JPH0264921A - Focus error detector - Google Patents
Focus error detectorInfo
- Publication number
- JPH0264921A JPH0264921A JP63216571A JP21657188A JPH0264921A JP H0264921 A JPH0264921 A JP H0264921A JP 63216571 A JP63216571 A JP 63216571A JP 21657188 A JP21657188 A JP 21657188A JP H0264921 A JPH0264921 A JP H0264921A
- Authority
- JP
- Japan
- Prior art keywords
- light
- focus error
- photodetectors
- phase difference
- outputs
- Prior art date
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- Pending
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- 238000013507 mapping Methods 0.000 claims abstract description 6
- 238000001514 detection method Methods 0.000 claims description 30
- 230000003287 optical effect Effects 0.000 abstract description 17
- 238000010586 diagram Methods 0.000 description 9
- 101000606504 Drosophila melanogaster Tyrosine-protein kinase-like otk Proteins 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 230000001427 coherent effect Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 201000009310 astigmatism Diseases 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
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- Automatic Focus Adjustment (AREA)
- Optical Recording Or Reproduction (AREA)
Abstract
Description
【発明の詳細な説明】
産業上の利用分野
本発明は、光デイスクドライブの自動焦点制御系に用い
られる焦点誤差検出装置に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a focus error detection device used in an automatic focus control system of an optical disk drive.
従来の技術
近年、焦点誤差検出装置は光デイスクドライブの基本的
機能を果たす装置として技術的に最重要視されている。2. Description of the Related Art In recent years, focus error detection devices have received the highest technical importance as devices that perform the basic functions of optical disk drives.
以下、図面を参照しながら、上述した従来の焦点誤差検
出装置の一実施例について説明する。Hereinafter, one embodiment of the above-mentioned conventional focus error detection device will be described with reference to the drawings.
第６図は従来の焦点誤差検出装置のブロック図を示すも
のである。第６図において、１０は記録情報列を意味す
る凹凸状のあるいは周囲と反射率を異にする情報ピット
がトランクに沿って形成された（あるいは情報トラック
を形成している）光記録媒体である。１はコヒーレント
光を発光する発光源、３はコヒーレント光を記録媒体１
０上に集光させる対物レンズである。４は光を電気信号
に変換する受光手段であって、後述のように２個の互い
に独立した受光素子４ａおよび４ｂに分割されている。FIG. 6 shows a block diagram of a conventional focus error detection device. In FIG. 6, reference numeral 10 denotes an optical recording medium in which uneven information pits representing recorded information sequences or information pits having a different reflectance from the surroundings are formed along the trunk (or information tracks are formed). . 1 is a light emitting source that emits coherent light; 3 is a recording medium 1 that emits coherent light;
This is an objective lens that focuses light onto 0. 4 is a light receiving means for converting light into an electric signal, and is divided into two mutually independent light receiving elements 4a and 4b as described later.
２は光記録媒体１０に入射した光の一部を透過させ、光
記録媒体１０を反射した光の一部を反射させる分光手段
である。５は受光素子４ａおよび４ｂのそれぞれの出力
の位相差を検出する位相比較手段、６は上記位相比較手
段出力の高域成分を除去する低域通過手段である。さら
に１４は自動焦点制御を実行するに必要なヒイルター等
を備えた自動焦点制御手段、１５は電気信号によって対
物レンズ３を駆動する対物レンズ駆動手段である。Reference numeral 2 denotes a spectroscopic means that transmits a portion of the light incident on the optical recording medium 10 and reflects a portion of the light reflected from the optical recording medium 10. Reference numeral 5 denotes phase comparison means for detecting the phase difference between the outputs of the light receiving elements 4a and 4b, and 6 is a low-pass means for removing high frequency components from the output of the phase comparison means. Furthermore, 14 is an automatic focus control means equipped with a heater etc. necessary for carrying out automatic focus control, and 15 is an objective lens drive means for driving the objective lens 3 by an electric signal.
以上のように構成された焦点誤差検出装置について、以
下その動作の説明をする。The operation of the focus error detection device configured as described above will be explained below.
まず、第７図（ａ）、 （ｂ）、 （Ｃ）に受光手段４
に投影される情報ピットの遠視野像を示す、同図（ａ）
は対物レンズ３の焦点深度内に記録面があるときの遠視
野像を表す。情報ピット端で回折した光が平面部分で反
射した光と互いに干渉しあうことにより同図の様な模様
になる。回折光は光軸に対して互いに対称な方向へ生じ
る。従って、干渉領域は、光軸を挟んで両側にできる。First, FIGS. 7(a), (b), and (C) show the light receiving means 4.
Figure (a) shows a far-field image of the information pit projected on the
represents a far-field image when the recording surface is within the focal depth of the objective lens 3. The pattern shown in the figure is created when the light diffracted at the edge of the information pit interferes with the light reflected from the flat surface. The diffracted lights are generated in mutually symmetrical directions with respect to the optical axis. Therefore, interference regions are formed on both sides of the optical axis.
同図（ロ）および（Ｃ）は対物レンズ３がそれぞれ近す
ぎる場合および遠すぎる場合を表している。それぞれ、
対物レンズ３が光記録媒体１０に設けられた情報トラッ
クにそってピットを走査しているときの様子を示してい
る。Figures (B) and (C) show cases in which the objective lens 3 is too close and too far, respectively. Each,
The objective lens 3 is shown scanning pits along an information track provided on the optical recording medium 10.
対物レンズ３の焦点位置に記録媒体１０があるときはピ
ント回折光と平坦部分反射光との干渉領域内部の光量分
布は変化せず、ただ干渉領域全体の総光量のみが変化す
る。ところが、対物レンズ３が記録媒体１０に対し近す
ぎる場合および遠すぎる場合は同図（ト））、 （Ｃ）
に示されるように、光量分布の移動がおこる。しかもそ
の移動方向は焦点誤差が正か負か（遠いか近いか）によ
って互いに反対向きとなる。When the recording medium 10 is at the focal position of the objective lens 3, the light amount distribution inside the interference region between the focused diffracted light and the flat portion reflected light does not change, but only the total light amount of the entire interference region changes. However, if the objective lens 3 is too close or too far from the recording medium 10,
As shown in , a shift in the light amount distribution occurs. Furthermore, the moving directions are opposite to each other depending on whether the focus error is positive or negative (far or near).
従ってこの受光素子４ａおよび４ｂの出力の位相差を検
出することによって焦点誤差信号を得ることができる。Therefore, a focus error signal can be obtained by detecting the phase difference between the outputs of the light receiving elements 4a and 4b.
光記録媒体１０は一般にはディスク状のものであり、ピ
ットは常にトラック周方向に定速で移動しているので、
安定した焦点誤差信号を検出できる。The optical recording medium 10 is generally disk-shaped, and the pits are always moving at a constant speed in the circumferential direction of the track.
A stable focus error signal can be detected.
以上述べた焦点検出方法は一般には位相差法と呼ばれて
おり、非点収差法やフーコー法などのように精密に調整
された検出光学系を必要としないのが特徴である。（例
えば、特公昭５６−３１６５１号公報、特公昭５Ｂ−２
３３３２号公報）発明が解決しようとする課題
しかしながら上記のような構成では、ピットが凹凸状に
形成されている場合、その凹凸の深さのばらつき等によ
って必然的に焦点誤差検出オフセットが発生するという
問題点を有していた。The focus detection method described above is generally called a phase difference method, and is characterized in that it does not require a precisely adjusted detection optical system like the astigmatism method or the Foucault method. (For example, Japanese Patent Publication No. 56-31651, Japanese Patent Publication No. 5B-2
However, in the above configuration, when pits are formed in an uneven shape, a focus error detection offset inevitably occurs due to variations in the depth of the unevenness. It had some problems.
すなわち、第８図に示されているように、遠視野像強度
分布はトラック周方向に非対称となり、その分位相差が
生じる。さらに、その位相差分はピットの分掌的な光学
的な高さ（深さ）に依存する。ピントの光学的な高さ（
深さ）がちょうどλ／４であるときには、その位相差分
すなわち焦点誤差検出オフセットはゼロになる（合焦点
時の光量分布は全く対称になる）が、ピットの光学的な
高さ（深さ）がそれより離れるに従って焦点誤差検出オ
フセットは大きくなる。That is, as shown in FIG. 8, the far-field image intensity distribution becomes asymmetrical in the circumferential direction of the track, and a phase difference occurs accordingly. Furthermore, the phase difference depends on the optical height (depth) of the pit. Optical height of focus (
When the depth (depth) is exactly λ/4, the phase difference, that is, the focus error detection offset becomes zero (the light intensity distribution at the focused point is completely symmetrical), but the optical height (depth) of the pit The focus error detection offset becomes larger as the distance from this point increases.
本発明は上記問題点に鑑み、ピット深さのばらつきによ
るフォーカスオフセットを逓減できる焦点誤差検出装置
を提供するものである。In view of the above problems, the present invention provides a focus error detection device that can reduce focus offset caused by variations in pit depth.
課題を解決するための手段
上記問題点を解決するために、本発明の焦点誤差検出装
置は、トラック写像方向に４個の受光素子を順次配列さ
せ、外側に配置された２個の受光素子の出力の位相差出
力と内側に配置された２個の受光素子の出力の位相差出
力とを適当なゲイン比でもって加算あるいは減算するよ
うな構成にした。Means for Solving the Problems In order to solve the above problems, the focus error detection device of the present invention sequentially arranges four light receiving elements in the track mapping direction, and The configuration is such that the phase difference output of the output and the phase difference output of the outputs of the two light receiving elements disposed inside are added or subtracted at an appropriate gain ratio.
作用
本発明は上記した構成によって、外側に配置された受光
素子によって焦点誤差検出を行い、そのとき生じるオフ
セット成分を内側に配置された受光素子でもってキャン
セルすることにより、焦点誤差検出オフセットを無くす
ることが可能となる。According to the above-described configuration, the present invention detects a focus error using a light-receiving element placed on the outside, and cancels the offset component generated at this time with a light-receiving element placed on the inside, thereby eliminating the focus error detection offset. becomes possible.
実施例
以下本発明の一実施例の焦点誤差検出装置について、図
面を参照しながら説明する。Embodiment Hereinafter, a focus error detection device according to an embodiment of the present invention will be described with reference to the drawings.
第２図は本発明の第１の実施例における焦点誤差検出装
置の構成図を示すものであり、第１図はその要部構成図
を示すものである。第１図、第２図において、■は発光
手段、２は分光手段、３は対物レンズ、４はトラック写
像方向に受光素子４ａ、４ｂ、４ｃ、および４ｄに分割
された受光手段、５１は受光素子４ｄの出力に対する受
光素子４ａの出力の位相を比較し、それに比例した電圧
を発生させる位相比較手段、５２は受光素子４ｂの出力
に対する受光素子４ｃの出力の位相を比較し、それに比
例した電圧を発生させる位相比較手段、６は位相比較手
段出力を適当なゲインでもって増幅する適当な係数を掛
ける係数手段、７は位相比較手段５１．５２の電圧出力
を加算する加算手段である。８は低域通過手段、ｌＯは
光記録媒体、１４は自動焦点制御手段、１５は対物レン
ズ駆動手段であり、これらは従来例で述べたものと同等
の機能を持つ。FIG. 2 shows a block diagram of a focus error detection device according to a first embodiment of the present invention, and FIG. 1 shows a block diagram of its main parts. In FIGS. 1 and 2, ■ is a light emitting means, 2 is a spectroscopic means, 3 is an objective lens, 4 is a light receiving means divided into light receiving elements 4a, 4b, 4c, and 4d in the track mapping direction, and 51 is a light receiving means. A phase comparing means 52 compares the phase of the output of the light receiving element 4a with respect to the output of the light receiving element 4d and generates a voltage proportional to the phase comparison; 6 is a coefficient means for multiplying the output of the phase comparison means by an appropriate coefficient to amplify it with an appropriate gain, and 7 is an addition means for adding the voltage outputs of the phase comparison means 51 and 52. 8 is a low-pass means, 10 is an optical recording medium, 14 is an automatic focus control means, and 15 is an objective lens driving means, which have the same functions as those described in the conventional example.
以上のように構成された焦点誤差検出装置について、以
下第１図、第２図、および第３図を用いてその動作を説
明する。The operation of the focus error detection device configured as described above will be described below with reference to FIGS. 1, 2, and 3.
まず、第３図は光記録媒体１０に記録されている１μｍ
長はどのピットマークを再生したときの受光素子４ａ、
受光素子４ｂ、受光素子４ｃ、受光素子４ｄの各出力を
プロットしたものである。First, FIG. 3 shows the 1 μm recorded on the optical recording medium 10.
The length indicates which pit mark was reproduced by the light receiving element 4a,
Each output of the light receiving element 4b, the light receiving element 4c, and the light receiving element 4d is plotted.
それぞれにおいて、横軸は時間、縦軸は信号振幅を表し
ている。パラメータはデフォーカス量である。ピント深
さはλ／６程度である。この図から明らかなことは、光
記録媒体ｌＯが対物レンズ３の焦点位置より遠ざかるか
近づくと外側の受光素子４ａ、４ｄの出力の位相は互い
に反対方向に大きくずれるが、内側の受光素子４ｂ、４
ｃの出力の位相はそれほど変化せず、ピット深さに起因
した定常オフセットのみが検出される。よって、焦点誤
差は外側の受光素子４ａ、４ｄの出力の位相差から求め
ればよく、内側の受光素子４ｂ、４ｃの出力の位相出力
はオフセットの補正信号として用いれば良いことになる
。In each, the horizontal axis represents time and the vertical axis represents signal amplitude. The parameter is the amount of defocus. The depth of focus is approximately λ/6. What is clear from this figure is that when the optical recording medium 10 moves away from or approaches the focal position of the objective lens 3, the phases of the outputs of the outer light receiving elements 4a and 4d shift greatly in opposite directions, but the inner light receiving element 4b, 4
The phase of the output of c does not change much, and only a steady offset due to the pit depth is detected. Therefore, the focus error can be determined from the phase difference between the outputs of the outer light receiving elements 4a and 4d, and the phase output of the inner light receiving elements 4b and 4c can be used as an offset correction signal.
位相比較手段５１の出力には焦点誤差検出成分とオフセ
ット成分が含まれており、位相比較手段５２の出力には
主にオフセット成分が含まれている。従って、位相比較
手段５２の出力に適当な係数を掛けあわせて、位相比較
手段５１の出力と加算（あるいは減算）すれば、定常オ
フセット成分の全く含まない焦点誤差検出信号を得るこ
とができる。The output of the phase comparison means 51 contains a focus error detection component and an offset component, and the output of the phase comparison means 52 mainly contains an offset component. Therefore, by multiplying the output of the phase comparison means 52 by an appropriate coefficient and adding (or subtracting) the resultant to the output of the phase comparison means 51, a focus error detection signal containing no stationary offset component can be obtained.
以上のように本実施例によれば、外側受光素子４ａ、４
ｄの位相差検出出力に適当な係数を掛けた内側受光素子
４ｂ、４ｃの位相差検出出力を加えることによって焦点
誤差検出オフセットを無くすることができる。As described above, according to this embodiment, the outer light receiving elements 4a, 4
By adding the phase difference detection outputs of the inner light receiving elements 4b and 4c obtained by multiplying the phase difference detection output of d by an appropriate coefficient, the focus error detection offset can be eliminated.
以下本発明の第２の実施例を示す。第５図は本発明の第
２の実施例の焦点誤差検出装置の要部構成図である。同
図において、６１は制御信号に応じてゲインを変えるこ
とのできる係数手段である。A second embodiment of the present invention will be described below. FIG. 5 is a block diagram of the main parts of a focus error detection device according to a second embodiment of the present invention. In the figure, reference numeral 61 is a coefficient means whose gain can be changed according to a control signal.
他は先の実施例で説明したのと同等の機能を果たすもの
である。The others perform the same functions as those described in the previous embodiment.
上記のように構成された焦点誤差検出装置について、以
下その動作を説明する。先の実施例ではトランク上に記
されたとットマークの真上を読み取り光線が通過した際
に得られる各受光素子の出力の位相差について述べたが
、ここではオフトラック時における位相差について簡単
に説明する。The operation of the focus error detection device configured as described above will be described below. In the previous example, we described the phase difference between the outputs of each light receiving element obtained when the reading beam passes directly above the dot mark marked on the trunk, but here we will briefly explain the phase difference when off-track. do.
第４図に読み取り光線が互いに隣接するトランク上に設
けられた２個のピットの間を走査したときの各受光素子
の出力の梯子を示す。第３図と異なるのは、内側にある
受光素子４ｂ、４ｃの出力の合焦点時における位相差は
殆どゼロであることである。さらにデフォーカスすると
、それに伴って位相差が生じる。従って、先の実施例で
示した方法でもって焦点誤差検出をおこなうと、オフト
ラック時ではオフセットが補正されないため、オフトラ
ック時とオントラック時ではフォーカスオフセット量が
異なることとなり、例えばトラックジャンプ等する際に
フォーカス方向に外乱を受けることになる。FIG. 4 shows a ladder of outputs of each light receiving element when a reading beam scans between two pits provided on adjacent trunks. The difference from FIG. 3 is that the phase difference between the outputs of the inner light receiving elements 4b and 4c when they are in focus is almost zero. Further defocusing causes a phase difference. Therefore, if focus error detection is performed using the method shown in the previous embodiment, the offset will not be corrected when off-track, so the amount of focus offset will be different between off-track and on-track. For example, if a track jump occurs, etc. When this happens, disturbances will be received in the focus direction.
そこで、本実施例ではトラックジャンプの時等、トラッ
キング制御が働いていないときは、位相検出手段５２の
出力を増幅するゲインを適当に変え、オフトラック時と
オントラック時における焦点検出オフセット量をほぼ等
しくさせる。係数手段６１はトラッキング制御がオン（
ＯＮ）であるかオフ（ＯＦＦ）であるかを示す制御信号
に応じてゲインを変えることができるものである。Therefore, in this embodiment, when the tracking control is not working, such as during a track jump, the gain for amplifying the output of the phase detecting means 52 is appropriately changed, so that the amount of focus detection offset during off-track and on-track is approximately equal. make them equal. The coefficient means 61 has tracking control turned on (
The gain can be changed depending on a control signal indicating whether the power is ON or OFF.
以上のように、トラッキング制御が働いていないときに
は、オフトラック時とオントラック時における焦点検出
オフセット量をほぼ等しくなるように係数手段６１のゲ
インを切り変えるようにしたことによって、焦点制御系
への外乱を除去することができる。As described above, when the tracking control is not working, the gain of the coefficient means 61 is changed so that the focus detection offset amounts during off-track and on-track are approximately equal, thereby controlling the focus control system. Disturbances can be removed.
発明の効果
以上のように本発明は、トラック写像方向に受光素子を
順次配列させ、外側に配置された２個の受光素子の出力
の位相差出力と内側に配置された２個の受光素子の出力
の位相差出力とを適当なゲイン比でもって加算あるいは
減算することにより、焦点誤差検出オフセットをキャン
セルすることが可能となる。Effects of the Invention As described above, the present invention sequentially arranges light-receiving elements in the track mapping direction, and generates a phase difference output between the outputs of two light-receiving elements arranged on the outside and the output of two light-receiving elements arranged on the inside. By adding or subtracting the output phase difference output with an appropriate gain ratio, it becomes possible to cancel the focus error detection offset.
第１図は本発明の第１の実施例の要部を示すブロック図
、第２図は本発明の第１の実施例のブロック図、第３図
は本発明の第１の実施例の動作を説明するためのグラフ
、第４図は本発明の第２の実施例の動作を説明するため
のグラフ成因、第５図は本発明の第２の実施例の要部を
示すブロック図、第６図は従来例の構成図、第７図、第
８図は従来例の動作説明図である。
４ ａ、 ４ ｂ、 ４ ｃ、 ４ ｄ・・−・
・受光素子、５１゜５２・・・・・・位相比較手段、６
・・・・・・係数手段、７・・・・・・加算手段。
代理人の氏名 弁理士 粟野重孝 はか１名第３１！１
図
第
図
第
図
第
図
ムテッ牛ングＯＮ１０ＦＦFIG. 1 is a block diagram showing the main parts of the first embodiment of the present invention, FIG. 2 is a block diagram of the first embodiment of the present invention, and FIG. 3 is the operation of the first embodiment of the present invention. 4 is a graph for explaining the operation of the second embodiment of the present invention. FIG. 5 is a block diagram showing the main parts of the second embodiment of the present invention. FIG. 6 is a configuration diagram of a conventional example, and FIGS. 7 and 8 are operation explanatory diagrams of the conventional example. 4 a, 4 b, 4 c, 4 d...
・Photodetector, 51°52...Phase comparison means, 6
... Coefficient means, 7... Addition means. Name of agent: Patent attorney Shigetaka Awano 31st! 1 ON10FF
Claims (3)
持った第一の受光素子と、第二の受光素子と、第三の受
光素子と、第四の受光素子と、上記第一および第四の受
光素子の出力信号の位相を比較し、両者の位相差に応じ
た電気信号を出力する第一の位相比較手段と、上記第二
および第三の受光素子の出力信号の位相を比較し、両者
の位相差に応じた電気信号を出力する第二の位相比較手
段と、上記第二の位相比較手段の出力を適当なゲインで
もって増幅する係数手段と、上記第一の位相比較手段と
係数手段との出力を加算あるいは減算する加算手段とを
備えたことを特徴とする焦点誤差検出装置。(1) A first light-receiving element, a second light-receiving element, a third light-receiving element, a fourth light-receiving element, and the first and fourth light-receiving elements each having the function of independently converting the amount of light into an electrical signal. A first phase comparison means that compares the phases of the output signals of the four light receiving elements and outputs an electrical signal according to the phase difference between the two, and compares the phases of the output signals of the second and third light receiving elements. , a second phase comparison means for outputting an electrical signal according to the phase difference between the two, a coefficient means for amplifying the output of the second phase comparison means with an appropriate gain, and the first phase comparison means. 1. A focus error detection device comprising: an addition means for adding or subtracting an output from a coefficient means.
光素子と、第四の受光素子はトラックの写像方向に順次
配列されたことを特徴とする特許請求の範囲第（１）項
記載の焦点誤差検出装置。(2) The first light-receiving element, the second light-receiving element, the third light-receiving element, and the fourth light-receiving element are arranged sequentially in the track mapping direction. 1) The focus error detection device described in section 1).
ない時とで係数手段のゲインを変えたことを特徴とする
特許請求の範囲第（１）項記載の焦点誤差検出装置。(3) The focus error detection device according to claim (1), characterized in that the gain of the coefficient means is changed depending on when the tracking control is functioning and when it is not functioning.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63216571A JPH0264921A (en) | 1988-08-31 | 1988-08-31 | Focus error detector |
| DE88310704T DE3882918T2 (en) | 1987-11-17 | 1988-11-14 | Focus control system for optical disk device with light-sensitive elements in the focal plane of the image of the information structure. |
| US07/272,054 US4998235A (en) | 1987-11-17 | 1988-11-14 | Focus detection system for an optical disk drive using photo sensor elements in the far field of information pits |
| EP88310704A EP0317224B1 (en) | 1987-11-17 | 1988-11-14 | Focus detection system for an optical disk drive using photo sensor elements in the far field of information pits |
| KR1019880015148A KR910006658B1 (en) | 1987-11-07 | 1988-11-17 | Detecting apparatus of focus error |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63216571A JPH0264921A (en) | 1988-08-31 | 1988-08-31 | Focus error detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0264921A true JPH0264921A (en) | 1990-03-05 |
Family
ID=16690509
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63216571A Pending JPH0264921A (en) | 1987-11-07 | 1988-08-31 | Focus error detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0264921A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005083693A1 (en) * | 2004-03-01 | 2005-09-09 | Pioneer Corporation | Tracking error signal generation device and tracking error signal generation method |
-
1988
- 1988-08-31 JP JP63216571A patent/JPH0264921A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005083693A1 (en) * | 2004-03-01 | 2005-09-09 | Pioneer Corporation | Tracking error signal generation device and tracking error signal generation method |
| US7440364B2 (en) | 2004-03-01 | 2008-10-21 | Pioneer Corporation | Tracking error signal generation device and tracking error signal generation method |
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