Radiant energy – Source with recording detector
Reexamination Certificate
2001-04-02
2002-09-24
Hannaher, Constantine (Department: 2878)
Radiant energy
Source with recording detector
C250S591000
Reexamination Certificate
active
06455867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image detector having a recording-side photoconductive layer, a reading-side photoconductive layer, and stripe electrodes. In the image detector, an electrostatic latent image is temporarily recorded by applying recording light to the recording-side photoconductive layer, and the recorded electrostatic latent image is reading out through the stripe electrodes by applying reading light to the reading-side photoconductive layer.
2. Description of the Related Art
Conventionally, various apparatuses such as facsimile apparatuses, copiers, radiographic imaging apparatuses use image detectors. Some radiographic imaging apparatuses designed for medical applications use as an image detector an optical-reading type solid-state radiographic image detector (or an optically readable electrostatic recording medium which records radiographic images), which comprises a photoconductive body (layer) made of a material exhibiting conductivity in response to exposure to radiation such as X rays. For example, the photoconductive body (layer) is a selenium plate. In the above radiographic imaging apparatuses, recording electromagnetic radiation (which may be called recording light) is applied to the solid-state radiographic image detector, so that charges having a polarity (hereinafter called a latent-image polarity), out of the charges (pairs of opposite charges) generated in the photoconductive body (layer) by the exposure to the recording electromagnetic radiation, are stored as latent-image charges in a charge storage region of the solid-state radiographic image detector, and the amount of the latent-image charges stored in each area (corresponding to a pixel) of the charge storage region corresponds to the exposure dose of the recording electromagnetic radiation in the area. Thus, radiographic image information is recorded in the form of a latent image. Thereafter, a reading-side electrode layer of the solid-state radiographic image detector is scanned with reading electromagnetic radiation (which may be called reading light) so that the amount of signal charges corresponding to the latent-image charges recorded in each area of the solid-state radiographic image detector is detected in the form of an electric signal (current). Thus, the recorded radiographic image information is read out. Typically, the above recording electromagnetic radiation is realized by X rays, and the above reading electromagnetic radiation is realized by a laser beam or a line-shaped light band. The above radiographic imaging technique is disclosed in U.S. Pat. No. 5,268,569, International Patent Publication WO-A1-98/59261, and Japanese Unexamined Patent Publication Nos. 9(1997)-5906, 2000-162726, 2000-284056, and 2000-284057. The contents of the above patent publications are incorporated by reference in the present patent application.
In particular, the Japanese Unexamined Patent Publication Nos. 2000-162726, 2000-284056, and 2000-284057 disclose solid-state radiographic image detectors which are constructed by forming a recording-side electrode layer (first electrode layer), a recording-side photoconductive layer, a charge transport layer, a reading-side photoconductive layer, and a reading-side electrode layer (second electrode layer) in this order so that a charge storage region is realized between the recording-side photoconductive layer and the charge transport layer. The recording-side electrode layer (first electrode layer) is transparent to recording light. The recording-side photoconductive layer generates charges and exhibits conductivity when the recording-side photoconductive layer is exposed to the recording light which has passed through the recording-side electrode layer. The charge transport layer behaves as almost an insulator against charge carriers having the latent-image polarity (i.e., the same polarity as the latent-image charges), and behaves as almost a conductor of charge carriers having the opposite polarity to the latent-image polarity (which is hereinafter called a transport polarity). The charges having the transport polarity are called transport charges. The reading-side photoconductive layer generates charges and exhibits conductivity when the reading-side photoconductive layer is exposed to reading light. The reading-side electrode layer (second electrode layer) is transparent to the reading light. When the reading light is applied to the reading-side photoconductive layer through the reading-side electrode layer, the electric signal corresponding to the amount of the latent-image charges stored in each area of the charge storage region is detected through the reading-side electrode layer.
In addition, the Japanese Unexamined Patent Publication Nos. 2000-162726, 2000-284056, and 2000-284057 disclose techniques for detecting the amount of signal charges. According to the disclosed techniques, the reading-side electrode layer includes a striped (or comb) electrode array comprised of a number of linear electrodes which are elongated in the feeding direction in the scanning of the reading-side photoconductive layer with the reading light, and arranged parallel to each other. The linear electrodes are respectively connected to detection amplifiers. The reading light has a cross section of a line shape elongated in the main scanning direction, which is perpendicular to the feeding direction, and is moved in the feeding direction for scanning the entire area of the reading-side photoconductive layer through the reading-side electrode layer. The above technique for detecting the amount of signal charges is called a line-reading-out method.
According to the above line-reading-out method, the amounts of signal charges corresponding to pixels of the reading-side photoconductive layer located on each line in the main scanning direction are concurrently read out. Therefore, the reading speed can be increased. In addition, since the reading-side electrode layer is divided into the linear electrodes, the distributed (load) capacitance of each detection amplifier decreases, and therefore the S/N ratio can be increased. Further, since the positions in which the latent-image charges are stored can be fixed to the positions in which the linear electrodes are arranged, the structural noise can be reduced. That is, the line-reading-out method has various advantages.
Further, the Japanese Unexamined Patent Publication Nos. 2000-284056 and 2000-284057 disclose an image detector in which linear charging electrodes (linear charge-read-out electrodes) are arranged parallel to the linear electrodes constituting the striped electrode array so that the linear charging electrodes can be used in the operation of detecting the amount of the latent-image charges in the form of the electric signal. Hereinafter, the linear electrodes constituting the striped electrode array may be called light-entrance electrodes.
When the linear charging electrodes are arranged as above, additional capacitors are formed between the charge storage region and the respective linear charging electrodes, and it is therefore possible to store the transport charges in the linear charging electrodes by charge rearrangement before reading out the electric signal corresponding to the amount of the latent-image charges, where the transport charges have the opposite polarity to that of the latent-image charges stored in the charge storage region by the recording. Therefore, the amounts of the transport charges distributed to the capacitors which are formed between the charge storage region and the light-entrance electrodes can be decreased by the provision of the linear charging electrodes. Accordingly, the amount of signal charges detected by the image detector can be increased, and thus the readout efficiency can be increased. Further, the above advantage of the provision of the linear charging electrodes and the advantages (e.g., the great responsiveness) of the provision of the striped electrode array can coexist.
Furthermore, when the transmittance of t
Gabor Otilia
Hannaher Constantine
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