Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-05-10
2003-02-04
Kim, Robert H. (Department: 2882)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S484400
Reexamination Certificate
active
06515270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image read-out method and apparatus. This invention particularly relates to a radiation image read-out method and apparatus, wherein light emitted by a stimulable phosphor sheet is detected with a line sensor.
2. Description of the Prior Art
It has been proposed to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a stimulable phosphor sheet, which comprises a substrate and a layer of the stimulable phosphor overlaid on the substrate. Stimulating rays, such as a laser beam, are deflected and caused to scan pixels in the radiation image, which has been stored on the stimulable phosphor sheet, one after another. The stimulating rays cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted successively from the pixels in the radiation image having been stored on the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal by photoelectric read-out means. The stimulable phosphor sheet, from which the image signal has been detected, is then exposed to erasing light, and radiation energy remaining thereon is thereby released.
The image signal, which has been obtained from the radiation image recording and reproducing systems, is then subjected to image processing, such as gradation processing and processing in the frequency domain, such that a visible radiation image, which has good image quality and can serve as an effective tool in, particularly, the efficient and accurate diagnosis of an illness, can be obtained. The image signal having been obtained from the image processing is utilized for reproducing a visible image for diagnosis, or the like, on film or on a high resolution cathode ray tube (CRT) display device. The stimulable phosphor sheet, from which residual radiation energy has been released with the erasing light, can be used again for the recording of a radiation image.
Novel radiation image read-out apparatuses for use in the radiation image recording and reproducing systems described above have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568 and 60(1985)-236354. In the proposed radiation image read-out apparatuses, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, a line light source, such as a fluorescent lamp, a cold cathode fluorescent lamp, or a light emitting diode (LED) array, for irradiating linear stimulating rays onto a stimulable phosphor sheet is utilized as a stimulating ray source, and a line sensor comprising a plurality of photoelectric conversion devices arrayed along the length direction of a linear area of the stimulable phosphor sheet, onto which the stimulating rays are irradiated by the line light source, is utilized as photoelectric read-out means. Also, the proposed radiation image read-out apparatuses comprise scanning means for moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction, which is approximately normal to the length direction of the linear area of the stimulable phosphor sheet.
As for techniques for detecting the light, which is emitted by the stimulable phosphor sheet, with the line sensor, a technique may be considered, in which the emitted light is guided by a cylindrical lens or optical fibers to the line sensor. A technique may also be considered, in which the line sensor is located close to the stimulable phosphor sheet so as to directly receive the emitted light without an optical system intervening between the line sensor and the stimulable phosphor sheet.
However, in cases where the line light source is employed and the emitted light is detected with the line sensor, the light is emitted from the linear area, instead of a point, on the stimulable phosphor sheet. Therefore, in order for an image having high sharpness to be obtained, not only the intensity of the emitted light but also the information concerning the position of light emission must be detected accurately.
Specifically, if the emitted light spreads and impinges upon the line sensor, the light emitted from a single point on the stimulable phosphor sheet will impinge upon a plurality of photoelectric conversion devices constituting the line sensor. Therefore, in such cases, the position, from which the light is emitted, and the intensity of the emitted light cannot be detected accurately. For example, in cases where the light emitted by the stimulable phosphor sheet is guided by a cylindrical lens extending in the length direction of the line sensor, the emitted light is converged with respect to the direction normal to the length direction of the line sensor (i.e., with respect to the direction having a curvature). However, in such cases, the emitted light diverges with respect to the length direction of the line sensor (i.e., with respect to the direction having no curvature). Therefore, a high light collecting efficiency cannot be obtained, and the position from which the light is emitted cannot be detected accurately.
With the technique for guiding the emitted light through optical fibers to the line sensor or the technique for directly receiving the emitted light by the line sensor, the end faces of the optical fibers or the line sensor must be located close to the stimulable phosphor sheet. However, in the image read-out operation, the stimulable phosphor sheet is moved relative to the line sensor. Therefore, it is necessary for a spacing to be left between the line sensor and the stimulable phosphor sheet. The spacing between the line sensor and the stimulable phosphor sheet is markedly larger than the spacing (e.g., approximately 0.1 mm) between adjacent photoelectric conversion devices of the line sensor. Accordingly, as in the cases where the cylindrical lens is employed, a high light collecting efficiency cannot be obtained, and the position from which the light is emitted cannot be detected accurately.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a radiation image read-out method, wherein an intensity of light emitted by a stimulable phosphor sheet and a position from which the light is emitted are capable of being detected with a high light collecting efficiency and a high spatial resolution, and an image having a high sharpness is capable of being formed from information having been obtained from the detection of the emitted light.
Another object of the present invention is to provide an apparatus for carrying out the radiation image read-out method.
The present invention provides a radiation image read-out method, comprising the steps of:
i) linearly irradiating stimulating rays, which have been produced by a line light source, onto an area of one surface of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation,
ii) receiving light, which is emitted from the linear area of the one surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of the other surface of the stimulable phosphor sheet corresponding to the linear area of the one surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet, the received light being subjected to photoelectric conversion performed by the line sensor, and
iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from the length direction of the linear area of the stimulable phosphor sheet,
where
Fuji Photo Film Co. , Ltd.
Kim Robert H.
Song Hoon K.
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