JP2006119427A - Laser machining method and laser machining device, and structure fabricated therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser machining method with which a face to be machined of a workpiece is machined extending over a wide range even when no moving portion exists. <P>SOLUTION: In the laser machining method, the work piece 7 is machined by phase modulating a laser beam P emitted from a laser light source 2 with a spatial phase modulation element 3, guiding the laser beam P to an image forming optical system 4, and making the laser beam P irradiate the workpiece 7 with the image forming optical system 4. The workpiece 7 is laser machined by using a synthetic data, comprising an image reproducing hologram data to reproduce a machined shape of the work piece 7 and a positional transferring hologram data to reproduce the image at a predetermined position for machining, as an input data to be inputted to the spatial phase modulation element 3, and sequentially varying the synthetic data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser processing method suitable for manufacturing a processed product having a two-dimensional shape or a three-dimensional shape, such as a MEMS (microelectronic mechanical system), a diffractive optical element, and an optical disc master, and in particular, a photonic crystal and a diffractive optical device. The present invention relates to a laser processing method and a laser processing apparatus that can be applied to manufacture of a structure having a large number of fine holes, such as elements, printed circuit boards, and nozzles of inkjet printers, and a structure manufactured thereby.

  Laser light can concentrate energy precisely in a minute area, so that materials such as surface patterning, drilling, cutting, cutting, etc. of metal or synthetic resin are directly processed, such as lithography and stereolithography. In recent years, it is used for processing forms that chemically change materials, processing modifications such as material modification, alteration, etc. In recent years, it has been used to manufacture ultra-fine two-dimensional structures and three-dimensional structures with a resolution of 1 μm or less. Various products such as refractive optical elements, diffractive optical elements, optical disc masters, electric circuits, MEMS elements, etc., are widely used and manufactured using this laser processing method. In the claims and specification of the present invention, “processing” includes the above-described various processing forms.

  As a conventional laser processing method, a method is known in which laser light is focused on a workpiece, and the workpiece is processed by moving the focusing point and the workpiece relative to each other (laser). Processing method 1).

  Further, there is also known a method of projecting the shape of the mask onto the work surface of the work piece by irradiating the work piece with laser light through the mask, thereby processing the work piece ( Laser processing method 2).

  The laser processing method 1 includes a processing method for moving a processing surface of a workpiece in a direction perpendicular to the optical axis of laser light (irradiation light), and a processing method using a galvano scanner or the like. A processing method for scanning a condensing point of laser light is known. In particular, according to a processing method using a galvano scanner, high-speed and high-precision processing is possible.

  In the laser processing method 2, three-dimensional processing is performed by using a processing method for forming a highly accurate shape at a time by reducing and projecting the mask shape onto the processing surface of the workpiece, and a gray scale mask. Processing methods are known.

  However, the laser processing method 1 has a problem that the throughput is small when processing is performed over a wide range of the processing surface of the workpiece. In the laser processing method 2, since the laser light is shielded by the mask, there is a problem that the utilization efficiency of the laser light becomes very low depending on the shape to be projected. Further, there is an inconvenience that the processing shape of the workpiece is uneven due to the unevenness of the intensity of the laser light applied to the mask.

  Therefore, in order to solve these problems in the laser processing method, a method of performing a laser processing by forming a specific hologram reproduction image on a workpiece using a diffractive optical element or a holographic element (hologram element) has been proposed. (For example, refer to Patent Document 1).

A method of processing by adjusting a laser light irradiation pattern by using a spatial phase modulation element instead of a diffractive optical element has also been proposed (for example, see Patent Document 2).
JP 2002-66769 A Japanese Patent No. 3430531

  However, in the laser processing method using a hologram reproduction image, the light utilization efficiency is high and the processing surface of the workpiece can be processed at one time. However, to process the workpiece over a wider range, the hologram reproduction It is necessary to perform processing a plurality of times by combining a hologram element for obtaining an image and a mechanical moving means.

  As the mechanical moving means, means for driving a stage on which a workpiece is placed, means for moving the position of the imaging optical system, and means for deflecting laser light by a movable device such as a galvano scanner have been proposed. However, since these mechanical movement means require a high-precision drive device, the entire laser processing apparatus becomes expensive, and since the mechanical movement is performed, the accuracy of position control is reduced due to vibration generated during acceleration / deceleration. Problem arises.

  Further, in the processing method using the hologram reproduction image, speckle noise appears on the reproduction surface of the hologram image (the processing surface of the workpiece), and thus there is a problem that the processing shape of the workpiece is deteriorated.

  In order to reduce this speckle noise, the technique disclosed in Japanese Patent No. 3430531 proposes a method for optimally adjusting the beam diameter of laser incident light. In addition, in the technique disclosed in Japanese Patent No. 3475947, a plurality of hologram images are prepared, and these hologram images are projected onto the workpiece at substantially the same position, and the speckle noise is integrated. A method for reducing the speckle noise has been proposed.

  In addition, the method disclosed in Japanese Patent Laid-Open No. 2001-71168 proposes a method of reducing speckle noise by reducing the interference effect by moving the hologram element by a small distance in the optical axis direction or in a direction perpendicular to the optical axis. ing.

  However, the techniques disclosed in these publications are limited in reducing speckle noise.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is a laser processing method and a laser capable of performing processing over a wide range of a processing surface of a workpiece without a movable part. It is to provide a processing apparatus.

  An object of the present invention is to provide a laser processing method suitable for reducing speckle noise.

  Other objects will be apparent from the description of the specification.

  The principle of the present invention is to use a spatial phase modulation element that performs phase modulation of laser light to perform laser processing, and to apply a predetermined machining shape to a workpiece as data to be input to the spatial phase modulation element. Laser beam to obtain the processed shape of the workpiece from the image reproduction hologram data, using the combined data of the image reproduction hologram data and the position-moving hologram data for reproducing the hologram reproduction image at a predetermined position of the workpiece At the same time, the irradiation position of the laser beam is controlled by the position movement hologram data.

  Here, “synthesis” means adding the phase modulation amount of the image reproduction hologram data and the phase modulation amount of the position movement hologram data for each pixel, and when the spatial phase modulation element exceeds the amount capable of phase modulation, An operation of subtracting the amount of phase modulation by the spatial phase modulation element from the amount of phase modulation obtained by addition. Here, since the amount of phase modulation of the spatial phase modulation element is 2π, the synthesized data is the phase modulation amount obtained by adding the phase modulation amount of the image reproduction hologram data and the phase modulation amount of the position moving hologram data. Is obtained by subtracting 2π from.

  By performing laser processing a plurality of times while changing the composite data, a specific processing shape can be formed over a wide range on the workpiece without using a mechanical movable mechanism.

  When changing the composite data, only the position movement hologram data may be changed, only the image reproduction hologram data may be changed, or both the position movement hologram data and the image reproduction hologram data may be changed. .

  In particular, when a periodic structure is processed and formed on the workpiece, the periodic structure can be processed and formed by performing laser processing a plurality of times while changing only the position moving hologram data. Since it is not necessary to calculate and create each time, it is possible to speed up the formation of the periodic structure.

  Furthermore, if image reproduction hologram data capable of reproducing a plurality of discrete point images is used as the image reproduction hologram data, a hologram reproduction image having almost no speckle noise due to laser beam interference can be obtained. It is possible to obtain a complicated and highly accurate machining shape by performing laser processing a plurality of times using synthesized data obtained by synthesizing such image reproduction hologram data and position movement hologram data. be able to.

  The present invention uses the above principle, and the laser processing method according to claim 1 is directed to the imaging optical system by phase-modulating the laser light emitted from the laser light source by the spatial phase modulation element. In a method for processing a workpiece by irradiating the workpiece with a laser beam by an image optical system, an image reproduction hologram for reproducing the processed shape of the workpiece as input data input to the spatial phase modulation element Using the composite data composed of data and position-moving hologram data for performing image reproduction at a predetermined processing position, laser processing is performed on the workpiece while sequentially changing the composite data.

  According to a second aspect of the present invention, in the method of the first aspect, the image reproduction hologram data is used to reproduce a plurality of discrete point images.

  A laser processing method according to claim 3 is the method according to claim 2, wherein a plurality of image reproduction hologram data for reproducing a plurality of discrete point images is prepared, and the plurality of point images are reproduced. Laser processing is performed while changing both the image reproduction hologram data and the position movement hologram data.

  The laser processing method according to claim 4 is the method according to any one of claims 1 to 3, wherein the hologram data relating to a direction parallel to the surface to be processed has a sawtooth shape or a substantially sawtooth phase. It is the data which has distribution.

  The laser processing method according to claim 5 is the method according to any one of claims 1 to 3, wherein the hologram data relating to a direction perpendicular to the surface to be processed is Fresnel zone plate-like or substantially It is data having a phase distribution of a Fresnel zone plate.

  The laser processing method according to claim 6 is the method according to claim 5, wherein a distance from the spatial phase modulator to the main plane of the imaging optical system is equal to a focal length of the imaging optical system. It is characterized by.

  A laser processing method according to a seventh aspect of the present invention is the method according to any one of the first to third aspects, wherein the position-moving hologram data includes hologram data related to a direction parallel to the processing surface and This is combined position movement hologram data obtained by combining hologram data in a direction perpendicular to the processing surface.

  A laser processing method according to an eighth aspect of the present invention is the method according to any one of the first to seventh aspects, wherein the wavefront measuring means measures the wavefront of the laser light input to the spatial phase modulation means, Input means for inputting the combined data to the spatial phase modulation element; and computer means for correcting distortion of the wavefront measured by the wavefront measuring means, the computer means generating correction data, and generating the spatial phase modulation The corrected composite data is input to the means.

  The laser processing method according to claim 9 is the method according to any one of claims 1 to 8, wherein the laser processing is performed while adjusting an irradiation time or an irradiation intensity of the laser light. To do.

  The laser processing method according to claim 10 is the method according to any one of claims 1 to 9, wherein a part of the workpiece is transparent to laser light. .

  The laser processing method according to claim 11 is the method according to any one of claims 1 to 10, wherein the laser light source is an ultrashort pulse laser light source having a pulse width of several picoseconds or less. It is characterized by.

  13. A laser processing apparatus according to claim 12, comprising: a laser light source; a spatial phase modulation element that phase-modulates laser light emitted from the laser light source; and a laser beam that is phase-modulated by the spatial phase modulation element. An image forming optical system for irradiating the light source, input means for controlling the spatial phase modulation element by composite data including image reproduction hologram data and position moving hologram data for performing image reproduction at a predetermined processing position, and the image reproduction hologram It has at least a computer that calculates data and position movement hologram data and outputs them to the input means.

  According to a thirteenth aspect of the present invention, there is provided a structure manufactured by the laser processing apparatus according to the twelfth aspect.

  According to the first aspect of the present invention, even when laser processing is performed over a wide range of a workpiece, it is possible to provide a processing method with high light utilization efficiency and high flexibility. In particular, the direct removal processing method that directly removes the material of the workpiece requires a large amount of energy for the processing, and there is a limit to the amount of processing that can be removed at one time, and the processing must be performed in multiple steps. It is suitable for using the position movement hologram data as the processing position movement means.

  According to the second aspect of the present invention, since the hologram reproduction image is a discrete point image, speckle noise can be reduced.

  In particular, even when the finished machining shape has many lines and surfaces, the desired machining shape is divided into multiple points and machining is performed while changing the composite data, thereby reducing the effect of speckle noise. Can be done. Further, when it is desired to form a processed shape having a periodic structure, a processed shape having a periodic structure can be formed by combining at least one image reproduction hologram data and position movement hologram data. As a result, the time required to calculate the hologram image can be shortened, and a processed shape having a periodic structure can be quickly formed.

  According to the third aspect of the present invention, the degree of freedom in processing can be increased without calculating the hologram image each time processing is performed.

  According to the invention described in claim 4, since the processing is performed a plurality of times while changing the image reproduction hologram data and the sawtooth data, the complicated processing shape is divided into a plurality of simple shapes for processing. It is possible. When calculating a complex-shaped hologram reproduction image, the calculation error increases. However, since the calculation is divided into a plurality of simple images, the error in hologram image reproduction can be reduced. This makes it possible to process with higher accuracy.

  According to the fifth aspect of the present invention, the reproduction position of the hologram reproduction image in the optical axis direction can be moved.

  According to the sixth aspect of the present invention, the combined focal length can be adjusted to the focal length of the Fresnel zone plate by adjusting the distance between the spatial phase modulator and the imaging optical system to the focal length of the imaging optical system. In addition, the size of the hologram reproduction image can be made constant regardless of the focal length of the Fresnel zone plate.

  According to the seventh aspect of the present invention, the hologram data relating to the direction horizontal to the surface to be processed and the hologram data relating to the direction perpendicular to the surface to be processed are calculated and synthesized to generate position movement hologram data. As a result, the calculation can be simplified. As a result, the time required to calculate the position movement hologram data can be reduced, and processing can be performed at high speed.

  According to the invention described in claim 8, since the wavefront measuring means for measuring the wavefront of the laser light incident on the spatial phase modulator is provided and the wavefront of the laser light is measured, the input to the spatial phase modulator. It is possible to feedback the synthesized data. As a result, a hologram reproduction image with higher accuracy can be obtained, and a processed shape with higher accuracy can be obtained.

  The processing depth and processing shape depend on the intensity of the laser beam, the irradiation time, and the number of pulses. When obtaining the desired processing shape with high accuracy, it is necessary to set the optimum laser beam intensity and irradiation time. However, according to the ninth aspect of the invention, it is possible to perform processing with higher accuracy. In this case, it is desirable to prepare processing shape data with respect to laser light intensity and irradiation time. In addition, when performing a plurality of times of processing, it is possible to process a three-dimensional shape by changing the laser irradiation time when continuously irradiating laser light, and changing the number of times of irradiation when using a pal laser.

  According to the invention described in claim 10, a structure having a three-dimensional shape change and a workpiece having a three-dimensional property change are formed inside an object transparent to the laser beam used for processing. It becomes possible to do. Furthermore, since the laser beam irradiation shape can be freely controlled, it is also possible to produce a free structure in a transparent body. For example, optical element microreactors (chemical reactors such as photonic crystals, optical waveguides, diffractive optical elements) ) Can be produced.

  According to the invention described in claim 11, since the processing can be performed using the ultrashort pulse laser beam having a pulse width of several ps or less, the interaction time between the workpiece and the laser beam becomes very short, The influence of heat propagation can be kept small.

  In addition, since ultra-short pulse laser light generates very strong energy instantaneously, it has an advantage that it can be directly removed even on difficult-to-work products such as diamond, glass, and oxide.

  Also, since ultrashort pulse laser light has a very strong peak power, it can be processed using a two-photon absorption process, and it can be processed inside an object that is transparent to the laser light. According to this laser processing method, it is possible to align three-dimensionally, so that processing can be performed at an arbitrary position inside the transparent body with high alignment accuracy.

  According to the invention described in claim 12, the laser processing described in any one of claims 1 to 11 can be performed.

  According to invention of Claim 13, the structure which has a highly accurate fine process part can be provided.

  Embodiments of a laser processing method according to the present invention will be described below with reference to the drawings.

(Embodiment of laser processing method according to claim 1)
1 to 4 show an embodiment of the laser processing method according to the first aspect. FIG. 1 shows a schematic configuration of a laser processing apparatus for carrying out the laser processing method according to claim 1.

  In FIG. 1, reference numeral 1 denotes a laser processing apparatus. The laser processing apparatus 1 includes a laser light source 2, a spatial phase modulator 3, an imaging lens (imaging optical system) 4, a controller (input means) 5, and a calculator 6. The laser light P emitted from the laser light source 2 is subjected to phase modulation by the spatial phase modulator 3, and the laser light P ′ subjected to the phase modulation is condensed by the imaging lens 4 to be processed 7 Is irradiated. The spatial phase modulator 3 is controlled by a controller 5, and input data S 1 to the controller 5 is calculated by a calculator 6.

  Here, an Nd: YAG laser is used as the laser light source 2, and light having a wavelength of 532 nm (nanometers), which is the second harmonic of the Nd: YAG laser, is used as the laser light P. Here, the imaging lens 4 is a lens having a focal length f = 10 mm (millimeter), and the distance d between the imaging lens 4 and the spatial phase modulator 3 is 10 mm here.

  The spatial phase modulator 3 includes a type that causes a phase difference depending on the alignment direction of the liquid crystal, a type that uses an electro-optical effect, and a type that uses a magneto-optical effect. The spatial phase modulator 3 using the optical effect is desirable because of its high response speed. The spatial phase modulator 3 is classified into a reflective type and a transmissive type. In this embodiment, a transmissive type spatial phase modulator 3 is shown. A modulator can also be used.

  In this embodiment, specifically, as the spatial phase modulator 3, the number of pixels is N (N = 512 pixels × 512 pixels), the pixel pitch is 30 μm (micron meter), and the wavelength of the laser light P is “2π. An electro-optical type capable of performing phase modulation of "" with 256 gradations is used.

  Laser processing of the workpiece 7 is performed a plurality of times while inputting composite data described below to the spatial phase modulator 3 and changing the composite data.

  FIG. 2A is a processed shape image (corresponding to a hologram reproduction image) G1 showing an example when the workpiece 7 is processed by the first processing, and FIG. 2B is a reproduction of the processed shape image G1. It is a phase modulation type computer-generated hologram image (image reproduction hologram data) G2 calculated as described above. This computer-generated hologram image G2 has 256 gradations, and can have a maximum phase modulation of “2π” with N pixels (N = 512 pixels × 512 pixels). Here, the processed shape image G1 is a discrete point image having a lattice shape.

As a method for calculating the hologram image, an iterative Fourier transform method, a simulated annealing method, or the like can be used, and these calculation methods are described in detail in the following papers. Please refer to the paper.
“1. N.Yoshikawa and T.Yatagai, Appl. Opt. 33,863-867 (1994)
2. J. Fienup, Opt. Eng. 19, 297-305 (1980) ''
Since the iterative Fourier transform method can calculate a hologram reproduction image having a large number of pixels in a shorter time than the simulated annealing method, it is desirable to use this iterative Fourier transform method.

  FIG. 2C shows position movement hologram data G3, and this position movement hologram data G3 shows a case where the spatial frequency is lower than position movement hologram data described later. That is, the position movement hologram data G3 is a position movement hologram image corresponding to a case where the position interval is large. The combined data obtained by adding to the computer-generated hologram image G2 and the position movement hologram data G3 is the combined data G4 shown in FIG. Here, “addition” means that the position-moving hologram data G3 is added to the computer-generated hologram image G2 for each pixel, and the calculated phase modulation amount exceeds the amount (2π) that can actually be phase-modulated for each pixel. In this case, an operation of subtracting a value of “2π” from the phase modulation amount obtained by calculation to obtain actual input data is performed.

  The position movement hologram data G3 is used to move the reproduction position of the hologram image, and the position movement hologram data G3 can also be calculated using an iterative Fourier transform method, a simulated annealing method, or the like. The synthesized data G4 is input to the spatial phase modulator 3, whereby the first laser processing is performed on the workpiece 7.

  FIG. 3A is a processed shape image G5 showing an example when the workpiece 7 is processed in the second processing, and FIG. 2B is a phase calculated so that the processed shape image G5 is reproduced. This is a modulation type computer-generated hologram image G6. Here, the processed shape image G5 and the processed shape image G1 are the same hologram reproduction image, and therefore the computer-generated hologram image G6 is also the same image reproduction as the computer-generated hologram image G2. Hologram data. FIG. 3C shows position movement hologram data G7, which shows a case where the spatial frequency is higher than the position movement hologram data G3. That is, the position movement hologram data G7 is a position movement hologram image corresponding to a case where the position interval is small. The combined data obtained by adding to the computer-generated hologram image G6 and the position movement hologram data G7 is the combined data G8 shown in FIG. The combined data G8 is input to the spatial phase modulator 3, whereby the second laser processing is performed on the workpiece 7.

  FIG. 4 is a view showing an example in which laser processing is performed on the processing surface 7a of the workpiece 7. FIG. 4A shows a processing shape formed on the processing surface 7a by the first laser processing. 4B shows a set G9 of discrete points, and FIG. 4B shows a set G10 of discrete points as a processing shape formed on the processing surface 7a by the second laser processing and a processing surface by the first laser processing. A set G9 of discrete points as a machining shape formed in 7a is shown. The discrete point set G10 is translated in the horizontal direction with respect to the discrete point set G9. In FIG. 4B, a part of the discrete point set G9 and a part of the discrete point set G10 are shown. A state where and are overlapped is shown.

  In this way, by repeating the operation of performing laser processing on the workpiece 7 while changing the composite data, laser processing can be performed over a wide range without having a mechanical movable part.

In the embodiment of the laser processing method according to claim 1, the laser processing is performed by moving the reproduction position of the hologram reproduction image by changing the position-moving hologram data. However, the computer-generated hologram images G <b> 2 and G <b> 6 are used. Laser processing may be performed by using a method of changing both the computer-generated hologram images G2 and G6 and the position movement hologram data G3 and G7.
(Embodiment of laser processing method according to claim 2)
FIG. 5 shows an embodiment of the laser processing method according to claim 2. In the laser processing method according to claim 1, the hologram reproduction image reproduced by the spatial phase modulation element 3 is a set of discrete points, and a large number of discrete points are formed on the workpiece 7 by one processing. It could be formed on the work surface.

  In the embodiment of the laser processing method according to claim 2, a laser processing method for forming a set of discrete points on the processing surface 7a by performing processing a plurality of times while changing the position movement data to be added will be described. To do.

  First, as shown in FIG. 5, the processed shape of the processed surface 7a of the workpiece 7 to be finally obtained is G11. This processed shape G11 means a state in which the processing surface (surface) 7a is processed entirely.

  In order to obtain the processed shape G11 shown in FIG. 5, a hologram reproduction image (matrix image made up of 3 × 3 discrete points) corresponding to the processed shape G12 shown in FIG. The position of the hologram reproduction image (matrix image made up of 3 × 3 discrete points) formed on the processing surface 7a and corresponding to the processing shape G12 shown in FIG. Then, a processing shape G13 shown in FIG. 6B is formed on the processing surface 7a, and the position of the hologram reproduction image (matrix image made up of 3 × 3 discrete points) is similarly used by using the position movement hologram data. 6 (c), and then the position of the hologram reproduction image (matrix image made up of 3 × 3 discrete points) is changed using the position-moving hologram data. Figure By repeating this many times such as forming the machining shape G15 shown in (d), the machining shape G16 shown in FIG. 6E, that is, the machining shape G11 shown in FIG. 5 is finally formed. .

  In this embodiment, the laser processing is performed while changing only the position moving hologram data. However, the laser processing is performed while changing both the position moving hologram data and the computer generated hologram image (image reproduction hologram data). Alternatively, laser processing may be performed while changing only the computer generated hologram image.

  Here, the interval between the discrete point images needs to be wide enough that the interference does not affect the laser processing, but in order to perform the processing efficiently, a plurality of computer generated hologram images obtained by the computer are used. It is desirable that the number of (image reproduction hologram data) is smaller and the interval between discrete point images is as close as possible.

In the hologram reproduction image using the Fourier transform function of the imaging lens 4, the following document shows that the function of the amplitude distribution of the point image on the processing surface 7 a of the processing object 7 is expressed by sinc (λ / NA). It is stated.
"Applied Physics Vol.69 No.1, 57-60 (2000)"
The symbol λ indicates the wavelength of the laser beam, and NA indicates the numerical aperture of the imaging lens (imaging optical system) 4.

  The relationship between this sinc (λ / NA) and speckle noise of the laser beam P will be described below.

  As shown in FIG. 7, it is assumed that the hologram surface H1 is composed of a large number of cells Hc synthesized by the computer 6. In this case, as shown in FIG. 7, the hologram reproduction image appears on the image surface corresponding to the hologram surface H1, that is, the processed surface 7a, in a state where a plurality of laser light spots S are superimposed.

  The amplitude intensity distribution Q of one spot S is expressed using a function called sinc (λ / NA). Therefore, an overlapping portion of the laser light occurs between the spots, and an interference phenomenon occurs. Here, sinc (λ / NA) extends to infinity, and mathematically, even if the distance between the points is separated infinitely, a slight interference occurs.

However, the intensity of the sinc function once becomes “0” at a point away from the center by λ / NA. Therefore, as for the interval between the point images, if the two point images are separated by λ / NA or more, strong interference occurs. Therefore, as for the interval between the point images, it is sufficient if the distance between the two point images is about λ / NA.
(Embodiment of the invention according to claim 3)
FIG. 8 is an explanatory diagram when a plurality of computer generated hologram images (image reproduction hologram data) are prepared and laser processing is performed. As shown in FIG. 8A, the processing surface 7a is formed by a plurality of cells Hc ′. And one point Gx is made to correspond to one cell Hc ′, and it is possible to freely select whether or not to form a point Gx for each cell Hc ′.

  When the number of cells Hc ′ on the surface 7a to be processed is N, 2 N computer hologram images (image reproduction hologram data) are required to determine whether or not to form the point Gx. However, considering symmetry, the number can be greatly reduced.

While changing the position movement hologram data by adding position movement hologram data to this computer generated hologram image (image reproduction hologram data), the discrete point images shown in FIGS. 8B to 8E are processed. By machining to 7a, a complicated shape G17 shown in FIG. 9 can be obtained.
(Embodiment of Invention According to Claim 4)
10 to 14 are explanatory views of an embodiment according to a fourth aspect of the present invention. Sawtooth-shaped data is used as position movement hologram data in the horizontal direction with respect to the processing surface 7a, and a computer generated hologram image (image reproduction hologram data) is added to the sawtooth-shaped data.

  FIG. 10A shows a sawtooth shape m1, and this sawtooth shape m1 has an asymmetrical inclination. By inputting the sawtooth shape m1 to the spatial phase modulator 3, the traveling direction of the laser beam P can be tilted by the angles θx and θy in the X-axis and Y-axis directions. The reproduction position of the reproduced image is shifted in parallel on the processing surface 7a. The angles θx and θy are about several milliradians, and can be calculated by applying the paraxial optical system formula.

  When the sawtooth shape data shown in FIG. 10A is input to the spatial phase modulator 3, as shown in FIG. 11, the laser light P is converted into X by a spatial phase modulator 3 in a plane perpendicular to the optical axis O1. It is displaced to a position translated from the optical axis by Δx in the direction. FIG. 11 does not show a state where the optical axis O1 is translated by ΔY in the Y direction, but this is omitted for the sake of simplification of the drawing.

The deviation amount of the reproduction position of the hologram reproduction image on the processing surface 7a of the workpiece 7 is expressed by the following equation: ΔX = tan θx · (2-f / d)
ΔY = tan θy · (2-f / d)
Represented by

  Accordingly, the phase modulation amount Φ (x, y) of the coordinates X, Y of an arbitrary point of the spatial phase modulator 3 using ΔX, ΔY is expressed by the following [Equation 1].

この数１式において、符号ａ_x、符号ａ_yはそれぞれ空間位相変調器３のＸ方向の画素ピッチ、Ｙ方向の画素ピッチであり、符号ｍは整数であり、Φ（ｘ,ｙ）が０から２πまでの値となるように調整するための係数である。

In this equation 1, the symbols a _x and a _y are the pixel pitch in the X direction and the pixel pitch in the Y direction of the spatial phase modulator 3, respectively, the symbol m is an integer, and Φ (x, y) is 0. Is a coefficient for adjusting to a value from 2 to 2π.

  The minimum wavefront slope given by the sawtooth shape m1 is approximately expressed as λ × (8 / M) / N · a. Here, the symbol λ is the wavelength, the symbol M is the number of phase modulation gradations, the symbol N is the number of pixels (the number of pixels) in the spatial phase modulator 3, and the symbol a is the pixel pitch.

  Here, it is assumed that there is modulation for 8 gradations over all pixels as the minimum wavefront slope. If there is a modulation of 8 gradations, a theoretical efficiency of 95% can be obtained as a diffraction efficiency, which is considered to be sufficient.

  Here, the minimum slope of the wavefront is about 1.9 μradians, and this value is considered to be the approximate minimum resolution. The typical positioning accuracy of a galvano scanner is 5 μ radians to 10 μ radians. According to the embodiment of the invention according to claim 4, positioning can be performed with a higher resolution without using moving parts such as a galvano scanner. Is possible.

  At this time, the positioning accuracy of the laser beam P irradiated to the workpiece 7 is about 20 nm (nanometer). The positioning accuracy value depends on the spatial phase modulator 3, and higher positioning accuracy can be obtained by using a pixel having a larger number of pixels or a larger number of gradations that can be modulated.

The sawtooth shape m1 does not need to be a sawtooth in a strict sense, and may be any shape similar to the sawtooth shape m1. For example, the data of quantization m2 shown in FIG. 10B may be used, or the data of a linear shape m3 having a slope instead of sawtooth may be used as shown in FIG. 10C. Furthermore, it is possible to use one having a slightly curved curve instead of a straight line.
(Embodiments of the invention according to claims 5 and 6)
In the embodiment of the present invention, in order to move the hologram reproduction image in the vertical direction with respect to the processing surface 7a, as shown in FIG. 12, the phase of the Fresnel zone plate shape or substantially Fresnel zone plate shape m4 is obtained as the image reproduction hologram data. Data with distribution is used. In this embodiment, the distance d (see FIG. 11) between the spatial phase modulator 3 and the imaging lens 4 is made equal to the focal length f of the imaging lens 4.

  According to this embodiment, the size of the hologram reproduction image can be made constant regardless of the focal length of the Fresnel zone plate.

That is, the focal length f ′ of the synthetic lens composed of the focusing lens 4 having the focal length f and the Fresnel zone plate having the focal length f1 is expressed by the thin lens formula:
1 / f ′ = (1 / f) + (1 / f1) − (d / f · f1)
It is represented by

  Therefore, when d = f1, the focal length f 'is the focal length f1 of the Fresnel zone plate, and the size of the hologram reproduction image is constant regardless of the focal length f1 of the Fresnel zone plate.

Here, although one imaging lens 4 is shown as the imaging optical system, the imaging optical system may be configured by combining a plurality of lenses. The spatial phase modulator 3 and the imaging optical system are arranged such that the combined focal length f of the system is equal to the distance from the spatial phase modulator 3 to the imaging optical system to the main plane of the combining lens. In this case, the focal position deviation amount ΔZ is expressed by the equation ΔZ = f ² / R
Represented by

  Here, the symbol f is the focal length of the imaging optical system, and the symbol R is the curvature of the Fresnel zone plate data on the wavefront of the plane wave of the laser beam P. That is, the curvature for converting a plane wave into a spherical wave.

  On the other hand, the phase modulation amount Φ (x, y) of arbitrary coordinates x, y of the spatial phase modulator 3 is given by the following [Equation 2].

なお、請求項４に係わる実施例と請求項５、６に係わる実施例とを組み合わせて、被加工面７ａに対して水平な方向に関するホログラムデータと被加工面７ａに対して垂直な方向に関するホログラムデータとを計算しかつ合成して位置移動ホログラムデータを作成しても良い。
（請求項８に係わる発明の実施例）
図１３は請求項８に係わる発明の実施例を説明するための説明図である。図１に示す光学部品と同一の光学部品には同一符号を付してその詳細な説明は省略することにし、異なる部分についてのみ説明する。

It should be noted that the hologram data related to the direction parallel to the processing surface 7a and the hologram related to the direction perpendicular to the processing surface 7a are combined by combining the embodiment according to claim 4 and the examples according to claims 5 and 6. The position movement hologram data may be created by calculating and combining the data.
(Embodiment of the invention according to claim 8)
FIG. 13 is an explanatory diagram for explaining an embodiment of the invention according to claim 8. The same reference numerals are given to the same optical components as those shown in FIG. 1, and detailed description thereof will be omitted, and only different portions will be described.

  In the laser processing apparatus 1 shown in FIG. 13, a part of the laser light P emitted from the laser light source 2 is branched by the beam sampler 8 and guided to the wavefront measuring device (wavefront measuring means) 9. As the wavefront measuring device 9, a microlens type, a Shack-Hartmann type, or a type that interferes with a beam is used.

  The output signal S2 from the wavefront measuring device 9 is input to the computer 6. The computer 6 creates wavefront correction data based on the output signal output from the wavefront measuring device 9, and this wavefront correction data is input to the controller 5, and the controller 5 uses the synthesized data converted by the wavefront correction data as a space. Output toward the phase modulation element 3.

According to this embodiment, a hologram reproduction image with higher accuracy can be obtained, so that a processed shape with higher accuracy can be obtained.
(Embodiment of the invention according to claim 9)
In this embodiment, as shown in FIG. 14, the workpiece is processed while adjusting the intensity of the laser beam P, adjusting the irradiation time of the laser beam P, or adjusting the intensity and irradiation time of the laser beam P. Processing of the object 7 is performed.

  In FIG. 14, the same optical components as those shown in FIG. 1 are denoted by the same reference numerals and detailed description thereof will be omitted, and only different portions will be described.

  The laser light P emitted from the laser light source 2 is guided to the spatial phase modulator 3 through the half-wave plate 10, the Glan-Thompson prism 11, and the shutter 12. The half-wave plate 10 and the Glan-Thompson prism 11 are used to adjust the intensity of the laser beam P, and the shutter 12 is used to adjust the irradiation time of the laser beam P.

  The laser light P output from the laser light source 2 is usually linearly polarized light. The intensity of the laser light P is changed by changing the polarization direction of the laser light P by the half-wave plate 10 and passing through the Glan-Thompson prism 11. Is adjusted.

  When the degree of linear polarization of the laser beam P is small, two Glan-Thompson prisms 11 are provided and the intensity of the laser beam P is adjusted by rotating one of the Glan-Thompson prisms 11 about the optical axis. Can do.

  The irradiation time or the number of irradiation pulses of the laser beam P is adjusted by opening / closing control of the shutter 12. The shutter 12 may be an electronic shutter such as a mechanical shutter, an acousto-optic element, or an electro-optic element.

According to this embodiment, the intensity of the laser beam, the irradiation time, and the number of irradiation pulses can be adjusted, so that processing of a three-dimensional shape with higher accuracy can be performed.
(Embodiments of the invention according to claims 10 to 13)
FIG. 15 is an explanatory diagram for explaining an embodiment of the laser processing apparatus 1 of the invention according to claims 10 to 13. The laser light source 2 is supplied with a pulse laser beam P having a pulse width of 100 fs (femtosecond). A generated Ti: Sapphire laser is used.

  The laser light source 2 may be an ultrashort pulse laser light source having a pulse width of several picoseconds or less.

  The laser processing apparatus 1 includes an intensity adjustment mechanism 13 that adjusts the intensity of the laser light P and a shutter mechanism 14 that adjusts the number of irradiation pulses of the laser light P.

The spatial phase modulator 3 is controlled by the controller 5 similarly to the laser processing apparatus 1 shown in FIG. 1, and control information from the computer 6 is output to the controller 5. Further, the strength adjusting mechanism 13, the shutter adjusting mechanism 14, and a stage described later are controlled by the computer 6.
The calculator 6 includes hologram calculation means, sawtooth shape calculation means, and Fresnel zone shape calculation means. After passing through the intensity adjusting mechanism 13 and the shutter mechanism 14, the laser beam P is phase-modulated by the spatial phase modulator 3 and guided to the dichroic mirror 15, and the dichroic mirror 15 forms an imaging lens (imaging optical system). 4, and is irradiated onto the processing surface 7 a of the workpiece 7 by the imaging lens 4.

  The workpiece 7 is placed on the stage 16, the position with respect to the imaging lens 4 is adjusted as appropriate, and the workpiece surface 7 a of the workpiece 7 is observed by the microscope 17. The microscope 17 is generally composed of a lens barrel 18 having an objective lens (not shown) and a CCD camera 19, and the processing shape of the processing surface 7 a of the workpiece 7 is observed by the microscope 17.

  According to this, a hologram reproduction image can be reproduced inside a substance transparent to laser light such as glass, polymer, transparent oxide, etc., and laser processing such as alteration and hole generation can be performed. It is also possible to cure only the reproduction part of the hologram reproduction image using a photo-curable material. In addition, a structure having a fine processed portion with high accuracy can be manufactured.

It is a schematic diagram which shows an example of the laser processing apparatus used for the laser processing method concerning Claim 1 of this invention. It is explanatory drawing of the hologram data used for the 1st process of the laser processing method concerning Claim 1 of this invention, Comprising: (a) is a hologram reproduction image, (b) is an image for obtaining this hologram reproduction image Hologram image corresponding to reproduction hologram data, (c) is a hologram image corresponding to position movement hologram data, (d) is a composite hologram image (composite data) of the hologram image shown in (b) and the hologram image shown in (c). (Hologram images corresponding to) are shown respectively. It is explanatory drawing of the hologram data used for the 2nd process of the laser processing method concerning Claim 1 of this invention, Comprising: (a) is a hologram reproduction image, (b) is an image for obtaining this hologram reproduction image Hologram image corresponding to reproduction hologram data, (c) is a hologram image corresponding to position movement hologram data, (d) is a composite hologram image (composite data) of the hologram image shown in (b) and the hologram image shown in (c). (Hologram images corresponding to) are shown respectively. It is explanatory drawing of the laser processing method concerning Claim 1 of this invention, Comprising: (a) is the process shape formed in the to-be-processed surface of a workpiece, (b) is formed in the to-be-processed surface of a workpiece. Each processed shape is shown. It is explanatory drawing which shows the processing shape formed in the to-be-processed surface by the Example of the laser processing method concerning Claim 2 of this invention. It is explanatory drawing for demonstrating the procedure for forming the process shape shown in FIG. 5, Comprising: (a) is the state by which the 3x3 matrix-like point was formed in the to-be-processed surface by the 1st process. (B) shows a state in which the position is shifted to the right by the second machining and 3 × 6 matrix-like points are formed on the surface to be machined, and (c) shows the position by the third machining. Is a state where 3 × 3 matrix dots are further formed on the processing surface on which 3 × 6 matrix dots are formed, and (d) shows the processing by the fourth machining. A state in which 6 × 6 matrix points are formed on the surface is shown, and (e) shows a state in which the entire surface of the processed surface is finally processed by the n-th processing. It is explanatory drawing for demonstrating the principle why a speckle noise is reduced by the laser processing method concerning Claim 2 of this invention. It is explanatory drawing of the Example concerning Claim 3 of this invention, Comprising: (a) shows the state which divided | segmented the to-be-processed object into several cells, (b) is each cell by the 1st process. The processing points to be formed are indicated, (c) indicates the processing points to be formed in each cell by the second processing, and (d) is to be formed in each cell by the third processing. The processing points are shown, and (e) shows the processing points to be formed in the respective cells by the fourth processing. It is explanatory drawing which shows an example of the process shape formed in the to-be-processed surface by the laser processing method concerning Claim 3. It is a figure which shows an example of the position movement hologram data used for the laser processing method concerning Claim 4, (a) is a sawtooth shape, (b) is a staircase type (quantization type) shape as a substantially sawtooth shape, (c). Indicates an inclined shape constituting a part of the sawtooth shape. It is explanatory drawing which shows an example of the laser beam displaced using the laser processing method concerning Claim 4. It is a figure which shows an example of the position movement hologram data used for the laser processing method concerning Claim 5, and is sectional drawing which shows a Fresnel zone plate shape. It is a schematic diagram which shows an example of the laser processing apparatus used for the laser processing method concerning Claim 8. It is a schematic diagram which shows an example of the laser processing apparatus used for the laser processing method concerning Claim 9. It is a schematic diagram which shows an example of the laser processing apparatus concerning Claims 10 thru | or 13.

Explanation of symbols

2 ... Laser light source 3 ... Spatial phase modulation element 4 ... Imaging lens (imaging optical system)
5 ... Controller 6 ... Calculator 7 ... Workpiece P ... Laser beam

Claims (13)

A laser for processing a workpiece by phase-modulating laser light emitted from a laser light source by a spatial phase modulation element and guiding the laser beam to an imaging optical system, and irradiating the workpiece with the laser light by the imaging optical system. In the processing method,
As the input data input to the spatial phase modulation element, composite data including image reproduction hologram data for reproducing the processed shape of the workpiece and position movement hologram data for reproducing the image at a predetermined processing position is used. A laser processing method, wherein laser processing is performed on the workpiece while sequentially changing.   The laser processing method according to claim 1, wherein the image reproduction hologram data is used to reproduce a plurality of discrete point images.   A plurality of image reproduction hologram data for reproducing a plurality of discrete point images is prepared, and laser processing is performed while changing both the image reproduction hologram data for reproducing the plurality of point images and the position movement hologram data. The laser processing method according to claim 2, wherein:   2. The position-moving hologram data is hologram data relating to a direction horizontal to the surface to be processed, and the hologram data is data having a sawtooth-shaped or substantially sawtooth-shaped phase distribution. The laser processing method according to claim 3.   The position movement hologram data is hologram data in a direction perpendicular to the surface to be processed, and the hologram data is data having a phase distribution in a Fresnel zone plate shape or a substantially Fresnel zone plate shape. The laser processing method according to any one of claims 1 to 3.   6. The laser processing method according to claim 5, wherein a distance from the spatial phase modulator to a main plane of the imaging optical system is equal to a focal length of the imaging optical system.   The position movement hologram data is synthesized position movement hologram data obtained by combining hologram data relating to a direction horizontal to the processing surface and hologram data relating to a direction perpendicular to the processing surface. The laser processing method according to any one of claims 1 to 3.   Wavefront measurement means for measuring the wavefront of the laser light input to the spatial phase modulation means, input means for inputting the synthesized data to the spatial phase modulation element, and correction of distortion of the wavefront measured by the wavefront measurement means 8. The computer unit according to claim 1, wherein the computer unit generates correction data, and the corrected combined data is input to the spatial phase modulation unit. The laser processing method as described in.   The laser processing method according to any one of claims 1 to 8, wherein laser processing is performed while adjusting an irradiation time or irradiation intensity of the laser light.   The laser processing method according to claim 1, wherein a part of the workpiece is transparent to laser light.   The laser processing method according to any one of claims 1 to 10, wherein the laser light source is an ultrashort pulse laser light source having a pulse width of several picoseconds or less.   A laser light source, a spatial phase modulation element that phase-modulates laser light emitted from the laser light source, an imaging optical system that irradiates a workpiece with the laser light phase-modulated by the spatial phase modulation element, and the space An input means for controlling the phase modulation element by composite data including image reproduction hologram data and position movement hologram data for performing image reproduction at a predetermined processing position; and calculating the image reproduction hologram data and position movement hologram data A laser processing apparatus having at least a computer for outputting to the input means;   A structure manufactured by the laser processing apparatus according to claim 12.

Images