Hockey puck shaped continuous diffuse illumination apparatus and method

The method and apparatus for providing a continuous, uniformed, diffused light environment for use in conjunction with an electronic machine vision or manual microscope inspection system, particularly for inspection of specular surfaces such as ball bearings, reflective packaging and other shiny surfaces. The illumination device includes a source of light which is associated with at least the secondary diffusers to provide secondary diffused illumination, of an object to be observed, substantially along the observation axis of the object. The same light source may also illuminate a rear surface of the primary diffuser. The height of the illumination device is approximately three and one half times the clear aperture dimension of the illumination device or less. The illumination devices is arranged to provide uniformed illumination of the object with light which is equal in intensity and character to facilitate accurate viewing of the entire area of the object to be viewed.

FIELD OF THE INVENTION 
The invention pertains to a method and apparatus for permitting electronic 
machine vision of light reflecting objects wherein a true observation of 
the surface being viewed is obtained by masking potential reflections 
resulting along the observation axis due to observation windows and 
cameras, or other non-illuminating discontinuities in the illumination 
environment. 
DESCRIPTION OF THE RELATED ART 
Electronic machine vision apparatus is commonly employed in conjunction 
with automatic machining, assembly and inspection apparatus, particularly 
of the robotics type. Television cameras are commonly employed to observe 
the object being machined, assembled, or inspected, and the signal 
received and transmitted by the camera can be compared to a standard 
signal or database to determine if the observed article is properly 
machined, oriented, and/or assembled. Also, machine vision apparatus is 
widely used in inspection and flaw detection applications whereby 
inconsistencies and imperfection in both hard and soft goods can be 
rapidly ascertained and adjustments or rejections instantaneously 
effected. 
Machine vision apparatus detects abnormalities by comparing the signal 
generated by the camera with a predetermined signal indicating proper 
dimensions, appearance, orientation, or the like. In order to achieve 
consistent and accurate results when using machine vision apparatus 
employing electronic cameras, it is very important that consistent and 
uniform lighting of the observed object occur, as the lighting will 
seriously affect the vision signal generated and produce irregular signals 
even though no fault may exist in the object being observed other than it 
is not uniformly illuminated. 
Illumination problems in machine vision applications are particularly 
present when the object being observed has a shiny specular surface. For 
instance, in the inspection of soldered circuits such as used with printed 
circuit boards the highly reflective nature and uneven surface geometry of 
the solder makes it very difficult to obtain an accurate electronic 
signal, and the same is true when machine vision inspecting ball bearings, 
reflective packaging, and other objects having shiny surfaces or areas, 
particularly irregular shiny surfaces. 
When utilizing machine vision techniques and apparatus in shiny surface 
applications, it is common to employ complicated lighting systems for 
illuminating the object being observed, and it is a purpose of such 
lighting systems to eliminate shadows, highlights, underlights, 
reflections and other lighting characteristics caused by shiny convex 
surface objects. An illumination device which achieves many of the objects 
of the present invention is disclosed in a related patent of the Inventor, 
namely, U.S. Pat. No. 5,461,417 issued Oct. 24, 1995. That patent 
discloses a device which provides a first source of primary diffused light 
which illuminates a major portion of the object to be observed, except for 
a portion effected by the opening and a second source of diffused light 
provided along the observation axis to illumination the portion of the 
object effected by the opening. One of the major drawbacks associated with 
such device is that it is relatively large and bulky and the design is not 
readily adapted for miniaturization due to its geometry. 
OBJECTION OF THE INVENTION 
Wherefore, it is an object of the present invention to overcome the above 
noted disadvantages of the illumination devices currently available. 
It is an object of the invention to provide a method and apparatus for 
illuminating an object to be observed by machine vision cameras wherein a 
diffused illumination of the object is produced which is continuous in 
nature and is free of dark or void portions and bright portions capable of 
generating erroneous vision signals. 
Another object of the invention is to provide a method and apparatus for 
illuminating specular objects to be observed by electronic machine vision 
cameras, film cameras, or human observers, wherein the object is uniformly 
illuminated by a primary, off-observation axis source of diffused light 
emitting from a surface adjacent the object, having an observation window 
or viewing orifice to permit vision along an observation axis that is 
masked against reflection by the object. 
Another object of the invention is to provide a method and apparatus for 
illuminating specular objects to be observed by electronic machine vision 
cameras wherein the object is illuminated by diffused light emitted from 
an off-observation axis diffuse light source of a shape and size 
sufficient to provide substantially uniform illumination over the entire 
surface of the object to be observed while also supplying diffused light 
along the observation axis through an observation window to permit 
accurate vision along an observation axis. 
Yet another object of the invention is to provide a method and apparatus 
which supplies diffused light along the observation axis of an intensity 
and character substantially equal to the intensity and character of the 
primary diffused light illuminating the object while facilitating 
miniaturization of the illumination device. 
Still another object of the invention is to provide an illumination device 
which is very compact in size and occupies a volume of between about 0.5 
to 30 cubic inches, or possibly smaller. 
A still further object of the invention is to form the first and second 
diffusers from a single monolithic component so that the height of the 
illumination device is approximately equal to a clear aperture dimension 
of the illumination device and the width or diameter of the illumination 
device is approximately three (3) times the clear aperture dimension. 
A still further object of the invention is to calibrate the primary 
diffuser surface, prior to use, to ensure uniformed illumination of the 
object to be observed by the primary diffuser surface. 
Yet a further object of the invention is to minimize the height of the 
light source assembly by utilizing a curved beam splitter. 
A further object of the invention is, in one embodiment, to utilize a 
single light source to illuminate both the primary and the secondary 
diffusers so that the single light provides both the off axis diffuse 
illumination as well as the diffuse illumination provided along the 
observation axis. 
Still another object of the invention is to provide a compact illumination 
device which is compact in size and has a camera incorporated therein. 
SUMMARY OF THE INVENTION 
The invention relates to a compact diffuse lighting device for evenly 
illuminating a desired portion of an object when observed along an 
observing axis extending through an object observing location, said 
diffuse illumination device comprising a first diffuser surface, for 
supplying diffused light, defining an opening through which the observing 
axis passes, said first diffuser surface being arranged to supply a 
primary diffused light to provide said even illumination of the desired 
portion of the object, when placed at the observing location and viewed 
along said observing axis, except for a portion of the object effected by 
the opening; a light source for supplying secondary diffused light to 
illuminate a desired portion of the object; and a partially reflective 
mirror for supplying said secondary diffused light along the observing 
axis to evenly illuminate each portion of the object effected by the 
opening to produce, when a primary diffused light illuminates said 
surface, said even illumination of the object when viewed along the 
observing axis; wherein said light source for supplying secondary diffused 
light is located adjacent said first diffuser surface for supplying said 
primary diffused light. 
The invention also relates to a method of evenly illuminating a desired 
portion of an object to be observed, when observed along an observing axis 
extending through an object observing location, via a compact diffuse 
lighting device, said method comprising the steps of supplying diffused 
light, via a first diffuser surface defining an opening through which the 
observing axis passes, and arranging said first diffuser surface to supply 
a primary diffused light to provide said even illumination of the desired 
portion of the object, when placed at the observing location and viewed 
along said observing axis, except for a portion of the object effected by 
the opening; supplying secondary diffused light, via a light source, to 
illuminate a desired portion of the object; and using a partially 
reflective mirror to supply said secondary diffused light along the 
observing axis to evenly illuminate each portion of the object effected by 
the opening to produce, when a primary diffused light illuminates said 
surface, said even illumination of the object when viewed along the 
observing axis; and locating said light source, for supply secondary 
diffused light, adjacent said first diffuser surface for also supplying 
said primary diffused light. 
The present invention further relates to an improved illumination system 
for inspecting a surface. In particular, the present invention can be used 
to verify an opposed alignment between a stencil or solder mask (a first 
surface) with respect to a circuit board (a second surface) to identify 
any misalignment of the stencil with respect to the circuit board. If any 
misalignment is detected by the system, the circuit board is adjusted 
relative to the stencil, or vice versa, so that a precise alignment 
between those two surfaces is achieved. Thereafter, the circuit board can 
be brought into contact with the screen to apply solder paste to the 
circuit board. The inspection system, equipped with the improved 
illumination devices according to the present invention, can again be 
utilized to illuminate and inspect the applied solder paste on both the 
circuit board and on the screen when the circuit board and screen are 
separated, e.g. to determine whether adequate solder paste is applied, to 
determine if excess solder paste is applied, to determine if solder paste 
is applied in the wrong location, to determine if any holes are blocked by 
the solder paste or have excess solder paste, to determine any 
discontinuity or interruption in the solder paste, etc. Based on the 
results on the inspection, excess solder can be squeegeed or otherwise 
removed from the stencil. 
As will be appreciated from the following description, the method and 
apparatus permitting the practice of the invention is relatively simple 
and inexpensive as compared with prior art devices incapable of providing 
a true continuous diffused light as provided by the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to FIGS. 1-8, a first embodiment of the present invention will 
now be described in detail. This embodiment is a compacted illumination 
device having a height to width ratio of about 1:3, i.e. a height of 
approximately 1 inch and a diameter of approximately 3 inches. The compact 
illumination device 2 comprises an exterior housing 4 which comprises a 
substantially planar top wall 3 and a substantially cylindrical side wall 
5 which are connected to one another by a small radius curved transition 
to form a unitary monolithic structure. The end of the exterior housing 4 
opposite the top wall 3 is an open end which, prior to use, is covered by 
an outer diffuser 10. An observation device 1, such as a camera, a human 
observer, or some other suitable observation device is positioned along 
the observation axis A at a location remote from the object O to be 
observed with the compact illumination device 2 positioned between the 
observation device 1 and the object O to be observed. The top wall 3 of 
the exterior housing 4 has a centrally located aperture 8 formed therein 
which, during use, is centered about the observation axis A. A 
frusto-conical side wall 6 extends from the top wall 3 of the exterior 
housing inwardly and downwardly along the observation axis A toward the 
object O to be observed. The side wall 6 is truncated by a plane P which 
extends obliquely, e.g. at a 45.degree. angle, with respect to the 
observation axis A thereby forming an elliptical end surface 7 at the 
smaller diameter truncated end of the truncated frusto-conical side wall 
6. The elliptical surface 7 of the exterior housing 4 supports a first 
surface of the beam splitter or partially reflective mirror 18. The 
exterior housing 4 can be manufactured from metal or may be molded from a 
plastic or some other synthetic or other suitable material. Preferably the 
exterior housing 4 is opaque. 
The top wall 3 of the exterior housing is also provided with a wire 
aperture 9 (FIG. 6) which allows a fiber optic light source(s) to extend 
therethrough or an electrical cord to pass through the exterior housing 
and supply electrical power to the interior components of the exterior 
housing, e.g. the lights. A further detailed description concerning the 
supply of electrical power to the illumination source will follow 
hereinafter. 
As previously indicated, the outer diffuser 10 covers the open end of the 
exterior housing 4 and is provided with a centrally located circular 
viewing aperture 12 which, when the outer diffuser 10 is attached to the 
housing 4, is aligned with the centrally located aperture 8 of the 
exterior housing. The outer diffuser 10 comprises a first planar ring 
shaped diffuser section 11 and a frusto-conical diffuser section 13. The 
ring-shaped diffuser 11 and the frusto-conical diffuser 13 are integrally 
formed with one another, e.g. they are molded as a unitary monolithic 
diffuser component from a translucent material such as DELRIN.RTM., which 
is a thermoplastic polymer material sold by I.E. DuPont de Nemours & 
Company, Inc. Other suitable materials, which provide desired diffused 
illumination characteristics when illuminated by a light source, may also 
be employed. The exterior housing 4 is preferably manufactured from black 
colored DELRIN.RTM.. 
The frusto-conical diffuser 13 extends from the ring-shaped diffuser 11 
along the observation axis A toward the top wall 3. The ring-shaped 
diffuser 11 is truncated by the plane P which extends obliquely, e.g. at a 
45.degree. angle, with respect to the observation axis A thereby forming a 
second elliptical surface 17 at the larger diameter truncated end of the 
truncated frusto-conical diffuser 13. The elliptical surface 17 of the 
outer diffuser 10 supports a second opposed surface of the beam splitter 
or partially reflective mirror 18. The outer diffuser 10 must be 
transparent to allow diffused light to pass therethrough. 
The outer diffuser 10 is provided with a plurality of screw holes 21, e.g. 
4 holes, spaced about the perimeter of the outer diffuser 10 which are 
alignable with a plurality of tapped screw holes 19, e.g. 4 holes, 
provided in the side wall 5 of the exterior housing 4. The outer diffuser 
10 is releasably secured to the exterior housing 4 via plurality of screws 
20 passing through the screw holes 21 and threadingly engaging with the 
tapped screw holes 19. When the outer diffuser 10 is secured to the 
exterior housing 4, those two components define an interior cavity 22 
which accommodates the internal components. It is to be appreciated that a 
variety of other known releasable attachment mechanisms, for attaching the 
outer diffuser 10 to the exterior housing 4, may be also employed. 
An illumination source 24, such as a flexible LED circuit supported by a 
backing material, a ring light, fiber light, etc., is accommodated within 
the interior cavity 22 defined by the outer diffuser 10 and the exterior 
housing 4. The illumination source 24 is secured to the inner surface of 
the side wall 5 by a suitable fastening device (not shown), e.g. a 
screw(s), glue, etc. 
In the embodiment shown in FIG. 2, in which the illumination source 24 has 
a diameter of approximately 2.6 inches, the flexible circuit has a length 
of approximately 8.12 inches and a width of approximately 1 inch. A 
plurality of individual high intensity LEDs, e.g. 75, are supported along 
the length of the flexible illumination circuit and each of the individual 
LEDs is interconnected, via a plurality of wires (not shown in detail), to 
an electrical cord 28 which extends out of the exterior housing 4 through 
the wire aperture 9. The electrical cord 28 has a suitable electrical 
contact or plug 30, at a remote opposite end thereof, for facilitating 
connection of the illumination source 24 to an appropriate power supply. 
If desired, an inner cylindrical or partially cylindrical diffuser 26 can 
be positioned within the interior cavity 22 and located between the 
illumination source 24 and the second diffuser 14 to further assist with 
diffusing the light directed by the illumination source 24 toward the 
frusto-conical diffuser 13. 
A suitable beam splitter 18, such as 0.010 inch half-silvered optical clear 
lucite member, is sandwiched, e.g. by compression, between the oval 
surface 7 of the housing and the oval surface 17 of the frusto-conical 
diffuser 13. The beam splitter 18 is typically secured to either one or 
both oval surfaces 7, 17 by glue or some other adhesive component. During 
use, the beam splitter 18 reflects a desired amount of light, e.g. between 
about 20% to 80% and preferably about 50%, which passes through the 
frusto-conical diffuser 13 along the observation axis A toward the object 
while allowing a desired amount of light, e.g. about 20% to 80% and 
preferably about 50%, reflected by the object to be observed to pass 
through the beam splitter 18 and be viewed by the observation device 1. 
It is to be appreciated that the illumination source 24 is positioned to 
provide both illumination of the primary diffuser, i.e. the illumination 
source 24 illuminates a rear surface of the ring diffuser 11 to provide a 
primary source of illumination, as well as illumination of the secondary 
diffuser, i.e. the illumination source 24 illuminates a rear surface of 
frusto-conical diffuser 13 to provide diffused illumination along the 
observation axis. 
FIG. 1 shows one arrangement for using an observation device 1, such as a 
camera, for viewing an object O to be observed. The compact illumination 
device 2 is located at a desired distance, e.g. a few inches or less, 
above the object O to be observed and is provided with a single source of 
light 24 so that both direct primary diffused light and reflected 
secondary diffused light illuminate the object O. A mirror 62 is located 
at a desired distance above the opening 8 of the exterior housing 4 and 
arranged at a position of approximately 45.degree. angle relative to the 
observation axis. The observation device 1 is positioned so that the image 
of the object passes through the beam splitter 18 and is reflected by the 
mirror 62 to a lens (not numbered) of the observation device 1 for 
viewing. 
The observation device 1 communicates the sensed image to a computer 64 via 
suitable wiring or cabling. The computer 64, in turn, may be connected, 
via a suitable wiring or cabling, to a conveying apparatus or means 66 
which conveys one of the illumination device 2 or the object O to be 
observed relative to the other. The computer 64 then transmits, via 
suitable wiring or cabling, the sensed image to a control device 68 which 
manipulates the information, as desired for one of accepting or rejecting 
the object O being observed, reproducing an image of the object O, or 
initiating any further desired manufacturing or inspection step required 
of the application at hand. As such teaching with respect to the above 
additional processing is well known in the art, a further detailed 
discussion concerning the same is not provided herein. 
With reference now FIGS. 9-11, a second embodiment of the illumination 
device according to the present invention will now be discussed. This 
embodiment is similar to the previously discussed embodiment and includes 
an exterior housing 4 having a top wall 3 and a side wall 5. The outer 
diffuser 40 includes a centrally located circular diffuser aperture 42 as 
well as a ring shaped planar diffuser 44 and a truncated second diffuser 
46, as with the first embodiment. The truncated surface 50 of the second 
diffuser 46 supports the beam splitter 18 which, due to the overall shape 
of the truncated second diffuser 46 as well as an inner contoured surface 
52 of the exterior housing 4, the two members mate with one another to 
maintain the beam splitter 18 in a desired curved configuration. 
The truncated surface 50 of the second diffuser 46 has an outer contour 
surface 47 which is somewhat oval in shape, as can be seen in FIG. 11 of 
the drawings. The inner contoured surface 52 supported by the exterior 
housing 4 is also contoured so that when the beam splitter 18 is 
sandwiched between the contour surface 47 of the second diffuser 46 and 
the inner contoured surface 52 of the exterior housing 4, the beam 
splitter 18 will be forced into a generally partial conical configuration 
and arranged to illuminate the object O with secondary diffused light. The 
term "conical", as used in this application, includes elliptical, 
spherical, cylindrical, egg-shaped or any other appropriated curved 
surface capable of directing light along the observation axis toward the 
object to be observed. One conical such configuration is shown in FIG. 10 
of the drawings. 
According to the second embodiment, a transparent cover 60, of plastic, 
glass or the like (e.g. clear Lucite.RTM., which is a material sold by 
I.E. DuPont de Nemours & Company, Inc.), is secured to and seals the 
centrally located aperture 8 of the exterior housing 4. The transparent 
cover 60 prevents dirt or other contaminants from coming into contact with 
the beam splitter 18. 
The exterior housing includes a light absorbing panel, layer, coating or 
surface 86 located adjacent a rear surface of the beam splitter 18 to 
absorb diffused light which passes through the beam splitter. The 
intensity of the light generated by the light source 24 may be adjustable 
by a rheostat 69 to adjust the intensity and character of the light cast 
upon the object O. It is to be appreciated that the computer 64 (FIG. 1) 
can be coupled to the rheostat 69 for automatically adjusting the 
intensity and character of the light cast upon the object. As such 
teaching is well-known in the art, further detailed discussion concerning 
the same is not provided herein. 
As can be seen in FIG. 10, a fan 70 may be connected with an inlet 74 of 
the exterior housing 4, via an air supply conduit 72. The exterior housing 
4 is also provided with an exhaust air outlet 76 to discharge the air 
supplied to the interior of the illumination device via the fan 70. The 
purpose of air supplied by the fan 70 is to cool the internal components 
of the illumination device, e.g. the light(s), and prevent overheating of 
the same. If desired, a grating, wire mesh or some other protective member 
may cover the exhaust outlet 76. 
In the second embodiment shown in FIGS. 9-11, the exterior housing has an 
outer diameter of about 6.02 inches (152.9 mm), a height of 1.71 inches 
(43.5 mm), the central aperture has a width of 1.18 inches wide (30.00 
mm), angle X is equal to 20.1 degrees and dimension Y is 0.49 inches (12.4 
mm). In addition, the ellipse has a major radius of 1.86 inches (47.2 mm) 
and a minor radius of 1.60 inches (40.5 mm). Lastly, the center of the 
ellipse is located 0.23 inches (5.8 mm) below the outer diffuser 40. The 
ellipse is rotated about a central elongate axis to define the partially 
spherical shape to be occupied by the curved beam splitter 18. 
Prior to the use or sale of the compact illumination device according to 
the present invention, the outer diffuser is calibrated to ensure 
uniformed illumination and a further discussion concerning the same is 
provided with reference to FIG. 12. This is achieved by connecting the 
illumination source 24 to a supply of electricity E and attaching the 
compact diffused illumination device 2 to suitable calibration equipment. 
Thereafter, the diffused light cast by the ring diffuser 11 illuminates a 
piece of photographic film F, or the like. In the event that cast light 
from the ring diffuser 11 provides uniformed illumination, the 
photographic film F will be uniformly illuminated over its entire surface 
area. If, however, the cast light from the ring diffuser 11 does not 
provide uniformed illumination of the photographic film F, i.e. one or 
more areas of the ring diffuser 11 allow more light to pass therethrough 
and/or one or more areas allow less light to pass therethrough, the 
photographic film will detect and reveal such nonuniform illumination. 
Thereafter, the exposed photographic film F or a reproduction of the 
photographic image printed on acetate is glued, pasted, secured, coated or 
applied on an inner surface of the ring diffuser 11 to mask the 
imperfections contained in the ring diffuser 11 so that, following 
calibration, a substantially uniformed illumination will be provided by 
the outer surface of the ring diffuser 11. An important feature of the 
above calibration technique is to alter or modify the outer diffuser so 
that when that diffuser is overlayed or coated with a semi-opaque pattern 
having a desired optical pattern, the outer diffuser provides a 
substantially uniform primary illumination of the object with diffused 
light. 
It is to be appreciated that the area of the photographic film to be 
illuminated should be the same size as the ring diffuser 11 to facilitate 
applying the exposed photographic film or a reproduction of the 
photographic image to an inner surface of the ring diffuser 11 to mask the 
imperfections. Further, the photographic film and the ring diffuser 11 
should have alignment indica to facilitate accurate alignment of those two 
components relative to one another. Such alignment and orientation must be 
maintained so that the photographic film or reproduction can be accurate 
applied to the inner surface of the ring diffuser 11 to provide the 
desired masking and uniform illumination. 
The beam splitter 18 is typically 60/1000 of an inch thick and the opposed 
beam splitter surfaces are each conventionally provided with silvered 
strips, or otherwise treated, so that the beam splitter 18 constitutes 
both a reflective surface and a light previous surface wherein light may 
pass through the beam splitter 18 from the object O for observation by the 
camera 1, and the beam splitter 18 also reflects the diffused light 
generated by the light source. Alternatively, the beam splitter 18 can be 
formed by a half silvered membrane pellicle of nitrocellulose or plastic 
material, such as "MYLAR", which has advantageous beam splitting 
characteristics in certain applications. Either material used as the beam 
splitter mirror 18 may be provided in a curved configuration having a 
concave face disposed towards both the object 0 and the light source 24 
and a convex face disposed towards the observation means, such as a 
machine vision camera. This configuration provides an increased range of 
incident angles for the diffused light supplied along the observation axis 
while reducing the height of the light source 24. 
The light diffusers may be formed of treated glass, plastic, or other light 
translucent material capable of evenly diffusing light cast upon the 
diffuser by the light source. The light sources may consist of a plurality 
of lamps, ring lights, incandescent bulbs, diodes, optical fibers or any 
other illumination source capable of generating a relatively uniform panel 
of light cast upon the diffuser and such diffused light illuminates the 
beam splitter 18 and is projected along the observation axis A toward the 
object. It will be appreciated that this light is coaxial with and 
coincides with the observation axis A. The size of the beam splitter 18 is 
such that the diffused light reflected therefrom along the axis is 
sufficient to completely occupy the observation window such that the 
window will be "filled" with the diffused light emitting from second 
diffuser and the light source. It will be understood that the light source 
and translucent light diffuser may be varied in size, shape and relative 
proximity to one another to create continuous uniform illumination across 
objects of different sizes or at different working distances. 
Upon practicing the invention, a beam splitter similar to those shown in my 
co-pending application Ser. No. 07/750,257 filed Aug. 27, 1991, now U.S. 
Pat. No. 5,187,611 may be employed. In the practice of the invention, 
control means permit accurate control and variation of the diffused light 
being generated and reflected by the beam splitter in order to equate the 
beam splitter projected light to that supplied by the primary diffused 
light source. 
It is to be appreciated that the thickness and transparency of the primary 
and secondary diffusers can be manipulated and/or adjusted as desired to 
facilitate even illumination of the object to be observed. Such teaching, 
which is more clearly set forth in U.S. patent application Ser. No. 
08/501,213 filed Jul. 11, 1995, is incorporated herein by reference. 
Turning now to FIGS. 13-17, a detailed description concerning a third 
embodiment of the present invention will now be provided concerning only 
the new features. In this embodiment, a video camera 77 is combined or 
integrated into the illumination device to form a compact integrated unit 
78. The height of the illumination source is generally shown by bracket H 
and comprises the beam splitter 84, the height of the primary and 
secondary light source(s), the thickness of the primary diffuser as well 
an separating distance panel or member 93. The "height" of the 
illumination source, as referred to herein and in the appended claims, 
means the distance measured from a top or outer most surface of the beam 
splitter 84 to a bottom or lower most surface of the outer diffuser 92 
when measured parallel to the observation axis A (see FIG. 18). 
As with the previous embodiments, a partial circular secondary illumination 
source 81, e.g. a curved array of LEDs, is accommodated within the cavity 
22 formed by the exterior housing 80, a top surface 80' of the housing and 
the outer diffuser 92. The secondary light source 81 is arranged to 
illuminate a rear surface of the frusto-conical diffuser 82 to provide 
diffused light to the curved beam splitter 84 so that a portion of the 
light is reflected along the observation axis (e.g. about 50% of the light 
is reflected by the beam splitter 84 while about 50% of the diffused light 
passes through the beam splitter 84 and is absorbed by the light trap 86 
located adjacent but behind the beam splitter 84. In this embodiment, the 
beam splitter 84 is glued to the diffuser 82. The secondary illumination 
source 81 is supplied with electrical power via wires 88 to supply the 
illumination device with electrical power. An electrical power source E is 
coupled to an electrical connector 90, via an electrical cord 100, which 
in turn is coupled to the wires 88. 
The primary light source 91 is arranged to provide primary illumination of 
the field-of-view FV. As can be seen in this embodiment, the primary light 
source 91 is divided or partitioned into three co-axially arranged primary 
illumination zones, labeled as B, C and D. A plurality of opaque, curved 
reflective baffles 94 are utilized to divide or segment the primary 
illumination source 91 into its co-axial arranged zones. Each illumination 
zone is positioned to direct or channel light over a portion of the outer 
diffuser 92 to provide illumination of the desired angle of incident of 
the field-of-view FV, e.g. illumination zones B, C, D and S, respectively, 
supply diffused light over angle of incident B', C', D' and S' as can be 
seen in FIG. 13. Each illumination zone B, C and D is electrically coupled 
to the wires 88 (not shown in detail) for supplying electrical power to 
the individual LEDs. 
It is to be appreciated that the supply of electrical power to each 
illumination zone B, C and D of the primary illumination source 91 can be 
either manually controlled or, as shown in the embodiment of FIG. 13, be 
automatically controlled by a computer 64 or some other control device 
(FIG. 19). As with the previous embodiment, the computer 64 may be coupled 
to a conveying device 66 for providing relative movement between the 
compact unit 78 and the object to be observed. The illumination zone B, C, 
D and S can be operated separately from one another or in any desired 
combination to achieve a wide variety of illumination effects including 
"dark-field" illumination, "bright-field" illumination and continuous 
diffuse illumination. The computer 64 may be programmed, if desired, to 
automatically ascertain which combination of illumination zones, e.g. B, 
C, D and/or S, achieves optimum illumination of the object for any given 
application. 
An opaque panel 93 separates the primary illumination source 81 from the 
remainder of the compact unit. The opaque panel 93 is provided with an 
opening which facilitates visual inspection of the object to be observed 
by the camera 77. The video camera 77 (e.g. a board-level video camera 
such as ULTRAK BC 460/P, for example) is supported, via a bracket or the 
like, adjacent the top inner surface 80' of the compact unit 78 and 
positioned to receive light reflected along the illumination axis A for 
viewing a desired portion of object located in the field-of-view FV. The 
video camera 77 is provided with an adjustable video camera lens 95. A 
camera focusing knob 96 is provided with a rotatable cylindrical member 97 
which extends along and is located adjacent the lens 95. The cylindrical 
member 97 is coupled to the lens 95 via an endless rubber belt 99 or the 
like for facilitating focusing adjustment of the camera 77, i.e. any 
rotation of the focusing knob 96 causes rotation of the cylindrical member 
97 which, in turn, transmits such rotation to the lens 95 via the endless 
belt 99. As such adjustment is well known in this art, a further detailed 
description concerning the same is not provided herein. 
It is to be understood that this embodiment could be provided with a set of 
at least four separate rheostats for manually controlling the illumination 
characteristics of each of the four illumination zones B, C, D and S 
separately from one another. If desired, the number of illumination zones 
can be varied, i.e. increased or decreased, depending on the illumination 
application at hand. 
With reference now to FIG. 18, a ray tracing diagram is shown for 
determining the necessary curvature of the beam splitter 84 for that 
application. As can be seen in that figure, the ray tracing paths for a 
left region L, a central region C" and a right R region of the object O to 
be observed are shown. As such ray tracing is well-known in the art, a 
further detailed description concerning the same is not provided herein. 
The contour of the curved beam splitter is determined by such ray tracing 
and it will be appreciated that such contour depends upon the distance 
that the top surface of the object O is spaced SP from a bottom of the 
illumination device 2, the clear aperture dimension CA of the illumination 
device, the height H of the illumination device, etc. In this embodiment, 
the clear aperture CA, the spacing SP of the bottom portion of the 
illumination device from the object O to be observed, and the height H of 
the illumination device are all about equal, e.g. about 2.95 inches (74.93 
mm) while the width is about three (3) times the clear aperture dimension. 
An important feature to bear in mind is that the second diffuser is not 
permitted in any way to provide direct illumination of the desired surface 
of the object O to be observed. 
According to this invention, the height H of the illumination source is 
about three (3) times the minimum transverse dimension of the opening 
provided in the outer diffuser, preferable about two (2) times the minimum 
transverse dimension of the opening provided in the outer diffuser, and 
most preferable about one (1) times the minimum transverse dimension of 
the opening provided in the outer diffuser. 
Turning now to FIG. 19, a detailed description concerning a triggering 
mechanism, for use in combination with the present invention, will now be 
provided. The integration unit 78, as with the previous embodiment, 
contains three illumination zones B, C and D as well as the other 
components shown in FIG. 13. For the sake of clarity, however, those 
components are not shown in detail in this Figure. The integrated unit 78 
is additionally provided with a movable triggering mechanism 102 which is 
connected to a power source E via an electric cable or wire 104. The 
electric wire 104 must facilitate movement of the triggering mechanism 102 
along an elongate slot 106 to supply electrical power thereto and allow 
the desired automatic sequencing of all of the possible combinations of 
illumination zones B, C and D. The triggering mechanism 102 is provided 
with an electrical contact 108, coupled to the electric wire 104, which is 
arranged to supply electrical power from the power source 100 to a desired 
one of the seven electrical contacts 110. As the trigger mechanism 102 is 
moved along the slot 106, the electric contact 108 engages with a desired 
one of the mating electrical contacts 110 and supplies electrical power 
thereto for a very short period of time, e.g. a fraction of a second. 
During such movement of the triggering mechanism 102, the electric contact 
108 first supplies electrical power to the first electrical contact 110, 
then to the second electrical contact 110, then the third electrical 
contact 110, and so forth until all electrical contacts 110 have been 
separately supplied with electrical power. 
As can be seen in FIG. 19, the first electrical contact 110 only supplies 
electrical power to illumination zone B; the second electrical contact 110 
supplies electrical power to illumination zone B and C; the third 
electrical contact 110 supplies electrical power to only illumination zone 
C; the fourth electrical contact 110 supplies electrical power to 
illumination zones B and D; the fifth electrical contact 110 supplies 
electrical power to only illumination zone D; the sixth electrical contact 
110 supplies electrical power to illumination zones B, C and D; and the 
seventh electrical contact 110 only supplies electrical power to 
illumination zone D. This triggering arrangement facilitates illumination 
of the object 0 to be observed by all possible illumination combinations 
of the illumination zones B, C and D by a hard wiring arrangement. 
The observation device or camera 77 is coupled to the triggering mechanism 
so as to generate at least one image during each possible combination of 
the illumination zones, e.g. the observation device generates at least 
seven images, so that the integrated unit 78 can then employ that 
information as desired. If the integrated unit 78 is also equipped with a 
computer, the computer can be coupled with the triggering mechanism and 
the observation device to determine which illumination combination 
provides the best image of the object to be observed and employ that image 
for further processing. As such feature is well known to those skilled in 
this art, a further detail description concerning the same is not provided 
herein. 
It is to be appreciated that the triggering mechanism 102 can be biased 
into the position shown in FIG. 19, by a (compression) spring 114 or some 
other biasing means, so that the triggering mechanism 102 is returned an 
original position ready for a further illumination cycle. The arrangement 
shown in FIG. 19 is particularly suitable for a hand-held scanning device 
for scanning bar code information off various items and products. The 
operator would position the object O along the observation axis A and 
merely slide, move, squeeze, pull or otherwise actuate the trigger 
mechanism 102 to traverse the trigger along the slot 106 and then release 
the trigger 102 at the end of the slot thereby allowing the spring 114 to 
return the trigger mechanism 102 back to its originally position for 
further scanning. 
If desired, the trigger mechanism can be biased or forced against the 
electrical contacts 110 to insure that a good electrical connection 
between the contacts 108 and 110 is achieved. 
Turning now to FIG. 20, a brief description concerning a second triggering 
mechanism, for use in combination with the present invention, will now be 
provided. The integration unit 78 contains four illumination zones B, C, D 
and S as well as the other components shown in FIG. 13. For the sake of 
clarity, however, those components are not shown in detail in this Figure. 
The integrated unit 78 is also provided with a movable triggering 
mechanism 102, as with the previous embodiment, as well as fifteen 
electrical contacts 110 each hard wire for one of fifteen possible 
illumination combinations. As the trigger mechanism 102 is moved along the 
slot 106, the electric contact 108 engages with a desired one of the 
mating electrical contacts 110 and supplies electrical power thereto for a 
very short period of time, e.g. a fraction of a second. During such 
movement of the triggering mechanism 102, the electric contact 108 first 
supplies electrical power to the first electrical contact 110, then to the 
second electrical contact 110, then the third electrical contact 110, and 
so forth until all fifteen electrical contacts 110 have been separately 
supplied with electrical power. 
Turning now to FIGS. 21 through 23, a detailed description concerning a 
fourth embodiment of the illumination device 2, according to the present 
invention, will now be provided. The primary light source 91, according to 
this embodiment, is accommodated within the exterior housing 4 and 
arranged to provide primary illumination to the field-of-view FV. The 
primary light source 91 can either be manually controlled or automatically 
controlled by a computer or some other control device (FIG. 19). As with 
the previous embodiment, the computer may be coupled to a manipulation 
device 120 (FIG. 24) to control the orientation of one surface 136 
relative to another surface 138 during the manufacturing process of an 
object, for example. 
The primary light source 91 comprises a plurality of spaced lighting 
emitting diodes (not separately numbered). The primary illumination source 
91 is covered by a planar diffuser 92 which has a central aperture 
provided therein. The central aperture is located along the observation 
axis to facilitate inspection of the object 6 to be observed. The planar 
diffuser 92 is secured to the exterior housing in a conventional manner, 
e.g. screws, glue, etc. 
An opaque panel 93 separates the primary illumination source 91 from the 
remainder of the illumination device 2. The opaque panel 93 is provided 
with a central opening, which is larger than the opening in the planar 
diffuser 92, to facilitate visual inspection of an object to be observed 
by the camera 122 (FIG. 24). 
The camera 122 is coupled, by conventional cabling 126, to a vision 
processor 124. The vision processor 124, in turn, is coupled to a host 
computer 128 via conventional cabling 130. Finally, the host computer 128 
is coupled, via conventional cabling 132, to the manipulation device 120 
of a manufacturing system to facilitate control of a first surface 136 
relative to a second surface 138. 
A variation of this embodiment of the invention, relative to the embodiment 
of FIG. 13, relates to the replacement of the frusto-conical diffuser with 
a planar diffuser 82 (FIGS. 21 and 22). In addition, the secondary light 
source 81 is a planar array of a plurality of illumination elements, e.g. 
an array of twelve light emitting diodes (LEDs) arranged in a two by four 
array for illuminating a first surface of the planar secondary diffuser 
82. The planar secondary diffuser 82, according to this embodiment, has a 
first longitudinal edge which contacts a surface of the opaque panel 93. 
The planar diffuser member 82 extends from the opaque panel 93 at an angle 
of about 40 to 75 degrees or so, more preferably an angle of about 60 
degrees. By this arrangement, the diffuser is located in a tilted back 
position, i.e. not extending normal to the opaque panel 93. 
A rectangular beam splitter 84, altered into a curved configuration, is 
positioned along the observation axis A for reflecting the light supplied 
by the planar diffuser member 82 along the observation axis A of the 
illumination device 2. Lastly, a light trap 86 is located at a position 
remote from the secondary diffuser 82 to absorb any light which is not 
reflected by and passes through the beam splitter 84. 
In a preferred form of the invention, a mirror reflective self-adhesive 
tape 116, such as Silverlux SS-95P High Performance Specular Silver 
Reflective Film manufactured by 3M Electronic Display Lighting, of St. 
Paul, Minn. under the tradename 3M Silverlux is applied to both opposed 
inwardly facing surfaces, e.g. an inwardly facing surface of the exterior 
housing 4 as well as the adjacent surface of the opaque panel 93. Further, 
the inwardly facing perimeter or circumferential side wall 5 of the 
exterior housing 4 in the area between the circuit board 119 and the 
diffuser 82, as shown in FIG. 22, is preferably provided with the mirror 
reflective tape 116. When the mirror reflective tape is applied to all of 
these inwardly facing surfaces in the area between the circuit board 119 
and the diffuser 82, such taped surfaces assist with redirecting any 
scattered light from the secondary light source 81 back toward the 
secondary diffuser 82 and facilitate providing a brighter, more uniform 
secondary diffused illumination along the observation axis A. 
A flat white diffusely reflecting self-adhesive tape 118, such as Scotchcal 
Electrocut Film manufactured by 3M Electronic Display Lighting, of St. 
Paul, Minn. under the trade name 3M Scotchcal, can be provided on a front 
surface of a circuit board 119 carrying the array of light emitting 
diodes, i.e. the surface of the circuit board 119 facing the diffuser 82 
and supporting the array of twelve light emitting diodes. The flat white 
diffusely reflecting self-adhesive tape 118 further assists, in 
combination with the mirror reflective tape 116, with redirecting any 
scattered light from the secondary light source 81 back toward the 
secondary diffuser 82 and facilitates providing a brighter, more uniform 
secondary diffused illumination along the observation axis A. 
The inventors have found that by replacing the frusto-conical diffuser with 
a planar diffuser 82, such modification can cause the generation of dark 
ring(s) or area(s) to form on the surface 6 being inspected. The darkness 
problem is believed to be caused by having insufficient light passing 
through an elongate portion of a central cylindrical portion 95 of the 
outer diffuser 92, which projects inwardly along the observation axis A 
toward the beam splitter 84. The inventors have found that by providing a 
suitable surface contour, e.g. providing a chamfer or beveled surface 111, 
at the joint between the planar surface of the outer diffuser 92 and the 
central cylindrical portion 95, such arrangement significantly minimizes 
or eliminates the formation of a dark ring(s) in the illumination supplied 
to the surface 6 to be inspected. Secondly, if the end wall of the central 
cylindrical portion 95 of the outer diffuser 92, located immediately 
adjacent the beam splitter 84, is provided with a gradual taper 113, e.g. 
from a very thin wall thickness to a normal thickness of the diffuser 
wall, such taper also assists with minimizing or eliminating the formation 
of a dark ring(s) in the illumination supplied to the surface 6 to be 
inspected. 
It is to be appreciated that the chamfered or beveled surfaces, provided 
between the two mating surfaces of the outer diffuser 92, and the taper of 
the end surface of the central cylindrical portion 95 can be replaced with 
a curved or radiused surface as such radiusing also assists with 
significantly minimizing or eliminating any dark rings formed in the 
provided illumination supplied to the surface 6 to be inspected. 
Turning now to FIG. 24, one application of the illumination device 2 of 
FIG. 21, for example, will now be described. As can be seen in this 
figure, a pair of compact illumination devices 2 are utilized. The 
illumination devices 2 are used in combination with a prism shape member 
140 which is provided with a pair of reflective mirror surfaces 142, 144 
which are located at an angle of 90 degrees with respect to one another. 
These mirror surfaces 142, 144 are located on opposite sides of a planar 
field separating baffle 146 which divides the field of view of the camera 
into two (2) separate fields of view. The inventors have found that by 
extending the length of the field separation baffle 146 from an elongate 
edge of the prism shape member 140 to a location closely adjacent to lens 
121 of the camera 122, e.g. within an eighth of an inch or so, greatly 
improves the separation of the perceived fields of view and assists the 
system with maintaining the two (2) fields of view completely separate 
from one another. 
An observation axis A.sub.1 is defined between the camera lens 121 and the 
first inspection surface 136 to be observed and this observation axis 
A.sub.1 is altered due to a reflection off the first reflective mirror 
surface 142 of the prism shape member 140. A second observation axis 
A.sub.2 extends from the camera lens 121 to the second inspection surface 
138 to be observed and this observation axis A.sub.2 is altered due to a 
reflection off the second reflective mirror surface 144 of the prism shape 
member 140. A first illumination device 2, according to the embodiment of 
FIG. 21, for example, is supported by conventional framework (not shown) 
and centered with respect to the first observation axis A.sub.1 at a 
location between the first surface 136 to be inspected and the reflective 
prism member 140. A second illumination device 2 is similarly supported by 
conventional framework (not shown) and centered with respect to the second 
observation axis A.sub.2 at a location between the second surface 138 to 
be inspected and the reflective prism member 140. Due to this arrangement, 
the camera 122 is able to view simultaneously a pair of opposed, spaced 
apart surfaces 136, 138 to be inspected and can gather information with 
respect to each of these facing surfaces 136, 138. 
With reference now to FIG. 25, a diagrammatic image of the first inspection 
surface 136 is shown on the left, in that Figure, while a diagrammatic 
image of the second opposed inspection surface 138 is shown on the right 
in of that Figure. The field separation baffle 146 facilitates complete 
separation between the two fields of view and provides a sharp line of 
demarcation between the first and second surfaces. It is apparent from the 
diagrammatic images shown in this Figure that the first inspection surface 
136, shown on the left, is vertically aligned while the second inspection 
surface 138, shown on the right, is slightly misaligned or skewed relative 
to the vertically aligned of the first inspection surface 136. The camera 
122 senses this misalignment and conveys this image information to the 
vision processor 124 which, in turn, provides suitable information 
concerning the detected misalignment to the host computer 128. The host 
computer 128 then determines the necessary adjustment to correct the 
detected misalignment and supplies the appropriate correction information 
to the manipulation device 120. Finally, the manipulation device 120 
appropriately rotates, turns, slides, moves and/or adjusts the second 
inspection surface 138 with respect to the first surface 136, or vice 
versa, so that the two surfaces are properly aligned with one another. 
It is to be appreciated that a variety of different arrangements could be 
utilized to achieve the desired mechanical illumination combinations of 
the various illumination zone B, C, D and/or S. It is intended that all 
such modification would be readily apparent to one skilled in this art and 
thus are to be considered within the scope of this invention. 
If height is not a critical feature for a given application, it is to be 
appreciated that the position of the secondary light source S and the 
diffuser can be switched with that of the observation device 1 so that the 
beam splitter would allow diffuse secondary light to pass therethrough and 
reflect light reflected from the object to the lens. 
The embodiment of FIGS. 26-30 is a compacted illumination device having a 
two by six array of LED's (FIGS. 27-30) and having a height to width ratio 
of about 1:2, i.e. a height of approximately 1 inch and diameter of 
approximately 2 inches. The primary diffuser 92 and primary light source 
91 are housed in an aluminum ring housing. This aluminum ring housing 150 
comprises a substantially cylindrical side wall 151 with a substantially 
planar bottom wall 152 having a clear aperture 153. The diameter of clear 
aperture 153 is approximately 0.25" or less that the outside diameter of 
the exterior housing. 
As is shown in FIG. 26, the thickness of A relative to the thickness of B 
of the primary diffuser is varied to create uniform illumination. 
The ring housing and primary diffuser can also be made as a single piece 
from white delrin. 
The secondary diffuser 82, secondary light source 81, and beamsplitter are 
held between two substantially planar side walls 154. The back wall 86 has 
through holes and the side walls are threaded such that the back wall 
holds the side walls 154 at the appropriate spacing to provide the 
required illumination to the object being viewed. The back wall 86 serves 
as a light trap. There is a top plate over the area between the back 
surface 156 of the secondary circuit board 119 and the front surface of 
the secondary diffuser. This entire assembly is attached to the aluminum 
or delrin ring housing 150 with four screws. 
Mirror reflective tape is applied to all of these inwardly facing surfaces 
in the area between the circuit board 119 and diffuser 82, such taped 
surfaces assist with redirecting any scattered light from the secondary 
light source 81 back toward the secondary diffuser 82 and facilitate 
providing a brighter, more uniform secondary diffused illumination along 
the observation axis A. 
A flat white diffusely reflecting self-adhesive tape 118 is provided on the 
front surface of the circuit board 119 carrying the array of light 
emitting diodes, i.e. the surface of the circuit board 119 facing the 
diffuser 82 and supporting the array of twelve light emitting diodes. The 
flat white diffusely reflecting self-adhesive tape 118 is also applied to 
the rear of the primary circuit board 93 except in the area between the 
secondary circuit board 119 and secondary diffuser 82. The flat white 
diffusely reflecting self-adhesive tape 118 further assists, in 
combination with the mirror reflective tape 116, with redirecting any 
scattered light from the secondary light source 81 back toward the 
secondary diffuser 82 and facilitates providing a brighter, more uniform 
secondary diffused illumination along the observation axis A. 
The flat white diffusely reflecting self-adhesive tape 118 and/or the 
mirror reflective tape is also provided on the inside diameter of the 
primary circuit board. The flat white diffusely reflecting self-adhesive 
tape 118 further assists, in combination with the mirror reflective tape 
116, with redirecting any scattered light from the primary and secondary 
light sources back toward the primary and secondary diffusers, in 
particular to the top of the primary diffuser. 
Since certain changes may be made in the above described illumination 
device, without departing from the spirit and scope of the invention 
herein involved, it is intended that all of the subject matter of the 
above description or shown in the accompanying drawings shall be 
interpreted merely as examples illustrating the inventive concept herein 
and shall not be construed as limiting the invention.