JPH0392815A - Conversion system for laser light intensity distribution - Google Patents

Abstract

PURPOSE:To vary the light intensity distribution of a laser luminous flux continuously by a single optical system by putting a laser light intensity conversion optical system in zooming operation while specific conditions are satisfied. CONSTITUTION:The light intensity distribution is converted by utilizing a spherical aberration. A 1st group G1 consisting of two lenses L1 and L2 has a positive refractive index and S1(h1)>0, where the spherical aberration when parallel luminous flux is made incident from an incidence side is denoted as S1(h1) for the height h1 of the incident light beam. Further, S2(h2)<0, where S2(h2) is the spherical aberration when parallel luminous flux is made incident on a 2nd group G2 consisting of two lenses L3 and L4 while having positive refracting power from 'projection side' for the height h2 of the light beam. Those spherical aberration conditions are satisfied and the distance between the lenses is varied while the inequalities I and II are satisfied, thereby performing the zooming operation. Consequently, the light intensity distribution of the projection luminous flux can be varied continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser light intensity distribution conversion optical system. The present invention can be used in microlens manufacturing technology.

[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. This Gaussian light intensity distribution is effectively used in the production of microlenses. In other words, if photo-CVD is performed while the substrate surface is irradiated with a laser beam, the temperature of the substrate will have a temperature distribution that follows the Gaussian intensity distribution of the laser beam, making it impossible to obtain microlenses with curved surfaces. can.

[Problems to be Solved by the Invention] However, the lens surface shape of the microlens is required to have various shapes depending on the design conditions of the lens.

Therefore, in consideration of versatility when manufacturing microlenses, it is preferable that the light intensity distribution on the beam cross section of the laser beam can be realized not only a Gaussian distribution but also a non-Gaussian distribution. Not only one type,
It would be desirable to be able to achieve different types of distributions.

A method using two laser beams has been proposed as a method of realizing a desired temperature distribution on a substrate depending on the lens surface shape of the microlens to be fabricated (Japanese Patent Application Laid-Open No. 1983-1999).
260104, etc.), there is a problem that the optical system becomes complicated and expensive due to the use of two laser beams.

The present invention has been made in view of the above-mentioned circumstances, and aims to provide a novel laser light intensity conversion optical system that can continuously convert the light intensity distribution of a laser beam with a single optical system. do.

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

The laser beam intensity conversion optical system of the present invention emits a laser beam that is incident as a substantially parallel beam, and changes the light intensity distribution on the beam cross section of the emitted laser beam to the beam cross section of the incident laser beam. This is a Keplerian-type optical system J that can continuously perform a light intensity distribution conversion to differ from the light intensity distribution by zooming, and is composed of four elements in two groups.

The "King Group" is composed of two lenses and has positive refractive power.

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

Let h2 be the ray height when a ray that enters the first group from the incident side at a ray height h1 exits from the second group, and the spherical aberration in the first group is s+ (h+), and the spherical aberration in the second group is When the spherical aberration at 32 (h2), the absolute value of these spherical aberrations is given by the argument h. , h2, and the laser light intensity conversion optical system is (1) SE(hl)>O
and Sz(h2)<0(II) S+(h+)+32
(h2) It is configured so that zooming can be performed while satisfying the condition l < 0.1.

[Function] Regarding the conversion of the light intensity distribution of the laser beam, a method using spherical aberration is APPLIED OPTICS.
Vol. 4, No. 1l (1965, pp. 1400-1403) also describes a method using the sine condition in JP-A-63-188.
It is disclosed in Publication No. 115.

However, all of these methods aim to convert a Gaussian light intensity distribution to obtain a uniform light intensity distribution.

In the present invention, the light intensity distribution is converted by utilizing spherical aberration.

The first group consisting of two lenses has a positive refractive index,
When the spherical aberration when a parallel beam is incident on this from the incident side is 31 (hl) with respect to the incident beam height h,
Let S1(t++)>O.

In addition, the second lens is composed of two lenses and has positive refractive power.
The spherical aberration when a parallel beam enters the group from the exit side J is S 2 .. ( h 2 ) for the beam height h2.
When it is assumed that S2(h2)<Q.

If the first and second groups satisfying such spherical aberration conditions are combined in a manner that satisfies the above condition (II), a substantial afocal system can be obtained. That is, when a substantially parallel light beam is made incident on this optical system, a substantially parallel light beam is emitted.

At this time, due to the above-mentioned combination of spherical aberrations, the light at the periphery of the incident light beam is emitted to a part near the center of the light beam cross section in the output light beam, and the light at the center of the light beam in the input light beam is emitted to the peripheral part of the light beam cross section in the exit light beam. It is ejected at a part close to . As a result, the light intensity distribution of the emitted light beam becomes different from the light intensity distribution of the incident light beam. The above condition (I). (
By performing zooming while changing the distance between each lens while satisfying II), it is possible to continuously change the light intensity distribution of the emitted light beam.

Furthermore, the larger the spherical aberration generated, the wider the region that can be converted.

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

Referring to FIG. 1, in this figure, the reference numeral G1 indicates the first group, and the reference numeral G2 indicates the second group.

The first group G1 is composed of two meniscus lenses Ll and L2, and has positive refractive power as a whole. The second group G2 is composed of a convex lens L3 and a negative meniscus lens L4, and 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 in Figure 1) is Ri, the distance between the first lens surfaces is D1, and the refractive index of the j-th lens counting from the incident side (wavelength 1060
(for 0 nm) as Nj, these are given as follows.

i Ri Di j N
j1. 17.512 4.541 1
2.402 85.961 Variable 3 -19.323 9.206 2
2.404 -25.818 Variable 5 14.004 3.262
3 2.406 -5.450 Variable 7 -2.867 4.433
4 2.408 -12.468 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 2.00 18.30 3.00
At this time, the spherical aberration of the first group is shown in FIG. 2(a), and the spherical aberration of the second group is shown in FIG. 2(b). At this time, condition (II) is of course satisfied.

In this state, when a parallel laser beam having a Gaussian distribution 5-1 as shown by the solid line in Figure 5 is input from the input side, the light intensity distribution in the emitted beam will be as shown by curve 5 in Figure 5. -2, it becomes a non-Gaussian distribution type.

At this time, the focal length fr of the first group is 19.957, the focal length of the second group is
The group focal length f2=3.532.

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

i 2 4 6 Di
1. 50 20. 30
2. 06The spherical aberration of the first group at this time is shown in Figure 4 (a
), and the spherical aberration of the second group is shown in FIG. 4(b). At this time, the condition (H) is St(To) + Sz(h2)
l<0.01, which is extremely well satisfied.

In this state, when a parallel laser beam having a Gaussian distribution 5-1 as shown by the solid line in Figure 5 is input from the input side, the light intensity distribution in the emitted beam will be as shown by curve 5 in Figure 5. -3 distribution.

At this time, the focal length of the first group f,=20. OO, the focal length of the second group r2=5,00.

In this embodiment, the focal lengths of the first group and the second group are f,, f2
The range is 19.95≦f1≦20.0, 3.5≦f2≦5.0
Condition (I). Zooming can be performed while satisfying (II), and by this zooming, the light intensity distribution of the emitted light beam is approximately as shown in curve 5-2 in FIG. 5-3
Continuously change the distribution between.

[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 constructed as described above, it is possible to convert the light intensity of a laser beam having a Gaussian distribution into a non-Gaussian distribution, and also to continuously change the shape of the distribution. Therefore, it can be effectively used for adjusting the light intensity distribution of a light beam for optical CVD for manufacturing microlenses.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining the present invention according to an embodiment, and FIG. 5 is a diagram for explaining an example of conversion of light intensity distribution according to the embodiment. Size'Ll-4 fit

Claims (1)

[Claims] 1. 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 calculated as the light intensity on the cross section of the incident laser beam. It is a Keplerian-type optical system that can continuously transform the light intensity distribution by zooming to make it different from the distribution. It is composed of 4 elements in 2 groups, and the ray height when the ray enters the first group from the incident side at a ray height h_1 and exits from the second group is h_2, and the ray height in the first group is h_2. When the spherical aberration is S_1 (h_1) and the spherical aberration in the second group is S_2 (h_2), the absolute values of these spherical aberrations increase monotonically as the argument increases, and (I) S_1 (h_1) >0 and S_2(h_2)<
0(II) | S_1(h_1)+S_2(h_2)1<0
．． A laser light intensity distribution conversion optical system that can perform zooming while satisfying the following condition. 2. In claim 1, the focal length of the first group is f_1, and the focal length of the second group is f_2.
Then, the range of changes in focal length due to zooming is as follows: 19.95≦f_1≦20.0, 3.5≦f_2≦5.
1. A laser light intensity distribution conversion optical system characterized in that the intensity distribution is 0.