JPH0375612A - Optical system for converting distribution of laser beam intensity - Google Patents

Abstract

PURPOSE:To convert laser beam intensity and to change the form of the conversion by specifying the focal length and spherical aberration of a Kepler type of 4-element constitution in two groups constituted of a 1st group and 2nd group which are respectively constituted of two elements of lenses and have a positive refracting power. CONSTITUTION:This optical system is made of the 4-element constitution in two groups of the Kepler type. The 1st group G1 is constituted of two elements of the lenses L1, L2 and has the positive refracting power. The 2nd group G2 is also constituted of two elements of the lenses L3, L4 and has the positive refracting poer. If the height of the ray at the exit pupil when the ray made incident at the height h1 of the ray (0<=h1<=3.2mm) on the incident pupil of the 1st group is emitted from the 2nd group, is designated as h2, focal length and spherical aberration of the 1st group, designated respectively as f1, S1(h1), and the focal length and spherical aberration of the 2nd group, designated respectively as f2, S2(h2), equation I to equation V are satisfied during zooming. The beam intensity of the laser beam flux having a Gaussian distribution is converted to the distribution having a flat distribution region in this way; in addition, the continuous change of the diameter of the flat distribution region is possible.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a laser light intensity distribution conversion optical system.

[Prior Art] As is well known, the light intensity distribution of a laser beam on a cross section of the beam follows a Gaussian distribution. For this reason, there are problems with the accuracy of processing techniques using laser beams, and in view of this problem, efforts are being made to make the light intensity distribution on the cross section of the laser beam uniform. An optical system for converting such a light intensity distribution is a laser light intensity distribution conversion optical system.

A relatively successful example of an optical system for converting laser light intensity distribution is that disclosed in Japanese Unexamined Patent Publication No. 188115/1983.

[Problems to be Solved by the Invention] However, in the above laser light intensity distribution conversion optical system, the conversion mode of the light intensity distribution is unique, and the converted laser light intensity distribution cannot be changed or adjusted.

The present invention was made in view of the above-mentioned circumstances, and
The object of the present invention is to provide a novel laser light intensity distribution conversion optical system that can convert laser light intensity and change the conversion mode.

[Means to solve the problem] The present invention will be explained below.

The laser beam intensity distribution converting optical system of the present invention is designed to convert a laser beam that is incident as a substantially parallel beam to an approximately parallel beam, and change the light intensity distribution on a cross section of the emitted laser beam to a substantially uniform light intensity. An optical system that converts a distribution into a distribution including a flat distribution area and that can continuously change the diameter of the flat distribution area by zooming.

This laser light intensity distribution conversion optical system is a Keplerian type 2
It consists of 4 elements in a group.

The "first group" is composed of two lenses and has positive refractive power. The "second group" is also composed of two lenses and has positive refractive power.

Then, the ray height h1 (0≦h,≦3
．． 2a+m) is the ray height at the exit pupil when it exits from the second group, and the focal length and spherical aberration in the first group are f, S, respectively.

(hi) Focal length and spherical aberration in the second group.

When fz and 5z (hz) respectively, during zooming, (I) 19.9j; 7≦f, ≦20.0 (II)
2. 'ZO<l:f,<; 2.66 (III)
S+(hx)>O and 5z(h2)<.

(IV) 1si(hx)+5z(hz)l<
0.02 (■) 0.26 ≦S□ (ht=3.
2mm)≦0.33.

[Function] APP is a method that utilizes spherical aberration to convert a Gaussian laser light intensity distribution to obtain a uniform light intensity distribution.
LIED 0PTIC5 Volume 4 No. 11 (1965.14
00-1403), and a method using the sine condition is disclosed in Japanese Patent Application Laid-Open No. 188115/1983.

The present invention utilizes spherical aberration.

The first group consisting of two lenses has a positive refractive index,
When the spherical aberration when a parallel light beam is incident on this from the incident side is S□ (hl) with respect to the incident ray height h□,
s, (ht)>o (condition (III)).

In addition, the second lens is composed of two lenses and has positive refractive power.
The spherical aberration when a parallel beam of light is incident on the group from the "exit side" is the ray height h! When 52 (hz) for
52(h2)<O.

The first one that satisfies such spherical aberration conditions. When the second group is combined so as to satisfy the above condition (VI), a substantial afocal system is obtained. That is, when a substantially parallel light beam is made incident on this optical system, a substantially parallel light beam is emitted.

Referring to FIG. 6, the conditions under which the light beam with the incident light beam height hl and the light beam with the exit light beam height h2 are parallel to each other are hx,
hx, together with S and focal length f, f2 in the figure, h,=
(f, -5)h1/(f1+s). In order for this condition to hold strictly, the spherical aberration S□(h,
), and it is necessary that the spherical aberration SR (hz) of the second group for the ray with the exit ray height h2 satisfies the following: If the difference between the absolute values of the spherical aberrations 5s (ht) and 5z (hz) is small enough to satisfy the following, the emitted light ray will be approximately parallel to the incident light ray.

At this time, if condition (V) is satisfied as well as conditions (1) and (II), the diameter of the flat distribution region in the light intensity distribution of the emitted light beam can be continuously changed by zooming.

[Example] Hereinafter, description will be given based on specific examples.

Referring to FIG. 1, in this figure, the symbol G1 indicates the first group, and the symbol G2 indicates the second group. 6 First group G1
is composed of two meniscus lenses Ll and L2, and has positive refractive power as a whole. The second group G2 also has two meniscus lenses L3. L4, which also has positive refractive power as a whole.

The radius of curvature of the i-th lens surface counting from the incident side (left side of the construction drawing) is Rj, the distance between the i-th lens surfaces is Di, and the refractive index of the j-th lens counting from the incident side (wavelength jo & o
oγ ablation) as Nj, these are given as follows.

i Ri Di j N
jl 17.512 4.541 1
2.40285°961 Variable 3 -19.323 9.206 2 2
．． 404-25.818 Variable 5 2.841 2.183 3 2-
406 6.505 Variable 7 -5.079 2.393 4 2.
408 -14.598 The lens arrangement shown in FIG. 1 shows a state in which the above variable amount takes the following values.

1 2 4 6 Di 1.5 18.373 2.131The spherical aberration of the first group G1 at this time is shown in Fig. 2(a).

Further, the spherical aberration of the second group G2 is shown in FIG. 2(b). child(
7) To'i! ! 5t (hx=3.2m++)=0.
33 Thea'J, of course condition (VI) is satisfied.

At this time, the focal length f of the first group is 20.00, and the focal length f2 of the second group is 2.66.

In this state, when a parallel laser beam having a Gaussian distribution 5-1 as shown by the solid line in FIG. It becomes a non-Gaussian distribution type as shown by curve 5-2. That is, with respect to the incident light beam having a beam diameter of 12.8 mm, the intensity distribution of the output light beam is made uniform with an accuracy of ±0.25% up to a region with a beam diameter of 0' and 8+++ m. This region (region with radius dO) is called a flat distribution region.

FIG. 3 shows the lens arrangement when the variable amount is set as follows.

1 2 4 6 Di 2-0 17.311 3.5 The spherical aberration of the first group G1 at this time is shown in Fig. 4(a), and the second
The spherical aberration of group G2 is shown in FIG. 4(b).

At this time, the focal path of the first group! ! f□=19.9t7.
The focal length f of the second group is 2.20. Also, St.
(ht=3.2mm)=0.26.

In this state, the parallel laser beam that enters with the Gaussian distribution 5-1 described above is the fifth in the output beam.
As shown by curve 5-3 in the figure, the area with a beam diameter of 0°5 mm (
The intensity distribution is converted into a uniform light intensity distribution with an accuracy of ±0.25% up to the region of radius dl).

In this way, in this embodiment, the focal paths of the first group and the second group!
The range of f, , f2 is 19.9 digits 7≦ f, ≦20.0, 2.20≦f2
1 condition (III) in the range of ≦2.66, I″i) to (
Zooming can be performed while satisfying V), and by this zooming, the light intensity distribution of the emitted light flux changes continuously from the distribution between the curves 5-2 and 5-3 in Fig. 5, and becomes a flat distribution. The diameter of the area changes continuously.

[Effects of the Invention] As described above, according to the present invention, a novel laser light intensity distribution conversion optical system can be provided. Since this optical system is configured as described above, it is possible to convert the light intensity of a laser beam having a Gaussian distribution into a distribution that includes a flat distribution area, and also to continuously change the diameter of the flat distribution area. . Therefore 1
For example, if it is used as a light beam for optical CVD for producing microlenses, Beresoth-type lenses can be produced.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams for explaining the present invention based on examples, and Figure 6 is a diagram for explaining conditions (m. '6) place) z (tn 仄) dust check f jinmon (＾) (mu) A A horse 7ﾉｹｹﾎﾎﾎﾎｲｲｲ

Claims (1)

[Claims] A laser beam that enters as a substantially parallel beam is emitted as a substantially parallel beam, and the light intensity distribution on a cross section of the beam in the emitted laser beam is a distribution that includes a flat distribution area of substantially uniform light intensity. and continuously change the diameter of the flat distribution area by zooming, the optical system comprises a first group and a second group, each of which is composed of two lenses and has a positive refractive power. It is a Keplerian type composed of 4 elements in 2 groups, and the entrance pupil of the first group has a ray height h_1 (0≦h_1≦3
．． Let h_2 be the ray height at the exit pupil when the incident light ray exits from the second group, and let the focal length and spherical aberration in the first group be f_1 and S_1(
h_1), the focal length and spherical aberration in the second group,
When f_2 and S_2(h_2) respectively, these are (I) 19.957≦f_1≦20.0 (II) 2.20≦f_2≦2.66 (III) S_1(h_1)>0 and S_2( h_2)<
0 (IV) | S_1 (h_1) + S_2 (h_2) | ≦0
．． 02(V)0.26≦S_1(h_1=3.2mm)
A laser light intensity distribution conversion optical system that can perform zooming while satisfying the condition of ≦0.33.