address defined by the standard is used. When the channel bit number B and the channel bit rate F are used, K is a value defined by 30 F / B. In the optical disk on which the time address is recorded, the constant K is “30”.
[0014]
(Equation 6)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R₁・ Sp @
[0015]
(Equation 7)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R₂・ Sp @
[0016]
Also in this case, the radial position of the laser spot is changed from the first position to the second position in a short time, and the track pitch on any optical disk on which the address is recorded can be easily and easily obtained by using the above equation (6) or (7). Detection can be performed in a short time.
[0017]
Embodiment
a. Explanation of basic principles
Before describing a specific embodiment of the present invention, a basic principle used in the embodiment will be described.
[0018]
As shown in FIG. 3A, the distance (hereinafter, also referred to as radius) from the center of the optical disc DK to an appropriate first position in the radial direction is represented by r.₁[M], and the distance (hereinafter, also referred to as a radius) of the second position outside the first position from the center is r.₂[M], an area S [m of an annular portion (illustrated, hatched portion) sandwiched between a first circle passing through the first position and a second circle passing through the second position.²] Is represented by the following equation (8).
[0019]
(Equation 8)
S = π · (r₂ ²-R₁ ²)
[0020]
On the other hand, when the tracks in the annular portion sandwiched between the first and second circles in FIG. 3A are linearly extended and represented as a band, the result is as shown in FIG. 3B. Assuming that the width of the strip, ie, the track pitch, is P [m] and the length, ie, the track length, is L [m], the area S [m] of the strip²] (Equal to the area S of the annular portion in FIG. 3) is represented by the following Expression 9.
[0021]
(Equation 9)
S = PL
[0022]
From Equations 8 and 9, the radius r₁, Radius r₂, The track length L and the track pitch P, the following equation 10 holds.
[0023]
(Equation 10)
P = π · (r₂ ²-R₁ ²) / L
[0024]
The optical disk DK rotates at a constant linear speed regardless of the position of the laser spot in the radial direction. Therefore, this linear velocity is expressed as v_ln[M / sec], and when the rotation speed (the number of rotations per unit time) of the optical disk DK when the laser spot is at an arbitrary radius r [m] position is sp [r / min], the following Expression 11 is established. I do.
[0025]
[Equation 11]
v_ln= 2π · r · sp / 60
[0026]
The optical disc DK will be described by dividing into an optical disc DK in which an address whose number increases by "1" is recorded as an address of the optical disc DK and an optical disc DK in which a time address is recorded. First, an optical disk DK on which an address whose number increases by “1” is recorded will be described. In the optical disk DK, the number of channel bits per unit of address B is a value defined by the standard (for example, in the case of a DVD, Is 38,688), and the number of times that a signal generated for each bit occurs per unit time, that is, the channel bit rate F is also a value determined by the standard (for example, 26.16 [MHz] for DVD). It is. The time per bit (ie, cycle) is the reciprocal of the channel bit rate F, and the time per unit of address (ie, cycle) is a value obtained by multiplying the reciprocal 1 / F by the number of channel bits B. Then, the linear velocity v is calculated in the time per unit of the address._ln, The length Ls [m] of one unit of the address is calculated as shown in the following Expression 12.
[0027]
(Equation 12)
Ls = (B / F) · v_ln＝ B ・ 2π ・ r ・ sp / (60 ・ F)
[0028]
Since the address of the optical disk DK increases by one, the first position (radius r₁Address n)₁And the second position (radius r₂Address n)₂Then (n₂> N₁), These addresses n₂, N₁The difference n₂-N₁Is multiplied by the length Ls of one unit of the address, the track length L [m] at the first position and the second position is calculated as shown in Expression 13 below.
[0029]
(Equation 13)
L = (n₂-N₁) ・ Ls
[0030]
Using Equations 11 and 12, Equation 13 is transformed as Equation 14 below.
[0031]
[Equation 14]
L = (n₂-N₁) · (B / F) · 2π · r · sp / 60
[0032]
By substituting the track length L expressed by the equation (14) into the equation (10), the track pitch P is expressed by the following equation (15).
[0033]
(Equation 15)
P = 30 · (F / B) · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R ・ sp｝
[0034]
In Equation 15, since the number of channel bits B and the channel bit rate F are values determined by the standard, these values B and F can be treated as constants. If the calculation result of 30 · F / B is prepared in advance as a constant K, the track pitch P is calculated by executing the following equation (16).
[0035]
(Equation 16)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R ・ sp｝
[0036]
Next, an optical disc DK in which a time address is recorded as an address of the optical disc DK will be described. In the optical disc DK, since the address is recorded by adding the time per unit of address, the first position is recorded. (Radius r₁Address n)₁And the second position (radius r₂Address n)₂Then (n₂> N₁), The difference n between these addresses₂-N₁Is the time required for the laser spot to move from the first position to the second position, and the address difference n₂-N₁Linear velocity v_ln, The track length L [m] at the first position and the second position is calculated as shown in Expression 17 below.
[0037]
[Equation 17]
L = (n₂-N₁) ・ V_ln
[0038]
Using Equation 11, Equation 17 is transformed into Equation 18 below.
[0039]
(Equation 18)
L = (n₂-N₁) · 2π · r · sp / 60
[0040]
By substituting the track length L expressed by the equation (18) into the equation (10), the track pitch P is expressed by the following equation (19).
[0041]
[Equation 19]
P = 30 · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R ・ sp｝
[0042]
Here, assuming that “30” is the constant K, Equation 19 becomes the same as Equation 16, and Equation 16 is also applicable to the optical disc DK on which a time address is recorded as the address of the optical disc DK. I understand.
[0043]
Thus, the radius r of any of the first and second positions₁, R₂And address n₁, N₂Is measured, the rotation speed sp when the laser spot is at an arbitrary radius r is measured, and a constant K is determined according to the recording condition of the optical disk DK, whereby the track pitch P can be calculated.
[0044]
Further, r in Equation 16 is an arbitrary radius, and the radius r is₁Or radius r₂The rotation speed sp at that time may be referred to as the rotation speed sp.₁Or rotation speed sp₂Then, the following Expression 20 and Expression 21 are established.
[0045]
(Equation 20)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R₁・ Sp₁｝
[0046]
(Equation 21)
P = K · (r₂ ²-R₁ ²) / ｛(N₂-N₁) ・ R₂・ Sp₂｝
[0047]
Therefore, according to equation (20) or (21), the radius r of any of the first and second positions is₁, R₂And address n₁, N₂And the laser spot has a radius r₁Position or radius r₂Speed sp when in position₁Or rotation speed sp₂Is measured, the track pitch P can be calculated.
[0048]
b. Specific embodiment
Hereinafter, a specific example of a track pitch measuring method and a measuring device for measuring a track pitch using the above-described basic principle will be described.
[0049]
As shown in FIG. 1, the measuring apparatus includes a spindle motor 11 for rotating the optical disk DK around its central axis. A support plate 13 for mounting the optical disk DK is fixed to a rotation shaft 12 of the spindle motor 11. The spindle motor 11 has a built-in encoder 11a that detects the rotation of the rotating shaft 12 and outputs a rotation detection signal indicating the rotation. Specifically, the encoder 11a outputs a reference signal φ every time the rotating shaft 12 passes through the reference rotation position as a rotation detection signal._OAnd a pulse train signal φ that repeats a high level and a low level by a predetermined minute rotation angle of the rotation shaft 12._A, Φ_BIs output. In this case, these pulse train signals φ_A, Φ_BAre shifted from each other by π / 2. The rotation detection signal indirectly indicates the rotation speed (or rotation angular speed) of the optical disc DK.
[0050]
Further, the spindle motor 11 is fixed to the support member 14. The support member 14 is allowed only to be displaced in the radial direction of the optical disc DK, and is driven in the same direction according to the rotation of the feed motor 15. The rotation shaft of the feed motor 15 is constituted by a screw rod 16, which is screwed to a nut (not shown) fixed to the support member 14. The feed motor 15 has a built-in encoder 15a that detects the rotation of the screw rod (rotary shaft) 16 and outputs a rotation detection signal indicating the rotation. This rotation detection signal also has the same reference signal φ as that of the spindle motor 11._OAnd pulse train signal φ_A, Φ_BThe rotation detection signal indirectly indicates the relative position of the spindle motor 11 and the optical disk DK with respect to the pickup device 17, in other words, the distance from the center of the optical disk DK of the laser spot formed on the optical disk DK by the pickup device 17. Represent.
[0051]
The measuring device also includes a pickup device 17 arranged to face the optical disc DK. The pickup device 17 includes a laser light source 17a, a collimator lens 17b, a beam splitter 17c, a quarter-wave plate 17d, an objective lens 17e, a cylindrical lens 17f, a four-division photodetector 17g, and the like. The reflected light is received and a light receiving signal is output. The pickup device 17 also includes a track actuator 17h and a focus actuator 17i. The track actuator 17h finely moves the objective lens 17e in the radial direction of the optical disc DK so that the laser spot accurately follows the track of the optical disc DK. The focus actuator 17i finely moves the objective lens 17e in a direction perpendicular to the disk surface of the optical disk DK to accurately form a laser spot on the recording layer of the optical disk DK.
[0052]
The spindle motor 11, the feed motor 15, and the pickup device 17 are connected to a disk rotation servo control circuit 21, a feed servo control circuit 22, and a track / focus servo control circuit 23, respectively. 21 to 23.
[0053]
The disk rotation servo control circuit 21 controls the rotation of the spindle motor 11 using the light receiving signal from the pickup device 17 so that the optical disk DK always rotates at a constant linear velocity. Specifically, a wobble signal or a pit signal is extracted from the light receiving signal from the pickup device 17, and the rotational speed of the spindle motor 11 is servo-controlled so that the wobble signal or the pit signal has a standardized frequency. Thus, the linear velocity of the optical disc DK at the position where the laser spot is formed with respect to the pickup device 10 is kept constant.
[0054]
The feed servo control circuit 22 uses the rotation detection signal from the encoder 11a of the feed motor 15 to change and control the radial position of the pickup device 17 with respect to the optical disk DK. Specifically, the radial position of the support member 14 (spindle motor 11) on the optical disk DK is calculated based on the rotation detection signal. In other words, the radial position (radius) where the laser spot is formed relative to the center of the optical disk DK ) Is calculated, and using this radial position (radius), control is performed so that the laser spot is formed at the designated target radial position on the optical disc DK. Further, the feed servo control circuit 22 also receives a light receiving signal from the pickup device 17 so that the vibration of the objective lens 17e during the track following control by the track actuator 17h in the pickup device 17 is at the neutral position (position of the optical axis). Is controlled to be performed mainly.
[0055]
The track / focus servo control circuit 23 uses the light receiving signal from the pickup device 17 to drive and control the track actuator 17h to perform track following control of the objective lens 17e. The track / focus servo control circuit 23 drives and controls the focus actuator 17i based on the light receiving signal to perform focus control on the objective lens 17e.
[0056]
A computer device 30 for controlling the servo control circuits 21 to 23 is also connected to these servo control circuits 21 to 23. The computer device 30 includes a CPU, a ROM, a RAM, a hard disk, and the like, and executes the program in FIG. 2 to calculate a track pitch. The computer device 30 is supplied with a rotation detection signal from the encoder 11a of the spindle motor 11 and a rotation detection signal from the encoder 15a of the feed motor 15 for calculating the track pitch. The light receiving signal from the pickup device 17 is also supplied via the recording signal reproducing circuit 31. The recording signal reproducing circuit 31 extracts and outputs a signal (data) recorded on the optical disc DK based on a light receiving signal from the pickup device 17.
[0057]
Next, the operation of the track pitch measuring device configured as described above will be described. First, the optical disk DK on which the address is recorded is fixed on the support plate 13. Then, it instructs the computer device 30 to start measurement using a start switch (not shown) or the like. At this time, the laser light source 17a of the pickup device 17 is activated so that the optical disk DK is irradiated with the laser light from the pickup device 17.
[0058]
The computer device 30 starts executing the program in step 100 of FIG. 2, and sets the radial position of the pickup device 17 with respect to the optical disc DK to the first position in step 102. More specifically, the feed servo control circuit 22 is operated to move the spindle motor 11 and the support plate 13 in the radial direction of the optical disc DK by the rotation of the feed motor 15 so that the laser spot by the pickup device 17 is adjusted to the diameter of the optical disc DK. To the first position in the direction. The first position may be an arbitrary position.
[0059]
Next, in step 104, the computer 30 instructs the disk rotation servo control circuit 21 and the track / focus servo control circuit 23 to start servo control. In response, the disk rotation servo control circuit 21 causes the spindle motor 11 to start rotating. In this case, the disk rotation servo control circuit 21 uses the light receiving signal (wobble signal or pit signal) from the pickup device 17 to control the rotation of the spindle motor 11 so that the optical disk DK rotates at a constant linear velocity. Further, the track / focus servo control circuit 23 controls the drive of the track actuator 17h and the focus actuator 17i based on the received light signal to perform the track following servo control and the focus servo control.
[0060]
Next, the computer device 30 inputs the rotation detection signals from the encoders 15a and 11a of the feed motor 15 and the spindle motor 11 at step 106, and also receives the light receiving signal from the pickup device 17 into the recording signal reproducing circuit 31. To enter through. Then, based on the rotation detection signal from the encoder 15a of the feed motor 15, the radius r of the first position where the laser spot is currently formed is shown.₁Is calculated. Also, based on the rotation detection signal from the encoder 11a of the spindle motor 11, the rotation speed sp₁(The number of rotations per unit time) is calculated. Further, from among the light receiving signals from the pickup device 17 via the recording signal reproducing circuit 31, that is, from the signals recorded on the optical disk DK, the address n₁Take out.
[0061]
Next, in step 108, the length Ls [m] per unit of address is calculated by executing the operation of the following expression 22 by substituting the constant K (= 30 · F / B) into the above expression 12. In this case, the constant K in the following Expression 22 is a constant defined by the recording condition of the optical disc DK. In the optical disc DK on which the address whose number increases by “1” is recorded, the channel bit number B and the channel bit Using the rate F, K = 30 · F / B. In the optical disk DK on which the time address is recorded, K = 30. In the optical disc DK on which the time address is recorded, Ls [m] is regarded as a length per unit time. This is the linear velocity v_ln[M / sec].
[0062]
(Equation 22)
Ls = B · 2π · r₁・ Sp / 60 ・ F = π ・ r₁・ Sp / K
[0063]
Next, in step 110, the computer 30 instructs the disk rotation servo control circuit 21 and the track / focus servo control circuit 23 to stop the operation. In response, the disk rotation servo control circuit 21 stops the operation control of the spindle motor 11. Further, the track / focus servo control circuit 23 stops the track following and focus following control of the pickup device 17.
[0064]
Next, in step 112, the computer device 30 sets the radial position of the pickup device 17 with respect to the optical disk DK to the second position in the same manner as in step 102. The second position may be any position as long as it is different from the first position, but a position as far as possible from the first position is preferable in order to reduce the error. In the present embodiment, the second place value is set at a relatively outside position outside the first position.
[0065]
Next, in step 114, the computer device 30 restarts the operation control of the disk rotation servo control circuit 21 and the track / focus servo control circuit 23, as in step 104. As a result, the optical disk DK rotates at a constant linear velocity, and the pickup device 17 follows the track and focus.
[0066]
Next, the computer device 30 determines in step 116 the radius r of the second position where the laser spot is currently formed in the same manner as in step 106.₂And the address n₂Take out. In this case, the rotation speed sp of the optical disc DK is₂It is not necessary to calculate (the number of rotations per unit time). Then, in step 118, the address n calculated by the processing of steps 106, 108 and 116₁, Length Ls per unit of address and address n₂The track length L [m] from the first position to the second position is calculated by executing the calculation of the following Expression 23 which is the same as Expressions 13 and 17 using the above.
[0067]
(Equation 23)
L = (n₂-N₁) ・ Ls
[0068]
After calculating the track length L in step 118, in step 120, the track length L and the radius r calculated by the processing in steps 106 and 116 are calculated.₁, R₂The track pitch P of the optical disk DK is calculated by executing the same operation of the following Expression 24 as the above Expression 10 using the above.
[0069]
[Equation 24]
P = π · (r₂ ²-R₁ ²) / L
[0070]
After the processing in step 120, an end processing is executed in step 122. In this end processing, the operations of the servo control circuits 21 to 23 are controlled to stop, and the operations of the spindle motor 11, the feed motor 15, and the actuators 17h and 17i of the pickup device 17 also stop. Then, in step 124, the execution of this program ends.
[0071]
As can be understood from the above description of the operation, according to the above embodiment, each radius r at the first and second positions in the radial direction of the optical disc DK on which the laser spot is formed.₁, R₂, The address n of each position₁, N₂And the rotation speed sp of the optical disk DK when the laser spot is at the first position₁Are detected, and these detected values r₁, R₂, N₁, N₂, Sp₁The track pitch P is calculated by executing the operations of the above-mentioned equations 22 to 24 using. The movement of the laser spot from the first position to the second position is simple and short because the relative position of the pickup device 17 in the radial direction with respect to the optical disc DK is simply switched without following the laser spot. The track pitch P can be measured in time. In addition, by using K defined by the recording condition of the address of the optical disc DK in the calculation formula, the track pitch P in every optical disc DK on which the address is recorded can be detected easily and in a short time.
[0072]
In the above-described embodiment, the length Ls and the track length per unit of the address are calculated by executing the operations of the above Expressions 22 to 24 (corresponding to Expressions 12, 13, 13, and 10 of the basic principle). After sequentially calculating L, the track pitch P is calculated. However, the detection value r₁, R₂, N₁, N₂, Sp₁Is substituted into Equation 20 described in the above basic principle to calculate the track pitch P, it is completely equivalent to the case of the above embodiment. In this case, the processing of Steps 108 and 118 in the above embodiment may be omitted, and the calculation of Equation 20 may be performed in Step 120. The constant K in Equation 20 is a constant defined by the recording condition of the address of the optical disc DK as described in the basic principle, and the optical disc DK on which the address whose number increases by “1” is recorded. Is a value defined by K = 30 · F / B, using the number of channel bits B per unit of address and the channel bit rate F defined by the standard. In the optical disk DK on which the time address is recorded, the constant K is “30”.
[0073]
In the above embodiment, the rotation speed sp when the laser spot is at the first position is set.₁Is used to calculate the track pitch P. However, since the linear velocity of the optical disk DK is always constant, the rotation speed sp when the laser spot is at the second position is calculated.₂May be used to calculate the track pitch P. In this case, the rotation speed sp of step 106₁Is omitted, and in step 116 the rotational speed sp₂Is calculated. In this case, the calculation of the sector length Ls in step 108 is performed between step 116 and step 118, and the radius r₁And rotation speed sp₁Instead of radius r₂And rotation speed sp₂It is better to use. Also in this modification, the detection value r₁, R₂, N₁, N₂, Sp₂May be substituted into Equation 21 described in the basic principle to calculate the track pitch P. Also in this case, the constant K in Equation 21 is a constant defined by the recording condition of the address of the optical disc DK. For the optical disc DK on which the address whose number increases by “1” is recorded, it is determined by the standard. If the number of channel bits B per unit of the address and the channel bit rate F are used, K is a value defined by 30 F / B. In the optical disk DK on which the time address is recorded, the constant K is “30”.
[0074]
In addition, the radius r₁, R₂And rotation speed sp₁, Sp₂Alternatively, the track pitch P may be calculated by using the radius r and the rotation speed sp of another arbitrary position and executing the calculation of Expression 16 described in the basic principle.
[0075]
Further, in the above embodiment, in order to change the relative position of the pickup device 17 with respect to the radial direction of the optical disc DK, a device that moves the spindle motor 11 and the optical disc DK relative to the pickup device 17 using the feed motor 15 is used. The present invention is applied to the present invention. However, in the present invention, the pickup device 17 only needs to change the radial position relative to the optical disc DK, and the spindle motor 11 and the optical disc DK are fixed, and the pickup device 17 is moved to the spindle motor 11 and the optical disc DK. The present invention is also applied to a device that is moved with respect to.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing a track pitch measuring device for an optical disc according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a program executed by the computer device of FIG. 1;
FIG. 3A is a schematic plan view of an optical disk, and FIG. 3B is a diagram in which tracks included in an area S of FIG.
[Explanation of symbols]
DK: optical disk, 11: spindle motor, 11a: encoder, 15: feed motor, 15a: encoder, 17: pickup device, 21: disk rotation servo control circuit, 22: feed servo control circuit, 23: track / focus servo control circuit , 30 ... Computer device, 31 ... Recording signal reproducing circuit.

Claims (6)

In a track pitch measuring method for measuring a track pitch of an optical disc on which an address is recorded,
A pickup device that forms a laser spot on the optical disc and receives laser light reflected from the optical disc, and is capable of reading an address recorded on the optical disc;
A rotation mechanism for rotating the optical disk around its central axis such that the position of the laser spot on the optical disk has a constant linear velocity with respect to the pickup device;
A radial position changing mechanism capable of changing a radial relative position of the pickup device with respect to the optical disk;
Distance detecting means for detecting a distance from the center of the optical disc to a radial position where the laser spot is formed,
Using rotation speed detection means for detecting the rotation speed of the optical disc,
A distance detected by the distance detecting means, first and second distances relating to two different first and second positions at which the laser spot is formed, and an address read by the pickup device; And a first address and a second address recorded at a second position, and a distance detected by the distance detecting means and related to an arbitrary position including the first or second position where the laser spot is formed. And calculating a track pitch of the optical disk based on the rotation speed detected by the rotation speed detection means and the rotation speed of the optical disk when the laser spot is at the arbitrary position. A method for measuring the track pitch of an optical disc. The method of measuring a track pitch of an optical disc according to claim 1,
A track pitch measuring method for an optical disk, wherein the laser spot is moved from the first position to the second position using the radial position changing mechanism. 3. The method for measuring a track pitch of an optical disc according to claim 1 or 2,
The detected first and second distances are denoted by r ₁ and r ₂ , the read first and second addresses are denoted by n ₁ and n _2, and the distance with respect to the detected arbitrary position is denoted by r. Assuming that the detected rotational speed is sp, the track pitch is P, and a predetermined constant is K, the track pitch of the optical disc is calculated according to the following equation (1). Measuring method.

4. The method of measuring a track pitch of an optical disk according to claim 1, wherein
A method for measuring a track pitch of an optical disc, wherein the first position or the second position is adopted as the arbitrary position. Applied to an optical disk that records addresses,
A pickup device that forms a laser spot on the optical disc and receives a laser beam reflected from the optical disc to read an address recorded on the optical disc;
A rotation mechanism for rotating the optical disk around its central axis such that the position of the laser spot on the optical disk has a constant linear velocity with respect to the pickup device;
A track pitch measuring device for an optical disc, comprising: a radial position changing mechanism that can change a radial relative position of the pickup device with respect to the optical disc;
Distance detecting means for detecting a distance from the center of the optical disc to a radial position at which the laser spot is formed,
Rotation speed detection means for detecting the rotation speed of the optical disc;
By controlling the position changing mechanism, the state where the laser spot is at the first radial position of the optical disk is shifted to a state where the laser spot is at the second radial position different from the first radial position of the optical disk. State change control means for causing
A state in which the distance detected by the distance detecting means and an address read by the pickup device are input while the laser spot is at the first radial position of the optical disc, and the laser spot is at the second radial position of the optical disc The distance detected by the distance detecting means and the address read by the pickup device are input, and the laser spot is detected by the rotational speed detecting means in a state where the laser spot is at the first or second position in the radial direction of the optical disk. An optical disk track pitch measuring device, comprising: a rotation speed input device; and a calculating means for calculating a track pitch of the optical disk using the input distance, address and rotation speed. An apparatus for measuring a track pitch of an optical disk according to claim 5,
The detected distance and read address when the laser spot is at the first radial position on the optical disk are r ₁ and n ₁ , and the detected distance and read address when the laser spot is at the second radial position on the optical disk. Are r ₂ and n ₂ , the input detected rotational speed is sp, the track pitch is P, and a predetermined constant is K, the calculation means is calculated as Accordingly, an apparatus for measuring the track pitch of an optical disc configured to calculate the track pitch P.

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