WO1999053488A1

WO1999053488A1 - Method and apparatus for exposing master disk for optical disk

Info

Publication number: WO1999053488A1
Application number: PCT/JP1999/001875
Authority: WO
Inventors: Akira Miyamae; Kimio Nagasaka
Original assignee: Seiko Epson Corporation
Priority date: 1998-04-08
Filing date: 1999-04-08
Publication date: 1999-10-21
Also published as: TW445441B

Abstract

A method and apparatus for exposing a master disk for an optical disk to light, in which the width of the spot of a laser beam projected onto a master disk coated with a photosensitive material can be easily adjusted in a wide range. A method of machining a master disk for an optical disk in which grooves or pits are formed by irradiating a master disk (109) coated with a photosensitive material with a laser beam (102) focused to the master disk (109) through an objective (108), wherein the astigmatism is adjusted by an astigmatism generating section (119) provided along the optical axis of the laser beam (102), and the focal point is adjusted by automatic focal point adjusting means (114) to adjust the width of the spot with a high degree of freedom in a wide range.

Description

Patent application title: Method and apparatus for exposing a master for an optical disc

Technical field

The present invention relates to a process for processing an optical disc master, and more particularly to an exposure method and an exposure apparatus for an optical disc master, and a master processed by the same.

^ Scenic technology

Optical discs are usually produced by using a stamper provided with a concavo-convex pattern such as guide grooves (groups) and pre-pits, and transferring the concavo-convex pattern by injection molding or the like. As a means for forming the concavo-convex pattern of the stamper, a method of exposing and recording a laser beam continuously or light-modulated on an original master coated with a photosensitive material is generally used. The photosensitive material exposed by the above-described exposure is developed to form a concavo-convex pattern, and the surface is plated to be transferred to a metal surface to form a stamper.

In the above exposure process, as shown in FIG. 2, the laser beam 102 reflected by the mirrors 103, 105, 107 is condensed by the objective lens 108, and the master 10 9 Form an image on the photosensitive material coated on top and expose. At this time, a signal is input to the acousto-optic modulator 104 and the acousto-optic deflector 106 to modulate and deflect the laser beam 102 to record a desired pattern group or pit. it can. Master 1 0

Numeral 9 is circular, and it is mounted on a turntable 110

By gradually moving 1 13 in the radial direction, a spiral group or pit 1 12 is created. At this time, the laser beam 1◦2 and the objective lens 1

08 has the aberration removed as much as possible, and the spot 111 of the laser beam 102 is circular. Here, the spot is an image forming portion of the laser beam on the surface of the master, and the diameter of the spot is called a spot size, and the position on the spot optical axis is called an in-focus position.

In recent years, land group recording has been proposed as a high-density recording medium. Has been used. In this method, data is recorded both in groups and between groups (lands). As such a method, for example, Japanese Patent Application Laid-Open No. Hei 7-291186 discloses an optical recording medium having a tracking group and a pre-pit string, and when the interval between groups is P, the pre-bit string is The center line is formed so as to be shifted to the right or left by almost P / 4 from the center line of the group, and no group is formed in the preformat area composed of the pre-pit rows. A land group recording type optical information recording medium is disclosed. For exposing an optical disc master that requires a group and a prepit array as described above, it is necessary to form light spots of various widths on the master according to the pattern of the group or the prepit array. Here, the spot width is a spot size perpendicular to the scanning direction, that is, in the radial direction. In particular, in order to form a wide pre-pit, an oval spot having a short axis in the scanning direction is desirable in order to increase the resolution in the scanning direction of the laser beam.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 9-240966 discloses a method in which a light-shielding plate is driven by a piezoelectric element to adjust a spot width. In the method of adjusting the spot width using a light-shielding plate as described above, it is necessary to increase the light-shielding amount in order to obtain a large spot width, and the amount of light required to expose the photosensitive material is insufficient. There was a problem of doing it. In addition, since the light-shielding plate is driven by the piezoelectric element, the driving range of the piezoelectric element is limited, and the adjustment range of the spot width is limited.

Therefore, the present invention provides a method for processing a master for an optical disk, which can easily and widely adjust the width of an optical spot formed on the master without an insufficient amount of exposure light, and a method for processing the same. The present invention provides a stamper that uses the optical disk and an optical disk that is molded and manufactured from the stamper. Disclosure of the invention

The present invention relates to a master exposure apparatus that irradiates a modulated laser beam to a master coated with a photosensitive material and forms a latent image of a group or pits on an optical recording medium on the master. A laser beam generating means for emitting a laser beam; an intensity modulation means for intensity-modulating the laser beam with a supplied information signal; and an objective lens for condensing the intensity-modulated laser beam on the master. Focusing position adjusting means for adjusting the height position (distance between the master and the objective lens); beam scanning means for relatively scanning the focused laser beam on the master; A master exposure apparatus is provided, comprising: an astigmatism setting unit provided between the focusing position adjustment units to impart astigmatism to the laser beam and arbitrarily setting the degree of the astigmatism. .

As a result, since the focused laser beam contains astigmatism in the radial direction, spots of various widths can be obtained without a shortage of the exposure light amount by slightly changing the focus position. . The astigmatism is adjustable, so that the laser beam is adjustable in radial width.

Preferably, by setting the degree of the astigmatism and the height position of the objective lens in accordance with the input, the scanning width of the laser beam or the shape of the beam spot is set as desired. The master exposure apparatus further includes a master adjustment unit.

According to such a configuration, it is possible to set various shapes of the beam spot by two parameters (astigmatism and objective lens position). The scanning width is determined by the shape of the beam spot. For example, it is possible to finely adjust the spot shape by selecting the spot shape relatively roughly according to the astigmatism parameter and finely setting the objective lens position parameter by servo control.o

Preferably, the setting range of the height position of the objective lens includes the astigmatism astigmatism. As a result, a beam spot having a different direction in the major axis direction of the ellipse is obtained, and the selection range of the beam spot shape can be expanded.

Preferably, the astigmatism setting means includes at least two cylindrical lenses arranged so that the laser beams pass therethrough and a distance between the two lenses is variable, and adjusts a distance between the two lenses. The degree of the astigmatism Set.

With this configuration, it is possible to variably set (adjust) astigmatism.

The master exposure apparatus of the present invention preferably includes automatic setting means for setting the amount of astigmatism according to an instruction.

With this configuration, the astigmatism can be adjusted instantaneously, and a wide range of groups or pits having different widths can be created on the same master without a shortage of exposure light quantity. .

The present invention also provides an exposure method of a master for forming a latent image by converging a light beam by an objective lens on a master on which a photosensitive film is formed and scanning the photosensitive film with an obtained light spot. A plurality of correspondences between the amount of astigmatism of the light beam, the distance of the objective lens from the master and the shape of the light spot are stored in advance, and when setting a light spot of a desired shape, The astigmatism of the light beam and the position of the objective lens are adjusted with reference to the amount of astigmatism corresponding to the shape of the corresponding light spot and the distance of the objective lens from the master.

According to this configuration, if the shape of the spot of the light beam is specified, the shape of the beam spot is automatically set with the position of the objective lens and the astigmatism as two parameters.

Further, the present invention provides an exposure apparatus for a master, which irradiates an intensity-modulated light beam from an optical pickup onto a master on which a photosensitive film is formed, and scans the photosensitive film with the light beam to form a latent image. And an astigmatism adjusting means capable of adjusting the amount of astigmatism by giving astigmatism to the light beam; and an objective lens for condensing the light beam on the master to form an optical spot. Focus adjustment means for adjusting the distance from the master; spot data storage means for previously storing a plurality of correspondences between the amount of astigmatism, the distance of the objective lens from the master and the shape of the optical spot; The amount of astigmatism and the distance from the master of the objective lens corresponding to the shape of the designated optical spot are read out from the spot data storage means, and the amount of astigmatism and the master of the objective lens are read out. Or Setting the distance to it that the astigmatism adjusting means and focusing means And an exposure setting device for setting an original master.

According to this configuration, if the desired beam spot shape is designated (selected), the beam spot shape is automatically set (adjusted) to the designated shape.

Also provided is a master manufactured using the above-described exposure method. In such a master, the width of the CRUBE ゃ BIT can be changed widely in one master.

Hereinafter, the basic principle of the method for processing a master according to the present invention will be described. Figure 4 shows the ideal beam focusing state without aberration. When the focal point 401 is set to the in-focus position, the spot shape is circular, and the spot size becomes the minimum value. Next, Fig. 5 shows the spot shape when astigmatism is present in this beam. In this case, the spot shape changes to 501 a, 501 b, and 501 c, and changes as the focus position changes. That is, at the focal point 501a in the scanning direction, an oval having a major axis in the radial direction, at the focal point 501c, an oval having a major axis in the scanning direction, and at about 501b, which is almost in between, It becomes substantially circular. Since this shape changes continuously between 501 a and 501 c, that is, between the astigmatic difference 502, the focusing position can be adjusted between them to obtain an arbitrary width. You can get a spot.

Next, a method for generating the astigmatism will be described. In FIG. 6, a cylindrical lens 601 and a cylindrical lens 602 are arranged in the optical path of the parallel light with their optical axes aligned. Assuming that the focal length of the cylindrical lens 601 is f 1 and the focal length of the cylindrical lens 602 is f 2, the relative distance between the two lenses is f 1 + f 2 as shown in (a). In the case of, no astigmatism occurs. However, if the relative distance between the two lenses is longer than f1 + f2, as in (b), or short, as in (c), astigmatism will occur according to the difference, and its magnitude will be large. The length can be controlled by adjusting the relative distance between the two lenses. The magnitude of astigmatism and the astigmatism 502 correspond to 1: 1 in the same optical system, and the larger the astigmatism, the greater the astigmatism, so a larger spot width can be obtained. .

Also, as shown in FIG. 7, even if the two cylindrical lenses are concave and convex, no aberration occurs when the focal points of the two lenses are matched as shown in (a), but (b), ( When the relative distance is changed as in c), astigmatism is reduced by the same principle. appear.

As described above, in a system having astigmatism, it is possible to obtain spots having various shapes and widths by adjusting the focus position and adjusting the amount of astigmatism. As a result, the width of the spot can be easily adjusted over a wide range without insufficient exposure light quantity. The adjustment of the in-focus position and the adjustment of the amount of astigmatism may be performed independently of each other. However, if used in combination, adjustment in a wider range and a higher degree of freedom is possible. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram showing the overall configuration of an exposure apparatus that performs the master processing method of the present invention. FIG. 2 is an optical path diagram showing the entire configuration of a conventional mastering method. FIG. 3 is an example of the astigmatism generation unit used in the mastering method of the present invention. FIG. 4 is a principle diagram showing a spot shape when there is no astigmatic difference. FIG. 5 is a principle diagram showing a spot shape when there is astigmatism. FIG. 6 is a principle diagram showing a method of adjusting the amount of astigmatism using two convex cylindrical lenses. FIG. 7 is a principle diagram showing a method for adjusting the amount of astigmatism using two cylindrical lenses. FIG. 8 is an example showing various spot shapes in a combination when the in-focus position and the amount of astigmatism are respectively changed. FIG. 9 is an explanatory diagram illustrating an example of an apparatus for setting the shape and scanning width of a laser spot by adjusting the amount of astigmatism and the force of a laser beam. FIG. 10 is a block diagram illustrating a configuration example of the controller shown in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram illustrating an example of an exposure apparatus that performs an optical disk master processing method according to an embodiment of the present invention. The laser beam 102 emitted from the laser device 101 is reflected by the mirrors 103, 105, and 107, and is incident on the objective lens 108. After the intensity is modulated as necessary at 4 and the astigmatism is added at the astigmatism generation unit 119, deflection is performed as necessary at the acousto-optic deflector 106. receive. The laser beam transmitted through the objective lens 108 is condensed on a master 109 coated with a photosensitive material, and spots 111 are formed on the surface of the master. A movable optical table 1 13 equipped with an objective lens 108, a mirror 107, an acousto-optic deflector 106, and an astigmatism generator 1 119 gradually moves at a constant speed in the radial direction of the master 109. At the same time, the master 1109 is mounted on the turntable 110 and rotated, so that the groups or pits 112 are recorded in a spiral shape on the master.

The focus servo system 114 includes a semiconductor laser 115, a two-segment photodiode 116, a control circuit 117, and a focus actuator 118. The light emitted from the semiconductor laser is reflected by the mirror 107, passes through the peripheral edge of the objective lens 108, is reflected by the master disk 109, and is reflected on the opposite peripheral edge of the objective lens 108. The light passes through the portion, is reflected again by the mirror 107, and enters the two-division photodiode 116. Here, when the relative distance between the objective lens 108 and the master 109 changes, the optical axis position of the incident light of the two-divided photodiode 116 changes, so that the output of the two photodiodes has a difference. appear. The difference between the outputs is used as an error signal, which is amplified by the control (focus) circuit 117 and applied to the focus actuator 118 to perform feedback control of the focus position. . Normally, control is performed so that the relative distance between the objective lens 108 and the master disk 109 remains constant so that the spot size does not change during exposure. Since the laser beam of the semiconductor laser 115 has a different wavelength from the recording laser beam 102, the photosensitive material applied to the master 109 is not exposed to light, and adverse effects such as interference are caused. Nor.

The astigmatism generator 1 19 is composed of two convex cylindrical lenses 301 and 302 having the same focal length f as shown in FIG. 3, and the two lenses have the optical axis of the laser beam 1. It is equal to the optical axis of 0 2 and its relative distance is approximately equal to the sum of the focal lengths of the two lenses, 2 f. Here, the exit-side lens 302 is a mechanism that can automatically adjust the relative distance between the entrance-side lens 301 and the feed screw 303 and the stepping motor 304 by an instruction from the controller 300. It has become. Since the amount of astigmatism of the laser beam 102 changes depending on the relative distance between the two lenses, the amount of astigmatism can be automatically adjusted. The laser beam with astigmatism added is at spot 1 1 1 As shown in FIG. 5, various oval spots are formed depending on the focus position. By changing the set value of the control circuit 1 17, the focus position changes, and the spot shape can be automatically adjusted.

FIG. 8 is an example of various spot shapes when the in-focus position and the astigmatism amount are respectively changed. The shape of the beam spot is set according to the in-focus position and the amount of astigmatism. These in-focus positions, astigmatism amounts, and spot-shaped table data are held in a memory described later as data. To increase the resolution in the bit scanning direction, an oval shape with a short axis in the scanning direction is desirable. To achieve this purpose, the state must be changed between a, b, and c in Fig. 8. Is good. However, when the resolution in the scanning direction is not required as in the case of a single group, this is not a limitation, and the state can be selected more freely. Since the setting of the focus servo system and the setting of the controller of the astigmatism generation unit can be performed automatically, groups or pits of various widths can be obtained by the same exposure process on the same master.

FIG. 9 and FIG. 10 show another embodiment. In this example, the table shown in Fig. 8 for the relationship between the distance between the objective lens and the master (the height position of the objective lens), the amount of astigmatism, and the spot shape is stored in advance on the data base. ing. The controller 305a gives the shape corresponding to the spot shape selected by the operator, and adjusts the distance between the objective lens and the master and the amount of astigmatism as well as the focus sensors 117 and Set by controlling the stepping mode.

The controller 305a includes, for example, a CPU 351, a RAM 352, an input unit 353, a motor drive control unit 354, a 0 / oct conversion unit 355, a ROM 356, and the like. Is done. The ROM 356, which is a non-volatile memory, stores programs (boot program, OS, control program, etc.) related to the CPU 351 and the table information (database) shown in FIG. The random access memory RAM 352 stores 〇S, control programs, processing data, and the like, and is used for data processing. The input unit 353 includes a keyboard switch, a sunset panel, and the like, and can specify a spot shape. If necessary, the contents, operation procedures, and An indicator for displaying the slot shape can be provided. When the operator specifies the spot shape from the input unit 353 to the CPU 351, the CPU 351 calculates the distance data and the astigmatism amount of the objective lens corresponding to the spot shape. Read from the ROM 356 database. Convert the distance data of the objective lens to the bias voltage of the focus servo, and set the voltage data in the D / A converter 355. A bias voltage is supplied from the D / A converter 355 to the focus servo 117. Thereby, the distance of the objective lens from the master is set, and the focus servo is performed based on the distance. In addition, in order to set an inter-lens distance corresponding to the amount of astigmatism, a rotation angle of the stepping mode corresponding to the inter-lens distance is obtained. This is set as the target value in the motor drive controller 354. The motor drive control section 354 rotates the stepping motor 304 by giving a pulse only for the rotation angle corresponding to the difference between the current rotation angle of the motor from the reference position and the target rotation angle. Control. In this manner, the position of the objective lens and the distance between the two cylindrical lenses are determined, and the spot shape of the laser beam specified in the exposure apparatus, and accordingly, the scanning width of the laser beam are set.

In the above example, two convex cylindrical lenses are used as the means for adjusting the astigmatism amount. However, as shown in FIG. 7, convex and concave cylindrical lenses 71 1 and 70 2 may be used in combination. In addition, another method may be used as long as the method can adjust the amount of astigmatism.

In the above example, the focus servo system 114 is used as the automatic focusing position adjusting means. However, the automatic focusing position adjusting means may be provided independently of the focusing servo system.

The master may be not only a recording medium (disk) driven in rotation but also a recording medium moved in the X and Y directions. The present invention is also applicable to these exposure apparatuses and information recording apparatuses. Industrial applicability

As described above, according to the master disc exposure method and the exposure apparatus of the present invention, a group or a pit is exposed using a laser beam containing astigmatism, and the focus position is adjusted. Since the adjustment and the astigmatism amount can be performed, the width of the light spot formed on the master can be easily adjusted over a wide range without insufficient exposure light quantity. As a result, it is possible to provide an optical disk master, a stamper, and an optical disk molded and manufactured from the optical disk, which have a high quality or a variable group or pit width.

In particular, various elliptical spots having a minor axis in the scanning direction enable groups or pits of various widths to be obtained without impairing the resolution in the scanning direction.

Further, according to the present invention, the spot shape of a specified light (laser) beam can be quickly determined using the data of the objective lens position, the amount of astigmatism, and the beam spot shape based on the data. It can be set in the exposure apparatus, and the condition is good.

Claims

The scope of the claims

1. A master disc exposure device that irradiates a modulated laser beam to a master disc coated with a photosensitive material and forms a latent image of grooves or pits on an optical recording medium on the master disc, and a laser beam that emits a laser beam Generating means;

Intensity modulation means for intensity-modulating the laser beam with the supplied information signal, and focus position adjustment means for adjusting a height position of an objective lens for condensing the intensity-modulated laser beam on the master,

Beam scanning means for relatively scanning the converged laser beam on the master; and laser beam generating means and focusing position adjusting means provided between the laser generating means and the focusing position adjusting means to impart astigmatism to the laser beam. Astigmatism setting means capable of arbitrarily setting the amount of bracket astigmatism;

Master exposure apparatus equipped with:

2. By setting the amount of astigmatism and the height position of the objective lens according to the input, the scanning width of the laser beam or the spot shape of the laser beam is set as desired. 2. The master exposure apparatus according to claim 1, further comprising a laser beam spot adjustment unit.

3. The master exposure apparatus according to claim 2, wherein the setting range of the height position of the objective lens includes the astigmatism astigmatism difference.

4. The astigmatism setting means includes at least two cylindrical lenses arranged so that the laser beams pass therethrough and a distance between the two lenses is variable, and by adjusting a distance between the two lenses. The master exposure apparatus according to claim 1, wherein a degree of the astigmatism is set.

5. The master exposure apparatus according to claim 1, further comprising an automatic setting unit configured to set the astigmatism amount according to an instruction.

6. A method of exposing a master on which a light beam is condensed by an objective lens on a master on which a photosensitive film is formed, and which scans the photosensitive film with an obtained light spot to form a latent image. So,

A plurality of correspondences between the amount of astigmatism of the light beam and the distance of the objective lens from the master and the shape of the light spot are stored in advance,

When a light spot having a desired shape is set, the amount of astigmatism corresponding to the shape of the corresponding light spot and the distance from the master of the objective lens are referred to. An exposure method of a master disc, wherein each adjustment of astigmatism and the position of the objective lens is performed.

7. An exposure apparatus for a master, which irradiates an intensity-modulated light beam from a light up onto a master on which a photosensitive film is formed, and scans the photosensitive film with the light beam to form a latent image,

Astigmatism adjusting means for giving astigmatism to the light beam and adjusting an amount of the astigmatism;

Focus adjusting means for adjusting a distance of the objective lens, which forms the light spot by condensing the light beam on the master, from the master;

Spot data storage means for storing in advance a plurality of correspondences between the amount of the astigmatism, the distance from the master of the objective lens and the shape of the light spot,

The amount of the astigmatism corresponding to the shape of the designated light spot and the distance from the master of the objective lens are read out from the spot data storage means, and the amount of the astigmatism and the amount of the objective lens from the master are read. Data setting means for setting a distance to the astigmatism adjustment means and focus adjustment means, respectively;

Master exposure device equipped with

8. A master produced by using the exposure method according to claim 6.