JP2013101243A - Multi-focal optical system and laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a condensing point by sufficiently removing color aberration, and controlling spherical aberration.SOLUTION: A multi-focal optical system includes: an optical beam expansion lens system 34 and a condenser lens system 38. The optical beam expansion lens system is a combination lens system of a concave lens 10 and a set 20 (20-1 to 20-4) of division lenses, and the division lenses are respectively arranged at different positions from one another along an optical axis such that a coaxial optical system is configured. Since the set of the division lenses is moved along the optical axis, its distance from the concave lens can be adjusted.

Description

  The present invention relates to a multifocal optical system that focuses a light beam at a plurality of positions, and a laser processing apparatus including the multifocal optical system.

  2. Description of the Related Art In recent years, laser processing apparatuses that process a workpiece by irradiating a laser beam have been actively used in processes for manufacturing various devices that support electronics and photonics. A typical example of this type of laser processing apparatus is a laser processing apparatus for cutting a workpiece.

  In this laser processing apparatus, a laser beam is condensed inside a plate-like workpiece by a lens optical system, and a crack is formed in a condensing portion. And a crack row is formed inside the workpiece by moving the laser beam relative to the workpiece. When such a crack row is formed, a crack is formed along the thickness direction starting from each crack forming the crack row. When stress is applied to the workpiece processed in this manner, the workpiece is cut along a reserve for cutting line.

  A plurality of laser processing apparatuses for cutting a workpiece have been proposed so far (see, for example, Patent Documents 1 to 7). One of the factors that determine the form of the above-mentioned cracks formed in the cutting processing by these laser processing devices is that the condensing characteristic of the lens system that guides the output light beam of the laser light source provided in the processing device to the workpiece It is.

  When cutting a workpiece with a laser processing device, if the workpiece is thin, if the laser beam can be sufficiently focused, the width of a material loss (kerf loss) region called a “kerf loss” region Is narrowly limited and a suitable cutting is realized. That is, when the workpiece is thin, it is preferable to use the laser processing apparatus disclosed in Patent Document 1. However, when the workpiece becomes thicker, it is difficult to form a crack along the depth direction even if stress is applied only by forming cracks in a line along the planned cutting line.

  Therefore, a method of forming a cutting line by forming a plurality of crack rows side by side along the planned cutting line in the thickness direction of the workpiece. As one of these methods, there is a method in which a laser beam is condensed at a plurality of locations along the thickness direction of the workpiece, and the laser beam is scanned once. However, the cutting line formed by this method is not limited to the condensing lens system, the shape of the crack line formed at a shallow position from the surface of the workpiece and the crack line formed at a deep position. Unlike the shape of the above, inconveniences such as an increase in the width of the kerfloss region occur.

  Also, a method of forming a cutting line by scanning a laser beam several times so that a crack row is formed at a position where the depth from the surface of the workpiece is different for each scan of the laser beam. There is. This method requires time proportional to the number of scans.

  In view of the above, a special contrivance is applied to the lens system that guides the output light beam of the laser light source to the workpiece, and a cutting line in which a plurality of crack rows are arranged in the thickness direction of the workpiece is formed once for the laser light beam. A laser processing apparatus that can be formed by scanning is disclosed.

  For example, a lens system that guides the output light beam of a laser light source to a workpiece is configured to condense two laser light beams having different wavelengths from each other at different depths in the workpiece using a single objective lens. A laser processing apparatus is disclosed in which cracks are formed in two rows in the thickness direction of a workpiece along a planned cutting line by a single scan of a laser beam (see Patent Document 2).

  Furthermore, by using a single lens formed as a composite of a plurality of partial lenses with different focal lengths, a function of condensing light at a plurality of locations in the thickness direction of the workpiece along the planned cutting line was provided. A laser processing apparatus is also disclosed (see Patent Documents 3 to 5). By using such a lens system, a plurality of crack rows are formed in the thickness direction of the workpiece along the line to be cut by one scanning of the laser beam.

  According to the laser processing apparatuses disclosed in Patent Documents 2 to 5, the crack row formed at a shallow position from the surface of the workpiece and the crack row formed at a deep position are formed in substantially the same shape.

  Further, it is a laser processing apparatus for cutting a transparent dielectric material substrate such as sapphire, and in order to achieve precise dicing with a small deviation from the planned cutting line and a narrow width of the kerf region, a sharp damaged groove is formed ( A laser processing apparatus characterized by scribing) is disclosed (see Patent Document 6). In this laser processing apparatus, an astigmatism optical system is formed using a concave cylindrical lens and a convex cylindrical lens, and a multifocal optical system capable of forming a tetrahedral focusing spot by using the astigmatism optical system is used. Yes. A sharp V-shaped damaged groove (V-shaped crack) is formed by the tetrahedral focusing spot formed by this multifocal optical system.

  In addition, an optical system that divides the laser light beam into a plurality of light beams having different propagation directions or a plurality of light beams having different divergence angles is arranged at the front stage of the condenser lens system, and the plurality of light beams are collected. A laser processing apparatus is disclosed in which light is condensed at different positions by an optical lens system to form a group of cracks consisting of a plurality of cracks inside the workpiece (see Patent Document 7). According to this laser processing apparatus, a plurality of cracks are formed on a parallel surface separated in the depth direction from the surface of the workpiece, or a plurality of cracks arranged along the depth direction are formed. These cracks can be intentionally formed to have different sizes and shapes. That is, it is possible to appropriately form a crack group that can guide the formation direction of a crack so that a crack along a desired direction is formed.

  As described above, in a laser processing apparatus that cuts a workpiece with a laser beam, a suitable cutting process is realized by devising a lens system that guides the output light beam of a laser light source to the workpiece. Cracks are formed to make it happen.

  Further, the multifocal optical system is used not only in the above-described laser processing apparatus but also in an optical apparatus that records and reproduces signals on and from an optical disk (see, for example, Patent Document 8). By using a multifocal optical system, this optical apparatus achieves a good signal recording / reproducing function for each of a plurality of types of optical disks having different thicknesses, while reducing manufacturing and inspection costs. Thus, the multifocal optical system has a plurality of application fields in addition to the laser processing apparatus.

Japanese Patent No. 3683580 JP 2004-337903 A JP-A-10-128569 JP 2000-5892 A JP 2010-167449 A JP 2007-21548 A JP 2011-56544 A JP 2000-214383 A

  The laser processing apparatus disclosed in Patent Document 2 includes an optical system that expands two laser light beam diameters, and an optical system that combines two light beams into one condensing lens. Yes. Therefore, the optical system required until the laser beam is input to the workpiece is complicated, and the size of the apparatus itself is increased.

  Further, in the laser processing apparatus configured to collect light at different depths in the workpiece disclosed in Patent Documents 3 to 5, the condensing lens itself has partially different curvatures. Since the lens has a complicated shape having a refracting curved surface, a special technique is required for manufacturing the condenser lens. In addition, since the condensing lens has a complicated shape, it is necessary to correct chromatic aberration for each part having a curved surface with different curvatures. It is difficult to make corrections effectively. Even in the case of laser light, the wavelength spectrum has a finite wavelength bandwidth, and it is necessary to effectively remove the chromatic aberration of the condensing lens in order to effectively condense into a minute region.

  In Patent Document 3, one lens constituting a multifocal optical system is divided into a plurality of divided lenses, and each divided lens is arranged at a different position along the optical axis so as to be a coaxial optical system. However, the function for effectively removing the spherical aberration is not taken into consideration. Here, the spherical aberration means a so-called vertical spherical aberration in which the condensing position (position intersecting the optical axis) differs depending on the distance from the optical axis of the light beam input to the lens. To do.

  As described above, the multifocal optical system is used not only for laser processing but also for an optical device for recording / reproducing signals on / from an optical disc. In the technical field where these multifocal optical systems are applied and used, it is common to condense a light beam effectively in a desired narrow region. For this purpose, it is necessary to effectively remove chromatic aberration and spherical aberration (hereinafter, both chromatic aberration and spherical aberration may be simply referred to as aberration) that cause the condensing region to expand.

  Furthermore, the laser beam is focused on a plurality of positions along the depth direction inside the workpiece, and is mounted on a laser processing apparatus that forms a cutting line by simultaneously scanning a plurality of focused points. The multifocal optical system is required to be focused so that the laser beam condensed at a deep position from the surface is not scattered by a crack formed at a position closer to the focused position.

  This is because light is scattered by a crack formed at a shallow position from the surface of the workpiece, so that light that should be collected at a position deeper than the crack is difficult to collect. That is, by receiving the scattering caused by the crack formed at the shallow position, the crack that should be formed at the deeper position is not formed, or the crack region is formed wider than planned.

  As described above, a multifocal optical system that has a small and simple configuration and sufficiently eliminates aberrations can be widely used not only in a processing apparatus but also in an optical apparatus that records and reproduces signals with respect to the optical disk described above. Be available. In addition, a condensing point is formed at a deeper position than the condensing position only by the light beam that does not pass through the condensing point formed near the surface of the object to which the light beam such as the workpiece is incident. If the multifocal optical system is realized, the multifocal optical system is suitable for use in an apparatus for performing laser processing such as cutting.

  The inventor divides one of the lenses constituting the multifocal optical system into a plurality of divided lenses, and arranges the divided lenses at different positions along the optical axis so as to be a coaxial optical system. This led to the solution of the above-mentioned problems. That is, even if this split lens is divided, it functions as a lens. Therefore, if these split lenses are arranged at different positions along the optical axis so as to form a coaxial optical system, they are located at different positions on the optical axis. It was noted that a multifocal optical system in which a focal point is formed is realized.

  Furthermore, if the multifocal optical system is composed of a light beam expansion lens system and a condenser lens system, and any of the lenses constituting the light beam expansion lens system is divided into two or more divided lenses, this It was found that the spherical aberration of the multifocal optical system can be effectively removed.

  Therefore, according to the gist of the present invention, the following multifocal optical system and a laser processing apparatus including the multifocal optical system are provided.

  The multifocal optical system according to the first aspect of the present invention includes a light beam expansion lens system that is arranged on the side where the light beam is input and expands the diameter of the light beam, and the light beam expansion lens system that is provided downstream of the light beam expansion lens system And a condensing lens system arranged so as to share the optical axis.

  The light beam expansion lens system includes a lens system having a negative refractive power disposed on the side to which the light beam is input, and a lens having a positive refractive power disposed downstream of the lens system having the negative refractive power. This is a combination lens system with this system. Both lens groups are arranged so that the light beam output from the lens system having negative refractive power is input to the lens system having positive refractive power. Any one of the lenses constituting the light beam expansion lens system is divided into two or more divided lenses, and each of the divided lenses is different from each other along the optical axis so as to share the optical axis. It is arranged at a position and configured as a set of split lenses.

  Here, a lens system having negative refractive power can be configured as a single concave lens, and a lens system having positive refractive power can also be configured as a single convex lens. This convex lens is divided into two or more divided lenses.

  Further, it is preferable that the group of split lenses can be moved along the optical axis.

  The basic configuration of the laser processing apparatus of the second invention includes the multifocal optical system of the first invention described above, and by inputting the light beam to the multifocal optical system, the light beam is deepened into the workpiece. It is set as the structure formed as a condensing point in several positions along a direction. That is, this laser processing apparatus forms a condensing point at a plurality of positions along the depth direction inside the workpiece, and simultaneously applies a plurality of the condensing points along the planned cutting line of the workpiece. An apparatus for forming a cutting line by scanning.

  The group of split lenses constituting the multifocal optical system mounted on the laser processing apparatus of the second invention is the surface of the workpiece among the cracks formed along the depth direction in the workpiece. It is preferable to arrange them so that the light beams focused at a deep position are not scattered by a crack formed at a position closer to the surface than the deep position so as to avoid the crack. .

  According to the multifocal optical system of the first invention, any one of the lenses constituting the lens system having a positive refractive power is divided into two or more divided lenses, and these divided lenses have a coaxial optical system. Arranged to compose. Therefore, by using a lens that has been subjected to chromatic aberration correction, such as an achromatic lens, as the lens to be divided, the divided lens functions as a condenser lens while maintaining the effect of correcting the chromatic aberration.

  That is, in order to form a condensing lens formed by connecting a plurality of regions having different focal lengths, it is necessary to correct chromatic aberration for each of the plurality of regions having different focal lengths. On the other hand, according to the multifocal optical system of the first invention, it is only necessary to correct chromatic aberration with respect to one lens to be divided, so that a multifocal optical system in which chromatic aberration correction is made remarkably easily is realized. .

  In the multifocal optical system according to the first aspect of the present invention, the group of split lenses can be adjusted along the optical axis to adjust the distance from the lens system having negative refractive power. It is possible to appropriately adjust the magnitude of the generated spherical aberration.

  According to the basic configuration of the laser processing apparatus of the second invention, two laser beams are not required unlike the laser processing apparatus disclosed in Patent Document 2 described above, so that the light beam is input to the workpiece. The optical system required for this is simplified, and the apparatus itself can be miniaturized.

  Although details will be described later, when the multifocal optical system of the first invention is used in a laser processing apparatus or the like, a split lens constituting a lens system having a positive refractive power, which is a constituent element of a light beam expansion lens system, is used. A technique of finely adjusting the position of the condensing point in the workpiece by moving along the optical axis can be realized. According to this method, it is possible to control the condensing characteristic of the condensing point. That is, the multifocal optical system is configured so that the distance of the split lens to the lens system having a negative refractive power can be adjusted in the light beam expansion lens system, so that a plurality of lenses formed inside the workpiece are formed. It is possible to effectively correct spherical aberration that determines the light condensing performance of the light condensing point.

  Further, by arranging the plurality of divided lenses mounted on the laser processing apparatus of the second invention so as to be focused while avoiding scattering due to cracks, it is possible to effectively focus at a position deeper than this crack. It becomes possible to make it.

FIG. 2 is a schematic sectional view showing the multifocal optical system of the first invention cut along a plane including the optical axis. FIG. 2 is a schematic perspective view of a light beam expansion lens system constituting the multifocal optical system of the first invention. It is a schematic block diagram of a laser processing apparatus. It is a diagram showing the workpiece, (A) is a plan view of the workpiece viewed from the side on which the light beam is incident, (B) is a cross-sectional view along the II line of FIG. 4 (A) FIG. 4C is a cross-sectional view taken along line II-II in FIG. 4A, and FIG. 4D is a plan view of the workpiece after cutting viewed from the side on which the light beam is incident. FIG. 5 is a schematic cross-sectional structure diagram showing the laser processing apparatus of the second invention cut along a plane including the optical axis of a multifocal optical system included in the apparatus. It is a diagram showing a workpiece processed by the laser processing apparatus of the second invention, (A) is a plan view of the workpiece viewed from the side on which the light beam is incident, (B) is a diagram of FIG. (A) is a cross-sectional view taken along line II, (C) is a cross-sectional view taken along line II-II in FIG. 6 (A), and (D) is an incident light beam of the workpiece after cutting. It is the top view seen from the done side. It is a figure where it uses for description of the light-shielding plate inserted between a light beam expansion lens system and a condensing lens system. The relationship between the lens surface of each lens and the surface of the workpiece that constitutes the light beam expansion lens system and the condenser lens system is schematically shown with respect to the optical axis shared by the light beam expansion lens system and the condenser lens system. FIG. It is a figure where it uses for description about the influence which the difference in the position where a division | segmentation lens arrange | positions has on spherical aberration. Adjust the position of at least one of the condensing lens system and the light beam incident surface of the workpiece, and adjust the condensing point to be formed on the surface of the workpiece to form a condensing point in the workpiece. It is a figure which shows the spherical aberration and the shape of a condensing point which generate | occur | produce in the case of doing. (A) shows spherical aberration, and (B) shows the shape of the focal point. After adjusting the condensing point to be formed on the surface of the workpiece, adjust the position of the convex lens that constitutes the light beam expansion lens system, and the condensing point forms a condensing point in the workpiece It is a figure which shows the spherical aberration to generate | occur | produce and the shape of a condensing point. (A) shows spherical aberration, and (B) shows the shape of the focal point.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, each figure which shows the multifocal optical system and laser processing apparatus of this invention has shown each component schematically to such an extent that this invention can be understood, and this invention is not limited to the example of illustration. Absent. Moreover, in each figure, the same component is shown with the same number, and the overlapping description about these functions may be omitted.

<Multifocal optical system of the first invention>
With reference to FIGS. 1 and 2, an embodiment of the multifocal optical system of the first invention will be described. As shown in FIG. 1, the multifocal optical system of the first invention includes a light beam expansion lens system 34 and a condensing lens system 38. As a general configuration, the light beam expanding lens system 34 is disposed at the rear stage of a lens system having a negative refractive power disposed on the side where the light beam 32 is input and the lens system having the negative refractive power. And a lens system having a positive refractive power. The light beam output from the lens system having negative refractive power is input to the lens system having positive refractive power.

  Each lens of the light beam expansion lens system 34 is divided into two or more divided lenses, and each of the divided lenses is arranged at a different position along this optical axis so as to share the optical axis. Has been.

  A lens system having negative refracting power can be constituted by a single concave lens, and a lens system having positive refracting power can also be constituted by a single convex lens. Here, a case where a lens system having negative refractive power and a lens system having positive refractive power are each constituted by one lens will be described as an example. Further, it is assumed that the convex lens is divided into two or more divided lenses.

  Therefore, in FIGS. 1 and 2, the lens system having negative refractive power is configured as a concave lens 10, and the lens system having positive refractive power is configured as a convex lens 20. The condensing lens system 38 is also generally formed as a combination lens system including a plurality of lenses, but in FIG. 1 and FIG. 2, it is configured by a single convex lens, which is the simplest configuration. An example is shown.

  The light beam expansion lens system 34 is disposed on the side where the light beam 32 output from the laser device or the like is input, and expands the diameter of the light beam 32 to generate and output the light beam 36. Further, the condenser lens system 38 is arranged at the rear stage of the light beam expansion lens system 34 so as to receive the light beam 36 so as to share the optical axis 14 of the light beam expansion lens system 34.

  The light beam expansion lens system 34 is a combination lens system of a concave lens 10 disposed on the side where the light beam 32 is input and a convex lens 20 disposed downstream of the concave lens 10. The light beam output from the concave lens 10 is input to the convex lens 20. The convex lens 20 is divided into four divided lenses 20-1 to 20-4. In FIG. 1, among the divided lenses 20-1 to 20-4, the divided lenses 20-1 and 20-4 are shown. However, since this is a sectional structural view cut along a plane including the optical axis, the divided lens 20 This is because -2 and 20-3 cannot be displayed.

  Of course, when each of the lens system having a positive refractive power and the lens system having a negative refractive power constituting the light beam expanding lens system 34 is formed as a combined lens system including a plurality of lenses, these lenses are used. Any one of the lenses may be divided into divided lenses. As for which lens is divided, a lens that can be easily manufactured may be selected.

Each of the split lenses 20-1 to 20-4 is arranged at different positions along the optical axis 14 so as to constitute a coaxial optical system sharing the optical axis 14, and is configured as a set of split lenses. . The light beam 36 outputted from the split lens 20-1 to 20-4 is focused at the focal point F ₁ to F ₄ by the condenser lens system 38 is input to the condenser lens system 38 (FIG. 1 Indicates the condensing points F ₁ and F ₄ ). The light beam 36 output from the split lenses 20-1 to 20-4 is adjusted to be a condensed beam or a diffused light beam, not a parallel light beam. Therefore, the light beams output from each of the split lenses 20-1 to 20-4 are condensed at different positions on the optical axis 14 by the condenser lens system 38. By the way, if the light beam 36 is adjusted to be a parallel light beam, the light beam output from each of the split lenses 20-1 to 20-4 is the same on the optical axis 14 by the condenser lens system 38. Focused on the position.

  FIG. 2 shows a schematic perspective view of the light beam expansion lens system 34 in order to make it easy to see the shapes of the concave lens 10 and the split lenses 20-1 to 20-4 constituting the light beam expansion lens system 34 and their arrangement relationships.

  FIGS. 1 and 2 show an example in which the convex lens 20 is divided into four divided lenses 20-1 to 20-4, but is not limited to four divided, such as two or three You may divide | segment as a division lens.

  As shown in FIG. 2, divided lenses 20-1 to 20-4 are formed by dividing two orthogonal surfaces passing through the center of the convex lens 20, and each of the divided lenses 20-1 to 20-4 has an optical axis 14. Are arranged at different positions along the optical axis 14 so as to share the same. Here, the optical axis 14 means that each of the divided lenses 20-1 to 20-4 has a shape as the convex lens 20 before the division, and the divided lenses 20-1 to 20-4 are divided. It means the optical axis when the divided lenses 20-1 to 20-4 are arranged with the respective optical axes corresponding to the front convex lens 20 matched.

  Even if the convex lens 20 has a partial defect, its function as a lens is essentially the same as before the defect has occurred and the amount of collected light is reduced. Accordingly, the respective optical axes virtually determined as the divided lenses 20-1 to 20-4 having the shape as the convex lens 20 before the division, are here divided lenses 20-1 to 20-. Each of the optical axes of 4 shall be called.

  The division lens 20-1 to 20-4 formed by dividing the convex lens 20 before division into two orthogonal surfaces passing through the center of the convex lens 20 by using a lens with chromatic aberration correction such as an achromatic lens. The lens functions as a lens having positive refractive power while maintaining the effect of correcting the chromatic aberration.

  By configuring the multifocal optical system to include a light beam expansion lens system 34 and a condensing lens system 38, the multifocal optical system can be used as a laser processing apparatus or an optical apparatus that records and reproduces signals to and from an optical disk. When used, by adjusting the position of the convex lens 20 constituting the light beam expansion lens system 34, the condensing point can be adjusted to be formed at a target position. For example, this will be described in detail later, but the condensing position is set after the plane where the refractive index changes, such as the surface of the workpiece, the slide glass surface of the microscope, or the surface of the optical disk material. In this case, it means that it is possible to easily cope with the spherical aberration generated by the plane on which the refractive index changes.

<Laser processing equipment>
In order to contribute to an understanding of the configuration and operation of the laser processing apparatus of the second invention, referring to FIGS. 3 and 4, a light beam condensing point is formed at one point inside the workpiece, and the workpiece is processed. A basic configuration of a laser processing apparatus for forming a crack row by scanning this condensing point along the scheduled cutting line will be described. In other words, the laser processing apparatus described here has a function of forming cracks in a row in the workpiece along the planned cutting line, and is a suitable apparatus for use when the workpiece is thin. is there.

  On the other hand, the laser processing apparatus according to the second invention, which will be described later with reference to FIGS. 5 and 6, uses the multifocal optical system according to the first invention to cause the light beam to enter the inside of the workpiece in the depth direction. The laser processing apparatus shown in FIG. 3 and FIG. 4 is characterized in that it collects light at a plurality of positions along a plurality of points and forms a plurality of crack rows by simultaneously scanning a plurality of light condensing points. The basic configuration of the laser processing apparatus of the second invention is the same.

  As shown in FIG. 3, the laser processing apparatus focuses the light beam at a position indicated by F inside the work piece 40, thereby centering the position indicated by F along the planned cutting line of the work piece. Cracks are formed in the local area where The workpiece 40 is a plate-shaped object such as a glass plate or a silicon substrate.

  The work piece 40 is fixed to a work stage 46. The work stage 46 has the vertical direction of the light beam incident surface 42 of the work piece as the z axis direction, and the x axis direction and the y axis direction (not shown) , A direction orthogonal to the x-axis direction) and a z-axis direction. By adjusting the position by sliding the work stage 46 in the z-axis direction, the light beam condensing position (position indicated by F) can be set as appropriate with reference to the light beam incident surface 42 of the workpiece. . Also. By moving the work stage 46 in the x-axis direction or the y-axis direction, a crack row is formed along the scheduled cutting line set in the workpiece 40.

  As shown in FIG. 3, the laser processing apparatus includes a laser light source 30, a light beam expansion lens system 26, and a condenser lens system 38. The laser light source 30 outputs a light beam 32. The light beam expansion lens system 26 expands the output diameter of the light beam 32 output from the laser light source 30, and generates and outputs a light beam 36. The condensing lens system 38 forms the input light beam 36 into a condensing beam.

  The light beam output from the condenser lens system 38 is input to the workpiece 40 from the light beam incident surface 42 of the workpiece, and is condensed in the workpiece 40 (position indicated by F).

  The light beam expansion lens system 26 is a combination lens system of a concave lens 22 and a convex lens 24. The concave lens 22 and the convex lens 24 can each be formed as a combined lens system in which a plurality of lenses are combined.

  The concave lens 22 converts the light beam 32 output from the laser light source 30 into a diffused light beam and outputs it. The light beam output from the concave lens 22 is input to the convex lens 24, and a light beam 36 adjusted so as to have any one of a parallel light beam, a condensed beam, and a diffused light beam is output. The light beam 36 is condensed at a position indicated by F by the condenser lens system 38.

  In order to input the light beam output from the condensing lens system 38 to the workpiece 40 and condense it from the light beam incident surface 42 to a position of a certain depth D (position indicated by F), for example, first, light The position of the work stage 46 on which the workpiece 40 is mounted is adjusted in the z-axis direction so that the focal point of the beam 36 coincides with the light beam incident surface 42 of the workpiece. Then, the light beam incident surface 42 may be raised along the z-axis direction by nD. Here, n is the refractive index of the workpiece 40.

  In this way, once the condensing point is set to be formed at the position D below the light beam incident surface 42, the work piece is scanned so that the condensing point is scanned along the cutting planned line of the workpiece 40. The object 40 is moved in the x-axis direction or the y-axis direction by the work stage 46. When the light beam 32 is output from the laser light source 30 and the condensing point is scanned in this way, cracks are formed in a line along the planned cutting line of the workpiece 40 (not shown in FIG. 3). Are formed side by side.

  With reference to FIGS. 4A to 4D, the process of cutting the workpiece 40 will be specifically described. 4A is a plan view of the workpiece 40 viewed from the light beam incident surface 42 side, and FIG. 4B is a cross-sectional view taken along the line II in FIG. FIG. 4C is a cross-sectional view taken along line II-II in FIG. 4A, and FIG. 4D is a plan view of the workpiece after cutting viewed from the light beam incident surface 42 side.

  As shown in FIG. 4 (A), a scheduled cutting line 44 defined by two-dot broken lines 44-1 and 44-2 is set on the light beam incident surface 42 of the workpiece. The interval between the two-dot broken lines 44-1 and 44-2 means the width of the planned cutting line for the workpiece 40. Accordingly, the condensing point of the light beam by the condensing lens system 38, which is indicated by F, is formed so as to be formed approximately at the center of the planned cutting line 44 defined by the two-dot broken lines 44-1 and 44-2. The position of the workpiece 40 is adjusted by moving it in the x-axis direction or the y-axis direction shown in FIG. 3, and the z-axis direction is adjusted so as to be formed on the light beam incident surface 42 of the workpiece. Then, the position of the light beam incident surface 42 is adjusted in the z-axis direction so that the condensing point of the light beam 36 is formed at a predetermined position below the light beam incident surface 42.

  After adjusting the position of the workpiece 40 in this way, the light beam is moved relative to the workpiece 40 so that the light beam is scanned along the scheduled cutting line 44. As a result, as shown in FIGS. 4B and 4C, cracks C are formed in a line at predetermined positions below the light beam incident surface 42 along the planned cutting line of the workpiece 40. . Since cracks are formed in the local range around the condensing point F, in FIGS. 4 (B) and (C), cracks are formed surrounding the condensing point F in a star shape. Local is shown. Since the region surrounded by the star shape with the condensing point F as the center corresponds to the material structure destruction region or the modified region of the workpiece 40, this region is referred to as a crack C for convenience.

  When the crack C is formed, the material constituting the workpiece is instantaneously expanded in this region. As a result, a local fracture region C ′ extends from the crack C and is formed. Since the cracks C are formed in a line at equal depth from the light beam incident surface 42, as shown in FIGS. 4B and 4C, the local fracture region C ′ is the thickness of the work piece. It is easy to form along the direction.

  When the rows of cracks C shown in FIGS. 4 (B) and 4 (C) are formed in a line at equal depth from the light beam incident surface 42, the work piece 40 is moved to a two-dot broken line 44 with a relatively small force. As shown in FIG. 4D, the workpieces 40-1 and 40-2 can be divided along the planned cutting lines defined by -1 and 44-2. Thus, if the crack C is formed by condensing the light beam in the workpiece 40, the workpiece 40 can be cut along the planned cutting line 44.

<Laser processing apparatus of the second invention>
With reference to FIGS. 5 to 7, an embodiment of the laser machining apparatus of the second invention will be described. The laser processing apparatus of the second invention forms condensing points at a plurality of positions along the depth direction inside the workpiece by using the multifocal optical system of the first invention shown in FIGS. 1 and 2. And a cutting line is formed by simultaneously scanning a plurality of condensing points along the planned cutting line of the workpiece. That is, the laser processing apparatus of the second invention is characterized in that a cutting line is formed by simultaneously scanning a plurality of condensing points.

  As shown in FIG. 5, the laser processing apparatus of the second invention includes a laser light source 30, a light beam expansion lens system 34, and a condensing lens system 38. This configuration is basically the same as the laser processing apparatus described with reference to FIG. However, the light beam expansion lens system 26 included in the laser processing apparatus described with reference to FIG. 3 is a combination lens system of the concave lens 22 and the convex lens 24, whereas the light included in the laser processing apparatus of the second invention. The beam expansion lens system 34 is a combined lens system of the concave lens 10 and the convex lens 20 disposed at the subsequent stage of the concave lens 10. The convex lens 20 is divided into divided lenses 20-1 to 20-4.

  In the light beam expanding lens system 34, as shown in FIG. 5, the concave lens 10 is attached to the lens barrel 52, and the convex lens 20 (divided lenses 20-1 to 20-4) is attached to the lens barrel 56. Then, a part of the lens barrel 56 is inserted into the lens barrel 52 so as to be movable along the optical axis 14. A barrel fixing screw 54 for fixing the barrel 56 is attached to the barrel 52. After adjusting the positional relationship of the lens barrel 56 with respect to the lens barrel 52, the lens barrel 56 can be fixed to the lens barrel 52 by tightening the lens barrel fixing screw 54.

  FIG. 5 shows an example in which the light beam expansion lens system 34 is configured by the concave lens 10 and the convex lens 20 (divided lenses 20-1 to 20-4), but is limited to such a combination of lenses. There is nothing. It is also possible to form the concave lens 10 and the convex lens 20 as a plurality of combination lens systems. In this case, which lens of the plurality of lenses constituting the convex lens 20 is divided is arbitrary. If a lens having a large aperture as much as possible is selected as a lens to be divided, it is easy to process.

  Further, the condensing lens system 38 is configured by attaching a total of three condensing lens groups 72 including a concave lens 72-1, convex lenses 72-2 and 72-3 to a lens barrel 70. Here, the condensing lens system 38 is a combination lens system composed of three lenses, but what kind of lenses are used to compose the condensing lens system 38 is arbitrary.

  The laser processing apparatus of the second invention is a laser processing apparatus configured to include the multifocal optical system of the first invention. As described with reference to FIG. 1, the light output from the condenser lens system 38 The beams are focused at different positions on the optical axis 14. That is, the light beam output from the condenser lens system 38 is input to the workpiece 40 from the light beam incident surface 42 of the workpiece, and is condensed at a plurality of positions in the workpiece 40. As described above, since the light beam is condensed at a plurality of positions, the light beam 36 output from each of the split lenses 20-1 to 20-4 is not a parallel light beam but a condensed beam or diffused light. It is adjusted to be a beam.

  In order to input the light beam output from the condensing lens system 38 to the workpiece 40 and condense it at a plurality of positions at a certain depth from the light beam incident surface 42, for example, the condensing lens system 38 The work stage on which the work piece 40 is mounted is adjusted in the z-axis direction so that the focal point formed at the position farthest from the back principal point of the workpiece coincides with the light beam incident surface 42 of the work piece To do. Subsequently, the convex lens 20 (divided lenses 20-1 to 20-4) is moved along the optical axis 14 in the z-axis direction so as to set the condensing point at a position below the light beam incident surface 42 to be formed. The distance from the concave lens 10 may be adjusted. In FIG. 5, illustration of the position of the condensing point D formed in the work stage and the workpiece 40 is omitted.

  If the condensing point formed at the position farthest from the back principal point of the condensing lens system 38 is set to be formed at the position D below the light beam incident surface 42, the cutting line of the workpiece 40 will be cut. The workpiece 40 is moved in the x-axis direction or the y-axis direction (a direction perpendicular to the x-axis direction) so that the plurality of condensing points are simultaneously scanned along. If the light beam is output from the laser light source 30 and the condensing point is scanned in this way, the light beam is scanned in the thickness direction of the workpiece along the planned cutting line of the workpiece 40 by one scanning of the light beam. Cracks are formed side by side in a plurality of rows.

  With reference to FIGS. 6 (A) to (D), the process of cutting the workpiece 40 will be specifically described. 6 (A) is a plan view of the workpiece viewed from the light beam incident surface 42 side, and FIG. 6 (B) is a cross-sectional view taken along line II of FIG. 6 (A). ) Is a cross-sectional view taken along the line II-II in FIG. 6 (A), and FIG. 6 (D) is a plan view as viewed from the light beam incident surface 42 side of the workpiece after cutting.

  As shown in FIG. 6 (A), a scheduled cutting line 44 defined by two-dot broken lines 44-1 and 44-2 is set on the light beam incident surface 42 of the workpiece. After adjusting the position of the workpiece 40 as described above, the light beam is moved relative to the workpiece 40 so that the light beam is scanned along the scheduled cutting line 44. By doing so, as shown in FIGS. 6B and 6C, cracks are arranged in a plurality of rows at predetermined positions below the light beam incident surface 42 along the planned cutting line 44 of the workpiece 40. It is formed.

  In the example shown in FIGS. 6A to 6D, the convex lens 20 is processed by a laser processing apparatus having a multifocal optical system formed as divided lenses 20-1 and 20-2 which are equally divided into two. An example is shown. Alternatively, the convex lens 20 is collected on this light shielding plate by a multifocal optical system formed as divided lenses 20-1 to 20-4 equally divided into four and a laser processing apparatus further provided with a light shielding plate described later. The example of a process processed in the state adjusted so that a light spot may be formed in two places is shown.

As shown in FIGS. 6B and 6C, condensing points are formed at two locations along the depth direction of the workpiece 40. Since cracks are formed in the local area around each condensing point, in FIGS. 6 (B) and 6 (C), the concentrating points F ₁ and F ₂ are surrounded by a star shape. The local area where cracks are formed is shown. Since the region surrounded by the star shape with the condensing points F ₁ and F ₂ as the centers corresponds to the material structure destruction region or the modified region of the workpiece 40, these regions are referred to as cracks C ₁ and C for convenience. It shall be shown as ₂ .

When the cracks C ₁ and C ₂ are formed, the constituent material of the workpiece 40 is instantaneously expanded in this region. As a result, a local fracture region C ′ extends from the cracks C ₁ and C ₂ . Since the cracks C ₁ and C ₂ are formed in a row at equal depths from the light beam incident surface 42, as shown in FIGS. 6 (B) and 6 (C), the local fracture region C ′ is processed. It is easy to form along the thickness direction of the object 40.

When the rows of cracks C ₁ and C ₂ shown in FIGS. 6B and 6C are formed in a row at equal depths from the light beam incident surface 42, the workpiece 40 is formed with a relatively small force. Can be divided into workpieces 40-1 and 40-2 as shown in FIG. 6 (D) along the planned cutting line 44 defined by the two-dot broken lines 44-1 and 44-2. In this way, if the cracks C ₁ and C ₂ are formed by condensing the light beam in the workpiece 40, the workpiece 40 is cut along the planned cutting line 44 even if the workpiece 40 is a thick material. It becomes possible to do.

  As described above, when the convex lens 20 constituting the light beam expansion lens system 34 of the multifocal optical system provided in the laser processing apparatus of the second invention is divided into four divided lenses 20-1 to 20-4. Even if it exists, it is possible to form a condensing point in two places along the depth direction of the workpiece 40. As described above, in order to adjust the number of the condensing points, the light processing plate 60 is inserted between the light beam expanding lens system 34 and the condensing lens system 38 in the laser processing apparatus of the second invention.

<Shading plate>
With reference to FIGS. 7A to 7C, the light shielding plate 60 will be described. As shown in FIGS. 7A to 7C, the light shielding plate 60 is a circular plate so as to selectively transmit the light beam that has passed through any of the above-described split lenses 20-1 to 20-4. Is formed in a fan shape. For example, the light shielding plate shown in FIG. 7A has a vertical angle of 90 degrees on the circular plate so as to selectively transmit the light beam that has passed through any one of the split lenses 20-1 to 20-4. It is formed in a fan shape. Similarly, the light shielding plate shown in FIG. 7 (B) is configured to selectively transmit the light beam that has passed through any two of the split lenses 20-1 to 20-4. In order to selectively transmit the light beam that has passed through any three of the divided lenses 20-1 to 20-4, the light beams are formed in a fan shape having apex angles of 180 degrees and 270 degrees, respectively.

  If a light shielding plate shown in FIG. 7 (A) is inserted between the light beam expansion lens system 34 and the condensing lens system 38, a condensing point can be formed at one place in the workpiece 40. is there. Similarly, if the light shielding plate shown in FIG. 7 (B) is inserted, it is possible to form condensing points at two locations along the depth direction in the workpiece 40, as shown in FIG. 7 (C). If a light shielding plate is inserted, it is possible to form condensing points at three locations along the depth direction in the workpiece 40. If the light shielding plate 60 is not inserted between the light beam expansion lens system 34 and the condensing lens system 38, condensing points may be formed at four locations along the depth direction in the workpiece 40. Is possible.

  As described above, the shape of the hollow portion (penetrating portion) of the light shielding plate 60 is determined by how many divided lenses the convex lens 20 constituting the light beam expansion lens system 34 is divided into. As described above, when the convex lens 20 is divided into four divided lenses 20-1 to 20-4, the shape of the cut-out portion of the minimum area is a fan shape with an apex angle of 90 degrees. Good.

  Generally, when N is an integer of 2 or more and the convex lens 20 is divided into N divided lenses 20-1 to 20-N, the shape of the cut-out portion of the smallest area is 360 / N What is necessary is just to use the fan type which is degree. In this way, by preparing (N-1) types of light shielding plates and selecting and using them appropriately, the light shielding plate 60 is not inserted between the light beam expansion lens system 34 and the condenser lens system 38. By selecting and inserting one or more light shielding plates, it is possible to arbitrarily select 1 to N locations along the depth direction in the workpiece 40 to form a condensing point It is.

  The cut-out portion of the light shielding plate 60 can be formed by punching the circular plate into a fan shape as described above, but the shape of the cut-through portion is not limited to the fan shape. For example, the shape of the cut-out portion can be arbitrarily determined, for example, by forming one or more small circular cut-out portions at equal intervals on the circumference at a constant distance from the center of the circular plate.

<Aberration of multifocal optical system provided in laser processing apparatus>
As described above, the lens system having the negative refractive power by moving the lens system (convex lenses 20-1 to 20-4) constituting the light beam expanding lens system 34 along the optical axis direction. By adjusting the distance to the (concave lens 10), it is possible to adjust so that the focal point is formed at a target position inside the workpiece 40. By adopting such an adjustment method, it is possible to arbitrarily control the degree of spherical aberration that defines the shape of the focal point formed in the workpiece 40. This point will be described with reference to FIGS.

  First, spherical aberration generated by the light beam expansion lens system 34, the condensing lens system 38, and the light beam incident surface 42 of the workpiece will be described with reference to FIG. If the spherical aberrations generated on the optical system and the light incident surface 42 are added so as to cancel each other, the focal point F in the workpiece 40 is blurred (the spread of the light intensity distribution due to the aberration). ) Becomes smaller. By reducing the size of the focal point F in the workpiece 40, suitable cutting with a narrow width of the kerfloss region is realized.

With respect to the optical axis 100 shared by the light beam expansion lens system 34 and the condensing lens system 38, the lens surface of each lens constituting the light beam expansion lens system 34 and the condensing lens system 38 and the light beam of the workpiece The relationship with the incident surface 42 can be schematically shown as shown in FIG. In FIG. 8, the passing point of the light beam 102 of the light beam is shown to be tracked. That indicates a passing point of the light beam expansion lens system of the lens disposed on the incident end of the light beam 34 lens group constituting the lens surface S ₁ at P _1, the lens group constituting the light beam expander lens system 34 Representing the lens surface S _i of an arbitrary lens, the passing point of this lens surface is indicated by P _i (i is an integer of 2 or more).

Further, a passing point on behalf of the lens surface of any lens of the lens group constituting the condenser lens system 38 the lens surface S _j shown in P _j, of the lens surface S _k of lenses arranged thereto from downstream The passing point is indicated by P _k (j and k are each an integer of 3 or more and j <k). A passing point of the workpiece on the light beam incident surface 42 is indicated by P _n (n is an integer of 4 or more).

In order to identify the light beam incident on the lens surface, which is a refractive surface, and the light beam incident surface of the workpiece, the surface numbers assigned to the incident surfaces are separated by hyphens. For example, the light beam of the incident light beam on the lens surface S ₁ of the lens disposed at the incident end of the light beam of the lens group constituting the light beam expansion lens system 34 is denoted by 102-1 and counted from this lens surface. the ray of the incident light beam to the j-th refractive surface S _j is indicated with 102-j.

  Spherical aberration occurs every time the light beam passes through the refracting surface. This spherical aberration depends on the shape of the refracting surface and the refractive indexes on both sides of the refracting surface. The concave lens and the convex lens are each surrounded by two refracting surfaces. The first refracting surface is a boundary surface between air and the lens component (generally optical glass), and the second refracting surface. Is the interface between the lens component and air. A single lens or lens system is defined by a plurality of refractive surfaces. Therefore, spherical aberration that occurs in an optical system such as a single lens or lens system appears as the sum of spherical aberrations that occur on each of the refractive surfaces that define these optical systems.

  In general, the value of spherical aberration generated in a lens system having negative refractive power and the value of spherical aberration generated in a lens system having positive refractive power are almost equal to each other and their signs are opposite to each other. . That is, the sum of spherical aberrations occurring on each of the two refracting surfaces defining the concave lens or the even number of refracting surfaces defining the combined lens system having negative refractive power, and the two refracting surfaces defining the convex lens, or The total sum of spherical aberrations occurring on each of the even number of refracting surfaces defining the combination lens system having a positive refractive power is in a mutually canceling relationship.

The condensing lens system 38 including the refracting surfaces S _j and S _k is a lens system having a positive refractive power. Further, (corresponding to S _n is a set of the identification code indicating the refractive surface) light beam entrance surface 42 of the workpiece if the plane can be treated as a lens system having a negative refractive power. This is because when the condensed beam is vertically incident on the light beam incident surface 42 of the workpiece, the light beam of the condensed beam is refracted by the light beam incident surface 42 and the degree of condensing is reduced (approaching the parallel light flux). ) That is, the light beam incident surface 42 of the workpiece has an effect equivalent to the effect received by being incident on the concave lens by the light beam incident surface 42 of the workpiece.

  Further, as described above, the light beam 36 output from the light beam expansion lens system 34 is output from the condensing lens system 38 to form a condensing point at a plurality of locations inside the workpiece 40. It is adjusted to be a condensed beam or a diffused light beam. That is, when the light beam incident surface 42 of the workpiece is a flat surface or a concave surface, the light beam 36 output from the light beam expansion lens system 34 is adjusted to a condensed beam, and the light beam incident surface of the workpiece is adjusted. When 42 is a convex surface, the light beam 36 output from the light beam expansion lens system 34 is adjusted to be a condensed beam or a diffused light beam.

  In other words, when the light beam incident surface 42 of the workpiece is flat or concave, the light beam incident surface 42 is negatively refracted when discussing the spherical aberration of the multifocal optical system provided in the laser processing apparatus. In order to cancel the spherical aberration generated on the light beam incident surface 42, the light beam expansion lens system 34 is made to function as a lens system having a positive refractive power. Is preferred. On the other hand, when the light beam incident surface 42 of the workpiece is a convex surface, if this curvature is sufficiently small, it can be regarded as a lens system having negative refractive power, and if this curvature is sufficiently large, a lens having positive refractive power Since it can be regarded as a system, it is preferable that the light beam expansion lens system 34 functions as a lens system having a positive or negative refractive power in accordance with the magnitude of the polarities of the light beam incident surface 42 of the workpiece.

  Further, the value of the spherical aberration generated when the light beam passes through the light beam expansion lens system 34, the condensing lens system 38, and the light beam incident surface 42 of the workpiece is the convex lens 20 (divided lenses 20-1 to 20). It is also changed by moving the group 20-4 along the optical axis 14 and changing the distance from the concave lens 10.

  Before describing the method of adjusting the position of the condensing point by actively using this property, referring to FIG. 9, there is a difference in the positions where the split lenses 20-1 to 20-4 are arranged. Let us examine the effect on spherical aberration. As shown in FIG. 9, the convex lens 20 constituting the light beam expansion lens system 34 is divided into four divided lenses 20-1 to 20-4 and each has a different position along the optical axis 14 so as to share the optical axis 14. Is arranged.

FIG. 9 shows representatively the refracting surfaces S _q and S _{q + 1} and the refracting surfaces S _q ′ and S _{q + 1} ′ that define the convex lens surfaces of the lens group constituting the light beam expansion lens system 34. is there. For example, when the dividing lens defined by the refracting surfaces S _q and S _{q + 1} is 20-4 and the dividing lens defined by the refracting surfaces S _q ′ and S _{q + 1} ′ is 20-1, the dividing lens is Since the lens 20-4 and the split lens 20-1 are arranged at different positions, the spherical aberration caused by the refracting surfaces S _q and S _{q + 1} and the refracting surfaces S _q ′ and S _{q + 1} ′. Each has a different effect on the shape of the focal point formed in the workpiece 40.

However, the arrangement interval between the divided lenses is substantially equal to the interval between the plurality of condensing points formed in the workpiece 40, and is about several μm to several tens of micrometers. On the other hand, the arrangement interval of the light beam expansion lens system 34 and the condensing lens system 38, and the light beam incident surface 42 of the workpiece is at least about several millimeters. Big enough. That is, the difference in spherical aberration caused by the refractive surfaces S _q and S _{q + 1} and the refractive surfaces S _q ′ and S _{q + 1} ′ being arranged at different positions with respect to the optical axis is The spherical aberration generated from the light beam expansion lens system 34 and the condensing lens system 38 is sufficiently small and negligible.

  The following is presented when forming a condensing point inside the workpiece 40 by actively utilizing the property that the value of the spherical aberration generated by changing the distance of the convex lens 20 from the concave lens 10 can be adjusted. By applying the first or second method as appropriate, the magnitude of the spherical aberration can be controlled by comparing the first and second simulation results.

  The first method is a method of adjusting the position of at least one of the condensing lens system and the light beam incident surface of the workpiece so that the focal point is formed at a desired position in the workpiece. It is. In the second method, at least one of the condensing lens system and the light beam incident surface of the workpiece is formed so that the focal point is formed at an arbitrary position determined with reference to the light beam incident surface of the workpiece. This is a technique in which the position is adjusted, and then the convex lens is moved to finely adjust the focal point to be formed at a desired position in the workpiece.

  The first simulation result is a result of the magnitude of spherical aberration with respect to the focal point obtained when the first method is used. The second simulation result is obtained when the second method is used by setting an arbitrary position determined based on the light beam incident surface 42 of the workpiece as the position of the light beam incident surface 42 itself. It is the result obtained about the magnitude | size of the spherical aberration with respect to a condensing point.

  FIGS. 10 (A) and (B), FIGS. 11 (A) and (B) are diagrams showing the first and second simulation results, respectively, and the shape of the focal point formed in the workpiece 40. It is a figure which shows the spherical aberration and the shape of this condensing point which are the factors which determine this.

  That is, FIGS. 10 (A) and 10 (B) show that the position of at least one of the condensing lens system 38 and the light beam incident surface 42 of the workpiece is adjusted so that the light beam condensing point is the light beam of the workpiece It shows the spherical aberration and the size of the condensing point that occur when adjusted to be formed on the incident surface. 11 (A) and 11 (B) show that the position of at least one of the condenser lens system 38 and the light beam incident surface 42 of the work piece is adjusted so that the light beam condensing point is the light beam of the work piece. After adjusting so as to be formed on the incident surface 42, the convex lens 20 is moved along the optical axis 14 to finely adjust the position where the condensing point is formed, and the position of 500 μm below the light beam incident surface 42 of the workpiece. The spherical aberration and the size of the condensing point that occur when the lens is formed are shown.

  Here, the simulation evaluation was performed assuming that the convex lens 20 is a single lens that is not divided. As described above, the arrangement interval between the divided lenses is sufficiently smaller than the arrangement interval of the light beam expansion lens system 34, the condensing lens system 38, and the light beam incident surface 42 of the workpiece. Even if the simulation is performed assuming that the lens is a single lens, the result has no substantial effect.

In this simulation, the following assumptions were made. The light beam 32 output from the laser light source 30 was assumed to be a Gaussian light beam of TE ₀₀ fundamental mode. That is, the intensity distribution is given by a Gaussian function and is a substantially parallel light beam. The radius of the light beam is defined as the distance from the center where the light intensity at the center of this light beam decreases to e ^-2 (e is the base of natural logarithm), and the diameter of the light beam 32 is assumed to be 3 mm .

  The light beam expansion lens system 34 is an afocal lens system, and the light beam 32 output from the laser light source 30 is converted into a light beam (light beam 36) having a diameter of 7 mm by the light beam expansion lens system 34. It was assumed that it was shaped and input to the condenser lens system 38. In the laser processing apparatus according to the second aspect of the invention, the light beam output from the light beam expansion lens system 34 has either a condensed beam or a diffused light beam, but these light beams are very close to parallel light beams. Because of the shape, even if it is assumed that the light beam expansion lens system 34 is an afocal lens system, there is no substantial influence on the simulation result.

  The condenser lens system 38 was assumed to be an objective lens having a numerical aperture (NA) of 0.35 and a magnification of 20 times. Furthermore, the workpiece 40 was assumed to be a parallel plate made of quartz glass having a refractive index of 1.45. Accordingly, the light beam incident surface 42 of the workpiece is a flat surface.

  In FIGS. 10 (A) and 11 (A), the vertical axis indicates the distance from the optical axis of the light beam constituting the light beam output from the condenser lens system 38 in units of mm, and the horizontal axis Indicates the condensing position, which is the intersection of the light beam constituting the light beam and the optical axis. That is, the horizontal axis indicates so-called spherical aberration in which the condensing position varies depending on the distance from the optical axis of the light beam constituting the light beam.

10 (B) and 11 (B) show the spread magnitude of the light intensity distribution at the focal point formed at a position of 500 μm from the light beam incident surface 42 of the workpiece. The condensing points shown in FIG. 10 (B) and FIG. 11 (B) are shown by isointensity lines that are connected at the same light intensity, and the isointensity line shown by the outermost circle is the center of the condensing point. This is an isointensity line in which the light intensity is e ⁻² when the light intensity is 1.

  The spherical aberration shown in FIG. 10 (A) is maximum at a distance of 1.75 mm from the optical axis, and its magnitude is 8 μm. On the other hand, the spherical aberration shown in FIG. 11A is 3.1 μm at the maximum. Further, when the size of the condensing point shown in FIG. 10 (B) is compared with the size of the condensing point shown in FIG. 11 (B), the size of the condensing point shown in FIG. 11 (B) is clearly small. From these simulation results, the method of adjusting the distance from the concave lens 10 by moving the convex lens 20 along the optical axis 14 and adjusting the focal point to be formed at a desired position in the workpiece 40. It has been shown that it is possible to effectively reduce the magnitude of spherical aberration with respect to the focal point formed in the workpiece 40 by taking

  In the laser processing apparatus of the second invention, as described above, the position of the convex lens 20 (a set of the divided lenses 20-1 to 20-4) is adjusted to form a condensing point at a desired position in the workpiece 40. By adopting the second method of adjusting as described above, the spherical aberration can be reduced as compared with the case of using the first method. This is because, when the condensing point is formed in the work piece 40 by the first method, spherical aberration generated in the condensing optical system constituted by the light beam expansion lens system 34 and the condensing lens system 38, Spherical aberration that occurs in the condensing optical system according to the second method, while it cannot be adjusted according to the shape of the light beam incident surface 42 of the workpiece and the position where the condensing point is formed This is due to being able to adjust.

  However, it is not always necessary to adjust the size of the focal point formed in the workpiece 40 so as to be minimized. For example, depending on the physical properties of the workpiece, it may be advantageous to set the width of the kerfloss region wider. In such a case, as described above, the condensing lens system 38 is configured such that any one of the condensing points is formed at an arbitrary position determined with reference to the light beam incident surface 42 of the workpiece. A method may be used in which the position is adjusted and then the convex lens 20 is moved and finely adjusted so that the focal point is formed at a desired position in the workpiece 40. If such a technique is taken, the size of the condensing point formed in the workpiece 40 can be arbitrarily set by appropriately setting an arbitrary position determined based on the light beam incident surface 42. Is possible.

  As described above, the effect that the size of the condensing point formed in the workpiece 40 can be freely determined is that the split lenses 20-1 to 20- of the multifocal optical system included in the laser processing apparatus of the second invention. The group of 4 is obtained by being able to adjust the distance from the concave lens 10 along the optical axis.

10, 22, 72-1: Concave lens
14, 100: Optical axis
20, 24, 72-2, 72-3: Convex lens
20-1 to 20-4: Split lens
26, 34: Light beam expansion lens system
30: Laser light source
32, 36: Light beam
38: Condensing lens system
40, 40-1, 40-2: Workpiece
42: Light beam entrance surface of workpiece
44: Cutting line
46: Work stage
52, 56, 70: Tube
54: Tube fixing screw
60: Shading plate
72: Condensing lens group
102: Laser beam

Claims (9)

A light beam expansion lens system which is arranged on the side where the light beam is input and expands the diameter of the light beam;
A multifocal optical system comprising a condenser lens system disposed so as to share an optical axis with the optical beam expansion lens system, following the optical beam expansion lens system,
The light beam expanding lens system has a negative refracting power lens system disposed on the light beam input side, and a positive refracting power disposed downstream of the negative refracting lens system. A combination lens system with a lens system,
Any of the lenses constituting the light beam expansion lens system is divided into two or more split lenses,
Each of the split lenses is configured as a set of split lenses arranged at different positions along the optical axis so as to share the optical axis. The lens system having negative refractive power is one concave lens, and the lens system having positive refractive power is one convex lens,
2. The multifocal optical system according to claim 1, wherein the convex lens is divided into two or more divided lenses.   3. The multifocal optical system according to claim 1, wherein the group of the divided lenses can be moved along the optical axis. The multifocal optical system according to any one of claims 1 to 3,
A light beam is input to the multifocal optical system, condensing points are formed at a plurality of positions along the depth direction inside the workpiece, and a plurality of the collecting points are formed along a cutting line of the workpiece. A laser processing apparatus that forms a cutting line on the workpiece by simultaneously scanning light spots. The group of split lenses is
Among the cracks formed corresponding to the condensing points formed along the depth direction in the workpiece, an optical path of a light beam that is condensed at a deep position from the surface of the workpiece is 5. The laser processing apparatus according to claim 4, wherein the laser processing apparatuses are arranged so as to avoid the crack formed at a position closer to the surface than a deep position.   Between the light beam expansion lens system and the condensing lens system, a part of the light beam output from the light beam expansion lens system is cut off and a condensing point that is condensed into the workpiece is collected. 6. The laser processing apparatus according to claim 4, wherein a light shielding plate for limiting the number is inserted. A laser processing apparatus for processing the workpiece having a flat surface,
The light beam expanding lens system and the condensing lens system are arranged such that the light beam is expanded as a condensing beam by the light beam expanding lens system and is in a positional relationship input to the condensing lens system. The laser processing apparatus according to claim 4, wherein the laser processing apparatus is arranged. A laser processing apparatus for processing the workpiece whose surface is concave on the input side of the light beam,
The light beam expanding lens system and the condensing lens system are arranged such that the light beam is expanded as a condensing beam by the light beam expanding lens system and is in a positional relationship inputted to the condensing lens system. The laser processing apparatus according to claim 4, wherein the laser processing apparatus is arranged. A laser processing apparatus for processing a workpiece whose surface is convex on the input side of the light beam,
The light beam expansion lens system expands the light beam so that the light beam is expanded into either a condensed light beam or a diffused light beam and has a positional relationship inputted to the condensing lens system. The laser processing apparatus according to claim 4, wherein a lens system and the condenser lens system are disposed.