Radiant energy – Source with recording detector
Reexamination Certificate
2002-08-13
2004-04-20
Porta, David (Department: 2878)
Radiant energy
Source with recording detector
C250S581000
Reexamination Certificate
active
06724006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid state radiation detector having an electric accumulator for accumulating electric charges, in an amount corresponding to either a dosage of irradiated radiation or luminous energy of light emitted by excitation of the radiation, as electric charges for a latent image.
2. Description of the Related Art
Presently, in the field of radiography for the purpose of medical diagnosis or the like, there are proposed various radiation image recording and retrieving apparatuses, each of which uses a solid state radiation detector (hereinafter simply referred to as a detector) provided with an electrostatic recording medium. The electrostatic recording medium accumulates electric charges obtained by detecting radiation in an electric accumulator as electric charges for a latent image, and the electric charges for a latent image thus accumulated are outputted after being converted into electric signals to represent radiation image information. Although various types of solid state radiation detectors for use in such apparatuses have been disclosed, a typical example is a detector adopting an optical readout mode for retrieving the accumulated electric charges by irradiating retrieving light (an electromagnetic wave for retrieval) onto the detector. Such a mode is adopted in terms of an electric-charge readout process for reading the accumulated electric charges outward.
In Japanese Unexamined Patent Publication Nos. 2000-105297, 2000-284056 and 2000-284057, there are disclosed solid state radiation detectors of an optical readout type, which is capable of striking a balance between a high-speed response upon readout and efficient retrieval of signal electric charges. The above-mentioned solid state radiation detectors refer to an electrostatic recording medium formed by stacking a first electrode having transmissivity with respect to light emitted by radiation for recording or by excitation of the radiation (such light will be hereinafter referred to as recording light); a recording photoconductive layer which takes on conductivity by receiving the recording light; a charge transport layer acting substantially as an insulator with respect to electric charges of the same polarity as the electric charges to be charged on the first electrode and acting substantially as a conductor with respect to electric charges of the reverse polarity to the electric charges of the same polarity; a retrieving photoconductive layer which takes on conductivity by receiving irradiation of retrieving light (an electromagnetic wave for retrieval); and a second electrode having transmissivity with respect to the retrieving light in the order described above, in which signal electric charges (electric charges for a latent image) carrying image information are accumulated in an electric accumulator formed on an interface between the recording photoconductive layer and the charge transport layer.
Moreover, especially in the above-mentioned Japanese Unexamined Patent Publication Nos. 2000-284056 and 2000-284057, there are disclosed electrostatic recording mediums, in which the second electrode having transmissivity with respect to the retrieving light is formed as a stripe electrode including multiple photoelectric charge pair generating line electrodes having transmissivity with respect to the retrieving light, and multiple photoelectric charge pair non-generating line electrodes are provided alternately with and mutually parallel to the photoelectric charge pair generating line electrodes in order to output electric signals at a level corresponding to an amount of the electric charges for a latent image being accumulated in the electric accumulator.
By providing the second electrode with a sub stripe electrode composed of the multiple photoelectric charge pair non-generating line electrodes as described above, a new capacitor is formed between the electric accumulator and the sub stripe electrode, whereby transported charges of the reverse polarity from the electric charges for a latent image accumulated in the electric accumulator by the recording light can be also charged on the sub stripe electrode owing to rearrangement of electric charges upon retrieval. In this way, it is possible to reduce an amount of the transported charges to be distributed to a capacitor formed between the stripe electrode and the electric accumulator via the retrieving photoconductive layer, so that it is relatively smaller as compared to a case where the sub stripe electrode is not provided. As a result, it is made possible to enhance retrieving efficiency by means of increasing an amount of signal electric charges extractable out of the detector, and to strike a balance between a high-speed response upon readout and efficient retrieval of the signal electric charges.
Incidentally, various modes have been disclosed for enhancing an S/N ratio of a detected signal in the electrostatic recording medium provided with the above-described sub stripe electrode.
For example, the amount of signal electric charges extractable outward is increased and the retrieval efficiency is thereby enhanced if the amount of the transported charges to be distributed to the capacitor formed between the sub stripe electrode and the electric accumulator via the retrieving photoconductive layer is larger than the amount of the transported charges to be distributed to the capacitor formed between the stripe electrode and the electric accumulator via the retrieving photoconductive layer. Accordingly, by setting a pair of a photoelectric charge pair generating line electrode and a photoelectric charge pair non-generating line electrode is defined as one cycle, there are disclosed various modes for enhancing the retrieving efficiency and thereby enhancing the S/N ratio, such as a mode of optimizing such a cycle or a mode of optimizing a ratio between a width of the photoelectric charge pair generating line electrode and a width of the photoelectric charge pair non-generating line electrode. However, further enhancement in the S/N ratio is still desired.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the foregoing circumstances. It is an object of the present invention to provide a solid state radiation detector including an electrostatic recording medium provided with a sub stripe electrode, which is capable of further enhancing an S/N ratio thereof.
A solid state radiation detector according to the present invention concerns a solid state radiation detector including an electrostatic recording medium formed by serially stacking a first electrode having transmissivity with respect to recording light, a recording photoconductive layer which takes on conductivity by receiving irradiation of the recording light, an electric accumulator for accumulating electric charges in an amount corresponding to luminous energy of the recording light as electric charges for a latent image, a retrieving photoconductive layer which takes on conductivity by receiving irradiation of retrieving light, and a second electrode provided with multiple photoelectric charge pair generating line electrodes having transmissivity with respect to the retrieving light and multiple photoelectric charge pair non-generating line electrodes in a manner that the photoelectric charge pair generating line electrodes and the photoelectric charge pair non-generating line electrodes are disposed alternately. Here, the solid state radiation detector includes means for detecting electric currents on the photoelectric charge pair generating line electrodes to be connected to the photoelectric charge pair generating line electrodes, means for detecting electric currents on the photoelectric charge pair non-generating line electrodes to be connected to the photoelectric charge pair non-generating line electrodes, and signal synthesizing means for synthesizing a signal detected by the means for detecting electric currents on the photoelectric charge pair generating line electrodes and a s
Fuji Photo Film Co. , Ltd.
Porta David
Sung Christine
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