JPH10308886A - Contour correction circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contour correction circuit by which a level of a signal to be outputted is adjusted to a prescribed or a desired level even when a frequency characteristic of the contour correction circuit is changed. SOLUTION: A contour correction circuit 1 changes a frequency characteristic of a video signal received under the control of a control circuit 3 to provide an output of a contour correction signal; a control circuit 3 controls operation of the contour correction circuit 1 and provides an output of a control signal in response to the frequency characteristic of the contour correction device to a multiplier circuit 2; and the multiplier circuit 2 multiplies the contour correction signal with a control signal outputted from the control circuit 3 and provides an output video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction device, and more particularly to a contour correction device for performing a contour correction on a video signal output from a television camera or the like.

[0002]

2. Description of the Related Art Conventionally, an interlace system (interlaced scanning system) has been frequently used as a system for realizing high-resolution display of a signal output from a television camera or the like. The interlace method is a method of scanning a phosphor on a display or the like every other row, and is also useful as a method for reducing flickering or the like in a moving image.

However, when a signal is processed by the interlace method, flicker may occur on the display screen. In order to reduce the flicker, a method of correcting a signal output from a television camera or the like has been proposed.

The above-mentioned conventional correction method is disclosed in
"Vertical contour correction device" disclosed in JP-A-1010892
There is. FIG. 4 shows a block diagram of the vertical contour correction device.

As shown in FIG. 4, this vertical contour correction device includes an input terminal 8 for inputting a signal indicating whether or not an input video signal is a moving image, and an input terminal 8 when the input signal is a moving image. Multipliers 15, 16 and 17 for multiplying the signals by predetermined coefficients, an adder 18 for adding the signals output from the multipliers 15, 16 and 17, and a signal output from the adder 18 as a vertical contour correction signal A coefficient unit 19 for multiplying the vertical contour correction signal by a coefficient K, and an adder 20 for adding a signal output from the coefficient unit 19 and a luminance signal.

[0006] As described above, this vertical contour correction device
The coefficient unit 19 performs correction by multiplying the vertical contour correction signal by a coefficient. Here, as a coefficient K to be applied to the vertical contour correction signal by the coefficient unit 19, the range of K is −1 to +1.
Has been changed. As the value of K approaches +1, the vertical contour of the displayed image is emphasized, and the value of K becomes −
The closer to 1, the weaker the outline in the vertical direction of the displayed image is, so that the correction is performed.

[0007]

However, in the conventional contour correction device as described above, the input signal may be used after being divided into several frequency steps. The frequency characteristics are fixed for the entire device, and there is no function for changing the frequency characteristics of the entire device.

Therefore, the change in the level of the output signal when the frequency step to be used changes and the frequency characteristic of the device changes is output without any modification.
Therefore, in a certain frequency step, the output level is too high, and conversely, in a certain frequency step, the output level is too low, so that the level of the output signal is constant or a desired level. As a result, there is a problem that the image on the display screen displayed based on the output video signal becomes difficult to see.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a contour correcting device capable of setting a level of a signal to be output to be constant or a desired level regardless of the frequency characteristics of the contour correcting device. Aim.

[0010]

According to the first aspect of the present invention,
Contour correction means for changing the frequency characteristic of the input video signal based on the control of the control circuit and outputting a contour correction signal, and controlling the change in the frequency characteristic of the contour correction means,
A control circuit that outputs a control signal to the multiplying circuit; and a multiplying circuit that multiplies the contour correction signal by the control signal output from the control circuit and outputs an output video signal.

Therefore, according to the present invention, the frequency step used for the contour correction device is determined, and when the frequency characteristics of the entire device are determined, it is possible to calculate the level of the output signal. Since the control circuit controls the multiplication circuit based on the calculation result,
The level of the output video signal can be set to an appropriate value.

According to a second aspect of the present invention, in the first aspect of the invention, the contour correcting means includes a 5-tap bandpass filter, a 3-tap lowpass filter, and a signal output from the 5-tap bandpass filter. , A signal output from the 3-tap low-pass filter or a signal obtained by cascading the 5-tap band-pass filter and the 3-tap low-pass filter. And a changeover switch for switching the connection.

Therefore, according to the present invention, the operation of the first aspect of the present invention can be obtained, and the contour correcting means has a changeover switch for switching the frequency by switching the connection and outputting the frequency. Since the switch can be switched by the control circuit, an appropriate frequency step can be selected as the frequency step to which the output signal belongs.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the control signal sets a level of an output video signal output from the multiplication circuit to a frequency step to which the output video signal belongs. Regardless, the signal is set to a constant level.

Therefore, according to the present invention, the operation of the invention described in claim 1 or 2 can be obtained, and the control circuit integrally controls the frequency step control of the entire apparatus and the control of the multiplication circuit. By doing so, the level of the output video signal can be kept constant even if the frequency characteristics are changed.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the control signal sets a level of an output video signal output from the multiplication circuit to a frequency step to which the output video signal belongs. Regardless, the signal is set to a predetermined level.

Therefore, according to the present invention, the operation of the invention described in claim 1 or 2 can be obtained, and the control signal output from the control circuit is changed according to the frequency characteristic of the entire device. The output video signal can be set to a desired level by multiplying the control signal by the multiplying circuit by the contour correction signal output from the contour correction means.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a contour correcting device according to the present invention will be described with reference to the drawings. FIG.
FIG. 1 shows a block diagram of an embodiment of the contour correction device according to the present invention.

The contour correction device shown in FIG. 1 is capable of receiving an input video signal and changing its frequency characteristic under the control of a control circuit 3.
A multiplication circuit 2 for multiplying an output signal as an outline correction signal output from the outline correction circuit 1 by a control signal output from the control circuit 3 and outputting an output video signal; And a control circuit 3 for controlling operation and outputting a control signal to the multiplication circuit 2.

Next, the operation of the contour correction device shown in FIG. 1 will be described. As shown in FIG. 1, the input video signal is input to the contour correction circuit 1. A contour correction circuit 1 multiplies a contour correction signal based on an input video signal by a multiplication circuit 2
Output to At this time, an appropriate frequency step to which the contour correction signal belongs is selected by the control of the control circuit 3.

As described above, the control circuit 3 is a frequency changeover switch (not shown) provided in the contour correction circuit 1.
And an appropriate frequency step is set as the frequency step to which the signal output from the contour correction circuit 1 belongs.

The contour correction signal output from the contour correction circuit 1 is input to the multiplication circuit 2. Further, the control circuit 3 outputs a control signal to the multiplication circuit 2.

The multiplying circuit 2 having received the contour correction signal and the control signal multiplies these two signals and outputs an output video signal.

Here, when the output device for outputting the input video signal is a television camera or the like, the horizontal frequency characteristics of the contour correction signal output from the contour correction circuit are such that the emphasized frequency is visually easy to see. Alternatively, it may be changed by the control circuit 3 in consideration of the video finally displayed on the screen.

Further, as a device for changing the frequency characteristic in the contour correction device shown in FIG. 1, a plurality of low-pass filters (LPF) for passing low frequency components and a band-pass filter (B) for passing certain frequency components are used.
By using a filter in combination with PF),
The use of frequency steps separated into several steps is realized. This filter is preferably provided in the contour correction circuit 1.

FIG. 2 is a block diagram showing an embodiment of a frequency step switching circuit included in the contour correction circuit 1 shown in FIG.

This frequency switching circuit has a 5-tap BP
F11 and the 3-tap LPF12 are cascaded.
Further, a frequency for switching the connection between the branch line connected between the 5-tap BPF 11 and the 3-tap LPF 12 and the output line from the 3-tap LPF 12 to switch the signals output from these filters. It has a changeover switch 10.

However, the frequency switching circuit is the same as that shown in FIG.
However, the present invention is not limited to such a circuit as shown in FIG. 1 and is, for example, a frequency switching circuit that can select a signal output from any of the 5-tap BPF11, the 3-tap LPF12, or the 5-tap BPF11 and the 3-tap LPF12 There may be.

In general, since the frequency characteristics of a circuit change depending on the frequency used, if the frequency is separated into several steps, the response in each frequency step will not be constant.

FIG. 3 is a graph showing the individual frequency characteristics of the signal output from each of the above filters and the frequency characteristics of the signal output when each filter is connected.

FIG. 3A shows the characteristics of the signal output from the 3-tap LPF 12, FIG. 3B shows the characteristics of the signal output from the 5-tap BPF 11, and FIG. In (c) of FIG. 3, 3 is used to change the frequency.
The characteristic of the signal output when the tap LPF and the 5-tap BPF are connected in cascade is shown. In FIG. 3C, the graphs indicated by the broken lines are the characteristic (a) of the signal output from the 3-tap LPF 12 and the 5-tap BPF 1
2 shows the characteristic (b) of the signal output from No. 1.

In FIGS. 3 (a), 3 (b) and 3 (c), the horizontal axis represents the frequency in units of the sampling frequency fs, and the vertical axis represents the output from each filter when the maximum value is 1. 3 shows the level of the signal to be transmitted.

In the graph shown in FIG. 3A which shows the characteristics of the signal output from the 3-tap LPF 12, a low-frequency component is output, and the graph shown in FIG. 3B which shows the characteristics of the signal output from the 5-tap BPF 11. 3), a frequency band centered on a quarter frequency of the sampling frequency fs is output. In the graph shown in FIG. 3C, a signal output from a filter that combines them is
It can be seen that the output is superimposed.

These figures (a), (b) and (c) in FIG.
As is clear from the graph shown in FIG. 5, when each frequency step is used by switching, the response, that is, the level of the output signal changes at each frequency step, and does not become constant or a predetermined level.

Therefore, in the contour correction device according to the present embodiment, the control circuit 3 calculates in advance the response at each frequency step of the contour correction signal output from the contour correction circuit 1 in order to control the variation of the response. The response at each frequency step can be easily calculated at the stage of designing the contour correction device, or at a subsequent calculation.

The multiplication circuit 2 multiplies the contour correction signal.
In, the level correction is performed by multiplying the signal output from the control circuit 3 based on the response calculated in advance by the contour correction signal output from the contour correction circuit 1.

This level correction may be performed so that the level in each frequency step is constant, or may be corrected to a predetermined level so that a desired level is obtained. This selection can be made by changing the signal output from the control circuit 3.

Therefore, according to the present embodiment, the control circuit 3 outputs a signal for correcting the level difference in consideration of the level difference at each frequency step of the output video signal in advance, and the multiplication circuit 2 is fixed. Or, since the correction is performed to obtain the desired value, the frequency used changes,
Even when the frequency characteristics of the entire apparatus change, the response to each frequency can be kept constant or a predetermined value.

[0039]

As is apparent from the above description, according to the present invention, a multiplying circuit for multiplying the output of the contour correcting circuit is provided, and the level is corrected in accordance with the frequency characteristic by the multiplying circuit. In addition, it is possible to provide a contour correction device capable of keeping the level of a correction signal constant even when the frequency characteristic of the contour correction device changes.

In the contour correcting means, a switch for switching the frequency is provided, and the connection of the switch is switched by the control circuit. Therefore, a contour correcting device capable of selecting an appropriate frequency step is provided. Can be provided.

Further, since the contour correction circuit and the multiplication circuit are integrally controlled by the control circuit, the correction signal is increased for a frequency at which the contour correction signal is visually effective. Besides, in addition to making the level correction constant, when an output video signal output from the contour correction device according to the present invention is displayed on a screen, the correction control is performed so that the display can be visually viewed better. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of a contour correction circuit according to the present invention.

FIG. 2 is a block diagram of an embodiment of a circuit for switching a frequency of the contour correction circuit shown in FIG. 1;

FIG. 3 is a graph showing output characteristics at each frequency step of a signal output by the contour correction circuit shown in FIG. 1;
(A) is a graph showing the characteristics of the signal output from the 3-tap LPF, (b) is a graph showing the characteristics of the signal output from the 5-tap BPF, and (c) is the 3-tap LPF.
It is a graph which shows the characteristic of the output signal at the time of cascade-connecting PF and 5-tap BPF.

FIG. 4 is a block diagram showing a configuration of a conventional vertical contour correction device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outline correction circuit 2 Multiplication circuit 3 Control circuit 10 Frequency switch 11 5-tap band-pass filter 12 3-tap low-pass filter

Claims (4)

[Claims] 1. A contour correction means for changing a frequency characteristic of an input video signal based on control of a control circuit and outputting a contour correction signal, and controlling a change in the frequency characteristic of the contour correction means and controlling the multiplication circuit. A contour correction device comprising: a control circuit that outputs a signal; and a multiplication circuit that multiplies the contour correction signal by a control signal output from the control circuit and outputs an output video signal. 2. The contour correcting means includes: a 5-tap bandpass filter; a 3-tap lowpass filter; a signal output from the 5-tap bandpass filter;
A signal output from the 3-tap low-pass filter or a signal obtained by cascading the 5-tap band-pass filter and the 3-tap low-pass filter is output. 2. The contour correction device according to claim 1, further comprising a changeover switch for switching the connection. 3. The control signal according to claim 1, wherein the level of the output video signal output from the multiplying circuit is a constant level regardless of a frequency step to which the output video signal belongs. Or the contour correction device according to 2. 4. The control signal according to claim 1, wherein the level of the output video signal output from the multiplication circuit is a predetermined level regardless of a frequency step to which the output video signal belongs. 3. The contour correction device according to 1 or 2.