Apparatus for use in the determination of focal spot size in X-ray tubes

Claim 2

In an apparatus for use in the determination of focal spot size in X-ray tubes, means for determining the position of the central beam comprising: a lens structure, said lens structure defining a pair of parallel upper and lower planes each providing a regular pattern of markings of distinctive opacity to X-rays, each pattern defining an array of discrete position coordinates in the respective plane, each array being the projection of the other in a direction perpendicular to said planes, means for assembling a photographic film in close proximity to the lower plane at a predetermined orientation relative thereto, and means for locating the assembly with respect to an X-ray tube so that the central beam impinges perpendicularly on said upper plane, whereby to derive a composite photographic image of said patterns of markings in which the image components corresponding to the respective patterns coincide at the position of the central beam.

Claim 3

An apparatus according to claim 1, wherein each pattern of markings is a grid pattern formed by intersecting sets of linear markings which are opaque to X-rays.

Claim 4

An apparatus according to claim 2, in which each pattern of markings is a rectangular grid pattern.

Claim 5

An apparatus according to claim 1, wherein the lens structure is constituted by a block which is transparent to X-rays, the block having a pair of parallel upper and lower planar surfaces defining said upper and lower planes, each surface providing a grid pattern of intersecting linear grooves, said markings being constituted by wires extending along the grooves.

Claim 6

In an apparatus for use in the determination of focal spot size in X-ray tubes, means for determining the position of the central beam comprising: a rigid tubular housing adapted for connection at one end to an X-ray tube in registration with a port thereof, a lens structure, said lens structure defining a pair of parallel upper and lower planes each providing a regular pattern of markings of distinctive opacity to X-rays, each pattern defining an array of discrete position co-ordinates in the respective plane, each array being the projection of the other in a direction perpendicular to said planes, a lens holder, the lens structure being mounted within the holder, a carrier member coupled to the other end of said housing and supporting the lens holder within the housing so that the central beam will impinge perpendicularly on said upper plane of the lens structure, and a closure cap for assembly with the tubular housing to close said other end thereof, the closure cap providing means for locating a photographic film and being retained by said carrier member so that the photographic film lies in close proximity to the lower plane of the lens structure at a predetermined orientation relative thereto, whereby to derive a composite photographic image of said patterns of markings in which the image components corresponding to the respective patterns coincide at the position of the central beam.

Claim 7

In an apparatus for use in the determination of focal spot size in X-ray tubes, means for determining the position of the central beam comprising: a rigid tubular housing adapted for connection at one end to an X-ray tube in registration with a port thereof, a lens structure, said lens structure defining a pair of parallel upper and lower planes each providing a regular pattern of markings of distinctive opacity to X-rays, each pattern defining an array of discrete position co-ordinates in the respective plane, each array being the projection of the other in a direction perpendicular to said planes, a lens holder, the lens structure being mounted within the holder, a carrier member coupled to the other end of said housing and supporting the lens holder within the housing so that the central beam will impinge perpendicularly on said upper plane of the lens structure, and a closure cap for assembly with the tubular housing to close said other end thereof, the closure cap providing means for locating a photographic film and being retained by said carrier member so that the photographic film lies in close proximity to the lower plane of the lens structure at a predetermined orientation relative thereto, whereby to derive a composite photographic image of said patterns of markings in which the image components corresponding to the respective patterns coincide at the position of the central beam.

Claim 8

An apparatus according to claim 5, including a pinhole assembly which is interchangeable with the lens holder and the lens structure to be supported by the carrier member, the pinhole assembly including a first cylindrical block supported by the carrier member and having an eccentric bore therein, means for rotating the first cylindrical block about a first axis parallel to the axis of the tubular housing, a second cylindrical block located within said eccentric bore, means for rotating the second cylindrical block about a second axis parallel to the first, and a pinhole element mounted on the second cylindrical block, the pinhole element providing a pinhole which is aligned with a through-bore in the second block which is parallel to and offset from said first and second axes.