JPH09171153A - Illumination optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form various patterns with the least loss of light quantity by providing an element for bisecting a laser beam, an optical element including condensing elements having different power in two directions orthogonal to an optical axis, and an element for compositing respective luminous fluxes from the optical element again. SOLUTION: The collimated laser beams 1 are bisected and reflected by a beam splitter 2, and further reflected at a right angle by a mirror 3. The luminous flux is made incident on the optical element 5 consisting of two condensing elements 4 having the different power in two directions on a plane orthogonal to the optical axis and condensed in a slit state, and further changed to two parallel luminous fluxes through the optical element 5'. Meanwhile, the luminous flux transmitted through the beam splitter 2 is made incident on the optical element 8 and condensed in the slit state orthogonal to the slit by the luminous flux reflected by the beam splitter 2. The luminous flux is changed to two parallel luminous fluxes through the optical element 8' and composited with two parallel luminous fluxes changed through the optical element 5'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern projection used for observing a surface shape, a defect, etc. of an object and projecting a pattern in which slit light is combined as an index for autofocus on the object. Illumination optics.

[0002]

2. Description of the Related Art The following three techniques are known as pattern projection techniques. That is, a desired pattern mask is put in a collimated laser beam to shield light other than the pattern, and the desired pattern mask is
A method of projecting the illuminated mask pattern with an optical system by uniformly illuminating it using normal lamp Koehler illumination or laser and fly eye lens array integrator pseudo-Kohler illumination, etc. In this method, a pattern obtained by inverse Fourier transforming the pattern is placed at the pupil position of the optical system, and a desired pattern is formed on the object as its Fourier image.

[0003]

By the way, in the above method and method, since the illumination light is masked, the light amount loss is large, and since the pseudo Koehler illumination is performed by the laser light, the optical system becomes complicated and expensive. There is a problem that speckle noise occurs. Also, in the above method, since the pupil is masked, the amount of light is insufficient,
Further, there is a problem that it is difficult to fabricate a mask for inverse Fourier transform of the pattern and to arrange the pattern at the pupil position of the optical system.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to combine slit light with almost no loss of the light amount of laser light. The present invention aims to provide an illumination optical system capable of forming various patterns.

[0005]

In order to achieve the above object, an illumination optical system according to the present invention comprises a laser beam collimated into parallel light, an element for splitting the laser beam into at least two, and the element for splitting the laser beam. An optical element including at least one light-collecting element having different powers in two directions orthogonal to the optical axis, disposed in each optical path of the generated light beam, and an element for recombining the light beams from the optical element. I have it. As a result, at least one (not circular or square) pattern having different shapes in the two directions in the plane is formed, and these patterns are coaxially combined.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to describing the embodiments, the concept of the present invention will be described with reference to FIG. As shown in FIG. 1, the collimated laser beam 1 is split into two by a first beam splitter 2, and the light flux reflected by this beam splitter 2 is further reflected at a right angle by a mirror 3.
This light beam reflected at a right angle is 2 in the plane orthogonal to the optical axis.
The light is incident on an optical element 5 formed by arranging two condensing elements (cylindrical lenses) 4 having different powers in different directions and condensed in a slit shape. The slit-shaped light flux thus condensed is an optical element in which cylindrical lenses 4'and 4'having different focal lengths from the condenser element 4 are arranged in parallel so as to face the condenser lenses 4 and 4, respectively. It is converted into two parallel light beams via 5 '. These two parallel light beams are reflected by the mirror 6
Is reflected at a right angle by, is guided to the second beam splitter 7, and is transmitted therethrough.

On the other hand, the light beam which has passed through the first beam splitter 2 has the same structure as that of the optical element 5 and is incident on the optical element 8 which is installed in a state of being rotated by 90 ° about the optical axis. The light beam reflected by the beam splitter 2 is condensed into a slit shape orthogonal to the case of the light beam. This condensed slit-shaped light beam is transmitted through the optical element 8'which is constructed in the same manner as the optical element 5'and is opposed to the optical element 8 in a state of being rotated by 90 ° about the optical axis. It is converted into two parallel light beams. The two parallel light fluxes are reflected by the second beam splitter 7 and are combined with the two parallel light fluxes reflected by the mirror 6. The pattern of the combined light flux becomes a cross pattern as shown in FIG. In this case, the light quantity of each light beam forming the cross beam is only about half of the light quantity of the laser light 1, and is almost equal to the original light quantity after combining, and there is almost no light quantity loss on the way, so that a bright pattern is obtained. .

Next, an embodiment of the present invention will be described. Example 1 FIG. 1 shows the configuration of this example. In this embodiment, the collimated laser beam 1 is 10 mm × 10 mm
And is linearly polarized at an angle of 45 ° with respect to the paper surface. A polarization beam splitter is used as the first beam splitter 2, and reflects a component that vibrates in the plane of the drawing. The cylindrical lens 4 forming the optical element 5 has an effective range of 10 mm × 5 mm and a focal length of 100 mm. Further, the cylindrical lens 4 ′ forming the optical element 5 ′ has an effective range of 10 mm ×.
A lens with a focal length of 1 mm and a focal length of 20 mm is used. Thus, two slit-shaped parallel luminous fluxes having a size of 10 mm × 1 mm can be obtained. As the second beam splitter 7, a polarization beam splitter that transmits a component that vibrates in the paper surface is used.

The luminous flux transmitted through the first beam splitter 2 is a component vibrating in a direction perpendicular to the plane of the drawing. The luminous flux transmitted through the optical elements 8 and 8'is reflected by the mirror 6 to form two slits. -Shaped parallel luminous flux is rotated by 90 ° to form two slit-shaped parallel luminous fluxes with a size of 10 mm × 1 mm, which are reflected by the polarization beam splitter 7 and are reflected by the mirror 6
Are combined with the two slit-shaped parallel luminous fluxes reflected by and transmitted through the polarization beam splitter 7. As a result, a double beam pattern composed of slit light with a size of 10 mm × 1 mm as shown in FIG. 2 is obtained, and there is almost no light amount loss.

Embodiment 2 Also in this embodiment, an optical system having the same structure as that shown in FIG. 1 is used. However, randomly polarized laser light is used as the laser beam 1, and the first beam splitter 2
3 is used as the second beam splitter 7, and the other optical elements are the same as those in the first embodiment. As the slit mirror 9, the reflection mirror 6
A reflective mirror coat is used on the entire surface except for the slit-shaped portion 9a which transmits only the two parallel light beams reflected by the. The pattern of the obtained slit light is similar to that shown in FIG. 2, and there is almost no light amount loss.

Embodiment 3 FIG. 4 shows the configuration of this embodiment. In this embodiment, the collimated laser light 1 is guided to a rectangular equally spaced diffraction grating 10 having a phase difference of about 0.63π or 1.36π at that wavelength. The diffraction grating 10 having such a phase difference divides the incident light into three light beams of 0th order light (light that travels straight) and ± 1st order light. in this case,
The intensity of the luminous flux divided into three becomes substantially equal. These three
The split luminous flux is guided to a trapezoidal prism 11 formed by shaping the apex portion of a triangular prism into a flat surface, where the ± first-order light is refracted so as to become a luminous flux parallel to the optical axis. Then, each light flux is condensed into a slit shape by the anamorphic lens 12, and collimated by the anamorphic lens 13 having different power. In this case, the power and direction of each anamorphic lens are determined so that the slit-shaped parallel light fluxes generated in the above anamorphic lens system have the same shape and form an angle of 60 °.
Next, these collimated light beams are guided to the trapezoidal prism 14 and refracted, and are combined by the diffraction grating 15 configured similarly to the diffraction grating 10. The pattern of the luminous flux thus obtained is as shown in FIG.

In this embodiment, each light flux is focused by one anamorphic lens 13, respectively.
Instead of this, it is also possible to use an anamorphic lens array or an anamorphic condensing element having a diffractive optical element as shown in FIG. 6 to form a more complicated pattern.

Embodiment 4 FIG. 7 shows the configuration of this embodiment. In this embodiment, the collimated laser light 1 is the triangular prism 1
The light is guided to 6 and divided into two, and further guided to another triangular prism 17 to be made into two parallel light beams parallel to the optical axis.
Then, these parallel light fluxes are generated in the third embodiment shown in FIG.
It is molded and synthesized by an anamorphic afocal system having the same structure as described above and used.

Embodiment 5 FIG. 8 shows the construction of this embodiment. This example is
For example, when the combined cross-shaped slit light L is incident on the projection surface 18 at an angle θ as shown in FIG. 8A, the cross pattern appearing on the projection surface 18 becomes 1 / sin θ. In consideration of being magnified twice, the anamorphic magnification of the molding optical system is adjusted in advance so that the cross light having the dimensional ratio as shown in FIG. As shown in FIG. 8C, a cross pattern having the same vertical and horizontal lengths can be obtained.

Although the respective embodiments have been described above, it is needless to say that the present invention is not limited to this, and various combinations of illumination lights can be obtained.

As described above, the illumination optical system according to the present invention has the following features in addition to the features described in the above claims.

(1) The illumination optical system according to claim 1, wherein the two power directions of the condensing element are different in each of the divided luminous fluxes. This allows at least two patterns to have different directions.

(2) The illumination optical system according to claim 1 or (1), wherein the optical elements are arranged so as to face each other so that their power directions coincide with each other. As a result, it is possible to enlarge or reduce while maintaining the direction and shape of each pattern, and it is also possible to convert into a parallel light flux.

(3) When the recombined light flux is incident on the irradiation object at an angle, the shape of the light flux before composition is determined in advance in consideration of the enlargement / reduction of the irradiation range depending on the angle. The illumination optical system according to claim 1. This makes it possible to obtain a desired pattern on the projection surface.

(4) The element for dividing the laser beam into at least two is a refractive optical element or a diffractive optical element.
The illumination optical system described in. This makes it possible to provide an optical system that makes the best use of the characteristics of each element. For example, if a diffractive optical element is used, it is possible to divide the light flux into three by one element.

(5) The illumination optical system according to claim 1, wherein the optical element is a refractive optical element or a diffractive optical element. This makes it possible to provide an optical system that makes the best use of the characteristics of each element. For example, if a diffractive optical element is used, an aspherical effect can be provided by arbitrarily adjusting the pitch, and the aberration can be made smaller than that of the spherical element of the refraction system. When the laser oscillates a plurality of lights having different wavelengths, it is possible to correct chromatic aberration by combining a refraction element and a diffraction element.

(6) The illumination optical system according to claim 1, wherein the element for recombining the light flux is a refractive optical element or a diffractive optical element. This makes it possible to provide an optical system that makes the most of the characteristics of each element. For example, if a diffractive optical element is used,
It is also possible to combine three light fluxes into one with one element.

(7) The illumination according to claim 1, wherein at least two collimated laser beams are used instead of the collimated laser beam and the element for dividing the laser beam into at least two. Optical system. This makes it possible to obtain a complicated pattern by combining each laser light into a desired shape without splitting the light from one laser and changing the wavelength of each laser light. If so, it is possible to obtain a pattern in which a plurality of wavelengths are mixed.

[0024]

As described above, according to the present invention, it is possible to provide an illumination optical system capable of projecting various patterns with almost no loss of light amount.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of an illumination optical system according to the present invention.

FIG. 2 is a diagram showing a pattern of illumination light obtained by the embodiment shown in FIG.

FIG. 3 is a front view of a slit mirror used in another embodiment of the illumination optical system according to the present invention.

FIG. 4 is a diagram showing the configuration of still another embodiment of the illumination optical system according to the present invention.

5 is a diagram showing a pattern of illumination light obtained by the embodiment shown in FIG.

6 is a front view of a diffractive optical element that can be applied to the embodiment shown in FIG.

FIG. 7 is a diagram showing a part of the configuration of still another embodiment of the illumination optical system according to the present invention.

8A and 8B are explanatory views of still another embodiment of the illumination optical system according to the present invention, FIG. 8A shows a state in which illumination light is obliquely incident on the projection surface, and FIG. 8B is a diagram showing incident illumination light. FIG. 7C is a diagram showing a cross pattern, and FIG. 9C is a diagram showing a cross pattern when the illumination light shown in FIG. 7B is incident on the projection surface.

[Explanation of symbols]

 1 Laser Light 2,7 Beam Splitter 3,6 Mirror 4,4 'Condensing Element (Cylindrical Lens) 5,5', 8,8 'Optical Element 9 Slit Mirror 10,15 Diffraction Grating 11,14 Trapezoidal Prism 12,13 Anamorphic lens 16,17 Trigonal prism 18 Projection surface

Claims (1)

[Claims] 1. A laser beam collimated into parallel light,
An element which divides the laser beam into at least two, and an optical element which is arranged in each optical path of the light beam divided by the element and includes at least one condensing element having different powers in two directions orthogonal to the optical axis. And an element for recombining the light fluxes from the optical element.