Patent Publication Number: US-2020298345-A1

Title: Laser processing device

Description:
TECHNICAL FIELD 
     One aspect of the present invention relates to a laser processing device. 
     BACKGROUND ART 
     Patent Literature 1 describes a laser processing device including a holding mechanism configured to hold a workpiece and a laser irradiation mechanism configured to irradiates the workpiece held by the holding mechanism with laser light. In the laser irradiation mechanism of the laser processing device, components arranged on an optical path of the laser light from a laser oscillator to a converging lens are arranged in one housing, and the housing is secured to a wall portion erected on a base of the laser processing device. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 5456510 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the laser processing device as described above, a wavelength of the laser light suitable for processing may vary depending on specifications of the object to be processed, processing conditions, and the like. 
     An object of one aspect of the present invention is to provide a laser processing device adaptable to a plurality of wavelength bands. 
     Solution to Problem 
     A laser processing device according to one aspect of the present invention is a laser processing device configured to emit laser light on an object to perform laser processing of the object, the laser processing device including: a laser output unit configured to output the laser light; a spatial light modulator configured to reflect the laser light output from the laser output unit while modulating the laser light in accordance with a phase pattern; and an objective lens configured to converge the laser light from the spatial light modulator toward the object, in which the spatial light modulator includes an entrance surface at which the laser light enters, a reflective surface configured to reflect the laser light entering from the entrance surface toward the entrance surface, and a modulation layer arranged between the entrance surface and the reflective surface and configured to display the phase pattern to modulate the laser light, and a dielectric multilayer film having a high reflectance region in a plurality of wavelength bands non-contiguous with each other is formed on the reflective surface. 
     In the laser processing device, the laser light is modulated in accordance with the phase pattern of the spatial light modulator, and then is converged toward the object by the objective lens. The spatial light modulator includes the entrance surface at which the laser light enters, the reflective surface configured to reflect the laser light entering from the entrance surface, and the modulation layer arranged between the entrance surface and the reflective surface. When entering from the entrance surface and passing through the modulation layer, the laser light is modulated in accordance with the phase pattern. In addition, the laser light is modulated also when reflected by the reflective surface and then again passing through the modulation layer, and is emitted from the spatial light modulator. Here, on the reflective surface, the dielectric multilayer film is formed having the high reflectance region in the plurality of wavelength bands non-contiguous with each other. Therefore, with the spatial light modulator, it is possible to modulate the laser light while reducing loss on the reflective surface of the laser light of the plurality of wavelength bands. Accordingly, the laser processing device is adaptable to the plurality of wavelength bands. 
     A laser processing device according to one aspect of the present invention may further include a pattern holding unit configured to hold a distortion correction pattern as the phase pattern for correcting distortion given to a wavefront of the laser light depending on flatness of the reflective surface, in which the pattern holding unit holds the distortion correction pattern different for each of the wavelength bands. Generally, the reflective surface of the spatial light modulator has a predetermined flatness for each spatial light modulator. However, to correct the distortion given to the wavefront of the laser light depending on the flatness, a phase modulation amount is required different depending on the wavelength. Therefore, as in this case, if the distortion correction pattern is held different for each of the wavelength bands, the laser processing device is easily and reliably adaptable to the plurality of wavelength bands. 
     A laser processing device according to one aspect of the present invention may further include a table holding unit configured to hold a table in which a luminance value of an image signal for displaying the phase pattern on the modulation layer and a phase modulation amount of the phase pattern are associated with each other, in which the table holding unit holds the table different for each of the wavelength bands. Here, for the laser light of a certain wavelength, a table is prepared in which luminance values of, for example, 256 gradations of the image signal are assigned to (associated with) the phase modulation amounts for one wavelength (2π), whereby a phase modulation pattern suitable for the wavelength can be easily displayed on the modulation layer. 
     However, if the same table is used for laser light having a wavelength shorter than the wavelength, luminance values of smaller gradations are used for the phase modulation amounts for one wavelength, so that reproducibility drops of the wavefront after the modulation. To cope with this, in this case, the table is held different for each of the wavelength bands. For this reason, it is possible to use a table suitable for each wavelength band, and degradation of the reproducibility of the wavefront can be suppressed. 
     In the laser processing device according to one aspect of the present invention, an antireflective film having a high transmittance region in the plurality of wavelength bands may be formed on the entrance surface. In this case, the loss of the laser light can be further reduced, and the laser processing device is reliably adaptable to the plurality of wavelength bands. 
     In the laser processing device according to one aspect of the present invention, the plurality of wavelength bands may include a first wavelength band of greater than or equal to 500 nm and less than or equal to 550 nm, and a second wavelength band of greater than or equal to 1000 nm and less than or equal to 1150 nm. Alternatively, in the laser processing device according to one aspect of the present invention, the plurality of wavelength bands may include a third wavelength band of greater than or equal to 1300 nm and less than or equal to 1400 nm. In these cases, the laser processing device is adaptable to each wavelength band. Note that, the laser light of the first wavelength band is suitable for internal absorption type laser processing on a substrate made of sapphire, for example. In addition, the laser light of each of the second wavelength band and the third wavelength band is suitable for internal absorption type laser processing for a substrate made of silicon, for example. 
     Advantageous Effects of Invention 
     According to one aspect of the present invention, a laser processing device can be provided adaptable to a plurality of wavelength bands. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic configuration diagram of a laser processing device used for forming a modified region. 
         FIG. 2  is a plan view of an object to be processed for which the modified region is formed. 
         FIG. 3  is a sectional view of the object to be processed taken along the line of  FIG. 2 . 
         FIG. 4  is a plan view of the object to be processed after laser processing. 
         FIG. 5  is a sectional view of the object to be processed taken along the line V-V of  FIG. 4 . 
         FIG. 6  is a sectional view of the object to be processed taken along the line VI-VI of  FIG. 4 . 
         FIG. 7  is a perspective view of a laser processing device according to an embodiment. 
         FIG. 8  is a perspective view of an object to be processed attached to a support table of the laser processing device of  FIG. 7 . 
         FIG. 9  is a sectional view of a laser output unit taken along the ZX plane of  FIG. 7 . 
         FIG. 10  is a perspective view of a part of the laser output unit and a laser converging unit in the laser processing device of  FIG. 7 . 
         FIG. 11  is a sectional view of the laser converging unit taken along the XY plane of  FIG. 7 . 
         FIG. 12  is a sectional view of the laser converging unit taken along the line XII-XII of  FIG. 11 . 
         FIG. 13  is a sectional view of the laser converging unit taken along the line XIII-XIII of  FIG. 12 . 
         FIG. 14  is a diagram illustrating an optical arrangement relationship among a reflective spatial light modulator, a 4f lens unit, and a converging lens unit in the laser converging unit of  FIG. 11 . 
         FIG. 15  is a partial sectional view of a reflective spatial light modulator in the laser processing device of  FIG. 7 . 
         FIGS. 16( a ) and 16( b )  are a graph illustrating a reflectance characteristic of a reflective film illustrated in  FIG. 15  and a graph illustrating a transmittance characteristic of an antireflective film provided on a front surface of a transparent substrate, respectively. 
         FIGS. 17( a ) and 17( b )  each are a graph illustrating distortion of a front surface of a pixel electrode illustrated in  FIG. 15 . 
         FIGS. 18( a ) and 18( b )  each are a diagram illustrating a distortion correction pattern displayed on a liquid crystal layer illustrated in  FIG. 15 . 
         FIGS. 19( a ) and 19( b )  each are a diagram illustrating a table in which a luminance value of an image signal and a phase modulation amount are associated with each other. 
         FIGS. 20( a ) and 20( b )  each are a diagram illustrating a table in which a luminance value of an image signal and a phase modulation amount are associated with each other. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, one embodiment of one aspect of the present invention will be described in detail with reference to the drawings. In the drawings, the same elements or corresponding elements are denoted by the same reference numerals, and overlapping explanations may be omitted. 
     In a laser processing device according to the embodiment, laser light is converged at an object to be processed to form a modified region within the object to be processed along a line to cut. Therefore, formation of the modified region will be described at first with reference to  FIGS. 1 to 6 . 
     As illustrated in  FIG. 1 , a laser processing device  100  includes a laser light source  101  configured to cause laser light L to oscillate in a pulsating manner, a dichroic mirror  103  arranged so as to change a direction of the optical axis (optical path) of the laser light L by 90°, and a converging lens  105  configured to converge the laser light L. The laser processing device  100  further includes a support table  107  configured to support an object to be processed  1  that is an object to which the laser light L converged by the converging lens  105  is emitted, a stage  111  that is a moving mechanism configured to move the support table  107 , a laser light source controller  102  configured to control the laser light source  101  in order to adjust the output, pulse width, pulse waveform, and the like of the laser light L, and a stage controller  115  configured to control the movement of the stage  111 . 
     In the laser processing device  100 , the laser light L emitted from the laser light source  101  changes the direction of its optical axis by 90° with the dichroic mirror  103  and then is converged by the converging lens  105  within the object to be processed  1  mounted on the support table  107 . At the same time, the stage  111  is moved, so that the object to be processed  1  moves with respect to the laser light L along a line to cut  5 . Thus, a modified region along the line to cut  5  is formed in the object to be processed  1 . While the stage  111  is moved here for relatively moving the laser light L, the converging lens  105  may be moved instead or together therewith. 
     Employed as the object to be processed  1  is a planar member (for example, a substrate or a wafer), examples of which include semiconductor substrates formed of semiconductor materials and piezoelectric substrates formed of piezoelectric materials. As illustrated in  FIG. 2 , in the object to be processed  1 , the line to cut  5  is set for cutting the object to be processed  1 . The line to cut  5  is a virtual line extending straight. In a case where a modified region is formed within the object to be processed  1 , the laser light L is relatively moved along the line to cut  5  (that is, in the direction of arrow A in  FIG. 2 ) while a converging point (converging position) P is set within the object to be processed  1  as illustrated in  FIG. 3 . Thus, a modified region  7  is formed within the object to be processed  1  along the line to cut  5  as illustrated in  FIGS. 4, 5 and 6 , and the modified region  7  formed along the line to cut  5  becomes a cutting start region  8 . The line to cut  5  corresponds to an irradiation schedule line. 
     The converging point P is a position at which the laser light L is converged. The line to cut  5  may be curved instead of being straight, a three-dimensional one combining them, or one specified by coordinates. The line to cut  5  may be one actually drawn on a front surface  3  of the object to be processed  1  without being restricted to the virtual line. The modified region  7  may be formed either continuously or intermittently. The modified region  7  may be formed in either rows or dots, and only needs to be formed at least within the object to be processed  1 , on the front surface  3 , or on a back surface. A crack may be formed from the modified region  7  as a start point, and the crack and the modified region  7  may be exposed at an outer surface (the front surface  3 , the back surface, or an outer peripheral surface) of the object to be processed  1 . A laser light entrance surface in forming the modified region  7  is not limited to the front surface  3  of the object to be processed  1  but may be the back surface of the object to be processed  1 . 
     Incidentally, in a case where the modified region  7  is formed within the object to be processed  1 , the laser light L is transmitted through the object to be processed  1  and is particularly absorbed near the converging point P located within the object to be processed  1 . Thus, the modified region  7  is formed in the object to be processed  1  (that is, internal absorption type laser processing). In this case, the front surface  3  of the object to be processed  1  hardly absorbs the laser light L and thus does not melt. On the other hand, in a case where the modified region  7  is formed on the front surface  3  or the back surface of the object to be processed  1 , the laser light L is particularly absorbed near the converging point P located on the front surface  3  or the back surface, and removal portions such as holes and grooves are formed (surface absorption type laser processing) by being melted from the front surface  3  or the back surface and removed. 
     The modified region  7  is a region in which density, refractive index, mechanical strength and other physical characteristics are different from the surroundings. Examples of the modified region  7  include a molten processed region (meaning at least one of a region resolidified after having been once molten, a region in the molten state, and a region in the process of resolidifying from the molten state), a crack region, a dielectric breakdown region, a refractive index changed region, and a mixed region thereof. Other examples of the modified region  7  include a region where the density of the modified region  7  has changed compared to the density of an unmodified region in a material of the object to be processed  1 , and a region formed with a lattice defect. In a case where the material of the object to be processed  1  is single crystal silicon, the modified region  7  can also be said to be a high dislocation density region. 
     The molten processed region, refractive index changed region, region where the density of the modified region  7  has changed compared to the density of the unmodified region, and region formed with the lattice defect may further incorporate the crack (cracking or microcrack) therewithin or at an interface between the modified region  7  and the unmodified region. The incorporated crack may be formed over the whole surface of the modified region  7  or in only a portion or a plurality of portions thereof. The object to be processed  1  includes a substrate made of a crystalline material having a crystal structure. For example, the object to be processed  1  includes a substrate formed of at least one of gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO3, and sapphire (Al2O3). In other words, the object to be processed  1  includes, for example, a gallium nitride substrate, a silicon substrate, a SiC substrate, a LiTaO3 substrate, or a sapphire substrate. The crystalline material may be either an anisotropic crystal or an isotropic crystal. In addition, the object to be processed  1  may include a substrate made of a non-crystalline material having a non-crystalline structure (amorphous structure), and may include a glass substrate, for example. 
     In the embodiment, the modified region  7  can be formed by forming a plurality of modified spots (processing marks) along the line to cut  5 . In this case, the plurality of modified spots gathers to be the modified region  7 . Each of the modified spots is a modified portion formed by a shot of one pulse of pulsed laser light (that is, laser irradiation of one pulse: laser shot). Examples of the modified spots include crack spots, molten processed spots, refractive index changed spots, and those in which at least one of them is mixed. As for the modified spots, their sizes and lengths of the crack occurring therefrom can be controlled as necessary in view of the required cutting accuracy, the required flatness of cut surfaces, the thickness, kind, and crystal orientation of the object to be processed  1 , and the like. In addition, in the embodiments, the modified spots can be formed as the modified region  7 , along the line to cut  5 . 
     [Laser Processing Device According to Embodiments] 
     Next, the laser processing device according to the embodiments will be described. In the following description, the directions orthogonal to each other in the horizontal plane are defined as the X-axis direction and the Y-axis direction, and the vertical direction is defined as the Z-axis direction. 
     [Overall Configuration of Laser Processing Device] 
     As illustrated in  FIG. 7 , a laser processing device  200  includes a device frame  210 , a first moving mechanism (moving mechanism)  220 , a support table  230 , and a second moving mechanism  240 . Further, the laser processing device  200  includes a laser output unit  300 , a laser converging unit  400 , and a controller  500 . 
     The first moving mechanism  220  is attached to the device frame  210 . The first moving mechanism  220  includes a first rail unit  221 , a second rail unit  222 , and a movable base  223 . The first rail unit  221  is attached to the device frame  210 . The first rail unit  221  is provided with a pair of rails  221   a  and  221   b  extending along the Y-axis direction. The second rail unit  222  is attached to the pair of rails  221   a  and  221   b  of the first rail unit  221  so as to be movable along the Y-axis direction. The second rail unit  222  is provided with a pair of rails  222   a  and  222   b  extending along the X-axis direction. The movable base  223  is attached to the pair of rails  222   a  and  222   b  of the second rail unit  222  so as to be movable along the X-axis direction. The movable base  223  is rotatable about an axis parallel to the Z-axis direction as the center. 
     The support table  230  is attached to the movable base  223 . The support table  230  supports the object to be processed  1 . The object to be processed  1  includes a plurality of functional devices (a light receiving device such as a photodiode, a light emitting device such as a laser diode, a circuit device formed as a circuit, or the like) formed in a matrix shape on the front surface side of a substrate made of a semiconductor material such as silicon. When the object to be processed  1  is supported on the support table  230 , as illustrated in  FIG. 8 , on a film  12  stretched over an annular frame  11 , for example, a front surface  1   a  of the object to be processed  1  (a surface of the plurality of functional devices side) is pasted. The support table  230  holds the frame  11  with a clamp and suctions the film  12  with a vacuum chuck table, to support the object to be processed  1 . On the support table  230 , a plurality of lines to cut  5   a  parallel to each other and a plurality of lines to cut  5   b  parallel to each other are set in a grid pattern so as to pass between adjacent functional devices on the object to be processed  1 . 
     As illustrated in  FIG. 7 , the support table  230  is moved along the Y-axis direction by operation of the second rail unit  222  in the first moving mechanism  220 . In addition, the support table  230  is moved along the X-axis direction by operation of the movable base  223  in the first moving mechanism  220 . Further, the support table  230  is rotated about the axis parallel to the Z-axis direction as the center by operation of the movable base  223  in the first moving mechanism  220 . As described above, the support table  230  is attached to the device frame  210  to be movable along the X-axis direction and the Y-axis direction, and to be rotatable about the axis parallel to the Z-axis direction as the center. 
     The laser output unit  300  is attached to the device frame  210 . The laser converging unit  400  is attached to the device frame  210  via the second moving mechanism  240 . The laser converging unit  400  is moved along the Z-axis direction by operation of the second moving mechanism  240 . As described above, the laser converging unit  400  is attached to the device frame  210  so as to be movable along the Z-axis direction with respect to the laser output unit  300 . 
     The controller  500  includes a Central Processing Unit (CPU), Read Only Memory (ROM), Random Access Memory (RAM), and the like. The controller  500  controls operation of each unit of the laser processing device  200 . 
     As an example, in the laser processing device  200 , a modified region is formed within the object to be processed  1  along each of the lines to cut  5   a  and  5   b  (see  FIG. 8 ) as follows. 
     First, the object to be processed  1  is supported on the support table  230  such that a back surface  1   b  (see  FIG. 8 ) of the object to be processed  1  becomes the laser light entrance surface, and each of the lines to cut  5   a  of the object to be processed  1  is aligned in a direction parallel to the X-axis direction. Subsequently, the laser converging unit  400  is moved by the second moving mechanism  240  such that the converging point of the laser light L is located at a position apart from the laser light entrance surface of the object to be processed  1  by a predetermined distance within the object to be processed  1 . Subsequently, while a constant distance is maintained between the laser light entrance surface of the object to be processed  1  and the converging point of the laser light L, the converging point of the laser light L is relatively moved along each line to cut  5   a . Thus, the modified region is formed within the object to be processed  1  along each of the lines to cut  5   a.    
     When the formation of the modified region along each of the lines to cut  5   a  is completed, the support table  230  is rotated by the first moving mechanism  220 , and each of the lines to cut  5   b  of the object to be processed  1  is aligned in the direction parallel to the X-axis direction. Subsequently, the laser converging unit  400  is moved by the second moving mechanism  240  such that the converging point of the laser light L is located at a position apart from the laser light entrance surface of the object to be processed  1  by a predetermined distance within the object to be processed  1 . Subsequently, while a constant distance is maintained between the laser light entrance surface of the object to be processed  1  and the converging point of the laser light L, the converging point of the laser light L is relatively moved along each line to cut  5   b . Thus, the modified region is formed within the object to be processed  1  along each line to cut  5   b.    
     As described above, in the laser processing device  200 , the direction parallel to the X-axis direction is a processing direction (scanning direction of the laser light L). Note that, the relative movement of the converging point of the laser light L along each line to cut  5   a  and the relative movement of the converging point of the laser light L along each line to cut  5   b  are performed by the movement of the support table  230  along the X-axis direction by the first moving mechanism  220 . In addition, the relative movement of the converging point of the laser light L between the lines to cut  5   a  and the relative movement of the converging point of the laser light L between the lines to cut  5   b  are performed by the movement of the support table  230  along the Y-axis direction by the first moving mechanism  220 . 
     As illustrated in  FIG. 9 , the laser output unit  300  includes a mounting base  301 , a cover  302 , and a plurality of mirrors  303  and  304 . Further, the laser output unit  300  includes a laser oscillator  310 , a shutter  320 , a λ/2 wave plate unit  330 , a polarizing plate unit  340 , a beam expander  350 , and a mirror unit  360 . 
     The mounting base  301  supports the plurality of mirrors  303  and  304 , the laser oscillator  310 , the shutter  320 , the λ/2 wave plate unit  330 , the polarizing plate unit  340 , the beam expander  350 , and the mirror unit  360 . The plurality of mirrors  303  and  304 , the laser oscillator  310 , the shutter  320 , the λ/2 wave plate unit  330 , the polarizing plate unit  340 , the beam expander  350 , and the mirror unit  360  are attached to a main surface  301   a  of the mounting base  301 . The mounting base  301  is a planar member and is detachable with respect to the device frame  210  (see  FIG. 7 ). The laser output unit  300  is attached to the device frame  210  via the mounting base  301 . That is, the laser output unit  300  is detachable with respect to the device frame  210 . 
     The cover  302  covers the plurality of mirrors  303  and  304 , the laser oscillator  310 , the shutter  320 , the λ/2 wave plate unit  330 , the polarizing plate unit  340 , the beam expander  350 , and the mirror unit  360  on the main surface  301   a  of the mounting base  301 . The cover  302  is detachable with respect to the mounting base  301 . 
     The laser oscillator  310  oscillates linearly polarized laser light L in a pulsating manner along the X-axis direction. The wavelength of the laser light L emitted from the laser oscillator  310  is included in any of the wavelength bands of from 500 nm to 550 nm, from 1000 nm to 1150 nm, or from 1300 nm to 1400 nm. The laser light L in the wavelength band of from 500 nm to 550 nm is suitable for internal absorption type laser processing on a substrate made of sapphire, for example. The laser light L in each of the wavelength bands of from 1000 nm to 1150 nm and from 1300 nm to 1400 nm is suitable for internal absorption type laser processing for a substrate made of silicon, for example. The polarization direction of the laser light L emitted from the laser oscillator  310  is, for example, a direction parallel to the Y-axis direction. The laser light L emitted from the laser oscillator  310  is reflected by the mirror  303  and enters the shutter  320  along the Y-axis direction. 
     In the laser oscillator  310 , ON/OFF of the output of the laser light L is switched as follows. In a case where the laser oscillator  310  includes a solid state laser, ON/OFF of a Q switch (acousto-optic modulator (AOM), electro-optic modulator (EOM), or the like) provided in a resonator is switched, whereby ON/OFF of the output of the laser light L is switched at high speed. In a case where the laser oscillator  310  includes a fiber laser, ON/OFF of the output of a semiconductor laser constituting a seed laser and an amplifier (excitation) laser is switched, whereby ON/OFF of the output of the laser light L is switched at high speed. In a case where the laser oscillator  310  uses an external modulation device, ON/OFF of the external modulation device (AOM, EOM, or the like) provided outside the resonator is switched, whereby ON/OFF of the output of the laser light L is switched at high speed. 
     The shutter  320  opens and closes the optical path of the laser light L by a mechanical mechanism. Switching ON/OFF of the output of the laser light L from the laser output unit  300  is performed by switching ON/OFF of the output of the laser light L in the laser oscillator  310  as described above, and the shutter  320  is provided, whereby the laser light L is prevented from being unexpectedly emitted from the laser output unit  300 , for example. The laser light L having passed through the shutter  320  is reflected by the mirror  304  and sequentially enters the λ/2 wave plate unit  330  and the polarizing plate unit  340  along the X-axis direction. 
     The λ/2 wave plate unit  330  and the polarizing plate unit  340  function as the output adjusting unit configured to adjust the output (light intensity) of the laser light L. In addition, the λ/2 wave plate unit  330  and the polarizing plate unit  340  each function as the polarization direction adjusting unit configured to adjust the polarization direction of the laser light L. The laser light L having sequentially passed through the λ/2 wave plate unit  330  and the polarizing plate unit  340  enters the beam expander  350  along the X-axis direction. 
     The beam expander  350  collimates the laser light L while adjusting the diameter of the laser light L. The laser light L having passed through the beam expander  350  enters the mirror unit  360  along the X-axis direction. 
     The mirror unit  360  includes a support base  361  and a plurality of mirrors  362  and  363 . The support base  361  supports the plurality of mirrors  362  and  363 . The support base  361  is attached to the mounting base  301  so as to be position adjustable along the X-axis direction and the Y-axis direction. The mirror (first mirror)  362  reflects the laser light L having passed through the beam expander  350  in the Y-axis direction. The mirror  362  is attached to the support base  361  such that its reflective surface is angle adjustable around an axis parallel to the Z-axis, for example. 
     The mirror (second mirror)  363  reflects the laser light L reflected by the mirror  362  in the Z-axis direction. The mirror  363  is attached to the support base  361  such that its reflective surface is angle adjustable around an axis parallel to the X-axis, for example, and is position adjustable along the Y-axis direction. The laser light L reflected by the mirror  363  passes through an opening  361   a  formed in the support base  361  and enters the laser converging unit  400  (see  FIG. 7 ) along the Z-axis direction. That is, an emission direction of the laser light L by the laser output unit  300  coincides with a moving direction of the laser converging unit  400 . As described above, each of the mirrors  362  and  363  includes a mechanism configured to adjust the angle of the reflective surface. 
     In the mirror unit  360 , the position adjustment of the support base  361  with respect to the mounting base  301 , the position adjustment of the mirror  363  with respect to the support base  361 , and the angle adjustment of the reflective surface of each of the mirrors  362  and  363  are performed, whereby the position and angle of the optical axis of the laser light L emitted from the laser output unit  300  are aligned with respect to the laser converging unit  400 . That is, each of the plurality of mirrors  362  and  363  is a component configured to adjust the optical axis of the laser light L emitted from the laser output unit  300 . 
     As illustrated in  FIG. 10 , the laser converging unit  400  includes a housing  401 . The housing  401  has a rectangular parallelepiped shape with the Y-axis direction as the longitudinal direction. The second moving mechanism  240  is attached to one side surface  401   e  of the housing  401  (see  FIGS. 11 and 13 ). A cylindrical light entrance unit  401   a  is provided in the housing  401  so as to face the opening  361   a  of the mirror unit  360  in the Z-axis direction. The light entrance unit  401   a  allows the laser light L emitted from the laser output unit  300  to enter the housing  401 . The mirror unit  360  and the light entrance unit  401   a  are separated from each other by a distance in which mutual contact does not occur when the laser converging unit  400  is moved along the Z-axis direction by the second moving mechanism  240 . 
     As illustrated in  FIGS. 11 and 12 , the laser converging unit  400  includes a mirror  402  and a dichroic mirror  403 . Further, the laser converging unit  400  includes a reflective spatial light modulator  410 , a 4f lens unit  420 , a converging lens unit (objective lens)  430 , a drive mechanism  440 , and a pair of distance measuring sensors  450 . 
     The mirror  402  is attached to a bottom surface  401   b  of the housing  401  so as to face the light entrance unit  401   a  in the Z-axis direction. The mirror  402  reflects the laser light L entering the housing  401  via the light entrance unit  401   a  in a direction parallel to the XY plane. The laser light L collimated by the beam expander  350  of the laser output unit  300  enters the mirror  402  along the Z-axis direction. That is, the laser light L as parallel light enters the mirror  402  along the Z-axis direction. For that reason, even if the laser converging unit  400  is moved along the Z-axis direction by the second moving mechanism  240 , a constant state is maintained of the laser light L entering the mirror  402  along the Z-axis direction. The laser light L reflected by the mirror  402  enters the reflective spatial light modulator  410 . 
     The reflective spatial light modulator  410  is attached to an end  401   c  of the housing  401  in the Y-axis direction in a state where the reflective surface  410   a  faces the inside of the housing  401 . The reflective spatial light modulator  410  is, for example, a reflective liquid crystal (Liquid Crystal on Silicon (LCOS)) Spatial Light Modulator (SLM), and reflects the laser light L in the Y-axis direction while modulating the laser light L. The laser light L modulated and reflected by the reflective spatial light modulator  410  enters the 4f lens unit  420  along the Y-axis direction. Here, in a plane parallel to the XY plane, an angle α formed by an optical axis of the laser light L entering the reflective spatial light modulator  410  and an optical axis of the laser light L emitted from the reflective spatial light modulator  410 , is an acute angle (for example, from 10° to 60°). That is, the laser light L is reflected at an acute angle along the XY plane in the reflective spatial light modulator  410 . This is for suppressing an incident angle and a reflection angle of the laser light L to inhibit the degradation of diffraction efficiency, and for sufficiently exerting performance of the reflective spatial light modulator  410 . Note that, in the reflective spatial light modulator  410 , for example, the thickness of a light modulation layer in which a liquid crystal is used is extremely thin as several micrometers to several tens of micrometers, so that the reflective surface  410   a  can be regarded as substantially the same as a light entering and exiting surface of the light modulation layer. 
     The 4f lens unit  420  includes a holder  421 , a lens  422  on the reflective spatial light modulator  410  side, a lens  423  on the converging lens unit  430  side, and a slit member  424 . The holder  421  holds a pair of the lenses  422  and  423  and the slit member  424 . The holder  421  maintains a constant mutual positional relationship between the pair of lenses  422  and  423  and the slit member  424  in a direction along the optical axis of the laser light L. The pair of lenses  422  and  423  constitutes a double telecentric optical system in which the reflective surface  410   a  of the reflective spatial light modulator  410  and an entrance pupil plane (pupil plane)  430   a  of the converging lens unit  430  are in an imaging relationship. 
     Thus, an image of the laser light L on the reflective surface  410   a  of the reflective spatial light modulator  410  (an image of the laser light L modulated in the reflective spatial light modulator  410 ) is transferred to (imaged on) the entrance pupil plane  430   a  of the converging lens unit  430 . A slit  424   a  is formed in the slit member  424 . The slit  424   a  is located between the lens  422  and the lens  423  and near a focal plane of the lens  422 . Unnecessary part of the laser light L modulated and reflected by the reflective spatial light modulator  410  is blocked by the slit member  424 . The laser light L having passed through the 4f lens unit  420  enters the dichroic mirror  403  along the Y-axis direction. 
     The dichroic mirror  403  reflects most (for example, from 95% to 99.5%) of the laser light L in the Z-axis direction and transmits part (for example, from 0.5% to 5%) of the laser light L along the Y-axis direction. Most of the laser light L is reflected at a right angle along the ZX plane in the dichroic mirror  403 . The laser light L reflected by the dichroic mirror  403  enters the converging lens unit  430  along the Z-axis direction. 
     The converging lens unit  430  is attached to an end  401   d  (an end on the opposite side from the end  401   c ) of the housing  401  in the Y-axis direction via the drive mechanism  440 . The converging lens unit  430  includes a holder  431  and a plurality of lenses  432 . The holder  431  holds the plurality of lenses  432 . The plurality of lenses  432  converges the laser light L at the object to be processed  1  (see  FIG. 7 ) supported by the support table  230 . The drive mechanism  440  moves the converging lens unit  430  along the Z-axis direction by driving force of a piezoelectric device. 
     The pair of distance measuring sensors  450  is attached to the end  401   d  of the housing  401  so as to be respectively located on both sides of the converging lens unit  430  in the X-axis direction. Each of the distance measuring sensors  450  emits light for distance measurement (for example, laser light) to the laser light entrance surface of the object to be processed  1  (see  FIG. 7 ) supported by the support table  230 , and detects the light for distance measurement reflected by the laser light entrance surface, thereby acquiring displacement data of the laser light entrance surface of the object to be processed  1 . Note that, for the distance measuring sensors  450 , sensors can be used of a triangulation method, a laser confocal method, a white confocal method, a spectral interference method, an astigmatism method, and the like. 
     In the laser processing device  200 , as described above, the direction parallel to the X-axis direction is the processing direction (scanning direction of the laser light L). For that reason, when the converging point of the laser light L is relatively moved along each of the lines to cut  5   a  and  5   b , out of the pair of distance measuring sensors  450 , one of the distance measuring sensors  450  being relatively advanced with respect to the converging lens unit  430  acquires the displacement data of the laser light entrance surface of the object to be processed  1  along each of the lines to cut  5   a  and  5   b . Then, the drive mechanism  440  moves the converging lens unit  430  along the Z-axis direction on the basis of the displacement data acquired by the distance measuring sensors  450  such that a constant distance is maintained between the laser light entrance surface of the object to be processed  1  and the converging point of the laser light L. 
     The laser converging unit  400  includes a beam splitter  461 , a pair of lenses  462  and  463 , and a profile acquisition camera (intensity distribution acquisition unit)  464 . The beam splitter  461  divides the laser light L transmitted through the dichroic mirror  403  into a reflection component and a transmission component. The laser light L reflected by the beam splitter  461  sequentially enters the pair of lenses  462  and  463 , and the profile acquisition camera  464  along the Z-axis direction. The pair of lenses  462  and  463  constitutes a double telecentric optical system in which the entrance pupil plane  430   a  of the converging lens unit  430  and an imaging surface of the profile acquisition camera  464  are in an imaging relationship. Thus, an image of the laser light L on the entrance pupil plane  430   a  of the converging lens unit  430  is transferred to (imaged on) the imaging surface of the profile acquisition camera  464 . As described above, the image of the laser light L on the entrance pupil plane  430   a  of the converging lens unit  430  is the image of the laser light L modulated in the reflective spatial light modulator  410 . Therefore, in the laser processing device  200 , an imaging result by the profile acquisition camera  464  is monitored, whereby an operation state of the reflective spatial light modulator  410  can be grasped. 
     Further, the laser converging unit  400  includes a beam splitter  471 , a lens  472 , and a camera  473  for monitoring an optical axis position of the laser light L. The beam splitter  471  divides the laser light L transmitted through the beam splitter  461  into a reflection component and a transmission component. The laser light L reflected by the beam splitter  471  sequentially enters the lens  472  and the camera  473  along the Z-axis direction. The lens  472  converges the entering laser light L on an imaging surface of the camera  473 . In the laser processing device  200 , while an imaging result by each of the cameras  464  and  473  is monitored, in the mirror unit  360 , the position adjustment of the support base  361  with respect to the mounting base  301 , the position adjustment of the mirror  363  with respect to the support base  361 , and the angle adjustment of the reflective surface of each of the mirrors  362  and  363  are performed (see  FIGS. 9 and 10 ), whereby a shift can be corrected of the optical axis of the laser light L entering the converging lens unit  430  (a positional shift of intensity distribution of the laser light with respect to the converging lens unit  430 , and an angular shift of the optical axis of the laser light L with respect to the converging lens unit  430 ). 
     The plurality of beam splitters  461  and  471  is arranged in a cylindrical body  404  extending along the Y-axis direction from the end  401   d  of the housing  401 . The pair of lenses  462  and  463  is arranged in a cylindrical body  405  erected on the cylindrical body  404  along the Z-axis direction, and the profile acquisition camera  464  is arranged at an end of the cylindrical body  405 . The lens  472  is arranged in a cylindrical body  406  erected on the cylindrical body  404  along the Z-axis direction, and the camera  473  is arranged at an end of the cylindrical body  406 . The cylindrical body  405  and the cylindrical body  406  are arranged side by side in the Y-axis direction. Note that, the laser light L transmitted through the beam splitter  471  may be absorbed by a damper or the like provided at an end of the cylindrical body  404 , or may be used for an appropriate purpose. 
     As illustrated in  FIGS. 12 and 13 , the laser converging unit  400  includes a visible light source  481 , a plurality of lenses  482 , a reticle  483 , a mirror  484 , a semitransparent mirror  485 , a beam splitter  486 , a lens  487 , and an observation camera  488 . The visible light source  481  emits visible light V along the Z-axis direction. The plurality of lenses  482  collimates the visible light V emitted from the visible light source  481 . The reticle  483  gives a scale line to the visible light V. The mirror  484  reflects the visible light V collimated by the plurality of lenses  482  in the X-axis direction. The semitransparent mirror  485  divides the visible light V reflected by the mirror  484  into a reflection component and a transmission component. The visible light V reflected by the semitransparent mirror  485  is sequentially transmitted through the beam splitter  486  and the dichroic mirror  403  along the Z-axis direction, and is emitted via the converging lens unit  430  to the object to be processed  1  supported by the support table  230  (See  FIG. 7 ). 
     The visible light V emitted to the object to be processed  1  is reflected by the laser light entrance surface of the object to be processed  1 , enters the dichroic mirror  403  via the converging lens unit  430 , and is transmitted through the dichroic mirror  403  along the Z-axis direction. The beam splitter  486  divides the visible light V transmitted through the dichroic mirror  403  into a reflection component and a transmission component. The visible light V transmitted through the beam splitter  486  is transmitted through the semitransparent mirror  485  and sequentially enters the lens  487  and the observation camera  488  along the Z-axis direction. The lens  487  converges the entering visible light V on an imaging surface of the observation camera  488 . In the laser processing device  200 , an imaging result by the observation camera  488  is observed, whereby a state of the object to be processed  1  can be grasped. 
     The mirror  484 , the semitransparent mirror  485 , and the beam splitter  486  are arranged in a holder  407  attached on the end  401   d  of the housing  401 . The plurality of lenses  482  and the reticle  483  are arranged in a cylindrical body  408  erected on the holder  407  along the Z-axis direction, and the visible light source  481  is arranged at an end of the cylindrical body  408 . The lens  487  is arranged in a cylindrical body  409  erected on the holder  407  along the Z-axis direction, and the observation camera  488  is arranged at an end of the cylindrical body  409 . The cylindrical body  408  and the cylindrical body  409  are arranged side by side in the X-axis direction. Note that, each of the visible light V transmitted through the semitransparent mirror  485  along the X-axis direction and the visible light V reflected in the X-axis direction by the beam splitter  486  may be absorbed by a damper or the like provided on a wall portion of the holder  407 , or may be used for an appropriate purpose. 
     In the laser processing device  200 , replacement of the laser output unit  300  is assumed. This is because the wavelength of the laser light L suitable for processing varies depending on the specifications of the object to be processed  1 , processing conditions, and the like. For that reason, a plurality of the laser output units  300  is prepared having respective wavelengths of emitting laser light L different from each other. Here, prepared are the laser output unit  300  in which the wavelength of the emitting laser light L is included in the wavelength band of from 500 nm to 550 nm, the laser output unit  300  in which the wavelength of the emitting laser light L is included in the wavelength band of from 1000 nm to 1150 nm, and the laser output unit  300  in which the wavelength of the emitting laser light L is included in the wavelength band of from 1300 nm to 1400 nm. 
     On the other hand, in the laser processing device  200 , replacement of the laser converging unit  400  is not assumed. This is because the laser converging unit  400  is adapted to multiple wavelengths (adapted to a plurality of wavelength bands non-contiguous with each other). Specifically, the mirror  402 , the reflective spatial light modulator  410 , the pair of lenses  422  and  423  of the 4f lens unit  420 , the dichroic mirror  403 , the lens  432  of the converging lens unit  430 , and the like are adapted to the multiple wavelengths. 
     Here, the laser converging unit  400  is adapted to the wavelength bands of from 500 nm to 550 nm, from 1000 nm to 1150 nm, and from 1300 nm to 1400 nm. This is implemented by designing the components of the laser converging unit  400  so as to satisfy desired optical performance, such as coating the components of the laser converging unit  400  with a predetermined dielectric multilayer film. Note that, in the laser output unit  300 , the λ/2 wave plate unit  330  includes a λ/2 wave plate, and the polarizing plate unit  340  includes a polarizing plate. The λ/2 wave plate and the polarizing plate are optical devices having high wavelength dependence. For that reason, the λ/2 wave plate unit  330  and the polarizing plate unit  340  are provided in the laser output unit  300  as different components for each wavelength band. 
     [Optical Path and Polarization Direction of Laser Light in Laser Processing Device] 
     In the laser processing device  200 , as illustrated in  FIG. 11 , the polarization direction of the laser light L converged at the object to be processed  1  supported by the support table  230  is a direction parallel to the X-axis direction, and coincides with the processing direction (scanning direction of the laser light L). Here, in the reflective spatial light modulator  410 , the laser light L is reflected as P-polarized light. This is because in a case where a liquid crystal is used for the light modulation layer of the reflective spatial light modulator  410 , when the liquid crystal is oriented such that the liquid crystal molecules are inclined in a surface parallel to the plane including the optical axis of the laser light L entering and exiting the reflective spatial light modulator  410 , phase modulation is applied to the laser light L in a state where the rotation of the plane of polarization is inhibited (for example, see Japanese Patent No. 3878758). 
     On the other hand, in the dichroic mirror  403 , the laser light L is reflected as S-polarized light. This is because, for example, when the laser light L is reflected as the S-polarized light rather than when the laser light L is reflected as the P-polarized light, the number of coatings is reduced of the dielectric multilayer film for making the dichroic mirror  403  adapt to the multiple wavelengths, and designing of the dichroic mirror  403  becomes easier. 
     Therefore, in the laser converging unit  400 , the optical path from the mirror  402  via the reflective spatial light modulator  410  and the 4f lens unit  420  to the dichroic mirror  403  is set along the XY plane, and the optical path from the dichroic mirror  403  to the converging lens unit  430  is set along the Z-axis direction. 
     As illustrated in  FIG. 9 , in the laser output unit  300 , the optical path of the laser light L is set along the X-axis direction or the Y-axis direction. Specifically, the optical path from the laser oscillator  310  to the mirror  303 , and the optical path from the mirror  304  via the λ/2 wave plate unit  330 , the polarizing plate unit  340 , and the beam expander  350  to the mirror unit  360  are set along the X-axis direction, and the optical path from the mirror  303  via the shutter  320  to the mirror  304 , and the optical path from the mirror  362  to the mirror  363  in the mirror unit  360  are set along the Y-axis direction. 
     Here, as illustrated in  FIG. 11 , the laser light L having traveled to the laser converging unit  400  from the laser output unit  300  along the Z-axis direction is reflected by the mirror  402  in a direction parallel to the XY plane, and enters the reflective spatial light modulator  410 . At this time, in the plane parallel to the XY plane, an acute angle α is formed by the optical axis of the laser light L entering the reflective spatial light modulator  410  and the optical axis of the laser light L emitted from the reflective spatial light modulator  410 . On the other hand, as described above, in the laser output unit  300 , the optical path of the laser light L is set along the X-axis direction or the Y-axis direction. 
     Therefore, in the laser output unit  300 , it is necessary to cause the λ/2 wave plate unit  330  and the polarizing plate unit  340  to function not only as the output adjusting unit configured to adjust the output of the laser light L but also as the polarization direction adjusting unit configured to adjust the polarization direction of the laser light L. 
     [4f Lens Unit] 
     As described above, the pair of lenses  422  and  423  of the 4f lens unit  420  constitutes the double telecentric optical system in which the reflective surface  410   a  of the reflective spatial light modulator  410  and the entrance pupil plane  430   a  of the converging lens unit  430  are in the imaging relationship. Specifically, as illustrated in  FIG. 14 , the distance of the optical path between the center of the lens  422  on the reflective spatial light modulator  410  side and the reflective surface  410   a  of the reflective spatial light modulator  410  is a first focal length f1 of the lens  422 , the distance of the optical path between the center of the lens  423  on the converging lens unit  430  side and the entrance pupil plane  430   a  of the converging lens unit  430  is a second focal length f2 of the lens  423 , and the distance of the optical path between the center of the lens  422  and the center of the lens  423  is a sum of the first focal length f1 and the second focal length f2 (that is, f1+f2). In the optical path from the reflective spatial light modulator  410  to the converging lens unit  430 , the optical path between the pair of lenses  422  and  423  is a straight line. 
     In the laser processing device  200 , from a viewpoint of increasing an effective diameter of the laser light L on the reflective surface  410   a  of the reflective spatial light modulator  410 , a magnification M of the double telecentric optical system satisfies 0.5&lt;M&lt;1 (reduction system). As the effective diameter is increased of the laser light L on the reflective surface  410   a  of the reflective spatial light modulator  410 , the laser light L is modulated with a high-precision phase pattern. From a viewpoint of inhibiting the optical path from becoming longer of the laser light L from the reflective spatial light modulator  410  to the converging lens unit  430 , it is possible to set 0.6&lt;M≤0.95. Here, (the magnification M of the double telecentric optical system)=(the size of the image on the entrance pupil plane  430   a  of the converging lens unit  430 )/(the size of the object on the reflective surface  410   a  of the reflective spatial light modulator  410 ). In the case of the laser processing device  200 , the magnification M of the double telecentric optical system, the first focal length f1 of the lens  422 , and the second focal length f2 of the lens  423  satisfy M=f2/f1. 
     From a viewpoint of reducing the effective diameter of the laser light L on the reflective surface  410   a  of the reflective spatial light modulator  410 , the magnification M of the double telecentric optical system may satisfy 1&lt;M&lt;2 (enlargement system). As the effective diameter is reduced of the laser light L on the reflective surface  410   a  of the reflective spatial light modulator  410 , the magnification can be reduced of the beam expander  350  (see  FIG. 9 ), and in the plane parallel to the XY plane, the angle α (see  FIG. 11 ) is reduced formed by the optical axis of the laser light L entering the spatial light modulator  410  and the optical axis of the laser light L emitted from the reflective spatial light modulator  410 . From the viewpoint of inhibiting the optical path from becoming longer of the laser light L from the reflective spatial light modulator  410  to the converging lens unit  430 , it is possible to set 1.05≤M≤1.7. 
     [Reflective Spatial Light Modulator] 
     As illustrated in  FIG. 15 , the reflective spatial light modulator  410  includes a silicon substrate  213 , a drive circuit layer  914 , a plurality of pixel electrodes  214 , a reflective film  215  such as a dielectric multilayer mirror, an alignment film  999   a , a liquid crystal layer (modulation layer)  216 , an alignment film  999   b , a transparent conductive film  217 , and a transparent substrate  218  such as a glass substrate, which are layered in this order. 
     The transparent substrate  218  includes a front surface  218   a . As described above, the front surface  218   a  can be regarded as substantially constituting the reflective surface  410   a  of the reflective spatial light modulator  410 , but more specifically, the front surface  218   a  is an entrance surface at which the laser light L enters. That is, the transparent substrate  218  is made of a light transmitting material such as glass, for example, and transmits the laser light L entering from the front surface  218   a  of the reflective spatial light modulator  410  to the inside of the reflective spatial light modulator  410 . The transparent conductive film  217  is formed on a back surface of the transparent substrate  218 , and includes a conductive material (for example, ITO) which transmits therethrough the laser light L. 
     The plurality of pixel electrodes  214  is arranged in a matrix on the silicon substrate  213  along the transparent conductive film  217 . Each pixel electrode  214  is made of a metal material such as aluminum, for example, while its front surface  214   a  is processed flat and smooth. The front surface  214   a  reflects the laser light L entering from the front surface  218   a  of the transparent substrate  218  toward the front surface  218   a . That is, the reflective spatial light modulator  410  includes the front surface  218   a  at which the laser light L enters, and the front surface  214   a  configured to reflect the laser light L entering from the front surface  218   a , toward the front surface  218   a . The plurality of pixel electrodes  214  are driven by an active matrix circuit provided in the drive circuit layer  914 . 
     The active matrix circuit is provided between the plurality of pixel electrodes  214  and the silicon substrate  213 , and controls an applied voltage to each of the pixel electrodes  214  in accordance with a light image to be output from the reflective spatial light modulator  410 . Such an active matrix circuit includes a first driver circuit configured to control the applied voltage for pixel rows arranged in the X-axis direction, and a second driver circuit configured to control the applied voltage for pixel rows arranged in the Y-axis direction, which are not illustrated, for example, and a predetermined voltage is applied to the pixel electrode  214  of a pixel specified by the driver circuits, by the controller  500 . 
     The alignment films  999   a ,  999   b  are arranged on both end surfaces of the liquid crystal layer  216 , respectively, so as to align a group of liquid crystal molecules in a fixed direction. The alignment films  999   a ,  999   b  are made of a polymer material such as polyimide, of which surfaces coming into contact with the liquid crystal layer  216  are subjected to rubbing, and the like. 
     The liquid crystal layer  216  is arranged between the plurality of pixel electrodes  214  and the transparent conductive film  217  and modulates the laser light L according to an electric field formed between each pixel electrode  214  and the transparent conductive film  217 . That is, when a voltage is applied to the pixel electrodes  214  by the active matrix circuit of the drive circuit layer  914 , an electric field is formed between the transparent conductive film  217  and the pixel electrodes  214 , and the alignment direction of liquid crystal molecules  216   a  changes according to a magnitude of the electric field formed in the liquid crystal layer  216 . When the laser light L enters the liquid crystal layer  216  through the transparent substrate  218  and the transparent conductive film  217 , the laser light L is modulated by the liquid crystal molecules  216   a  while passing through the liquid crystal layer  216 , and reflected by the reflective film  215 , and then modulated again by the liquid crystal layer  216 , and emitted. 
     At this time, the voltage applied to each of the pixel electrodes  214  is controlled by the controller  500 , and, in accordance with the voltage, a refractive index changes in a portion sandwiched between the transparent conductive film  217  and each of the pixel electrodes  214  in the liquid crystal layer  216  (the refractive index changes of the liquid crystal layer  216  at a position corresponding to each pixel). Due to the change in the refractive index, the phase of the laser light L can be changed for each pixel of the liquid crystal layer  216  in accordance with the voltage applied. That is, phase modulation corresponding to the hologram pattern can be applied by the liquid crystal layer  216  for each pixel. 
     In other words, a modulation pattern as the hologram pattern applying the modulation can be displayed on the liquid crystal layer  216  of the reflective spatial light modulator  410 . The wavefront is adjusted of the laser light L that enters and is transmitted through the modulation pattern, and shifts occur in phases of components of individual rays constituting the laser light L in a predetermined direction orthogonal to their traveling direction. Therefore, the laser light L can be modulated (for example, intensity, amplitude, phase, and polarization of the laser light L can be modulated) by appropriately setting the modulation pattern to be displayed in the reflective spatial light modulator  410 . 
     In other words, depending on the voltage applied to each pixel electrode  214 , a refractive index distribution is generated in the liquid crystal layer  216  along the arrangement direction of the pixel electrodes  214 , and a phase pattern that can apply phase modulation to the laser light L is displayed on the liquid crystal layer  216 . That is, the reflective spatial light modulator  410  includes the liquid crystal layer (modulation layer)  216  arranged between the front surface  218   a  and the front surface  214   a  and configured to display the phase pattern to modulate the laser light L. 
     Subsequently, the reflective spatial light modulator  410  will be described in more detail. The reflective spatial light modulator  410  is configured to be adaptable to the plurality of wavelength bands non-contiguous with each other (multi-wavelength adaptable) such as a first wavelength band of greater than or equal to 500 nm and less than or equal to 550 nm, a second wavelength band of greater than or equal to 1000 nm and less than or equal to 1150 nm, and a third wavelength band of greater than or equal to 1300 nm and less than or equal to 1400 nm. For that reason, on the front surface  214   a  of the pixel electrode  214 , the reflective film  215  is formed, and the reflective film  215  is a dielectric multilayer film having a high reflectance region in the plurality of wavelength bands.  FIG. 16( a )  is a diagram illustrating an example of a reflectance characteristic of the reflective film  215 . As illustrated in  FIG. 16( a ) , here, the reflective film  215  has a high reflectance region RR 1  corresponding to the first wavelength band, a high reflectance region RR 2  corresponding to the second wavelength band, and a high reflectance region RR 3  corresponding to the third wavelength band. 
     Low reflectance regions are respectively formed between the high reflectance regions RR 1  to RR 3 . Thus, the high reflectance regions RR 1  to RR 3  are non-contiguous with each other in a high reflectance range. Here, the high reflectance region is a region where the reflectance is greater than or equal to 95%. Therefore, here, the low reflectance region is a region where the reflectance is less than 95%. Note that, as described above, the reflective film  215  has the plural high reflectance regions RR 1  to RR 3  non-contiguous with each other (in the high reflectance range), but it is also possible to make the high reflectance region RR 1  to the high reflectance region RR 3  contiguous in the high reflectance range. That is, as an example, the reflective film  215  can also be configured to have a high reflectance over the entire wavelength range from 500 nm that is the lower limit of the first wavelength band to 1400 nm that is the upper limit of the third wavelength band. However, in this case, the number of dielectric multilayer films increases, and the film thickness of the reflective film  215  increases. As a result, a large voltage is required to display a predetermined phase pattern in the liquid crystal layer  216 . Therefore, as described above, it is advantageous to set only the respective target wavelength bands (the first wavelength band to the third wavelength band) to the high reflectance, to suppress the increase in the film thickness of the dielectric multilayer film. 
     On the front surface  218   a  of the transparent substrate  218 , an antireflective film (not illustrated) is formed having a high transmittance region in the plurality of wavelength bands.  FIG. 16( b )  is a diagram illustrating an example of a transmittance characteristic of the antireflective film. As illustrated in  FIG. 16( b ) , the antireflective film provided on the front surface  218   a  has a high transmittance region TR 1  corresponding to the first wavelength band, a high transmittance region TR 2  corresponding to the second wavelength band, and a high transmittance region TR 3  corresponding to the third wavelength band. Note that, in  FIG. 16( b ) , the solid line illustrates a transmittance range of 0% to 100% (vertical axis on the left side), and the broken line illustrates a transmittance range of 90% to 100% (vertical axis on the right side). In addition, the high transmittance region here is a region where the transmittance is approximately greater than or equal to 98%. 
     Here, the front surface  214   a  of the pixel electrode  214  has a predetermined flatness. That is, the front surface  214   a  may have a predetermined distortion. When the front surface  214   a  is distorted, distortion is also applied to the wavefront of the laser light L reflected by the front surface  214   a . For this reason, the laser processing device  200  includes a distortion correction pattern that is a phase pattern for correcting distortion of the wavefront.  FIG. 17( a )  is a graph illustrating an example of the distortion. In the example of  FIG. 17( a ) , a case is illustrated in which the distortion occurs over the front surface  214   a  of the plurality of pixel electrodes  214  depending on a warp of the silicon substrate  213 , for example. 
       FIG. 17( b )  is a graph in which an amount of distortion in  FIG. 17( a )  is divided by the wavelength of the laser light L so as to obtain an amount of distortion converted into the wavelength. In addition, in  FIG. 17( b ) , the horizontal axis is converted into the pixel number (pixel position) of the pixel electrode  214 . As illustrated in  FIG. 17( b ) , for the amount of distortion converted into the wavelength, fold-backs S 1  and S 2  are formed at each one wavelength (2π). For this reason, in the case of being converted into the wavelength, the amount of distortion at each pixel varies between those of when the wavelength of the laser light L is 1064 nm (solid line) and when the wavelength of the laser light L is 532 nm (broken line), for example. That is, different phase modulation amounts (that is, distortion correction patterns) are required depending on the wavelength of the laser light L. 
       FIG. 18( a )  illustrates a distortion correction pattern for a wavelength of 1064 nm, and  FIG. 18( b )  illustrates a distortion correction pattern for a wavelength of 532 nm. Note that, actually,  FIGS. 18( a ) and 18( b )  each illustrate an image signal for displaying the distortion correction pattern on the liquid crystal layer  216 . In the image signal, the distribution of the luminance value corresponds to the distribution of the refractive index of the liquid crystal layer  216  via the voltage. Therefore, the image signal of each of  FIGS. 18( a ) and 18( b )  is equivalent to the phase pattern (distortion correction pattern). As illustrated in  FIGS. 18( a ) and 18( b ) , the distortion correction pattern for the wavelength of 1064 nm includes a pattern corresponding to the fold-back S 1 , whereas the distortion correction pattern for the wavelength of 532 nm includes patterns respectively corresponding to the fold-backs S 1  and S 2  (the fold-back period is half). 
     As described above, the laser processing device  200  holds the distortion correction pattern different for each of the plurality of wavelength bands (that is, includes a pattern holding unit). The pattern holding unit may be configured in the controller  500  or in the reflective spatial light modulator  410 . Here, at least distortion correction patterns are held corresponding to three wavelength bands of the first wavelength band, the second wavelength band, and the third wavelength band. Each of the distortion correction patterns is a pattern obtained by converting a distortion correction amount into each wavelength, that is, a pattern in which the fold-backs S 1  and S 2  of the distortion correction amount (phase modulation amount) are formed at a period corresponding to the wavelength. 
     Here, the laser processing device  200  includes a table (hereinafter referred to as “Look-Up table (LUT)”) in which the luminance value of the image signal for forming the phase pattern in the liquid crystal layer  216  and the phase modulation amount of the phase pattern are associated with each other. Subsequently, the LUT will be described.  FIG. 19( a )  is a diagram illustrating an example of a relationship between the voltage applied to the liquid crystal layer  216  and the phase modulation amount (wavelength indication) applied to the laser light L by the liquid crystal layer  216 .  FIG. 19( b )  is a diagram illustrating an example of the LUT. As illustrated in  FIG. 19( a ) , for example, to apply a phase modulation for one wavelength (1064 nm) to the laser light L having a wavelength of 1064 nm, it is sufficient that a voltage of approximately 2 V is applied to the liquid crystal layer  216 . 
     Therefore, as illustrated by the solid line in  FIG. 19( b ) , by assigning the voltages of 0 V to 2 V to the luminance value of 256 gradations of the image signal, the phase modulation amounts of 0 to a (for one wavelength) of the laser light L of 1064 nm and the luminance values of 256 gradations can be associated with each other. On the other hand, as illustrated in  FIG. 19( a ) , to apply a phase modulation for one wavelength (532 nm) to the laser light L having a wavelength of 532 nm, it is sufficient that a voltage smaller than 2 V (for example, about 1.2 V) is applied to the liquid crystal layer  216 . Note that, the phase modulation amount is not an absolute amount but a difference. For that reason, it is also possible to use a region of about 2.4 V to 3.5 V in the laser light of 532 nm, as the LUT, for example. Since the characteristics such as the response speed of the liquid crystal change in the voltage range to be used, it is possible to use the optimum voltage range depending on the application. 
     Therefore, as described above, if the voltages of 0 V to 2 V are assigned to the luminance values of 256 gradations of the image signal, as illustrated in  FIG. 19( b ) , for the laser light L of 532 nm, phase modulation amounts (for example, 4π) larger than 2π (one wavelength) are associated with the luminance values of 256 gradations. Therefore, for the phase modulation amounts for 2π (one wavelength) of the effective laser light L of 532 nm, luminance values are used of smaller gradations than 256 gradations (for example, 128 grayscales). For this reason, when the same LUT is used for the plural wavelengths, the reproducibility degrades of the wavefront after modulation of the laser light L having a relatively short wavelength among the plural wavelengths. 
     To cope with this, the laser processing device  200  holds the LUT different for each of the wavelength bands. As an example, the laser processing device  200  holds a LUT (see  FIG. 20( a ) ) in which the phase modulation amounts of 0 to 2π (for one wavelength) of the laser light L of 1064 nm and the luminance values of 256 gradations are associated with each other by assigning the voltages of 0 V to 2 V to the luminance values of 256 gradations of the image signal as described above, and a LUT (see  FIG. 20( b ) ) in which the phase modulation amounts of 0 to 2π (one wavelength) of the laser light L of 532 nm and the luminance values of 256 gradations are associated with each other by assigning voltages of 0 V to 1.2 V to the luminance values of 256 gradations of the image signal. The LUTs in  FIGS. 20( a ) and 20( b )  can be expressed differently from each other by displaying the wavelength on the vertical axis. 
     As described above, the laser processing device  200  holds the LUT different for each of the wavelength bands (that is, includes a table holding unit). The table holding unit may be configured in the controller  500  or in the reflective spatial light modulator  410 . Here, at least LUTs are held corresponding to three wavelength bands of the first wavelength band, the second wavelength band, and the third wavelength band. In each LUT, for the shorter wavelength band, smaller phase modulation amounts converted into the wavelength are associated with the luminance values of certain gradations (here, 256 gradations). 
     As described above, in the laser processing device  200 , the laser light L is modulated in accordance with the phase pattern of the reflective spatial light modulator  410 , and then converged by the converging lens unit  430  toward the object to be processed  1 . The reflective spatial light modulator  410  includes the front surface  218   a  of the transparent substrate  218  at which the laser light L enters, the front surface  214   a  of the pixel electrode  214  configured to reflect the laser light L entering from the front surface  218   a , and the liquid crystal layer  216  arranged between the front surface  218   a  and the front surface  214   a.    
     When entering from the front surface  218   a  and passing through the liquid crystal layer  216 , the laser light L is modulated in accordance with the phase pattern. In addition, the laser light L is modulated also when being reflected by the front surface  214   a  and again passing through the liquid crystal layer  216 , and is emitted from the reflective spatial light modulator  410 . Here, on the front surface  214   a , the reflective film  215  is formed that is a dielectric multilayer film having the high reflectance regions RR 1  to RR 3  in the plurality of wavelength bands non-contiguous with each other. Therefore, with the reflective spatial light modulator  410 , it is possible to modulate the laser light L while reducing the loss on the front surface  214   a  of the laser light L of the plurality of wavelength bands. Accordingly, the laser processing device  200  is adaptable to the plurality of wavelength bands. 
     The laser processing device  200  includes the pattern holding unit (for example, the controller  500 ) configured to hold the distortion correction pattern as the phase pattern for correcting distortion given to the wavefront of the laser light L depending on the flatness of the front surface  214   a  of the pixel electrode  214 . The pattern holding unit holds the distortion correction pattern different for each of the wavelength bands. As described above, the front surface  214   a  of the pixel electrode  214  has a predetermined flatness for each reflective spatial light modulator  410 . However, to correct the distortion given to the wavefront of the laser light L depending on the flatness, the phase modulation amount is required different depending on the wavelength. Therefore, as described above, if the distortion correction pattern is held different for each of the wavelength bands, the laser processing device is easily and reliably adaptable to the plurality of wavelength bands. 
     The laser processing device  200  includes the table holding unit (for example, the controller  500 ) configured to hold the LUT in which the luminance value of the image signal for displaying the phase pattern on the liquid crystal layer  216  and the phase modulation amount of the phase pattern are associated with each other. The table holding unit holds the LUT different for each of the wavelength bands. As described above, for the laser light L of a certain wavelength, the LUT is prepared in which the luminance values of, for example, 256 gradations of the image signal are assigned to (associated with) the phase modulation amounts for one wavelength (2π), whereby a phase modulation pattern suitable for the wavelength can be easily displayed on the liquid crystal layer  216 . 
     However, if the same LUT is used for the laser light L having a wavelength shorter than the wavelength, luminance values of smaller gradations are used for the phase modulation amounts for one wavelength, so that reproducibility drops of the wavefront after the modulation. To cope with this, the laser processing device  200  holds the LUT different for each of the wavelength bands. For this reason, it is possible to use a LUT suitable for each wavelength band, and degradation of the reproducibility of the wavefront can be suppressed. 
     Further, in the laser processing device  200 , on the front surface  218   a  of the transparent substrate  218 , the antireflective film is formed having the high transmittance regions TR 1  to TR 3  in the plurality of wavelength bands. For this reason, the loss of the laser light L can be further reduced, and the laser processing device is reliably adaptable to the plurality of wavelength bands. 
     The above is one embodiment of one aspect of the present invention. One aspect of the present invention is not limited to the above-described embodiment, but may be modified within a range not changing the gist of each claim, or may be applied to another. 
     For example, the above-described embodiment is not limited to one configured to form the modified region  7  within the object to be processed  1 , and may be one configured to perform another laser processing such as ablation. The above-described embodiment is not limited to a laser processing device used for laser processing of converging the laser light L within the object to be processed  1 , and may be a laser processing device used for laser processing of converging the laser light L at the front surface  1   a ,  3  or the back surface  1   b  of the object to be processed  1 . 
     In the above embodiment, the imaging optical system constituting the double telecentric optical system in which the reflective surface  410   a  of the reflective spatial light modulator  410  and the entrance pupil plane  430   a  of the converging lens unit  430  are in the imaging relationship is not limited to the pair of lenses  422  and  423 , and may be one including the first lens system (for example, a doublet, three or more lenses, or the like) on the reflective spatial light modulator  410  side, and the second lens system (for example, a doublet, three or more lenses, or the like) on the converging lens unit  430  side, or the like. 
     In the laser converging unit  400 , the dichroic mirror  403  is the mirror configured to reflect the laser light L having passed through the pair of lenses  422  and  423  toward the converging lens unit  430 ; however, the mirror may be a total reflection mirror. 
     The converging lens unit  430  and the pair of distance measuring sensors  450  are attached to the end  401   d  of the housing  401  in the Y-axis direction; however, the converging lens unit  430  and the pair of distance measuring sensors  450  only need to be attached at a side closer to the end  401   d  from the center position of the housing  401  in the Y-axis direction. The reflective spatial light modulator  410  is attached to the end  401   c  of the housing  401  in the Y-axis direction; however, the reflective spatial light modulator  410  only need to be attached at a side closer to the end  401   c  from the center position of the housing  401  in the Y-axis direction. In addition, the distance measuring sensors  450  may be arranged only on one side of the converging lens unit  430  in the X-axis direction. 
     INDUSTRIAL APPLICABILITY 
     A laser processing device can be provided adaptable to a plurality of wavelength bands. 
     REFERENCE SIGNS LIST 
     
         
           1  object to be processed 
           100 ,  200  laser processing device 
           214   a  front surface (reflective surface) 
           215  reflective film (dielectric multilayer film) 
           216  liquid crystal layer (modulation layer) 
           218   a  front surface (entrance surface) 
           300  laser output unit 
           410  reflective spatial light modulator (spatial light modulator) 
           430  converging lens unit (objective lens) 
           500  controller (pattern holding unit, table holding unit) 
         L laser light.