Radiation solid-state detectors, and radiation image...

Radiant energy – Source with recording detector – Including a light beam read-out

Reexamination Certificate

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C250S580000

Reexamination Certificate

active

06770901

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation solid-state detector having a charge storing section which stores charges of a quantity corresponding to the dose of the projected radiation as latent image charges, and a method and device for using the detector to record radiation image information as a static latent image or read out the recorded static latent image.
2. Description of the Prior Art
To reduce the dose of exposure of the subject and improve the performance of diagnosis in medical radiation photographing, etc., a method (for example, U.S. Pat. No. 4,535,468, etc.) has been known up to now which uses, as a photosensitive material, a radiation solid-state detector (a static recorder) with a photoconductor, such as a selenium plate, responding to radiation, such as X-ray; projects the X-ray onto the detector, and stores the charges of the quantity corresponding to the dose of the projected radiation in the charge storing section in the detector for recording of radiation image information as a static latent image; and uses a laser beam or a line light source to scan the detector in which the radiation image information has been recorded, for reading out the radiation image information from the detector.
The method according to the above-mentioned U.S. Pat. No. 4,535,468 uses a three-layer structure detector which has an X-ray photoconductive layer, a charge storing layer (also called an intermediate layer or a trap layer) for storing of charges generated in the X-ray photoconductive layer, and a photoconductive layer for reading in this order, and in recording, applies a high voltage across the electrodes provided on both sides of the three layer structure, and projects X-ray to store latent image charges in the charge storing layer, and then short-circuits the electrodes to read out the latent image charges. With this method, the photoconductive layer for reading in the detector is thinner than the X-ray photoconductive layer in order to increase the reading speed for improving the response.
However, with the method according to the above-mentioned U.S. Pat. No. 4,535,468, the photoconductive layer for reading is thinner than the X-ray photoconductive layer, therefore, a problem results that the quantity of the signal charges detected from the outside is small. Further, the charge mobility is low for both electron and hole, and so, the charge storing layer cannot be thin. This is because increasing the charge mobility decreases the response speed, resulting in a residual image being produced. In other words, with this method, it is difficult to make the high speed response in reading compatible with efficient taking out of signal charge.
On the other hand, in Japanese Patent Application No. 10 (1998)-232824 and Japanese Patent Application No. 10 (1998)-271374, the present applicant has proposed a radiation solid-state detector which allows the high speed response in reading to be compatible with the efficient signal charge taking out, a recording device for recording of radiation image information in this detector, and a method and device for reading out the radiation image information from the detector in which the radiation image information has been recorded as a static latent image.
This method as stated in Japanese Patent Application No. 10 (1998)-232824, etc. uses a radiation solid-state detector provided with a photoconductive layer for recording which exhibits conductivity when irradiated with the radiation for recording or the light emitted by excitation on this radiation, a charge transporting layer which acts almost as an insulator for the latent image charges, while acting roughly as a conductor for transported charges having a polarity opposite to that of the latent image charges, and a photoconductive layer for reading which exhibits conductivity when irradiated with the electromagnetic wave for reading in this order. Radiation for recording is projected onto the photoconductive layer for recording in the detector, and by storing the charges of the quantity corresponding to the dose of the projected radiation in the charge storing section formed roughly at the boundary between the photoconductive layer for recording and the charge transporting layer, radiation image information is recorded as a static latent image. By reading out the static latent image, the radiation image information is provided.
The radiation solid-state detector according to the present invention is a radiation solid-state detector which further improves the detector, etc. as stated in the above-mentioned Japanese Patent Application No. 10 (1998)-232824, and Japanese Patent Application No. 10 (1998)-271374, i.e., a radiation solid-state detector which has a charge storing section for storing charges in a quantity corresponding to the dose of radiation which has been projected, and records radiation image information as a static latent image in the charge storing section,
wherein a first electrode layer having a permeability to radiation for recording or light emitted by excitation on the radiation, a photoconductive layer for recording which exhibits a conductivity when irradiated with the radiation for recording or the light, a photoconductive layer for reading which exhibits a conductivity when irradiated with an electromagnetic wave for reading, and a second electrode layer having a permeability to the electromagnetic wave for reading are provided in this order,
and a first conductive member for outputting an electric signal corresponding to the quantity of the latent image charges stored in the charge storing section formed between the photoconductive layer for recording and the photoconductive layer for reading is provided in the second electrode layer or between the first electrode layer and the second electrode layer.
The first conductive member may have any shape, but, it is preferable that the shape has no effect on the process of latent image forming (transferring and storing of the latent image charges) in recording, or the process of charge-recoupling of the latent image charges with charges opposite in polarity to the latent image charges, i.e., the transported charges. For example, when the first conductive member is provided in the photoconductive layer for recording or on the face of the photoconductive layer for recording which is for the photoconductive layer for reading, the shape is preferably that which will not hinder the latent image charges generated in the photoconductive layer for recording being transferred to the charge storing section. When the first conductive member is provided in the photoconductive layer for reading or in the later-described charge transporting layer or trap layer, the shape is preferably that which will not hinder the transported charges generated in the photoconductive layer for reading being transferred to the charge storing section. For this, it is recommended to take such a measure as providing holes having a desired shape, such as a circle and a square, in correspondence with the pixels, or providing an elongated rectangular hole extending along the direction of the pixel arrangement.
When this first conductive member is disposed in the photoconductive layer for recording, it is preferably permeable to the radiation for recording or the light emitted by excitation at the time of radiation, so that the radiation or the like can sufficiently get into the photoconductive layer for recording, and thus the charge generation process in the photoconductive layer is not affected.
To enhance the response in reading, the smaller the sum of the thickness of the layer forming the charge storing section and that of the photoconductive layer for reading for a given thickness of the photoconductive layer for recording, the better.
The electrode constituting the second electrode layer and/or the first conductive member of the radiation solid-state detector are preferably a stripe electrode comprising a number of linear electrodes.
The term “linear electrode” means an electrode having a long

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