Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/8806—Specially adapted optical and illumination features
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/90—Investigating the presence of flaws or contamination in a container or its contents

Definitions

• This application pertains to the art of video inspection, and more particularly to specialized illumination and image capture therefor.
• the invention is particularly applicable to inspection of discrete specimens, particularly those having specific areas of particular interest.
• the application will be described with particular reference thereto, although it will appreciated if the invention has broader application as in any video inspection environment for which acquisition of detailed images is desirable.
• a first generation of improvement to the video inspection system was associated with improvements and basic inspection algorithms.
• a subsequent generation of improvement was directed toward improving the actual image captured.
• Such systems employed such components as a solid-state LED array, optionally coupled with a diffuser, to obtain more homogeneous lighting.
• a solid-state LED array optionally coupled with a diffuser, to obtain more homogeneous lighting.
• a diffuser to obtain more homogeneous lighting.
• the more uniform an illumination field the more accurate a resultant, captured image would be.
• Another concern with video inspection systems is competing objectives of analysis. More particularly, an overall analysis of an image is often desirable. However, detailed analysis of a sub-portion of the specimen is also advantageous. This latter advantage is particularly necessary for specimens having a high stress area or the like.
• Such competing goals often require multiple inspection stations. At a first station, an over all specimen image may be captured and analyzed. Subsequent stations may allow for focusing attention on a particular, specialized area. Such systems require duplication of illumination systems and image acquisition systems. They also require more space on a fabrication line to accommodate multiple inspection stations. Finally, the results of an analysis of both stations must be harmonized and synchronized.
• a video inspection illumination system which employs a beam splitter. Light from a light source is directed to this beam splitter. A portion of the light from the light source is then directed to a discrete part or specimen in a viewing area.
• the light source is advantageously provided with a diffuser to render its resultant light more homogeneous. Light reflected from the specimen is communicated back through the beam splitter to a camera arrangement for image acquisition.
• a second beam splitter is provided to capture light reflected from the specimen after passing through the first beam splitter.
• This beam splitter communicates a first light portion to a first camera and a second light portion to a second camera.
• One of these cameras provides sufficient magnification to allow for selected, detailed analysis of a subportion of the entire specimen.
• a comparison is made with resultant, captured images to allow for selective rejection of a specimens not achieving preselected criteria.
• An advantage of the present invention is the provision of an inspection system which allows for capture and analysis of highly detailed images. Yet another advantage of the present invention is the provision of an inspection system allows for capturing and analysis of multiple images of a single specimen in a single workstation.
• Another advantage of the present invention is the provision of a detailed inspection system which requires fewer parts and provides enhanced specimen throughput.
• FIGURE 1 illustrates the overall inspection illumination and image capture system of the subject invention
• FIGURE 2 illustrates, in detail, the illumination subportion and ray diagram of the system of FIGURE 1;
• FIGURE 3 illustrates a programmable light source as suitably implemented in connection with the systems of
• FIGURE 1 illustrates an automated video inspection system A which includes an illumination subsystem B and an image acquisition subsystem C
• the disclosed system facilitates enhanced defect detection and optical inspection which is particularly suited for discrete parts, as is used in the container industry.
• the system provides for convergent illumination from a light source which may be either programmable or non-programmable.
• the system also provides divergent illumination from either of these light sources.
• a suitable light source is formed by a solid- state illumination source, such as a pulsed array of light emitting diodes.
• a solid- state illumination source such as a pulsed array of light emitting diodes.
• Strobed light which includes the noted LED array, inert gas strobes, and the like, maintaining an advantage of "freezing* 1 moving specimens so that an image may be obtained.
• Continuous light sources require the addition of a commonly-available electronic shutter mechanism to "freeze” a captured image.
• a multi-spectrum light source is also advantageously provided in certain applications for the reasons noted below.
• the system allows for optically magnifying an image portion while utilizing normal camera optics to acquire discrete images. Resultant information on defects generated is made available for subsequent analysis and comparison.
• a light source 10 is used to generate light generally in a direction dl.
• the light source 10 is advantageously programmable so as to selectively generate light, as will be described in detail below.
• Light from the light source 10 is passed through a diffuser 12 to increase homogeneity thereof.
• the diffuser 12 is advantageously comprised of a translucent or transparent material, such as glass or plastic.
• the surface is optically "rough” in such a way that incident light will transmit through the medium and be modified so as to be uniformly distributed over some area as diffused, transmissively scattered light.
• the particular properties of the diffusion are highly application specific. Selection may be made by choice of translucence, transparency, and roughness.
• the beam splitter 16 functions as a light splitter insofar as a portion of the light will pass through, generally maintaining the direction d,. other of the light will be reflected at an angle of reflection 2 generally equal to the angle incidence ⁇ , between the incident light direction d, and the generally planar beam splitter 16.
• the portion of the incident light reflected from the beam splitter 16 travels generally along direction
• the beam splitter 16 suitably is comprised of optically surfaced piano-glass plates with metalized coatings. Such beam splitters are commercially available. The property of the beam splitter 16 is generally to both transmit and reflect incident light with equal intensity, but with unequal splitting. For example, 60%/40% splitting is suitably used. Such a splitter may be found with Product No. G72.502 from Edmund Scientific Corp. of Barrington, New Jersey. As with the diffuser, it must be appreciated that the particulars of a particular light splitter are highly application specific.
• the field lens 20 is comprised of a plano-convex singlet geometry.
• the field lens 20 is comprised of a plano-convex singlet geometry.
• a series of similar specimens like that provided at 24 are each propagated to the viewing area 22 via a conveyor means 26, such as a moving belt or the like.
• the convergent illumination on an imaged specimen is utilized, as shown above.
• the object or specimen is disposed in space at a distance less than a prime focal distance from a vertex or piano surface of the field lens 20.
• illumination is incident as a distributed, shaped, convergent source.
• a diffuse array illumination source When a diffuse array illumination source is implemented, it appears as an infinitely distant continuum. A homogeneous nature of the diffuse source is maintained in the specimen illumination as a result of a uniform illuminating field. It must be appreciated that in the above-described arrangement, a specimen is to be imaged is located inside a prime focal distance of the field lens 20. This results in a desirable structuring of specimen illumination.
• the specimen illumination may also be directed through any other modifying optical elements.
• modifying elements are suitably beam splitters, mirrors, lenses, or the like.
• Such optical elements may be disposed either prior to or following the field lens, as defined from the light source 10, to the specimen 24.
• a specimen may also be located outside of a prime focal distance. This would result in a continuously divergent illumination field with similar characteristics as described above for the continuously convergent illumination field.
• the objective is the generation and capture of a specimen image for purposes of analysis. This is accomplished by arranging a system geometry such that an imaging device, that is, camera and optics, essentially looks through the field lens at a specimen.
• reflected light is passed through the field lens 20, it is propagated again to the beam splitter 16. Again, a portion of the light will be reflected and a portion transmitted according to the optical characteristics of the beam splitter 16 as noted above.
• the transmitted portion is indicated generally along direction d 4 .
• a second beam splitter 30 which functions as an image splitter.
• a portion of light is reflected along direction d 5 , while a portion continues along direction d 4 .
• the relative apportionment is dictated by choosing the properties of a the image splitter 30.
• application to certain specimens may be served by implementation of multiple spectrum light. See, for example, U.S. Patent Application Serial No. 07/990,009, entitled VIDEO INSPECTION SYSTEM EMPLOYING MULTIPLE SPECTRUM LED ILLUMINATION, commonly assigned to the subject application, the contents of which are incorporated herein by reference.
• the splitter 30 may also be formed of a color separator.
• the portion of light directly passed through image splitter 30 is communicated to a main image camera 34.
• the main image 34 functions to capture an image of an entire specimen.
• a reflected portion traveling generally along direction d 5 is communicated to a second camera 36 which functions as a magnified camera in the preferred embodiment.
• the magnified camera 36 is used to explore a special area of interest ("AOI") on a discrete specimen.
• AOI area of interest
• the magnified camera 36 may be advantageously used to enhance a main rivet picture.
• the field lens provides for pre- enlargement of an image prior to using integral camera optics disposed within magnified camera 36 to enlarge a generated image.
• Each of the cameras 34 and 36 are suitably comprised of solid-state, charge-coupled devices ("CCDs") . Digitized images captured therefrom are communicated to any suitable image analyzing unit 42 which are commercially available and within the understanding of one of ordinary skill in the art.
• the main image camera 34 has a typical field of view (“FOV”) in the range of 3 to 5 inches. Again, such is highly application specific and is provided merely as an example of a preferred embodiment.
• the magnified camera 36 is provided with a focus to a specific region of interest on the specimen. In the preferred embodiment, its field of view is suitably 0.25".
• Captured images one analyzed, facilitate selective rejection of unacceptable specimens as dictated by preselected criteria by selective enable ent of a rejection mechanism, such as illustrated by an error blow- off unit 44.
• a unit such as that 44 will remove a defective specimen from the conveyor means 26.
• FIGURE 2 a ray trace diagram of the illumination subsystem B of FIGURE 1 is provided. The numbering provided in connection with claim 1 has been maintained herein.
• the anti-reflective coating noted above will be noted to be provided generally at 46.
• a light controller 48 is utilized to accomplished controllable lighting as detailed below.
• the light source 10 is comprised of a programmable light source 50. Often times specimens are circular in nature, such as is found by the container industry. Thus, a circular arrangement for the light source 10 is provided by the illustration.
• a suitable light source for the preferred embodiment is comprised of a plane of solid-state light devices, such as light emitting diodes ("LEDs") . Such planar rays of LEDs have been well described in the prior art and will not be repeated herein. Arranging LEDs in a series of concentric, controllable areas allows for selective control of illumination.
• the LEDs are arranged in separate controllable zones, zones 1-4. Each of these zones is selectively controllable. Thus, intensity, enablement, or duration of light elements of the particular zone may be provided. This allows for selective control of specimen illumination to eliminate at artifacts, such as hot spots, which is highly contingent on a specific part to be inspected.
• a programmable light source 10 may also be comprised of an inert gas or xenon strobe which may also be programmable by employing a series of co-axial, individually activated tube portions.

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• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 1995
  • 1995-05-22 EP EP95921336A patent/EP0777850A4/en not_active Withdrawn
  • 1995-05-22 JP JP8508718A patent/JPH10505155A/en active Pending
  • 1995-05-22 WO PCT/US1995/006435 patent/WO1996007076A1/en not_active Ceased
  • 1995-05-22 AU AU26440/95A patent/AU2644095A/en not_active Abandoned

Patent Citations (3)

Non-Patent Citations (2)

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