EP0592558A1 - Structure d'ecran et de film unique possedant des proprietes radiologiques fortement ameliorees - Google Patents

Structure d'ecran et de film unique possedant des proprietes radiologiques fortement ameliorees

Info

Publication number
EP0592558A1
EP0592558A1 EP92914871A EP92914871A EP0592558A1 EP 0592558 A1 EP0592558 A1 EP 0592558A1 EP 92914871 A EP92914871 A EP 92914871A EP 92914871 A EP92914871 A EP 92914871A EP 0592558 A1 EP0592558 A1 EP 0592558A1
Authority
EP
European Patent Office
Prior art keywords
phosphor
silver halide
binder
screen
coated
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP92914871A
Other languages
German (de)
English (en)
Inventor
Jacob Beutel
Daniel J. Mickewich
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Publication of EP0592558A1 publication Critical patent/EP0592558A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7701—Chalogenides
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
    • C09K11/7767—Chalcogenides
    • C09K11/7769—Oxides
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
    • C09K11/7767—Chalcogenides
    • C09K11/7769—Oxides
    • C09K11/777—Oxyhalogenides
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
    • G03C5/16—X-ray, infrared, or ultraviolet ray processes
    • G03C5/17—X-ray, infrared, or ultraviolet ray processes using screens to intensify X-ray images
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • G21K2004/04—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens with an intermediate layer
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • G21K2004/06—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens with a phosphor layer
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K4/00—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens
    • G21K2004/08—Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens with a binder in the phosphor layer

Definitions

  • This invention relates to the field of radiology and more specifically to a film/screen structure that can greatly improve image sharpness and resolution. Even more specifically, this invention relates to single ultraviolet emitting screens in conjunction with single- side coated silver halide elements.
  • X-ray intensifying screens used to increase the ability of a photographic element to capture the image produced thereon are well-known in the art, these prior art screens generally have been used in pairs with double-side coated photographic elements.
  • These intensifying screen elements are generally created from a phosphor dispersion in a binder coated on a suitable support. Many phosphors are in commercial use in intensifying screens. However, since most of these phosphors emit visible blue to green light (in the wavelength range from 400 to 550 nm) spectrally sensitized silver halide elements are used to match the film's spectral response characteristics to the phosphor's emission.
  • Another way to increase the sharpness of double- side coated film/two-screen systems is to decrease print-through, i.e., to prevent light emanating from the front screen from exposing the photographic emulsion on the back side of the double coated film and vice versa, by placing a layer under the photographic emulsions on both sides of the film, which layer absorbs the actinic light emanating from the screens and prevents this light from penetrating to the other side of the film.
  • print-through i.e., to prevent light emanating from the front screen from exposing the photographic emulsion on the back side of the double coated film and vice versa
  • UV screens ultraviolet emitting screens
  • Van Stappen U.S. 3.912,933, October 14, 1975 does teach a particular element that can be used for mammography, for example.
  • This element requires a single-side coated silver halide element with a particular grain size, an antihalation layer coated on the film element and a high speed X-ray screen in operative contact therewith.
  • this system was one of the first successful elements designed specifically for mammographic and extremity X-ray evaluations, the structure is complex, requiring a dischargeable antihalation dye layer. Additionally, this Van Stappen element was designed specifically for mammographic and extremity evaluations.
  • an X-ray intensifying screen comprising an ultraviolet emitting X-ray phosphor having a peak emission between 300 and 390 nm with the proviso that at least 80% of the ultraviolet emission of said phosphor is between 300 and 390 nm, wherein said phosphor is dispersed in a binder, said binder absorbing no more than 10% of said ultraviolet emission from said phosphor, and wherein the mean free path for absorption of a photon emitted by said phosphor when excited by X- radiation is less than 2 cm, and wherein said phosphor dispersed in said binder is coated on a support; and, (b) a single side, gelatino silver halide coated element in operative association therewith.
  • the Figure is a drawing which diagrammatically compares the resolution obtainable using the film/screen system of this invention with some prior art systems by showing the spreading of the light in systems with different mean free paths for light absorption.
  • UV-ray phosphors which emit in the ultraviolet (UV) when exposed to X- radiation. Although these phosphors may also produce improved image quality, it is also well-known that X-ray intensifying screens prepared from these UV emitting phosphors, produce very low contrast and Dmax on conventional silver halide elements used therewith.
  • UV emitting phosphors are, for example, Ta ⁇ 4 , either unactivated or activated with gadolinium, bismuth, lead, cerium or mixtures of these activators; LaOBr activated with gadolinium or gadolinium and thulium; and La 2 ⁇ 2 S activated with gadolinium, among others.
  • Most of these phosphors emit mainly in the UV, e.g., 300 to 390 nm, although some small amount of light, e..g., up to 20% and preferably less than 10%, may also be emitted below 300 and above 390 nm.
  • UV emitting phosphors will emit in the range of 300 to 390 nm and preferably in the range of 310 to 360 nm.
  • the conversion efficiency of the phosphor i.e., the efficiency with which the energy carried by an X-ray quantum absorbed by this phosphor, is converted to light photons emitted by the phosphor, should be higher than 5%.
  • These phosphors may be prepared as is well-known in the prior art and then mixed with a suitable binder before coating on a suitable support. Once prepared in this manner, this element is conventionally known as an X-ray intensifying screen and is eminently suitable for radiological evaluations.
  • X-ray intensifying phosphors that do not function within the metes and bounds of this invention. These include the following:
  • a screen of the type encompassed by the phosphors described in this invention will comprise a support, an intensifying phosphor layer, and a topcoat or protective layer therefor.
  • a reflective layer such as a whitener, e.g., Ti ⁇ 2 dispersed in a suitable binder, may also be added to the screen structure.
  • this reflective layer is interposed between the phosphor layer and the support, or, alternatively, the whitener may be dispersed directly into the support.
  • the reflective layer generally increases the light output of the intensifying screen during use.
  • the protective layer is important to protect the phosphor layer against mechanical damage.
  • the protective layer should generally also be UV transparent so that the flow of UV light from the phosphor is not decreased. Those layers that are known to absorb a great deal of UV light, e.g., polyethylene terephthalate films, for example, are not particularly ⁇ seful within this invention.
  • the intensifying screen absorbs X-rays that impinge thereon and emits energy having a wavelength that is readily captured by the photographic silver halide X-ray film associated therewith.
  • Effective X-ray intensifying phosphors based on yttrium, gadolinium or lutetium tantalate are known. These particular phosphors, with the monoclinic M' phase, is particularly effective in capturing X-rays. Some of these tantalate phosphors are also efficient emitters of UV light and are particularly preferred within the metes and bounds of this invention. They are generally prepared according to the methods of Brixner, U.S. Pat. No. 4,225,653, and the information contained in this reference is incorporated herein by. reference thereto.
  • These phosphors are those which emit at least 80% of the light within the range of 300 to 390, and ' preferably within 310 to 360 nm and are generally manufactured by mixing the various oxides and firing in a suitable flux at elevated temperatures. After firing, deagglomerating and washing, the phosphor is mixed with a suitable binder in the presence of a suitable solvent therefore and coated on a support, with the proviso that said binder absorbs less than 10% of any UV light emitted from said phosphor, a so-called "transparent" binder. All of these steps are described in the aforementioned Brixner reference and all are well-known in the prior art. A protective topcoat may also be applied over this phosphor coating, in fact it is so preferred.
  • the mean free path for adsorption of a photon emitted by the phosphor of this invention will be defined as the average distance which a light photon emitted by the phosphor travels within the structure of the screen before this photon is absorbed therein. Light which is emitted at an angle with respect to that light emitted perpendicular to the screen's surface is more likely to be absorbed when the mean free path is short.
  • the mean free path for light absorption should be less than 2 cm, and preferably less than 1 cm, in order to properly function.
  • binders which will function within this invention are those that are well-known in the art and which absorbs no more than 10% of the UV light emitted by the phosphor. These include resinous materials such as poly(methyl methacrylate) , poly(n- butyl methacrylate), poly(isobutyl methacrylate, copolymers of n-butyl methacrylate and isobutyl methacrylate, among others.
  • resinous materials such as poly(methyl methacrylate) , poly(n- butyl methacrylate), poly(isobutyl methacrylate, copolymers of n-butyl methacrylate and isobutyl methacrylate, among others.
  • Carboset® 525 average molecular weight 260,000, Acid No. 76-85
  • Carboset® 526 average molecular weight 200,000, Acid No. 100
  • Carboset® XL- 27 average molecular weight 30,000, Acid No. 8, etc. may also be mentioned.
  • the silver halide element we prefer may be comprised of spherical or cubic silver chloride grains wherein the chloride represents at least 50 mole percent of the emulsion, or tabular silver halide grains wherein said tabular grains are silver bromide, silver chloride, silver iodide or mixtures thereof and at least 50% of these grains are tabular grains with a grain thickness of less than 0.5 microns, preferably between 0.21 and 0.30 microns, and an average aspect ratio of at least 2:1 (preferably an aspect ratio of between 4.0 and
  • the grains are generally made into an emulsion using a binder such as gelatin, and are sensitized with gold and sulfur, for example. Other adjuvants such as antifoggants, wetting and coating aides, dyes, hardeners etc. may also be present if necessary.
  • the emulsions may also be formed from conventional shaped silver bromoiodide grains made by balanced double jet or splash procedures provided that their Dmax does not decrease significantly on exposure to UV light in the wavelength range from 300 to 390 nm compared to exposure to visible light (wavelengths greater than 400 nm) .
  • a conventional photographic support such as a dimensionally stable polyethylene terephthalate film suitably coated with a resin sub followed by a gel sub supra thereto.
  • a resin sub followed by a gel sub supra thereto.
  • auxiliary layers supra to the emulsion and on the opposite side of the support may also be employed to provide protection from scratches, curl and the like.
  • the film support for the photographic emulsion layer may contain a dye to impart a tint therein, e.g., a blue tint, in fact it is so preferred.
  • a dye to impart a tint therein e.g., a blue tint
  • the emulsions useful within the ambit of this invention are generally UV sensitive in and of themselves, it may not be required to add any kind of sensitizing or desensitizing dye thereto. However, if required, a small amount of a sensitizing dye might advantageously be added. Additionally, it is also conventional to add a sensitizing dye to tabular emulsions in order to increase their ability to respond to light.
  • Tabular grain silver halide products are well-known in the prior art and present the user with some considerable advantages over conventional grain products, e.g., semi-spheroidal grains, for example.
  • the tabular products can usually be coated at a much lower coating weight without loss of covering power. They can be hardened with smaller amounts of conventional hardeners, presenting quite a significant advantage over the conventional grains.
  • Tabular chloride emulsions are also well-known and are described by Maskasky in U.S. 4,400,463, 8/23/83 and also by Wey, U.S. 4,399,205.
  • Some other references which describe the manufacture and use of tabular grain elements are Dickerson, U.S. 4,414,304; Wilgus et al., U.S. 4,434,226; Kofron et al., U.S. 4,439,520; and Tufano and Chan, U.S. 4,804,621.
  • a single X- ray intensifying screen is made by dispersing YTa0 4 phosphor made as described above, in a mixture of acrylic resins using a solvent. This mixture is then coated on a polyethylene terephthalate support containing a small amount of anatase Ti ⁇ 2 whitener dispersed therein. The phosphor may be coated to a coating weight of ca. 15 to 110 mg of phosphor per cm 2 . A topcoat of sty . rene/acrylonitrile copolymer is coated thereon and dried.
  • the film element is a single-side coated, gelatino silver halide element conventionally prepared as is well-known to those of normal skill in the art, preferably, a tabular emulsion containing a small amount of a blue sensitizing dye therein.
  • This emulsion will also have been raised to its optimum level of sensitivity by the addition of gold and sulfur as well as by the addition of antifoggants and the like. Wetting and coating agents will also be present.
  • the coating weight of this element may be between 60 and 100 mg of silver/dm 2 , for example.
  • the single-side coated, gelatino silver halide element is placed in a conventional cassette with the X-ray intensifying screen described above.
  • This element is then placed in proximity to the object which is to be examined, e.g., a human patient.
  • the preferred geometric arrangement is to have the front, i.e., the phosphor side of the screen facing the x-ray beam and the emulsion coating of the film facing the front of the screen.
  • X-rays are generated from a source, pass through the object, and are absorbed by the intensifying screens. UV light given off as a result of X-ray absorption, will expose the film element contained therein. A high quality image which has high detail can thus be obtained.
  • the extremely sharp image which is obtained is significantly sharper than an image which would be obtained with a screen having the same coating weight but which emits visible light or which emits ultraviolet light whose mean free path for light absorption in the screen is longer than 2 cm.
  • the elements of this invention may advantageously be employed for any radiological evaluation and excellent image quality and image sharpness will be observed. Where fine detail is a requisite, e.g., mammography and extremity evaluations, these elements are eminently suitable.
  • Example 1 is considered to represent the best mode thereof. All parts and percentages are by weight unless otherwise indicated.
  • Acrylic resin ave. mol. wt. 260,000; acid no. 76-85; B. F. Goodrich Co., Cleveland, OH
  • the crucible was then placed in a standard, commercial, high temperature furnace and fired at about 1200°C for about 8 hours and then at about 1250°C for about 16 hours.
  • the f rnace was then allowed to cool and the contents of the crucible weighed and washed thoroughly with water to remove the flux.
  • This material was then added to the binder Solution A using about 200 g of phosphor/60 g of binder solution.
  • This mixture was placed in a plastic container along with about 85 g of 1 cm diameter corundum balls (ca. 15 balls) and this mixture was then ball milled for about 12 to 16 hours at room temperature with a rotation speed of about 60 rpm.
  • the ball milled suspension was filtered through a 75 mesh Nylon bag and coated onto a suitable support.
  • the support used was 0.010 inch thick, dimensionally stable polyethylene terephthalate film containing a small amount of a whitener, e.g., anatase Ti ⁇ 2 , dispersed therein.
  • the coating weight of the phosphor dispersion placed thereon is in the range from about 10 to about 100 mg of phosphor per cm 2 .
  • An overcoat layer is prepared from the following solutions:
  • Styrene/acrylonitrile copolymer resin Dow Chemical Co., Midland, MI
  • Acrylic resin ave. mol. wt. 30,000; acid no. 80, B. F. Goodrich Co., Cleveland, OH
  • a gel solution is prepared by mixing the following ingredients until a thick gel forms:
  • This mixture is coated on top of the phosphor coating using a doctor knife with a 0.004 inch gap.
  • the resulting top-coat is air dried for 12-16 hours at 40°C.
  • two additional screens were prepared.
  • the phosphor of these controls was made as above but with an activator present, e.g., 2-4% niobium.
  • the control screens were prepared with a coating weight of 15 mg/cm 2 and 30 mg/cm 2 and were coated and overcoated similar to the screen of this invention as described above.
  • the control screens have a major emission peak at about 400 nm and thus are not considered to be UV emitters within the ambit of this invention.
  • the Film Element A conventional, tabular grain, blue sensitive X-ray emulsion was prepared as well-known to one of normal skill in the art. This emulsion had tabular silver iodo bromide grains. After precipitation of the grains, the average aspect ratio was determined to be about 5:1 and the thickness about 0.2 ⁇ m. The procedures for making tabular grains of this nature are fully described in Nottorf, U.S. 4,772,886 and Ellis, U.S. 4,801,522, the contents of which are incorporated herein by reference.
  • One of each of the aforementioned screens were used to expose samples of X-ray film elements made above.
  • the screen was placed in a vacuum bag along with the single-side coated X-ray film element and given an exposure to a 60 KVP X-ray source with a tungsten cathode. After exposure, the films were developed in a standard X-ray developer formulation, fixed, washed and dried.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Conversion Of X-Rays Into Visible Images (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Abstract

Structure d'écran et de film à rayons X permettant de produire une image à très haute définition. Cette structure comprend un écran comportant du phosphore émettant des U.V. dont la crête d'émission principale est située entre 300 et 390 nm, et qui est dispersé dans un liant et déposé en couche sur un support classique. L'élément à film est un élément à l'halogénure d'argent recouvert sur un seul côté. On peut utiliser cette structure pour tout type de bilan radiologique nécessitant une définition très élevée, ladite structure étant beaucoup plus perfectionnée que celle de l'état de la technique.
EP92914871A 1991-07-03 1992-07-02 Structure d'ecran et de film unique possedant des proprietes radiologiques fortement ameliorees Withdrawn EP0592558A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US72516091A 1991-07-03 1991-07-03
US725160 1991-07-03
PCT/US1992/005443 WO1993001522A1 (fr) 1991-07-03 1992-07-02 Structure d'ecran et de film unique possedant des proprietes radiologiques fortement ameliorees

Publications (1)

Publication Number Publication Date
EP0592558A1 true EP0592558A1 (fr) 1994-04-20

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EP92914871A Withdrawn EP0592558A1 (fr) 1991-07-03 1992-07-02 Structure d'ecran et de film unique possedant des proprietes radiologiques fortement ameliorees

Country Status (4)

Country Link
EP (1) EP0592558A1 (fr)
JP (1) JPH06509183A (fr)
AU (1) AU2306492A (fr)
WO (1) WO1993001522A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5221846A (en) * 1991-11-27 1993-06-22 E. I. Du Pont De Nemours And Company Radiographic system with improved image quality
US5853945A (en) * 1996-06-03 1998-12-29 Fuji Photo Film Co., Ltd. High-contrast silver halide photographic material and photographic image forming system using the same
JP4759741B2 (ja) * 2005-03-22 2011-08-31 国立大学法人徳島大学 蛍光材料及びｘ線増感基板

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5017440A (en) * 1989-09-29 1991-05-21 E. I. Du Pont De Nemours And Company Adhesion between phosphor and topcoat layers of an X-ray intensifying screen
US5145743A (en) * 1990-10-25 1992-09-08 E. I. Du Pont De Nemours And Company X-ray intensifying screens with improved sharpness

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9301522A1 *

Also Published As

Publication number Publication date
WO1993001522A1 (fr) 1993-01-21
JPH06509183A (ja) 1994-10-13
AU2306492A (en) 1993-02-11

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