DETAILED ACTION
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 02/04/2026 has been entered.
Response to Arguments
Applicant's arguments filed 02/04/2026 have been fully considered but they are not persuasive.
Applicant argues that the “combination of Imai with Woratz, Chouf, Ogawa, and Olivier fails to disclose or suggest, "wherein a distance of the focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam,"” (Page 7 of Applicant’s remarks filed 02/04/2026). While the derivation provided in the final rejection does not completely calculate the Rayleigh length, the mathematics of a minimum Rayleigh length based on given variables is calculatable and dependent based on the wavelength and spot diameter provided in the prior art. Thus, it should be noted that the interpretation of the claim has not changed (namely that the distance of a focal point of the laser beam from the entrance surface of the workpiece corresponds to the thickness of the workpieces being processed, which would be less than two times that of the Rayleigh length) but merely the calculation of the Rayleigh length is clarified by fixing mathematical calculations. The applicant in Pages 6-7 of their remarks filed 02/04/2026 states that one of ordinary skill in the art would readily realize that the Rayleigh length is defined and calculatable from the radius of the laser beam in the focus point and the wavelength of the laser light.
Thus, one of ordinary skill in the art using the formula that the applicant indicated to calculate the Rayleigh length along with the wavelength (Imai Column 12 Lines 29-31) and spot diameter (Imai Column 2 Lines 47-56) provided in Example 1 of Imai would result in
w
0
=
s
p
o
t
_
d
i
a
m
e
t
e
r
2
=
0.2
m
m
2
=
0.1
m
m
as the beam waist is half that of the beam diameter at the beam focus, and thus the Rayleigh length would be:
Z
R
=
π
*
w
0
2
λ
=
π
*
0.1
m
m
2
976
n
m
=
32.2
m
m
It should be noted that the above values were chosen to minimize the Rayleigh length such as to provide the most generous minimum value calculation of the Rayleigh length of Example 1 in Imai. It should also be noted that the values chosen are ones found in Example 1 of Imai, which are the same values used in the rejection of claim 8 provided in the final rejection.
Since Column 13 Lines 44-47 of Imai teaches that the thickness of the workpieces to be processed are between 1 to 12mm, and Oliver teaches that the focal points of two laser beams are positioned close to the top and bottom surfaces (Oliver Paragraph 46) wherein the thickness of the workpiece is between 0.8mm and 20mm (Paragraph 19 Claim 18 of Oliver), said distance of a focal point of the laser beam from the entrance surface of the workpiece would be less than two times the Rayleigh length. Although the refractive index is not included in the calculations, the refractive index of materials is greater than one. This would result in the wavelength being lower, and thus the resulting Rayleigh length to be higher. As such, including the refractive index in the calculations would only increase the Rayleigh length, wherein the provided range of workpiece thickness would still satisfy the limitation.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claim(s) 1-2, 4-5, 7, 9, and 11-16 is/are rejected under 35 U.S.C. 103 as being unpatentable over Imai (US 9172202 B2) in view of WORATZ (US 20220379402 A1), Chouf (US 8278591 B2), OGAWA (JP 2001321978 A), and Olivier (US 20050067393 A1).
Regarding claim 1, Imai (US 9172202 B2) teaches a method for laser cutting a workpiece having a thickness of less than 6 mm (Column 11 Lines 9-14, cutting using laser beam 4 under the conditions that the thickness of the workpiece 9 is 4 mm to 12 mm; Column 2 Lines 4-6 and Column 13 Lines 4-7, plate thickness in the range of 1mm to 12mm is used in examples), the method comprising:
directing a first laser beam, a second laser beam (Column 9 Lines 16-27, two laser beams 4a and 4b; Column 5 Lines 19-22, laser beams 4 are emitted from the output end 3 are irradiated to a workpiece 9), and a gas jet at an entrance surface of the workpiece (Column 5 Lines 23-37, gas is introduced as an assist gas wherein gas is jetted from the tip opening such as to remove molten material from a cutting kerf) such that the first and second laser beams at least partially overlap one another on the workpiece (Figure 9 Column 7 Lines 1-3, two laser beams are coupled and coaxialized such as to overlap each other),
wherein the first laser beam has a smaller focus diameter than the second laser beam (Column 12 Lines 51-56, spot diameter of the fiber laser beam 4a is smaller than the spot diameter of the semiconductor laser beam 4b),
wherein a power proportion of the second laser beam is lower than that of the first laser beam (Column 3 Lines 36-39, power density of the second laser beam is smaller than the power density of the first laser beam), and
wherein a cutting kerf is formed on the entrance surface of the workpiece (Column 12 Line 63 – Column 13 Line 5, surface roughness of the material and a cutting line at depth 1mm is investigated which indicates the formation of a cutting kerf)
Imai fails to teach:
wherein a beam parameter product of the first laser beam is at most 5 mm*mrad,
a power proportion of the second laser beam of a total laser power is less than 20%
a cutting kerf with a broken cutting edge,
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam, and
wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
WORATZ (US 20220379402 A1) teaches a machining apparatus for laser machining, comprising:
a power proportion of the second laser beam of a total laser power is less than 20% (Paragraph 68, laser source module 18a generates a power of 20kW and the laser source modules 18b and 18c generates laser powers of 0.2kW which is less than 20% of the total laser power)
wherein a cutting kerf with a broken cutting edge is formed on the entrance surface of the workpiece (Paragraph 73, chamfered areas 20b and 20c are generated by the edge regions of the laser beam)
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with WORATZ and have the second beam have parameters as specified such as to form a cutting edge as specified. This would have been done to provide a favorable surface finish of the workpiece (WORATZ Paragraph 7).
Imai modified with WORATZ fails to teach:
a beam parameter product of the first laser beam is at most 5 mm*mrad,
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam, and
wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
Chouf (US 8278591 B2) teaches a cutting method having at least one fiber-based laser, wherein:
a beam parameter product of the first laser beam is at most 5 mm*mrad (Column 3 Lines 1-2, quality factor of the laser is between 1 and 8 mm*mrad),
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Chouf and have a beam parameter product below 5 mm*mrad. This would have been done because the smaller the Beam Parameter Product, the better the beam quality (Chouf Column 3 Lines 25-30).
Imai modified with WORATZ fails to teach:
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam, and
wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
OGAWA (JP 2001321978 A) teaches a method of laser beam machining, wherein:
a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam (Figures 4-5 Paragraph 29, YAG laser beam LB1 has a focus point wherein the CO2 laser beam LB2 used for preheating is not focused and therefore has low energy density and is clearly from the figures that the laser beam LB2 would have a focal point closer to the opposite side of the workpiece than the entrance surface).
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with OGAWA and have the focal point of laser beam used for cutting is closer to the entrance surface than a laser beam of different wavelength used for preheating the workpiece. This would have been done to prevent the occurrence of fine cracks in the workpiece while also achieving faster processing and energy savings (OGAWA Paragraphs 9-10).
Imai modified with OGAWA fails to teach:
a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
However, one of ordinary skill in the art would readily recognize that the Rayleigh length is defined and calculatable from the radius of the laser beam in the focus point and the wavelength of the laser light as admitted by Page 7 of the Applicant’s remarks filed 02/04/2026. For gaussian beams, the formula for the Rayleigh length is
Z
R
=
π
*
w
0
2
λ
wherein
λ
is the radius of the laser beam and
w
0
is the beam waist.
Imai Column 12 Lines 47-56 teaches that the spot diameter of the first laser beam is 0.2mm1. Thus, the beam waist can be calculated as
w
0
=
s
p
o
t
_
d
i
a
m
e
t
e
r
2
=
0.2
m
m
2
=
0.1
m
m
Thus, by using the wavelength (Imai Column 12 Lines 29-31) and calculated beam waist, the Rayleigh length would be:
Z
R
=
π
*
w
0
2
λ
=
π
*
0.1
m
m
2
976
n
m
=
32.2
m
m
It should be noted that the above values were chosen to minimize the Rayleigh length such as to provide the most generous minimum value calculation of the Rayleigh length of Example 1 in Imai. Calculating the Rayleigh length using the spot diameter of the second spot diameter would result in
Z
R
=
π
*
w
0
2
λ
=
π
*
0.4
m
m
2
976
n
m
=
514.8
m
m
Olivier (US 20050067393 A1) teaches a laser cutting apparatus, wherein the focal points of the two lasers are positioned within the workpiece close to the top and bottom surface of the workpiece respectively (Paragraph 46) and further wherein the thickness of the workpiece to be cut is between 0.8mm and 20mm (Paragraph 19 Claim 18).
Column 13 Lines 44-47 of Imai teaches that the thickness of the workpieces to be processed are between 1 to 12mm, and Oliver teaches that the focal points of two laser beams are positioned close to the top and bottom surfaces (Oliver Paragraph 46) wherein the thickness of the workpiece is between 0.8mm and 20mm (Paragraph 19 Claim 18 of Oliver). As such, the distance of the focal point of the second laser beam, positioned on the lower surface of the workpiece, at a distance of 0.8mm to 20mm from the entrance (front) surface of the workpiece would reasonably be less than two times the Rayleigh length.
Although the refractive index is not included in the calculations, the refractive index of materials is greater than one. The formula for the Rayleigh length including refractive index is
Z
R
=
π
*
n
w
0
2
λ
wherein n is the refractive index.
This would result in the wavelength being lower, and thus the resulting Rayleigh length to be higher. As such, including the refractive index in the calculations would only increase the Rayleigh length, wherein the provided range of workpiece thickness would still satisfy the limitation.
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Olivier and have the first and second laser beams be respectively focused on the top and bottom surfaces of the workpieces such that the distance between the focal point of the second laser beam from the top surface is at most twice a Rayleigh length of the second laser beam. This would have been such that the lasers would be beneficially focused on the top and the bottom surfaces of the workpiece to increase the cutting speed (Olivier Paragraph 11) based on the thickness of the workpiece to be cut, which is an obvious engineering choice.
Regarding claim 2, Imai as modified teaches the method as claimed in claim 1.
Chouf further teaches:
the beam parameter product of the first laser beam is at most 3 mm*mrad (Column 3 Lines 1-2, quality factor of the laser is between 1 and 8 mm*mrad)
It would have been obvious for the same motivation as claim 1.
Regarding claim 4, Imai as modified teaches the method as claimed in claim 1, wherein
the thickness of the workpiece is less than 5 mm (Column 11 Lines 9-14, cutting using laser beam 4 under the conditions that the thickness of the workpiece 9 is 4 mm to 12 mm; Column 2 Lines 4-6 and Column 13 Lines 4-7, plate thickness in the range of 1mm to 12mm is used in examples)
WORATZ further teaches:
wherein the power proportion of the second laser beam of the total laser power is less than 15% (Paragraph 68, laser source module 18a generates a power of 20kW and the laser source modules 18b and 18c generates laser powers of 0.2kW which is less than 15% of the total laser power).
It would have been obvious for the same motivation as claim 1.
Regarding claim 5, Imai as modified teaches the method as claimed in claim 1, wherein
the thickness of the workpiece is less than 3 mm (Column 13 Lines 44-47, plat thickness in a range of 1 to 12mm; Column 2 Lines 4-6 and Column 13 Lines 4-7, plate thickness in the range of 1mm to 12mm is used in examples)
WORATZ further teaches:
wherein the power proportion of the second laser beam of the total laser power is less than 7% (Paragraph 68, laser source module 18a generates a power of 20kW and the laser source modules 18b and 18c generates laser powers of 0.2kW which is less than 20% of the total laser power).
It would have been obvious for the same motivation as claim 1.
Regarding claim 7, Imai as modified teaches the method as claimed in claim 1.
OGAWA further teaches:
the focal point changes due to difference in refractive index, which is inversely proportional to the wavelength of the lasers (Paragraph 29)
It would have been obvious for the same motivation as claim 1.
Olivier further teaches:
a distance between the focus point of the first laser beam and the focus point of the second laser beam is not more than 2 mm (Paragraph 46, the focal points of the two lasers are positioned within the workpiece close to the top and bottom surface of the workpiece respectively; Paragraph 19 Claim 18, thickness of the workpiece to be cut is between 0.8mm and 20mm)
It would have been obvious for the same motivation as claim 1.
Regarding claim 9, Imai as modified teaches the method as claimed in claim 1, wherein
a focus diameter of the second laser beam is at least twice and/or at most five times a focus diameter of the first laser beam (Column 12 Lines 47-56, spot diameter D1 of the fiber laser beam 4a and spot diameter D2 of the semiconductor laser beam 4b at the irradiation point are 0.2mm D1 and 0.8mm D2).
Regarding claim 11, Imai as modified teaches the method as claimed in claim 1, wherein
the first laser beam and second laser beam are overlaid concentrically with respect to one another (Figure 9 Column 7 Lines 1-3, two laser beams are coupled and coaxialized such as to overlap each other).
Regarding claim 12, Imai as modified teaches the method as claimed in claim 1, wherein:
the first laser beam and second laser beam emerge from a multicore fiber having a first fiber core for the first laser beam and a second fiber core for the second laser beam (Column 6 Lines 60-62, fiber laser beam emitted from a core end face of the active fiber 20 is introduced in to the core 22a of the passive fiber 22; Column 6 Lines 63-67, semiconductor laser beam emitted from the semiconductor laser beam source are coupled into the inner cladding of the passive fiber)
WORATZ further teaches:
the first laser beam and second laser beam emerge from a multicore fiber having a first fiber core for the first laser beam and a second fiber core for the second laser beam (Fig. 2b Paragraph 69, laser beam is transported into the fiber core 16a and edge region of the laser beam is transported into the edge region 16b).
It would have been obvious for the same motivation as claim 1.
Regarding claim 13, Imai as modified teaches the method as claimed in claim 12.
Chouf further teaches:
the first fiber core has a diameter of at most 100 um (Column 3 Lines 36-47, the diameter of the fiber is chosen based on the amount of laser power that has to be delivered such that fiber used will have a diameter of 50micrometers under some circumstances).
It would have been obvious for the same motivation as claim 1.
Regarding claim 14, Imai as modified teaches the method as claimed in claim 1.
Chouf further teaches:
a gas pressure of the gas jet is at least 16 bar (Column 2 Lines 63-65, assist gas pressure is between about 0.1 bar and 25 bar and is chosen according to the thickness to be cut).
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Chouf and have a gas pressure of less than 16 bar. This would have been done to properly provide the gas based on the thickness to be cut (Chouf Column 2 Lines 63-65).
Regarding claim 15, Imai as modified teaches the method as claimed in claim 1, wherein
the laser cutting apparatus is a laser fusion cutting apparatus (Column 5 Lines 23-37, assist gas is used to remove molten metal from a cutting curf during laser cutting).
Regarding claim 16, Imai as modified teaches the method as claimed in claim 1, wherein
the workpiece is at least one of metallic and electrically conductive (Column 5 Lines 23-37, metal workpiece).
Claim(s) 3 is/are rejected under 35 U.S.C. 103 as being unpatentable over Imai (US 9172202 B2) in view of WORATZ (US 20220379402 A1), Chouf (US 8278591 B2), OGAWA (JP 2001321978 A), and Olivier (US 20050067393 A1) as applied to claim 1 above, and further in view of Nakamae (US 20140054275 A1).
Regarding claim 3, Imai as modified teaches the method as claimed in claim 1.
Imai as modified fails to teach:
a radius of the cutting edge is at least 20 um and/or at most 100 um.
Nakamae (US 20140054275 A1) teaches a cutting tool, wherein:
a radius of the cutting edge is at least 20 um and/or at most 100 um (Table IV Paragraph 84, curvature of the cutting-edge ridgeline is controlled by adjusting a relative position of the cutting tool with respect to the focal position of the laser beam such that the radius of the cutting edge is between 20um and 100um).
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Nakamae and have the radius of the cutting edge range from 20 um to 100 um. This would have been done to adjust the cutting edge to the desired shape (Nakamae Paragraph 11).
Claim(s) 10 is/are rejected under 35 U.S.C. 103 as being unpatentable over Imai (US 9172202 B2) in view of WORATZ (US 20220379402 A1), Chouf (US 8278591 B2), OGAWA (JP 2001321978 A), and Olivier (US 20050067393 A1) as applied to claim 1 above, and further in view of Olsen (US 20100044353 A1) and Yuanyuan (The Beam Characteristics of High Power Diode Laser Stack).
Regarding claim 10, Imai as modified teaches the method as claimed in claim 1.
Imai as modified fails to teach:
a far field divergence of the first laser beam and a far field divergence of the second laser beam differ by at most 100 mrad
Olsen (US 20100044353 A1) teaches a method and system for laser processing wherein both the first laser beam (melt ejection beam) and a second laser beam (melt ejection beam) have a beam parameter product of 10mm*mrad, 5 mm*mrad, or 1 mm*mrad, or less than 0.5 mm*rad (Olsen Paragraphs 62 and 102). One of ordinary skill in the art would have found it obvious to have both laser beams have a lower beam parameter product since higher power densities can be achieved when focusing the laser to a focal spot (Olsen Paragraphs 62 and 102).
Page 4 of Yuanyuan (The Beam Characteristics of High Power Diode Laser Stack) teaches that the formula for solving for a Beam Parameter Product (BPP) is the beam waist radius of lasers
(
w
0
)
times the far-field divergence angle of laser divided by two (
θ
/
2
)
or
B
P
P
=
w
0
*
θ
/
2
. Thus, the formula for solving for the far-field divergence angle of the laser is
θ
=
2
*
B
P
P
w
0
. Since the beam parameter product for both lasers are known to be 0.5 mm*mrad or less (Olsen Paragraphs 62 and 102) and the spots diameters of the first laser beam and the second laser beam are known to be 0.2mm and 0.8mm (Imai Column 12 Lines 51-54; Column 3 Lines 5-6, focused beam diameter between 0.1mm and 0.5mm)2, the formula can be used to solve for the far-field divergence angle of the lasers. The resulting beam waist radius are:
w
0
=
s
p
o
t
_
d
i
a
m
e
t
e
r
2
=
0.2
m
m
2
=
0.1
m
m
w
0
=
s
p
o
t
_
d
i
a
m
e
t
e
r
2
=
0.8
m
m
2
=
0.4
m
m
And thus, the far-field divergence angles can be calculated to be:
θ
f
i
r
s
t
=
2
*
B
P
P
w
0
=
2
*
0.5
m
m
*
m
r
a
d
0.1
m
m
=
10
m
r
a
d
θ
s
e
c
o
n
d
=
2
*
B
P
P
w
0
=
2
*
0.5
m
m
*
m
r
a
d
0.4
m
m
=
2.5
m
r
a
d
Even if the applicant argues that the secondary laser of Olsen is not explicitly said to have a beam diameter of 0.8mm, increasing the beam diameter of the secondary laser would not result in a far field divergence first laser beam and a far field divergence of the second laser beam differing by at most 100 mrad as increasing the size or beam waist radius of the laser lowers the far field divergence angle of the second laser. Since Paragraph 144 teaches that the diameter of the melt-ejection beam exceeds the diameter of the melting beam, the far field divergence first laser beam and a far field divergence of the second laser beam will differ by at most 100mrad given that the first laser beam has a beam waist diameter of 5 mrad and the second laser beam has a BPP of 0.5mm*rad.
Claim(s) 17 is/are rejected under 35 U.S.C. 103 as being unpatentable over Imai (US 9172202 B2) in view of WORATZ (US 20220379402 A1), Olsen (US 20100044353 A1), OGAWA (JP 2001321978 A), and Olivier (US 20050067393 A1).
Regarding claim 17, Imai (US 9172202 B2) teaches a laser cutting apparatus for laser cutting a workpiece along a cutting line (Column 11 Lines 9-14, cutting using laser beam 4), the apparatus comprising:
a laser light source device for overlaying a first laser beam and a second laser beam in a cutting zone (Figure 9 Column 7 Lines 1-3, two laser beams are coupled and coaxialized such as to overlap each other), wherein the first laser beam has a smaller focus diameter than the second laser beam (Column 12 Lines 51-56, spot diameter of the fiber laser beam 4a is smaller than the spot diameter of the semiconductor laser beam 4b),
a nozzle for directing a gas jet at the cutting zone (Paragraph 51, gas inlet 8a and tip opening 8b directs assist gas toward the processing region); and
Imai fails to teach:
wherein a beam parameter product of the first laser beam is at most 5 mm*mrad, and
wherein a power proportion of the second laser beam of a total laser power is less than 20%
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to an entrance surface than the focus point of the second laser beam, and wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
a movement device for moving the cutting zone relative to the workpiece along the cutting line.
WORATZ (US 20220379402 A1) teaches a machining apparatus for laser machining, comprising:
a power proportion of the second laser beam of a total laser power is less than 20%; (Paragraph 68, laser source module 18a generates a power of 20kW and the laser source modules 18b and 18c generates laser powers of 0.2kW which is less than 20% of the total laser power)
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with WORATZ and have the second beam have parameters as specified such as to form a cutting edge as specified. This would have been done to provide a favorable surface finish of the workpiece (WORATZ Paragraph 7).
Imai modified with WORATZ fails to teach:
wherein a beam parameter product of the first laser beam is at most 5 mm*mrad
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam, and wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
a movement device for moving the cutting zone relative to the workpiece along the cutting line.
Olsen (US 20100044353 A1) teaches a laser cutting apparatus, comprising:
a beam parameter product of the first laser beam is at most 5 mm*mrad (Paragraph 62, melting beam has a beam parameter of less than 5 mm*mrad),
a movement device for moving the cutting zone relative to the workpiece along the cutting line (Paragraph 178, movement provided by motion arrangement for moving the laser beams with respect to the workpiece).
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Olsen and have a beam parameter product below 5 mm*mrad. This would have been done because it is known in the art that the smaller the Beam Parameter Product, the better the beam quality as evidenced by Column 3 Lines 25-30 of Chouf (US 8278591 B2).
It would further have been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Olsen and include a movement device. This would have been done to move laser beam relative to the workpiece (Olsen Paragraph 178).
Imai modified with Olsen fails to teach:
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam, and wherein a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
OGAWA (JP 2001321978 A) teaches a method of laser beam machining, wherein:
wherein a focus point of the first laser beam lies upstream of a focus point of the second laser beam in a propagation direction of the first laser beam or the second laser beam, so that the focus point of the first laser beam is closer to the entrance surface than the focus point of the second laser beam (Figures 4-5 Paragraph 29, YAG laser beam LB1 has a focus point wherein the CO2 laser beam LB2 used for preheating is not focused and therefore has low energy density and is clearly from the figures that the laser beam LB2 would have a focal point closer to the opposite side of the workpiece than the entrance surface).
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with OGAWA and have the focal point of laser beam used for cutting is closer to the entrance surface than a laser beam of different wavelength used for preheating the workpiece. This would have been done to prevent the occurrence of fine cracks in the workpiece while also achieving faster processing and energy savings (OGAWA Paragraphs 9-10).
Imai modified with OGAWA fails to teach:
a distance of a focus point of the second laser beam from the entrance surface of the workpiece is at most twice a Rayleigh length of the second laser beam
However, one of ordinary skill in the art would readily recognize that the Rayleigh length is defined and calculatable from the radius of the laser beam in the focus point and the wavelength of the laser light as admitted by Page 7 of the Applicant’s remarks filed 02/04/2026. For gaussian beams, the formula for the Rayleigh length is
Z
R
=
π
*
w
0
2
λ
wherein
λ
is the radius of the laser beam and
w
0
is the beam waist.
Imai Column 12 Lines 47-56 teaches that the spot diameter of the first laser beam is 0.2mm. Thus, the beam waist can be calculated as
w
0
=
s
p
o
t
_
d
i
a
m
e
t
e
r
2
=
0.2
m
m
2
=
0.1
m
m
Thus, by using the wavelength (Imai Column 12 Lines 29-31) and calculated beam waist, the Rayleigh length would be:
Z
R
=
π
*
w
0
2
λ
=
π
*
0.1
m
m
2
976
n
m
=
32.2
m
m
It should be noted that the above values were chosen to minimize the Rayleigh length such as to provide the most generous minimum value calculation of the Rayleigh length of Example 1 in Imai. Calculating the Rayleigh length using the spot diameter of the second spot diameter would result in
Z
R
=
π
*
w
0
2
λ
=
π
*
0.4
m
m
2
976
n
m
=
514.8
m
m
Olivier (US 20050067393 A1) teaches a laser cutting apparatus, wherein the focal points of the two lasers are positioned within the workpiece close to the top and bottom surface of the workpiece respectively (Paragraph 46) and further wherein the thickness of the workpiece to be cut is between 0.8mm and 20mm (Paragraph 19 Claim 18).
Column 13 Lines 44-47 of Imai teaches that the thickness of the workpieces to be processed are between 1 to 12mm, and Oliver teaches that the focal points of two laser beams are positioned close to the top and bottom surfaces (Oliver Paragraph 46) wherein the thickness of the workpiece is between 0.8mm and 20mm (Paragraph 19 Claim 18 of Oliver). As such, the distance of the focal point of the second laser beam, positioned on the lower surface of the workpiece, at a distance of 0.8mm to 20mm from the entrance (front) surface of the workpiece would reasonably be less than two times the Rayleigh length.
Although the refractive index is not included in the calculations, the refractive index of materials is greater than one. The formula for the Rayleigh length including refractive index is
Z
R
=
π
*
n
w
0
2
λ
wherein n is the refractive index.
This would result in the wavelength being lower, and thus the resulting Rayleigh length to be higher. As such, including the refractive index in the calculations would only increase the Rayleigh length, wherein the provided range of workpiece thickness would still satisfy the limitation.
It would have thus been obvious to someone of ordinary skill in the art before the filing date of the claimed invention to have modified Imai with Olivier and have the first and second laser beams be respectively focused on the top and bottom surfaces of the workpieces such that the distance between the focal point of the second laser beam from the top surface is at most twice a Rayleigh length of the second laser beam. This would have been such that the lasers would be beneficially focused on the top and the bottom surfaces of the workpiece to increase the cutting speed (Olivier Paragraph 11) based on the thickness of the workpiece to be cut, which is an obvious engineering choice.
Conclusion
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/F.J.W./Examiner, Art Unit 3761
/WOODY A LEE JR/Primary Examiner, Art Unit 3761
1 The Office further notes that it is well known in the art that focusing the laser beam at the surface of a sheet is advantageous in maximizing the cutting efficiency and to achieve the cleanest and most accurate cut as evidenced by Column 1 Lines 27-30 of Weeks (US 5227606 A) and Paragraph 172 of Shapiro (US 20170045877 A1).
2 The Office further notes that it is well known in the art that focusing the laser beam at the surface of a sheet is advantageous in maximizing the cutting efficiency and to achieve the cleanest and most accurate cut as evidenced by Column 1 Lines 27-30 of Weeks (US 5227606 A) and Paragraph 172 of Shapiro (US 20170045877 A1).
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