JPH0369083B2 - - Google Patents
Info
- Publication number
- JPH0369083B2 JPH0369083B2 JP20052783A JP20052783A JPH0369083B2 JP H0369083 B2 JPH0369083 B2 JP H0369083B2 JP 20052783 A JP20052783 A JP 20052783A JP 20052783 A JP20052783 A JP 20052783A JP H0369083 B2 JPH0369083 B2 JP H0369083B2
- Authority
- JP
- Japan
- Prior art keywords
- lens
- refractive index
- semiconductor laser
- light source
- condition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000004065 semiconductor Substances 0.000 claims description 13
- 230000010355 oscillation Effects 0.000 claims description 3
- 230000004075 alteration Effects 0.000 description 9
- 230000003287 optical effect Effects 0.000 description 7
- 238000005498 polishing Methods 0.000 description 3
- 230000005855 radiation Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229920003217 poly(methylsilsesquioxane) Polymers 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Landscapes
- Lenses (AREA)
Description
【発明の詳細な説明】
本発明は光情報記録、光学的読み取り装置、レ
ーザービームプリンタ等の光ビームスキヤン装置
において半導体レーザからの放射光を平行ビーム
にコリメートするめの屈折率分布型コリメートレ
ンズに関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gradient index collimating lens for collimating light emitted from a semiconductor laser into a parallel beam in an optical beam scanning device such as an optical information recording device, an optical reading device, or a laser beam printer. It is.
上記装置のコリメートレンズは、半導体レーザ
からの放射光を低収差でコリメートするためその
残留波面収差がλ/4以内に納まることが必須条
件である。ここでλは半導体レーザの発振波長で
あり一般的には760≦λ≦850nmである。また小
型軽量であることや廉価であることも要求され
る。 The collimating lens of the above device collimates the light emitted from the semiconductor laser with low aberration, so it is essential that the residual wavefront aberration is within λ/4. Here, λ is the oscillation wavelength of the semiconductor laser, and is generally 760≦λ≦850 nm. It is also required to be small, lightweight, and inexpensive.
上記のような光ビームスキヤン装置に使用され
る波長は一般に単波長であるため、レンズの透過
率が出来る限り高い方がその分レーザーの発光パ
ワーを抑制でき、信頼性を向上させることが可能
となる。したがつて対策としてレンズ表面に反射
防止膜を施し、レンズ枚数も極力少なくすること
が有利である。 Since the wavelength used in the above-mentioned optical beam scanning device is generally a single wavelength, the higher the transmittance of the lens as possible, the more the laser emission power can be suppressed and the reliability can be improved. Become. Therefore, as a countermeasure, it is advantageous to apply an antireflection film to the lens surface and to reduce the number of lenses as much as possible.
以上説明したような諸要求を一応満足するコリ
メータレンズは屈折率の一様な通常の球面レンズ
3〜4枚で構成したものが知られている。しかし
この種の従来の球面レンズは球研磨する加工面が
6〜8面と多くしかもレンズ径が非常に小さいも
のであるため、研磨加工が難しく且つレンズの組
合せに高度の技術が要求され、かなりのコストア
ツプにつながつてしまう。 A collimator lens that satisfies the various requirements described above is known to be composed of three or four ordinary spherical lenses having a uniform refractive index. However, with this type of conventional spherical lens, there are 6 to 8 surfaces to be polished, and the lens diameter is very small, making polishing difficult and requiring advanced technology to combine the lenses. This will lead to an increase in costs.
本発明の目的は従来の球面レンズ系からなるコ
リメートレンズと同等またはそれ以下の残留波面
収差を呈し、かつ光の入出射面が平らな2面から
なりしたがつて研磨加工が極めて容易で安価に量
産できる半導体レーザ用屈折率分布型カリメート
レンズを提供することにある。 The object of the present invention is to exhibit a residual wavefront aberration equal to or less than that of a collimating lens made of a conventional spherical lens system, and to have two flat light entrance/exit surfaces, which makes polishing extremely easy and inexpensive. The object of the present invention is to provide a gradient index calimeter lens for semiconductor lasers that can be mass-produced.
本発明の半導体レーザ用コリメートレンズは、
中心rの距離における屈折率n(r)がn2(r)=
no2〔1−(gr)2+h4(gr)4+h6(gr)6+…〕で表わ
される円柱状透明媒質からなる屈折率分布型ロツ
ドレンズであつて以下の条件を満たすことを特徴
とする。 The collimating lens for semiconductor laser of the present invention is
The refractive index n(r) at the distance from the center r is n 2 (r)=
No 2 [1-(gr) 2 +h 4 (gr) 4 +h 6 (gr) 6 +...] A graded index rod lens made of a cylindrical transparent medium, which satisfies the following conditions. do.
(1) r1=∞
(2) r2=∞
(3) 6.70≦Z+fB≦7.30mm
(4) 2ro≧2.0mm
(5) 1.60≦no≦1.65
(6) 0.18≦g≦0.22mm-1
(7) 0.38≦h4≦0.87
(8) 1h61<5
(9) 0.21≦NA≦0.24
(10) 760≦λ≦850nm
上記(1)〜(10)の条件においてr1、r2はレンズ入射
面、出射面の曲率半径、Zはレンズ長、fBは光源
(物体)側バツクフオーカス、roは有効半径、
NAは光源側の開口数、noは中心軸上の屈折率、
g、h4、h6は分布定数で、λは半導体レーザの発
振波長である。(1) r 1 =∞ (2) r 2 =∞ (3) 6.70≦Z+f B ≦7.30mm (4) 2ro≧2.0mm (5) 1.60≦no≦1.65 (6) 0.18≦g≦0.22mm -1 (7) 0.38≦h 4 ≦0.87 (8) 1h 6 1<5 (9) 0.21≦NA≦0.24 (10) 760≦λ≦850nm Under the conditions (1) to (10) above, r 1 and r 2 are The radius of curvature of the lens entrance surface and exit surface, Z is the lens length, f B is the back focus on the light source (object) side, ro is the effective radius,
NA is the numerical aperture on the light source side, no is the refractive index on the central axis,
g, h 4 and h 6 are distribution constants, and λ is the oscillation wavelength of the semiconductor laser.
上記条件のうち条件(1)、(2)はレンズの入射端面
出射端面が平面であることを示し、両面が平らな
ため同時に多数個を固めて平面研磨を行なうこと
ができ、研磨時の加工能率が著しく向上し加工コ
ストを大幅に低減できる特長を有する。 Among the above conditions, conditions (1) and (2) indicate that the entrance end face and the exit end face of the lens are flat, and since both sides are flat, it is possible to consolidate many lenses at the same time and perform flat polishing. It has the advantage of significantly improving efficiency and significantly reducing processing costs.
条件(3)は条件(9)の開口数NAを決めるもので、
この範囲から出るとNAが大きすぎたり小さすぎ
たりする。条件(4)は有効径を決めるもので、前述
のような光ビームスキヤン装置では一般的に2mm
φの有効径が必要とされ、よつてレンズ外径は2
mmφより大きい値が選ばれる。条件(5)、(6)は、条
件(9)のNAと条件(4)の有効径を満しかつ一定のバ
ツクフオーカスfBを得るために必要な屈折率分布
定数でNOは中心光軸上の屈折率でgは屈折率の
勾配をあらわし、一般レンズの球面の曲率半径を
相当する。gは大きすぎるとfBが短かくなりす
ぎ、小さすぎるとNAが小さすぎてしまう。条件
(7)はレンズの球面差を小さくするための屈折率分
布定数h4の条件である。この範囲はレンズ長さ
Z、中心屈折率NO、g定数により若干異なる
が、第2図に示す用にNO=1.63、g=0.2とした
場合レンズ長Zは3.6≦Z≦4.24の範囲でないと
条件(9)を満たさない。その時最適なh4は第2図中
の上下直線で狭まれた領域で2重斜線内は波面収
差がλ/8以内に納まる条件で斜線内はλ/4内
に納まる範囲である。例えばZ=3.6mmだと0.52
≦h4≦0.72で波面収差WsはWs≦λ/8となる。
0.38≦h4≦0.82ではWs≦λ/4である。条件(8)は
レンズ外周近くの球面差に影響する屈折率分布定
数h6に関する条件である。この条件を越えると周
辺部で大きな高次収差、特に5次収差が発生し球
面収差が著しく悪化する。条件(9)は半導体レーザ
からの放射角を効率よくかつ一様な強度をもつ平
行光にコリメートするための条件で、一般的にレ
ーザの放射角は方向により異なる小さい方で約
15°前後のものが多いためHAに換算して、NA〜
0.25またはそれ以下とした。レンズのNAが小さ
すぎると効率が低下してしまうし、大きすぎると
半導体レーザの放射角がその活性層の方向とその
直角方向で異なるため、円形断面の平行ビームが
得られず、楕円の断面をもつ平行光となつてしま
う。このためレンズのNAは0.21ないし0.24の範
囲内とする必要がある。 Condition (3) determines the numerical aperture NA of condition (9),
Outside this range, the NA will be too large or too small. Condition (4) determines the effective diameter, which is generally 2 mm in the optical beam scanning device described above.
An effective diameter of φ is required, so the lens outer diameter is 2
A value larger than mmφ is chosen. Conditions (5) and (6) are the refractive index distribution constants necessary to satisfy the NA of condition (9) and the effective diameter of condition (4) and to obtain a constant back focus f B , and NO is on the central optical axis. In the refractive index, g represents the gradient of the refractive index, and corresponds to the radius of curvature of the spherical surface of a general lens. If g is too large, f B will be too short, and if g is too small, NA will be too small. conditions
(7) is a condition for the refractive index distribution constant h 4 to reduce the spherical difference of the lens. This range varies slightly depending on the lens length Z, center refractive index NO, and g constant, but when NO=1.63 and g=0.2 as shown in Figure 2, the lens length Z must be within the range of 3.6≦Z≦4.24. Condition (9) is not satisfied. In this case, the optimum h 4 is the area narrowed by the vertical straight lines in FIG. 2, where the wavefront aberration is within λ/8 within the double diagonal lines, and within λ/4 within the diagonal lines. For example, if Z = 3.6mm, it is 0.52
When ≦h 4 ≦0.72, the wavefront aberration Ws becomes Ws≦λ/8.
When 0.38≦h 4 ≦0.82, Ws≦λ/4. Condition (8) is a condition regarding the refractive index distribution constant h 6 that affects the spherical difference near the outer periphery of the lens. If this condition is exceeded, large high-order aberrations, especially fifth-order aberrations, will occur in the peripheral areas, and spherical aberrations will significantly worsen. Condition (9) is a condition for efficiently collimating the radiation angle from a semiconductor laser into parallel light with uniform intensity. Generally, the radiation angle of a laser varies depending on the direction, and is approximately
Since many of them are around 15°, converting to HA, NA~
0.25 or less. If the NA of the lens is too small, the efficiency will decrease, and if it is too large, the radiation angle of the semiconductor laser will be different in the direction of its active layer and in the direction perpendicular to it, making it impossible to obtain a parallel beam with a circular cross section, but with an elliptical cross section. It becomes parallel light with . For this reason, the NA of the lens needs to be within the range of 0.21 to 0.24.
第1図に本発明に係る半導体レーザ用屈折率分
布型レンズの作用を示す。1ガラスあるいは合成
樹脂等の透明円柱状媒質から成るロツドレンズで
あり、このレンズ1の入射端面4および出射端面
5は光軸0−0に垂直な平行平面である。また、
2は半導体レーザ光源で3はレンズ絞りである。
レンズ1の入射端面4からfBの距離におかれた光
源2から拡散放射される光線はレンズ1によつて
平行光にコリメートされ、半径roの開口をもつ絞
り3を通した後、情報記録媒体等に放射される。 FIG. 1 shows the function of the gradient index lens for semiconductor lasers according to the present invention. The lens 1 is a rod lens made of a transparent cylindrical medium such as glass or synthetic resin, and the entrance end surface 4 and exit end surface 5 of this lens 1 are parallel planes perpendicular to the optical axis 0-0. Also,
2 is a semiconductor laser light source, and 3 is a lens aperture.
Light rays diffusely emitted from a light source 2 placed at a distance f B from the incident end surface 4 of a lens 1 are collimated into parallel light by a lens 1, and after passing through an aperture 3 having an aperture with a radius of ro, information is recorded. Emitted to the medium, etc.
以上説明した本発明のコリメータレンズの数値
実施例を次に示す。 Numerical examples of the collimator lens of the present invention described above will be shown below.
実施例 1 r1=∞ r2=∞ Z=3.60mm 2ro=2.0mm no=1.63 g=0.2 0.52<h4<0.72 h6=0.30 NA=0.21 fB=3.50mm fB+Z=7.10mm 実施例 2 (λ=780nm時) r1=∞ r2=∞ Z=4.24mm 2ro=2.0mm no=1.63 g=0.2 0.62<h4<0.78 h6=0.30 NA=0.24 fB=2.7mm fB+Z=6.94mmExample 1 r 1 =∞ r 2 =∞ Z=3.60mm 2ro=2.0mm no=1.63 g=0.2 0.52<h 4 <0.72 h 6 =0.30 NA=0.21 f B =3.50mm f B +Z=7.10mm Implementation Example 2 (When λ=780nm) r 1 =∞ r 2 =∞ Z=4.24mm 2ro=2.0mm no=1.63 g=0.2 0.62<h 4 <0.78 h 6 =0.30 NA=0.24 f B =2.7mm f B +Z=6.94mm
第1図は本発明のレンズの諸元を示す断面図、
第2図は波面収差をλ/8ないしλ/4以内にす
るための屈折率分布定数h4の領域を示す図であ
る。
1……屈折率分布型ロツドレンズ、2……光源
(半導体レーザー)、3……絞り、4……入射端
面、5……射出端面。
FIG. 1 is a sectional view showing the specifications of the lens of the present invention;
FIG. 2 is a diagram showing the range of the refractive index distribution constant h 4 for keeping the wavefront aberration within λ/8 to λ/4. DESCRIPTION OF SYMBOLS 1... Gradient index rod lens, 2... Light source (semiconductor laser), 3... Aperture, 4... Incidence end surface, 5... Output end surface.
Claims (1)
n2(r)=no2〔1−(gr)2+h4(gr)4+h6(gr)6+
…〕
で表わされる円柱状透明媒質からなる屈折率分布
型ロツドレンズであつて、以下の条件を満たすこ
とを特徴とする半導体レーザ用コリメータレン
ズ。 (1) r1=∞ (2) r2=∞ (3) 6.70≦Z+fB≦7.30mm (4) 2ro≧2.0mm (5) 1.60≦no≦1.65 (6) 0.18≦g≦0.22mm-1 (7) 0.38≦h4≦0.87 (8) 1h61<5 (9) 0.21≦NA≦0.24 (10) 760≦λ≦850nm ただし、r1、r2は入射面、出射面の曲率半径、
Zはレンズ長、fBは光源(物体)側バツクフオー
カス、roは有効半径、NAは光源側の開口数、no
は中心軸上の屈折率でg、h4、h6は屈折率分布定
数、λは半導体レーザの発振波長。[Claims] 1. The refractive index n(r) at a distance r from the center is
n 2 (r) = no 2 [1-(gr) 2 +h 4 (gr) 4 +h 6 (gr) 6 +
…]
A collimator lens for a semiconductor laser, which is a graded refractive index rod lens made of a cylindrical transparent medium represented by: (1) r 1 =∞ (2) r 2 =∞ (3) 6.70≦Z+f B ≦7.30mm (4) 2ro≧2.0mm (5) 1.60≦no≦1.65 (6) 0.18≦g≦0.22mm -1 (7) 0.38≦h 4 ≦0.87 (8) 1h 6 1<5 (9) 0.21≦NA≦0.24 (10) 760≦λ≦850nm However, r 1 and r 2 are the radius of curvature of the entrance surface and exit surface,
Z is the lens length, f B is the back focus on the light source (object) side, ro is the effective radius, NA is the numerical aperture on the light source side, no
is the refractive index on the central axis, g, h 4 and h 6 are the refractive index distribution constants, and λ is the oscillation wavelength of the semiconductor laser.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP20052783A JPS6091316A (en) | 1983-10-26 | 1983-10-26 | Distributed refractive index type collimator lens for semiconductor laser |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP20052783A JPS6091316A (en) | 1983-10-26 | 1983-10-26 | Distributed refractive index type collimator lens for semiconductor laser |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS6091316A JPS6091316A (en) | 1985-05-22 |
JPH0369083B2 true JPH0369083B2 (en) | 1991-10-30 |
Family
ID=16425789
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP20052783A Granted JPS6091316A (en) | 1983-10-26 | 1983-10-26 | Distributed refractive index type collimator lens for semiconductor laser |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS6091316A (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06337347A (en) * | 1993-03-30 | 1994-12-06 | Konica Corp | Optical system including distributed refractive index type optical element |
JP3485685B2 (en) * | 1995-08-04 | 2004-01-13 | オリンパス株式会社 | Refractive index single lens |
JP2002196181A (en) * | 2000-12-25 | 2002-07-10 | Nippon Sheet Glass Co Ltd | Optical fiber attached with lens function and its manufacturing method |
JP2002328259A (en) | 2001-04-26 | 2002-11-15 | Nippon Sheet Glass Co Ltd | Optical element |
-
1983
- 1983-10-26 JP JP20052783A patent/JPS6091316A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS6091316A (en) | 1985-05-22 |
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