Radiation image read-out method and apparatus Number:6,806,486 from the United States Patent and Trademark Office (PTO) owispatent Stimulating rays produced by a line light source are linearly irradiated onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation. Light emitted from the exposed linear area of the sheet is received with a line sensor comprising photoelectric conversion devices arrayed along each of a length direction of the linear area of the stimulable phosphor sheet and a direction normal to the length direction. The sheet is moved 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 sheet. Operation processing is performed on outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the sheet.<H apparatus, Radiation, Radiation, image, 6806486.html, Patent, pto, 6806486

Title: Radiation image read-out method and apparatus

Abstract: Stimulating rays produced by a line light source are linearly irradiated onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation. Light emitted from the exposed linear area of the sheet is received with a line sensor comprising photoelectric conversion devices arrayed along each of a length direction of the linear area of the stimulable phosphor sheet and a direction normal to the length direction. The sheet is moved 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 sheet. Operation processing is performed on outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the sheet.

Patent Number: 6,806,486 Issued on 10/19/2004 to Isoda, et al.

Inventors: Isoda; Yuji (Kanagawa-ken, JP); Nishihata; Sumihiro (Kanagawa-ken, JP); Arakawa; Satoshi (Kanagawa-ken, JP); Takahashi; Kenji (Kanagawa-ken, JP); Miyagawa; Ichirou (Kanagawa-ken, JP); Kohda; Katsuhiro (Kanagawa-ken, JP)
Assignee: Fuji Photo Film Co., Ltd. (Kanagawa, JP)

Appl. No.: 09/885,069

Filed: June 21, 2001

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
329320	Jun., 1999	6326636

Foreign Application Priority Data


Jun 10, 1998 [JP]			10-162311
Jun 12, 1998 [JP]			10-164572
Jun 15, 1998 [JP]			10-167012
Jun 22, 1998 [JP]			10-174521
Jul 13, 1998 [JP]			10-197408
Jul 24, 1998 [JP]			10-209479
Mar 29, 1999 [JP]			11-087285
Mar 29, 1999 [JP]			11-087286

Current U.S. Class: 250/586 ; 250/584; 250/585

Field of Search: 250/586,584,585,484.4 313/504

References Cited [Referenced By]

U.S. Patent Documents


4535238	August 1985	Takahashi et al.
4752557	June 1988	Tsuchino et al.
4767927	August 1988	Ohyama et al.
4816679	March 1989	Sunagawa et al.
4831626	May 1989	Watanabe et al.
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4914294	April 1990	Fukai et al.
4922103	May 1990	Kawajiri et al.
5028783	July 1991	Arakawa
5038037	August 1991	Saotome
5371377	December 1994	Struye et al.
5427858	June 1995	Nakamura et al.
5483081	January 1996	Hosoi
5591982	January 1997	Kohda
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5661306	August 1997	Arakawa
5747825	May 1998	Gilblom et al.
5877508	March 1999	Arakawa et al.
5880476	March 1999	Suzuki
5949532	September 1999	Schrof et al.
5965897	October 1999	Elkind et al.
6072855	June 2000	Arakawa
6075250	June 2000	Fukui et al.
6204495	March 2001	Iwabuchi
6239448	May 2001	Kawai
6310357	October 2001	Fuchs et al.
6313477	November 2001	Yasuda et al.
6392249	May 2002	Struye et al.

Foreign Patent Documents


62-36599	Feb., 1987	JP
1-101540	Apr., 1989	JP
2-129600	May., 1990	JP

Primary Examiner: Bruce; David V.
Assistant Examiner: Kiknadze; Irakli
Attorney, Agent or Firm: Sughrue Mion, PLLC

Parent Case Text

This is a divisional of application Ser. No. 09/329,320 filed Jun. 10, 1999, U.S. Pat. No. 6,326,636 B1, the disclosure of which is incorporated herein by reference.

Claims

What is claimed is:

1. 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 a front 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 front surface of the stimulable phosphor sheet exposed to the linear stimulating rays, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of said linear area of the stimulable phosphor sheet, the received light being subjected to photoelectric conversion performed by said line sensor, iii) moving the stimulable phosphor sheet with respect to said line light source and said line sensor and in a direction different from a length direction of said linear area of the stimulable phosphor sheet, and iv) successively reading outputs of said photoelectric conversion devices of said line sensor in accordance with said movement, wherein said line light source is constituted of an organic EL device.

2. The method of claim 1, further comprising the step of monitoring an intensity of the stimulating rays emitted from the organic EL device.

3. The method of claim 2, further comprising the step of modulating the emission intensity of the organic EL device in accordance with a result of the monitoring step.

4. The method of claim 3, wherein the modulating step is performed such that the emission intensity of the organic EL device becomes equal to a predetermined value.

5. The method of claim 1, further comprising reflecting the stimulating rays toward a surface of the stimulable phosphor sheet with a mirror, and wherein light emitted from the stimulable phosphor sheet is transmitted through the mirror to provide optical path overlap between emitted light and light output from the light source.

6. The method of claim 1, wherein the stimulable phosphor sheet is permeable to the emitted light and the emitted light is received from the front surface of the the stimulable phosphor sheet and a back surface of the stimulable phosphor sheet.

7. The method of claim 1, wherein the organic EL device comprises a white light emitting device and a red color filter.

8. The method of claim 1, wherein the organic EL device produces stimulating light rays having a line width of approximately 100 micrometers.

9. A radiation image read-out method, comprising the steps of: i) irradiating stimulating rays, which have been produced by a surface light source, onto a front 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 area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays, with an area sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by said area sensor, and iii) reading outputs of said photoelectric conversion devices constituting said area sensor, wherein said surface light source is constituted of an organic EL device.

10. The method of claim 9, further comprising the step of monitoring an intensity of the stimulating rays emitted from the organic EL device.

11. The method of claim 10, further comprising the step of modulating the emission intensity of the organic EL device in accordance with a result of the monitoring step.

12. The method of claim 11, wherein the modulating step is performed such that the emission intensity of the organic EL device becomes equal to a predetermined value.

13. The method of claim 9, further comprising reflecting the stimulating rays toward a surface of the stimulable phosphor sheet with a mirror, and wherein light emitted from the stimulable phosphor sheet is transmitted through the mirror to provide optical path overlap between emitted light and light output from the light source.

14. The method of claim 9, wherein the stimulable phosphor sheet is permeable to the emitted light and the emitted light is received from the front surface of the the stimulable phosphor sheet and a back surface of the stimulable phosphor sheet.

15. The method of claim 9, wherein the organic EL device comprises a white light emitting device and a red color filter.

16. The method of claim 9, wherein the organic EL device produces stimulating light rays having a line width of approximately 100 micrometers.

17. A radiation image read-out apparatus, comprising: i) a line light source for linearly irradiating stimulating rays onto an area of a front 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) a line sensor for receiving light, which is emitted from the linear area of the front surface of the stimulable phosphor sheet exposed to the linear stimulating rays, and performing photoelectric conversion of the received light, said line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of said linear area of the stimulable phosphor sheet, iii) scanning means for moving the stimulable phosphor sheet with respect to said line light source and said line sensor and in a direction different from a length direction of said linear area of the stimulable phosphor sheet, and iv) reading means for successively reading outputs of said photoelectric conversion devices of said line sensor in accordance with said movement, wherein said line light source is constituted of an organic EL device.

18. The apparatus of claim 17, further comprising a monitoring means for monitoring an intensity of the stimulating rays emitted from the organic EL device.

19. The apparatus of claim 18, further comprising a modulating means for modulating the emission intensity of the organic EL device in accordance with the monitored intensity.

20. The apparatus of claim 19, wherein the emission intensity of the organic EL device is modulated to be equal to a predetermined value.

21. The apparatus of claim 17, further comprising a mirror disposed to direct light from the line light source to a surface of the stimulable phosphor sheet, said mirror transmitting light emitted from the stimulable phosphor sheet, said mirror causing at least partial optical path overlap of the emitted light and light from the light source.

22. The apparatus of claim 17, wherein the stimulable phosphor sheet is permeable to the emitted light and the emitted light is received from the front surface of the the stimulable phosphor sheet and a back surface of the stimulable phosphor sheet.

23. The apparatus of claim 17, wherein the organic EL device comprises a white light emitting device and a red color filter.

24. The apparatus of claim 17, wherein the organic EL device produces stimulating light rays having a line width of approximately 100 micrometers.

25. A radiation image read-out apparatus, comprising: i) a surface light source for irradiating stimulating rays onto a front 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) an area sensor for receiving light, which is emitted from the area of the front surface of the stimulable phosphor sheet exposed to the stimulating rays, and performing photoelectric conversion of the received light, said area sensor comprising a plurality of arrayed photoelectric conversion devices, and iii) reading means for reading outputs of said photoelectric conversion devices constituting said area sensor, wherein said surface light source is constituted of an organic EL device.

26. The apparatus of claim 25, further comprising a monitoring means for monitoring an intensity of the stimulating rays emitted from the organic EL device.

27. The apparatus of claim 26, further comprising a modulating means for modulating the emission intensity of the organic EL device in accordance with the monitored intensity.

28. The apparatus of claim 27, wherein the emission intensity of the organic EL device is modulated to be equal to a predetermined value.

29. The apparatus of claim 25, further comprising a mirror disposed to direct light from the surface light source to a surface of the stimulable phosphor sheet, said mirror transmitting light emitted from the stimulable phosphor sheet, said mirror causing at least partial optical path overlap of the emitted light and light from the light source.

30. The apparatus of claim 25, wherein the stimulable phosphor sheet is permeable to the emitted light and the emitted light is received from the front surface of the the stimulable phosphor sheet and a back surface of the stimulable phosphor sheet.

31. The apparatus of claim 25, wherein the organic EL device comprises a white light emitting device and a red color filter.

32. The apparatus of claim 25, wherein the organic EL device produces stimulating light rays having a line width of approximately 100 micrometers.

Description

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 or an area 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, 60(1985)-236354, and 1(1989)-101540. 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 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.

FIGS. 6A, 6B, and 6C are explanatory views showing relationship between a line width of light emitted by a stimulable phosphor sheet and a photoelectric conversion device constituting a conventional line sensor. In FIG. 6A, a beam width (a line width) of light M emitted linearly (i.e., in a linear pattern extending along a direction normal to the plane of the sheet of FIG. 6A) by a stimulable phosphor sheet 50 is represented by d.sub.M. FIGS. 6B and 6C show the distribution of the intensity of the emitted light M along the line width direction. As illustrated in FIG. 6B, in cases where the emitted light M is collected by a line sensor, in which a light receiving width d.sub.P of each photoelectric conversion device is smaller than the line width d.sub.M, the light collecting efficiency cannot be kept high. Also, as illustrated in FIG. 6C, in cases where the emitted light M is collected by a line sensor, in which the light receiving width d.sub.P of each photoelectric conversion device is approximately equal to the line width d.sub.M, the light collecting efficiency can be kept high. However, in such cases, since the size of each pixel is large, the problems occur in that the resolution cannot be kept high. (The same problems occur also when each photoelectric conversion device has a rectangular shape such that the length along the line width direction may be larger than the length in the direction along which the line extends.)

The emitted light M has the intensity distribution shown in FIGS. 6B and 6C since the line width of the stimulating rays L becomes large before impinging upon the stimulable phosphor sheet 50, since, as illustrated in FIGS. 3A and 3B, the stimulating rays L of a line width d.sub.L (<d.sub.M) having entered into the stimulable phosphor sheet 50 are scattered in the stimulable phosphor sheet 50, and since the emitted light M having occurred in the stimulable phosphor sheet 50 is scattered in the stimulable phosphor sheet 50 before being radiated out of the surface of the stimulable phosphor sheet 50.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a radiation image read-out method, wherein desired resolution is obtained and the efficiency, with which light emitted by a stimulable phosphor sheet is collected by a line sensor, is kept high.

Another object of the present invention is to provide a radiation image read-out method, wherein directivity of stimulating rays radiated out of a line light source is kept high, the intensity of the radiated stimulating rays is kept high, and an image having a high signal-to-noise ratio is thereby obtained.

A further object of the present invention is to provide a radiation image read-out method, which enables a radiation image read-out apparatus to be formed in a smaller outer shape than that of a conventional radiation image read-out apparatus.

A still further object of the present invention is to provide a radiation image read-out method, wherein a line light source and a line sensor are utilized and an image signal appropriate for reproduction of a visible radiation image having a high signal-to-noise ratio is capable of being obtained.

Another object of the present invention is to provide a radiation image read-out method, wherein a line light source and a line sensor are utilized and image signals for energy subtraction processing are capable of being obtained easily.

A further object of the present invention is to provide a radiation image read-out method, wherein light emitted by a stimulable phosphor sheet is detected quickly and accurately as with a photomultiplier, the efficiency with which the weak emitted light is utilized is enhanced, and an image signal appropriate for reproduction of a visible radiation image having a high signal-to-noise ratio is capable of being obtained.

The specific object of the present invention is to provide apparatuses for carrying out the radiation image read-out methods.

A first radiation image read-out method in accordance with the present invention is characterized by detecting light, which is emitted from a linear area of a stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along two-dimensional directions, performing operation processing on outputs of the photoelectric conversion devices, which outputs have been obtained at respective scanning positions and correspond to an identical site on the stimulable phosphor sheet, and thereby enhancing a light collecting efficiency.

Specifically, the present invention provides a first 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 a front 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 front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of photoelectric conversion devices arrayed along each of a length direction (i.e., a major axis direction) of the linear area of the stimulable phosphor sheet and a direction (i.e., a minor axis direction) normal to the length direction, the received light being subjected to photoelectric conversion performed by the line sensor,

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,

iv) successively reading outputs of the line sensor in accordance with the movement, and

v) performing operation processing on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet.

As the line sensor, an amorphous silicon sensor, a charge coupled device (CCD) image sensor, a CCD image sensor with back illuminator, a metal oxide semiconductor (MOS) image sensor, or the like, may be employed. The line sensor may comprise a plurality of sensor chips (CCD image sensor chips, MOS image sensor chips, or the like) arrayed in a straight line or in a zigzag pattern along the length direction of the linear area of the stimulable phosphor sheet. Each of the sensor chips may comprise a plurality of photoelectric conversion devices arrayed in two-dimensional directions and in a matrix-like pattern or in a zigzag pattern.

In the first radiation image read-out method in accordance with the present invention, as the line light source, a fluorescent lamp, a cold cathode fluorescent lamp, a light emitting diode (LED) array, or the like, may be employed. The line light source is not limited to a light source having a linear shape as in the fluorescent lamp and may be one of various other light sources, such as broad area lasers (e.g., a broad area semiconductor laser) and electroluminescence (EL) devices, which irradiate one-dimensional stimulating rays onto the surface of the stimulable phosphor sheet. The LED array or the broad area laser should preferably be employed as the line light source, and a cylindrical lens, or the like, for suppressing spread of the stimulating rays to the direction (i.e., the minor axis direction), which is normal to the length direction (i.e., the major axis direction) of the line of the stimulating rays, such that the stimulating rays having been radiated out of the light source may take on the form of the linear stimulating rays on the surface of the stimulable phosphor sheet.

The stimulating rays may be radiated continuously out of the line light source or may be pulsed stimulating rays radiated intermittently out of the line light source. From the point of view of reducing noise, the stimulating rays should preferably be pulsed stimulating rays having high intensity.

The length of the irradiation region of the stimulating rays, which have been radiated out of the line light source, on the stimulable phosphor sheet, the length being taken along the major axis direction, should preferably be equal to or longer than the length of one side of an effective image storing region of the stimulable phosphor sheet. In cases where the length of the irradiation region of the stimulating rays on the stimulable phosphor sheet is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the stimulating rays may be irradiated from an oblique angle with respect to the side of the effective image storing region of the stimulable phosphor sheet.

In order for the degree of convergence of the stimulating rays, which have been radiated out of the line light source, on the stimulable phosphor sheet to be enhanced, the aforesaid cylindrical lens, a slit, a SELFOC lens (rod lens) array, a fluorescent light guiding sheet, an optical fiber bundle, or the like, or a combination of two or more of the above-enumerated elements should preferably be located between the line light source and the stimulable phosphor sheet. In cases where the optimum secondary stimulation wavelength for the stimulable phosphor sheet is approximately 600 nm, the fluorescent light guiding sheet should preferably contain Eu.sup.3+ (luminescence center) as an activator of a fluorescent substance and should preferably be constituted of a glass or polymeric medium.

The beam width of the stimulating rays, which have been radiated out of the line light source, on the stimulable phosphor sheet should preferably fall within the range of 10 .mu.m to 4,000 .mu.m.

In order for the degree of convergence of the light, which is emitted from respective areas of the stimulable phosphor sheet, on the line sensor to be enhanced, a distributed index lens array, such as a SELFOC lens array or a rod lens array, constituted of an image forming system in which an object surface and an image surface correspond to each other in one-to-one relationship, a cylindrical lens, a slit, an optical fiber bundle, or the like, or a combination of two or more of the above-enumerated elements should preferably be located between the stimulable phosphor sheet and the line sensor.

A stimulating ray cut-off filter (a sharp cut-off filter or a band-pass filter) for transmitting only the light emitted by the stimulable phosphor sheet and filtering out the stimulating rays should preferably be located in the optical path of the emitted light between the stimulable phosphor sheet and the line sensor. In this manner, the stimulating rays should preferably be prevented from impinging upon the line sensor.

The size of a light receiving surface of each of the photoelectric conversion devices constituting the line sensor is set to be smaller than the beam width of the light, which is emitted by the stimulable phosphor sheet exposed to the stimulating rays having the beam width described above, on the light receiving surface of the line sensor. A plurality of the photoelectric conversion devices are arrayed along each of the length direction (i.e., the major axis direction) of the beam of the emitted light and the beam width direction (i.e., the minor axis direction). The length of the entire line sensor is set to be approximately equal to or longer than the length of the beam of the emitted light, and the width of the entire line sensor is set to be approximately equal to the beam width of the emitted light. The plurality of the photoelectric conversion devices may be arrayed in a matrix-like pattern such that they may stand in a straight line along each of the major axis direction and the minor axis direction. Alternatively, the photoelectric conversion devices may be arrayed such that they may stand in a straight line along the major axis direction and in a zigzag pattern along the minor axis direction. As another alternative, the photoelectric conversion devices may be arrayed such that they may stand in a straight line along the minor axis direction and in a zigzag pattern along the major axis direction. As a further alternative, the photoelectric conversion devices may be arrayed such that they may stand in a zigzag pattern along each of the major axis direction and the minor axis direction.

In cases where the line sensor is constituted of a large number of photoelectric conversion devices and there is the risk that adverse effects will occur with respect to a transfer rate, memory devices corresponding to the respective photoelectric conversion devices may be utilized, and an electric charge having been accumulated in each of the photoelectric conversion devices during a charge accumulation period may be stored in the corresponding memory device. In the next charge accumulation period, the electric charge may be read from each memory device. In this manner, the charge accumulation time may be prevented from becoming short due to an increase in the charge transfer time.

The number of the photoelectric conversion devices arrayed in each row along the major axis direction of the line sensor should preferably be at least 1,000. The length of the line sensor, as measured at the light receiving surface, should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet.

As will be understood from the specification, it should be noted that the term "moving a stimulable phosphor sheet with respect to a line light source and a line sensor" as used herein means movement of the stimulable phosphor sheet relative to the line light source and the line sensor, and embraces the cases wherein the stimulable phosphor sheet is moved while the line light source and the line sensor are kept stationary, the cases wherein the line light source and the line sensor are moved while the stimulable phosphor sheet is kept stationary, and the cases wherein both the stimulable phosphor sheet and the line light source and the line sensor are moved. In cases where the line light source and the line sensor are moved, they should be moved together with each other.

The term "position of movement" as used herein means the position at the time at which the photoelectric detection is performed by the line sensor and does not mean the position through which the stimulable phosphor sheet or the line light source and the line sensor pass at any given instant during the movement.

The direction along which the stimulable phosphor sheet is moved with respect to the line light source and the line sensor (i.e., the direction different from the length direction of the exposed linear area of the stimulable phosphor sheet) should preferably be the direction approximately normal to the length direction of the exposed linear area of the stimulable phosphor sheet (i.e., should preferably be the minor axis direction). However, the direction along which the stimulable phosphor sheet is moved with respect to the line light source and the line sensor is not limited to the minor axis direction. For example, in cases where the lengths of the line light source and the line sensor are longer than one side of the stimulable phosphor sheet as described above, the stimulable phosphor sheet may be moved with respect to the line light source and the line sensor along an oblique direction with respect to the direction approximately normal to the length direction of the line light source and the line sensor or along a zigzag movement direction, such that approximately the entire surface of the stimulable phosphor sheet may be uniformly exposed to the stimulating rays.

The line light source and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. In cases where the line light source and the line sensor are located on opposite surface sides of the stimulable phosphor sheet, the substrate of the stimulable phosphor sheet, or the like, should be formed from a material permeable to the emitted light, such that the emitted light may permeate to the surface side of the stimulable phosphor sheet opposite to the surface on the stimulating ray incidence side.

The operation processing may be simple addition processing, weighted addition processing, or one of various other kinds of operation processing. In cases where the simple addition processing or the weighted addition processing is employed, addition means may be utilized as means for performing the operation processing.

Unless otherwise specified, the foregoing explanation of the first radiation image read-out method in accordance with the present invention also applies to various other radiation image read-out methods in accordance with the present invention, which will be described later.

A second radiation image read-out method in accordance with the present invention is characterized by reading out a radiation image, which has been stored on a stimulable phosphor sheet, by irradiating a linear laser beam, which has been radiated out of a broad area laser, onto the stimulable phosphor sheet.

Specifically, the present invention also provides a second 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 a front 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 front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front surface of the stimulable phosphor sheet, with a line sensor comprising a plurality of arrayed photoelectric conversion devices, the received light being subjected to photoelectric conversion performed by the line sensor,

iii) moving the stimulable phosphor sheet with respect to the line light source and the line sensor and in a direction different from a length direction of the linear area of the stimulable phosphor sheet, and

iv) successively reading outputs of the photoelectric conversion devices of the line sensor in accordance with the movement,

wherein the line light source is a broad area laser, which linearly radiates out the stimulating rays.

In the second radiation image read-out method in accordance with the present invention, the laser beam (i.e., the stimulating rays) may be radiated continuously out of the broad area laser or may be a pulsed beam radiated intermittently out of the broad area laser. From the point of view of reducing noise, the laser beam should preferably be a pulsed beam having high intensity. The wavelength of the laser beam produced by the broad area laser may fall within the range of 600 nm to 1,000 nm and should preferably fall within the range of 600 nm to 700 nm.

The length of the irradiation region of the laser beam, which has been radiated out of the broad area laser, on the stimulable phosphor sheet, the length being taken along the major axis direction, should preferably be equal to or longer than the length of one side of the effective image storing region of the stimulable phosphor sheet. In cases where the length of the irradiation region of the laser beam on the stimulable phosphor sheet is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the laser beam may be irradiated from an oblique angle with respect to the side of the effective image storing region of the stimulable phosphor sheet.

The term "broad area laser" as used herein means the laser which produces the laser beam in the linear pattern. The broad area laser should preferably be a broad area semiconductor laser constituted such that the length of the active layer along the major axis direction may fall within the range of 50 .mu.m to 1,000 .mu.m and the length of the active layer along the minor axis direction may fall within the range of 0.1 .mu.m to 10 .mu.m. However, the broad area laser employed in the second radiation image read-out method in accordance with the present invention is not limited to the broad area semiconductor laser and may be one of various other lasers which produces the laser beam in the linear pattern.

The line sensor employed in the second radiation image read-out method in accordance with the present invention may comprise the plurality of the photoelectric conversion devices arrayed along only the length direction (i.e., the major axis direction). Alternatively, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction and the minor axis direction, which is normal to the major axis direction.

In the second radiation image read-out method in accordance with the present invention, as in the first radiation image read-out method in accordance with the present invention, the line sensor may comprise the plurality of the photoelectric conversion devices arrayed along each of the major axis direction of the linear area of the stimulable phosphor sheet and the minor axis direction normal to the major axis direction, and the operation processing may be performed on the outputs of the photoelectric conversion devices, which outputs have been obtained at respective positions of movement and correspond to an identical site on the stimulable phosphor sheet. In such cases, if the beam width of the light emitted by the stimulable phosphor sheet is larger than the width of each photoelectric conversion device, the line sensor as a whole can receive the emitted light over approximately the entire beam width. The operation processing, such as addition processing, is performed on the outputs of the photoelectric conversion devices, which outputs correspond to an identical site on the stimulable phosphor sheet. In this manner, the light receiving efficiency can be enhanced.

The number of the photoelectric conversion devices arrayed along the major axis direction of the line sensor should preferably be at least 1,000. The length of the line sensor, as measured at the light receiving surface, should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. In cases where the length of the light receiving surface of the line sensor is longer than the length of one side of the effective image storing region of the stimulable phosphor sheet, the line sensor may be located obliquely with respect to the side of the effective image storing region of the stimulable phosphor sheet.

The broad area laser and the line sensor may be located on the same surface side of the stimulable phosphor sheet or on opposite surface sides of the stimulable phosphor sheet. In cases where the broad are a laser and the line sensor are located on opposite surface sides of the stimulable phosphor sheet, the substrate of the stimulable phosphor sheet, or the like, should be formed from a material permeable to the emitted light, such that the emitted light may permeate to the surface side of the stimulable phosphor sheet opposite to the surface on the stimulating ray incidence side.

The stimulating rays irradiated to the stimulable phosphor sheet should preferably have an intensity falling within a range such that the power may not vary. In cases where the stimulating rays has an intensity falling within a range such that the power may vary, the intensity of the stimulating rays may be monitored with a monitoring means. When variation in power occurs, the broad area laser may be modulated with broad area laser modulating means more quickly than the photoelectric conversion speed of the photoelectric conversion devices such that the power of the broad area laser may become equal to a predetermined value. In this manner, adverse effects of power variation may be suppressed.

Third and fourth radiation image read-out methods in accordance with the present invention are characterized by overlapping part of an optical path of stimulating rays from a line light source to a stimulable phosphor sheet and part of an optical path of emitted light from the stimulable phosphor sheet to a line sensor, thereby reducing the space occupied by the optical paths and reducing the size of an entire radiation image read-out apparatus.

Specifically, the present invention further provides a third radiation image read-out method, comprising the steps of:

i) linearly radiating stimulating rays, which have been produced by a line light source,

ii) guiding the linear stimulating rays to an area of a stimulable phosphor sheet, on which a radiation image has been stored, with stimulating ray guiding means, 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,

iii) guiding light, which is emitted from the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, with emitted light guiding means to a line sensor comprising a plurality of photoelectric conversion devices arrayed along a length direction of the linear area of the stimulable phosphor sheet,

iv) receiving the emitted light with the line sensor, the received light being subjected to photoelectric conversion performed by the line sensor,

v) 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, and

vi) successively reading outputs of the line sensor in accordance with the movement,

wherein at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.

The term "overlapping of optical paths" as used herein means that the center point of the stimulating rays and the center point of the emitted light overlap each other.

The overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.

As the stimulating ray guiding means, the aforesaid cylindrical lens, the slit, the SELFOC lens (rod lens) array, the aforesaid fluorescent light guiding sheet, the optical fiber bundle, a hot mirror, a cold mirror, or the like, or a combination of two or more of the above-enumerated elements may be employed.

The hot mirror is a dichroic mirror having been set so as to reflect the stimulating rays and to transmit the light emitted by the stimulable phosphor sheet. The cold mirror is a dichroic mirror having been set so as to transmit the stimulating rays and to reflect the light emitted by the stimulable phosphor sheet.

As the emitted light guiding means, the distributed index lens array, such as the SELFOC lens array or the rod lens array, constituted of an image forming system in which an object surface and an image surface correspond to each other in one-to-one relationship, the cylindrical lens, the slit, the optical fiber bundle; the hot mirror, the cold mirror, or the like, or a combination of two or more of the above-enumerated elements may be employed.

The stimulating ray cut-off filter (the sharp cut-off filter or the band-pass filter) for transmitting only the light emitted by the stimulable phosphor sheet and filtering out the stimulating rays should preferably be located in the optical path of the emitted light between the stimulable phosphor sheet and the line sensor and at a position that does not overlap the optical path of the stimulating rays. In this manner, the stimulating rays should preferably be prevented from impinging upon the line sensor.

The size of a light receiving surface of each of the photoelectric conversion devices constituting the line sensor should preferably fall within the range of 10 .mu.m to 4,000 .mu.m, and should more preferably fall within the range of 100 .mu.m to 500 .mu.m. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000. The length of the line sensor should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. The plurality of the photoelectric conversion devices may be arrayed in a straight line or in a zigzag pattern along the major axis direction.

In the third radiation image read-out method in accordance with the present invention, the line light source and the line sensor are located on the same surface side of the stimulable phosphor sheet.

The foregoing explanation of the third radiation image read-out method in accordance with the present invention also applies to a fourth radiation image read-out method in accordance with the present invention, which is described below.

As in the first radiation image read-out method in accordance with the present invention, the fourth radiation image read-out method in accordance with the present invention is characterized by utilizing a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along two-dimensional directions, in lieu of the line sensor employed in the third radiation image read-out method in accordance with the present invention, detecting light, which is emitted from a linear area of a stimulable phosphor sheet, with the line sensor, performing operation processing, such as addition, on outputs of the photoelectric conversion devices, which outputs have been obtained at respective scanning positions and correspond to an identical site on the stimulable phosphor sheet, and thereby enhancing a light collecting efficiency.

Specifically, in the fourth radiation image read-out method in accordance With the present invention, the first radiation image read-out method in accordance with the present invention is modified such that the linear stimulating rays are guided with stimulating ray guiding means to the area of the stimulable phosphor sheet, the light, which is emitted from the linear area of the stimulable phosphor sheet, is guided with emitted light guiding means to the line sensor, and at least part of an optical path of the stimulating rays from the line light source to the stimulable phosphor sheet and at least part of an optical path of the emitted light from the stimulable phosphor sheet to the line sensor overlap each other.

The overlapping of at least part of the optical path of the stimulating rays and at least part of the optical path of the emitted light should preferably be achieved by utilizing at least part of optical elements, which constitute the stimulating ray guiding means, and at least part of optical elements, which constitute the emitted light guiding means, in common with each other.

Fifth and sixth radiation image read-out methods in accordance with the present invention are characterized by utilizing a stimulable phosphor sheet having light emission region partitioned by a stimulating ray reflecting partition member into a plurality of fine cells.

Specifically, the present invention still further provides a fifth 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 a front 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 front surface of the stimulable phosphor sheet exposed to the linear stimulating rays or from a linear area of a back surface of the stimulable phosphor sheet corresponding to the linear area of the front 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,

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, and

iv) successively reading outputs of the line sensor in accordance with the movement,

wherein a light emission region of the stimulable phosphor sheet is partitioned by a stimulating ray reflecting partition member, which extends in a thickness direction of the stimulable phosphor sheet, into a plurality of fine cells.

In the fifth radiation image read-out method in accordance with the present invention, the size of the light receiving surface of each of the photoelectric conversion devices constituting the line sensor should preferably fall within the range of 10 .mu.m to 4,000 .mu.m, and should more preferably fall within the range of 100 .mu.m to 500 .mu.m. The number of the photoelectric conversion devices arrayed along the length direction of the line sensor should preferably be at least 1,000. The length of the line sensor should preferably be longer than or equal to the length of one side of the effective image storing region of the stimulable phosphor sheet. The plurality of the photoelectric conversion devices may be arrayed in a straight line or in a zigzag pattern along the major axis direction.

The stimulable phosphor sheet employed in the fifth radiation image read-out method in accordance with the present invention comprises a substrate and a stimulable phosphor layer overlaid on the substrate. As will be described later with reference to FIG. 17A, the stimulable phosphor layer comprises a stimulable phosphor material, which emits light upon stimulation thereof, and the stimulating ray reflecting partition member, which partitions the stimulable phosphor material into a plurality of fine cells and suppresses scattering of the stimulating rays. As will be described later with reference to FIG. 17B, the stimulable phosphor material other than its front surface is surrounded by the stimulating ray reflecting partition member and the substrate. Alternatively, as will be described later with reference to FIG. 17C, the stimulable phosphor material other than its front surface is surrounded by only the stimulating ray reflecting partition member. The stimulable phosphor sheet may be produced by filling the stimulable phosphor material in the fine cells, which have been defined by only the stimulating ray reflecting partition member or by the stimulating ray reflecting partition member and the substrate.

Each of the stimulable phosphor material and the stimulating ray reflecting partition member should preferably be formed from a binder and a stimulable phosphor dispersed in the binder. The reflectivity of the stimulating ray reflecting partition member with respect to the stimulating rays should be higher than the reflectivity of the stimulable phosphor material with respect to the stimulating rays. For such purposes, by way of example, the binder-to-phosphor ratio (i.e., the B/P ratio) in the stimulable phosphor material may be set to be higher than the B/P ratio in the stimulating ray reflecting partition member. Alternatively, the particle size of the stimulable phosphor in the stimulable phosphor material may be set to be larger than the particle size of the stimulable phosphor in the stimulating ray reflecting partition member.

A coloring agent, such as an ultramarine, may be added to the stimulating ray reflecting partition member. Alternatively, as the stimulable phosphor contained in the stimulating ray reflecting partition member, a stimulable phosphor of a kind different from the stimulable phosphor contained in the stimulable phosphor material may be employed. For example, the stimulable phosphor contained in the stimulating ray reflecting partition member may be an ultraviolet light (UV light) emitting phosphor, which emits UV light capable of effecting primary stimulation of the stimulable phosphor. In cases where the stimulating ray reflecting partition member contains the coloring agent, the term "reflectivity of a stimulating ray reflecting partition member with respect to stimulating rays" as used herein means the reflectivity of the stimulating ray reflecting partition