Digital camera system, camera body of digital camera, and interchangeable lens Number:7,435,020 from the United States Patent and Trademark Office (PTO) owispatent A camera system according to the present invention includes an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, the image circle being set larger than the imaging range to include the imaging range therein, a mount portion to which the interchangeable lens is mounted, and an opening portion having an opening for allowing luminous flux from the interchangeable lens to pass through, being located at a position spaced from the imaging surface by a predetermined distance, wherein the size of the opening of the opening portion is equal to or larger than a square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening of the opening portion, and the angle .theta. satisfies: 12 degrees.ltoreq..theta., wherein a distance between the opening of the opening portion and the imaging surface, herein referred to as flange back (FB), is: 35 mm.ltoreq.FB.ltoreq.50 mm.<H interchangeable, digital, Digital, camera, , 7435020.html, Patent, pto, 7435020

Title: Digital camera system, camera body of digital camera, and interchangeable lens

Abstract: A camera system according to the present invention includes an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, the image circle being set larger than the imaging range to include the imaging range therein, a mount portion to which the interchangeable lens is mounted, and an opening portion having an opening for allowing luminous flux from the interchangeable lens to pass through, being located at a position spaced from the imaging surface by a predetermined distance, wherein the size of the opening of the opening portion is equal to or larger than a square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening of the opening portion, and the angle .theta. satisfies: 12 degrees.ltoreq..theta., wherein a distance between the opening of the opening portion and the imaging surface, herein referred to as flange back (FB), is: 35 mm.ltoreq.FB.ltoreq.50 mm.

Patent Number: 7,435,020 Issued on 10/14/2008 to Kawai, et al.

Inventors: Kawai; Sumio (Hachioji, JP), Ogata; Yasuzi (Tokyo, JP)
Assignee: Olympus Corporation (Tokyo, JP)

Appl. No.: 11/125,428

Filed: May 10, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10465410	Jun., 2003	6910814

Foreign Application Priority Data


Jun 12, 2003 [JP]			2003-168383

Current U.S. Class: 396/529 ; 348/360; 348/376; 396/535

Current International Class: G03B 17/02 (20060101)

Field of Search: 396/529,535 348/294,335,373,376

References Cited [Referenced By]

U.S. Patent Documents


4733258	March 1988	Kojima et al.
5381176	January 1995	Tanabe et al.
6463222	October 2002	Ito et al.
6742943	June 2004	Ushiro
6910814	June 2005	Kawai et al.
2002/0025164	February 2002	Satoshi

Foreign Patent Documents


0 541449	May., 1993	EP
05 130 469	May., 1993	JP
06 037 289	Feb., 1994	JP
11 088 783	Mar., 1999	JP
2000 196953	Jul., 2000	JP
2001-59988	Mar., 2001	JP
2003 158 666	May., 2003	JP
2003 134390	May., 2003	JP
2003-134390	May., 2003	JP
2003-158666	May., 2003	JP

Primary Examiner: Perkey; W. B.
Attorney, Agent or Firm: Volpe and Koenig P.C.

Claims

What is claimed is:

1. A camera body of digital camera to which an interchangeable lens having a predetermined image circle is removably mounted, the camera body comprising: an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, the image circle being set larger than the imaging range to include the imaging range therein; a mount portion to which the interchangeable lens is mounted; an opening portion having an opening for allowing luminous flux from the interchangeable lens to pass through, being located at a position spaced from the imaging surface by a predetermined distance; and wherein the size of the opening of the opening portion is equal to or larger than a square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening of the opening portion, and the angle .theta. satisfies: 12 degrees<.theta., wherein the distance between the opening of the opening portion and the imaging surface, herein referred to as flange back (FB), is: 35 mm<FB<50 mm.

2. A digital camera system according to claim 1, wherein the angle .theta. further satisfies: .theta..ltoreq.14 degrees.

3. A camera body according to claim 1, further comprising a connecting terminal provided in said mount portion in an area outside of a square formed by connecting ends of the segments and within a circumscribed circle of the square.

4. A camera body according to claim 3, wherein the connecting terminal is electrically connected to a terminal provided in the interchangeable lens when the interchangeable lens is mounted to the camera body.

5. A camera body according to claim 3, wherein the connecting terminal communicates with the interchangeable lens when the interchangeable lens is mounted to the camera body.

6. A camera body according to claim 3, wherein the connecting terminal supplies power to the interchangeable lens when the interchangeable lens is mounted to the camera body.

7. A camera body according to claim 3, wherein the connecting terminal is provided for detecting mounting of the interchangeable lens to the camera body.

8. A camera body according to claim 1, further comprising a connecting terminal provided in the mount portion in an area outside of a plane tilted by 10 degrees in a direction spaced from a long side of the imaging surface with respect to an optical axis and extended to the opening portion and within a circumscribed circle of the square.

9. A camera body according to claim 1, further comprising a connecting terminal provided in the mount portion in an area outside of a plane tilted by 8 degrees in a direction spaced from the short side of the imaging surface with respect to an optical axis and extended to the opening portion and within a circumscribed circle of the square.

10. A camera body according to claim 1, further comprising: a mirror movable between a position entering into a photographic optical path and an exiting position; and a mirror box holding the mirror, wherein the mirror box has an interior of a size which permits passage of luminous flux through an area surrounded by segments tilted by 10 degrees in a direction along a short side and by 8 degrees in a direction along a long side in a direction spaced from four corners of the imaging range with respect to an optical axis and extended to the mount portion, which imaging range is rectangular and the long sides are longer than the short sides.

11. A camera body according to claim 1, wherein a diameter Di of an image circle circumscribing the imaging range of the image surface satisfies: 21.ltoreq.Di.ltoreq.23 mm.

12. A camera body according to claim 1, wherein: Dm/Di.gtoreq.1.8 where a diameter of a circumscribed circle of the mount portion opening portion is Dm, and a diameter of an image circle circumscribing the imaging range of the image surface is Di.

13. An interchangeable lens which can be mounted to the camera body set forth in claim 1, the interchangeable lens comprising: a lens side mount portion for attaching the interchangeable lens to the camera body; and a lens side opening portion provided in the lens side mount portion and having an opening through which luminous flux can pass for forming an image in the image circle; wherein the interchangeable lens allows forming of an image in the image circle.

14. A digital camera system having predetermined image circle, the camera system comprising: a camera body; an interchangeable lens having a lens side mount portion for attaching the interchangeable lens to the camera body and a lens side opening portion having an opening through which luminous flux can pass for forming an image in the image circle and allowing the forming of the image circle, the camera body having an image pickup device having an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, a body side mount portion located at a position spaced from the imaging surface by a predetermined distance and a body side opening portion having an opening for allowing luminous flux from the interchangeable lens to pass through, the image circle being set larger than the imaging range to include the imaging range therein, wherein a size of the body side opening of the opening portion is equal to or larger than a square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening of the opening portion, and the angle .theta. satisfies: 12 degree<.theta., wherein, the distance between the body side opening of the opening portion and the image surface, hereinafter referred to as flange back (FB), is: 35 mm<FB<50 mm.

15. A digital camera system according to claim 14, wherein the angle .theta. satisfies: .theta..ltoreq.14 degrees.

16. A digital camera system according to claim 14, further comprising: a mirror movable between a position entering a photographic optical path and am exiting position; and a mirror box holding the mirror; wherein the mirror box has an interior of a size which permits passage of luminous flux through an area surrounded by segments tilted by 10 degrees in a direction along a short side and by 8 degrees in a direction along a long side in a direction spaced form four corners of the imaging range with respect to an optical axis and extended to the mount portion.

17. A digital camera system according to claim 14, wherein a diameter Di of the image circle satisfies: 21<Di<23 mm.

18. A digital camera system according to claim 14, wherein Dm/Di>1.8 where a diameter of a circumscribed circle of the square is DM, and diameter of the image circle is Di.

Description

This application claims benefits of copending application Ser. No. 10/465,410 filed Jun. 19, 2003 and Japanese Application No. 2003-168383 filed in Japan on Jun. 12, 2003, the contents of which are incorporated by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital camera system having an interchangeable lens and a camera body to which the interchangeable lens can be attached.

2. Related Art Statement

An image pickup device in a recent digital camera has a narrow dynamic range. Furthermore, it is difficult to receive and performs photoelectric conversion on light emitted diagonally at a predetermined angle or larger. Therefore, the influence of the decrease in amount of peripheral light is more significant than a silver halide camera. In order to solve the problem, Japanese Unexamined Patent Application Publication No. 6-37289 discloses a technology for increasing an opening diameter of a micro-lens on the periphery of an image pickup device. According to the disclosed technology, the opening diameter of a micro-lens of an image pickup device is increased continuously toward the periphery.

In order to reduce the influence of the decrease in amount of peripheral light, Japanese Unexamined Patent Application Publication No. 5-130469 discloses a technology for forming a light path of an image pickup device such that the vignetting of a light beam can be prevented in a light path from a photographic lens to the image pickup device. A video camera disclosed in the patent document has a larger opening in an image frame plate so as to prevent vignetting, and the strength of the image frame plate in a diagonal direction of the opening is reinforced by a projection.

On the other hand, a lens interchangeable, single-lens reflex type digital camera system has been disclosed. For example, an electronic camera disclosed in Japanese Unexamined Patent Application Publication No. 11-88783 relates to a single-lens reflex type electronic camera having a solid-state imaging device such as a CCD in a film opening by using the body of a conventional silver halide camera.

SUMMARY OF THE INVENTION

A camera system according to the present invention includes an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, the image circle being set larger than the imaging range to include the imaging range therein, a mount portion to which the interchangeable lens is mounted, and an opening portion having an opening for allowing luminous flux from the interchangeable lens to pass through, being located at a position spaced from the imaging surface by a predetermined distance, wherein the size of the opening of the opening portion is equal to or larger than a square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening of the opening portion, and the angle .theta. satisfies: 12 degrees .ltoreq..theta., wherein a distance between the opening of the opening portion and the imaging surface, herein referred to as flange back (FB), is: 35 mm.ltoreq.FB.ltoreq.50 mm

A digital camera system and camera body for use with an interchangeable lens is disclosed. The digital camera system includes an interchangeable lens having a predetermined image circle and a lens side mount portion for attaching the interchangeable lens to a camera body and a lens side opening portion provided in the lens mount portion through which luminous flux can pass for forming an image in the image circle and allowing the forming of an image in the image circle, and a camera body having an image pickup device having an imaging range with a given aspect ratio of 4:3 on an imaging surface within the image circle, a body side mount portion located at a position apart from the imaging surface by a predetermined distance and a body side opening portion provided in the body side mount portion for allowing luminous flux from the interchangeable lens to pass through. In this case, the size of the body side opening portion is equal to or larger than the square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the body side opening portion, and the angle .theta. satisfies: 12 degrees.ltoreq..theta..

A camera body according to the present invention of a digital camera to which an interchangeable lens is removably mounted, includes an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, and a mount portion to which the interchangeable lens is mounted, the mount portion having an opening portion for allowing luminous flux from the interchangeable lens to pass through, being located at a position apart from the imaging surface by a predetermined distance. In this case, the size of the opening portion is equal to or larger than the square formed by connecting ends of segments tilted by an angle .theta. with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening portion, and the angle .theta. satisfies: 12 degrees.ltoreq..theta..

Another digital camera system according to the present invention has a predetermined image circle. The digital camera system includes an interchangeable lens, which can form an image within the image circle, the lens having a lens side mount portion for mounting the interchangeable lens to a camera body and a lens side opening portion provided in the lens side mount portion for allowing luminous flux for forming an image in the image circle to pass through, and a camera body having an image pickup device having an imaging surface, a body side mount portion provided at a position apart from the imaging surface by a predetermined distance, and a body side opening portion provided in the body side mount portion, for allowing luminous flux from the interchangeable lens to pass through. In this case, the body side opening portion satisfies: Dm/Di.gtoreq.1.8

where the minimum circle diameter including the opening portion is Dm and the diameter of the image circle is Di.

A digital camera body according to the invention to which an interchangeable lens having a predetermined image circle can be removably mounted is provided, the digital camera body including an image pickup device having an imaging surface of an imaging range with a predetermined aspect ratio, a mount portion to which the interchangeable lens is mounted, the mount portion being located at a position apart from the imaging surface by a predetermined distance, and an opening portion provided in the mount portion, for allowing luminous flux from the interchangeable lens to pass through. In this case, the size of the opening portion is equal to or larger than the circumscribed circle of the square formed by connecting ends of segments tilted by a predetermined angle with respect to an optical axis diagonally from four corners of the imaging range and extended to the opening portion and satisfies: Dm/D.gtoreq.1.8 where the minimum circle diameter including the opening portion is Dm and the diameter of the image circle is Di.

An interchangeable lens according to the present invention is removably mounted to a digital camera body. The interchangeable lens includes a mount portion for mounting to the digital camera body, and an opening portion provided in the mount portion, for allowing luminous flux to pass through. In this case, Dml/Dc.gtoreq.1.8 is satisfied where the diameter of the circumscribed diameter of the imaging range of the digital camera body is Dc and the minimum circle diameter including the opening portion is Dml.

Another digital camera system according to the present invention has a predetermined image circle. The digital camera system includes interchangeable lenses, which can form an image within the image circle, each of the lenses having a lens side mount portion for mounting the interchangeable lens to a camera body, and a lens side opening portion provided in the lens side mount portion for allowing luminous flux for forming an image within the image circle to pass through, and a camera body having an image pickup device having an imaging range with the aspect ratio of 4:3 on an imaging surface within the image circle, a body side mount portion provided at a position apart from the imaging surface by a predetermined distance and a body side opening portion provided in the mount portion for allowing luminous flux from the interchangeable lens to pass through. In this case, the lens side opening portion of an interchangeable lens having the widest outermost light beam of an exit luminous flux among the interchangeable lenses has a size equal to or larger than the size of the square formed by connecting ends of a first plane formed by tilting the long side of the imaging range by a predetermined angle .theta.1 apart with respect to an optical axis and extending the long side to the lens side opening portion and a second plane formed by tilting the short side of the imaging range by a predetermined angle .theta.2 apart with respect to the optical axis and extending the short side to the lens side opening portion. In this case, the angles .theta.1 and .theta.2 satisfy: 10 degrees.ltoreq..theta.1 and 8 degrees.ltoreq..theta.2.

Another digital camera according to the present invention has a predetermined image circle. An interchangeable lens, which can form an image within a given image circle, can be removably mounted to the mount portion of the camera body. An opening portion having an opening for allowing luminous flux from the interchangeable lenses to pass through is located a predetermined distance from an image surface of an image pickup device in the camera body, the image pickup device having an imaging range with a predetermined aspect ratio. The size of the opening of the opening portion is equal to or larger than the size of a square formed by connecting ends of segments tilted outwardly by an angle .theta. with respect to an optical axis and extending to the opening of the opening portion, wherein the angle .theta. is given by .theta..gtoreq.12 degrees and the distance between the opening of the opening portion and the image surface, herein referred to as flange back (FB), is: 35 mm.ltoreq.FB.ltoreq.50 mm

The other features and advantages of the present invention will be apparent from descriptions below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram (including a partial section view) of a lens replaceable single-lens reflex type digital camera in a digital camera system according to a first embodiment of the invention;

FIG. 2 is a perspective diagram of a digital camera body of the digital camera in FIG. 1;

FIG. 3 is a vertical section diagram of a mount portion, mirror box portion and imaging unit where an interchangeable lens is attached to the camera body of the digital camera in FIG. 1;

FIG. 4 is an exploded perspective diagram around the mount portion of the camera body in FIG. 1;

FIG. 5 is a light beam diagram showing the emission of an object luminous flux captured from an interchangeable lens barrel to an image pickup device in the digital camera in FIG. 1;

FIG. 6 is a graph showing a relationship of a luminous flux angle .theta. incident on a photoelectric conversion surface of an image pickup device and F number of an interchangeable lens in the digital camera in FIG. 1;

FIG. 7 is a graph showing mount diameters Dn for F numbers of an interchangeable lens in the digital camera in FIG. 1 by using FBs as parameters;

FIG. 8A is a diagram showing a longitudinal section (section in X-direction) of a photoelectric conversion surface where a center luminous flux and peripheral luminous flux through a wide angle interchangeable lens barrel attached to the digital camera in FIG. 1 are emitted to the photoelectric conversion surface (image forming surface);

FIG. 8B shows a latitudinal section (section in Y-direction) of a photoelectric conversion surface where a center luminous flux and peripheral luminous flux through a wide angle interchangeable lens barrel attached to the digital camera in FIG. 1 are emitted to the photoelectric conversion surface (image forming surface);

FIG. 9A is a diagram showing a longitudinal section (section in XZ-direction) of a photoelectric conversion surface where a center luminous flux and peripheral luminous flux through a replacement telephoto lens barrel attached to the digital camera in FIG. 1 are emitted to the photoelectric conversion surface (image forming surface);

FIG. 9B is a diagram showing a latitudinal section (section in YZ-direction) of a photoelectric conversion surface where a center luminous flux and peripheral luminous flux through a replacement telephoto lens barrel attached to the digital camera in FIG. 1 are emitted to the photoelectric conversion surface (image forming surface);

FIG. 10 is a diagram showing an effective screen range (effective imaging range) and recording screen range (imaging and recording screen) of a photoelectric conversion surface of an image pickup device in the digital camera in FIG. 1 and image circles corresponding to the ranges;

FIG. 11 is a light beam diagram showing a relationship of a mount opening and the circumscribed circle with respect to an imaging range inscribing a reference image circle of the image pickup device in the digital camera in FIG. 1;

FIG. 12 is a light beam diagram showing a relationship between an image circle circumscribing an imaging range of an image pickup device applied in a digital camera according to a second embodiment of the invention and a circumscribed circle of a mount opening;

FIG. 13A shows a light beam diagram of a section along a ZX surface (horizontal surface) between a photoelectric conversion surface of the image pickup device and the mount opening portion in the digital camera in FIG. 12;

FIG. 13B shows a light beam diagram of a section along a ZY surface (vertical surface) between a photoelectric conversion surface of the image pickup device and the mount opening portion in the digital camera in FIG. 12; and

FIG. 14 is a diagram showing an imaging range of a 4/3 type image pickup device and the image circle on an imaging range of a square type image pickup device applied in a digital camera according to a third embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the invention will be described with reference to drawings.

FIG. 1 is a perspective diagram (including a partial section view) of a lens replaceable single-lens reflex type digital camera in a digital camera system according to a first embodiment of the invention. FIG. 2 is a perspective diagram of a digital camera body of the digital camera. FIG. 3 is a vertical section diagram of a mount portion, mirror box portion and imaging unit where an interchangeable lens is attached to the camera body of the digital camera. FIG. 4 is an exploded perspective diagram around the mount portion of the camera body.

A digital camera 1 of a digital camera system according to this embodiment includes a digital camera body and multiple kinds of interchangeable lens, which can be attached to the camera body and has unique opening shapes of a mount portion and mirror box portion corresponding to a contained image pickup device. Before the description of the opening shape, internal constructions of a digital camera body (called camera body hereinafter) 11 and interchangeable lens barrel 12 as an interchangeable lens will be described with reference to FIGS. 1 to 4.

The interchangeable lens barrel 12 is a lens barrel containing multiple kinds of photographic optical system 12a having various kinds of focal distances as shown in FIGS. 5 and 6, which will be described later. The interchangeable lens barrel 12 has a lens side mount portion 37, which can be attached to the body side mount portion 47, which will be described later, of the camera body 11.

The camera body 11 is a so-called single-lens reflex type camera body including various components provided inside the camera body portion 11a and having a body side mount portion in the front of the surface such that the lens barrel 12 for holding a photographic optical system 12a can be removably attached. In other words, the substantial center portion of the front side of the camera body portion 11a has an exposure opening of a predetermined size, which can guide object luminous flux into the camera body portion 11a. A body side mount portion 47 is provided on the periphery of the exposure opening.

A more detailed construction of the camera body 11 will be described. First of all, various operation members for operating the camera body portion 11a, such as a release button 17 for generating instruction signals for starting a photographic operation, are provided at a predetermined position of the upper surface portion or back surface portion of the camera body 11a.

The camera body portion 11a has, at predetermined positions, a front plate 41, a body side mount portion 47, a mirror box 42, a finder 13, a shutter portion 14, an imaging unit 15 and multiple circuit substrates including a main circuit substrate 16. The front plate 41 has a body side opening portion 41a in the front of the surface side of the camera body portion 11a. The body side mount portion 47 is located on the front surface portion 41b of the front plane 41. The mirror box 42 is fixed behind the mount portion of the front plane 41. The finder 13 is provided for forming a desired object image, which is formed by the photographic optical system 12a, at a predetermined position different from the position on the photoelectric conversion surface 27a, which is an imaging surface of the image pickup device 27. The finder 13 is a so-called observation optical system. The shutter portion 14 is supported by a projection 42f behind the mirror box 42 and includes a shutter mechanism for controlling the time for irradiating object luminous flux to a photoelectric conversion surface of the image pickup device 27. The imaging unit 15 is a unit fixed and held behind the shutter portion 14 by the projection 41f of the front plate 41. The imaging unit 15 includes the image pickup device 27 for obtaining object imaging signals from object light through the imaging optical system 12a. Various electric members of electric circuits such as an image signal processing circuit for performing various kinds of signal processing on the image signals obtained by the image pickup device 27 are implemented on the multiple circuit substrates such as main circuit substrate 16. A dust-preventive filter 21 is provided in the front of the surface of the imaging unit 15. The dust-preventive filter 21 prevents adherence of dust to the photoelectric conversion surface of the image pickup device.

The mirror box 42 has a mirror box opening portion 42a and a space behind the mirror box opening portion 42a. The mirror box opening portion 42a pivotally supports a reflector 13b and allows the passage of object luminous flux from the photographic optical system 12a without vignetting of the luminous flux for forming an image on the photoelectric conversion surface 27a of the image pickup device 27.

The reflector 13b lies in the space behind opening portion 42a and can pivotably move between a reflecting (dotted-line) position for reflecting incident luminous flux to the finder 13 side and a turnout (solid-line) position turning out from the reflecting position.

The finder 13 includes the reflector 13b, a pentaprism 13a and an eyepiece 13c. The reflector 13b is arranged to guide object luminous flux through the photographic optical system 12a by bending the optical axis of the object luminous flux to the observation optical system side. The pentaprism 13a receives luminous flux emitted from the reflector 13b and forms an erect image. The eyepiece 13c forms an image best suitable for enlarging and observing an image formed by the pentaprism 13a.

The reflector 13b, as set forth above, moves between the turnout position away from an optical axis O of the photographic optical system 12a and a predetermined position on the optical axis. Normally, the reflector 13b is located at a predetermined angle, such as 45 degrees, with respect to the halo on the optical axis of the photographic optical system 12a. Thus, when the camera 1 is at the normal state, the optical axis of the object luminous flux having passed through the photographic optical system 12a is bent by the reflector 13b and is reflected to the pentaprism 13a side above the reflector 13b.

On the other hand, while the camera is performing a photographic operation and during the actual exposure operation, the reflector 13b moves from the optical path of the photographic optical system 12a to the aforesaid predetermined turnout position. Thus, the object luminous flux is guided to the image pickup device side and forms an image on the photoelectric conversion surface.

The shutter portion 14 is similar to those generally used in a conventional camera, such as a focal plane type shutter mechanism and a driving circuit for controlling operations of the shutter mechanism.

The imaging unit 15 includes the image pickup device 27, an image pickup device fixing plate 28, an optical low-pass filter (called LPF hereinafter) 25, a low-pass filter receiving member 26, an image pickup device storage case member 24 (called CCD case 24 hereinafter), a dust-preventive filter receiving member 23, the dust-preventive filter 21, a piezoelectric element 22 and a press member 20. The image pickup device 27 constituted by a CCD for obtaining image signals corresponding to the light irradiated onto the photoelectric conversion surface of the image pickup device 27 through the photographic optical system 12a is shown in FIG. 3 and so on. The image pickup device fixing plate 28 is constituted by a thin-plate like member for fixing and supporting the image pickup device 27. The optical LPF 25 is an optical element on the photoelectric conversion surface of the image pickup device 27, for removing high frequency components from an object luminous flux irradiated through the photographic optical system 12a. The low-pass filter receiving member 26 is constituted by an elastic member substantially in a frame shape and is provided on the periphery between the optical LPF 25 and the image pickup device 27. The CCD case 24 stores, fixes and holds the image pickup device 27 and supports the optical LPF 25 by closely abutting to the periphery and the vicinity. A predetermined position of the CCD case 24 is in close contact with the dust-preventive filter receiving member 23. The dust-preventive filter receiving member 23 is provided in the front of the surface side of the CCD case 24 and is in close contact with the periphery or the vicinity. The dust-preventive filter 21 is a dust-preventive member supported by the dust-preventive filter receiving member 23 and faces toward the optical LPF 25 at a position spaced apart from the optical LPF 25 by a predetermined distance in the front of the surface side of the optical LPF 25 on the photoelectric conversion surface side of the image pickup device 27. The piezoelectric element 22 is provided on the periphery of the dust-preventive filter 21 and removes dust by applying a predetermined amount of vibration to the dust-preventive filter 21. The press member 20 is constituted by an elastic body for connecting, fixing and holding the dust-preventive filter 21 to the dust-preventive filter receiving member 23 in an air-tight manner.

The image pickup device 27 performs photoelectric conversion processing on object luminous flux received by the photoelectric conversion surface 27a of the image pickup device 27 through the photographic optical system 12a. Thus, the image pickup device 27 can obtain image signals corresponding to the object image on the photoelectric conversion surface. The image pickup device 27 may be a 4/3 type charge-coupled device or the like. In this case, the term "4/3 type" refers to the size of the image pickup device, and a 4/3 type image pickup device has an image circle with the diameter of about 21.2 to 25 mm.

The image pickup device 27 is implemented at a predetermined position on the main circuit substrate 16 through the image pickup device fixing plate 28. An image signal processing circuit and work memory, not shown, are implemented together on the main circuit substrate 16. Thus, output signals from the image pickup device 27, that is, image signals obtained through optoelectric processing are transmitted to the image signal processing circuit. A protection glass (not shown for simplicity) is attached in front of the photoelectric conversion surface of the image pickup device 27.

The signal processing performed in the image signal processing circuit includes various kinds of signal processing such as processing for converting image signals obtained from the image pickup device 27 to signals suitable for recording. In this case, the image signals correspond to the image formed on the optoelectric surface of the image pickup device 27 by the photographic optical system 12a held within the lens barrel 12 attached to the body side mount portion 47. These kinds of signal processing are the same as processing normally performed in a general digital camera for handling electronic image signals.

The optical LPF 25 is provided in the front of the surface side of the image pickup device 27 through the low-pass filter receiving member 26. The optical LPF 25 is constituted by crystal, which is an optical element having a double refraction characteristic. The optical LPF 25 further contains an infrared absorbing glass.

The CCD case 24 covers the optical LPF 25. The CCD case 24 has a rectangular opening substantially at the center. The optical LPF 25 and image pickup device 27 are provided in the opening from the back. A step 24a having a substantial L-shaped section is provided on the internal periphery on the back side of the opening.

As described above, the low-pass filter receiving member 26 constituted by an elastic member is provided between the optical LPF 25 and the image pickup device 27. The low-pass filter receiving member 26 is provided at a position avoiding an effective range of the photoelectric conversion surface on the periphery of the front surface side of the image pickup device 27. Furthermore, the low-pass filter receiving member 26 is abutted to the vicinity of the periphery of the back side of the optical LPF 25. The optical LPF 25 and the image pickup device 27 are in constant contact with each other, through member 26, substantially in an air-tight manner. Thus, elastic force toward the optical axis by the low-pass filter receiving member 26 acts on the optical LPF 25.

Then, the periphery of the front surface side of the optical LPF 25 is located so as to be in contact with the step 24a of the CCD case 24 substantially in an air-tight manner. Thus, the position in the optical axis direction of the optical LPF 25 is controlled against the elastic force by the low-pass filter receiving member 26 for attempting to move the optical LPF 25 toward the optical axis.

In other words, the optical LPF 25 laid within the opening of the CCD case 24 from the back surface side is positionally controlled by the step 24a in the optical axis direction. Thus, the optical LPF 25 is prevented from coming out from the inside of the CCD case 24 toward the front surface side.

In this way, after the optical LPF 25 is inserted from the back surface side into the opening of the CCD case 24, the image pickup device 27 is located on the back surface side of the optical LPF 25. In this case, the low-pass filter receiving member 26 is held at its periphery between the optical LPF 25 and the image pickup device 27.

As described above, the image pickup device 27 is implemented on the main circuit substrate 16 through the image pickup device fixing plate 28. The image pickup device fixing plate 28 is fixed through a spacer 28a with a screw into a screw hole from the back surface side of the CCD case 24. The main circuit substrate 16 is fixed to the image pickup device fixing plate 28 with a screw through a spacer 16a.

The dust-preventive filter receiving member 23 is fixed to the screw hole of the CCD case 24 in the front of the surface side of the CCD case 24 with a screw. A peripheral slot having a substantial ring shape is provided at a predetermined position in the front of the surface side on the periphery side of the CCD case 24. On the other hand, a ring-shape projection to fit to the peripheral slot of the CCD case 24 has a substantial-ring form at a predetermined position on the back surface side of the periphery side of the dust-preventive filter receiving member 23. Therefore, when the ring-shape projection fits into the peripheral slot, the CCD case 24 and the dust-preventive filter receiving member 23 fit into each other substantially in an air-tight manner in a ring-shaped area, that is, in an area having the peripheral slot and the ring-shaped projection.

The dust-preventive filter 21 contains glass and has a circular or polygonal plate as a whole. An area extending at least from the center of the dust-preventive filter 21 to the edge is transparent. The transparent area faces toward the front surface side of the optical LPF 25 through a predetermined space. The dust-preventive filter 21 is fixed and is held by a press member 20 such that the dust-preventive filter 21 can be associated with the dust-preventive filter receiving member 23 in an air-tight manner. The press member is constituted by an elastic body such as a flat spring.

The dust-preventive filter receiving member 23 has a circular or polygonal opening in the vicinity of the substantial center of the dust-preventive filter receiving member 23. The opening is designed to be large enough for object luminous flux through the photographic optical system 12a to illuminate the photoelectric conversion surface of the image pickup device 27 at the back.

The body side mount portion 47 has a square body side mount opening portion 41a, a body side mount plate 45, a mount spring 46, a contact spring holder 51, a contact spring 53, a mount contact frame 52, and mount contact pins 54. The body side mount opening portion 41a is provided within the front surface portion 41b of the front plate 41, as shown in FIGS. 3 and 4. The body side mount plate 45 and the mount spring 46 are fixed to the front surface portion 41b. A mount flexible substrate (called FPC hereinafter) 55 is attached to the contact spring 53. The mount contact pins 54 is a camera body side connecting terminal. The end of the mount FPC 55 is connected to a lens drive control portion and/or a power supply portion within the camera body 11.

The body side mount plate 45 has a bayonet 45a on the internal periphery of the opening. The mount spring 46 has a spring portion 46d. The body side mount plate 45 is fixed to the front plate 41 with the mount spring 46 being inserted on the back of the body side mount plate 45, by passing each screw 61 through a screw inserting hole 45c and screwing each screw into an opening portion screw portion 41c. A mount lock pin 44 is provided on the periphery of the front surface portion 41b of the front plate 41.

Nine mount contact pins 54 are inserted to pin holes 52c of the mount contact frame 52. The contact spring holder 51 is fixed to and is supported by the mount contact frame 52 by screwing each screw 62 into the screw hole 52b through a screw inserting hole 51a. The fixed and supported mount contact pins 54 are forced, extended and held toward the front of the mount contact frame 52 by nine contact springs 53 attached to the contact spring holder 51.

The mount contact frame 52 having the contact spring holder 51 is fixed outward under the square body side opening portion 41a by screwing each screw 63 to a screw hole 41d through the screw inserting hole 52a. Thus, the bottom part of the body side mount opening portion 41a can be obtained. When the mount contact frame 52 is attached, the mount contact pins 54 are arranged in the form of a circular arc inside of the opening portion 45a of the body side mount plate 45 and under the body side opening portion 41a.

On the other hand, as shown in FIG. 3, the lens side mount portion 37 of the interchangeable lens barrel 12 has a lens side mount opening portion 31a and bayonet nails 31b, which can associate with the bayonet 45a of the body side mount plate 45. Furthermore, nine mount contacts 33 are arranged in the form of a circular arc at the bottom of the lens side mount opening portion 31a. The nine mount contacts 33 are lens side connecting terminals held by the terminal holder 32. The mount contacts 33 are connected to the lens side FPC 34. The lens side FPC 34 has a power supply line and/or an electric drive control line and is connected to a focus driving portion, for example, within the interchangeable lens barrel 12.

In order to attach the interchangeable lens barrel 12 to the camera body 11 having the above-described construction, the lens side mount portion 37 of the interchangeable lens barrel 12 is rotationally fitted into the mount plate 45 of the body side mount portion 47. Then, the bayonet nails 31b are associated therewith such that the lens can be attached. Under the lens-attached condition, the interchangeable lens barrel 12 is electrically connected to the drive control portion of the camera body 11 through the connecting terminal portion so as to allow the control for focus, zoom and iris driving. An object luminous flux enters the finder 13 or the image pickup device 27 through the lens side mount opening portion 31a and the body side mount opening portion 41a, and the object can be observed or be shot.

Here, the form of the mount opening of the lens mount portion 37 and/or the body side mount portion 47 for passing luminous flux and the form of luminous flux passing portion of the mirror box 42 will be described.

In the description below and the drawings, the direction along the optical axis O is the Z-direction. The object side (lens side) of the Z-direction is the front while the image pickup device side (image-forming side) is the back. The direction orthogonal to the optical axis O and along the longer side in the imaging range (photoelectric conversion surface) of the image pickup device is an X-direction (horizontal direction). The left and right are determined from the object viewpoint. The direction orthogonal to the optical axis O and along the shorter side of the imaging range (photoelectric conversion surface) of the image pickup device is a Y-direction (vertical direction).

In a digital camera system according to this embodiment, in order for object luminous flux captured by the interchangeable lens barrel 12 to enter to the periphery of the imaging range of the image pickup device 27, the mount portion and the member, such as a mirror box, between the image pickup device and the lens must have openings. In other words, in order to guide light uniformly to the center and periphery of the image pickup device, the openings must have a form allowing the same luminous flux angle as the luminous flux angle of the luminous flux from the end to the center of the imaging range. In this case, as the degrees of the tilt of the main light beam of a luminous flux incident on the periphery to the optical axis increases, the size of the openings can be reduced.

FIG. 5 is a light beam diagram showing an entering state of an object luminous flux captured from the interchangeable lens barrel 12 to the image pickup device 27.

As shown in FIG. 5, the object luminous flux entering from the exit pupil diameter D0 of the interchangeable lens barrel 12 and the center and peripheral luminous flux entering to the center and periphery of the optical axis O of the photoelectric conversion surface 27a on the imaging range of the image pickup device 27 have a luminous flux angle .theta. about the respective main light beams, where the luminous flux angle .theta. refers to an angle of one side of a luminous flux (that is, half angle).

In order to prevent a shortage in light amount of the periphery in the imaging range, the vignetting of the peripheral luminous flux must be prevented at the lens side mount opening portion 31a (having at least an opening range Rm mentioned later), the body side mount opening portion 41a (opening having the opening range equal to the opening range Rm mentioned later for preventing the vignetting of luminous flux passing therethrough) and a light passing portion of the mirror box 42. At the limit of the longer focal distance side (Tele side), the photographic optical system 12a requires a shown lens side opening portion 31a because the main light beam of the peripheral luminous flux is parallel to the optical axis O. On the other hand, on the short focal distance side (Wide side) shorter than the long focal distance, the photographic optical system 12a requires an opening 31a' narrower than the lens side opening portion 31a because the main light beam of the peripheral luminous flux is a light beam tilting toward the optical axis O.

In the photographic optical system 12a, when an object distance is at infinity, the exit pupil position 12a0 of the exit pupil diameter DO is spaced from the photoelectric conversion surface 27a, which is at an image-forming position), by a focal distance f. The luminous flux angle .theta. is expressed by: tan(.theta.)=D0/(2.times.f) EQ1 The relationship of the exit pupil diameter D0, the focal distance f and F No. (the F-number) is: F No.=f/D0. Based on EQ1, the relationship between the luminous flux angle .theta. and the F-number is: .theta.=tan.sup.-1(1/(2.times.F No.)) EQ2

FIG. 6 is a graph showing a relationship between the luminous flux angle .theta. and the F-number (or Av value). In FIG. 6, when the slope of the main light beam is 5 degrees or 10 degrees, the luminous flux angle .theta. is an angle of the outer light beam of a peripheral luminous flux with respect to the optical axis O. The angle of the slope of the main light beam is plus in the counterclockwise direction in FIG. 5.

The mount diameter Dm (FIG. 11) of the mount portion (such as lens side opening portion 31a or the body side opening portion 41a) required at the position spaced from the imaging surface by a predetermined distance (flange back) FB with respect to an image circle (having a diameter Di, see FIG. 11) including the imaging range of the photoelectric conversion surface 27a is expressed by: Dm=Di+2.times.FB.times.tan .theta. EQ3 or Dm=Di+FB/F No. EQ4

As described above, the image pickup device 27 is a 4/3 type CCD and has an imaging range of the photoelectric conversion surface 27a of 17.8 mm (long side).times.13.4 mm (short side) with an aspect ratio of about 4:3 (where the imaging range corresponds to an effective pixel range L-w2.times.L-h2 mentioned later, see FIG. 10). The diameter Di2 of the image circle I-ce circumscribing the square imaging range is 22.28 mm.

FIG. 7 is a graph indicating mount diameters for F-numbers by using FBs as parameters when the value of the diameter Di2 is applied to the diameter Di of the image circle of the image pickup device 27 based on EQ4.

The luminous flux angle .theta. required for capturing an object bundle from an interchangeable lens depends on the intensity of the used lens in principle. In other words, as the intensity of the used lens increases (that is, as the F number decreases), the luminous flux angle .theta. must be increased. For example, in order to guide a luminous flux having the F No. 2.8 to the end of the image circle, the luminous flux angle .theta. is about 10 degrees. In order to guide a luminous flux having F No. 1.4, the luminous flux angle .theta. is about 20 degrees (FIG. 6). In this way, by increasing the luminous flux angle .theta., the lens having larger intensity can be used. However, as shown in the graph, the relationship of the applicable F-numbers and luminous flux angles .theta. is not linear. Then, when a lens having a small F No. is used, the luminous flux angle .theta. must be rapidly increased.

Generally, the F No. of a wide angle lens is smaller while the F No. of a telephoto lens is larger. Generally, when a focal distance is about 50 mm, the F No. is about 1.4. When the focal distance is about 300 mm, the F No. is about 2 to 2.8. This is because, a telephoto lens is no longer practical when the F No. is small.

As described above, the main light beam of a peripheral luminous flux is not always parallel to the optical axis. Especially, when a wide-angle lens is used, the amount of the slope is increased. For example, FIGS. 8 and 9 show a light beam diagrams of a wide-angle lens and a telephoto lens, respectively.

FIGS. 8A, 8B and 9A, 9B are diagrams showing states where the center luminous flux and peripheral luminous flux enter the photoelectric conversion surface (Image-forming surface) 27a of an image pickup device. FIGS. 8A, 8B show a case where a wide angle interchangeable lens barrel (with f 12.55 mm and F No. 1.4) is attached. FIGS. 9A, 9B show a case where a telephoto interchangeable lens barrel (with f 300 mm and F No. 2.8). FIGS. 8A and 9A show sections in a longer side direction (XY section) of the photoelectric conversion surface 27a. FIGS. 8B and 9B show sections in a shorter side direction (YZ section) of the photoelectric conversion surface 27a.

The angles .alpha.-w1 and .alpha.-w2 of inclination of the main light beam of a peripheral luminous flux by a wide-angle photographic optical system 12aW shown in FIGS. 8A and 8B are about 5 degrees. The angles .alpha.-t1 and .alpha.-t2 of the main light beam of the peripheral luminous flux by a telephoto photographic optical system 12aT shown in FIGS. 9A and 9B are smaller than the angles of inclination of the main light beam of the wide-angle photographic optical system 12aW.

Based on this fact, no problems occur if the luminous flux angle .theta. is set to be compliant with the lens having an F No. 3 to 4 or below when the amount of inclination of the main light beam is zero. More preferably, the luminous flux angle .theta. is set to be compliant with the lens having the F No. 2 to 2.8 or below.

In order to satisfy the optical characteristic, the proper size of the camera body must be practically obtained while in consideration of the proper F-number. Therefore, the compliant F-number is applied from the viewpoint of the size of the camera body as described below.

In other words, the height of a camera body of a lens replaceable silver halide camera system is about 90 to 120 mm. The thickness is about 60 to 80 mm. That is, a size which is extremely larger than the height and the thickness is not practical. In order to obtain a height of about 90 to 100 mm, the mount opening diameter must be about 50 mm or below and preferably smaller than 45 mm. The diameter is desirably about 40 mm. In order to achieve the thickness of about 60 to 80 mm as described above, the flange back FB must be about 35 to 50 mm.

Apparently from the relationship between the mount opening diameter and the F number of the image pickup device 27 shown in FIG. 7, which is a 4/3 type CCD, when the size of the opening diameter is limited, the luminous flux angle .theta. must be set so as to have the compliant F number larger than F numbers 1.4 to 1.8 and more preferably F numbers 1.6 to 2.2.

In order to achieve the optical limitation and a practical body size, the luminous flux angle .theta. is preferably set to be compliant with the lens having F-numbers 1.4 to 4. More preferably, the luminous flux angle .theta. is set to be compliant with the lens having F-numbers 1.6 to 2.8.

Therefore, when the circle of the reference opening is a circle obtained by extending a predetermined image circle to the opening portion in a direction away from the optical axis O by a predetermined angle in accordance with the compliant F number as described above, the desired compliant F number can be obtained.

Since the real imaging range of the image pickup device 27 is rectangular, the required shape of the opening does not have to be circular. At least a square inscribing the reference opening is only required. Therefore, an opening is required having a size larger than the square formed by connecting ends of a segment extending to the opening portion in a direction away from the optical axis by a predetermined angle in accordance with the proper F number diagonally from the square of the imaging range.

According to this embodiment, the diameter Di of the image circle corresponding to the recording screen range is 21 to 23 mm or 21.6 to 22.7. The diagonal length of the recording range inscribing the image circle is about half (21.6 mm) of the diagonal line of a 135-format screen. In other words, when a lens having the focal distance of 50 mm is used in a digital camera according to this embodiment, the angle of view can be the same as the angle obtained when a lens having the focal distance of about 100 mm is used in a 135-format camera. Therefore, the correlation of the angle of view with respect to the 135-format camera can be realized only by doubling the focal distance of the lens.

The imaging range on the photoelectric conversion surface 27a of the image pickup device 27 is a screen with the aspect ratio of 4:3 inscribing the image circle. No practical problems occur when luminous flux from the lens can reach onto the recording screen range within the imaging range. However, an image circle larger than the image circle corresponding to the recording screen range to some extent is desirably set in consideration of errors occurring in manufacture and in assembly.

FIG. 10 is a diagram showing a valid screen range (valid imaging range) and recording screen range (imaging and recording range) in the photoelectric conversion surface 27a of the image pickup device 27 (see FIG. 3) and image circles corresponding to the ranges.

In the image pickup device 27, as shown in FIG. 10, a recording screen range L-w1.times.L-h1 must be smaller than a valid screen range L-w2.times.L-h2. The recording screen range L-w1.times.L-h1 is a range to be actually converted to electric signals as image information during image processing and to be captured. The valid screen range L-w2.times.L-h2 is an entirely shootable range of the image pickup device 27. This is because the outer area around a required recording pixel (called peripheral pixel area hereinafter) is required for creating the recording pixel by the image pickup device 27. Furthermore, due to the precision limits in dimension of the image pickup device 27 itself and positional errors in assembly of the image pickup device 27 to the camera body 11 through the image pickup device fixing plate 28 and the front plate 41, the position of the optical axis O is displaced from the center of the valid screen range L-w2.times.L-h2 of the image pickup device 27. In order to absorb the displaced amount, the valid screen range L-w2.times.L-h2 is taken larger than the recording screen range L-w1.times.L-h1 as described above.

The form of the opening must be determined so as to prevent vignetting of the object luminous flux in a range entering to the valid screen range L-w2.times.L-h2 as the imaging range, which is passing through the interchangeable lens barrel 12 and the camera body 11. The decrease in light amount of peripheral light in the valid screen range L-w2.times.L-h2 must be prevented.

The circumscribed circle of the recording screen range L-w1.times.L-h1 is the recording screen image circle I-cr, and the diameter is Di1. The circumscribed circle of the valid screen range (imaging range) L-w2.times.L-h2 including the peripheral pixel area is a valid screen image circle (imaging range image circle) I-ce of the valid screen range (imaging range), and the diameter is Di2. In the real design, the valid screen image circle I-ce is slightly larger. The increased amount .DELTA.d is added to the diameter Di2 of the valid screen image circle I-ce, and the valid screen image circle I-ce is added to the recording screen image circle I-cr. Then, an image circle I-c0 having a diameter Di3 can be obtained. By applying the imaging range of the image circle I-c0, the form of the openings can be set. More specifically, the image circle I-co having the increased amount .DELTA.d of about 1 mm is handled as a reference image circle corresponding to the recording screen range. However, in the description below, the form of openings are set by using the valid screen image circle I-ce as an imaging range image circle (which is a reference image circle I-c having the diameter Di mentioned below) and by using the valid screen range L-w2.times.L-h2 as an imaging range (imaging range Ri mentioned below). The size of the valid screen range (imaging range) L-w2.times.L-h2 is 17.8 mm.times.13.4 mm according to this embodiment.

The diameter Dm of the circumscribed circle Im for the square mount opening range Rm, which is a reference opening guided by a luminous flux angle .theta. of a predetermined half angle diagonally from the end of the imaging range Ri inscribing the reference image circle I-c is determined as follows.

In this case, the mount opening range Rm minimizes the size of the form of the lens side mount opening portion 31a. In other words, the lens side mount opening portion 31a of the interchangeable lens having the maximum mount opening portion among interchangeable lenses of the camera system is set to be sufficient to cover at least the square of the mount opening range Rm (where the minimum mount opening range of the lens side mount opening portion 31a is Rm). The body side mount opening 41a is also set to at least the size of the square opening range Rm. Thus, the form of