JP3518351B2 - Method of forming composite shape on workpiece surface by energy beam and article obtained by this method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a complex shape on a surface of a work piece by an energy beam, and more specifically, a non-uniform recess is distributed on the surface of a work piece which can be thermally melted by using the energy beam. The present invention relates to a method for providing a microstructure having a composite shape.

[0002]

2. Description of the Related Art US Pat.
Proposed as found in 128,752 and U.S. Pat. No. 4,842,782. In order to provide a complex shape in which uneven recesses are distributed over a wide range of surfaces, it is necessary to precisely control the energy beam and use a mask having a complicated shape.

[0003]

However, there is a problem in that it is difficult to manufacture a mask having a complicated shape and the cost becomes very high. Therefore, it is required to quickly realize a complex shape on the surface of the work piece at low cost.

[0004]

The present invention has been accomplished in order to meet the above-mentioned requirements, and forms a complex shape having non-uniform recesses by using a simple optical system and a mask having a simple shape. Provide a way to do. In the method of the present invention, first, a composite shape is determined, and this composite shape is decomposed into a simple and regular corrugated pattern having different characteristics, and then the surface of the work piece is irradiated with an energy beam to form the work piece. It is formed by melting the individual wavy patterns on the surface of each layer in order, and has the above regularity.
The waveform pattern has a plurality of sine wave periods . Therefore,
The desired composite shape can be obtained easily, efficiently and inexpensively.
In addition, three-dimensional with an uneven pattern over a wide range
There is an effect that it is possible to create a structure .
Furthermore, the waveform pattern of the energy beam to be irradiated first
The amplitude of the waveform pattern to be irradiated next is
Then, the difference in energy absorption rate between the side of the recess and the feeling of valley
Error can be kept small and precise machining is possible.
It will be.

Preferably, the composite shape is decomposed into a sinusoidal regular waveform pattern by an approximation method using orthogonal transformation such as Fourier analysis.

By using a mask having a plurality of opaque rings arranged on concentric circles, one period portion of the regular waveform pattern can be projected onto the material to be processed by diffraction of the energy beam passing through the mask and the optical system. By moving the material to be processed with respect to the mask and the optical system, one cycle portion is made continuous to obtain a regular waveform pattern. In order to continuously form another regular corrugated pattern on the surface of the material to be processed, the same mask is used to change the magnification of the optical system or a mask having another characteristic. Further, it is desirable to use a mask in which a plurality of mask units each composed of an opaque ring arranged on the concentric circle are arranged.

Further, in order to precisely form the sinusoidal wave pattern, it is preferable that the beam intensity of the energy beam applied to the side wall of the recess is higher than that applied to the valley or the top of the recess.

Further, one of the regular corrugated patterns can be projected on the surface of the material to be processed by using the vapor deposition mask deposited on the surface of the material to be processed. This vapor deposition mask has a shape in which a plurality of mask units in which a plurality of mask rings having different energy beam transmittances are arranged around a central opening are arranged. The energy beam incident on the vapor deposition mask is controlled so as to project another regular waveform pattern in the absence of the vapor deposition mask, and the energy beam is radiated through the vapor deposition mask to form a complex shape. As a result, a complex shape can be realized by scanning the surface of the work piece once with the energy beam.

Instead of using a mask, it is also possible to distribute a plurality of beam spots having a regularly changing beam intensity from an energy beam and to provide them to the work surface by using an optical system including a special lens. . The beam spots are regularly arranged to define one of regular wave patterns. By changing the magnification of the optical system, one of the regular waveform patterns is first projected on the surface of the work material at the first magnification, and then the other regular waveform pattern is projected on the same surface at the second magnification. As a result, a desired composite pattern can be formed on the surface of the material to be processed by two or more projecting operations with different magnifications.

A laser beam having a predetermined pulse frequency is preferably used as the energy beam.
By scanning this laser beam on the surface of the material to be processed in synchronization with the pulse frequency, a complex shape can be created over a wide range. Alternatively, the workpiece may be moved relative to a fixed optical system to create a complex shape over a wide range. The laser beam used in the present invention preferably has a short wavelength or a short pulse in order to perform precise laser melting.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a system for forming a composite shape of uneven recesses on the surface of a work piece. The techniques disclosed herein can be applied to create light diffusers for luminaires, microstructured components, tribological surfaces, and other complex three-dimensional structures. More specifically, the method of the present invention is a light diffusing plate or a micro optical lens having a composite shape in which uneven pitches are distributed with a pitch of 1 to 50 μm and an aspect ratio of 0.6 to 2.0. Alternatively, a micro-structured component having a complex shape in which uneven recesses having an aspect ratio of 0.1 to 0.5 are distributed at a pitch of 0.01 to 50 μm, or distributed at a pitch of about 0.05 μm. It can be used to fabricate an infrared or visible light sensor having a complex shape in which uneven recesses having a depth of about 0.5 μm are distributed.

This system includes an energy source 10 for generating an energy beam for processing a work piece 1 by melting.
Have. The energy beam source 10 is a short pulse, especially a K having a wavelength of 248 nm and a pulse width of 30 ns.
It is desirable to generate an rF excimer laser. Other lasers, such as high peak CO ² gas lasers,
A YAG laser or the like can be used in consideration of compatibility with the workpiece 1.

The workpiece 1 is a meltable material such as polymethylmethacrylate (PMMA), polycarbonate (PC), polyester, polystyrene, cellulose resin, polyimide, liquid crystal polymer, silicon nitride, alumina, boron nitride, gold, copper. Made of alloy, tungsten, aluminum. Depending on the desired properties, the composite shape
For example, it is determined by computer simulation. FIG. 2A shows an example of this composite shape P, which is composed of a large number of continuously distributed non-uniform recesses. This composite shape P is obtained by Fourier approximation using two sinusoidal waveform patterns W1 and W as shown in FIGS. 2 (b) and 2 (c).
It is decomposed into 2. The waveform patterns W1 and W2 decomposed in this way have different pitches (frequency) and different heights (amplitude). Depending on the complexity and precision required,
The composite shape P may be decomposed into three or more sinusoidal waveform patterns selected from those represented as the Fourier series of this composite shape. In this embodiment, the first waveform pattern W
1 and the second waveform pattern W2 are f (x) = − 15, respectively.
+15 sin (2πx / 30), g (x) =-8 + 8s
Shown as in (2πx / 24). Therefore, the complex shape is represented by h (x) = f (x) + g (x).

The sinusoidal waveform patterns W1 and W2 thus obtained are formed so as to be sequentially superposed on the surface of the workpiece 1 by using an optical system to reproduce a composite shape. The optical system is provided with a pair of fixed mirrors 11 and 12 to guide the laser beam B from the beam source 10 to the pair of cylindrical lenses 13 and 14, and the cylindrical lens produces a laser beam having a substantially rectangular (25 mm x 8 mm) cross section. Shape to a square (25 mm x 25 mm) cross section. The shaped laser beam B passes through the attenuator 15 and the mask 20, is reflected by the scan mirror 17, and reaches the workpiece 1 placed on the table 2 through the condenser lens 18. The mask 20 may be provided between the scan mirror 17 and the condenser lens 18.

FIG. 4 shows an example of a mask used to project one of the sinusoidal waveform patterns on the surface of the material to be processed. The mask 20 is formed by forming a plurality of opaque rings 22 on a transparent quartz substrate 21 in a circle having a diameter of 300 μm and arranged in concentric circles by chrome vapor deposition. The rest of the mask 20 is also chrome vapor deposited to be opaque. The opaque rings are 2 μm wide and are spaced at 2 μm intervals to form transparent rings through which the laser beam passes. When the laser beam passes through the mask 20, a diffraction pattern having a beam intensity for one cycle of a substantially sine wave is obtained as shown in FIG. This diffractive sine wave pattern is projected onto the workpiece 1 through the condenser lens 18 having a focal length of 100 mm at a magnification of 1/10, and the scan mirror 17 oscillates at an appropriate frequency to spread the laser beam over a wide range of 1 × 1 mm. And scan the surface of the work piece. By irradiating the surface of the workpiece with laser beams having different beam intensities inside the outermost opaque ring, an array of beam spots S as shown in FIG. 7 is formed on the surface of the workpiece. As shown on the right side and the lower side of the figure, one of the waveform patterns W1 and W2 running in the directions orthogonal to each other of the workpiece is formed by laser melting. In this example, the energy density was adjusted to 5.0 mJ / mm ² by the attenuator 15 and a laser beam of 30 shots was irradiated through the mask to form a corresponding waveform pattern.

Instead of using the mask of FIG. 4, it is also possible to use a collective mask 30 as shown in FIG.
This collective mask is the mask 2 consisting of a plurality of opaque rings.
A plurality of mask units corresponding to 0 are arranged on the substrate. The rest of the substrate is chrome vapor-deposited and opacified.

After forming the first waveform pattern W1, the magnification of the optical system is changed to form the second waveform pattern on the surface of the work material so as to be superimposed on the first waveform pattern. Realizes a complex shape consisting of recesses. If desired, different corrugated patterns can be formed at different magnifications to obtain a more precise composite shape. When forming a more precise composite shape, it is preferable to first form a waveform pattern having a large amplitude and then form the next waveform pattern.

Rather than changing the magnification, it is possible to use different masks to create different corrugated patterns on the work piece surface. For example, using three types of masks, a waveform pattern W having a pitch of 30 μm and a height of 9 μm
1. Wave pattern W with pitch of 12 μm and height of 3 μm
2. Waveform patterns W3 each having a pitch of 5 μm and a height of 1.3 μm are formed on the material to be processed, and a composite shape is reproduced by combining these. The first mask has a diameter of 240μ
It has a circular mask unit array in which the center distance is m and the center distance is 300 μm, and each mask unit has the same configuration as that in FIG. The second mask has an array of circular mask units having a diameter of 96 μm and a center-to-center distance of 120 μm, and the third mask has a diameter of 40 μm and a center-to-center distance of 50 μm.
It has an array of circular mask units lined up with m. A work piece is irradiated with a laser beam having an energy density of 5.0 mJ / mm ² in 30 pulses through the first mask, then 10 laser pulses through the second mask, and then a laser pulse through the third mask. Is irradiated for 4 pulses. Each laser irradiation is performed at a magnification of 1/10.

FIG. 8 shows two different masks 31, 32.
The following shows an example of forming a similar composite shape by using, and in these masks, circular openings 34 having different diameters are arranged at the same pitch. The first and second masks 31 and 32 each independently form the first and second waveform patterns as shown immediately below the mask in the figure, and the resultant composite shape is shown in the figure. Shown on the right.

FIG. 9 shows two different masks 31A and 3A.
2A shows an example in which a similar composite shape is formed. In these masks, the circular opening 34A having the same diameter is 18
They are arranged with a phase difference of 0 degree. First and second mask 31
A and 32A each independently form the first and second waveform patterns as shown immediately below the mask in the figure, and the resulting composite shape is shown on the right side of the figure. The circular openings 34 and 34A have a diameter sufficiently smaller than the beam diameter of the incident laser beam, and the laser beam is moved so as to traverse the opening to form a circular recess on the surface of the workpiece. Since the amount of laser beam passing through this opening gradually increases from the peripheral edge of the opening toward the center,
The circular recess formed by laser melting will have a cross-section with a generally sinusoidal pattern. This circular opening 34,
Instead of 34A, the mask 20 shown in FIG. 4 may be used.

In order to form a complex shape over a wide range by means of a waveform pattern, as shown in FIGS. 10 (a) and 10 (b), the laser beam is scanned in one direction and then in a direction orthogonal thereto. can do. Over a wide range
For example, the work piece 1 is moved with respect to the optical system after the waveform pattern is formed at a distance corresponding to several cycles of the waveform. Alternatively, as shown in FIGS. 11A and 11B, the workpiece is moved with respect to the optical system while the workpiece is irradiated with the laser beam in the fixed optical system. In this method, the table 2 on which the workpiece is placed is moved in synchronization with the pulse of the laser beam. For example, 150Hz
While irradiating the laser beam pulse with the frequency of 13
Move the table at mm / sec. The method of moving the table in this manner is useful in that the aberration can be reduced in the optical system and the complex shape can be accurately reproduced.

FIG. 12 shows a vapor deposition mask 40 that can be used in the method of the present invention. The mask 40 is vapor-deposited on the flat surface of the workpiece 1 before laser beam irradiation, and one of the regular waveform patterns is projected. This mask 40
In, a mask unit 41 having two concentric mask rings 43 and 44 having different transmittances is arranged around a central opening 42 having a diameter of 30 μm. The inner mask ring 43 is formed in a region of 30 μm to 70 μm in diameter by vapor deposition of silver.
The outer mask ring 44 is formed to a thickness of 00Å, and the outer mask ring 44 is formed in a region of 70 μm to 100 μm in diameter by copper vapor deposition.
It is formed with a thickness of 0Å. Aluminum is deposited on the remaining portion 45 to a thickness of 5000 Å. The mask units 41 thus formed are arranged with a center-to-center distance of 100 μm. The inner silver vapor deposition mask ring 43, the outer copper vapor deposition mask ring 44 and the remaining aluminum vapor deposition region 45 are made of KrF.
72% and 59% for the excimer laser beam
%, 9%, and a uniform intensity laser beam is irradiated over the entire area of the vapor deposition mask, the result shown in FIG.
As shown in the lower left of 3, the pitch is 100 μm and the height is 3
The first sine wave pattern of μm is projected. In practice, the laser beam whose intensity is adjusted so as to independently project the second sinusoidal waveform pattern having a pitch of 50 μm and a height of 1 μm is irradiated through the vapor deposition mask 40 to form the first and second waveform patterns. Form a compounded composite shape. By this technique, a composite shape can be obtained by irradiating the portion covered with the vapor deposition mask 40 with the laser beam only once. Incident laser beams with different intensities can be obtained using masks, special lenses or other techniques with optical systems.

FIG. 14 shows another system for carrying out the method of the present invention. This system has an energy beam source 100 that generates a short-pulse laser beam and a pair of fixed mirrors 111 and 112. A laser beam B from the beam source is guided to a scan mirror 117 through a pair of attenuators 115 and 116. Then, the laser beam is passed through the pair of cylindrical lenses 113 and 114, and the laser beam having a substantially rectangular (25 mm x 8 mm) cross section is shaped into a square (25 mm x 25 mm) cross section. The laser beam B thus shaped is applied to the surface of the workpiece 1 placed on the table through the fly-eye lens 120. The fly-eye lens 120 is an array of 25 micro-convex lenses, and is used to decompose an incident laser beam having a square cross section into a beam spot array. This beam spot array is obtained by using the mask shown in FIG. Figure 7
The beam intensity is regularly changed in each beam spot to give a sinusoidal waveform pattern on the surface of the material to be processed. By using the fly-eye lens 120 and changing the magnification of the optical system, different sinusoidal waveform patterns can be given to the surface of the workpiece. The laser beam is adjusted by attenuators 115 and 116 so as to have an energy density of 5.0 mJ / mm ^2, and gives a complex shape to the surface of the workpiece 1 made of polycarbonate. This composite shape has a first sine wave pattern having a pitch of 1000 μm and a height of 50 μm, a second sine wave pattern having a pitch of 500 μm and a height of 30 μm, and a pitch of 250 μm and a height of 5 μm. It is a combination with a certain third sinusoidal waveform pattern. The first waveform pattern is formed by irradiating 170 pulses of a laser beam through the fly-eye lens 120 at a magnification of 1/5, and the second waveform pattern is formed on the first waveform pattern through the fly-eye lens 120 and a magnification of 1 /. It is formed by irradiating 100 pulses of the laser beam at 10, and finally the third waveform pattern is formed on the composite pattern through the fly-eye lens 120 at a magnification of 1 /.
It is formed by irradiating 17 pulses of a laser beam at 20 to obtain a desired composite shape. The first, second and third waveform patterns are projected by scanning the laser beam through the fly-eye lens 120 by the scan mirror 117, and 25 mm ² , 6.2 respectively by one scanning.
5 mm ^2, a waveform pattern is formed in a square area of 1.5625mm ^2. Therefore, the composite shape is formed over a wider range by horizontally moving the table on which the workpiece 1 is placed with respect to the optical system.

In addition to using the mask and the fly-eye lens disclosed herein, the method of changing the intensity of the laser beam while moving the beam spot along the surface of the work piece is used to directly change the laser beam. It is also possible to irradiate the surface of the work material. FIG. 15A shows a simple method of forming a sinusoidal waveform pattern by directly irradiating a laser beam. One cycle of a desired sine waveform is divided into eight sections S1 to S8, and the laser intensity is changed according to the average amplitude in each section to adjust the melting depth. Therefore, by simply repeating the step of moving the workpiece with respect to the beam so as to draw a simple sine wave pattern while changing the beam intensity, a composite shape composed of two or more sine wave patterns can be created. Although a laser beam can be easily adjusted when forming a sinusoidal waveform pattern, the mask 20 shown in FIG.
As shown in FIG. 15B, one cycle of the sine waveform is formed at one time, or as shown in FIG. 15C using the mask 30 shown in FIG. 6 or the fly-eye lens 120 shown in FIG. Forming two or more cycles is advantageous in terms of increasing the efficiency of forming the composite shape.

When a sinusoidal wave pattern is formed by laser melting, the intensity of the incident laser beam on the inclined surface of the side wall of the recess of this pattern is low, so that the sinusoidal wave pattern can be accurately matched as shown by the dotted line in FIG. I may not do it. In order to avoid such an undesired effect and form a more accurate sinusoidal waveform pattern, the intensity of the laser beam applied to the side wall is adjusted so as to draw an accurate waveform. When this is performed, it is effective to repeat the step of forming the same waveform pattern twice. For example, the intended sine waveform pattern is the function g (x) = 15 sin
In the case of (2πx / 30), the function f (x) = 7.
The waveform at g (x) can be approximated by repeating the step of forming a sine wave represented by 5 sin (2πx / 30). In order to approximate the sine waveform more accurately, it is preferable to increase the number of steps for shaping the same waveform. The sine waveform f (x) can be obtained by using the above mask or fly-eye lens or changing the intensity of the laser beam. Furthermore, one sinusoidal waveform may be formed using two or more masks or fly-eye lenses designed to compensate for the reduction in beam intensity directed at the sidewalls of the recess.

The composite shape can be reproduced by combining the features described above. Also, the method of the present invention can be applied to the fabrication of a master mold for reproducing a product having a microstructured surface. In this case, a work piece having a microstructure can be formed by using a known method called LIGA technology, and then a master die can be formed by electroforming. The recess of the composite shape becomes finer,
If the aspect ratio becomes 1.0 or more at a pitch of several μm or less, it becomes difficult to reproduce by a master mold. In this case, the master mold may be used to provide the product with one of the basic waveform patterns, and then the product may be provided with another one or more waveform patterns to obtain the final composite shape. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a system for carrying out a method for forming a composite shape on a surface of a work piece according to a first embodiment of the present invention.

FIG. 2A is a diagram showing a composite shape. (B) is FIG. 2 (a)
The figure which shows the regular waveform pattern decomposed from the shape of FIG.
2C is a diagram showing a regular waveform pattern decomposed from the shape of FIG.

FIG. 3 is a diagram showing a method of shaping a recess of a regular waveform pattern.

FIG. 4 is a plan view of a mask used in the above system.

5 is a diagram showing the intensity of a beam diffracted through the mask of FIG.

FIG. 6 is a schematic plan view of another mask used in the above system.

FIG. 7 is a schematic view showing a cross section of a mask image projected on the surface of a material to be processed and a waveform pattern formed on the surface of the material to be processed.

FIG. 8 is a schematic diagram showing two different masks used in the system to image different corrugated patterns, the cross-sectional shape of the workpiece surface formed by the masks, and the resulting cross-section of the composite shape.

FIG. 9 is a schematic diagram showing two different masks used in the system to image different corrugated patterns, the cross-sectional shape of the workpiece surface formed by the masks, and the resulting cross-section of the composite shape.

FIG. 10A is a diagram showing a method of scanning a laser beam for forming a composite shape along one direction of a work material. FIG. 6B is a diagram showing a method of scanning a laser beam for forming a composite shape along a direction orthogonal to each other in a workpiece.

FIG. 11A is a diagram showing a method of moving a workpiece along one direction of the workpiece. FIG. 6B is a diagram showing a method of moving the material to be processed along directions orthogonal to each other.

FIG. 12 is a plan view of a vapor deposition mask for displaying a regular waveform pattern on the surface of a material to be processed.

13 is a diagram showing a method of forming a composite shape by using the vapor deposition mask shown in FIG.

FIG. 14 is a schematic diagram illustrating a system for performing a method according to another embodiment of the present invention for forming a composite shape of non-uniform depressions on the surface of a work piece.

FIG. 15 (a) is a schematic view showing one method used in the present invention for forming a regular corrugated pattern on the surface of a work material. FIG. 3B is a schematic view showing another method used in the present invention to form a regular corrugated pattern on the surface of the work material. FIG. 3C is a schematic view showing another method used in the present invention for forming a regular corrugated pattern on the surface of the work material.

[Explanation of symbols]

1 Work material 2 tables 10 Energy beam source 11 mirror 12 mirror 13 Cylindrical lens 14 Cylindrical lens 15 Attenuator 17 scan mirror 18 Condensing lens 20 masks 21 Crystal substrate 22 Opaque ring 30 masks 31 mask 32 masks 34 opening 40 evaporation mask 41 Mask unit 42 Central opening 43 Inner ring 44 outer ring 100 beam source 111 mirror 112 mirror 113 Cylindrical lens 114 Cylindrical lens 115 Attenuator 116 Attenuator 117 scan mirror 120 fly eye lens

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G02B 3/00 G02B 3/00 A (56) References JP-A-3-155491 (JP, A) Japanese Patent Publication No. 8-504132 ( (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 26/00-26/42

Claims (14)

(57) [Claims] 1. A method of forming a composite shape defined by a number of non-uniform recesses on a surface of a work material, the method comprising the steps of: determining the composite shape; Decompose the shape into a simple and regular wavy pattern with different characteristics; irradiating the surface of the work piece with an energy beam and melting it onto the surface of the work piece to superimpose the individual wavy pattern in order. those formed as by a plurality period of the waveform pattern sine wave having the regularity
Have . 2. The waveform pattern of the energy beam for initial irradiation
Make sure that the turn has a larger amplitude than the waveform pattern to be emitted next.
The method of claim 1, wherein: 3. The process as claimed in claim 1 or 2, characterized in that decomposed into regular waveform pattern of the sinusoidal shape by approximation by orthogonal transformation to the composite shape. 4. A mask having opaque rings arranged on a plurality of concentric circles is used, and one period portion of the regular waveform pattern is projected onto a surface of a workpiece by an energy beam passing through the mask. The method according to 3 . 5. A single vapor deposition mask vapor-deposited on the surface of a workpiece is used to project one of the plurality of regular corrugated patterns, and the vapor deposition mask surrounds the central opening concentrically. A plurality of mask units composed of a plurality of mask rings adjacent to each other and having different transmissivities are arranged, and an energy beam that forms another regular corrugated pattern of the regular patterns forms the vapor deposition mask. The method according to claim 3 , characterized in that it is illuminated through to achieve said composite shape. 6. The according to claim 3, the energy beam directed to the side wall of the recess being formed by melting, characterized in that the large beam intensity than the energy beam directed to the next vertex and the valley of the recess the method of. 7. using different types of masks irradiated with the energy beam on the workpiece, each mask or claim 1, characterized in that Projects the workpiece surface of each regular wave pattern of the The method described in 2 . 8. An optical system including a special lens that disperses the energy beam into a plurality of beam spots on the surface of a workpiece, each beam spot having a beam intensity that changes regularly, 3. A method according to claim 1 or 2 , characterized in that the spots are arranged in a uniform manner to form the regular wave pattern. 9. One of the regular corrugated patterns is projected at a first magnification on the surface of the workpiece by changing the magnification of the optical system, and then another regular corrugated pattern is formed on the same surface at a second magnification. 9. The method according to claim 8 , characterized in that it is projected. 10. A single mask and a single optical system for projecting one of the regular corrugated patterns onto the surface of a work piece by the energy beam through the mask,
Characterized in that by changing the magnification of the optical system, first of all, the one regular waveform pattern is projected on the surface of the workpiece at the first magnification, and then another regular waveform pattern is projected at the second magnification. The method according to claim 1 or 2 . 11. The energy beam is a pulsed laser beam that is applied to the work piece at a predetermined frequency, and the laser beam scans the surface of the work piece in synchronization with the pulse frequency and the surface. The method according to claim 1 or 2 , wherein the composite shape is realized over a wide range of. 12. The method according to claim 11 , wherein the laser beam has a short wavelength or a short pulse width. 13. An optical system including means for projecting the regular corrugated pattern onto the surface of a workpiece is fixed, and the workpiece is moved with respect to the optical system to move the surface of the workpiece. The method according to claim 1 or 2 , wherein the composite shape is realized over a wide range. 14. An article made according to the method of claim 1, wherein the article is formed from the material to be processed, has the composite shape, and has a non-uniform recess having the composite shape. Is distributed at a pitch of 0.01 to 50 μm and has an aspect ratio of 0.1 to 2.0.