Radiant energy – Source with recording detector – Using a stimulable phosphor
Reexamination Certificate
1998-06-26
2001-03-27
Hannaher, Constantine (Department: 2878)
Radiant energy
Source with recording detector
Using a stimulable phosphor
C250S581000, C250S584000, C250S586000, C250S228000
Reexamination Certificate
active
06207968
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to diagnostic imaging using photostimulatable X-rays.
BACKGROUND OF THE INVENTION
It is known to use low dosage X-rays so as to provide latent images which may be stimulated off-line so as to expose the hidden images. Such a technique is disclosed, for example in U.S. Pat. No. 4,547,670. As disclosed in EP 423 891 the latent images are produced by X-rays which impinge on a specially coated film containing a suitably reactive material. The latent image is stored in the coating as a spatially distributed pattern of excited electrons which are trapped in a manner quantitatively indicative of an amount of electromagnetic energy spatially distributed on the film. A visible image can be derived from the resultant latent image by inducing the trapped electrons to fluoresce such that the intensity of the fluorescence is quantitatively indicative of the intensity of the spatially distributed X-ray radiation which was originally absorbed by the film. After the information has been extracted, the entire film is exposed to light, thereby leveling off all of the X-ray excitable electrons to a non-energized state, thus conditioning the film for re-use.
Image scanners have become very common for converting many types of analog input data into computer compatible information. Such scanners have a laser light source for directing on to a film which is generally disposed on a surface of a drum, and are further equipped with means for reading the light reflected by the film.
FIG. 1
shows such a radiographic latent image reader for exposing a phosphor storage sheet to an excitation laser beam as described in JP 6019014. A laser beam
30
from a laser light source
16
is reflected by mirrors
22
and
24
, passes through a selecting mirror
26
and a condensing lens
28
, and irradiates the recording surface
12
of a stimulatable phosphor
10
. The fluorescence generating by the phosphor
10
is condensed by the lens
28
, reflected by the mirror
26
and detected by a fluorescence detecting device
20
after its red light reflections are cut by a filter
34
. By subjecting the reader to transverse motion in the direction shown by the arrow
15
so as completely traverse the width of the recording surface
12
, the entire surface of the phosphor
10
may be read.
It is apparent, therefore, that in the system described in JP 6019014, complex imaging and scanning optics are required which are cumbersome and space-consuming. This, in turn, militates against the provision of more than one scanning optics per drum so as to scan along only a fraction of thereof, thereby allowing different sections of the film to be scanned by more than one scanning optics simultaneously. As a result, such prior art systems are relatively slow.
It would obviously be desirable to replace the complex imaging and scanning optics of JP 6019014 with a compact unit allowing several such units to be provided along the width of the film, so as to allow parallel processing thereof. The prior art makes no attempt to address this requirement.
U.S. Pat. No. 4,302,671 (Kato et al.) discloses a radiation image readout device for reading a stimulatable phosphor. The radiation image readout device includes a photosensor for detecting light produced by the phosphor upon its being stimulated, and a reflecting optical element like a mirror located between the phosphor and the photosensor for reflecting stimulating rays advancing between the phosphor and the photosensor towards the phosphor. The reflecting optical element has a very small size not to intercept the light emitted by the phosphor and detected by the photosensor as much as possible.
The stimulatable phosphor is mounted on a rotary drum and the photosensor is secured to a readout head which is movable in the direction of the axis of the drum. Stimulation of the phosphor is achieved by means of a laser mounted parallel to the drum's axis so as to direct a beam of laser light between the photosensor and the drum so as to be reflected by the mirror toward the stimulatable phosphor plate.
Such an arrangement is also not adapted for multiple reading heads since the stimulating laser beam is directed towards the photosensor along the axis of the drum. Consequently, at most two reading heads might possibly be employed in back-to-back arrangement with respective laser beams directed in opposite directions towards each other. There is no obvious way to employ such an arrangement for the simultaneous stimulation and reading of more than two points on the phosphor. Furthermore the arrangement lacks compactness, is relatively slow and expensive.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a reading head for a laser scanner in which the above-mentioned drawbacks are overcome so as to allow several compact reading heads to be provided each for reading a respective section of a film.
According to the invention there is provided a reading head for a optical scanning device, said reading head comprising:
a housing having at least one bore for accommodating therein a respective photo-multiplier tube and a non-intersecting lateral bore for accommodating therein a stimulating light source for producing a stimulating beam having a first wavelength,
a focusing lens mounted in association with the stimulating light source for focusing the stimulating beam on a film of the scanning device so as to produce stimulated fluorescent light having a second wavelength in said film at a point of contact by said stimulating beam,
a window within the housing for mounting therein a filter for transmitting therethrough the stimulated fluorescent light whilst substantially blocking reflections of the stimulating beam,
mounting means associated with said housing for mounting the housing in spaced relationship with said film so as to direct the stimulating light beam perpendicular to the film such that a distance from the film to an internal periphery of the lateral bore within the housing is equal to a focal length of the focusing lens, and
registration means within the housing for registering the stimulating light source within the lateral bore so that the focusing lens is in precise registration with said internal periphery.
The reading head according to the invention is compact such that the path of the stimulating beam lies very close to the photo-multiplier tube. Preferably the reading head is adapted to accommodate within the central bore thereof a side-entry photo-multiplier tube, allowing an end the photo-multiplier tube to be brought into close proximity with the film thus reducing still further the size of the reading head. Such a construction allows for a plurality of reading heads to be mounted in tandem, thus allowing respective sections of a film to be read in parallel and reducing the cycle time for reading the complete film. Furthermore, side-entry photo-multiplier tubes are less expensive than front-entry photo-multiplier tubes and thus the reading head according to the invention is not only more compact and simpler than hitherto proposed scan systems but is also less costly. The reduction in cost is, of course, particularly significant when multiple reading heads are provided.
REFERENCES:
patent: 4302671 (1981-11-01), Kato et al.
patent: 4547670 (1985-10-01), Sugimoto et al.
patent: 5229608 (1993-07-01), Lange et al.
patent: 5399877 (1995-03-01), Carter et al.
patent: 0 142 839 (1985-05-01), None
patent: 0 423 891 A1 (1991-04-01), None
patent: 0 667 540 A1 (1995-08-01), None
patent: 6713349 (1969-08-01), None
Kinebuchi Takao, Latent Image Reader, Jan. 28, 1994, Pub. No. 06-019014, Filed Jul. 03, 1992, Journal: Section: P, Section No. 1729, vol. 18, No. 223, p. 167, Apr. 21, 1994 (19940421).
Hannaher Constantine
Israel Andrew
Nath Gary M.
Nath & Associates PLLC
Novick Harold L.
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