JPH11265025A - Electronic still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To branch an optical path for autofocusing at a position not related to the thickness of a camera and to restrain the thickness of a camera body equal to that of a single lens reflex camera by providing a detection system for autofocusing which is positioned in the optical path of a reduction optical system with a means for branching a part of luminous flux. SOLUTION: A finder mirror 1 guides at least a part of a photographing optical system to a finder for confirming the angle of view at the time of non- photographing. An image pickup mirror 6 enters at least a part of space where the mirror 1 is retreated and which is occupied by the mirror 1 at the time of photographing and guides the luminous flux in a different direction from the mirror 1. An image-formation lens system 10 forming a photographic image on a CCD 12 is arranged in the direction of the luminous flux guided by the mirror 6 when the mirror 6 is in a photographing state. In the optical path, a part of the luminous flux is branched to the detection system for autofocusing and the luminous flux transmitted through a reflection mirror 9 is guided to an AF unit 15 by a sub mirror 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electronic still camera using a reduction optical system.

[0002]

2. Description of the Related Art In recent years, many electronic still cameras for recording a still image / image signal captured by an electric image pickup device such as a CCD on a semiconductor memory, a magnetic recording medium, or the like are commercially available.

Further, for a single-lens reflex camera for silver halide photography,
Many interchangeable lenses are widely used. If this single-lens reflex camera interchangeable lens can be used for electronic still cameras,
This is a great user benefit.

Most cameras in recent years have been autofocused, and the autofocus function can be said to be an essential function now.

[0005] A system using an interchangeable lens for a single-lens reflex camera for an electronic still camera has been released or proposed as an electronic still camera using an image pickup element having an image pickup size close to that of a silver halide photograph, and a small one. In order to use an imaging device of a size, an electronic still camera in which a reduction optical system is arranged behind the film surface of a conventional silver halide camera, using a half mirror and a concave mirror shown in JP-A-7-87369, There is an electronic still camera or the like that employs folding in a mirror box.

Further, the present applicant has disclosed an electronic type in which the optical path is distributed in the single-lens reflex type mirror box by the operation of two movable mirrors in the past according to the case of finder observation and the case of shooting. A still camera is proposed.

[0007]

However, a conventional electronic still camera using an interchangeable lens for a single-lens reflex camera has the following disadvantages. That is, in the electronic still camera using the imaging size of the above-described imaging device, which is close to a silver halide photograph, since the imaging device is created by a semiconductor process, when the size becomes close to the silver halide photograph, it becomes very expensive, It cannot be used for general-purpose electronic still cameras. In an electronic still camera in which a reduction optical system is disposed behind the film surface of a conventional silver halide camera in order to use a small-sized image pickup device, the reduction optical system is disposed behind the film surface. However, there is a problem that the thickness of the film increases and the holding property deteriorates. The electronic still camera disclosed in Japanese Patent Application Laid-Open No. 7-87369 has a problem that an autofocus mechanism cannot be incorporated. The electronic still camera proposed in the past by the present applicant has a movable mirror for guiding light to the viewfinder as a half mirror, and an AF single-lens reflex camera having an AF sensor at a position where a film exists. By implementing the autofocus function, there is a disadvantage that the thickness of the body is increased by the thickness of the AF sensor as compared with a conventional AF single-lens reflex camera.

The present invention has been made in view of the above points, and enables a small-sized image pickup device to be used in a conventional electronic still camera using an interchangeable lens for a single lens reflex camera, It is an object of the present invention to provide an electronic still camera capable of auto-focusing with a thickness suppressed to be equal to a conventional single-lens reflex camera.

[0009]

The present invention can solve the above-mentioned problems by providing the following constitution.

(1) An image pickup device for photoelectrically converting a subject image formed by a photographing optical system into an electric signal, and a signal processing means for generating a video signal from the electric signal obtained by the image pickup device. In an electronic still camera, a first movable mirror that guides at least a part of a photographing optical system to a viewfinder for confirming an angle of view during non-photographing, the first movable mirror retracts during photographing, and is occupied by the first movable mirror. A second movable mirror that enters at least a part of the space that has been guided and guides a light beam in a direction different from that of the first movable mirror; and when the second movable mirror enters a shooting state, the second movable mirror In an electronic still camera including a reduction optical system that is arranged in a direction of a light flux guided by a mirror and forms a captured image on the image pickup device, a detection system for autofocus positioned in an optical path of the reduction optical system is used. An electronic still camera provided with means for branching a part of a light beam.

(2) In the electronic still camera described in the above item (1), when the second movable mirror is in a photographing state, an optical path is guided to a lower side of the camera, and the reduction optical system is provided below the camera. The third to bend parallel
Is provided in the reduction optical system, and the third mirror is constituted by a half mirror, and is arranged so as to guide the light transmitted through the third half mirror to the auto-focus detection element. Electronic still camera.

[0012]

Embodiments of the present invention will be described below.

(First Embodiment) FIGS. 1 to 5 show a first embodiment according to the present invention.

FIG. 1 is a perspective view showing a main configuration of a digital still camera according to the present embodiment. In this FIG.
The figure shows a state in which the interchangeable lens is removed, and 1 is a finder mirror, which is in a retracted state in this figure.

The finder mirror 1 is movable and is driven by an actuator 2. Reference numeral 3 denotes a finder screen, on which a condenser lens is integrally formed like a Fresnel lens. Reference numeral 4 denotes a pentaprism, and reference numeral 5 denotes an eyepiece. A finder is formed by the finder screen 3, the pentaprism 4, and the eyepiece 5.

Reference numeral 6 denotes an imaging mirror, and 7 denotes an imaging mirror driving actuator. In this drawing, the imaging mirror is in an imaging state.

8 is a field lens, 9 is a reflection mirror,
10 is an imaging lens system, 11 is an optical low-pass filter,
Reference numeral 12 denotes a CCD, and 13 denotes an aperture shutter unit.

The vicinity of the center of the reflection mirror 9 is constituted by a half mirror.

Reference numeral 14 denotes a sub-mirror, and 15 denotes an AF unit.
It is led to the F unit.

FIG. 2 is an explanatory view of the configuration of the digital still camera of FIG. 1 as viewed from the back, and FIGS. 3 and 4 are views as viewed from the side, with an interchangeable lens mounted.

2 to 4 corresponding to those in FIG. 1 are denoted by the same reference numerals.

FIG. 3 shows a viewfinder observation, and FIG. 4 shows an image pickup and AF.

The finder mirror 1 and the imaging mirror 6 are
At the time of finder observation, the luminous flux from the photographing lens is set to the position shown in FIG.

During imaging and AF, the lens is set at the position shown in FIG. 4, and the light beam from the lens is guided to the imaging and AF system below the camera.

An interchangeable lens 16 is an interchangeable lens used in an autofocus single-lens reflex camera.

The interchangeable lens 16 incorporates a lens driving motor 17, an electromagnetically driven aperture 18, and a lens control circuit. Focus control and aperture driving are performed by control from the camera body.

Reference numeral 20 denotes a camera control circuit. The camera control circuit 20 and the lens control circuit 1
9 is electrically connected by mount contacts 21 and 22.

Reference numeral 23 denotes a photometric unit. Based on the photometric result of the photometric unit 23, the shutter speed and the aperture value are temporarily determined based on a predetermined program diagram.

The determination of the shutter speed and the final aperture value will be described later.

Reference numeral 24 denotes an image capturing and storing circuit.

The operation of the electronic still camera based on the above configuration and the photographing sequence based on the flowchart of FIG. 5 will be described.

In the photographing standby state, the camera is in the state shown in FIG. 3 and the finder mirror is down.

When a shutter button (not shown) is pressed, a photographing sequence is started, and the flow advances to step S101.

In step S101, the light amount is detected by the photometric unit 23, and the shutter speed and the aperture value are temporarily determined with reference to a predetermined program chart. In step S102, the finder mirror 1 is driven by the actuator 2 to the retracted position shown in FIG. In step S103, the imaging mirror 6 is driven by the imaging mirror driving actuator 7 to the position shown in FIG. 4, which is the imaging position. In step S104, the process waits until the bound of the imaging mirror 6 stops.

In this embodiment, the timer is determined.

The operations of the following steps S105 to S109 and steps S110 to S112 are performed with time overlap. By overlapping in time, the effect of reducing the shutter time lag can be obtained.

In step S105, the charge on the CCD 12 is discarded, and the camera is ready for imaging. In step S106, the aperture shutter unit 13 is driven, and the exposure operation is performed by controlling the shutter speed and the aperture value temporarily determined by the photometry in S101. In step S107, electric charges are taken out from the CCD 12 and temporarily stored in a memory. Since the signal taken in here is pre-exposure data, the data can be thinned out as necessary. In step S108, the aperture value and the shutter speed at the time of the main exposure are determined from the pre-exposure data. In step S109, a white balance is determined from the pre-exposure data.

Here, the contents of steps S110 to S112 operating in parallel with steps S105 to S109 will be described.

In step S110, a signal is extracted from the AF unit 15, and a required driving amount of the lens is obtained by a predetermined calculation.

This AF system uses a phase difference AF system widely used in an autofocus single-lens reflex camera.

In step S111, the lens extension amount is sent to the lens control circuit 19, and the lens is driven by a predetermined amount by the lens driving motor 17. In step S112, defocus detection is performed again. If the defocus amount is within the focusing range, the focusing operation ends, and the flow advances to the next step S113. If the defocus amount is equal to or more than the predetermined amount, the lens extension amount is calculated, and step S111 is performed.
Return to

In the above sequence, the determination of the final exposure amount and the focus adjustment are completed.

In step S113, the electric charge of the CCD 12 is discarded, and the camera is ready for imaging. In step S114, the aperture shutter unit 13 is driven, and an exposure operation is performed with the aperture value and the shutter speed determined in S108. Since the final exposure is determined from the data temporarily exposed in this manner, the exposure accuracy is improved. In step S115, the electric charge is taken out from the CCD 12, and is temporarily stored in the memory in the image taking / storing circuit 24. In step S116, the imaging mirror 6 and the finder mirror 1 are returned to the positions shown in FIG. In step S117, image processing such as matrix processing, white balance processing, and gamma correction processing is performed on the image data captured in the memory of the image capturing storage circuit 24. In step S118, the data formed as one color image by the image processing in step S117 is compressed.

In this embodiment, JPEG compression using DCT and Huffman coding is performed.

In the next step S119, the compressed data is written to a nonvolatile memory for storage. Thus, the photographing sequence ends.

In this embodiment, the space in the mirror box of the conventional interchangeable lens single-lens reflex camera is effectively used, and the optical path branching to the autofocus detection system is performed in the middle of the optical path to the imaging system. With this configuration, the electronic still camera body can be made thinner and autofocus can be performed.

(Second Embodiment) FIG. 6 is a perspective view showing a main structure of a second embodiment according to the present invention.

The second embodiment shows a configuration applied to a combined camera of an electronic still camera and a silver halide camera. Further, since the second embodiment is similar in many parts to the first embodiment, corresponding parts are denoted by the same reference numerals and description thereof will be omitted.

In this embodiment, a shutter 30 and a film 31 are arranged at the same position as that of a conventional single-lens reflex camera.

A changeover switch (not shown) switches between electronic still photography and silver halide photography to perform a photography operation.

When taking a silver halide photograph, the viewfinder mirror 1 and the imaging mirror 6 are set to the retracted positions (the state shown in FIG. 6).

According to this embodiment, a thin composite camera for electronic still and silver halide photography can be realized.

[0053]

As described above, the first embodiment according to the present invention is described.
According to the embodiment of the present invention, an image pickup device that photoelectrically converts a subject image formed by a photographing optical system into an electric signal, and a signal processing unit that generates a predetermined video signal from the electric signal obtained by the image pickup device Electronic still camera with
The first movable mirror that guides at least a part of the light beam from the photographing optical system to the viewfinder for confirming the angle of view during non-photographing and the first movable mirror retracted during photographing and were occupied by the first movable mirror. A second movable mirror that enters at least a part of the space and guides the light beam in a direction different from the first movable mirror;
When the second movable mirror enters a shooting state, the electronic still camera includes a reduction optical system that is arranged in a direction of a light beam guided by the second movable mirror and forms a captured image on the image sensor. By providing a means for branching a part of the light beam to the detection system for auto focus located in the optical path of the optical system, the optical path branch for auto focus can be branched at a position unrelated to the thickness direction of the camera,
The effect is that the thickness of the body can be reduced to the same level as the conventional single-lens reflex camera.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main configuration of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the back surface configuration of the first embodiment of the present invention.

FIG. 3 is an explanatory side view illustrating a configuration of the first embodiment of the present invention during finder observation.

FIG. 4 is an explanatory side view illustrating a configuration of the first embodiment of the present invention during imaging.

FIG. 5 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 6 is a perspective view showing a main configuration of a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 finder mirror 2 actuator 3 finder screen 4 pentaprism 5 eyepiece 6 imaging mirror 7 actuator for driving imaging mirror 8 field lens 9 reflection mirror 10 imaging lens system 11 optical low-pass filter 12 CCD 13 aperture shutter unit 14 sub-mirror 15 AF unit

Claims (2)

[Claims] 1. An electronic device comprising: an image pickup device that photoelectrically converts a subject image formed by a photographing optical system into an electric signal; and a signal processing unit that generates a video signal from the electric signal obtained by the image pickup device. In a still camera, a first movable mirror that guides at least a part of an imaging optical system to a viewfinder for confirming an angle of view during non-shooting, and a first movable mirror that retracts during shooting and are occupied by the first movable mirror. A second movable mirror that enters at least a part of the space and guides the light beam in a direction different from that of the first movable mirror, and the second movable mirror when the second movable mirror is in a shooting state. In an electronic still camera including a reduction optical system that is arranged in the direction of the light flux guided by the imaging device and forms a captured image on the imaging device, the detection of the light flux is performed by an autofocus detection system that is located in the optical path of the reduction optical system. An electronic still camera, comprising means for branching a part. 2. The electronic still camera according to claim 1, wherein when the second movable mirror is in a photographing state, an optical path is guided to a position below the camera, and the reduction optical system is arranged in parallel with the lower surface of the camera. A third mirror, which is bent in such a manner as to be included in the reduction optical system, wherein the third mirror is constituted by a half mirror, and is arranged so as to guide light transmitted through the third half mirror to a detection element for autofocus. An electronic still camera characterized in that: