Optical: systems and elements – Diffraction – From zone plate
Reexamination Certificate
1999-08-02
2001-11-06
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Diffraction
From zone plate
C359S569000, C359S575000
Reexamination Certificate
active
06313948
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for inspecting components and particularly to one using an array of light sources and video devices as a means of evaluating a component for conformance to spatial form criteria.
Presently, there is an ever increasing demand to obtain high quality products which has resulted in a significant increase in the use of non-contact inspection systems. In order for a complex machine to operate as designed, it is necessary that all of its sub-components comply with quality criteria. In some manufacturing settings, customers require 100% inspection of component parts. For example, fasteners used in the automobile industry and elsewhere often must be individually inspected to determine if they meet spatial form criteria.
Numerous types of inspection systems are presently utilized. One type of system uses contact probes which touch a component at various points to determine if its dimension or profile meet certain criteria. However, contact devices have inherent limitations in that they are subject to wear and generally require that the component and the contact probe be accurately positioned during the evaluation process. Moreover, such devices are generally slow to operate and are limited in terms of the number of criteria and complexity of profiles which they can evaluate. A variety of non-contact systems are also known using a variety of techniques. For example, ultrasonic inspection systems examine reflected sound waves as a means of characterizing a component. Various systems based on photodetection utilizing single channel photodetectors are also known. In addition, laser gauging systems are used in which specific dimensional measurements can be obtained.
However, although known non-contact inspection systems are generally extremely useful, they have certain limitations. Many of the presently available non-contact gauging systems require complex data processing approaches which impose speed limitations in part evaluations. For example, systems utilizing two-dimensional photosensitive arrays impose extreme data processing requirements, which has the effect of reducing part throughput. Preferably, evaluation of a workpiece can be conducted in a rapid enough fashion that the parts can be directly sorted into qualified or disqualified part streams. The systems which are capable of such high speed inspection lack valuable signal processing capabilities such as edge detection and real time imaging. Edge detection enhances the accuracy of the inspection enabling the parts inspection system to overcome the inherent limitations of discrete photodetectors. Early photodetection systems and ultrasonic systems provided part shape information based on the signal strength of a transducer. This information was only an approximation of the parts shape and not a true image of the part. For example single channel photodetectors could generate a single output related to the amount of occluded light. Over a set period of time this single channel photodetector gives an approximation of the part shape, but not an actual picture of the part. There is a need in the art for a high speed inspection system with powerful signal processing capabilities which include edge detection and real time imaging.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved non-contact inspection system is provided which enables rapid inspection to be conducted permitting parts to be immediately sorted in terms of being in conformance or out of conformance with spatial form criteria. Moreover, a hard copy of part geometry can be generated from a shadow image or occluded light profile of the part pointing out specific shape discrepancies. For example, for a threaded fastener, the diameter, length, profile and threads can be evaluated. When producing fasteners, the process often begins with wire stock which is fed into a cold heading or screw type forming machine. The part is die-formed or cut in a machine into a shape that may include several diameters and possibly a threaded or knurled length. The formed part may require secondary operations such as thread rolling, heat treating, planing, etc. It is not uncommon for one or more of the processes to fail to produce the desired geometry of part. The occurrence of such defects is often not adequately monitored through random part selection or other quality assurance processes which do not provide a 100% inspection.
In the present invention parts move by gravity or other means along a track through a test section. The part shape is determined through use of a CCD line array/camera, although any type of photodetector may be used. A collimated uniform light source in the form of a sheet is generated in the proximity of the part to be inspected. This uniform sheet of light will allow a highly detailed part examination. The extent and time to which the sheet of light is occluded by the part is related to its shape. As the part moves through the test section containing the CCD line array, the CCD line array will measure the occluded light and generate an output signal to a signal processor. The signal processor will measure the time the part takes to pass over the CCD line array and combine this time information with the occluded light output signal to generate an image of the part. The part measurements of interest are its length and various radial profiles.
A part detection array utilizes a plurality of light sources and CCD line arrays in a radial arrangement around the part to be examined. The part detection array will measure the occluded light from a matched or paired light source which is proximate to the part. In the preferred embodiment of the invention a light source is coupled to a diffractive beam shaper which provides a uniform sheet of light. The uniform sheet of light is used to attain an even intensity pattern over a certain area. The shadows created by the parts because of the use of the uniform sheet of light are indistinct and lack sharp transitions to the lighted areas. In order to interpret these blurred shadow edges special software detailed below has been created to define the location of the actual edge. Each light source used in the array will emit only a certain frequency of light and each CCD line array will include a filter to allow only its matched frequency to be detected. In this manner there will be no cross-talk generated between each light source and its matched CCD line array.
Further objects, features, and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.
REFERENCES:
patent: 2812685 (1957-12-01), Vossberg
patent: 4067652 (1978-01-01), Bohlander
patent: 4260260 (1981-04-01), Letort et al.
patent: 4410237 (1983-10-01), Veldkamp
patent: 4532723 (1985-08-01), Kellie et al.
patent: 4547037 (1985-10-01), Case
patent: 4875777 (1989-10-01), Harding
patent: 4880991 (1989-11-01), Boehnlein et al.
patent: 5148317 (1992-09-01), Foresi
patent: 5164995 (1992-11-01), Brooks et al.
patent: 5212707 (1993-05-01), Haidel et al.
patent: 5229883 (1993-07-01), Jackson et al.
patent: 5237451 (1993-08-01), Saxe
patent: 5315427 (1994-05-01), Rauch et al.
patent: 5383021 (1995-01-01), Hanna
patent: 5548418 (1996-08-01), Gaynor et al.
patent: 5568263 (1996-10-01), Hanna
patent: 5608530 (1997-03-01), Gates
patent: 5757523 (1998-05-01), Wood et al.
patent: 5888846 (1999-03-01), Hasman et al.
patent: 5986807 (1999-11-01), Fork
patent: 6002520 (1999-12-01), Hoch et al.
patent: 6025938 (2000-02-01), Kathman et al.
patent: 6046812 (2000-04-01), Baik et al.
patent: 6072631 (2000-06-01), Guenther et al.
patent: A 0149921 (1986-07-01), None
patent: 62-288505 A (1987-12-01), None
patent: 63-262512 A (1988-10-01), None
patent: SU 1569766 (1990-06-01), None
Brinks Hofer Gilson & Lione
Jr. John Juba
Spyrou Cassandra
LandOfFree
Optical beam shaper does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical beam shaper, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical beam shaper will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590985