Optical coherence imaging can measure hole depth in real-time (> 20 kHz) during laser drilling without being blinded by intense machining light or incoherent plasma emissions. Rapid measurement of etch rate and stochastic melt relaxation makes these images useful for process development and quality control in a variety of materials including metals, semiconductors and dielectrics. The ability to image through the ablation crater in materials transparent to imaging light allows the guidance of blind hole cutting even with limited a priori knowledge of the sample.

Significant improvement in hole depth accuracy with the application of manual feedback from this imaging has been previously demonstrated [1]. However, the large quantity of raw data and computing overhead are obstacles for the application of coherent imaging as a truly automatic feedback mechanism. Additionally, the high performance components of coherent imaging systems designed for its traditional application in biological imaging are costly and may be unnecessary for materials processing. In this work, we present a coherent imaging system design that costs less than a fifth of comparable commercial products. We also demonstrate streamlined image processing suited for automated feedback that increases processing speed by two orders of magnitude.

1.
Webster
,
P.J.L.
,
Yu
,
J.X.Z
,
Leung
,
B.Y.C.
,
Anderson
,
M. D.
,
Yang
,
V.X. D.
&
Fraser
,
J.M.
(
2010
)
In situ 24 kHz coherent imaging of morphology change in laser percussion drilling
,
Optics Letters
35
,
646
648
.
2.
Leech
,
P.W.
(
2009
)
Laser ablation of multilayered hot stamping foil
,
Journal of Materials Processing Technology
209
,
4281
4285
.
3.
Tokarev
,
V.N.
,
Lopez
,
J.
&
Lazare
,
S.
(
2000
)
Modelling of high-aspect ratio microdrilling of polymers with UV laser ablation
,
Applied Surface Science
168
,
75
78
.
4.
Kumar
,
A.
,
Sapp
,
M.
,
Vincelli
,
J.
&
Gupta
,
M.C.
(
2010
)
A study on laser cleaning and pulsed gas tungsten arc welding of Ti-3Al-2.5V alloy tubes
,
Journal of Materials Processing Technology
210
,
64
71
.
5.
Khan
,
M.M.A.
,
Romoli
,
L.
,
Fiaschi
,
M.
,
Sarri
,
F.
&
Dini
,
G.
(
2010
)
Experimental investigation on laser beam welding of martensitic stainless steels in a constrained overlap joint configuration
,
Journal of Materials Processing Technology
210
,
1340
1353
.
6.
Nayak
,
N.C.
,
Lam
,
Y.C.
,
Yue
,
Y.C.
&
Sinha
,
A.T.
(
2008
)
CO2-laser micromachining of PMMA: the effect of polymer molecular weight
,
Journal of Micromechanics and Microengineering
18
,
095020
.
7.
Pratap
,
B
,
Arnold
,
C.B.
&
Pique
,
A.
(
2003
)
Depth And Surface Roughness Control On Laser Micromachined Polyimide For Direct-Write Deposition
, in
the Proceedings of Micromachining and Microfabrication Process Technology VIII
,
San Jose, California, USA
,
217
225
.
8.
Temnov
,
V.V.
,
Sokolowski-Tintenm
,
K.
,
Zhou
,
P.
, &
von der Linde
,
D.
(
2004
)
Femtosecond time-resolved interferometric microscopy
,
Applied Physics A: Materials Science and Processing
78
,
483
489
.
9.
Dietrich
,
J.
,
Brajdic
,
M.
,
Walther
,
K.
,
Horn
,
A.
,
Kelbassa
,
L.
&
Poprawe
,
R.
(
2008
)
Investigation of increased drilling speed by online high-speed photography
,
Optics and Lasers in Engineering
46
,
705
710
.
10.
Lausten
,
R.
&
Balling
,
P.
(
2001
)
On-the-fly depth profiling during ablation with ultrashort laser pulses: A tool for accurate micromachining and laser surgery
,
Applied Physics Letters
79
,
884
886
.
11.
Fercher
,
A.F.
,
Drexler
,
W.
,
Hitzenberger
,
C. K.
&
Lasser
,
T.
(
2003
)
Optical coherence tomography−principles and applications
,
Reports on Progress in Physics
66
,
239
303
.
12.
Webster
,
P.J.L.
,
Yu
,
J.X.Z
,
Leung
,
B.Y.C.
,
Anderson
,
M.D.
,
Hoult
,
T.P.
&
Fraser
,
J.M.
(
2010
)
Coaxial real-time metrology and gas assisted laser micromachining: process development, stochastic behavior and feedback control
, in
the Proceedings of SPIE Photonics West: MOEMS
,
San Francisco, California, USA
,
759003
.
13.
Yu
,
J.X.Z
,
Webster
,
P.J.L.
,
Leung
B.Y.C.
&
Fraser
,
J.M.
(
2010
)
High quality percussion drilling of silicon with a CW fiber laser beam
, in
the Proeceedings of SPIE Photonics West: LASE
,
San Francisco, California, USA
,
75840W
.
14.
Webster
,
P.J.L.
,
Muller
,
M.S
&
Fraser
,
J.M.
(
2007
)
High speed in situ depth profiling of ultrafast micromachining
,
Optics Express
15
,
14967
14972
.
15.
Webster
,
P.J.L.
,
Leung
,
B.Y.C
,
Yang
,
V.X.D
, &
Fraser
,
J.M.
(
2010
)
Guidance of hard tissue ablation by forward viewing optical coherence tomography
, in
the Proceedings of SPIE Photonics West: BiOS
,
San Francisco, California, USA
75540Z
.
16.
Thorlabs
(
2010
)
Optical Coherence Tomography Imaging Systems
,
Thorlabs Product Catalogue
V
20
,
1353
1393
.
17.
Lindner
,
M. W.
,
Andretzky
,
P.
,
Kiesewetter
,
F.
&
Hausler
,
G.
(
2002
) Spectral Radar: Optical Coherence Tomography in the Fourier Domain, in
B. E.
Bouma
and
G. J.
Tearney
(eds)
Handbook of Optical Coherence Tomography
,
Marcel Dekker
,
335
357
.
18.
Wojtkowski
,
M.
,
Leitgeb
,
R.
,
Kowalczyk
,
A.
,
Bajraszewski
,
T.
&
Fercher
,
A. F.
(
2002
)
In vivo human retinal imaging by Fourier domain optical coherence tomography
,
Journal of Biomedical Optics
7
,
457
463
.
19.
Leitgeb
,
R.
,
Hitzenberger
,
C.K.
&
Fercher
,
A.F.
(
2003
)
Performance of fourier domain vs. time domain optical coherence tomography
,
Optics Express
11
,
889
894
.
20.
Yun
,
S.H.
,
Tearney
,
G.J.
,
de Boer
,
J.F.
&
Bouma
,
B.E.
(
2004
)
Motion artifacts in optical coherence tomography with frequency-domain ranging
,
Optics Express
12
,
2977
2998
.
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