JP3385646B2 - Image processing circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing circuit for performing horizontal contour correction on an image signal displayed on a viewfinder of a video camera.

[0002]

2. Description of the Related Art Concerning image signals displayed on a viewfinder of a video camera, contour correction has been conventionally performed as follows. A black and white CRT display device is usually used for the viewfinder of a video camera.
Only the luminance signal of the image is supplied to the RT display device. Contour correction is performed on this luminance signal.

First, a change point is extracted from the luminance signal displayed on the viewfinder, and an aperture correction signal corresponding to the change point is generated. Next, this aperture correction signal is added to the luminance signal to perform contour correction. The contour-corrected luminance signal is displayed on the viewfinder. By the contour correction processing described above, the contours of the respective objects in the image can be clarified and displayed, and the photographer can easily determine the composition of the imaging target.

FIG. 7 is a diagram showing a luminance signal obtained by conventional contour correction processing and a contour-corrected image. In FIG. 7, the diagram shown in (A) shows the waveform of the luminance signal whose contour has been corrected, and the diagram shown in (B) shows the image whose contour has been corrected. The luminance signal waveforms of the portions a to i attached to (A) correspond to the portions of the same reference numeral shown in (B).

As can be seen from FIG. 7, contour correction adds an aperture correction signal of a magnitude corresponding to each change point of the brightness signal to the change point, and when this brightness signal is displayed on the screen, it is displayed on the screen. Boundaries of parts having different brightness are emphasized. The vertical lines indicated by a and b in FIG. 7B appear bright due to the increased brightness on the actual screen, but are shown as black lines for convenience of illustration.

[0006]

The contour correction of the luminance signal displayed on the viewfinder of the conventional video camera is as follows.
Generate an aperture correction signal for the entire luminance signal,
Since this is performed by adding the aperture correction signal to the luminance signal, there is a problem that the contour correction is performed even at the boundary of the horizontal blanking period.

Usually, the viewfinder often displays both ends of the horizontal blanking period of the luminance signal, and since the change in the luminance signal in this part is large, the luminance at both ends of the viewfinder is high. And the image blurs after passing. Therefore, there is a problem that it is difficult to compose the composition of the imaging target. In a normal television receiver, since the horizontal synchronizing signal of the luminance signal is recreated and used based on the blanking signal, this problem does not occur, but the viewfinder of a video camera that does not perform such processing In particular, it becomes a problem.

The image processing circuit of the present invention has been made in view of the above-mentioned problems of the prior art. Even if contour correction is performed, the brightness at both ends of the screen of the viewfinder does not unnecessarily increase, Therefore, an object of the present invention is to provide an image processing circuit capable of performing contour correction processing of a luminance signal without image bleeding in the portion, and thus capable of obtaining an image of a viewfinder in which the composition of an imaging target can be easily taken. And

[0009]

In order to achieve the above object, an image processing circuit of the present invention comprises a correction signal generating means for generating an aperture correction signal of a luminance signal, a horizontal blanking period of the luminance signal, and A muting means for invalidating the aperture correction signal corresponding to the boundary of the horizontal blanking period, and when the luminance signal is displayed on the screen, an aperture correction signal corresponding to the effective portion of the screen is displayed. To generate.

A circuit for performing contour correction processing on the luminance signal of the image displayed on the viewfinder of the video camera, and adding means for adding the luminance signal and the aperture correction signal processed by the mute means. Further, when the luminance signal is displayed on the screen, contour correction is performed on an effective portion of the screen.

[0011]

The aperture correction signal is generated for the portion where the luminance signal changes, and the aperture correction signal is invalidated during the horizontal blanking period of the luminance signal and the period before and after the horizontal blanking period.
The aperture correction signal subjected to this processing is added to the luminance signal to perform contour correction. This processing prevents the aperture correction signal waveform having a large amplitude generated at both ends of the horizontal blanking period from being superimposed on the luminance signal, and prevents the luminance of this portion from being unnecessarily increased.

[0012]

Embodiments of the image processing circuit of the present invention will be described below. FIG. 1 is a diagram showing a configuration of a video camera 1 to which an image processing circuit of the present invention is applied. In FIG. 1, an image pickup device 10 is composed of an optical system, a CCD image pickup element, and the like, and converts an optical image of an image pickup target into an electric image signal. The image processing circuit 11 processes the image signal input from the image pickup device 10, and the VID recorded in the recording device 12 is processed.
The EO signal, the viewfinder signal (VF1) displayed on the viewfinder 17, and the horizontal synchronizing pulse used for the contour correction processing are generated.

The recording device 12 records the VIDEO signal from the image processing circuit 11 on a recording medium such as an 8 mm video tape. The aperture correction circuit 2 generates an aperture signal (AP) for the luminance signal (VF1) signal input from the image processing circuit 11 based on the change point of the luminance signal. The configuration and operation of the aperture correction circuit 2 will be described later with reference to FIGS. 3 and 4.

The gate signal generation circuit 14 is an aperture signal (AP) generated by the aperture correction circuit 2 based on the horizontal synchronizing pulse input from the image processing circuit 11.
Gate signal (GAT) used to mute
E) is generated. The gate circuit 15 uses a gate signal (GA
Based on TE), the horizontal blanking period of the viewfinder signal (VF1) of the aperture signal (AP) and the aperture signals (AP) before and after it are invalidated (muted).
To generate a corrected aperture correction signal (AC).

Now, the generation of the horizontal synchronizing pulse in the image processing circuit 11 and the generation of the gate signal (GATE) in the gate signal generating circuit 14 will be described. Figure 2
Generates a horizontal synchronization pulse and a gate signal (GA
It is a figure explaining generation of TE).

The image processing circuit 11 compares the viewfinder signal (VF1) with the voltage indicated by a in the figure as a threshold value. When the voltage of the viewfinder signal (VF1) is lower than the voltage a, the logical value 1 is output, and when the voltage is high, the logical value 0 is output. In this way, the horizontal sync pulse shown in FIG. 2 is generated.

In the gate signal generating circuit 14, a delay pulse 1 is generated by adding a delay of about 1 cycle to the horizontal synchronizing pulse as shown by b in the figure. Further, the delay pulse 2 is generated by giving a delay of a degree shown by c in the figure. Using a set-reset (SR) flip-flop or the like, a gate signal (GAT) whose logical value changes to 0 at the rising edge of the delay pulse 1 and changes to the logical value 1 at the rising edge of the delay pulse 2
E) is generated.

To generate the delay pulse 1 and the delay pulse 2 from the horizontal synchronizing pulse, for example, a one-shot multi-trigger circuit is used. Further, for example, a clock having a frequency that is an integral multiple of the horizontal synchronizing signal synchronized with the horizontal synchronizing signal is generated, a shift register delays the clock by a predetermined number of clocks, and the clock is generated by a synchronous process. You may.

The adder circuit 16 delays the viewfinder signal (VF1), and the aperture correction circuit 2 and the gate circuit 15 delay the aperture correction signal (A) for image processing.
In addition to compensating the delay caused in C), the viewfinder signal (VF1) is added with the aperture correction signal (AC) to perform contour correction to generate a display signal (VF2). The viewfinder 17 displays the display signal (VF2).

FIG. 3 is a diagram showing the configuration of the aperture correction circuit 2. FIG. 4 is a diagram showing the waveform of each part of the aperture correction circuit 2. The signal waveforms of the respective portions a to e in FIG. 3 are shown in FIG. 4 with the same reference numerals.

In FIG. 3, delay lines 20 and 21 are provided.
Is a predetermined time τ for each input signal, eg 1
This circuit gives a delay of 00 nsec. The adder circuit 22 is
The input viewfinder signal (VF1) and the signals delayed by 2τ by the delay lines 20 and 21 are added. The multiplication circuit 23 is an addition circuit 22.
The output signal of is set to 1/2.

The subtraction circuit 24 subtracts the output signal of the address reproduction circuit 23 from the signal delayed by the delay line 20. The adder circuit 25 adds the inputs and outputs of the subtraction circuit 24.

In FIG. 4, the waveform indicated by a is the signal waveform of the portion a of the aperture correction circuit 2, that is, the waveform of the viewfinder signal (VF1). For simplification of description, the case where the viewfinder signal (VF1) is a simple square wave is shown. The viewfinder signal (VF1) is sequentially delayed by the delay lines 20 and 21, and has a waveform shown in FIGS.

The adding circuit 22 and the multiplying circuit 23 are shown in FIG.
The signal waveforms of a and c are added and further halved.
The output waveform of the multiplication circuit 23 is shown in FIG. 4d. Subtraction circuit 24
And the addition circuit 25 subtracts the output signal of the multiplication circuit 23 from the output signal of the delay line 20,
Aperture (AP) correction signal as shown in FIG.

The operation of the video camera 1 will be described below.
FIG. 5 is a diagram showing a waveform of each signal of the video camera 1. FIG. 6 is a diagram showing an image when the display signal (VF2) is displayed on the viewfinder 17. Note that FIG.
The portions indicated by a to f for the display signal (VF2) shown in FIG. 6 correspond to the portions of the screen shown in FIG. Also, FIG.
In FIG. 1, a waveform in which the luminance signal changes stepwise as the viewfinder signal (VF1) is illustrated for simplification of description, and the case where the aperture correction circuit 2 and the like process this viewfinder signal (VF1) will be described below. Will be explained. Further, the density of the diagonal lines in FIG. 6 corresponds to the luminance. That is, the higher the density of the diagonal lines, the lower the brightness.

The image signal picked up by the image pickup device 10 is processed by the image processing circuit 11 to generate a VIDEO signal, a viewfinder signal (VF1) and a horizontal synchronizing pulse. Of these signals, the VIDEO signal is recorded by the recording device 12, and the other signals are input to the aperture correction circuit 2 and the gate signal generation circuit 14, respectively.

The aperture correction circuit 2 generates an aperture signal (AP) shown in FIG. 5 at a change point of the viewfinder signal (VF1) shown in FIG. The gate signal generation circuit 14 generates the gate signal (GATE) shown in FIG. 5 based on the horizontal synchronizing pulse shown in FIG. These signals are input to the gate circuit 15.

The gate circuit 15 has a gate signal (GAT).
If E) is a logical one, the aperture signal (A
P) is output as it is, and when the gate signal (GATE) has a logical value of 0, the AP circuit is muted and the value of the aperture signal (AP) corresponding to the portion where the gate signal (GATE) has a logical value of 0. Is set to 0V, and the aperture correction signal (AC) shown in FIG. 5 is generated.

By this processing, the waveforms which are harmful to display on the viewfinder 17 and which are generated during the horizontal blanking period of the viewfinder signal (VF1) and before and after it are nullified. The adder circuit 16 adds a delay τ to the viewfinder signal (VF1) to compensate the delay generated in the aperture correction signal (AC) for signal processing,
Further, the aperture correction signal (AC) is added to generate the display signal (VF2) shown in FIG.

As can be seen by referring to the display signal (VF2) in FIG. 5, the display signal (VF2) is not subjected to harmful contour correction before and after the horizontal blanking period shown in the waveform of FIG. 7 (A). The contour correction is performed only on the portion effectively required for the display of the viewfinder 17. Therefore, on the screen of the viewfinder 17, c to c shown in FIG.
Only the contour of the boundary of each region of i is corrected, and FIG.
The lines at both ends of the screen as shown in a and b do not appear.

For this reason, it is possible to obtain an image on the viewfinder 17 in which there is no unnecessary increase in the brightness at both ends of the screen, and thus there is no bleeding and the composition of the object to be imaged is easily taken. Besides the above description, the image processing circuit of the present invention can have various configurations, for example, as described as a modification in the embodiment.

[0032]

As described above, according to the image processing circuit of the present invention, it is possible to suppress an unnecessary increase in the luminance generated at both ends of the viewfinder simply by providing a simple additional circuit in the aperture correction circuit. Image bleeding in this area can be effectively suppressed. Therefore, it is possible to provide a photographer who uses a video camera with an image on the viewfinder that makes it easy to take a composition.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a video camera to which an image processing circuit of the present invention is applied.

FIG. 2 is a diagram illustrating generation of a horizontal synchronization pulse and generation of a gate signal (GATE).

FIG. 3 is a diagram showing a configuration of an aperture correction circuit.

FIG. 4 is a diagram showing a waveform of each part of the aperture correction circuit.

FIG. 5 is a diagram showing a waveform of each signal of the video camera.

FIG. 6 is a diagram showing an image when a display signal (VF2) is displayed on a viewfinder.

FIG. 7 is a luminance signal obtained by conventional contour correction processing;
FIG. 9 is a diagram showing an image whose contour has been corrected. here,
The diagram shown in (A) shows the waveform of a contour-corrected luminance signal, and the diagram shown in (B) shows a contour-corrected image.

[Explanation of symbols]

1 ... Video camera 2 ... Aperture correction circuit 20, 21 ... Delay line 22, 25 ... Adder circuit 23 ... Multiplier circuit 24 ... Subtraction circuit 10 ... Imaging device 11 ... Image processing circuit 12 ... Recording device 14 ... Gate signal generation circuit 15 ... Gate circuit 16 ... Adder circuit 17 ... Viewfinder

Claims (2)

(57) [Claims] 1. A correction signal generating means for generating an aperture correction signal of a luminance signal, and a horizontal blanking period of the luminance signal, and invalidating the aperture correction signal corresponding to a boundary of the horizontal blanking period. An image processing circuit, which has a mute means, and generates an aperture correction signal corresponding to an effective portion of the screen when the brightness signal is displayed on the screen. 2. A circuit for performing contour correction processing on a luminance signal of an image displayed on a viewfinder of a video camera, comprising: an addition means for adding the luminance signal and the aperture correction signal processed by the mute means. The method further comprises: when the brightness signal is displayed on a screen, contour correction is performed on an effective portion of the screen.
The image processing circuit according to.