Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Our Reference: PTC-198-B PATENT
HEADLIGHT AIMING APPARATUS
BACKGROUND OF THE INVENTION
Field of the Invention:
The present invention relates, in general, to
vehicle headlight aiming apparatus and methods.
Description of the Art:
Vehicle headlights project a light beam forward
of a vehicle to illuminate the roadway for a driver.
High beam and low beam headlights either in separate
light bulbs or implemented by dual filaments and lens in
a single bulb project different light patterns.
Headlights must be aimed according to
standards, such as an SAE standard in the United States
and different but similar standards in Europe and Japan.
Typically, a light beam is projected onto a target board
set 25 feet in front of the vehicle. An ideal light beam
pattern or image imprinted on the target board is '
manually compared with the light beam image or pattern
from the vehicle and manual adjustments, as necessary,
made to the headlight support structure to properly
coincide the headlight beam pattern with the standard
image pattern.
Another method utilizes the reflection of a
light beam from a vehicle headlight through a lens and
off of a screen to a camera which produces a digitized
image of the reflected light beam. The focal length of
the lens and the distance between the lens and the screen
are optically equivalent to the 25 foot distance between
the headlight and target board described above. The
digitized image is then analyzed by an algorithm executed
by a processor to locate the highest intensity pattern or
"hot spot" which is considered to be the main optical
axis of the headlight. The headlight is adjusted, as
necessary, to align the hot spot with the hot spot of a
properly aligned headlight according to the various
standards.
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Different aiming algorithms are necessary since
the intensity contours of different style lamps varies by
the particular market. Both left hand and right hand
headlight algorithms are also needed. Typically,
however, these algorithms are very sensitive to hardware
noise and require additional processing to remove "aim
bounce" which has the effect of reporting varying
aimpoint values during static repeatability testing.
Since all headlights including both low and
high beam lights in each vehicle made in a manufacturing
plant must be properly aimed, consideration must be taken
as to the integration of the headlight aiming procedure
in the typically high speed production line. Due to high
production rates, vehicles have been directed to a
plurality of individual headlight aiming stations. The
multitude of stations adds expense to the aiming
operation and may introduce variability in the aiming
results between the. different stations. Other aiming
apparatus, which have been incorporated directly into the
production line,~must be moved into a position in front
of each vehicle at the proper time. This has met with
. problems in repeatably aligning the headlight aiming
apparatus with each vehicle.
Thus, it would be desirable to provide a
headlight aiming apparatus and method which utilizes an
improved algorithm for greater aiming accuracy. It would
also be desirable to provide a headlight aiming apparatus
and method which is usable with a plurality of different
headlight image patterns. It would also be desirable to
provide a headlight aiming apparatus which can be easily
integrated into a vehicle assembly line.
SUMMARY OF THE INVENTION
The present invention is an aiming apparatus
suitable for aiming a vehicle headlight mounted in an
adjustable frame on a vehicle to a standard or reference
aiming pattern.
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The headlight aiming apparatus of the present
invention includes a housing having a focusing lens
mounted in one side. A screen is mounted in the housing
and spaced from the lens at a prescribed distance to
focus a headlight pattern image striking the lens on the
screen where it is reflected to an image sensing means
mounted in the housing and spaced from the screen. The
image sensing means senses the reflected headlight image.
Means are coupled to or formed as a part of the
image sensing means for converting the sensed image to
digital image representations which are output to a
processor means. A memory means is disposed in data
communication with the processor means and stores
standard image patterns of properly aimed headlights.
The processor means is responsive to the output of the
image converting means and the standard headlight aiming
patterns stored in the memory means for determining
differences between a reflected headlight pattern sensed
and output from the converting means and a reference
pattern stored in memory. In response to any determined
differences, the processor means generates correction
signals which are supplied to an adjusting means, such as
a power driven screwdriver engagable with the headlight
aiming frame on the vehicle. The adjusting means is
responsive to the correction signals for adjusting the
position of the headlight mounting frame to bring the
headlight pattern in substantial alignment with standard
headlight reference patterns.
Preferably, the processing means forms a sample
window of pixels in the digitized image and the model
image and multiplies the grayscale intensity values of
identical pixels in each image. The products are summed
to generate a correlation value for the sample window.
Since several sample windows are then formed, each offset
from other sample windows and the product and summation
steps are repeated to locate a sample window with the
highest correlation value. The center of this sample
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window is determined by the difference in the X and Y
axis from the center of the model image. In response to
the difference, the processor means generates a signal to
drive the adjusting means in a direction to reduce the
difference to zero.
In a preferred embodiment, a frame is disposed
transversely to a longitudinal axis of a vehicle. Means
are provided for movably mounting the housing on the
frame for movement between a home position and an aiming
position.
Optionally, means are mounted on the frame for
calibrating the home position of the housing each time
the housing moves to the home position. Preferably, the
calibrating means comprises a correctly aimed headlight
or a laser mounted on the frame generating a light beam
. coinciding with the hot spot of a properly aimed
headlight.
The memory means also stores X and Y axis
position signals for the moving means. Means,
coordinating with the particular vehicle, are used to
select the X and Y positions of the moving means to
repeatably position the housing in the proper aiming
position for each headlight on each vehicle or vehicles.
Means are also provided for varying the speed
of rotation of the adjusting means in proportion to the
magnitude of the difference between the reflected
headlight pattern and the stored reference pattern on a
pixel-by-pixel basis. Preferably, pulse width modulated
drive means, responsive to the output signal from the
processor means, controls to the adjusting means to vary
the frequency of electrical power supplied to the
adjusting means.
The present invention also defines a method for
aiming a vehicle headlight to a standard or reference
aiming image pattern. The method comprises the steps of:
focusing a light beam from a vehicle headlight
onto a reflective surface; sensing the intensity of the
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reflected light beam from the surface on a pixel-by-pixel
basis in a matrix of pixels; forming a sample window
matrix of pixels, multiplying the grayscale value of each
pixel in the sample window with the value of the
corresponding pixel :in the model image, summing all of
the products for each sample window to form a correlation
value, forming consecutive sample windows offset from
each other, forming a correlation value for each sample
window determining t;he center along X and Y axes of the
sample window using t:he highest correlation value;
determining difference between the center of the sample
window with the highest correlation and the center of the
model image in at least one axis; and activating an
adjustment means enc~agable with a headlight mounting
frame to adjust the headlight position in at least one
axis to reduce the difference to zero.
According t:o one aspect of the invention, there
is provided an apparatus far aiming a vehicle headlight
to a standard aiming image, the apparatus comprising:
means for storing standard headlight aiming image
pattern as a standard image matrix;
means for sensing light emitted from a headlight,
the sensing means c~e~rre:ratlIlg an output on a pixel-by-
pixel basis proport:ianal to the sensed light intensity of
each pixel;
means, responsive to the output from the sensing
means, fo:r convert:in.g the output to an intensity
magnitude value for each pixel in a sensed image matrix;
means for forming a p-~urality of offset sample
matrices, each formed of a portion of the sensed image
matrix anc~ a plura_1_ity of corresponding standard image
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sub-matrices each fc>rmed of a portion of the standard
image matrix;
means for determining the offset sample matrix
having the highest correlation to a corresponding
standard image sub--matrix;
means for determining the center of the offset
sample matrix having' the highest correlation;
means, responsive to the means for determining the
center of the offset sample matrix, for determining the
difference between the center of the offset sample matrix
and the center of ~~h.e corresponding standard image sub-
matrix, t:he differen-ce determining means generating a
difference output signal having a magnitude proportional
to the difference; and
means, responsive to the difference output, for
activatin~~ an adjustment means engagable with headlight
support t~~ adjust th.e support to reduce the difference to
zero.
According to another aspect of the invention,
there is ;erovided <r method of aiming a vehicle headlight
to a stan~~ard image pattern, the method comprising the
steps of:
storing a standard image pattern as a standard image
matrix;
focussing a light beam from a vehicle headlight onto
a reflective surface;
sensing the intensity of the reflected light beam
from the ;surface om a. pixel-by--pixel basis in a sensed
image matrix;
assi~~ning a magnitude value to each pixel in the
sensed im<~ge matrix;
forming a plurality oi= consecutively offset sample
matrices, each formed of a portion of the sensed image
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matrix;
forming a plur<~lity of corresponding standard image
sub-matrices, each formed of a portion of the standard
image matrix;
determining the offset sample matrix having the
highest correlation to a corresponding standard image
sub-matrix;
determining the=_ center of the offset sample matrix
having the highest correlation;
determining a difference between the center of the
offset sample matrix having the highest correlation with
the center of the corresponding standard image sub-
matrix; and
activating an adjustment means engagable with a
headlight adjustment: frame to adjust the headlight
position in at least. one axis.
The headlight aiming apparatus and method of
the present invention provides a highly accurate aiming
process which eliminates certain of the problems when
encountered with previously devised vehicle headlight
aiming apparatus. The present apparatus is capable of
storing many different headlight aiming patterns or
images thereby enabling the apparatus to be used in
multiple applicatior.,s or in a single production line for
many different style vehicles. The present apparatus is
also easily integrated into a vehicle production line
without r~squiring multiple aiming stations.
BRIEF DESCRIPTION OF THE DRAWING
The various features, advantages and other uses
of the pr.=_sent invention will become more apparent by
referring to the following detailed description and
drawing in which:
Fig. 1 is a front elevational view of a
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headlight aiming app>aratus constructed in accordance of
the teachings of t:he present invention;
Fig. 2 is a left side elevational view of the
apparatus shown in Fig. 1;
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Fig. 3 is a plan view of the apparatus shown in
Fig. 1;
Fig. 4 is a partially broken away, perspective
view of the camera housing shown in Figs. 1 and 2;
Fig. 5 is a block diagram of the control means
employed with the apparatus shown in the preceding
Figures;
Fig. 6 is a side elevational view of a
headlight mounting and adjustment structure;
Fig. 7 is a pictorial representation of the
headlight aiming process employed in the apparatus of the
present invention;
Fig. 8 is a perspective view of the gantry
shown in Fig. l; but with additional features;
Fig. 9 is a perspective view showing the camera
positioning means mounted on the gantry shown in Figure
9; and
Fig. 10 is an exploded, perspective view of
another embodiment of the camera housing of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawing, and to Figs. 1-3
in particular, there is depicted a vehicle headlight
aiming apparatus 10. The apparatus 10 includes means for
moving a reflected light beam detecting means or camera
into position in front of a vehicle headlight.
Preferably, the moving means includes a gantry 12 which
is positioned transverse to the longitudinal axis of a
vehicle located adjacent to the gantry 12. The gantry 12
includes a lower frame formed of a plurality of
vertically extending legs 14 which are securely mounted
at one end to a floor surface.
An upper frame is formed of four vertically
extending legs 16 each of which is joined at one end to
one of the legs 14 of the lower frame. Four generally
horizontally extending, interconnected tubular members,
each denoted by reference number 18 are fixed to the
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vertical legs 16. Angular braces 20 extend between each
vertical leg 16 and an adjacent horizontal leg 18. As
shown in Fig. 2, a pair of horizontally extending slide
rails 22 are mounted on two of the horizontal tubular
members 18 of the upper frame.
As shown in Figs. 1 and 2, a movable mounting
rack denoted by reference number 30 is movably mounted
for horizontal movement along the tubular members 18.
The movable rack 30 includes an upper frame structure
formed of four interconnected tubular members generally
connected in a square or rectangular shape as shown in
Fig. 3. Four, elongated, vertically extending legs 32
are connected at upper ends to the tubular members 31 and
depend downward therefrom.
A vertically~extending slide member 34 is
slidably mounted on each of the vertical legs 32 as shown
in Fig. 2. A vertical moving means is coupled to the
four slide members 3'4 for vertically adjusting the
position of the four slide members 34 and the camera
housing attached to the vertical slide members 34 as
described hereafter. A hollow tubular member 36 is
centrally located between and connected to the vertical
slide members 34 by braces 38. A ball nut 42 is mounted
at one end of the hollow tubular member 36 and
threadingly receives a ball screw 42 therethrough. The
ball screw 42 extends from the ball nut 42 to a bi-
directional output shaft of an electric drive motor 44
mounted on the upper frame of the movable rack 30.
Energization of the drive motor 44, as described
hereafter, will cause rotation of the ball screw 42 in
one of two directions. Rotation of the ball screw 42
results in vertical movement of the tubular member 32 via
the ball nut 40 in an upward or downward direction
depending on the direction of rotation of the ball screw
42 to thereby adjust the vertical position of the tubular
member 36 and the vertical slide members 34 connected
thereto.
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As shown in Figs. 1-3, a horizontal drive means
is mounted to the gantry 12 and connected to the upper
frame of the movable rack 30. The horizontal drive means
horizontally translates the movable rack 30 along two of
the horizontal members 18 of the upper frame of the
gantry 12. As shown in Fig. 2, slide rail engaging
members 46, each having a longitudinal through bore, are
spaced apart on opposite sides of the upper frame of the
movable rack 30 and slidably receive the slide rails 22
attached to two of the upper frame members 18 of the
gantry 12.
The horizontal drive means includes an electric
drive motor 24 mounted at one end of the upper frame of
the gantry 12. The drive motor 24 has a bi-directionally
rotatable output shaft which engages a gear reducer 25.
The gear reducer 25 drives a sprocket which engages a
toothed drive belt 26 formed in a continuous loop. The
opposite end of the-drive belt 26 passes around a roller
mounted on the upper frame. A plate 28 is fixed to the
drive belt 26 and to the upper frame of the movable rack
to couple horizontal movement of the drive belt 26 to
horizontal movement of the rack'30.
As shown in Figs. 1-2, a frame 50 formed of
interconnected tubular members is connected by brackets
25 to one each the vertical slide members 34 and to the
tubular member 36. A housing 52 is fixedly connected to
the frame members 50 by brackets for vertical movement
with movement of the vertical slide members 34 via the
drive motor 44, the ball screw 42, the ball nut 40 and
30 the centrally located tubular member 36 as described
above.
The gantry 12, depicted as an alternate, but
preferred embodiment in Fig. 8, is substantially
identical to that described and shown above in Figs. 1-3;
but includes several modifications. A pair of safety
light reflectors 180 and a corresponding pair of light
emitters 182 are mounted on the legs 14 of the gantry 12
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in aligned pairs to provide a safety curtain or envelope
about the movement path of the camera housing 52 along
the gantry 12.
A vehicle presence detector 184 is mounted on
the gantry 12, such as on one of the horizontal members
18 as shown in Fig. 8. The vehicle presence detector
184, by example only, is in the form a light emitter
which is aimed at a suitable light reflector mounted on
the floor or other structure in front of the gantry 12.
Passage of a vehicle through a light beam extending
between the light emitter 184 and the associated light
reflector will cause the light emitter 1,84 to provide a
signal to the controller indicating that a vehicle has
approached the headlight aiming apparatus 10.
Various overtravel limit switches are mounted
on the gantry 12 for detecting the position of the camera
moving means. Limit switches 186 and 188 are mounted at
opposite ends of one of the horizontal members 18 for
detecting extreme lateral positions of the camera moving
means. A shock absorber 190 mounted on the gantry 12 to
provide a cushion for return of the camera moving means
to a home position.
A control panel 192 is mounted on the side of
one pair of vertical legs 14 of the gantry 12.
A top rail 258 is mounted on each horizontal
leg 18 and supports the circular cross-section slide rail
22. An additional rail 197 is mounted by legs to one
horizontal leg 18 and extends above the leg 18 to support
a gear rack 199.
A preferred embodiment of the camera moving
means is shown in greater detail in Fig. 9. A plate or
carriage 194 carries a pair of aligned pillow blocks 195
on each of two opposed sides which engage the tubular
rods 24 mounted on the two horizontal rails attached to
the top of the horizontal legs 18 of the gantry 12.
An enclosure or junction box 196 is mounted on
the carriage 194 and housing electrical connections to
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the various electrical components mounted on the carriage
194 as described hereafter.
The horizontal drive motor 24 is mounted on the
carriage 194 and has an output shaft connected to the
5 gear reducer 25. An encoder 200 is coupled to the gear
reducer 25 to provide horizontal position output signals
or pulses. A pinion gear 201 is driven by the gear
reducer 25 and engages the gear rack 199 mounted on the
rail 197 affixed to one horizontal leg l8 of the gantry
10 12. Bi-directional rotation of the pinion gear 201 along
the gear rack 199 drives the carriage 194 horizontally
along the rails 22.
The output shaft of the vertical drive motor 44
is coupled to a threaded shaft or jack screw 42 which
extends through a centrally located aperture in the
carriage 194. An encoder 198 is coupled to the shaft 42
to provide position information relating to the linear
position of the shaft 42 upon bi-directional energization
of the vertical drive motor 44 as described above.
Four apertures, each denoted by reference
number 202, are located near the corners of the carriage
194. A guide rod 204 is extensible through each aperture
202 as shown in Figs. 9 and 10. The guide rods 204 are
fixedly mounted on the housing 52 and extend through
hollow guide cylinders or sleeves 206 fixedly mounted on
and extending from the bottom surface of the carriage 194
and aligned with one aperture 202 in the carriage 194.
In this manner, rotation of the threaded shaft 42 by the
vertical drive motor 44 causes the threaded shaft 42 to
screw into or out of the jack cylinder 43 mounted on the
housing 52 which results in vertical movement of the
housing 52.
As shown in Fig. 9, a detector 208, such as a
proximity switch, is mounted on the carriage 194 adjacent
one guide rod 204. The detector 208 is positioned to
detect the absence of the end of the adjacent guide rod
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' 204 for an indication of vertical downward overtravel of
the housing 52.
Another detector, such as a limit switch 209,
is mounted on the carriage 194 and positioned to detect
an end cap on the end of rod 204 when the rod 204 and
attached housing 52 is at a vertical home position.
As shown in greater detail in one embodiment in
Fig. 4, the housing 52 comprises a generally four-sided
enclosure having a pair of spaced side walls 54, a bottom
wall 56, a top wall 58, and a rear or back wall 60. A
door or front cover 62 is pivotally connected, such as by
a hinge, to one edge of one of the side walls 54 and is
lockingly engagable with the opposed side wall 54 to
close the interior of the housing 52; while at the same
time allowing access to the components mounted within the
interior of the housing 52. An aperture 61 is formed in
the door 62 and receives a transparent cover plate 63. A
bottom slide plate 64 is disposed within the housing 52
and slidingly overlays the bottom wall 56 of the housing
52.
A pair of generally U-shaped channel members 66
are mounted at one end of the bottom slide plate 64 and
extend vertically therefrom. Although only one is shown
in Fig. 4, a pair of adjustable support assemblies 74
fixedly connect each channel member 66 to one edge of the
bottom slide plate 64. The channel members 66 support a
focusing lens 68, such as a flat FRESNEL lens. Resilient
pads 70 and a spacer 72 are mounted in each channel
member 66 for resiliently supporting the lens 68 in the
channel members 66.
SAE headlight aiming tests require that the
headlight beam be imaged on a surface spaced 25 feet from
the vehicle headlight. The focal length of the lens 68
is chosen so that a headlight beam image is formed on the
back wall 60 of the housing 52 which is comparable to an
image formed 25 feet from the vehicle headlight.
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An image sensing means or camera 80 is secured
to the bottom slide plate 64 via a mount 82. The camera
80 may be any type of camera for sensing the image
reflected off of the flat black back wall 60 of the
housing 52. Preferably, the camera 80 is a CCD type
camera which has a plurality of light sensor cells
arranged in a 512x480 pixel matrix. By example only, the
camera 80 may be a Panasonic camera, model number WV-
BP500. A six millimeter F12 lens is mounted on the
camera 80.
Fig: 10 depicts an alternate embodiment of the
camera housing 52. The housing 52 is substantially
identical to the housing 52 described above and shown in
Fig. 4 in that it includes a pair of spaced side walls
54, the top wall 58, a bottom wall, and a rear or back
wall. A door or front cover 62, shown in Fig. 4, is
pivotally connected to one end of one of the side walls
54 and is lockingly.~engagable with the housing 52 by
means of suitable latches mounted on the front door or
cover. The front door includes an aperture 61 which
receives a transparent cover plate 63 as shown in Fig. 4.
In the embodiment shown in Figs. 8, 9 and 10,
an external mounting plate 254 is mounted on the top wall
58 of the housing and receives mounting pads at the ends
of the guide rods 204 and jack cylinder 43. An internal
mounting plate 256 is mounted on an inner surface of the
top wall 58 of the housing 52.
The camera slide tray 210 is slidably mounted
in the housing 52 by a two-part slide including slide
element mounted on the slide tray 210 and a mating
element, not shown, mounted on the housing 52. The slide
tray 210 includes a back wall 212, a pair of spaced side
walls 214, and a bottom wall 216. The camera slide tray
210 is sized to slidably fit within the housing 52 as
shown in Fig. 10.
The camera 80 is mounted on the bottom wall 216
of the slide tray 210. A screen or reflective surface
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218 is adjustably mounted within the slide tray 210.
Adjustable mounting means includes a plurality of
threaded rods 220 which fixedly extend from the back wall
212 through apertures in the screen 218 and bores in a
plurality of mounting blocks 222. A threaded fastener,
such as a nut 224, is mounted about each rod 220 and
threaded into engagement with the front surface of the
screen 218 to fix the position of the screen 218 relative
to the camera 80. The four threaded rods 220, the
fasteners 224 and the mounting blocks 222 enable the
vertical and horizontal angular position of the screen
218 to be adjusted relative to the camera 80 by extension
and retraction of the rods 220 relative to the back wall
212.
The focusing lens 68 is part of a lens package
or assembly 230. As described above, the focusing lens
68 is preferably a flat FRESNEL lens. The lens 68 is
disposed between two protective, transparent sheets 232,
which are preferably formed of a strong material, such as
LEXAN. A frame 234 formed of angle iron has a plurality
of apertures spaced along the top and bottom edges for
receiving threaded fasteners 236 which extend through the
apertures in the frame 234, and each of the protective
sheets 232 and the lens 68, for holding the various
elements of the lens assembly 230 in an assembled
relationship within the frame 234.
Lens frame mounting and adjustment means are
provided for mounting the lens assembly 230 in the slide
tray 210; while providing vertical and horizontal
adjustment of the lens 68 relative to the screen 218.
The adjustment means includes elongated fasteners 238,
such as hex head bolts, which extend through apertures in
the vertical side legs of the frame 234 and the sides of
each of the protective plates 232 and the lens 68. A
biasing means, such as a compression spring 240, is
disposed about the threaded shank of each fastener 238
between the innermost protective sheet 232 and a pair of
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lens mounting blocks 242. The lens mounting blocks 242
are fixedly secured, such as by welding or fasteners, to~
the inner surfaces of the side walls 214 of the slide
tray 210 and include a pair of spaced bores which
slidably receive the shanks of the threaded fasteners
238. Suitable nuts, not shown, are mounted about the
shanks of the fasteners 238 after the shanks pass through
the lens mounting blocks 242. In this manner, vertical
and horizontal adjustments in the position of the lens 68
may be attained by rotating the hex head of any of the
fasteners 238.
Also mounted on the vertical tubular members 32
shown in Fig. l is a control panel 86 having a touch
screen LCD display 88 and a plurality of manual
pushbuttons or selector switches 90 for providing various
inputs to the control means described hereafter. The
display 88 displays various menus or status information
to an operator as well as. providing touch input
selections.
Also mounted on one of the vertical legs 14 of
the gantry 12 is a calibration means for calibrating the
housing 52 after each aiming operation. The calibration
means includes a light source, such as a vehicle
headlight 92, which is attached by a mounting bracket 94
to one of the vertical legs 14 of the gantry 12.
Additional details concerning the calibration features of
the present invention will be described hereafter.
Alternately, as shown in Fig. 8, the
calibration means is formed of a laser mounted in a
housing 250 attached to a frame extending from one of the
vertical legs 14 of the gantry 12. Any suitable laser
may be used, such as a Metrologic laser, for example.
The laser is aimed through an aperture 252 in the housing
250 and is aligned with the lens 68 in the camera housing
52 when the camera housing 52 is at the calibration
position.
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As shown in Fig. 2, a screwdriver mounting
frame structure 96 is affixed to one of the horizontal
tubular members 18 of the gantry frame. The frame
structure 96 extends along the length of the gantry 12
5 and supports one or two cable reels 98. A cable 100
extends from each cable reel 98 and is connected to an
electric motor driven screwdriver 102 which has a
rotatable bit 104 mounted therein. The screwdriver 102
may be any conventional power screwdriver, such as one
10 sold by DeSoutter.
Only one screwdriver 102 is shown in Fig. 2.
However, it will be understood that two screwdrivers 102
and 103, as shown in Figs. 6 and 8, are typically mounted
via separate cables 100 and reels 98 to the frame 96 and
15 are slidingly movable along the frame 96 to adjust a
vehicle headlight in both X and Y axes.
The screwdriver 102 or screwdriver 103 has a
bi-directionally rotatable output shaft, with the '
polarity of the voltage applied to the drive motor of the
screwdriver 102 and 103 determining the direction of
rotation of the output shaft and the bit 104 connected
thereto.
Referring now to Fig. 5, there is depicted a
control means mounted separate from the gantry 12 which
controls the operation of vehicle headlight aiming
apparatus 10.
The control means includes a controller, such
as .a microprocessor, mini computer, etc., having a
central processing unit (CPU) 110 which executes a
control program stored in a memory 112. By example only,
the CPU 110 is a 66 MHz 80486 processor. A keyboard 114
is connected to the CPU 110 for inputting various
information to the CPU 110. A display 116 is also
connected to the CPU 110 for displaying various output
data.
A digital signal processor 118 is also input to
the CPU 110 and, also, controls the display 116 for
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displaying the digitized image output from the camera 80.
By example, the digital signal processor 118 is an IM-LC
processor made by Matrox, Dorval, Quebec, Canada and acts
as a frame grabber for the output of the camera 80.
Although the CPU 110 is capable of directly
controlling the operation of the screwdrivers 102 and 103
as well as the X and Y drive motors 24 and 44, in an
exemplary embodiment, a programmable logic controller or
PLC 120 is connected in data communication with the CPU
110. By example only, the PLC may be an Allen Bradley
PLC model 5/30 which is connected to the CPU 110 by a
conventional data highway or bus utilizing Allen Bradley
data communication protocol. The outputs of the control
panel 86; i.e., signals from a mode selector switch,
start and stop pushbuttons, or other operator input, are
input to the PLC 120. The PLC 120 is response to various
inputs executes a stored control program to activate
various outputs as described hereafter.
Further inputs to the PLC 120 include signals
122 and 124 which are respectively output from the
horizontal encoder 200 connected to the X axis drive
motor 24 and the vertical encoder 198 connected to the Y
axis drive motor 44. Any conventional encoder may be
employed which generates a pulse for each predetermined
amount of rotation of the motor output shaft to indicate
the position of the movable member driven by the
respective motors 24 and 44. The encoder outputs 122 and
124 are input to the PLC 120 and used by the PLC 120 when
executing its control program to generate signals to X
and Y drivers 126 and 128 respectively connected to the X
and Y drive motors 24 and 44. By example only, the X and
Y drivers 126 and 128 may be variable frequency drives,
such as a variable frequency drive model number 1305 sold
by Allen Bradley.
Also input to the PLC 120 is an input signal
labeled "BODY STYLE" which may be a signal indicating the
particular vehicle style which is undergoing headlight
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aiming. As several different vehicle styles containing
different headlight arrangements and/or headlight
positions may be tested by a single headlight aiming
apparatus 10, the "BODY STYLE" signal 130 provides an
indication of which body style is undergoing test.
Finally, an X axis over travel limit switch 132
and a Y axis over travel limit switch 134, shown in Fig.
5, are mounted on the gantry 12 and the rack 30 to
indicate an overtravel of the horizontal position of the
mounting rack 30 and the vertical slide members 34.
The apparatus 10 is capable of different modes
of operation which may be selected by the operator. Such
modes include "teach or manual", "run" and "auto". In
the teach or manual mode, as selected via the display
screen 88 or one of the selector switches or pushbuttons
90 on the control panel 86, the CPU 110 enters a teach
mode in which the pushbuttons 90 on the control panel 86
may be employed to activate the drive motors 24 and 44 to
move the mounting rack 30 to the desired vertical and
horizontal position with respect to a vehicle headlight
disposed adjacent to the gantry 12. It will be
understood that a conventional vehicle centering
mechanism will typically be employed to center the
vehicle with respect to the gantry 12 and to precisely
align or square the vehicle headlight to the lens 68 in
the housing 52.
As shown in Fig. 6, a conventional vehicle
headlight 136 is adjustably mounted in a support
structure or panel 138 on the vehicle. A pair of flanges
140 and 142 extend from a head lamp mounting ring 144
which surrounds the headlight 136. An X axis adjustment
screw 146 and a Y axis adjustment screw 148 extend
through the support structure or panel 138 and
respectively engage the flanges 140 and 142 on the
headlight mounting ring 144. Rotation of the screws 146
and 148 via the screwdrivers 102 and 103 will cause the
position of the respective mounting flanges 140 and 142
~~ ~~8~
18
to be adjusted with respect to the fixed vehicle support
structure 138 thereby changing the orientation of the
headlight 136 along the X and Y axes to center or align
the aim of the headlight 136 according to an established
headlight aiming standard, such as SAE, European or Japan
standards.
Continuing with the teach mode, when a test
headlight or a vehicle having a properly aimed headlight
is positioned adjacent the gantry 12, the mounting rack
30 will be manually moved in the X and Y directions until
the housing 52 is aligned with the headlight 36. The CPU
110 then receives a image from the camera 80 of the light
beam image reflected off of the back wall 60 of the
housing 50 and into the camera 80. The CPU 110 digitizes
the image on a pixel by pixel basis and converts each
pixel to a grayscale intensity value. Since the camera
80 in an exemplary embodiment of the present invention
has a pixel matrix of 512x480 pixels arranged in rows and
columns, respectively, the CPU 110 stores in the memory
112 a digitized grayscale image of each pixel of the test
headlight. The CPU 110 is capable of recognizing this
stored image as the standard or model image for the
particular style headlight and the particular mounting
position of the headlight on a vehicle.
This teach process is repeated for each
headlight position on the vehicle, such as for all high
beam and low beam headlights as well as any optional fog
lights. The CPU 110 stores a model image for each
headlight and each mounting position of each headlight in
the memory 112.
This teach process will also be repeated for
all of the different body styles of vehicles which may be
tested by a single aiming apparatus 10.
Also during the teach process, the X and Y axis
positions of the housing 52 as output by the encoders 198
and 200 coupled to each of the drive motors 24 and 44
will be stored in the memory of the PLC 120. This
2 ~ ~~~~a
19
enables the PLC 120 to move the housing 52 to the desired
headlight position for each headlight on a vehicle or
vehicle style undergoing aiming.
After all of the model headlight aiming model
images are stored in the memory 112, the apparatus 10 can
be placed in either "run" or "auto " mode. The "run" mode
represents a single headlight aiming test; while the
"auto" mode represents a continuous operation of repeated
headlight aiming tests for a single vehicle or each of a
number of successive vehicles move into proximity with
the apparatus 10.
As "run" and "auto" modes are similar, the
following description will be for the operation of the
apparatus 10 in aiming a single headlight in "run" mode.
It will be understood that a similar process is executed
by the apparatus 10 for each headlight on a vehicle in
the "auto" mode.
In general, the CPU 110 executes a normalized
grayscale correlation algorithm stored in the memory 112
to determine the best fit or correlation between the
model image for a particular headlight and the actual
image as sensed by the camera 80. This algorithm is set
forth below:
i=N i=N i=N
N~ ~ I i ~ Mi
IiMi
r= i=1 i=1
i=1
i=N i=N i=N i=N
[N~ Ii-(~ Ii)Z J LN~Mi-(~Mi)2J
i=1 i=1 i=1 i=1
where:
I = grayscale pixel intensity
N = total number of pixels in model (i.e.,
512x480)
Ii = image pixel number
Mi = model pixel number
2~8~~~7
The CPU 110 forms a sample window of n x n
pixels. By way of example, the sample window is 128x128
pixels as shown by the sample window 156 in Fig. 7. For
clarity in understanding the present invention, the
5 sample window 156 is shown superimposed over the
digitized grayscale image of the reflected headlight beam
from the headlight 136 as would be displayed on the
display 116.
In executing the algorithm, the CPU 110
10 multiplies the grayscale intensity of the first pixel 158
as digitized from the actual reflected light beam from
the headlight 136 with the corresponding model pixel
intensity. This process is repeated for each pixel in
the sample window 156 and the corresponding pixels in a
15 similarly formed model image. Each of the products are
then summed to provide a correlation or match value for
the window 156. Next, the CPU 110 forms a second window
which is offset from the first window by one pixel.
Thus, in the second sample window, the first pixel is
20 pixel 160 shown in Fig. 7. The first row of pixels in
the second sample window will extend one pixel beyond
that of the first sample window 156. Multiplication of
the grayscale intensity of each sample pixel and the
corresponding model pixel is then performed, with the
products summed to provide a correlation value for the
second window.
This process is repeated for successive windows
starting at each of the pixels in the first row of pixels
before a window is formed starting with the first pixel
in the second row of pixels. After all of the pixels in
the rows and columns of the sample and model pixel matrix
have been utilized by the algorithm, the CPU 110
determines the highest correlation value between the
sample windows and the corresponding model windows, which
highest correlation value indicates the closest match
between the sample windows and the model windows. Of
course, in the example above, as the sample window 155 is
~~~~3~7
21
outside of the actual light image 154, all of the
products and summations thereof will be zero. However, -
specific numeric values will be generated when the sample
windows contain pixels in the light image 154.
Since the center of each sample window, such as
sample window 156, can be determined by the CPU 110, the
center of the window having the highest correlation value
to the model is then determined by the CPU 110. The CPU
110 then calculates the distance along the X and Y axes
for the window on the model image which indicates a
proper aiming position of the headlight 136. V~Ihen the
differences between the X and Y dimensions in the sample
window and the corresponding model image window are
calculated, the CPU 110 outputs a signal to the PLC 120
which in turn supplies a voltage to the X and Y
screwdrivers 102 and 103 causing rotation of the bits 104
of the screwdrivers 102 and 103 in a particular direction
of rotation depending upon the polarity of the voltage
applied to the drive motors in each screwdriver 102 and
103. As soon as the operator activates the on pushbutton
106 in each screwdriver 102 and 103, as shown in Fig. 6,
after engaging the bits 104 with the respective
adjustment screws 146 and 148, the screwdrivers 102 and
103 will cause rotation of the headlight adjustment
screws 146 and 148.
The CPU 110 continues to re-execute the
algorithm to determine the subsequent sample windows
having the highest correlation value or match with the
model. As this is done while the screwdrivers 102 and
103 are rotating the adjustment screws 146 and 148, the
difference between the center of the sample window having
the highest correlation value and the center of the model
image will progressively decrease until the center of the
sample window matches the corresponding position of the
model image thereby indicating a properly aimed
headlight.
22
If, after the screwdrivers 102 and 103 start to
rotate the adjustment screws 146 and 148, the difference
between the actual position of the center of the
headlight and the center of the model image increases,
the CPU 110 will generate a signal to the PLC 120 which
will immediately reverse the polarity of the voltage
applied to the screwdrivers 102 and 103 causing rotation
of the bits 104 in the opposite direction.
After the headlight 136 is properly aimed to
the selected standard, the PLC 120 outputs a signal to
the control panel 86 indicating that the aiming sequence
has been completed and deactivates the screwdrivers 102
and 103. The operator then removes the screwdrivers 102
and 103 from the adjustment screws 146 and 148 and
proceeds to the next headlight or the next vehicle if all
the headlights on a particular vehicle have been
correctly aimed.
After the.-headlight aiming operation has been '
completed, the PLC 120 generates signals to the drive
motors 24 and 44 to move the rack 30 and the housing 52
to the home position shown in Fig. 1. In this position,
the housing 52 is aligned with the calibration light 92.
The CPU 110 then reexecutes the algorithm, as described
above, to verify that the housing 52 and the camera 80
are in the normal mounting position on the rack 30.
In summary, the headlight aiming apparatus and
method of the present invention provides a highly
accurate headlight aiming apparatus and method which can
be easily integrated into a vehicle production line. The
apparatus is usable with many different style vehicle
headlight configurations as well as with different aiming
image standards.
