Patent Number: 047456310
Section: summary

The present invention is directed to apparatus for generating radiation to detect objects, such as objects in a baggage detection type structure. In particular, the present invention is directed to a flying spot type generator in which a beam of radiation is formed into a flying spot of the radiation which passes throguh objects to be inspected and is thereafter detected. Flying spot type scanners have been suggested in the prior art, as may be seen in U.S. Pat. Nos. 3,808,444 to Schneeberger et al and 3,884,816 to Takahashi. Such previous schemes have suffered from the ability to produce output signals representing the entire dimension of the object being inspected. Moreover, large spot characteristics have been used which only achieves a coarse measurement. These prior art devices do not contribute to operable imaging systems. Further, prior art scanners utilizing a scanning pencil beam of x-rays may be seen in U.S. Pat. No. Re. 28,544. This device involves a rotating disk having slots at the edges to form an x-ray for beam into a scanning pencil beam. Such an arrangement is relatively complicated in forming a scanning flying spot of radiation. In the state of art radiographic security systems now used, such as used to inspect carry-on baggage for commercial airlines, semiconductor memory systems are provided to store a digitized, dissected x-ray image such as presented in U.S. application, Ser. No. 384,826, filed June 3, 1982, of which the present inventor is a co-inventor. Dissection of the image into its picture elements (pixels) is predominently achieved today in such arrangements by using a fan-shaped beam of x-rays through which the object passes on a conveyor belt , and a linear array of discrete x-ray detectors behind the object. This current technology uses on the order of 500 such discrete detectors which are usually photodiodes, and the subsequent electronic circuitry requires hundreds of current to voltage converters and preamplifiers, and several multiplexers. Such an arrangement is complex. The present invention resides in a greatly simplified arrangement. Namely, a flying spot of x-rays is generated from a cylindrical shell with helical slots in which image readout takes place in a single long detector. This results in a great simplification of the readout circuitry. Accordingly, the present invention defines a compact device for generating a flying spot of x-rays. This arrangement essentially resides in a structure for the formation of a coarse fan-beam of x-rays which is directed onto a rotating elongated cylinder having at least two helical slots to form a flying spot of x-rays. The flying spot passes through an object to be detected and is then detected by an elongated detector.