U.S. patent number 3,837,198 [Application Number 05/351,728] was granted by the patent office on 1974-09-24 for stereoscopic gage and gaging system.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to Paul T. Higgins.
United States Patent |
3,837,198 |
Higgins |
September 24, 1974 |
STEREOSCOPIC GAGE AND GAGING SYSTEM
Abstract
A stereoscopic optical system for gaging the surface of articles
having complex contours or shapes is described. The system projects
complementary sets of stereoscopic patterns on the article being
gaged to determine the conformity of the article's surface to the
desired contour or configuration. Nonconforming surfaces perturb
the relationship between the complementary patterns imaged on the
surface, of the article being gaged, giving a visual indication of
a nonconformity. The perturbed relationship between the
complementary patterns imaged on the surface of the article may
also be detected electro-optically providing an electrical signal
indicative of the nonconformity which can be used to initiate a
number of automatic or semiautomatic machine operations including
in-situ correction of the nonconforming surface.
Inventors: |
Higgins; Paul T. (Orchard Lake,
MI) |
Assignee: |
The Bendix Corporation
(Southfield, MI)
|
Family
ID: |
23382125 |
Appl.
No.: |
05/351,728 |
Filed: |
April 16, 1973 |
Current U.S.
Class: |
72/18.2; 72/37;
416/223R; 29/407.04; 29/889.7; 416/61 |
Current CPC
Class: |
G01B
11/2509 (20130101); Y10T 29/49336 (20150115); Y10T
29/49769 (20150115) |
Current International
Class: |
G01B
11/25 (20060101); G01B 11/24 (20060101); B21c
051/00 (); B23q 017/00 () |
Field of
Search: |
;353/7,10
;356/2,164,165,166,168,237 ;350/132 ;29/156.8B,156.8H,407
;72/7,8,10,34,37,9 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Combs; E. M.
Attorney, Agent or Firm: Ignatowski; James R.
Claims
What is claimed is:
1. A system for gaging the surface of an object and automatically
reshaping the surface of the object to conform to a given
configuration comprising:
means for supporting the object in a predetermined position;
means having a fixed relationship to said supported object for
optically imaging from spatially separated vantage points at least
two complementary stereoscopic patterns on the surface of said
object, wherein the spatial relationship between said at least two
patterns imaged on the surface of the object is indicative of the
conformity of the object's surface to a desired configuration;
means detecting the spatial relationship between said at least two
imaged patterns and for generating from said spatial relationship
electrical signals indicative of the conformity of said surface to
said desired configuration;
means responsive to the signals generated by said relationship
detecting means for computing corrective signals; and
means responsive to said corrective signals for reshaping said
object to conform to said desired configuration.
2. The system of claim 1 wherein said means for imaging
include:
first projector means for imaging the first pattern on the surface
of said object; and
second projector means spatially separated from said first
projector means along a line generally parallel to the surface of
said object being gaged for imaging a second pattern on the surface
of said object wherein the images said first pattern and said
second pattern superimpose at predeterminable points in space
defining the desired position of the surface of the object being
gaged.
3. The system of claim 2 wherein said first pattern and said second
pattern each include at least one discrete image projected on the
surface of the object being gaged at a predetermined location,
wherein said at least one discrete image of said first pattern and
at least one discrete image in said second pattern form a
complementary set of images which superimpose at predetermined
points in space, said points in space defining a desired position
of the surface being gaged at said predetermined location.
4. The system of claim 2 wherein said first and second patterns
each include a plurality of said discrete images forming a
plurality of said complementary sets of images which superimpose at
a plurality of predetermined locations on the surface of said
object.
5. The system of claim 4 wherein said first projector means and
said second projector means include means for coding said patterns
whereby each discrete image projected by said first projector means
can be distinguished from each complementary image projected by
said second projector means.
6. The system of claim 5 wherein said means for determining the
relationship between said stereoscopic patterns include:
means responsive to said discrete images for generating electrical
signals indicative of the location of each image; and
means for correlating said electrical signals and generating
signals indicative of the correlation between the two discrete
images in each of said complementary sets so correlated.
7. The system as claimed in claim 6 wherein said means for
computing includes:
means responsive to said correlation signals for generating signals
indicative of the position of the nonconforming surface with
respect to said desired surface at each predetermined location;
and
means responsive to the signals indicative of the position of said
nonconforming surface at each location for generating said
corrective signals.
8. The system of claim 7 wherein said nonconformity is a twist,
said means for operating on said object are means responsive to
said corrective signals for applying a torque to said object with
sufficient force and in a direction determined to remove said
twist.
9. The system as claimed in claim 7 wherein nonconformity is a
bend, said means for operating on said object are means responsive
to said corrective signals for applying a force to said object in a
direction and with a magnitude determined to remove said bend.
10. The system as claimed in claim 7 wherein said nonconformity is
a twist and a bend, said means for operating on said object
includes means responsive to said corrective signals for applying a
torque to said object in a direction determined to remove said
twist and means responsive to said corrective signals for applying
forces on said object at predetermined locations determined to
remove said bend.
11. The system as claimed in claim 7 wherein said nonconformity is
excessive material at said predetermined locations said means for
operating on said object includes means responsive to said
corrective signals for removing material from the surface of said
object said predetermined locations.
12. A method for gaging and correcting the surface of an object to
conform to a desired configuration comprising:
placing the object in a supporting fixture configured to hold the
surface of the object to be gaged in a predetermined position;
projecting onto the surface of the object to be gaged from
spatially separated vantage points two stereoscopic patterns which
superimpose at determined positions in space defining the desired
position of the surface of the object;
detecting the spatial relationship between said two patterns to
generate a signal indicative of the position of the object's
surface from the desired position; and
operating on said supported object with means receiving said
signals to reshape the supported object until said two stereoscopic
patterns superimpose on the surface thereof.
13. The method of claim 12 wherein said step of projecting further
includes the step of coding at least one of said two stereoscopic
patterns so that said stereoscopic patterns can be distinguished
one from the other.
14. The method of claim 13 wherein said step of coding
includes:
filtering, with a first filter transmitting a distinct color, one
of said two patterns; and
filtering, with a second filter transmitting a distinct color
different from the color transmitted by said first filter, the
second of said two patterns.
15. The method of claim 13 wherein said one pattern has at least
one discrete image and said second pattern has at least one
discrete image and said at least one discrete image of said first
pattern and said at least one discrete image of said second pattern
combine on the surface of the object to form a complementary set,
and said complementary set of images superimpose at a predetermined
point in space defining the desired position of the surface being
gaged at at least one predetermined location on the surface of the
object, said step of operating includes:
engaging with said supported object, means for reshaping the
surface of said object in said at least one predetermined location;
and
reshaping with said means for reshaping the surface of said object
to cause said complementary set of images to superimpose on the
surface of said object at said predetermined locations.
16. The method of claim 15 wherein said means for reshaping
includes means for generating reshaping forces, said step of
reshaping includes:
engaging with said supported object, said force generating means in
at least one predetermined place; and
bending and twisting the object by applying at said at least one
predetermined place, forces having a magnitude and direction
determined to reshape said object to the desired configuration
causing said complementary set of images to superimpose on the
surface of the reshaped object at said at least one predetermined
location.
17. The method of claim 15 wherein said means for reshaping
includes means for removing excess material, said step of reshaping
includes:
engaging with said supported object said means for removing excess
material in at least one predetermined location; and
removing from the surface of said object with said means for
removing material sufficient to cause said complementary images to
superimpose in the surface of the object at said at least one
predetermined location.
18. The method of claim 13 wherein said one pattern has at least
one discrete image and said second pattern has at least one
discrete image and said at least one image of said one pattern and
said at least one image of said second pattern combine on the
surface of the object to form a complementary set, and said
complementary set of images superimpose at predetermined points in
space defining the desired position of the surface being gaged at
at least one predetermined location on the surface of the object,
said step of detecting comprising:
electro-optically detecting the location of said at least one image
of said first and second pattern, imaged on the surface of said
object to generate electrical signals indicative of the location of
each image;
correlating the electrical signals indicative of the location of
said at least one image in said first pattern with the electrical
signals indicative of the location of said at least one image in
said second pattern forming a complementary set to generate
correlation signals indicative of the separation between the images
in said first and second patterns at said predetermined location;
and
computing from said correlation signals the magnitude and direction
of the displacement of the object's surface from the desired
position at said at least one predetermined location and generating
corrective electrical signals indicative of the displacement of the
object's surface from the desired position at said predetermined
location.
19. The method of claim 18 wherein said means for reshaping
includes means for applying reshaping forces, said step of
operating comprises:
twisting and bending the supported object with said force applying
means in response to said corrective signals.
20. The method of claim 18 wherein said means for reshaping
includes means for removing material, said step of operating
comprises:
removing excessive material from the surface of said object by said
material removing means in response to said corrective signal.
Description
BACKGROUND OF THE INVENTION
The production gaging of complex three-dimensional surfaces remains
as one of the most tedious and time consuming operations in the
manufacture of contoured parts such as turbine blades, airfoils or
other articles where the contour is critical to the function or fit
of the article. Various types of mechanical and optical gages as
evidenced by U.S. Pat. Nos. 2,621,556 "Comparator for Testing
Turbine Blades and the Like" by Beardsley et al; 2,668,475 "Optical
Apparatus for Inspecting the Contour of Articles" by J. Walker et
al; 3,318,009 "Blade Examining Apparatus" by E. J. Tishler et al;
and 3,588,256 "Optical Profile Projector" by P. Derossi are
presently being used to gage three-dimensional surfaces, however,
these methods are quite cumbersome and slow and the gaging and
correction must be performed on different fixtures.
The inventive stereoscopic gage described in this application
overcomes the objections of the gages of the prior art in many
instances permits the correction to be performed without removing
the object from the gage.
The art of stereoscopy, wherein an observer mentally combines the
images of two pictures taken from spatially separated vantage
points to give the impression of depth, is well known. A
stereoscopic microscope for measuring depths based on this
principle is disclosed in U.S. Pat. No. 2,769,370 by R. E.
Tompkins. Another adaptation of the stereoscopy to surface
measurements is disclosed in U.S. Pat. No. 3,523,736 by S. C.
Bottomley. In this patent an image from a single target is divided
into two separate images each of which is obliquely incident on the
surface of the object being gaged from spatially separated vantage
points. The angle of incidence of the two images in the Bottomley
patent are opposite but equal from a line normal to the plane of
the surface being gaged so that the light reflected by the first
image from the surface of the object is received by the optics
imaging the second image and vice versa. The two images are then
recombined by appropriate optics (mirrors and a beam splitter) so
that the two reflected beams are coincident when the surface being
gaged in in a predetermined position and has a predetermined
angular disposition with respect to the incident images. A lateral
displacement of the surface being gaged from the predetermined
position or an angular disposition of the surface from the
predetermined angle will cause the two recombined images to no
longer be coincident but be laterally displaced, the lateral
displacement of the two images being proportional to the lateral
displacement or angular displacement of the surface being gaged
from the predetermined position. The method disclosed in the
Bottomley patent has the following disadvantages: (1) although it
is capable of measuring a displacement of the surface, no means are
provided for determining the direction of the displacement of the
surface from the desired position; (2) the method of the Bottomley
patent provides no means for distinguishing an angular displacement
from a lateral displacement; and (3) the method of the Bottomley
patent is limited to the measurement of flat surfaces only and is
not applicable to determining the conformity of a curved surface.
The inventive system and method overcome the deficiencies of the
Bottomley patent and the other cited art by employing a further
extention of the stereoscopic principles to optical gaging.
A pseudo three-dimensional image of an object can be constructed in
space by stereoscopically projecting the images of two
complementary stereo pictures or patterns. The complementary
stereoscopic patterns may be made by photographing an object from
spatially separated vantage points or by constructing the patterns
by other means from the geometrical parameters of the object and
the optical projection systems. This concept can probably be best
illustrated by referring to FIG. 1. Two stereo pictures or patterns
10 and 20 having complementary parallel straight line images 12 and
22, respectively, are projected into space by a stereoscopic
projection system consisting of two independent optical systems 14
and 24. The two optical systems 14 and 24 form two separate
parallel images (dotted lines) 16 and 26 at the common focal plane
30 of the stereoscopic projection systems. The common focal plane
30 is defined in this context as the plane of exact focus of the
two optical systems 14 and 24. In the following discussion, the
location of the image is discussed with relation to an orthogonal
coordinate system having one axis parallel to a common axis of the
projection system, as shown on the figure. The Z axis is parallel
to the optical axis of the projection system and represents depth,
while the X and Y coordinates are the horizontal and vertical
directions in a plane normal to the Z axis.
The images projected by the optical systems illustrated in FIG. 1
will remain in relatively good focus some finite distance in front
of or behind the plane of exact focus due to the depth of field of
the two optical systems. Therefore, the two projected parallel
images 16 and 26 can be imaged on an infinisimal number of planes
normal to the Z axis both before or behind the focal plane 30.
Further, if the depth of field of the two optical systems 14 and 24
is sufficient, the two projected images 16 and 26, which are
spatially separated at the focal plane 30, will superimpose, one
upon the other, on a plane 31 (dashed line) other than, but
parallel to, the focal plane 30, forming a single projected image
32 having common X, Y, and Z coordinates. The distance "d" measured
in the Z direction between the focal plane 30 and the plane 31
where the two images are superimposed is indicative of the true or
desired location of the object's surface with respect to the focal
plane of the projection system. Further, the superimposed images on
plane 31 not only determines the Z displacement of the original
object from the focal plane 30, but also the position of the planar
axes X and Y due to spatial separation of the two pictures 10 and
20.
It is readily recognized that if the complementary images are not
parallel to each other but canted at an angle .alpha. and .alpha.'
to each other as shown on FIG. 2, a plane wherein all the
corresponding points of the two projected images are superimposed
is also canted or at an angle .beta. to the focal plane 30 wherein
the angle .beta. of the image plane 31 with respect to the focal
plane 30 is proportional to the angles .alpha. and .alpha.' of the
images 12 and 22 on the patterns 10 and 20 respectively. Likewise
where the two complementary images are curved lines 18 and 28 as
shown on FIG. 3, the plane where the corresponding points of the
two projected images superimpose is a cureved plane 33. In this
manner, the points in space where the two complementary
stereoscopic images superimpose may be used to define a surface of
almost any desirable contour.
The inventive gage utilizes the above principle for gaging the
surface contours of three-dimensional objects by projecting on the
surface of the object being gaged, a number of complementary
stereoscopic images which define the contour of the desired
surface. The conformity of nonconformity of the surface of the
gaged object to the desired surface contour can then be determined
by whether or not the projected images superimpose on the surface
of the object. The gaging may be further enhanced by projecting
each one of the corresponding images in a different color so that
the direction of the nonconformity can be easily determined. For
example, if the images projected from the left picture are blue and
the images projected from the right picture are red, then the
superimposed images formed on the surface of the object would be
the combination of red and blue and be a gray. However, if the
surface of the object is high, i.e., forward of the plane where the
two images would superimpose, two colored images would appear on
the surface of the object, as shown on plane 30 of FIG. 1. The
image on the left would be blue and the image on the right would be
red. If the surface of the object was low, i.e., behind the plane
where the two images superimpose, again two colored images would be
formed. However, this time their order would be reversed and the
red image would be on the left and the blue image would be on the
right. Therefore, by projecting the images from each picture in a
different color, not only can a nonconformity of the surface being
gaged be detected, but also the direction of the nonconformity with
respect to the desired contour.
This method of gaging is not only applicable to the gaging of
single parts but also may be extended to determine the relationship
of assembled parts to determine correct assembly or it even can be
used to determine best fir for subsequent machining of a rough part
by insuring that there is sufficient stock along the desired
surface for the subsequent machining operation.
SUMMARY OF THE INVENTION
The invention is directed to a stereoscopic optical gage for gaging
the surface of a contoured object or objects to determine the
conformity of the object being gaged to the desired contour or
shape. The gage consists of a holding mechanism for holding the
object in a fixed spatial relationship to two spatially separated
optical system projecting stereoscopic images, on the object to be
gaged. The two optical systems, each contain a stereoscopic mask
(picture) having a plurality of corresponding images, which when
projected by the spatially separated optical systems superimpose at
various points in space and define the desired surface contour at
predetermined locations. The projected images may be a point, a
straight line or any other geometrical shape which defines the
desired contour.
In its simplest embodiment, the projected images of the
stereoscopic gage may be visually observed by an operator and the
fault corrected, where possible by the operator using an
appropriate tool. Because the inventive stereoscopic gaging method
does not contact the surface being gaged, corrective operations
such as twisting, bending or removing excess material may be
accomplished in-situ, without removing the part from the gage's
holding mechanism.
A more sophisticated embodiment of the inventive gage is completely
automated, having electro-optical sensors monitoring the projected
images. Nonconformities are determined by means of well-known
correlation techniques, and with the aid of a computer, the
corrections may be automatically applied.
One object of the invention, therefore, is to provide a
non-contacting stereoscopic gage for gaging the surface of an
object with respect to a desired shape or contour.
Another object of the invention is to provide a stereoscopic gage
in which the magnitude and direction of the nonconformity of the
surface being gaged can be accurately determined.
A further object of the invention is to provide a stereoscopic gage
wherein the nonconformity may be automatically detected and
corrected without removal from the gage.
And still further another object of the invention is to provide a
stereoscopic gage suitable for the production gaging of objects
with complex contoured surfaces which is quicker and more accurate
than the gages presently being used.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective drawing illustrating the basic principles
of stereoscopic projection forming an image normal to the
projection axis.
FIG. 2 is a perspective drawing illustrating the basic principles
of stereoscopic projection forming an image on a plane not normal
to the projection axis.
FIG. 3 is a perspective drawing illustrating the basic principles
of stereoscopic projection forming an image on a curved plane.
FIG. 4 is a perspective drawing showing the stereoscopic gage.
FIG. 5 is a top view of a turbine blade showing the relationship of
the two projected images when the turbine blade is twisted.
FIG. 5A is an end view of the turbine blade of FIG. 5 showing the
displacement of the surface from its desired position due to the
twist.
FIG. 6 is a top view of a turbine blade showing the relationship of
the two projected images when the turbine blade has a bend.
FIG. 7 is a top view of a turbine blade showing the relationship of
the two projected images when the surface of the turbine blade is
concave or convex.
FIG. 8 is a cross-sectional view of the two projection systems
showing the relationship of major component parts.
FIG. 9 is a side view of a fully automated gaging and straightening
system showing the component parts and their
inter-relationship.
DETAILED DESCRIPTION
FIG. 4 shows a preferred embodiment of the inventive stereoscopic
gage 100. An object or article to be gaged, illustrated as a
turbine blade 102 is mounted in a holding fixture 104 configured to
support the turbine blade in a fixed position with respect to the
gage. A pin 106 or other type of keying device insures the proper
orientation of the turbine blade in the holder. Two spatially
separated stereoscopic optical systems 108 and 110 are rigidly
supported above the turbine blade by a support 112. Both the
support 112 and the holding fixture 104 are rigidly supported from
a common base 114 providing a fixed relationship between the two
optical systems 108 and 110 and the supported turbine blade 102.
The optical system 108 projects, as illustrated by rays 116, 118,
and 120, a blue stereoscopic pattern which when imaged on the
surface of the turbine blade 102 forms a plurality of blue straight
line images 122, 124, and 126 respectively. Optical system 110 also
projects, as illustrated as rays 128, 130, and 132, a complementary
red stereoscopic pattern which when imaged on the surface turbine
blade 102 superimpose on the blue straight line images 122, 124,
and 126 respectively causing the images 122, 124, and 126 to turn
gray. The two projected images which form lines 122, 124 and 126
respectively are hereinafter referred to as a complementary set of
images. Although the embodiment illustrated in FIG. 4 only shows
three complementary sets of images defining the contour of the
turbine blade at predetermined locations, the concept may be
readily extended to project many more complementary sets of images
which not only define the contours at different locations but could
also be used to determine the location and size of holes, the
position and height of bosses or the characteristics of other
topographical features of importance.
The operation of the gage is discussed with reference to FIGS. 5-7.
Consider a turbine blade 102 shown on FIG. 4 in which the blade
section has an excessive twist in the clockwise direction when
viewed from the tip end as shown in FIG. 5A. The actual contour of
the blade is shown as a solid line 200 while the desired contour is
shown as a dashed line 202. Because the surface of the section
having the excessive twist lies below the desired surface, the
complementary sets of images are no longer superimposed over their
entire length and the red line images 124R and 126R separate from
the blue line images 124B and 126B in the nonconforming area. The
separation between the two lines in the nonconforming area is a
measure of the displacement of that part of the turbine blade from
its desired position. For example, if the red and blue images
arrive at the surface of the turbine blade from opposite directions
at an angle of 45.degree. with respect to blade surface, then the
separation (center to center) of the two lines is twice the
displacement of the surface from its desired position. As the
angles of incidence change for various other points on the blade,
the relationship between the separation and the displacement also
changes but can be precisely determined from simple geometric
relationships. Once the nonconformity is detected, the operator
may, with an appropriate tool twist or otherwise distort the blade
back to its desired shape without removing from the holding
fixture.
Had the twist in FIG. 5 been counterclockwise, a similar pattern
would have been observed, however, the red and blue lines would
have been reversed indicating that the nonconforming surface was
higher than the desired surface.
FIG. 6 illustrates a typical pattern where the turbine blade has a
vertical bend which places the tip of the blade closer to the
stereoprojector than desired. Since the contour is correct, the
projected images remain basically as straight lines but since the
surface is higher than desired, the red lines 124R and 126R and
blue lines 124B and 126B are separated by a distance which is a
measure of the nonconformity as shown. The relationship of the
projected images for a lateral or horizontal bend is dependent upon
the contour of the surface being gaged. For convex or concave
curved surfaces, the projected line images would not be parallel.
Referring to FIG. 7, red lines 124R and blue lines 124B show the
pattern for a convex surface and red lines 126R and blue lines 126B
show the pattern for a concave surface. A horizontal displacement,
however, may also be determined by the alignment of auxiliary
images with definable structures along the turbine blade, such as a
boss, hole or even the edge of the blade itself. It is to be
appreciated that the surface nonconformities and the resultant
complementary set of images illustrated in FIGS. 5-7 are
exaggerated for illustration purposes. In reality the stereoscopic
gage is quite sensitive to surface nonconformities, and
displacements less than .005 inches can be determined by an
operator using a 2x or 3x magnifier.
The details of the stereoscopic optical projection systems 108 and
110 are shown in FIG. 8. Although in the general discussion of
stereoscopic imaging the optical axes of the projection systems
were illustrated as being parallel to each other and generally
normal to the plane of the surface being gaged, it is well known in
the projection and photographic arts that off axis imaging such as
that used in the stereoscopic gage can be significantly improved by
canting the two projection systems slightly towards each other. The
canting substantially increases the overlapping area of the two
projected images, reduces the off axis performance requirements of
the projection lens, increases the depth of field of the projected
image and thereby permits the spatial separation between the two
stereoscopic projection systems to be increased. All of the above
factors tend to improve the performance of the stereoscopic gage.
Referring to projection system 108, a light source shown as an
incandescent lamp 302 with a condensor lens 304 illuminates a mask
or picture 306 containing the stereoscopic pattern having a set of
transparent images on an otherwise opaque background. The light
tramsitted by the transparent images is than projected onto the
article being gaged by projection lens 308 forming magnified images
of the pattern on the mask. A color filter 310 is inserted between
the condensor lens and the mask to impart to the projected images a
distinguishing color. Referring to projection system 110, a light
source also shown as an incandescent lamp 302 with a condensor lens
304 illuminates a mask or picture 316 containing a complementary
set of transparent images on an otherwise opaque background. A
color filter 320 is inserted between the condensor lens and the
mask to impart to the image projected by system 110 a color
contrasting to the color of the images projected by system 108.
Other features such as heat absorbing filters, optical baffles,
lamp cooling systems and focusing mechanisms normally incorporated
into operative projection systems are not shown since they are
immaterial to the discussion.
The complementary image masks in the projection systems may be made
in any convenient manner. One method would be to photograph,
through the projection optics, the surface of an article having the
desired configuration with appropriate gaging patterns applied
along the surface at predetermined locations. Enhancement of the
photographically reproduced gaging pattern may be accomplished by
painting the surface to be photographed black and applying white
gaging patterns in the appropriate locations. A positive
photographic transparency would produce the desired complementary
masks one for each projection system having opaque backgrounds with
transparent images. Of course, the article may be painted white
with black gaging patterns and the article photographed with
negative film, but this represents a procedural difference which is
immaterial to the invention.
The gaging patterns may also be computer generated using the
physical parameters of the projection systems and the desired
surface of the article to be gaged. The computer generated masks
would be particularly advantageous where minor changes in the
pattern of an existing mask are desired or necessary to account for
minor design changes.
A fully automated embodiment of the invention is illustrated in
FIG. 9. An object to be gaged illustrated as a turbine blade 402 is
rigidly supported in a predetermined position by a holding fixture
404 mounted on supporting structure 406. Two stereoscopic
projectors 408 and 410 projecting complementary stereoscopic images
412, 414 and 416 on the surface of the turbine blade 402. The two
stereoscopic projectors are rigidly attached to a support bridge
418 which holds the stereoscopic projectors in a fixed relationship
to the turbine blade. A detector 420 is also attached to the
support bridge 418 and monitors the position of the projected
images on the turbine blade. The detector 420 may be a television
type camera capable of distinguishing between the two projected
images. Where the projected images are of different colors, a color
filter wheel, adapted to synchronously rotate with the scan rate of
the television camera, may be mounted between the image and the
photosensitive surface of the camera. The color filters are
selected so that the television camera tube is sensitive to only
one set of the two projected color images at any given time.
Therefore, during a given scan the television camera tube would
generate a series of electrical pulses indicative of the position
of each projected image of a given color. On the subsequent scan
the second filter would be imposed between the camera tube and the
object and the camera tube would generate a second series of
electrical pulses indicative of the position of the second set of
colored images. Although the illustrated embodiment shows a single
sensor monitoring the complete set of projected images, some gaging
aplications may warrant the use of an individual sensor for each
image or a preselected number of images.
The electrical signals generated by the sequential scan lines are
stored in correlator 422. The correlator 422 electronically
correlates the electrical signals indicative of the position of the
corresponding colored images in each pattern and generates signals
indicative of magnitude and direction of the displacement between
the corresponding images. The correlation information is
transmitted to computer 424 which stores the information until the
complete pattern projected on the blade is scanned. After one or
more complete scans have been stored, the computer analyzes the
stored correlated data for each scanned image and determines the
conformity or the nonconformity of the gaged surface to the desired
surface. The output of the computer are error signals which are
indicative of the magnitude and direction of the nonconformity, the
type of nonconformity such as a twist, a bend or a bow. The
signals, such as a signal indicative of twist in a given direction
are applied to a buffer amplifier 426 which generates corrective
signals operative to activate a reshaping device 428. For example,
reshaping device 428 in response to the corrective signals
generated by the buffer amplifier, may engage the end of the
turbine blade and apply a rotational torque in a direction
calculated to remove the nonconforming twist. The reshaping device
428 may also respond to corrective signals from amplifiers 430 and
432 and generate linear forces to remove nonconforming bends.
Although the reshaping device 428 is illustrated as a single device
capable of removing both twists or bends, it is understood that
individual devices may be used to perform each function
independently. Other reshaping devices such as ram 434 responsive
to control signals from the computer through buffer amplifier 436
may be spaced at various positions along the length and breadth of
the turbine blade to perform various other corrective
functions.
While the preferred embodiment shown in FIG. 9 shows the automated
gage directing or controlling relatively simple mechanical
corrective functions will be apparent to those skilled in the art
that more sophisticated machining or corrective functions may be
controlled by the automated stereoscopic gage. These may include
grinding or machining material from preselected areas of the
surface to achieve conformity or automatically aligning a part for
subsequent machining or assembly.
Other changes in the preferred embodiments are also possible within
the scope of the invention. For example, in the fully automated
embodiment, the two projected stereoscopic images need not be of
different colors but may have other identifying characteristics
which could be electrooptically determined. The identifying
characteristic could be a difference in brightness of the two
images or the light sources may be modulated at different
frequencies. These alternative methods would eliminate the need for
the color filter wheel described in the preferred embodiment
without departing from the spirit of the invention. Accordingly, it
is intended that the illustrative and descriptive materials herein
be used to illustrate principles of the invention and not to limit
the scope thereof.
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