JPH02288554A - Contour improving circuit - Google Patents

Abstract

PURPOSE:To obtain a contour emphasis circuit without preshoot and overshoot by switching an input signal, the output of a 1st delay device and the output of a 2nd delay device with a timing pulse. CONSTITUTION:The 1st delay circuit 11 for an input signal, the contour emphasis circuits 12, 13, 14 adding preshoot and overshoot, the 2nd delay circuit 18 retarding the output of a contour emphasis circuit, switches 19, 21 receiving the input signal, the output of the 2nd delay circuit and the output of the contour emphasis circuit, and 1st and 2nd differentiating devices 12, 16 controlling the switches 19, 21, an absolute value circuit 15 and 1st and 2nd level comparators 17, 20 are provided on the contour emphasis circuit. Then the input signal, the contour correction output of the output of the 1st delay device, and the output of the 2nd delay device are switched by a timing signal generated by the 1st differentiating circuit for the output of the 1st delay device, the absolute value circuit, the 2nd differentiating circuit and the level comparators. Thus, the contour emphasis circuit without the preshoot and the overshoot is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a circuit for improving contours of video signals.

2. Description of the Related Art In recent years, efforts have been actively made to improve image quality in the fields of televisions, video tape recorders, and the like.

An example of an edge enhancement circuit, which is one of the conventional high-image-quality circuits mentioned above, will be described below with reference to the drawings. Third
The figure shows the configuration of a conventional edge enhancement circuit. 1 is the first differentiator, 2 is the second differentiator, 3 is the input signal and the second differentiator.
This is a subtracter that takes the difference between the outputs of the differentiators.

The operation of the contour emphasizing circuit configured as described above will be explained below.

First, the input signal is passed through the first differentiator and the second differentiator to 2
Create the second derivative waveform. By subtracting this from the input signal using a subtracter 3, a contour emphasis signal with sharp preshoot and overshoot at the edges can be obtained.

Problems to be Solved by the Invention However, with the above configuration, there is a problem in that the more the outline is emphasized, the larger the pre-shoot and bud-bur shoot become, resulting in an unnatural image.

The present invention overcomes the above problems and provides a pre-shoot.

This provides a natural contour enhancement circuit without overshoot.

Means for Solving the Problems In order to solve the above problems, the contour improvement circuit of the present invention includes an input signal delay circuit and a preshoot.

Contour enhancement circuit unit for adding overshoot 1 A delay circuit for delaying the output of edge enhancement, the input official name, a second delay device output 9 first and second switches to which the output of the contour correction circuit is input; The control device includes first and second differentiators, an absolute value circuit, and first and second level comparators.

Operation The present invention has the above-described configuration, and provides three outputs: the first delay device output, the contour correction output of the first delay device output, and the second delay device output.
A first differentiating circuit, an absolute value circuit, and a second differentiating circuit.

By switching using a timing signal generated from a level comparator, a contour emphasizing circuit without preshoot or overshoot can be obtained.

Embodiments Hereinafter, contour improvement circuits according to embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a contour improvement circuit in an embodiment of the present invention.

In FIG. 1, 11 is a first delay device, 12 is a first differentiator, 13 is a third differentiator, and 14 is a subtraction that takes the difference between the output of the third differentiator and the output of the first delay device. 18 is the second delay device, 19.21 is the first and second switch, 16 is the absolute value circuit of the first differentiator, 16 is the second differentiator output, 1
7 and 20 are level comparators.

The operation of the contour improvement circuit configured as described above will be explained below with reference to FIGS. 1 and 2. FIG. 2 shows the waveform operation of each part in FIG. 1. First, an input signal as shown in (a) of FIG. 2 is input to the 11 first delay device. The signal delayed by the 11 delay devices becomes as shown in FIG. 2 Φ). The first delay device output is differentiated through 12 first differentiators and through 13 third differentiators.

Taking the difference between the third differentiator output and the first delay device output, we get
A contour emphasis signal with overshoot and preshoot as shown in FIG. 2(e) is obtained. When this signal is input to the 18 second delay devices, the output becomes as shown in FIG. 2(f). Next, when the output of the 12 first differentiators is passed through 16 absolute value circuits, it becomes the waveform shown in Figure 2 (C), and when it is further passed through the 16 second differentiators, it becomes the waveform shown in Figure 2 (d). It will be like that. When this output is input to a level comparator 17 and a pulse is generated that turns ON when it exceeds a certain reference level, the waveform becomes as shown in FIG. 2 (9). Similarly,
When the output of the 16 second differentiators is input to the level comparator 20 and a pulse is generated that turns ON when the output falls below a certain reference level, the waveform becomes as shown in FIG. 2 (b).

Here, 19 SW1 has the 14 subtracter output shown in FIG. 2(e) at the contact point on the x1 side, and 18 SWl shown in FIG. 2(1)
The second delay output of 17 is connected to the Y side contact, and the 17 first
is controlled by the output of the level comparator. Also, 21 S
W2 has the input signal shown in FIG. 2 (, ) on the Y2 side, the output of SW1 19 on the x2 side, and is controlled by the output of the level comparator 2o.

First, when the output of the level comparator 17.20 is OFF, it is fx to SWltiXlm, 5W21-iX2 side. In the section tl in Fig. 2 (cr), S W 1 HaY1911 t S W 2 HaX
2 (II J knee't. At this time, the output is
The waveform shown in FIG. 2(f) is output. Next, in the section t2 in FIG. 2(q), SWl is on the X side, SW2
is on the x2 side.

Therefore, at this time, the waveform shown in FIG. 2(e) is output.

Next, in the section t3 in FIG. 2(b), S
Wl is on the x1 side,! 3W2 is on the Y2 side.

Therefore, at this time, the waveform shown in FIG. 2(a) is output. Next, in the section t4 in FIG. 2(q),
SWl is on the Yl side, and SW2 is on the X2 side. At this time, the waveform shown in FIG. 2(f) is output. Next, in the section t5 in FIG. 2(q), S W
1 tri X (III, S W 2 ij:
X2 ml (!: fZ tte'E?) At this time, the waveform shown in Fig. 2 (e) is output. Next, the waveform shown in Fig. 2 (h) is output.
In section 70, SWl is on the X side, SW
2 is on the Y2 side, and the waveform shown in FIG. 2(a) is output.

The overall output waveform resulting from the above series of switch operations is
It will look like figure (i).

As described above, according to this embodiment, the first delay circuit for the input signal, the edge enhancement circuit for adding preshoot and overshoot, the second delay circuit for delaying the output of the edge enhancement circuit, the input signal, 2 delay circuit outputs 2 contour correction circuit outputs as inputs, first and second switches, first and second differentiators, absolute value circuits, and first
By providing a configuration of a second level comparator and a second level comparator, the three outputs of the first delay unit output, the contour correction output of the first delay unit output, and the second delay unit output are transmitted to the first delay unit. By switching according to timing signals generated from the outputs of the first differentiating circuit, the absolute value circuit, the second differentiating circuit, and the level comparator, a contour emphasizing circuit without preshoot or overshoot can be obtained.

As described above, according to the present invention, an ideal contour enhancement circuit without preshoot and overshoot can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of FIG. 1, and FIG. 3 is a block diagram of a conventional configuration example. 11.18...First and second delay devices, 12°13.16...Differentiator, 15...Absolute value circuit, 17.20...・Level comparator,
14... group/subtractor, 19, 21... switch. Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
figure time

Claims (1)

[Claims] a first delay device for delaying an input signal; and a contour correction means for obtaining a contour correction signal with an enhanced contour by adding a preshoot and an overshoot to the rising and falling portions of the output signal of the delay device, respectively. a second delay device that delays the contour correction output; a first switch that receives the contour correction output and the second delay device output; and a first switch that receives the first switch output and the input signal as inputs. a second switch to
a first differentiator that differentiates the output of the first delay device; an absolute value circuit for the output of the differentiator; a second differentiator that differentiates the absolute value circuit; , a contour improvement circuit comprising: a control section for the first and second switches, comprising first and second level comparators for comparing with a second reference value.