JP2006179135A - Optical disk and beam profile measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk and a beam profile measuring method which can measure a beam profile in the direction different from the scanning direction of a beam and also can smoothly measure the beam profiles of various optical pickups by a single disk. <P>SOLUTION: The disk 100 is radially divided into three areas, i.e. A, B, and C. Each area is formed circumferentially (beam scanning direction) into a reflecting area 101 and a non-reflection area 102 with a pattern as shown in Fig. (b). Namely, in the area A, a reflecting area 101 and a non-reflecting area 102 are formed making their boundaries perpendicular to the circumferential direction. Further, in the areas B and C, a reflecting area 101 and a non-reflecting area 102 are formed making their boundaries tilt at 45° counterclockwise and clockwise to the circumferential direction, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc suitable for use in measuring a profile (intensity distribution, spot size, etc.) of a beam emitted from an optical pickup and a beam profile measuring method using the same.

The beam condensing capability of the optical pickup greatly affects the recording / reproducing characteristics of the optical disc apparatus. For this reason, the profile of the outgoing beam is measured at the time of manufacturing the optical pickup. In this measurement, the spot diameter of the condensed spot on the disk, its intensity distribution, and the like are measured. Here, the spot diameter is usually defined by a range showing an intensity distribution of Ps = Po / e ² (e: natural logarithm) when the peak intensity is Po.

As a beam profile measurement method, for example, a technique described in Patent Document 1 below is known. Here, an optical disk having a pit-land pattern longer than the beam spot diameter is used, and the intensity distribution of the laser beam is obtained from the differential waveform of the RF signal when this is reproduced. Then, the spot diameter of the laser beam is obtained based on the obtained intensity distribution.
JP 2002-32920 A

  According to such a conventional technique, while the beam is scanned along the pit-land pattern, the intensity distribution of the beam spot is measured based on the intensity change, and therefore only the intensity distribution in the scanning direction can be measured. Inconvenience occurs. In an optical pickup, when considering crosstalk or the like for adjacent tracks, an intensity distribution in a direction different from the scanning direction is also important.

  In addition, since the conventional technology uses beam interference by pits, the relationship between the beam diameter and the pit width and the relationship between the beam wavelength and the pit depth influence the measurement. For this reason, in the above prior art, even if the same type of optical pickup is used, the beam profile cannot be measured smoothly if the beam diameter or beam wavelength deviates from the appropriate range. Since the beam diameter and beam wavelength are different, the beam profile cannot be measured smoothly with a single disk.

The present invention provides an optical disc and a beam profile measuring method that can solve these problems, can measure a beam profile in a direction different from the beam scanning direction, and can smoothly measure the beam profiles of various optical pickups with a single disc. The task is to do.

  In view of the above problems, the present invention has the following features.

  According to the first aspect of the present invention, in the optical disk for measuring a beam profile, a high reflection area and a low reflection area having a width that can directly include a beam spot focused and irradiated from an optical pickup are arranged along the beam scanning direction. And the angle of the boundary between the high reflection region and the low reflection region with respect to the beam scanning direction is set at least two or more.

  Here, as described in claim 2, the angle of the boundary can be set to an angle perpendicular to the beam scanning direction and an angle inclined by a predetermined angle with respect to this angle.

  Further, as described in claim 3, the angle of the boundary is set to an angle perpendicular to the scanning direction of the beam and an angle inclined by a predetermined angle clockwise and counterclockwise with respect to this angle. Can do.

  As described in claim 4, such an optical disc can be divided into a plurality of areas in the radial direction of the disc, and the boundary angle can be different between the areas.

  Furthermore, as described in claim 5, a track for guiding the beam in the scanning direction is formed, and a boundary between the high reflection region and the low reflection region is arranged in a region where the track is missing. can do.

  A sixth aspect of the present invention is a beam profile measuring method for measuring a profile of a beam spot focused and irradiated on an optical disk from an optical pickup using the optical disk according to any one of the first to fifth aspects, A differential waveform is obtained from a beam intensity change waveform when the beam scans the boundary between the reflection region and the low reflection region, and a beam profile of the beam spot in a direction perpendicular to the boundary is obtained based on the differential waveform. Features.

In the present invention, the high reflection region and the low reflection region mean regions where the reflection intensities of the beams are different from each other. These regions can be configured, for example, by providing a region where the reflective layer exists and a region where the reflective layer does not exist. Or it can also comprise by providing the area | region where a reflection layer falls, and the area | region where a reflectance falls by irregular reflection thru | or formation of a fine unevenness | corrugation.

  According to the present invention, since the high reflection region and the low reflection region are wide enough to include the beam spot, the beam profile can be measured smoothly even if the size of the beam spot varies. be able to. In addition, it does not use interference due to pits as in the above prior art, but uses a change in reflection intensity in the high reflection region and low reflection region, so that the beam profile can be measured smoothly even if the beam wavelength varies. Can be done.

  When the beam profile is measured for different types of optical pickups, the size of the high reflection region and the low reflection region may be set to a size that can include the largest beam spot as it is.

  The effects and significance of the present invention will become more apparent from the following description of embodiments.

  In the following embodiments, the “high reflection region” and the “low reflection region” in the present invention are shown as the reflection portion 101 and the non-reflection portion 102. In addition, the “track” in the present invention is shown as a pit row (FIG. 5), a groove (FIG. 6), or a land (FIG. 7) in the following embodiments.

However, the following embodiment is merely one embodiment of the present invention, and the meaning of the terminology of the present invention or each constituent element is not limited to that described in the following embodiment. Absent.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 1 shows a configuration of a disc (beam profile measuring optical disc) according to the embodiment.

  Referring to FIG. 2A, the disk 100 is divided into three areas (areas A, B, and C) in the radial direction. In each area, a reflecting portion 101 and a non-reflecting portion 102 are formed in the circumferential direction (beam scanning direction) in the pattern shown in FIG. That is, in the area A, the reflective portion 101 and the non-reflective portion 102 are formed so that the boundary between the reflective portion 101 and the non-reflective portion 102 is perpendicular to the circumferential direction. In areas B and C, the reflective portion 101 and the non-reflective portion 102 are formed such that the boundary between the reflective portion 101 and the non-reflective portion 102 is inclined 45 degrees counterclockwise and clockwise relative to the circumferential direction. ing.

  The reflective portion 101 and the non-reflective portion 102 are alternately formed over the entire circumference. Here, the reflecting portion 101 and the non-reflecting portion 102 are formed so that the angular pitch is constant when viewed from the center of the disc. Further, the reflecting portion 101 and the non-reflecting portion 102 are set to be sufficiently wide to include the beam spot as it is at all positions on the disc.

  When the beam scans area A, the beam profile in the scanning direction is measured. Further, when the beam scans the areas B and C, the beam profile in the direction perpendicular to each boundary is measured. The beam profile measurement method will be described later.

  FIG. 2 shows a cross-sectional structure of the disk 100.

  First, referring to FIG. 1A, the disk 100 has a structure in which a reflective layer 12, a protective layer 13, and a printing layer 14 are sequentially laminated on a substrate 11. Here, the reflective layer 12 is formed only in the formation region of the reflective portion 101. The reflective layer 12 can be formed using an existing semiconductor manufacturing process. Or after forming a reflective layer uniformly, it can form by the method of excising the area | region of the non-reflective part 102 with a high power laser.

  The reflective portion 101 and the non-reflective portion 102 may be formed by forming a fine structure 12a in the formation region of the non-reflective portion 102 as shown in FIG. Specifically, an uneven structure (fine structure 12a) having a pitch and depth of several hundred nm (preferably about 100 nm to 200 nm) is formed on the surface of the substrate 11 in the formation region of the non-reflective portion 102, and the reflection is formed thereon. Layer 12 is formed. As a result, the reflectance of the non-reflective portion 102 can be greatly changed as compared with the reflectance of the reflective portion 101.

  The formation of the fine structure 12a can be performed, for example, by the following process.

  First, a resist is applied to the silicon master by spin coating. The resist used here is for an electron beam. Thereafter, the concavo-convex structure having the pitch is formed by EB drawing (electron beam cutting). After this drawing, development processing is performed and RIE processing is performed. Further, oxygen plasma ashing is performed to remove the remaining resist. Thereby, an uneven structure is formed on the silicon master (Si master).

  Next, Ni sputtering is performed on the Si base, and Ni is deposited by electrolytic plating. Then, the deposited Ni layer is peeled off from the Si master and a stamper is produced. Using this stamper, the substrate 11 is produced by injection molding. Thereby, the substrate 11 onto which the concavo-convex structure (fine structure 12a) is transferred is formed.

  Note that the fine structure 12a and the decrease in reflectance due thereto are also described in Japanese Patent Application No. 2004-304488 filed earlier by the present applicant.

  FIG. 3 shows a beam profile measurement method in areas A, B, and C.

First, referring to FIG. 4A, when the beam scans area A in the disk circumferential direction, the reflected light intensity P changes as shown in the middle of FIG. Here, the reflected light intensity Pn at T = Tn is the total amount of reflected light when the beam enters the reflecting portion 101 and is at the position of time Tn. Therefore, by differentiating the reflected light intensity P with respect to time T, as shown in the lower part of the figure, a beam spot (a converged converged spot on the reflecting layer 12) in the approach direction to the reflecting part 101 (A direction in the figure) ) Intensity distribution can be obtained. From this intensity distribution, for example, on the basis of the Ps = Po / e ^2, it is possible to determine the spot size of the beam spot in the direction.

Similarly, when the beam scans areas B and C, the reflected light intensity P is differentiated with respect to time T, so that the approach direction to the reflecting portion 101 (directions B and C in FIGS. ) Can be obtained. However, in these cases, since the boundary between the reflecting part 101 and the non-reflecting part 102 is inclined by 45 degrees with respect to the beam scanning direction, the beam starts from entering the reflecting part 101 until it finishes entering. A scanning distance of √2 times the diameter is required. Therefore, the intensity distribution of the beam spot can be obtained by differentiating the reflected light intensity P with respect to time T and further compressing it by 1 / √2 times in the time axis direction. From this intensity distribution, the spot diameter of the beam spot in each direction can be obtained based on, for example, Ps = Po / e ² .

  FIG. 4 shows a processing flow at the time of beam profile measurement.

When the measurement of the beam profile is started, the disk rotation servo (constant linear velocity) and the focus servo are both turned on in S101 and S102, and then the optical pickup accesses the area A in S103. In S104, the reproduction RF signal at the time of area A scanning is differentiated to obtain the intensity distribution of the beam spot in the disk circumferential direction (beam scanning direction). Further, from the intensity distribution, Ps = Po / e The range of ² is calculated, and the spot diameter of the beam spot in the direction is obtained.

When the profile of the beam spot in the disk circumferential direction is measured, the optical pickup accesses the area B in S105. In S106, the reproduction RF signal at the time of area B scanning is differentiated, and further compressed by 1 / √2 times in the time axis direction, so that it is inclined 45 degrees clockwise with respect to the beam scanning direction. The intensity distribution of the beam spot in the direction (direction B in FIG. 3B) is obtained. Further, the range of Ps = Po / e ² is calculated from the intensity distribution, and the spot diameter of the beam spot in the direction is obtained.

Thereafter, the optical pickup accesses the area C in S107, differentiates the reproduction RF signal during the area C scanning in S108, and further compresses this by 1 / √2 times in the time axis direction. The intensity distribution of the beam spot in the direction inclined by 45 degrees counterclockwise with respect to the beam scanning direction (direction C in FIG. 3C) is obtained. Further, the range of Ps = Po / e ² is calculated from the intensity distribution, and the spot diameter of the beam spot in the direction is obtained.

When the beam profile in each direction is measured as described above, the beam profile in the disk radial direction is calculated in S109. For example, the calculation is performed by approximating the intensity distribution of the beam spot in the disk radial direction based on the intensity distribution in each direction measured as described above, and the range of Ps = Po / e ² from the calculated intensity distribution. To calculate the spot diameter of the beam spot in the direction.

  According to this processing flow, the beam profiles in the A direction, the B direction, and the C direction shown in FIG. 3 can be measured smoothly. Further, the beam profile in the disc radial direction can be approximately calculated.

  In this processing flow, for example, the disk rotation servo detects the access position (radial distance) of the optical pickup in the disk radial direction, and rotates the disk so that the linear velocity is constant based on the detected access position. This is done by driving. In this case, means (scale sensor) or the like for detecting the access position (radial distance) of the optical pickup is required on the drive side.

  FIG. 5 shows another configuration example of the optical disc 100.

  In this configuration example, the track for guiding the beam is formed concentrically or in a spiral shape, and the above-described reflecting portion 101 and the non-reflecting portion are formed in a region where the continuity of the track is lost (beam profile measurement area). 102 is formed. Here, the track is formed by a series of pit rows. In addition, the address of each track (for example, the track number from the inner circumference side of the disk) is recorded by a pit string. In this configuration example, the disk can be controlled to rotate at a constant linear velocity by monitoring the amplitude period of the reproduction RF signal during pit scanning.

  When the disk according to this configuration example is used, the beam profile measurement process is performed in substantially the same manner as the process flow shown in FIG. However, in this case, a processing step for turning on the tracking servo is added as a processing step. With the addition of such processing steps, the beam is correctly incident on the boundary between the reflecting portion 101 and the non-reflecting portion 102 at an angle of 45 degrees or 45 degrees, respectively. That is, in the above-described embodiment, since the track for guiding the beam is not formed, the beam is slightly deviated from the normal incident angle with respect to the boundary between the reflecting portion 101 and the non-reflecting portion 102 due to disc eccentricity or the like. There is a possibility that the measurement accuracy of the beam profile is slightly lowered due to the incident light. In contrast, in this configuration example, since the beam is guided to the track until just before entering the beam profile measurement area, the beam is at the boundary between the reflecting portion 101 and the non-reflecting portion 102 even if there is a disc eccentricity or the like. On the other hand, it enters without deviating from the normal incident angle. Therefore, according to the present configuration example, the measurement accuracy of the beam profile can be increased as compared with the above embodiment.

  The beam guiding track can also be formed by grooves and lands as shown in FIGS. In this case, the address of each track may be recorded by wobbling the groove or land as in the existing DVD. Further, by monitoring the amplitude period of the wobble signal during groove or land scanning, the disk can be controlled to rotate at a constant linear velocity.

  In addition, in the above embodiment, the disk is divided into three areas in the radial direction, and the boundary angle between the reflecting portion 101 and the non-reflecting portion 102 is different for each area. The variation in angle is not limited to this. For example, as shown in FIG. 8A, the disk is divided into five areas in the radial direction, the boundary angle is 90 degrees with respect to the disk circumferential direction, and areas B and C are in the disk circumferential direction. On the other hand, 45 degrees clockwise and counterclockwise, and areas D and E may be 60 degrees clockwise and counterclockwise with respect to the disk circumferential direction. In this way, the measurable direction of the beam profile can be increased, and the approximate calculation of the profile in other directions (for example, the disk radial direction) can be made closer to the actual profile.

  Further, without dividing the disk in the radial direction, for example, as shown in FIG. 8B, the angle of the boundary between the reflecting portion 101 and the non-reflecting portion 102 with respect to the beam scanning direction changes linearly according to the radial position. You may make it let it. In this case, if the address of each track is given by a pit row or wobble as described above, the boundary angle between the reflecting portion 101 and the non-reflecting portion 102 at the current beam scanning position based on this address information on the drive side. Can be detected. Therefore, it is possible to measure beam profiles in more directions.

  In addition, in the above-described embodiment, the reflective optical disc is exemplified, but the present invention can also be applied to a transmissive optical disc. In this case, the reflection unit 101 and the non-reflection unit 102 are configured to have different light transmittances.

  Further, in the above description, the area is divided in the radial direction, but the area may be divided in the circumferential direction so that the angle of the boundary between the reflecting portion 101 and the non-reflecting portion 102 is different for each area.

The embodiment of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

The figure which shows the structure of the optical disk which concerns on embodiment The figure which shows the cross-section of the optical disk which concerns on embodiment The figure explaining the beam profile measuring method which concerns on embodiment Flowchart at the time of beam profile measurement processing according to the embodiment The figure which shows the other structural example of the optical disk which concerns on embodiment The figure which shows the other structural example of the optical disk which concerns on embodiment The figure which shows the other structural example of the optical disk which concerns on embodiment The figure which shows the other structural example of the optical disk which concerns on embodiment

Explanation of symbols

100 disk 101 reflecting portion 102 non-reflecting portion 12 reflecting layer 12a fine structure

Claims (6)

A high reflection area and a low reflection area having a width that can directly include a beam spot condensed and irradiated from an optical pickup are arranged along the scanning direction of the beam, and the height with respect to the scanning direction of the beam is At least two or more angles of the boundary between the reflection region and the low reflection region are set,
An optical disc characterized by the above. In claim 1,
The boundary angle is set to an angle perpendicular to the beam scanning direction and an angle inclined by a predetermined angle with respect to this angle.
An optical disc characterized by the above. In claim 2,
The boundary angle is set to an angle perpendicular to the scanning direction of the beam and an angle inclined by a predetermined angle clockwise and counterclockwise with respect to this angle.
An optical disc characterized by the above. In any one of Claims 1 thru | or 3,
The disk is divided into a plurality of areas in the radial direction of the disk, and the boundary angle is different between the areas.
An optical disc characterized by the above. In any of claims 1 to 4,
A track for guiding the beam in the scanning direction is formed, and a boundary between the high reflection region and the low reflection region is disposed in a region where the track is missing.
An optical disc characterized by the above. A beam profile measuring method for measuring a profile of a beam spot focused and irradiated from an optical pickup onto a disc using the optical disc according to claim 1,
A differential waveform is obtained from a beam intensity change waveform when a beam scans the boundary between the high reflection region and the low reflection region, and a beam profile of the beam spot in a direction perpendicular to the boundary is obtained based on the differential waveform. ,
A beam profile measuring method.

Images