US2400066A - Television apparatus - Google Patents

Description

y 4, 1946. G. BEERS 2,400,066

TELEVISION APPARATUS Original Filed May 2, 1942 To fkmwnrrre-w INVENTOR ATTORNEY Patented May 14, 1946 UNITED TELEVISION APPARATUS George L. Beers, Haddonfield, N. 3., assignor to Radio Corporation of America, a corporation of Delaware Original application May 2, 1942, Serial No. 441,445. Divided and this application March 22, 1945, Serial No. 584,157

Claims.

This invention is directed to television apparatus and particularly to a view finder for use on television cameras, and constitutes a division of my copending application for Letters Patent, Serial No. 441,445, which was filed May 2, 1942, and is now United States Patent No. 2,384,232, granted September 4, 1945.

In its preferred form herein described the invention has asits object that of providing a, view finder which, when used cooperatively with a telee vision camera tube, will give satisfactory performance of the television system irrespective of the sensitivity of the pickup tube.

In the operation of television systems the image signals which are transmitted to the receiving points may originate from the scanning of motion picture film, for instance, or from direct pickup in a studio or out of doors. The present invention is particularly concerned with the latter type of pickup and, as such, is directed to a form of view finder which not only provides the camera operator with a view of the scene of which the image is to be focused upon the television camera pickup tube for the production of the television signals, but also indicates when the lens picking up the scene is properly focused thereon.

The present invention is one which is intended to simplify and improve the performance of television camera equipment and accordingly it will be found that among the various objects of the invention are those of providing a view finder which at all times shall accurately indicate when the television camera is properly focused upon the desired scene or object.

Another object of the invention is that of providing a television view finder which not only will define the particular portion of the scene which it is desired to convert into the television image, but shall also reproduce a sufiicient portion of the scene external to the camera field so that the cameraman will know in advance what areas will be included in the field of the camera if he "pans the camera in any direction.

Still other objects and advantages of the invention are those of providing a system which is efficient in its operation, relatively free from complex parts and yet capable of being controlled by a single operator.

In the past it has been found that with the increase in sensitivity of television camera tubes and with an adequate amount of illumination on the desired scene, the camera lens can frequently be stopped down to provide a greater depth of focus while still being able to produce an adequate signal output from the television pickup tube.

side of the television picture area. Unless the view finder provides this information, the cameraman will not know in advance what will be included in the picture if he pans the camera in any direction. In television studios several sets are frequently used in limited space, so that a camera can be changed quickly from one scene to another. This makes itnecessary for the cameraman to know what is included in a small area outside the held of his camera, so that he does not inadvertently include an edge of an undesired set in the picture. If the view finder does not provide an image of this additional area, itis frequently necessary for the cameraman to move his head sufliciently so that he can look along one side of the camera to determine the effect of panning" the camera in a desired direction. Not only is this inconvenient, but when the cameraman looks around the camera at the brighter scene and then again IOOks at the image in the view finder, it is necessary for his eyes to readjust themselves to the difference in the light intensity.

Essentially the present invention comprises ways and means by which a desired image is focused upon the mosaic of a television pickup tube.

In one of its preferred forms, the invention comprises a pair of optical systems. One of the optical systems is arranged to direct the light of the image on to the television camera scanning tube used for picking up the scene to be transmitted and for translating the light values of that scene into electrical signal impulses which are then transmitted in an appropriate manner to receiving stations. The second optical system is arranged to direct light from the scene upon a view finder screen which is within the viewing range of the camera operator.

on the mosaic of a camera pickup tube on one hand, and upon the separate view finder viewing screen on the other hand. By providing an ar-' rangement whereby the area of the camera tube mosaic which is scanned may be controlled, the effect of changing the focal length of the camera lens or of changing the distance between the scene and the camera can be achieved by employing novel means which are included in one embodiment of the invention. a

The view finder is controlled simultaneously with the control of the scanned area of the pickup tube mosaic so that it indicates at all times the area of the scene which is being converted into the television image.

The invention is schematically illustrated by the accompanying drawing which shows a plurality of optical systems which is utilized in combination with a camera pickup tube and a view finding screen area.

Referring now to the drawing for a further understanding of the invention, there is provided within the camera housing it, a pair of lens elements [3 and I5 which are each capable of being moved along their axes i4 and I9 respectively in the directions shown by the arrow. Adjustment of the lenses l3 and I5 backward and forward is provided by means of asuitable focus control knob (not shown) which is usually located on the rear portion of the housing and connected with a suitable shaft or spindle, preferably passing directly through the housing and supported in the housing walls in bearing members (not shown specifically but set forth in the parent application). The control shaft usually has attached to it a suitable gear or pinion element which is adapted to control in any desired manner the backward and forward lens motion, as conventionally indicated, to effect image focus.

In one portion of the housing element ll there is provided a camera pickup tube 27 having a mosaic element 29, onto which the light forming the image is adapted to fall when focused thereupon by the lens element I3.

The camera tube 2'! is conventionally represented as being of the type known in the art as the Iconoscope, which has been described in many publications of the prior art, such, for instance, as in the article entitled Television pickup tubes with cathode ray beam scanning, by Messrs. Iams and Rose, as published in the Proceedings of the Institute of Radio Engineers for August, 1937, volume 25, No. 6, commencing on page 1048. This tube is merely represented as schematic of various types of tubes which can be used with equal efficiency.

Developed within the tube 21 is a cathode ray beam 3! which is arranged to scan the mosaic element 29 in accordance with its position of impact thereon, as controlled by the horizontal defleeting coils 33-33 and the vertical deflectin coils 35-35. The impact of the cathode ray beam upon the mosaic element releases to an external circuit signals representative of the image, in known manner; Thus, output television signals are then supplied to a pre-amplifier 31, usually contained within the camera housing and schematically represented herein. The output from the pro-amplifier 31 is then supplied to the transmitter (not shown) and its appropriate amplifiers and modulators from the terminal point 39.

In order that the operator may be able to determine exactly the scene being transmitted and to maintain that scene properly focused upon the camera tube 2'1, a view finder screen 9? is provided within the housing l i.

Horizontal deflection control circuits W and vertical deflection control circuits 59, each conventionally represented since they are, per so, well known, are provided. These circuits are connected to energize the horizontal and vertical deflection coil pairs 33-93 and 35-35 in well known manner. 1

As was explained, for instance, in Iams Patent, No. 2,098,390, of November 9, 1937, by varying the amplitude of deflection of the cathode ray beam across the mosaic target, the area of the target which is scanned may be controlled.

Changes in position of rotation of the control knob ll are arranged to control the amplitude of deflection of the cathode ray beam 3i developed within the scanning tube 21. When the control knob ll is turned, it is adapted to rotate a spindle or shaft 69 which is supported in a suitable bearing member, not shown, both at the point where it entezs the housing H and at some intermediate po n At the end of the shaft or spindle 99, remote from the control knob, there is a gear H which is arranged to mesh with a second gear l3, which, in turn, rotates a spindle 15. This spindle has both right and left hand threads, with the division between right and left hand threads being made about midway thereof.

Carried upon the spindle and adapted to be controlled by a rotation thereof are two slidable elements TI and 19 which are prevented from tuming as the spindle 15 rotates, but by means of guide elements not shown, are arranged to slide laterally in opposite directions. Attached to the slidable elements 11 and 19, respectively, are the vertical wires 8| and 93 of a view finding mask to define the area A over which the view is to be scanned. As the slidable elements I1 and 19 move in the direction shown by the arrows, the wires 8! and B3 are likewise brought closer together, or farther apart, as the case may be, with respect to each other, and are prevented from rotating by means of the guide element into which they are fitted. For any rotation of the shaft or spindle 15, this motion is translated to a second shaft or spindle 81 by means of a pair of gear elements 89 carried 0n the end of the shaft or spindle l5 and the shaft or spindle 91.

In a manner similar to that heretofore explained, a similar pair of slider elements 9| and 93 is adapted to slide on right and left hand threads of the spindle 81, so as to move the wire mask elements 95 and 96 upwardly and downwardly, A

and toward and away from each other within the guide member 91, as indicated. Thus, the wire mask elements Ill-83 and 95-96 together define an area A which is representative of the image area tobe scanned in the camera tube 21.

For the purpose of controlling the amplitude of deflection of the scanning beam of the camera tube 21 in both the horizontal and vertical directions, the movable elements '59 and 93 respectively are arranged to vary the slider element on the potentiometer elements 6i and 5'! respectively, which are connected to the horizontal deflection control unit 51 and the vertical deflection control unit 59, so that the area of the mosaic target 29 which is traversed by the scanning cathode ray beam 3! shall be varied.

Simultaneously with a variance in the amplitude of deflection of the cathode ray beam in the tube 21, provision is made for varying the focus of the cathode ray beam in a manner similar to that shown, for instance, by the Iams patent above referred to so that the scanning detail shall be increased in the tube 21 for, reduction in the area scanned. In this way the reduced size pattern of the transmitter may be expanded on the image reproducing tube of television receiving instrumentalities to retain the desired size and aspect of the picture viewed and still maintain the desired image detail. The increase in scanning detail is obtained by decreasing the size of the scanning spot on the mosaic target 29, while, at the same time, retaining the same time period to traverse each horizontal path of scanning and the complete number of vertical paths of scanning, so that the frame periodicity and line periodicity remain invariant.

As was shown by the aforesaid Iams patent, a um'control is adapted to be provided for simultaneously focusing the beam 3| to a more sharply defined spot so as to vary the scanning detail in order that the area corresponding to the area A on the mask shall be scanned in greater detail. The focus control for adjusting the position of the lenses has likewise been omitted from this diagram for the sake of simplicity.

I claim:

1. Image transmission apparatus comprising an image scanning transmission tube having included therein a light sensitive target optical means for directing the light of an image upon the tube target, a cathode ray source for producing an electron beam within the tube and means for causing the produced electron beam to scan the target to produce signal output energy therefrom which is proportional to the optical image upon the target, a view finder observation screen, optical means to focus light representing the said image and its contiguous border areas along a second light path to produce upon the view finder observation screen an image representation which includes within its boundary limits the image focused upon the image scanning transmission tube, an adjustable masking means associated with the observation screen to define predetermined selected portions of the image, control means for varying the masking area relative to the complete image viewed upon the said view finder observation screen, and means op rating simultaneously with the said last named means for controlling the scanning of the image area of the tube target by the said electron beam so that the scanned area includes only that fractional portion of the complete image in the view finder screen which is defined by the said masking means.

2. The system claimed in claim 1 comprising, in addition, means 'for varying the cross-sectional area of the scanning cathode ray beam with variances in scanned target area so that the scanning detail is substantially inversely proportional to changes in total scanned target area.

3. Television camera apparatus including, in combination, a television camera tube having a substantially planar light sensitive mosaic element for receiving optical images which are then converted by a scanning cathode ray beam so as to develop output video signals representative of the optical image, a substantially planar view finder observation screen arranged substantially coplanarly relative to the camera tube mosaic, optical means to focus light rays representing an image upon both the camera tube mosaic and the view finder screen with the image directed upon the view finder screen including border areas contiguous to those of the image area directed upon the mosaic, adjustable masking means associated with the view finder screen to define the predetermined selected image areas, means to adjust the image area defined within the View finder masking means, and means operating under the control of and simultaneously with the said adjustable means for controlling the scanning of the image area of the mosaic target so that the scanned area of the camera tube mosaic embodies a fractional portion of the total image area observable on the view finder screen.

4. Television camera apparatus for use in combination with a television camera tube which has a light sensitive mosaic target element adapted to receive optical images and which target element is then scanned by a cathode ray beam to develop output video signals which represent the impinging light image comprising a substantially planar view finder observation screen supported substantially eo-planarly with and spaced apart from the mosaic target element of the camera tube, optical means to focus light rays representing an optical image upon both the mosaic target of the camera tube and the said view finder observation screen with the image directed upon the view finder observation screen including also border areas of the optical image contiguous to those of the image area directed upon the mosaic target of the camera tube, adjustable masking means associated with the view finder observation screen for defining predetermined selected image areas, and means operating under the control of and simultaneously with the said adjustable masking means of the view finder observation screen for controlling the amplitude of scannin of the light sensitive mosaic target by the scanning cathode ray beam within the said camera tube so that the scanned area of the camera tube mosaic target is substantially similar to that defined by the adjustable masking means of the view finder observation screen but of a fractional area relative thereto.

5. Television camera apparatus for use in combination with the television camera tube having a substantially planar light sensitive target element for receiving optical images which are adapted to be scanned by a cathode ray beam to develop output video signals comprising a substantially planar view finder observation screen arranged substantially coplanarly with respect to the light sensitive target of the camera tube, an optical means to focus light rays representative of an optical image upon both the light sensitive target of the camera tube and the view finder observation screen with the image directed upon the view finder observation screen corresponding to that directed upon the light sensitive target of the camera tube with the addition thereto of border areas contiguous there with, adjustable masking means associated with the view finder observation screen to define thereon predetermined selected image areas, and means operating simultanously with and under the control of the said adjustable means for controlling the area or the light sensitive target element of the camera tube encompassed by the scanning beam during the p du t n of th aforesaid video signal outputs so that the scanned image area of the light sensitive target of the camera tube embodies a fractional part only of the total image area observable upon the view finder observation screen.

GEORGE L. BEERS.

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