JPH01129202A - Grating optical element - Google Patents
Grating optical elementInfo
- Publication number
- JPH01129202A JPH01129202A JP62287483A JP28748387A JPH01129202A JP H01129202 A JPH01129202 A JP H01129202A JP 62287483 A JP62287483 A JP 62287483A JP 28748387 A JP28748387 A JP 28748387A JP H01129202 A JPH01129202 A JP H01129202A
- Authority
- JP
- Japan
- Prior art keywords
- grating
- optical element
- diffraction efficiency
- light
- order diffraction
- 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
- 230000003287 optical effect Effects 0.000 title claims abstract description 36
- 239000000758 substrate Substances 0.000 claims abstract description 15
- 230000000737 periodic effect Effects 0.000 claims 1
- 239000000126 substance Substances 0.000 claims 1
- 230000002457 bidirectional effect Effects 0.000 abstract description 9
- 239000003989 dielectric material Substances 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000013500 data storage Methods 0.000 description 1
- 238000000609 electron-beam lithography Methods 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000000699 topical effect Effects 0.000 description 1
Landscapes
- Diffracting Gratings Or Hologram Optical Elements (AREA)
- Optical Head (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
この発明は、光学機器、特に光ディスクへの情報の記録
、再生を行う光ヘッドに用いられる格子光学素子に関す
る。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a grating optical element used in optical equipment, particularly in an optical head for recording and reproducing information on an optical disk.
・〔従来の技術〕
光学機器、特に光ディスクへの情報の記録、再生を行う
光ヘッドに用いられる格子光学素子は大別して、透過ま
たは反射の１次回折光のみを用いる第１のタイプと、透
過または反射の＋１次回折光、−１次回折光の両者また
はどちらか一方を用いる第２のタイプがある。・[Prior art] Grating optical elements used in optical devices, especially optical heads that record and reproduce information on optical disks, can be roughly divided into two types: a first type that uses only transmitted or reflected first-order diffracted light, and a first type that uses only transmitted or reflected first-order diffracted light; There is a second type that uses either or both of reflected +1st-order diffracted light and -1st-order diffracted light.
第１のタイプは格子光学素子をコリメートレンズ、ある
いはフォーカシングレンズに用いた場合に相当する。The first type corresponds to the case where the grating optical element is used as a collimating lens or a focusing lens.
第２のタイプは、さらに２つに分けられ、第１は光源か
らの放射光に対する透過光と回折光を利用するもので、
光ヘッドでは、３ビーム法によるトラック誤差検出装置
で用いられるサブビーム発生用の格子がこれに相当する
。第２は本発明と最も関連の深いもので、ある方向から
の光に対しては透過光を用い、それとは逆方向へ進む光
に対しては１次回折光を利用するものである。光へ・ノ
ドでは、焦点誤差検出、トラック誤差検出、光軸分離の
３つの機能を有する格子光学素子が相当する。The second type is further divided into two types; the first type uses transmitted light and diffracted light from the light emitted from the light source;
In an optical head, this corresponds to a sub-beam generation grating used in a tracking error detection device using a three-beam method. The second method is most closely related to the present invention, in which transmitted light is used for light coming from a certain direction, and first-order diffracted light is used for light traveling in the opposite direction. In the optical direction, a grating optical element has three functions: focus error detection, tracking error detection, and optical axis separation.
以下この格子光学素子を、特に双方向光学素子と呼ぶこ
とにする。この双方向格子光学素子の動作原理ニツイテ
は、Ｙ、ＫＩＭ（ＩＲＡ、 Ｓ、ＳｔｌＧＡＭＡ、 Ｙ
、ＯＮＯ著のＴｏｐｉｃａｌ Ｍｅｅｔｉｎｇ ｏｎ
０ｐｔｉｃａｌ Ｄａｔａ ＳｔｏｒａｇｅＴｅｃｈｎ
ｉｃａｌ Ｄｉｇｅｓｔ ５ｅｒｉｅｓ １９８７の第
１０巻、１７８頁から１８１頁に掲載のＡ Ｃｏｍｐａ
ｃｔ ０ｐｔｉｃａｌ Ｈｅａｄ−ｕｓｉｎｇ Ｈｏｌ
ｏｇｒａｐｈｉｃ ０ｐｔｉｃａｌ ［！１ｅｎ＋ｅｎ
ｔ ｆｏｒ ＣＤ Ｐｌａ−ｙｅｒ ”と題する論文、
および財団法人 光産業技術振興協会発行の光メモリシ
ンポジウム゛８６論文集の９３頁から９８頁に掲載の、
木村端夫、須釜成人。Hereinafter, this grating optical element will be particularly referred to as a bidirectional optical element. The working principle of this bidirectional grating optical element is Y, KIM (IRA, S, StlGAMA, Y
, Topical Meeting on by ONO
0ptical Data Storage Techn.
A Compa published in ical Digest 5eries 1987, Volume 10, pages 178 to 181
ct 0ptical Head-using Hole
graphic 0ptical [! 1en+en
A paper entitled “T for CD Player”,
and pages 93 to 98 of the Proceedings of the Optical Memory Symposium 86 published by the Photonics Industry and Technology Promotion Association.
Hanao Kimura, Shigeru Sugama.
小野雄三著の「複数機能ホログラムを用いた小型光ヘッ
ド」と題する論文に詳述されている！従来の双方向格子
光学素子は電子ビーム描画、およびフォトリソグラフィ
技術を用いて作製されている。第２図は、このようにし
て作成された双方向格子光学素子を示すが、基板ｌ上に
作製された格子２の断面形状は略矩形状である。It is explained in detail in a paper titled "Small optical head using multifunctional hologram" written by Yuzo Ono! Conventional bidirectional grating optical elements are fabricated using electron beam writing and photolithography techniques. FIG. 2 shows a bidirectional grating optical element produced in this manner, and the cross-sectional shape of the grating 2 produced on the substrate l is approximately rectangular.
双方向格子光学素子では、透過光と１次回折光の両方を
利用することから、光利用率は、双方向格子光学素子の
光利用率と１次回折効率の積で表される。格子の断面形
状が矩形である場合、基板での反射損、吸収等が無いと
仮定しても、理論的に得られる光利用率は約１０％（１
／π２）であり、光けの損失が大きいという欠点を有し
ていた。Since the bidirectional grating optical element uses both transmitted light and first-order diffraction light, the light utilization rate is expressed as the product of the light utilization rate of the bidirectional grating optical element and the first-order diffraction efficiency. When the cross-sectional shape of the grating is rectangular, even assuming that there is no reflection loss or absorption on the substrate, the theoretical light utilization rate is about 10% (1
/π2), and had the drawback of large loss of light.
本発明の目的は、このような欠点を除去し、高い光利用
率を持つ格子光学素子を提供することにある。An object of the present invention is to eliminate such drawbacks and provide a grating optical element with high light utilization efficiency.
本発明は、透明基板と、この透明基板上に形成された格
子よりなる格子光学素子において、前記格子の断面形状
は、前記格子の０次回折効率と１次回折効率の積が矩形
断面形状格子のＯ次回折効率と１次回折効率の積よりも
大きくなるような、格子工周期内での左右非対称性を有
することを特徴としている。The present invention provides a grating optical element comprising a transparent substrate and a grating formed on the transparent substrate, wherein the cross-sectional shape of the grating is such that the product of the 0th-order diffraction efficiency and the 1st-order diffraction efficiency of the grating is a rectangular cross-sectional grating. It is characterized by having left-right asymmetry within the grating period, which is greater than the product of the O-th order diffraction efficiency and the first-order diffraction efficiency.
矩形格子では、光利用率は主に格子の深さによって決定
され、光利用率が最大となるよう格子深さを選択しても
、＋１次回折光と等強度の一１次回折光の存在によって
制限されてしまう。したがって、高光利用率を得るため
には、−１次回折効率が低く＋１次回折効率が高い格子
を作製すればよい。このような格子は、格子の断面形状
を格子の１周期内で左右非対称になるようにすれば得る
ことができる。In a rectangular grating, the light utilization rate is mainly determined by the depth of the grating, and even if the grating depth is selected to maximize the light utilization rate, it is limited by the presence of the 11st-order diffracted light, which has the same intensity as the +1st-order diffracted light. It will be done. Therefore, in order to obtain a high light utilization rate, it is sufficient to fabricate a grating with a low -1st order diffraction efficiency and a high +1st order diffraction efficiency. Such a grating can be obtained by making the cross-sectional shape of the grating asymmetric within one period of the grating.
また、格子断面が第３図に示すように三角波状で、かつ
薄いとみなされる場合、格子の高さをｈ、格子の屈折率
をｎとしたとき（ｎ−１） ・ｈ・（２π／λ）で与
えられる格子の頂部と底部の光学的位相差をψ０とし、
格子４の頂部から格子の基板１に降ろした垂線が基板と
交わる位置から格子の周期の端までの距離ｐを格子のピ
ッチＬで除した数をαとしたとき、この格子の光利用率
ηは理論的に次式で与えられる。In addition, when the grating cross section is triangular wave-like and thin as shown in Figure 3, when the height of the grating is h and the refractive index of the grating is n, (n-1) ・h・(2π/ Let the optical phase difference between the top and bottom of the grating given by λ) be ψ0,
When α is the distance p from the point where a perpendicular drawn from the top of the grating 4 to the substrate 1 of the grating intersects with the substrate to the end of the grating period by the pitch L of the grating, the light utilization rate η of this grating is is theoretically given by the following equation.
第４図に種々のψ。、αについてηを計算した結果を示
す。この図から矩形格子の最大光利用率ｌ／π２を越え
るψ。、αの条件は非常に緩いことがわかる。Figure 4 shows various ψ. , the results of calculating η for α are shown. From this figure, it can be seen that ψ exceeds the maximum light utilization rate l/π2 of the rectangular lattice. , it can be seen that the conditions for α are very relaxed.
第１図に本発明の第１の実施例を示す。透明基板１上に
誘電体の格子３が形成されており、その断面形状は鋸歯
状である。第１図に示した鋸歯状格子３では右側へ回折
する＋１次回折光は左側へ回折する一１次回折光よりも
強いため、左右対称な格子の場合よりも高い光利用率が
得られる。FIG. 1 shows a first embodiment of the present invention. A dielectric lattice 3 is formed on a transparent substrate 1, and its cross-sectional shape is sawtooth. In the sawtooth grating 3 shown in FIG. 1, the +1st order diffracted light diffracted to the right is stronger than the 1st order diffracted light diffracted to the left, so a higher light utilization rate can be obtained than in the case of a bilaterally symmetrical grating.
第５図に本発明の第２の実施例を示す。透明基板１上に
形成された誘電体の格子５の断面形状は三角波状で、格
子の頂部と底部の位相差を０．９ π、αを０．８とし
ている。本実施例においても、高い光利用率が得られる
。FIG. 5 shows a second embodiment of the invention. The dielectric grating 5 formed on the transparent substrate 1 has a triangular cross-sectional shape, and the phase difference between the top and bottom of the grating is 0.9 π and α is 0.8. Also in this example, a high light utilization rate can be obtained.
第６図に本発明の第３の実施例を示す。本実施例では透
明基板１上に形成された誘電体の格子６の頂部は隣接周
期内へ入り込んだ断面形状となっている。本実施例に示
す断面形状でも１０％を越える光利用率を得るための形
状的条件は緩く、試作の結果１４％の効率を持つ格子光
学素子が得られた。FIG. 6 shows a third embodiment of the present invention. In this embodiment, the top of the dielectric grating 6 formed on the transparent substrate 1 has a cross-sectional shape that extends into the adjacent period. Even with the cross-sectional shape shown in this example, the geometrical conditions for obtaining a light utilization rate exceeding 10% were relaxed, and as a result of trial production, a grating optical element with an efficiency of 14% was obtained.
以上述べた実施例では基板は透明で、格子は誘電体とし
たが格子上面に光反射層を形成して、反射型光学素子と
して用いることももちろん可能である。In the embodiments described above, the substrate is transparent and the grating is made of a dielectric material, but it is of course possible to form a light reflective layer on the upper surface of the grating and use it as a reflective optical element.
なお、本発明の格子の作製は、電子ビーム描画法を用い
て格子形状に合わせて電子ビームのドーズ量を変化させ
る方法、あるいは矩形断面格子に斜め方向からイオンビ
ームを照射する方法等を用いて行える。The grating of the present invention can be manufactured by using an electron beam lithography method in which the dose of the electron beam is varied according to the shape of the grating, or by irradiating a rectangular cross-sectional grating with an ion beam from an oblique direction. I can do it.
本発明によれば、高い光利用率を持つ双方向上δ子光学
素子が得られる。この双方向格子光学素子に用いられる
断面形状の格子は従来と全く同一の手法により複製が得
られ、量産性Ｇこも富むと０う利点がある。According to the present invention, a bidirectional upper δ-element optical element with high light utilization efficiency can be obtained. The cross-sectional grating used in this bidirectional grating optical element can be reproduced using exactly the same method as in the past, and has the advantage of being mass-producible.
第１図は本発明の第１の実施例を説明するための図、
第２図は従来の技術を説明するための図、第３図、第４
図は本発明の詳細な説明するための図、
第５図は本発明の第２の実施例を説明するための図、
第６図は本発明の第３の実施例を説明するための図であ
る。
ｌ ・・・基）反
２・・・矩形格子
３・・・鋸歯状格子
４．６・・・格子
５・・・三角波状格子
代理人弁理士 岩 佐 義 幸０次回折光
第１図
第２図
α“ρ／を
第３図
第４図Fig. 1 is a diagram for explaining the first embodiment of the present invention, Fig. 2 is a diagram for explaining the conventional technique, Figs.
The figures are diagrams for explaining the present invention in detail, Figure 5 is a diagram for explaining the second embodiment of the present invention, and Figure 6 is a diagram for explaining the third embodiment of the present invention. It is. l...Group)Anti2...Rectangular lattice 3...Sawtooth lattice 4.6...Grid 5...Triangular wave latticeRepresentative patent attorneyYoshiyuki Iwasa0th order diffracted light Figure 1Figure 2 Figure α“ρ/Figure 3 Figure 4
Claims (2)
りなる格子光学素子において、 前記格子の断面形状は、前記格子の０次回折効率と１次
回折効率の積が矩形断面形状格子の０次回折効率と１次
回折効率の積よりも大きくなるような、格子１周期内で
の左右非対称性を有することを特徴とする格子光学素子
。(1) In a grating optical element consisting of a transparent substrate and a grating formed on the transparent substrate, the cross-sectional shape of the grating is such that the product of the 0th-order diffraction efficiency and the 1st-order diffraction efficiency of the grating is a rectangular cross-sectional grating. A grating optical element characterized by having left-right asymmetry within one period of the grating that is greater than the product of the 0th-order diffraction efficiency and the 1st-order diffraction efficiency.
子の頂部と底部の光学的位相差をψ＿０とし、前記格子
の頂部から前記基板に降ろした垂線が前記基板と交わる
位置から前記格子の周期端までの距離を、前記格子のピ
ッチで除した数をαとしたとき、 ▲数式、化学式、表等があります▼ なる関係を満足することを特徴とする特許請求の範囲第
１項記載の格子光学素子。(2) The cross-sectional shape of the grating is substantially triangular wave-like, the optical phase difference between the top and bottom of the grating is ψ_0, and the grating is measured from a position where a perpendicular line drawn from the top of the grating to the substrate intersects with the substrate. Claim 1, which satisfies the following relationship: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ where α is the number obtained by dividing the distance to the periodic end of the lattice by the pitch of the lattice. lattice optical element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62287483A JPH01129202A (en) | 1987-11-16 | 1987-11-16 | Grating optical element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62287483A JPH01129202A (en) | 1987-11-16 | 1987-11-16 | Grating optical element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH01129202A true JPH01129202A (en) | 1989-05-22 |
Family
ID=17717926
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62287483A Pending JPH01129202A (en) | 1987-11-16 | 1987-11-16 | Grating optical element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH01129202A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06196726A (en) * | 1992-12-24 | 1994-07-15 | Canon Inc | Light receiving element, and displacement detector equipped with this light receiving device |
| KR100519636B1 (en) * | 2001-10-05 | 2005-10-07 | 마쯔시다덴기산교 가부시키가이샤 | Diffraction optical element and optical head using the same |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59149305A (en) * | 1983-02-16 | 1984-08-27 | Agency Of Ind Science & Technol | Formation of diffraction grating |
| JPS6242103A (en) * | 1985-08-20 | 1987-02-24 | Nippon Sheet Glass Co Ltd | Manufacture of blaze grating |
-
1987
- 1987-11-16 JP JP62287483A patent/JPH01129202A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59149305A (en) * | 1983-02-16 | 1984-08-27 | Agency Of Ind Science & Technol | Formation of diffraction grating |
| JPS6242103A (en) * | 1985-08-20 | 1987-02-24 | Nippon Sheet Glass Co Ltd | Manufacture of blaze grating |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06196726A (en) * | 1992-12-24 | 1994-07-15 | Canon Inc | Light receiving element, and displacement detector equipped with this light receiving device |
| KR100519636B1 (en) * | 2001-10-05 | 2005-10-07 | 마쯔시다덴기산교 가부시키가이샤 | Diffraction optical element and optical head using the same |
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