EP0494890B1 - Method for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode, and also a method for correcting an image intensifier tube - Google Patents
Method for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode, and also a method for correcting an image intensifier tube Download PDFInfo
- Publication number
- EP0494890B1 EP0494890B1 EP90914167A EP90914167A EP0494890B1 EP 0494890 B1 EP0494890 B1 EP 0494890B1 EP 90914167 A EP90914167 A EP 90914167A EP 90914167 A EP90914167 A EP 90914167A EP 0494890 B1 EP0494890 B1 EP 0494890B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- anode
- cathode
- image intensifier
- oblong
- intensifier tube
- 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.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/86—Vessels; Containers; Vacuum locks
- H01J29/89—Optical or photographic arrangements structurally combined or co-operating with the vessel
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
- H01J31/505—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output flat tubes, e.g. proximity focusing tubes
Abstract
Description
- The invention relates to a method for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode.
- An oblong image intensifier tube of the proximity-focus type is described in the Dutch Patent 183,914. Such oblong image intensifier tubes are frequently used in so-called slit radiography apparatuses. The cathode is in that case sensitive to X-ray radiation, while the anode provides an output image corresponding to the incident X-ray radiation via an anode window which may possibly comprise an optical fibre plate. In such an application, the anode and the cathode may have a length of, for example, 40 cm and a width of, for example, 4 cm.
- In practice the problem arises that it is difficult to make such long image intensifier tubes which have a uniform conversion factor over the entire active surface. Conversion factor is understood to mean the ratio between the radiation incident at the cathode side and the resultant output radiation at the anode side. It is also possible for the conversion factor to alter locally during the service life of such an image intensifier tube as a consequence of ageing phenomena.
- From US-A-4187002 it is known in an intensifier tube with circular input and output screens to measure the light output at a number of separate points on the anode when the cathode is illuminated simultaneously or sequentially as opposite points. Then a mark is made consisting of rectangular areas, each area corresponding to one of said points of the anode.
- There is therefore a need for a facility enabling correction of an oblong image intensifier tube so that the conversion factor is, so to speak, equalized.
- The object of the invention is to provide such a facility. To this end, a method for manufacturing a correction mask for an image intensifier tube according to claim 1 is provided.
- A method for correcting an image intensifier tube of the proximity-focus type having an oblong cathode and anode and an anode window matching the anode is characterized, according to the invention, in that a strip-type transparent carrier which is provided with a blackening in at least one oblong region is placed as a mask against the anode window.
- The invention will be described in greater detail below with reference to the drawing.
- Figure 1 shows diagrammatically an example of an apparatus in which an image intensifier tube of the proximity-focus type having an oblong cathode and anode is used;
- Figure 2 shows diagrammatically two examples of graphs which reproduce the output signal of an oblong proximity-focus image intensifier tube as a function of the distance from one end of the tube for a given input signal;
- Figure 3 shows diagrammatically an example of a correction mask for an oblong image intensifier tube.
- Figure 1 shows diagrammatically an example of an apparatus in which an image intensifier tube of the proximity-focus type having an oblong cathode and anode is used. The apparatus shown is an apparatus, known per se, for slit radiography in which a part of a patient 1, for example the thorax, is scanned with a flat fan-
shaped X-ray beam 3 via aslit diaphragm 2. To this end, anX-ray source 4 can be used which is rotatable about an axis which is parallel to the slit of the slit diaphragm and preferably extends through the X-ray focus of the X-ray source, as shown in Figure 1. - An
image intensifier tube 6 which may, for example, have acathode 7 and ananode 8 having a length of 40 cm and a height of 2.5 cm is situated behind the patient and is synchronously moved concomitantly with the scanning movement of the X-ray beam in a manner such that, after having passed through the patient, the flat fan-shaped X-ray beam always falls on the cathode of the image intensifier tube. In this application, the cathode is sensitive to X-ray radiation and emits electrons which provide, at the anode side, a visible output image which may be used, for example, to illuminate aphotographic plate 9. - It is clear that it is important for the conversion factor of the image intensifier tube to be as uniform as possible over the entire length (and height) thereof.
- In this connection, it is pointed out that, in the application shown, a uniform variation of the conversion factor in the longitudinal direction of the tube in particular is important because any irregularities in the height direction are equalized during the formation of the image as a consequence of the scanning movement taking place at right angles to the longitudinal direction.
- It is furthermore pointed out that it is advisable in practice to arrange for the conversion factor to increase from the centre of the anode towards the two ends of the anode in order to compensate for the so-called vignetting effect. In this way, a surface, for example, a photographic film, situated at some distance from the anode can be illuminated more uniformly.
- It has been found that the theoretically required variation of the output signal of the anode as a function of the position can in practice be approximated by a parabolic curve.
- Figure 2 shows diagrammatically two graphs which reproduce qualitatively the intensity C of the light provided by the oblong anode as a function of the distance X from one of the ends of the image intensifier tube for a given irradiation of the cathode which is uniform over the entire length.
- The curves shown therefore represent the conversion factor as a function of the position on the anode.
- The curves shown have been measured with the aid of a photosensitive cell which emits an electrical signal corresponding to the intensity of the incident light in response to incident light. According to the invention, such a cell is moved along the anode in the longitudinal direction of the anode during a uniform irradiation of the oblong cathode and then provides output signals of the type shown in Fig. 2 which are representative of the variation of the conversion factor of the tube.
- The required uniform illumination of the cathode preferably takes place via a slit-type diaphragm whose opening extends at right angles to the longitudinal direction of the cathode and is moved in the longitudinal direction of the cathode synchronously with the photosensitive cell at the anode side. In this way, possible measuring errors resulting from the radiation scattering occurring in the tube are essentially avoided.
- As will be indicated in still greater detail below, a number of parallel strips extending in the longitudinal direction of the anode at various heights can advantageously be scanned. To this end, use may be made of a single photosensitive cell which is moved consecutively at different heights along the anode, or of a number of cells which each simultaneously scan a strip of the anode. A number of photosensitive cells may, for example, be placed above one another in a holder, which holder is then passed along the anode so that a number of curves of the type shown in Figure 2 are generated for each tube.
- It is pointed out that it is a question of a relative movement. It is therefore also possible to move the tube between, on the one hand, a stationery radiation source and any diaphragm device and, on the other hand, one or more photosensitive elements in a direction corresponding to the longitudinal direction of the anode.
- Figure 2A shows a relatively widely varying
curve 20 which has minima at 21 and 22 and which has relative maxima at 23 and 24 which are also considerably different from one another. The conversion factor is therefore too low at 21 and 22 and in fact too high at 23 and 24. - In order to make a correction mask, a required value line is first sought which approximates to the measured
curve 20 as well as possible. The required value line represents a desired variation of the conversion factor and could, for example, be a horizontal straight line. As pointed out above, however, a parabolic curve such as shown at 25 in Figure 2A is preferable. - Since the
minima minima - For the same tube, but now provided with a correction mask, Figure 2B shows by way of example a second
experimental curve 26 having aparabolic curve 27 approximating to said curve. It can be seen that the difference between theexperimental curve 20 and the associatedparabolic curve 25 is appreciably greater than the only slight difference between theexperimental curve 26 and theparabolic curve 27. - According to the invention, the desired degree of correction can be obtained for any value of X by attenuating the light provided by the anode in a manner such that the residual light corresponds to the value of the required value line at the relevant value of X.
- At a distance X₁ from the end of the tube or the anode chosen as the origin, there is a difference D between the experimental curve and the required value line in the case of Figure 2A. If the value of C associated with X₁ is denoted by C(X₁) an attenuation of the light provided by the anode by a factor of D/C(X₁) is therefore needed at the position X₁.
- Such an attenuation can be obtained in a simple way by using a mask which has an appropriate blackening at the relevant position. In this way, starting from the experimental curve and the required value line, the attenuation required for any value of X, and consequently the required blackening of a correction mask to be manufactured, can be determined.
- The measured values are preferably fed to a computer which is then also able to determine the required value line best approximating to the measured value curve and the difference between the measured values and the required values. If coupled to a printer, the computer is then also able to print out an image of a strip-type correction mask which is suitable for correcting the measured strip of the anode. The print-out may be composed in a simple way of a black line which varies in thickness and, depending on the thickness when viewed in height, masks a more or less large section of the measured strip of the anode if it is provided at the correct position in front of the anode window.
- The print-out may also be composed of a raster of black dots which vary in thickness. The abovementioned black line which varies in thickness may, moreover, likewise be made up of dots such as is usual when computer printers are used.
- Figure 3 shows an example of a mask pattern which has been printed out in the way described and which, in the example shown, is intended to correct five
strips 30 to 34 inclusive which extend parallel to one another with a mutual gap in the longitudinal direction of the anode. - The mask pattern can be printed out in a simple manner, for example photographically, in dimensions corresponding to the dimensions of the anode window on a transparent carrier which is suitable for mounting on the outside on the anode window.
- The lines shown in Figure 3 and varying in thickness are broken at 35 and 36. This means that at those positions no correction was necessary. It could also mean that the required value line is too high at those positions, i.e. above the experimental curve, and that the chosen required value line is possibly not the optimum required value line. Which of the two situations occurs can be checked in a practical situation using images of the type shown in Figure 2.
- An image intensifier tube can therefore be corrected relatively simply in the manner described above. In addition, after a certain period of use during which ageing phenomena could occur in the image intensifier tube, the correction mask may be replaced by a more up-to-date mask, so that an expensive image intensifier tube acquires a longer service life.
Claims (13)
- Method for manufacturing a correction mask for an image intensifier tube,
in which the cathode is essentially uniformly illuminated over the entire surface with radiation to which the cathode is sensitive;
in which during the illumination of the cathode, the intensity of the light provided by the anode is measured at different positions thereof as experimental values;
in which the differences between the experimental values and a required value is determined;
and in which a transparent carrier is manufactured which across the anode is provided with a blackening which represents the differences between the experimental values and an associated required value
characterized
in that the image intensifier is of the proximity-focus type having an oblong cathode and anode;
in that the intensity of the light provided by the anode is measured in at least one narrow strip-type region, extending in the longitudinal direction of the anode, as a function of the distance from one of the ends of the anode;
in that the measured values obtained in this way for each strip-type region are reproduced in a graph as an experimental curved;
in that a required value line approximating to the experimental curve as well as possible is determine for each experimental curve;
in that the required value line is lower than, or at most equal to the minimum of the experimental curve at the position of the minimum;
in that for each position along the length of the anode the differences between the experimental curve and the required value line are determined as a function of the distance from one of the ends of the anode;
and in that the blackening is provided in at least one oblong region of the transparent carrier, the blackening representing the difference between an experimental curve and an associated require value line as a function of the distance from one of the ends of the anode. - Method according to Claim 1, characterized in that a parabolic curve is chosen as the required value line.
- Method according claim 1 or 2, characterized in that in the at least one oblong region the blackening is formed by a line which varies in thickness.
- Method according to Claim 3, characterized in that the line is formed by black dots.
- Method according to one of the preceding claims, characterized in that the blackening in the at least one oblong region is determined by a computer on the basis of the experimental curve and the required value line and is printed out by means of a printer as a line which varies in thickness.
- Method according to Claim 5, characterized in that the line which varies in thickness is transferred photographically to a transparent carrier.
- Method according to one of the preceding claims, characterized in that the uniform illumination of the cathode is obtained by illuminating the cathode via a slit-type diaphragm extending at right angles to the longitudinal direction of the cathode, the diaphragm and the cathode being moved with respect to one another in the longitudinal direction of the cathode.
- Method according to one of the preceding claims, characterized in that the intensity of the light provided by the anode is measured with the aid of at least one photosensitive cell, the photosensitive cell and the anode being moved relatively with respect to one another in the longitudinal direction of the anode.
- Method according to Claims 7 and 8, characterized in that the slit-type diaphragm and the at least one photosensitive cell are moved synchronously with respect to the cathode or the anode.
- Method according to one of the preceding claims, characterized in that the intensity of the light provided by the anode is measured in at least two strip-type regions extending in the longitudinal direction of the anode parallel to one another with a gap and in that a transparent carrier is manufactured which is provided with a blackening in oblong regions corresponding to the at least two strip-type regions.
- Method for correcting an image intensifier tube of the proximity-focus type having an oblong cathode and anode and an anode window matching the anode, characterized in that a strip-type transparent carrier which is provided with a blackening in at least one oblong region extending substantially over the whole length of the oblong anode is placed as a mask against the anode window.
- Method according to Claim 11, characterized in that the mask used is a mask obtained in accordance with one of Claims 1 to 10 inclusive.
- Slit radiography device comprising an X-ray source a slit-type diaphragm for forming an X-ray fan beam an image intensifier tube of the proximity focus type having an oblong cathode and anode in the path of the fan beam and means for scanning an object with the fan beam characterized in that the image intensifier tube has an anode window provided with a mask obtained by a method according to one of the claims 1 to 10.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL8902443A NL8902443A (en) | 1989-10-02 | 1989-10-02 | METHOD FOR MANUFACTURING A PROXIMITY FOCUS-TYPE IMAGERIZER TUBE WITH PROLIMED CATHODE AND ANODE, AND METHOD FOR CORRECTING AN IMAGE AMPLIFIER TUBE. |
NL8902443 | 1989-10-02 | ||
PCT/EP1990/001642 WO1991005364A1 (en) | 1989-10-02 | 1990-09-26 | Method for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode, and also a method for correcting an image intensifier tube |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0494890A1 EP0494890A1 (en) | 1992-07-22 |
EP0494890B1 true EP0494890B1 (en) | 1995-11-29 |
Family
ID=19855383
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP90914167A Expired - Lifetime EP0494890B1 (en) | 1989-10-02 | 1990-09-26 | Method for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode, and also a method for correcting an image intensifier tube |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP0494890B1 (en) |
JP (1) | JPH05504016A (en) |
CN (1) | CN1050790A (en) |
AU (1) | AU637411B2 (en) |
CA (1) | CA2066156A1 (en) |
DE (1) | DE69023916D1 (en) |
IL (1) | IL95833A (en) |
NL (1) | NL8902443A (en) |
WO (1) | WO1991005364A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102016220096B3 (en) * | 2016-10-14 | 2018-02-08 | Siemens Healthcare Gmbh | Method for generating X-ray image data |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4187002A (en) * | 1975-05-21 | 1980-02-05 | Thomson-Csf | Film for correcting spatial irregularity in the gain of optical images of intensifier tubes |
JPS5247672A (en) * | 1975-10-15 | 1977-04-15 | Hitachi Ltd | Illuminance correction filter and manufacturing method thereof |
NL183914C (en) * | 1979-02-02 | 1989-02-16 | Optische Ind De Oude Delft Nv | ROENTGEN IMAGE AMPLIFIER. |
AU531837B2 (en) * | 1979-05-10 | 1983-09-08 | Kishinevsky Gosudarstvenny Universitet Imeni V.I. Lenina | Image intensifier |
-
1989
- 1989-10-02 NL NL8902443A patent/NL8902443A/en not_active Application Discontinuation
-
1990
- 1990-09-26 DE DE69023916T patent/DE69023916D1/en not_active Expired - Lifetime
- 1990-09-26 AU AU64154/90A patent/AU637411B2/en not_active Ceased
- 1990-09-26 WO PCT/EP1990/001642 patent/WO1991005364A1/en active IP Right Grant
- 1990-09-26 EP EP90914167A patent/EP0494890B1/en not_active Expired - Lifetime
- 1990-09-26 JP JP2513269A patent/JPH05504016A/en active Pending
- 1990-09-26 CA CA002066156A patent/CA2066156A1/en not_active Abandoned
- 1990-09-27 IL IL9583390A patent/IL95833A/en not_active IP Right Cessation
- 1990-09-29 CN CN90108026.8A patent/CN1050790A/en active Pending
Also Published As
Publication number | Publication date |
---|---|
CN1050790A (en) | 1991-04-17 |
EP0494890A1 (en) | 1992-07-22 |
AU637411B2 (en) | 1993-05-27 |
AU6415490A (en) | 1991-04-28 |
CA2066156A1 (en) | 1991-04-03 |
WO1991005364A1 (en) | 1991-04-18 |
IL95833A0 (en) | 1991-06-30 |
DE69023916D1 (en) | 1996-01-11 |
JPH05504016A (en) | 1993-06-24 |
NL8902443A (en) | 1991-05-01 |
IL95833A (en) | 1994-01-25 |
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