JPH0235508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for removing ghosts contained in a detected signal in a home television receiver, and is capable of reducing changes in brightness and saturation after ghost removal. This is the purpose.

FIG. 1 shows a configuration in which a ghost removal device is added to a television receiver circuit, and FIG. 2 shows a conventional ghost removal device. In FIG. 1, 1 is an intermediate frequency amplification/video detection circuit, 2 is an added ghost removal device, 3 is a video signal processing/amplification circuit,
4 is a chroma signal processing amplifier circuit. A is a video detection output signal whose amplitude is kept constant through automatic gain control by an intermediate frequency amplifier circuit, and B is a CRT drive signal. In FIG. 2, 5 is a transversal filter, 6 is a weighting coefficient correction circuit, and 7 is a clamp circuit and analog clamp circuit that clamps the television signal from the transversal filter before and after the rise of the vertical synchronizing signal, excluding the horizontal period. It is a digital conversion circuit. 8 is a timing pulse generation circuit, which converts the subcarrier signal fsc of E, the horizontal synchronization signal and the vertical synchronization signal pulse into a sampling pulse of 3×fsc, a pulse indicating one horizontal period centered on the rising edge of the vertical synchronization signal, and 7. Generates clock pulses that transfer digital signals directly to memory. 10 is a memory, and 9 is an arithmetic circuit that obtains ghost information from digital values in the memory and calculates a tap correction signal. C shows a video detection signal subjected to automatic gain control at the intermediate frequency stage input to the ghost remover, and D shows an output signal from the ghost remover. In such a ghost removal device, the output D changes after ghost removal, and the resulting signal is input to the video processing circuit and the chroma processing circuit.

The video detection signal is automatically gain-controlled at the video intermediate frequency, and the luminance signal is not gain-controlled by the video processing circuit. On the other hand, the chroma signal is automatically gain controlled in the chroma processing circuit. The chroma processing circuit has automatic gain control based on the magnitude of the burst signal, but it is assumed that a reference video detection signal is input. For example, if a 0.3vP-P all-red chroma signal is superimposed on the luminance signal 70IRE, the CRT is adjusted to drive correctly in that state. Here, if the input amplitude of the video detection signal is reduced, images with different brightness and chroma will result. Due to the influence of the ghost, the detected signal on which the ghost is superimposed has a different amplitude from that in the case without the ghost, so the brightness and chroma are different from those in the case without the ghost at the time of transmission. Since the ghost removal device 2 performs ghost removal based on the falling portion of a reference signal for ghost removal, for example, a vertical synchronization signal, when a ghost with a phase of 0° is superimposed, the amplitude of the luminance signal becomes small. However, the chroma signal is automatically gain controlled in the chroma processing circuit so that the amplitude is the same as when there is no ghost. This is the same as when the input of the video detection signal is reduced when there is no ghost, and the ratio of brightness and saturation is not correct in the matrix circuit.

4-1 in FIG. 4 shows the detected signal before the ghost is removed, and 4-2 shows the output signal of the ghost removing device 2 after the ghost is removed. The amplitude of the luminance signal becomes small as I before ghost removal and J after ghost removal. Since the chroma signal is subject to automatic gain control, the chroma signal operates at the matrix stage so that it has the original adjusted amplitude, so even if the luminance signal becomes small, it operates at a constant value. This state is shown in K and L. Therefore, if the ghost is removed as a result, the ratio of the chroma signal to the luminance signal will be different. As a result, ghosts are removed, but the ratio of brightness and saturation at the time of transmission is not correctly reproduced on the CRT, resulting in changes in saturation and brightness.

FIG. 3 shows a ghost removal device in one embodiment of the present invention. 11, 13, 14, 15, 16,
17 is the same circuit as 5, 6, 7, 8, 9, and 10 in FIG. 2, and 12 is a gain control circuit. Fifth
The figure shows the configuration of the gain control circuit 12, where 18 is an analog multiplier and 19 is a digital-to-analog converter.

P in FIG. 6 shows the input waveform to the analog-to-digital conversion circuit before ghost removal. The digital values for each sample point in the 1/2 horizontal period before and after the rising edge of the vertical synchronization signal are transferred to the memory by DMA transfer, and the maximum digital value is set as α. Q is the waveform after ghost removal, and its maximum value is β. R indicates a memory column transferred by DMA, and S indicates a memory that stores its maximum value before and after ghost removal.

Using the digital values before and after ghost removal, perform α/β calculation processing, and use the digital value as 19
By operating the digital-to-analog converter and controlling the analog multiplier, changes in brightness and saturation can be prevented. By using such a ghost removal device that is equipped with a gain control circuit that controls the output after ghost removal, it is possible to restore the brightness and saturation to the original level when receiving a signal without ghosts, and even after ghost removal, the reception You can get high quality TV images.

As described above, the present invention is equipped with a transversal filter and its tap weighting coefficient correction circuit, and obtains tap correction information from the output of the transversal filter to correct the tap weighting coefficient of the transversal filter. In a device for removing ghosts contained in a signal, tap correction information is obtained from a digital value that is converted from analog to digital of the output signal of a transversal filter and directly transferred to a memory within a sampling time, and is obtained from the digital value. The present invention is characterized in that it is equipped with a circuit that controls the gain of the television signal after ghost removal and before luminance/chroma signal separation, and it is possible to reduce changes in brightness and saturation after ghost removal. It is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the connection of a ghost removal device to a television circuit, FIG. 2 is a block diagram of a conventional ghost removal device, and FIG. 3 is a block diagram of a ghost removal device according to an embodiment of the present invention. 4 is a diagram showing changes in the matrix stage of luminance signals and chroma signals before and after ghost removal by a conventional ghost removal device, FIG. 5 is a diagram showing an embodiment of the gain control circuit in the present invention, and FIG. The figure is a diagram for explaining a gain control circuit. DESCRIPTION OF SYMBOLS 11... Transversal filter, 12... Gain control circuit, 13... Weighting coefficient correction circuit, 14... Clamp circuit/AD conversion circuit, 15... Timing pulse generation circuit, 16... Arithmetic circuit, 17... Memory.

Claims (1)

[Claims] 1. Equipped with a transversal filter and its tap weighting coefficient correction circuit, which obtains tap correction information from the output signal of the transversal filter, and corrects the tap weighting coefficient of the transversal filter so as to be included in the television signal. In an apparatus for removing ghost components, the above-mentioned tap correction information is obtained from a digital value that is converted from analog to digital of the output signal of the transversal filter and directly transferred to the memory within the sampling time, and the ghost component is removed using the above-mentioned digital value. A ghost removal device comprising a circuit for controlling the gain of a television signal after removal and before luminance/chroma signal separation.