Патент USA US2108827код для вставки
Feb. 22,- 1938. I A. McL. NICOLSON 2,108,827 TELEVISION SCANNING SYSTEM F?ed July 7. 1950 a Sheeté-Sheet 1 INVENTOR A/exander MELmH Mrs/son. BY @A/KWM ATTORNEY Feb. 22, 1938. A. Mc|_. NICOLSQN I 2,108,827 ' TELEVIS ION SCANNING SYSTEM _ Filed July '7. 1930 ‘ 3 Sheets-Sheet 2 His-.- E /40 \ \ i5 Sea/min Gene/afar.’ 75 INVENTOR BY @QA/K WM ATTORNEY Feb; 22,_ 1938.- A, Mc|_, NICOLSON 2,108,827 ‘TELEVISION SCANNING SYSTEM Filed July 7. 1930 _ } 3 Sheets-Sheet 3 "7.515.. E __73.;___’_____’___. 77076. INVENTOR ' A/exdna’er MQLean Abba/$017. BY QM/KM ATTORN EY Patented Feb. 22, 1938 amass? . UNITED? STATES PATENT orrics 2,108,827; TELEVISION SCANNING SYSTEM Alexander McLean NicolsomNew York, 7N. Y.,ias signor to, Communication Patents, Inc., New York, N. Y., a corporation of Delaware Application July 7, 1930, Serial No. 466,079 24 Claims. (o1.17s_7_.,2) ' This , invention relates to television systems, the cathode is not uniformly illuminated. This andparticularly to the scanning apparatus em ployed in such systems. An object of the invention is to more e?iciently 5 transmit pictures by wire or wireless means vfrom fact, coupled with the fact that the emissivity is not directly proportional to the illumination, one station to another, so that a complete elec trical image is formed in-a fraction of a second, permitting the transmission of motion pictures between stations. 10 Another object of this invention is to facilitate. the scanning of scenes at a considerable distance from the transmitting apparatus. 1 ' I The point of operation on the photocell char acteristic curve is determined by the total re - flected light falling on the cathode, and this point may be‘changed and controlled by the insertion‘ of light ?ltersofsmokedglass and the like‘be tween the object and the cathode of thecell. 10, This action is analogous to the biasing of the i A further object of'the invention is to utilize the non-linear characteristic of a photoelectric 15 cell for obtaining differential illuminating cur» rents in accordance with the light and shade intensities of objects. forms the basis of this invention. - control grid of a-vacuum tube. V , ‘ With the; image on the cathode itself, a Search ing ray of light, produced in any well known manner, but preferably, in the form of an elec- 1;.5 trodynamic are along electrode rails in a mag netic ?eld, may be employed for scanning the A still further object of the invention is to in crease the ef?ciency of scanning apparatus by re-, 20 generation. , in the electrical transmission‘of the images, of objects or pictures thereof from a transmitting station to a receiving station in the form of elec trical impulses characterized by the light and 5 dark intensities of the objects or pictures, the image. Such scanning systems are disclosed in my co-pending. applications Ser. No. 397,826, ?led October '7, 1929 and. Ser. No. 450,025, ?led 20 May 5, 1930. Since the intensity of the light of the searching ray is substantially constant, varié ations in the current output of the cell are ob tained through the non-linear characteristic of the photoelectric cell. For example, when the 25 common manner in which the impulses are ob tained is the projection of a searching or scan~ scanning ray is projected upon the portion of the hing ray'of light on the objects or pictures. The varying intensities of the reflectedlight are in 30 tercepted by a photoelectric cell or plurality light from the object originating from the sun or , thereof, to effect the transformation into electri cal vibrations, which are transmitted from station to station. ' _ , It is well known that the intensity of light de~ creases rapidly with distance from the source. t is obvious, therefore, that if objects are to be successfully scanned in the usual manner from a considerable distance, an extremely high power light source is required in order to obtain a su?i ,19 cient variation‘ in the intensity of the reflected light upon a photoelectric, cell positioned approx imately the same distance from the object. Even ' with such a light source, this method is not desir .15 able, from the convenience standpoint. , In the present invention, a distant or near scene is scanned by obtaining an image of the scene upon the cathode of a photoelectric cell which has a non-linear characteristic. The focusing of the image on the cathode of thecell 50 will produce a steady total emission of electrons to the anode of the cell, and produce a steady electric current in the input circuit of the photo electric current ampli?er. Although total emis sion remains substantially constant, the emission is not uniform over, the entire cathode, because cell which is least illuminated by the re?ected an arti?cial lighting'system, a certain increase'in the steady value of ‘the photocell current is ob- 3O tained. The amount of this increase is entirely dependent upon the amount of light originally falling upon this area. Now, ‘if the scanning ray moves to another portion or unit area of the im age having brighter illuminationpan increase'of .35 photocell current will occur, having a value greater than that caused by the ray falling on the ?rst portion. This variation in current in accordance with the light and dark intensities of the image will reproduce the image at a receiv- 40~ ing station. The characteristic of a photocell is comparable to the grid voltage-plate current characteristic of a three element vacuum tube, that is, it has a double in?ection. In the present system the 45 lower bend of this curve is employed similarly to the portion used in a grid leak detector for radio reception. When the scanning ray falls on por tions of the cathode having small illumination, small increases in photoelectric current are ob‘- 50 tained, while proportionally larger increases 00 our from scanning the brighter portions of the image.- This relation is the same as that found whenan. object is directly scanned by the search ing ray. . 2 2,108,827 This invention also contemplates the impres sion of a portion of the generated photoelectric which, after ampli?cation, are transmitted to cell currents after ampli?cation upon the scan ning ray producing means to intensify the ray Referring now to Fig. 3, a portion of a char acteristic curve of the photoelectric cell is shown, the co-ordinates of which are light intensity in proportionally to the light and shade of the image, thereby amplifying and emphasizing the non-linear emission characteristic of the cell. The details of the invention will be more fully ' understood. by. reference to the accompanying ' drawings, irrwhich:v Figure 1 is a perspective diagrammatic ar rangement of a single cathodeésingle anode photoelectric cell scanning system; Fig. 2 is a cross~sectional view of another em 15 bodiment of scanning apparatus, in which a dou lumens and photoelectric cell current in micro amperes. The complete curve may be found in any treatise on photoelectric cells, and if car- . ried to the saturation point, will be found to have a second in?ection in the, reverse direction. Only the lower portion of this curve is utilized in the present invention, this portion being com parablelto the lower inflection of the grid volt age-plate current characteristic of a vacuum tube. Of course, the upper bend can be employed in ‘ole anode tube is employed, the cathode of which the same manner as in detection with vacuum has a de?nite curvature. tubeshaving a-positive bias. Figs. 3, 4 and 5 are curves representing the op 20 receiving apparatus. erating characteristics of the photoelectric cell. Referring to Fig. 1 speci?cally, a photoelectric cell is shown diagrammatically in the form of a camera. The cell has a cathode 5 and an anode 6, the cathode beingof an opaque material, coated with a light sensitive material such as potassium 25 or the like, well known in the art, while the anode is a metallic ring shown in the form of a square, but which may have any con?guration. , These elements of the tube which in practice are con tained in an evacuated or gas ?lled transparent envelope, are shown connected in the input cir cuit of an amplifier system comprising a vacu Assuming an im~ age has been projected on the cathode of a cell of the character shown, a steady flow of cur~ rent will occur between the elements thereof, 20 depending upon the total amount of light re ceived from the scene to be transmitted. On the curve, the least illuminated area may be rep resented by the point 3i which will produce a certain amount of photoelectric cell current. An 25 other element of the cathode receiving the high est illumination is shown by the point 32, pro ducingv another value of photoelectric cell cur rent. The integration over this curveprovides 30 the steady'current value of thecell output. In Fig. 4, another representation of this phe with a potential from a source 8, while the ele ments in the tube are shunted by a resistance nomenon of the tube is illustrated. The heavy line 34 on the left hand side of the drawings rep resents the cathode, while the heavy line 35 on 35 Q for varying the impedance of the input to the vacuum tube 1. The vacuum tube is energized the anode, the drawings being a cross-section um tube 7. The photoelectric cell is provided from a ?lament battery 5 l and a plate potential battery Hi. The output of the battery is con; nected through output transformer £3 to an am 40 pli?er M, which in turn is connected to trans mitting apparatus 45 for transmission of the photoelectric cell currents. The transmission may be either over an antenna system H or wire conductors l8 chosen by the operation of a switch 45 E9. Connected to the transmitter is also a scan ning generator 22 for producing a scanning ray the right hand side of the drawings represents 35 of these elements. The varying density lines represent the number of electrons ?owing from particular points on the cathode, the drawings illustrating the non-uniformity of emission from 40 the cathodes as the light is projected thereon in different intensities. The total amount of cur rent generated by the cell, however, is a substan tially steady value in spite of any changing scenes, the changing scenes causing only a re 45 distribution of activity. In Fig. 5, these relations are shown by a curve for a scanning screen 23. The impulses from plotted between time and photoelectric cell cur the scanning generator are transmitted along rent. The dotted line 3% represents thesteady with the photoelectric cell currents for synchro . value of current obtained by the focussing of the nizing the receiving screen with the transmitter. scene on the cathode, while the wavy line 3? It is to be understood that any type of scan is the variation in the photocell currentv caused ning system which provides a sharp exploring by the scanning thereof by the scanning appa~ ray of substantially constant intensity, may be ratus. The addition of the scanning ray will used to scan the image. , increase the photoelectric cell current, and a min 55 55 There isalso shown in Fig. l a camera 25 with imum will always be above that of the steady its pinhole 26, for producing a scanning beam value caused by the re?ected light from the of light, and a focusing lens 28 which may be scene. 7 adjusted to properly focus an object on the Returning now to Fig. 3, which shows how o'athode. A light intensity controlling screen the wavy line 31 of 5 is obtained, we may 60 60 is interposed between the lens 28 and the assume that the light intensity of the scanning anode B, but the screen may also be placed be ray is equal to‘ the distance a between the ver tween the scene and the lens. tical parallel lines. That is, the illumination of An object positioned at O for instance, which all. unit areas of the cathode is increased by a 65 may be a near or far scene, may have light pro consecutively by the ray passing over them. iected upon it from either the sun or arti?cial sources. A portion of this projected light is re When the arc is projected, therefore, on a dark ?ected through the focusing lens 28, the screen 28, the anode 5 onto the photoelectric cell cath ode 5, as shown at I. This image is then scanned 70 by the ray of light produced by the screen 28 and projected through the pinhole 26 of the camera 25. Because of they non-linear char acteristic of the cell, varying currents are set 75 up in the input circuit of the vacuum tube 1, portion of the image on the cathode, the increase in photoelectric cell current may be considered as the distance between the ?rst set of horizon tal lines I). As the ray shifts to a portion which 70 has abrighter illumination, for instance as shown by the middle set of vertical lines, the increase in photoelectric current will be that shown by the distance between the middle set of horizon tal lines 0. When the are again advances to a 75 2,198,827 still more illuminated portion of the‘ cathode, the increase in photoelectric cell current is that ' shown by the distance d betweenthe upper set of horizontal lines. It is seen, therefore, ‘that although the scanning ray has a constant in tensity, the increase in photoelectric cell cur rent is dependent upon the illumination of the cathode by the light re?ected from the scene. As the ray is projected over the cathode in any desired con?guration, it illuminates the light and dark areas with light of constant intensity, but 15 produces a. variation in the photoelectric cell output current, in accordance withthe light and dark portions of the image on the cathode. The operation of this circuit is identical with that of a direct scanning system in which the increase in photoelectric cell current is deter mined by the intensity of the re?ected light from a directly scanned object, that is, the lightpor .20 tions of the object will re?ect morelight and produce a higher value of photoelectric cell cur rent. The present system, however, instead of projecting the light to great distances with the extreme loss in intensity through distance, has 25 a substantially constant scanning range with no lossoi scanning power due to the ‘varying length of the light projection paths. In- this way the system is extremely efficient for the scanning of 1 or a singleitube with a double anode, as shown. For instance, the grid ?ll is connected to the oath ode 45 of the photoelectric cell, while the anode M of the cell, is connected through a variable inductance 6,! to an anode 62 of the vacuum tube. Similarly, the anodeélé of the cell is connected through a variableinductance 63 to the anode M of- thevacuum ‘tube, ‘ A resistance 65 is connected in shunt to these elements for controlling the operation of the cell. A plate potential ‘66 for 10 the vacuum tube, supplies also the operating voltage for photoelectric cell through the primary of the output transformer 61, chokes 68 and 69, in parallel, variable inductances BI and 63‘ in parallel, anodes (it? and $5 in parallel, cathode 15 Q3, and grid (it. An increase in emission of the cathode to either of the anode-s of the cell will produce an increase in the voltage on the input circuit of the tube, which will be transmitted through the output transformer _61 to an ampli 29 ?er ‘Hi. The output circuit has a variable in ductance ll connected therein which is employed for feed-back purposes. The inductances, there fore, El and 6t and ‘El may be used to produce a certain amount of regeneration. The scanning 2.5 arc is supplied from a scanning generator 15 through conductors‘lt. The output of the am pli?er ‘is is alsoconnected to conductors 176, for distant scenes, and this e?iciency is maintained ' the purpose of increasing the intensity of the arc asv the photoelectric, cell ‘currents are in 30 30 in the scanningof near objects. The direct scan— ning of an image on an ordinary screen does creased. not produce the photocell current contrast values. by‘ increasing the intensity of the scanning ray in proportion to- the increase in photoelectric'cell current. That is, should the current be consid erably increased by the scanning ray falling on 3.5 as will the present system... . . In Fig. 2 of the drawings, a cross section of a television camera is illustrated, with its external regeneration circuits. In this ?gure, a casing 40 encloses a photoelectric cell 4|, a scanning arc screen 122 with respective lenses .43 and 44a. The photoelectric cell 4| is shown with a curved cath 40 ode 46 and anodes 4,4 and 45, arrangedon oppo site sides of the cathode, and conforming to the curvature of the cathode. The cathode in this cell is translucent, and will transmit light through This action will produce regeneration - a highly illuminated area of the cathode, this increase will be augmented hythe‘substantially simultaneous increase in the scanning ray in tensity. When the ray falls on a less illuminated area, 'the contrast will be much greater than 40 with the normal scanning ray. . The photoelectric cell currents and the are producing currents are segregated by a ?lter it as well as being able to hold the image of a I? in the output circuit of the system. The output scene projected thereon intercepting sufficient light for this purpose. The advantage. of the curved cathode is that the projection path of the ray of light from the rails 41 of the scanning terminals ‘it may be connected to transmission ap paratus such as shown at H5 in Fig. l. With the scanning generator a direct current source, it is unnecessary to employ a ?lter. system 42 is always a constant distance from the cathode and image thereon. In this manner the intensity of the normal light is maintained con stant at the image. Thedouble anode arrange ment of this system provides a more efficient The above described television scanning system is particularly adaptable to the transmission of 50 distant scenes, but it is also particularly e?icient photocell, since the cathodeqmay be made‘ trans cut image can be formed on the cathode of the for the transmission of details of near objects. By using a special focus lens, an extremely clear 55 lucent with active material on both sides thereof. celLwhich when scanned by an arc of constant 55 intensity with regeneration, will produce espe cially ?ne definition, in a reproduced image. In the scanning ray of the screen 41 is projected on cell currents caused by the varying length of pro 60 jection path for the scanning ray, such as exists This arrangement is also advantageous from the mechanical point of View. ,An object O is pro jected on the left hand side of the cathode’, while the right hand side. The photoelectric cell is mounted on. an ad justable stand 58, while the scanning apparatus is mounted on a. similar stand 5|, the adjustment of the elements of which is controlled by the thumb locking screws 52 and 53, respectively. The scanning apparatus is shown with a cooling jacket having a ?uid passage 54 and heat dis sipating material 55 such as steel wool and the like, surrounding the jacket. Heat conveying 70 fluids pass through the ?uid channel to maintain the screen electrode rails ill’ at a constant tem perature. A ?eld winding in series with the rail electrodes ill is also cooled by the jacket system. The external circuits of this system include a .75 photoelectric cell ampli?er having either two tubes this system there is no distortion in the photo when objects are scanned directly. . The non-linear characteristic of a photoelec tric cell is adaptable for other uses outside the art of television, and the invention is to be limited 65 only by the scope of the appended claims. What is claimed is: ‘ 1. In a television system, a light sensitive de vice having a cathode, means for focusing an optical image of a scene to be transmitted on said 70 cathode, and means for scanning with a ray of light said optical image while it is focused on said cathode. . ‘ 2. In a television system, ‘a photoelectric cell, an electrodynamic arc screen, an ampli?er for 75 2,108,827 the currents generated by said photoelectric cell, and means for feeding a portion of said photo‘ electric cell currents to said are screen. 3. In a television system, a camera, a photo 10 electric cell having its cathode placed at the 14. In a television transmission system, a light sensitive device having a cathode, means for focusing re?ected light from a scene to be trans focus of said camera, means for scanning an ob mitted on said cathode of said device'to produce a ject focused on said cathode with a light ray, and de?nite electron emission, and means for simul~ means for transmitting the varying electric. cur rents transmitted by said photoelectric cell. taneously scanning with a ray of light an optical 4. In an electrical transmission system, a tele vision’ camera, said camera including a light sensitive device and a scanning screen, and means for simultaneously focusing the light from said scanning screen, and the re?ected light external of said camera on said light sensitive device. 5. In an electrical transmission system, a photoelectric cell, and an electrodynamic arc V scanning screen for scanning said cell, said photo electric cell having a curved cathode to maintain 20 the projection path of light from said scanning screen constant for every position of said scan— ning light. - 6. In a television transmitting apparatus, a photoelectric cell having a translucent cathode, 25 anodes positioned on opposite sides thereof, means for scanning one side of said cathode with a visible light beam, and means for focusing on the other side of said cathode the scene to be trans~ , mitted over said television system. 30 7. In a television transmission apparatus, a photoelectric cell, scanning means for scanning one side of the cathode of said cell, means for focusing an object to be transmitted on the other side of said cathode, means for amplifying the 35 currents generated by said scanning means, and means for impressing a portion of said generated currents on the light producing means for said scanning system. ampli?er having its input connected to said cathode and anode, means for focusing an image on said cathode to generate a certain value of current in said cell, and means for producing 45 variations in said current value, said means in— cluding a constant light ray source. 9. An electrical generator system in accordance with claim 8, in which said last mentioned means comprises an electrodynamic are light scanning 50 system. 10. In a television image of said scene formed on said cathode by said focused reflected light while said optical 10 image is on said cathode to cause actuation of said’ cathode approximately in accordance with the square law. ' 15. In a television transmission system, a light sensitive device, means for focusing the image of a scene to be transmitted on said device, said image generating electrons at a point on the charac teristic curve of said device which is non-linear, and means for scanning with a ray of light the optical image of said scene while it is focused on said device to increase and decrease the output therefrom non-uniformly in unit areas during the projection thereon of equal light intensities. 16. A television transmission system in ac cordance with claim 15, in which said scanning means comprises a self-luminous, self-propelling electrical discharge. ' 17. The method of transforming the light densities of the unit areas of an image into elec trical currents proportional thereto with a light- '' sensitive device, comprising combining the cur rents produced by the light from‘the entire image projected on said device with the current pro duced by a unit area scanning beam scanning said image, the total current being determined by the light intensity-output current characteristic of said device. 18. In a television system, a photosensitive de 8. In an electrical generator system, a photo 40 electric cell having a cathode and an anode, an transmission system, a photoelectric cell, means for focusing the re?ect ed light from a scene to be transmitted on said cell to produce a definiteelectron emission in said cell, 55 and means for Varying said emission in different proportions in accordance with the variations in light intensities on said cell, said means includ ing a luminous electrical discharge source of con stant intensity. 60 nels positioned adjacent said electrodes for hous ing a circulatory heat conveyor. 11. In combination, an electronic device hav ing an electron emissive surface activated by light, means for projecting on said surface non uniformly distributed light of a substantially con stant value, and means for uniformly increasing 65 the light on consecutive unit areas of said surface. 12. A combination in accordance with claim 11, in which said last mentioned means comprises a television scanning system including an electro dynamic discharge screen. 13. In a television system, a photoelectric cell, 70 a scanning device for generating activating light for said cell, said device comprising an electro dynamic arc in a magnetic ?eld electrodes for determining the path of said arc, and means for 75 cooling said device, said means including chan vice, means for projecting an optical image on said device, means for simultaneously scanning 40 with a ray of light said optical image while it is projected on said device to produce electrical currents proportional to the light densities of the unit areas of said image, the variations in said currents being determined by the characteristic 45 of said device and means for biasing each unit area of said device with light producing said image. 19. A method of television which comprises ?rst energizing the photoelectric surface of a limited 50 area, then sensitizing the said photoelectric "sur face with an image of a View, simultaneously traversing said surface with a scanning beam of strong illumination and causing the photoelectric values to be impressed upon a transmitting 55 medium and repeating these steps in the trans mission of each individual image. 20. In a television system, a light sensitive de vice, means for projecting an optical image of an object on said device, and means for scanning with a ray of light said optical image while it is projected on said device. 21. The method of transmissing images of ob jects electrically with a light sensitive device, comprising projecting an optical image of said ob 65 ject upon said device and scanning with a ray of light said optical image while it is projected on said light sensitive device. 22. The method of transmitting pictures of objects electrically, comprising obtaining an opti 70 cal image of said object on the cathode of a photoelectric cell, scanning with a ray of light said optical image while it is obtained on said cell, and transmitting the variations in current pro duced in said cell by said scanning ray. 75 2,108,827 23. In a television system, a light sensitive de vice, means for obtaining an optical image of an object on said device, and means for scanning with a ray of light said optical image While it is 5 obtained on said light sensitive device. 24. The method of transmitting images of ob S jects electrically with a light sensitive device, comprising obtaining an optical image of said ob ject upon said device and scanning with a ray of light said optical image While it is obtained on said light sensitive device. ALEXANDER McLEAN NIC'OLSON.