JPH0468675A - Automatic focusing device for image pickup device - Google Patents

Abstract

PURPOSE:To reduce malfunction when starting magnetic recording by initializing a focusing operation based on a recording start signal by a magnetic recording device. CONSTITUTION:When starting magnetic recording, a magnetic recording device 7 inputs a recording start signal R to a control circuit 4. When the signal R is inputted, the circuit 4 initializes the focusing operation. When a motor 5 is rotated to move a lens 1 in one direction and a focus evaluation value A is increased with the movement of the lens 1, the motor 5 is rotated in the same direction and reversely when the evaluation value A is decreased with the movement of the lens 1, the motor 5 is rotated backward so as to guide the eveluation value A into a maximum. Therefore, even when malfunction is generated in the focusing operation before starting magnetic recording, focusing is correctly executed when starting magnetic recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic focusing device used in a video camera.

[Conventional technology]

FIG. 2 is a block diagram showing the operating principle of a conventional automatic focusing device disclosed in, for example, Japanese Patent Publication No. 39-5265. In the figure, (1) is a lens, (5) is a lens ( 1) a motor connected to the optical focusing mechanism;
(6) is a drive circuit that drives the motor (5), (2)
is an image sensor that receives the light □ passed through the lens (1) and converts it into an electrical signal, and (3) is a signal processing circuit that converts the output signal of the image sensor (2) into a video signal (luminance signal). , (4) is a signal indicating the degree of focus matching (focus evaluation value "A") from the video signal output from the signal processing circuit (3).
), and the above drive circuit (
6) is a control circuit that controls the signal processing circuit (7), and (7) is the signal processing circuit that controls the signal processing circuit (3).
This is a magnetic recording device that records video signals output by

Next, the operation of the above configuration will be explained.

Lenses generally have low-pass characteristics with respect to spatial frequencies, and spatial frequency components finer than the resolution of the lens do not pass through the lens. Furthermore, it is known that when the lens system is out of focus, the passband for this spatial frequency exhibits an even narrower low-pass characteristic.

The light incident through the lens (1) is converted into an electrical signal by the image sensor (2), and further processed by the signal processing circuit (3).
The signal is converted into a video signal (luminance signal) by a magnetic recording device (7), and recorded by a magnetic recording device (7). When the lens (1) is not in focus, this video signal is also band-limited and exhibits a low-pass characteristic, corresponding to the low-pass characteristic of the lens (1) with respect to the spatial frequency. Therefore, the magnitude of the high frequency component in the video signal is determined by the degree of focus of the lens (1), and the larger the high frequency component is, the closer to the in-focus state it is. It can be a value representing the degree of focus (focus evaluation value).

The control circuit (4) adjusts the lens (1) to bring the device into focus so that the focus evaluation value (A) becomes maximum.

child Next, the above control operation will be explained in detail.

Now, considering the case where the motor (5) rotates and moves the lens (1) in one direction, if the focus evaluation value (A) increases as the lens (1) moves, then Lens (1)
is approaching focus, the control circuit (4) outputs a control signal to the drive circuit (6) to rotate the motor (5) in the same direction and continue to drive the lens (1).

Conversely, if the focus evaluation value (A) decreases as the lens (1) moves, the lens (1) is moving away from the focus point, so the control circuit (4) ) and outputs a control signal to drive the lens (1) in the opposite direction.

In this way, the control circuit (4) eventually controls the focus evaluation value (
Work to maximize A). At the maximum point of the focus evaluation value (A), the lens (1) is in a focused state, and in this way, this conventional example constitutes an automatic focusing device.

[Problem to be solved by the invention]

However, the conventional automatic focusing device of an imaging device has a problem in that noise components in the focus evaluation value cause a misjudgment of an in-focus state at a point other than the true in-focus point, and the in-focus state is recorded as is.

The present invention has been made to solve the above-mentioned problems, and in particular, it is an object of the present invention to provide an automatic focusing device that can reliably perform focusing operations during recording in a magnetic recording device. do.

[Means for Solving the Problems] In order to achieve the above object, a control circuit for an automatic focusing device according to the present invention inputs a signal indicating the start of a recording operation of a magnetic recording device, and thereby controls the focusing operation. Initialize the camera to ensure focus, or adjust the optical focus adjustment mechanism and check the focus state.
The configuration is such that focus alignment can be reliably obtained at least at the start of the magnetic recording operation.

[Operation] The control circuit in the automatic focusing device of the imaging device according to the present invention initializes the focusing operation by a signal indicating the start of the recording operation output from the magnetic recording device, or
Drive the motor to adjust the optical focus and confirm that it is in focus.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of an automatic focusing device for an imaging device according to an embodiment of the present invention, in which (1) is a lens, and (5) is a focal point 714 of the lens (1).
A motor connected to the M mechanism, (6) a drive circuit that drives the motor (5), (2) an image sensor that receives light passing through the lens (1) and converts it into an electrical signal, and (3) a drive circuit that drives the motor (5). A signal processing circuit that converts the signal of the image sensor (2) into a video signal (luminance signal), and (4) a focus evaluation that indicates the degree of focus matching from the video signal output from the signal processing circuit (3). A control circuit that detects the value (A) and controls the drive circuit (6) so as to maximize it; (7) is a magnetic recording device that records the video signal output from the signal processing circuit (3); (R) is a signal indicating the start of magnetic recording output by the magnetic recording device (7).

Next, the operation of the above configuration will be explained with reference to FIG.

In FIG. 1, (R) is a signal indicating the start of magnetic recording output by the magnetic recording device (7). Generally, when magnetic recording is started by operating the magnetic recording device (7), the recording start signal ( R) is output.

The operation of the embodiment when there is no recording start signal (R) is no different from the conventional example described above. That is, the light incident through the lens (1) is converted into an electrical signal by the image sensor (2), Furthermore, a signal processing circuit (3
) indicates that the video signal (luminance signal) is close to a linear state, so the magnitude of this high frequency component is set as a value representing the degree of focus (focus evaluation value A), and the control circuit (4) Focus evaluation value (A) leads to focus.

In other words, if we consider the case where the motor (5) is rotating and moving the lens (1) in one direction, the focus evaluation signal is output, and conversely, the focus evaluation value (A) is , decreases with the movement of the lens (1), the lens (1) is moving away from focus, so the control circuit (4) controls the drive circuit (6).
Rotate the motor (5) in the opposite direction and move the lens (
In this way, the control circuit (4) outputs the control signal to drive the focus evaluation value (A) to the maximum. At the maximum point of the focus evaluation value (A), the operation of the lens (1) until it comes into focus is no different from the conventional example.

Incidentally, there are various noise factors for the focus evaluation value (A), and one of the major ones is, for example, a change in the subject itself when changing the direction of the imaging device (panning). In other words, if the video signal changes due to a change in the position of the subject, the focus evaluation M (A) will naturally change, but the focus evaluation value (
In such an automatic focusing device that operates based on A), changes in focus evaluation value (A) due to panning and changes in focus evaluation value (A) due to focus adjustment cannot be distinguished, and the focus evaluation value ( The maximum point in A) may be misrecognized, resulting in a malfunction such as stopping at a focus adjustment position that is out of focus matching point.

On the other hand, the imaging device usually starts operating before the magnetic recording device (7) to check (monitor) the image, and the normal usage is to adjust the focus before starting magnetic recording. For this reason, it is more convenient for camera use to perform automatic focus adjustment even while video is being monitored. However, for this reason, during the monitoring operation, the automatic focusing device may malfunction due to erroneous recognition of the maximum point of the above-mentioned focus evaluation value (A).

The magnetic recording device (7) in this embodiment inputs a recording start signal (R) to the control circuit (4) at the start of magnetic recording. When the recording start signal (R) is input manually, the control circuit (4) initializes the focus alignment operation or starts driving the focus alignment mechanism. When the focus alignment operation is initialized, the motor [5] rotates and moves the lens (1) in one direction, and the focus evaluation value (A) increases as the lens (1) moves. If so, rotate the motor (5) in the same direction, and conversely, if the focus evaluation value (A) decreases as the lens (]) moves, rotate the motor (5) in the opposite direction to The operation to maximize the evaluation value (A) is performed once again. The recording start signal (R
) by starting the focus adjustment mechanism and comparing the focus evaluation value (A) before the start of driving with the focus evaluation value (A) after driving, the focus evaluation value can be determined without noise or malfunction. It can be confirmed that the vehicle has stopped stably at the maximum point (A).

With this configuration, even if the focus adjustment operation malfunctions before the start of magnetic recording, correct focus adjustment will be performed at the start of magnetic recording. In addition, a recording start signal (R
) is set to be input to the control circuit (4) about 1 second before the start of magnetic recording, the focus alignment operation will be completed by the time the actual magnetic recording starts, and stable video recording will be possible. becomes. In a magnetic recording device that performs so-called linking operation, generally a reproducing operation is performed for a short period of time, so the start of this reproducing operation can also be used as a recording start signal (R).

In this way, in this embodiment, the focus alignment operation is initialized based on the recording start signal from the magnetic recording device to ensure focus alignment again, so that there is no possibility of malfunction at least at the start of magnetic recording. It is possible to obtain an autofocusing device with less

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an automatic focusing device that is unlikely to malfunction at least at the start of magnetic recording, and is effective in automatically adjusting the focus to the optimum position in a video camera. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an automatic focusing device for an imaging apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of an example of a conventional automatic focusing device. (1)...Lens, (2)...Image sensor, (4)...
...Control circuit, (7)...Magnetic recording device, (R)...
- Recording start signal. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) An automatic system that detects a signal indicating the degree of focus alignment from a video signal obtained from an image sensor equipped with a lens having an optical focus adjustment mechanism, and drives the optical focus adjustment mechanism to maximize the signal. In an automatic focusing device of an imaging device adopting a focusing method, when used in combination with a magnetic recording device for video signals, the operation of the automatic focusing device is initialized by a signal indicating the start of recording of the magnetic recording device. An automatic focus adjustment device for an imaging device, characterized in that the automatic focus adjustment device for an imaging device is configured to start driving the optical focus adjustment mechanism.