JPH03185974A - Contour correction circuit - Google Patents

Abstract

PURPOSE:To suppress production of blooming by multiplying a 1st differentiating signal and a 2nd differentiating signal whose polarity is inverted with 1st and 2nd contour correction signals so as to suppress a white level thereby obtaining a contour correction signal. CONSTITUTION:A subtractor 9 subtracts an input luminance signal (a) from a 1st delay signal (b) to output a 1st contour correction signal (d). Moreover, a subtractor 10 subtracts a 2nd delay signal (c) from the signal (b) to output a 2nd contour correction signal (e). A differentiating device 11 differentiates the signal (a) to send a 1st differentiating signal (f) and a differentiating device 12 outputs a 2nd differentiating signal (g), which is a signal resulting from differentiating the signal (b) and the result is inverted by an inverter 13. A multiplier 14 multiplies signals (d), (f) and multiplies signals (e), (g), they are added and outputted as a contour correction signal (h). Thus, the waveform of the signal subjected to contour correction is a waveform whose white level is suppressed thereby suppressing the production of blooming.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contour correction circuit used in color television receivers and video equipment.

[Prior Art] Figure 3 is a block circuit diagram of a conventional contour correction circuit.
) are signal input terminals, (2) and (3) are delay lines, (4
) is an adder, (5) is a 1/2 multiplier, (6) is a subtracter,
(7) is a mixer, and (8) is an output terminal for the contour-corrected luminance signal.

Next, the operation of the circuit will be explained. Figure 4 is a signal waveform diagram of each part of this conventional example.
The diagram (a1 shown) is manually created, and the delay lines (2> and (3)
), each of which is delayed by a certain amount of time, as shown in Figure 4(b),
The waveform shown in (c) becomes a signal of c. Next, an adder (4) adds the input signal a and the second delayed signal C, and a multiplier (5) adds a signal d whose amplitude has been compressed to 1/2.
(shown in FIG. 4(d)), the first delayed signal S is subtracted by a subtracter (6) to obtain the contour correction signal e having the waveform shown in FIG. 4(e).

The mixer (7) mixes the first delayed signal and the contour correction signal e, and outputs the contour-corrected luminance signal to the output terminal (8).

[Problems to be Solved by the Invention] Since the conventional contour correction circuit is configured as described above, when the input signal is a signal with a high degree of modulation such as a white character,
Since contour correction signals of the same level are added to the white side and the black side of the luminance signal, blooming occurs and white characters etc. become blurred, which is a problem.

This invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an outline correction circuit that does not cause blue predominance even in the case of high-level luminance No. 78 such as white characters.

[Means for Solving the Problems] The contour correction circuit according to the present invention delays input luminance signals by a predetermined amount, and delays these input signals and the first . means for creating a contour correction signal from a second delayed signal; a first differential signal that differentiates the input signal; and a second differential signal that differentiates the first delayed signal and has a polarity reversed; Means and this first. The apparatus includes means for multiplying the second differential signal and the contour correction signal so as to suppress the level on the white side, and means for mixing the multiplied signal and the first delayed signal.

[Operation] The multiplication means adds the first differential signal and the second differential signal by inverting their polarities and suppressing the signal level on the white side. Therefore, the waveform of the contour-corrected signal output from the mixing means has its own level side suppressed, and blooming does not occur.

[Embodiment of the Invention] FIG. 1 is a block circuit diagram of an embodiment of the invention, and FIG. 2 is a signal waveform diagram of each part thereof. In the figure, (9)
, (10) is the first. a second subtractor, (11);

(12) is the first. The second differentiator, (13) is the inverter, (
14) is a multiplier, Ql-Qa is a transistor forming the multiplier, and (15) is a bias circuit.

Next, the operation will be explained.

The operations of the delay lines (2) and (3) are the same as in the conventional example, so a description thereof will be omitted. A subtracter (9) converts the human luminance signal a (shown in FIG. 2(b)) from the first delayed signal b (shown in FIG. 2(b)).
a) as shown) to output a first contour correction signal d having a waveform shown in FIG. 2(d). On the other hand, the subtractor (10) is
From the first delayed signal to the second delayed signal C (Fig. 2 (C)
(shown in the figure) to output a second contour correction signal e having a waveform shown in FIG. 2(e). The differentiator (11) differentiates the human luminance signal a and sends out a first differential signal having the waveform shown in FIG. 2(f), and the differentiator (12) differentiates the first delayed signal a. The inverter (13) inverts its polarity and sends out a second differential signal g (shown in FIG. 2(g)).

The first differential signal f is input to the bases of Ql and Q2 of the multiplier C14), and the second differential signal f is input to the bases of Q3 and Qa.
Since the differential signal g of is input, the first contour correction signal d is input to the base of Q5, and the second contour correction signal e is input to the base of Q6, from the multiplier (14),
A waveform signal obtained by adding a waveform signal obtained by multiplying the first contour correction signal d and the first differential signal f, and a waveform signal obtained by multiplying the second contour correction signal e and the second differential signal g. A contour correction signal h (shown in FIG. 2(h)) is output. That is,
To explain with reference to the waveform diagram in FIG. 2, during the period T+, the first contour correction signal d is at the black level and the first differential signal f is on the + side, so Ql and Q2 are turned on, and the contour correction signal d is on the + side. The signal has a large preshoot waveform on the black side as shown in FIG. 2(h). Next, during period T2, the second contour correction signal e is at the white level and the second differential signal g is at one side, so Q
3, Q4 is turned off, and the contour correction signal is as shown in Fig. 2 (h
), the overshoot waveform has a low level on the white side. Next, the same operation occurs in the periods Ts and T4, and the contour correction signal eventually becomes a waveform in which the black level is high and the white side level is suppressed, as shown in FIG. 2(h). The resulting contour correction signal suppresses the occurrence of bluing. Note that the bias circuit (15) applies an appropriate bias voltage to the bases of Q+ to Q4 so that the multiplication path (14) operates as described above.

Note that in the above embodiment, the first. The second differential signals f, g are directly applied to the multiplier (14) Ql, Q2Q3 . If the input luminance signal a is input to the base of Q4, but if the configuration is configured such that signals below a certain level are sliced and input through coring circuits, when the level of the input luminance signal a is small, the first. The second differential signal f1g is not manually input to the integrator (14), and a contour correction signal with a suppressed level on the white side is obtained only when the level is large, so that the contour correction effect is improved.

Further, in the above embodiment, the first. second contour correction signal d,
e separately from the first. Multiplied by the second differential signals f and g,
Contour correction signal e created with the conventional circuit shown in Fig. 3 (Fig. 4 (
e)), 1st. A similar effect can be obtained by using a configuration in which the second differential signals f and g are multiplied.

[Effects of the Invention] As described above, according to the present invention, the first. a second delay device; a first delay device; To the contour correction signal created with the second subtractor,
Since the contour correction signal is obtained by multiplying the differential signal of the input video signal and the signal by inverting the polarity of the differential signal of the first delayed signal so as to suppress the level on the white side, it is possible to obtain a contour correction signal with a high white level. Even for a luminance signal, there is an advantage that a contour correction circuit that performs contour correction without causing blooming can be obtained.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of an embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part of this embodiment, Fig. 3 is a block circuit diagram of a conventional contour correction circuit, and Fig. 4 is this conventional example. FIG. 3 is a signal waveform diagram of each part of FIG. (2), (3)...Delay line, (7)...Mixer, (9), (to)...Subtractor, (11),
(12)...Differentiator, (13)...Inverter, (14
)...multiplier. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) Means for delaying an input signal by a predetermined amount and creating a contour correction signal by taking the difference between each signal, a first differential signal obtained by differentiating the input signal, and a polarity of the differential signal of the first delayed signal. means for creating a second differential signal that is inverted;
means for multiplying the contour correction signal by the first and second differential signals so that a white level is suppressed; and means for mixing the multiplied signal and the first delayed signal. Contour correction circuit.