JPH11285881A - Lighting device and method, and laser beam machining device and method using such lighting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable consistent laser beam machining by using a projection optical system, making the immobile face of a laser generator an object face, and converging a laser beam on an image face which is a face to be illuminated consisting of a mask provided with a machining pattern, and thereby lighting this face with an uniform beam intensity distribution. SOLUTION: A laser beam B0 with a small pulse width from a excimer laser generator 1 is converged by an immobile face projection optical system 4 like a lens using as an object face an immobile face 2 having an uniform beam intensity distribution, with the converged beam B1 image-formed on the face 3 to be illuminated of the image face of the optical system 4. As a result, a machining pattern in the mask radius D0 of the face 3 is illuminated with a uniform intensity. The laser beam B2 along the reference optical axis C, which contains the machining pattern having the prescribed intensity distribution thus obtained, is projected and image-formed on a prescribed position on a face 5 to be machined, as a machining laser beam B3 by means of a projection optical system 6 for machining, so that a prescribed laser beam machining is performed as specified by the machining pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to illumination using a laser beam and laser processing using the illumination, and more particularly to a laser using a laser beam with a small pulse width such as an excimer laser oscillator. Related to processing.

[0002]

2. Description of the Related Art Excimer lasers that emit laser light having a high peak output in the ultraviolet region are used for various kinds of processing. In a conventional mask projection type excimer laser processing apparatus 101, as shown in FIG.
105 provided with a processing pattern 104 such as an aperture (aperture) pattern by a laser beam 103 from
And further irradiates the laser light 106 from the illuminated opening pattern 104 of the mask 105 with the processing projection optical system 10.
7, the processing of the processing surface 108 is performed by projecting the processing light 109 onto the processing surface 108.

In the case of such a conventional excimer laser processing apparatus 101, an illumination beam 1 from a laser light source 102 is used.
When the alignment of the mask 105, which is the surface to be illuminated, is properly performed with respect to the mask 103, as shown in FIG.
Can be processed by projecting the aperture pattern 104 onto the surface 108 to be processed with the shape / intensity distribution 110 according to the aperture pattern 104 by the projection optical system 107 for processing.

[0004]

However, in the case of emitting a laser beam with a small pulse width, such as an excimer laser oscillator, a deviation tends to occur in the beam emission direction (pointing stability problem).

When a deviation occurs in the beam emitting direction, as shown in FIGS. 8A and 8B, the position of the illumination light 103a at the mask 105 (surface) is changed to the aperture pattern 10 as shown in FIG.
4 and the illumination light 103 on the surface of the mask 105.
Of the aperture pattern 104 is not uniformly illuminated, and the pattern 104
There is also a possibility that the position of the laser beam 106a incident on the laser beam 106a shifts, and as a result, the intensity distribution 110a of the processing projection light 109a on the processing surface 108 changes, resulting in uneven processing. Therefore, for example, in the case of drilling, the hole shape such as the hole diameter and the hole depth may be deviated from a predetermined shape, and in the case of an exposure apparatus, the exposure amount and the exposure intensity distribution may deviate from a predetermined size and a predetermined etching may be performed. And so on.

In the case of an excimer laser oscillator, such a deviation in the beam emission direction has been empirically caused by gas exchange, cleaning of the resonator, temperature changes of various components constituting the oscillator, and the like. it is conceivable that. It should be noted that such a situation is not limited to the excimer laser oscillator, but also applies to other laser oscillators to some extent.

Further, in a laser oscillator having a large mode volume and a high gain, such as an excimer laser oscillator, the divergence angle (beam divergence angle) of the emitted beam tends to be large, and the beam intensity distribution changes depending on the distance from the light source. (The problem of beam intensity distribution). That is, although the beam has a high intensity and a relatively uniform intensity distribution near the laser light source, the beam spreads greatly away from the light source, resulting in a non-uniform intensity distribution having a low intensity. Therefore, although it is originally desirable to perform the processing near the light source, it is often the case that the surface to be processed cannot be formed near the light source due to restrictions on the processing apparatus side.
As a result, it is necessary to use a non-uniform beam with low intensity at a distance from the light source for processing, or to perform processing in a state of low energy utilization using only a relatively uniform part of the spread beam. was there.

Although some countermeasures have been taken in the past to solve these problems, none of them has been satisfactory.

One of the conventional countermeasures is to stabilize the light source. For example, an excimer laser oscillator is made to be an external resonator type, and the arrangement of a resonator mirror which has the most influence on the beam emission direction and the like is mechanically changed. It is intended to be stabilized stably. However, for a processing laser with a relatively large output, it is necessary to remove the resonator mirror for maintenance such as periodic cleaning of the resonator, and it is necessary to adjust the mirror position each time. Limited stabilization.

Another conventional countermeasure is to provide a margin in the design. In anticipation that a certain degree of variation may occur in the illumination position, the illumination range is set so as to minimize the influence of the variation. It is intended to limit the use of laser light. However, in this case, the energy utilization rate of the laser beam becomes extremely low, and there is a possibility that the processing speed is significantly reduced.

[0011] Yet another conventional measure is to automatically adjust the alignment. In the conventional laser processing apparatus 101, as shown in FIG. 9, the optical path of the laser beam 103 from the laser oscillator 101 is changed by, for example, a pair of mirrors 111 and 112, and then the laser beam 1 is changed.
03 is applied to the mask 105 to illuminate the processing pattern 104 on the mask 105, and a laser beam 106 from the processing pattern 104 is irradiated with a processing optical system 107 by a processing optical system 107.
At the time of alignment adjustment, the laser beam 103 is irradiated from the mask pattern 104 onto the processing projection optical system 107 and from the position in the P direction at which the laser beam 103 is irradiated onto the mask 105. It is necessary to adjust the angles in the S and T directions of the mirrors 111 and 112 in order to adjust the direction (angle) at which the laser beam 106 is emitted and the position in the Q direction at which the laser beam 106 enters the processing projection optical system 107. As one conventional countermeasure in such a laser processing apparatus 101, the beam position is monitored at two points on the optical path from the laser oscillator 101 to the processing surface 108, and the beam position is shifted according to the beam position shift. In order to adjust the angle and position of the optical element between the two points by feedback control, two beam position measuring devices (comprising a fluorescent screen, a CCD camera and its power supply, and a housing) and two automatic moving optical mounts ( Mount body and mount drive device (driver) and control device (computer,
An image capturing device, a camera signal switching device, a control panel, and control software). However, in this auto-alignment system, it is necessary not only to provide a space for installing the beam position measuring device in the processing optical system, but also to optimize various parameters at the time of feedback control. It is inevitable that optimization will be required and the system will become a large and complex system as a whole.

Yet another conventional measure is to use a homogenizing optical system called a homogenizer. An input beam having a non-uniform intensity distribution is homogenized by a homogenizer composed of an optical system combining a plurality of optical elements. It is intended to be extracted as a beam. However, the homogenizer is not only expensive and difficult to handle, but when a homogenizer is used, it is difficult to avoid an increase in the beam divergence angle.

By the way, the present inventor considers how to align an illuminated portion and a processed portion with laser light from an excimer laser oscillator when conducting research on various applications of the excimer laser oscillator. Empirically found that the vicinity of the light source side beam waist (the portion where the beam is most narrowed) of the beam that spreads at a relatively large beam divergence angle can be regarded as having almost no change in position. In the specification, a surface or a region including a beam position that can be regarded as hardly fluctuating (referred to as a “fixed position”) is referred to as a “fixed surface”. Then, it was thought that the influence of the beam divergence angle and the problem of pointing stability could be minimized.

The present invention has been made in view of the above-mentioned points, and an object thereof is based on the above-mentioned new findings.
An object of the present invention is to provide an illuminating apparatus and method capable of stably providing a relatively high-intensity beam to an illuminated portion to be illuminated with laser light, and a laser processing apparatus and method using the illuminating apparatus or method. is there.

[0015]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned object is achieved basically by setting an immovable surface of a laser oscillator as an object surface and forming an image on an illuminated surface to be illuminated by laser light from the oscillator. An illumination device having a projection optical system as a surface, an illumination method of illuminating an illuminated surface by forming an image of a fixed surface of a laser oscillator on an illuminated surface to be illuminated by laser light from the oscillator, and This is achieved by a laser processing apparatus having the illumination device, and a laser processing method of processing an object to be processed by laser light illuminating a surface to be illuminated by the illumination method.

Here, the "immobile surface" is, as described above,
The position of the laser beam in the width direction and the optical axis direction refers to a beam surface at a position that does not actually fluctuate.
It is not necessary to be strictly immovable, and it is sufficient that the fluctuation is practically small. Further, if the fluctuation is relatively small compared to other parts (for example, if the fluctuation is extremely small compared to the surroundings, ) Good. Since the immobile surface is usually near the light source,
The intensity distribution of the beam is relatively uniform. The fixed surface may be inside or outside the laser oscillator.

In the illuminating apparatus and method according to the present invention, an image having an immobile surface as an object surface is formed on the surface to be illuminated. Therefore, the fluctuation of the direction and the divergence angle of the laser light emitted from the laser oscillator. Irrespective of the above, the intensity distribution of the immobile surface can be realized as it is on the illuminated surface. Therefore, it is possible to actually irradiate the entire illuminated surface with a relatively uniform intensity distribution and a relatively high intensity. Further, in the laser processing apparatus and method according to the present invention, since the workpiece is processed by the laser light illuminating the illuminated surface, the laser light having the intensity distribution defined by the illuminated surface is illuminated. Laser processing can be performed by irradiating the surface to be processed from the surface.

As the fixed surface projection optical system, any one can be selected according to the application. For example, even in a magnified or reduced projection system using a single lens or a compound lens, the magnification is changed depending on the direction in the cross section of the beam. A different projection system may be used, such as an infinity corrected projection system that does not depend on the distance to the illuminated part. Also, a field lens is provided at the surface to be illuminated to suppress the divergence angle of the beam from the surface to be illuminated, or a condenser lens is provided near the light source to suppress the spread of the beam at the surface to be illuminated. You may. Further, the fixed surface projection optical system may include a zoom lens.

Although the laser oscillator typically comprises an excimer laser oscillator, other lasers having a small pulse width, lacking pointing stability, and having a relatively large beam divergence angle may be used instead.

Incidentally, in order to adjust the alignment between the laser light from the laser oscillator and the surface to be illuminated, the fixed surface projection optical system may be configured to be adjustable, typically the position is adjustable. In the case of the laser processing device, further, in order to adjust the alignment between the laser light from the illuminated surface and the processed surface,
The fixed surface projection optical system may be configured to be adjustable, typically position adjustable.

In laser processing, for example, a mask on which a pattern to be processed is formed is arranged on the surface to be illuminated. In this case, since the entire processing pattern on the mask can be placed under illumination with a maximum uniform intensity, laser processing is performed by projecting and irradiating a laser beam having a shape or intensity distribution according to the processing pattern onto the processing surface. Can do. As a mask,
It may be something like an aperture mask, something like a phase shift mask, or any other mask. The illuminated object to be arranged on the illuminated surface may be any other object instead of the mask.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment according to the present invention will be described with reference to the accompanying drawings.

[0023]

In FIG. 1, reference numeral 1 denotes a laser oscillator such as an excimer laser oscillator, 2 denotes a stationary surface of the laser oscillator, 3 denotes a mask having a processing pattern as an object to be illuminated, and 4 denotes an immovable surface. Is a thin single lens as an immovable surface projection optical system for projecting an image onto the mask 3 as an object surface, 5 is a surface to be processed, and 6 is a processing optical system for projecting a processing pattern of the mask 3 onto the surface 5 to be processed. is there. In the illustrated example, although the fixed surface 2 is inside the laser oscillator 1, the fixed surface 2 is located at the position shown by the imaginary line 1a.
May be outside the laser oscillator 1a. C is the original optical axis.

For example, the laser beam B0 that has spread out of the range A on the immobile surface 2 located on one side of the original optical axis C is condensed by the single lens 4 as a laser beam B1, and in this example, the laser beam B1 has a size of 1: 1. An image is formed on the mask 3 as an image D0. Assume that the fixed surface 2 has a radius A around the original optical axis C.
Assuming that the laser beam B0 comes out of the range, the laser beam B0
Radius D0 on the mask 3 regardless of the divergence angle of
Is formed, and the processing pattern having the radius D0 on the mask 3 is almost uniformly illuminated by the laser beam B1 with an intensity distribution similar to the intensity distribution on the stationary surface 2. Note that, from the characteristics of the imaging system 4, this is because the direction of the laser beam emitted from the laser oscillator 1, that is, the laser beam emitted from the fixed surface 2 is shifted from the original optical axis C as shown in FIG. The same is true if you have Therefore, the laser oscillator 1
Even if the state of emission of the laser beam B0 from the mask 3 changes, the area of the radius D0 on the mask 3 is practically always illuminated.

The position of the fixed surface 2 is determined by, for example, a position change of the focused light B1 at a proper position by aligning the optical axis of a thin single lens 4 having a known focal length with respect to the laser light B0 (more precisely, The position on the optical axis at which the ratio of the amount of position variation to the image width is minimized is found by observation as an image plane, and the position and the focal length of this image plane may be determined by a well-known geometrical optics formula for a thin single lens. Strictly speaking, even if the position of the immobile surface 2 fluctuates to some extent in time, or considerably changes due to the influence of gas exchange or the like or the cleaning of the resonator mirror, the illumination area on the mask 3 is not changed. It can be expected that the projection optical system 4 is much more stable than the case without the projection optical system 4. When the position of the resonator mirror is adjusted, the position of the fixed surface 2 may be obtained again. Further, when absorbing the fluctuation of the fixed surface in the optical axis direction, the projection optical system 4 may be provided with an infinity correction optical system or a zoom lens which will be described later with reference to FIG. Good.

In any case, by forming a processing pattern in an area within the radius D0 of the mask 3, the processing pattern is always illuminated with a substantially uniform intensity. The laser beam B2 is emitted from the processing pattern 3 with an intensity distribution as described above (for example, a spatially almost uniform intensity distribution in the opening) and with a small deviation from the reference optical axis C.
Is projected and imaged by the processing projection optical system 6 at a predetermined position on the processing surface 5 as a laser beam B3 having an intensity distribution as specified in the above, and predetermined processing is performed on the processing surface 5 become.

In FIG. 1, for simplicity of explanation,
Although the processing projection optical system 6 is shown by a single lens, any conventional projection optical system may be used as the projection system 6. Further, in this specification, a mask whose processing pattern is an aperture pattern is described as an example of the illuminated surface or the illuminated body 3, but the illuminated surface (illuminated body) is not a laser but a laser. Any object that is illuminated during processing may be used. Also, the laser illuminating apparatus and method of the present invention can be used for purposes other than laser processing, in which case the illuminated object to be arranged on the illuminated surface is any object to be illuminated by the laser light source. Is fine.

The fixed surface projection optical system for forming an image on the illuminated surface (mask surface) 3 with the fixed surface 2 as an object surface is replaced with a (a) in FIG. 2), even if the lens 11 performs reduction projection (A> D1), it performs enlarged projection (A <D) as illustrated in FIG. 2B.
2) The lens 12 may be used. The lens 11 is suitable when the spread of the light emitting portion on the fixed surface 2 is relatively large compared to the size of the processing pattern 3 or when it is desired to increase the intensity of the illumination light as much as possible. This is suitable for the case where the mask pattern 3 is relatively large compared to the extent of the spread or when the intensity of the illumination light is not desired to be too high. The lenses 4, 11, and 12 may be thick single lenses or compound lenses instead of thin single lenses.

In addition, the fixed surface projection optical system may be a system in which lenses are spatially separated from each other in place of a lens formed as an integral object. In this case, a combination of lenses having different refraction characteristics and magnifications depending on directions, such as a cylindrical lens, may be combined. For example, a plurality of plano-convex lenses having a convex lens surface forming a cylindrical lens surface may be combined.
In the example of FIG. 3 in which a plan view is shown in (a) and a front view is shown in (b), the fixed surface projection optical system 13 includes a convex / planar lens 14 including a cylindrical lens whose central axis extends in a vertical direction. It is formed by combining with a similar convex / planar lens 15 whose central axis extends in the horizontal direction. Such a fixed surface projection optical system 13 is suitable, for example, when the shape of the light emitting portion of the fixed surface and the shape of the region to be illuminated are different (when the aspect ratio is different).

The fixed surface projection optical system may be any imaging optical system as long as it has a predetermined optical imaging performance, and the type, number, material and the like of the optical components constituting the optical system are desired. For example, a reflection surface or a diffraction grating may be used. Hereinafter, examples of the fixed surface projection optical system will be further listed, but the fixed surface projection optical system used in the present invention is not intended to be limited to these.

As shown in FIG. 4, the fixed surface projection optical system is such that the fixed surface 2 is located at the focal point of the lens on the object side, and the mask 3 as the irradiated surface is located at the focal point of the lens on the image side. May be something. In this case, as shown in FIG. 4A, the fixed surface projection optical system 16 makes the lens 17 on the object side and the lens 18 on the image side coincide with the sum of the focal lengths of the two lenses 17, 18. However, even if the afocal projection optical system is separated by a certain distance, as shown in FIG. 4B, the fixed surface projection optical system 19 includes the lens 17 on the object side and the lens 18 on the image side. May be an infinity-corrected projection optical system in which the distance between them can be changed so that the distance between them is set to an arbitrary distance. In the fixed surface projection optical system 16 in the form of the afocal projection optical system, laser light having the same properties as in the fixed surface 2 is obtained at the mask 3. In the fixed surface projection optical system 19 in the form of an infinity corrected projection optical system, even if the distance between the fixed surface 2 and the mask 3 is changed, the distance between the fixed surface 2 and the object side lens 17 and the mask 3 The intensity of the laser beam illuminating the mask 3 and the distribution thereof can be kept constant only by keeping the distance between the laser beam and the image plane side lens 18 constant. Also,
In the fixed surface projection optical system 19 in the form of an infinity corrected projection optical system, unless the reference optical axis C is actually changed, the position of the fixed surface 2 is changed with the attachment / detachment of the resonator mirror during cleaning of the mirror. Even if there is a large fluctuation, it is only necessary to adjust the position of the object-side lens 17 along the optical axis C, so that the adjustment of the projection optical system 19 is easy,
Further, even when the mask pattern 3 is replaced with a mask having a significantly different thickness, the lens 18 on the image plane side may be replaced.
It is only necessary to adjust the position along the optical axis C, so that the adjustment of the projection optical system 19 is easy.

Further, as the fixed surface projection optical system, as shown in FIG. 5, a divergence angle of a beam may be reduced by using a focusing lens in combination with an imaging lens. in this case,
As shown in FIG. 5A, a field lens 20 is arranged as a condensing lens near the mask surface 3 which is an image surface, and a fixed surface projection optical system 22 is formed in combination with the imaging lens 21. Beam B from processing pattern 3 provided on the illuminated surface
Even if the divergence angle of 2 is made smaller, FIG.
As shown in FIG. 2, a condenser lens 23 is arranged as a condensing lens near the immobile surface 2 which is an object surface,
4 may be combined with the stationary surface projection optical system 25 to reduce the divergence angle of the beam B1 incident on the illuminated surface 3. The latter fixed surface projection optical system 25 includes a fixed surface 2
Is located outside the laser oscillator or in the vicinity of the laser beam emitting portion of the oscillator, the former projection optical system 22 can be used regardless of the position of the fixed surface 2. If desired, both the condenser lens and the field lens may be combined with the imaging lens to form a fixed surface projection optical system.
Of course, the imaging optics to be combined with these condenser lenses may be any other imaging means instead of a single lens.

The fixed surface projection optical system may be a zoom lens which can continuously change the focal length without changing the image plane position by moving a part of the optical system in the optical axis direction, or A zoom lens may be provided as a part. In this case, the energy density on the projection plane (illuminated plane) can be changed by changing the projection magnification. If the zoom optical system is independent in the vertical and horizontal directions of the surface to be illuminated, the illumination area of the surface to be illuminated can be changed as desired.

Next, taking the laser processing apparatus 30 using the fixed surface projection optical system 22 shown in FIG. 5A as an example, the alignment of the optical axis of the laser processing apparatus 30 will be described with reference to FIG. explain. In FIG. 6,
1 and FIG. 5A are denoted by the same reference numerals as those in FIG. 1A and FIG. 5A, and in FIG. 9 in the same optical element adjustment direction as the optical element adjustment direction in FIG. The same reference numerals are used.

In the laser processing apparatus 30 shown in FIG.
In order to adjust the illumination or irradiation position in the P direction with respect to, the position of the main imaging lens 21 of the fixed surface projection optical system 22 is adjusted in the E direction, and the laser beam B11 emitted from the lens 21 is adjusted. Since this adjustment is a single adjustment, it can be performed easily and reliably. However, in the laser processing apparatus 30, since the immobile surface 2 is imaged on the mask 3, this adjustment may be actually performed at the time of the initial setting. No adjustment is actually required during operation. On the other hand, in order to adjust the position Q (the angle at which the laser light B2 is emitted from the mask 3) at which the laser light is incident on the processing projection optical system 6, the field lens 20 needs to be G
The direction of the laser beam B12 emitted from the field lens 20 may be adjusted by adjusting the position in the direction. Therefore, unlike the conventional laser processing apparatus shown in FIG. 9, the laser processing apparatus 30 not only does not require a pair of mirror pairs 111 and 112, but also has an optical axis alignment with respect to the illuminated surface 3. In practice, it becomes unnecessary. Further, in order to adjust the laser beam to the processing projection optical system 6 (or the processing surface 5), the position of the field lens 22 in the G direction may be adjusted independently. It can be done easily and reliably.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a laser processing apparatus using a lighting device according to a preferred embodiment of the present invention.

2A and 2B are schematic explanatory views of a lighting device according to another preferred embodiment of the present invention, wherein FIG. 2A shows a case where an immobile surface is reduced and formed, and FIG. 2B shows a case where an immobile surface is enlarged and formed. .

FIGS. 3A and 3B schematically illustrate a lighting device according to another preferred embodiment of the present invention, wherein FIG. 3A is a schematic plan view and FIG. 3B is a schematic front view.

4A and 4B are schematic explanatory views of a lighting device according to still another preferred embodiment of the present invention, wherein FIG. 4A shows a case where an afocal projection optical system is used, and FIG. Indicates the case where

5A and 5B are schematic explanatory views of a lighting device according to still another preferred embodiment of the present invention, wherein FIG. 5A shows a case where a field lens is used, and FIG. 5B shows a case where a condenser lens is used.

FIG. 6 is a schematic explanatory view showing alignment adjustment in a laser processing apparatus according to a preferred embodiment of the present invention using the illumination apparatus of FIG. 5A.

FIG. 7 is an explanatory diagram in the case where there is no deviation in the direction of illumination light in a conventional laser processing apparatus.

FIG. 8 is an explanatory diagram in a case where there is a deviation in the direction of illumination light in a conventional laser processing apparatus.

FIG. 9 is an explanatory diagram of alignment adjustment in a conventional laser processing apparatus.

[Explanation of symbols]

Reference Signs List 1 laser oscillator 2 fixed surface 3 illuminated surface (mask, processing pattern) 4, 11, 12, 13, 16, 19, 22, 25 fixed surface projection optical system 5 processed surface 6 processing projection optical system 14, 15 cylindrical Lens 17, 18 Lens 20 Field lens 23 Condenser lens 30 Laser beam machine B0, B1, B11, B12, B2, B3 Laser light (laser beam) C Reference optical axis (original optical axis) E, G Adjustment direction P, Q Deviation (to be adjusted) direction

Claims (8)

[Claims] 1. An illumination apparatus having a projection optical system in which a stationary surface of a laser oscillator is an object surface and a surface to be illuminated by laser light from the oscillator is an image surface. 2. The lighting device according to claim 1, wherein the laser oscillator is an excimer laser oscillator. 3. The illumination device according to claim 1, wherein the projection optical system is configured to be adjustable so as to adjust the alignment between the laser light from the laser oscillator and the surface to be illuminated. 4. A laser processing apparatus comprising the illumination device according to claim 1, wherein the illumination device illuminates the illumination surface to process the workpiece. 5. The laser processing apparatus according to claim 4, wherein a mask on which a processing pattern is formed is arranged on an illuminated surface of the illumination apparatus. 6. The laser processing apparatus according to claim 4, wherein the projection optical system is configured to be adjustable so as to adjust the alignment between the laser light from the illuminated surface and the processed surface. 7. An illumination method for illuminating an illuminated surface by forming an image of a stationary surface of a laser oscillator on an illuminated surface to be illuminated by laser light from the oscillator. 8. The laser processing method according to claim 7, wherein the workpiece is processed by a laser beam illuminating a surface to be illuminated.