Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
1999-12-27
2003-06-03
Epps, Georgia (Department: 2873)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S370110
Reexamination Certificate
active
06573507
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus for obtaining an image signal which represents a radiation image, from a solid-state radiation detector, which converts incident radiation into an electric signal. This invention also relates to a solid-state radiation detector for use in the radiation image read-out method and apparatus.
2. Description of the Prior Art
Radiation image recording and read-out apparatuses utilizing radiation film or stimulable phosphor sheets have heretofore been used widely for obtaining radiation images for medical diagnosis, or the like.
Also, recently, various radiation image recording and read-out apparatuses utilizing solid-state radiation detectors (comprising semiconductors as major parts), which detect radiation and feed out image signals, have been proposed and have widely been used in practice. As the solid-state radiation detectors utilized in the radiation image recording and read-out apparatuses, various types of solid-state radiation detectors have been proposed. Typical examples of the solid-state radiation detectors include photo conversion types or direct conversion types of solid-state radiation detectors, in which accumulated electric charges (also referred to as the latent image charges) carrying image information are detected with thin-film transistors (TFT's), and improved direct conversion types of solid-state radiation detectors, in which the latent image charges carrying image information are detected by scanning with reading light.
The photo conversion types of solid-state radiation detectors comprise solid-state detection means (two-dimensional image read-out means) and a fluorescent material overlaid upon the solid-state detection means. The solid-state detection means comprises an insulating substrate and a plurality of photoelectric conversion devices, which are formed in a two-dimensional pattern on the insulating substrate and which are provided with charge accumulating sections for accumulating electric charges. When the fluorescent material is exposed to radiation carrying image information, it converts the radiation into the fluorescence. The fluorescence is detected, and the thus obtained electric charges are accumulated at the charge accumulating sections of the photoelectric conversion devices. The TFT's, each of which is connected to one of the photoelectric conversion devices, are operated successively, and the accumulated charges are thereby converted into a radiation image signal and fed out. The photo conversion types of solid-state radiation detectors are described in, for example, Japanese Unexamined Patent Publication Nos. 59(1984)-211263 and 2(1990)-164067, PCT International Publication No. WO92/06501, and SPIE Vol. 1443, Medical Imaging V; Image Physics (1991), pp. 108-119.
The direct conversion types of solid-state radiation detectors comprise solid-state detection means and a radio-conductive material overlaid upon the solid-state detection means. The solid-state detection means comprises an insulating substrate and a plurality of charge collecting electrodes, which are formed in a two-dimensional pattern on the insulating substrate and each of which corresponds to one pixel. When the radio-conductive material is exposed to radiation carrying image information, it generates electric charges carrying the image information. The direct conversion types of solid-state radiation detectors are described in, for example, “Material Parameters in Thick Hydrogenated Amorphous Silicon Radiation Detectors,” Lawrence Berkeley Laboratory, University of California, Berkeley, Calif. 94720 Xerox Parc. Palo Alto. Calif. 94304; “Metal/Amorphous Silicon Multilayer Radiation Detectors, IEE TRANSACTIONS ON NUCLEAR SCIENCE, Vol. 36, No. 2, April 1989; and Japanese Unexamined Patent Publication No. 1(1989)-216290. In the direct conversion types of solid-state radiation detectors, solid-state detecting devices comprise the charge collecting electrodes and the radio-conductive material as the major parts. When the accumulated charges carrying the radiation image information are to be. detected as an image signal from the direct conversion types of solid-state radiation detectors, as in the aforesaid photo conversion types of solid-state radiation detectors, the solid-state detecting devices are scanned with the TFT's, each of which is connected to one of the solid-state detecting devices.
The improved direct conversion types of solid-state radiation detectors have been proposed by the applicant in Japanese Patent Application No. 10(1998)-232824. The improved direct conversion types of solid-state radiation detectors are improved over the direct conversion types of solid-state radiation detectors and utilize a photo reading technique for performing the reading operation by the scanning with reading light. The improved direct conversion types of solid-state radiation detectors comprise:
i) a first electrical conductor layer having permeability to recording radiation,
ii) a recording photo-conductive layer, which exhibits photo-conductivity (in the strict sense, radio-conductivity) when it is exposed to the recording radiation having passed through the first electrical conductor layer,
iii) a charge transporting layer, which acts approximately as an insulator with respect to electric charges having a polarity identical with the polarity of electric charges occurring in the first electrical conductor layer, and which acts approximately as a conductor with respect to electric charges having a polarity opposite to the polarity of the electric charges occurring in the first electrical conductor layer,
iv) a reading photo-conductive layer, which exhibits photo-conductivity (in the strict sense, electromagnetic wave conductivity) when it is exposed to a reading electromagnetic wave, and
v) a second electrical conductor layer having permeability to the reading electromagnetic wave,
the layers being overlaid in this order. In the improved direct conversion types of solid-state radiation detectors, latent image charges carrying image information are accumulated at an interface between the recording photo-conductive layer and the charge transporting layer. The first electrical conductor layer and the second electrical conductor layer act as electrodes. Also, in the improved direct conversion types of solid-state radiation detectors, solid-state detecting devices comprise the recording photo-conductive layer, the charge transporting layer, and the reading photo-conductive layer as the major parts.
In the improved direct conversion types of solid-state radiation detectors, the reading of the latent image charges (i.e., the reading of the electrostatic latent image represented by the latent image charges) may be performed with a technique, wherein the second electrical conductor layer (i.e., a reading electrode) is constituted of a flat plate-shaped electrode, and the reading electrode is scanned with spot-like reading light, such as a laser beam, the latent image charges being thereby detected. Alternatively, the latent image charges may be read with a technique, wherein the reading electrode is constituted of comb tooth-shaped electrodes (i.e., stripe-shaped electrodes), and the stripe-shaped electrodes are scanned with light, which is produced by a line light source extending along a direction approximately normal to the longitudinal direction of each stripe-shaped electrode, the scanning with the light being performed in the longitudinal direction of each stripe-shaped electrode. In this manner, the latent image charges are detected. In cases where either one of the reading techniques is employed, the solid-state radiation detector is formed as a two-dimensional solid-state radiation detector constituted of a plurality of solid-state detecting devices, which are arrayed in a substantially matrix-like form and each of which corresponds to one pixel. Specifically, as for the solid-state radiation detector itself, it cannot be said that the ind
Epps Georgia
Harrington Alicia M.
Sughrue & Mion, PLLC
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