U.S. patent application number 13/242843 was filed with the patent office on 2012-12-06 for methods for measuring at least one physical characteristic of a component.
Invention is credited to Stanley P. Johnson, Lawrence J. Zagorsky.
Application Number | 20120305815 13/242843 |
Document ID | / |
Family ID | 40849842 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305815 |
Kind Code |
A1 |
Johnson; Stanley P. ; et
al. |
December 6, 2012 |
METHODS FOR MEASURING AT LEAST ONE PHYSICAL CHARACTERISTIC OF A
COMPONENT
Abstract
In some embodiments, an inspection system includes a movable
collimated light source, a sensing device, a positioning device and
a retention mount. The movable collimated light source defines a
source optical path and is capable of causing a collimated light
beam to propagate along the source optical path. The sensing device
defines a sensor optical path. The positioning device includes a
positioning device stage that is movably disposed relative to the
positioning device, sensing device and movable collimated light
source. The retention mount is non-movably disposed on the
positioning device stage and disposed within the sensor optical
path such that when an item is retained within the retention mount,
the item blocks at least a portion of the collimated light
beam.
Inventors: |
Johnson; Stanley P.;
(Simsbury, CT) ; Zagorsky; Lawrence J.; (Lincoln,
RI) |
Family ID: |
40849842 |
Appl. No.: |
13/242843 |
Filed: |
September 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12383141 |
Mar 20, 2009 |
8035094 |
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13242843 |
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11391521 |
Mar 27, 2006 |
7745805 |
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12383141 |
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10460941 |
Jun 13, 2003 |
7227163 |
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11391521 |
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61070112 |
Mar 20, 2008 |
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60389357 |
Jun 17, 2002 |
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Current U.S.
Class: |
250/559.01 |
Current CPC
Class: |
G01N 21/89 20130101;
G01B 11/2433 20130101; G01B 11/2425 20130101 |
Class at
Publication: |
250/559.01 |
International
Class: |
G01B 11/24 20060101
G01B011/24 |
Claims
1. An inspection system, comprising: a movable collimated light
source defining a source optical path, said movable collimated
light source being operable to cause a collimated light beam to
propagate along said source optical path; a sensing device defining
a sensor optical path; a positioning device including a positioning
device stage, wherein said positioning device stage is movably
disposed relative to said positioning device, said sensing device
and said collimated light source; and a retention mount non-movably
disposed on said positioning device stage, said retention mount
being disposed within said sensor optical path such that when an
item is retained within said retention mount, said item blocks at
least a portion of said collimated light beam.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 12/383,141 filed Mar. 20, 2009,
now U.S. Pat. No. 8,035,094, which claims the benefit of U.S.
Provisional Patent Application Ser. No. 61/070,112, filed Mar. 20,
2008 and is a continuation-in-part of U.S. application Ser. No.
11/391,521 filed Mar. 27, 2006, now U.S. Pat. No. 7,745,805, which
is a continuation-in-part of U.S. application Ser. No. 10/460,941
filed Jun. 13, 2003, now U.S. Pat. No. 7,227,163, which claims the
benefit of U.S. Provisional Patent Application Ser. No. 60/389,357,
filed Jun. 17, 2002, all of which are incorporated herein by
reference in their entireties.
FIELD OF THE INVENTION
[0002] This disclosure relates generally to a method and system for
inspecting components and more particularly to a method and system
for optically inspecting the physical characteristics of externally
threaded components, such as thread gages, screws, bolts and other
externally threaded components having varied configurations.
BACKGROUND OF THE INVENTION
[0003] As society becomes increasingly reliant upon technology,
mechanical and electromechanical systems, such as aircraft,
automobiles, weapons systems and power systems, are called upon to
perform an ever increasing number of functions. One downside to
this is that, in some situations, a failure of a single threaded
component in the system may cause a catastrophic failure of the
entire system possibly resulting in the loss of millions of dollars
and hundreds of lives. In an attempt to reduce the probability of a
catastrophic systems failure, critical and some non-critical
systems are required to satisfy predetermine operating tolerances
before they may be used. As such, key threaded components within
these systems, i.e. threaded components whose failure may cause a
catastrophic system failure such as screws and/or gages, must also
satisfy operating tolerances. If a threaded component fails to
satisfy these required design tolerances and/or performance
specifications, a degradation of system performance and/or a total
system failure may occur resulting in damage to the system and/or
injury/loss of life to an operator.
[0004] One of the current systems used for inspecting the physical
characteristics of a threaded component employ an attribute
inspection approach that measures the characteristics of the
threaded component via a contact measurement technique which does
not protect product design limits. This technique uses GO and/or No
Go ring gages that are adjusted, or calibrated, to a desired thread
measurement via Go and/or No Go setting plugs. Unfortunately, this
technique does not ensure the integrity of design limits and
because this approach is dependent upon human interaction, this
technique has the disadvantage of being time consuming,
subjectively inaccurate and unreliably repeatable for tight
operating tolerances, thus permitting threaded components having
dimensionally non-conforming characteristics to pass inspections.
Moreover, there is a considerable wear factor on the measuring
instruments, requiring the Go, No Go setting plugs to be inspected
and replaced often.
[0005] Another approach used for measuring external thread gages
utilizes three wires communicated to the gage being measured. The
three wires are of a known diameter and are typically disposed
between the threads of a component such that the wires protrude
from the threads, wherein two wires are disposed on one side of the
threaded component and one wire is disposed on the opposing side of
the threaded component. The diameter over the wires is then
measured via a human inspector. Because the wires are of a known
diameter, this allows certain characteristics of the threads to be
determined by measuring the width of the wires disposed between the
threads. Unfortunately, this approach is also dependent upon human
interaction. If the inspector measuring the distance over the wires
compresses the wires too much, the wires may become deformed
resulting in an inaccurate measurement. Additionally, the surface
finish of a threaded component may adversely affect the accuracies
of these measurements. Moreover, because the wires are loose and
are not held between the threads, the wires may be dropped which
may result in the wires becoming contaminated with dirt, the wires
being lost or, if someone steps on them, the wires being
deformed.
[0006] Furthermore, different operators will generate different
gage pressures on the wires which may cause erroneous readings.
Thus, this approach has the similar disadvantage of being time
consuming, subjectively inaccurate and unreliably repeatable for
tight operating tolerances, thus also permitting threaded
components having dimensionally non-conforming characteristics to
pass inspections. Additionally, the reliability and repeatability
of this measurement is very poor because an operator must measure
angles using an optical projection which is also time consuming,
inaccurate and often fails to satisfy current product and gage
calibration specifications. As such, the Measurement Uncertainty
Factor (MUF) in many situations exceeds the required tolerances and
as a result, the required accuracies for complete certification of
these methods have thus far been unobtainable.
[0007] Another disadvantage to current measuring systems involves
the human element required to obtain the actual physical
measurement of the component and the data obtained from that
measurement. As such, the accuracy of the equipment used to obtain
the measurements is very questionable. For example, using current
technology and methods, if two different people measure the same
characteristics of a single component, it is highly probable that
they will obtain different results. Another example involves when
the component being measured is not be correctly aligned within the
inspection system. This is undesirable because data obtained from
the measurement of an incorrectly aligned component will most
likely contain errors related to the misaligned component and thus
the resultant measurement will be incorrect. Still yet another
example involves errors in the functional size of the component due
to deviations or waviness in the helical path of the thread. This
creates an assembly problem in that parts may not assemble
correctly. This is undesirable because data obtained responsive to
an incorrect function size is unreliable and may result in a
failure of the component or assembly. Another example involves
deviations (in lead, flank angle error, pd error, major & minor
diameter error, root radius roundness, etc.) from the true line
measurements of the component.
SUMMARY OF THE INVENTION
[0008] An inspection system is provided and includes a collimated
light source defining a source optical path, wherein the collimated
light source is operable to cause a collimated light beam to
propagate along the source optical path. The inspection also
includes a sensing device defining a sensor optical path, wherein
the sensor optical path is substantially perpendicular to the
source optical path. Furthermore, the inspection system includes a
positioning device having a positioning device stage, a reflecting
device, wherein the reflecting device is disposed on the
positioning device to be within the source optical path to receive
the collimated light beam. The reflecting device causes a reflected
collimated light beam to propagate along the sensor optical path to
the sensing device. The inspection system also includes a retention
mount, where a portion of the retention mount is disposed within
the sensor optical path such that when a component is retained
within the retention mount, the component blocks at least a portion
of the reflected collimated light beam such that a silhouette is
generated and incident upon the sensing device, where the sensing
device generates data responsive to the silhouette. Moreover, the
inspection system includes at least one processing device, wherein
the at least one processing device is communicated with the sensing
device to receive at least a portion of the data, wherein the
processing device is configured to process the data responsive to
at least one of a smoothing algorithm, a functional size algorithm
and a centering algorithm.
[0009] A method for measuring physical characteristics of a
component using an inspection system is provided wherein the
inspection system includes a light source, a sensing device, a
reflecting device, and a retention mount, at least one of which is
movably associated with the inspection system. The method includes
associating a component with the inspection system such that the
component is disposed within the retention mount, operating the
inspection system to cause the light source to emit a collimated
light beam propagating along a source optical path, reflecting the
collimated light beam via the reflecting device to cause a
reflected collimated light beam to propagate along a sensor optical
path such that the reflected collimated light beam is incident upon
the component to produce a component silhouette which is incident
upon the sensing device, generating image data responsive to the
component silhouette and processing the image data to generate
resultant data responsive to at least one of a plurality of
physical characteristics of the component, wherein the resultant
data is responsive to at least one of a smoothing algorithm, a
functional size algorithm and a centering algorithm.
[0010] A machine-readable computer program code is provided, where
the program code including instructions for causing a controller to
implement a method for measuring physical characteristics of a
component using an inspection system, wherein the inspection system
includes a light source, a sensing device, a reflecting device, and
a retention mount, at least one of which is movably associated with
the inspection system. The method includes associating a component
with the inspection system such that the component is disposed
within the retention mount, operating the inspection system to
cause the light source to emit a collimated light beam propagating
along a source optical path, reflecting the collimated light beam
via the reflecting device to cause a reflected collimated light
beam to propagate along a sensor optical path such that the
reflected collimated light beam is incident upon the component to
produce a component silhouette which is incident upon the sensing
device, generating image data responsive to the component
silhouette and processing the image data to generate resultant data
responsive to at least one of a plurality of physical
characteristics of the component, wherein the resultant data is
responsive to at least one of a smoothing algorithm, a functional
size algorithm and a centering algorithm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing and other features and advantages of the
present invention will be more fully understood from the following
detailed description of illustrative embodiments, taken in
conjunction with the accompanying drawings in which like elements
are numbered alike in the several Figures:
[0012] FIG. 1 shows a perspective side view of a component
inspection system;
[0013] FIG. 2 shows a side view of a component inspection
system;
[0014] FIG. 3 shows a close up side view of a component inspection
system;
[0015] FIG. 4 shows a front view of a component inspection
system;
[0016] FIG. 5 shows a close up perspective front view of a
component inspection system;
[0017] FIG. 6 shows a close up front offset view of a component
inspection system having a component disposed between arbors;
[0018] FIG. 7 shows a schematic block diagram of a collimated light
source;
[0019] FIG. 8 shows a front view of a component disposed between
arbors of a component inspection system;
[0020] FIG. 9 shows a schematic block diagram of a component
inspection system;
[0021] FIG. 10 shows a side view of a threaded component;
[0022] FIG. 11 show a side view of a threaded component;
[0023] FIG. 12 shows a block diagram illustrating an overall method
for measuring the characteristics of a component using a component
inspection system;
[0024] FIG. 13 shows a block diagram illustrating a component/gage
selection algorithm;
[0025] FIG. 14 shows a GUI screen capture of a component/gage
selection screen;
[0026] FIG. 15 shows a GUI screen capture of a component/gage
selection screen;
[0027] FIG. 16 shows a GUI screen capture of a component/gage
selection screen;
[0028] FIG. 17 shows a GUI screen capture of a component/gage
selection screen;
[0029] FIG. 18 shows a GUI screen capture of a component/gage
selection screen;
[0030] FIG. 19 shows a block diagram illustrating a calibration
algorithm;
[0031] FIG. 20 shows a reference arbor knee and a search box;
[0032] FIG. 21 shows a display device illustrating lens distortion
measurements;
[0033] FIG. 22 shows a block diagram illustrating a component
measurement algorithm;
[0034] FIG. 23 shows a block diagram illustrating an R&R
algorithm;
[0035] FIG. 24 shows a side view of a symmetrically threaded
component;
[0036] FIG. 25 shows a side view of a silhouette being projected
onto a sensing device of the component inspection system of FIG. 1
generated by a collimated light beam incident upon the
symmetrically threaded component of FIG. 24;
[0037] FIG. 26 shows a front view of a sensing device of the
component inspection system of FIG. 1 with a silhouette of the
symmetrically threaded component of FIG. 24;
[0038] FIG. 27 is a graph of the x-z plane showing a parametric
representation of the embedding of the flank of a symmetrically
threaded component onto the x-z plane;
[0039] FIG. 28 is a graph of the x-z plane showing a parametric
representation of the embedding of the flank of a symmetrically
threaded component onto the x-z plane, including an aberration;
[0040] FIG. 29 is a block diagram illustrating a method for
measuring the physical characteristics of a component using the
component inspection system of FIG. 1; and
[0041] FIG. 30 is a block diagram illustrating a method for
correcting aberrations in a component silhouette generated by the
component inspection system of FIG. 1;
[0042] FIG. 31 is a block diagram illustrating a method for
accounting for deviations from true line measurements of a threaded
component in a component silhouette generated by the component
inspection system of FIG. 1;
[0043] FIG. 32 is a block diagram illustrating a method for
determining the functional size of a product or gage in a component
silhouette generated by the component inspection system of FIG. 1;
and
[0044] FIG. 33 is a block diagram illustrating a method for
accounting for misalignment of a component in the component
inspection system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0045] An exemplary embodiment is described herein by way of
illustration as may be applied to the measurement and inspection of
threaded gages and product, such as screws, bolts and other
externally threaded components. However, while an exemplary
embodiment is shown and described hereinbelow, it should be
appreciated by those skilled in the art that the invention is not
limited to the embodiment(s) and application(s) as described
herein, but also to any component and/or measurement where accuracy
in tolerance measurement is critical, such as taps, splines; gears,
internal bores, integral plane cylindrical bores, internal threads,
internal/external diameters and/or material composition and/or
strength. Moreover, those skilled in the art will appreciate that a
variety of potential implementations and configurations are
possible within the scope of the disclosed embodiments.
[0046] Referring to FIGS. 1-8, an inspection system 100 is shown
and described. In accordance with an exemplary embodiment,
inspection system 100 includes a collimated light source 102, a
sensing device 104, a reflecting device 106, a component support
device 108 and a system support structure 110. System support
structure 110 includes a base support structure 112, a base
structure 114, a bridge structure 116 defining a bridge cavity 118,
a light source mounting device 120 and a sensor mounting device
122. Base support structure 112 is disposed to be supportingly
associated with base structure 114 and base structure 114 is
disposed to be supportingly associated with bridge structure 116,
wherein bridge cavity 118 is disposed between bridge structure 116
and base structure 114.
[0047] Collimated light source 102 may be associated with base
structure 114 via light source mounting device 120 such that light
emitted from collimated light source 102 propagates along a source
optical path which is defined by collimated light source 102 and
which is parallel to base structure 114. Sensing device 104 may be
associated with bridge structure 116 via sensor mounting device
122, wherein sensing device 104 defines a sensor optical path which
perpendicularly intersects the source optical path. Although, base
structure 114 and bridge structure 116 may be constructed from a
non-metallic polymer casting, it is contemplated that base
structure 114 and bridge structure 116 may be constructed from any
shock, vibration and/or movement attenuating material(s) and/or
composite(s) suitable to the desired end purpose.
[0048] Component support device 108 includes a positioning device
124 and a mounting base 126, wherein mounting base 126 is
associated with base structure 114. Positioning device 124 includes
a positioning stage 128 and a component retainer 130, wherein
component retainer 130 is associated with positioning stage 128 and
includes a first arbor 132 separated from a second arbor 134 via an
arbor cavity 136 and wherein at least one of first arbor 132 and/or
second arbor 134 includes a notched potion, or arbor reference
"knee" position 220. Positioning stage 128 may be positionally and
controllably configurable in all planes (such as x-plane, y-plane,
z-plane) relative to mounting base 126 via a motor operated by a
motor controller. At least one of first arbor 132 and second arbor
134 are configurable for retaining a component within component
retainer 130. Reflecting device 106 may be associated with
positioning stage 128 such that reflecting device 106 is disposed
at an angle of 45.degree. relative to the surface of positioning
stage 128 and such that reflecting device 106 is disposed in the
same plane as first arbor 132, second arbor 134 and arbor cavity
136 (i.e. sensor optical path). Additionally, component support
device 108 may be disposed within bridge cavity 118 such that
reflecting device 106 is disposed at the intersection of the source
optical path and the sensor optical path. Although reflecting
device 106 is shown as a high quality 0.25 wave length first
surface style mirror, reflecting device 106 may be any high quality
reflective surface device suitable to the desired end purpose.
[0049] Sensing device 104 includes a high resolution camera 137
having a microscope-type telecentric optical lens 138 and although
sensing device 104 is shown as being powered via an external power
source, sensing device 104 may be powered using any power source
suitable to the desired end purpose, such as a battery. Moreover,
although microscope type tele-centric optical lens 138 is shown as
having a magnification factor of 2.6.times., microscope type
tele-centric optical lens 138 may have any magnification factor
suitable to the desired end purpose. Furthermore, although sensing
device 104 is a VISICS CCD camera having a microscope type
telecentric optical lens system with 2.6.times. magnification, it
is contemplated that sensing device 104 may be any sensing device
suitable to the desired end purpose.
[0050] Referring to FIG. 7, collimated light source 102 includes a
Light Emitting Diode (LED) 140, a collimating lens 142 and a lens
cap 144 having a lens slot 146 disposed to minimize the stray
emission of light emitted from collimating lens 142. In addition,
collimated light source 102 may be associated with base structure
114 such that collimating lens 142 is in optical line of sight with
reflecting device 106. Moreover, although collimated light source
102 is shown as being powered via an external power source,
collimated light source 102 may be powered using any power source
suitable to the desired end purpose, such as a battery.
[0051] Inspection system 100 is constructed such that when LED 140
is energized a beam of light is emitted from LED 140 and is
projected such that the beam of light becomes incident upon
collimating lens 142. Collimating lens 142 collimates the beam of
light to create a collimated light beam 148, which is then emitted
from collimating lens 142. Upon exiting collimating lens 142,
collimated light beam 148 propagates along the source optical path
and becomes incident upon reflecting device 106, which is disposed
at an angle of 45.degree. relative to the surface of positioning
stage 128. Reflecting device 106 then reflects incident collimated
light beam 148 and the reflected collimated light beam 150
propagates along the sensor optical path to become incident upon
sensing device 104. However, because reflecting device 106 is
disposed in the same plane as first arbor 132, second arbor 134 and
arbor cavity 136 (i.e. sensor optical path), before reflected
collimated light beam 150 becomes incident upon sensing device 104,
reflected collimated light beam 150 becomes incident upon first
arbor 132, second arbor 134 and arbor cavity 136. As such, when a
component is disposed within component retainer 130 to be between
first arbor 132 and second arbor 134, reflected collimated light
beam 150 becomes partially blocked by the component, first arbor
132 and/or second arbor 134 and as a result, a shadow or silhouette
of the component, first arbor 132 and/or second arbor 134 is
created and communicated to sensing device 104.
[0052] Referring to FIG. 9, an overall block diagram of inspection
system 100 is shown and described. Inspection system 100 is shown
as including a processing device 152 having a display device 154,
camera controller circuitry 156 and a communications port 158,
wherein processing device 152 is disposed to be in communication
with collimated light source 102, sensing device 104 and
positioning device 124. In accordance with an exemplary embodiment,
collimated light source 102 is shown in optical communication with
reflecting device 106 such that collimated light beam 148 emitted
from collimated light source 102 is incident upon reflecting device
106. Reflecting device 106 reflects collimated light beam 148 to
produce reflected collimated light beam 150. Sensing device 104 is
shown in optical communication with reflecting device 106 such that
reflected collimated light beam 150 is incident upon sensing device
104 to be received by high resolution camera 137 via microscope
type tele-centric optical lens 138. Thus, when a component is
disposed between first arbor 132 and second arbor 134, the
silhouette of the component, first arbor 132 and/or second arbor
134 is also received by high resolution camera 137.
[0053] High resolution camera 137 converts the silhouette image
into image data and communicates this image data to processing
device 152, wherein the image data is responsive to the interaction
between the component and reflected collimated light beam 148
received by telecentric optical lens 138. Processing device 152
then examines this image data to determine if more image data is
required. If more image data is required, processing device 152
instructs sensing device 104 to obtain more image data. If
necessary, processing device 152 may control the position of
positioning device 126 via communications port 158 to dispose
positioning device 126 as necessary in a manner responsive to the
desired image data. Although processing device 152 is shown as
being communicated with positioning device 126 via an RS-232 or
RS-422 communications port, processing device 152 may be
communicated with positioning device 126 via any device and/or
method suitable to the desired end purpose, such as via wireless
communications. Moreover, camera controller circuitry 156 may be
communicated with processing device 152 via any method and/or
device suitable to the desired end purpose. Furthermore, although
high resolution camera 137 is shown as an electronic camera being
able to support an image size of up to at least 1296.times.1016
pixels, high resolution camera 137 may be any high resolution
camera 137 suitable to the desired end purpose.
[0054] It is further contemplated that, although display device 150
is shown as a flat panel display device having a 1280.times.1024
display capability, display device 150 may be any display device
and/or method suitable to the desired end purpose. Additionally,
although processing device 152 is shown as a computer system
operating an MS Windows 2000 operating system (or higher version)
and having a Pentium processor with at least 128 Mb RAM, Ethernet
network capability and a wireless communications device, such as a
modem, DSL or T1 line, processing device 148 may be any processing
device suitable to the desired end purpose. Positioning device 126
may also include a cast iron stage with a glass slide and a linear
motor having crossed rollers with patented anti-creep technology.
The linear motor allows for at least plus and minus three (3)
inches of travel in both X and Y axes and allows for a maximum load
of at least 635 Kg. Positioning device 126 may also include a
digital motor (servo) controller having an integral drive with a
digital current loop and is communicated with processing device 152
via an RS-232/RS-422 communications port. Additionally, the digital
motor (servo) controller may be capable of supporting a 10-30 amp
peak, 6-15 amps continuous and a 170-300 VDC bus and although the
digital motor (servo) controller shown as being capable of
supporting movement in the X and Y axis, it should be appreciated
that digital motor (servo) controller may also be capable of
supporting movement in the Z axis, as well.
[0055] Referring to FIG. 10 and FIG. 11, a side view of an
externally threaded component, such as a threaded product is shown
and discussed. A component thread is a combination of a thread
ridge and groove, typically of uniform section, that is produced by
forming a groove with a helix on an external or internal surface of
a cylinder or cone. Because the component thread is designed to
operate in association with an opposing component thread, it is
essential that certain key physical characteristics relating to
thread size and thread form be tightly controlled. As such, it is
desirable to measure these thread size characteristics and thread
form characteristics as accurately as possible. The thread size
characteristics include the major diameter, the minor diameter, the
functional diameter and the pitch diameter and the thread form
characteristics include the pitch, the lead, the uniformity of
helix angle, the flank angle and the included angle, each one of
which is discussed in more detail hereinbelow.
[0056] The major diameter of the component is the diameter or width
of an imaginary cylinder, called the major cylinder, whose surface
would be parallel to the straight axis of the component and whose
surface would bound the crests of an external thread or the roots
of an internal thread. However, although both threaded gages and
threaded products typically have a full form major diameter,
threaded gages also typically have a truncated major diameter. As
such, a threaded gage includes a full form major diameter and a
truncated major diameter and a threaded product only includes a
full form major diameter. The full form major diameter, for both a
threaded gage and a threaded product, may be defined as a composite
measurement responsive to the major radius (which may be defined as
the distance between the component axis and one surface of the
major cylinder or one half of the major diameter) measured on the
0.degree. side of the full form threads and the major radius
measured on the 180.degree. side of the full form threads. However,
for a threaded gage, the truncated major diameter may be defined as
a composite measurement responsive to the major radius measured on
the 0.degree. side of the truncated threads and the major radius
measured on the 180.degree. side of the truncated threads.
[0057] The minor diameter of the component is the diameter of an
imaginary cylinder, or minor cylinder, whose surface would be
parallel to the straight axis of the component and whose surface
would bound the roots of an external thread or the crests of an
internal thread. Thus, the minor radius, which may be defined as
the distance between the component axis and one surface of the
minor cylinder or one half of the minor diameter, and which is
typically measured using the first thread on the 0.degree. side, is
typically determined using a best fit radius that is tangential to
the flanks and that has no reversals.
[0058] The pitch of a thread having uniform spacing may be defined
as the distance, measured parallel to the axis, between
corresponding points on adjacent thread forms in the same axial
plane and on the side of the axis. Thus, the pitch may be defined
as the number of threads per inch (TPI) and the pitch distance may
be defined as 1/TPI, wherein TPI is measured parallel to the thread
axis, from a point on one flank to the corresponding point on the
next available flank. The pitch diameter of the component is the
diameter or width of an imaginary cylinder, called the pitch
cylinder, whose surface would be parallel to the axis of the thread
or component and whose surface would intersect the profile of a
straight thread such that the width of the thread ridge and the
thread groove are equal.
[0059] Thus, the pitch diameter of a threaded gage, which typically
includes full form threads and truncated threads, includes a pitch
diameter front and a pitch diameter back, wherein the pitch
diameter front is responsive to the leading and trailing angles of
the thread, the lead and the crest width of the threads at the
truncated location and wherein the pitch diameter back is
responsive to the leading and trailing angles of the thread, the
lead and the crest width of the threads at the full form location.
Whereas the pitch diameter of a threaded component, which typically
includes only full form threads, includes only a pitch diameter
front, wherein the pitch diameter front is responsive to the
leading and trailing angles of the thread, the lead and the crest
width of the threads.
[0060] The lead may be defined as the axial distance moved by the
component in relation to the amount of angular rotation, when a
threaded component is rotated about its axis with respect to a
fixed mating thread. Thus, the lead is the amount of axial travel
when the threaded component is turned one full turn or 360.degree.
and pitch is the distance measured parallel to the axis from a
point on one flank to the corresponding point on the adjacent
flank. Any deviation in lead tends to increase the functional
diameter of the external thread (or decrease the functional
diameter of the internal thread) and rapidly consumes the allowed
operating pitch diameter tolerance of a threaded component. A
deviation in lead may result in non-engagement of a screw thread
with its mating part at all but a few points. Thus, when the
threaded parts are assembled, and torque is applied, the result is
pressure being applied to only a few, and possibly only one
pressure flank. As such, any deviation in lead may produce a
non-engagement condition for some threads and cause a failure in
engaging threads at the point of pressure flank engagement due to
non-engagement.
[0061] The helical path deviation of a thread is a wavy deviation
from a true helical advancement or a non-uniformity of helix angle.
In a similar manner as the lead, a deviation in the helical path
causes an increase in the functional size of the component in
proportion to the amount of waviness. Thus, all of the statements
that were made concerning a deviation in lead also apply to a
deviation in helical path and similarly, a deviation of helical
path may result in partial engagement of the thread flanks with the
result that torque pressures may not be evenly distributed and may
result in pre-load relaxation.
[0062] The included angle of a thread is the angle between the
flanks of the thread measured in an axial plane. The flank angles
are the angles between the individual flanks and the perpendicular
to the axis of the thread measured in an axial plane. A flank angle
of a symmetrical thread is commonly referred to as the half
included angle or the half angle of a thread. A deviation in the
flank angle may result in a failure of the thread when the product
is exposed to line loads or when torque is applied. This is because
an improper flank engagement may create an unevenly distributed
pressure load along the flank rather than the pressure load being
distributed evenly along the flank.
[0063] Other important physical characteristics of the component
include the functional size diameter, the taper characteristic of
the pitch cylinder and the out-of-roundness, all of which can
generate a non-engagement condition. In fact, distortion or
deviation from specifications of any of the physical
characteristics discussed herein may cause varying degrees of
non-engagement.
[0064] The functional, or virtual, diameter of a thread (external
or internal) may be defined as the resultant size of the product
thread taking into account the effect of lead, helical path
deviation, flank angle deviation, taper and out-of-roundness. As
such, it may be seen that the functional diameter is the pitch
diameter of the enveloping thread of perfect pitch, lead and flank
angles, having full depth of engagement, but that are clear at
crests and roots, of specified lengths of engagement. For an
external thread, the functional diameter may be derived by adding
the cumulative effects of deviations to the pitch diameter (for
internal threads subtracting the cumulative effects of deviations),
including variations in lead and flank angles over a specified
length of engagement. Thus, it should be clear that the effects of
taper, out-of-roundness and surface defects may be positive or
negative on either external or internal threads, respectively.
[0065] The taper characteristic of the pitch cylinder is simply a
tapering of the pitch cylinder of the thread. As can be seen, a
tapered thread fails to give a complete thread engagement, which
may lead to a product failure caused by uneven torque pressure
conditions on pressure flanks and pre-load relaxation.
[0066] The out-of-roundness of the pitch cylinder, which is any
deviation of the pitch cylinder from round, limits the thread
engagement and allows for only line contact with the mating thread
and typically includes two types of out-of-roundness: Multi-lobe or
Oval.
[0067] With the desired physical characteristics of a threaded
component to be measured explained hereinabove, an overall method
for measuring these characteristics is provided and described
hereinbelow. Furthermore, it is contemplated that each of the
methods, calculations and algorithms described herein, may be
performed via a system operator and/or via an automated system.
[0068] Referring to FIG. 12, an overall method 300 for measuring
the characteristics of a component using inspection system 100 is
shown and discussed. In accordance with an exemplary embodiment,
inspection system 100 and component 162 may be obtained, as shown
in block 302, wherein inspection system 100 includes a light source
102, a sensing device 104, a reflecting device 106, and a component
support device 108. Information regarding the type of threaded
component 162 such as a screw, gage, bolt and/or other component,
to be measured is determined and communicated to inspection system
100 via system software, as shown in block 304. Although, this may
be accomplished via a system operator who enters information
regarding threaded component 162 into processing device 152 via a
mouse or keyboard in a manner responsive to a component/gage
selection algorithm 400, it should be appreciated that component
information may be stored in a database and retrieved via sensors,
such as bar code readers.
[0069] Once component 162 has been selected and component
information communicated to processing device 152 has been
completed, component 162 is associated with inspection system 100
to be disposed within component support device 108, as shown in
block 306. This may be accomplished by a system operator disposing
component 162 within component retainer 130 such that component 162
is retained within arbor cavity 136 via first arbor 132 and second
arbor 134. Inspection system 100 is then operated to perform a
pre-calibration lens distortion analysis to determine any parabolic
lens distortion factors, as shown in block 308. This
pre-calibration lens distortion analysis is a curve fitting routine
that is performed prior to the calibration procedure and that is
separate from the system lens distortion measurement and correction
that is part of the calibration procedure and that is used to
compensate for any parabolic distortion that is inherent in optical
lens 138. Moreover, although the lens distortion analysis is
provided by the lens manufacturer, it should be appreciated that
any suitable lens distortion analysis method may be independently
developed and/or used.
[0070] In order to perform this analysis, collimated light source
102 emits a collimated light beam that becomes incident upon
reflecting device 106, thus causing a reflected collimated light
beam to become incident upon sensing device 104. Sensing device 104
receives this reflected collimated light beam and generates image
data responsive to this reflected collimated light beam. Because
the reflected collimated light beam is unimpeded, the image data
generated by sensing device 104 is only responsive to the
characteristics of collimated light source 102, reflecting device
106 and sensing device 104. Thus, the image data may be examined to
determine if lens 138 of sensing device 104 contains any
imperfections or distortions. As such, processing device 152
examines the image data to determine whether any variations of
image intensity exist within a predefined field of view of lens
138. This may be accomplished by examining portions of the
generated image data responsive to a number of various image
locations within the field of view of lens 138, wherein the
examined portions are responsive to locations within the vertical
and horizontal span of the field of view, ranging from the bottom
to the top and from the left hand side to the right hand side of
the field of view.
[0071] For example, the image data to be examined may include data
points responsive to a plurality of locations on lens 138 that
represent the vertical span of lens 138 (or of the field of view of
lens 138) for both the 0.degree. and 180.degree. side of at least
one arbor. The results for each of these data points, which
represent the actual vertical distortion characteristics of lens
138, may then be plotted on an actual vertical gradient chart (and
compared with an ideal vertical gradient chart provided by the
manufacturer of lens 138, wherein the ideal vertical gradient chart
represents the ideal lens characteristics. In a similar fashion,
the image data to be examined may also include data points
responsive to a plurality of locations on lens 138 that represent
the horizontal span of lens 138 (or of the field of view of lens
138). As above, the results for each of these data points, which
represent the actual horizontal distortion characteristics of lens
138, are then plotted on an actual horizontal gradient chart and
compared with an ideal horizontal gradient chart provided by the
manufacturer of lens 138, wherein the ideal horizontal gradient
chart represents ideal lens characteristics. Any deviations between
the actual vertical/horizontal gradient charts and the ideal
vertical/horizontal gradient charts are recorded and stored for
later application in subsequent calculations and/or measurements.
It should be noted that, in order to minimize any effect of lens
distortion on the measurements, the areas of interest, i.e. areas
of component 162 to be measured, are almost always disposed in the
center of the field of view for lens 138.
[0072] Once this has been completed, inspection system 100 is
operated to cause positioning stage 128 to be disposed such that
the reflected collimated light beam is incident upon component 162,
as shown in block 310. The reflected collimated light beam incident
upon component 162 produces a silhouette of component 162 and/or
first arbor 132 which is projected to be incident upon sensing
device 104. Sensing device 104 generates image data responsive to
silhouette of component 162 and first arbor 132 and communicates
this image data to processing device 152 which processes the image
data to generate resultant data, as shown in block 312. Processing
device 152 then instructs inspection system 100 to perform a system
calibration in a manner responsive to a predetermined calibration
algorithm 500, as shown in block 314. Upon completion of
predetermined calibration algorithm 500, inspection system 100
performs a component measurement in a manner responsive to a
predetermined component measurement algorithm 600, predetermined
calibration algorithm 500 and/or the results of lens distortion
analysis, as shown in block 316. Once the component measurement has
been completed, component information is then displayed to the
system operator via display device 154 and/or via a printed
certificate or report. In accordance with an exemplary embodiment,
component/gage selection algorithm 400, predetermined calibration
algorithm 500 and predetermined component measurement algorithm 600
are discussed in more detail below.
[0073] Referring to FIG. 13, a block diagram of a component/gage
selection algorithm 400 is shown and described. It should be noted
that although component/gage selection algorithm 400 is described
for component/gage selection screen 214 herein, as configured for a
threaded product, component/gage selection algorithm 400 may be
modified as required for various component selections.
[0074] Referring to FIG. 14, upon starting inspection system 100, a
component/gage selection screen 200 is displayed to a system
operator via display device 154. Component/gage selection screen
200 may be created in a Graphical User Interface (GUI) format
having a plurality of pull-down menus 202 and software buttons 204
that allow known physical characteristics of a component to be
measured to be communicated to inspection system 100 via a mouse
and/or keyboard. Pull-down menus 202 may include at least one of a
component size selection pull down menu 206, a TPI pull down menu
208, a Class selection pull down menu 210 and a thread length pull
down menu 211 and software buttons 204 may include at least one of
a unit selection button 212, a component selection button 214, a
set plug/work plug selection button 216 and a go/not go selection
button 218. It should be appreciated that component selection
button 214 allows for the selection of a plurality of types of
components to be inspected, including a plain diameter gage, a
threaded gage, a product, an X-calibration block, a Y-calibration
block and a Roll. It should also be appreciated that pull-down
menus 202 and software buttons 204 may be displayed to a system
operator in a manner responsive to component selection button
214.
[0075] For example, referring to FIG. 15, if component selection
button 214 is configured for a plain diameter gage, plurality of
pull-down menus 202 and plurality of selection buttons 204
displayed to a system operator include at least one of a unit
selection button 212 and a plain diameter gage size pull down-menu
213. Referring to FIG. 16, if component selection button 214 is
configured for a threaded gage, plurality of pull-down menus 202
and plurality of selection buttons 204 displayed to a system
operator include at least one of unit selection button 212, set
plug/work plug selection button 216, go/not go selection button
218, component size selection pull down menu 206, TPI pull down
menu 208 and Class selection pull down menu 210. Referring to FIG.
17, if component selection button 214 is configured for a threaded
product, plurality of pull-down menus 202 and plurality of
selection buttons 204 displayed to a system operator include at
least one of a unit selection button 212, set plug/work plug
selection button 216, go/not go selection button 218, component
size selection pull down menu 206, TPI pull down menu 208, Class
selection pull down menu 210 and a thread length menu 211.
Additionally, when component selection button 214 is configured for
a threaded product, a pitch diameter measurement menu 217 may be
displayed. Referring to FIG. 18, a component/gage selection screen
202 is shown for component selection button 214 configured for a
calibration block.
[0076] In the case of a threaded component 162, once component/gage
selection screen 200 is displayed, the system operator selects the
system of units inspection system 100 is to use when measuring
threaded component 162, such as English or Metric units, via unit
selection button 212, as shown in block 402. The system operator
then selects the type of component that inspection system 100 will
be measuring (i.e. a threaded component), via gage/product
selection button 214, as shown in block 404, and (in the case of a
gage) whether it is a set plug or a work plug, via set plug/work
plug selection button 216, as shown in block 406. Also in the case
of a gage, once this has been accomplished, the system operator
selects whether this is a go or not/go, via go/not go selection
button 218, and the gage size of the component is selected, via
gage size selection pull-down menu 206, as shown in block 408. In
the case of a component, the Threads Per Inch (TPI) and the Class
of the component are then selected, via TPI pull down menu 208, as
shown in block 410 and Class selection pull down menu 210,
respectively, as shown in block 412.
[0077] Upon completion of the system startup procedure, inspection
system 100 begins performing a system calibration procedure
responsive to predetermined calibration algorithm 500. Referring to
FIG. 19 and FIG. 20, once the system calibration procedure has been
initiated, positioning stage 128 is moved to a predetermined
starting position, or HOME position, as shown in block 502. It is
contemplated that any location of positioning stage 128 may be
selected as the HOME position. At this point, all encoders are
zeroed and all positional measurements are determined with
reference to this HOME position. An Arbor reference adjustment is
then performed to properly locate the arbor reference "knee"
position 220, as shown in block 404, wherein arbor reference "knee"
position 220 is a notch disposed on at least one of first arbor 132
and/or second arbor 134. A software "constraint window" or search
box is created within the field of view of lens 138 and image data
representing the image contained within this search box is then
examined to locate arbor reference "knee" position 220. Arbor
reference "knee" position 220 may be located by analyzing this
image data for differences in pixel intensities to identify where
the horizontal arbor surface ends and the vertical arbor surface
begins. This vertical arbor surface is arbor reference "knee"
position 220. Once arbor reference "knee" position 220 is located,
blue crosshairs 222 are disposed at arbor reference "knee" position
220 and displayed to the system operator via display device 154 to
allow the system operator to visually confirm arbor reference
"knee" position 220. It should be stated that arbor reference
"knee" position 220 must be contained with this search box for
predetermined calibration algorithm to continue. If arbor reference
"knee" position 220 is not disposed within the search box,
predetermined calibration algorithm terminates.
[0078] In accordance with an exemplary embodiment, the lens system
distortion measurements are then conducted, as shown in block 506.
Referring to FIG. 21, this may be accomplished by operating
inspection system 100 such that positioning stage 128 relocates
arbor reference "knee" position 220 to four distinct
position/locations within the field of view of lens 138 on the
0.degree. side of at least one of first arbor 132 and/or second
arbor 134. These four distinct position/locations are located at a
lower vertical field of view position 135, a lower middle vertical
field of view position 137, a upper middle vertical field of view
position 139 and an upper vertical field of view position 141. At
each of these four vertical locations, three horizontal
measurements are made and include a left measurement 143, a center
measurement 145 and a right measurement 147. This measurement data
may be obtained by observing and/or analyzing the image data
corresponding to the particular points of measurement. The results
of this observation/analysis may then be recorded for use in
subsequent calculation. This sequence is then repeated on the
180.degree. side of at least one of first arbor 132 and/or second
arbor 134. It should be appreciated that a total of 24 measurements
(i.e. 12 on the 0.degree. side and 12 on the 180.degree. side) are
stored and thus, become part of the calculated lens distortion
measurement performed near the end of the calibration cycle. As
discussed above, the lens system distortion routine, and thus the
distortion equations, may be provided by the manufacturer of lens
system 138 or may be generated responsive to the component to be
inspected.
[0079] Once the lens system distortion measurements have been
conducted, the X-Axis calibration is performed, as shown in block
508. The X-Axis calibration may be accomplished by locating the
center position, the left extreme and the right extreme of field of
view 230 of lens 138 and using these data points to calculate the
inches per step, inches per pixel and/or the steps per inch
calibration factors for the X-Axis. One way to determine center
position, left extreme and right extreme of field of view 230 is to
move arbor reference knee position 220 to the extreme left hand
side of field of view 230 and register this location as the left
extreme. Arbor reference knee position 220 is then moved to the
extreme right hand side of field of view 230 and this location is
registered as the right extreme. Arbor reference knee position 220
should then be moved to a point midway between the left extreme and
the right extreme of field of view 230. This point will be the
center of field of view 230 and should be registered as the center
position. This ensures minimal distortion from lens 138.
[0080] Upon completion of the X-Axis calibration, a Y-Axis
calibration at the 1.sup.st 0.degree. diameter is performed, as
shown in block 510. The Y-Axis calibration at the 1.sup.st
0.degree. diameter may be accomplished by using the lower middle
center location and upper middle center location obtained during
the lens system distortion measurement to calculate the inches per
step, inches per pixel and/or the steps per inch calibration
factors for the Y-Axis. The lower middle vertical location is then
determined and is used to measure the radius for the 0.degree. side
(which may later be added to the radius for the 180.degree. side to
determined the diameter of the arbor).
[0081] Upon completion of the Y-Axis calibration at the 1.sup.st
0.degree. diameter, a Y-Axis 2.sup.nd 0.degree. diameter
determination is performed, as shown in block 512. The
determination of the Y-Axis 2.sup.nd 0.degree. diameter may be
accomplished by moving positioning stage 128 such that arbor
reference knee position 220 on the 0.degree. side of the arbor is
disposed at a lower vertical location, a lower middle vertical
location, an upper middle vertical location and an upper vertical
location of field of view 230. At each of these locations,
inspection system 100 performs three horizontal measurements, a
left horizontal measurement, a center horizontal measurement and a
right horizontal measurement. This data may be stored and may
become part of the calculated lens distortion factors determined
toward the end of the calibration cycle. It should be appreciated
that the lower middle vertical location may be the final position
to be measured and may be used to measure the radius for the
180.degree. side, which may later be added to the radius of the
0.degree. side to determine the arbor diameter.
[0082] Upon completion of the Y-Axis 2.sup.nd 0.degree. diameter
determination, a Y-Axis diameter determination is performed, as
shown in block 514. The determination of the Y-Axis 2.sup.nd
diameter may be accomplished by moving the left arbor reference
location to determine the location of the arbor relative to the
right arbor reference and lens 138. A single measurement is taken
in the center of field of view 230 to minimize distortion and is
used to determine the radius and to compute the tangent correction
factor that is used to compensate for any misalignment of the
Y-Axis of positioning stage 128 with the Y-Axis of lens 138.
[0083] Once this has been completed, a Y-Axis 2.sup.nd 180.degree.
diameter determination is performed, as shown in block 516, by
moving positioning stage 128 to the 180.degree. side (same X-Axis
position) to measure the radius. The Y-Axis tangent correction
factor is then determined, as shown in block 518. This compensates
for a component that may be disposed between first arbor 132 and
second arbor 134 in a non-level (i.e. horizontal) manner. Moreover,
this may be accomplished by using the measurements taken at the
right and left sides of the arbor and both the X and Y measurement
information from the encoders and the image measurement tools are
used to compute the tangent correction factor. It should be noted
that all subsequent Y-Axis measurements include this compensation
factor. All of the information obtained above are then used to
determine the lens distortion factor, as shown in block 520, which
is then used for all subsequent X and Y measurements, including any
light source and/or system stage positional distortions/errors
(i.e. Abbe*stage errors).
[0084] It is contemplated that predetermined component measurement
algorithm 600 is responsive to the component being measured. As
such, predetermined component measurement algorithm 600 is
explained for various types of components to be measured and
includes a threaded product and a threaded gage. It should be
appreciated that all measurements may be conducted by observing
and/or analyzing image data to determine desired points of interest
on threaded component 162, such as the thread ridges and grooves.
These points of interest may be located by examining the image data
and identifying variations in pixel intensities to establish
silhouette edge points of threaded component 162. Once these points
of interest have been identified, desired physical characteristics
of threaded component 162 may be determined using known
mathematical, geometric and/or trigonometric relationships.
[0085] Upon completion of predetermined calibration algorithm 500,
positioning stage 128 is positioned back to arbor reference knee
position 220 and component measurement algorithm 600 is initiated,
as shown FIG. 22. At this point, the Flank registration is
performed, as shown in block 602. This may be accomplished by
disposing positioning stage 128 such that component 162 is
positioned to an initial X and Y location by moving positioning
stage 128 one half inch away from arbor reference knee position 220
in the X direction and toward component 162. Positioning stage 128
is then moved in the Y direction such that the lower limit of the
pitch diameter at the centerline of field of view 230 is
approximated. A software measurement tool is then placed at the
centerline to find the flank angle crossings at the centerline. The
stage is then moved again away from arbor reference knee position
220 in the X-axis direction to align the minor diameter with the
left edge of field of view 230. All subsequent measurements rely on
moving in pitch lead increments in the X-axis direction. It should
be noted that the pitch lead increments are determined by the
component selection and are published at the top of the Lead
Standards readouts. It should be appreciated that, for threaded
gages, the truncated measurements will be conducted at thread #2
and the full form measurements will be conducted at thread #6. The
term 4.times. refers to the number of threads for the third lead
measurement and indicates that it is being made over a span of four
threads and the term /10 indicates that there are ten threads
available on this component.
[0086] Once the flank registration has been performed, the 1.sup.st
full thread 0.degree. side truncated measurements are conducted, as
shown in block 604. This may be accomplished by repositioning
positioning stage 128 on the first thread on the 0.degree. side
designated as the truncated thread location. This designation is
dependent upon the thread numbers and thus upon the selection of
component 162. Using the silhouette image data, processing device
152 then determines the minor radius, the major radius (for set
plug only), the pitch radius, the lead pitch, the lead/trail flank
angles and the included angles. The major radius is determined via
the major diameter, which is a composite measurement based on the
major radius of the 0.degree. and corresponding 180.degree. side of
the threads. Thus, the major radius is determined by summing the
individual measurements along the thread flat and dividing by the
number of measurements collected. The number of measurement
locations may be determined by taking 70% of the thread width, as
determined by predetermined thread tables, and centering them on
the center of the thread. This major radius average is then
combined from both the 0.degree. and the 180.degree. sides to get
the major diameter. For a gage, this process is performed for both
truncated and full form locations and for a product, this process
is performed only for the full form location.
[0087] The pitch diameter calculation (for both truncated and full
form location), which is based on the leading and trailing angles,
major diameter, pitch lead and crest width at the location in
question (i.e. truncated or full form), may be determined by the
equation:
PD=MD-(Cot(PL/2)-CW,
[0088] Where, PD is pitch diameter, MD is major diameter, PL is
pitch lead and CW is crest width. The lead front measurement, which
is responsive to the difference between the groove distance and the
ridge distance along the leading/trailing/leading flanks may be
determined by positioning a software measurement tool along the
X-axis and moving the tool vertically around the pitch diameter
until the groove distance minus the ridge distance is minimized.
The tool is then repositioned at the minimized location and the
groove distance and the ridge distance are added to determine the
lead front. The lead back measurement, which is responsive to the
difference between the groove distance and the ridge distance along
the trailing/leading/trailing flanks may similarly be determined by
positioning a software measurement tool along the X-axis and moving
the tool vertically around the pitch diameter until the groove
distance minus the ridge distance is minimized. The tool is then
repositioned at the minimized location and the groove distance and
the ridge distance are added to determine the lead back.
[0089] In an additional embodiment, the determination of the Pitch
Diameter (PD) may include a Correction Factor (CF) to adjust for
any aberrations that may be present in the silhouette image data.
Referring to FIG. 24, a symmetrically threaded object 800 is shown
having a plurality of threads 802. The Pitch Diameter (PD) for the
threaded object 800 having thread grooves 804 and thread ridges 806
may be described simply as the distance between a point on the
0.degree. side of the object and the 180.degree. of the object
where the width of the thread ridge, g.sub.1, and the thread
groove, g.sub.2, are equal. However referring to FIG. 25 and FIG.
26, as the collimated light beam 808 falls incident upon the object
800, a shadow image 810 may be created and may fall incident upon
the sensing device 812 along with the silhouette image 814. As
such, the silhouette image data generated by the sensing device 812
may include data responsive to the shadow image 810 and as such,
the physical characteristics of the object 800, such as the Pitch
Diameter (PD) may be skewed and inaccurate.
[0090] To compensate for any aberrations of the shadow image 810
within the silhouette image data, a Correction Factor (CF) may be
generated and applied to the process for determining the Pitch
Diameter (PD). As such, the Pitch Diameter (PD) may be represented
by the equation:
PD.sub.Final=PD.sub.Observed-CF,
wherein PD.sub.Final is the Pitch Diameter (PD) adjusted for any
aberrations, PD.sub.Observed is the Pitch Diameter (PD) as measured
and containing any aberrations and CF is the Correction Factor (CF)
representing any aberrations.
[0091] For example, one embodiment for compensating for any
aberrations includes generating a Correction Factor (CF) responsive
to the shadow image and subtracting the Correction Factor (CF) from
the silhouette image data generated by the sensing device, wherein
the Correction Factor (CF) may be determined by parametrically
representing one flank of a thread (i.e. the rear side of a thread
ridge) in 3-D space having an x-axis, a y-axis and a z-axis as an
embedding of a strip into a 2-D space having only the x-axis and
the z-axis. Referring to FIG. 27, for objects or components having
symmetrical threads, using only two variables (r, t), a first
point, r.sub.1, representing the minor diameter of the thread on
the x-z axis, and a second point, r.sub.2, representing the major
diameter of the thread on the x-z axis, is shown in the x-z plane
connected via a straight line, K.sub.x-z, which is drawn between
the two points r.sub.1 and r.sub.2. The variable R is the 2-D
representation of the Pitch Diameter (PD) in the x-z plane and t is
the flank angle which may be represented as the angle between the
line K.sub.x-z drawn between the two points, r.sub.1 and r.sub.2,
in the x-z plane and the projection K.sub.x-y of the line K.sub.x-z
onto the x-y plane. Additionally, the variable L.sub.x-z is the
lead angle of the thread and the variable m is the tangent of the
flank angle, t. The variable r is a point on the x-z plane which
represents the distance between the z-axis and a point on the line
K.sub.x-z and thus may range from half of the minor diameter to
half of the major diameter. As such, we can parameterize the above
relationships using the following equations:
x=r cos(t),
y=r sin(t), and
z=mr+Lt/2n.
[0092] This embedding can then be projected onto the x-z plane by
using the equations:
x=r cos(t), and
z=mr+Lt/2n,
to obtain the determinant of the Jacobian matrix, wherein the
Jacobian matrix is defined by:
J ( x 1 xn ) = [ .differential. z 1 .differential. x 1
.differential. z 1 .differential. xn .differential. zn
.differential. x 1 .differential. zn .differential. xn ] .
##EQU00001##
As is well known, the Jacobian matrix is the matrix of all
first-order partial derivatives of a vector-valued function and may
be representative of the `best` linear approximation to a
differential function near a given point. Thus, using the equations
as derived hereinabove,
x=r cos(t), and
z=mr+Lt/2n,
the Jacobian matrix J(x.sub.1 . . . x.sub.n) may be represented
as:
J ( x 1 xn ) = [ cos ( t ) - r sin ( t ) m L / 2 .pi. ] .
##EQU00002##
Solving the Jacobian matrix J(x.sub.1 . . . x.sub.n) to find the
set of points of the shadow image (i.e. ribbon) on the x-z plane
gives the following:
J=((L/2.pi.)cos(t)+mr sin(t))=0,
where,
r=-(L/(2.pi.m tan(t))).
[0093] Referring to FIG. 28, if the value of R is set to half of
the Pitch Diameter (PD) of the thread, the point on the projection
of the ribbon that is directly to the "right" of the point where
r=R and t=0 may be determined. This is a point on the ribbon that
has the same z-coordinate as the Pitch Diameter (PD) point
(x,y,z)=(R,0,mR) and thus, it can be seen that at the Pitch
Diameter (PD) point (x,y,z), z=mR. Plugging z=mR into the equation
for z gives the following:
z = mR = mr + Lt ( 2 .pi. m ) , r = R - Lt ( 2 .pi. m ) ,
##EQU00003##
and combining equation (1) with equation (2) gives the
following:
- L 2 .pi. m tan ( t ) = R - Lt 2 .pi. m , ##EQU00004##
and
L+(2.pi.mR-Lt)tan(t)=0,
which must be solved for each given value of L, m and R. Having the
flank angle, t, these equations may be solved to obtain r, wherein
half of the displacement of the Pitch Diameter (PD) is the
x-coordinate of the point on the ribbon minus the x-coordinate of
the Pitch Diameter (PD) point (x,y,z)=(R,0,mR) or simply, r
cos(t)-R. Thus, it should be appreciated that the Correction Factor
(CF) may be assumed to be twice this amount and may be given by the
equation:
CF=2(r cos(t)-R).
Thus, the Pitch Diameter for a symmetrically threaded object
adjusted for any aberrations, PD.sub.Final, may be determined by
applying the Correction Factor (CF) above into equation (1) to give
the following equation:
PD.sub.Final=PD.sub.Observed-2(r cos(t)-R),
[0094] In a similar fashion, for objects or components having
asymmetrical threads, such as buttresses, the methodology applied
hereinabove may be used for both flanks (due to the asymmetry the
calculations should be conducted for each flank). As such, a simple
geometric argument using the above approach for both flanks may
combine the two results in a kind of weighted average to give:
C F = ( d 1 tan ( a 1 ) + d 2 tan ( a 2 ) ) ( tan ( a 1 ) + tan ( a
2 ) ) , ##EQU00005##
wherein d1 and d2 are the shadow corrections for the two flank
angles treated separately as symmetrical threads and a1 and a2 are
the respective flank angles. Given the above, the Pitch Diameter
for an asymmetrically threaded object adjusted for any aberrations,
PD.sub.Final, may be determined by applying the Correction Factor
(CF) above into equation (1) to give the following equation:
PD Final = PD Observed - ( d 1 tan ( a 1 ) + d 2 tan ( a 2 ) ) (
tan ( a 1 ) + tan ( a 2 ) ) . ##EQU00006##
[0095] Referring to FIG. 29, a block diagram illustrating a method
900 for measuring the physical characteristics of a component using
an inspection system is shown and includes associating an object
with the inspection system 100 such that the object is disposed
within the retention mount, as shown in operational block 902. The
inspection system is operated to cause the light source to emit a
source collimated light beam which propagates along the source
optical path, as shown in operational block 904. As the source
collimated light beam propagates along the source optical path the
source collimated light beam is at least partially incident upon
the reflecting device to generate a reflected collimated light beam
that propagates along the sensor optical path to be at least
partially incident upon the object, as shown in operational block
906. This creates a silhouette of the object, wherein at least a
portion of the silhouette is incident upon the sensing device which
in response generates initial image data. This initial image data
is processed to generate resultant image data responsive to at
least one of a plurality of physical characteristics of the object,
as shown in operational block 908, wherein the initial image data
is processed responsive to at least one predetermined algorithm to
correct for any aberrations in the initial image data. As discussed
hereinabove, the predetermined algorithm may be responsive to the
type of object being inspected. For example, if the object is a
threaded object having symmetrical threads, then the predetermined
algorithm may be at least partially responsive to the equation:
CF=2(r cos(t)-R),
However, if the object is a threaded object having asymmetrical
threads, then the predetermined algorithm may be at least partially
responsive to the equation:
C F = ( d 1 tan ( a 1 ) + d 2 tan ( a 2 ) ) ( tan ( a 1 ) + tan ( a
2 ) ) . ##EQU00007##
[0096] Referring to FIG. 30, a block diagram illustrating a method
1000 for correcting aberrations in a component silhouette generated
by inspection system 100 is shown and includes associating the
object 800 with the inspection system 100, as shown in operational
block 1002, and operating the inspection system 100 to cause the
light source to emit a source light beam that propagates along the
source optical path to at least partially incident upon the object
800, as shown in operational block 1004. The source light beam is
reflected to create a reflected light beam that propagates alone a
sensor optical path to be at least partially incident upon the
object 800 to produce a silhouette 814 of the object 800 that is at
least partially incident upon the sensing device 812, as shown in
operational block 1006, wherein the sensing device 812 generates
initial image data responsive to the silhouette and any aberrations
in the silhouette. The initial image data is then processed to
generate resultant image data, as shown in operational block 1008.
This may be accomplished by generating initial Pitch Diameter (PD)
data from the initial image data, as shown in operational block
1010. This initial Pitch Diameter (PD) data is then parameterized
and expressed in a Jacobian Matrix, J(x.sub.1 . . . x.sub.n), as
shown in operational block 1012, and the Jacobian Matrix,
J((x.sub.1 . . . x.sub.n), is solved responsive to a plurality of
physical characteristics of the object to generate Correction
Factor (CF) data, as shown in operational block 1014, wherein the
plurality of physical characteristics may include at least one of
the lead angle, the flank angle, the major diameter and the minor
diameter. Once the Correction Factor (CF) data is determined, the
initial Pitch Diameter (PD) data is processed responsive to the
Correction Factor (CF) data to obtain the resultant Pitch Diameter
(PD) data, as shown in operational block 1016.
[0097] The multi thread lead, which is responsive to the distance
between the lead front and the lead back measurements, may now be
determined. Additionally, the lead angle may be determined by an
optimistic theoretical line of best fit along the leading flanks of
the thread on the 0.degree. side at the truncated location. The
trailing angle may be determined by an optimistic theoretical line
of best fit along the trailing flanks of the thread on the
0.degree. side at the truncated location. The included angle may
then be determined by adding the leading angle and trailing
angle.
[0098] At this point, the 2.sup.nd thread 0.degree. side full form
measurements are then made, as shown in block 606. This may be
accomplished by repositioning positioning stage 128 on the second
thread on the 0.degree. side designated as the full form thread
location. As discussed above, this designation is dependent upon
the thread numbers and thus upon the selection of component 162.
Using the silhouette image data, processing device 152 then
determines the minor radius, the major radius, the pitch radius and
the lead pitch.
[0099] The 1.sup.st full thread 180.degree. side truncated
measurements are then conducted, as shown in block 608, and may be
accomplished by repositioning positioning stage 128 on the first
thread on the 180.degree. side designated as the truncated thread
location. Using the silhouette image data, processing device 152
then determines the minor radius, the major radius (for set plug
only), the pitch radius and the lead pitch.
[0100] The 2.sup.nd thread 180.degree. side full form measurements
are then made, as shown in block 610. This may be accomplished by
repositioning positioning stage 128 on the second thread on the
180.degree. side designated as the full form thread location. Using
the silhouette image data, processing device 152 then determines
the major radius, the pitch radius and the lead pitch.
[0101] The component values and limits are then updated and the
results are displayed to a system operator and/or printed out in
certificate form and positioning stage 128 is repositioned to arbor
reference knee position 220, as shown in block 612.
[0102] It is further contemplated that inspection system 100 may
perform an R&R (reliability & repeatability) measurement
procedure in a manner responsive to a predetermined R&R
algorithm 700. Referring to FIG. 23, a block diagram illustrating
predetermined R&R algorithm 700 is shown and discussed. Upon
initiation of predetermined R&R algorithm 700, positioning
stage 128 is positioned into the load position and component 162 is
disposed to be retained between first arbor 132 and second arbor
134, as shown in block 702. R&R algorithm 700 is then
activated, as shown in block 704. As discussed hereinabove,
inspection system 100 then performs predetermined calibration
algorithm 500 and predetermined component measurement algorithm
600, as shown in block 706. At this point, once predetermined
component measurement algorithm 600 has been completed, the system
operator may elect to have inspection system 100 pause every seven
cycles for rotation of component 162, as shown in block 708. The
measurement cycle may then repeated as many times as desired and
the results may then be displayed to the system operator via
display device 154 or via a printed certificate or report, as shown
in block 710.
[0103] In accordance with an additional embodiment, it should be
appreciated that the inspection system 100 may also operate by
configuring other elements of the inspection system 100 other than
the positioning stage 128, such as by moving at least one of the
collimated light source 102, the sensing device 104 and/or the
reflecting device 106. For example, instead of the positioning
stage 128 being positionally and controllably configurable in all
planes (such as x-plane, y-plane, z-plane) relative to the mounting
base 126 via a motor operated by a motor controller, at least one
of the collimated light source 102, the sensing device 104 and/or
the reflecting device 106 may be positionally and controllably
configurable in all planes (such as x-plane, y-plane, z-plane)
relative to the mounting base 126 via at least one motor operated
by at least one motor controller such that the component being
measured is kept stationary.
[0104] In this embodiment, the at least one collimated light source
102, the sensing device 104 and/or the reflecting device 106 may be
positionally and controllably configurable in all planes (such as
x-plane, y-plane, z-plane) relative to the mounting base 126 via
communications port 158 as necessary in a manner responsive to the
desired image data. The at least one collimated light source 102,
the sensing device 104 and/or the reflecting device 106 may be
positionally and controllably configurable in all planes (such as
x-plane, y-plane, z-plane) relative to the mounting base 126 using
the processing device 152 which may be communicated with the at
least one motor controller via an RS-232 and/or an RS-422
communications port and/or any device and/or method suitable to the
desired end purpose, such as via wireless communications.
[0105] In this embodiment the inspection system 100 may be operated
as discussed hereinbefore. For example, consider the overall method
300 for measuring the characteristics of the component 162. Once
the pre-calibration lens distortion analysis has been conducted,
the inspection system 100 may be operated to cause the at least one
collimated light source 102, the sensing device 104 and/or the
reflecting device 106 to be disposed such that the reflected
collimated light beam is incident upon component 162, as shown in
operational block 310. The reflected collimated light beam incident
upon component 162 produces a silhouette of component 162 and/or
first arbor 132 which is projected to be incident upon the sensing
device 104. As discussed hereinbefore, the sensing device 104
generates image data responsive to the silhouette of the component
162 and the first arbor 132 and communicates this image data to
processing device 152 which processes the image data to generate
resultant data, as shown in operational block 312. The processing
device 152 then instructs the inspection system 100 to perform a
system calibration in a manner responsive to the predetermined
calibration algorithm 500, as discussed in further detail herein
and as shown in operational block 314. Upon completion of the
predetermined calibration algorithm 500, the inspection system 100
performs a measurement of the component 162 in a manner responsive
to the predetermined component measurement algorithm 600 as
discussed in further detail herein, the predetermined calibration
algorithm 500 and/or the results of lens distortion analysis, as
shown in operational block 316. Once the component measurement has
been completed, component information may then be displayed to the
system operator via the display device 154 and/or via the printed
certificate or report.
[0106] As above, upon completion of the system startup procedure,
the inspection system 100 may begin by performing a system
calibration procedure responsive to the predetermined calibration
algorithm 500. Referring again to FIG. 19 and FIG. 20, once the
system calibration procedure has been initiated, the at least one
collimated light source 102, the sensing device 104 and/or the
reflecting device 106 may be configured to be disposed in a HOME
position, as shown in operational block 502, wherein it is
contemplated that any location of at least one collimated light
source 102, the sensing device 104 and/or the reflecting device 106
may be selected as the HOME position. At this point, all encoders
are zeroed and all positional measurements are determined with
reference to this HOME position. An Arbor reference adjustment is
then performed to properly locate the arbor reference "knee"
position 220, as shown in operational block 504, wherein the arbor
reference "knee" position 220 is a notch disposed on at least one
of first arbor 132 and/or second arbor 134. A software "constraint
window" or search box is created within the field of view of lens
138 and image data representing the image contained within this
search box is then examined to locate arbor reference "knee"
position 220. Arbor reference "knee" position 220 may be located by
analyzing this image data for differences in pixel intensities to
identify where the horizontal arbor surface ends and the vertical
arbor surface begins. This vertical arbor surface is arbor
reference "knee" position 220. Once arbor reference "knee" position
220 is located, blue crosshairs 222 are disposed at arbor reference
"knee" position 220 and displayed to the system operator via
display device 154 to allow the system operator to visually confirm
arbor reference "knee" position 220. It should be stated that arbor
reference "knee" position 220 must be contained with this search
box for predetermined calibration algorithm to continue. If arbor
reference "knee" position 220 is not disposed within the search
box, predetermined calibration algorithm terminates.
[0107] As discussed in more detail hereinbefore, the lens system
distortion measurements may then be conducted, as shown in
operational block 506. Referring again to FIG. 21, this may be
accomplished by operating inspection system 100 such that the at
least one collimated light source 102, the sensing device 104
and/or the reflecting device 106 is configured to locate the arbor
reference "knee" position 220 to four distinct position/locations
within the field of view of lens 138 on the 0.degree. side of at
least one of first arbor 132 and/or second arbor 134. These four
distinct position/locations are located at a lower vertical field
of view position 135, a lower middle vertical field of view
position 137, a upper middle vertical field of view position 139
and an upper vertical field of view position 141. At each of these
four vertical locations, three horizontal measurements are made and
include a left measurement 143, a center measurement 145 and a
right measurement 147. This measurement data may be obtained by
observing and/or analyzing the image data corresponding to the
particular points of measurement. The results of this
observation/analysis may then be recorded for use in subsequent
calculation. This sequence is then repeated on the 180.degree. side
of at least one of first arbor 132 and/or second arbor 134. It
should be appreciated that a total of 24 measurements (i.e. 12 on
the 0.degree. side and 12 on the 180.degree. side) are stored and
thus, become part of the calculated lens distortion measurement
performed near the end of the calibration cycle. As discussed
above, the lens system distortion routine, and thus the distortion
equations, may be provided by the manufacturer of lens system 138
or may be generated responsive to the component to be
inspected.
[0108] Once the lens system distortion measurements have been
conducted, the X-Axis calibration is performed, as shown in
operational block 508. The X-Axis calibration may be accomplished
by locating the center position, the left extreme and the right
extreme of field of view 230 of lens 138 and using these data
points to calculate the inches per step, inches per pixel and/or
the steps per inch calibration factors for the X-Axis. One way to
determine center position, left extreme and right extreme of field
of view 230 is to move arbor reference knee position 220 to the
extreme left hand side of field of view 230 and register this
location as the left extreme. Arbor reference knee position 220 is
then moved to the extreme right hand side of field of view 230 and
this location is registered as the right extreme. Arbor reference
knee position 220 should then be moved to a point midway between
the left extreme and the right extreme of field of view 230. This
point will be the center of field of view 230 and should be
registered as the center position. This ensures minimal distortion
from lens 138.
[0109] Upon completion of the X-Axis calibration, a Y-Axis
calibration at the 1.sup.st 0.degree. diameter is performed, as
shown in operational block 510. The Y-Axis calibration at the
1.sup.st 0.degree. diameter may be accomplished by using the lower
middle center location and upper middle center location obtained
during the lens system distortion measurement to calculate the
inches per step, inches per pixel and/or the steps per inch
calibration factors for the Y-Axis. The lower middle vertical
location is then determined and is used to measure the radius for
the 0.degree. side (which may later be added to the radius for the
180.degree. side to determined the diameter of the arbor).
[0110] Upon completion of the Y-Axis calibration at the 1.sup.st
0.degree. diameter, a Y-Axis 2.sup.nd 0.degree. diameter
determination is performed, as shown in operational block 512. The
determination of the Y-Axis 2.sup.nd 0.degree. diameter may be
accomplished by configuring the at least one collimated light
source 102, the sensing device 104 and/or the reflecting device 106
such that arbor reference knee position 220 on the 0.degree. side
of the arbor is disposed at a lower vertical location, a lower
middle vertical location, an upper middle vertical location and an
upper vertical location of field of view 230. At each of these
locations, inspection system 100 performs three horizontal
measurements, a left horizontal measurement, a center horizontal
measurement and a right horizontal measurement. This data may be
stored and may become part of the calculated lens distortion
factors determined toward the end of the calibration cycle. It
should be appreciated that the lower middle vertical location may
be the final position to be measured and may be used to measure the
radius for the 180.degree. side, which may later be added to the
radius of the 0.degree. side to determine the arbor diameter.
[0111] Upon completion of the Y-Axis 2.sup.nd 0.degree. diameter
determination, a Y-Axis diameter determination is performed, as
shown in operation block 514. The determination of the Y-Axis
2.sup.nd diameter may be accomplished by moving the left arbor
reference location to determine the location of the arbor relative
to the right arbor reference and lens 138. A single measurement is
taken in the center of field of view 230 to minimize distortion and
is used to determine the radius and to compute the tangent
correction factor that is used to compensate for any misalignment
of the Y-Axis of positioning stage 128 with the Y-Axis of lens
138.
[0112] Once this has been completed, a Y-Axis 180.degree. diameter
determination is performed, as shown in operational block 516, by
configuring the at least one collimated light source 102, the
sensing device 104 and/or the reflecting device 106 to the
180.degree. side (same X-Axis position) to measure the radius. The
Y-Axis tangent correction factor is then determined, as shown in
operation block 518. This compensates for a component that may be
disposed between first arbor 132 and second arbor 134 in a
non-level (i.e. horizontal) manner. Moreover, this may be
accomplished by using the measurements taken at the right and left
sides of the arbor and both the X and Y measurement information
from the encoders and the image measurement tools are used to
compute the tangent correction factor. It should be noted that all
subsequent Y-Axis measurements include this compensation factor.
All of the information obtained above may then be used to determine
the lens distortion factor, as shown in operational block 520,
which is then used for all subsequent X and Y measurements,
including any light source and/or system stage positional
distortions/errors (i.e. Abbe*stage errors).
[0113] Referring again to the predetermined component measurement
algorithm 600 and upon completion of the predetermined calibration
algorithm 500, the at least one collimated light source 102, the
sensing device 104 and/or the reflecting device 106 may be
positioned back to arbor reference knee position 220 and component
measurement algorithm 600 is initiated, as shown FIG. 22. At this
point, the Flank registration is performed, as shown in operational
block 602. This may be accomplished by disposing the at least one
collimated light source 102, the sensing device 104 and/or the
reflecting device 106 such that component 162 is positioned to an
initial X and Y location approximately one half inch away from the
arbor reference knee position 220 in the X direction and toward the
component 162. The at least one collimated light source 102, the
sensing device 104 and/or the reflecting device 106 may then be
configured such that the lower limit of the pitch diameter at the
centerline of field of view 230 is approximated. A software
measurement tool is then placed at the centerline to find the flank
angle crossings at the centerline. The at least one collimated
light source 102, the sensing device 104 and/or the reflecting
device 106 may then be configured to align the minor diameter with
the left edge of field of view 230. All subsequent measurements
rely on moving in pitch lead increments in the X-axis direction. It
should be noted that the pitch lead increments are determined by
the component selection and are published at the top of the Lead
Standards readouts. It should be appreciated that, for threaded
gages, the truncated measurements will be conducted at thread #2
and the full form measurements will be conducted at thread #6. The
term 4.times. refers to the number of threads for the third lead
measurement and indicates that it is being made over a span of four
threads and the term /10 indicates that there are ten threads
available on this component.
[0114] As above, once the flank registration has been performed,
the 1.sup.st full thread 0.degree. side truncated measurements are
conducted, as shown in operational block 604. This may be
accomplished by configuring the at least one collimated light
source 102, the sensing device 104 and/or the reflecting device 106
to the first thread on the 0.degree. side designated as the
truncated thread location. This designation is dependent upon the
thread numbers and thus upon the selection of component 162. Using
the silhouette image data, processing device 152 then determines
the minor radius, the major radius (for set plug only), the pitch
radius, the lead pitch, the lead/trail flank angles and the
included angles. The major radius is determined via the major
diameter, which is a composite measurement based on the major
radius of the 0.degree. and corresponding 180.degree. side of the
threads. Thus, the major radius is determined by summing the
individual measurements along the thread flat and dividing by the
number of measurements collected. The number of measurement
locations may be determined by taking 70% of the thread width, as
determined by predetermined thread tables, and centering them on
the center of the thread. This major radius average is then
combined from both the 0.degree. and the 180.degree. sides to get
the major diameter. For a gage, this process is performed for both
truncated and full form locations and for a product, this process
is performed only for the full form location.
[0115] It should be appreciated that all of the measurements taken
by configuring the positioning stage 128 relative the at least one
collimated light source 102, the sensing device 104 and/or the
reflecting device 106 may be conducted by configuring the at least
one collimated light source 102, the sensing device 104 and/or the
reflecting device 106 relative to the component, either
individually or as a group. As such, the present invention
contemplates that any element of the inspection system 100 may be
configured to provide the proper perspective to conduct the any of
the measurements disclosed and/or contemplated herein. It should
also be appreciated that the inspection system 100 may be
configured with digital recognition capability to automatically
determine the component and/or component characteristic to be
measured. For example, the component 162 may include a bar code
(either printed and/or etched) that describes the type of component
and/or the component characteristic to be measured.
[0116] It is contemplated that certain anomalies related to the
centering of the component, the functional size of the component
and excessive deviations from the true line may be present in the
component measurements. To account for these anomalies, the
following novel and unique algorithms can be applied to the
inspection system (as disclosed herein and in U.S. application Ser.
Nos. 11/391,521 and 11/502,678 and U.S. Pat. No. 7,227,163, the
contents and disclosures of which are incorporated herein by
reference in their entireties). It is contemplated that these
algorithms can be applied to an inspection system where the
component to be measured is moved into place for measurements or to
an inspection system where the components of the inspection system
(i.e. mirrors, camera, light source, etc) are moved into place for
measurements relative to the component.
[0117] To address and account for excessive deviations from true
line measurements of the threaded component, various parameters of
the threaded component measurements (as desired) may be `smoothed`,
where outlier measurement values are removed & the remaining
measurement values are averaged (single or multiple averages may be
obtained as desired). This operation may be repeated as desired. To
accomplish this task, regression analysis may be used to obtain
final smoothing data which accounts for these deviations and may
include one or more of:
[0118] 1) Conducting a standard least square linear regression
analysis;
[0119] 2) Conducting a q-trimmed linear regression analysis;
and
[0120] 3) Conducting a resistant regression procedure;
where, the terminal residuals (outliers) outside of about .+-.2
sigma standard deviation may be generated and the refits may be
generated or measured. It is contemplated that continuous and/or
repeated measurements may be made as desired. Also, other sigma
standard deviation values may be used responsive to a desired
accuracy. For example, a .+-.10 sigma standard deviation or a
.+-.0.2 sigma standard deviation may be used.
[0121] Accordingly, one embodiment of a method for removing
excessive deviations from the "true line" may include generating
and fitting a least squares line by minimizing
k = 1 n .omega. k ( y k - ( a + bx k ) ) 2 , ##EQU00008##
Where, a is the intercept of b, b is the determined/theoretical
slope (can be estimated, calculated or measured), k is the number
of values generated, x.sub.k and y.sub.k are the residuals
(outliers) for each coordinate pair, and w.sub.k is the
included/excluded least square lines fit, where the values of
w.sub.k will be either zero (excluded) or one (included). The
theoretical estimates for the slope b and the intercept a are then
determined as follows,
b ^ = S xy S xx = k = 1 n .omega. k ( x k - x _ ) ( y k - y _ ) k =
1 n .omega. k ( x k - x _ ) 2 , a ^ = y _ - b ^ x _
##EQU00009##
where, x and y are the means of the x and y coordinates of where
the measurements were taken and a and {circumflex over (b)} are the
estimates of a and b. From this estimate, the residuals for each of
the coordinate pairs (x.sub.k, y.sub.k) may be calculated
using,
r.sub.k=y.sub.k-(a.sub.--{circumflex over (b)}x.sub.k).
This is the amount by which the data points differ from the
corresponding points predicted to lie on the line and r(k) is the
residual for each of the coordinate pairs x.sub.k, y.sub.k. The
residuals may be sorted from lowest to highest (or highest to
lowest if desired) as given by,
r.sub.1.ltoreq.r.sub.2.ltoreq. . . . .ltoreq.r.sub.n.
These values may be trimmed by identifying those points whose
residuals have the highest absolute values and either remove them
or weight them using a weighting variable w, where w may be
responsive to the measurements taken and acceptable repeatability
and accuracy tolerances. For example, if the weighting variable w
is set to w.sub.k=0 for the points to be trimmed this would
effectively make the acceptable repeatability and accuracy
tolerances equal to 0. Once this is done, refit the least squares
line and use that refit line to determine the required parameters
for the product or gage. Although as many as approximately 30% of
the points may be trimmed, typically only about 5%-10% of the
points may be trimmed (depending on the surface finish of the
component) prior to the refit of the least squares line.
[0122] An alternative approach also involves fitting the least
squares line and calculating the residuals. However, this approach
involves trimming the residuals outside of about 2 or 2.5 standard
deviations as given by,
S = 1 n - 1 k = 1 n .omega. k ( x k - x _ ) 2 ##EQU00010##
where n is the number of residuals. By using a two (2) standard
deviation criterion, approximately about 5% of the data may be
trimmed and the line can be refit by using the least squares
estimates on the reduced (trimmed) data set.
[0123] Accordingly, in both of the above approaches, the algorithm
can be simply stated as, [0124] 1) Fit the line to original data
generated in accordance with the thread profile; [0125] a.
Calculate residuals; [0126] b. Sort residuals; [0127] c. Trim data
set; [0128] i. Fit line to trimmed data; [0129] ii. Calculate new
residuals; [0130] iii. Sort new residuals; [0131] iv. Trim new data
set; [0132] v. Repeat as desired or necessary; and [0133] 2)
Compute screw thread geometric parameters using the re-trimmed data
set (e.g. flank angles (leading, trailing & included), leads,
major diameter, minor diameter & pitch diameter).
[0134] Referring to FIG. 31, a block diagram illustrating a method
1100 for accounting for excessive deviations from the true line
measurements of a threaded component by smoothing at least one
parameter (individually or together) of the threaded component
measurement(s) (as desired) is shown and includes fitting a least
squares line to original data generated responsive to the thread
profile of the threaded component, as shown in operational block
1102. The residuals are then determined as discussed herein and
sorted into a new data set, as shown in operational block 1104. The
new data set is then trimmed by fitting a second least squares line
to the new data set, as shown in operational block 1106 and
determining and sorting new residuals, as shown in operational
block 1108. It is contemplated that one or more of the operational
blocks 1102-1108 may be repeated as many times as desired. The
`adjusted` (new) screw thread geometric parameters are then
determined using the re-trimmed data set, as shown in operational
block 1110.
[0135] It should be appreciated that the above approaches can be
applied to all measurements of the component including the major
diameter, the pitch diameter, lead, angles, minor diameter, and
helix variation. It is contemplated that, rather than using a least
squares fit approach, another approach may use a minimum absolute
deviation fit, where it is minimized by,
k = 1 n .omega. k y k - ( a + bx k ) . ##EQU00011##
Additionally, it is also contemplated that an orthogonal least
squares approach could also be used, i.e. measure the deviations
perpendicular to the screw thread flank. However, the calculations
for this approach are more complex. It should be appreciated that
the full data set should be retained and each point referenced by
whether it is retained or trimmed. In general, the higher the
standard deviation of the residuals, the lower the quality of the
screw thread.
[0136] In accordance with the invention, the functional size
(f.sub.s) of a component is the measurement of the pitch diameter
plus the cumulative effect of the profile variations (lead, angle,
helical path deviation). One method for accounting for deviations
in the functional size of the threaded product or gage or portions
of measurements of the threaded product or gage is described
hereinafter and includes determining the functional size f.sub.s of
the product or gage responsive to,
f.sub.s=pd+L(HP)+A,
where, [0137] pd=actual measured pitch diameter; [0138]
avg=(leading flank angle+trailing flank angle)/2; [0139] std=30
degrees standard flank angle (which may be given in deg or rad);
[0140] HP=Helical Path; [0141] p=specified pitch distance=1/TPI
(Threads per Inch); [0142] dp=error in pitch distance=error in lead
assuming 1 start thread (may be neg or pos); [0143] L=axial travel
advance per unit rotation; and [0144] A=|1.5*p*tan(avg-std)|,
(where .parallel. means absolute value); Accordingly, pd is the
diameter of the cylinder that passes through the thread profile
where the thread groove and the thread ridge are equal on the
0.degree. side and the 180.degree. side of the component parallel
to the axis of the thread. Essentially, the functional size
(f.sub.s) may be represented by the value of the pitch diameter
plus the cumulative effect of all of the thread profile variations.
Accordingly, it should be appreciated that if there is no error
(i.e. dp=0), then the f.sub.s=pd. However, if an error is present
(i.e. dp=.+-.) then the f.sub.s=pd+L+A, where pd=pitch diameter of
the thread profile, L=lead error of the thread profile and A=angle
error of the thread profile.
[0145] Referring to FIG. 32, a block diagram illustrating a method
1200 for determining the functional size f.sub.s of a product or
gage in accordance with one embodiment of the invention is shown
and includes determining the actual pitch diameter pd, as shown in
operational block 1202. The average flank avg is determined, as
shown in operational block 1204, where avg is the sum of the
leading flank and the trailing flank divided by 2. The standard
flank angle std, the specified pitch distance p and the error in
pitch distance dp is determined, as shown in operational block
1206, where the standard flank angle is 30 degrees (may be given in
rads or degs), the specified pitch distance is the threads per inch
and the error in pitch distance is the error in lead assuming a 1
start thread (may be neg or pos). The lead error of the thread
profile L is determined, as shown in operational block 1208, and is
given axial travel advance per unit rotation. The angle error A
(deviation from 30.degree.) of the thread profile is determined, as
shown in operational block 1210, and is given by
|1.5*p*tan(avg-std)|, (where .parallel. means absolute value). The
functional size f.sub.s is then determined, as shown in operational
block 1212, and is given as the sum of the pitch diameter pd of the
thread profile, the lead error L of the thread profile and the
angle error A of the thread profile.
[0146] In accordance with the invention, in making measurements of
a product (or gage), it is important to make sure that the product
or gage is as straight as possible relative to the lens system of
the inspection system. Any deviation from a straightly aligned
product or gage may have an adverse affect on the measure of the
component. Accordingly, one embodiment of a method for centering a
product or gage in an inspection system is described herein. It is
contemplated that the centering algorithm can be applied to an
inspection system where the component to be measured is moved into
place for measurements or to an inspection system where the
component of the inspection system (i.e. mirrors, camera, light
source, etc) are moved into place for measurements relative to the
component.
[0147] Referring to FIG. 33, a block diagram 1300 illustrating one
embodiment of a method for accounting for misalignment of a
component using a centering algorithm is shown. Once the product or
gage is staged or disposed in the measuring device, a centerline
value is determined, as shown in operational block 1302. This may
be accomplished by taking a measurement of the product or gage at a
first point on the 0.degree. side of the product or gage
(preferably on the longest threaded side first, but other locations
are also contemplated). A measurement is also taken at the first
point on the 180.degree. side of the product or gage (again,
preferably on the longest threaded side, but other locations are
also contemplated). The center point at the first point is then
determined, as shown in operational block 1304, by subtracting
these measurement values and dividing by two (2). This step is
repeated for at least one other point (for both 0.degree. side and
180.degree. side) along the product or gage, as shown in
operational block 1306 and operational block 1308, preferably at
the other end of the product or gage. A centerline of the product
or gage is then established by projecting a line between the center
point of the first measured center position and the center point of
the second measured center position, as shown in operational block
1310. It should be appreciated that if more than two center points
along the product or gage are used, then a centerline of the
product or gage may be determined by using a line of best fit
between the center points of the first point, the second point, the
third point, etc.
[0148] It should be appreciated that the measurements described
hereinabove for lens distortion analysis, predetermined calibration
algorithm 500, predetermined component measurement algorithm 600
and/or R&R algorithm 700 may be accomplished by examining the
image data for pixel intensity. This allows inspection system 100
to locate and record known positions on lens 138, first arbor 132,
second arbor 134 and/or component 162 as data points. Using these
data points, the physical characteristics of lens 138, first arbor
132, second arbor 134 and/or component 162 may be calculated via
any method suitable to the desired end purpose, such as
geometric/trigonometric relations, estimations and/or
predictions.
[0149] In accordance with an exemplary embodiment, it is
contemplated that multiple measurements may be made at each of the
measurement locations in a manner responsive to predetermined
component thread specifications. Moreover, the image data may be
processed to include a plurality of discrete pixel elements.
Processing device 142 then conducts each of the measurements by
examining each pixel of the plurality of discrete pixel elements to
determine the physical characteristics of component 154 as
discussed hereinabove. It is further contemplated that image data
may be displayed via any display device suitable to the desired end
purpose, such as a paper printout, a computer screen, a television,
a plasma display and/or a Liquid Crystal Display (LCD). Although
the component physical characteristics are determined by processing
the image data as discussed hereinabove, the component physical
characteristics may be determined by processing the image data
using any device and/or method suitable to the desired end purpose.
Inspection system 100 may also be operated and/or monitored via a
network connection, such as a wireless network (cellular, pager,
RF), Local Area Network, Wide Area Network, Ethernet and/or
Modem.
[0150] It is contemplated that processing device 152 may store
image data and measurement results in a data storage device and/or
a volatile memory of processing device 152 (e.g. RAM). It should
also be noted that image data may be stored in a volatile and/or a
non-volatile memory location which may be disposed in any location
suitable to the desired end purpose, such as a remote server. In
addition, the data storage device may be used to store individual
component data and/or group component data which may be specific to
a desired purpose, such as data for a specific user, component part
and/or a specific end user device, wherein the component data may
include a large range of information, such as user specific data
and/or component part history data.
[0151] In accordance with an exemplary embodiment, inspection
system 100 may be a self-calibrating and automated for inspection
of multiple components. Moreover, inspection system 100 allows for
non-contact measurements which reduce and/or eliminate high
inspection costs, operator feel, fatigue, uncertainties and/or
error. Inspection system 100 allows for the generation of automatic
certificates and information output files. Moreover, inspection
system 100 includes built-in repeatability and reliability
(R&R) qualification and testing programs and allows for an
extremely fast measurement cycle. The measurement and reporting
cycles are typically performed in less than two minutes duration.
Furthermore, inspection system 100 has an accuracy of about
0.000020 or less. This could never be realized using the current
"Attributes" or variables measuring system. Also, inspection system
100 is about 25 times faster than using an "Attributes" or
variables measuring system, which will only measure one of the
multiple component characteristics required for inspection to
satisfy current specifications.
[0152] A machine-readable computer program code and/or a medium
encoded with a machine-readable computer program code for measuring
the characteristics of component 162 using inspection system 100,
the code and/or medium including instructions for causing a
controller to implement a method including operating inspection
system 100, wherein inspection system 100 includes collimated light
source 102, a sensing device 104 optically communicated with
collimated light source 102 and processing device 152, wherein
processing device 152 is communicated with the sensing device 104,
disposing component 162 such that component 162 is associated with
inspection system 100, positioning component 162 such that
component 162 is disposed to partially impede the optical
communication between the sensing device 104 and the collimated
light source 102, operating the collimated light source 102 such
that a collimated light beam is incident upon component 162 to
cause a silhouette of component 162 to be received by the sensing
device 104, wherein the sensing device 104 generates image data
responsive to the silhouette, communicating the image data to
processing device 152, processing the image data to determine
desired characteristics of component 162 and displaying the
characteristics to a user.
[0153] In accordance with an exemplary embodiment, the processing
of FIGS. 12-13, FIG. 19, FIGS. 22-23 and FIGS. 29-30 may be
implemented by a controller disposed internal, external or
internally and externally to inspection system 100. In addition,
processing of FIGS. 12-13, FIG. 19, FIGS. 22-23 and FIGS. 29-30 may
be implemented through a controller operating in response to a
computer program. In order to perform the prescribed functions and
desired processing, as well as the computations therefore (e.g.
execution control algorithm(s), the control processes prescribed
herein, and the like), the controller may includes, but not be
limited to, a processor(s), computer(s), memory, storage,
register(s), timing, interrupt(s), communication interface(s), and
input/output signal interface(s), as well as combination including
at least one of the foregoing.
[0154] The invention may be embodied in the form of a computer or
controller implemented processes. The invention may also be
embodied in the form of computer program code containing
instructions embodied in tangible media, such as floppy diskettes,
CD-ROMs, hard drives, and/or any other computer-readable medium,
wherein when the computer program code is loaded into and executed
by a computer or controller, the computer or controller becomes an
apparatus for practicing the invention. The invention can also be
embodied in the form of computer program code, for example, whether
stored in a storage medium, loaded into and/or executed by a
computer or controller, or transmitted over some transmission
medium, such as over electrical wiring or cabling, through fiber
optics, or via electromagnetic radiation, wherein when the computer
program code is loaded into and executed by a computer or a
controller, the computer or controller becomes an apparatus for
practicing the invention. When implemented on a general-purpose
microprocessor the computer program code segments may configure the
microprocessor to create specific logic circuits.
[0155] While the invention has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, may modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed herein as the best mode
contemplated for carrying out this invention.
* * * * *