Patent GB-705297-A (GB)
Abstract: 705,297. X-ray or gamma-ray apparatus. WATSON, W. June 5, 1952 [June 8, 1951], No. 13607/51. Class 98(1) Apparatus for producing a substantially stationary X-ray or γ-ray image of a single plane of an object comprises an X-ray tube or a tube containing γ-ray emitting material, means for causing the tube to move in a circular orbit while directing its central ray constantly to a point on the axis of the orbit, a platform for supporting an object to be examined so that the intersection of the central ray and the axis of the orbit lies within the object, a fluorescent screen mounted and fixed parallel to the plane of the orbit and in the path of the rays after they have passed through the axis, the platform and the object, a plane mirror located beyond the fluorescent screen so that the screen may be viewed indirectly by reflection in the mirror, and either means for rotating the mirror, in synchrony with the movement of the tube, about an axis making a small angle to one normal to the plane of the mirror, including means for adjusting the small angle, or other means for imparting to the mirror a motion having an optical effect equivalent to the optical effect of such rotation. As shown, Fig. 1, a base 1 supports a column 3 carrying a slidable counterweighted bracket 21. An X-ray tube 19 is mounted on a plate 16, and three or more links 17 are trunnioned at opposite ends to the plate 16 and to the base 1. A collar 10 is splined to a shaft 8 rotatably mounted on the base 1, and links 13 connect collar 10 to a collar 14 loosely mounted on a stub shaft 15 on the plate 16. The collar 10 is movable along shaft 8 by a lever 6 pivoted to the base and engaging a peripheral groove on pulley 10. When shafts 8, 15 are coaxial, plate 16 is immovable, but otherwise the movement of a swash plate is imparted to plate 16. Tube 19 therefore moves in a circle without rotating on its own axis and with its principal ray. always directed to a fixed point on the axis of shaft 8. This point is arranged (by adjustment of lever 6) to lie within an object 25 resting on a table 4. The rays form a blurred, rotating image on a fluorescent screen 24 carried by bracket 21, and this image is viewed by reflection in a mirror 29 mounted on the shaft 31 of an electric motor 28, the normal to the mirror being at a small, variable angle to the shaft 31. When the.mirror is rotated in synchrony with the X-ray tube, a clear image of one section of the object 25 is seen by reflection therein, the depth of the section depending on the angle between mirror 29 and shaft 31. In modifications, mirror 29 and shaft 8 may have a common drive, or the mirror may be given a swash-plate motion by a ring of electromagnets, energized successively in synchrony with the rotation of shaft 8. The image is then reflected also in a second fixed mirror. The X-ray tube may be replaced. by a source of γ-rays. The image may be photographed, projected, or televised. A Bucky grid may be placed below the fluorescent screen. The rotatable mirror in any of the forms described may replace the rotatable block in the apparatus described in Specification 601,806. Specification 369,662 also is referred to.