KR100186713B1 - Device for compensating white level of luminance signal - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting a back level of a luminance signal. In the related art, a background of an image displayed on a cathode ray tube is displayed while displaying an image of a broadcast signal transmitted from a broadcasting station or an image of an external input signal input from the outside. If it was dark, the image of the object displayed with the background could not be clearly displayed, so the background and the object could not be distinguished. According to the present invention, a reference maximum value and a maximum value of a luminance signal input to a luminance signal input at a middle level value or more (back level) of a luminance signal of a video signal received from a broadcasting station or a luminance signal of an externally input video signal are determined. By correcting the back level of the luminance signal by adding the correction value, the background and the object of the image displayed on the cathode ray tube can be distinguished more clearly.

Description

Back level correction device for luminance signal

1 is a circuit diagram according to an embodiment of the present invention.

2 is a timing diagram according to an embodiment of the present invention.

3 is a circuit diagram according to the conventional invention.

* Explanation of symbols for main parts of the drawings

11: Clamp and analog / digital converter 13: Sync signal separator

15: PLL and clock oscillator 17: maximum value detector

19: 1H memory unit 21: correction value calculator

23: back level detector 25: line delay unit

27: comparison unit 29: back level correction unit

31: Clipper SW1: Switching IC

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain adjusting device for adjusting gains of luminance and chroma signals in a television receiver for processing a broadcast signal or an external signal. The present invention relates to an apparatus for correcting a back level of a luminance signal, which is capable of more effectively distinguishing an object and a background displayed on a cathode ray tube by upwardly correcting the back level of the luminance signal.

In general, a television receiver for receiving and processing a broadcast signal transmitted from a broadcasting station includes a luminance signal (Yin) and a chroma signal (Cin) from an input image signal processed by a tuner, an intermediate frequency processor, or the like, as shown in FIG. A composite image signal filter 101 for filtering the signal, an amplifier OP1 for adjusting the brightness gain by the luminance gain control variable resistor (YVR), and an amplifier for controlling chromatic gain by the chromatic gain control variable resistor (CVR). An gain control unit 102 configured to amplify the levels of the luminance signal Yin and the chroma signal Cin output from the composite video signal filter 101 to a predetermined level, and the gain control unit 102. ) Is applied to gain-adjusted luminance signal (Yin) and chromaticity signal (Cin) to generate RGB signal by RGB (Red.Green.Blue) matrix circuit, and it is used for contrast adjustment circuit and brightness. ess) consisting of a Chroma IC (103) adapted to pass through an adjustment circuit and applied to the cathode ray tube driving circuit, and a cathode ray tube (104) for displaying an image by RGB signals output from the Chroma IC (103). It is.

In the television receiver as described above, a composite video signal filter 101 to which an input video signal through a tuner or an input video signal input from the outside is applied, separates the luminance signal Yin and the chroma signal Cin from the input video signal. When applied to the gain control unit 102, the gain control unit 102 and the luminance signal (Yin) and chromaticity that can process the level of the applied luminance signal (Yin) and chroma signal (Cin) in the chroma IC 103 Amplified to the level of the signal (Cin) is applied to the chroma IC (103).

Looking at this in more detail by the luminance signal (Yin) applied to the amplifier (OP1) of the gain control unit 102 by varying the resistance value of the variable resistor (YVR) for the brightness gain control connected to adjust the gain of the amplifier (OP1) The gain of the amplifier OP1 to which the luminance signal Yin of the composite image signal filter 101 is applied, that is, the level of the luminance signal Yin is adjusted to correspond to the resistance value of the variable resistor YVR for luminance gain adjustment. It is applied to the IC 103.

In addition, the chroma signal Cin applied to the amplifier OP2 of the gain adjusting unit 102 varies the resistance value of the chromatic gain adjusting variable resistor CVR connected to adjust the gain of the amplifier OP2, thereby making it complex. The gain of the amplifier OP2 to which the chroma signal Cin of the image signal filter 101 is applied, that is, the level of the chroma signal Cin, is adjusted to correspond to the resistance value of the variable resistor CVR for chromatic gain adjustment. 103).

The chroma IC 103 to which the gain-adjusted luminance signal Yin and the chroma signal Cin are applied, the RGB signal circuit and the contrast / brightness adjustment circuit, and the cathode ray tube driver are applied to the luminance signal Yin and the chroma signal Cin. Processing to output the RGB signal to the cathode ray tube 104.

That is, the RGB matrix circuit of the chroma IC 103 to which the luminance signal Yin and the chroma signal Cin processed by the gain adjusting unit 102 are applied, converts the luminance signal Yin and the chroma signal Cin into an RGB signal. It demodulates again, and the contrast and brightness are adjusted by the contrast adjusting circuit and the brightness adjusting circuit and applied to the cathode ray tube driving circuit.

Then, the cathode ray tube driving circuit of the chroma IC 103 amplifies the level of the RGB signal to a level necessary for driving the cathode ray tube 104 and supplies the cathode ray tube 104 to the cathode ray tube 104 so that the cathode ray tube 104 is output from the broadcasting station. An image of a broadcast signal or an image of an external input signal input from the outside is displayed.

In the television receiver as described above, the gain of the video signal in which the RF modulation ratio is received varies depending on the channel for each channel (SBS, KBS, MBC, etc.) in which the broadcast signal of each broadcasting station is received. The gain of the video signal is also different depending on the type of screen (called a landscape screen, a portrait screen, etc.) displayed on the cathode ray tube, and thus has different contrast ratios. This allows the viewer to adjust the contrast or brightness to distinguish the image from the background, but when the screen is overall bright or the screen is medium brightness, the black part or the white part is too bright. do.

The present invention has been made to solve the problem that can be issued in the conventional television receiver as described above, and by correcting a portion of the brightness signal of the video signal that is detected above the intermediate level by a certain level of the image displayed on the cathode ray tube It is an object of the present invention to provide a device for correcting a back level of a luminance signal that facilitates identification of a background and an object.

In order to achieve the above object, the present invention provides a clamp and an analog / clamp configured to clamp a level of a luminance signal and convert the luminance signal into a digital signal so that the luminance signal of a video signal input from a broadcasting station or an external source maintains a constant level. A digital conversion means, a synchronous signal separation means for separating the synchronous signal from the luminance signal and inverting and amplifying it to output a horizontal synchronous signal (H.sync) and a clamp pulse, and a horizontal synchronous signal separated from the synchronous signal separation means A luminance signal level for adjusting the level of the luminance signal, including a PLL and a clock oscillating means configured to oscillate the clock pulse CLK by a signal H.sync and a reference signal fed back from a not-shown 1 / N divider In the regulating device,

A maximum value detecting means configured to detect a maximum value of the luminance signal output from the clamp and the analog / digital converting means, and comparing the maximum value detected by the maximum value detecting means with a reference maximum value of the luminance signal therebetween; A correction value calculating means for calculating a correction value, a 1H memory means configured to store a luminance signal corresponding to 1H among the luminance signals output from the clamp and the analog / digital converting means, and the memory by the 1H memory means. A back level detecting means for detecting only a luminance signal of a back level value among the luminance signals, and a back level for adding a correction value output from the correction value calculating means to a luminance signal detected by the back level detecting means. A correction means and a volume equal to or greater than a reference maximum value among luminance signals outputted from the back level correction means; A clipping means configured to clip a signal, a line delay means configured to delay a luminance signal output from the 1H memory means for a predetermined time, and a value of the luminance signal output from the 1H memory means and a reference intermediate level value A comparison means configured to output a low / high level switching signal, and a switching means configured to select an output of the clipping means and an output of the line delay means by an on / off operation by the switching signal output from the comparing means. It is characterized by being.

Hereinafter, the configuration according to an embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

According to the present invention, as shown in FIG. 1, a clamp and an analog / digital converter 11 for clamping the input luminance signal Y to maintain a constant level and converting the input luminance signal Y into a digital signal, A sync signal separator 13 for separating the sync signal from the luminance signal Y, inverting and amplifying the sync signal, and outputting a horizontal sync signal H.sync and a clamp pulse, and the sync signal separator 13 To a luminance signal level control device of a television receiver including a PLL and a clock oscillator 15 for oscillating the clock pulse CLK by the horizontal horizontal synchronization signal H, sync and the reference signal fed back from the 1 / N divider. In

The maximum value detector 17 detects the maximum value of the luminance signal Y output from the clamp and the analog / digital converter 11, and the maximum value detected by the maximum value detector 17 and the reference of the luminance signal. Compensation value calculating unit that calculates the difference value, that is, the correction value, against the maximum value (that is, 100 IRE, that is, the maximum value of the luminance signal level divided into 100 IRE including the white level and the black level). 21, 1H memory unit 19 for storing a 1H luminance signal among the luminance signals output from the clamp and analog / digital converter 11, and among luminance signals stored in the 1H memory unit 19. The back level detector 23 detects (passes) only a luminance signal equal to or greater than a reference intermediate level value 50 IRE, and the correction value calculator 21 outputs the luminance signal detected by the back level detector 23. The back level correction unit 29 that adds the correction value, and the image The clipper 31 for clipping the luminance signal above the reference maximum value among the luminance signals whose back level is corrected by the back level correction unit 29 and the luminance signal output from the 1H memory unit 19 are delayed for a predetermined time and output. A line delay unit 25 and a comparison unit 27 for outputting a low / high level switching signal in contrast to the intermediate level value and the reference intermediate level value of the luminance signal output from the 1H memory unit 19; It consists of a switching IC (SW1) which switches on / off by the switching signal output from the comparator 27 and selects the output of the clipper 31 and the luminance signal output of the line delay unit 25.

Here, the comparing unit 27 outputs a high level switching signal when the value of the luminance signal input from the broadcasting station or the outside is smaller than the reference intermediate level value of the luminance signal, and outputs a high level switching signal. When the value of the signal is larger than the reference intermediate level value, the low level switching signal is output. The luminance signal applied from the 1H memory unit 19 includes the back level detector 23 and the line delay unit 25. At the same time delayed in and is supplied to the adder 29 and the switching IC (SW1).

2 is a timing diagram of an image signal for explaining an embodiment of the present invention.

Referring to the operation and effect according to an embodiment of the present invention configured as described above are as follows.

According to the present invention, when the luminance signal Y of a video signal input from a broadcasting station or an external device is input to the clamp and analog / digital converter 11 and the synchronization signal separator 13, the synchronization signal separator 13 is a luminance signal. The sync signal included in (Y) is separated and the horizontal sync signal H.sync is supplied to the PLL and the clock oscillator 15 to cause the PLL and the clock oscillator 15 to clock clock pulses as shown in FIG. While CLK can be oscillated, a clamp pulse is supplied to the clamp and the analog / digital converter 11 so that the level of the luminance signal can be adjusted.

Subsequently, the clamp and the analog / digital converter 11 to which the clamp pulse is input from the synchronization signal separator 13 may change the level of the luminance signal Y due to a signal state such as ghost or cable broadcasting. In this case, as shown in (a) of FIG. 2, the luminance signal adjusted to a constant level is converted into a digital signal while clamping the luminance signal Y by the clamp voltage Vc so that the luminance signal can be maintained at a constant level. The luminance signal as shown in FIG. 2A is supplied to the maximum value detector 17 and the 1H memory unit 19, respectively.

Then, the maximum value detector 17 detects the maximum value Vpeak of the luminance signal Y input as shown in FIG. 2A and supplies it to the correction value calculator 21.

The correction value calculating unit 21 to which the maximum value Vpeak of the luminance signal Y is supplied is a reference maximum value stored in a memory unit (not shown), where the reference maximum value is shown in FIG. As described above, the maximum value of the normal luminance signal is 100 IRE, which includes both the white band and the black band of the luminance signal.

That is, as shown in (a) of FIG. 2, the difference value Va obtained by subtracting the maximum value Vpeak of the luminance signal Y from the reference maximum value of 100 IRE is obtained and applied to the back level correction unit 29. do.

Then, the 1H memory unit 19 into which the luminance signal converted into the digital signal by the clamp and the analog / digital converting unit 11 is input as shown in FIG. The level detector 23, the line delay unit 25, and the comparison unit 27 are supplied to the level detector 23, the line delay unit 25, and the comparison unit 27, respectively.

Accordingly, the back level detector 23 detects a luminance signal equal to or greater than the luminance signal value applied from the 1H memory unit 19, and outputs a luminance signal input over the intermediate level value among the luminance signals of 1H for a predetermined time (Δt). It is applied to the back level correction unit 29 while delaying. That is, the back level detector 23 delays only the luminance signal at the level to which the level is to be corrected among the 1H luminance signals for a predetermined time DELTA t and applies it to the back level correction unit 29.

Then, as shown in (b) of FIG. 2, the back level correction section 29 detects the correction value detected by the correction value calculating section 21 for luminance signals of intermediate level or higher applied by the back level detection section 23. FIG. When the level is corrected by (Va) and supplied to the clipper 31, the clipper 31 determines whether there is a part that is inputted above the maximum value in the air in preparation for the maximum value of the corrected luminance signal compared to the reference maximum value (100 IRE). Done. A portion of the corrected luminance signal detected to be equal to or greater than the reference maximum value is subjected to a clipping operation and applied to the input terminal L of the switching IC SW1. The line delay unit 25, like the back level detector 23, delays the luminance signal input from the 1H memory unit 19 for a predetermined time [Delta] t after the time delay of one side terminal H of the switching IC SW1. ) Is applied.

Next, the comparison unit 27 compares the magnitude of the luminance signal input from the 1H memory unit 19 with the reference intermediate level value 50 IRE to the switching IC SW1 at a low / high level switching signal. Is applied after a time delay for a predetermined time Δt.

That is, the comparison unit 27 compares the value of the luminance signal input from the broadcasting station or the outside with the reference intermediate level value and outputs a high level switching signal when the luminance signal is smaller than the reference intermediate level value. SW1 is connected to the output terminal of the line delay unit 25, and if the value of the input luminance signal is larger than the reference intermediate level value, the low level switching signal is outputted so that the switching IC SW1 outputs the output terminal of the clipper 25. To be connected to.

As a result, when the value of the luminance signal is detected to be lower than the reference intermediate level value, the switching IC SW1 is connected to the line delay unit 25 by a high level switching signal output from the comparing unit 27, and the predetermined time ( [Delta] t) A luminance signal whose time is delayed, i.e., a luminance signal which is input lower than the reference intermediate level value, is applied to the chroma IC not shown through the switching IC SW1 without the level being corrected. In addition, when the value of the luminance signal is detected to be higher than the reference intermediate level value, the switching IC SW1 is connected to the clipper 31 by a low level switching signal output from the comparator 27, and the predetermined time (Δt) time. The delayed luminance signal, that is, the luminance signal input higher than the reference intermediate level value is corrected by the correction value V and applied to the chroma IC not shown via the switching IC SW1. Therefore, by processing the image signal corrected by a certain level for the portion corresponding to the back level of the luminance signal in the chroma IC, it is displayed more clearly on the screen displayed on the cathode ray tube. That is, the background and the object of the screen displayed on the cathode ray tube can be more surely selected.

As described above, according to the present invention, the reference maximum value and the luminance signal input to the luminance signal input at or above the intermediate level value (back level) among the luminance signal of the video signal received from the broadcasting station or the luminance signal of the externally input video signal. By correcting the back level of the luminance signal by adding the correction (difference) value of the maximum value of, the background and the object of the image displayed on the cathode ray tube can be distinguished more clearly.

Claims (3)

A luminance signal level adjusting device comprising a clamp and an analog / digital converter for clamping an input luminance signal (Y) to maintain a constant level and converting the input luminance signal (Y) into a digital signal, the luminance signal output from the clamp and the analog / digital converter. A maximum value detector for detecting a maximum value of (Y); A correction value calculator for calculating a correction value against a reference maximum value of the maximum luminance signal detected by the maximum value detector; A 1H memory unit which stores a 1H luminance signal among the luminance signals outputted from the clamp and the analog / digital converter; A back level detector which detects only a luminance signal of a back level among the luminance signals stored in the 1H memory unit; A back level correction unit which adds a correction value output from the correction value calculating unit to the luminance signal detected by the back level detector; A clipper for clipping a luminance signal equal to or greater than a reference maximum value among luminance signals outputted from the back level correction unit; A line delay unit for delaying the luminance signal output from the 1H memory unit by a predetermined time and outputting the delayed signal; A comparator for outputting a low / high level switching signal by comparing a luminance signal value output from the 1H memory unit with a reference intermediate level value; And a switching IC configured to select an output of the clipper and an output of the line delay unit by an on / off operation by the switching signal output from the comparator. The low level switching device of claim 1, wherein the comparing unit outputs a high level switching signal when a value of the luminance signal input is smaller than a reference intermediate level value, and switches a low level when the value of the input circuit signal is larger than a reference intermediate level value. And a back level correction device for a luminance signal, characterized in that it is configured to output a signal. The apparatus of claim 1, wherein the luminance signal applied from the 1H memory unit is delayed by the same time in the back level detector and the line delay unit.