JPH05342676A - Test device for magnetic-optical disk - Google Patents
Test device for magnetic-optical diskInfo
- Publication number
- JPH05342676A JPH05342676A JP16819892A JP16819892A JPH05342676A JP H05342676 A JPH05342676 A JP H05342676A JP 16819892 A JP16819892 A JP 16819892A JP 16819892 A JP16819892 A JP 16819892A JP H05342676 A JPH05342676 A JP H05342676A
- Authority
- JP
- Japan
- Prior art keywords
- magneto
- optical
- phase difference
- optical disk
- signal
- 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.)
- Pending
Links
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、磁気光学効果を利用し
て記録媒体に情報を記録、再生する光磁気ディスク内に
存在する局所的な複屈折の異常、異物の存在による反射
光量の変化、等を検出するのに好適な検査装置に関し、
特に位相差の変化から欠陥を検出する光磁気ディスク検
査装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local birefringence abnormality existing in a magneto-optical disk for recording and reproducing information on a recording medium by utilizing a magneto-optical effect, and a change in reflected light quantity due to the presence of foreign matter. Regarding inspection equipment suitable for detecting,
In particular, the present invention relates to a magneto-optical disk inspection apparatus that detects defects from changes in phase difference.
【０００２】[0002]
【従来の技術】製品レベルの光磁気ディスクの欠陥等の
検査装置としては、ディスクドライブ装置を用いて、信
号未記録状態のディスクの記録領域をトレースし、ディ
スクの反射率の変化により欠陥等の異常部を検出するも
の、あるいはディスクに光磁気信号を記録し、記録した
信号を再生、２値化して異常の有無を判定するもの等が
ある。また、ディスク基板の複屈折や光磁気膜の局所的
な異常に起因する位相差の変化を検出する装置としては
偏光状態の変化を検出する種々の位相差測定装置が用い
られる。2. Description of the Related Art A disk drive device is used as a device for inspecting defects of a magneto-optical disk at a product level, and a recording area of a disk in which a signal is not recorded is traced to detect defects such as a change in reflectance of the disk. There is a method of detecting an abnormal portion, or a method of recording a magneto-optical signal on a disc and reproducing the recorded signal and binarizing the signal to determine whether or not there is an abnormality. Further, as a device for detecting a change in phase difference due to birefringence of a disk substrate or a local abnormality in a magneto-optical film, various phase difference measuring devices for detecting a change in polarization state are used.
【０００３】図５は従来の位相差測定装置の一例を示す
構成図である。図中、６１で示される半導体レーザから
出射した直線偏光状態の光束はコリメーターレンズ６２
で平行光化された後、ビーム整形プリズム６３、ビーム
スプリッタ６４、ビームスプリッタ６５を経て対物レン
ズ６６で光磁気ディスク６７の媒体面に絞り込まれる。
媒体面で反射した光束は、対物レンズ６６を通り、ビー
ムスプリッタ６５でその一部が反射され、１／２波長板
６８及び位相補償板６９を通過した後、集光レンズ７０
を経て偏光ビームスプリッタ７１で互いに直交する２つ
の偏光光束に分離し夫々検出器７２，７３に入る。１／
２波長板６８は通過する直線偏光光束の偏光面を偏光ビ
ームスプリッタ７１の入射面に対し４５°回転させる方
位に設置する。位相補償板６９には、バビネソレイユの
補償板が一般に用いられる。媒体面で反射した光束のう
ちビームスプリッタ６５を透過した光束は、ビームスプ
リッタ６４で反射され、集光レンズ７４を経て検出器７
５に至る。検出器７５はサーボ信号を検出するための検
出器であり、ここから得られた信号を用いて対物レンズ
６６で絞り込まれた光束を光磁気ディスク６７の媒体面
に合焦させ、またトラッキング制御を行なう。FIG. 5 is a block diagram showing an example of a conventional phase difference measuring apparatus. In the figure, a linearly polarized light beam emitted from the semiconductor laser denoted by 61 is a collimator lens 62.
After being collimated by the laser beam, the beam is passed through the beam shaping prism 63, the beam splitter 64, and the beam splitter 65, and then narrowed down to the medium surface of the magneto-optical disk 67 by the objective lens 66.
The light flux reflected by the medium surface passes through the objective lens 66, a part of it is reflected by the beam splitter 65, and after passing through the ½ wavelength plate 68 and the phase compensation plate 69, the condenser lens 70.
Then, the polarized beam splitter 71 separates the two polarized light beams orthogonal to each other and enters the detectors 72 and 73, respectively. 1 /
The two-wave plate 68 is installed in a direction in which the plane of polarization of the linearly polarized light passing therethrough is rotated by 45 ° with respect to the plane of incidence of the polarization beam splitter 71. A Babinet Soleil compensator is generally used as the phase compensator 69. Of the light flux reflected by the medium surface, the light flux transmitted through the beam splitter 65 is reflected by the beam splitter 64, passes through the condenser lens 74, and then the detector 7
Up to 5. The detector 75 is a detector for detecting a servo signal, and uses the signal obtained from the detector 75 to focus the light flux narrowed down by the objective lens 66 on the medium surface of the magneto-optical disk 67 and to perform tracking control. To do.
【０００４】この装置を用いて光磁気ディスクの位相差
を測定するには、一定の周波数の信号を記録した被測定
ディスクから得られる、差動増幅器７６の出力としての
光磁気信号の振幅をモニターしながら、位相補償器６９
を用いて位相を変化させる。被測定ディスクによって発
生した位相差が位相補償器６９で打消された状態におい
て光磁気信号の振幅は最大になるので、このときの位相
補償器６９の補償量が被測定ディスクの位相差をあらわ
す。In order to measure the phase difference of a magneto-optical disk using this device, the amplitude of the magneto-optical signal as the output of the differential amplifier 76 obtained from the disk under test on which a signal of a constant frequency is recorded is monitored. Meanwhile, the phase compensator 69
Use to change the phase. Since the amplitude of the magneto-optical signal is maximized when the phase difference generated by the measured disk is canceled by the phase compensator 69, the compensation amount of the phase compensator 69 at this time represents the phase difference of the measured disk.
【０００５】また、図１０はバビネ・ソレイユ位相補償
器を用いた光磁気ディスクの位相差測定装置の概略を示
すものである。図１０に示すように、光磁気信号が記録
された光磁気ディスク８２にレーザ光を照射して光磁気
信号を再生する光学系の光路に、バビネ・ソレイユ位相
補償器９５を挿入して、光ビームに与える位相差を少し
づつ変化させながら光磁気信号の振幅変化を読み取り、
振幅が最大となる点の位相差を最小２乗法等の数値解析
手段により推定していた。FIG. 10 schematically shows a phase difference measuring device for a magneto-optical disk using a Babinet-Soleil phase compensator. As shown in FIG. 10, a Babinet-Soleil phase compensator 95 is inserted in the optical path of an optical system for reproducing a magneto-optical signal by irradiating the magneto-optical disk 82 on which the magneto-optical signal is recorded with laser light, Read the amplitude change of the magneto-optical signal while changing the phase difference given to the beam little by little,
The phase difference at the point where the amplitude is maximum is estimated by a numerical analysis means such as the least square method.
【０００６】[0006]
【発明が解決しようとしている課題】かかる従来技術に
おいて、反射率の変化のみで欠陥部を検出する装置で
は、異物等の反射光量を低下させる欠陥は検出できる
が、複屈折に起因する異常のような偏光状態の変化は検
出できない。また光磁気信号を再生、２値化する方法で
は単純な反射光量の変化と偏光状態の変化の区別がつか
ない。In such a prior art, a device for detecting a defective portion only by changing the reflectance can detect a defect such as a foreign substance that reduces the amount of reflected light, but it does not seem to be an abnormality caused by birefringence. No change in the polarization state can be detected. Further, in the method of reproducing and binarizing the magneto-optical signal, it is impossible to distinguish between a simple change in the amount of reflected light and a change in the polarization state.
【０００７】図５で説明した位相差測定装置を用いて偏
光状態の変化を検出する場合には、補償位置を検出する
ために補償器を用いて位相を変化させながら正常部と異
常部両方について多数回測定を行なう必要があり手間を
要するという問題がある。When detecting the change in the polarization state using the phase difference measuring device described in FIG. 5, both the normal part and the abnormal part are changed while changing the phase using the compensator to detect the compensation position. There is a problem that it is necessary to carry out the measurement a large number of times, which is troublesome.
【０００８】特に、従来例では、バビネ・ソレイユ位相
補償器を用いるため、次のような欠点があった。Particularly, in the conventional example, since the Babinet-Soleil phase compensator is used, there are the following drawbacks.
【０００９】（１）位相差を少しづつずらしながら光磁
気信号振幅を測定するため、測定点数が多く測定時間が
長かった。(1) Since the magneto-optical signal amplitude is measured while slightly shifting the phase difference, the number of measurement points is large and the measurement time is long.
【００１０】（２）位相差の変化が不連続なため、最小
２乗法等によって真値を推定しており、測定誤差が大き
かった。(2) Since the change in the phase difference is discontinuous, the true value is estimated by the method of least squares and the measurement error is large.
【００１１】（３）バビネ・ソレイユ位相補償器の寸法
が大きいため、装置全体が大がかりなものになってしま
っていた。(3) Due to the large size of the Babinet-Soleil phase compensator, the entire apparatus has become large-scale.
【００１２】また、従来の検出方法及び装置では、位相
差変化を与える手段が１つであるため、１つの再生信号
波形しか同時に得ることができない。そのため、信号振
幅の劣化がゴミ等の異物によって生じる反射率の低下で
あるのか、複屈折の異常によって生じる位相差変化を伴
う偏光状態の変化に起因するものであるのか判別するこ
とができないという解決すべき課題があった。Further, in the conventional detection method and apparatus, since there is only one means for giving the phase difference change, only one reproduced signal waveform can be obtained at the same time. Therefore, it is impossible to determine whether the deterioration of the signal amplitude is a decrease in reflectance caused by a foreign substance such as dust or a change in the polarization state accompanied by a phase difference change caused by an abnormality in birefringence. There was a task to be done.
【００１３】[0013]
【課題を解決するための手段】本発明は、上述した課題
を解決するため、所定の方向に偏光した光束を磁気的に
情報が記録された記録媒体上に照射し、磁気光学効果に
より前記情報に応じて偏光状態に変調を受けた前記媒体
からの反射又は透過光束を、互いに直交する方向に偏光
する２つの光束に分割し、該分割された２つの光束を夫
々検出手段で検出し、検出された信号の差動出力で光磁
気信号を検出する光磁気ディスクの検査装置において、
前記光束の通過する光路中に複数の異なる位相差変化を
与える手段を設け、該手段を介して得られた複数の異な
る位相差変化に対応する光磁気信号を演算処理すること
により前記記録媒体内の位相差変動及び欠陥を検出する
ことを特徴とする光磁気ディスク検査装置をその手段と
するものである。In order to solve the above problems, the present invention irradiates a recording medium on which information is magnetically recorded with a light beam polarized in a predetermined direction, and the information is recorded by a magneto-optical effect. The reflected or transmitted light beam from the medium whose polarization state has been modulated in accordance with the above is split into two light beams which are polarized in directions orthogonal to each other, and the two divided light beams are respectively detected by the detection means and detected. In the inspection device of the magneto-optical disk that detects the magneto-optical signal with the differential output of the signal,
In the recording medium, means for providing a plurality of different phase difference changes is provided in the optical path through which the light flux passes, and a magneto-optical signal corresponding to the plurality of different phase difference changes obtained through the means is arithmetically processed. The magneto-optical disk inspecting device is characterized by detecting the phase difference fluctuation and the defect.
【００１４】また、本発明によれば、位相板を光磁気信
号記録再生光学系の光路に挿入して、光磁気ディスクと
同時に回転させる手段を設けることにより、光ビーム
に、ディスクの回転に同期した連続的な位相差の変化を
与えるようにしたものである。Further, according to the present invention, by inserting a phase plate into the optical path of the magneto-optical signal recording / reproducing optical system and providing means for rotating the magneto-optical disk at the same time, the light beam is synchronized with the rotation of the disk. The continuous phase difference is continuously changed.
【作用】上記異なる複数の位相差を与えられた状態に対
して、局所的な複屈折の変化を有する箇所は、周囲の正
常部とは一定のずれをもって光磁気信号振幅が増減す
る。一方、単なる反射強度の低下をもたらす欠陥は、周
囲の正常部に対し常に一定の比率で振幅が低下する。従
ってこの２つの状態の信号振幅を比較演算することで欠
陥の弁別が可能となる。With respect to the above-mentioned state where a plurality of different phase differences are given, the amplitude of the magneto-optical signal increases and decreases at a portion having a local change in birefringence with a constant deviation from the surrounding normal portion. On the other hand, a defect that merely causes a decrease in reflection intensity has a constant decrease in amplitude with respect to the surrounding normal part. Therefore, the defect can be discriminated by comparing and calculating the signal amplitudes of these two states.
【００１５】[0015]
（実施例１）図１は本発明に用いられる検査装置の光学
系部の構成図をあらわす。図中、１は半導体レーザ、２
はコリメーターレンズ、３はビーム整形プリズム、４及
び５はビームスプリッタ、６は対物レンズ、７は被測定
物である光磁気ディスク、８は１／２波長板、９はビー
ムスプリッタ、１０及び１５は互いに異なる位相差を有
する位相板、１１及び１６は集光レンズ、１２及び１７
は偏光ビームスプリッタ、１３，１４，１８，１９は光
検出器、２０及び２１は検出器、をあらわす。(Embodiment 1) FIG. 1 shows a configuration diagram of an optical system portion of an inspection apparatus used in the present invention. In the figure, 1 is a semiconductor laser, 2
Is a collimator lens, 3 is a beam shaping prism, 4 and 5 are beam splitters, 6 is an objective lens, 7 is a magneto-optical disk which is an object to be measured, 8 is a half-wave plate, 9 is a beam splitter, and 10 and 15. Are phase plates having different phase differences from each other, 11 and 16 are condenser lenses, and 12 and 17
Is a polarization beam splitter, 13, 14, 18, and 19 are photodetectors, and 20 and 21 are detectors.
【００１６】図１において、半導体レーザ１から出射し
た光束が光磁気ディスク７に至り、該光磁気ディスクの
媒体面で反射された光束は、ビームスプリッタ５でその
一部が反射されて１／２波長板８に入射し、ビームスプ
リッタ５を透過した光束はビームスプリッタ４で反射さ
れて集光レンズ２２を経たのちサーボ信号検出用の検出
器２３に入射する。以上説明した部分は図５の従来例と
同様の構成及び機能を有するので更なる説明は省略す
る。In FIG. 1, the light flux emitted from the semiconductor laser 1 reaches the magneto-optical disk 7, and the light flux reflected by the medium surface of the magneto-optical disk is partially reflected by the beam splitter 5 to be 1/2. The light beam that has entered the wave plate 8 and transmitted through the beam splitter 5 is reflected by the beam splitter 4, passes through a condenser lens 22, and then enters a detector 23 for detecting a servo signal. The part described above has the same configuration and function as the conventional example of FIG.
【００１７】さて、１／２波長板８を通過した光束はビ
ームスプリッタ９によってほぼ等分に反射及び透過する
２つの光束に分割される。反射した光束は位相板１０の
作用により、互いに直交する偏光成分間に一定の位相
差、例えば１５°の位相差を与えられた後、集光レンズ
１１を経て偏光ビームスプリッタ１２で互いに直交する
偏光成分を有する２つの光束に分かれ、夫々検出器１３
及び１４に入射する。検出器１３及び１４の出力は差動
増幅器２０で差動増幅され、第１の光磁気信号ＲＦ−１
となる。The light beam that has passed through the half-wave plate 8 is split by the beam splitter 9 into two light beams that are reflected and transmitted substantially equally. The reflected light beam is given a constant phase difference, for example, a phase difference of 15 °, between polarization components orthogonal to each other by the action of the phase plate 10, and then passes through the condenser lens 11 and is polarized by the polarization beam splitter 12 to be orthogonal to each other. It is divided into two luminous fluxes each having a component
And 14 are incident. The outputs of the detectors 13 and 14 are differentially amplified by the differential amplifier 20, and the first magneto-optical signal RF-1
Becomes
【００１８】同様に、ビームスプリッタ９を透過した光
束は、位相板１５で位相板１０とは異なる位相差、例え
ば−１５°、を互いに直交する偏光成分間に与えられた
後、集光レンズ１６、偏光ビームスプリッタ１７、光検
出器１８，１９を経て差動増幅器２１に第２の光磁気信
号ＲＦ−２を与える。Similarly, the light beam that has passed through the beam splitter 9 is given a phase difference different from that of the phase plate 10 by the phase plate 15, for example, −15 °, between polarization components orthogonal to each other, and then the condenser lens 16 is provided. The second magneto-optical signal RF-2 is given to the differential amplifier 21 via the polarization beam splitter 17 and the photo detectors 18 and 19.
【００１９】図２（ａ），（ｂ）は夫々光磁気信号ＲＦ
−１及びＲＦ−２の波形をあらわす図である。光磁気信
号は予め光磁気ディスク７に一定の周波数で記録されて
いるものとすれば、その再生信号の振幅は一定の値とな
り、従って図中に破線で示すエンベロープ波形も一定と
なるはずである。ところが、もし光磁気ディスクに局所
的な欠陥や複屈折の異常部が存在すると、図中３１，３
２あるいは３１’，３２’で示すようにエンベロープ波
形にも局部的な変動が現れる。2 (a) and 2 (b) respectively show a magneto-optical signal RF.
It is a figure showing the waveform of -1 and RF-2. If the magneto-optical signal is recorded beforehand on the magneto-optical disk 7 at a constant frequency, the amplitude of the reproduction signal will have a constant value, and therefore the envelope waveform shown by the broken line in the figure should also be constant. .. However, if the magneto-optical disk has a local defect or an abnormal portion of birefringence, it is 31, 3 in the figure.
As shown by 2 or 31 ', 32', local variations appear in the envelope waveform.
【００２０】このような欠陥や複屈折の異常等は信号の
品位を劣化させ、場合によっては信号の２値化再生を妨
げることがあるので、これらの有害な部分を検出して予
め交替処理などの処置をとる必要がある。また検出する
のみでなく、これらの有害部分が製造工程のどの過程で
発生したかを分析し適切な対策を施す必要もある。Since such defects and abnormalities in birefringence may deteriorate the quality of the signal and interfere with the binarization and reproduction of the signal in some cases, these harmful parts are detected and replacement processing is performed in advance. It is necessary to take action. In addition to detection, it is necessary to analyze at which stage in the manufacturing process these harmful parts occurred and take appropriate measures.
【００２１】しかるに従来の検出方法及び装置では図２
の（ａ）又は（ｂ）いずれか一方の再生信号波形しか同
時には得られず、これから信号振幅の劣化がゴミ等の異
物によって生じる反射率の低下であるか、複屈折の異常
によって生じる偏光状態の変化に起因するものであるか
を判別することは出来なかった。However, in the conventional detection method and apparatus, FIG.
(A) or (b), only the reproduced signal waveform can be obtained at the same time, and the deterioration of the signal amplitude from this is the decrease in reflectance caused by foreign matter such as dust, or the polarization state caused by abnormal birefringence. It was not possible to determine whether it was due to the change in.
【００２２】図３は本発明に係る検査装置の信号処理系
を含む全体のブロック図である。以下同図を用いて上述
の問題を解決する本発明の方法を説明する。図中、４０
は図１で説明した検査装置をブロックで表わしたもの、
４１は後述する信号処理のためのトリガ信号を発生する
タイミング回路、４２及び４３はＲＦ平滑回路で、検査
装置４０から得られた光磁気信号ＲＦ−１，ＲＦ−２を
ＡＣ結合後、平滑回路によってプラス側、マイナス側そ
れぞれ低周波の包絡線信号に変換する機能を有する。４
４，４５はＡ／Ｄ変換回路で、包絡線信号をタイミング
回路から発生したトリガ信号のタイミングでＡ／Ｄ変換
し演算回路４６に送り込む。演算回路４６は２種類の包
絡線信号に対し後述する演算を行ない、その結果をＣＰ
Ｕ４７に送り込む。ＣＰＵ４７はこれら信号処理系全体
の制御を行なうとともに、演算回路４６から得られた情
報を用いて、局所的な欠陥のレベル判定、欠陥の種類判
別等の処理を行なう。FIG. 3 is an overall block diagram including a signal processing system of the inspection apparatus according to the present invention. The method of the present invention for solving the above problems will be described below with reference to FIG. 40 in the figure
Is a block diagram of the inspection device described in FIG.
Reference numeral 41 is a timing circuit for generating a trigger signal for signal processing, which will be described later, and 42 and 43 are RF smoothing circuits. After the magneto-optical signals RF-1 and RF-2 obtained from the inspection device 40 are AC-coupled, a smoothing circuit is provided. Has a function of converting into a low-frequency envelope signal for each of the plus side and the minus side. Four
Reference numerals 4 and 45 are A / D conversion circuits, which perform A / D conversion of the envelope signal at the timing of the trigger signal generated from the timing circuit and send it to the arithmetic circuit 46. The arithmetic circuit 46 performs the operation described later on the two types of envelope signals, and outputs the result to the CP.
Send to U47. The CPU 47 controls the entire signal processing system, and uses the information obtained from the arithmetic circuit 46 to perform processing such as local defect level determination and defect type determination.
【００２３】図４はＲＦ平滑回路４２，４３および演算
回路４６の出力波形を示す図である。図中（ａ）は、図
２（ａ）で示した光磁気信号ＲＦ−１の片波包絡線、
（ｂ）は同じく図２（ｂ）の光磁気信号ＲＦ−２の片波
包絡線をあらわす。これらの波形には前述の欠陥部に相
当する箇所５１，５１’，５２，５２’も含まれてい
る。欠陥の存在しない部分の包絡線は一定の出力Ｖ１及
びＶ２となる。図１の光学系部分の位相が０で、ビーム
スプリッタ９の透過光と反射光の分割比が等しく、かつ
位相板１０及び１５の与える位相差が前述の例の如く互
いに異符号で等しい量である場合にはＶ１とＶ２は光磁
気ディスクの位相差のみに比例する。（ａ），（ｂ）で
示される波形を夫々Ａ／Ｄ変換した後、演算回路４６に
より以下に述べる演算を行なった結果が（ｃ）で表わさ
れる。FIG. 4 is a diagram showing output waveforms of the RF smoothing circuits 42 and 43 and the arithmetic circuit 46. In the figure, (a) is a single-wave envelope of the magneto-optical signal RF-1 shown in (a) of FIG.
Similarly, FIG. 2B shows a single-wave envelope of the magneto-optical signal RF-2 shown in FIG. These waveforms also include locations 51, 51 ', 52, 52' corresponding to the above-mentioned defective portions. The envelope of the part where there is no defect has constant outputs V1 and V2. When the phase of the optical system portion of FIG. 1 is 0, the transmitted light of the beam splitter 9 and the reflected light have the same division ratio, and the phase differences provided by the phase plates 10 and 15 are equal to each other with different signs as in the above example. In some cases V1 and V2 are proportional only to the phase difference of the magneto-optical disk. After the waveforms shown in (a) and (b) are A / D converted, respectively, the result of the following calculation by the calculation circuit 46 is shown in (c).
【００２４】演算回路４６において行なう演算は、まず
（ａ）の波形のＡ／Ｄ変換信号の平均値を求め、これを
正常部の光磁気信号Ｖ１０とする。同様に（ｂ）の波形
から求めた平均値をＶ２０とし、Ａ／Ｄ変換された
（ａ），（ｂ）の波形の各々のデータＶ１，Ｖ２に対
し、 なる演算処理を行なう。In the calculation performed by the calculation circuit 46, first, the average value of the A / D converted signals having the waveform of (a) is obtained, and this is used as the magneto-optical signal V10 of the normal portion. Similarly, the average value obtained from the waveform of (b) is set to V20, and for each data V1 and V2 of the A / D converted waveforms of (a) and (b), Is performed.
【００２５】その結果、平均的な振幅値を示す正常部
は、演算結果がほぼゼロとなる。一方図４（ａ），
（ｂ）で５１，５１’で示される複屈折の異常部は周囲
の正常部とは一定値だけずれて振幅が増加あるいは減少
するので、上記の演算により一定の差分が発生する（図
４（ｃ）の５３）。またゴミ等に起因する位相差変化を
伴わない欠陥部では、平均値に対し常に一定の割合で反
射率が低下するので、上記演算結果はほぼゼロとなる。
（図４（ｃ）の５４）。従って、図４（ｃ）に破線で示
すような判定レベルを設ければ、これによって複屈折等
の位相差異常に起因する欠陥と、その程度を検知するこ
とができる。位相変化を伴わない欠陥は図（ａ），
（ｂ）の波形の加算から、あるいは従来行われているよ
うに光検出器の和信号を直接モニターすることによって
検出することができる。As a result, the calculation result of the normal part showing an average amplitude value becomes almost zero. On the other hand, FIG.
The abnormal portion of birefringence indicated by 51, 51 'in (b) shifts from the surrounding normal portion by a constant value and the amplitude increases or decreases, so a constant difference is generated by the above calculation (Fig. 4 ( 53) of c). Further, in the defect portion which is not accompanied by the phase difference change due to dust or the like, the reflectance is always reduced at a constant rate with respect to the average value, and therefore the above calculation result is almost zero.
(54 in FIG. 4 (c)). Therefore, by providing the determination level as shown by the broken line in FIG. 4C, it is possible to detect the defect that is always caused by the phase difference such as birefringence and the degree thereof. The defect without phase change is shown in Figure (a),
It can be detected by adding the waveforms shown in (b) or by directly monitoring the sum signal of the photodetector as is conventionally done.
【００２６】前述の演算回路においては、平均値Ｖ１
０，Ｖ２０の代りに中央値（メジアン）や最多値（モー
ド）を採用することも可能で、予測される欠陥の種類や
頻度に応じて種々の演算上の工夫が可能である。In the arithmetic circuit described above, the average value V1
It is also possible to adopt a median value (median) or a maximum value (mode) instead of 0 and V20, and various arithmetic devices can be devised in accordance with the predicted defect type and frequency.
【００２７】また、図１に示した装置の光学系の位相板
を除く位相差が既知（例えば０°）であれば、信号の振
幅から被測定ディスクの平均的な位相差を知ることもで
きる。前出の例の如く、位相板にプラスマイナス等量の
位相差を与えたとき、信号の平均値がＶ１０，Ｖ２０で
あれば信号振幅は位相差のコサインに比例するから、こ
れらの平均値を用いて内挿あるいは外挿することにより
ディスクの平均的な位相差が求められる。If the phase difference of the optical system of the apparatus shown in FIG. 1 excluding the phase plate is known (for example, 0 °), the average phase difference of the measured disk can be known from the amplitude of the signal. .. As in the above-mentioned example, when the plus and minus equal amounts of phase difference are given to the phase plate, if the signal average values are V10 and V20, the signal amplitude is proportional to the cosine of the phase difference. The average phase difference of the disk can be obtained by using the interpolation or the extrapolation.
【００２８】位相板の位相差は既知であればどのような
値でも良く、また必ずしも２枚使う必要もない。１枚だ
け用いるとすれば、位相板のない光路は位相差ゼロであ
り、他方に位相差がゼロ以外の既知のものを設けること
になる。The phase difference of the phase plate may be any value as long as it is known, and it is not always necessary to use two plates. If only one sheet is used, the optical path without the phase plate has a zero phase difference, and the other optical path has a known phase difference other than zero.
【００２９】また、図１の装置においては２枚の位相板
を用いる２つの光路に光束を分割したが、より多くの光
路に分割しても良い。Further, in the apparatus of FIG. 1, the light beam is divided into two optical paths using two phase plates, but it may be divided into more optical paths.
【００３０】本実施例においては光磁気ディスクを用い
て説明を行なったが、本発明の対象とする範囲はもちろ
ん光磁気ディスクに限定されることはなく、ＣＤ等の再
生専用ディスク、ライトワンス型の光ディスク、相変化
型の光ディスクにも適用可能である。Although a magneto-optical disk has been used in the description of this embodiment, the scope of the present invention is not limited to the magneto-optical disk, and a read-only disk such as a CD or a write-once type disk is not limited. The present invention can also be applied to the above optical discs and phase change type optical discs.
【００３１】（実施例２）図６は本発明の他の実施例を
表わす図面であり、同図において８１は一軸異方性を有
する位相板、８２は光磁気ディスク、８３は位相板８１
及び光磁気ディスク８２を同時に回転させるスピンドル
モータ、８４は半導体レーザ、８５は半導体レーザ８４
から発した放射光を平行光線に変換するコリメータレン
ズ、８６は光磁気ディスク８２に反射されて戻って来た
光を検出光学系に導く偏光ビームスプリッタ、８７は戻
り光を光検出器に集光させる集光レンズ、８８は戻り光
のＰ偏光成分とＳ偏光成分を分離する偏光ビームスプリ
ッタ、８９及び９０は光検出器、９１は各偏光成分の差
から光磁気信号を出力する差動増幅器、９２はレーザ光
を光磁気ディスク８２の記録膜上に集光させる対物レン
ズ、９３はレーザの偏光方向を変える１／２波長板、９
４はレーザの進行方向を変える全反射ミラーである。(Embodiment 2) FIG. 6 is a view showing another embodiment of the present invention, in which 81 is a phase plate having uniaxial anisotropy, 82 is a magneto-optical disk, and 83 is a phase plate 81.
And a spindle motor for simultaneously rotating the magneto-optical disk 82, a semiconductor laser 84, and a semiconductor laser 84.
The collimator lens for converting the emitted light emitted from the light into parallel rays, 86 is a polarization beam splitter for guiding the light reflected by the magneto-optical disk 82 and returned to the detection optical system, and 87 is the return light focused on the photodetector. A condensing lens, 88 is a polarization beam splitter that separates the P-polarized component and the S-polarized component of the return light, 89 and 90 are photodetectors, and 91 is a differential amplifier that outputs a magneto-optical signal from the difference between the polarized components. Reference numeral 92 designates an objective lens for condensing the laser light on the recording film of the magneto-optical disk 82, 93 designates a ½ wavelength plate for changing the polarization direction of the laser, 9
Reference numeral 4 denotes a total reflection mirror that changes the traveling direction of the laser.
【００３２】半導体レーザ８４は、図示されていない制
御手段により、その出力パワーを再生レベルに固定され
ており、放射されたレーザ光は、コリメータレンズ８５
によって平行光線に変換された後、偏光ビームスプリッ
タ８６、全反射ミラー９４を経由し、対物レンズ９２に
よって、回転している光磁気ディスク８２の記録膜上に
焦点を結ぶ。光磁気ディスク８２にはあらかじめ光磁気
信号を記録しておき、図示されていないフォーカス及び
トラッキング制御手段により、該光磁気信号上にレーザ
光を集光させることにより、再生信号を得ることができ
る。The output power of the semiconductor laser 84 is fixed at the reproduction level by a control means (not shown), and the emitted laser light is collimated by a collimator lens 85.
After being converted into parallel rays by, the light passes through the polarization beam splitter 86 and the total reflection mirror 94, and is focused on the recording film of the rotating magneto-optical disk 82 by the objective lens 92. A magneto-optical signal is recorded in advance on the magneto-optical disk 82, and a reproduction signal can be obtained by focusing laser light on the magneto-optical signal by a focus and tracking control means (not shown).
【００３３】このようにして得られた再生光は、対物レ
ンズ９２、全反射ミラー９４を経由し、偏光ビームスプ
リッタ８６によって位相板８１へ導かれる。位相板８１
は、旋光方向の異なる２枚の水晶板を光軸が直交するよ
うに貼り合わせたもので、直径約８ｃｍ、位相差９０°
のものを得た。位相板８１はスピンドルモータ８３によ
って光磁気ディスク８２と同時に回転しており、回転角
に応じて図８に示すような位相差を再生光に与える。こ
うして、位相板８１を通過した再生光は、集光レンズ８
７、偏光ビームスプリッタ８８によってＰ偏光成分及び
Ｓ偏光成分に分けられて光検出器８９，９０上に集光さ
れ電気信号に変換された後、差動増幅器９１によって光
磁気信号となる。The reproduced light thus obtained is guided to the phase plate 81 by the polarization beam splitter 86 via the objective lens 92 and the total reflection mirror 94. Phase plate 81
Is a structure in which two crystal plates with different optical rotation directions are attached so that their optical axes are orthogonal to each other. The diameter is about 8 cm and the phase difference is 90 °.
Got one. The phase plate 81 is rotated simultaneously with the magneto-optical disk 82 by the spindle motor 83, and gives the reproduction light a phase difference as shown in FIG. 8 according to the rotation angle. Thus, the reproduction light that has passed through the phase plate 81 is collected by the condenser lens 8.
7. The polarization beam splitter 88 divides the P-polarized component and the S-polarized component into light components, which are collected on the photodetectors 89 and 90 and converted into electric signals, which are then converted into magneto-optical signals by the differential amplifier 91.
【００３４】光磁気ディスクの位相差が円周方向に均一
で、例えば−３０°の位相差を持つ場合、位相板８１の
回転角が約２０．６°のとき、カー回転角に無関係にＰ
偏光成分及びＳ偏光成分は直流分だけとなり、光磁気信
号振幅が極小（ゼロ）となる。この様子を図９に示す。
逆に、光磁気信号振幅が極小値を示すところの位相板の
回転角θを検出することにより、光磁気ディスクの位相
差δを次式で逆算することが可能となる。 δ＝−ｔａｎ-1（ｓｉｎ2 ２θ／ｃｏｓ２θ） 光磁気信号の測定には、デジタルオシロスコープを用
い、位相板の回転に同期して信号を取り込むようにすれ
ば、光磁気ディスクが１回転する間に位相差を測定する
ことができ、測定時間は大幅に短縮される。しかも位相
差の変化が連続的であるため、正確な測定が可能とな
る。When the phase difference of the magneto-optical disk is uniform in the circumferential direction and has a phase difference of, for example, -30 °, when the rotation angle of the phase plate 81 is about 20.6 °, P is independent of the Kerr rotation angle.
The polarized component and the S polarized component are only the direct current component, and the amplitude of the magneto-optical signal becomes minimum (zero). This state is shown in FIG.
On the contrary, by detecting the rotation angle θ of the phase plate at which the amplitude of the magneto-optical signal exhibits the minimum value, the phase difference δ of the magneto-optical disk can be calculated back by the following equation. δ = −tan −1 (sin 2 2θ / cos 2θ) A digital oscilloscope is used to measure the magneto-optical signal, and if the signal is taken in in synchronization with the rotation of the phase plate, the magneto-optical disk can be rotated once. Since the phase difference can be measured, the measurement time is greatly shortened. Moreover, since the change in phase difference is continuous, accurate measurement is possible.
【００３５】また、光磁気ディスクが１回転する間に光
磁気信号振幅が４つの極小値を持つことから、各極小値
の位置に対応する位相差が一致しなければ、ディスク円
周方向の位相差にバラツキがあることがわかる。Further, since the magneto-optical signal amplitude has four minimum values during one rotation of the magneto-optical disk, if the phase difference corresponding to the position of each minimum value does not match, the position in the circumferential direction of the disk. It can be seen that there are variations in the phase difference.
【００３６】さらに、バビネ・ソレイユ位相補償器を用
いる場合に比べて装置の大きさを半分以下にすることが
可能となった。Furthermore, the size of the device can be reduced to half or less as compared with the case where the Babinet-Soleil phase compensator is used.
【００３７】尚、位相板８１は、一軸異方性を与える物
質であればよく、雲母等の複屈折性を示す天然結晶及び
人工結晶、あるいは高分子の一軸延伸フィルム等を用い
てもよい。与える位相差も９０°に限ることなく、測定
対象の持つ位相差より大きい値であればよい。The phase plate 81 may be any substance that gives uniaxial anisotropy, and natural crystals and artificial crystals showing birefringence such as mica, or uniaxially stretched polymer film may be used. The applied phase difference is not limited to 90 ° and may be any value larger than the phase difference of the measurement target.
【００３８】また、１／２波長板９３は光磁気ディスク
に入射する光の偏光方向を変えたい場合に光路に挿入す
るものであり、基板と膜の位相差を分離したい場合等に
用いる。The half-wave plate 93 is inserted in the optical path when it is desired to change the polarization direction of the light incident on the magneto-optical disk, and is used when it is desired to separate the phase difference between the substrate and the film.
【００３９】（実施例３）図７は本発明の他の実施例を
示す図面である。これは、前述の実施例を、光磁気ディ
スクの内周部、あるいは、直径が比較的小さな光磁気デ
ィスクの測定に適するように改造したものであり、図７
の偏光ビームスプリッタ８６に反射ミラーの機能を持た
せることにより、対物レンズ９２を光磁気ディスク８２
の内周部に位置させることが可能となった。全反射ミラ
ー９４を省略したことを除いて、他の構成は前述の実施
例と同様である。(Embodiment 3) FIG. 7 is a view showing another embodiment of the present invention. This is a modification of the above-described embodiment so as to be suitable for the measurement of the inner peripheral portion of the magneto-optical disk or the magneto-optical disk having a relatively small diameter.
The objective lens 92 is moved to the magneto-optical disk 82 by making the polarized beam splitter 86 of the above have a function of a reflection mirror.
It has become possible to locate it on the inner circumference of the. Except that the total reflection mirror 94 is omitted, the other structure is the same as that of the above-described embodiment.
【００４０】[0040]
【発明の効果】以上説明したように、本発明の検査装置
によれば、比較的簡単で小型化された構成により、複屈
折等に起因する位相差変化を伴なう欠陥と一様な反射率
低下を生じる欠陥を容易に弁別することが可能となり、
更には平均的な位相差も知ることができる等、従来にな
い効果を生むものである。従って光磁気ディスクの検査
工程に本発明の装置を導入すれば、工程の管理、不良原
因の解析や予防に多大なる効果を及ぼす。As described above, according to the inspection apparatus of the present invention, a defect accompanied by a phase difference change caused by birefringence or the like and a uniform reflection can be obtained by a relatively simple and compact structure. It becomes possible to easily discriminate defects that cause a decrease in
Furthermore, it is possible to obtain an effect that has not been obtained in the past such that the average phase difference can be known. Therefore, if the apparatus of the present invention is introduced into the magneto-optical disk inspection process, it has a great effect on the process control, the analysis of the cause of the defect, and the prevention.
【００４１】また、一軸異方性の位相板を光磁気信号記
録再生光学系の光路に挿入し、光磁気ディスクと同時に
回転させることにより、光磁気ディスクの位相差を短時
間で正確に測定でき、さらに装置を小型化することがで
きるという効果がある。By inserting a uniaxially anisotropic phase plate into the optical path of the magneto-optical signal recording / reproducing optical system and rotating it simultaneously with the magneto-optical disk, the phase difference of the magneto-optical disk can be accurately measured in a short time. Further, there is an effect that the device can be further downsized.
【図１】本発明に係る検査装置の光学系部の構成図、FIG. 1 is a configuration diagram of an optical system section of an inspection device according to the present invention,
【図２】図１の装置で得られる光磁気信号の波形をあら
わす図、2 is a diagram showing a waveform of a magneto-optical signal obtained by the apparatus of FIG.
【図３】本発明に係る検査装置の全体を表わすブロック
図、FIG. 3 is a block diagram showing the entire inspection apparatus according to the present invention,
【図４】本発明の検査装置による信号波形の演算処理過
程を説明する図、FIG. 4 is a diagram for explaining a calculation process of a signal waveform by the inspection device of the present invention;
【図５】従来の位相差測定装置の構成をあらわす図。FIG. 5 is a diagram showing a configuration of a conventional phase difference measuring device.
【図６】本発明の他の実施例を示す図、FIG. 6 is a view showing another embodiment of the present invention,
【図７】本発明の他の実施例を示す図、FIG. 7 is a view showing another embodiment of the present invention,
【図８】位相板によって与えられる光ビームの位相差を
示す図、FIG. 8 is a diagram showing a phase difference of a light beam provided by a phase plate,
【図９】光磁気ディスクの信号振幅を示す図、FIG. 9 is a diagram showing a signal amplitude of a magneto-optical disk,
【図１０】従来の技術を説明するための図である。FIG. 10 is a diagram for explaining a conventional technique.
１ 半導体レーザ ５ ビームスプリッタ ７ 光磁気ディスク ８ １／２波長板 ９，１７ 偏光ビームスプリッタ １０，１６ 位相板 ８１ 位相板、 ８２ 光磁気ディスク、 ８３ スピンドルモータ、 ８４ 半導体レーザ、 ８５ コリメータレンズ、 ８６ 偏光ビームスプリッタ、 ８７ 集光レンズ、 ８８ 偏光ビームスプリッタ、 ８９，９０ 光検出器、 ９１ 差動増幅器、 ９２ 対物レンズ、 ９３ １／２波長板、 ９４ 全反射ミラー、 ９５ バビネ・ソレイユ位相補償器。 DESCRIPTION OF SYMBOLS 1 semiconductor laser 5 beam splitter 7 magneto-optical disk 8 1/2 wavelength plate 9,17 polarization beam splitter 10, 16 phase plate 81 phase plate, 82 magneto-optical disk, 83 spindle motor, 84 semiconductor laser, 85 collimator lens, 86 polarization Beam splitter, 87 condensing lens, 88 polarizing beam splitter, 89, 90 photodetector, 91 differential amplifier, 92 objective lens, 93 1/2 wavelength plate, 94 total reflection mirror, 95 Babinet-Soleil phase compensator.
Claims (4)
情報が記録された記録媒体上に照射し、磁気光学効果に
より前記情報に応じて偏光状態に変調を受けた前記媒体
からの反射又は透過光束を、互いに直交する方向に偏光
する２つの光束に分割し、該分割された２つの光束を夫
々検出手段で検出し、検出された信号の差動出力で光磁
気信号を検出する光磁気ディスクの検査装置において、 前記光束の通過する光路中に設けられた２つの異なる位
相差変化を与える手段と、 該手段を介して得られた２つの異なる位相差変化に対応
する光磁気信号を演算処理することにより、前記記録媒
体内の位相差変動を伴う欠陥を検出する手段とを有する
ことを特徴とする光磁気ディスク検査装置。1. A reflection from a medium, which is polarized in a predetermined direction, is irradiated onto a recording medium on which information is magnetically recorded, and the polarization state is modulated according to the information by a magneto-optical effect. Alternatively, the transmitted light flux is divided into two light fluxes polarized in directions orthogonal to each other, the two divided light fluxes are respectively detected by the detection means, and the magneto-optical signal is detected by the differential output of the detected signals. In a magnetic disk inspecting apparatus, means for providing two different phase difference changes provided in an optical path through which the light flux passes, and magneto-optical signals corresponding to the two different phase difference changes obtained through the means. A magneto-optical disk inspecting device, comprising means for detecting a defect accompanied by a phase difference variation in the recording medium by performing arithmetic processing.
なる位相差変化を与える手段の一方の手段により得られ
る波形のＡ／Ｄ変換信号の平均値をＶ１０，他方の前記
手段により得られる波形の平均値をＶ２０，またそれぞ
れの波形の欠陥の存在しない部分の包絡線の一定の出力
をＶ１，Ｖ２としたとき、 Ｖ１，Ｖ２に対し、Ｖ１−（Ｖ１０／Ｖ２０）×Ｖ２な
る演算を行なうことを特徴とする請求項１に記載の光磁
気ディスク検査装置。2. An arithmetic mean of the A / D conversion signal of the waveform obtained by one of the means for giving the two different phase difference changes, and the waveform obtained by the other means. When V1 is the average value of V1 and V1 and V2 are constant outputs of the envelopes of the portions where there is no defect in each waveform, the calculation of V1− (V10 / V20) × V2 is performed on V1 and V2. The magneto-optical disk inspection apparatus according to claim 1, wherein
位相差変化を与えることを特徴とする請求項１に記載の
光磁気ディスク検査装置。3. The magneto-optical disk inspection apparatus according to claim 1, wherein the means for applying the phase difference change provides a plurality of phase difference changes.
性の位相板と、 該位相板を光磁気ディスクと同時に回転させる手段と、 該位相板により位相変化された信号から、前記光磁気デ
ィスクの欠陥を検査する手段とを有することを特徴とす
る光磁気ディスク検査装置。4. A magneto-optical disc inspection apparatus, a uniaxially anisotropic phase plate inserted in the optical path of a magneto-optical signal recording / reproducing optical system, means for rotating the phase plate simultaneously with the magneto-optical disc, A magneto-optical disk inspecting apparatus, comprising means for inspecting a defect of the magneto-optical disk from a signal whose phase has been changed by a phase plate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16819892A JPH05342676A (en) | 1992-06-04 | 1992-06-04 | Test device for magnetic-optical disk |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16819892A JPH05342676A (en) | 1992-06-04 | 1992-06-04 | Test device for magnetic-optical disk |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05342676A true JPH05342676A (en) | 1993-12-24 |
Family
ID=15863610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16819892A Pending JPH05342676A (en) | 1992-06-04 | 1992-06-04 | Test device for magnetic-optical disk |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05342676A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7397752B2 (en) | 2003-05-14 | 2008-07-08 | Sharp Kabushiki Kaisha | Pickup for magneto-optical recording medium |
| JP2014082272A (en) * | 2012-10-15 | 2014-05-08 | Sharp Corp | Inspection device and inspection method for solar cell module |
-
1992
- 1992-06-04 JP JP16819892A patent/JPH05342676A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7397752B2 (en) | 2003-05-14 | 2008-07-08 | Sharp Kabushiki Kaisha | Pickup for magneto-optical recording medium |
| JP2014082272A (en) * | 2012-10-15 | 2014-05-08 | Sharp Corp | Inspection device and inspection method for solar cell module |
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