JPH0514823A - Switching circuit for picture processor - Google Patents

Abstract

PURPOSE:To eliminate influence to a picture due to switching operation, and to prevent the deterioration of the picture by switching a signal related to picture processing during a period in which no picture is being constructed after the command of switching is given. CONSTITUTION:A change-over switch 1 switches and selects alternatively two picture signals A, B so as to make A or B an output picture signal. A switching control part 2 is constituted of a D type flip flop, and to its input (D terminal), a switching command signal commanding the change-over switch 1 to execute the switching is given. At this time, the change-over switch 1 is not simultaneously switched, but when a horizontal synchronizing signal or a vertical synchronizing signal required for constructing the picture is given to the clock input (CK terminal) of the control part 2, the switching operation of the change-over switch 1 is controlled by its output (Q terminal). Thus, for instance, in the case that the picture signal A is selected till then, the picture signal B is selected and made the output picture signal by the switching.

Description

Detailed Description of the Invention

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device switching circuit for switching signals in an image processing device such as a television or a video tape recorder which handles image signals.

[0003]

2. Description of the Related Art In an image processing apparatus such as a video tape recorder (VTR) or a computer display,
Various image processes are performed to display various images on the screen.

In such image processing, there are cases where a plurality of image signals necessary for the image construction are directly switched to form the image. In such a case, for example, when two image signals are switched and selectively output, the image signals are switched by a changeover switch controlled by a changeover command signal for instructing the changeover. That is, the changeover switch operates at the same time when the changeover command signal is given, and the image signal is changed over.

On the other hand, in the analog image signals which are switched in this way, there is always a slight potential difference of the DC component between the respective image signals. Therefore, when such image signals are switched, it is necessary to perform amplitude limiting processing by, for example, a clamp circuit in order to adjust the DC component potential difference between the respective image signals.

However, when the screen is constituted by the image signal, that is, when the image signal is displayed on the screen, the image signal is instantaneously switched at the same time as the switching command signal by the changeover switch as described above. And, because it takes some time for the operation of the clamp circuit described above to follow the switching of the image signal, until this tracking, the luminance signal changes due to the potential difference between the image signals before and after switching, The image is adversely affected and the image is deteriorated.

On the other hand, even in a changeover switch for changing over a signal not directly related to an image signal, the influence of noise at the time of changeover may be propagated by a pulse wave or the like in a power supply line or a ground line to disturb an image. ..

[0008]

As described above,
In the signal changeover switch in the conventional image processing apparatus, signal changeover is performed at the same time as the changeover command signal. Therefore, the effect of this switching appears on the screen,
There was a problem that the image was deteriorated.

Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a switching circuit for an image processing apparatus capable of suppressing image deterioration.

[Constitution of Invention]

[0011]

In order to achieve the above object, the present invention provides a switching means for switching a signal relating to image processing, and a period in which an image is not constituted by an image signal based on a switching command signal. And a switching control means for performing the switching operation of the switching means.

[0012]

In the above structure, the present invention switches the signal relating to the image processing during the period when the image configuration is not performed after the switching is instructed.

[0013]

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

FIG. 1 is a diagram showing the configuration of an embodiment of an image device switching circuit according to the present invention. The switching circuit of the embodiment shown in the figure performs switching control by using a horizontal synchronizing signal or a vertical synchronizing signal which is peculiar to the image structure by the image signal.

In FIG. 1, the switching circuit for an image device comprises a changeover switch 1 and a changeover control section 2.

The changeover switch 1 has two image signals A,
B is switched and selected alternatively, and the selected image signal A or image signal B is used as the output image signal.

The changeover control unit 2 is composed of a D-type flip-flop circuit (F / F), and the changeover switch 1
Control the switching operation of. The F / F2 has its input (D terminal) supplied with a changeover command signal for instructing the changeover switch 1 to change over, and its clock input (CK terminal) supplied with a horizontal sync signal or a vertical sync signal necessary for image construction. The output (Q terminal) controls the changeover operation of the changeover switch 1. That is, the F / F 2 takes in the switching command signal in synchronization with the horizontal synchronizing signal or the vertical synchronizing signal, and switches the changeover switch 1 by the taken-in switching command signal.

In such a configuration, as shown in the operation timing chart of FIG. 2, when the switching command signal changes from the low level to the high level at an arbitrary time and the switching command is given to the switching control unit 2, it At the same time, the changeover switch 1 does not change over, but when a horizontal synchronizing signal or a vertical synchronizing signal is given to the changeover control unit 2, a changeover command signal is given from the output Q of the changeover control unit 2 to the changeover switch 1. That is, the switching command signal is given to the switching control unit 2 in synchronization with the horizontal synchronizing signal or the vertical synchronizing signal. As a result, the changeover switch 1 is changed over. For example, when the image signal A has been selected until then, the image signal B is selected by changing over the changeover switch 1 and becomes the output image signal.

As described above, in the switching circuit according to the present invention, the switching of the image signal is not performed even when the switching command signal is given, and the first horizontal synchronizing signal or the vertical synchronizing signal after the switching command signal is given. The image signal is switched by inputting the signal. As a result, the switching of the image signal is performed in a period in which the image signal for forming the image does not appear on the screen, that is, in the period in which the image is not formed. Therefore, the switching operation of the switching circuit changes the luminance signal. It is possible to prevent adverse effects on the image, such as image deterioration, and suppress image deterioration.

The present invention is not limited to the above-described embodiment. For example, the changeover switch 1 does not selectively select an image signal, but changes the transmission path of the image signal by the changeover operation. It may be a switch having such a configuration.

Further, even if the signal to be switched is not the image signal, it is possible to obtain the same effect as described above even if it is a signal used for image processing used in the image processing apparatus.

[0022]

As described above, according to the present invention, the switching of the signals related to the image processing is performed during the period when the image is not formed after the switching is instructed. The influence on the image can be avoided, and the suppression of the image deterioration can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of a switching circuit for an image processing apparatus according to the present invention.

FIG. 2 is a diagram showing an operation timing chart of the circuit shown in FIG.

[Explanation of symbols]

 1 Changeover switch 2 Changeover control section

Claims (1)

Claim: What is claimed is: 1. A switching means for switching a signal relating to image processing, and a switching control means for performing a switching operation of the switching means during a period when an image is not formed by the image signal based on the switching command signal. A switching circuit for an image processing device, comprising: