JPH02259702A - Polarization diffraction element - Google Patents
Polarization diffraction elementInfo
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- JPH02259702A JPH02259702A JP1081707A JP8170789A JPH02259702A JP H02259702 A JPH02259702 A JP H02259702A JP 1081707 A JP1081707 A JP 1081707A JP 8170789 A JP8170789 A JP 8170789A JP H02259702 A JPH02259702 A JP H02259702A
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- light
- grating
- polarization
- order diffracted
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- 230000010287 polarization Effects 0.000 title claims abstract description 61
- 239000000758 substrate Substances 0.000 claims abstract description 15
- 230000005540 biological transmission Effects 0.000 abstract 1
- 230000004907 flux Effects 0.000 abstract 1
- 230000003287 optical effect Effects 0.000 description 25
- 238000001514 detection method Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000005530 etching Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229920002120 photoresistant polymer Polymers 0.000 description 2
- 206010041662 Splinter Diseases 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000005305 interferometry Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- Diffracting Gratings Or Hologram Optical Elements (AREA)
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Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、光ピツクアップなどに用いられる回折素子に
係り、詳しくは、入射光を異なる偏光成分の光束に分離
する偏光回折素子に関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a diffraction element used for optical pickup, etc., and specifically relates to a polarization diffraction element that separates incident light into light beams of different polarization components. .
従来より、格子間隔が光の波長程度に形成された回折格
子は、偏光特性を有することが知られている（に、Ｙｏ
ｋｏｍｏｒｉ、”Ｄｉｅｌｅｃｔｒｉｃ ｓｕｒｆａｃ
ｅ−ｒｅｌｉｅｆｇｒａｔｉｎｇｓ ｗｉｔｈ ｈｉｇ
ｈ ｄｉｆｆｒａｃｔｉｏｎ ｅｆｆｉｃｉｅｎｃｙ。It has been known that a diffraction grating with a grating interval approximately equal to the wavelength of light has polarization properties (Yo et al.
komori, “Dielectric surfac
e-relief gratings with hig
h diffraction efficiency.
Ａｐｐｌｙｅｄ ０ｐｔｉｃｓ Ｖｏｌ、２３．Ｎｏ、
１４．ｐｐ２３０３．１９８４）。Applied Optics Vol, 23. No,
14. pp2303.1984).
第５図に示すように、偏光回折素子２１は、ガラスなど
の透明な基板２２の一方の面に、格子間隔が入射光の所
定の波長程度に形成されて偏光特性を有する回折格子２
３が、二光束干渉法などの方法により形成されている。As shown in FIG. 5, the polarization diffraction element 21 includes a diffraction grating 2 having polarization characteristics, which is formed on one surface of a transparent substrate 22 such as glass, with a grating interval approximately equal to a predetermined wavelength of incident light.
3 is formed by a method such as two-beam interferometry.
回折格子２３は、例えば、フォトレジストからなり、そ
の厚さおよび格子間隔がそれぞれ２μｍ、０．５μｍに
設定されている。また、回折格子２３は、Ｐ偏光成分を
ほぼ１００％透過させるとともに、Ｓ偏光成分をほぼ１
００％回折させるように作製されている。The diffraction grating 23 is made of, for example, photoresist, and its thickness and grating interval are set to 2 μm and 0.5 μm, respectively. Moreover, the diffraction grating 23 transmits almost 100% of the P polarized light component, and transmits approximately 100% of the S polarized light component.
It is made to cause 00% diffraction.
このような偏光回折素子２１に、例えば波長が０．８μ
ｍの入射光２４をブラッグ角で入射させると、入射光２
４のうちＰ偏光成分がＯ次回折光２４ａとして回折格子
２３を透過し、１次回折光２４ｂとして回折されること
はほとんどない。一方、入射光２４のうちＳ偏光成分が
１次回折光２４ｂとして回折格子２３により回折され、
０次回折光２４ａとして透過することはほとんどない。For example, the polarization diffraction element 21 has a wavelength of 0.8μ.
When the incident light 24 of m is incident at the Bragg angle, the incident light 2
The P-polarized light component among the four polarized light components is transmitted through the diffraction grating 23 as O-order diffracted light 24a, and is hardly diffracted as first-order diffracted light 24b. On the other hand, the S-polarized component of the incident light 24 is diffracted by the diffraction grating 23 as first-order diffracted light 24b,
It is almost never transmitted as the 0th order diffracted light 24a.
また、このようにして分離された０次回折光２４ａおよ
び１次回折光２４ｂの偏光成分を検出するには、それぞ
れを集光レンズ２５・２６を介して光検出器２７・２８
に集光させて行う。In addition, in order to detect the polarization components of the 0th-order diffracted light 24a and the 1st-order diffracted light 24b separated in this way, they are passed through condensing lenses 25 and 26 to photodetectors 27 and 28, respectively.
This is done by focusing the light on the
上記のように回折格子２３は、異なる偏光の光を分離す
る特性を有するので、光磁気記録再生装置における光ピ
ツクアップの偏光ビームスプリッタとして利用すること
ができる。偏光ビームスプリンタに偏光回折素子２１を
用いれば、部品点数を少なくして光ピツクアップの小型
・軽量化を図ることができる。As described above, the diffraction grating 23 has the characteristic of separating light of different polarization, and therefore can be used as a polarizing beam splitter for optical pickup in a magneto-optical recording/reproducing device. If the polarization diffraction element 21 is used in a polarization beam splinter, the number of parts can be reduced and the optical pickup can be made smaller and lighter.
ところが、上記従来の偏光回折素子２１では、回折格子
２３による回折光の回折角は入射光２４の波長に依存す
るので、例えば光源にレーザダイオードを用いた場合、
レーザダイオードから出射される光の波長が周囲の温度
変化により変化して上記回折角が変化してしまう。However, in the conventional polarization diffraction element 21, the diffraction angle of the diffracted light by the diffraction grating 23 depends on the wavelength of the incident light 24. For example, when a laser diode is used as the light source,
The wavelength of the light emitted from the laser diode changes due to changes in the surrounding temperature, and the above-mentioned diffraction angle changes.
例えば、入射光２４の波長が所定の波長であるとき、１
次回折光２４ｂは所定の回折角で回折され、集光レンズ
２６により光検出器２８に正しく集光される。このとき
、周囲温度が低下してそのときの入射光２４の波長が上
記所定の波長より小さくなると、回折角もそれに伴って
小さくなり、回折格子２３により回折された１次回折光
２４ｂは、図中の二点鎖線に示すように所定の光路から
大きく外れて進む。このため、１次回折光２４ｂが光検
出器２８の所定の位置に集光されなくなり、Ｓ偏光成分
の検出が行えなくなるという不都合が生じる。For example, when the wavelength of the incident light 24 is a predetermined wavelength, 1
The next diffraction light 24b is diffracted at a predetermined diffraction angle, and is correctly focused on the photodetector 28 by the condenser lens 26. At this time, when the ambient temperature decreases and the wavelength of the incident light 24 becomes smaller than the predetermined wavelength, the diffraction angle also becomes smaller accordingly, and the first-order diffracted light 24b diffracted by the diffraction grating 23 is As shown by the two-dot chain line, the light beam travels far away from the predetermined optical path. For this reason, the first-order diffracted light 24b is no longer focused on a predetermined position of the photodetector 28, resulting in the inconvenience that the S-polarized light component cannot be detected.
上記のように、偏光回折素子２１は、回折格子２３の格
子間隔が波長程度に設けられているので、入射光２４の
波長がわずかに変化しただけで回折角が大きく変化し、
１次回折光２４ｂの光路を移動させることになる。そこ
で、光検出器２日の受光部を大きくして、光路の外れた
１次回折光２４ｂを受光させることが考えられるが、偏
光回折素子２１を光検出器２８とともに光ピツクアップ
に組み込む場合、光ピツクアップも大型になるので、光
ピツクアップの小型・軽量化を図るうえでマイナス要因
となる。また、光検出器２８を大きくしても、光検出器
２８には１次回折光２４ｂの集光点が入射光２４の波長
の変化によって一定の位置に形成されなくなり、Ｓ偏光
成分の検出精度が低下するという問題点も生じる。As mentioned above, in the polarization diffraction element 21, since the grating spacing of the diffraction grating 23 is set to about the wavelength, a slight change in the wavelength of the incident light 24 causes a large change in the diffraction angle.
The optical path of the first-order diffracted light 24b is moved. Therefore, it is conceivable to increase the size of the light receiving part of the photodetector 2 to receive the first-order diffracted light 24b that is out of the optical path. This also increases the size of the optical pickup, which is a negative factor when trying to make the optical pickup smaller and lighter. Furthermore, even if the photodetector 28 is made larger, the focal point of the first-order diffracted light 24b will no longer be formed at a fixed position on the photodetector 28 due to changes in the wavelength of the incident light 24, and the detection accuracy of the S-polarized light component will decrease. There also arises the problem of a decrease in the power.
さらに、１次回折光２４ｂを回折する回折角が１００″
前後となるので、１次回折光２４ｂと０次回折光２４ａ
とが大きく離れて進むこととなるため、光検出器２７・
２８を互いに離間した位置に設けなければならない。こ
のため、光ピツクアップが大型になり、上記の場合と同
様光ピツクアップの小型・軽量化を図ることが困難とな
っていた。Furthermore, the diffraction angle for diffracting the first-order diffracted light 24b is 100″
Since they are before and after, the 1st-order diffracted light 24b and the 0th-order diffracted light 24a
The photodetector 27 and
28 must be provided at positions spaced apart from each other. As a result, the optical pickup becomes large, making it difficult to reduce the size and weight of the optical pickup as in the case described above.
ところで、回折格子２３は、Ｐ偏光成分をほぼ１００％
透過させ、Ｓ偏光成分をほぼ１００％回折させるように
作製されるが、実際には、入射光２４が１つの回折格子
２３のみに入射する場合、Ｐ偏光成分がＯ次回折光２４
ａとして透過する際の回折効率η。９、およびＳ偏光成
分が１次回折光２４ｂとして回折される際の回折効率η
１．はともに０．９９程度である。このため、回折格子
２３を透過したＯ次回折光２４ａには、０．０１程度の
回折効率η。、で回折格子２３を透過したＳ偏光成分が
わずかに含まれる。また、回折格子２３により回折され
た１次回折光２４ｂには、０．０１程度の回折効率η、
ｐで回折格子２３により回折されたＰ偏光成分がわずか
に含まれる。By the way, the diffraction grating 23 absorbs almost 100% of the P polarized light component.
However, in reality, when the incident light 24 enters only one diffraction grating 23, the P polarized light component becomes the O-order diffracted light 24.
Diffraction efficiency η when transmitted as a. 9, and the diffraction efficiency η when the S-polarized component is diffracted as the first-order diffracted light 24b.
1. are both about 0.99. Therefore, the O-order diffracted light 24a transmitted through the diffraction grating 23 has a diffraction efficiency η of about 0.01. , a slight amount of the S-polarized light component transmitted through the diffraction grating 23 is included. Furthermore, the first-order diffracted light 24b diffracted by the diffraction grating 23 has a diffraction efficiency η of about 0.01,
A small amount of the P-polarized light component diffracted by the diffraction grating 23 at p is included.
このように、１つの回折格子２３に入射光２４を分離さ
せた場合、所望の偏光成分におけるそれ以外の偏光成分
の割合、すなわち偏光度は、０次回折光２４ａにおいて
回折効率η６ｐに対する回折効率η。、の比で表され、
１次回折光２４ｂにおいて回折効率η、に対する回折効
率η１９の比で表される。これに従って、０次回折光お
よび１次回折光における偏光度を求めると、ともに約０
．０１となりＰ偏光成分とＳ偏光成分との分離度が実用
できる程度に十分満足しうるものであるとはいえない。In this way, when the incident light 24 is separated into one diffraction grating 23, the ratio of the other polarized light components in the desired polarized light component, that is, the degree of polarization, is the diffraction efficiency η with respect to the diffraction efficiency η6p in the 0th-order diffracted light 24a. , expressed as the ratio of
In the first-order diffracted light 24b, it is expressed as the ratio of the diffraction efficiency η19 to the diffraction efficiency η. According to this, the degree of polarization of the 0th-order diffracted light and the 1st-order diffracted light is found to be approximately 0.
．． 01, and it cannot be said that the degree of separation between the P-polarized light component and the S-polarized light component is sufficiently satisfactory for practical use.
本発明に係る偏光回折素子は、上記課題を解決するため
に、入射光の所定の波長程度の幅を有する格子間隔で形
成された第１の回折格子と第２の回折格子とが、それぞ
れ平板状の基板における異なる面に設けられており、上
記第１の回折格子と第２の回折格子とは、互いに等しい
格子間隔を有し、かつ、互いの格子方向が一致するよう
に形成されていることを特徴としている。In order to solve the above problems, the polarization diffraction element according to the present invention has a first diffraction grating and a second diffraction grating formed with a grating interval having a width approximately equal to a predetermined wavelength of incident light. The first diffraction grating and the second diffraction grating are provided on different surfaces of a shaped substrate, and the first diffraction grating and the second diffraction grating are formed so that they have equal grating intervals and their grating directions match. It is characterized by
上記の構成により、偏光回折素子に所定の波長の入射光
が入射すると、この入射光のうち第１の回折格子を透過
したＯ次回折光は、さらに第２の回折格子も透過する一
一方、上記入射光のうち第１の回折格子により回折され
た１次回折光は、第２の回折格子に入射し、ここでさら
に回折される。入射光は、このようにして異なる偏光成
分の光束に分離される。With the above configuration, when incident light of a predetermined wavelength enters the polarization diffraction element, the O-order diffracted light that has passed through the first diffraction grating is further transmitted through the second diffraction grating, while Of the incident light, the first-order diffracted light that is diffracted by the first diffraction grating enters the second diffraction grating, where it is further diffracted. The incident light is thus separated into beams of different polarization components.
一般に、回折光の回折角は、回折格子の格子間隔と入射
光の波長とによって決まるので、第１の回折格子の格子
間隔と第２の回折格子の格子間隔とを互いに等しくすれ
ば、第１の回折格子による回折角と第２の回折格子によ
る回折角とが等しくなる。それゆえ、第１の回折格子に
より回折された１次回折光が、第２の回折格子に入射し
回折されると、０次回折光と平行になって偏光回折素子
から出射される。Generally, the diffraction angle of diffracted light is determined by the grating spacing of the diffraction grating and the wavelength of the incident light. Therefore, if the grating spacing of the first diffraction grating and the grating spacing of the second diffraction grating are made equal to each other, The diffraction angle by the second diffraction grating becomes equal to the diffraction angle by the second diffraction grating. Therefore, when the first-order diffracted light diffracted by the first diffraction grating enters the second diffraction grating and is diffracted, it is emitted from the polarization diffraction element in parallel with the zero-order diffraction light.
ここで、例えば、入射光の波長が短くなると、第１の回
折格子および第２の回折格子による１次回折光の回折角
がともに小さ（なる。しかしながら、それぞれの回折格
子は、格子間隔が互いに等しく設けられているので、所
定の波長の入射光を入射させた場合と同様、上記回折角
が互いに等しくなり、１次回折光はやはり０次回折光と
平行に出射される。また、１次回折光は、上記回折角が
小さくなることにより、所定の光路から外れて基板内を
進むが、基板は薄く設けられているので、上記光路の外
れはごくわずかなものとなり、１次回折光が偏光回折素
子から出射する位置もわずかにずれるだけである。それ
ゆえ、このような偏光回折素子を光ピツクアップに組み
込む場合、１次回折光を集光レンズ等の光学系を介して
光検出器に集光させることにより、入射光の波長が変化
しても光検出器の所定の位置で１次回折光を検出するこ
とができる。Here, for example, as the wavelength of the incident light becomes shorter, the diffraction angles of the first-order diffraction light by the first diffraction grating and the second diffraction grating become smaller. However, the grating intervals of each diffraction grating are equal to each other. Since the diffraction angles are equal to each other and the first-order diffraction light is emitted in parallel with the zero-order diffraction light, the first-order diffraction light is As the diffraction angle becomes smaller, it deviates from the predetermined optical path and travels inside the substrate, but since the substrate is thin, the deviation from the optical path is minimal, and the first-order diffracted light is emitted from the polarization diffraction element. Therefore, when incorporating such a polarization diffraction element into an optical pickup, the first-order diffracted light is focused on a photodetector via an optical system such as a condensing lens. Even if the wavelength of the incident light changes, the first-order diffracted light can be detected at a predetermined position of the photodetector.
また、偏光回折素子により分離された０次回折光と１次
回折光とが平行に進むので、これらの偏光成分を検出す
る場合、検出のための光検出器を近接して設けて、光検
出器を設けるスペースを小さくすることができる。それ
ゆえ、偏光回折素子を光ピツクアップに組み込む場合、
光ピツクアップの小型・軽量化を容易に図ることができ
る。In addition, since the 0th-order diffracted light and the 1st-order diffracted light separated by the polarization diffraction element travel in parallel, when detecting these polarized light components, a photodetector for detection must be installed close to the photodetector. The space required can be reduced. Therefore, when incorporating a polarization diffraction element into an optical pickup,
Optical pickups can be easily made smaller and lighter.
さらｋこ、入射光を２つの回折格子を通過させることに
より、Ｏ次回折光および１次回折光における偏光度を小
さくして偏光成分の分離度を高め、偏光検出の精度を向
上させることができる。Furthermore, by passing the incident light through two diffraction gratings, it is possible to reduce the degree of polarization of the O-order diffracted light and the first-order diffraction light, increase the degree of separation of polarized light components, and improve the accuracy of polarization detection.
〔実施例１〕
本発明の一実施例を第１図ないし第３図に基づいて説明
すれば、以下の通りである。[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 3.
第１図に示すように、偏光回折素子１は、ガラス等から
なる透明、かつ、平板状の基板２の両面にそれぞれ回折
格子３・４が設けられている。回折格子３・４は、格子
間隔が入射光５０波長程度に設定されるとともに、いず
れも格子方向が図中の紙面と直交する方向と一致してい
る。また、回折格子３・４は、例えば、基板２をエツチ
ングを施すことにより、レリーフ型回折格子として作製
される。As shown in FIG. 1, the polarization diffraction element 1 includes diffraction gratings 3 and 4 provided on both sides of a transparent, flat substrate 2 made of glass or the like. The grating spacing of the diffraction gratings 3 and 4 is set to about 50 wavelengths of incident light, and the grating directions of both gratings coincide with the direction perpendicular to the plane of the drawing. Further, the diffraction gratings 3 and 4 are manufactured as relief type diffraction gratings by etching the substrate 2, for example.
第２図に示すように、回折格子３・４は、等しい格子間
隔り内に矩形状の凸部６・・・が形成されている。上記
回折格子３・４は、入射光５のうち、その電界が第１図
の紙面と平行に振動するＰ偏光成分をほぼ１００％透過
させるとともに、入射光５のうち、その電界が第１図の
紙面と直交する方向に振動するＳ偏光成分をほぼ１００
％回折させるように設けられている。このため、例えば
、第１図の入射光５の波長を０．８μｍとし、基板２の
屈折率ｎを１．５とした場合、格子間隔りが約０．５μ
ｍ、格子の深さもが約１μｍ、および格子間隔りに対す
る凸部６の幅り、の比、すなわちデューティＤ、／Ｄが
０．５に設定されている。As shown in FIG. 2, the diffraction gratings 3 and 4 have rectangular convex portions 6 formed within equal grating intervals. The diffraction gratings 3 and 4 transmit almost 100% of the P-polarized component of the incident light 5 whose electric field vibrates parallel to the plane of the paper in FIG. The S-polarized light component vibrating in the direction perpendicular to the plane of the paper is approximately 100
% diffraction. Therefore, for example, if the wavelength of the incident light 5 in FIG. 1 is 0.8 μm and the refractive index n of the substrate 2 is 1.5, the lattice spacing is approximately 0.5 μm.
m, the depth of the grating is also about 1 μm, and the ratio of the width of the convex portion 6 to the grating interval, that is, the duty D, /D is set to 0.5.
上記の構成において、入射光５が偏光回折素子１に入射
角θ１．で入射すると、Ｐ偏光成分は、０次回指光５ａ
として回折格子３・４を透過し、偏光回折素子１から出
射する。一方、入射光５のＳ偏光成分は、１次回折光５
ｂとして回折格子３により回折角θ１で回折され、さら
に回折格子４により回折角θ２で回折されて偏光回折素
子１から出射する。In the above configuration, the incident light 5 enters the polarization diffraction element 1 at an incident angle θ1. , the P polarized light component becomes the 0th order light 5a
The light passes through the diffraction gratings 3 and 4 as a beam and exits from the polarization diffraction element 1. On the other hand, the S-polarized component of the incident light 5 is the first-order diffracted light 5
As b, the light is diffracted by the diffraction grating 3 at a diffraction angle θ1, further diffracted by the diffraction grating 4 at a diffraction angle θ2, and output from the polarization diffraction element 1.
このとき、上記回折角θ１ ・θ２は、回折格子３・４
の格子間隔りと入射光５の波長により決まるので、回折
格子３・４が互いに等しい格子間隔りで形成されている
場合、回折角θ１ ・θ２も等しくなり、０次回指光５
ａおよび１次回折光５ｂが偏光回折素子１から平行に出
射する。また、入射光の波長をλとしたときの、入射光
５の入射角θｉ１を
θｔ＋＝ｓｉｎ −’ （λ／２Ｄ）
なる式を満たす、いわゆるブラッグ角に設定しておけば
、上記入射角θｉｆを回折格子３により回折された１次
回折光５ｂが回折格子４に入射する入射角θｉｚと等し
くすることができ、回折格子３・４の特性をそろえやす
くなる。At this time, the above diffraction angles θ1 and θ2 are the diffraction gratings 3 and 4.
Since it is determined by the grating spacing of
a and the first-order diffraction light 5b are emitted from the polarization diffraction element 1 in parallel. Furthermore, if the incident angle θi1 of the incident light 5 is set to the so-called Bragg angle that satisfies the formula θt+=sin −' (λ/2D), where the wavelength of the incident light is λ, then the above incident angle θif can be made equal to the incident angle θiz at which the first-order diffracted light 5b diffracted by the diffraction grating 3 enters the diffraction grating 4, making it easier to match the characteristics of the diffraction gratings 3 and 4.
次に、上記のように分離された０次回指光５ａおよび１
次回折光５ｂの検出について説明する。Next, the 0th order light beams 5a and 1 separated as described above are
Detection of the next diffracted light 5b will be explained.
第３図に示すように、０次回指光５ａの光路上には、偏
光回折素子１から所定の距離をおいて集光レンズ７が設
けられるとともに、所定の集光位置に光検出器８が設け
られている。一方、１次回折光５ｂの光路上には、偏光
回折素子１から所定の距離をおいて集光レンズ９が設け
られるとともに、所定の集光位置に光検出器１０が設け
られている。光検出器８・１０は、それぞれパッケージ
１１・１２内に配されている。As shown in FIG. 3, a condenser lens 7 is provided on the optical path of the 0th-order index light 5a at a predetermined distance from the polarization diffraction element 1, and a photodetector 8 is provided at a predetermined condensing position. It is provided. On the other hand, a condenser lens 9 is provided on the optical path of the first-order diffracted light 5b at a predetermined distance from the polarization diffraction element 1, and a photodetector 10 is provided at a predetermined condensing position. The photodetectors 8 and 10 are arranged in packages 11 and 12, respectively.
このような構成において、なんらかの原因で入射光５の
波長が所定の波長より短くなると、回折角θ、・θ２が
ともに小さくなり回折角θ。In such a configuration, if the wavelength of the incident light 5 becomes shorter than a predetermined wavelength for some reason, both the diffraction angles θ and .theta.2 become smaller and the diffraction angle θ becomes smaller.
θ２′となる。このため、回折格子３により回折された
１次回折光５ｂは、図中二点鎖線で示すように所定の光
路から外れて進み、回折格子４に入射する位置もずれる
ことになる。しかしながら、基板２は薄く設けられてい
るので、上記光路の外れはごくわずかなものとなり、１
次回折光５ｂが偏光回折素子１から出射する位置もわず
かにずれるだけである。また、前記のように、回折格子
３・４の格子間隔は互いに等しいので、回折角θ。θ2'. Therefore, the first-order diffracted light 5b diffracted by the diffraction grating 3 travels away from the predetermined optical path as shown by the two-dot chain line in the figure, and the position where it enters the diffraction grating 4 is also shifted. However, since the substrate 2 is thin, the deviation of the optical path is very small, and 1
The position where the next diffraction light 5b exits from the polarization diffraction element 1 is also slightly shifted. Furthermore, as described above, since the grating intervals of the diffraction gratings 3 and 4 are equal to each other, the diffraction angle θ.
・θ２′も同様に等しくなり、１次回折光５ｂは０次回
指光５ａと平行に偏光回折素子１から出射される。それ
ゆえ、入射光５の波長が小さ（なっても、偏光回折素子
１における１次回折光５ｂの出射位置に大きくずれが生
じることなく、１次回折光５ｂを集光レンズ９により光
検出器１０の所定の位置に集光させることができる。- θ2' is also made equal, and the first-order diffracted light 5b is emitted from the polarization diffraction element 1 in parallel with the zero-order index light 5a. Therefore, even if the wavelength of the incident light 5 is small (even if the wavelength of the incident light 5 becomes small), the output position of the first-order diffracted light 5b in the polarization diffraction element 1 does not shift significantly, and the first-order diffracted light 5b is directed to the photodetector 10 by the condenser lens 9. The light can be focused at a predetermined position.
さらに、回折格子３・４による偏光度について説明する
。Furthermore, the degree of polarization by the diffraction gratings 3 and 4 will be explained.
第１図に示すように、入射光５が回折格子３を透過した
Ｏ次回指光５ａは、実際には、回折効率η。２で透過し
たＰ偏光成分以外に、回折効率η。。As shown in FIG. 1, the O-order pointing light 5a of the incident light 5 transmitted through the diffraction grating 3 actually has a diffraction efficiency η. In addition to the P-polarized component transmitted by 2, the diffraction efficiency η. .
で透過したＳ偏光成分がわずかに含まれている。It contains a small amount of the S-polarized light component that was transmitted through the camera.
このときの偏光度は、回折効率η。２・η０．をそれぞ
れ０．９９および０．０１とすると、約０．０１となる
。The degree of polarization at this time is the diffraction efficiency η. 2・η0. Assuming that they are 0.99 and 0.01, respectively, it becomes approximately 0.01.
そして、回折格子３と同じ回折効率η。２・η。５を有
する回折格子４に上記０次回指光５ａが入射すると、回
折効率η。、・η。３がそれぞれ二乗され、Ｐ偏光成分
が回折効率η。ｐ′で透過し、Ｓ偏光成分が回折効率η
。Ｓ′で透過する。そこで、上記と同様に０次回指光５
ａの偏光度を求めると約０゜０００１となり、例えば、
回折格子３のみを透過した場合に比べ１／１００の値と
なる。The diffraction efficiency η is the same as that of the diffraction grating 3. 2・η. When the zero-order light 5a is incident on the diffraction grating 4 having a diffraction efficiency of η. ,・η. 3 are each squared, and the P polarization component is the diffraction efficiency η. p′, and the S polarized component has a diffraction efficiency η
. Transmits at S'. Therefore, as above, the 0th order instruction 5
The polarization degree of a is approximately 0°0001, for example,
The value is 1/100 compared to the case where only the diffraction grating 3 is transmitted.
一方、入射光５は、Ｐ偏光成分の回折効率ηＩｐおよび
Ｓ偏光成分の回折効率η、５で回折格子３により１次回
折光５ｂとして回折される。そして、この１次回折光５
ｂは回折格子４に入射し、Ｐ偏光成分が回折効率ηｔｐ
ｔで回折され、Ｓ偏光成分が回折効率η、３′で回折さ
れる。従って、回折効率η、ｐ・η、をそれぞれ０．０
１および０．９９とすると、１次回折光５ｂの偏光度は
回折格子３で約０．０１となり、回折格子４で約０．
ＯＯＯ１となる、これは、０次回指光５ａに含まれるＳ
偏光成分がほとんどないと考えてよいほど小さくなり、
１次回折光５ｂに含まれるＰ偏光成分も同様に小さくな
ることを意味している。On the other hand, the incident light 5 is diffracted by the diffraction grating 3 as first-order diffracted light 5b with a diffraction efficiency ηIp of the P-polarized light component and a diffraction efficiency η,5 of the S-polarized light component. And this first-order diffracted light 5
b is incident on the diffraction grating 4, and the P polarized light component has a diffraction efficiency ηtp
t, and the S-polarized component is diffracted with a diffraction efficiency η,3'. Therefore, the diffraction efficiency η and p・η are each 0.0.
1 and 0.99, the degree of polarization of the first-order diffracted light 5b is approximately 0.01 at the diffraction grating 3, and approximately 0.01 at the diffraction grating 4.
OOO1, which is S included in the 0th order instruction 5a
It is so small that it can be considered that there is almost no polarization component,
This means that the P-polarized light component included in the first-order diffracted light 5b also becomes smaller.
従って、上記のように、入射光５を回折格子３・４に通
過させることにより、入射光５におけるＰ偏光成分とＳ
偏光成分との分離度を実用に十分満足しうる程度に高く
することができる。Therefore, as described above, by passing the incident light 5 through the diffraction gratings 3 and 4, the P polarization component and the S
The degree of separation from polarized light components can be made high enough to be practically satisfactory.
〔実施例２〕
続いて、本発明の他の実施例を第４図に基づいて説明す
る。なお、前記実施例１と同様の機能を有する部材には
、同一の番号を付記しその説明を省略する。[Embodiment 2] Next, another embodiment of the present invention will be described based on FIG. 4. It should be noted that members having the same functions as those in the first embodiment will be denoted by the same numbers and their explanations will be omitted.
第４図に示すように、０次回指光５ａおよび１次回折光
５ｂをともに集光する集光レンズ１３が、それぞれの回
折光の光路上に設けられるとともに、集光レンズ１３に
よる所定の集光位置に光検出器８・１０が同一のパッケ
ージ１４内に配されている。As shown in FIG. 4, a condenser lens 13 for condensing both the 0th-order index light 5a and the 1st-order diffracted light 5b is provided on the optical path of each diffracted light, and a predetermined condensing lens 13 is provided on the optical path of each diffracted light. The photodetectors 8 and 10 are placed in the same package 14 at the same location.
このような構成では、Ｏ次回指光５ａおよび１次回折光
５ｂを１つの集光レンズ１３により、両部光成分のほぼ
中間位置に集光させて、光検出器８・１０を同一のパッ
ケージ１４内の基板部に並べて配置したり、Ｓｔ等の単
一の半導体基板上に形成するなどして近接して配置する
ことができる。In such a configuration, the O-order light 5a and the 1st-order diffracted light 5b are condensed by one condenser lens 13 to a position approximately midway between the two light components, and the photodetectors 8 and 10 are housed in the same package 14. They can be arranged side by side on the inner substrate part, or formed on a single semiconductor substrate such as St, and arranged close to each other.
なお、本実施例および前記実施例１の偏光回折素子１で
は、回折格子３・４を基板２の両面に工°ツチングによ
り形成しているが、これ以外に、例えばフォトレジスト
などで形成してもよいのは勿論である。また回折格子３
・４の格子の形状も１、第２図に示すような矩形に限定
されるものではない。In the polarization diffraction element 1 of this example and the above-mentioned example 1, the diffraction gratings 3 and 4 are formed on both sides of the substrate 2 by etching, but in addition to this, they may be formed of, for example, photoresist. Of course, it is also good. Also, the diffraction grating 3
- The shape of the lattice 4 is not limited to the rectangular shape shown in FIGS. 1 and 2.
本発明に係る偏光回折素子は、以上のように、入射光の
所定の波長程度の幅を有する格子間隔で形成された第１
の回折格子と第２の回折格子とが、それぞれ平板状の基
板における異なる面に設けられており、上記第１の回折
格子と第２の回折格子とは、互いに等しい格子間隔を有
し、かつ、互いの格子方向が一致するように形成されて
いる構成である。As described above, the polarization diffraction element according to the present invention has a first grating formed with a grating interval having a width approximately equal to a predetermined wavelength of incident light.
a diffraction grating and a second diffraction grating are provided on different surfaces of a flat substrate, and the first diffraction grating and the second diffraction grating have equal lattice spacing, and , the lattice directions are formed to match each other.
これによれば、入射光は、第１の回折格子および第２の
回折格子により異なる偏光成分の光束として分離されて
、偏光回折素子から常に平行に出射される。それゆえ、
入射光の波長が変化しても上記偏光成分の光束間の平行
関係を保つことができる。According to this, the incident light is separated into light beams of different polarization components by the first diffraction grating and the second diffraction grating, and is always emitted in parallel from the polarization diffraction element. therefore,
Even if the wavelength of the incident light changes, the parallel relationship between the light beams of the polarized light components can be maintained.
従って、偏光回折素子を光ピツクアップに組み込む場合
、異なる偏光成分を検出する光検出器を近接した位置に
設けることにより、光ピツクアップの小型化を図ること
ができる。また、集光レンズ等の光学系を介して、それ
ぞれの偏光成分を光検出器の所定の位置に導くことによ
り、偏光成分の検出精度を向上させることができるとい
う効果を奏する。Therefore, when a polarization diffraction element is incorporated into an optical pickup, the optical pickup can be made smaller by providing photodetectors for detecting different polarization components in close positions. Further, by guiding each polarized light component to a predetermined position of the photodetector via an optical system such as a condensing lens, it is possible to improve the detection accuracy of the polarized light component.
【図面の簡単な説明】
第１図ないし第３図は本発明の一実施例を示すものであ
って、第１図は偏光回折素子の構成および偏光回折素子
による入射光の回折の状態を示す縦断面図、第２図は回
折格子の構成を示す第１図の部分拡大図、第３図は偏光
回折素子により分離された偏光成分を検出する構成を示
す縦断面図、第４図は本発明の他の実施例を示すもので
あって、偏光回折素子により分離された偏光成分を検出
する構成を示す縦断面図である。
第５図は従来例の偏光回折素子の構成および偏光回折素
子による入射光の回折の状態を示す縦断面図である。
２は基板、３・４は回折格子である。
特許出願人 シャープ 株式会社纂
図
罵
図
某
！
フ１[Brief Description of the Drawings] Figures 1 to 3 show an embodiment of the present invention, and Figure 1 shows the configuration of a polarization diffraction element and the state of diffraction of incident light by the polarization diffraction element. 2 is a partially enlarged view of FIG. 1 showing the configuration of the diffraction grating, FIG. 3 is a vertical sectional view showing the configuration for detecting polarized light components separated by a polarization diffraction element, and FIG. 4 is a partial enlarged view of FIG. FIG. 7 is a vertical cross-sectional view showing another embodiment of the invention and showing a configuration for detecting polarized light components separated by a polarization diffraction element. FIG. 5 is a vertical cross-sectional view showing the configuration of a conventional polarization diffraction element and the state of diffraction of incident light by the polarization diffraction element. 2 is a substrate, and 3 and 4 are diffraction gratings. Patent Applicant: SHARP Co., Ltd. F1
Claims (1)
成された第１の回折格子と第２の回折格子とが、それぞ
れ平板状の基板における異なる面に設けられており、上
記第１の回折格子と第２の回折格子とは、互いに等しい
格子間隔を有し、かつ、互いの格子方向が一致するよう
に形成されていることを特徴とする偏光回折素子。1. A first diffraction grating and a second diffraction grating formed with a grating interval having a width approximately equal to a predetermined wavelength of incident light are provided on different surfaces of a flat substrate, and A polarization diffraction element characterized in that the diffraction grating and the second diffraction grating have equal grating intervals and are formed so that their grating directions coincide with each other.
Priority Applications (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1081707A JPH02259702A (en) | 1989-03-31 | 1989-03-31 | Polarization diffraction element |
| US07/500,292 US5085496A (en) | 1989-03-31 | 1990-03-28 | Optical element and optical pickup device comprising it |
| CA002013538A CA2013538C (en) | 1989-03-31 | 1990-03-30 | Optical element and optical pickup device comprising it |
| DE69033972T DE69033972T2 (en) | 1989-03-31 | 1990-03-30 | Optical component and optical playback device provided with it. |
| EP97111248A EP0803868B1 (en) | 1989-03-31 | 1990-03-30 | Optical element and optical pickup device comprising the same |
| DE69032301T DE69032301T2 (en) | 1989-03-31 | 1990-03-30 | Optical element and optical scanning device containing the same |
| EP90303482A EP0390610B1 (en) | 1989-03-31 | 1990-03-30 | Optical element and optical pickup device comprising the same |
| KR1019900004358A KR0144569B1 (en) | 1989-03-31 | 1990-03-30 | Optical elements and optical pick-up device comprising it |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1081707A JPH02259702A (en) | 1989-03-31 | 1989-03-31 | Polarization diffraction element |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02259702A true JPH02259702A (en) | 1990-10-22 |
Family
ID=13753856
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1081707A Pending JPH02259702A (en) | 1989-03-31 | 1989-03-31 | Polarization diffraction element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02259702A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0462757A2 (en) * | 1990-06-13 | 1991-12-27 | Sharp Kabushiki Kaisha | Polarization diffraction element and polarization detector employing the same |
| JPH04257801A (en) * | 1991-02-13 | 1992-09-14 | Sharp Corp | Manufacture of polarized light diffraction element |
| JPH05216386A (en) * | 1991-10-11 | 1993-08-27 | Internatl Business Mach Corp <Ibm> | Hologram system |
| JPH06222706A (en) * | 1992-12-17 | 1994-08-12 | Internatl Business Mach Corp <Ibm> | Hologram system and its manufacture |
| US5473470A (en) * | 1992-09-28 | 1995-12-05 | Sharp Kabushiki Kaisha | Polarization detector |
| JP2008233216A (en) * | 2007-03-16 | 2008-10-02 | Ricoh Co Ltd | Beam-splitting element |
| JP2008233226A (en) * | 2007-03-16 | 2008-10-02 | Ricoh Co Ltd | Beam-splitting element |
| WO2010127347A3 (en) * | 2009-05-01 | 2011-02-17 | Toyota Motor Engineering And Manufacturing North America, Inc. | Grating structure for splitting light |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57155508A (en) * | 1981-02-23 | 1982-09-25 | Xerox Corp | Polaroid beam splitter |
-
1989
- 1989-03-31 JP JP1081707A patent/JPH02259702A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57155508A (en) * | 1981-02-23 | 1982-09-25 | Xerox Corp | Polaroid beam splitter |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0462757A2 (en) * | 1990-06-13 | 1991-12-27 | Sharp Kabushiki Kaisha | Polarization diffraction element and polarization detector employing the same |
| US5257131A (en) * | 1990-06-13 | 1993-10-26 | Sharp Kabushiki Kaisha | Polarization diffraction element and polarization detector employing the same |
| JPH04257801A (en) * | 1991-02-13 | 1992-09-14 | Sharp Corp | Manufacture of polarized light diffraction element |
| JPH05216386A (en) * | 1991-10-11 | 1993-08-27 | Internatl Business Mach Corp <Ibm> | Hologram system |
| US5473470A (en) * | 1992-09-28 | 1995-12-05 | Sharp Kabushiki Kaisha | Polarization detector |
| JPH06222706A (en) * | 1992-12-17 | 1994-08-12 | Internatl Business Mach Corp <Ibm> | Hologram system and its manufacture |
| JP2008233216A (en) * | 2007-03-16 | 2008-10-02 | Ricoh Co Ltd | Beam-splitting element |
| JP2008233226A (en) * | 2007-03-16 | 2008-10-02 | Ricoh Co Ltd | Beam-splitting element |
| WO2010127347A3 (en) * | 2009-05-01 | 2011-02-17 | Toyota Motor Engineering And Manufacturing North America, Inc. | Grating structure for splitting light |
| US8264773B2 (en) | 2009-05-01 | 2012-09-11 | Toyota Motor Engineering And Manufacturing North America, Inc. | Grating structure for splitting light |
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