Optical: systems and elements – Deflection using a moving element
Reexamination Certificate
1997-08-08
2001-03-13
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
C359S197100
Reexamination Certificate
active
06201623
ABSTRACT:
This invention relates to surface topography enhancement, and more particularly to a method and apparatus for producing a topographically enhanced representation of an object.
Many imaging systems are known for producing a representation of the surface of the object. The simplest of such systems would be a photocopier, for example, where the object is illuminated to form a latent image on a selenium drum. Optical scanners for scanning images into computers are well known.
The problem with such systems is that they do not make good representations of topographically rich surfaces, the two-dimensional nature of such systems inherently being ill-suited to the reproduction of topographical detail.
U.S. Pat. No. 4,920,385 discloses an apparatus for inspecting surface flaws wherein the surface is scanned with a moving light beam. However, this apparatus does not provide the desired resolution of topological features.
An object of the present invention is to provide a system capable of enhancing the representation of topographical detail in a two-dimensional image.
According to the present invention there is provided an apparatus for producing a topographically enhanced representation of an object, comprising a light source for generating a band of light for illuminating the object, said band of light defining an edge zone of finite width due to diffraction effects with an intensity profile that falls off rapidly with distance in a transverse direction relative to said band of light, said finite width being sufficient to accommodate an image strip; an arrangement for progressively advancing said band of light over the object in said transverse direction; and means for scanning said object at a grazing angle along said image strip within said edge zone as said band of light progressively advances over said object.
By “falls of rapidly” is meant that the change of intensity is similar to that experienced in the edge zone of a collimated band of light from a slit, although it can be generated by other means. Typically this change in intensity is in the order of a factor of two over a distance of about 0.08 inches. In such an embodiment, the surface to be inspected is illuminated by a light source which produces a collimated band of light from a slit bounded by an edge zone where diffraction effects are noticeable. Along either edge of this band the intensity drops off rapidly as the distance from the edge increases.
This area or strip is the edge-of-light zone resulting from diffraction from the edges of the slit. Its width is very narrow but finite and its characteristics can be modified by changing the angle of the illumination source. An image strip focused on the surface at a grazing angle of preferably 3 to 6 degrees in this zone is used to gather the intensity changes caused by slope changes on the surface. Small changes in slope cause large shifts in light intensity.
A line scanner is preferably used to collect the intensity data. The image strip normally has a width of only a pixel or two roughly measured to be 0.001 in. This easily fits into the edge-of-light zone used in the scanner, which has a zone width close to 0.08 in. Depending upon where the strip is located within the zone, the intensity shifts go from high to low or low to high. As the scanner travels along the surface the edge of light moves with it. The enhanced image is constructed by combining the strips together.
The end result is a high resolution image with brighter or darker areas highlighting surface slope changes.
The invention also provides a method of producing a topographically enhanced representation of an object, comprising progressively moving a light beam over the surface of the object, said light beam having a zone whose intensity changes rapidly with distance, and scanning said object at a grazing angle in said zone as the light beam is moved over the surface.
REFERENCES:
patent: 4863268 (1989-09-01), Clarke et al.
patent: 4900153 (1990-02-01), Weber et al.
patent: 4920385 (1990-04-01), Clarke et al.
patent: 2133 871 (1984-08-01), None
(Marks & Clerk)
National Research Council of Canada
Phan James
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