US2398705A

US2398705A - Television system

Info

Publication number: US2398705A
Application number: US429016A
Authority: US
Inventors: Alfred N Goldsmith
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1942-01-31
Filing date: 1942-01-31
Publication date: 1946-04-16
Anticipated expiration: 1963-04-16

Description

April 16, @4 A. N. GOLD-SMWH TELEVISION SYSTEM Filed Jan. .'51, 1942 Wmv WM. WN

'AIIQVAENTOR HI A ATTORNEY Patented Aprrl, l

` UNITE-o STATES j PAraNr ori-"lola", H :..aassosl TELEVISION s'rs'raiu` Ames N. Goldman, New urk. N. Y., wim: u Radio Corporation of America, New York N. Y., a corporationof Delaware t Y Application umm-y s1, 194s. ssi-armsteun l s claims.' (ci. 11a-as) The present invention relates to television systems and is particularly adapted to television systems wherein the size and aspect ratio of the television image produced at the receiving apparatus is proportional or related to or representative of the distance separating the point of instantaneous reception and the point from which television -video or picture signals are, transmitted..

'Ihe invention in its preferred form is so constituted that the size of the television image produced at the receiving apparatus is related to the received signal strength in order that the re-y produced image size may be indicative of the distance separating the transmitting station from the receiving station. Furthermore, the preferred form of the invention is so constituted that the aspect ratio ofthe receiver image is also related to the received signal strength in order that the image produced'at the receiver may have a variable aspect ratio in order to produce a quantitative or qualitative visual -indication of the subject matter being transmitted.

The invention is designed'primarily for use in an airplane and is so constituted that the pilot by incoming planes. o Naturally, if the airport of the plane 'may have reproduced before him aV visual indication in proper perspective of the airport or landing field that he isapproaching. In order that aproper visual representation of the landing iield may be reproduced on vthe picture tube of the receiving apparatus. it is necessary to effect a control of the size of the reproduced image in accordance with ther distance of the l plane from the landing held and, lfurthermore,

it is desirable to alter the aspect ratio of the reproduced image inaccordance with the distance of the plane from the landing held or in accordance with the angle subtended between the line of sight to the airport and a horimntal plane coinciding with the airport. When both the size of the reproduced image and the aspect ratio are automatically altered in accordance with `the o distance of the plane from the landing field, then an instructive visual indication will be presented to the pilot of the plane. 4

In accordance with the present invention it is only necessary to transmit from the airport froml the airport in all directions 'for reception were visible from a distance of say miles and from an altitude of for example 5,000 feet the relative size of the airport'would be quite small and dimensions of the airport-parallel to the line of sight would naturally be foreshortened by reason of the angle from which the airport is observed. When a system incorporating the features of thisinventio'n is provided in the incoming airplanethe received video or picture signais, when applied to the present invention, cause an image to be reproduced on the receivingV tube inthe airplane, the size of the image being a function lof the distance of the plane from the airport and the aspect ratio -of the image beins also a function of that distance. As the plane approaches the airport the size of the reproduced image gradually and automatically increases and, furthermore, at the same time the aspect ratio of the received image is automatically altered to correspond to the change in the-viewing angle by reason of the approach of the plane to the airport. Such a system is particularly desirable ,when the airplane .is approachingl a duced upon a screen or viewing surface in such a manner that the size of the reproduced image ,may be 'a measureor function of the distance video or picture signals representative of a'single visual representation, the transmitted representation being thatl which would normally be sent froma point immediately above the particular airport. Video or picturesignals representing a view of the airport taken from a point directly above the airport may therefore be transmitted separating the receiving point from the transmitting point.

Another obiect of the present invention resides in the provision of means whereby television im ages may lac-obtained and produced on the screen ,or viewing surface insuch a manner that the aspectratio of the reproduced image may be al measure or function of the distance Separating the receiving point from the transmitting point.

o Astill further purpose of the present invention resides in the provision 'of means for automaticallyialtering or varying the sizeof the produced image on the viewing'surfaoe or screen of the receiving tube in accordance with variations in the signal strength of the received signals transmitted from a particular point adjacent or near the significant surface. l

Still another purpose of the present invention resides in the provision of means for automaticallvand gradually altering` the aspect ratio or the proportionate dimensions of the produced image at the receiver in accordance with the signal strength of the received signals.

' A still further object of the present invention resides in the provision of means for visually indicating and for quantitatively or qualitatively depicting the relative size and dimensions of a significant surface in accordance with the displacement and viewing angle of the receiver'V from the particular significant surface.

Still other purposes and advantages of the present invention will become more apparent to those skilled in the art from the following de tailed description particularly when considered with the drawing wherein:

Figure l represents a-preferred form of the present invention.

Figure 2 shows a plurality of outlines indicating the relative size and dimensions of received images.

Figure 3 shows a plurality of curves1 representing the control of various elements of the system and Figure 4 represents graphically the change in the relative size of a. significant surface in accordance with the position of the viewer.

Referring now to the drawing and particularly to Figure 4 there is shown asigniilcant surface A-C which may represent a landing field or airport. Above the ground surface is shown a broken line representing the line offlight of an approaching airplane. Along this line of ight are shown three points X, Y and Z representing three dierent positions of an airplane. Naturally, when the airplane is at position Z which is directly over the airport, the. dimensions of the airport or signiilcant surface-A-C will appear quite large and the surface will not be distorted v by reason of any Obliquity of vision. If, howaseavos the same significant surface when the receiving station or airplane is at a position corresponding to the point X or at some remote point with respect to the location of the airport. Under these conditions the dimensions of the airport in a direction parallel to the line of night (the vertical dimensions on the screen) are materially reduced for two reasons; one being the distance from the airport, and the other being the relative viewing angle. The horizontal dimensions cf the airport, however, are reduced by reason of distance only since obliquity of vision does not effect a reduction-in this dimension ofthe reduced image,v As the plane approaches the airport the size of the reproduced image is increased and the aspect ratio is decreased or altered so that at various stages of the approach of the plane to the airport the received image might cover areas represented by the rectangles 8, 6, 4 and 2, respectively. It is to be understood, however, that the change in the dimensions and the change in the aspect ratio of the produced image on the receiving tube is gradual and is not stepwise.

It may be appreciated therefore that when a circuit arrangement is provided to alter the size and aspect ratio of the produced image in an airplane a natural depiction of the airport is produced simulating an actual viewof the airport from the airplane.

In Figure l is shown one form of the present invention for accomplishing the above desired purposes and results. An antenna system I 0 is shown which receives the signals transmitted from the transmitting station at the airport or reduced to a dimension corresponding to the line D-E which is drawn normal to the line of sight Y-B. Y,If the airplane is,A located at the point indicated at X then the over-ali dimensions of the airport will be further reduced and the dimension oi the significant surface parallel to the direction of flight will be very greatly reduced by A reason of the decreased viewing angle. The dimension of the airport in the direction of flight will therefore be reduced to correspond to the length F-G as shown in Figure 4. The apparent dimensions of the airportin a. direction perpendicular to the direction of approach is aected only as a function of distance since the viewing angle doesnot cause any foreshortening in that particular direction. Foreshorte, however, is eective to materially reduce the apparent dimensions of' the airport or signicant surface in a direction parallel to the line of flight.

Figure 2 shows a series of rectangles which represent the dimensions of the produced images on the receiving tube i'n the airplane.- The largest rectangle 2, for example,'represents the dimensions' and aspect ratio presented on the viewing 'screen of the receiving tube when the plane is significant surface and the antenna supplies radio I2 as well as to a radio frequency amplifier and detector It. Demodulated picture or video signals from the receiver i2 are then applied to a video or picture signal amplifier I6 which, in turn, supplies amplified video or picture signals to the control electrode i8 of an image producing tube 2li. These signals are applied by Way of coupling condenser 22. The image producing tube 20 also includes a heating element 24, a cathode 26, a first anode 28 and a second anode 3U. When proper operating potentials are applied to the electrodes of the tube a focused cathode ray beam is generated. For deflecting the cathode ray beam in a horizontal direction horizontal deflecting plates 32 are provided and likewise for deflecting the cathode ray beam in a vertical direction vertical deflecting. plates 34 are provided.

The television video or picture signal receiver and demodulator l2 also supplies synchronizing signals to a horizontal .deflection generator 36 and to avertical deflection generator 38. Naturally proper horizontal and vertical synchronizing impulses are transmitted from the transmitting station as is conventional and well known in television transmission practice. These synchronizing signals that are applied to the horizontal deection generator 36 and to the vertical deflection generator 3B cause the deflection generators to produce voltage variations of substantially .saw tooth wave form or of a wave form necessary to deflect the cathode ray beam in the receiving tube 20 in mutually perpendicular directims and at the proper uniform rates. The voltage variations which are developed by the horizontal deflection generator 38- are applied to a horizontal deflection amplifier 4I! while the output from horizontal deflection amplier 40 is applied to the horizontal deflecting-electrodes 32. Similarly the output from the vertical deflection When the horizontal and vertical deection ampliers 4l) and 42 are operated at substantially i optimum eiiiciency and gain the voltage variations supplied thereby are suillcient to cause the cathode ray beam to be deilected over substantially the4 entire screen or Vtarget area 44' ofthe television image-producing. tube 42li to produce thereon electro-optical images. of any control on the horizontal and vertical defiection amplifiers the size of the scanned area on the viewing screen 44 of the cathode ray tube 20 would remain substantially xed. Furthermore. the aspect ratio or Vrelative;dimensions of the scanned area would remain relatively xed.

For effecting a control of the size and relative dimensions ofthe scanned area, the signals which are derived from the radio frequency amplifier and detector it arek applied to a horizontal dimension variation amplifier 46 and toa vertical dimension variation amplier48. These amplifiers supply a biasing potential or a control potential to the horizontal and

vertical amplifiers

40 and 42 respectively in order to control the gain or amplification of the deflection amplifiers. Nat-` urally the signal output from the radio frequency amplifier and detector i4 is a function of the re ceived signal strength since it is preferable that no automatic volume control action be included in this portion of the circuit. Accordingly, potential variations are applied to the horizontal and vertical dimension variation amplifiers 46 and 48, the potentials being a function of the intensity of the reived signals at the antenna l0. After these voltages have been appropriately amplified they are then applied to the horizontal and vertical deflection amplliiers 40 and 42;

Since the horizontal dimension ofthe produced image is to be varied in accordance ywith the reasesflosi Y `tion-of the distance of the receiver or airplane i from the transmitter or airport.

`Assuming the-'horizontal and vertical dimen- In 4the absence sions of the produced image to v be unity when the receiver is directly above the airport and at al point represented by Z in Figure 4, then it may be seen that if the plane is flying from the airport the horizontal and vertical dimensionswill be de lcreased according to dierent functions. By an inspection of Figure 3 it is evident that a vertical vdiniensionwill decrease more rapidly as a function of increasing distance than-will the horizontal dimension for the corresponding distance.

Likewise,as a plane approaches an airport the .first produced image will appearv quite small inI lheight. and will have a relatively largeaspect ratio. Both dimensions of the produced .image will be materially reduced but the vertical dimension will be decreased-by an amount considerably in excess ofthe decrease in the horizontal divmension. Y As the plane approaches the airport both dimensions will be increased as the distance between the airplane and the airport is decreased but the percentage increase in the vertical dimension will be more rapid than the percentage increase in the horizontal direction. Accordingly,

ceived signal strength to indicate distance only from the airport or significant surface, it is desirable to alter the ampliication of the horizontal deflection amplifier lili` according to a predetermined function, the function being represented by way'of example by the curve Il! shown in Fisure 3. .The curve 50 shows the horizontal picture gain'or ampliiicationof the horizontal deflection i amplifier 40 is permitted to increase by voltage control from Vthe horizontal. dimension variation amplifier 46 in a manner represented by the curve 50 in Figure 3. I

The vertical dimensions on the produced image. t

however, must be altered torepresent both distance andl Obliquity of vision. Accordingly, the vertical deeotion amplifier 42 should be supplied with control potentials such that the gain or arnpliilcation of the vertical deflection amplifier will vary in accordance with a curve such as shown-at 52 in Figure 3 as a function of the received signal strengths. ,The vertical dimension variation amplifier 48 therefore responds to the received signalstrength to produce control voltage variations which when applied to the vertical deiiection ain- Dlier 42 will be effective to alter the vertical deection voltages in a manner represented bythe curve 52 in Figure 3. This curve shows the vertical picture or image dimension asa percentage or fraction of its maximum value4 (corresponding to the dimensions of 2 in Figure 2) andas a func` claims.

there is presented before the pilot a proper or natural visual representation of the airport and the produced image will depict not only the proper visual size of the airport but also the propel` visual dimensions or aspectk ratio of the airport.

In the patent to Goldsmith, #2,168,566, is shown and described a system wherein the relative size only of the received image is altered in accordance with received signal strength. Such a system is naturally'of considerable assistance in guiding aircraft or ships into airports or harbors where due to bad weather conditions or to darkness a direct and accurate view of the ultimate point of destination cannot be obtained by direct vision. In thecase of a ship, it is not necessary that theaspect ratio or relative proportions or dimensions of the proposed image be altered,

, however, in the caseof an aircraftV or airplane it is desirable to alter not only the over-all dimensions but at the same time to alter the relative dimensions of the image since, as the aircraft approaches the landing field, not only does the size of the landing field change but also the aspect ratioor relative dimensions of the airport changes because of the changefin the, obliquity of vision. Accordingly, through the use of the present invention it is possible to produce a qualitative visual indication simulating and depicting the normal view of the approaches airport. 'I'his is accomplished by not only `automatically and gradu- .aily varying the size of theV produced image but also simultaneously, automatically and gradually altering `the relative dimension; of the produced image to simulate changesin thel angle of sight. Various alterations and modifications of the present invention may Ibecome apparent to those skilled in the art and it is desirable that any and all` such modincations .and alterations `be con'- sidered within thepurvlew of the present invention except as limited by the hereinafter appended I claim:

1. A television receiver comprising means forceived signals for controlling the size and aspect:

ratio of the produced electro-optical images so as to represent the geographic separation and the angle of vision from the receiver to the point of transmission.

2. A television receiver, means for receiving video and accompanying synchronizing signals, means for producing, in accordance with the received video signals, electro-optical images representative of a signicant area at the point of transmission, means for controlling, in accordance with the received synchronizing signals, the rate and spatial position at which the video signals are translated into electro-optical eects,

and automatic volume controlled means for controlling, in accordance with the strength of the received signals, both the size and the ratio of the dimensions of the produced electro-optical image to qualitatively represent the geographic separation and angle of vision from lthe receiver to the point of transmission,

3. A television receiver, means for receiving video and accompanying synchronizing signals, means for producing, in accordance with the received video signals, electro-optical images representative of a signicant surface at the point of transmission, means responsive to the synchronizing signals for controlling the rate and spatial position at which the video signals are translated into electro-optical effects, means responsive to the strength of the received video signals for automatically changing the horizontal dimension of the produced electro-optical images according to one function, and means also responsive to the strength of the received video signals for automatically changing the vertical slgnlcant surface near the point of transmission,

and means responsive to received signal strength for automatically changing the horizontal dimensions of the produced electro-optical images according to a predetermined function, and means responsive to received signal strength for automatically changing the vertical dimensions of the produced electro-optical images according to a diierent function, whereby Iboth the size and the aspect ratio of the produced electro-optical images may be changed in accordance with the received signal strength.

5'. A method of producing. television images comprising the steps of receiving videosignals, i

producing bi-dimensional electro-optical images under the control of the received video signals, and developing automatic volume controlled energy measured as a predeterminedv function of variations in a received signal strength due to changing geographic separation of the receiving point and the signal transmission point for controlling each of the two dimensions of the produced electro-optical images so as thereby to vary the aspect ratio.

6. A method of producing television images comprising the steps of receiving video signals producing bi-dimensional electro-optical images under the control of the received video signals, developing automatic volume controlled energy measured as a function of the variation in received signal strength for modifying one dimension of the electro-optical images, and then developing independent automatic volume controlled energy measured as a predetermined function of variation in the received signal strength for controlling the second of the two dimensions of the electro-optical images, whereby the aspect ratio of the developed images varies substantially in accordance with the received sig'nal strength as representative of the yariations in geographic separation of the receiving point and the point of transmission.

ALFRED N. GOLDSMITH.