JPH04196699A - Chrominance edge correcting circuit - Google Patents

Abstract

PURPOSE:To eliminate the adverse effect on hue due to the contour emphasis processing by performing the contour emphasis processing in a system which is completely independent of the hue information system and adding the hue information after the emphasis processing is performed. CONSTITUTION:The phase information signals obtained from a phase detecting circuit 20 represent the hue which is supplied to a multiplying section 60 through a delaying section 40 for the timing adjustment. The phase information signal has a constant amplitude and it is sinusoidal signal with phase modulation. On the other hand, an amplitude detecting circuit 30 has no relationship with hue, detects the amplitude (saturation level of color) and supplies the amplitude information to the edge correcting circuit 50. The edge correcting circuit 50 takes out the higher region components (edge correcting signals) of the amplitude variation, adjusts the gain, adds to the original amplitude information, and the contour corrected chrominance amplitude signals are inputted to the multiplying section 60. Thus, carrier chrominance signals are obtained at output terminals 70. The signals keep the hue variation of the carrier chrominance signal as it is and the variation of the saturation level is steep.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application)] The present invention relates to a color edge correction circuit for correcting the outline of a color signal in, for example, a television receiver or the like.

(Prior Art) In the NTSC television signal, the luminance signal is 4.
2M)12 bands, whereas the color difference signals are narrowly defined as 1.5MHz for the I signal and 0.5M)Iz for the SQ signal. When this standard was decided, it was said that it was decided based on visual characteristics, but it has become clear that this is not necessarily sufficient. There are several problems in image quality caused by narrowband color difference signals. For example, with vertical striped patterns, there is a decrease in color reproducibility, an unnatural discontinuity of chromaticity that can be called color breakup at color edges, and a phenomenon where colors run out, which can be called color blurring at color edges. occurrence etc.

The deterioration in color reproducibility cannot be improved unless the standards of the I and Q signals are changed to widen the band, but it can be said that it does not feel unnatural to the receiving user who is not informed of the original image. However, in recent years, attention has been focused on improving color edge portions, and several conventional color edge correction circuits have been proposed.

There are broadly two types of color edge correction methods.

One method is to perform edge correction while the color signal is modulated by the color subcarrier, and the other method is to perform edge correction on the color signal while it is being modulated by the color subcarrier. This method performs edge correction at each signal stage after demodulation. However, both the former and the latter have the problem that if unnecessary signals such as ringing occur during edge correction, edge emphasis at the point of change in color saturation appears as a change in hue.

The situation will be explained using the latter case where edge correction is performed after demodulation as an example.

FIG. 6 shows how two colors are represented as vectors and demodulated onto one axis, the Q axis. For simplicity, vector A is dark red (103,5°) to light magenta (60
, 7°), the color changes to vector B. Here, when changing from A to B, the length of the vector projected onto the Q axis does not change, and Qa and Qb match as shown in the figure. On the other hand, the length of the vector projected onto the I axis changes from Ia to Ib.

Suppose here that when the contour of the I signal, which is a change on the l-axis, is emphasized, ringing occurs and partially reaches the value of Ic. Then, as shown in the figure, the vector C is expressed by Qb and Ic, which is 347
The hue will be around blue. In other words, while ringing occurs when the brightness signal outline is emphasized, it becomes a white or black border.

Ringing during contour enhancement on the I and Q axes of color signals or on the (B-Y) and (R-Y) axes is caused by different colors (in the case of Figure 6, blue appears at the boundary between the border and magenta). It appears as a border and is very unsightly.

Even when the outline of the color signal is enhanced while being modulated by the color subtransport, the hue changes in the same way.

This is because the modulated color signal has both saturation and hue information, and signal processing may change the phase of its carrier wave, which changes the hue.

(Problems to be Solved by the Invention) As described above, the conventional color edge correction method has a problem in that when malfunctions such as ringing and changes in saturation occur, the hue changes and image quality deteriorates.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a color edge correction circuit that does not affect changes in hue even when ringing occurs or saturation changes.

[Structure of the Invention] (Means for Solving the Problem) The present invention includes: a phase information signal detection means for detecting the hue of an input color video signal and obtaining a phase information signal; and detecting the degree of saturation of the input color video signal. an edge correction means for extracting edge information from the output of the amplitude detection means and adding it to the output of the amplitude detection means to correct the contour;
The apparatus further includes a multiplication processing means for obtaining a carrier color signal by multiplying the amplitude signal obtained from the edge correction means by the phase information signal obtained from the phase information detection means.

(Function) With the above means, the contour enhancement process is performed in a system completely independent from the hue information system, and the hue information is added after the emphasis process, so the contour enhancement process affects the hue. will not be given.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. A carrier color signal Cln is introduced into the input terminal 10, and this color signal is input to the phase detection circuit 20 and the amplitude detection circuit 30. The phase information signal obtained from the phase detection circuit 20 represents the hue and is supplied to the multiplier 60 via the delay device 40 for time adjustment. The phase information signal obtained from the phase detection circuit 20 is
It is a sine wave signal with constant amplitude and phase modulation. On the other hand, the amplitude detection circuit 30 detects amplitude (color saturation) regardless of hue, and supplies this amplitude information to the edge correction circuit 50. The edge correction circuit 50 extracts the high frequency component (edge correction signal) of the amplitude change, adjusts the gain thereof, and adds it to the original amplitude information. As a result, the edge correction circuit 50 obtains a contour-corrected color amplitude signal. This amplitude signal is input to multiplier 60.

To illustrate the output vector of the amplitude detection circuit 30, the change from the dark red vector A shown in FIG. 6 to the light red vector B is as shown in FIG. 3(a). In the figure, it is shown as a vector with an angle of 0'', but it is a scalar quantity that indicates the length of the vector, that is, the degree of color saturation.A abs to B
The only difference is the abs. Furthermore, the lunar information signal obtained from the phase detection circuit 20 has a constant amplitude and only changes from vector A to vector B, as shown in FIG. 3(b).

Therefore, at the output terminal 70, a carrier color signal is obtained in which the change in hue of the carrier color signal is maintained as it is, and the saturation level is sharply changed. Even if ringing occurs, unlike the conventional method, a border of a different color does not occur at the contour, but only a border of the shade of the color that each point has. In other words, in the case of the example shown in Figure 6,
Even if there is a change in ringing or saturation, the edge between the dark red and light magenta will only be bordered by red darker than vector A and magenta lighter than vector B.

Then, it is possible to obtain a sharp contour with an emphasized change in color saturation.

FIG. 2 shows a specific example of the phase detection circuit 20, in which the carrier color signal is input to the amplifier 23 via the input terminal 21 and amplified. Then, the amplitude is limited to a constant value by the limiter 24, and the signal is led out to the output terminal 22 via a band pass filter (BPF) centered at 3.58 MHz.

FIG. 4 shows another embodiment of the invention.

In the previous embodiment, only the amplitude component of the color signal was used to obtain the contour correction signal, but since the color signal and the luminance signal have a high correlation, the edges of the luminance signal are detected to create the edge correction signal. Good too. In the embodiment shown in FIG. 4, an edge correction signal created from a luminance signal and an edge correction signal created from amplitude information of a chrominance signal are combined in a synthesis circuit 90, and the output of this synthesis circuit 90 is sent to an adder 100 to generate amplitude information. I am trying to add it to. The luminance signal Yin is input from the terminal 11 to the edge correction signal horizontal circuit 52. On the other hand, the edge correction signal detection circuit 51 uses the color amplitude information from the amplitude detection circuit 30 to create an edge correction signal. Both edge correction signals are combined in a combining circuit 90 and added to amplitude information in an adder 100. Other parts are the same as in the previous embodiment.

FIG. 5 shows yet another embodiment. In the embodiment shown in FIG. 1, the output of the delay device 40 itself is multiplied by edge-corrected amplitude information, but in this embodiment, the output of the delay device 40 is separated into an I-axis component and a Q-axis component. Then, each component is multiplied by amplitude information. That is, the output of the delay device 40 is input to the 1-axis component extraction circuit 8 and the Q-axis component extraction circuit 82.

The outputs of each extraction circuit 81 and 82 are output from multipliers 61 and 62.
are input respectively. Each multiplier 61, 62 receives edge-corrected amplitude information from the edge correction circuit 50. As a result, the edge-corrected I-axis component and Q-axis component are obtained at the output terminals 71 and 72, respectively.

[Effects of the Invention] As explained above, according to the present invention, it is possible to obtain color edge correction that does not affect changes in hue even if ringing occurs or changes in saturation, and image quality is improved. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of the phase detection circuit shown in FIG. 1, and FIG. 3 is shown to explain the operation of the circuit of this invention. The vector diagrams, FIGS. 4 and 5 are circuit diagrams showing other embodiments of the present invention, and FIG. 6 is a vector diagram shown to explain the operation of a conventional color edge correction circuit. 20... Phase detection circuit, 30... Amplitude detection circuit, 4
0...Delay device, 50...Edge correction circuit, 60...
- Multiplier, 51.52... edge correction signal detection circuit,
90...Synthesis circuit, 100...Adder. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 (a) 270' (b) Figure 3 Figure 6

Claims (3)

[Claims] (1) Phase information signal detection means for detecting the hue of an input color video signal and obtaining a phase information signal; amplitude detection means for detecting the degree of saturation of the input color video signal; and edge information of the output of the amplitude detection means. edge correction means for extracting the amplitude signal and adding it to the output of the amplitude detection means to correct the contour; and multiplying the amplitude signal obtained from the edge correction means by the phase information signal obtained from the phase information detection means. and a multiplication processing means for obtaining a carrier color signal. (2) The phase information detection means outputs each phase information signal of the I-axis and Q-axis components of the input color video signal, and the multiplication processing adjustment means outputs an amplitude signal for each of the phase information signals. 2. The color edge correction circuit according to claim 1, wherein the color edge correction circuit performs multiplication. (3) The edge correction means is characterized in that the edge information is a signal obtained by combining an edge correction signal obtained by detecting an edge of the luminance signal and an edge correction signal obtained by detecting an edge of the amplitude information. The color edge correction circuit according to item 1.