DE2719086A1 - Colour TV receiver with CRT colour temp. matched to ambient light - has photoresistors in each video channel with red, green or blue filters exposed to ambient light - Google Patents

Abstract

The colour television receiver has the colour temperature of its picture adjuster to suit the colour of the ambient light, e.g. daylight or artificial light. This accomplished by adjusting the gain of one or more of the video output stages (1-3). The red, gree and blue amplifier paths contain photosensitive resistors (11-13) that alter the gain. These resistors receive ambient light via red, green and blue filters respectively. The resistors and colour filters are exposed at the rear of the receiver or obtain their light via light guides.

Description

Color television receiver

The invention relates to a color television receiver having one of the Environment-brightness-dependent amplification of the video power amplifier state of the art Es it is known that the brightness of television receivers depends on the brightness to regulate the environment automatically. This is where a photosensitive resistor is used (LDR) introduced in such a way in the circuit for regulating the brightness, that with decreasing ambient brightness, the brightness of the screen is also lower will.

This type of automatic brightness adjustment to the environment has also been applied to color televisions. (PHILIPS color television receiver D 26 K 184 Rubens 110 SL, service documents 6.72 Serv. 2812/2) The disadvantage here is that changes in the color temperature of the environment were not taken into account.

For example, the same picture from a color television set appears in daylight or fluorescent tube light with a red cast and with light from incandescent lamps with a blue cast. It Was there a need for a color-taste regulator or complaints about the "wrong" color of the Image would have to be accepted on an ongoing basis.

Task The task of color television receivers is to determine the color temperature of the image to match the color of the surroundings.

The task is cited in the characterizing part of claim 1 Means solved.

Advantages The color of a color television receiver is always subjective correct, regardless of whether the color television set is in daylight or in light operated by incandescent lamps.

Flavor controls are no longer necessary.

If all 3 color channels are regulated, it is advantageous to do so simultaneously an automatic brightness adjustment to the surroundings is achieved.

Are the light-dependent resistors and the associated filters on or near the back or side walls of the color television set arranged, then the light of the background and the side is mainly from them Surroundings of the television set, especially for the correction of the color temperature is necessary because the television picture, background and lateral surroundings are from the viewer be viewed together.

The technical structure of the color television set is particularly simple, when the light-dependent resistors are on the printed circuit boards of the color amplifier and the light is fed from the filters to there via glass fiber optics. Under certain circumstances, filters can even be saved if the glass fiber optics be colored accordingly.

Explanation of the invention In the figure, the invention is based on a Embodiment explained in more detail.

The embodiment is a color television recipient with so-called RGB output stages, in which for the 3 basic colors red (R), green (G) and blue (B) 3 separate color amplifiers 1, 2 and 3 are provided which demodulated the and processed color signals, each one for itself and amplifying the cathode 4, 5 and 6 feed a color picture tube 7.

In the exemplary embodiment, the individual RGB output stages are voltage dividers upstream of the resistors 8, 9 and lo and the light-dependent resistors 11, 12 and 13 exist.

According to the invention, the light-dependent resistors are filter disks 14, 15, 16 set forward in such a way that the light-dependent resistor 11 in the red channel by means of the red filter 14 only receives red components from the ambient lighting, the light-dependent resistor 12 in the green color channel by means of the green filter 15 only Receives green components from the surrounding lighting and the light-dependent resistance 13 in the blue channel through nin blue filter 16 only blue components from the ambient lighting receives.

If, for example, a color television set is now in an environment with a pronounced Red color (red light, red wallpaper, red carpet, etc.) is used, the light-dependent resistor 11 in the red channel more conductive than the light-dependent resistors 12 and 13 and the gain in the red channel will be greater than that in the blue and green channels.

This lowers the color temperature of the television picture. That The image gets a red cast and adapts to the surroundings.

If the same color television set is brought into a room, e.g.

is illuminated with fluorescent tubes with a bluish tint, it becomes light-dependent Resistor 13 of the blue channel supplied more light than the rest of the light-dependent Resistors 11 and 12. The color temperature of the picture rises and the color of the picture adapts itself again to the surroundings.

A particular advantage of the arrangement according to the exemplary embodiment is a general adjustment to the room brightness. Is e.g. the ambient brightness dark (light switched off), the amplifications of all 3 color channels are reduced and reduce the contrast and brightness of the image. The reverse occurs when e.g.

the device is operated in a room flooded with sunlight.

Now all 3 color channels regulate themselves to the greatest possible gain and maximum brightness. The picture thus automatically adapts to its setting the environment.

Instead of the gain control of the color output stages by variable Voltage divider can also be a gain control through light-sensitive, im Correct sense acting negative feedback resistances take place. When exposed to light, the negative feedback is reduced and the gain is increased.

L e r s e i t e

Claims (5)

Claims color television receiver with one of the ambient brightness depending on the amplification of the video output stages e t that the amplification of at least one video output stage (1 and / or 2 and / or 3) in the sense of adapting the color temperature of the screen image to the environmental colors is changeable. 2. Color television receiver according to claim 1 d a d u r c h g e k e n n -z e i c h n e t that in the red, green and blue amplifier trains light-dependent Resistors (11, 12, 13) are included that regulate the gain and those above assigned red, green and blue filters (14, 15, 16) can be supplied with ambient light is. 3. Color television receiver according to claim 1 and 2 d a d u r c h g e -k It is noted that color filters (14, 15, 16) and light-dependent resistors (11, 12, 13) arranged on or near the rear wall of the color television set are. 4. Color television receiver according to claim 2 and 3 d a d u r c h g e -k It is noted that the supply of ambient light to the light-dependent Resistors (11, 12, 13) are made via glass fiber optics. 5. Color television receiver according to claim 1 to 4 d a d u r c h g e -k It is noted that the color filters (14, 15, 16) are appropriately colored Fiber optics are formed.