JPH04329507A - Image pickup device - Google Patents

Abstract

PURPOSE:To provide the image pickup device having an automatic focusing function which stops focusing operation when a lens cap is mounted without exerting any influence upon automatic focusing control in normal image pickup operation. CONSTITUTION:The image pickup device has the automatic focusing function based upon variation of the high frequency component of a video signal and is equipped with an automatic focusing control circuit 10 which controls the focusing operation of a focus lens 1 by inputting open state information on an iris 2, the output of the video signal high-frequency component from a peak detecting circuit 9, and automatic gain control information from a video signal control circuit 11 controlling a process circuit 6 generating a video signal by performing gamma correction and automatic gain control circuit over the video signal, and the automatic focusing circuit 10 quits the focusing operation by stopping driving the focus lens when the iris is open and automatic gain control is maximum.

Description

[Detailed description of the invention]

3,

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus such as a video camera that performs an automatic focusing operation (hereinafter referred to as autofocus) using changes in high frequency components of a video signal.

0002

[Prior Art] Conventionally, in an imaging device equipped with this type of autofocus, when the subject has very few high-frequency components, the distance ring moves the focusable range of the focus lens at a high speed in order to find the subject. A configuration is known in which a focusing operation is performed, and after several search operations, a distance ring for moving a focusing lens is stopped at a focusing position. Then, the high-frequency component immediately after the focus lens stops is held, and if a subject containing more high-frequency components than that is entered, the focusing operation is re-orbited.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, if the change in the high frequency component required to restart the focusing operation (hereinafter referred to as the restart threshold) is made too large, the long focal length In the large blur state, the blur is too high and the high frequency component disappears, causing the problem that even when panning, the video signal does not change and the focusing operation does not restart.On the other hand, if the restart threshold is set too small, the lens cap may be removed. However, due to the increase in noise signal (noise) due to auto gain control (AGC) and the uneven dark current of the image sensor CCD, it is very easy to restart the camera, and in the end, the focusing operation is repeated and the focus lens is driven electrically. A problem has arisen in that the battery is significantly consumed.

[0004] This invention was made to solve the above-mentioned problems of the prior art, and allows the focusing operation to be performed when the lens cap is attached without affecting the autofocus during normal imaging. It is an object of the present invention to provide an imaging device having an automatic focusing function that stops.

[0005]

[Means for Solving the Problems] Therefore, an imaging device according to the present invention is an imaging device having an automatic focusing function based on a change in the high frequency component of a video signal, and which has iris opening state information from an iris encoder. , the output of the video signal high frequency component from the peak detection circuit, and the automatic gain control information from the video signal control circuit that controls the process circuit that applies gamma correction and automatic gain control to the video signal and generates the video signal. and an autofocus control circuit that controls the focusing operation of the focus lens, and when the iris is open and the automatic gain control is at the maximum, the autofocus control circuit stops driving the focus lens and stops the focusing operation. It is an object of the present invention to achieve the above object by a configuration characterized by the following.

[0006]

[Operation] With the above configuration, the autofocus control circuit determines that the iris is open based on the iris open state information input from the iris encoder, and that the automatic gain control is maximized based on the automatic gain control information input from the video signal control circuit. In this case, the focus lens will stop driving and the focusing operation will be canceled.

[0007] With the above control, there is no problem with normal autofocus imaging, and moreover, the focusing operation is automatically stopped when the lens cap is attached.

[0008] When the lens cap is removed, the iris is no longer open or the automatic gain control is no longer at its maximum, so the autofocus control circuit resumes focusing operation and performs normal autofocus. It becomes possible to take images of

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The imaging apparatus according to the present invention will be described below with reference to embodiments. FIG. 1 is a block diagram showing one embodiment of the present invention. Light from the subject passes through a focus lens 1 and an iris 2 and reaches an image sensor CCD4. CCD
4, the light is photoelectrically converted and amplified by a preamplifier 5. The amplified electrical signal is subjected to gamma correction and automatic amplification gain control (hereinafter referred to as AGC) in the process circuit 6 and output as a video signal.The process circuit 6 also sends the video state to the video signal control circuit 11, Video signal control circuit 11
The video signal to be output is controlled by.

[0010] The output of the process circuit 6 is input to a band pass filter 7 and filtered, and then passed to a gate circuit 8.
can be gated. Then, the peak value of the high frequency component signal gated by the peak detection circuit 9 is held and output to the autofocus control circuit 10.

The autofocus control circuit 10 controls the focus lens 1 by reading the output of the peak detection circuit, the output of the iris encoder 3, and the AGC information of the video signal control circuit 11, that is, a signal indicating the effectiveness of the AGC. Performs autofocus control. The video signal control circuit 11 also controls the iris 2 using the video signal sent from the process circuit 6.

12 is a focus motor driver, and 13 is an iris driver. Reference numeral 14 denotes a focus motor, which drives the focus lens 1 to perform a focusing operation by power supply and control from the focus motor driver 12.

With the above configuration, the autofocus control circuit 1
0 reads the output of the iris encoder 3, which is the iris open state information, and the AGC information of the video signal control circuit 11, and determines and controls the activation of the focusing operation.

FIG. 2 is a starting flowchart of the focusing operation. In step S1, it is determined based on the input from the iris encoder 3 whether the iris 2 is open. If iris 2 is not open, step S
Proceeding to step 4, the restart threshold Th0 is selected and the focusing operation is restarted based on that value. If the iris 2 is open, the process proceeds to step S2, and it is determined whether the AGC effectiveness is at its maximum based on the input from the video signal control circuit 11. If not, the process proceeds to step S4, where the restart threshold Th0 is set. Select and control focus. If the AGC is the maximum, the process advances to step S3, and the focus motor driver 12
The focus motor 14 that drives the distance ring is stopped.

[0015] With the above control, for example, if the search operation is stopped after photographing a low-contrast subject, if the fluctuation range of the high frequency component that is the focus signal due to panning becomes equal to or greater than the restart threshold Th0, the focusing operation will be restarted. I do. Note that the restart threshold Th0 is set to a value such that large panning causes restart.

Furthermore, when determining whether the lens cap is attached, that is, when the AGC is at its maximum effectiveness and the iris is open, the focus motor is forcibly stopped regardless of the focus signal (high frequency component). With this kind of control, when the lens cap is attached, even if there is a fluctuation in the focus signal due to noise caused by AGC or uneven dark current, the lens cap prevents light input to the CCD and AE (automatic exposure control) is activated. As long as the AGC is at its maximum and the iris is open, the focusing operation drive of the focus lens 1 will not be restarted, and the battery will not be consumed by unnecessary focusing operations when the lens is capped.

[0017]

As explained above, according to the present invention, the iris is open based on the iris open state information input from the iris encoder, and the automatic gain control is performed based on the automatic gain control information input from the video signal control circuit. When is at the maximum, driving of the focus lens is stopped and focusing operation is stopped.

[0018] When the lens cap is removed,
When the iris is no longer open or the automatic gain control is no longer at its maximum, the autofocus control circuit restarts the focusing operation and normal autofocus imaging becomes possible.

[0019] With the above control, the long focal length lens,
Automatic focus control allows you to focus and capture images even when the camera is out of focus due to panning. What's more, when a lens cap is attached, the iris is open and the automatic gain control is at its maximum, so it detects that the lens cap is attached and automatically stops the focusing operation. Restarting can be reliably prevented, and since movement of the focus lens is stopped without a search operation at the same time as attachment of the lens cap is detected, battery consumption due to unnecessary driving of the focus lens can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment.

FIG. 2 is a focusing operation startup flowchart of one embodiment.

[Explanation of symbols]

1 Focus lens 2 Iris 3 Iris encoder 4 Image sensor (CCS) 6 Process circuit 9 Peak detection circuit 10 Autofocus control circuit 11 Video signal control circuit 12 Focus motor driver 14 Focus motor

Claims (1)

[Claims] 1. An imaging device having an automatic focusing function based on a change in a high frequency component of a video signal, comprising: iris opening state information from an iris encoder; output of a high frequency component of the video signal from a peak detection circuit; An autofocus control circuit that controls the focusing operation of a focus lens by inputting automatic gain control information from a video signal control circuit that controls a process circuit that applies gamma correction and automatic gain control to a video signal and generates a video signal. An imaging device comprising: an autofocus control circuit that stops driving the focus lens and stops focusing operation when the iris is open and the automatic gain control is at a maximum.