JP2622616B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an imaging device.

[Conventional technology]

FIG. 2 is a block diagram showing the operation principle of a conventional automatic focusing apparatus disclosed in, for example, Japanese Patent Publication No. 39-5265, wherein (1) is a lens, and (5) is a lens (5). A motor connected to the optical focusing mechanism of 1),
(6) is a drive circuit for driving the motor (5), (2)
Denotes an image sensor that receives light passing through the lens (1) and converts the light into an electric signal; (3) a signal processing circuit that converts an output signal of the image sensor (2) into a video signal (luminance signal);
(4) detects a signal (focus evaluation value "A") indicating the degree of focus matching from the video signal output from the signal processing circuit (3), and drives the drive circuit ( 6)
And (7) a magnetic recording device for recording a video signal output from the signal processing circuit (3).

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

A lens generally has a low-pass characteristic with respect to a spatial frequency, and a spatial frequency component finer than the resolution of the lens does not pass through the lens. It is also known that when the lens system is out of focus, the pass band for this spatial frequency exhibits a narrower low-pass characteristic.

The light incident through the lens (1) is converted into an electric signal by the image sensor (2), further converted into a video signal (luminance signal) by the signal processing circuit (3), and recorded by the magnetic recording device (7). . When the lens (1) is out of focus, this video signal is also band-limited and exhibits a low-pass characteristic, corresponding to the low-pass characteristic for the spatial frequency of the lens (1). Therefore, the magnitude of the high frequency component in the video signal depends on the degree of focusing of the lens (1),
Since the larger the high-frequency component, the closer to the in-focus state, it is possible to set the magnitude of this high-frequency component to a value representing the degree of focusing (focus evaluation value).

The control circuit (4) adjusts the lens (1) so as to maximize the focus evaluation value (A) and guides the apparatus to focus.

 Next, the above control operation will be described in detail.

Now, assuming that the motor (5) rotates and moves the lens (1) in one direction, if the focus evaluation value (A) increases with the movement of the lens (1), Since the lens (1) is approaching focusing, the control circuit (4) rotates the motor (5) in the same direction with respect to the drive circuit (6) to control the lens (1) so as to continue driving the lens (1). Is output. Conversely, if the focus evaluation value (A) decreases with the movement of the lens (1), the lens (1) has moved away from the focus, and the control circuit (4) uses the drive circuit (6). ), The motor (5) is reversed, and the lens (1) is turned in the opposite direction.
And outputs a control signal to drive.

In this way, the control circuit (4) eventually works to guide the focus evaluation value (A) to the maximum. Focus evaluation value (A)
At the maximum point, the lens (1) is in focus,
Thus, in this conventional example, an automatic focusing apparatus is configured.

[Problems to be solved by the invention]

However, the conventional auto-focusing device of the image pickup apparatus has a problem that the noise component of the focus evaluation value causes an erroneous determination of a focus state other than the true focus state, and magnetic recording is performed as it is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an image pickup apparatus capable of reliably performing a focusing operation during recording of a magnetic recording apparatus.

[Means for solving the problem]

An imaging apparatus according to the present invention includes an imaging unit that photoelectrically converts light from a subject into an image, an optical focus adjustment unit that adjusts a focus of light from the subject incident on the imaging unit, and an image output from the imaging unit. Processing means for processing a signal to be converted into a video signal, and driving means for detecting the state of focus alignment based on the video signal obtained by the signal processing means and driving the optical focus adjustment means for achieving a focused state. Recording means for recording the video signal, and when a recording start signal indicating the start of recording is output from the recording means, the operation for focusing the driving means is initialized, and the recording start signal is output. And control means for controlling the driving means to start driving the driving means when the driving is not performed.

[Action]

In the present invention, the imaging unit captures an image of a subject, converts a signal output from the imaging unit into a video signal, and records the video signal in the recording unit. The focus adjustment state is detected by the video signal, and the optical focus adjustment means is driven by the drive means so as to achieve the focused state. When a recording start signal is output from the recording unit, an operation for focusing the driving unit is initialized. When the recording start signal is not output, the driving unit is driven without initializing the operation for focusing the driving unit.

Thereby, when recording an image, it is possible to record the image in a state where the focus is surely achieved.

(Example of the invention)

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to an embodiment of the present invention. In FIG. 1, (1) is a lens, (5) is a motor connected to a focus adjustment mechanism of the lens (1), (6) is a drive circuit for driving the motor (5),
(2) an image sensor that receives light passing through the lens (1) and converts the light into an electric signal; and (3) a signal processing circuit that converts a signal of the image sensor (2) into a video signal (luminance signal). ,
(4) detects a focus evaluation value (A) indicating the degree of focus matching from the video signal output from the signal processing circuit (3), and controls the drive circuit (6) so as to guide the focus evaluation value (A) to the maximum. (7) is a magnetic recording device for recording a video signal output from the signal processing circuit (3), and (R) is a signal indicating the start of magnetic recording output from the magnetic recording device (7). It is.

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

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

The operation of the embodiment when there is no recording start signal (R) is not different from the above-mentioned conventional example. That is, the light incident through the lens (1) is
Is converted into an electric signal, and further converted into a video signal (luminance signal) by the signal processing circuit (3) and recorded by the magnetic recording device (7).

The magnitude of the high-frequency component in the video signal is determined by the degree of focusing of the lens (1), and the larger the high-frequency component, the closer to the in-focus state. (Focus evaluation value A), and the control circuit (4) adjusts the lens (1) so as to maximize the focus evaluation value (A) and guides the apparatus to focus.

That is, now the motor (5) rotates and the lens (1)
Considering the case where is moved in one direction, if the focus evaluation value (A) increases with the movement of the lens (1), the lens (1) is approaching the focus. The control circuit (4) rotates the motor (5) in the same direction with respect to the drive circuit (6), and outputs a control signal so as to continue driving the lens (1). Conversely, the focus evaluation value ( If A) decreases as the lens (1) moves, the control circuit (4) controls the drive circuit (6) by using the motor (5) because the lens (1) has moved away from focusing. And outputs a control signal to drive the lens (1) in the opposite direction.

In this way, the control circuit (4) eventually works to guide the focus evaluation value (A) to the maximum. Focus evaluation value (A)
At the maximum point, the operation until the lens (1) is brought into a focused state is not different from the conventional example.

By the way, there are various noise factors for the focus evaluation value (A). For example, one of the large noise factors changes the direction of the imaging device (panning).
This is the change of the subject itself in such a case. That is, even when the video signal changes due to a change in the position of the subject, the focus evaluation value (A) naturally changes, but such an automatic focus matching device that operates based on the focus evaluation value (A) In this case, a change in the focus evaluation value (A) due to panning cannot be distinguished from a change in the focus evaluation value (A) due to the focus matching operation, and the maximum point of the focus evaluation value (A) is erroneously recognized, and focus adjustment is performed. An erroneous operation such as stopping at an out-of-point focus adjustment position may occur.

On the other hand, the imaging apparatus usually starts its operation before the magnetic recording apparatus (7) to check (monitor) an image in many cases. Since it is a common usage mode to adjust the focus before the start of magnetic recording, it is more convenient in actual use to perform the automatic focus adjustment operation even during the video monitor operation. However, for this reason, the automatic focusing apparatus may malfunction due to erroneous recognition of the maximum point of the focus evaluation value (A) during the monitor operation.

The magnetic recording apparatus (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, the control circuit (4) initializes the focus adjustment operation or starts driving the focus adjustment mechanism. When the focus adjustment operation is initialized, the motor (5) rotates to move the lens (1) in one direction, and the focus evaluation value (A) increases with the movement of the lens (1). If the focus evaluation value (A) decreases with the movement of the lens (1), the motor (5) is rotated in the reverse direction to rotate the motor (5) in the same direction. The operation of maximizing the evaluation value (A) is performed again. The drive of the focus adjustment mechanism is started by the input of the recording start signal (R) without initializing the focus matching operation, and the focus evaluation value (A) before the start of the drive and the focus evaluation value (A) after the drive are started.
Can be confirmed that the stop is stable at the maximum point of the focus evaluation value (A) without malfunction due to noise.

With this configuration, correct focus adjustment is performed at the start of magnetic recording even if the focus alignment operation malfunctions before the start of magnetic recording. The control circuit (4) sends the recording start signal (R) about one second before the start of magnetic recording.
In this case, the focus adjustment operation has been completed at the start of the actual magnetic recording, and stable video recording can be performed. Generally, in a magnetic recording apparatus that performs so-called splicing, a reproduction operation is temporarily performed for a short period of time before the start of magnetic recording. Therefore, the start of the reproduction operation can be used as a recording start signal (R).

As described above, in this embodiment, since the focus matching operation is initialized based on the recording start signal from the magnetic recording device to ensure the focus matching again, a malfunction may occur at least at the start of magnetic recording. An imaging device with less noise can be obtained.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to obtain an imaging device that does not cause a malfunction in focusing at the time of starting recording of a video image. By adjusting it, it has an excellent effect of recording a video with high image quality.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an imaging apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of an example of a conventional automatic focusing apparatus. (1) ... lens, (2) ... imaging element, (4) ... control circuit, (7) ... magnetic recording device, (R) ... recording start signal. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] An imaging means for photoelectrically converting light from a subject into an image, an optical focus adjusting means for adjusting a focus of light from the subject incident on the imaging means, and a signal outputted from the imaging means. Signal processing means for processing to convert the image into a video signal; driving means for detecting the state of focus adjustment based on the video signal obtained by the signal processing means, and driving the optical focus adjustment means to achieve a focused state; Recording means for recording a video signal, when a recording start signal indicating the start of recording is output from the recording means, performs initialization of the operation for focusing the driving means, when the recording start signal is not output, A control unit for controlling the driving unit to start driving the driving unit.