JPH0337837A - Tilt detector for optical disk - Google Patents
Tilt detector for optical diskInfo
- Publication number
- JPH0337837A JPH0337837A JP17275389A JP17275389A JPH0337837A JP H0337837 A JPH0337837 A JP H0337837A JP 17275389 A JP17275389 A JP 17275389A JP 17275389 A JP17275389 A JP 17275389A JP H0337837 A JPH0337837 A JP H0337837A
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- Prior art keywords
- tilt
- light
- disk
- diffraction grating
- optical
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- 230000015572 biosynthetic process Effects 0.000 abstract description 5
- 238000010586 diagram Methods 0.000 description 4
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Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
この発明は、CD(コンパクト・ディスク)LD(レー
ザ・ビジョン・ディスク)等の光デイスク装置において
、チルトエラー(ディスク面に対する光ヘツド光軸の傾
き)を検出するためのチルト検出装置に関し、簡易な構
成でチルトエラ検出を実現したものである。Detailed Description of the Invention [Field of Industrial Application] The present invention is aimed at preventing tilt errors (the optical axis of the optical head relative to the disk surface) in optical disk devices such as CDs (compact discs) and LDs (laser vision discs). The present invention relates to a tilt detection device for detecting tilt errors, and achieves tilt error detection with a simple configuration.
CDプレーヤやLVプレーヤ等の光デイスク装置におい
ては、光ヘッドの対物レンズの中心輔はディスクに対し
て垂直となるように設計されている。ところがディスク
が傘形に反っているような場合には、たとえその量がわ
ずかであってももはやディスクと対物レンズの関係は垂
直ではなくなり、光ヘッドの信号読取り性能に重大な影
響(クロストーク妨害等)を与えてしまう。In optical disc devices such as CD players and LV players, the center of the objective lens of the optical head is designed to be perpendicular to the disc. However, if the disk is warped into an umbrella shape, even if the amount is small, the relationship between the disk and the objective lens is no longer perpendicular, which has a serious effect on the signal reading performance of the optical head (crosstalk interference). etc.).
このような不都合を防止するために、チルトサーボを設
けて光ヘツド全体の傾きを調整するようにしている。従
来のチルトサーボにおいては、チルトエラーを検出する
ために第2図に示すようなチルトセンサ10を光ヘッド
に取り付けていた。In order to prevent such inconveniences, a tilt servo is provided to adjust the tilt of the entire optical head. In the conventional tilt servo, a tilt sensor 10 as shown in FIG. 2 is attached to the optical head in order to detect tilt errors.
このチルトセンサ10はLED12から放射される光線
をディスク18に照射して、その反射光をLED12の
両側部に設けたフォトダイオード16で受光するように
構成されている。ディスク18に対して光ヘツド光軸に
傾きがない場合はフォトダイオード14.16の受光量
は等しいが、傾きがあると受光量に差か生じる。そこで
、この差に応じて光ヘッドのチルト角を制御することに
より、光ヘツド光軸を常にディスク面に対して垂直に保
つようにしている。The tilt sensor 10 is configured to irradiate a disk 18 with light rays emitted from an LED 12 and to receive the reflected light by photodiodes 16 provided on both sides of the LED 12. If the optical axis of the optical head is not tilted with respect to the disk 18, the amounts of light received by the photodiodes 14 and 16 are the same, but if there is a tilt, there will be a difference in the amount of light received. Therefore, by controlling the tilt angle of the optical head according to this difference, the optical axis of the optical head is always kept perpendicular to the disk surface.
前記従来のチルト検出装置によれば、光ディスクの信号
検出光学系とは別に第2図のチルトセンサ10を設けな
ければならないので、部品点数が増え、光ヘッドの小型
軽量化に不利であった。According to the conventional tilt detection device, the tilt sensor 10 shown in FIG. 2 must be provided separately from the optical disk signal detection optical system, which increases the number of parts and is disadvantageous in reducing the size and weight of the optical head.
二の発明は、従来の技術におけるこのような問題点を解
決して、簡易な構成でチルト検出を実現して光ヘッドの
小型軽量化を図った光ディスクのチルト検出装置を提供
しようとするものである。The second invention aims to solve these problems in the conventional technology and provide an optical disc tilt detection device that achieves tilt detection with a simple configuration and reduces the size and weight of the optical head. be.
この発明は、光ディスクの信号検出光学系に設けられて
ディスク径方向に回折光を形成させてディスク面に照射
させるチルトビーム形成用回折格子と、この回折光のデ
ィスク反射光を検出するチルト用受光素子と、このチル
ト用受光素子の検出出力に基づいてチルトエラーを検出
するチルトエラー検出手段とを具備してなるものである
。This invention relates to a tilt beam forming diffraction grating that is provided in a signal detection optical system of an optical disk and forms diffracted light in the disk radial direction and irradiates the disk surface with the diffraction grating, and a tilt light receiving device that detects the disk reflected light of the diffracted light. The device includes a tilt error detection means for detecting a tilt error based on the detection output of the tilt light receiving element.
この発明によれば、信号検出用ビームはチルトビーム形
成用回折格子に入射されて、ディスク径方向に回折光が
形成され、この回折光はチルトビームとしてディスク面
に照射される。そして、その反射光はチルト受光素子に
受光されて、この受光素子の検出出力に基づいてチルト
エラー検出手段でチルトエラーが検出される。According to this invention, the signal detection beam is incident on the tilt beam forming diffraction grating to form diffracted light in the disk radial direction, and this diffracted light is irradiated onto the disk surface as a tilt beam. Then, the reflected light is received by the tilt light receiving element, and a tilt error is detected by the tilt error detection means based on the detection output of the light receiving element.
これによれば、光ディスクの信号検出光学系にチルトビ
ーム形成用回折格子を設けて回折光を形成して、この回
折光をチルトビームとしてチルト検出に用いるようにし
たので、チルトビームを形成するためのLED等の手段
は不要となり、構成を簡略化して、光ヘッドの小型軽量
化を図ることができる。According to this, a diffraction grating for forming a tilt beam is provided in the signal detection optical system of an optical disk to form a diffracted light, and this diffracted light is used as a tilt beam for tilt detection. This eliminates the need for means such as LEDs, simplifies the configuration, and allows the optical head to be made smaller and lighter.
この発明の一実施例を第1図に示す。光ヘツド20にお
いて、レーザダイオード22から発射されたレーザビー
ム24は、トラッキングビーム形成用回折格子26に入
射されて、トラッキングビームが形成される。回折格子
26から出力される0次光はさらにチルトビーム形成用
回折格子28に入射されてチルトビームが形成される。An embodiment of this invention is shown in FIG. In the optical head 20, a laser beam 24 emitted from a laser diode 22 is incident on a tracking beam forming diffraction grating 26 to form a tracking beam. The zero-order light output from the diffraction grating 26 is further incident on the tilt beam forming diffraction grating 28 to form a tilt beam.
チルトビーム形成用回折格子28の格子パターンはトラ
ッキングビーム形成用回折格子26の格子パターンに対
して直角に形成されている。これら回折格子26.28
はそれぞれ単体のものを格子パターンを直角にして配置
するほか、第3図に示すように平板状のガラス体27の
表面、裏面に回折格子26.28をそれぞれ形成して一
体構成とすることもできる。The grating pattern of the tilt beam forming diffraction grating 28 is formed at right angles to the grating pattern of the tracking beam forming diffraction grating 26. These diffraction gratings 26.28
In addition to arranging individual gratings with their grating patterns at right angles, it is also possible to form an integral structure by forming diffraction gratings 26 and 28 on the front and back surfaces of a flat glass body 27, respectively, as shown in FIG. can.
チルト形成用回折格子28は光ビームが通過できる大き
さがあれはよく、2つの回折格子26゜28の格子パタ
ーンはディスク上でのビームスポットの間隔が情報読取
用ビームスポットに対してそれぞれ20〜30μm程度
になるように調整される。The tilt-forming diffraction grating 28 has a size that allows the light beam to pass through, and the grating patterns of the two diffraction gratings 26 and 28 have a beam spot interval on the disk of 20 to 20 degrees with respect to the information reading beam spot. The thickness is adjusted to about 30 μm.
回折格子26.28の格子パターンは、例えば第4図に
示すように平板状ガラス体2つに凹凸を形成した体積位
相形として溝底することができる。The grating pattern of the diffraction gratings 26 and 28 can be formed into a volume phase type groove in which irregularities are formed on two flat glass bodies, as shown in FIG. 4, for example.
格子のピッチは対物レンズ34およびコリメータレンズ
32の黒点距離、レーザダイオード使用波長、回折格子
26.28と発光点との間隔などにもよるが、使用波長
を0.78μmとすると、20μm前後である。また凹
凸のデユーティはa:b−1: 1前後である。The pitch of the grating depends on the sunspot distance of the objective lens 34 and collimator lens 32, the wavelength used by the laser diode, the distance between the diffraction grating 26, 28 and the light emitting point, etc., but if the wavelength used is 0.78 μm, it is around 20 μm. . Further, the duty of the unevenness is approximately a:b-1:1.
回折格子26.28で形成される回折光を第1図中に拡
大して示す。回折格子26の1次光が回折格子28で再
び回折した時の0次光を“0〜0”で示す。同様に回折
格子26の+1次光、−1次光が回折格子28で再び回
折したときの0次光(トラッキングビーム)をそれぞれ
“+1−0”“−1−0”で示す。また、回折格子26
の0次光が回折格子28で回折したときの+1次光。The diffracted light formed by the diffraction gratings 26 and 28 is shown enlarged in FIG. The zero-order light when the first-order light of the diffraction grating 26 is diffracted again by the diffraction grating 28 is indicated by "0-0". Similarly, the 0th order light (tracking beam) when the +1st order light and the -1st order light of the diffraction grating 26 are diffracted again by the diffraction grating 28 are shown as "+1-0" and "-1-0", respectively. In addition, the diffraction grating 26
+1st order light when the 0th order light of is diffracted by the diffraction grating 28.
1次光(チルトビーム)をそれぞれ“0−+1”“0−
−1°で示す。The primary light (tilt beam) is "0-+1" and "0-" respectively.
Shown at -1°.
回折格子26.28から出力される上記ビーム群は、信
号検出光学系を構成するハーフミラ−30、コリメータ
レンズ32、対物レンズ34を介してディスク18の記
録面に照射される。ディスク18の記録面に対するビー
ム群の照射状況を第1図に拡大して示す。0−0次光は
情報読取ビームとして記録トラック上に照射される。+
10次光、−1−0次光はトラッキングビームとして0
−0次光の前後位置で記録トラック中央から左右に少し
外れて照射される。O−+1次光、01次光はチルトビ
ームとして0−50次光の左右位置でディスク18のラ
ジアル方向の位置に照射される。0−0次光とO−+1
次光、0−−1次光とのビームスポット間距離は例えば
20〜30μm程度にそれぞれ設定されている。The beam group outputted from the diffraction gratings 26 and 28 is irradiated onto the recording surface of the disk 18 via a half mirror 30, a collimator lens 32, and an objective lens 34, which constitute a signal detection optical system. The state of irradiation of the beam group onto the recording surface of the disk 18 is shown in an enlarged scale in FIG. The 0-0 order light is irradiated onto the recording track as an information reading beam. +
The 10th order light, -1-0th order light is 0 as a tracking beam.
The light is irradiated at the front and back positions of the -0th-order light slightly to the left and right from the center of the recording track. The O-+ first-order light and the 01-order light are irradiated as tilt beams onto positions in the radial direction of the disk 18 at the left and right positions of the 0-50th order light. 0-0 order light and O-+1
The distance between the beam spots of the order light and the 0th to 1st order light is set, for example, to about 20 to 30 μm.
ディスク18からの反射光は対物レンズ34およびコリ
メータレンズ32を介してハーフミラ−30で反射され
て8分割受光素子36に入射される。8分割受光素子・
36は中央に情報信号読取用およびフォーカス制御用に
4分割受光素子a−dが配され、これを挟んで接線方向
にトラッキング用受光素子e、fが配され、ラジアル方
向にチルト用受光素子g、hが配されている。この8分
割受光素子は、同一基板上に構成されている。4分割受
光素子a −dには0−0次光のディスク反射光が受光
される。トラッキング用受光素子e、 fには+1−
0次光、−1−0次光のディスク反114光がそれぞれ
受光される。チルト用受光素子g。The reflected light from the disk 18 passes through the objective lens 34 and the collimator lens 32, is reflected by the half mirror 30, and enters the eight-divided light receiving element 36. 8 division light receiving element・
In 36, four-divided light receiving elements a to d are arranged in the center for information signal reading and focus control, tracking light receiving elements e and f are arranged tangentially across this, and a tilting light receiving element g is arranged in the radial direction. , h are arranged. These eight-divided light receiving elements are constructed on the same substrate. The 0-0 order light reflected from the disc is received by the four-divided light receiving elements a to d. +1- for tracking light receiving elements e and f
The 0th-order light and the -1-0th order light beams opposite the disk are each received. Tilt light receiving element g.
hには0−+1次光、0−−1次光のディスク反射光が
それぞれ受光される。The disk reflected light of the 0-+1st order light and the 0--1st order light are received at h.
8分割受光素子36の受光信号の信号処理回路を第5図
に示す。4分割受光素子a −dの受光信号は対角線位
置のものどうしが加算器40.42で加算される。加算
出力はさらに加算器44で加算されてHF信号が得られ
、情報再生に利用される。また、上記加算出力は引算器
46で引算されて、フォーカスエラー検出信号が得られ
、フォーカスサーボに利用される。FIG. 5 shows a signal processing circuit for the light-receiving signal of the eight-divided light-receiving element 36. The light-receiving signals of the four-divided light-receiving elements a to d at diagonal positions are added by adders 40 and 42. The addition outputs are further added in an adder 44 to obtain an HF signal, which is used for information reproduction. Further, the above addition output is subtracted by a subtracter 46 to obtain a focus error detection signal, which is used for focus servo.
トラッキング用受光素子e、fの受光信号は引算器48
で引算されて、トラッキングエラー検出信号が得られ、
トラッキングサーボに利用される。The light reception signals of the tracking light receiving elements e and f are sent to a subtracter 48.
The tracking error detection signal is obtained by subtracting
Used for tracking servo.
チルト用受光素子g、hの受光信号は引算器50で引算
されて、チルトエラー検出信号が得られ、チルトサーボ
に利用される。The light reception signals of the tilt light receiving elements g and h are subtracted by a subtracter 50 to obtain a tilt error detection signal, which is used for tilt servo.
第1図の装置によるチルトエラー検出動作について第6
図を参照して説明する。光ヘツド20の光軸(0−0次
光の光軸)がディスク18の記録面に対して垂直で傾き
がない場合は、0−0次光(1?を粗読取ビーム)と〇
−+1次光、0−−1次光(チルトビーム)は第6図(
a)に示すようにディスク18の記録面に照射される(
ビームスポット間隔は20〜30μm程度)。このとき
、ディスク18からのチルトビームの反射光は第6図(
b)に点線で示すようになり、斜線で示した部分が反射
光としてそれぞれ受光素子g、hに受光される(斜線の
外側の部分は対物レンズ34の入#1@から外れるので
受光されない)。光ヘツド20の光軸がディスク18の
記録面に対して垂直で傾きがない場合は、斜線で示した
2つの部分の面積は等しいので、受光素子g、hの受光
量は等しく、第5図の引算器50から出力されるチルト
エラー検出信号のレベルは零となる。Regarding the tilt error detection operation by the device shown in Figure 1, Section 6
This will be explained with reference to the figures. If the optical axis of the optical head 20 (the optical axis of the 0-0th order light) is perpendicular to the recording surface of the disk 18 and has no inclination, the 0-0th order light (1? is the coarse reading beam) and the 0-+1 The order light, 0--first order light (tilt beam) is shown in Figure 6 (
As shown in a), the recording surface of the disk 18 is irradiated with light (
The beam spot interval is about 20 to 30 μm). At this time, the reflected light of the tilt beam from the disk 18 is shown in FIG.
The light is now shown by the dotted line in b), and the shaded portions are received as reflected light by the light receiving elements g and h, respectively (the portions outside the shaded areas are not received because they are outside the #1@ of the objective lens 34). . If the optical axis of the optical head 20 is perpendicular to the recording surface of the disk 18 and is not tilted, the areas of the two shaded areas are equal, so the amount of light received by the light receiving elements g and h is equal, as shown in FIG. The level of the tilt error detection signal output from the subtracter 50 becomes zero.
これに対して、光ヘツド20光輔がディスク18の記録
面に対して垂直からずれると、チルトビームの反射光は
第6図(c)に点線で示すようになり、斜線で示した2
つの部分の面積が一方は増大し、他方は減少する。この
ため、受光素子ghの受光量がアンバランスとなり、第
5図の引算器50からその差に応じたチルトエラー険出
信号が出力される。チルトサーボはこのチルトエラー検
出信号が零になるように動作して、光ヘツド光軸がディ
スク面に垂直になるように制御する。傾きの方向が逆に
なった場合には、チルトエラー検出信号の極性が反転し
て、やはり光ヘツド光軸がディスク面に垂直になるよう
に制御される。On the other hand, when the optical head 20 is deviated from perpendicular to the recording surface of the disk 18, the reflected light of the tilt beam becomes as shown by the dotted line in FIG.
The area of the two parts increases on one side and decreases on the other. As a result, the amount of light received by the light receiving element gh becomes unbalanced, and the subtracter 50 in FIG. 5 outputs a tilt error detection signal corresponding to the difference. The tilt servo operates so that this tilt error detection signal becomes zero, and controls the optical axis of the optical head to be perpendicular to the disk surface. If the direction of the tilt is reversed, the polarity of the tilt error detection signal is reversed, and the optical axis of the optical head is controlled to be perpendicular to the disk surface.
なお、隣接するトラックビット等によるそれぞれのチル
トビームの反射光量への影響は、次のような理由から実
用上は全く問題のない程度となる。Note that the influence of adjacent track bits on the amount of reflected light of each tilt beam is of a level that poses no problem in practice for the following reasons.
まず所定のトラックに位置合せされているメインビーム
に対しチルトビームは、左右双方へ対称に照射されてお
り、これらチルトビームの一方がトラック上にあり、他
方が全くトラック以外に位置するというような状況はあ
り得ず、これらにもとづく大きな非対称性は生じない。First, the tilt beams are radiated symmetrically to both the left and right sides of the main beam, which is aligned to a predetermined track, and one of these tilt beams is on the track, and the other is located completely outside the track. There are no such situations, and no major asymmetries arise based on them.
次に各チルトビーム照射位置におけるトラックビット等
の個々の変化の相違であるが、これはチルト検出制御の
時定数が一般に数秒〜数十秒と遅いため、チルト検出光
量を充分に積分することが可能となり、もってこれら個
々のトラックビット相違は充分回避できるのである。Next, there are differences in individual changes in track bits, etc. at each tilt beam irradiation position, but this is because the time constant of tilt detection control is generally slow, ranging from several seconds to several tens of seconds, making it difficult to sufficiently integrate the amount of tilt detection light. This makes it possible to completely avoid these individual track bit differences.
前記実施例では、トラッキングビーム形成用回折格子2
6の後にチルトビーム形成用回折格子28を配置したが
、この逆であってもよい。In the above embodiment, the tracking beam forming diffraction grating 2
Although the tilt beam forming diffraction grating 28 is disposed after the tilt beam forming grating 28, the opposite may be used.
また、この発明が適用される信号検出光学系の配置は、
第1図のものに限らず各種配置に適用することができる
。Furthermore, the arrangement of the signal detection optical system to which this invention is applied is as follows:
The arrangement is not limited to that shown in FIG. 1, and can be applied to various arrangements.
また、この発明は、3ビ一ム方式以外の光ヘッドにも適
用することができる。Further, the present invention can be applied to optical heads other than the 3-beam type.
以上説明したように、光ディスクの信号検出光学系にチ
ルトビーム形成用回折格子を設けて回折光を形成して、
この回折光をチルトビームとしてチルト検出に用いるよ
うにしたので、チルトビームを形成するためのLED等
の手段は不要となり、構成を簡略化して、光ヘッドの小
型軽量化を図ることができる。As explained above, a tilt beam forming diffraction grating is provided in the optical disc signal detection optical system to form diffracted light.
Since this diffracted light is used as a tilt beam for tilt detection, means such as an LED for forming a tilt beam are not required, and the configuration can be simplified and the optical head can be made smaller and lighter.
第1図は、この発明の一実施例を示す図で、光ヘツド内
の構成例を示す図である。
第2図は、従来のチルトセンサを示す正面図および平面
図である。
第3図は、第1図における回折格子26.28の構成例
を示す斜視図である。
第4図は、回折格子26.28の格子パターン例を示す
斜視図である。
第5図は、第1図の8分割受光素子36の受光信号の信
号処理回路構成例を示すブロック図である。
第6図は、第1図の装置によるチルトエラー検出動作を
示す図である。
]8・・・光ディスク、20・・・光ヘッド、28・・
・チルトビーム形成用回折格子、36・・・8分割受光
素子、a −d・・・情報読取およびフォーカス用受光
素子、e、f・・・トラッキング用受光素子、g、h・
・・チルト用受光素子、
O・・・引算器
(チルトエラー
検出手段)FIG. 1 is a diagram showing an embodiment of the present invention, and is a diagram showing an example of the configuration inside an optical head. FIG. 2 is a front view and a plan view showing a conventional tilt sensor. FIG. 3 is a perspective view showing an example of the configuration of the diffraction gratings 26, 28 in FIG. 1. FIG. 4 is a perspective view showing an example of the grating pattern of the diffraction gratings 26, 28. FIG. 5 is a block diagram showing an example of the configuration of a signal processing circuit for a light reception signal of the eight-divided light receiving element 36 of FIG. FIG. 6 is a diagram showing a tilt error detection operation by the apparatus of FIG. 1. ]8... Optical disk, 20... Optical head, 28...
- Diffraction grating for tilt beam formation, 36... 8-division light receiving element, a - d... Light receiving element for information reading and focusing, e, f... Light receiving element for tracking, g, h.
...Tilt light receiving element, O...Subtractor (tilt error detection means)
Claims (2)
ク径方向に回折光を形成させてディスク面に照射させる
チルトビーム形成用回折格子と、この回折光のディスク
反射光を検出するチルト用受光素子と、このチルト用受
光素子の検出出力に基づいてチルトエラーを検出するチ
ルトエラー検出手段とを具備してなる光ディスクのチル
ト検出装置。(1) A tilt beam forming diffraction grating that is installed in the signal detection optical system of the optical disc and forms diffracted light in the disc radial direction and irradiates it onto the disc surface, and a tilt light receiving element that detects the disc reflected light of this diffracted light. and tilt error detection means for detecting a tilt error based on the detection output of the tilt light receiving element.
であり、前記チルトビーム形成用回折格子がトラッキン
グビーム形成用回折格子に対して格子パターンが略々直
角方向に形成され、前記チルト用受光素子がトラッキン
グ用受光素子の配列方向に対して略々直角方向に2素子
で配列されて、4素子の情報読取およびフォーカス用受
光素子および2素子のトラッキング用受光素子とともに
合計8分割の受光素子として同一基板上に配列されてな
る請求項1記載の光ディスクのチルト検出装置。(2) The signal detection optical system of the optical disk is of a three-beam type, the grating pattern of the tilt beam forming diffraction grating is formed in a direction substantially perpendicular to the tracking beam forming diffraction grating, and the tilt light receiving element are arranged in two elements in a direction substantially perpendicular to the arrangement direction of the tracking light-receiving elements, and together with the four information reading and focusing light-receiving elements and the two tracking light-receiving elements, the same light-receiving element is divided into eight parts in total. 2. The optical disk tilt detecting device according to claim 1, wherein the optical disc tilt detecting device is arranged on a substrate.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP17275389A JPH0337837A (en) | 1989-07-04 | 1989-07-04 | Tilt detector for optical disk |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP17275389A JPH0337837A (en) | 1989-07-04 | 1989-07-04 | Tilt detector for optical disk |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH0337837A true JPH0337837A (en) | 1991-02-19 |
Family
ID=15947687
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP17275389A Pending JPH0337837A (en) | 1989-07-04 | 1989-07-04 | Tilt detector for optical disk |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0337837A (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07153104A (en) * | 1993-11-26 | 1995-06-16 | Victor Co Of Japan Ltd | Optical pickup and optical disk device |
US5751680A (en) * | 1995-12-13 | 1998-05-12 | Hitachi, Ltd. | Optical disk drive |
WO2004070716A1 (en) * | 2003-02-10 | 2004-08-19 | Sharp Kabushiki Kaisha | Optical pickup device |
US7577076B2 (en) | 2003-03-14 | 2009-08-18 | Ricoh Company, Ltd. | Tilt sensor using diffraction grating |
US7755991B2 (en) | 2002-05-23 | 2010-07-13 | Nec Corporation | Method for detecting radial tilt of optical recording medium in optical head device, optical head device, and optical information recording/reproducing device |
-
1989
- 1989-07-04 JP JP17275389A patent/JPH0337837A/en active Pending
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07153104A (en) * | 1993-11-26 | 1995-06-16 | Victor Co Of Japan Ltd | Optical pickup and optical disk device |
US5751680A (en) * | 1995-12-13 | 1998-05-12 | Hitachi, Ltd. | Optical disk drive |
US7755991B2 (en) | 2002-05-23 | 2010-07-13 | Nec Corporation | Method for detecting radial tilt of optical recording medium in optical head device, optical head device, and optical information recording/reproducing device |
WO2004070716A1 (en) * | 2003-02-10 | 2004-08-19 | Sharp Kabushiki Kaisha | Optical pickup device |
US7577076B2 (en) | 2003-03-14 | 2009-08-18 | Ricoh Company, Ltd. | Tilt sensor using diffraction grating |
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