JPH04329078A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To correctly perform an autofocus action even in an object having a high luminance part in a video signal by providing an auto focusing device to judge the necessity or unnecessity of the high luminance part in the video signal and selecting the removing or non-removing of the high luminance part. CONSTITUTION:When a high luminance part exists in a video signal, the position or number of the high luminance part is detected by a high luminance part detecting circuit 11, and when the high luminance part exists except the central part in the video signal or even when the part is in the center part and the number is small, a switch circuit 14 is controlled by a control circuit 13, the high luminance part in the video signal is removed by a gate circuit 12, and when the high luminance part is collected into the central part in the video signal and scattered at the whole video signal, the switch circuit 14 is controlled by the control circuit 13, the high luminance part in the video signal is not removed, the necessity or unnecessity is judged by the position or number of the high luminance part and the correct automatic focusing action can be performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus device for a video camera.

0002

2. Description of the Related Art In recent years, demand for video cameras has been rapidly increasing due to their miniaturization and weight reduction. Autofocus devices make video cameras easier to handle and contribute to their further widespread use.

A conventional autofocus device will be explained below. FIG. 2 shows a block diagram of a conventional autofocus device, in which 1 is a lens with a focus adjustment device, and 10 is a motor that drives this device. 2 is an image sensor that converts optical information of a subject into an electrical signal; 3 is an image sensor 2
4 is a process circuit that performs gamma correction, blanking processing, addition of synchronization signals, etc., and converts the electrical signal into a television signal. 6 is a synchronization signal generator which generates a synchronization signal, a blanking signal, a vertical synchronization signal, a horizontal synchronization signal, etc. Reference numeral 5 denotes a scanning drive circuit for the image sensor 2. 7 is a circuit for extracting a high frequency component from the output from the preamplifier, the extracted high frequency component is processed by an arithmetic processing circuit 8, and the motor is driven so that the high frequency component is maximized. Through circuit 9,
The motor 10 drives the focus adjustment device of the lens 1 to obtain a focused state. However, when imaging a high-brightness subject, the high-frequency components in the video signal remain large even when the subject is not in focus, and the high-frequency components are saturated in the high-frequency component detection circuit, causing the autofocus device to Due to the problem of malfunction, if the image of the subject includes a high brightness part in the output video signal of the image sensor 2,
A high-brightness portion detection circuit 11 detects the high-brightness portion, and a gate circuit 12 removes the high-brightness portion from the output video signal of the image sensor 2. was input so that the in-focus state could be obtained as described above.

0004

[Problem to be Solved by the Invention] However, in such an autofocus device of a video camera, if there is a high brightness part in the video signal, it is removed without determining whether the high brightness part is necessary or unnecessary. Therefore, there was a problem in that the autofocus device operated unstablely.

The present invention solves these conventional problems, and provides an autofocus system that determines whether a high-brightness part in a video signal is necessary or unnecessary and selects whether or not to remove the high-brightness part. It provides equipment.

[0006]

[Means for Solving the Problems] The autofocus device of the present invention drives the focus motor so that the level of high frequency components in the output video signal of the image pickup device on which the object image is formed on the light receiving surface is maximized. a high-brightness portion detection circuit for detecting the position or number of high-brightness portions in a subject image; a gate circuit for removing high-brightness portions based on the output of the detection unit; and a control circuit for controlling whether or not to remove high-brightness portions. The control circuit is configured to select whether or not to remove a high-brightness portion of a subject image.

[0007]

[Operation] With this configuration, it is possible to determine whether high-brightness parts in the video signal are necessary or unnecessary, and to select whether or not to remove the high-brightness parts, allowing autofocus without removing the necessary high-brightness parts. This means that you will be able to perform the actions.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic focusing device according to an embodiment of the present invention will be described below with reference to FIG.

Reference numeral 12 denotes a gate circuit for removing high-brightness portions in the video signal; 11 a high-brightness portion detection circuit for detecting the position or number of high-brightness portions in the subject image; and 13, an output of the high-brightness portion detection circuit 11. 14 is a switch circuit that selects whether or not to remove the high-brightness portion. Note that the blocks numbered 1 to 10 are the same as those in FIG.

When there is a high brightness part in the video signal, the position or number of the high brightness part is detected by the high brightness part detection circuit 11. If the number of video signals is small, the control circuit 13 controls the switch circuit 14, and the gate circuit 12 removes the high brightness portion in the video signal.
In addition, if the high-brightness portion is concentrated in the center of the video signal or scattered throughout the video signal, the control circuit 13 controls the switch circuit 14 to remove the high-brightness portion of the video signal. It is possible to perform an autofocus operation by determining whether or not the high-brightness portion is necessary based on the position or number of the high-brightness portion.

[0011]

As can be seen from the above description, the present invention can achieve the effect that autofocus operation can be performed correctly even for a subject having a high-brightness portion in the video signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an autofocus device in an embodiment of the present invention.

[Figure 2] Block diagram showing a conventional autofocus device

[Explanation of symbols]

1 Lens with a focusing device 2 Imaging device 3 Preamplifier 4 Process circuit 5 Image sensor drive circuit 6 Synchronous signal generator 7 High frequency component detection circuit 8 Arithmetic processing circuit 9 Motor drive circuit 10 Motor 11 High brightness part detection circuit 12 Gate circuit 13 Control circuit 14 Switch circuit

Claims (1)

[Claims] 1. Means for driving a focus motor so that the level of high frequency components in an output video signal of an image sensor on which a subject image is formed on a light-receiving surface is maximized; It has a high-brightness part detection circuit that detects the number of objects, a gate circuit that removes the high-brightness part based on the output of the high-brightness part detection circuit, and a control circuit that controls whether or not to remove the high-brightness part. An autofocus device characterized by selecting whether or not to remove a high-luminance part of an image.