US 3417242 A
Description (OCR text may contain errors)
R. W. WINDEBANK IMAGE INTENSIFICATION SYSTEM COMPRISING REMOTE CONTROL MEANS FOR VARYING THE SIZE OF THE Filed Sept. 20. 1965 REMOTE VARIABLE FIELD CONTROL FIG. 1
CONTROL UNIT POWER SUPPLY T IMAGE 2 Sheets-Sheet 1 lNl/ENTOR 7' W. Wl/VDEBA/VK IMAGE INTENSIFICATIZ) TO GRID 32 R W. WINDEBANK N SYSTEM COMPRISING REMOTE CONTROL MEANS FOR VARYING THE SIZE OF THE OUTPUT IMAGE Filed Sept. 20. 1965 2 Sheets-Sheet 2 TO 52 GRID a I PLUG TO EXTERNAL UNIT F/G. Z
IIVVENTOR ROBERT W W/A/DEBA/VK United States Patent 3,417,242 IMAGE IN'IENSIFICATION SYSTEM COMPRISING REMOTE QONTROL MEANS FOR VARYIN G THE SIZE OF THE OUTPUT IMAGE Robert W. Windebank, Fairfield, Conn assignor to The Machlett Laboratories, Incorporated, Springdale, Conn., a corporation of Connecticut Filed Sept. 20, 1965, Ser. No. 488,638 4 Claims. (Cl. 250-835) ABSTRACT 0F THE DISCLOSURE An image intensifier tube having a plurality of electrodes therein for directing an electron beam from an input screen to an output screen for providing a visible output image corresponding to an invisible input image, a high voltage control unit being connected to the electrodes for varying the voltages applied thereto and consequently varying the sizes of the portion of the input image which is reproduced at the output screen, and remote low voltage control means which may be safely handled by an operator for independently and individually controlling portions of the high voltage unit whereby voltages to the intensifier tube electrodes may be individually varied in a continuous and safe manner.
This invention relates to image intensifier tubes and systems and has particular reference to control means for an image intensifier tube which is operable to vary the size of the output image with respect to a selected area of the input image.
The prior art contains many various types of image intensifier tubes, structures and controls therefor. One thereof comprises an image intensifier tube which is pro vided adjacent one end with an input screen or target of selected diametric size and an output screen or target which is considerably smaller than the input screen. In the operation of the tube, a pattern of input radiation of any desired frequency impinges upon the input screen which contains fluorescent material which emits fluorescent image of the incoming radiation pattern onto a photoemissive material which forms an electron beam corresponding to the pattern of the incoming radiation. The electron beam is compressed and focussed toward the small output screen and impinges upon a material therein which converts the electron image into a visible image in the normal operation of a tube of this type.
The incoming radiation may be of any selected frequency such as light in the visible portion of the spectrum, or invisible radiation such as X-rays, infra-red or ultraviolet or other radiation to which the fluorescent material is responsive.
In the use of such an image intensifier it is often helpful if the output image, instead of corresponding to the entirie input image, could be made to corresponnd to only a small portion of the input image. It is further helpful if such an output image, which corresponds to the small portion of the input image, could be enlarged or blown up to occupy the entire output screen. This function is especially beneficial in the case of X-ray image intensifiers which in their normal operation are used to view relatively large areas or specimens, but which can be controlled to permit closer inspection of only a small portion of the area. For example, in the medical profession a practitioner can easily view a large area of the chest cavity of a patient. However, upon inspection he may find is desirable to closely examine only a small portion of the chest cavity, such as the patients heart, lungs or other selected area.
3,417,242 Patented Dec. 17, 1968 ice In accordance with this invention, means is provided for electronically adjusting the image intensifier tube so that the output image may be varied in size within a relatively wide range. Such adjustment results in either increasing or decreasing the size of the selected area of the output image, as desired, and in the case where the selected area of the image is increased in size or zoomed, electronically, the resolution is enhanced.
Electronic zooming in the presently described invention is achieved by first applying to the three grids within the tube selected grid voltages designed to display an input picture (such as a 9 inch mode, for example) on a one-inch output screen. Then a second selection of grid voltages are applied to expand the input display so that only the image represented by the control portion of the input picture will fill the one-inch output screen. For example, any selected portion of the input picture (using the 9 inch mode as an example) may be utilized, such as the central six-inch diameter portion or the central fourinch diameter portion, or other selected portion and may be projected onto the output screen.
In the present invention, the ratio of input image size to output image size may be varied, either magnified or minified, and may be performed continuously or in a step fashion, while still maintaining adequate focus.
A further feature of this invention is the provision of an electronic control system for image intensifier tubes, which system employs the variable field principle and wherein all elements which are subjected to high voltages, sometimes as high as 9000 volts or more, are located remote from the control elements which are intended to be hand-held and manually operated, thus reducing shock hazard often encountered by persons operating equipment of this type. The use of low voltage for control also reduces the insulation requirement and minimizes the bulk of movable control units.
These and other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein:
FIG. 1 is a horizontal or axial sectional view of an image intensifier tube incorporated into a system embodying the invention;
FIG. 2 is a circuit diagram of the variable field control unit; and
FIG. 3 is a circuit diagram of the remote control unit.
Referring more particularly to the drawings wherein like characters of reference designate like parts throughout the several views, there is shown in FIG. 1 an image intensifier tube 10 which for the purposes of this description is incorporated in an X-ray system for converting an X-ray image of a subject 12 into a visible light image which is adapted to be viewed by the human eye or improssed upon a light sensitive film in a camera 14.
In the system an X-ray tube 16 generates a beam of X-radiation which is directed onto and through the object or specimen 12. In passing through the object 12, the X-rays from X-ray image or pattern which corresponds to variations in the X-ray absorption characteristics of the object being X-rayed. This X-ray image is directed onto the intensifier tube 10 which comprises a metal housing 18 provided at one end with a window 20 which is transparent to the incoming radiation. In X-ray tubes such WindOWs may conveniently be made of beryllium or other -X-ray transparent metal or of a glass which contains little or no lead or other ingredient which absorbs substantial amounts of X-radiation. Upon the inner surface of the window is located an input screen 22 which comprises a layer 24 of X-ray responsive fluorescent phosphor. This phosphor layer 24 is activated and made fluorescent by the image-bearing beam of X-radiation and consequently generates a fluorescent image corresponding to the X-ray image. The fluorescent image activates a second layer 26 which comprises photo-emitting material such as any of the known materials which emit electrons in response to incoming photons. This photocathode 26 thus generates a beam 28 of electrons which varies throughout its cross-sectional area to correspond to the fluorescent image. For greater efliciency, a thin X-ray transparent light-reflecting layer (not shown) of material such as aluminum may be provided between the glass support and fluorescent layer 24 to reflect all light toward the photocathode, as is well known in the art.
The internally generated beam 28 of electrons is focussed by suitable annular grid electrodes 30, 32 and 34 onto an output screen 36 which is located in the opposite end of the tube upon a glass faceplate 38 through which the resultant visible image may be viewed. Output screen 36 conveniently comprises a layer of phosphor which converts the electron image impinging thereon into a visible image in the normal manner of a tube of this type, and the resultant visible image may be viewed by the human eye with the aid of suitable optics indicated diagrammatically by element 40, or may be directed to camera 14, as desired.
In conventional X-ray image intensifiers of the type described, the input screen 22 is relatively large, having a selected diameter which may be, for example, six inches or nine inches in diameter, or even larger or smaller, as desired. However, the output screen is relatively small, usually being not much greater than one inch in diameter, and oftentimes only about one-half inch in diameter. Consequently, it is often desirable that a small portion only of the output image be enlarged for closer inspection. This is accomplished in the presently described tube by electronic zooming as will be described.
To continue the present example, it will be assumed that the input screen 22 has a diameter of about nine inches and the output screen 36 is about one inch in diameter. Focussing of the electron image from input screen 22 onto output screen 36 i accomplished by the threestage system embodying grids 30, 32 and 34, each of which normally has its own control and each of which exerts a control over some aspect of the output display. This means that not only can the electron beam be properly focussed, but that the tube can be adjusted to present a picture which has minimum astigmatism and which has good resolution.
Applicant has, in accordance with this invention, provided means to vary the electrical characteristics of the electronic system whereby it is possible to produce an expanded display of a portion of the input image. With this invention, with one selection of grid voltages the tube will display on its one-inch output screen a normal nine-inch mode picture. However, with a second selection of grid voltages the display on this same tube may be expanded so that only the image represented by the central six-inch portion of the nine-inch input will fill the one-inch output screen. Although a six-inch portion of the display is used in the present example, it is to be understood that other sized portions may be used as desired, and that such Zooming or variable field control may be accomplished in either a multi-stepped fashion or continuously. Thus, there will be produced on the same out-put image area the selected area of the input image, which is always displayed at its maximum enlargement for the collimated or shuttered field employed. Since the output image completely fills the output screen, it will completely fill the film frame or other optical device with which the tube is preadjusted, without required additional adjustments of the device and/or tube with each zooming operation.
The circuit involved in controlling the grid voltages, however, required considerable ingenuity since with tubes of thi character extremely high voltages are used, as high as 9000 volts or more. This presents a danger to an operator who controls the device with. hand-held devices.
Therefore, in further accordance with this invention, there is provided means for isolating the high voltage portions of the control circuit from the handheld remote manually-operated control unit. In fact, the remote unit has voltages of less than volts to control up to 10,000 volts, which permits use of normal low-voltage wiring systems. Also, the low voltage remote unit requires components which are small. compact and light weight.
In the system shown in FIG. 1 there is provided the variable field control unit 42 which is connected to each of the grids 30, 32 and 34 and which is supplied with power from a suitable power supply 44 which also supplies power to the tube anode 46 in the usual manner of tubes of this type. A remote low voltage manual control unit 48 is connected to the variable field control unit 42 through cable 50 which permits the unit 48 to be strategically located away from the high voltage unit and to be portable.
The variable field control unit 42 comprises a high voltage triode 52 (FIG. 2) which is connected as a variable reactance device. The reactance of the tube 52 is controlled by varying the cathode bias. The anode of the tube 52 is connected by lead 54 through a protective resistance to grid 34 of image intensifier tube 18. The grid of the tube is grounded in this instance since a positive potential is available.
Switch 56 is connected to the cathode of tube 52 for controlling the potential applied to the cathode. Switch 56 is part of a ganged switch, the other switch portions of which are connected to other elements to be described. The potential for the cathode of tube 52 is obtained from low voltage potential dividers 58 which have a maximum of 50 volts applied.
A second tube 60 is similarly connected by its cathode to the potential dividers through switch portion 62 and by its anode through a protective resistance to grid 32 of the image intensifier tube 18. Grid 30 of the image intensifier tube 18 is connected to switch portion 64.
All switch portions and positive potential are connected to a plug 65 into which is connected a mating plug 66 (FIG. 3) for connection of the remote control unit 48. In FIG. 3 it will be seen that three switches 68, 68a and 68b which may be suitably ganged or individually operated, are connected through a series 70 of potentimeters so that the potentials on the grids of the image intensifier tube may be manually controlled. The potentiometers in the system may be adjusted to be linear or nonlinear, as may be necessary, and may be operated if desired by a single control knob.
In one exemplary tube, a nine-inch input image has been found to provide an image occupying the full diameter of the output screen when grid 30 has an applied voltage of about volts, grid 32 has an applied voltage of about 1500 volts, and grid 34 has: an applied voltage of about 4000 volts. To increase the projected image size of the central six-inch portion of the input image, the potential on grid 30 is increased up to about 300 volts, on grid 32 up to about 700 volts, and on grid 34 up to about 6200-8000 volts.
This variation in potentials effectively shortens the focal length of the electron path, that is, the path length between the photocathode 26 and the focal or crossover point 72 (FIG. 1). Decrease in grid potentials will, of
course, lengthen the focal path so as to concentrate the input image into a smaller area of the output screen 36 in cases where greater intensity of the output image is desired.
It will be apparent that the advantages and objectives of this invention have been achieved to produce a novel image intensifier system having variable output image sizes, a result which has filled a long felt need. It will be apparent that various modifications and changes may be made by those skilled in the art in the system shown and described without departing from the spirit of the invention as expressed in the accompanying claims. Accordingly, it is to be understood that all matter shown and described is to be interpreted as illustrative and not in a limiting sense.
1. The combination of an image intensifier tube having an input screen for receiving an input radiation pattern and converting said pattern into an electron beam having a corresponding pattern, an output screen for converting said electron beam into a visible image, and a plurality of electrodes between said screens for focusing said electron beam onto the output screen, 7
and control means connected with said electrodes for electronically varying the size of the area of the electron beam which engages the output screen,
said control means comprising a high voltage variable field control unit having a power supply connected to said electrodes, and remote low voltage control means electrically connected to said variable field control unit for operating said variable field control unit and consequently varying the voltages applied to the electrodes.
2. The combination set forth in claim 1 wherein said remote low voltage control means includes a ganged switch having one side connected to the high voltage field control unit and a plurality of low potential divider circuits connected to the other side of said switch for individually remotely controlling the voltage supplied to each individual electrode in the image intensifier tube.
3. The combination set forth in claim 2 wherein said low potential divider circuits include potentiometers whereby the voltages to the individual electrodes may be varied in a continuous manner.
4. The combination set forth in claim 3 wherein said high voltage field control unit includes grounded grid high voltage triodes providing variable reactances controlled by varying the cathode biases thereof, the anodes of the triodes being electrically connected to said electrodes of the image intensifier tube, and said potentiometers are individually connected to respective cathodes of said triodes through said ganged switch for varying the cathode potentials in a continuous manner and consequently varying the voltages supplied to said electrodes in the image intensifier tube.
References Cited UNITED STATES PATENTS 3,225,204 12/1965 Schagen et al. 250-213 ARCHIE R. BORCHELT, Primary Examiner.
US. Cl. X.R. 250-213