Optik
124 (2013) 2928–
2931
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at
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Optik
j
o
ur
nal
hom
epage:
www.elsevier.de/ijleo
Design
of
Dammann
grating
based
on
the
parallel
recombination
simulated
annealing
algorithm
Bin
Wu
∗
,
Jiehu
Kang,
Wenqiang
Han
State
Key
Laboratory
of
Precision
Measuring
Technology
and
Instruments,
Tianjin
University,
Tianjin
300072,
People’s
Republic
of
China
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
23
April
2012
Accepted
25
August
2012
Keywords:
Forging
measurement
Projection
of
characteristic
dots
Dammann
grating
PRSA
a
b
s
t
r
a
c
t
Photography
is
an
applicable
method
for
online
dimensional
measurement
of
hot
forgings
and
artificial
marked
dots
help
detailed
information
capture
in
photographic
measurement.
But
traditional
physical
characteristic
dots
array
is
not
fitted
in
high
temperature
forging
measurement
conditions.
In
high
tem-
perature
situation,
non-contacted
optical
marked
dots
array
generated
by
Dammann
grating
is
a
preferred
choice.
This
paper
puts
forward
using
parallel
recombination
simulated
annealing
algorithm
(PRSA)
to
optimize
the
design
of
Dammann
grating
which
is
used
as
optical
projector
to
produce
19
×
19
dots
array.
The
Dammann
grating
is
designed
and
tested
in
practical
forging
measurement,
entirely
meeting
the
vision
measurement
requirements.
© 2012 Elsevier GmbH. All rights reserved.
1.
Introduction
In
manufacturing
industry,
large
forgings
play
important
roles
as
essential
equipment
components.
To
improve
efficiency
of
forg-
ing’s
production
and
reduce
material
margin,
the
real
time
accurate
online
dimensional
measurement
of
large
forgings
is
of
great
sig-
nificance
in
manufacturing.
Large
forgings
online
measurement
is
to
obtain
main
dimensional
sizes
to
determine
whether
the
products
meet
the
quality
requirements
and
measurement
sys-
tem
needs
to
adapt
the
tough
forging
fields
with
high
temperature,
so
conventional
measurement
methods
are
difficult
to
be
applied
in
large
forging’s
online
measurement.
Because
of
non-contacted,
high
speed
characteristics,
photographic
measurement
technol-
ogy
could
satisfy
the
measurement
conditions
very
well
and
it
has
become
a
main
technique
for
forging
size
measurement.
Photographic
measurement
restores
three-dimensional
coor-
dinates
based
on
surface
characteristic
points.
It
is
necessary
to
artificially
add
some
features
on
surface
for
measurement
when
surface
features
of
objects
are
not
easily
identified
or
adequately
convey
rich
details.
Physical
characteristics
affect
the
real
morphol-
ogy
of
the
measured
object
and
on
the
other
hand,
high
temperature
in
forging
measurement
conditions
does
not
allow
using
physical
pasting.
Compared
to
physical
dots
array,
optical
characteristic
dots
produced
by
optical
projector
are
very
suitable
in
high
temperature
conditions.
∗
Corresponding
author
at:
Room
203,
State
Key
Laboratory
of
Precision
Measure-
ment
Technology
and
Instruments,
Tianjin
University,
Tianjin,
People’s
Republic
of
China.
Tel.:
+86
136
42080876;
fax:
+86
022
27404778.
E-mail
addresses:
wubin@tju.edu.cn
(B.
Wu),
wqhann@gmail.com
(W.
Han).
Dammann
grating
is
a
kind
of
binary
phase
grating
in
which
the
incident
light
produce
Fraunhofer
diffraction
and
can
get
opti-
cal
dots
qualified
for
photographic
measurement.
By
optimization
design
of
Dammann
grating,
the
high
efficiency
and
uniform
distri-
bution
optical
projector
can
be
realized.
Traditional
design
methods
of
Dammann
grating
include
genetic
algorithm
(GA),
simulated
annealing
algorithm
(SA)
and
steepest-decent
algorithm
(SDA).
GA
has
strong
global
search
ability,
but
the
local
search
ability
is
relatively
poor.
With
the
increase
of
diffraction
order,
the
effi-
ciency
of
SDA
reduces
and
the
solutions
would
be
unstable.
GA
and
SA
have
been
used
by
Zhou
and
Liu
[1]
and
Keys
et
al.
[2]
to
optimize
Dammann
grating.
Luo
used
SAT-GRG
[3],
but
with
very
slow
converge
speed
is
very
slow.
In
order
to
get
as
much
efficiency
and
uniform
distribution
dots
array
as
possible,
this
paper
presents
an
efficient
global
optimization
algorithm,
par-
allel
recombination
simulated
annealing
algorithm
(PRSA)
[4]
to
optimize
the
design
of
Dammann
grating.
A
structured
light
pro-
jector
with
19
×
19
lattice
was
designed
using
laser
as
light
source,
achieving
desired
result
in
large
hot
forging
online
measurement
system.
2.
Overall
approaches
2.1.
The
choice
of
light
source
Hot
forging’s
temperature
is
about
850–1250
◦
C
and
the
wavelength
of
forging
is
mainly
600
nm.
In
order
to
avoid
the
interference
from
stray
light,
high
power
green
laser
is
used
as
projector’s
light
source.
The
system
choice
is
200
mW,
531.4
nm
green
light
semiconductor
laser.
The
fixed
filter
on
the
camera
ensures
that
the
measurement
signal
will
not
be
submerged.
0030-4026/$
–
see
front
matter ©
2012 Elsevier GmbH. All rights reserved.
http://dx.doi.org/10.1016/j.ijleo.2012.08.078