US 3663821 A
Image intensifier device and method for image intensification in which a bundle of ionizing radiation containing an intelligence pattern impinges upon a fluorescent layer of an anode luminary structure to produce fluorescence and whose fluorescent output excites the further emission of photons from an adjacent image intensifier structure of the solid state type, the latter being connected in series with a unipotential source of high voltage and high frequency and said high voltage effecting further light emission from said intensifier structure, said unipotential source being further connected to a conducting layer of said fluorescent anode and to an actuating relay in a series arrangement such that said unipotential of high frequency is released to said image intensifier in an instantaneous "surge flow" concurrent with the transmission of the ionizing bundle through the face of an evacuated tube containing said fluorescing anode luminary unit and said image intensifier structure in cascade arrangement and further; said image intensifier being connected to a source of high alternating field frequency to further activate said image intensifier to produce light emission and an intensified image therefrom; the said activation being due to excitation of a dielectric layer so that the ionizing bundle evokes "charge transport" therethrough to an adjoining radiation-transparent opaque layer, and a photoelectro-luminescent phosphor layer, said activation being reinforced by the concurrently applied high voltage potentials to the conductor boundary layers of said intensifier structure, to produce a stored conductivity pattern upon an image target having a long-time storage function for scansion by a cathode-ray beam of electrons, said pattern being a replica of the original image inherent in the ionizing bundle of rays.
Description (OCR text may contain errors)
United States Patent Finkle 15] 3,663,821 51 May 16, 1972  IMAGE INTENSIFIER DEVICE AND METHOD FOR RECEIVING RADIANT ENERGY IMAGES FOR CONVERSION AND INTENSIFICATION  Inventor: Jack Finkle, 918 East 14th Street,
Brooklyn, NY. 1 1230  Filed: Mar. I1, 1969  Appl. No.: 806,323
Related US. Application Data  Continuation-impart of Ser. Nos. 306,897, Sept. 5, 1963, Pat. No. 3,436,550, and Ser. No. 459,529, May 24, 1965, Pat. No. 3,482,104.
 U.S.Cl. ..250/2l3 VT,313/65, 313/101  ..l-l0lj 31/50 [58} Field ofSearch ..250/2l3 VT; 313/65, 101
 References Cited UNITED STATES PATENTS 2,928,969 3/1960 Schneeberger.... 250/213 VTX 3,436,550 5/1968 Finkle ..250/2l3 3,482,104 12/1969 Finkle ..250/2l3 VT Primary Examiner-James W. Lawrence Assistant Examiner-D. C. Nelms Arrorney-Friedman and Goodman m..sexea 6 l5 RADIATION- TRANSPARENT CGNDJCTING- RELAY LAYER 7 BASE PLATE 5 IMAGE INTENSIFIER L F um'r 25 FLUORESCENT IMAGE UNIT 24 i r a X-RAY i j BUNDLE 2 ABSTRACT type, the latter being connected in series with a unipotential source of high voltage and high frequency and said high voltage effecting further light emission from said intensifier structure, said unipotential source being further connected to a conducting layer of said fluorescent anode and to an actuating relay in a series arrangement such that said unipotential of high frequency is released to said image intensifier in an instantaneous surge flow" concurrent with the transmission of the ionizing bundle through the face of an evacuated tube containing said fiuorescing anode luminary unit and said image intensifier structure in cascade arrangement and further; said image intensifier being connected to a source of high altemating field frequency to further activate said image intensifier to produce light emission and an intensified image therefrom; the said activation being due to excitation of a dielectric layer so that the ionizing bundle evokes "charge transport" therethrough to an adjoining radiation-transparent opaque layer, and a photoelectro-luminescent phosphor layer, said activation being reinforced by the concurrently applied high voltage potentials to the conductor boundary layers of said intensifier structure, to produce a stored conductivity pattern upon an image target having a long-time storage function for scansion by a cathode-ray beam of electrons, said pattern being a replica of the original image inherent in the ionizing bundle of rays.
7 Claims, 1 Drawing Figure omouggrzni Lumnggceur wnospupn LAYER 9 RADIATION-TRANSPARENTCONDUCTING .LAIER ensz LAYER u SlGNAL LAYER l2 TORAGE LAYER l 3 mace swans: ranger umr 2s vvvvii I? Q BASE PLATE 2 CONDUCTIVE "L GLASS LAYER 3 FLUORESCENT LAYER 4 1 VIDEO AMPLIFIER LOW 21 HIGH VOLTAGE VOLTAGE S U P PLY SU P PLY l STORAGE TU a: W l l l 35 Patented May 16, 1972 El AY E R G 9 T RCH U Y M AN LO R O N E R A P S M. A MR E4 N .0 T m MD UA LR OPAQU Qua LEQLRL; L ma. 6 R D I AT IO N 1 BASE LAYER u SIGNAL LA YER l2 MAGE STORAGE TARGET UNIT 26 I7 V. IX fl. I i
TRANSPARENT CONDUCTING- 7. R E. I A L A. c. SUPPLY C. HIGH VOLTAGE SUPPLY LOW VOLTAGE H S UPPLY lAClx' FINKIJE INVENTOR I ATTORNEYS IMAGE INTENSIFIER DEVICE AND METHOD-FOR RECEIVING RADIANT ENERGY IMAGES FOR CONVERSION AND INTENSIFICATION This is a continuation-in-part of both application Ser. No. 306,897, filed Sept. 5, 1963, now US. Pat. No. 3,436,550, and application Ser. No. 459,529, filed May 24, 1965, now U.S. Pat. No. 3,482,104.
The above abstract together with the following specification anddrawing constitutes a preferred embodiment of my inventive device which I prefer to call by the name of TELEX- ICON taken from the Greek and meaning: to transmit X-ray images at a distance, being a device for receiving X-ray images for reproduction and transmission.
This invention relates to an improved method of image intensification and a novel image transducer device called by me a Telexicon for use as a receiver of images produced by ionizing radiation or such rays emitted by bombardment of high energy particles such as neutrons, or by other similar means including but not limited to gamma radiation or other particulate radiation. More particularly, it relates to an image pick-up tube adapted to receive X-ray images of whole body radiation of individuals for biologic study by radiologists or of inanimate objects by industrial radiologic means for testing and examination or for the viewing of interiors of inanimate objects. It is not limited to the examination of stationary objects or persons but is also designed to be used for the examination of movable objects.
This invention further relates to the production and intensification of light images produced by ionizing radiation in luminescent materials and to the storage of said luminescent images in a special storage target having a long-time storage function for later reproduction and review. The invention differs from prior image intensifiers of similar character by the close alignment of a novel fluorescing anode structure toa photo-electro-luminescent image intensifier of the solid-statetype, together with a special circuitry for the concurrent stimulation of the fluorescent layers of the units by both the input ionizing bundle of radiation and an input potential activation means.
In this novel transducer device it is proposed to make use of the phenomenon of photo electro-luminescence employing the joint activation of an image intensifier structure by a fluorescent image produced by ionizing rays and by theaction of the rays on a dielectric photoconductor layer of said image intensifier. The input ionizing radiation is utilized to activate or excite fluorescence jointly in a fluorescent layer of a novel anode structure and in a luminescent layer of an image intensifier structure that adjoins it in order to produce a light image that can be intensified by the high voltage potentials serving to activate the intensifier structure to electro-luminescence. It is inherent in the design of these two structures that the emission of said photonic image should have the character and definition of the input mosaic image inherent in the ionizing bundle of radiation causing luminescence. The image intensifier structure is concurrently activated by this ionizing bundle as it traverses the various layers making up the two structures. It is also proposed to make use of a three-layer two-sided special target having a long-time storage capacity for light image storage. Such a target can be useful for intermittent scansion by a slow-scan cathode-ray beam from a scanning gun for image transmission. It is further intended to make use of a charging pulse or surge of high unipotential source of input voltage to the image intensifier structure to provide immediate image intensification by means of special relay and circuit means.
Accordingly, it is an object of this invention to provide an improved image intensifier device and method of image intensification employing joint excitation of luminescing structures with concurrent activation of said structures by high DC and AC potential means with photonic emission of luminescing layers and by a change in state in a dielectric by transmission of a bundle of ionizing radiation therethrough so that the phenomenon of "photo-electro-luminescence occurs with increased amplification.
A correllary object of this invention is to provide a new and improved image pick-up tube for X-rays and to limit the amount of radiation that a patient may receive during radiography.
Another object of the present invention is to improve the image-forming anode structures of photo-electro-luminescent devices so that increased image intensification is obtainable.
A further object is to provide a system of televising X-ray images.
In the prior art, images were intensified either by contrast enchancement of an electron image produced by impingement of ionizing radiation on a fluorescent layer or photocathode structure alone or in combination together with other electron image intensifying means, the resultant intensified image thereupon being either viewed directly, stored or reproduced by means of a scanning beam. In this invention it is proposed to make use of the ionizing action of the bundle of X-radiation that passes through the various layers of the luminary transducer device to serve as an initiator of fluorescent light production in the fluorescent image unit (24) as well as luminescence in the image intensifier unit (25) stacked in cascade arrangement.
The single drawing FIGURE is a representational embodiment of the preferred invention in cross-section serving to show the structure of the new device in detail and taken in conjunction with this specification portrays the method of operation of the device to produce the aforementioned objects.
It is well known that ionizing rays have the property to alter the resistance of a dielectric employed in a typical solid state image intensifier unit. The ionizing ray bundle 1 can both serve as a light-image-producing agent as well as an initiator of electro-luminescence in the image intensifier unit structure. Taken in conjunction with the fluorescent image forming member 24, the light image produced by the intensifier unit structure 25 is a replica of the input image inherent in the ionizing bundle l which is the activating agent for image formatiomThe phenomenon of photo-electro-luminescence is initiated by the stimulation of the image intensifier unit 25 by both the light emitted by the fluorescent layer 4 of luminescent anode-unit 24 and the penetrating action of the ionizing bundle 1' through the various layers of both units 24 and 25.
Referring to the drawing in the Figure a source of ionizing radiation (not shown) exterior to tube 1 is activated and the ionizing bundle I with an image is made to strike the tube face towards base plate 2 and penetrates each layer in turn of the luminary unit 24. This unit is similar to and can be compared to a typical input fluorescent screen for production of X-ray images. The base plate 2 can be formed of any metal layer as a support for layer 3 and 4 and to act also as a light mirror. The intermediate layer 3 is composed of conductive glass and fluorescing layer 4 may be composed of any suitable light-emitting phosphor compound with an activator and/or halogen as is known in the art. The usage of intermediate layer 3 is novel in that its function is to transmit a high unidirectional voltage potential from voltage tap 29 to relay 15 and thence to image intensifier unit 25, thus activating said unit. This voltage pulse takes the form of a surge action.
The phenomenon of photo-electro-luminescence is initiated by the X-rays striking the dielectric layer 6 of the image intensifier unit 25. This layer has a high impedance and is composed of any substance whose resistance is high such as stannous chloride deposited in a layer on a base plate 5 of glass contiguous with an electro-luminescent phosphor layer 9 and intermediate opaque layer 8, to form a sandwich between two radiation-transparent conducting layers 7 and 10. The radiation bundle 1' causes a decrease in resistance at each point of the dielectric 6 with a flow of holes and electrons through the layer 6 so that phosphor layer 9 becomes luminescent. The DC and AC activating switches 36 and 37 have been previously closed so that charge transport takes place resulting in electro-luminescence, a phenomenon well-known in the art.
In addition to the X-radiation from the input beam, the photoelectro-luminescence is further activated by the light emission from fluorescent layer 4 of luminescent anode unit 24. This phenomenon will be sustained by the activating potential even though the input radiation is cut off. This saves so much energy in X-ray exposures that the patients body will not be impaired even with prolonged examinations.
The present invention represents certain improvements and modifications in my prior inventions and is particularly adapted to the field of X-ray image formation and enhancement.
The invention differs from the previous image intensifier structures employing high voltage potentials to the input leads of such structure s layers by reason of use of a surge or catalytic effect of the applied DC voltage potential by the employment of conducting glass layer 3 in the luminary anode unit 24 and activating relay in series arrangement with unipotential voltage source 29. The relay 15 is meant to act as a DC valve to permit passage of the unipotential voltage to the input lead 7 of intensifier structure 25. This valve or relay" may also be compared to the geiger counter in action in which pulses of radiation act to ionize the gas in a geiger tube to be subsequently recorded by a counter. The valve thus is means to act as a unidirectional gate to release a potential surge to the image intensifier unit 25, thereby activating it to produce electro-luminescence. RElay 15 may be constructed in various ways as is known in the art to perform in this manner.
The above-mentioned geiger tube, such as the typical Geiger Mueller tube, is well known in the art to be a useful detector of ionizing radiations. The Geiger Mueller tube is used for the detection of hard X-ray radiation, gamma radiation from radium and cosmic rays. The geiger tube is excited by the ionization of the gas therein by fast moving atomic particles which enter the geiger tube from the outside and constitute the radiation which passes through the geiger tube. Under given operating conditions, it may be operated as a proportional counter to give an amplification as high as several millions, while as a geiger counter it can give an amplification of thousands of millions of times. The Geiger Mueller tube has an amplification factor so high that the presence of one electron within the counter tube is sufficient to cause the geiger tube to operate as a relay tube directly without any further amplification.
The conventional geiger tube is glass, inclosing a rarified gas under a considerable vacuum. Within the glass tube, standing in the rarified gas, is a hollow metal cylinder having a small wire inside. The cylinder is connected to the negative pole ofa power-pack" machine in a typical counting circuit for counting ionizing pulses of X-rays with an electrical pressure up to 1,000 volts or more.
The gas in the geiger tube is not conductive, there being no flow of current in the geiger tube until radiation hits it, such as the radiations of the input image consisting of X-rays. There is however a high electrical voltage pressure in the geiger tube between the geiger tube elements. The gas is usually of one of the inert gases, such as argon. The conducting cylinder is usually copper and the wire is usually of five mils tungsten, the wire being attached at either end by small springs. The geiger tube is preferably constructed of a glass shape including a diameter of about 1 inch and a length of about 5 inches. A voltage of 300 to 1,500 or more volts is introduced depending upon the gas used in the geiger tube, its pressure and the geometry of the geiger counter. This voltage must be just less than enough to break down the wire-to-cylinder gap.
In theory, when radiation from some source outside the geiger tube, such as the radiations of the input image consisting of X-rays, penetrates the wall of the geiger tube, its gas becomes conductive and what is conventionally called ionization" occurs. The planetary system of the gas atoms has been disturbed and altered, so that the electrons in each orbit has been imparted with energy to move out of the orbital shells. The electrons produced in the gas will be moved toward the wire with increasing kenetic energy and, in the strong electrical field near the wire, obtain sufficient energy to ionize the gas, producing thereby more electrons. These in turn are accelerated, and an avalanche of electrical charges is initiated. This avalanche sets up a flow of current in the external circuit. Thus, before the entrance of the tube by the input rays, there was nothing to disturb the electrical balance in the tube, and the negative and positive charges of the gaseous atoms were in balance, wherein there was no electrical flow. However, the input X-rays altered this balance to create a flow of current in the tube circuit. The above sets forth only one example of how the incident X-rays are capable of activating relay 15, using conventional means well known in the art.
The Sylvania Electric Co. has devised a relay made up of a neon lamp and a PC. Gap Cell operable at 250 volts rms. and 400 cps.
For instance, relay 15 may also include a wheatstone bridge circuit in balance with it being designed so that the incoming high voltage pulse will offset the balance in the circuit and thereby allow passage of the pulse" to conductor layer 7 of stratum 25. Such relays are known in the art.
In the preferred embodiment of this invention, it is contemplated also to make use of a glass threshold switch" as described in the publication Physical Review Letters, Nov. l l. 1968, and based on the invention of Mr. Stanford R. Ovshinsky, to employ the Ovshinsky-Effect whereby a layer of glass of a desired thickness is used in a circuit to pennit passage of a pulse of current of alternating frequency at a threshold dependent upon the thickness of the conducting glass. Such a glass has been made by Mr. Ovshinsky composed of a mixture of tellurium, arsenic, silicon, germanium, and other common elements (manufactured by his firm, Energy Conversion Devices, Troy, Mich. For instance, the conductive layer 3 ofthe luminary fluorescent unit 24 can be fabricated of this type glass as well as the relay 15. It can be fabricated to pass the higher voltage potentials at 800 cps.
It may be desirable in some instances of radiography to change operation of the device from a certain high DC current to another high DC current of another frequency in accordance with the thickness of the body under examination and the K.V.P. necessary to be used by the X-ray operator. For this purpose I have provided as alternative means, a potentiometer switching means 40 for varying the DC voltage potential from either source 21 or 22, (low and high voltage supply sources). The higher the voltage pulse, the greater light emission results.
It is preferable that a combination of both DC potential and AC potential be employed together for best results. The high DC current may be cut off by means of switch 36 and the high AC potential waveform from source 23 then continued with switch 37 remaining closed after photo-electro-luminescence has been initiated in the intensifier section 25.
In another preferred embodiment of this invention, it is designed to make use of the ionization action of the input radiation beam to ionize a gas-filled tube such as a thyratron in relay 15 to permit passage of the high DC voltage potential to conductor layer 7 in order to activate unit 25. Such tubes are known in the art, and the gating circuitry need not be shown.
The ionizing rays can thus serve as both a light-image forming agent as well as an initiator of electro-luminescence. The latter phenomenon, once initiated is dependent upon the magnitude of the increased voltage applied to the boundary conductor layer 7 and 10 of the image intensifier unit 25. The photons emitted by the latter are directed to a typical image storage target 26 having a long-time storage characteristic. The storage of the emitted light image in the target 26 is cumulative as long as the image intensifier unit 25 persists in emitting light. Subsequently, the target 26 is scanned by a beam of electrons 18 from a cathode ray gun 27. The target can be operated either positively or negatively by varying the voltage to the signal layer 12 as is known in the art and the stored charges can be either removed by means of the output signal lead 31 or otherwise. The return aspect of the cathode ray l8 scanning beam is utilized to afford increased electron multiplication by means of electron multiplier assembly 19 as is also known in the art. The return beam 18' is made to obtain signal intelligence from the rear surface of the target unit 26 and depending upon the polarity of the charge at each point either restores the charge or conveys a surplus of charges to the multiplier dynodes 19. The resultant signal is conveyed by output lead 33 to either a video amplifier 20 and/or directly to another storage tube 34, or to an image duplicator device or to a viewer tube 35. Scanning is achieved by means of the deflection assembly 16 and 17 and 16 and 17' consisting of electromagnetic and electrostatic means. A slow scan beam is preferably utilized.
Target structure 26 is a composite-type target of three layers with a base layer 11, a signal conductor layer 12 and a storage layer 13. The base layer 11 is preferably translucent to light emitted by the image-emitting layer of the intensifier unit 25 and may be composed of glass or mica in sheet form. The signal layer 12 may be formed of a coating of selenium, tin oxide or tin chloride, or bismuth which can convert X-rays directly into electrons. The layer 13 may be constituted by evaporation onto layer 12 by suitable evaporation methods known in the art and also layer 12 onto layer 1 1. Layer 13 may be formed of cadmium selenide noted for its long storage ability, or a mixture of red antimony tri-sulfide and antimony oxide, or lead oxide or amorphous (spongy red variety) selenium. Output lead 31 is connected to a load resistor, a source of voltage and a capacitator to develop video signals (not shown but known in the art).
In this invention it is intended to make use of target layers having the property of photoconduction, plus charge retention. As is well known in the art, certain photoconductive materials have a high resistance in darkness, and a low resistance when illuminated. Satisfactory photo-conductive materials for example are selenium, Cu2)O, germanium, thallium sulfide or lead sulfide or the selenide. Robert J. Schneeberger et al. in their U.S. Pat. No. 3,148,297 employ a mixture of arsenic and selenium to store an image of halftones in response to electron bombardment. In his patent No. 3,879,400 Schneeberger employs a photoconductive substance combined with anothersubstance such as gold, having an atomic number higher than 51 to produce a charge replica in response to X-rays. R.C. Palmer in his U.S. Pat. No. 2,937,233 employs cadmium sulphide in a photoconductive layer adjacent to a fluorescent layer and being light-responsive. Sheldon in U.S. Pat. No. 2,894,159 employs on the other hand specially treated selenium in his storage target (page 9, lines 5-12), (page 4, line 51-64). Also, in his U.S. Pat. No. 2,699,512 issued Jan. 1 l, 1955, Sheldon employs a photoconductive layer of either antimony tri-sulphide or cadmium sulphide deposited upon a layer of selenium (page 5, lines 6l7 and page 2, lines 77-81). Palmer in his U.S. Pat. No. 2,937,233 also employs cadmium sulphide as a photoconductive material (page 2). If the light emitted by the electro-luminescent layer 9 is blue, antimony tri-sulphide being sensitive to blue light may be employed as layer 12. The emitted fluorescent image produces within the photoconductive layer a pattern in the electrical conductivity and on the surface of said layer a pattern of potentials according to the pattern of said fluorescent light image.
in storage tubes use is also made of the retentive ability of some materials to exhibit photoconductive lag which has been observed in some insulators having a high resistance. Photoconductive lag means that the conductivity pattern within layer 12 and the potential pattern on the uncovered surface of layer 13 persists for many seconds or longer depending upon the storage ability of the materials used for layer 13.R.J.Schneeberger et al. in U.S. Pat. No. 3,148,297, page 4 lines 45-52, found that utilization of an antimony tri-sulfide layer as a storage layer and a mixture of arsenic and selenium as photoconductive layer enhances the sensitivity of the target with regard to charge retention or storage of an image and also that employing an intermediate layer of indium as between said layers will further enhance the storage effect of said image.
In U.S. Pat. to Robert R. Goodrich, No. 2,654,852 issued on Oct. 6, 1953 is described one method of forming a target. His target employs a combination of antimony oxide with red antimony trisulfide. He recommends that the antimony oxide be kept below 5 percent by computed volume. See also U.S. Pat. No. 2,775,719 to S. Hansen of Dec. 25, 1956.
Paul K. Weimer in his U.S. Pat. 2,654,853, issued Oct. 6, 1953 also describes the use of red amorphous selenium and a method of preparation of a photoconductive layer utilizing the metal for good results.
While the above two patents employ targets for cathode-ray devices, they also have application to the fabrication of storage targets of the composite type. Other useful combinations are also known in the art and may be similarly employed and it is not intended to restrict the use of such a storage-type target with the materials mentioned above.
Normally in a TV pick-up tube efforts are made to insure that picture signals are completely erased each scanning cycle, if the fuzzing of moving objects is to be avoided. However, this is not necessary for a camera tube for X-ray images as a repetitive image enhances the stored image. My storage tube used as an X-ray pick-up tube shows this time lag as a result of a very high target capacity in combination with a low velocity and intensity scanning ray beam from a scanning gun. The composite type storage targets are condensers charged positively by the photo-conduction and discharged by the scanning beam current. The target potential builds up proportionately to the time of exposure to the light image impinging upon the target. These are the conditions which cause a long time constant for discharge of a condenser. The slope of the charging curve of a target is determined by the capacity of the target and by the photoconduction which is determined by the materials making up the photoconduction layer. With use of some materials storage up to an hour or more is possible. The capacity and function of a composite storage target may be increased by using a photoconductive layer of a high resistance adjoining a signal or backing layer of low resistance for current flow, such as silver. The charging and discharging of the stored charges has been adequately described in the art.
Since the ionizing input bundle l in traversing the various tube unit layers will also traverse the target layers, it may be preferable to construct the transparent glass base plate 11 of lead glass to avoid any magnifying distortion of the scanned image.
An annularcontrol grid 14 is positioned adjacent to and in register with the outer surface of the target layer 13. This control grid may be maintained at ground potential or at high positive potential to attract or repel the scanning ray beam 18 from the scanning gun 27.
The opposite side of target 26 is scanned by a low velocity beam 18 from cathode ray gun 27 to achieve repeated scansions. it is preferred to have a scanning rate of 800-1 ,000 line frequency as utilized in some radar installations in France. This beam is generated by an electron gun consisting of a cathode 27, a beam intensity control grid, and a positive accelerating electrode 46 having a potential relative to the cathode of, for example, plus 300 volts. The relatively high initial velocity of the scanning beam is reduced to substantially zero when the electrons reach the target by the decelerating electrode 14. At the target plate sufficient electrons are removed from the beam to neutralize the positive charge at that point on the target surface and the remainder return toward the electron gun along substantially the same path as the scanning beam under the influence of the electric field produced partly by the positive electrode at the gun area. The returning electrons 18' then strike the dynode plates of the electron multiplier 19 where further augmentation of the return current through electron multiplication takes place. The output current flows through a load resistor 45 as is customary in the art to output lead 33. Direct current source 44 supplies the electron multiplier 19 and the accelerating electrode with positive potential.
The scanning beam 18 is caused to scan over the surface of target surface 13 in accordance with a predetermined pattern such as the pattern of a plurality of fine closely spaced lines as used in television. This pattern is produced by supplying a linear sawtooth current of line and frame frequency to the horizontal and vertical deflection yoke represented by figures l6 and 17. These currents are generated by the vertical and horizontal deflection circuits associated with the tube as with standard practice. Therefore, any modulation of the return current 18 constitutes the video signal. (For circuitry in detail, see US. Pat. No. 2,955,158 of R. H. K. Gebel, issued Oct. 4, 1960, and No. 2,549,072 of D. W. Epstein, issued Apr. 17, 1951 from which this invention is adapted in part: scanning systems, etc.) (Also, see US. Pat. No. 2,835,822 of F. E. Williams, issued May 20, 1958 for E-L Unit construction and operation).
My present invention may be applied, not only to X-ray or other image-reproducing means as described above, but also to means intended to detect the presence of radiation, or to register the incidence of each photon of such radiation, without indicating the distribution of its intensity in space as is necessary for radiation image reproduction.
It is not intended to restrict the scope of this invention to the employment of X-ray or gamma radiations with fluorescent or reactive layers but other corpuscular radiations and suitable reactive layers are intended to be similarly comprehended. For example, the X-ray reactive fluorescent layer in unit 24 may be omitted and in its place substituted a neutron reactive substance. More particularly, the neutron beam used for the internal investigation of a body would pass through the front face of the pick-up tube 1 and strike a neutron reactive layer preferably containing atoms of the group boron, lithium, uranium and gadolinium. Between this layer and the adjoining image intensifier unit 25 would be placed a photoconductive layer such as amorphous selenium. In place of the transparent conductor layer 7 another thin metal film layer may be em ployed, such as silver to act as a conductor from one photoconductor to the next so that there would be achieved a transference of photoconduction holes and electrons to the electro-luminescent phosphor layer adjoining the dielectric layer 6.
While I have described my invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.
1. An image transducer tube responsive to X-rays, comprismg:
an evacuated envelope having an entrance end transparent to incident X-rays;
a luminary receiving unit in said envelope disposed adjacent said entrance end for irradiation by said X-rays, said receiving unit including a radiation-permeable base adjacent said entrance end and a radiation permeable fluorescent layer spaced from said base and said entrance end with an intermediate radiation-permeable conductive layer disposed between said base and said fluorescent layer in a plane with said entrance end, said conductive layer being connected in a series arrangement to a source of unipotential current;
relay means disposed in said series arrangement to serve as a valve to electronically gate transmission of said unipotential current so that a pulsed effect is released, said relay means being activated by said X-rays; and
an image intensifier structure disposed in said envelope confronting said fluorescent layer, said pulsed effect activating said image intensifier structure for receiving a fluorescent image from said fluorescent layer, said fluorescent image resulting from both emitted light by said fluorescent layer of said unit and penetrating action of said X-rays through said unit, said image intensifier structure including luminescent means to produce an intensified light image resulting from said fluorescent image and said penetrating X-rays.
2. An image transducer tube as defined in claim 1, wherein said tube further comprises a receiving target disposed in said envelope for storing energy of said intensified light image and beam-generating means for periodically scanning said target.
3. An image transducer tube as defined in claim 1, wherein said image intensifier structure comprises a photoconductive layer proximal to said receiving unit, an adjoining barrier layer opaque to said light rays and an adjoining photo-electro-luminescent layer defining said luminescent means in a planar array sandwiched with said photoconductive layer and said photo-electro-luminescent layer having an opaque layer intermediate between them to prevent light spreading in a transverse direction, said planar array being excited jointly by said penetrating X-rays from said entrance end and said fluorescent image from said receiving unit, and further said planar array being activated concurrent with said X-rays penetrating therethrough by an electric field applied to said array.
4. An image transducer tube as defined in claim 3, wherein said image intensifier structure further comprises a pair of conductive layers bracketing said photo-conductive and photo-electro-luminescent layers, and a further source of voltage including a variable potential connected across said conductive layers to stimulate electro-luminescence of said device by ionizing radiation.
5. An image transducer tube as defined in claim 1, wherein said tube further comprises an output storage target for storage of photonic image from said image intensifier structure, said storage target including a translucent base plate, an intermediate conductive signal plate, and a storage layer having a long-time storage function.
6. An image transducer tube as defined in claim 5, wherein said base plate of said storage target is provided with a lead glass material impermeable to ionizing radiation emitted to said target from said entrance end of said evacuated envelope.
7. An image intensifier device as defined in claim 2, wherein said receiving target includes a signal layer of spongy selenium and a storage layer of cadmium selenide.