US2186542A - Television system - Google Patents

Description

Jan. 9, 1940.

P. F. M. GLoEss 2,186,542

TELEVISION SYSTEM Filed Aug. l2, 1957 YE Fzg, I. 3-

yPatented Jan. 9,l

Nirso STATES PATENT OFFICE TELEVISION SYSTEM Paul Franois Marie Gloess, Paris, France, vassigner :to International `Standard Electric Corporation, New York,y N. Y.`

Application August 12,1937, serial No. 158,662 In France September 17,;19364 2 claims. Y (c1. 17e-#5.2)

The present invention relates to systems or apparatus for television and has as one object the elimination oi certain drawbacks Which at present exist particularly in scanning apparatus employing electronic means. l

It is known that in such apparatus frequencie lower than the frame frequency, and the socalled'D. C. component representing the mean brightness of the image, are eliminated.

Thev present invention has, in particular, the

object of controlling the currents emitted by an electronic or similar scanning system, While taking into consideration one or more mean characteristics of the scene'or image to be tele-z vised. This result may beattained by combining either with or inside the electronic scanning tube, a device sensitive to the mean characteristic of the scene to be televised which it is desired to keep under consideration, the currentproduced by this device being combined with the currents proceeding from the electronic scanning device.

The invention is explained in more detail in the following description based onl the accomv panying drawing, in which:

Fig. l shows schematically an element of an electronic scanning system;

Fig. 2 shows schematically the electric circuit corresponding to 'an embodiment of the invenments such as l. A'The circuit of the mosaic *ele-V ment considered is completed by a polarising battery B and a resistance R at the terminals of which are collected the image signals. There falls on the cathode I a ray of light 3 proceeding from a point of the scene to be televised.

The reaction of the ray of light 3 on the cathode 2 produces, in the well-known manner, an emission of photo-electrons. This emission of photoelectrons positively loads `the lcondenser C and thus produces a slowly Varying current inthe `resistance R. The same applies to all the elements of the mosaic and the corresponding currents are added yin the resistance R;

y denserC.l

Attire moment when the cathode scanning ray E passes over the element of the mosaic under consideration, it suddenly discharges the r condenser` C vand. the` correspondingdischarge current also passes throughv the resistanceR. The combination of these two currents practically eliminates the componentsof slow variations `of the discharge current of the elements of the mosaic, which current corresponds tothe mean illumination of the scene tobe televised. s The `embodimentshown schematically in Fig.

2 permits the complete imagesignal -to be reconstituted, that is to say, up to and including the zero frequency. lForthis purpose a photoelectric cell 5' is. employed,`having as far as possible, a characteristic of sensitivity x similar or,

corresponding to that of the mosaic employed.

This ce1l'5 is associated with an optical system (not shown in Fig 2) adapted to receive in a given proportion the same total luminous ilux of the scene to be televised as that receivedby l the mosaic. This cell iil is then associated with'V the elements of the'mosacin the manner shown' in Fig. 2 that is to say, the cell 5v associated with ay polarising battery 6 is connected, on the one hand, over the battery 6,' to the anode.

2 and, on the other hand, to the common electrcdeforming one of. theY armatures' of the con-- 1 The operation of the is thus as follows: The auxiliary cell 5 produces in the resistance R currents of slow varia- Iunit shown 'in Fig. 2V

tion which are identical and of opposite direction to those produced by the simultaneous charging of all the elements of the mosaic. In

this way the resistance R Willv no longer be travk ersed vexcept by the discharge current of the elementary condenser `of the mosaic and the potentials .collected on the terminals of R will thus represent solely the image signals. It yWill also be noted that the devicedescribed permits the direct component of this current also to be transmitted since condenser C does not affect operation of cell 5.

Fig. 3-s`hows an embodiment of the invention in which the scene AB to be televised is projected by means of an objective 6 on the mosaic 1 of a cathode ray tube 8 provided with a deflector system yfor the scanning ray shown in the form of a coil 9 which deilects the cathode rayl by means of the magnetic field which it produces. It is clear thatother types of deector systems may also be employed.v l

A second objective I0 projects an image of the same scene on a Window Il Whosedimensions,

may be adjusted in accordance with the portion of the scene which it is desired to televise.

Behind this adjustable window Il is an optical condenser I2 concentrating the luminous bundle which has passed through the Window II on a photo-electric cell I3 similar to the cell 5 shown in Fig. 2. The cell I3 is associated with the Various elements of the mosaicy in accordance with the manner shown in the caseY of the cell 5 on Fig. 2, The connection of the cell to the elements of the mosaic l and the resistance R has also not been shown in Fig. 3 in order not to complicate this drawing.

The dimensions of the opening of the window II and the position, of this opening may be adjusted either automatically or by manual control. Fig. 3 shows,-by way of. example, a manual control of the opening of the window by means of an operating knob I4, this control being combined with the means for controlling of the amplitude of the sweep of the cathode ray. This window or diaphragm Ii is composed of .two V- shapedelements, I5 and it. These two elements are connected 4to each other by means of pins I9, sliding in slots, such as Il and E8. These pins are movable along the diagonal of the'gure formed by the two branches 45 and I6, which, in the example under consideration, is in the form of a square, and may also slide in a slide, such as Z5, which permits the device to present to the objective I@ an opening which` remains square, its dimensions thus being adapted to be varied as desired. The adjustment of the screen may be made in the following 'mannerz-a spring 2G presses against the element I5 thereby forcing the elem-ent i5 to assume ,a particular position byA virtue of `the construction of the device previously described. The connection between the mechanical device and the manual control M is effected by means of a cable El connected to the element I6, passing over a pulley, such as 22, and

winding on a drum 23. vThis drum may ber mounted, for example,- directly on the axle of the adjusting knob ld and stops (not shown) may be provided in order to maintain the diaphragm at a particular opening.

On this same axle is mounted a potentiometer 2li which permits the deflection of thev cathode scanning ray to be adjusted, for example, bythe, v

currents passing through the deiiecting coils only one of which, 9, is shown in Fig. 3. This adjustment is performed so that the portion of the mosaic 'I scanned by the cathode ray corresponds to the size of the opening of the window II and, consequently, to the chosen portion of the scene to be televised.

The arrangement shown in Fig. 3 permits the applic-ation of the invention even in the case in which the amplitude or deflection of the scanning ray is caused to vary, particularly in order to obtain scenic effects on the screen of the receiver.

The invention which has been described in its application to television may also be employed for similarapplioations such as, for example, in facsimile transmission systems.

The invention is obviously not limited to the embodiments described which may undergo numerous modifications without departing from the limitsy of the invention, thus instead of a singlev additional photo-electric cell, several may be provided.

Although the embodiment described only serves to take into consideration the mean illumination of the scene or image to be televised, it is clear that the invention is not limited to this particular case and that, for exa ple, for the transmission of television in colourseveral compensating photo-electric cells, such as ti, might be employed, for example one cell for each fundamental colour ef the image.

What is claimed is:

l. A television transmitting system comprising an electronic scanning photo-electric `device for scanning an image of a eld of View, an auxiliary photo-electric device responsive to the average light value of said fieldv of view, an adjustable Window in front of said auxiliary device icr dening the area kof the field of View which is projected upon said auxiliary device, and means for simultaneously adjusting the aperture area of said window and the amplitude of sweep of the cathode ray of said photo-electric device rst mentioned.

2. A color ltelevision system wherein a separate transmitting arrangement according to claim l is utilized for each fundamental color to be transmitted.

PAUL FRANCOIS D/IARIE GLOESS.

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