Radiant energy – Source with recording detector – Including a light beam read-out
Reexamination Certificate
2000-08-21
2002-12-31
Epps, Georgia (Department: 2873)
Radiant energy
Source with recording detector
Including a light beam read-out
C250S580000
Reexamination Certificate
active
06501089
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid state radiation detector with a charge storage portion for storing an electric charge with a quantity corresponding to the dose of radiation irradiated, an image recording method and an image recorder for recording radiation image information on the charge storage portion as an electrostatic latent image by the use of the detector, and an image reading method and an image reader for reading out the recorded electrostatic latent image from the detector.
2. Description of the Related Art
Units, which employ an image detector, such as a facsimile, a copying machine, a radiation imaging unit, etc., are known.
For example, in the medical radiation imaging unit, for the purposes of a reduction in the radiation dose to which a subject is exposed, an enhancement in diagnosis performance, etc., a solid state radiation detector (electrostatic storage) with a photoconductor (layer) such as a selenium plate sensitive to radiation such as X-rays is employed as an image detector. X-rays are irradiated to the solid state radiation detector to store an electric charge with a quantity corresponding to the dose of the irradiated radiation in the charge storage portion of the detector as latent image charge. With the irradiation, radiation image information is recorded on the charge storage portion as an electrostatic latent image. The solid state radiation detector recorded with the radiation image information is scanned by a laser beam or a line light source to read out the radiation image information from the detector.(e.g., Japanese Unexamined Patent Publication No. 6(1994)-217322, U.S. Pat. No. 4,857,723, Japanese Unexamined Patent Publication No. 9(1997)-5906, etc.).
The method as described in the above-mentioned Japanese Unexamined Patent Publication No. 6(1994)-217322 uses, as an image detector, a solid state radiation detector in which (
1
) a conductive layer, (
2
) an X-ray photoconductive layer, (
3
) a dielectric layer, and (
4
) an electrode layer with a plurality of micro plates corresponding to pixels are stacked and also having a thin film transistor (TFT) connected to each micro plate. X-rays transmitted through a subject are irradiated to the solid state radiation detector to store latent image charge in a charge storage portion formed between each micro plate and the conductive layer. With the storage, the radiation image information is recorded in the solid state radiation detector. Next, the TFTs are scanned to read out the latent image charge stored in the charge storage portion from the solid state radiation detector. In this manner the radiation image information is read out from the solid state radiation detector.
The method as described in the above-mentioned U.S. Pat. No. 4,857,723 uses, as an image detector, a solid state radiation detector constructed so that both sides of a photoconductive layer are interposed between insulating layers and that the outsides of the insulating layers are interposed between stripe electrodes which have a plurality of line electrodes crossing one another. X-rays transmitted through a subject are irradiated to the solid state radiation detector to store latent image charges of opposite polarities in two charge storage portions formed at the interface between the photoconductive layer and the insulating layer, at the positions where both stripe electrodes cross. After the radiation image information is recorded in the solid state radiation detector, it is scanned with laser light (reading light) to read out the latent image charges stored in the charge storage portion from the solid state radiation detector. In this way the radiation image information is read out from the detector.
In the method as described in the above-mentioned Japanese Unexamined Patent Publication No. 9(1997)-5906, a solid state radiation detector, in which a trapping layer (first electrode layer), a reading photoconductive layer (recording photoconductive layer), and a second electrode layer (charge storage portion) are stacked in the recited order, is used as an image detector. With high voltage applied between electrodes disposed on both sides of the detector, uniform exposure light is irradiated to cause primary charging in the charge storage portion of the detector. Thereafter,both electrodes are short-circuited, or given high voltage, or made open circuit. With an electric field generated in the recording photoconductive layer, X-rays transmitted through a subject are irradiated to store latent image charge in the charge storage portion. After the radiation image information is recorded in the solid stage radiation detector, both electrodes are short-circuited. The solid stage radiation detector is scanned with laser light (reading light) to read out the latent image charge stored in the charge storage portion from the solid stage radiation detector. Thus, the radiation image information is read out from the detector.
However, method as described in the above-mentioned Japanese Unexamined Patent Publication No. 6(1994)-217322 has the disadvantage that the image detector is structurally complicated and the fabrication cost becomes high, because TFTs for reading electric charge are provided within the electrode layer equipped with micro plates.
In addition, the method as described in the above-mentioned U.S. Pat. No. 4,857,723 is a method in which the solid state radiation is structurally simple and the fabrication cost is low, but requires a structurally complicated expensive layer scanning system for reading out the latent image charge stored within the detector. Because of this, the method has the disadvantage that the reader is structurally complicated and the cost of the entire system from recording to reading becomes high.
Furthermore, the method as described in the abovementioned Japanese Unexamined Patent Publication No. 9(1997)-5906, in addition to the disadvantage found in the method described in the above-mentioned U.S. Pat. No. 4,857,723, requires a light source for causing primary charging in the charge storage portion of the detector, so it has the disadvantage that the detector is further increased in scale and the system costs become even higher.
SUMMARY OF THE INVENTION
It is the primary object of the present invention to provide an image detector, a recording method and a recorder for recording radiation image information in the image detector, and a reading method and a reader for reading out radiation image information from the image detector recorded with the radiation image information, which are capable of making its structure simple without using a thin film transistor, also reducing the fabrication cost, and making a simple read operation possible without using a light source for primary charging, or reading.
In accordance with the present invention, there is provided an image detector, which has a charge storage portion for storing an electric charge with a quantity corresponding to the quantity of a recording electromagnetic wave irradiated, for recording image information on the charge storage portion as an electrostatic latent image, the image detector comprising:
a first electrode layer with a first stripe electrode including a large number of line electrodes;
a photoconductive layer which exhibits photoconductivity when irradiated with the recording electromagnetic wave, and/or with light, emitted by excitation of the electromagnetic wave, which has a wavelength differing from the wavelength of the electromagnetic wave;
a rectifying layer; and
a second electrode layer with a second stripe electrode including a large number of line electrodes formed so as to cross the line electrodes of the first stripe electrode;
wherein the first electrode, the photoconductive layer, the charge storage portion, the rectifying layer, and the second electrode layer are stacked in the recited order.
The aforementioned recording electromagnetic wave refers to an electromagnetic wave incident on the detector. The electromagnetic wave will be sufficient if it
Epps Georgia
Fuji Photo Film Co. , Ltd.
Hanig Richard
Sughrue & Mion, PLLC
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