Radiant energy – Automatic/serial detection of similar sources
Patent
1991-05-24
1992-09-01
Fields, Carolyn E.
Radiant energy
Automatic/serial detection of similar sources
G01N 2304
Patent
active
051441357
DESCRIPTION:
BRIEF SUMMARY
SCOPE OF APPLICATION
The present invention relates to an image plate scanner for a device for scanning an image plate exposed by X-rays with the aid of laser beams.
STATE OF THE ART
From the EP-A-144 856 it is known to expose image plates in which, on a substrate material, a stimulable phosphor layer of BaFEu:X-crystals is disposed in a binding agent with the aid of X-rays. The recording of the X-ray image is effected by the action of the X-rays on the BaFEu:X-crystals. For the image plate scanning, the image plate is scanned with laser light, whereby the different quantities of X-rays absorbed by the image plate are converted into light possessing equivalent intensities. The light is then first converted into analog electrical signals, then into digital signals, following which the digitized image is processed further in a computer. The residual image quantity remaining on the image plate subsequent to the image plate scanning is then deleted in that the image plate is exposed to light. The thusly treated image plate can then be reused for image recording with the aid of X-rays. However, image plate scanners which are already known are subject to the disadvantage that the light yield in the image plate scanner is impaired, due to the circumstance that the sensitivity of the image plate scanner is unsatisfactory for many fields of application.
In order to improve the known image plate scanners, with the EP-OS 296 365, an image plate scanning device is proposed in which an image plate in the form of a circular plate is disposed on a rotatable disk carrier, the image plate being in this case constructed so as to be suitable for the storage of a beam image. The image plate carrier is provided with an electromotor having adjustable speeds, on whose drive shaft the image plate is detachably mounted. The image plate is scanned by means of an image element scanning unit while the image plate is in rotation, and the image element scanning unit is made to travel radially across the image plate at a preset speed of advance. In this case the image plate is subjected to radiation by a laser light from an He-Ne laser as a light source, and the image element scanning unit records the luminescence produced by the image plate at every specific point and is connected to a photomultiplier and a signal conditioning or preparation means. This image plate scanning device operates in such a way that the image dots to be scanned are indicated in a polar system of coordinates as a function of the radius R and the angle theta, and the pertinent intensities are detected with the aid of the image element scanning unit, while the speed of the frame supporting the image plate scanning unit is in a predetermined relationship to the rotational speed of the image plate carrier. In this case it is always the ease that the image plate scanning unit is displaced radially inwardly at a certain speed per rotation of the image plate so that the image plate is scanned in its entirety. Here the scanning is effected in concentric circles.
Since the velocity of the image plate is not changed, the closer the image element scanning unit approaches the central point of the image plate, the duration of the scanning per image element becomes increasingly longer radially form the outside toward the inside, i.e. the recording times within the outer area are extremely short. The drive assemblies for the image plate and for the radial adjustment of the image element scanning unit are independent of each other so that it is not ensured that, when scanning image plate to be compared, the scanning is invariably begun at the same starting point. This would lead to the generation of dissimilar scanning results.
Also in the devices proposed in the FR-A-34 38 300 and in the JP-Sho 63306760, spiral scanning is provided, however, no provision is made for uniform scanning. From the DE-OS 30 14 433, an assembly for the scanning of masters provided with graphic patterns is known, in which it is possible to determine the position of image dots of pixels with a grea
REFERENCES:
patent: 3712955 (1973-01-01), Miller
patent: 4922101 (1990-05-01), Hashive
patent: 4922102 (1990-05-01), Katayama
patent: 5003570 (1991-03-01), Whiting
"Maximum Performance Quasi Closed Loop Scanner Servo", Howard et al., Research Disclosure, Jan. 1981, p.s., Hampshire, GB.
Hendrix Jules
Lentfer Arno
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