U.S. patent number RE31,847 [Application Number 06/558,394] was granted by the patent office on 1985-03-12 for apparatus and method for producing images corresponding to patterns of high energy radiation.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to George W. Luckey.
United States Patent |
RE31,847 |
Luckey |
March 12, 1985 |
Apparatus and method for producing images corresponding to patterns
of high energy radiation
Abstract
The disclosure relates to an apparatus and method for recording
images on recording mediums which images correspond to high energy
radiation patterns. A temporary storage medium, such as an
infrared-stimulable phosphor or thermoluminescent material, is
exposed to an incident pattern of high energy radiation. A time
interval after exposure, a small area beam of long wave length
radiation or heat scans the screen to release the stored energy as
light. An appropriate sensor receives the light emitted by the
screen and produces electrical energy in accordance with the light
received. The information carried by the electrical energy is
transformed into a recorded image by scanning an information
storage medium with a light beam which is intensity modulated in
accordance with the electrical energy. Although the invention can
be used at any reproduction ratio, it is particularly usable in
recording images representative of large format high energy
patterns onto microfilm.
Inventors: |
Luckey; George W. (Rochester,
NY) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
26982260 |
Appl.
No.: |
06/558,394 |
Filed: |
December 5, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
320028 |
Jan 2, 1973 |
03859527 |
Jan 7, 1975 |
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Current U.S.
Class: |
250/581; 250/337;
250/484.4 |
Current CPC
Class: |
G03B
42/02 (20130101); G01T 1/2014 (20130101); G03C
5/16 (20130101) |
Current International
Class: |
G03B
42/02 (20060101); G01T 1/00 (20060101); G01T
1/29 (20060101); G03C 5/16 (20060101); G03C
005/16 () |
Field of
Search: |
;250/327.2,484.1,337
;378/99,171,58,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"The Reproduction of Colour" by R. W. G. Hunt, pp. 455-464 Fountain
Press, London, 1967. .
"Principles of Color Reproduction" by J.A.C. Yule, pp. 305-327,
John Wiley & Sons, Inc., New York, 1967..
|
Primary Examiner: Smith; Alfred E.
Assistant Examiner: Fields; Carolyn E.
Attorney, Agent or Firm: Husser; John D.
Claims
I claim:
1. An apparatus for producing an image corresponding to .[.a.].
.Iadd.an incident x-ray image .Iaddend.pattern .[.of radiation of a
first wavelength.]., using a medium .[.for.]. releasably storing an
.Iadd.energy .Iaddend.image .Iadd.pattern .Iaddend.representative
of .[.the.]. .Iadd.such incident x-ray image .Iaddend.pattern, said
apparatus comprising:
means for .[.applying a second wavelength of radiation to.].
.Iadd.scanning successive sub-areas of .Iaddend.said image storage
medium .Iadd.with a beam of low energy radiation of a second
wavelength .Iaddend.to cause .[.said.]. .Iadd.respective
.Iaddend.storage medium .Iadd.sub-areas sequentially .Iaddend.to
.[.emit a third wavelength of.]. .Iadd.release the stored energy in
the form of sequential, photoelectrically detectable
.Iaddend.radiation .[.having.]. .Iadd.emissions of a third
wavelength which constitute .Iaddend.an intensity pattern
representative of the stored image;
means for .Iadd.sequentially .Iaddend.sensing the third wavelength
radiation .Iadd.emissions .Iaddend.and for producing .Iadd.an
.Iaddend.electrical .[.energy in accordance therewith.].
.Iadd.signal representative of the incident x-ray image
pattern.Iaddend.; and
means for converting the electrical .[.energy.]. .Iadd.signal
.Iaddend.into an image corresponding to the .[.pattern of first
wavelength radiation.]. .Iadd.x-ray image. .Iaddend.
2. The invention of claim 1 wherein said converting means comprises
means for recording an image smaller than the .Iadd.x-ray image
.Iaddend.pattern .[.of first wavelength radiation.]..
3. An apparatus.Iadd., .Iaddend.using a medium .[.for.]. releasably
storing an .Iadd.energy .Iaddend.image .Iadd.pattern
.Iaddend.representative of .[.a.]. .Iadd.an incident x-ray image
.Iaddend.pattern.Iadd., .Iaddend..[.of radiation of a first
wavelength.]. for producing an image corresponding to the pattern
on a recording medium, said apparatus comprising:
means for scanning said storage medium with a .[.second wavelength
of.]. .Iadd.beam of low energy .Iaddend.radiation .Iadd.of a second
wavelength .Iaddend.to release .[.therefrom.]..Iadd., sequentially
from successive scanned medium portions, .Iaddend..[.a third
wavelength of.]. .Iadd.photo-detectable .Iaddend.radiation
.Iadd.emissions of a third wavelength and .Iaddend.intensity
.[.modulated.]. in accordance with the stored image .Iadd.pattern;
.Iaddend.
means synchronized with said scanning means for
.Iadd.photoelectrically .Iaddend.sensing the .Iadd.sequentially
.Iaddend.released third wavelength radiation .Iadd.emissions
.Iaddend.and for producing .Iadd.an .Iaddend.electrical
.[.energy.]. .Iadd.signal .Iaddend.representative .[.thereof.].
.Iadd.of the x-ray image pattern.Iaddend.; and
means for .[.transforming.]. .Iadd.converting .Iaddend.the
electrical energy.]. .Iadd.signal .Iaddend.into a recorded image
representative of the .Iadd.x-ray image .Iaddend.pattern.
4. The invention of claim 3 wherein said .[.transforming.].
.Iadd.converting .Iaddend.means comprises:
means for producing a fourth wavelength of radiation intensity
modulated in accordance with the electrical energy; and
means for recording the representative image on said recording
medium with said fourth wavelength radiation. .[.5. A method for
producing an image corresponding to a releasably stored image of a
pattern of high energy radiation, the method comprising the steps
of:
releasing the stored image as light energy modulated in accordance
with the image;
converting the modulated light energy into corresponding electrical
energy;
producing intensity modulated light which varies in accordance with
the electrical energy; and
recording with the intensity modulated light to form an image
corresponding
to the pattern of high energy radiation..]. .[.6. The invention of
claim 5 wherein the image recorded is smaller than the high energy
radiation
pattern..]. 7. A method of producing a recorded image corresponding
to a releasably stored image of a pattern of high energy radiation,
the method comprising the steps of:
releasing the stored image as emitted light on a point by point
basis and converting the image into electrical energy modulated in
accordance with the point by point intensity of the light
emitted;
converting the modulated electrical energy into correspondingly
modulated light; and
recording an image with said modulated light that represents the
high
energy radiation pattern on a point by point basis. 8. The
invention of claim 7 wherein the image recorded is smaller than the
pattern of high
energy radiation. 9. The invention of claim 7 wherein the modulated
light
is scanned to produce the recorded image. 10. An image forming
method using an energy storing medium which is characterized by an
ability to store .[.radiant.]. .Iadd.x-ray .Iaddend.energy of a
first wavelength and release that energy in the form of
.[.detectable.]. .Iadd.photo-detectable .Iaddend.radiation of a
second wavelength when stimulated .Iadd.by radiant energy of a
third wavelength, .Iaddend.said method comprising:
.[.simultaneously.]. exposing .Iadd.the operative portions of
.Iaddend.said medium to .[.a.]. .Iadd.respective portions of an
x-ray image .Iaddend.pattern of radiation of said first wavelength
.Iadd.to form in said medium a stored energy pattern corresponding
to said x-ray image pattern;
.Iadd.sequentially .Iaddend.stimulating .Iadd.successive portions
of .Iaddend.said medium to .Iadd.sequentially .Iaddend.release
.Iadd.stored .Iaddend.energy .Iadd.in the form of emissions
.Iaddend.of said second wavelength .Iadd.having intensities
respectively .Iaddend.corresponding to .Iadd.portions of
.Iaddend.said .Iadd.stored x-ray energy .Iaddend.pattern;
converting said energy .Iadd.emissions .Iaddend.of said second
wavelength to an electrical signal; and
using said electrical signal to control formation of an image
corresponding
to said .[.original.]. pattern of radiation. 11. An image forming
method using an intermediate medium capable of storing energy when
exposed to x-radiation, which energy is releasable as light when
stimulated by infrared radiation, said method comprising:
exposing said medium to a pattern of x-radiation to form a pattern
of stored energy in said medium;
scanning said medium with stimulating infrared radiation to release
light energy modulated in accordance with said pattern;
converting said light energy to an electrical signal;
using said electrical signal to modulate the intensity of a light
beam; and
scanning said modulated light beam across a light sensitive
recording material to form an image corresponding to said
.[.original.]. pattern of
x-radiation. 12. Apparatus for producing a recorded image
corresponding to a pattern of high energy radiation, using a medium
having temporarily stored therein an image representative of said
pattern as releasable energy, said apparatus comprising:
means for scanning said temporary storage medium to release the
stored energy therefrom;
means coordinated with said scanning means for sensing the energy
released and for transforming the released energy into electrical
energy; and
means for converting said electrical energy into an intensified
output
image corresponding to the pattern of high energy radiation. 13.
The invention of claim 12 wherein said medium for temporarily
storing an image comprises an infrared-stimulable phosphor screen
and said scanning means
comprises a source of infrared radiation. 14. The invention of
claim 12 wherein said medium for temporarily storing an image
comprises a thermoluminescent screen and said scanning means
comprises means for
scanning said medium with heat concentrated in a small area.
.Iadd.15. The invention defined in claim 1 or 3 wherein said
converting means includes means for modifying said electrical
signal to improve the image information thereof. .Iaddend.
.Iadd.16. The invention defined in claim 15 wherein said modifying
means improves the signal to noise ratio of said electrical image
signal. .Iaddend. .Iadd.17. The invention defined in claim 15
wherein said modifying means processes said electrical signal to
provide image edge enhancement. .Iaddend. .Iadd.18. The invention
defined in claim 15 wherein said modifying means processes said
electrical image signal to modify image intensity. .Iaddend.
.Iadd.19. The invention defined in claim 7 including, prior to the
step of converting said electrical energy into recording light, the
step of modifying said electrical energy to improve its image
information. .Iaddend. .Iadd.20. The invention defined in claim 19
wherein the electrical energy is modified to improve signal to
noise ratio. .Iaddend. .Iadd.21. The invention defined in claim 19
wherein the electrical energy is modified to provide image edge
enhancement. .Iaddend. .Iadd.22. The invention defined in claim 19
wherein the electrical energy is modified as to image intensity.
.Iaddend. .Iadd.23. The invention defined in claim 10 or 11
including the step of modifying said electrical signal, prior to
its use in formation of a corresponding image, to improve the image
information thereof. .Iaddend. .Iadd.24. The invention defined in
claim 23 wherein said electrical signal is modified to improve
signal to noise ratio. .Iaddend. .Iadd.25. The invention defined in
claim 23 wherein said electrical signal is modified to provide
image edge enhancement. .Iaddend.
.Iadd.26. The invention defined in claim 23 wherein said electrical
signal is modified as to image intensity. .Iaddend. .Iadd.27. A
radiographic imaging system comprising:
(a) image storage means having an image zone which is: (i)
responsive to an incident x-ray image pattern for producing a
corresponding stored energy pattern and (ii) responsive to
stimulating radiation for releasing energy so stored as light
emissions;
(b) means for supporting said image storage means;
(c) scanning means for effecting sequential application of such
stimulating radiation to successive image zone portions of said
image storage means to release energy stored therein as respective
sequential light emissions;
(d) detector means for optically collecting said sequential light
emissions and for producing an electrical signal corresponding to
said x-ray image pattern; and
(e) means for converting said electrical signal into an image
corresponding
to said x-ray image pattern. .Iaddend. .Iadd.28. Radiographic
imaging apparatus constructed to receive and cooperate with a
storage means having an image zone which is: (i) responsive to an
incident x-ray image pattern for producing a corresponding stored
energy pattern and (ii) responsive to stimulating radiation for
releasing energy so stored as light emissions, said apparatus
comprising:
(a) scanning means for sequentially applying such stimulating
radiation to successive image zone portions of a received image
storage means to release energy stored therein as respective
sequential light emissions;
(b) detector means for optically collecting said sequential light
emissions and for producing an electrical signal corresponding to
said x-ray image pattern; and
(c) means for converting said electrical signal into an image
corresponding to said x-ray image pattern. .Iaddend. .Iadd.29.
Radiographic imaging apparatus for receiving an image storage
medium having an image storage zone which:
(i) has been exposed to the image elements of an x-ray image and
stores energy in a pattern corresponding to said x-ray image and
(ii) is responsive to stimulating radiation to release stored
energy as light emission, said apparatus comprising:
(a) scanning means for sequentially applying such stimulating
radiation to successive portions of such a received storage medium
to release energy stored therein as respective sequential light
emissions;
(b) detector means for optically collecting said sequential light
emissions and for producing an electrical signal corresponding to
said x-ray image pattern; and
(c) means for converting said electrical signal into an image
corresponding to said x-ray image pattern. .Iaddend. .Iadd.30. An
improved imaging system for medical radiography, said system
comprising:
(a) image storage means having an image zone of a format that
comprises a plurality of image point portions which: (i) are
responsive to respective portions of an incident x-ray image
pattern to discretely store corresponding energy pattern portions
and (ii) are discretely responsive to stimulating radiation, of
lower quantum energy than said x-ray image pattern, to release
their stored energy pattern portions as respective emissions of
light radiation;
(b) means for supporting said image storage means;
(c) scanning means for discretely providing such stimulating
radiation sequentially on successive image point portions of said
image zone so as to sequentially release successive light emissions
in accordance with the stored energy pattern corresponding to the
exposed x-ray pattern;
(d) detector means for sensing the sequential light emissions
discretely and for producing, in response thereto, a time-varying
electrical signal containing image point information corresponding
to said x-ray image pattern; and
(e) means for converting said electrical signal into an image
corresponding
to said x-ray pattern. .Iaddend. .Iadd.31. The system defined in
claim 27 or 30, wherein said storage means is constructed to be
readily insertable into, and removable from, its operative location
relative to said scanning means. .Iaddend. .Iadd.32. The system
defined in claim 31 wherein said storage means is flexible.
.Iaddend. .Iadd.33. The system defined in claim 27 or 30, wherein
said storage means is constructed for facile transfer between a
separate operative location at which it is imagewise exposed
and
said scanning means. .Iaddend. .Iadd.34. An improved
medical-radiographic imaging apparatus useful with image storage
means having an image zone of a format size which accommodates a
medical x-ray image pattern and that comprises a plurality of image
point portions which: (i) are responsive to respective portions of
such an incident x-ray image pattern to discretely store
corresponding energy pattern portions and (ii) are discretely
responsive to stimulating radiation, of lower quantum energy than
said x-ray image pattern, to release their stored energy pattern
portions as respective emissions of light radiation, said apparatus
comprising:
(a) scanning means for discretely providing stimulating radiation
sequentially on successive image point portions of the image zone
of such image storage means so as to sequentially release
successive light emissions in accordance with the stored energy
pattern corresponding to the exposed x-ray image pattern; and
(b) detector means for sensing the sequential light emissions
discretely and for producing, in response thereto, a time-varying
electrical signal containing image point information corresponding
to said x-ray image pattern; and
(c) means for converting said electrical signal into an image
corresponding
to said x-ray pattern. .Iaddend. .Iadd.35. Medical radiographic
imaging apparatus constructed to receive and cooperate with image
storage means having an image zone that comprises a plurality of
image points which: (i) have been exposed to respective portions of
an incident x-ray image pattern to discretely store corresponding
energy pattern portions and (ii) are discretely responsive to
stimulating radiation, of lower quantum energy than said x-ray
image pattern, to release their stored energy pattern portions as
respective emissions of light radiation, said apparatus
comprising:
(a) scanning means for discretely providing stimulating radiation
sequentially on successive image point portions of the image zone
of a received image storage means so as to sequentially release
successive light emissions in accordance with the stored energy
pattern corresponding to the exposed x-ray image pattern;
(b) detector means for sensing the sequential light emissions
discretely and for producing, in response thereto, a time-varying
electrical signal containing image point information corresponding
to said x-ray image pattern; and
(c) means for converting said electrical signal into an image
corresponding
to said x-ray pattern. .Iaddend. .Iadd.36. The invention defined in
claims 1, 3, 12, 27, 28, 29, 30, 34 or 35 wherein said converting
means comprises: (i) means for storing an electrical image signal;
(ii) means for receiving an electrical image signal and displaying
a visible image corresponding to the information therein and (iii)
means for receiving an electrical image signal and recording an
image, corresponding to the information therein, on a record
medium. .Iaddend. .Iadd.37. The invention defined in claims 1, 3,
12, 27, 28, 29, 30, 34 or 35 wherein said converting means
comprises: (i) means for storing an electrical image signal and
(ii) means for receiving an electrical image signal and displaying
a visible image corresponding to the information therein. .Iaddend.
.Iadd.38. The invention in claims 1, 3, 12, 27, 28, 29, 30, 34 or
35 wherein said converting means comprises: (i) means for receiving
an electrical image signal and displaying a visible image
corresponding to the information therein and (ii) means for
receiving an electrical image signal and recording an image,
corresponding to the information therein, on a record medium.
.Iaddend. .Iadd.39. The invention defined in claims 1, 3, 12, 27,
28, 29, 30, 34 or 35 wherein said converting means comprises: (i)
means for storing an electrical image signal and (ii) means for
receiving an electrical image signal and recording an image,
corresponding to the information therein, on a record medium.
.Iaddend. .Iadd.40. The invention defined in claims 1, 3, 12, 27,
28, 29, 30, 34 or 35 wherein said converting means comprises: (i)
means for storing an electrical image signal; (ii) means for
receiving an electrical image signal and displaying a visible image
corresponding to the information therein; (iii) means for imagewise
processing such electrical image signal to provide image
intensification, improved signal to noise or image edge-enhancement
and (iv) means for receiving such image signal and recording a
modified image pattern on a record medium. .Iaddend. .Iadd.41. The
invention defined in claims 1, 3, 12, 27, 28, 29, 30, 34 or 35
wherein said converting means comprises: (i) means for storing an
electrical image signal; (ii) means for imagewise processing an
electrical image signal to provide image intensification, improved
signal to noise or image edge-enhancement and (iii) means for
receiving such image signal and recording a modified image pattern
on a record medium. .Iaddend. .Iadd.42. The invention defined in
claims 1, 3, 12, 27, 28, 29, 30, 34, or 35 wherein said converting
means comprises: (i) means for storing an electrical image signal;
(ii) means for receiving an electrical image signal and displaying
a visible image corresponding to the information therein and (iii)
means for imagewise processing such electrical image signal to
provide image intensification, improved signal to noise or image
edge-enhancement. .Iaddend. .Iadd.43. The invention defined in
claims 27, 28, 29, 30, 34 or 35 including means for providing
relative movement between said detector means and said image
storage means. .Iaddend. .Iadd.44. The invention defined in claims
27, 28, 29, 30, 34 or 35 wherein said detector means includes: (i)
photoelectric transducer means, (ii) light guide means, located
proximate said image storage means, for directing emitted light to
said transducer means; and (iii) means for providing relative
movement between said light guide means and said image storage
means during operation of said scanning means. .Iaddend. .Iadd.45.
The invention defined in claim 44 wherein the relative movement
between said light guide and image storage means is synchronized
with said scanning means so that said light guide is sequentially
in proximate locations respectively to stimulated point portions of
said
image storage means. .Iaddend. .Iadd.46. The invention defined in
claims 27, 28, 29, 30, 34 or 35 wherein said converting means
includes means for receiving said electrical image signal and
recording an image which corresponds to said exposed x-ray image
pattern, but which is reduced in format size relative to said
exposed x-ray image pattern. .Iaddend. .Iadd.47. The invention
defined in claims 27, 28, 29, 30, 34 or 35 wherein said converting
means includes means for receiving said electrical image signal and
displaying an image which corresponds to said exposed x-ray image
pattern, but which is reduced in format size relative to said
exposed x-ray image pattern. .Iaddend. .Iadd.48. A radiographic
imaging method comprising:
(a) exposing the image zone of a temporary image storage medium, of
the type that is: (i) responsive to an incident x-ray image pattern
for producing a corresponding stored energy pattern and (ii)
responsive to stimulating radiation for releasing energy so stored
as light emissions, to an x-ray image pattern;
(b) sequentially applying such stimulating radiation to successive
image zone portions of said image storage media to release energy
stored therein as respective sequential light emissions;
(c) optically collecting and photoelectrically detecting said
sequential light emissions to produce an electrical image signal
corresponding to said x-ray image pattern; and
(d) converting said electrical image signal into an image
corresponding to
said x-ray image pattern. .Iaddend. .Iadd.49. A radiographic
imaging method using a storage medium having an image zone that is
responsive to an incident x-ray image pattern for producing a
corresponding stored energy pattern and is responsive to
stimulating radiation for releasing energy so stored as light
emissions, said method comprising:
(a) exposing the image zone portions of such storage medium to
respective portions of an x-ray image pattern;
(b) sequentially applying such stimulating radiation to successive
image zone portions of said exposed storage medium to release
energy stored therein as respective sequential light emissions;
(c) optically directing said sequential light emissions to a
detector and photoelectrically detecting the emissions to produce
an electrical image signal corresponding to said x-ray image
pattern; and
(d) converting said electrical image signal to an image
corresponding to
said x-ray image pattern. .Iaddend. .Iadd.50. A radiographic
imaging method for use with an image storage medium having image
storage portions which: (i) have been exposed to an x-ray image and
store energy in a pattern corresponding to said x-ray image and
(ii) are responsive to stimulating radiation to release stored
energy as light emission, said method comprising:
(a) sequentially applying such stimulating radiation to successive
portions of said storage medium to release energy stored therein as
respective sequential light emissions;
(b) optically collecting and detecting said sequential light
emissions to produce an electrical image signal corresponding to
said x-ray image pattern; and
(c) converting said electrical image signal into an image
corresponding to said x-ray image pattern. .Iaddend. .Iadd.51. An
improved imaging method for medical radiography, said method
comprising:
(a) exposing, to an x-ray pattern constituting a medical
radiographic image, the plurality of image point portions that
comprise the image zone of an image storage medium, and that: (i)
are responsive to respective portions of an incident x-ray image
pattern to discretely store corresponding energy pattern portions
and (ii) are discretely responsive to stimulating radiation, of
lower quantum energy than said x-ray image pattern, to release
their stored energy pattern portions as respective emissions of
light radiation;
(b) discretely scanning such stimulating radiation sequentially
onto successive image point portions of said storage medium so as
to sequentially release successive light emissions in accordance
with the stored energy pattern corresponding to the x-ray image
pattern;
(c) discretely detecting the sequential light emissions and
producing, in response thereto, a time-varying electrical image
signal containing the image point information corresponding to said
x-ray image pattern; and
(d) converting said electrical image signal into an image
corresponding to
said x-ray image pattern. .Iaddend. .Iadd.52. An improved
medical-radiographic imaging method useful with image storage
medium having an image zone that comprises a plurality of image
point portions which: (i) are responsive to respective portions of
an incident x-ray image pattern to discretely store corresponding
energy pattern portions and (ii) are discretely responsive to
stimulating radiation, of lower quantum energy than said x-ray
image pattern, to release their stored energy pattern portions as
respective emissions of light radiation, said method
comprising:
(a) exposing the image point portions of said storage medium to an
x-ray pattern constituting a medical radiographic image;
(b) scanning such stimulating radiation sequentially onto
successive image point portions of said storage medium so as to
sequentially release successive light emissions in accordance with
the stored energy pattern corresponding to the x-ray image
pattern;
(c) detecting the sequential light emissions discretely and
sequentially, and photoelectrically producing, in response thereto,
an electrical image signal containing the image point information
of said x-ray image pattern; and
(d) converting said electrical image signal into an image
corresponding to
said x-ray image pattern. .Iaddend. .Iadd.53. The method defined in
claims 48, 49, 51 or 52 further including the step of transferring
said storage medium between x-ray exposing and scan-stimulating
locations after said exposing step. .Iaddend. .Iadd.54. A medical
radiographic imaging method useful with image storage medium having
an image zone that comprises a plurality of image points which: (i)
have been exposed to respective portions of an incident x-ray image
pattern to discretely store corresponding energy pattern portions
and (ii) are discretely responsive to stimulating radiation, of
lower quantum energy than said x-ray image pattern, to release
their stored energy pattern portions as respective emissions of
light radiation, said method comprising:
(a) scanning such stimulating radiation sequentially onto
successive image point portions of such storage medium so as to
sequentially release successive light emissions in accordance with
its stored energy pattern;
(b) photoelectrically detecting the sequential light emissions
discretely so as to produce a time-varying electrical image signal
containing image point information corresponding to said x-ray
image pattern; and
(c) converting said electrical image signal into an image
corresponding to said x-ray image pattern. .Iaddend. .Iadd.55. The
invention defined in claims 48, 49, 50, 51, 52 or 54 wherein said
detecting step includes providing relative movement between a
photoelectric detector means and said image storage medium.
.Iaddend. .Iadd.56. The invention defined in claims 48, 49, 50, 51,
52 or 54 wherein said detecting step includes, during said scanning
step, relatively moving said storage medium and a light guide which
is located proximate said image storage medium for directing light
emissions to a photoelectric transducer. .Iaddend. .Iadd.57. The
invention defined in claim 56 wherein the relative movement between
said light guide and image storage means is synchronized with said
scanning of stimulating radiation so that said light guide is
sequentially in proximate locations respectively to stimulated
point portions of said image storage means. .Iaddend. .Iadd.58. The
method defined in claims 48, 49, 50, 51, 52 or 54 wherein said
converting step includes: (i) storing said electrical image signal;
(ii) receiving said electrical image signal and displaying a
visible image corresponding to the information therein or (iii)
receiving said electrical image signal and recording an image
corresponding to the information therein on a record medium.
.Iaddend. .Iadd.59. The method defined in claims 48, 49, 50, 51, 52
or 54 wherein said converting step includes: (i) receiving said
electrical image signal and displaying a visible image
corresponding to the information therein and (ii) receiving said
electrical image signal and recording an image corresponding to the
information therein on a record medium. .Iaddend.
.Iadd.60. The method defined in claims 48, 49, 50, 51, 52 or 54
wherein said converting step includes: imagewise processing said
electrical image signal to provide image intensification, improved
signal to noise or image edge-enhancement. .Iaddend. .Iadd.61. The
method defined in claims 48, 49, 50, 51, 52 or 54 wherein said
converting step includes: (i) imagewise processing said electrical
image signal to provide image intensification, improved signal to
noise or image edge-enhancement and (ii) receiving such image
signal and recording a modified image on a record medium. .Iaddend.
.Iadd.62. The method defined in claims 48, 49, 50, 51, 52 or 54
wherein said converting step includes: (i) receiving said
electrical image signal and displaying a visible image
corresponding to the information therein and (ii) imagewise
processing said electrical image signal to provide image
intensification, improved signal to noise or image
edge-enhancement. .Iaddend. .Iadd.63. The method defined in claims
48, 49, 50, 51, 52 or 54 further comprising the steps of monitoring
the photoelectrically detected output of a stimulated medium test
portion, which has received a test exposure, and adjusting the
storage medium's exposures to stimulating
radiation in response to such detected output. .Iaddend. .Iadd.64.
The method defined in claim 63 wherein said adjusting step
comprises varying the scan rate of said stimulating radiation in
response to such detected output. .Iaddend. .Iadd.65. The method
defined in claims 48, 49, 50, 51, 52 or 54 further comprising the
steps of monitoring the photoelectrically detected output of a
stimulated medium test portion, which has received a test exposure,
and adjusting the amplification of the electrical image signal in
response to such detected test output. .Iaddend.
Description
This application is a reissue application for U.S. Pat. No.
3,859,527 issued on Jan. 7, 1975 on U.S. Ser. No. 320,028 filed
Jan. 2, 1973..Iaddend.
FIELD OF THE INVENTION
The instant invention relates to a system for radiography and more
particularly to an apparatus and method for converting a pattern of
high energy radiation into a recorded image using an intermediate
energy storing medium.
BACKGROUND OF THE INVENTION
Since x-rays are practically unfocusable with conventional optical
apparatus, prior art x-ray devices typically utilize contact
printing and do not provide direct image reduction capability.
Therefore, a need exists for an apparatus and method which will
provide a direct, small format image representative of a large
format pattern of high energy radiation without the necessity of a
large format radiographic film exposure.
DESCRIPTION OF THE PRIOR ART
Several prior art systems for the storage of an image
representative of an incident pattern of high energy radiation
exit. U.S. Pat. Nos. 2,482,813 and 2,482,814 to F. Urbach disclose
devices for storing images produced by incident ultraviolet light.
The stored images are subsequently retrieved by stimulation with
red or infrared radiation or by direct heating of the layer.
Scanning, as an image readout alternative, is taught in U.S. Pat.
No. 2,482,813, whereas U.S. Pat. No. 2,482,814 shows the uniform
flooding of a doubly activated phosphor screen with short
wavelength radiation. To form an image with the phosphor in
printing relation to a photosensitive recording medium, light of a
non-exciting wavelength exhausts the excitation of the phosphor in
proportion to the intensity distribution of the exposure to record
an image on the recording medium.
U.S. Pat. No. 2,482,815, also to F. Urbach, discloses a layer of
doubly activated phosphor excited with short wavelength radiation
including x-rays and particulate radiation. The excited layer is
placed in printing relation to a layer of photosensitive material
and stimulated to an image by uniformly distributed infrared light
to release the stored energy and expose the photosensitive
layer.
Other systems such as that disclosed in U.S. Pat. No. 2,468,452 to
H. W. Leverenz utilize stimulable phosphor screens which have the
ability to store energy supplied to them directly or indirectly by
cathode ray beams. When stimulated, the screens release energy in
the form of visible light. Materials such as those disclosed in
U.S. Pat. No. 2,468,452 will absorb and store cathode ray energy
and give up a portion of this stored energy as visible light when
irradiated with infrared light. Hence, phosphors that temporarily
store high energy incident radiation patterns for retrieval as
visible images an interval of time later by scanning or flooding
with non-visible electromagnetic radiation, such as infrared, are
known to those skilled in the art.
Another prior art system is shown in U.S. Pat. No. 3,582,651 to
Siedband. The device disclosed therein provides for image storage
and display. An image intensifier tube converts an incident x-ray
pattern into a corresponding electron image. The tube accelerates
the electrons toward the output screen of the intensifier. The
visible output screen image is optically coupled to a television
camera which produces an image for viewing or recording by well
known means.
Recorded thermal images called thermograms are obtainable by the
prior art method of optically scanning an infrared detector over a
field of view to produce electrical signals in accordance with the
infrared radiance exhibited by objects in the scanned field of
view. The method applies amplified and processed signals from the
infrared detector to a glow modulator tube. The tube output scans a
light sensitive surface synchronously with the scanning of the
field of view to provide the thermogram. Signals from the infrared
detector intensity modulate the glow modulator tube to produce a
black and white picture in which the point intensities of the
picture are related to the infrared radiance of corresponding
points in the scanned field of view.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an
apparatus and method for recording an image representative of an
intensity pattern of high energy radiation onto a storage medium. A
temporary storage medium, for example, any of certain phosphor
screens described below, stores energy from a high energy incident
pattern of x-rays or other such high energy electromagnetic or
particulate radiation. An infrared or heat source releases the
energy stored with the high energy exposure. An appropriate sensing
device receives the emitted energy and produces an electrical
signal therefrom. The electrical signal which is preferably
amplified is converted into an image for recording onto the desired
storage medium.
The invention is particularly useful in recording an image
representative of a large formal high energy radiation intensity
pattern, such as a human chest x-ray, onto a small format recording
medium, such as microfilm. The invention is practiced without using
the large format x-ray film required by prior art apparatus and
methods.
In a preferred embodiment, an infrared or heat source scans the
phosphor screen to release the stored energy as intensity modulated
light, the scanned out light varying in accordance with the image
stored on the screen. A sensor which is synchronizable with the
energy releasing scan, such as an image intensifier tube, receives
the intensity modulated light and produces electrical energy in the
form of a time varying electron emission or electrical signal
modulated in accordance with the intensity modulation of the
light.
The electrical signal is preferably amplified. The signal can also
be otherwise modified to obtain a better image than one obtainable
on radiographic film with conventional x-ray contact printing
methods. Some possible signal modifications are image
intensification, signal-to-noise ratio improvement, and
edge-enhancement. Available electrical apparatus afford other image
improvements.
After modification, if any, the electrical signal is converted into
a time varying modulated light beam which scans a recording medium,
such as microfilm, to record an image corresponding to the high
energy radition pattern. The image recorded is, in accordance with
a preferred embodiment, much smaller than the pattern of high
energy radiation it represents.
One object of the invention is to directly provide high quality
miniature medical radiographs from the large primary image
formats.
Another object of the present invention is to provide a small
radiographic image without loss of resolution or loss of speed.
Yet another object of the invention is to realize substantial
savings in the cost of making good medical radiographs.
One advantage of the instant invention is that a large input format
can be used in combination with a small output format without loss
of resolution or loss of speed.
Yet another advantage of the present invention is that in
accordance therewith, small, high quality, final images are formed
which are not available from typical prior art systems.
Another advantage of the invention is that the practice thereof
eliminates the need for large amounts of large format radiographic
film by essentially substituting therefor the use of small amounts
of microfilm.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the present invention will be
apparent to those skilled in the art from the following description
with reference to the drawings in which like characters denote like
parts and wherein:
FIG. 1 is a schematic diagram illustrating a scanning apparatus for
use in accordance with the invention;
FIG. 2 is a schematic representation of another embodiment of the
invention wherein magnetic tape or a CRT and photosensitive
recording film can be used as small format output devices;
FIG. 3 is a schematic showing of the scanner of the invention
employing a heat spot in thermal contact with the temporary storage
medium;
FIG. 4 is a schematic diagram showing an X-Y scanning apparatus for
use in accordance with the invention;
FIG. 5 is another view of the X-Y scanning apparatus of FIG. 4;
and
FIG. 6 is a schematic representation of an optical system for use
with the scanning apparatus of FIGS. 4 and 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As used herein, "light" includes electromagnetic radiation in the
visible, infrared, and ultraviolet portions of the spectrum. "High
energy radiation" includes x-rays, gamma rays, alpha rays, beta
rays, high energy neutrons and other similar forms of "hard" or
penetrating electromagnetic or particulate radiation.
The embodiments of the invention to be described incorporate
temporary image storage mediums that preferably comprise phosphors.
Useful phosphors will store an image representative of a pattern of
radiation within a first wavelength range, such as x-radiation, for
a desired period of time and emit light representative of the image
stored when irradiated with radiation within a second wavelength
range, such as the infrared.
The image retention time period desired will vary from less than a
second to a few minutes, or even a few hours, days or weeks, and
will depend on the embodiment of the invention to be used. In any
case, the phosphor selected for a particular embodiment should
satisfactorily retain an image of the high energy radiation pattern
for the desired length of time. Although not necessary, it is
highly desirable for the phosphor to be readily reusable.
Therefore, it is preferable that the phosphors not retain
significant image traces after readout. Alternatively, the phosphor
could be reducible to a neutral state by simple expedients such as
brief, uniform illumination, irradiation, or heating.
Phosphors transparent to their own emitted radiation are
particularly advantageous. Such phosphors include
SrS:Ce,Sm;SrS:Eu,Sm; ThO.sub.2 :E.sub.r ; and La.sub.2 O.sub.2
S:Eu,Sm; in hot pressed or fused crystal form. The SrS:Ce,Sm;
screen is insensitive to tungsten illumination. It can therefore be
easily handled under room light conditions. Ultraviolet-sensitive
phosphors can be used under fluorescent lighting if coated with an
ultraviolet filter layer. Phosphors sensitive to other portions of
the visible spectrum can be similarly filter coated.
Although hot pressed and fused crystal phosphors are preferred, the
temporary storage medium may comprise thermoluminescent,
radiochromic, radiophotoluminescent or infrared-stimulable
phosphors in the form of unitary crystals or small crystals
dispersed in an appropriate binder. It will be apparent to those
skilled in the art that other temporary storage mediums such as
photoconductor-panels or field effect
semiconductor-electroluminescent panels can also be used. In
choosing a temporary medium, the primary criterion is that a stored
image must be efficiently releasable as emitted energy with the
application of low energy radiation such as infrared light, heat,
long wavelength visible light, or an electric current.
Reference is now made to FIG. 1. A frame 10 retains two rotatable
shafts, 12 and 36, in parallel relationship. The shafts rotate
freely within bearings (not shown) located in the frame.
Two drums, 40 and 44, are rotatably mounted on shaft 36. A
temporary storage medium 41 as heretofore described is mounted on
drum 40. A light responsive recording medium 45, such as microfilm,
is mounted on drum 44. Pulleys 14 and 16 drive belts 50 and 52 to
simultaneously rotate drums 40 and 44 at the same rotational
velocity.
Shaft 36 has two sets of threads, 42 and 47. Drum 40 engages
threads 42 whereas drum 44 engages threads 47. The ratio of the
relative spacing of threads 42 and 47 is fixed. The ratio can be,
for example 1:4 so that for every revolution of the drums, drum 40
moves laterally four times as far as drum 44. For a distortion free
reproduction of the image to be recorded on medium 45 from medium
41, the ratio of the thread spacing should be the same as the ratio
of the circumference of medium wrapped drum 40 to the circumference
of the medium wrapped drum 44. Of course, image elongation in
either direction may be desired and thread spacing or drum diameter
ratios may be changed to accommodate a particular format.
As they rotate, pulleys 14 and 16, keyed to shaft 12, freely move
laterally along shaft 12 to retain alignment with their respective
drums. A motor 24 drives shaft 12 by a pulley 26 and belt 30
arrangement. Pulley ratios and motor speed are selected to supply a
desired rotational speed for the drums 40 and 44.
Source 46 directs a beam of infrared light through an interference
filter 62 onto an area 64 of infrared stimulable medium 41. If an
image is stored thereon, the phosphor of the medium emits light in
response to the stimulation. The emitted light is preferably
visible light, but may be ultraviolet or infrared light. Light
emitted from medium 41 in response to stimulation reflects from
interference filter 62 through a lens 68 onto the input face 72 of
an image intensifier tube 70. In response to the light, the
photocathode within the image intensifier tube creates electrical
energy in accordance with the intensity of the light impinging on
input face 72. The electrical energy of this embodiment is in the
form of an electron emission. Electron optics within the tube
accelerate the electrons emitted by input photocathode 72 to
produce an intensified image on an output phosphor 74. The light
emitted by phosphor 74 passes through a lens 76 onto a mirror 78.
Mirror 78 reflects the light through a lens 80 which focuses the
light to an image on an area 82 of recording medium 45. Area 82
corresponds to area 64 on phosphor 41 so that as the scanner is
operated, an image of reduced size corresponding on a point basis
with the image from phosphor 41 is recorded on microfilm 45.
Because magnetic intensifier tubes, particularly large format
tubes, rotate the image intensified up to about 3.degree., an image
rotator such as a prism can be included in the optics of the
apparatus to compensate for the rotation. No image rotator is shown
in FIG. 1 for the sake of clarity. Also, depending on the image
intensifier tube utilized, image reorientation is carried out by
optics known to those skilled in the art, such as an AMICI prism,
or pentaprism or fiber optics.
An arrangement which can take the place in FIG. 1 of the infrared
source 46, dichroic mirror 62, and lens assembly 68, is similar to
that described by Ball et al, Third Symposium on Photoelectronic
Image Devices, London 1965, Advances in Electronic Series, pp.
927-940. The assembly comprises a right angle prism, No. 60649A
obtained from the Edmond Scientific Company, disposed between two
f/2.8, 5 inch focal length Kodak Projection EKTANAR lenses. A "hot
mirror" interference filter is placed between the first lens and
drum 40. A mask having a rectangular aperture 0.480 inch wide and
1/2 cm. high is located very close to the drum 40 between the
filter 62 and the drum 40. A Varo Model 8606 intensifier tube is
used. A piece of 10mm thick Corning CS4-96 glass is placed just in
front of the photocathode of the intensifier tube.
The infrared source is a Kodak Instamatic movie light, containing a
650 watt tungsten lamp and operable at a variable AC potential from
a Variac transformer. The infrared source is disposed in front of
the hot mirror with 4 mm of Corning CS-2-58 glass and 2.4 mm of
Corning CS-7-56 glass between the source and the hot mirror. With
this arrangement, radiation from the source reflects from the hot
mirror onto the surface of the temporary storage screen. The
visible light released from the screen by the infrared radiation
passes through the hot mirror and the right angle prism-lens
assembly of Ball and is imaged onto the photocathode of the image
intensifier tube.
FIG. 2 shows a pulley and belt driven screen drum 140 rotatably
mounted on the threads 142 of a shaft 136. Drum 140 holds a
temporary storage medium 141 comprising an infrared stimulable
phosphor. An interference filter 162 transmits infrared light from
an infrared source 160 onto a small area 164 of drum 140. If an
image is stored therein, the phosphor of the temporary storage
medium 141 emits light at a predetermined wavelength, preferably in
the visible part of the spectrum, in response to the infrared light
beam incident thereon. Interference filter 162 reflects the emitted
light onto the input face 172 of a photomultiplier tube 170. Tube
170 produces electrical energy in the form of an electrical signal
modulated in accordance with the intensity of the light incident
thereon. The electrical signal is preferably amplified by an
amplifier 174, and transmitted to a disconnect switch 173. .Iadd.As
previously described, the signal from amplifier 174 can also be
otherwise modified, e.g. by signal modifying means 171, to obtain a
better image. Some of the image modifications possible with
available electrical apparatus, represented schematically by signal
modifying means 171, are image intensification, signal-to-noise
ratio improvement and edge-enhancement. .Iaddend.Depending on the
position of switch 173, the signal is either recorded onto magnetic
tape by well known means such as a tape deck as represented by a
block 175 or displayed on the face 177 of a high resolution cathode
ray tube 176. The image can be recorded onto microfilm 178 from the
display on tube face 177. If recorded onto microfilm 178,
conventional supply and take up reels 179 and 180 can be
appropriately controlled by conventional means to expose the
microfilm in accordance with a particular format.
A direct electron recording film such as one incorporating diynes
or polyynes can be used in a tube accommodating the passage of film
through itself. Such a tube electrically rather than optically
records an image.
A high intensity source of ultraviolet radiation can be modulated
in accordance with the light released from the phosphor to record
an image onto slow non-silver systems such as diazo films,
iodoform-sensitized materials, photosensitive polymers and other
such substances. An assembly of photomultipliers or
photocellamplifiers combinations and recording devices may be also
used to receive and record the phosphor output. A low light level
television system can be utilized to amplify, display, and record
light emitted from the stimulated phosphor. Combinations of an
image intensifier tube with a silicon intensifier target tube (SIT)
described by R. W. Engstrom and R. L. Rodgers in Optical Spectrum
5, pp. 26-31 (1971) are particularly suitable. A small format
representation of the phosphor output can also be electrostatically
recorded with an electrical discharge tube such as the "Printapix"
tube, a trademark of Litton Industries, Inc.
FIG. 3 illustrates another embodiment of the invention. A hollow,
transparent, screen drum 240 rotatably mounted on threaded shaft
236 carries a thermoluminescent phosphor temporary storage medium
241. Threaded shaft 236 supports a heat source 238. An electric
current carried to the source by wires 239, which run through the
tubular threaded shaft 236, activates heat source 238. Shaft 236
threadably engages a recording drum 244 holding a recording medium,
such as microfilm 245. Drums 240 and 244 are driven so that they
rotate at the same angular velocity. The threads and the
circumferences of the drums have a fixed ratio to one another as in
the FIG. 1 embodiment.
If the phosphor of medium 241 contains an image of a pattern of
high energy radiation, it emits light from an area 264 when
thermally stimulated by source 238. The light is preferably visible
light but may be ultraviolet or infrared. A mirror 262 deflects the
emitted light through a lens 268 onto the face 272 of an image
intensifier tube 270. The tube 270 receives the light, converts it
into electrical energy in the form of electrons, accelerates the
electrons, and creates an intensified light pattern therefrom on
its output face 274. Light from the output face 274 passes through
a collimating lens 276 onto a mirror 278 which deflects the light
beam through another lens 280. Lens 280 images the light onto an
area 282 of the recording medium 245 on drum 244. Areas 264 and 282
correspond so that as the scanner operates, the microfilm mounted
on drum 244 records an image representative of the high energy
radiation pattern.
FIGS. 4, 5 and 6 show an embodiment of the invention incorporating
an X-Y scanner for scanning out information from a large format
temporary storage medium and recording it onto a small format
storage medium. A sturdy frame 300 supports the scanner. A first
carriage 306 rides on tracks 302 and 304 mounted on frame 300.
Track 302 and a third track, 308, support a second carriage 310.
Tracks 302, 304 and 308 lie parallel in the X-direction, indicated
by the double headed arrow labeled X. Carriages 306 and 310 ride on
wheels 312 which roll on tracks 302, 304 and 308. The wheels 312
which ride on tracks 304 and 308 cannot be seen in FIGS. 4 and 5. A
reversible motor 314 supplies X-directional drive for both
carriages by driving a gear box 316 through a friction drive 318.
Gear box 316 turns two screw threaded shafts 315 and 317 at the
same rotational velocity through couplers 320 and 321. Screw shafts
315 and 317 thread through female receiving units 325 and 327
secured to the bases of carriages 306 and 310 so that as the
threaded shafts turn, the carriages 306 and 310 move in the
X-direction. The threads on shafts 315 and 317 are related by a
fixed ratio so that carriages 306 and 310 move relative to one
another in accordance with thread ratio. In the embodiment shown,
the ratio is 4:1. Thus, carriage 306 moves four times the distance
carriage 310 does for any given number of rotations of the threaded
shafts 315 and 317.
Reversible electric motors 319 and 324 implement Y-directional
movement as indicated by a double headed arrow Y. Motor 319 drives
a platform 322 with a rotatable threaded shaft 323 riding in
bearings 326 mounted on carriage 306. A base member 330, secured to
platform 322, slides on a track 328 mounted atop carriage 306.
Although FIG. 4 only shows one track, another is provided in the
cutaway region to provide support to the other side of platform
322. The threaded shaft 323 drives platform 322 by rotating through
a threaded female coupler 329 secured to platform 322.
Motor 324 rotating a threaded shaft 334 slides a platform 332
mounted on a base 339 across carriage 310. A groove 338 in base 339
slides on a track 336 secured to carriage 310. Motor 324 is
synchronized with motor 319 by well known electrical means (not
shown) to move plate 332 in the Y-direction at one fourth or other
desired fraction of the speed motor 319 moves plate 322.
Plate 332 is provided with a vacuum connection 340 and a vacuum
groove 342 for holding a small format recording medium on plate
332. Plate 322 supports a transparent pane of glass 344 which has a
vacuum groove 350 and vacuum connections 346 and 348 for retaining
a large format temporary storage medium thereon. Glass plate 344
fits over a removed center portion of plate 322 so that an infrared
source can be operated from below the plate. An area 351 outlined
with a dotted line represents the output area of the source. The
source is kept stationary relative to frame 300 so that an X-Y scan
results from operation of the scanner as above described.
FIG. 6 shows an optical system for use with the scanner of FIGS. 4
and 5. The optical system is stationarily supported above the glass
plate 344 and plate 332 of the X-Y scanner of FIGS. 4 and 5 by
means not shown. An infrared or heat source 360 disposed below mask
361 irradiates area 351 of plate 344 and an area 363 of temporary
storage medium 362. The phosphor in irradiated area 363 emits an
amount of visible light in accordance with any radiographic
exposure thereon. Prism 366 reflects the emitted light through a
lens 368 onto the input face 370 of an image intensifier tube 372.
The image is electrically intensified by well known means in the
tube. The intensified light output from tube 372 passes through a
pentaprism 374 to a lens 376. The lens focuses the light onto an
area 378 of a small format image recording medium such as microfilm
380. Area 378 on recording medium 380 corresponds to area 363 on
phosphor medium 362 so that as the scanner operates, it records a
representation of the radiographic image stored on the phosphor
onto film 380.
It will be appreciated that alternative X-Y scanning devices and
appropriate optical systems will be apparent to those skilled in
the art and the invention is not restricted to the embodiment shown
in FIGS. 4, 5 and 6.
One scanner installation can service several exposure stations so
that a hospital need only have one scanner for several remote x-ray
exposure installations. Exposed temporary storage phosphors can be
transferred from various x-ray exposure installations to a scanner
for recording.
In practicing the invention, there are no screen contact problems
as in the contact printing art where x-ray film must intimately
contact a phosphor screen in order to obtain a relatively high
resolution image on the film. Since in practicing the invention,
the phosphor screen does not come in contact with the film as do
phosphors and radiographic film in conventional x-ray devices,
thick overcoats or glass plates can enclose the screen to protect
environmentally sensitive phosphors such as readily oxidizable or
hydrophilic phosphors, from deterioration.
In the drum scanner embodiments of FIGS. 1-3, although exposure
could be made onto the temporary medium when mounted onto its drum,
the temporary storage medium used preferably should be flexible so
that one may easily mount and remove the screen from the scanning
drum. Too, a high energy radiation exposure is usually carried out
with a flattened phosphor screen. After exposure, one mounts the
screen on the scanning drum for release of the stored image.
In the X-Y scanner embodiment of FIGS. 4-6, the phosphor screens
need not be flexible because exposures and scan outs are made with
flat screens. Therefore, screens for use with X-Y scanners can
comprise bindless phosphor layers prepared by evaporation,
plasma-spraying, hot-pressing, and chemical vapor deposition.
Because binderless screens have greater absorption per unit
thickness than conventional radiographic screens, they offer the
advantage of greater radiographic speed with retention of image
quality.
Phosphors used in accordance with the invention should preferably
have good storage efficiency at room temperature. However, losses
of stored information by thermal decay or other phenomena are
somewhat compensatable by scanning an area of the phosphor which
has received a standard exposure, monitoring the image intensifier
output.Iadd., e.g. by output monitor circuit 284 (see FIG.
3),.Iaddend.and adjusting the gain of the intensifier.Iadd., e.g.
by gain adjustment circuit 285,.Iaddend.or the rate of
scanning.Iadd., e.g. by drive control 286, .Iaddend.to produce an
increased level of brightness. Phosphors which have high emission
efficiency when stimulated are desirable because less expensive
image amplification and optical equipment can be used with
them.
In one embodiment, an infrared beam or heat source scans an
appropriate temporary storage medium to release trapped carrier
electrons. The electrons are collected to form an electrical signal
which is amplified. The information carried by the signal is
displayed on a cathode ray tube or recorded onto a small format
image recording medium.
An appropriate sensor receives the intensity modulated light from
the temporary image storage medium. Since, in a preferred
embodiment, the stored high energy radiation image is scanned from
the temporary storage medium, a sensor synchronizable with the
scanning apparatus should be employed. Suitable sensors include
photomultiplier tubes, photocell amplifier combinations, image
intensifier tubes and low light level television camera tubes such
as image isocon or the silicon intensifier target tube. Channel
electron multipliers with appropriate photocathodes and output
screens and other high gain, low noise detectors can also be
used.
In practicing the invention, one may use a high gain image
intensifier, such as the Varo intensifier, which has a minimum gain
of about 35000 or the E.M.I. 9694 Image Intensifier Assembly which
has a minimum gain of 1,000,000, with minimal optical distortion of
the image. High gain and low distortion are advantageous, because
they permit the use of less efficient storage phosphors and faster
scanning rates. Fast scanning rates permit one scanner to serve
several exposure installations with a consequent decrease in the
cost per exposure. The use of intensifiers with fast decay output
phosphors is advantageous, because it prevents blurring of the
image and loss of sharpness.
An image intensifier based on the Bendix Chevron CEMA Model BX3040
can also be used.
The electrooptical amplification achieved in practicing the
invention provides for the use of relatively slow image recording
films which are rapidly processable with simple equipment.
Microfilm is the preferred recording medium because it is readily
available and inexpensive. However, other materials suitable for
recording the final images include diazo film, polyyne,
photosensitive polymer layers, iodoformsensitized film, di-yne
coatings, magnetic tape, embossed tape, and electrographic
layers.
The invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *