JPH0411232A - Electronic still camera incorporating stroboscope - Google Patents

Abstract

PURPOSE:To control focusing with simple constitution by setting the focusing ring of a lens at a specified position previously set by an autofocusing mechanism when photographing is executed by using a stroboscope. CONSTITUTION:Image light formed into an image on the image pickup surface of a soild-state image pickup element 2 through a photographing lens 1 is converted to an electric image-pickup signal by the element 2. The image-pickup signal is converted to a specified video signal by an image-pickup signal processing circuit 3 and supplied to a recording circuit 4. In such a case, the focusing of the photographing lens 1 is performed by turning the focusing ring attached to the photographing lens 1. When photographing is executed by using the stroboscope, the focusing ring of the lens 1 is set at a specified position previously set by an autofocusing mechanism. Thus, the arrival distance of the light from the stroboscope becomes short and the focusing ring is controlled to obtain a focusing position which is adjusted to the arrival distance of the light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electronic still camera with a built-in strobe.

[Summary of the invention]

The present invention is an electronic still camera with a built-in strobe that performs automatic focus control using an autofocus mechanism. This allows for focus control during shooting.

[Prior Art] Various so-called electronic still cameras that record still images as electrical video signals on magnetic disks have been developed. This electronic still camera requires focus adjustment by moving the focus ring or the like of the photographing lens, like a still camera using a normal silver halide film. In this case, some cameras have an autofocus mechanism that allows automatic focus adjustment. Conventionally, this autofocus mechanism detects the distance from the camera to the subject by some method, and moves the focus ring of the photographic lens in accordance with this distance information.

On the other hand, some video cameras detect focus information for autofocus control from the imaging signal itself and perform autofocus control without detecting distance. That is, when the focus adjustment of the lens is appropriate, the outline of the subject can be photographed clearly, so the image signal contains high frequency components. On the other hand, if the focus adjustment of the lens is not appropriate, the outline of the subject will be blurred and the image signal will not contain high-frequency components. Therefore, by detecting the amount of high-frequency components in the imaging signal, it is possible to detect whether the current focus adjustment state is appropriate or not, and autofocus control is performed.

Here, since the above-mentioned electronic still camera also uses a solid-state imaging device to obtain an electrical imaging signal, like a video camera, focus information for autofocus control is detected from this imaging signal itself. This method can be applied. By applying this autofocus method to electronic still cameras, there is no need to detect the distance from the camera to the subject, and the autofocus mechanism can be configured more easily than in still cameras that use silver halide film.

[Problem to be solved by the invention]

By the way, there are still cameras that have a built-in strobe that allows you to take pictures at night. In the case of conventional cameras with built-in strobes that use silver halide film, the distance to the subject is measured using infrared rays for autofocus control, so even when the subject is dark, such as at night, the distance Can be measured. On the other hand, with the method of detecting information for autofocus control from the image signal itself applied to the electronic still camera described above, if the subject is dark enough to require a strobe, the appropriate level will be reached unless the strobe is used. An image signal cannot be obtained, and the strobe must be fired several times to detect focus information before actually taking a picture.

In this way, firing the strobe many times to take a single photograph with a still camera has the disadvantage of being wasteful due to the lifespan of the flashlight.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic still camera that has a simple configuration and can perform good autofocus control even when using a strobe.

[Means to solve the problem]

For example, as shown in FIG. 1, the present invention is applicable to an electronic still camera with a built-in strobe in which automatic focus control is performed by moving the focus ring of a lens (1) by an autofocus mechanism, when photographing using a strobe. , the focus ring of the lens (1) is set at a predetermined position by an autofocus mechanism.

[Effect]

By doing this, when taking pictures using a strobe, the focus position will be at a fixed position, but when taking pictures using this strobe, the distance that the light from the strobe will reach is short, and the focus position will be adjusted to the distance that the light will reach. By controlling the focus position so that the subject is within the reach of the light from the strobe, it is possible to photograph the subject with good focus adjustment.

[Example] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

In Fig. 1, (1) indicates a photographing lens, and the image light formed on the imaging surface of a solid-state image sensor (2) through this photographic lens (1) is electrically converted into an image by this solid-state image sensor (2). This image signal is converted into a predetermined video signal by an image signal processing circuit (3), and this video signal is supplied to a recording circuit (4). After the recording circuit (4) performs recording processing, the recording video signal is supplied to the magnetic head (5) placed close to the magnetic disk (6), and the recording circuit (4) A video signal of a still image for one field or one frame is recorded.

In this case, the focus of the photographic lens (1) is adjusted by rotating a focus ring attached to the photographic lens, and in this example, this focus adjustment is automatically performed by a lens drive circuit (11), which will be described later. That's what I do. Focus adjustment by this lens drive circuit (11) is performed in two stages. That is, the rotational position of the focus ring that focuses from 3 m to infinity (hereinafter referred to as the long-distance focus position).

) and the rotational position W of the focus ring that focuses from 0.8 m to 3 m (hereinafter referred to as the short-distance focus position).

), two focus positions can be set.

To explain the configuration for performing this focus adjustment, the imaging signal processing circuit (3) supplies the imaging signal to the integrating circuit (8) via the bypass filter (7),
Only the high frequency components of the imaging signal are integrated by an integrating circuit (8). This integrating circuit (8) is a circuit that integrates high-frequency components included in the imaging signal for one screen. Then, the integral value data output by the integrating circuit (8) is supplied to the analog-to-digital converter (9), and after being converted into digital data by the analog-to-digital converter (9), the photographing operation of this camera is controlled. A central control unit (10) is supplied with the information. Then, the central control device (10) discriminates the supplied integral value data and sets the lens drive circuit (10) to a focus position that provides good integral value data.
This lens drive circuit (11) is supplied with a control command to the lens drive circuit (11).
) to drive the focus ring to the specified focus position.

Furthermore, the camera of this example is equipped with a strobe (not shown) so that it can take pictures even when the subject is dark, such as at night. In this case, the attached strobe has a relatively small guide number that allows light to travel up to 3 meters.

In this example, when photographing using a strobe, the central controller (10) controls the lens drive circuit (11) to drive the focus ring to a short distance focus position.

Next, the focus control operation when photographing with the electronic still camera of this example will be explained with reference to the flowchart of FIG.

First, the central control unit (10) determines the brightness of the subject and determines whether a strobe is required for photographing. At this time, when the brightness does not require a strobe, a control command to set the lens drive circuit (11) to a long-distance focus position is transmitted, the focus ring is set to a short-distance focus position, and the focus ring is set to a short-distance focus position. The solid-state imaging device (2) outputs an imaging signal, and the central controller (
10). Next, the lens drive circuit (11
) transmits a control command to set the focus ring to a short distance focus position, sets the focus ring to a short range focus position,
An imaging signal is output from the solid-state imaging device (2) at this short distance focus position, and the central controller (10) determines the integral value H2 of the high frequency component included in the imaging signal at this time. Then, the central controller (10) determines which value is larger between the integral value H at the long-distance focus position and the integral value H2 at the short-distance focus position, and the focus position when the value is larger is determined. A control command is transmitted to the lens drive circuit (11) to put photography into a standby state. At the focus position in this state, it becomes possible to take pictures for recording on the magnetic disk.

By doing so, photography is performed in a state where the focus position is controlled to have a large integral value of high frequency components, and autofocus control is performed based on the imaging signal.

On the other hand, when the brightness is such that a strobe is required, such as at night, it is not possible to detect the above-mentioned integral values H, H2 from the image signal unless the strobe is emitted. When the central controller (10) determines that it is in a state to perform the following, it transmits a control command to the lens drive circuit (11) to set the focus position to a short distance, and sets the focus ring to a focus position of a short distance. Shooting is performed at the focus position of the distance.

By doing this, when taking pictures using a strobe, the focus position is always a short distance focus position, but in this example, the distance of light from the attached strobe is up to 3 m. It is estimated that the subject is within 3 meters from the camera, and it is possible to take pictures with good focus adjustment at a close focus position where the subject is in focus at a distance of 3 meters or less. If the subject is at a distance of 3 meters or more from the camera, the focus position will not be appropriate, but in this case the light from the strobe will not reach the subject, so good photography will not be possible regardless of the focus position. , not a problem.

In the above-described embodiment, a photographic lens having two focus positions, one for a long distance and one for a short distance, was used, but the present invention can also be applied to a camera equipped with a photographic lens that allows more fine adjustment. In this case as well, the focus position may be selected in accordance with the distance traveled by the light from the attached strobe when photographing with the strobe. Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can take various other configurations.

(Effects of the Invention) According to the present invention, focus control during strobe photography can be performed satisfactorily with a simple configuration that detects focus information for autofocus control from the imaging signal itself.Therefore, even during strobe photography, the subject There is no need to measure the distance to the camera, simplifying the configuration of an electronic still camera that performs autofocus control.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a flowchart diagram for explaining an example. (1) is a photographing lens, (2) is a solid-state image sensor, (3) is an image signal processing circuit, (7) is a bypass filter, (8)
is an integrating circuit, (10) is a central control unit, and (11) is a lens drive circuit.

Claims (1)

[Claims] In an electronic still camera with a built-in strobe, where automatic focus control is performed by moving the focus ring of the lens using an autofocus mechanism, when shooting using a strobe, the focus ring of the lens is set in advance by the autofocus mechanism. An electronic still camera with a built-in strobe.