US2298870A - Television receiver - Google Patents

Description

vOct. 13, 1942. A. H. COOPER 2,293,870

TELEVISION RECEIVER Filed Dec. 12, 1940 Fi 1. Egg. 7

INVENTOR ATTORNEY Patented Oct. 13, 1942 asses-n TELEVISION Arthur Henry C 9)",

Industries Limited, Middlescx, England, a company 01 Electric & Musical Britain Inglantanignnrto m Great Application December 12, 1940, Serial No. 369,773 In Great Britain August 24, 1939 1 cum. (on 178-15) This invention relates to television receivers and is concerned with improvements in conditions under which the received pictures are viewed. It is. customary to exclude general external illumination from the screen of the receiver in order to avoid loss of intensity of illumination on the screen itself, but it is found that the strong contrast between the illuminationbi the screen and the surrounding semidarkness may cause eye-strain to viewers, particularly in a receiver employing a cathode ray tube capable of giving a very brilliant picture.

,The main cause of eye-strain is not due to the viewer trying to discern a dim picture in a darkened room, but to observation of a bright picture in a room darkened so as to avoid refiections from the front It is important that light should not fall directly upon the viewing screen, and the object of the present invention is to lessen the sharp contrast referred to and so to reduce or eliminate eyestrain, while avoiding loss of illumination of the screen itself.

According to the present invention in a television receiver or other apparatus employing a cathode ray tube upon the luminescent screen of which a pattern or picture is to be viewed, in order to reduce or eliminate eye-strain due to contrast between picture or pattern brilliance.

and the surrounding relative darkness, means are provided for illuminating the region behind said receiver or surroimding the luminescent screen of the cathode ray tube while avoiding detrimental illumination of the luminescent screen.

The illumination, which may be said to form a background, may be effective upon the walls behind and around the television receiver and may conveniently be effected by one or more electric lamps arranged so as to be concealed within the receiver cabinet but projecting illumination throughthe back, sides or both of the receiver upon the walls of the room or upon a screen provided for the purpose. Louvres may be provided in the side walls or back of the receiver in order to permit control of the degree of background illumination. Alternatively, or in addition, the lamps may be controlled by a resistance to enable them to so to provide a soft yellowish tinge to the illumination.

Instead of arranging electric lamps to provide illumination upon the walls behind or around the receiver, lamps may be arranged in suitable masking devices to cause illumination upon the surface surrounding the luminescent screen of the cathode ray tube. Again, a member, such as a glass rod, surrounding the luminescent screen may be formed or treated to cause dispersion of light from a lamp or lamps arranged of the cathode ray tube.

be under-run and at the endsgof the rod. Alternatively. the luminescent screen of the tube may be'disposed within an aperture in a glass panel the surface or which is treated asby grinding or stippling to cause dispersion of light at the surface of the panel from a lamp or lamps arranged at one or more edges of the panel.

In order that the invention may be more clearly understood and readily carried into effect, certain forms of apparatus embodying the invention will now be described in greater detail by way of example and reference will be made to the forms shown in Figures 1. 2, 3 and 4 of the accompanying drawing.

A television receiver equipped with a lighting arrangement in accordance with one method of carryin out the invention is provided with a pair of 40 watt lamps arranged in series and connected across the source of supply to the receiver. The lamps are fixed in holders at the back of the receiver so as to illuminate the walls in the region behind and immediately around the receiver suiilciently brightly to light up the whole room to an intensity at which viewers may move about freely, the illumination affording a broad border to the receiver.

In an alternative form of equipment a fairly high power lamp, for example a watt lamp, mounted in a holder fixed to the rear of the cabinet is connected in series with the supply to the lamps used for normal room lighting. when the receiver is not in use the 100 watt lamp is arranged to be short-circuited and the lamps supplying the normal room illumination are fully operative. When a switch serving to short-circuit the 100 watt lamp is opened the region behind the receiver is illuminated by this lamp and, due to the insertion of the 100 watt lamp, the intensity of the illumination provided by the normal room light is reduced. Such an arrangement provides the required bright area in the neighbourhood of the receiver while there is suilicient light in the rest of the room for purposes of comfort without involving detrimental illumination of the screen surface.

In order to avoid interference with the supply wiring at the point at which the receiver is connected, a suitable form of combined adaptor plug and switch with the necessary leads may be provided which will serve the purpose of connecting the 100 watt lamp in series with the lamps used for the room lighting when the receiver is in operation.

When one or more electric lamps are employed to illuminate the panel surface surrounding the luminescent screen of the cathode ray tube, such lamps are mounted within masking devices to ensure that their illumination shall not fall directly upon the luminescent screen itself.

It is well known that if a source of light is placed at the edge of a smooth glass panel the light will mainly be transmitted through the glass and become visible at the edges. If the surface of the glass panel is scored or ground or marked by roughening the glass surface in the form of letters, etc., the latter will become luminous due to scattering of the light at the scored surfaces. This principle may usefully be applied in carrying out the present invention and for example a glass rod having its surface scored by one or more lines may be arranged around the edge of the mask of the receiver screen, the light from the rod thus only appearing in the region about the edge of the mask. In such a case the electric lamp is mounted at the end or ends of the glass rod as shown in Figure 1 of the accompanying drawing.

In this figure a fragmentary panel I of a television receiver is shown having a cathode ray tube rod 3 surrounds that aperture. A line 4 is scored upon the surface of the glass rod so as to cause dispersion of light along the length of the rod from a lamp 5 the front of which is masked by a screen, not shown.

In Figure 2, three separate rods, 6, I and 8 are shown and three lamps 9, l and II are mounted between the ends of these rods, each rod being scored with a line 4 as in Figure 1.

Figure 3 of the drawing shows a glass panel l2 having an aperture i3 to receive the luminescent screen of the cathode ray tube. The front surface of the glass panel is ground, scored or stippled in such a manner to cause dispersion of light from electric lamps of which two, l4 and I5, are shown by way of example. In order to prevent the light transmitted through the panel from interfering with the luminescence of the picture screen, the embracing edge ii of the glass panel is suitably blackened.

In order to make maximum use of the light from thelamps l4 and I5 the edge l6 may be made reflecting as by a layer of silver before the blackening is applied.

Glow discharge lamps may be employed instead of those of the incandescent type shown and further means operating in a manner analogous to that of an automatic gain control arrangement may be provided to cause the illumination provided by these lamps to vary in accordance with picture brilliance so that there shall not at any time be undue contrast between the picture brilliance and the brilliance of the surrounding illumination. i

In Figure 4 there is shown schematically the receiver I03 having an antenna I III for receiving television signals accompanied by sound. The

2 mounted within an aperture and a glass receiver may be of any of the conventional forms so as to provide both a sound output to feed the loud speaker I01 and the picture'reproducing tube I09. As is well known, these receivers include an automatic voltage control I05. A portion of the automatically controlled voltage is fed to a suitable power supply 3, which power supply supplies'a glow discharge lamp III. The AVC voltage fed to the supply H3 is so poled that increases in signal increase the voltage supplied'tothe lamp II I so that the brilliance of the surrounding illumination is in accordance with that of the picture brilliance.

I claim:

1.; A television receiver comprising a cathode ray tube having a luminescent target area to be viewed, a masking surface surrounding the screen and an illuminating means positioned adjacent the target area and surrounding the masking surface in the area adjacent the target for illuminating the masking surface and thereby reducing contrast and eye-strain.

2. A television receiver comprising a cathode ray tube having a luminescent target area to be viewed, a masking surface having an aperture therein, and said target area being in register with said aperture, an illuminating means positioned adjacent the target area and surrounding the masking surface in the area adjacent the target area thereby reducing contrast and eye-strain.

3. A television receiver comprising a cathode ray tube having a luminescent screen area to be,

viewed, a masking surface having an aperture therein, said screen being in register with said aperture, and means comprising a circular glass rod positioned adjacent said screen and surrounding said aperture for illuminating. said masking surface only, said glass rod being scored on the surface facing said masking surface.

5. A television receiver comprising a cathode ray 'tube having a. lum' escent screen to be viewed, a masking surface having an aperture therein, said screen being in register with said aperture, and means comprising a plurality of light sources and a plurality of transparent arctuate rods positioned adjacent said masking surface and surrounding said screen, said plurality of rods being scored on the surface "facing said masking surface.

6. In a television receiver the method of eliminating eye strain due to contrast between picture brilliance and surrounding contiguous area of darkness, which comprises the steps receiving signaling energy representative of a picture to be reproduced, deriving from the received signaling energy other signals representative of the average brilliancy of the picture to be reproduced, illuminating the surrounding contiguous area of darkness only, and controlling the intensity of the illumination in accordance with the derived signals.

, 7. Television receiver comprising means to receive signals representative of a picture to be reproduced and accompanying sound signals,.

ARTHUR HENRY COOPER.

for illuminating the masking surface and

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