JP2711474B2 - Focus adjustment device for optical pickup device - Google Patents
Focus adjustment device for optical pickup deviceInfo
- Publication number
- JP2711474B2 JP2711474B2 JP27206689A JP27206689A JP2711474B2 JP 2711474 B2 JP2711474 B2 JP 2711474B2 JP 27206689 A JP27206689 A JP 27206689A JP 27206689 A JP27206689 A JP 27206689A JP 2711474 B2 JP2711474 B2 JP 2711474B2
- Authority
- JP
- Japan
- Prior art keywords
- light receiving
- receiving surface
- light
- amount
- focus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Description
本発明は光ピックアップ装置の焦点調整装置に関し，
特に，記録媒体上で反射された光を光分波器を介して焦
点の前方と後方に配設された２系統の光検出器上に照射
せしめ，各々の光検出光器の出力偏差により焦点調整機
構の位置制御を行う様にした焦点調整装置の改良に関す
る。The present invention relates to a focus adjustment device for an optical pickup device,
In particular, the light reflected on the recording medium is radiated through an optical demultiplexer onto two systems of photodetectors arranged in front and behind the focal point, and the focus is determined by the output deviation of each photodetector. The present invention relates to an improvement of a focus adjustment device that performs position control of an adjustment mechanism.
光ピックアップ装置の焦点調整装置としては，従来よ
り各種のものが知られているが，特に記録媒体上で反射
された光を光分波器を介して２系統の焦点に収束せし
め，該２系統の焦点の前方と後方に配設された２系統の
光検出器の出力偏差により焦点調整機構の位置制御を行
う様にした本発明の前提となる焦点調整装置の基本原理
を第１図及び第６図を参照して説明する。 尚，本明細書ではトラッキング方向をＸ軸，ディスク
の回転方向をＹ軸，フォーカシング方向をＺ軸として扱
う。 半導体レーザ１から射出された光はコリメートレンズ
２で平行光束にされて，ビーム整形プリズム3a・3b及び
ビームスプリッタ（ガラス3bと3c間の境界面Ｇ）を包含
する光学ブロック３に入射する。 コリメートレンズ２で平行光束に整形されたレーザ光
の光断面はレーザ光の性質によって一般に楕円強度分布
をしているので，ビーム整形プリズム3aにより真円補正
をする。 即ち，楕円の長軸が紙面に対して垂直方向であると仮
定した場合，レーザ光を例えば材質BK7（BSC7）で形成
されたビーム整形プリズム3aの面Ｅに入射角θで入射さ
せ，屈折角φで屈折させると，ビーム系は短軸方向にCO
Sφ/COSθだけ拡がって，略円形になる。 更に，レーザ光の波長λは一般に温度や発光強度によ
っても若干変化する性質を有し，上記の屈折角φも温度
や発光強度によって変化する。 そこで，屈折率に関して波長依存性や温度依存性があ
る例えば材質SF11（FD11）等のガラスで形成されたプリ
ズム3bを設け，レーザ光をガラス3aと3bの境界面Ｆに入
射角αで入射せしめ，屈折角βで屈折させることによっ
てレーザ光の波長依存性や温度依存性を補償している。 ガラス3bとガラス3cとの境界面Ｇは無位相ビームスプ
リッタを構成しており，レーザ光中のＰ偏光は70〜80％
が境界面Ｇを透過するとともに,S偏光は大半が境界面Ｇ
で反射する。 ガラス3cの底面には45度の傾斜面Ｈが形成されてお
り，コーティングが施されている。境界面Ｇを透過した
Ｐ偏光は傾斜面Ｈに入射角45度で入射して無位相で全反
射し，その光束はＺ軸方向に向けて，光学ブロック３か
ら射出する。光学ブロック３から射出した光は対物レン
ズ４によって図外のディスクに集光され，ディスクで反
射した光は再度対物レンズ４によって平行光束にされて
ガラス3cに入射し，傾斜面Ｈで全反射されて境界面Ｇに
入射する。 さて，光磁気ディスク方式の場合，ビームスポットが
ディスク記録面で反射される際に，その偏光面は情報ピ
ットを形成する垂直磁化によってカー（Kerr）角だけ回
転している。 従って，反射された光束が境界面Ｇに入射すると,P偏
光の20〜30％とＳ偏光が反射し，この反射光束は1/2波
長板５に入射し，後述のビームスプリッタ７に対して，
偏光面が45度傾斜される。 1/2波長板５から射出した光は集光レンズ６を通過し
てビームスプリッタ７に入射し，ビームスプリッタ７で
Ｐ成分とＳ成分に分割されて，焦点Ｆ及びＦ′に集光す
る。 焦点Ｆの前方及び焦点Ｆ′の後方にはディテクタ８及
び９が各々配置され，各々のディテクタ８・９の光軸近
傍には直径の等しい受光面Ａ・Ｂが各々形成されてい
る。 各々のディテクタ８・９に入射した光束Ｓのスポット
径をφSA及びφSBとした場合において，合焦時に各スポ
ット径φSA及びφSBは受光面Ａ・Ｂの径を余裕をもって
上回る。 又，望ましくは，各受光面Ａ及びＢの受光量を各々ａ
及びｂと定義した場合に，各々の受光量ａ及びｂが実質
的に等しくなる様にディテクタ８及び９の焦点Ｆ及び
Ｆ′に対する離反距離が設定される。 さて，この様な機構において，ディスク面が対物レン
ズ４に対して合焦時よりも近距離にある場合には，反射
光は焦点面Ｆ及びＦ′よりも遠方で収束する。従って，
各々のディテクタ８・９に入射する光束のスポット径を
各々φSA及びφSBと定義すると，各々のスポット径には
φSA＞φSBの関係が成立する。このことは受光面Ａに入
射する光は受光面Ｂに入射する光よりも拡散することを
意味するので，各々の受光面Ａ及びＢの検出光量にはａ
＜ｂの関係が成立する。 一方，ディスク面が対物レンズ４に対して合焦時より
も遠距離にある場合には，反射光は焦点面Ｆ及びＦ′よ
りも手前で収束する。従って，各々のディテクタ８・９
に入射する光束のスポット径にはφSA＞φSBの関係が成
立し，受光面Ｂに入射する光は受光面Ａに入射する光よ
りも拡散するので，各々の受光面Ａ及びＢの検出光量に
はａ＞ｂの関係が成立する。 従って，第６図に示す様に，受光面Ａ及びＢの出力を
差動増幅器12に加え，各々の系の検出光量の偏差ａ−ｂ
が０に収束する様に対物レンズ４を駆動すれば焦点調整
が行える。尚,13は補償回路を含むドライバを,14aはフ
ォーカスコイルを示す。2. Description of the Related Art Various types of focus adjustment devices for an optical pickup device have been known. In particular, light reflected on a recording medium is converged to two focal points via an optical demultiplexer, and the two systems are adjusted. FIGS. 1 and 2 show the basic principle of a focus adjustment device which is a premise of the present invention, in which the position control of a focus adjustment mechanism is performed based on output deviations of two systems of photodetectors disposed in front and behind a focal point. This will be described with reference to FIG. In this specification, the tracking direction is treated as the X axis, the disk rotation direction as the Y axis, and the focusing direction as the Z axis. Light emitted from the semiconductor laser 1 is converted into a parallel light beam by a collimating lens 2 and is incident on an optical block 3 including beam shaping prisms 3a and 3b and a beam splitter (a boundary surface G between the glasses 3b and 3c). Since the optical cross section of the laser beam shaped into a parallel light beam by the collimating lens 2 generally has an elliptical intensity distribution due to the properties of the laser beam, the perfect circular correction is performed by the beam shaping prism 3a. That is, assuming that the major axis of the ellipse is perpendicular to the plane of the paper, the laser beam is made incident on the surface E of the beam shaping prism 3a made of, for example, material BK7 (BSC7) at an incident angle θ, and the refraction angle When refracted by φ, the beam system becomes CO in the short axis direction.
It expands by Sφ / COSθ and becomes almost circular. Further, the wavelength λ of the laser light generally has a property that slightly changes depending on the temperature and the light emission intensity, and the refraction angle φ also changes depending on the temperature and the light emission intensity. Therefore, a prism 3b made of glass such as SF11 (FD11), which has a wavelength dependence and a temperature dependence with respect to the refractive index, is provided, and the laser beam is made incident on the boundary surface F between the glass 3a and 3b at an incident angle α. The wavelength dependence and the temperature dependence of the laser beam are compensated by refraction at the refraction angle β. The boundary surface G between the glass 3b and the glass 3c forms a phaseless beam splitter, and the P-polarized light in the laser beam is 70 to 80%.
Is transmitted through the interface G, and most of the S-polarized light is
Reflected by A 45 degree inclined surface H is formed on the bottom surface of the glass 3c, and is coated. The P-polarized light transmitted through the boundary surface G is incident on the inclined surface H at an incident angle of 45 degrees, is totally reflected without phase, and its light beam is emitted from the optical block 3 in the Z-axis direction. The light emitted from the optical block 3 is condensed by an objective lens 4 on a disc (not shown), and the light reflected by the disc is again converted into a parallel light beam by the objective lens 4 and is incident on the glass 3c. Incident on the boundary surface G. Now, in the case of the magneto-optical disk system, when the beam spot is reflected on the disk recording surface, its polarization plane is rotated by a Kerr angle due to perpendicular magnetization forming information pits. Therefore, when the reflected light beam enters the boundary surface G, 20-30% of the P-polarized light and the S-polarized light are reflected, and this reflected light beam enters the half-wave plate 5 and is transmitted to the beam splitter 7 described later. ,
The plane of polarization is tilted 45 degrees. The light emitted from the half-wave plate 5 passes through the condenser lens 6 and is incident on the beam splitter 7, where the light is split into a P component and an S component by the beam splitter 7, and is focused on the focal points F and F '. Detectors 8 and 9 are respectively disposed in front of the focal point F and behind the focal point F ', and light receiving surfaces A and B having the same diameter are formed near the optical axis of each of the detectors 8 and 9. When the spot diameter of the light beam S incident on each of the detectors 8 and 9 is φ SA and φ SB , each spot diameter φ SA and φ SB exceeds the diameter of the light receiving surfaces A and B with a margin during focusing. Preferably, the light receiving amounts of the respective light receiving surfaces A and B are respectively set to a
And b, the separation distances of the detectors 8 and 9 from the focal points F and F 'are set so that the received light amounts a and b are substantially equal. Now, in such a mechanism, when the disk surface is closer to the objective lens 4 than when focused, the reflected light converges farther than the focal planes F and F '. Therefore,
Defining with each phi SA and phi SB the spot diameter of the light beam incident on each detector 8.9, to each of the spot diameter is established the relationship φ SA> φ SB. This means that the light incident on the light receiving surface A is more diffused than the light incident on the light receiving surface B.
<B is satisfied. On the other hand, when the disk surface is farther from the objective lens 4 than when focused, the reflected light converges before the focal planes F and F '. Therefore, each detector 8, 9
The relation of φ SA > φ SB is established for the spot diameter of the light beam incident on the light receiving surface B, and the light incident on the light receiving surface B is diffused more than the light incident on the light receiving surface A. The relationship of a> b is established for the light quantity. Therefore, as shown in FIG. 6, the outputs of the light receiving surfaces A and B are applied to the differential amplifier 12, and the deviation ab of the detected light amount of each system is obtained.
If the objective lens 4 is driven so that converges to 0, the focus can be adjusted. Reference numeral 13 denotes a driver including a compensation circuit, and reference numeral 14a denotes a focus coil.
上記の様に，記録媒体からの反射光をビームスプリッ
タによって２系統のディテクタ上に分配し，検出光量偏
差によってサーボ系を作動させる様にした焦点調整装置
においては,2系統のディテクタでの検出光量が均衡して
いることが正常な作動のための前提条件となるものであ
る。 そこで，一般には２系統のディテクタ８・９における
受光量が均衡する様に1/2波長板５の位置調整を行う
が，この1/2波長板５の位置調整は極めて精密な調整が
必要になるという問題がある。 又,1/2波長板５の位置調整が精密に行われたとして
も，トラック間のクロストークやディスク平面での複屈
折等の影響によって生じる２系統のディテクタにおける
検出光量の不均衡に対しては従来の方式では対応でき
ず，常に焦点精度を確保できるという保証はなかった。As described above, in a focus adjustment device in which the reflected light from the recording medium is distributed to two systems of detectors by a beam splitter and the servo system is operated by a deviation of the detected light amount, the light amount detected by the two systems of detectors Is a prerequisite for normal operation. Therefore, in general, the position of the half-wave plate 5 is adjusted so that the amounts of light received by the two detectors 8 and 9 are balanced. However, the position adjustment of the half-wave plate 5 requires extremely precise adjustment. Problem. Also, even if the position of the half-wave plate 5 is precisely adjusted, the detection light quantity imbalance in the two detectors caused by the influence of crosstalk between tracks and birefringence on the disk plane, etc. Cannot be handled by the conventional method, and there was no guarantee that the focusing accuracy could always be ensured.
本発明はこの様な問題点に鑑みてなされたものであ
り,2系統のディテクタにおける検出光量の不均衡の影響
を受けることなく焦点調整を行える焦点調整装置を提供
することを目的とする。 要約すれば，本発明の光ピックアップ装置の焦点調整
装置は；焦点調整可能な対物レンズによって記録媒体上
に集光され，該記録媒体上で反射された光を前記対物レ
ンズと集光レンズと光分波器を介して２系統の焦点に収
束させ，該２系統の焦点の前方及び後方に各々２系統の
光検出器を配設し，該２系統の光検出器の出力偏差によ
り前記対物レンズをサーボ制御する様にした光ピックア
ップ装置の焦点調整装置を前提とするものであり；前記
２系統の各々の光検出器は，その光軸を中心として前記
集光レンズによって照射される光束スポットよりも小さ
い面積の中心受光面と，該中心受光面の周囲にあって該
中心受光面を含めた面積が前記光束スポットよりも大き
い面積となる周辺受光面とを有するとともに；一方の系
統の光検出器の中心受光面と周辺受光面の総受光量と他
方の系統の光検出器の中心受光面と周辺受光面の総受光
量の差に合焦点における総受光量に対する中心受光量の
成分比を乗じた値を補正値として算出する手段を備え，
前記各々の系統の光検出器の中心受光量偏差から前記算
出された補正値を減じた値をフォーカスエラー信号と
し，該フォーカスエラー信号が０に収束する様に前記対
物レンズをサーボ制御する様になされている。 望ましくは，本発明の光ピックアップ装置の焦点調整
装置は上記を前提として；前記２系統の光検出器を各々
の系統の焦点の前方及び後方に等距離離反させて配置す
るとともに；各々の系統の光検出器は同一形状の中心受
光面と周辺受光面とを有する様になされている。The present invention has been made in view of such a problem, and an object of the present invention is to provide a focus adjustment device capable of performing focus adjustment without being affected by an imbalance in detection light amounts between two detectors. In summary, the focus adjusting device of the optical pickup device according to the present invention comprises: a light source which is focused on a recording medium by an objective lens whose focus can be adjusted; The light is converged to two focal points via a duplexer, and two optical detectors are disposed in front of and behind the two focal points, respectively, and the objective lens is determined by an output deviation of the two optical detectors. And a focus adjusting device of an optical pickup device that servo-controls the light beam; each of the two photodetectors is arranged so that a light beam spot radiated by the condenser lens around its optical axis is A central light receiving surface having a smaller area and a peripheral light receiving surface surrounding the central light receiving surface and having an area including the central light receiving surface larger than the light beam spot; Heart of vessel Value obtained by multiplying the difference between the total received light amount of the light receiving surface and the peripheral light receiving surface and the total received light amount of the center light receiving surface of the other type of photodetector and the peripheral light receiving surface by the component ratio of the central light receiving amount to the total light receiving amount at the focal point Is provided as a correction value.
A value obtained by subtracting the calculated correction value from the center light receiving amount deviation of the photodetectors of the respective systems is used as a focus error signal, and the objective lens is servo-controlled so that the focus error signal converges to zero. It has been done. Preferably, the focus adjustment device of the optical pickup device of the present invention is based on the above-mentioned condition; the two systems of photodetectors are arranged equidistantly in front of and behind the focal points of each system, and The photodetector has a central light receiving surface and a peripheral light receiving surface having the same shape.
本発明においても反射光は光分波器で２分割されて焦
点の前後に配設された光検出器に投影される。 各々の系統の光検出器の中心受光面の受光量と周辺受
光面の受光量を加算した総受光量は焦点変動の影響を受
けないが，中心受光面の受光量は焦点変動に伴う光拡散
の度合に対応して変化する。 そこで，本発明においても基本的には各々の系統の光
検出器の中心受光量偏差によって対物レンズを駆動する
が，中心受光量は各々の系統の光検出器間に受光量の不
均衡があった場合には，受光量の不均衡成分を含むこと
になる。 上述の様に，各々の系統の光検出器の中心受光面の受
光量と周辺受光面の受光量を加算した総受光量は焦点変
動の影響は受けないが，受光量の不均衡の影響は受ける
ので，各々の系統の光検出器の総受光量の差を算出すれ
ば，この算出された差は各々の系統における光検出器の
総受光量の不均衡を示すことになる。 又，合焦点においては各々の系統の光検出器に投影さ
れる光束のスポット径は一定の値を示すので，総受光量
に対する中心受光量の成分比も一定の数値を示す事にな
り，この一定の成分比を上記で算出された各々の系統に
おける光検出器の総受光量の不均衡に乗じた値を補正値
とすれば，この補正値は受光量の不均衡中の中心受光面
に相当する成分を示す事になる。 そして，各々の系統の光検出器の中心受光量偏差から
上記の如くして算出された補正値を減じた値をフォーカ
スエラー信号とするので，合焦点近傍においてはフォー
カスエラー信号から光量不均衡成分は除去されることに
なり，このフォーカスエラー信号が０に収束する様に対
物レンズをサーボ制御すれば,2系統の光検出器の光量不
均衡に関わりなく対物レンズは常に合焦点を追跡するこ
とになる。In the present invention as well, the reflected light is split into two by an optical demultiplexer and projected onto photodetectors disposed before and after the focal point. The total amount of received light, which is the sum of the amount of light received at the center light-receiving surface and the amount of light received at the peripheral light-receiving surface of the photodetector of each system, is not affected by focus fluctuation. Changes according to the degree of Therefore, in the present invention, the objective lens is basically driven by the deviation of the center light reception amount of the photodetectors of each system. However, the center light reception amount has an imbalance in the light reception amount between the photodetectors of each system. In this case, an imbalance component of the amount of received light is included. As described above, the total received light amount obtained by adding the received light amount of the central light receiving surface and the received light amount of the peripheral light receiving surface of the photodetector of each system is not affected by the focus fluctuation, but the effect of the imbalance of the received light amount is Therefore, if the difference between the total light receiving amounts of the photodetectors in each system is calculated, the calculated difference indicates the imbalance in the total light receiving amount of the photodetectors in each system. Also, at the focal point, the spot diameter of the light beam projected on each system of photodetectors shows a constant value, so that the component ratio of the central light receiving amount to the total light receiving amount also shows a constant numerical value. If a value obtained by multiplying the imbalance of the total amount of received light of the photodetector in each system calculated above by the constant component ratio is set as a correction value, this correction value is applied to the central light receiving surface during the imbalance of the amount of received light. The corresponding components will be shown. Then, the value obtained by subtracting the correction value calculated as described above from the deviation of the center light receiving amount of the photodetectors of each system is used as the focus error signal. Will be eliminated, and if the objective lens is servo-controlled so that this focus error signal converges to 0, the objective lens will always track the focal point regardless of the imbalance in the amount of light of the two photodetectors. become.
以下図面を参照して本発明の１実施例を詳細に説明す
る。 本発明においても装置の構造は既述の従来例と基本的
には共通するので，第１図は本実施例の説明においても
使用し，更に，本実施例に係る光ピックアップ装置の全
体構成を第２図の斜視図に示すとともに，対物レンズ４
を駆動駆動するためのアクチュエータの詳細を第３図
（Ａ）の平面図，第３図（Ｂ）の正面図に示す。尚，第
２図において，既に説明した要素に関しては第１図と同
一の符号を付して重複した説明は省略し，これまでに説
明していない要素に関して詳述する。 15は対物レンズ４が固定されたアクチュエータ本体で
あり，アクチュエータ本体15の一方の脚部15aには弾性
を有する接続プレート16・17が各々ヒンジ部16a・17aで
接続されている。又，接続プレート16・17の他の一端は
図外の光学シーク機構に固定された取付部材18に各々ヒ
ンジ部16b・17bによって接続プレート16・17が平行状態
を維持する様に接続されている。 接続プレート16・17自体は弾性を有するものである
が，これらの外縁部には各々補強用の曲げ部16c・17cが
形成されているので，アクチュエータ本体15をＺ軸方向
に移動させる様な力を加えても，接続プレート16・17自
体には実質的に撓みが生せず,4箇所のヒンジ部16a・17a
・16b・17bが撓んでアクチュエータ本体15が対物レンズ
４の光軸が傾斜することなくＺ軸方向に移動する様にな
されている。 アクチュエータ本体15の他方の脚部15bにはフォーカ
スコイル14aが固着されており，フォーカスコイル14aの
巻き軸内には上記の光学シーク機構に固定されたＵ字型
のヨーク19が挿入され，ヨーク19にはマグネット20が固
着されている。従って，フォーカスコイル14aに通電す
ることによりアクチュエータ本体15をＺ軸方向に移動さ
せる様な力が発生する。 尚,14bはトラッキングコイルであり，トラッキングコ
イル14bに通電すると，アクチュエータ本体15がヒンジ
部16b・17bを中心として旋回する方向の力（即ち，アク
チュエータ本体15をＸ軸方向に移動させる力）が発生す
るが本発明はフォーカス制御に関するものであるので，
トラッキングコイル14bは本発明には直接的には関係し
ない。 次に，本発明の特徴点として第１図に示す様に各々の
ディテクタ８・９の中心受光面Ａ・Ｂの周囲には光束ス
ポットＳをいかなる状態においても十分にカバーし得る
大きさを持つ周辺受光面Ａ′・Ｂ′が配設されている。 次に，第４図は本発明の特徴点となる駆動回路の一例
を示したものである。 21はディテクタ８の中心受光面Ａの出力ａとディテク
タ９の中心受光面Ｂの出力ｂとの偏差を算出する減算回
路であり，この減算回路21の出力（ａ−ｂ）は各々の系
統のディテクタ８・９の中心受光面Ａ・Ｂの出力偏差を
示す。減算回路21の出力（ａ−ｂ）は減算回路22の正相
入力に加えられる。 23はディテクタ８の中心受光面Ａの出力ａと周辺受光
面Ａ′の出力ａ′を加算する加算回路であり，加算回路
23の出力（ａ＋ａ′）はディテクタ８の総受光量を示
す。加算回路23の出力（ａ＋ａ′）は減算回路24の正相
入力に加えられる。 同様に,25はディテクタ９の中心受光面Ｂの出力ｂと
周辺受光面Ｂ′の出力ｂ′を加算する加算回路であり，
加算回路25の出力（ｂ＋ｂ′）はディテクタ９の総受光
量を示す。加算回路25の出力（ｂ＋ｂ′）は減算回路24
の逆相入力に加えられる。 減算回路24は正相入力から逆相入力を減じるので，そ
の出力（ａ＋ａ′）−（ｂ＋ｂ′）はディテクタ８の総
受光量とディテクタ９の総受光量に不均衡があった場合
に，ディテクタ８の総受光量とディテクタ９の総受光量
の不均衡を示す事になる。 減算回路24の出力は分圧器26で所定の定数Ｋを乗じら
れて減算回路22の逆相入力に加えられる。 ここで，分圧器26の定数Ｋは合焦時におけるディテク
タ８の総受光量（ａ＋ａ′）に対する中心受光量ａの成
分比（a/a＋ａ′）を示している。尚，本実施例ではデ
ィテクタ８とディテクタ９と同一形状であるので，定数
Ｋは合焦時におけるディテクタ９の総受光量（ｂ＋
ｂ′）に対する中心受光量ｂの成分比（b/b＋ｂ′）を
も同時に示していることはいうまでもない。 そして，上述の様に減算回路24の出力はディテクタ８
の総受光量とディテクタ９の総受光量の不均衡を示して
いるので，減算回路22の逆相入力は，合焦時におけるデ
ィテクタ８及び９の総受光量の不均衡中の中心受光面Ａ
及びＢに相当する成分を示す事になる。 減算回路22の正相入力には，ディテクタ８・９の中心
受光面Ａ・Ｂの出力偏差を示す減算回路21の出力（ａ−
ｂ）が加えられているので，減算回路22の出力であるフ
ォーカスエラー信号FESは２系統のディテクタ８・９の
中心受光面Ａ・Ｂの出力偏差から合焦時におけるディテ
クタ８・９の総受光量の不均衡中の中心受光面に相当す
る成分を除去した値を示す。 減算回路22の出力であるフォーカスエラー信号FESは
ドライバ13に加えられ，フォーカスコイル14aを制御す
る。 尚，上記の説明から明らかな様にフォーカスエラー信
号FESは次の（式−１）で示される。 FES＝（ａ−ｂ）−Ｋ｛（ａ＋ａ′）−（ｂ＋ｂ′）｝
（式−１） 次に，上記事項及び第５図（Ａ）〜（Ｃ）を参照して
本実施例の作用を説明する。 尚，第５図（Ａ）はディスク面30が対物レンズ４に対
して合焦している時，第５図（Ｂ）はディスク面30が対
物レンズ４に対して合焦時よりも遠距離にある時，第５
図（Ｃ）はディスク面30が対物レンズ４に対して合焦時
よりも近距離にある時を各々示している。 始めに,2系統のディテクタ８・９に対する入射光量が
均衡している場合に関して説明する。 ２系統のディテクタ８・９に対する入射光量が均衡し
ている場合は，各々のディテクタ８・９の総受光量（ａ
＋ａ′）と（ｂ＋ｂ′）は等しい値になるので，（式−
１）における（ａ＋ａ′）−（ｂ＋ｂ′）は０になる。
即ち，第４図の減算回路21の出力が，そのまま減算回路
22の出力になるので（式−１）は（式−２）と書き替え
ることができる。 FES＝ａ−ｂ （式−２） 先ず，ディスク面30が対物レンズ４に対して合焦して
いる時には，ビームスプリッタ７で分割された光は焦点
Ｆ及びＦ′で収束するので，ディテクタ８に入射する光
束Ｓのスポット径φSAとディテクタ８に入射する光束Ｓ
のスポット径φSBは等しく同じ拡散の度合を示し，且
つ,2系統のディテクタ８・９に対する入射光量が均衡し
ている場合は，ディテクタ８・９の単位面積あたりの受
光量も等しくなるので，上記の（式−２）におけるａと
ｂの値も等しくなる。 従って，（式−２）におけるフォーカスエラー信号FE
Sは０になるので，サーボ系はその現状を維持する様に
作用する。 次に，ディスク面30が対物レンズ４に対して合焦時よ
りも遠距離にある時には，ビームスプリッタ７で分割さ
れた光は焦点Ｆ及びＦ′よりも手前で収束するので，第
５図（Ｂ）に示す様にディテクタ８に投影される光束の
スポット径φSAとディテクタ９に投影される光束のスポ
ット径φSBの間にはφSA＜φSBの関係が成立し，受光面
Ｂに対する入射光束は受光面Ａに対する入射光束よりも
拡散するので，上記の（式−２）におけるａとｂの間に
はａ＞ｂの関係が成立する。 従って，（式−２）は（式−３）と変形でき，ドライ
バ13はフォーカスコイル14aに正の電流を供給する。 FES＝ａ−ｂ＞０ （式−３） 但し；（ａ＞ｂ） フォーカスコイル14aに正の電流が供給されることに
よってフォーカスコイル14aとヨーク19間に作用する電
磁力によってアクチュエータ本体15は上方に移動して対
物レンズ４はディスク面30に近づく。 又，ディスク面30が対物レンズ４に対して合焦時より
も近距離にある時には，ビームスプリッタ７で分割され
た光は焦点Ｆ及びＦ′よりも奥で収束するので，第５図
（Ｃ）に示す様にディテクタ８に投影される光束のスポ
ット径φSAとディテクタ８に投影される光束のスポット
径φSBの間にはφSA＞φSBの関係が成立し，受光面Ａに
対する入射光束は受光面Ｂに対する入射光束よりも拡散
するので，上記の（式−１）におけるａとｂの間にはａ
＜ｂの関係が成立する。 従って，（式−２）は（式−４）と変形でき，ドライ
バ13はフォーカスコイル14aに負の電流を供給する。 FES＝ａ−ｂ＜０ （式−４） 但し；（ａ＜ｂ） フォーカスコイル14aに負の電流が供給されることに
よってフォーカスコイル14aとヨーク19間に作用する電
磁力によってアクチュエータ本体15は下方に移動して対
物レンズ４はディスク面30から離れる。 次に,2系統のディテクタ８・９に対する入射光量が不
均衡な場合に関して説明する。 ２系統のディテクタ８・９の総受光量（ａ＋ａ′）と
（ｂ＋ｂ′）がR1:R2（但しR1＋R2＝２でR1≠R2）の関
係がある時には，合焦点では各々のディテクタ８・９の
中心受光面の受光量ａとｂ間にも上記と同様にR1:R2の
関係が成立する。 （式−１）における中括弧の中身である減算回路24の
出力（ａ＋ａ′）−（ｂ＋ｂ′）がディテクタ８の総受
光量とディテクタ９の総受光量との間の不均衡を示して
いることは上述の通りである。 そして，この減算回路24の出力は分圧器26によって所
定の定数Ｋが乗じられて，減算回路22に逆相入力に与え
られるが，分圧器26によって乗じられる定数Ｋは，合焦
点におけるディテクタ８の総受光量（ａ＋ａ′）に対す
る中心受光量ａの成分比（a/a＋ａ′）及び合焦点にお
けるディテクタ９の総受光量（ｂ＋ｂ′）に対する中心
受光量ｂの成分比（b/b＋ｂ′）を示しているので，各
ディテクタ８・９の総受光量に生じている光量不均衡の
うちの合焦点における中心受光量の不均衡に相当する成
分が減算回路22の逆相入力に与えられることになる。 一方，減算回路22の正相入力には各ディテクタ８・９
の中心受光量の偏差（ａ−ｂ）を示す減算回路21の出力
が加えられているが，上記様に２系統のディテクタ８・
９の総受光量に不均衡が生じている時には当然に減算回
路21の出力（ａ−ｂ）も光量不均衡成分を含むことにな
る。 しかしながら，上記の様に本実施例では減算回路22に
よって減算回路21の出力から分圧器26の出力を減じてフ
ォーカスエラー信号FESを作成しており，分圧器26の出
力は各ディテクタ８・９の総受光量に生じている光量不
均衡のうちの合焦点における中心受光量の不均衡に相当
する成分を示しているので，合焦点近傍においてはフォ
ーカスエラー信号FESからは２系統のディテクタ８・９
に生じる光量不均衡成分は除去されることになる。 勿論，分圧器26によって設定される定数Ｋは合焦点に
おける総受光量に対する中心受光量の成分比（a/a＋
ａ′）を示しているので，合焦点から遠ざかると光量不
均衡成分の補正量に過不足が生じるが，合焦点近傍にお
いては光量の不均衡成分は上記の様に０に収束するの
で,2系統のディテクタにおける光量の不均衡に関わりな
く対物レンズ５は合焦位置に追従する。 次に，代数的に合焦点においてはフォーカスエラー信
号FESが０に収束することを説明する。 ２系統のディテクタ８・９の総受光量（ａ＋ａ′）と
（ｂ＋ｂ′）の間に上記の様にR1:R2の関係が成立する
時にはディテクタ９の総受光量（ｂ＋ｂ′）は（式−
５）で示され，又，合焦点においては，ディテクタ９の
中心受光量ｂは（式−６）で示される。 これを（式−１）に代入すると（式−１）は次の（式
−７）と展開でき，フォーカスエラー信号は２系統のデ
ィテクタ８・９間の光量の不均衡に関わりなく最終的に
は０に収束するので，サーボ系全体もディテクタ８・９
間の光量の不均衡に関わりなく対物レンズ４が合焦時に
追従する様に作動することになる。 以上の説明からも明らかな様に，本発明は基本的には
２系統のディテクタの中心受光量偏差が０に収束する様
に対物レンズをサーボ駆動するとともに，各々のディテ
クタの全体受光量に生じている光量不均衡中の合焦点に
おける中心受光量に相当する成分を上記の中心受光量偏
差から減じることによって，合焦点においては光量不均
衡の影響を除去できる様にしたものである。 従って，上記においては説明を単純化するとともに回
路構成をも単純化するために２系統のディテクタ８・９
が同一形状のものであるとして説明したが，配置スペー
ス等の関係で同一のディテクタを使用できない様な場合
でも各種の入力信号のゲイン等に回路上で適宜重み付け
をしたり，各々のディテクタの焦点位置からの離反距離
等を適宜調整することによって異形状のディテクタを使
用することも可能である。 又，本発明は焦点調整に関するものであるので，説明
や回路構成を単純化するために，単に中心受光面の外周
に周辺受光面を設けた例を示したが，これらのディテク
タはフォーカシング制御の他にトラッキング制御等に使
用されることが通例であり，その場合には一般に中心受
光面や周辺受光面を左右に２分割し，左右の光量比でト
ラッキング制御がなされる。そして，この様に中心受光
面や周辺受光面が２分割された場合には第４図に示す回
路の前段に左右の受光量を加算するための加算回路を追
加することによって本発明をそのまま適用することがで
きる。Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is also used in the description of the present embodiment because the structure of the device is basically the same as that of the above-described conventional example in the present invention, and the overall configuration of the optical pickup device according to the present embodiment is further described. As shown in the perspective view of FIG.
Details of the actuator for driving the actuator are shown in the plan view of FIG. 3A and the front view of FIG. 3B. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same elements as those described in FIG. 1, and a duplicate description will be omitted. Elements not described so far will be described in detail. Reference numeral 15 denotes an actuator main body to which the objective lens 4 is fixed, and connection legs 16 and 17 having elasticity are connected to one leg 15a of the actuator main body 15 by hinge portions 16a and 17a, respectively. The other ends of the connection plates 16 and 17 are connected to a mounting member 18 fixed to an optical seek mechanism (not shown) by hinge portions 16b and 17b so that the connection plates 16 and 17 maintain a parallel state. . Although the connection plates 16 and 17 themselves have elasticity, these outer edges are formed with bending portions 16c and 17c for reinforcement, respectively, so that a force for moving the actuator body 15 in the Z-axis direction is provided. , The connection plates 16 and 17 are not substantially bent, and the four hinge portions 16a and 17a
The actuator body 15 is moved in the Z-axis direction without tilting the optical axis of the objective lens 4 due to bending of 16b and 17b. A focus coil 14a is fixed to the other leg 15b of the actuator body 15, and a U-shaped yoke 19 fixed to the optical seek mechanism is inserted into a winding shaft of the focus coil 14a. Has a magnet 20 fixed thereto. Therefore, when the focus coil 14a is energized, a force is generated that moves the actuator body 15 in the Z-axis direction. Reference numeral 14b denotes a tracking coil. When a current is applied to the tracking coil 14b, a force is generated in a direction in which the actuator main body 15 turns around the hinge portions 16b and 17b (that is, a force for moving the actuator main body 15 in the X-axis direction). However, since the present invention relates to focus control,
Tracking coil 14b is not directly relevant to the present invention. Next, as a feature of the present invention, as shown in FIG. 1, the size around the central light receiving surfaces A and B of the respective detectors 8 and 9 is sufficient to cover the light beam spot S in any state. Peripheral light receiving surfaces A 'and B' are provided. Next, FIG. 4 shows an example of a driving circuit which is a feature of the present invention. Reference numeral 21 denotes a subtraction circuit for calculating a deviation between the output a of the central light receiving surface A of the detector 8 and the output b of the central light receiving surface B of the detector 9, and the output (ab) of the subtraction circuit 21 is used for each system. The output deviation of the central light receiving surfaces A and B of the detectors 8 and 9 is shown. The output (ab) of the subtraction circuit 21 is applied to the in-phase input of the subtraction circuit 22. 23 is an addition circuit for adding the output a of the central light receiving surface A of the detector 8 and the output a 'of the peripheral light receiving surface A'.
The output (a + a ′) of 23 indicates the total amount of light received by the detector 8. The output (a + a ') of the adding circuit 23 is applied to the positive phase input of the subtracting circuit 24. Similarly, reference numeral 25 denotes an addition circuit for adding the output b of the central light receiving surface B of the detector 9 and the output b 'of the peripheral light receiving surface B'.
The output (b + b ') of the addition circuit 25 indicates the total amount of light received by the detector 9. The output (b + b ') of the adding circuit 25 is
Applied to the negative phase input of Since the subtraction circuit 24 subtracts the negative-phase input from the normal-phase input, the output (a + a ')-(b + b') is obtained when the total received light amount of the detector 8 and the total received light amount of the detector 9 are unbalanced. 8 indicates an imbalance between the total received light amount of the detector 8 and the total received light amount of the detector 9. The output of the subtraction circuit 24 is multiplied by a predetermined constant K by a voltage divider 26 and applied to the negative phase input of the subtraction circuit 22. Here, the constant K of the voltage divider 26 indicates the component ratio (a / a + a ') of the center received light amount a to the total received light amount (a + a') of the detector 8 at the time of focusing. In this embodiment, since the detector 8 and the detector 9 have the same shape, the constant K is equal to the total amount of received light (b +
Needless to say, the component ratio (b / b + b ') of the center light reception amount b to b') is also shown. Then, as described above, the output of the subtraction circuit 24 is
The negative phase input of the subtraction circuit 22 is applied to the central light receiving surface A during the imbalance of the total received light amount of the detectors 8 and 9 during focusing.
And components corresponding to B. The non-inverting input of the subtraction circuit 22 includes the output (a−) of the subtraction circuit 21 indicating the output deviation of the central light receiving surfaces A and B of the detectors 8 and 9.
Since b) is added, the focus error signal FES, which is the output of the subtraction circuit 22, is based on the output deviation of the central light receiving surfaces A and B of the two detectors 8 and 9 and the total light reception of the detectors 8 and 9 during focusing. A value obtained by removing a component corresponding to the center light receiving surface during an imbalance in the amount is shown. The focus error signal FES output from the subtraction circuit 22 is applied to the driver 13 to control the focus coil 14a. Incidentally, as is apparent from the above description, the focus error signal FES is expressed by the following (Equation-1). FES = (ab) −K {(a + a ′) − (b + b ′)}
(Equation-1) Next, the operation of the present embodiment will be described with reference to the above matters and FIGS. 5 (A) to 5 (C). FIG. 5A shows a case where the disk surface 30 is in focus with respect to the objective lens 4, and FIG. The fifth
FIG. 4C shows a case where the disk surface 30 is closer to the objective lens 4 than at the time of focusing. First, a case where the amounts of incident light on the two detectors 8 and 9 are balanced will be described. When the amounts of incident light on the two detectors 8 and 9 are balanced, the total amount of received light (a
+ A ') and (b + b') have the same value.
(A + a ')-(b + b') in 1) becomes 0.
That is, the output of the subtraction circuit 21 in FIG.
(Equation-1) can be rewritten as (Equation-2) because the output is 22. FES = ab (Equation-2) First, when the disk surface 30 is focused on the objective lens 4, the light split by the beam splitter 7 converges at the focal points F and F '. The spot diameter φ SA of the light beam S incident on the detector 8 and the light beam S incident on the detector 8
If the spot diameters φ SB are equal and show the same degree of diffusion, and the amounts of incident light on the two systems of detectors 8 and 9 are balanced, the amount of received light per unit area of the detectors 8 and 9 is also equal. The values of a and b in the above (Equation-2) are also equal. Therefore, the focus error signal FE in (Equation 2)
Since S becomes 0, the servo system acts so as to maintain the current state. Next, when the disk surface 30 is farther from the objective lens 4 than when focused, the light split by the beam splitter 7 converges before the focal points F and F '. As shown in B), the relationship of φ SA <φ SB is established between the spot diameter φ SA of the light beam projected on the detector 8 and the spot diameter φ SB of the light beam projected on the detector 9. Since the incident light beam is more diffused than the incident light beam on the light receiving surface A, the relationship of a> b is established between a and b in the above (Equation-2). Therefore, (Equation-2) can be transformed into (Equation-3), and the driver 13 supplies a positive current to the focus coil 14a. FES = ab> 0 (Equation-3) where; (a> b) When a positive current is supplied to the focus coil 14a, the actuator body 15 is moved upward by an electromagnetic force acting between the focus coil 14a and the yoke 19. And the objective lens 4 approaches the disk surface 30. When the disk surface 30 is closer to the objective lens 4 than at the time of focusing, the light split by the beam splitter 7 converges deeper than the focal points F and F '. As shown in), the relationship φ SA > φ SB is established between the spot diameter φ SA of the light beam projected on the detector 8 and the spot diameter φ SB of the light beam projected on the detector 8, and the incident light on the light receiving surface A Since the light beam is more diffused than the light beam incident on the light receiving surface B, a between a and b in the above (Equation-1) is a
<B is satisfied. Therefore, (Equation-2) can be transformed into (Equation-4), and the driver 13 supplies a negative current to the focus coil 14a. FES = ab <0 (Equation-4); (a <b) The actuator body 15 is moved downward by an electromagnetic force acting between the focus coil 14a and the yoke 19 when a negative current is supplied to the focus coil 14a. To move the objective lens 4 away from the disk surface 30. Next, a case where the amounts of incident light on the two detectors 8 and 9 are imbalanced will be described. When the total amount of received light (a + a ′) and (b + b ′) of the two detectors 8 and 9 has a relationship of R 1 : R 2 (where R 1 + R 2 = 2 and R 1 ≠ R 2 ), the focal point is Similarly, the relationship of R 1 : R 2 is established between the light receiving amounts a and b of the central light receiving surfaces of the respective detectors 8 and 9. The output (a + a ')-(b + b') of the subtraction circuit 24, which is the content of the curly brackets in (Equation-1), indicates an imbalance between the total light receiving amount of the detector 8 and the total light receiving amount of the detector 9. This is as described above. The output of the subtraction circuit 24 is multiplied by a predetermined constant K by a voltage divider 26 and given to the negative-phase input to the subtraction circuit 22. The constant K multiplied by the voltage divider 26 is the output of the detector 8 at the focal point. The component ratio (a / a + a ') of the center received light amount a to the total received light amount (a + a') and the component ratio (b / b + b ') of the center received light amount b to the total received light amount (b + b') of the detector 9 at the focal point are shown. The component corresponding to the imbalance of the center received light amount at the focal point among the light amount imbalances occurring in the total received light amounts of the detectors 8 and 9 is given to the negative phase input of the subtraction circuit 22. Become. On the other hand, the detectors 8.9
The output of the subtraction circuit 21 indicating the deviation (ab) of the center light receiving amount of the two detectors is added as described above.
When an imbalance occurs in the total amount of received light of No. 9, the output (ab) of the subtraction circuit 21 naturally also includes a light amount imbalance component. However, as described above, in this embodiment, the focus error signal FES is created by subtracting the output of the voltage divider 26 from the output of the subtraction circuit 21 by the subtraction circuit 22, and the output of the voltage divider 26 is output from each of the detectors 8 and 9. Since the component corresponding to the imbalance of the center received light amount at the focal point out of the light amount imbalance occurring in the total received light amount is shown, the two systems of detectors 8.9 from the focus error signal FES near the focal point are shown.
Will be removed. Of course, the constant K set by the voltage divider 26 is the component ratio of the center received light amount to the total received light amount at the focal point (a / a +
a '), the amount of correction of the light quantity imbalance component becomes excessive or deficient as the distance from the focal point increases, but the light quantity imbalance component converges to 0 near the focal point as described above. The objective lens 5 follows the in-focus position irrespective of the light amount imbalance in the detectors of the system. Next, it will be explained that the focus error signal FES converges to 0 at the focal point algebraically. When the relationship of R 1 : R 2 is established as described above between the total received light amounts (a + a ′) and (b + b ′) of the two detectors 8 and 9, the total received light amount (b + b ′) of the detector 9 becomes ( Expression-
5), and at the focal point, the center received light amount b of the detector 9 is expressed by (Equation-6). By substituting this into (Equation-1), (Equation-1) can be developed into the following (Equation-7), and the focus error signal is finally obtained regardless of the light quantity imbalance between the two detectors 8 and 9. Converges to 0, so the entire servo system also has detectors 8.9
The objective lens 4 operates so as to follow the in-focus state irrespective of the light amount imbalance between the two. As is apparent from the above description, the present invention basically drives the objective lens by servo so that the center light receiving amount deviation of the two detectors converges to zero, and generates the total light receiving amount of each detector. By subtracting the component corresponding to the center light reception amount at the focal point during the light amount imbalance from the above center light amount deviation, the influence of the light amount imbalance at the focal point can be removed. Therefore, in the above description, two detectors 8 and 9 are used to simplify the description and the circuit configuration.
Are described as having the same shape. However, even when the same detector cannot be used due to the arrangement space or the like, the gains of various input signals are appropriately weighted on the circuit, and the focus of each detector is adjusted. It is also possible to use a detector having a different shape by appropriately adjusting the separation distance from the position and the like. Further, since the present invention relates to focus adjustment, an example in which a peripheral light receiving surface is simply provided on the outer periphery of the center light receiving surface for simplification of description and circuit configuration has been described, but these detectors are used for focusing control. In addition, it is generally used for tracking control or the like. In such a case, the center light receiving surface or the peripheral light receiving surface is generally divided into two right and left sides, and tracking control is performed with a left / right light amount ratio. When the center light receiving surface and the peripheral light receiving surface are divided into two in this way, the present invention can be applied as it is by adding an adding circuit for adding the left and right light receiving amounts to the stage preceding the circuit shown in FIG. can do.
以上説明した様に，本発明によれば焦点位置の前後に
配置された２系統のディテクタに対する入射光量に不均
衡が生じていたとしても合焦点においてはフォーカスエ
ラー信号から入射光量の不均衡は除去されることにな
り，対物レンズは入射光量の不均衡に関わりなく安定し
て合焦位置を追跡することが可能となる。 従って，本発明によれば,2系統のディテクタに分配さ
れる光量を調整するための1/2波長板の調整精度に対す
る要求も低くなり，その調整が容易になる。 又，クロストークも結果的にはグルーブに起因する入
射光量の不均衡と考えることができるので，クロストー
クによる焦点調整誤差も防止することができる。As described above, according to the present invention, the imbalance of the incident light amount is removed from the focus error signal at the in-focus point even if the incident light amount is imbalanced with respect to the two detectors arranged before and after the focal position. As a result, the objective lens can stably track the in-focus position regardless of the imbalance in the amount of incident light. Therefore, according to the present invention, the requirement for the adjustment accuracy of the half-wave plate for adjusting the amount of light distributed to the two detectors is reduced, and the adjustment is facilitated. In addition, since the crosstalk can be considered as an imbalance of the incident light amount resulting from the groove, a focus adjustment error due to the crosstalk can be prevented.
第１図は本発明の実施例に係る光ピックアップ装置の光
路を説明する図，第２図は上記光ピックアップ装置の斜
視図，第３図（Ａ）は第１図に示す光ピックアップ装置
のアクチュエータ部分の平面図，第３図（Ｂ）は第１図
に示す光ピックアップ装置のアクチュエータ部分の正面
図，第４図は本発明の実施例に係る光ピックアップ装置
のフォーカシングサーボ系の回路図，第５図（Ａ）はデ
ィスクが対物レンズの合焦位置にある時のディテクタ８
・９に対する投影パターンの説明図，第５図（Ｂ）はデ
ィスクが対物レンズの合焦位置よりも遠距離にある時の
ディテクタ８・９に対する投影パターンの説明図，第５
図（Ｃ）はディスクが対物レンズの合焦位置よりも近距
離にある時のディテクタ８・９に対する投影パターンの
説明図，第６図は従来の光ピックアップ装置のフォーカ
シングサーボ系の回路図。 １……半導体レーザ、２……コリメートレンズ ３……光学ブロック、Ｇ……ビームスプリッタ ４……対物レンズ、５……1/2波長板 ６……集光レンズ、７……ビームスプリッタ ８・９……ディテクタ、Ａ・Ｂ……中心受光面 Ａ′・Ｂ′……周辺受光面 14a……フォーカスコイル 15……アクチュエータ本体 19……ヨーク、20……マグネット 21・22・24……減算回路 23・25……加算回路、26……分圧器 30……ディスクFIG. 1 is a view for explaining an optical path of an optical pickup device according to an embodiment of the present invention, FIG. 2 is a perspective view of the optical pickup device, and FIG. 3 (A) is an actuator of the optical pickup device shown in FIG. FIG. 3B is a front view of an actuator portion of the optical pickup device shown in FIG. 1, FIG. 4 is a circuit diagram of a focusing servo system of the optical pickup device according to the embodiment of the present invention, and FIG. FIG. 5 (A) shows the detector 8 when the disc is at the in-focus position of the objective lens.
FIG. 5B is an explanatory view of a projection pattern for the detectors 8 and 9 when the disc is at a farther distance than the focus position of the objective lens, and FIG.
FIG. 6C is an explanatory diagram of a projection pattern on the detectors 8 and 9 when the disk is at a shorter distance than the focus position of the objective lens. FIG. 6 is a circuit diagram of a focusing servo system of the conventional optical pickup device. DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Collimating lens 3 ... Optical block, G ... Beam splitter 4 ... Objective lens, 5 ... 1/2 wavelength plate 6 ... Condensing lens, 7 ... Beam splitter 8. 9: Detector, AB: Central light receiving surface A ', B': Peripheral light receiving surface 14a: Focus coil 15: Actuator body 19: Yoke, 20: Magnet 21, 22, 24 ... Subtraction Circuits 23 and 25: Addition circuit, 26: Voltage divider 30: Disk
フロントページの続き (72)発明者 高木 正明 東京都板橋区志村２の16の20 株式会社 コパル内 (56)参考文献 特開 昭61−156536（ＪＰ，Ａ) 特開 昭60−93044（ＪＰ，Ａ) 特開 昭59−56234（ＪＰ，Ａ)Continuation of front page (72) Inventor Masaaki Takagi 16-20, Shimura 2 Itabashi-ku, Tokyo Copal Inc. (56) References JP-A-61-156536 (JP, A) JP-A-60-93044 (JP, A) JP-A-59-56234 (JP, A)
Claims (2)
体上に集光され，該記録媒体上で反射された光を前記対
物レンズと集光レンズと光分波器を介して２系統の焦点
に収束させ，該２系統の焦点の前方及び後方に各々２系
統の光検出器を配設し，該２系統の光検出器の出力偏差
により前記対物レンズをサーボ制御する様にした光ピッ
クアップ装置の焦点調整装置において， 前記２系統の各々の光検出器は，その光軸を中心として
前記集光レンズによって照射される光束スポットよりも
小さい面積の中心受光面と，該中心受光面の周囲にあっ
て該中心受光面を含めた面積が前記光束スポットよりも
大きい面積となる周辺受光面とを有するとともに， 一方の系統の光検出器の中心受光面と周辺受光面の総受
光量と他方の系統の光検出器の中心受光面と周辺受光面
の総受光量の差に合焦点における総受光量に対する中心
受光量の成分比を乗じた値を補正値として算出する手段
を備え， 前記各々の系統の光検出器の中心受光量偏差から前記算
出された補正値を減じた値をフォーカスエラー信号と
し，該フォーカスエラー信号が０に収束する様に前記対
物レンズをサーボ制御する様にしたことを特徴とする光
ピックアップ装置の焦点調整装置。1. An optical system according to claim 1, wherein said light is focused on a recording medium by a focus-adjustable objective lens and reflected by said recording medium to two focal points via said objective lens, condenser lens and optical demultiplexer. An optical pickup device which converges, and two optical detectors are respectively disposed in front of and behind the two focal points, and the objective lens is servo-controlled by an output deviation of the two optical detectors. In the focus adjusting device, each of the two photodetectors has a center light receiving surface having an area smaller than a light beam spot irradiated by the condensing lens around the optical axis thereof, and a photodetector around the center light receiving surface. And a peripheral light receiving surface whose area including the central light receiving surface is larger than the light beam spot, and the total light receiving amount of the central light receiving surface and the peripheral light receiving surface of the photodetector of one system and the other system. Photodetector core Means for calculating, as a correction value, a value obtained by multiplying a difference between a total light receiving amount of the light receiving surface and a peripheral light receiving surface by a component ratio of the central light receiving amount to the total light receiving amount at the focal point; A value obtained by subtracting the calculated correction value from the received light amount deviation is used as a focus error signal, and the objective lens is servo-controlled so that the focus error signal converges to zero. Focus adjustment device.
プ装置の焦点調整装置において， 前記２系統の光検出器を各々の系統の焦点の前方及び後
方に等距離離反させて配置するとともに， 各々の系統の光検出器は同一形状の中心受光面と周辺受
光面とを有することを特徴とする光ピックアップ装置の
焦点調整装置。2. A focus adjusting device for an optical pickup device according to claim 1, wherein said two systems of photodetectors are arranged equidistantly in front of and behind a focal point of each system. A focus adjusting device for an optical pickup device, wherein each of the photodetectors has a central light receiving surface and a peripheral light receiving surface having the same shape.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27206689A JP2711474B2 (en) | 1989-10-19 | 1989-10-19 | Focus adjustment device for optical pickup device |
| US07/689,282 US5200942A (en) | 1989-10-14 | 1990-10-15 | Focus adjusting apparatus for an optical pickup apparatus |
| DE69024635T DE69024635T2 (en) | 1989-10-14 | 1990-10-15 | Optical scanning unit with focus adjustment arrangement |
| PCT/JP1990/001325 WO1991006097A1 (en) | 1989-10-14 | 1990-10-15 | Device for adjusting focal point of an optical pickup device |
| EP90914962A EP0454854B1 (en) | 1989-10-14 | 1990-10-15 | Optical pickup apparatus comprising a focus adjusting apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27206689A JP2711474B2 (en) | 1989-10-19 | 1989-10-19 | Focus adjustment device for optical pickup device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03132928A JPH03132928A (en) | 1991-06-06 |
| JP2711474B2 true JP2711474B2 (en) | 1998-02-10 |
Family
ID=17508622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27206689A Expired - Lifetime JP2711474B2 (en) | 1989-10-14 | 1989-10-19 | Focus adjustment device for optical pickup device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2711474B2 (en) |
-
1989
- 1989-10-19 JP JP27206689A patent/JP2711474B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03132928A (en) | 1991-06-06 |
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