CN102087864A - 近场光学系统的倾斜调整控制方法 - Google Patents

近场光学系统的倾斜调整控制方法 Download PDF

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CN102087864A
CN102087864A CN2009102531748A CN200910253174A CN102087864A CN 102087864 A CN102087864 A CN 102087864A CN 2009102531748 A CN2009102531748 A CN 2009102531748A CN 200910253174 A CN200910253174 A CN 200910253174A CN 102087864 A CN102087864 A CN 102087864A
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disc
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林威志
乔治·林内
詹·范得凡
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Lite On IT Corp
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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/095Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
    • G11B7/0956Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0945Methods for initialising servos, start-up sequences
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1387Means for guiding the beam from the source to the record carrier or from the record carrier to the detector using the near-field effect
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372Lenses
    • G11B2007/13727Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing
    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0908Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only

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Abstract

一种近场光学系统的倾斜调整控制方法,包括:检测一透镜与一盘片间的一间距;提供对应于该间距的一增益值;检测一倾斜信号;根据该倾斜信号及该增益值得出一倾斜补偿值;以及根据该倾斜补偿值,对该透镜进行一倾斜调整控制。

Description

近场光学系统的倾斜调整控制方法
技术领域
本发明是有关于一种近场光学系统的倾斜调整控制方法。
背景技术
在目前具有一定规格大小的盘片中,为了提升盘片的储存容量,除了发展可擦写多层的盘片外,另可通过缩小读写的聚焦光点尺寸以提高单位面积的储存量,进而提升盘片的总储存容量。聚焦光点的尺寸大小一般决定于所使用的激光的波长大小以及所使用的光学系统的数值孔径值(NA,numerical aperture)的大小。其中,使用短波长的光源及高数值孔径的光学系统可产生较小的聚焦光点尺寸。
在近年来提升盘片的储存容量的发展中,激光的波长已逐渐缩短,其由红外线(CD)改成红光(DVD),然后再到蓝光。由于激光的波长已经缩短至蓝光,因而为了进一步提升盘片的储存容量,近年已有相关研究转往使用近场光学系统来读写盘片,通过提高NA值以产生更小的聚焦光点尺寸。为达成高NA值,近场光学系统一般使用物镜(凸透镜)与固态浸没透镜(solid immersion lens,SIL)的组合来产生聚焦光点。在使用近场光学系统读写盘片时,若搭配使用蓝光雷射,其SIL与盘片表面间的间距非常小,其约为30-100nm。
由于聚焦光束与盘片数据层之间的垂直度会影响碟机读写数据的能力及准确性,因此碟机在读/写盘片时,一般会对光学系统(光学头)进行倾斜调整控制,使聚焦光束与盘片数据层垂直。然而,如上所述,由于使用近场光学系统来读写盘片时,SIL与盘片表面相当接近,因此如何在对SIL进行倾斜调整控制时避免其与盘片发生碰撞是本领域技术人员重要的课题之一。
发明内容
本发明是有关于一种近场光学系统的倾斜调整控制方法,当对SIL进行倾斜调整控制时,根据SIL与盘片间不同的间距所对应的增益值来修正倾斜信号或SIL的倾斜补偿值,以避免错误地调整SIL倾斜。
本发明的一实施例提出一种近场光学系统的倾斜调整控制方法,包括:检测一透镜与一盘片间的一间距;提供对应于该间距的一增益值;检测一倾斜信号;根据该倾斜信号及该增益值得出一倾斜补偿值;以及根据该倾斜补偿值,对该透镜进行倾斜调整控制。
为让本发明的上述内容能更明显易懂,下文特举实施例,并配合所附图式,作详细说明如下。
附图说明
图1A显示SIL与盘片间的关系图。
图1B显示倾斜限度与间距间的关系。
图1C显示透镜与SIL的组合。
图2A显示光检测电路的示意图。
图2B显示间距误差信号(Gap error signal,GES)与间距D间的关系。
图3A显示在不同D值下,SIL倾斜角度(TA)与倾斜信号TS间的关系。
图3B显示在不同D值下,图3A中的SIL倾斜角度(TA)与倾斜信号TS的一次微分值间的关系。
图4显示根据本实施例的操作流程图。
[主要元件标号说明]
10:SIL
15:盘片
18:透镜
SS:SIL的顶端大小
D:SIL与盘片表面的间距
A1~D1:相位
610~650:步骤
具体实施方式
图1A显示SIL与盘片间的关系图,而图1B则显示倾斜限度与间距间的关系,在此,间距是SIL与盘片表面间的间距,而倾斜限度是SIL所能倾斜的最大限度。通常,倾斜限度与SIL的构造及SIL与盘片表面的间距有关。
在图1A中,距离SS代表SIL 10的顶端大小(tip size),而距离D则是SIL 10与盘片15表面间的间距。通常,SIL 10的顶端大小约为40μm。如图1B所示,当间距D约为100nm时,如果SIL 10的顶端大小约为40μm,则倾斜限度为5mrad(约0.275度)。这代表在此情况下,SIL的倾斜角(SIL的顶端面与盘片表面间的角度)不可超过5mrad。如超过此限度,则SIL顶端的边缘则会撞到盘片。
接着请参考图1C,图1C显示近场光学系统中透镜18与固态浸没透镜(SIL)10组合的示意图。如图所示,透镜18会收敛平行光,并使其产生不同入射角度的光束入射于SIL 10。根据NA=nSIL*sinθ的公式(其中nSIL为SIL的折射率,θ为光束的入射角),入射于SIL 10的不同角度的光束会具有不同的NA值。当NA值为1时的入射角度即为全反射角θc。以NA值为1作分界,若入射至SIL 10的光束的NA值小于1,亦即,光束的入射角小于全反射角θc,则光束会穿透SIL 10。另一方面,若入射至SIL 10的光束的NA值大于1,亦即,光束的入射角大于或等于全反射角θc,则光束会被SIL 10全反射。
如果要使近场光学系统形成聚焦光点于盘片15上,SIL 10与盘片15表面间的间距D必须远小于入射光的波长λ,通常,间距D<=λ/10。在这样的间距(间距D<<λ)之下,NA值小于1的光束虽然会穿透SIL 10聚焦在盘片上,但因为其聚焦光点的面积过大,所以并无法用来读写盘片上已经小于其聚焦光点解析极限尺寸的沟轨及记录点。相反的,NA值大于1的光束当SIL 10未靠近盘片至近场距离时虽然会被SIL 10全反射,但若SIL 10靠近盘片15表面至近场距离(间距D<=λ/10)时,通过光穿隧(photon tunnneling)效应的作用,NA值大于1的光束会穿过间距D而入射至盘片并聚焦于盘片15上。在近场光学系统中,碟机使用NA大于1的部分所聚焦而成的较小聚焦光点进行读写的工作。此外,分别经由透镜18中NA小于1与NA大于1部分所形成的两个聚焦光点,由于其聚焦光点位置并不在同一平面上,因此不会产生相互干扰的问题。
当聚焦于盘片上的光束由盘片反射回近场光学系统时,此反射光会由光检测电路(Photo Detection IC,PDIC)所接收。在此,光检测电路比如为四相位感应器(Quadrant photodiode),如图2A所示。当PDIC接收到由盘片反射的反射光后,其四个相位A1~D1会各别接收到位于该相位的反射光的信号强度,而将PDIC的某半边相位所接收到的光信号强度减去PDIC的另一半边相位所接收到的光信号强度便可得出SIL的倾斜信号TS。一般而言,倾斜信号TS可设计为TS=(A1+D1)-(B1+C1)或是TS=(B1+C1)-(A1+D1)。再者,针对另一倾斜方向,其亦可设计另一倾斜信号TS为TS=(A1+B1)-(C1+D1)或TS=(C1+D1)-(A1+B1)。此处提及的倾斜方向可为盘片的径向方向或切线方向。
除了可由PDIC接收到的光信号强度得出倾斜信号TS外,其所接收的信号强度总和可作为间距误差信号(Gap error signal,GES);亦即,GES=A1+B1+C1+D1。图2B显示间距误差信号(Gap error signal,GES)与间距D间的关系。由图2B可看出,当SIL逐渐接近盘片(也就是间距D愈小时)时,间距误差信号GES会逐渐衰减。特别是,如图2B所示,当间距D小于100nm时,也就是进入近场光学系统时,间距误差信号GES会开始呈一线性衰减,因此SIL在近场时与盘片的间距D可由间距误差信号GES得知。
在近场光学系统中的SIL的倾斜调整便是根据前述提及的倾斜信号TS的值来得知SIL的倾斜角度,进而推出SIL的倾斜补偿值以反向调整SIL的倾斜角度。然而,在相同的倾斜信号TS的值下,SIL实际的倾斜角度会根据SIL与盘片的间距D的不同而有所不同。
请参阅图3A,图3A显示在不同间距D值下,SIL倾斜角度(TA)与倾斜信号TS间的关系;图3B显示在不同D值下,图3A中的SIL倾斜角度(TA)与倾斜信号TS的一次微分值间的关系。
于图3A及图3B中,由于在不同的间距D值下,SIL有不同的倾斜限度(如图1所示),因此图中粗线条的范围表示在该间距D下,SIL不会撞到盘片的范围。由图3A及图3B可清楚看出,当SIL愈接近盘片时(间距D愈小时),倾斜信号TS的灵敏度(sensitivity)愈高,意即,SIL在相同的倾斜角度(TA)下,当间距D愈小时,由PDIC检测得出的倾斜信号TS的值愈大。同样地,在PDIC检测出相同的倾斜信号TS下,当间距D愈小时,SIL实际的倾斜角度(TA)愈小。例如,当倾斜信号TS为0.1时,间距D为20nm的倾斜角度(TA)约为1mrad,而间距D为50nm的倾斜角度(TA)约为2.5mrad。
在已知的倾斜调整控制中,其会直接以倾斜信号TS对应到的倾斜补偿值来调整SIL。此处提及的倾斜补偿值可为倾斜角度(TA)。因而,假设倾斜信号TS与倾斜补偿值的对应关系是以间距D为50nm为基准间距,则虽然实际间距D为20nm,但倾斜信号TS为0.1所对应到的倾斜补偿值仍为2.5mrad。若以此倾斜补偿值为2.5mrad去调整SIL则会产生过度补偿,甚至造成SIL与盘片发生碰撞。
因此,倾斜信号TS需考虑基准间距与实际间距之间的信号增益值来修正并产生正确的倾斜补偿值。故而,当在近场光学系统中使用闭回路反馈控制来控制SIL的倾斜调整控制时,随着间距D的变化,此闭回路反馈控制的增益值要随之变化。详细地说,当间距D变小时,因为在相同的倾斜角度下,倾斜信号TS会变大,故而反馈控制的增益要变小,以修正倾斜信号TS及其对应的倾斜补偿值。因此,本实施例提出利用自动增益控制的方式来补偿增益值的变化。
请参考图4,其显示根据本实施例的操作流程图。如图4所示,于步骤610中,检测SIL与盘片间的间距D。详细地说,如上述般,由于在近场光学系统中,间距误差信号GES与SIL与盘片间的间距D会呈现一线性的关系,因此SIL在近场时与盘片的间距D可由间距误差信号GES得知。
于步骤620中,提供对应于该检测出的间距D的一增益值。由于在相同的倾斜信号TS的值下,SIL实际的倾斜角度会根据SIL与盘片的间距D的不同而有所不同,因此,在此步骤中,根据检测出的间距D,提供对应的增益值。不同的间距D及其所对应的增益值可事先于碟机出厂前,通过测试而得出不同间距D值下,SIL倾斜角度(TA)与倾斜信号TS间的关系(如图3A所示),进而建立出一间距-增益值表。
于步骤630中,检测SIL的倾斜信号(TS)。如前所述,倾斜信号TS可由将PDIC的某半边相位所接收到的光信号强度减去PDIC的另一半边相位所接收到的光信号强度而得出。
于步骤640中,根据倾斜信号(TS)及对应的增益值得出SIL的倾斜补偿值。在此步骤中,可先将倾斜信号(TS)依增益值作修正后,再根据基准间距的倾斜信号TS与倾斜补偿值的对应关系,得出对应该修正后的倾斜信号TS的SIL的倾斜补偿值。或者,亦可直接先根据基准间距的倾斜信号TS与倾斜补偿值的对应关系找出基准倾斜补偿值,再将基准倾斜补偿值依增益值作修正后得出SIL的倾斜补偿值。接着,于步骤650中,根据倾斜补偿值,进行SIL的倾斜调整控制。于本实施例中,可以动态(反馈)方式来进行SIL的倾斜调整控制。
由于在已知的倾斜调整控制中,其是直接以检测到的倾斜信号作为SIL的倾斜补偿值来对SIL进行倾斜调整控制。然而在近场光学系统中,由于SIL与盘片的间距非常近,且其间距的大小会影响倾斜信号的灵敏度,为了避免SIL与盘片发生碰撞,本发明提出一种倾斜调整控制的方法,其根据不同的间距大小所对应增益值及检测到的倾斜信号来修正SIL的倾斜补偿值。根据本发明提出一种倾斜调整控制的方法,其可有效避免因倾斜信号的灵敏度的变化而产生错误的SIL倾斜补偿值,进而避免造成SIL与盘片发生碰撞。
综上所述,虽然本发明已以实施例揭露如上,然其并非用以限定本发明。本发明所属技术领域中具有通常知识者,在不脱离本发明的精神和范围内,当可作各种的更动与润饰。因此,本发明的保护范围当视所附的权利要求范围所界定者为准。

Claims (8)

1.一种近场光学系统的倾斜调整控制方法,包括:
检测一透镜与一盘片间的一间距;
提供对应于该间距的增益值;
检测倾斜信号;
根据该倾斜信号及该增益值得出倾斜补偿值;以及
根据该倾斜补偿值,对该透镜进行倾斜调整控制。
2.根据权利要求1所述的方法,其中,检测该透镜与该盘片间的该间距的该步骤包括:
根据间距误差信号来检测该透镜与该盘片间的该间距。
3.根据权利要求2所述的方法,其中该间距误差信号是光检测电路的所有相位所接收到的光信号强度的总和。
4.根据权利要求1所述的方法,其中该倾斜信号是将光检测电路的第一半边相位所接收到的第一光信号强度减去第二半边相位所接收到的第二光信号强度。
5.根据权利要求1所述的方法,其中该增益值可经由查询一间距-增益值表而得知。
6.根据权利要求1所述的方法,其中根据该倾斜信号及该增益值得出该倾斜补偿值的该步骤包括:
依该增益值修正该倾斜信号,并得出修正后的倾斜信号;以及
根据一基准间距得出对应该修正后的倾斜信号的该倾斜补偿值。
7.根据权利要求1所述的方法,其中根据该倾斜信号及该增益值得出该倾斜补偿值的该步骤包括:
根据一基准间距得出对应该倾斜信号的基准倾斜补偿值;以及
依该增益值修正该基准倾斜补偿值,并得出该倾斜补偿值。
8.根据权利要求1所述的方法,其中根据该倾斜补偿值,对该透镜进行该倾斜调整控制的该步骤包括:
使用动态反馈方式进行该倾斜调整控制。
CN2009102531748A 2009-12-04 2009-12-04 近场光学系统的倾斜调整控制方法 Pending CN102087864A (zh)

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