Laser irradiator, fabricating apparatus, and laser irradiation method

Abstract

A laser irradiator includes a laser light source to emit a laser beam in an emission direction, multiple upstream deflectors including at least one of a first deflector to deflect the laser beam in a first direction and a second deflector to deflect the laser beam emitted from the laser light source in a second direction different from the first direction, a downstream deflector in the emission direction to deflect the laser beam in a main scanning direction different from the emission direction, the first direction, and the second direction, and a control unit to control the downstream deflector to move an irradiation position of the laser beam to a first position in the main scanning direction, and one of the first deflector or the second deflector to change the irradiation position of the laser beam to a second position different from the first position.

Description

[DESCRIPTION][Title of Invention]LASER IRRADIATOR, FABRICATING APPARATUS, AND LASER IRRADIATION METHOD[Technical Field]

[0001] Embodiments of the present disclosure relate to a laser irradiator, a fabrication apparatus, and a laser irradiation method.[Background Art]

[0002] As a technique of irradiating an irradiation target region of an irradiation object to be irradiated with a laser beam, irradiation of a laser beam by raster scan is typically known.

[0003] For an irradiation pattern having many complicated structures such as a character string, the raster scan at a high scanning speed can shorten the time required for a series of laser irradiation operations, and a certain effect is obtained in increasing the productivity of the laser irradiator. However, in the raster scan, the laser beam is turned off in the non-irradiated region so that a useless scan time is generated. Thus, there is room to increase productivity.

[0004] Such a laser irradiator includes a deflector that deflects the laser beam. The deflector deflects the zero-order light beam emitted from the light source so that a predetermined position can be irradiated with a laser beam by operating, for example, a raster scan.

[0005] As a deflector that deflects the laser beam described above, for example, it is described in PTL1 that an acousto-optic deflector (AOD) system deflects the laser beam in a first direction and a galvano system deflects the laser beam in a second direction.[Citation List][Patent Literature]

[0006] [PTL 1]Japanese Unexamined Patent Application Publication No. 2012-528011[Summary of Invention][Technical Problem]

[0007] An object of the present disclosure is to efficiently irradiate an irradiation target region of an object with a laser beam.[Solution to Problem]

[0008] According to an embodiment of the present disclosure, a laser irradiator includes a laser light source to emit a laser beam in an emission direction, multiple upstream deflectors including atleast one of a first deflector to deflect the laser beam emitted from the laser light source in a first direction different from the emission direction and a second deflector that is disposed at downstream of the first deflector in the emission direction and deflects the laser beam emitted from the laser light source in a second direction different from the first direction, a downstream deflector downstream of the multiple upstream deflectors in the emission direction to deflect the laser beam in a main scanning direction different from the emission direction, the first direction, and the second direction, and a control unit to control the downstream deflector to move an irradiation position of the laser beam to a first position in the main scanning direction, and control one of the first deflector or the second deflector to change the irradiation position of the laser beam, deflected by the downstream deflector, to a second position different from the first position in the first direction or the second direction to irradiate an unirradiated region.According to an embodiment of the present disclosure a fabrication apparatus includes the laser irradiator to repeatedly irradiate an irradiation region of a powder bed sequentially formed by multiple powder layers with the laser beam to fabricate a three-dimensional article. According to an embodiment of the present disclosure, a laser irradiation method includes emitting a laser beam, deflecting an irradiation position of the laser beam to a first position by a downstream deflector, deflecting the irradiation position of the laser beam to a second position different from the first position by a first deflector and a second deflector, and irradiating an irradiation region of an object with the laser beam deflected by the one of the first deflector or the second deflector, and the downstream deflector.[Advantageous Effect of Invention]

[0009] According to an embodiment of the present disclosure, an irradiation target region of an object can be irradiated with a laser beam.[Brief Description of Drawings]

[0010] The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.[FIG. 1]FIG. 1 is a plan view of a laser irradiator different from an embodiment of the present disclosure.[FIG. 2]FIG. 2 is a flowchart of a marking process with a laser beam from the laser irradiator in FIG. 1.[FIG. 3]FIG 3 is a diagram illustrating a raster scan track by a galvano scanner and a deflection direction of an acousto-optic deflector.[FIG. 4A]FIG. 4A is a diagram illustrating an image pattern to be marked.[FIG. 4B]FIG. 4B is a diagram illustrating a typical marking method to mark the image pattern illustrated in FIG. 4A.[FIGS. 4C and 4D]FIGS 4C and 4D are diagrams illustrating marking methods by the laser irradiator illustrated in FIG. 2.[FIG. 5A]FIG. 5A is a diagram illustrating a configuration of a laser irradiator as viewed from the -y- direction to +y-direction, according to a first embodiment.[FIG. 5B]FIG. 5B is a diagram illustrating the configuration of the laser irradiator as viewed from the +x-direction to -x-direction, according to the first embodiment.[FIG. 6A]FIG. 6A is a diagram illustrating an example of a setting of a first acousto-optic deflector.[FIG. 6B]FIG. 6B is a diagram illustrating an example of a setting of a second acousto-optic deflector.[FIG. 6C]FIG. 6C is a diagram illustrating a deflectable region in the positions of the settings in FIGS.6A and 6B .[FIG. 7A]FIG. 7A is a diagram illustrating an image pattern to be marked.[FIG. 7B]FIG. 7B is a diagram illustrating an irradiation region that the laser irradiator according to a first embodiment can irradiate with a zero-order light beam.[FIG. 7C]FIG. 7C is a diagram illustrating an example of a laser marking method.[FIG. 8A]FIG. 8A is a diagram illustrating an irradiation region that the laser irradiator illustrated inFIG. 1 can irradiate with a zero-order light beam.[FIG. 8B]FIG. 8B is a diagram illustrating an example of a laser marking method.[FIG. 9 A]FIG. 9A is a diagram illustrating a relation between a deflection direction by a first acousto- optic deflector and a pixel size.[FIG. 9B]FIG. 9B is a diagram illustrating a relation between deflection directions by the first acoustooptic deflector and a second acousto-optic deflector, and a pixel size.[FIGS. lOA to 10D]FIGS. 10A to 10D are diagrams illustrating directions of laser beams deflected and passing through centers of pixels having different pixel sizes.[FIG. 11]FIG. 11 is a diagram illustrating a deviation from a pixel center due to a deflection direction of an acousto-optic deflector.[FIG. 12]FIG. 12 is a diagram illustrating the case where both a deviation from a pixel center due to the deflection direction of the AOD and a deviation from the image center due to the distance between the two deflection directions of the first AOD and the second AOD occur.[FIG. 13]FIG. 13 is a diagram illustrating multiple times of laser beam irradiation at a time of an acceleration-or-deceleration region.[FIG. 14]FIG. 14 is a diagram illustrating a case where two pixels are marked while a main scan by a galvano scanner passes through one pixel.[FIG. 15]FIG. 15 is a block diagram illustrating a control unit of a laser irradiator.[FIG. 16A]FIG. 16A is a diagram illustrating an example of marking.[FIG. 16B]FIG. 16B is a timing chart of control of a first acousto-optic deflector to the marking illustrated in FIG. 16A.[FIG. 17]FIG. 17 is a diagram illustrating an embodiment in which a first acousto-optic deflector and a second acousto-optic deflector have different deflection directions.[FIG. 18]FIG. 18 is a diagram illustrating a deflectable region according to an embodiment in which a laser irradiator includes three acousto-optic deflectors.[FIG. 19]FIG. 19 is a diagram illustrating a deflectable region according to an embodiment in which another laser irradiator different from the laser irradiator in FIG. 18 includes three acousto- optic deflectors.[FIG. 20]FIG. 20 is a diagram illustrating a deflection distance by a first acousto-optic deflector.[FIG. 21]FIG. 21 is a diagram illustrating a powder bed fusion apparatus.[Description of Embodiments]

[0010] Embodiments of the present disclosure will be described below with reference to the drawings. In the drawings, the same or like reference signs denote like elements having substantially the same or corresponding configurations, and descriptions thereof may be omitted.

[0011] Laser IrradiatorFIG. 1 is a plan view of a laser irradiator 200 different from an embodiment of the present disclosure. The laser irradiator 200 includes a laser oscillator 10 as a laser light source, an acousto-optic deflector (AOD) 20 as an upstream deflector, a galvano scanner 30 as a downstream deflector, and an f9 lens 40. In the following description, the acousto-optic deflector is referred to as an "AOD". The laser irradiator 200 includes only one AOD, which is particularly different from the laser irradiator according to an embodiment of the present disclosure described later.

[0012] The AOD 20 includes a piezoelectric transducer connected to the crystal and a radio frequency (RF) driver that drives the piezoelectric transducer. The RF driver drives the piezoelectric transducer so that the AOD 20 generates an acoustic wave of an RF frequency in the crystal, for example, in a frequency range between about 50 megahertz (MHz) and about 1500 MHz.

[0013] An incident laser beam is diffracted by the acoustic wave generated in the crystal in proportion to the RF frequency. A portion of the power of the incident laser beam is deflected as a first-order diffraction light beam (diffraction light) Al.

[0014] The laser beam emitted from the laser irradiator 200 is deflected by the AOD 20, and the first- order diffraction light beam (diffraction light) Al of the deflection light goes in the galvano scanner 30. The galvano scanner 30 raster-scans the f9 lens 40 with the laser beam that has gone in the galvano scanner 30 to generate a raster- scanned laser beam.

[0015] The raster- scanned laser beam goes in the 1'0 lens 40 that is a condenser lens. The marking object 50 as an irradiation object is irradiated with the laser beam emitted from the f9 lens 40 to form a mark on the surface (or inside) of the marking object 50.

[0016] The f9 lens 40 is configured to focus the laser beam with which the galvano scanner 30 has scanned the f9 lens 40 on the marking object 50. For example, the f9 lens 40 is configured to scan the marking object 50 on an imaging surface at a predetermined pitch with the laser beam with which the galvano scanner 30 scans the 1'0 lens 40 at each predetermined angle.

[0017] FIG. 2 is a flowchart from a step in which the laser oscillator 10 emits the light beam (laser beam) to a step in which the laser beam goes in the marking object 50 to form a mark at an irradiation position. The light beam emitted from the light source (step SI) goes in the AOD 20 (step S2) as an incident light beam, and a portion of the incident light beam is diffracted at an angle corresponding to the wavelength of the incident light beam, the sound velocity of the crystal of the AOD 20, and the frequency of the RF signal applied from the RF driver connected to the AOD 20, as the first-order diffraction light beam (diffraction light) Al. In the incident light beam to the AOD 20, another portion of the incident light beam that has not diffracted propagates straight as zero-order light beam (transmitted light beam) A0 as illustrated in FIG. 1, and is shielded (terminated) by the beam damper 35. In FIG. 1, the zeroorder light beam A0 is shielded by the beam damper 35. However, when the power of the zero-order light beam A0 is so low that the marking object 50 is not marked even if the zeroorder light beam A0 strikes the marking object 50, the zero-order light beam A0 may not be shielded.

[0018] The first-order diffraction light beam goes in the galvano scanner 30, and the galvano scanner 30 deflects the first-order diffraction light beam Al (step S3). The deflected light beam deflected by the galvano scanner 30 goes in the 1'0 lens 40 at an incident angle. The f9 lens 40 focuses the deflected light beam on a marking position of the marking object 50 corresponding to the incident angle (S4).

[0019] The surface of the marking portion on the marking object 50 irradiated with the laser beam is scraped or denatured by the laser beam. As a result, a mark visually recognizable is formed (step S5).

[0020] The galvano scanner 30 scans the f9 lens 40 with the diffracted light beam (first-order diffraction light beam) Al diffracted by the AOD 20. In other words, the AOD 20 and the galvano scanner 30 control the laser irradiation position on the marking object 50. Further, a beam diameter converter, a beam profile former, or a wave plate may be disposed before or after the AOD 20 of the laser irradiator 200 illustrated in FIG. 1.

[0021] As the laser oscillator 10, for example, a pulse oscillation laser having a wavelength of 355 nanometers (nm), 532 nm, or 1064 nm can be used. The pulse oscillation laser is a type of laser in which the laser output varies with time. The pulse width is, for example, several tens of femtoseconds (fs) to several hundreds of nanoseconds (ns).

[0022] As the laser oscillator 10, a continuous wave (CW) oscillation laser may be used by switching instead of the pulse oscillation laser. The CW oscillation laser is a type of laser that outputs a constant value of the laser output without changing with time.

[0023] The RF driver drives the AOD 20, and the first-order diffraction light beam propagates at an angle proportional to the RF frequency. Thus, the deflection position of the AOD 20 can be controlled by controlling the RF frequency.

[0024] The deflection control by the AOD 20 does not have inertia unlike the galvano scanner 30 and the polygon scanner. Accordingly, the deflection control by the AOD 20 can deflect the laser beam at high speed (e.g., in a time of 5 microsecond (ps) or less).

[0025] In addition, the deflection control by the AOD 20 can give a deflection position different for each pulse even to a pulse laser having a high repetition frequency (e.g., 200 kilohertz (kHz)). According to an embodiment of the present disclosure, the AOD 20 is used as the deflector, but the deflector is not limited to the AOD 20. The deflector may be any deflector having any response speed. The upstream deflector may be an acousto-optic element such as the AOD 20, or may be an electro-optic element such as an electro-optic deflector (EOD) or a mirror optical deflector using a piezoelectric element that can response with high speed.

[0026] As illustrated in FIG. 3, in the following description, the sub-scanning direction in raster scan by the galvano scanner is referred to as an x-direction, the main scanning direction is referred to as a y-direction, and in particular, the direction from the upstream side to the downstream side in raster scanning is referred to as the +x-direction of the sub-scanning direction. For example, the laser beam is deflected by the AOD in the direction of, for example, the arrow C with respect to the raster scan track (path of raster scan) B. The direction of arrow C is the deflection direction by the AOD. An angle 9 is an angle formed by a line segment in the direction of the arrow C with respect to the +x-direction. In the example illustrated in FIG. 3, the direction inclined by the angle 9 from the +x-direction to the +y-direction is the deflection direction of the AOD.

[0027] Marking of 4 x 5 Pixel ImageA specific marking method and an embodiment in which the time required for marking is shortened will be described with reference to the simple image pattern illustrated in FIGS. 4A to 4D. The marking is assumed to be performed on a 4 x 5 pixels image as illustrated in FIG. 4A. Although the image size is small, such as 4 x 5 pixels, for simplicity, the actual image size may be, for example, several hundred pixels x several hundred pixels or larger.

[0028] For convenience, the region HO in FIG. 4B is set to the coordinate (1, 1), the x-coordinate of the (m - l)-th column in the +x-direction from the region HO is set to m, the y-coordinate of the (n - l)-th row in the +y-direction is set to n, and the coordinate of (x, y) = (m, n) is simply described as (m, n). The pixels filled with gray are marking pixels (irradiation regions). The pixels filled with white are non-marking pixels (non-irradiation regions).

[0029] Typical MarkingFIG. 4B is a diagram illustrating the relation between the scan track of the laser beam and the laser irradiation position in a typical raster scan as a comparative example. The main scanning direction of the galvano scanner 30 is the y-direction, and the sub-scanning direction is the x-direction, and the scanning direction is a direction from the -x-direction to the +x- direction.

[0030] The main scan indicates scan in the column direction (±y -direction), and the sub-scan indicates movement to the following column. In a typical raster scan, all the main scan columns including at least one marking pixel are scanned. Thus, as illustrated in FIG. 4B, the marking of the marking pixel is completed by four main scans.

[0031] For simplicity, the laser light source is a pulsed laser unless otherwise specified in the following description. One pixel is marked by one pulse irradiation.

[0032] The laser irradiation pitch calculated from the galvano main scan speed and the laser repetition frequency (i.e., pitch [meter (m)] = galvano main scan speed [m / second (s)] / repetition frequency [1 / s]) is assumed to coincide with the pixel size. However, when multiple pulse irradiations are required for marking one pixel, when the light source is not a pulse laser, or even when the laser irradiation pitch and the pixel size do not coincide with each other, an embodiment of the present disclosure has the same effect.

[0033] Marking in Present EmbodimentFIG. 4C is a marking method by the laser irradiator illustrated in FIG. 2. In FIG. 4C, "the scan track of the laser beam by the galvano scanner (raster scan path by the downstream deflector)", indicates a scan track of the laser beam generated by raster scan of the galvano scanner 30 when the deflection angle of the AOD 20 is maintained at a certain reference value.

[0034] The deflection direction of the laser beam by the AOD 20 is a direction of 9 = 0 (+x- direction). The x- and y-coordinates of the scan track of the laser beam by the galvano scanner 30 at a certain time are represented by xO and yO, respectively.

[0035] The amounts of deviation of the x- and y-coordinates of the laser beam due to the deflection position control of the AOD 20 are represented by Ax and Ay (in pixel unit) as relative values from xO and yO, respectively. For example, when xO = 2 and Ax = 1, the x-coordinate of the irradiation position of the laser beam is 3. The maximum value and the minimum value of Ax are represented by Ax max and Ax min, respectively, and the maximum value and the minimum value of Ay are represented by Ay_max and Ay_min, respectively.

[0036] The scan range of the AOD 20 on the marking object 50 (on the marking surface) is determined by the scan angle of view of the AOD 20 and the f9 lens 40. The ranges of Ax and Ay are determined from the relation between the scan range of the AOD 20 and the pixel size.

[0037] For example, in an embodiment of the present disclosure, the focal length of the f9 lens is 200 millimeters (mm), the scan angle of view (range of deflection angle to be modulated) of the AOD 20 is 2 milliradian (mrad), and the pixel size is 200 pm x 200 pm. In this case, the scan range is 200 mm x 2 mrad = 400 pm.

[0038] Since 9 = 0, Ax_max - Ax_min and Ay_max - Ay_min are Ax_max - Ax_min = 400 pm x cos (9) / 200 pm = 2 and Ay_max - Ay_min = 400 pm x sin (9) / 200 pm = 0, respectively. Further, Ay / Ax = tan (9).

[0039] The scan track of the laser beam by the galvano scanner 30 is the scan track when Ax is minimized (i.e., Ax_min = 0), and the pixel size is 200 pm x 200 pm. In this case, Ax can take a range of 0 < Ax < 2.

[0040] The settings of xO, yO, and Ay in the marking method illustrated in FIG. 4C is listed in Table 1.

[0041] Table 1

[0042] In the first column of the main scan, the column of x = 1 is scanned with the laser beam as in FIG. 4B. The (1, 3) pixel is not the marking pixel but the non-marking pixel (non-irradiation target region), and the (2, 3) pixel is the unmarking pixel that has not been marked yet (yet-to- be irradiated region). Thus, when the scan track of the laser beam by the raster scan is (xO, yO) = (1, 3), the deflection position of the AOD 20 is controlled as Ax = 1, and the laser beam,which is turned off in the typical method, is turned on to irradiate the position of the pixel (2, 3) (unirradiated region) with the laser beam.

[0043] At (xO, yO) = (1, 4), since the (1, 4) pixel is a marking pixel, the (1, 4) pixel is irradiated with the laser beam as Ax = 0 by controlling the deflection position of the AOD 20. Similarly, at (xO, yO) = (1, 5), the deflection position of the AOD 20 is controlled as Ax = 1, and the laser beam, which is typically turned off, is turned on to irradiate the (2, 5) pixel (unirradiated region) with the laser beam.

[0044] Thus, the first main scan is completed, and the marking for two columns of x = 1 and 2 is completed. Further, for example, a column of xO = 3 is selected as the second main scan column, and Ax is set as Ax = 1, 1, 0, 0, and 1 for the positions of the scan track by the galvano scanner of (xO, yO) = (3, 5), (3, 4), (3, 3), (3, 2), and (3, 1), respectively.

[0045] In such a way, the marking of the marking image illustrated in FIG. 4A can be completed by two main scans, instead of four main scans in the typical method. The reason why the number of main scans can be reduced (i.e., high-speed marking) is that the laser irradiation position can be modulated for each pixel by a high-speed deflection scanning device such as the AOD 20, and marking can be performed during a time when the laser beam is turned off and marking is not performed in the typical raster scan.

[0046] In other words, since the galvano scanner 30 is combined with the AOD 20, the marking can be performed by the instantaneous deflective scan by the AOD 20 even at a timing when marking cannot be performed in the marking by the typical raster scan using only the galvano scanner 30. The present embodiment is particularly effective when a relatively sparse image pattern such as a character (having a large margin for use of laser output) is drawn in a short time by high-speed marking using raster scan.

[0047] In FIG. 4C, the column of xO = 3 in the second main scan is set. In addition, for example, as illustrated in FIG. 4D, the column of xO = 2 can be set in the scan.

[0048] The settings of xO, yO, and Ay in the marking method of FIG. 4D is listed in Table 2.

[0049] Table 2

[0050] In FIG. 4D, the main scan of the second column is set to x = 2, which is different from FIG. 4C. In other words, Ax is set as Ax = 2, 2, 1, 1, and 2 for the scan track positions of the galvano scanner 30 of (xO, yO) = (2, 5), (2, 4), (2, 3), (2, 2), and (2, 1), respectively. The same effect can be obtained by scanning as illustrated in FIG. 4D.

[0051] As illustrated in FIG. 4D, the deflection position of the laser beam by the AOD 20 as the first deflector is changed at the p-th raster scan and the (p + q)-th raster scan, where p and q are any integers, at predetermined coordinates in the raster scan direction between the p-th raster scan and the (p + q)-th raster scan. In other words, in FIG. 4D, for example, Ax = 1 when (xO, yO) = (1, 5), and Ax = 2 when (xO, yO) = (2, 5).

[0052] There are various marking methods that can achieve the same effect (high-speed marking). However, depending on the condition of the 1'0 lens 40, when there is a restriction of Ax < 1, the marking cannot be performed as in FIG. 4D. Thus, the marking method illustrated in FIG. 4C is preferable.

[0053] FIG. 5A is a diagram illustrating a configuration of a laser irradiator as viewed from the -y- direction to +y-direction, according to a first embodiment. FIG. 5B is a diagram illustrating the configuration of the laser irradiator as viewed from the +x-direction to -x-direction, according to the first embodiment. In the following description, the differences from the laser irradiator 200 illustrated in FIG. 1 will be mainly described.

[0054] As illustrated in FIGS. 5A and 5B, the laser irradiator 100 includes a laser oscillator 10 as a laser light source, a first acousto-optic deflector (AOD) 21 (first upstream deflector) as an upstream deflector, a second acousto-optic deflector (AOD) 22 (second upstream deflector) as another upstream deflector, half-wave plates 23 and 24, a galvano scanner 30 as a downstream deflector, and an f9 lens 40. The direction of the laser beam emission is adirection from the laser oscillator 10 to the marking object 50. In other words, the direction from the left to the right in FIGS. 5 A and 5B is the direction from the upstream side to the downstream side of the laser irradiation direction. The first AOD 21 and the second AOD 22 are disposed on the upstream side of the galvano scanner 30.

[0055] The marking object 50 that is an irradiation object according to the present embodiment is an object made of resin, such as a polyethylene terephthalate (PET) bottle. The laser irradiator 100 irradiates the surface of the resin with the laser beam so that the surface is processed so as to have a recess, and an image such as a character is formed on the surface of the resin. However, the object to be irradiated with the laser beam, according to the present disclosure, is not limited to this, and the object of laser beam irradiation is not limited to the formation of an image.

[0056] In the present embodiment, the first-order diffraction light beam D 1 diffracted by the first AOD 21 or the first-order diffraction light beam diffracted by the second AOD 22 is deflected by the galvano scanner 30 and goes in the f9 lens 40, and the marking object 50 is irradiated with the first-order diffraction light beam DI or the first-order diffraction light beam D2. The first AOD 21 and the second AOD 22 are not turned on (ON state) at the same time. In other words, the first AOD 21 and the second AOD 22 do not deflect the same laser beam, and the laser beam passes without being deflected by at least one of the first AOD 21 or the second AOD 22. However, there may be the case where the laser beam passes both the first AOD 21 and the second AOD 22.

[0057] The half-wave plates 23 and 24 are disposed on the upstream side of the first AOD 21 or the second AOD 22, respectively, and are used to align the polarization direction of the first AOD 21 or the second AOD 22.

[0058] The first AOD 21 and the second AOD 22 are disposed such that the deflection direction of the incident light beam deflected (diffracted) by the first AOD 21 and the deflection direction of the incident light beam deflected (diffracted) by the second AOD 22 are different from each other. Accordingly, the laser beam can be deflected in different directions whether the AOD 21 or the AOD 22 is turned on.

[0059] FIG. 6A is a diagram illustrating an example of a setting of the first AOD 21. FIG. 6B is a diagram illustrating an example of a setting of the second AOD 22. FIG. 6C is a diagram illustrating a deflectable region in the positions of the settings in FIGS. 6A and 6B.

[0060] As illustrated in FIG. 6A, the first AOD 21 is disposed so as to be inclined from the -Redirection to the -y-direction (the counterclockwise direction in FIG. 6A) by the angle 91 illustrated in FIG. 6A. Since the clockwise direction is the positive direction of the angle 9,the angle 9 1 is a negative value. As illustrated in FIG. 6B, the second AOD 22 is disposed so as to be inclined from the +x-direction to the +y-direction (the clockwise direction in FIG.6B) by the angle 92. These AODs deflect the incident laser beam in the same direction even on the mirror surface.

[0061] As illustrated in FIG. 6C, the region Fl deflectable by the first AOD 21 is a region in a direction inclined by an angle 91 from the irradiation position E of the zero-order light beam (a region in a direction inclined by an absolute value of the angle 91 in the counterclockwise direction), and the region F2 deflectable by the second AOD 22 is a region in a direction inclined by an angle 92 in the counterclockwise direction from the irradiation position E of the zero-order light beam. As described above, two AODs are disposed in this way so that the deflectable regions can be provided in two directions. As a result, the number of directions is increased as compared with the case where one AOD is disposed.

[0062] Since the AOD modulates the deflection direction by modulating the diffraction angle of the diffracted light beam, the AOD cannot deflect the region below the minimum diffraction angle of the first-order diffraction light beam. Specifically, the deflection cannot be performed in the range from the irradiation position E of the zero-order light beam to the distance LI illustrated in FIG. 6C. The width deflectable by the first AOD 21 is represented by the distance L2. Although the case where the 0 order light beam is deflected in the +x- direction is described in FIGS. 6A to 6C, the zero-order light beam may be deflected in -x- direction. The relation between the positions of the AODs and the deflectable regions on the image plane is an example, and the relation also changes depending on the configuration of the optical system disposed in the middle of the optical system, such as an optical system that rotates the image plane.

[0063] An example of a marking method (laser irradiation method) using the laser irradiator according to the present embodiment will be described in FIGS. 7A to 7C. FIG. 7A is a diagram illustrating an image pattern to be marked. FIG. 7B is a diagram illustrating an irradiation region that the laser irradiator can irradiate with a zero-order light beam. FIG. 7C is a diagram illustrating an example of a laser marking method using the laser irradiator according to the first embodiment. The black dot in FIG. 7B indicates the case where the position of the black dot is irradiated with the laser beam (i.e., the case where Ax and Ay = 9), and the same applies to FIG. 8B.

[0064] The case where an image of 7 pixels x 18 pixels illustrated in FIG. 7A is marked will be described. The entire region of the 7 pixels x 18 pixels arranged in a grid pattern includes the entire scanning region to be scanned by the laser irradiator of the present embodiment. Each pixel included in the entire scanning region is also referred to as a "scanning target region". Each pixel (scanning target region) includes a marking pixel (irradiation target region) that isirradiated with the laser beam and a non-marking pixel (non-irradiated region) that is not irradiated with the laser beam. In other words, the pixels filled with light gray in FIG. 7A are the particularly unmarked pixels of the marking pixels (particularly yet-to-be irradiated regions of the irradiation target region). The pixels filled with white are non-marking pixels (non-irradiation regions). The pixels filled in gray in FIG. 7C are marked pixels of the marking pixels (in particular, irradiated regions of the irradiation target region). In FIGS. 7 A to 7C, the angle 91 formed by the deflection direction of the first AOD 21 with respect to the +x-direction is -45 degrees, the angle 92 formed by the deflection direction of the second AOD 22 with respect to the +x-direction is 45 degrees, the focal length of the f9 lens 49 is 150 millimeters (mm), the angle range in which the first AOD 21 and the second AOD 22 can be diffracted is from 2 milliradians (mrad) to 4 mrad, and the pixel size is 106 micrometers (pm) x 106 pm. At this time, in FIG. 7B, the regions Fl and F2 in which the first AOD 21 and the second AOD 22 can be irradiated with the zero-order light beam with respect to the irradiation position E on the image plane is illustrated The deflectable range of the first AOD 21 and the second AOD 22 is 150 pm x 2 mrad = 300 pm, and the range that Ax can take is 0 < Ax < 2.

[0065] When the left end position at which the first AOD can deflect the laser beam is a point G (xO, yO), the number of pixels that can be irradiated with the laser beam is seven, i.e., (xO, yO), (xO + 1, yO - 1), (xO + 2, yO - 2), (xO, yO + 4), (xO + 1, yO + 5), (xO + 1, yO + 6), and (xO - 2, xO + 2), by selecting the case where only the first AOD 21 is turned ON (the first AOD 21 is turned ON and the second AOD 22 is turned OFF), the case where only the second AOD 22 is turned ON (the first AOD 21 is turned OFF and the second AOD 22 is turned ON), and both the first AOD 21 and the second AOD 22 are turned OFF. In the present embodiment, the point G is set as the reference deflection position by the first AOD 21. The reference deflection position is a point where Ax = Ay = 9. The phrase "the AOD is turned ON" indicates that the AOD deflects the laser beam and the phrase “the AOD is turned OFF" indicates that the AOD deflects the laser beam.

[0066] In FIG. 7C, the marking in the case where the main scan is performed in the column of xO = 1 is illustrated. In FIG. 7C, the cross mark of the laser irradiation position is omitted for convenience. The settings of xO, yO, Ax, Ay, x, and y in the this case are listed in Table 3. In the present embodiment, the path of raster scan by the galvano scanner passes through the center of the pixel, but the present disclosure is not limited to this.

[0067] Table 3

[0068] In the laser irradiator according to the present embodiment, all the marking pixels of the three columns of x = 1 to 3 could be marked by the main scan in the range of l < y < 16 at x = l. This is because either the first AOD 21 or the second AOD 22 deflects the zero-order light beam to irradiate unirradiated regions with the laser beam when the raster scan passes through the non-irradiated region. For example, the laser beam moving in the region of (x, y) = (1, 1) on the raster scan by the deflection using the galvano scanner is deflected by the second AOD 22 with Ax = 2 and Ay = 6 so that unirradiated region (x, y) = (3, 7) can be irradiated with the laser beam. The "position (region) on the raster scan" indicates a position through which the laser beam passes at the time of setting Ax = 0 and Ay = 0, and does not indicate all points on the raster scan track. In other words, the zero-order light beam is deflected to the point G that is the reference deflection position by the first AOD 21, and the point G is a point through which the laser beam passes when the second AOD 22 is turned off. However, the reference deflection position is not limited to the point G.

[0069] As a comparative example, the case where the image pattern illustrated in FIG. 7A is marked using the laser irradiator illustrated FIG. 1 will be described with reference to FIGS. 8 A and 8B. FIG. 8A is a diagram illustrating an irradiation region that the laser irradiator illustrated in FIG. 1 can irradiate with a zero-order light beam. FIG. 8B is a diagram illustrating an example of a laser marking method.

[0070] In the laser irradiator 200 illustrated in FIG. 1, since only one AOD 20 is disposed in the configuration, the deflectable region is the region F3 only as illustrated in FIG. 8A.

[0071] In FIG. 8B, the marking in the case where the main scan is performed in the column of xO = 1 is illustrated. In FIG. 8B, the cross mark of the laser irradiation position is omitted for convenience. The settings of xO, yO, Ax, Ay, x, and y in the this case are listed in Table 4. The symbol in the columns of x and y in Table 4 indicates that there is no pixel that can be marked.

[0072] Table 4

[0073] As illustrated in FIG. 8B, in the main scan of the column of xO = 1 by the laser irradiator illustrated in FIG. 1, all the marking pixels of x = 1 to 3 cannot be irradiated with the laser beam, and the marking pixel Hl remains as an unirradiated pixel. Thus, in the example illustrated in FIG. 7C, the column of xO = 4 can be selected as the second column. However, in FIG. 8B, the column of xO = 3 in which only one unirradiated pixel remains needs to be selected as the second column. As a result, a difference in efficiency occurs also in the marking of the second column. As compared with the laser irradiator illustrated in FIGS. 5 A and 5B according to the present embodiment, the difference in efficiency is caused by the fact that the number of choices of the deflectable region is small because only one AOD is used.

[0074] As described above, in the laser irradiator according to the present embodiment, the laser beam is deflected by the AOD from the path on the raster scan so that the irradiation target region disposed in the irradiation object can be efficiently irradiated with the laser beam. In particular, in the present embodiment, since multiple AODs of the upstream deflectors are disposed, the number of choices of deflectable positions can be increased as compared with the case where one upstream deflector is used as in the laser irradiator 200 illustrated in FIG. 1. As a result, as described in the comparison between FIGS. 7C and 8B, the laser irradiation can be efficiently performed on the irradiation target region to be irradiated with the laser beam. In particular, in the case of FIG. 8A in which only one direction is deflectable, the pixels arranged in the deflection direction within the scan in the same main scan column cannot be irradiated with the laser beam, and it becomes difficult to irradiate the pixels arranged in the deflection direction with the laser beam. However, in the present embodiment, multiple upstream deflectors deflects the laser beam in multiple deflection directions, pixels arranged in the same direction as one deflection direction by one upstream deflector can be irradiated with the laser beam deflected by another upstream deflector in a different direction.

[0075] Specifically, the irradiation efficiency of the laser beam in the case of FIG. 7C is compared with that in the case of FIG. 8B When the pulse period of the laser is r [s], 14 pixels are irradiated with the laser during 18 r in the case of FIG. 8B, but 15 pixels are irradiated with the laser during 16 r in the case of FIG. 7C. Thus, the irradiation efficiency of the present embodiment is superior by about 16%. In FIG. 7C, since a small pixel is used for convenience, the laser beam cannot be deflected at the position of y = 17, and 18, and the unirradiated regions of the irradiation target region cannot be irradiated with the laser beam. However, when there are pixels after y = 19, the laser beam may be deflected at the position of y = 17 and 18, and the unirradiated region may be irradiated with the laser beam. In such a large image, the number of pixels are increased in, for example, the x-direction, and the unirradiated region increases, so that the difference in irradiation efficiency between the present embodiment and the laser irradiator illustrated FIG. 1 becomes large. In addition, in consideration of the irradiation efficiency of the second column and following columns, the irradiation efficiency of the present embodiment is more increased.

[0076] As a method different from the present embodiment, the first AOD 21 and the second AOD 22 may be simultaneously used to form the deflectable region as a two-dimensional region. However, in this case, while the number of choices of the deflectable positions increases, there is an adverse effect of a decrease in diffraction efficiency. In other words, when the diffraction efficiency by AOD is about 80%, the energy amount of the first diffraction light beam of the present embodiment is 80% of the energy amount of the zero-order light beam. However, when two AODs are used simultaneously, the energy amount is reduced to 64% of the energy amount of the zero-order light beam. Accordingly, problems that sufficient laserirradiation cannot be performed on the irradiation object, and that the cost of the laser irradiator increases in order to perform sufficient laser irradiation. As described above, in the laser irradiator according to the present embodiment, both the irradiation of the laser beam with high efficiency to the irradiation object and the obtaining of the energy amount of the laser beam can be achieved.

[0077] When the deflection is performed only in the +x-direction, the x-coordinate of the main scan column for raster scan is set to the minimum x-coordinate in the unirradiated region of the image of the irradiation object. For example, the second column in FIG. 8B is at the position of x = 3. However, this is not limited to the case where the deflection can be performed in the -x-direction, and the x-coordinate of the main scan column for raster scan may be determined so that the x-coordinate can be changed to the minimum x-coordinate in the unirradiated region of the image of the object to be irradiated.

[0078] In the deflection position control of the AOD, there is a limitation on the response time due to the response characteristics (such as the relation between the sound velocity and the beam diameter) of the AOD element and the electrical characteristics of the control unit. When the pulse turning-on interval (the reciprocal of the repetition frequency) of the laser beam is T [s] and the time required for the deflection position control of the AOD is r [s], and if T > r, the deflection position can be controlled independently for each laser pulse. In other words, since Ax and Ay can be set independently for each laser irradiation, the degree of freedom is high, and the effect of speeding up marking is large. The time required for the deflection position control of the AOD is the time from when a certain region is irradiated with the laser beam to when the deflection position is changed to the deflection position adjusted to the next region (i.e., the deflection positions are changed to Ax and Ay adjusted to the next region).

[0079] When T < r, the time required for the deflection position control is longer than the pulse turning-on interval. Thus, the pulse is discarded at the time of deflection position control. In other words, the pulse is not turned on at a timing when the pulse can be turned on. In this case, the effect of high-speed marking may be obtained by controlling the number of deflection position change as small as possible.

[0080] The directions of deflection of the first AOD 21 and the second AOD 22 can be changed by changing the angles of installation of the first AOD 21 and the second AOD 22. It is preferable that the deflection direction is set to an angle at which an image can be efficiently formed in accordance with the irradiation pattern of the irradiation object. For example, in an irradiation pattern of an irradiation object on an x-y coordinate plane, when an angle formed between a line segment having a maximum length and a line segment parallel to the -Redirection is 9', it is preferable to set the deflection directions of the first AOD 21 and the second AOD 22 so that angles 91 and 92 are different from angles 9' and -9'. As describedabove, since it is most difficult to deflect the laser beam to the line segment in the same direction as the deflection direction, the irradiation target region can be efficiently irradiated with the laser beam by this setting. For example, in the example of FIG. 7A, since the line segment having the maximum length is a line segment parallel to the x-direction, it is preferable that the angles 91 and 92 are set to values different from 9 or 189 degrees.

[0081] The relation between the deflection position by the AOD and the pixel position will be described with reference to FIGS. 9A and 9B. FIG. 9A is a diagram illustrating a relation between a deflection direction by a first AOD and a pixel size. FIG. 9B is a diagram illustrating a relation between deflection directions by the first AOD and a second AOD, and a pixel size. The pixel size indicates the width in the x-direction and the width in the y- direction of one pixel (scanning target region) on the x-y coordinates on the irradiation object.

[0082] As in the example illustrated FIGS. 7A to 7C, the focal length of the f9 lens was 150 mm, and the angle range in which the first AOD and the second AOD can diffract the light beam was 2 mrad to 4 mrad. As illustrated in FIG. 9A, when the width of the pixel in the x-direction is Dx and the width of the pixel in the y-direction is Dy, the deflection direction of the first AOD can be set to pass through the center of the pixel by satisfying the following expression (2). For example, when the pixel has a square shape, in other words, when Dy / Dx = 1, the following expression (2) can be satisfied by setting 91 to ±45° or ±135°. In FIG. 9A, Dx = 100 pm, Dy = 50 pm, and 91 = ±arctan (50 / 100) = -0.464 radians (rad), so that the deflection direction by the first AOD can pass through the center of the pixel as illustrated in FIG. 9A. 91 = ±arctan (Dy / Dx) (2)

[0083] Further, as in FIG. 6C, the angle 92 formed by the deflection direction of the second AOD with respect to the +x-direction is set to be 0.464 rad, and the deflection direction is changed (i.e., positive or negative sign (±) is inverted) while the absolute value of the angle is the same so that the deflection directions of the first AOD and the second AOD are directed to a direction symmetrical with respect to the zero-order irradiation position E (a line segment in the x-direction passing through the zero-order irradiation position E).

[0084] At this time, as illustrated in FIG. 9B, the length 6 from the left end point G of the deflectable region Fl of the first AOD to the left end point F2A of the deflectable region F2 of the second AOD is 300 pm x sin (0.464 rad) x 2 = 269 pm, which is not an integer multiple of Dy. Thus, at least one of the points G or F2A is deviated from the center of the pixel.

[0085] As a countermeasure against the pixel deviation, there is a method of allowing the deviation of the irradiation position from the center of the pixel. As another method, there is a method of selecting, as the deflection position, not the leftmost points G and F2A but a position on the right side of the leftmost points G and F2A at which the distance 6 is an integer multiple ofDy. In this case, since a part of the left side of the deflection region cannot be set as the deflection position, the number of positions that can be changed may be reduced depending on the relation between the deflectable distance L2 and the pixel size. Still another method is to change the pixel size. In the above example, when Dx = 107.6 pm and Dy = 53.8 pm, 6 can be exactly five pixels. In addition, there is a method of selecting the x-coordinate of the laser beam irradiation position so that the y-coordinate distance between the deflectable region of the first AOD and the deflectable region of the second AOD is an integer multiple of Dy or a value close to this.

[0086] FIGS. 10A to 10D are diagrams illustrating directions of laser beams deflected and passing through centers of pixels having different pixel sizes. FIG. 11 is a diagram illustrating a deviation from the pixel center due to a deflection direction of an acousto-optic deflector. In FIG. 11, the arrow represented by the dotted line indicates the direction of deflection of the AOD. The same applies to the following drawings after FIG. 12.

[0087] Specifically, when the point G is (m, n) = (0,0), in each of the FIGS. 10A to 10D, the angle 0 (i.e., the direction of deflection of the AOD) is set so as to pass through (m, n) = (1, 1), (2, 1), (1, 2), (2, 3). Specifically, the angle 9 formed by the deflection direction of the AOD with respect to the sub-scanning direction of the galvano scanner is set so as to satisfy the following expression (3). Accordingly, the laser beam can be deflected from the point G on the track of the raster scan by the galvano scanner to the pixel center of each of the positions (m, n). n and m are integers.9 = ±arctan (n x Dy / m x Dx) (3)

[0088] As a method of adjusting the deflection angle 9, in addition to the method that rotates the AOD deflection direction around the z-axis as illustrated in FIGS. 5 A and 5B, a method that rotates the galvano scanner 30 around the z-axis, or a method that rotates the scan direction of the galvano scanner 30 without changing the optical system can be used. Since an incident light beam that goes in the AOD has a predetermined polarization direction with respect to the AOD, when the AOD is rotated, the polarization of the incident light beam is also rotated depending on the rotation of the AOD using, for example, a half-wave plate.

[0089] For example, when 91 = -arctan (Dy / (3 Dx)), and the laser beam position is deflected from the pixel (xO, yO) to the center of another pixel, the laser beam can be deflected only to the pixel represented by (xO + 3k, yO + k), where k is an integer. However, this limitation can be relaxed by allowing the deviation of the marking position. In other words, as illustrated in FIG. 11, the laser beam can be deflected to the point G and point F3 only by allowing the positional deviation, but the laser beam at the pixel (xO, yO) can be deflected also to the pixels represented by (x0 + 3k - 2, y0 + k - 1) and (x0 + 3k - 1, y0 + k), where k is an integer, by allowing the deviation of the irradiation position of Dy / 3 in the y-direction, where Dy is thepixel size in the y-direction. Thus, the deflection can be performed also to the points F3A and F3B.

[0090] FIG. 12 is a diagram illustrating the case where both a deviation from the pixel center due to the deflection direction of the AOD and a deviation from the image center due to the distance between the two deflection directions of the first AOD and the second AOD occur.

[0091] As illustrated in FIG. 12, there is the case where both the deviation from the pixel center due to the deflection direction of the AOD described in FIG. 11 and the distance 6 between the two deflection directions of the first AOD and the second AOD described in FIG. 9B occur. The overlapping of these two deviations may result in the deflection position being located at the center of the pixel. For example, in FIG. 12, 91 = -arctan (Dy / (3Dx)), 92 = arctan (Dy / (3Dx)), 6 = 5Dy / 3, and the point G at Ax = 9 and Ay = 9 is arranged at the center of the pixel. In this case, for example, in the deflection direction of the first AOD, the second point F3A from the left is shifted from the center of the pixel by Dy / 3 toward the upper side in FIG. 12, and in the deflection direction of the second AOD, the second point F4B from the left is disposed at the center of the pixel. This is because the deflection direction of the second AOD is shifted by 2Dy / 3 in the vertical direction of FIG. 12 with respect to the deflection direction of the first AOD with respect to the pixel center by 6 = 5Dy / 3. In the deflection direction of the first AOD, the first, fourth, seventh,, points from the left are arranged at the center of the pixel, while in the second AOD, the second, fifth, eighth,, points from the left are arranged at the center of the pixel.

[0092] The case where the laser irradiation pitch calculated from the galvano main scan speed and the repetition frequency is equal to the pixel size, i.e., the case where the number of laser irradiation is once while the galvano scan track passes through one pixel (and one pixel can be marked with one pulse) has been described above, but the other cases will also be described.

[0093] FIG. 13 is a diagram illustrating multiple times of laser beam irradiation at a time of an acceleration-or-deceleration region. In FIG. 13, only the first AOD is used as an example, and the case where the angle 9 between the deflection direction of the first AOD and the +x- direction is 0 is illustrated.

[0094] The galvano scanner 30 is accelerated to increase the main scan speed sufficiently. As illustrated in FIG. 13, the length required for acceleration or deceleration of the main scan speed is represented by A, the main scan length is represented by L, and the length of the marking image in the main scan direction is represented by Y. At this time, in the case of L - 2A < Y, i.e., in the case where the length of the region in which a sufficient main scan speed can be obtained is shorter than the total length of the image, the galvano scanner cannot generate a sufficient speed at the end portion of the image region in the main scan direction.Thus, there may be the case where twice or more of laser beam irradiation can be performed while the galvano scan track passes through one pixel in this region. For example, while the galvano scan track passes through the pixels (non-irradiation regions) of (xO, yO) = (1,1) in FIG. 13, two pixels of (5, 1) and (6, 1) are marked. Similarly, in the pixel of (xO, yO) = (1, 18) (irradiation region), two pixels of the pixel (1, 18) and the pixel (2, 18) are marked. Since the irradiation timings for the two pixels are different from each other, the irradiation positions are shifted in the main scan direction.

[0095] In the description above, although twice irradiation is described in the example for simplicity, the number of irradiation may be more than two. The number of pixel (xO, yO) that can be irradiated with the laser beam multiple times also varies in relation to the acceleration or deceleration length and the pixel size. In FIG. 13, L is greater than Y (i.e., L > Y), but L may be equal to or smaller than Y (i.e., L < Y). Multiple AODs are disposed so that the drawable range in the main scan direction can be larger than the main scan length. Thus, the entire image region can be drawn with L < Y. Although an example in which the pixels at the end in the main scan direction are drawn in the acceleration or deceleration region A is described in FIG. 13, the pixels at the other end by setting 9 to an angle other than 0 or by using the second AOD in this region can be drawn.

[0096] Alternatively, for example, the laser irradiation pitch calculated from the galvano main scan speed and the repetition frequency is set to one half of the pixel size. Accordingly, a method of marking two pixels while the galvano scan track passes through one pixel as illustrated in FIG. 14 can be also used. In FIG. 14, 9 = -arctan (Dy / 2Dx). In FIG. 14, the solid arrow represents the scan track of the laser beam by the galvano scanner 30, and the dotted arrows represent the deflection by the AOD, and the crosses represent the laser irradiation positions.

[0097] Although the laser irradiation pitch is set to be half of the pixel size as an example, the laser irradiation pitch may be smaller than half of the pixel size. In such a case, two or more pixels can be marked while the galvano scan track passes through one pixel. When the number of pulses that can be emitted while the galvano scan track passes through one pixel is m, if 9 = arctan (n x Dy / (m x Dx)), the number of pulses deflectable to the center of the pixel is large, which is preferable. Although FIG. 14 is a diagram illustrating the case where only the first AOD is used for simplicity, other AODs may be used.

[0098] The configurations of FIGS. 13 and 14 may be combined. For example, in the laser irradiator that can irradiate the pixels with the laser beam multiple times (e.g., twice in FIG. 14) while the galvano scan track passes through one pixel as illustrated in FIG. 14, the laser irradiator may have a configuration that can irradiate the pixels with the laser beam more frequent times (three times or more) in a section in which the main scan speed of the galvano scanner isaccelerated or decelerated as illustrated in FIG. 13 than times (twice) in a section in which the main scan speed of the galvano scanner is constant.

[0099] FIG. 15 is a block diagram illustrating a control unit of a laser irradiator.

[0100] As illustrated in FIG. 15, the control unit 150 of the laser irradiator includes an image pattern data input unit 151, a storage unit 152, a processing data generation unit 153, a laser irradiation control unit 154, and a first laser scanning control unit 157, and a second laser scanning control unit 158.

[0101] The processing data generation unit 153 generates processing data based on the image pattern data input to the image pattern data input unit 151. The processing data is input to the laser irradiation control unit 154, the first laser scanning control unit 157, and the second laser scanning control unit 158. The light intensity control unit 155 and the pulse control unit 156 in the laser irradiation control unit 154 determine the intensity of the laser beam to be irradiated, the pulse interval, and the like based on the processing data, and cause the laser oscillator 10 to irradiate the laser beam. The first laser scanning control unit 157 controls the ON-and-OFF state of the first AOD 21 and the second AOD 22 based on the processing data. The second laser scanning control unit 158 controls the galvano scanner 30 based on the processing data.

[0102] FIG. 16B is a timing chart of the control of a first AOD to an example of the marking illustrated in FIG. 16A. In FIGS. 16A and 16B, an example of the control using only the first AOD is illustrated for convenience. The correspondence between the value of aod_data and the deviation Ax due to deflection is as listed in Table 5 below.

[0103] Table 5

[0104] As illustrated in FIGS. 16A and 16B, the aod > data signal is a frequency value (4 bits in this case) of the RF signal applied to the AOD element, and the value of the frequency is reflected to the AOD element by the latch signal. The laser beam is turned on at the timing of the laser_pulse signal. The laser beam is deflected in the x-direction by the AOD element at an angle corresponding to the frequency value set at a time when the laser beam is turned on.

[0105] In order to adjust the timing of turning on the laser and the timing of deflection by the AOD, it is preferable to adjust the time between the laser_pulse signal and the latch signal. It is preferable that the latch signal is input prior to timing of turning on the laser in consideration of the latency of the response of the AOD.

[0106] Although an embodiment of the present disclosure has been described above, an embodiment is not limited to the configuration described above. An embodiment of the present disclosure may be modified without departing from the scope or spirit of the disclosure and may be determined appropriately in accordance with applications.

[0107] In the above description, the case where the laser beam is raster-scanned by the galvano scanner (downstream deflector) has been described, but an embodiment of the present disclosure is not limited to this. In other words, in the present disclosure, the laser beam deflected to a position other than the position at which the raster scan is performed by the downstream deflector may be deflected to multiple different positions by multiple upstream deflectors.

[0108] In the above description, the case where the raster scan track of the laser beam by the galvano scanner (downstream deflector) passes through the center position of the scanning target region has been described. In other words, the description has been given of the case where the main scan axis of raster scan coincides with the center axis of each column, where a line connecting the center positions of the pixels (pixels at the same position in the x-direction) in the same column is defined as the center axis of the column. However, the present disclosure is not necessarily limited to this, and the main scan axis of the raster scan may be shifted in the x-direction with respect to the center axis of the column.

[0109] In an embodiment described above, the case where the first-order diffraction light beam by AOD has been described as an example. However, the same effect can be obtained even if the minus first-order diffraction light beam or the second or more order diffraction light beam is used. Further, a combination of light beams having multiple orders can be used. For example, both a zero-order light beam and a first-order diffraction light beam can be combined to use.

[0110] In the above description, the case where the absolute values of the angle 91 and the angle 92 are the same is described, and in particular, in FIG. 6C, the angles 91 and 92 are set so as to be symmetrical with respect to the sub-scanning direction passing through the zero-order light beam E, i.e., so as to pass through the same x-coordinate, but the present disclosure is not limited to this.

[0111] For example, in an embodiment illustrated in FIG. 17, the absolute value of the angle 91 is larger than the absolute value of the angle 92, and the x-coordinate of the deflection direction Fl and the x-coordinate of the deflection direction F2 are also different. However, only the absolute values may be different, or the x-coordinates may be partially the same.

[0112] In the above description, the laser irradiator including only two AODs is described, but the laser irradiator may include three or more AODs. For example, the case where the laser irradiator includes a third AOD as an upstream deflector in addition to the first AOD and the second AOD will be described.

[0113] As illustrated in FIG. 18, the third AOD has a deflection direction different from those of the first AOD and the second AOD, and has an angle 93 = 0 formed by the deflection direction with respect to the +x-direction. Thus, the laser irradiator has a deflectable region F3 in addition to the deflectable regions Fl and F2. Accordingly, the number of choices of the deflectable positions is increased, and the laser irradiator can irradiate the object to be irradiated with the laser beam more efficiently. However, the values of 91, 92, and 93 can be set to any value.

[0114] In an embodiment described above, the case where only one AOD is in the ON state, i.e., multiple AODs are not simultaneously in the ON state, in the laser irradiator is described, but the present disclosure is not limited to this. For example, in an embodiment illustrated in FIG. 19, the first AOD 21 and the second AOD 22 are in the ON state at the same time. Thus, the laser irradiator illustrated in FIG. 19 can deflect the laser beam to a position in the deflection region represented by the arrow F3 and the rectangular deflection region J obtained by combining the arrow Fl and the arrow F2. Accordingly, the number of choices of the deflectable positions is increased, and the laser irradiator can irradiate an irradiation object with the laser beam more efficiently. However, when the position is changed to the inside of the rectangular region J, the energy efficiency of the laser beam is reduced as compared with the case where the laser beam is deflected to the region of the arrow F3. Thus, when the deflection region is changed to the rectangular deflection region J, for example, the irradiation density of the laser pulses may be increased. In particular, as illustrated in FIG. 19, the angles 91 and 92 are set so that the arrows Fl and F2 are perpendicular to each other. As a result, the diffraction efficiency of the laser beam can be increased when the laser beam is deflected to the rectangular region J, which is preferable.

[0115] In the above description, each deflection position is indicated as an arrow from a position on the raster scan for convenience. However, the actual scan truck of the laser beam is different from this, and is set so that the change time of the deflection position by each AOD becomes the shortest. For example, in the first AOD, as illustrated in FIG. 20, the first AOD deflects the zero-order light beam to a point HA at a distance "a" from the irradiation position E at a j-th order, and deflects the zero-order light beam to a point HB at a distance "b" from the irradiation point E at (j + 1 )-th order. The distances "a" and "b" are defined as deflection distances by the first AOD (distances from the point E when the beam is not deflected by the first AOD). In this case, from j-th section to (j + l)-th section, the deflection position of the first AOD is set to be a position between the point HA and the point HB. In other words, the deflection position by the first AOD is set to be a deflection distance between the deflection distance "a" from the point E and the change distance "b" in the deflection direction Fl by the first AOD. Deflection by another AOD may be interposed between the j-th and the (j + 1 )-th. In this case, from j-th section to (j + l)-th section, the deflection position of the first AOD is set to be a position between the point HA and the point HB.

[0116] The laser irradiator according to an embodiment of the present disclosure can be applied to a fabricating apparatus for a three-dimensional article (three-dimensional fabricating apparatus). FIG. 21 is a diagram illustrating a powder bed fusion apparatus 400 as an example of a three- dimensional fabricating apparatus.

[0117] A powder bed fusion apparatus 400 fabricates a three-dimensional article by fusing and bonding a predetermined irradiation region of a powder bed irradiated with the laser beam. The powder bed is formed by multiple powder layers irradiated with the laser beam in order. Specifically, the powder material is spread flat to form a layer. A predetermined position of the layer is irradiated with the laser beam, and the particles contained in the powder material are selectively sintered or melted to bond the particles.

[0118] Accordingly, a single layer is formed as one layer (fabricated layer) of multiple layers formed from the three-dimensional article. In other words, when the three-dimensional article is divided in the thickness direction, one layer is obtained. A powder material is further spread on the fabricated layer formed as described above, and the following fabricated layer is formed by laser beam irradiation.

[0119] This procedure is repeated, and the fabricated layers are stacked. As a result, a three- dimensional fabricated article is produced. The powder material includes a resin material or a metal material, and two or more of these materials may be mixed as appropriate, and an additive may be further added.

[0120] The powder bed fusion apparatus 400 includes a fabricating stage 310, a layer forming unit 320, a preheating unit 330, a thermometer 335, and a laser irradiator 100. The fabricating stage 310 is a stage in which a three-dimensional article is fabricated. The stage support 350 supports the fabricating stage 310 so that the position of the fabricating stage 310 is movable in the vertical direction.

[0121] The fabricating stage 310 is configured to be precisely movable in the vertical direction by the stage support 350. As the stage support 350, various configurations can be applied. For example, the stage support includes a holding unit that holds the fabricating stage 310, a guide that guides the holding unit in the vertical direction, and a ball screw engaged with a screw hole of the guide unit.

[0122] The layer forming unit 320 forms a layer. The layer forming unit 320 includes a powder supply 321 that supplies powder and a recoater 322a that flattens the powder of the fabricating stage 310.

[0123] The layer forming unit 320 has, for example, an edge of an opening through which the fabricating stage 310 rises and falls, an opening having the edge on substantially the same plane in the horizontal direction, and includes a powder material storage extending downward in the vertical direction from the opening. The powder supply 321 includes a supply piston disposed at the bottom of the powder material storage, and the supply piston rises and falls in the opening. The powder supply 321 may include a powder material storage and a nozzle disposed in the upper vertical direction with respect to the fabricating stage, and discharge the powder material on the same plane as the fabricating stage 310 in the horizontal direction.

[0124] The preheating unit 330 pre-heats the layer formed in the layer forming unit 320. The preheating unit 330 may be any unit that can heat at least a region in which the fabricated layer is to be formed on the surface of the layer and maintain the temperature of the region.

[0125] For example, the preheating unit 330 may include a first heater 331a that can heat the surface of the layer formed on the fabricating stage 310, or may further include a second heater 332 that heats the powder material before being supplied onto the fabricating stage. The preheating unit 330 may be configured to selectively heat a region in which a fabricated layer is to be formed, or may be configured to heat the entire inside of the apparatus and adjust the temperature of the surface of the formed layer to a predetermined temperature.

[0126] The first heater 331 includes multiple first heaters 331a, 33 lb, and 331c. The first heater 331a may heat the layer from the top surface, the first heater 33 lb may heat the layer from the side surface, and the first heater 331c may heat the layer from the bottom surface. Further, any combination of the multiple first heaters 331a, 331b, and 331c may be used. However, the surface temperature of the layer is likely to increase in the vicinity of the first heater 331a, 331b, and 331c, and the surface temperature of the layer is less likely to increase as the distance from the first heater 331a, 331b, and 331c increases.

[0127] Thus, in order to prevent temperature unevenness on the surface of the layer and deformation of the fabricated layer due to the temperature unevenness on the surface of the layer, it ispreferable that each of the first heater 331a, the first heater 33 lb, and the first heater 331c includes multiple heaters (i.e., multiple first heaters 331a, multiple first heaters 331b, and multiple first heaters 331c). It is preferable that the multiple first heaters 33 la are disposed so as to be separated from each other, the multiple first heaters 331b are disposed so as to be separated from each other, and the multiple first heater 331c are disposed so as to be separated from each other. At this time, it is preferable that the multiple first heaters 33 la are arranged at equal intervals, the multiple first heaters 331b are arranged at equal intervals, and the multiple first heaters 331c are arranged at equal intervals.

[0128] The thermometer 335 measures the temperature of the layer. The thermometer 335 may be any device that can measure the surface temperature of the region in which the fabricated layer is to be formed in a non-contact manner. For example, an infrared sensor or an optical pyrometer may be used.

[0129] The laser irradiator 100 irradiates the powder bed with the laser beam. The fabricated layer is formed by irradiating with the laser beam. The laser irradiator 100 includes a laser oscillator 10, a first AOD 21, a second AOD 22, half-wave plates 23 and 24, and a galvano scanner 30.

[0130] The laser irradiator 100 may include a laser window 343 through which the laser beam passes. The laser window 343 may be made of any material that allows the laser beam to pass therethrough.

[0131] In the powder bed fusion apparatus 400, if the preliminary temperature heated by the preheating unit 330 is uneven, the rate of change in the volume (specific volume) of the powder irradiated with the laser beam is also uneven, and the accuracy of the three- dimensional fabricated article is lowered. Thus, the temperature is measured by the thermometer 335, and the energy of the laser beam with which the laser irradiator 100 irradiates the power is adjusted based on the measured temperature.

[0132] Specifically, the energy given from the laser beam to the particles as the irradiated portion is increased when the preheating temperature is low, and the energy given from the laser beam to the particles as the irradiated portion is decreased when the preheating temperature is high.

[0133] The laser irradiator 100 controls an irradiation device and a scanner such that when the scanner scans two or more irradiation regions and a non-irradiation region sandwiched between the irradiation regions, the irradiation device and the scanner scan at a constant speed in the irradiation region and change the scan speed in the non-irradiation region. In other words, in order to increase or decrease the energy by laser irradiation, the laser irradiator 100 controls the energy by laser irradiation received by the particles per unit time by changing the scan speed of the laser scan.

[0134] The laser irradiator 100 illustrated in FIG. 21 can control the scanning speed with high accuracy for each irradiation region, and the energy of the laser beam for sintering or dissolving the powder particles can be controlled with high accuracy. As a result, the rate of change in the volume (specific volume) of the resin due to unevenness in the preliminary temperature can be made uniform, and the accuracy of the three-dimensional article due to the unevenness can be prevented from being lowered. According to an embodiment of the present disclosure, the laser output can be effectively used and the productivity can be increased in the raster scan of the laser beam.

[0135] Also, in the laser irradiator 100 disposed in the powder bed fusion apparatus 400, the laser irradiation can be efficiently performed on the irradiation target region of the laser irradiation object by applying the configuration of the embodiment described above.

[0136] Aspects of the present invention are as follows.First AspectA laser irradiator includes multiple upstream deflectors to deflect a laser beam and a downstream deflector disposed at a downstream side of the upstream deflector. The multiple upstream deflectors include at least one of a first upstream deflector and a second upstream deflector to deflect a laser beam deflected by the downstream deflector and irradiate an unirradiated region with the laser beam. The laser irradiator includes at least one of the case where only the first upstream deflector of the first upstream deflector or the second upstream deflector deflects the laser beam or the case where only the second upstream deflector of the first upstream deflector and the second deflector deflects the laser beam.Second AspectIn the laser irradiator according to the first aspect, the upstream deflector to deflect the laser beam at the same timing is one.Third AspectIn the laser irradiator according to the first or second aspect, the upstream deflector deflects the laser beam moving to a non-irradiated region by the downstream deflector at the time when the laser beam is deflected to a reference deflection position by the upstream deflector, to a position different from the reference deflection position to irradiate an unirradiated region separated from the non-irradiation region with the laser beam.Fourth AspectThe laser irradiator according to any one of the first to third aspects includes both the case where only the first upstream deflector deflects the laser beam and the case where only the second upstream deflector deflects the laser beam of the first upstream deflector and the second upstream deflector.Fifth AspectIn the laser irradiator according to any one of the first to fourth aspects, the multiple upstream deflectors perform multiple deflections having different directions.Sixth AspectIn the laser irradiator according to any one of the first to fifth aspects, the upstream deflector includes an acousto-optic element or an electro-optic element.Seventh AspectIn the laser irradiator according to any one of the first to sixth aspects, an interval time from a laser beam irradiation to an certain region to a laser beam deflection to a deflection position corresponding to the following region is equal to or less than a cycle of turning on the laser beam.Eighth AspectIn the laser irradiator according to any one of the first to seventh aspects, the downstream deflector raster- scans a region with the laser beam.Ninth AspectIn the laser irradiator according to the eighth aspect, the sub-scanning direction is the x- direction and the main scanning direction is the y-direction in the raster scan. In multiple scan target regions arranged in a grid shape of the irradiation object, the x-direction is a row of the scanning target region, the y-direction is a column of the scanning target region, and a line connecting the center positions of the x-direction of the scanning target region is the center axis. The main scanning axis of the raster scan by the downstream deflector matches the center axis of any one of the column, and the downstream deflectors deflect the laser beam to a position having a different value in the x-direction from a position on the raster scan at the time of deflectionTenth AspectIn the laser irradiator according to any one of the eighth to ninth aspects, the main scanning direction by the raster scan is the y-direction, the sub-scanning direction by the raster scan is the x-direction, the upstream side of the raster scan is a negative x-direction, and the downstream side of the raster scan is a positive x-direction. Among the irradiation target regions and the unirradiated regions of the irradiation object, the x-coordinate of the main scan column raster-scanned is determined such that a region having the minimum x-value of the main scan column raster-scanned can be irradiated with the laser beam. The region having the minimum value in the xi-direction can be irradiated with the laser beam at the time of raster scan.Eleventh AspectIn the laser irradiator according to the tenth aspect, an x-coordinate of the unirradiated region having the minimum value in the x-direction among the irradiation target regions and the unirradiated regions of the irradiation object is a column to be raster-scanned.Twelfth AspectIn the laser irradiator according to any one of the eighth to eleventh aspects, the main scanning direction by the raster scan is a y-direction, the sub-scanning direction by the rastercan is an x-direction, and in an x-y plane formed by the x-direction and y-direction, the following expression is satisfied, 9 = ±arctan((n x Dy) / (m x Dm)) (1), where 9 is an angle formed by a deflection angle of the upstream deflector with respect to the sub-scanning direction of the downstream deflector, Dx is an interval between adjacent scanning target regions in the x-direction, Dy is an interval between adjacent scanning target regions in the y- direction, and n and m are any integers.Thirteenth AspectIn the laser irradiator according to any one of the eighth and twelfth aspects, in an x-y plane in which the main scanning direction by the raster scan is a y-direction and the sub-scanning direction by the raster scan is an x-direction, an angle 9 is an angle formed by the deflection direction of the downstream deflector with respect to the sub- scanning direction of the downstream deflector. The laser irradiator includes multiple upstream deflectors having the same absolute value of the angle 9 and different directions.Fourteenth AspectIn the laser irradiator according to any one of the eighth and thirteenth aspects, in an x-y plane in which the main scanning direction by the raster scan is a y-direction and the sub-scanning direction by the raster scan is an x-direction, an angle 9 is an angle formed by the deflection direction of the downstream deflector with respect to the sub- scanning direction of the downstream deflector. The angle 9 is determined such that a deflection direction of the upstream deflector is different from a direction of the maximum line section formed in the irradiation target region of the irradiation object.Fifteenth AspectIn the laser irradiator according to any one of the eighth to fourteenth aspects, a j-th deflection distance by a upstream deflector is a distance a, and a (j + 1 )-th deflection distance by the upstream deflector is a distance b. The upstream deflector deflects a laser beam at a distance between the distance a and the distance b with respect to a position on the raster scan in a section in which the laser beam is deflected by the upstream deflector within a section between a j-th deflection position and a (j + l)-th deflection position.Sixteenth AspectThe laser irradiator according to any one of the eighth and fifteenth aspects irradiates regions multiple times with the laser beam while the raster scan by the downstream deflector passes through one scanning target region.Seventeenth AspectIn the laser irradiator according any one of the eighth and sixteenth aspects, in terms of the number of laser irradiation times while the raster scan passes through one scanning target region, the number of laser irradiation times in a section in which the raster scan is accelerated or decelerated is larger than the number of laser irradiation times in a section in which the raster scan is performed at a constant speed.Eighteenth AspectIn the laser irradiator according to any one of the first to seventeenth aspects, an irradiation object is made of resin, and the resin is irradiated with the laser beam to from a recess on the surface of the resin.Nineteenth AspectA fabricating apparatus includes the laser irradiator according to any one of the first to seventeenth aspects to repeatedly irradiate an irradiation region of a powder bed formed by multiple sequential layers of powder layers with a laser beam to fabricate a three-dimensional object.Twentieth AspectIn a laser irradiation method, a upstream deflector deflects a laser beam, and a downstream deflector deflects the laser beam deflected by the first upstream deflector to irradiate an irradiation object with the laser beam. The upstream deflector uses at least one of a first upstream deflector and a second upstream deflector to deflect the laser beam to irradiate an unirradiated region with the laser beam. The laser irradiation method includes at least one of the case where only the first upstream deflector deflects the laser beam of the first upstream deflector and the second upstream deflector or the case where only the second upstream deflector deflects the laser beam of the first upstream deflector and the second upstream deflector.

[0137] The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and / or features of different illustrative embodiments may be combined with each other and / or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above .

[0138] The present invention can be implemented in any convenient form, for example using dedicated hardware, or a mixture of dedicated hardware and software. The present invention may be implemented as computer software implemented by one or more networked processing apparatuses. The processing apparatuses include any suitably programmed apparatuses such as a general purpose computer, a personal digital assistant, a Wireless Application Protocol (WAP) or third-generation (3G)-compliant mobile telephone, and so on. Since the present invention can be implemented as software, each and every aspect of the present invention thus encompasses computer software implementable on a programmable device. The computer software can be provided to the programmable device using any conventional carrier medium (carrier means). The carrier medium includes a transient carrier medium such as an electrical, optical, microwave, acoustic or radio frequency signal carrying the computer code. An example of such a transient medium is a Transmission Control Protocol / Intemet Protocol (TCP / IP) signal carrying computer code over an IP network, such as the Internet. The carrier medium also includes a storage medium for storing processorreadable code such as a floppy disk, a hard disk, a compact disc read-only memory (CD- ROM), a magnetic tape device, or a solid state memory device.

[0139] Each of the functions of the described embodiments may be implemented by one or more processing circuits or circuitry. Processing circuitry includes a programmed processor, as a processor includes circuitry. A processing circuit also includes devices such as an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), and conventional circuit components arranged to perform the recited functions.

[0140] This patent application is based on and claims priority to Japanese Patent Application No. 2024-013002, filed on January 31, 2024, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.[Reference Signs List]

[0141] 10 Laser oscillator (light source)21 First AOD (upstream deflector or first upstream deflector)22 Second AOD (upstream deflector or second upstream deflector)30 Galvano scanner (downstream deflector)50 Marking object (irradiation object) 100 Laser irradiatorB Raster scan track by galvano scannerC Deflection direction of AODG Reference deflection position by the first AOD (reference deflection position by the upstream deflector) x Sub-scanning direction of raster scan y Main scanning direction of raster scan9 Angle formed by the deflection direction of AOD with respect to the sub-scanning direction of raster scan

Claims

[CLAIMS]

1. A laser irradiator comprising: a laser light source to emit a laser beam in an emission direction; multiple upstream deflectors including at least one of: a first deflector to deflect the laser beam emitted from the laser light source in a first direction different from the emission direction; and a second deflector downstream of the first deflector in the emission direction, the second deflector to deflect the laser beam emitted from the laser light source in a second direction different from the first direction; a downstream deflector downstream of the multiple upstream deflectors in the emission direction to deflect the laser beam in a main scanning direction different from the emission direction, the first direction, and the second direction; and a control unit configured to: control the downstream deflector to move an irradiation position of the laser beam to a first position in the main scanning direction; and control one of the first deflector or the second deflector to change the irradiation position of the laser beam, deflected by the downstream deflector, to a second position different from the first position in the first direction or the second direction to irradiate an unirradiated region.

2. The laser irradiator according to claim 1, wherein the control unit drives the one of the first deflector and the second deflector at different timings to deflect the laser beam in the first direction or the second direction.

3. The laser irradiator according to claim 1, wherein the control unit drives the one of the first deflector and the second deflector to deflect the laser beam in one of the first direction or the second direction to irradiate, with the laser beam, the unirradiated region separated from a non-irradiated region that is not to be irradiated with the laser beam when the first position is at the non-irradiated region.

4. The laser irradiator according to claim 1, wherein the downstream deflector includes a galvano scanner to raster-scan a scanning region in the main scanning direction and a sub-scanning direction, the first direction is inclined at a first angle relative to the sub-scanning direction, and the second direction is inclined at a second angle different from the first angle relative to the sub-scanning direction.

5. The laser irradiator according to claim 1, wherein the control unit drives: the first deflector to deflect the laser beam in the first direction multiple times; andthe second deflector to deflect the laser beam in the second direction multiple times, the first direction is inclined at a first angle relative to the main scanning direction, and the second direction is inclined at a second angle different from the first angle relative to the main scanning direction.

6. The laser irradiator according to claim 1, wherein the multiple upstream deflectors include an acousto-optic element or an electro-optic deflector.

7. The laser irradiator according to claim 1, wherein the control unit drives the laser light source and the multiple upstream deflectors to cause a time from a laser irradiation to an irradiation region by a laser beam to a deflection of the laser beam to a deflection position corresponding to a following irradiation region to be equal to or smaller than a turning-on interval of the laser beam.

8. The laser irradiator according to claim 4, wherein the control unit drives the downstream deflector to raster-scan an irradiation region having: columns of a scanning region in the main scanning direction; and rows of the scanning region in the sub-scanning direction intersecting the main scanning direction.

9. The laser irradiator according to claim 8, wherein the control unit drives the downstream deflector to move an irradiation position of the laser beam to a first position; and one of the first deflector and the second deflector to change the irradiation position of the laser beam to a second position different from the first position in the sub-scanning direction when a center axis connecting center positions of the columns and a main scan axis of raster scan by the downstream deflector are matched.

10. The laser irradiator according to claim 8, wherein the control unit: raster-scans a first column arranged in the main scanning direction intersecting an x-direction of the sub- scanning direction by the downstream deflector; determines an x-coordinate value of a second column including an unirradiated region, closest to the first column; and irradiates the unirradiated region of the second column by the first deflector or the second deflector during raster scan of the first column by the downstream deflector.

11. The laser irradiator according to claim 10, wherein a column raster- scanned includes an unirradiated region having a minimum x- coordinate value in an x-direction of the sub-scanning direction.

12. The laser irradiator according to claim 8, wherein a following equation is satisfied, 9 = ± arctan ((n x Dy) / (m x Dy)), whereDx is an interval between adjacent scanning regions in an x-direction of the sub-scanning direction,Dy is an interval between adjacent scanning regions in a y-direction of the main scanning direction,9 is an angle formed by the sub- scanning direction of the downstream deflector and a deflection direction of the first deflector or the second deflector in a x-y plane formed by the x-direction and the y-direction, and m and n are any integers.

13. The laser irradiator according to claim 8, wherein the multiple upstream deflectors have a same absolute vale of an angle 9 and deflection directions different from each other, where the angle 9 is an angle formed by the sub-scanning direction of the downstream deflector and each of the deflection directions of the multiple upstream deflectors in a plane formed by the main scanning direction and the sub-scanning direction.

14. The laser irradiator according to claim 8, wherein the control unit determines an angle 9 formed by the sub- scanning direction of the downstream deflector and a deflection direction of the first deflector or the second deflector in a plane formed by the main scanning direction and the sub-scanning direction, the deflection direction different from a direction of a maximum line section in an irradiation direction of an irradiation object.

15. The laser irradiator according to claim 8, wherein the first deflector or the second deflector deflects a laser beam between a first distance from a position on a raster scan and a second distance from another position equivalent to the position on the raster scan, different from the first distance, in a same deflection direction.

16. The laser irradiator according to claim 8, wherein the laser irradiator irradiates irradiation regions multiple times with the laser beam within a scanning region of raster scan by the downstream deflector.

17. The laser irradiator according to claim 8, wherein a number of laser irradiation times of the laser beam during raster scan of a section in which the raster scan is accelerated or decelerated by the downstream deflector in the main scanning direction is larger than a number of the laser irradiation times of the laser beam during the raster scan of another section in which the raster scan is performed at a constant speed by the downstream deflector in the main scanning direction.

18. The laser irradiator according to any one of claims 1 to 17, wherein the laser irradiator irradiates an irradiation object made of resin with a laser beam to form a recess on a surface of the irradiation object.

19. A fabrication apparatus comprising: the laser irradiator according to any one of claims 1 to 17 to repeatedly irradiate an irradiation region of a powder bed sequentially formed by multiple powder layers with the laser beam to fabricate a three-dimensional article.

20. A laser irradiation method comprising: emitting a laser beam; deflecting an irradiation position of the laser beam to a first position by a downstream deflector; deflecting the irradiation position of the laser beam to a second position different from the first position by a first deflector and a second deflector; and irradiating an irradiation region of an object with the laser beam deflected by the one of the first deflector or the second deflector, and the downstream deflector.

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