US2144040A - Intensifying foil for X-ray photography - Google Patents

Description

Jan. 17, 1939. I K. WURSTLIN 2,144,040

INTENSIFYING FOIL FOR X-RAY PHOTOGRAPHY Filed Nov' 5, 1936 Kar/ Wil/Sf/lh INVENTOR 4 ATTORNEY.

Patented Jan. 17, 1939 2,144,040

UNITED STATES PATENT OFFICE INTENSIFYING FOIL FOB X-RAY PHOTOGRAPHY Karl Wiiratlin, Berlin, Germany, asslznor a Kali-Chemie Aktiengesellschatt, Berlin, Germany, a joint-stock company of Germany Application November 5, 1936, Serial No. 109,204 In Germany October 9, 1935 Claims. (CL 250-80) The invention relates to improvements in X- material in the layers 3 and I is so chosen that my photography and more particularly toan imthe average grain'size in the layer 4 of the back proved combination of intensifying, screens or foil is smaller than in the layer 3 of the front foils. foil. In the embodiment shown in the drawing Such intensifying screens or toils are employed the layers 3 and 4 are applied on carrier layers 5 in x-ray photography for the purpose of shorten- 5 and B. The fluorescent layer may be attached ing the exposure time. The screens consist oi a to the carrier layer in any suitable manner, for layer of a fluorescent material, for instance crysexample with the aid of a transparent acetyl celtallized calcium tungstate which is chiefly aplulose lacquer.

plied on a carrier (cardboard, Celluloid sheet). The above described example in no way re- 10 The X-ray him which is to be exposed is placed stricts the scope of my invention. The important between two foils of this kind which when irstep merely consists inthe use of a fluorescent radiated with X-rays cause the X-ray. picture to material of flner grain size for the back foil than emit a. photographically efl'ective fluorescent light for the front foil. In all other respects the in- 13 and decrease the exposure time. tensifying foils may be produced in any sult- 15 The emclency of these intensifying foils is deable manner. For instance the carrier layer or termined mainly by two factors: The intensifying support for the fluorescent material may confactor and the definition or sharpness of the sist of cardboard or celluloid. Moreover, an inpicture. It is possible to improve the definition termediate layer may be arranged between such so oi the foil by using very thin layers or by dyeing a support and the fluorescent layer. It is also posthe fluorescent layer or by using a fluorescent sible to produce the intensifying foil without any material of very flne grain size, however, in all carrier layer or support. In this case the grained these cases the intensifying factor is impaired at or powderous fluorescent material is embedded in the same time. a gelatine layer. As a fluorescent material for 2.5 lit is an object oi my invention to improve the instance calcium tungstate m y be used. definition of the picture obtained by a foil com- The new eilect according to my invention does hination for X-ray photography without matenot depend on the actual grain size provided only rially impairing the intensifying factor. that the back foil consists of a finer material than It is another object of my invention to create the front foil. Also the efiect will be obtained it foil combinations which produce a good deflnithe coarse material is only partly replaced in the 30 tion and a favourable factor of intensification as back foil by flner material or even a somewhat well. coarser material may be used for the back toil as My invention also relates to a process for proan initial material, admixing thereto, however, ducing foil combinations for X-ray photography, a finer material for obtaining a smaller average 5 in which the fluorescent material of the back gra S e tha t at of t e front foil. 5 foil or lower toll is of a finer grain size than that I have found that a combination giving very oi the front foil or upper foil. favourable results as to sharpness of the picture li have found. that the definition of a foil comand intensifying factor is obtained for instance bination can be improved without materially deif a calcium tungstate powderhaving a particle creasing the intensifying factor, by using a fluo-= size of 3 to 5 microns (1 micron==0.o0l mm.) is 40 rescent material of difierent grain size for the used for the front foil and a mixture of 50 percent front and. back foil, the coarser material always by Weight of al ium tungstate of a P rticle size being employed for the front foil. of 3 to 5 microns and 50 percent by weight of A foil combination embodying my invention has a calcium tungstate of a particle size of 0.5 to l been illustrated, by way of example, in the acmicron for the back foil. 5

companying drawing, showing a perspective view I claim: f y n 5011 combination. The rrangement 1. A screen combination for intensification in consists of a front foil I and a back foil 2. The X-ray photography, comprising a front foil haviront foil i contains a layer 3 of grained fluores- 'ing a layer of fluorescent material and a back cent material. The back foil 2 contains a similar foil having a layer of the same fluorescent mato layer A or fluorescent material. terial, the average grain size of the fluorescent For exposing the photographic film I to the X- material of the back foil being smaller than the y i 18 P d w n t wo 1 1 l nd 2 n average grain size of the fluorescent material of the manner known per se. However, according the from; foil. M to my invention the grain size of the fluorescent 2. A combination of intensifying foils for x-ray ahotography, comprising a front foil having a layer of fluorescent material and a back foil having a layer of the same fluorescent material, the grains of the back foil being smaller in diameter than the grains of the fluorescent material of the front foil.

3, In an arrangement for Xray photography, a front including particles of fluorescent material and a back foil including a mixture of particles of the same material and of the same size as the particles of the front foil and particles of the same material and of a smaller size.

a. In a combination of intensifying foils for X-ray photography, 2. front foil comprising a layer of calcium tungstate having an average particle size in the order of 3 5 microns and a back foil comprising a fluorescent layer including calcium tungstate of a particle size in the order oi? 3-5 microns and calcium tungstate of a particle size of 0.5 to 1 micron.

5. In a combination of intensifying foils as claimed in claim 4, a back foil comprising approximately equal percentages by weight of the said particles in the order of 35 microns and of the said particles having a particle size of 0.5 to 1 micron.

KARL WiiRs'rLm.

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