Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/02—Viewing or reading apparatus
  • G02B27/022—Viewing apparatus
  • G02B27/023—Viewing apparatus for viewing X-ray images using image converters, e.g. radioscopes
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
  • G02B23/12—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices with means for image conversion or intensification
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/32—Fiducial marks and measuring scales within the optical system
  • G02B27/34—Fiducial marks and measuring scales within the optical system illuminated
• • 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

Definitions

• An image intensifier comprises a primary screen intended to receive a first image and a secondary screen emitting a second image, a function of the first.
• the intensifiers are for example used in medical radiology.
• the intensifier receives an image formed by X-rays which have passed through the body of a patient.
• the intensifier emits on its secondary screen a visible image which is a function of the image X received by the primary screen.
• the intensifier amplifies the intensity of the image received. In medical radiology, this amplification makes it possible to reduce the dose of X-radiation received by the patient.
• Amplification is carried out in a conventional manner by converting the radiation received by the primary screen into electrons emitted in a cavity where the vacuum prevails. The electrons are then accelerated by means of electrodes and then converted by the secondary screen into a visible image.
• the invention is not limited to medical radiology, it can be implemented in all types of intensifiers whatever the radiation received or emitted by the screens.
• the use of electrons accelerated by electrodes makes the intensifier sensitive to electromagnetic disturbances occurring in the environment of the intensifier. These disturbances create a spatial distortion of the image emitted by the secondary screen compared to the image received by the primary screen. It is possible to correct this distortion by placing a grid in front of the primary screen allowing or passing, in specific areas, the radiation received by the primary screen.
• the intensifier When using the intensifier to receive a useful image, it will of course be necessary to move the grid out of the scene observed by the primary screen of the intensifier. We can thus correct the useful image emitted by the output screen using the distortion values determined for each point of the image.
• the invention relates to an image intensifier comprising a primary screen intended to receive a first radiation and a secondary screen emitting a second radiation which is a function of the first radiation, characterized in that it also comprises means to project a localization test pattern produced using a third radiation onto the primary screen, and in that the secondary screen emits an image which is a function of the localization test pattern.
• the localization target is formed of a plurality of points distributed over the primary screen.
• the invention makes it possible, for example, to use an image intensifier in tomography which requires great control of the distortion to allow the reconstruction of three-dimensional images.
• the invention also makes it possible to use an image intensifier in applications requiring a perfect geometric superposition of two successive images such as for example digital angiometry by subtraction. Other non-medical applications also require low distortion and can therefore use an image intensifier according to the invention.
• FIG. 1 schematically shows in section a first embodiment an image intensifier according to the invention
• FIG. 2 schematically represents an example of an optical device making it possible to focus a localization target on the primary screen
• Figure 3 shows an embodiment of the device shown in Figure 2
• Figure 4 shows another embodiment of the device according to the invention.
• the image intensifier shown in FIG. 1 comprises a tube 1 substantially elongated along an axis 2.
• the tube 1 has an envelope 3 inside which there is a sufficient vacuum for electrons to move there.
• a primary screen 4 forms a first end of the casing 3 and a secondary screen 5 forms a second end of the casing 3.
• An entry window 6 makes it possible to seal the casing 3 at its level. first end. It is possible to do without the entry window 6 and, in this case, the secondary screen 5 seals the envelope at its first end. Likewise, the secondary screen 5 seals the envelope 3 at its second end.
• the intensifier shown in Figure 1 is used in medical radiology and can be placed outside the envelope 3, in front the entry window 6, a thin protective plate 8 permeable to X-rays, for example made of an aluminum-based alloy.
• the X-ray radiation enters the tube 1 substantially along the axis 2 in the direction materialized by the arrow 9.
• This radiation reaches the primary screen 4 through the plate 8 and the input window 6.
• the primary screen 4 comprises a scintillator material 10 on the face of the screen receiving the X-ray radiation and a photocathode 11 on the opposite face of the primary screen 4.
• the scintillator material 10 converts the X-ray radiation received by the primary screen 4 into light, for example visible. This light is then absorbed by photocathode 11 which converts it into electrons.
• the electrons are then emitted inside the envelope 3 in the direction of the secondary screen 6.
• the schematic path of the electrons inside the envelope 3 is shown in Figure 1 by an arrow 12 shown in lines interrupted.
• the tube 1 also includes several electrodes 13, 14, as well as an anode 15 located inside the envelope 3 making it possible to accelerate the electrons emitted by the photocathode 11 and to guide them towards the secondary screen 5.
• L acceleration of the electrons brings them energy allowing the intensification of the image.
• the secondary screen 5 receives the electrons emitted by the photocathode 11 and converts them into radiation, for example visible, emitted towards the outside of the envelope 3 in the direction of the arrow 9.
• This visible radiation can, for example, be analyzed by a camera, represented in FIG. 1 by its entrance pupil 20.
• the optical axis of the entrance pupil 20 is substantially coincident with axis 2.
• the intensifier comprises means for projecting a localization pattern on the primary screen 4.
• These means include, for example, a window 16 located in the envelope 3.
• This window allows radiation 17 distinct from X-rays to illuminate the primary screen 4.
• this radiation is shown by two lines 18 and 19 representing the extreme routes he can follow.
• the window 16 is positioned on the casing 3 so that the radiation 17 can light up substantially the entire surface of the primary screen 4.
• the window 16 is located between the electrodes 13 and 14, but it it is understood that other locations located on the envelope 3 may be suitable.
• the window 16 is located so that the radiation 17 illuminates the primary screen 4 by the face opposite to that which receives the X-ray radiation.
• the front of the primary screen 4 is defined by convention as the face through which the primary screen 4 receives X-ray radiation and the rear of the primary screen 4, the face through which the photocathode 11 emits electrons.
• the radiation 17 directly illuminates the photocathode 11 from the rear of the primary screen 4.
• the optical device shown diagrammatically in FIG. 2 comprises a source 21 emitting the radiation 17.
• the source 21 is advantageously monochromatic and focused using a lens 22 on the primary screen 4.
• a solid state laser such as those used as a pointer.
• This type of laser has the advantage of being inexpensive.
• the wavelength of the laser is chosen so that the photocathode 11 is sensitive to this wavelength.
• the beam of radiation 17, thus focused, is reflected on the surface of the diffracting grating 23 to be returned to the primary screen 4 on which the radiation 17 is focused.
• FIG. 3 represents an embodiment, given by way of example, of the device shown in FIG. 2.
• the means 16 comprise a prism 30.
• the radiation 17 coming from the source 21 passes through the prism 30 before entering the envelope 3 through the window 16.
• the prism 30 comprises three faces 31, 32 and 33.
• the radiation 17 penetrates into the prism 30 through the face 31 and exits through the face 32.
• the diffracting grating 23 is located on the third face 33 of the prism 30.
• This embodiment has the advantage of having only a few diopters on the path of the radiation 17.
• the diffracting grating 23 can be produced directly on the face 33 of the prism 30. It can also be produced on a support 34 separate from the prism 30.
• the support 34 is then bonded to the face 33 using an optical adhesive 35 with the same optical index as the prism 30. This same adhesive can also be used for bonding side 32 of prism 30 on window 16.
• the diffracting grating 23 can for example be produced using a periodic or holographic pattern.
• the source 21 is rigidly fixed to the casing 3. This is necessary so that the localization target, produced using radiation 17 maintains a constant position relative to the primary screen 4 even during possible movements of the image intensifier.
• FIG. 4 represents another embodiment of the invention, an embodiment adapted to an existing tube 1 on which it is not desired to make a window 16 distinct from the other existing windows. It is therefore possible to use a part 44 of the secondary screen 5 as a window for introducing the radiation 17 into the envelope 3. This part is then made transparent to the radiation 17.
• the secondary screen 5 comprises a scintillator material with phosphorus base intended to convert the electrons emitted by the photocathode 11 into visible radiation
• the phosphorus is removed from the secondary screen at the level of the part 44 in order to allow the radiation 17 to penetrate into the envelope 3.
• the source 21 is then located in the vicinity of the secondary screen and a prism 40 is used for example to return the radiation 17 towards the primary screen 4.
• the prism 40 is fixed on the part 44.
• FIG. 4 also shows an example of localization target 41 produced on the primary screen 4 using radiation 17.
• the localization target 41 is formed, for example, of regularly spaced points. These points form the intersections of the lines and columns of a grid.
• the primary screen 4 returns to the secondary screen 5 an image 42 of the localization target 41. This image 42 naturally takes up different points of the localization target 41. The distribution of these points is possibly altered by the distortion generated by the image intensifier.
• the example of localization target 41 represented in FIG. 4 can be implemented whatever the position of the window 16 on the surface of the envelope 3.
• the image 41 n is not complete, an area 43 of the image 42, corresponding to the part 44, appears hidden from an observer outside the envelope 3 due to the presence of the prism 40 on the secondary screen 5.
• the image intensifier comprises means for analyzing the distribution of the plurality of points of the localization target 41 received by the secondary screen (5). More precisely, the measurement of this distortion is carried out by analysis of the distribution of the points in the image. 42 of the localization target 41.
• the distortion can be determined by interpolation from the distortion measured for the points of the localization target 41 closest to the point considered in the image.
• the measurement can be absolute and the analysis consists in comparing the distribution of the points in the image 42 with respect to a theoretical distribution.
• the measurement can be relative, and, in this case, the comparison is made with respect to an image 42 produced during a calibration phase during which the distortion of the image is controlled.
• the distortion measurement can be carried out in the absence of X-radiation received by the primary screen 4.
• means are provided to interrupt the emission of the radiation 17 by the source 21.
• the radiation 17 doesn’t does not alter the emission of electrons by photocathode 11. It is therefore possible to carry out a distortion measurement even when the image intensifier is in normal operation and receiving X-radiation.
• the distortion measurement is very fast, in the order of a fraction of a second.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Astronomy & Astrophysics (AREA)
• Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
• Apparatus For Radiation Diagnosis (AREA)

Applications Claiming Priority (3)

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Citations (2)

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• 2001
  • 2001-05-18 FR FR0106601A patent/FR2824922B1/fr not_active Expired - Fee Related
• 2002
  • 2002-05-14 WO PCT/FR2002/001623 patent/WO2002095477A2/fr not_active Ceased
  • 2002-05-14 EP EP02738243A patent/EP1388021A2/de not_active Ceased
  • 2002-05-14 US US10/476,610 patent/US6960879B2/en not_active Expired - Fee Related
  • 2002-05-14 JP JP2002591888A patent/JP2004527092A/ja active Pending

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