Note: Descriptions are shown in the official language in which they were submitted.
CA 02563018 2006-10-10
OCCLUSIONLESS SCANNER FOR WORKPIECES
Field of the Invention
This invention relates to the field of scanners and in particular to a scanner
for
workpieces such as lumber workpieces wherein the scanner includes scanners
arranged so as
to collect comprehensive images of the workpiece notwithstanding partial
occlusion by the
workpiece transfers.
Back ground of the Invention
It is known in the prior art relating to scanners to scan workpieces such as
flitches in a sawmill to detect defects such as stain, shake, knots, etc using
so-called vision
scanners and to map the profile of a workpiece including any wane edges. The
results of such
scanning is used to assist in optimizing further processing of the workpiece
to recover the
highest value and/or volume of pieces cut from the workpiece.
Scanners for use in sawmills, planermills, logdecks, engineered wood product
machine centres such as veneer scanning, panel scanning and the like, or in
other wood
applications, may scan either lineally, that is, sequentially along the length
of the workpiece as
the workpiece is translated longitudinally through the scanner, or
transversely, that is,
simultaneously along the length of the workpiece as the workpiece passes
through the scanner
with the workpiece aligned transversely or laterally across the direction of
flow of workpieces
through the scanner. In the case of transverse scanning, conventionally the
workpieces are
delivered on an infeed such as an infeed employing a spaced apart parallel
array of lugged
transfer chains, smooth chains, belted transfers, etc. so as to pass each
workpiece separately
through a generally rectangular frame mounted laterally over and around the
end of the infeed
transfer. The scanner cameras and corresponding sources of illumination, such
as halogen
lamps, are typically mounted in the frame, often so as to simultaneously view
both the top and
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bottom surfaces of the workpiece as the workpiece passes between the upper and
lower beams
or arms of the frame. Each camera has a pixel array aligned in a known
orientation relative to
the workpiece, for example aligned along the length of the workpiece. Light
from the
corresponding light sources is reflected from the surface of the workpiece and
focussed by the
camera lens onto the pixel array.
If the scanner is a profiling scanner, upper and lower triangulation geometry
is
used to arrive at a differential thickness measurement of the workpiece from
movement of the
focussed light along the array of pixels in the upper and lower cameras, from
which a profile
of the workpiece is modelled by an associated processor as a wireframe profile
image. The
accuracy or resolution of the wireframe model is influenced by the scan
density, that is, the
number of cameras and associated light sources, each of which generate the
profile of a cross-
section of the workpiece; the more closely spaced cross-sections, the higher
the scan density
and the better the accuracy or resolution of the wireframe model of the
workpiece. The
wireframe model of the workpiece is used by an optimizer, that is, a processor
running
optimization software, to determine optimized downstream cutting solutions for
optimized
recovery from the workpiece.
If the scanner is a vision scanner, the cameras, rather than being used to
generate workpiece profile measurements, provide color and/or contrast data
from the
workpiece exterior surfaces within the field of view of each camera as the
workpiece translates
through the scanner. The color and/or contrast data is processed to generate
predictions of the
type and location of visnally detectable defects on the workpiece surfaces.
Defects may
include holes, splits, shake, pitch pockets, knots, bark or wane, stain, etc.
It is understood that the present description of the background of the
invention
is not intended to limit the scope or ambit afforded the claims directed to
the present invention
as the background description merely reflects applicant's understanding of the
present state of
the art of wood processing. For example, the present invention is not intended
to be restricted
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to either only vision scanning or profiling scanning or a combination of
vision and profile
scanning, whether in separate or in a single device or scanning package, as
the present
invention is intended to also include other forms of scanning such as multi-
spectral, x-ray,
microwave, etc.
Summary of the Invention
In so-called defect extraction, the type and location of defects on a
workpiece
are predicted by software based on data from one or more scanners. The data
from vision and
profiling scanners, or other forms of scanning, may be used in a complimentary
fashion to aid
in defect extraction. For example, profile information may aid in determining
whether a dark
spot on the surface of a board is a bark pocket, a smooth knot or a hole. hi
the present
invention it has been found advantageous to mount both vision scanners and
profile scanners
on a common frame so as to reduce cost and floor-space requirements, although
separate
frames may be employed. If scanning of a workpiece by both vision and
profiling scanners
may be done near simultaneously, then defect extraction is aided by minimizing
mis-alignment
of the workpiece between the scanners so as to minimize mis-alignment of the
vision and
profile data and increasing the available data processing time before a
cutting decision must be
implemented by the programmable logic controllers (PLCs) instructing the
actuators actuating
the downstream cutting devices. In particular, and by way of example, the
following methods
of implementation may be employed: the optimizer may hand off control
information to the
PLC for actuation; or the optimizer processor may control discrete
input/output for direct
control of the actuators. Alternatively, the PLC may itself optimize and
actuate the actuators.
One of the problems with mounting both vision and profiling scanners in a
common frame is interference between the two scanners. For example, if there
is not a
common light source for both scanners, and if the light source for one scanner
is emitting light
in a frequency which is within the detected frequency range of the other
scanner, then the light
source from the former scanner will interfere with the camera of the latter
scanner. For
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example, in one known arrangement in a scanning machine the lines of laser
light used as a
light source by the profile scanning cameras extend in a parallel spaced apart
array in cross-
sections over the workpiece along the length of the workpiece. The laser light
used may be in
the visible spectrum, for example red, or for example in the infra-red. Vision
scanning
cameras may detect the reflected stripes of laser light across the workpiece
depending on their
spectrum. This may interfere with the vision scanning camera processing the
broad spectrum
of reflected light ordinarily impinging the pixel arrays in the vision
scanning cameras, leaving
blind spots or stripes in the vision data mapping the surface of the
workpiece.
Apart from any interference between the profile and vision scanner light
sources affecting the vision scanner cameras, physical interference also
occurs because the
bottom view of the workpiece in the scanner, that is, the view looking
upwardly at the lower
surface of the workpiece is partially occluded by the parallel spaced-apart
chainways or other
forms of transfers carrying the workpiece. One solution takes advantage of the
lateral offset
between the infeed and the outfeed transfers. Typically the infeed transfer
translates the
workpiece through the scanner frame, and immediately downstream of the scanner
frame the
infeed hands-off to the outfeed transfer. In order for there to be a smooth
transition of the
workpiece from the infeed to the outfeed, the adjacent ends of the infeed and
outfeed are
laterally offset from one another and may be staggered for example in the case
of chainways so
as to overlap in the downstream direction. Thus the workpiece is physically
carried on the
outfeed transfer before being dropped from the end of the infeed transfer to
assure a smooth
transition. This arrangement of the infeed transfer laterally offset, for
example staggered,
relative to the outfeed transfer provides an opportunity to mount, for example
profile scanning
cameras which are offset and corresponding lights to minimize interference
between profiling
and vision scanners; and, secondly, offset relative to one another in the
downstream direction
to remove interference between the chainways and the vision scanning of the
lower surface of
the workpiece.
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In scanning technology, as profile scan density increases, the increased scan
density may preclude transfers being located between profile points simply due
to tight
density. In order to preclude occlusions of profile points it is an object to
provide the
occlusion-less scanning of the present invention also for profile scanning.
In a further embodiment of the present invention, which is not intended to be
limiting, for each vision scanning camera a pair of generally linear,
oppositely disposed arrays
of light emitting diodes (LEDs) are mounted on opposite sides of the
corresponding camera.
The LED's in the pair of arrays may be each independently switched on and off,
for example
by the use of corresponding dip switches, so that the light intensity
distribution on either side
of each camera in the array of vision scanning cameras may be tuned to produce
the desired
increase in lighting intensity towards the extremities of the field of view of
each camera,
thereby reducing the complexity of the time-consuming task in the prior art of
tuning the
intensity of the banks of halogen lights to adjust and optimize their light
intensity distribution.
Although it may be that LED lighting will allow occlusion-less scanning with
relative ease of
design, it is understood that LED lighting is not required as other forms of
lighting also work.
For example, fluorescent or halogen lighting as is currently used may also be
configured to
work.
In summary, the present invention may be characterized in one aspect as
including a lumber seamier for sequentially scanning a series of lumber
workpieces translating
in a downstream flow direction wherein the workpieces flow sequentially to the
scanner on an
infeed transfer such as a parallel array of infeed conveyors and sequentially
from the scanner
on an outfeed transfer such as a parallel array of outfeed conveyors, and
across an interface
between the infeed and outfeed transfers wherein:
a)
the workpieces are each conventionally oriented with their long axes
transverse
to the direction of flow of workpieces in the downstream direction,
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b) a scanner frame is mounted or mountable transversely across
the flow direction
generally at the interface between the infeed and outfeed transfers so that
the
series of lumber workpieces pass through a cavity defined by the frame as the
workpieces flow in the flow direction to transition between the infeed and
outfeed transfers, the downstream end of the infeed transfer laterally
adjacent
an upstream end of the outfeed transfer so as to create an overlap zone
between
the downstream end of the infeed transfer and the upstream end of the outfeed
transfer
c) a first scanner camera downstream and adjacent the downstream end of the
infeed transfer, a second scanner camera upstream and adjacent the upstream
end of the outfeed transfer, the first scanner camera having a first field of
view
and second scanner camera having a second field of view, the first and second
fields of view collectively covering laterally across the overlap zone so that
a
workpiece translating downstream through the overlap zone while on the
downstream end of the infeed transfer has a second portion of the workpiece
within the second field of view, and wherein as the workpiece continues to
translate downstream so as to pass onto the upstream end of the outfeed
transfer
a first portion of the workpiece contiguous with the second portion of the
workpiece passes through the first field of view,
d) wherein the first and second cameras generate corresponding
first and second
images of the first and second portions of the workpiece for transmitting the
images to a processor for generating a collective image of the first and
second
portions of the workpiece.
In one preferred embodiment the scanner cameras include upper and lower
arrays of scanner cameras and upper and lower scanner lights mounted or
mountable to upper
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and lower portions of the frame the lower scanner cameras and the lower
scanner lights
mounted or mountable below the infeed and outfeed transfers.
The lower array of scanner cameras and corresponding lower scanner lights
may be staggered across the overlap zone so that a first sub-array of the
lower array is
mounted between downstream-most ends of the infeed transfer, and so that a
second sub-array
of the lower array, is mounted between upstream-most ends of the outfeed
transfer, so that for
example for every second camera and light unit, corresponding fields of view
of the scanner
cameras corresponding to the lower array are not occluded by the infeed or
outfeed conveyors.
Advantageously the scanner cameras of the lower array are vision cameras.
The lower scanner lights may be LED light arrays, for example substantially
linear spaced
apart arrays of LEDs. Oppositely arranged pairs of the arrays of LEDs may be
mounted
aligned transversely across the flow direction and generally parallel= to the
frame. The
oppositely arranged ends of the arrays of LEDs may laterally overlap
corresponding ends of
next adjacent pairs of the arrays of LEDs.
The at least one upper array and the at least one lower array may include
lateral
arrays of both profiling cameras and vision cameras and their corresponding
the scanner lights.
The lateral arrays of LED lights may be mounted to the frame both above and
below the flow path of the workpieces in the flow direction through the
cavity. The lights may
be aligned so as to illuminate, respectively, upper and lower surfaces of the
workpieces as the
workpieces pass through the cavity, and may be inclined from the vertical to
also illuminate
edges of the workpiece. The lateral arrays of LED lights may include four
banks of the lateral
arrays of LED lights, including two upper banks and two lower banks each
angled towards
substantially a center of the cavity.
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In one embodiment the upper array of scanner cameras and corresponding
upper scanner lights and the lower array of scanner cameras and corresponding
lower scanner
lights include:
a) profiling
cameras and corresponding lights mounted within the cavity
and positioned to provide differential thickness measurement of the
workpieces passing through the cavity; and,
b) vision cameras and corresponding lights mounted to at least one side
of
the frame.
The seamier system according to the present invention may also be
characterized as including a plurality of scanners cooperating with a
corresponding plurality of
radiation sources. The scanners and radiation sources collectively are
spatially separated in a
transverse direction relative to a workpiece flow direction. The scanners have
overlapping
fields of view and produce scanned image data for processing by image
processing software.
The spatial separation allows removal by the image processing software of
portions of the
image data. The portions which are removed include images of interfering
transport
mechanisms which interfere with unobstructed images of workpieces carried in
the flow
direction by the transport mechanisms.
In one embodiment the present invention also includes a processor and in
particular an image processor having the image processing software. The
software includes
means for combining the image data from the scanners by delaying spatially the
image data
from a first scanner so as to join together the image data from the first
scanner with the image
data from a second scanner which is spatially separated in the transverse
direction. The
joining of the image data from the first and second scanners removes overlap
between the
images to obtain a complete and unobstructed image of the workpiece.
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A frame may be mounted so as to extend at least partially transversely around
the flow direction. The plurality of scanners and the corresponding plurality
of radiation
sources may be mounted to the frame in a laterally spaced array transversely
across the flow
direction.
The plurality of radiation sources include at least one array of light
emitting
diodes. Means, cooperating with the arrays of light emitting diodes, may be
provided for
selectively adjusting the intensity of emitted light. In one embodiment the
light emitted from
individual light emitting diodes amongst or including all of the LEDs may be
selectively
adjusted so as to provide a custom intensity distribution.
Advantageously, the arrays of light emitting diodes include oppositely
arranged
pairs of arrays of light emitting diodes mounted so as to be substantially
transversely aligned
across the flow direction and substantially parallel to the frame. The ends of
adjacent arrays in
the pairs of light emitting diodes may overlap.
The present invention also includes a scanning method which includes the steps
of:
a) providing a plurality of scanners and a corresponding plurality of
cooperating radiation sources which collectively are spatially separated in a
transverse
direction relative to a workpiece flow direction and wherein the plurality of
scanners have
overlapping fields of view,
b) producing corresponding scanned image data from the plurality of
scanners and transmitting the data for processing by image processing
software,
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c)
removing by the image processing software, portions of the image data
which include images of interfering transport mechanisms which interfere with
unobstructed
images of workpieces carried in the flow direction by the transport
mechanisms.
The method may further include the steps of providing a processor including an
image processor having the image processing software, and combining the image
data from the
plurality of scanners by delaying spatially the image data from a first
scanner so as to join
together the image data from the first scanner with the image data from a
second scanner,
wherein the first and second scanners are the spatially separated in the
transverse direction.
The step of joining of the image data from the first and second scanners
includes the step of
removing overlap between the image data from the first and second scanners to
obtain an
unobstructed image of the workpiece.
Brief Description of the Drawings
Figure la is a section view along line la-la in Figure lb.
Figure lb is the scanner according to one embodiment of the present invention
in front elevation partially cut away view.
Figure lc is a cross sectional view along line lc-lc in Figure la.
Figure Id is a sectional view along line Id-Id in Figure la.
Figure 2a is, in cross sectional end elevation view, an LED light bar
according
to one aspect of the present invention.
Figure 2b is the view of Figure 2a with the light bar mounted to a hanger and
pivoting bracket.
CA 02563018 2006-10-10
Figure 2c is a side elevation view of Figure 2b.
Figure 2d is a plan view of Figure 2c, partially cut away to show the arrays
of
LEDs.
Figure 2e is the hanger, bracket and light bar of Figure 2b mounted to a
scanner frame beam.
Figure 2f is an alternative embodiment of the pivotable light bar of Figure
2e.
Figure 3a is a further embodiment of the scanner according to the present
invention in cross sectional and elevation view.
Figure 3b is the scanner of Figure 3a in side elevation view.
Figure 3c is a sectional view along line 3c-3c in Figure 3a.
Figure 3d is a sectional view along line 3d-3d in Figure 3a.
Figure 4 is, in cross sectional end elevation view, a further embodiment of
the
scanner according to the present invention housed within a clamshell cowling.
Figure 5a is, in cross sectional end elevation view, a further embodiment of
the
scanner according to the present invention.
Figure 5b is in cross sectional end elevation view, a further embodiment of
the
scanner according to the present invention.
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Detailed Description of Embodiments of the Invention
In the embodiment of Figures la-I,d, a scanner frame 10 includes upper and
lower beams 12 which extend laterally across, respectively over and under,
infeed chainways
14 conveying lumber workpieces 16 in flow direction A. Beams 12 are supported
at their ends
by end columns 18.
Rigid mounting brackets 20 are rigidly mounted to beams 12 so as to support
profile cameras 22a and 22b within the cavity 10a defined within frame 10 by
beams 12 and
end columns 18. Workpiece 16 translates in direction A on infeed 14 between
the profile
cameras so that the upper profile cameras 22a scan the upper surface profile
of workpiece 16
and the lower profile cameras 22b scan the lower surface profile of workpiece
16.
Vision cameras 24 are either rigidly mounted to frame 10 or rigidly mounted
adjacent frame 10. They may be mounted immediately downstream of frame 10 as
illustrated
but may also be located upstream of profile scanners, or alternated upstream
and downstream
of the profile scanners or cameras (collectively referred to herein as
cameras). In the
illustrated embodiment the vision cameras are immediately downstream of the
fields of view
of the profile cameras so as to scan the upper and lower surfaces of workpiece
16 for defects.
The lower vision cameras 24' and 24", that is, the vision cameras scanning the
lower surface of
workpiece 16, may advantageously be laterally offset from one another as best
seen in Figure
lc. The laterally spaced apart array of infeed chainways 14 are parallel to
each other and
spaced apart at regular intervals across frame cavity 10a. Outfeed chainways
26 are also
parallel to each other and laterally spaced apart at regular intervals across
frame cavity 10a.
The downstream ends of the array of infeed chainways 14 overlap in a scanning
zone B seen in
Figures la and lc in the direction of flow with the upstream ends of the array
of outfeed
chainways 26 wherein zone B includes the hand-off or transition zone 28 seen
in Figure la
across which a workpiece 16 is handed off from the infeed chainways 14 onto
the outfeed
chainways 26.
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A first sub-array of vision cameras 24' and corresponding light bars 30'
mounted transversely on either side of their corresponding vision cameras 24',
are mounted
between the downstream ends of infeed chainways 14. A second sub-array of
vision cameras
24" and their corresponding light bars 30", also mounted transversely on
either side of their
corresponding vision cameras 24", are mounted between the upstream ends of
outfeed
chainways 26. Vision cameras 24' and 24" are mounted within scanning zone B on
opposite
sides of transition zone 28 so that the field of view of vision cameras 24'
are not occluded by
the upstream ends of outfeed chainways 26 or by the downstream ends of infeed
chainways
14, and the fields of view of vision cameras 24" are not occluded by the
upstream ends of
outfeed chainways 26 or the downstream ends of infeed chainways 14.
Consequently, a
workpiece 16 translating in direction A sequentially over the first sub-array
of vision cameras
24' and the second sub-array of vision cameras 24" have their lower surfaces
completely
scanned by the combination of the scanning by both vision cameras 24' and 24".
The video
data from the vision cameras may then be combined into a collective image by a
processor (not
shown) to provide an occlusionless mapping of the features of the lower
surface of workpiece
16, for example, for use in data processing to extract defect information for
use in defect
classification and prediction.
Because only the lower surfaces of workpieces 16 are occluded by the infeed
and outfeed chainways, the field of view of vision cameras 24 mounted to the
downstream
upper beam 12 of frame 10 do not have their downwardly looking field of view
occluded so
that only a single linear array of vision cameras 24 and their corresponding
light bars 30 are
needed to map the features of the upper surface of workpieces 16. However,
this is not
intended to be limiting as the top 'vision' scanners may follow the bottom
configuration of
vision scanners for ease of mounting purposes, or for aesthetics, or for cost
effective mounting
etc.
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As best seen in Figure lb. the fields of view 24a of vision cameras 24, 24'
and
24" may be vertically aligned when looking at frame 10 in front elevation
view.
As seen in Figures 2a-2f, light bars 30, 30' and 30", indicated collectively
in
Figures 2a-2e by reference numeral 30, may have in one embodiment not intended
to be
limiting, mounted within elongate light housing 32, linear arrays 34 of
closely spaced LEDs
36, each LED 36 projecting a light beam 36a through infinite lens 38. Each LED
36 may be
switched "on" or "off' by the actuation of a corresponding dip switch (not
shown) located
within light housing 32 and accessible through dip switch access ports 40. The
intensity of the
illumination within the profiling camera fields of view 24a may thus be
adjusted using the dip
switches so as to provide greater light intensity at the outer extremities of
the field of view and
less light intensity towards the center of the fields of view directly
underneath the
corresponding cameras.
Light bars 30 may be mounted to beams 12 by the use of hanger brackets 42 to
which light bars 30 are pivotally mounted by hinges 44. Housings 30 may thus
be pivoted
relative to beams 12. Narrow beam LED sources may align with the vision
scanner mounting
system, so that if one is moved, they all are moved, that is pivot and/or
adjust vertically and/or
horizontally as seen by way of example in Figures 2e and 2f.
This type of mounting system would be for an 'in-line' or 'in-axis'
lighting/vision scanner configuration. In Figure 3a, vision cameras 24, 24'
and 24" are angled
from the vertical along with their corresponding light bars 30 for use, for
example, when it is
desired to scan not only the upper and lower surfaces 16a and 16b respectively
of workpiece
16 but also the front and rear edges 16c and 16d respectively.
Alternatively, in the embodiment of Figure 4, the upper and lower surfaces and
front and rear edges of workpiece 16 are viewed by vision cameras 24' and 24
mounted,
respectively between the lower of beams 12, and the outer sides of the upper
of beams 12 and
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=
canted inwardly so that their fields of view cover the passage of workpieces
16 through cavity
10a on infeed chainways 14. Light bars 30 may be mounted underneath beams 12,
pivoted on
hinges 44, hanger brackets 42 mounted directly to beams 12. In this case,
because the linear
arrays 34 of LEDs 36 are not in line with cameras 24 as in the embodiments of
Figures la and
3a, light beams 36a may be wider that is, diverge greater than light beams 36a
for use where
light bars 30 are in line with cameras 24. In the embodiment of Figure 4, only
the upper
cameras 24 are inclined inwardly into cavity 10a. Alternatively, the lower
camera 24" for
viewing the lower surface of workpiece 16 may be mounted to the outside of a
lower
downstream beam 12 and are oriented vertically upwards.
Retro-fit embodiments are illustrated in Figures 5a and 5b, where vision
cameras
24 are retro-fit mounted to conventional scanner frames 10 containing
conventional profiling
cameras 22.
The scope of the claims should not be limited by the embodiments set forth in
the examples, but should be given the broadest interpretation consistent with
the description as
a whole.
