Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-07-26
2001-03-27
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S553000, C250S559340, C250S559460, C348S087000, C348S126000, C348S131000
Reexamination Certificate
active
06207946
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a lighting system for use with a machine vision apparatus, such as used in the inspection of semiconductor packages, wherein the lighting system automatically adapts to the particular object being inspected to provide an improved image of the object viewed by the vision apparatus to improve the accuracy of an inspection process or to carry out other processes.
BACKGROUND
In the manufacture of semiconductor or microelectronic circuits or so-called packages, several processes may be carried out by machine vision systems, including inspection of the package electrical leads to determine if any leads are out of place or damaged, or inspection of the package for certain markings placed thereon. Machine vision systems have been developed to carry out these tasks in view of the need to automate the manufacturing process for semiconductor packages, taking into consideration the substantial number of such packages which are produced. Moreover, many inspection and marking systems for processing semiconductor packages are adapted to handle various configurations of packages having different shapes, lead configurations and light reflecting characteristics.
In this last mentioned regard, a lighting system which is set up for the proper contrast or image for one type of package usually requires adjustment for a different type of package. Still further, packages of essentially the same type or configuration may be fabricated of different materials which have at least slightly different light reflectivity characteristics. Therefore, a vision apparatus adapted for inspecting a particular type of semiconductor package may not function properly if slight changes in materials used for the packages or any changes in the light reflectivity of the package occurs which will change the contrast and the quality of the image captured by the inspection or vision apparatus.
Accordingly, there has been a need for a lighting system for machine vision apparatus which is adaptable to vary the light intensity on various parts of an article or device being inspected, such as various types of integrated circuit or semiconductor packages, to enhance the image of the package, as viewed by a vision apparatus. Moreover, there has also been a need for a system which will automatically adjust the lighting imposed on different types of articles being inspected or otherwise viewed by a vision apparatus to enhance the accuracy of an inspection process or any process which requires machine vision of an article, such as an electronic circuit or semiconductor package. Still further, since the intensity and pattern of the lighting imposed on different articles being inspected is important, it is also important to provide for monitoring the failure of any part of the lighting system so that improper lighting and inspection of articles being illuminated by the system is not experienced. It is to accomplish the desiderata mentioned above and overcome problems associated with prior art apparatus that the present invention has been developed.
SUMMARY OF THE INVENTION
The present invention provides an improved lighting system for use with machine vision apparatus for inspecting or otherwise processing various types of articles including, in particular, electronic semiconductor devices or packages and the like.
In accordance with one important aspect of the present invention a lighting system is provided which is adapted to provide a predetermined contrast or image quality of an article being viewed by a machine vision apparatus so that an accurate image of the article being viewed is produced. One embodiment of the adaptive lighting system is preferably provided with an array of light emitting diodes (LEDs), which are arranged in multiple geometric segments so that a plurality of LEDs in one segment of the array may emit light of a certain intensity while the light emitting elements (LEDs) of other segments are adjusted to emit light of other intensities to optimize the image of an article being inspected, which image may be captured by a machine vision apparatus.
In accordance with another aspect of the present invention, an adaptive lighting system is provided which includes a programmable lighting array intensity control circuit which is operable to control a substantial number of segments of an LED lighting array, in particular. Moreover, the control circuit is operable in conjunction with a microprocessor which is operated with a program which performs lighting segment selection, intensity control for each segment energized and image intensity feedback.
In particular, the programmable intensity control circuit includes a plurality of digitally controlled potentiometers, all arranged on a monolithic CMOS microcircuit. The complete intensity control circuit, when interfaced with a digital input/output circuit connected to a microprocessor, will allow a vision apparatus to provide automatic adjustment of the light intensity on an article being illuminated and the provision of a substantial number of light intensity settings. The circuit is also adapted to include a constant current source for each lighting array segment and a single driver for both strobe and non-strobe illumination operations.
In accordance with still another aspect of the present invention, an adaptive lighting system is provided which includes a circuit for real time monitoring of light failure and providing a signal indicating at least one of the light segments of the lighting system has experienced a failure. The light failure monitoring circuit is included in a module provided for monitoring a failure of any of the lighting segments of the array or system and which includes an LED indicator for each light segment to indicate which segment has experienced a failure. The light failure monitoring circuit detects a discontinuity in or an open lighting circuit, reverse connections and LED failures resulting in either an open circuit or a short circuit.
In accordance with another aspect of the present invention, a lighting system is provided for use with machine vision apparatus which utilizes flash lamps and an array of fiber optic elements forming multiple light segments which may be used in place of or in addition to LED type lighting arrays to further increase the intensity of lighting for use in applications wherein the imaging system is required to capture an image of a moving object at very high “shutter” speeds. A lighting array including multiple bundles of fiber optic elements is coupled with an array of high intensity flash lamps providing the light source. A flash lamp driver/trigger circuit is operably coupled to the programmable light intensity controllers through DC to AC inverters. The flash lamps may be energized by a continuous high frequency signal or by a single pulse type signal to provide multiple modes of operation.
The invention also provides a method for adjusting the intensity of a lighting array for lighting semiconductor packages and the like, which may be carried out by computing the median gray value of an image of an article or object, readjusting the lighting intensity and recomputing the median gray value until an optimum setting is reached.
The adaptive lighting system of the present invention eliminates the need for microprocessor based digital to analog converter circuits of types commercially available at the time of development of the invention and which types have been sufficient to provide for only a very limited number of segments of a lighting array to be controlled.
REFERENCES:
patent: 4882498 (1989-11-01), Cochran et al.
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patent: 5365084 (1994-11-01), Cochran et al.
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patent: 5870203 (1999-02-01), Chiu et al.
Hoon Tan Seow
Jusoh Noor Ashedah Binti
Rao Sreenivas
Akin Gump Strauss Hauer & Feld L.L.P.
Lee John R.
Semiconductor Technologies & Instruments, Inc.
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