Image comparison device and method

Claim 2

An image comparison device comprising an electron tube having a storage electrode for transforming a radiation image projected onto one end of said tube into a charge image which may be sensed by electron impingement, a photoelectric cathode at the other end for transforming a radiation image into an electron beam of corresponding configuration simultaneously with the forming of said charge image, means for imaging said electron beam into superposition on said charge image within said tube whereby the potential of the latter is sensed, and means for developing an electrical signal representative of the accuracy of the coincidence of said beam on said charge image.

Claim 3

An image comparison device comprising an electron tube having a storage electrode for transforming a radiation image projected onto one end of said tube into a charge image which may be sensed by electron impingement, a photoelectric cathode at the other end for transforming a radiation image into an electron beam of corresponding configuration simultaneously with the forming of said charge image, means for imaging said electron beam into superposition on said charge image within said tube whereby the potential of the latter is sensed, and means for developing an electrical signal representative of the accuracy of the coincidence of said beam on said charge image.

Claim 4

An image comparison device comprising an electron tube having a storage electrode for transforming a radiation image projected onto one end of said tube into a charge image which may be sensed by electron impingement, a photoelectric cathode at the other end for transforming a radiation image into an electron beam of corresponding configuration simultaneously with the forming of said charge image, means for imaging said electron beam into superposition on said charge image within said tube whereby the potential of the latter is sensed, and means for developing an electrical signal representative of the accuracy of the coincidence of said beam on said charge image.

Claim 5

The device of claim 1 wherein said storage electrode has an extended area impervious to electron flow therethrough and is disposed to receive said electron beam from a first direction and the first-mentioned radiation image from a second and different direction.

Claim 6

The device of claim 2 wherein said storage electrode has opposite sides and including means for projecting the first-mentioned radiation onto one of said sides and said photoelectric cathode is disposed to project said electron beam onto the other side.

Claim 7

The device of claim 2 wherein said storage electrode is of planar shape and includes a layer of photoconductive material having a surface directly exposed to said electron beam, and means for deflecting said beam over said surface.

Claim 8

The device of claim 1 including an evacuated envelope having opposite end portions, one of said end portions having said storage electrode of an extended area mounted therein; said storage electrode including a layer of photoconductive material backed by a layer of conductive material; said photoconductive layer having an exposed surface facing the other end portion of said envelope; said other end portion of said envelope having said photoelectric cathode of an extended area mounted therein facing said exposed surface and a drift tube between said exposed surface and said cathode.

Claim 9

The device of claim 5 wherein said cathode and said photoconductive layer are essentially flat and parallel, said drift tube being positioned such that the axis thereof intersects the midportions of said cathode and said photoconductive layer, a focusing coil coaxially surrounding said envelope for focusing the electron beam onto said exposed surface, and deflection coils disposed about said envelope for scanning said beam over said exposed surface.

Claim 12

The method of claim 7 in which said storage electrode includes a semi-conductive extended area element, said charge image being developed on said element by establishing a charge thereover, and discharging discrete elemental areas of said element to provide said charge image.

Claim 13

The method of claim 8, including recharging said discharged areas when said electron beam image is focused onto said storage electrode.

Claim 14

The device of claim 1 including first and second photoelectric cathodes at each said end, said storage electrode disposed therebetween and including three contiguous layers, the central one of said layers being conductive and electron permeable, a second of said layers being an insulator and electron permeable, a third of said layers being a semiconductor of secondary electron induced conductivity, said second layer facing said first photoelectric cathode, electron-accelerating means disposed between said first photoelectric cathode and said second layer for imparting sufficient energy to the electrons of said electron beam to cause them to penetrate both said second and first layers and to enter said third layer, whereby said third layer becomes momentarily locally conductive, said third layer facing said second photoelectric cathode, said second photoelectric cathode emitting the electrons which form said electron beam, said imaging means including at least one accelerating electrode interposed between said second photoelectric cathode and said third layer which imparts energies to the last-mentioned electrons sufficient to charge said third layer to the potential of said second photoelectric cathode.

Claim 15

The device of claim 10 in which said third layer is one of the class of materials of potassium chloride.