DE1030939B - Image amplifier with an electron amplification screen arranged between the input screen emitting an electron image and the phosphorescent screen - Google Patents

Description

GERMAN

The invention relates, and in particular, to image intensifiers, preferably for radiological purposes on a single tube that takes a single x-ray or other image on their entrance bar and can produce a display of this image with output beams on your output screen, whose Brightness is increased many thousands of times, with the diameter of the output image sufficiently large is held so that it can be seen through a large exit pupil.

In order to achieve a gain in brightness to the extent mentioned above, without the Size of the image on the home screen in relation to which the input screen is so diminished that binocular vision of the output image with a large exit pupil is impracticable, a brightness enhancement is used for this Electron-emitting screen that responds to electron bombardment is used, as it is in itself from a Fernisebauffaufnahmemeröhre is known and the hereinafter referred to as an electron intensifying screen.

In the known use of such a screen in a television pickup tube, the exposed image is passed onto the photo-emissive layer while an electron beam passes the other side of the intensifying screen, inducing conductivity in the layer thereon. In contrast to this, the image intensifier according to the present invention is one Amplifier that has nothing to do with a pickup tube.

Also known is an image intensifier arrangement that has a photo-emitting input screen and an output light screen. In doing so, however a secondary emissive dynode array used for electron amplification.

The image intensifier according to the invention consists of a vacuum-tight vessel with an electron image emitting input screen, an output screen provided with a phosphor layer and an electron intensifying screen interposed therebetween, and the invention is featured in that the intensifying screen on its side facing the input screen has a conductive Layer also on its screen facing the exit Side a mosaic of photoelectrically emitting surface elements and one in between Carries a layer made of a material which has a conductivity which can be induced by electron impact, this intensifying screen being an auxiliary radiation source to expose the mosaic in order to achieve an electron balance from its emitting Surface elements, furthermore at least one image intensifier with one between which emits an electron image

Input screen and the

Phosphorescent screen arranged

Electron intensifying screen

Applicant:

Westinghouse Electric Corporation,
East Pittsburgh, Pa. (V. St. A.)

Representative: Dipl.-Ing. G. Weinhausen, patent attorney,
Munich 22, Widenmayerstr. 46

Claimed priority:
V. St. v. America March 17, 1954

Arthur Ernest Anderson and William Altar,

Pittsburgh, Pa. (V. St. Α.),
have been named as inventors

between the reinforcement screen and the exit screen located grid electrode and leads for generating voltages between the amplifier screen and associated with the input screen, the output bill and the grid electrode.

For a better understanding, the invention is shown in conjunction with exemplary embodiments described in more detail with the drawing. It shows

Fig. 1 is a schematic representation of the section through a tube according to the invention,

Fig. 2 is a schematic representation of the section through a reinforcing screen in the tube type used according to Fig. 1,

3 shows a schematic representation of a circuit and the auxiliary device for operating the in Fig. 1 shown tube in a different manner.

The tube shown in Fig. 1 has a vacuum-tight vessel 1 which, if desired, can be made of glass and in the vicinity of its one end a cathode screen 2 is arranged, which is made of a thin Glass wall 4 can exist, on the inner (concave) surface of which a thin layer of transparent conductive material 3 is applied, which in turn is a layer of a photo-emitting material, for example a cesium-antimony alloy 5 carries. The outer (convex) surface of the glass wall 4

809 528 / 36S

3 4

is covered with a layer of fluorescent material, the speed of this emission from surface element, for example made of zinc cadmium sulfide. to surface element over the surface of the mosaic beWhen an X-ray image on the layer 6 is correct. A fraction of these emitted electrons is projected into the wall of the vessel 1, which is missed in the wires of the grid 17, so that they impinge the light generated by this layer through the glass wall 4 5 miniumschicht 22 and this through and the conductive layer 3 is transmitted and generated and excite a luminescence in the phosphorous layer of the surface of the photo-emitting layer 5. For focusing the electrons on the electron image, which is a reproduction of the X-ray image impinging on the screen 12 and the output screen 19, layer 6. Any suitable means, for example an axially shown electron lens system focusing a verio magnetic field, may not be provided. The arrangement can be made in a smaller reproduction of this electron image in such a way that on the output screen an intensifying screen 12 which, in section in FIG. 21, generates a light image which is shown several thousand times. The screen 12 has a grid made of brighter than the fluorostall wire 13 produced in the input layer 6, which is a high ratio of the decorative light image. However, it does not allow anyone exposed to the solid surface and carries a layer 14 of reducing the average brightness of the original aluminum images, which is sufficiently thin that it differs in terms of brightness without proportional reduction in the low brightness for the electron lens system on it, which, as often found focused electrons can be essentially transparent if a high average brightness is in is. The other side of the aluminum layer 14 is overlaid with fluoroscopic images. The subsequent thin layer 15 made of a very flat working method as a photoconductor makes this possible, however, known insulating dielectric, for example, the references to arsenic tristlnd, which briefly reduce the average brightness without loss of its thickness at the point at which an electron (which has passed through the individual brightness differences due to the selection of the Ge-Aiummmmschicht 14) is penetrated by the speed of the electrons emitted by the mosaic 16, becomes conductive. The free surface of the 25 trons, if this is with a pulsating or intermittent insulating layer 15, is illuminated by a mosaic of animal light from the light source 23, photo-emitting material 16, for example Ca _w i _r d. The diaphragm 24 switches off the incidence of light sium-antimony alloy, covered. ^ the source 23 on the mosaic 16 alternately on and

At a short distance from the mosaic layer . During each switch-on period, a first grid 17 is located every 16 and a second grid 18 is charged to the voltage of the grid 17 in a similar surface element of the mosaic 16 by electron cohesion spacing therefrom. Output screen 19 has a layer 21 made of phos- The light from the source 23 is cut off on the screen facing the grid 18, the respective surface elements of the page being applied, as well as a coating 22 made of mosaic 16 by absorbing electrons with an aluminum that is sufficiently thin to discharge the speed that is not intercepted by the conductive tron, which is determined by the mosaic 16 keitsbild in the resistance layer 15. The phosphor layer 21 can be, for example, when the diaphragm 24 consists of zinc cadmium sulphide and allows the source 23 to again be applied to the mosaic 16, the inner surface of the end wall of the vessel 1 is applied to the discharged surface elements again on the chip. The photo-emitting layer 5, the aluminum 40 voltage of the grid 17 charged, the number of layers 14, the grids 17 and 18 and the aluminum from the respective surface elements emitted electrical coating 22 are provided with leads, by trons equal to the number of during the preceding-. which the electrical potential present on them denotes. Dark period which is recorded and wherein the electrical sources emitted by the respective surface elements as desired by electrical voltage (not shown) can be determined. For example, 45 trons for ventilation can be accelerated 14 to 20 kV negative at a point from the photo-emitting layer 5 to the aluminum layer-speaking position on the exit note 19, the grid 17 being made negative. The pure electron yield at each surface element opposite to layer 14 with SO to 100 kV positive surface element corresponds to the ratio of the Lei and the aluminum coating 22 compared to the latter with processing electrons to the electrons which this is about 5 kV positive. A light source 23 illuminates the resistive layer 15 applied, and this Ver-Mosaic 16 through a diaphragm 24 evenly. Ratio can be a hundred or more at room temperature

In the simplest way of working, in which it becomes one and increases as the temperature increases, the grating 18 is absent or connected to the grating 17 temperature of the layer 15. If, as in this case, it can and in which the light source 23 the Mosaic 16 Voltage between mosaic 16 and grid 17 is small, continuously illuminated, generates the X-ray image * incident on the fluorescent layer 6 must be small in terms of image resolution and / or an axial area of the photo-emitting Layer 5 an elec- magnetic field can be used to maintain the image sharpness tronenbild, which in its brightness distribution. An X-ray image can therefore be used for this purpose. The electrons of this elec- tron, which is excited by direct current and the same electron image to the tube 1, are used by the voltage between the 60-axis solenoid. If a voltage is applied to the layers 5 and 14 to act on the latter grid 18, which accelerates by a few so that they pass through these volts is negative compared to the grid 17, the and in the resistance layer 15 a distribution of the average brightness can be switched off and produce a contrast electrical conductivity, which is achieved as a conductivity gain. The speed at which a capability image can be viewed at which the opening and closing of the shutter 24 results in the rendition of the incident on the layer 6 must be sufficiently high to avoid the annoying initial X-ray image. The light field from the flickering in the image on the output screen 19 to the light source 23 causes the various surface areas to be obstructed. By a suitable choice of the interval T elements of the mosaic 16 emit electrons, whereby between the light pulses in relation to the specijedoch the conductivity image in the layer 15 the 70 fish resistance and to the dielectric constant

of layer 15 can reduce the contrast quality of the original image can be influenced in such a way that optionally the contrast at a desired brightness value is increased, since the time constant of the discharge of the mosaic elements is proportional to the specinschen Resistance and the dielectric constant of the resistance layer 15 for the respective brightness values is.

By changing the potential at the grid 18, the basic brightness value of the image on the output screen 22 can be changed as desired and the brightness value at which the strongest contrast between the image shadows can be set at will. This becomes the very important result achieved that a desired object or organ appears clearly on the screen 21, while the not desired organs fade in the background, with the help of a single tube.

Fig. 3 shows another embodiment of the image intensifier according to the invention, in which the DC voltage source 25 by an AC voltage source or a pulsating voltage source 31 of approximately 50 V is replaced and the diaphragm 24 is omitted is. The voltage from the source 31 can be approximately a sawtooth voltage. Since the arrangement according to FIG otherwise, as shown in Fig. 1, no detailed description thereof is required. In the arrangement of FIG. 3, the elements of this mosaic emit 16 electrons when the voltage of the source 31 is above a certain threshold value (as is the case with the elements of the mosaic in FIG. 1 is the case when light from the source 23 falls on it), the respective elements corresponding to the conductivity image in the resistive layer 15 pick up electrons (i.e. discharge the elements) when the voltage of the source 31 is below the threshold value (as is the case with the elements of the Mosaic in Fig. 1 is the case when the light from the source 23 is switched off). During that part each pulsation of the source 31 during which the voltage of the grid 17 is above its threshold value is, the electrons emitted by the respective elements of the mosaic 16 are applied of the output screen 19 accelerated. A controllable DC voltage source 32 holds the grid 18 by a few Volt negative with respect to the grid 17 and in this way enables the background brightness to be switched off and an effective increase in the contrast in the image on the screen 19 at any desired Shadow value.

In both the arrangement of Fig. 1 and that of Fig. 3, it may be desirable to have the resistor layer 15 to be heated so that it works at a temperature which causes the greatest change in conductivity each impacting electron results.

The layer 15 can be very thin so that image areas of very small size, i.e. H. of a Diameter of about the size of the film thickness, can be satisfactorily resolved. Even very thin films have both high gain and high resolution. A thickness of one Micron up has been found to be completely satisfactory.

If the fluorescent layer 6 is removed, the two embodiments shown can be used can be used to enhance ordinary light images. The use of materials for the layer 6, which emits light images when receiving rays other than X-rays, also falls within the scope of the invention.

Although the use of arsenic trisulfide has been proposed for layer 15, it is also possible to use arsenic trisulfide other substances that become conductive when the electrons hit, can be used, for example Selenium, cadmium sulphide and anthracene.

Claims (5)

Patent claims: 1. Image intensifier, preferably for radiological purposes, consisting of a vacuum-tight Vessel with an entrance screen that emits an electron image, one with a phosphor layer provided output screen and an electron intensifying screen arranged in between, characterized in that the intensifying screen (12) is attached to its the input screen (2) on the side facing a conductive layer (14), furthermore on its side facing the output screen (19) Side a mosaic (16) of photoelectrically emitting surface elements and in between a layer (15) made of a material which has a conductivity which can be induced by electron impact having this intensifying screen an auxiliary radiation source (23) for exposure of the mosaic (16) in order to achieve an electron exits from its emitting Surface elements, furthermore at least one between the reinforcing screen (12) and the output screen (19) located grid electrode (17) and leads for generating voltages between the intensifying screen (12) and the input screen (3), the output screen (19) and the grid electrode (17) are assigned. 2. Image intensifier according to claim 1, characterized in that in addition to a first grid electrode (17) a second grid electrode (18) between the former and the output screen (19) is arranged and adjustable means for generating a variable voltage between the first and second grid electrodes are provided. 3. Image intensifier according to claim 1 and 2, characterized in that the irradiating the mosaic (16) Light source (23) is a pulsating light source and a DC voltage between the Reinforcing screen (12) and the first grid electrode (17) is applied. 4. Image intensifier according to claim 1 and 2, characterized in that the voltage between the intensifying screen (12) and the first grid electrode (17) is pulsating. 5. Image intensifier according to claim 4, characterized in that that the between the reinforcing screen (12) and the first grid electrode (17) applied voltage is approximately a sawtooth voltage. Considered publications:
German Patent Nos. 692 039, 861 295;
U.S. Patent No. 2,544,755. 1 sheet of drawings © 809 528/3 «5.58