Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2003-01-03
2004-07-06
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S629000
Reexamination Certificate
active
06760161
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to machine vision systems for semiconductor chip bonding/attaching devices. More specifically, the present invention relates to an apparatus for providing different magnifications of an object based on the illumination color of the object.
BACKGROUND OF THE INVENTION
Semiconductor devices, such as integrated circuit chips, are electrically connected to leads on a lead frame by a process known as wire bonding. The wire bonding operation involves placing and connecting a wire to electrically connect a pad residing on a die (semiconductor chip) to a lead in a lead frame. Once all the pads and leads on the chip and lead frame have been wire bonded, it can be packaged, often in ceramic or plastic, to form an integrated circuit device. In a typical application, a die or chip may have hundreds or thousands of pads and leads that need to be connected.
There are many types of wire bonding equipment. Some use thermal bonding, some use ultra-sonic bonding and some use a combination of both. Prior to bonding, vision systems or image processing systems (systems that capture images, digitize them and use a computer to perform image analysis) are used on wire bonding machines to align devices and guide the machine for correct bonding placement.
Machine vision systems are generally used to inspect the device before, during or after various steps in the fabrication process. During such process steps, it may be necessary to obtain multiple views of the device under different magnification levels to determine whether the device meets predetermined quality standards. One measurement may require a large field of view to include as many fiducals as possible, while a second measurement may require a high resolution to image fine details.
In conventional systems, such multiple magnifications are handled by having a separate camera for each desired magnification level. Such a conventional device is shown in FIG.
1
. In
FIG. 1
, imaging device
100
includes objective lens
104
, aperture
106
, beam splitter
108
, mirror
110
, relay lenses
112
,
114
, and cameras
116
,
118
. In operation an image of device
102
is transmitted through object lens
104
as transmitted image
120
and in turn through aperture
106
as image
122
. Image
122
is incident on beam splitter
108
, which in turn divides the light from image
122
into first divided light rays
124
and second divided light rays
126
. Divided light rays
126
are then redirected by mirror
110
as divided light
128
.
Relay lenses
112
and
114
are selected so as to provide the desired magnification of divided light
124
and
128
, respectively, resulting in magnified images
130
and
132
, which are incident on cameras
116
and
118
, respectively. This system has a drawback, however, in that it requires a separate camera for each level of magnification desired, thereby increasing size and cost.
A second conventional system is shown in
FIGS. 2A and 2B
. In
FIGS. 2A and 2B
, a shutter
218
is used in combination with a second beam splitter
222
to receive two magnifications of device
202
with a single camera
216
. As shown in
FIG. 2A
, first beamsplitter
208
separates light rays
224
into light rays
226
,
228
, each being of about equal illumination, that is each of light rays
226
,
226
is about half the illumination of light rays
224
. When shutter
218
is in a first position, light rays
226
are prevented from reaching relay lens
214
. On the other hand, light rays
228
are magnified by relay lens
212
to become magnified light rays
230
. In turn, magnified light rays
230
are incident on second beamsplitter
222
, a portion (about 50%) of which is transmitted to camera
216
as light rays
236
. The remaining portion of magnified light rays
230
, however, is deflected by second beamsplitter
222
as lost light rays
234
. As a result, only about 25% of the light used to illuminate device
202
is actually received at camera
216
. In addition, the inclusion of shutter
218
increases the complexity and cost of this system.
Alternatively, when shutter is in a second position, light rays
228
are prevented from reaching relay lens
212
, while light rays
226
are directed through relay lens
214
by mirrors
210
,
220
as magnified light rays
232
. Similar to
FIG. 2A
, a portion
236
of magnified light rays
232
are received by camera
216
while remaining light rays
234
are lost. As is evident, a large portion of the illumination available for imaging is sacrificed due to the losses associated with first beam splitter
208
and second splitter
222
. The light from a single channel hits the second splitter and is split into a reflected portion
234
and transmitted portion
236
. Only one of these will be directed to camera
216
while the other is lost. This approach can also have reliability issues with respect to the moving shutter mechanism.
SUMMARY OF THE INVENTION
In view of the shortcomings of the prior art, it is an object of the present invention to provide one of multiple magnified views to an optical detector based on the wavelength of light illuminating the device being viewed.
The present invention is a vision system for use with a light source and providing a plurality of images of a device, the system comprises a first beamsplitter for receiving an image of the device illuminated by the light source, the beamsplitter providing a plurality of images of the device; a plurality of optical elements for receiving respective ones of the plural images of the device, each of the plurality of optical elements magnifying the image by a predetermined magnification factor to produce a plurality of magnified images; and a second beamsplitter for receiving the plurality of magnified images and filtering out all but one of the magnified images based on a wavelength of the light source.
According to another aspect of the invention, an optical detector receives the filtered magnified images from the second beamsplitter.
According to a further aspect of the invention, the optical detector is a camera.
According to still another aspect of the invention, the light has a wavelength in the visible spectrum.
According to yet another aspect of the present invention, the beamsplitters are dichroic splitters.
According to a further aspect of the invention, a first mirror is coupled between the first beam splitter and the second optical element and a second mirror is coupled between the second optical element and the second beam splitter.
These and other aspects of the invention are set forth below with reference to the drawings and the description of exemplary embodiments of the invention.
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patent: 5515169 (1996-05-01), Cargill et al.
patent: 5751473 (1998-05-01), Runciman
patent: 5982493 (1999-11-01), Lehnen et al.
patent: 6008943 (1999-12-01), Metelitsa
patent: 6407867 (2002-06-01), Hildebrandt
Beatson David T.
Brown Lawrence B.
Hoffman Christian
Woodward Michael
Epps Georgia
Harrington Alicia M.
Kulicke & Soffa Investments Inc.
RatnerPrestia
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