JPH0444473A - Signal processor for image pickup device - Google Patents

Abstract

PURPOSE:To obtain both a sense of proper resolution and proper S/N at all times by providing a means detecting a focus of a zoom lens, increasing the rate of addition of a contour signal to be added to a video signal at a wide angle mode with a short focus and decreasing the rate of addition in the telescope mode with a long focus. CONSTITUTION:A focus detection mechanism 4 detects how long the focus of a zoom lens is set and outputs a focus detection signal S to an addition rate variable circuit 13. The addition rate variable circuit 13 multiplies a predetermined addition rate Ai with a contour signal Ve corresponding to the inputted focus detection signal S and outputs the product to an adder circuit 11. The addition rate Ai is increased in the wide angle mode in which the focus of the zoom lens 1 is short to emphasize the contour of a video signal output Vo thereby enhancing a sense of resolution, and the rate Ai is decreased conversely in the telescope mode where the focus is long to improve the S/N. Thus, proper contour emphasis and well-balanced S/N are attained at all times.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a signal processing device used in a video camera, and more particularly, to a signal processing device that can obtain appropriate image quality regardless of the zoom angle of view in a video camera equipped with a zoom lens. [Conventional technology]

FIG. 2 is a block diagram showing the operating principle of a conventional signal processing device disclosed in, for example, Japanese Patent Publication No. 56-52512.
+11 is a zoom lens, (2) is a zoom lens (1)
an image sensor (3) that converts the formed optical image into an electrical signal;
) is a No. 3 processing circuit that converts the output of the image sensor (2) into a television signal, and among the components of the signal processing circuit (3), (11) is an addition circuit, (+21 is a contour signal extraction circuit) Next, the operation will be explained.The optical image formed by the zoom lens (+1) is converted into an electric signal Vi by the image sensor (2) and input to the signal processing circuit (3).The signal processing circuit (3) ) converts the optical information of the video into a television signal.The signal processing circuit (3) includes an addition circuit (11) and a contour signal extraction circuit (12) in addition to a circuit for generating a television signal. The video signal Vi is sent to the adder circuit (1
1) and is input to the contour signal extraction circuit (12). The contour signal extraction circuit (12) extracts the contour component of the video signal Vj and outputs the contour signal Ve.
Usually, a method is used in which a secondary image component signal of the video signal Vi is extracted and used. The adder circuit (11) receives the video signal Vi
and the contour signal Ve at a predetermined constant ratio A to obtain an output vO. That is, Vo=A-Ve+ (1-A)V i Here, if the addition ratio A of the adder circuit (II) is made large, the outline of the image is emphasized and the details of the subject are clearly visible, improving the sense of resolution. At the same time, the noise component also increases, which deteriorates the so-called signal-to-noise ratio and gives an unnatural visual impression. Therefore, the addition ratio A of the addition circuit (11) is appropriately set after comprehensively determining the balance between these factors. In addition, in order to achieve both S/N and resolution, the addition ratio A of the addition circuit (11) is determined based on the brightness of the video signal, etc.
Efforts are also being made to dynamically change the

[Problem to be solved by the invention]

Since the signal processing device of a conventional image pickup device is configured as described above, the addition ratio of the addition circuit is appropriately selected to achieve S/
It is difficult to achieve both N and resolution, and the optimal addition ratio is different between the telephoto end and the wide-angle end of the zoom lens, especially since subjects are photographed at various sizes with imaging devices that use zoom lenses. In many cases, there is a problem in that either S/N or resolution must be sacrificed. This invention was made in order to solve the above-mentioned problems, and provides imaging that can achieve both S/N and resolution by using the optimum addition ratio at any focal length of the zoom lens. The purpose is to obtain equipment.

[Means to solve the problem]

A signal processing device for an imaging device according to the present invention includes means for detecting the focal length of a zoom lens, and addition ratio variable means for changing the ratio at which a contour signal is added to a video signal according to the detected focal length detection signal. It is characterized by the following points.

[Effect]

The focal length detection means of the zoom lens in this invention is as follows:
Detects the focal length of the zoom lens and outputs the detection signal. The addition ratio variable means always adjusts S according to the focal length detection signal.
The addition ratio of the contour signal is changed to a value that is compatible with /N and resolution. Therefore, even if the focal length of the zoom lens changes, an image with good S/N and resolution can always be obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram of this embodiment, and the same parts as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. In the figure, (4) is the focal length detection mechanism of the zoom lens (1), which is composed of a potentiometer etc. connected to a mechanism (called a magnification variable mechanism or zoom mechanism) that changes the focal length of the zoom lens (1). , zoom lens (1)
A focal length detection signal S is output. (13) is an addition rate variable circuit that changes the addition rate Ai of the contour signal Ve to the video signal Vi in the addition circuit (in the process) according to the focal length detection signal S. Next, this embodiment The operation of the part that is different from the conventional example will be explained.The focal length detection mechanism (4) detects how much the focal length of the zoom lens (1) is set, and sends the focal length detection signal S to the variable addition rate circuit. (13). The addition rate variable circuit (13J) multiplies the contour signal Ve by a predetermined addition rate Ai corresponding to the value of the input focal length detection signal S, and outputs it to the addition circuit (13J). This addition ratio Ai is set to be larger at the wide-angle end where the focal length of the zoom lens (1) is shorter to emphasize the outline of the video signal output vO and increase the sense of resolution; At the telephoto end, it is set to be smaller to improve the S/N ratio.Generally, when shooting a similar subject, at the wide-angle end, the details of the subject are reduced and the resolution is insufficient.Such wide-angle shooting As mentioned above, the lack of resolution is compensated for by emphasizing the outline by increasing the addition ratio.Also, at the telephoto end, the details of the subject are enlarged. Although the resolution is sufficient, it gives the impression that the S/N is poor because small parts are visible.This S/N deterioration can be improved by reducing the addition ratio Ai.In this way, In this embodiment, the signal processing device of the imaging device can always perform appropriate edge enhancement and edge enhancement with a well-balanced S/N ratio regardless of the focal length of the zoom lens from the wide-angle side to the telephoto side. There is.

【Effect of the invention】

As described above, according to the present invention, a means for detecting the focal length of the zoom lens is provided, and when the focal length is short at wide angle, the addition ratio of the contour signal to be added to the video signal is increased to improve the sense of resolution. When using a telephoto lens with a long focal length, the addition ratio is reduced to eliminate S/N deterioration, so no matter where the focal length of the zoom lens is, it always maintains an appropriate resolution and S/N ratio. A feature is that a signal processing device for an imaging device can be obtained that can obtain both.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a signal processing device for an imaging device according to an embodiment of the present invention, and FIG. 2 is a block circuit diagram of a conventional signal processing device for an imaging device. (I) - Zoom lens, (3) - Signal processing circuit, (4) - Focal length detection mechanism, (ll) - Addition circuit, (12) - Contour signal extraction circuit, (+3) - ... Addition ratio = T-variable circuit In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a signal processing circuit of an imaging device configured to extract a contour signal from a video signal taken with a zoom lens and perform contour correction by adding the extracted contour signal to the original video signal, means for detecting the focal length of the zoom lens; and means for changing the ratio at which the contour signal is added to the video signal under the control of the detected focal length signal; 1. A signal processing device for an imaging device, characterized in that the signal processing device is configured to have a larger value and to become smaller toward a telephoto side.