# Patent

## Title
Camera and method of controlling operation of same

## Abstract

An image of subject formed optically is obtained by the finder unit. The subject is imaged electronically by an image sensing device, and a video signal, which represents an image within an autofocus target area inside the image of the subject of the subject obtained, is read out of the image sensing device. The image represented by the video signal is displayed on the display screen of a liquid crystal device which constitutes an electronic viewfinder. Looking through the finder unit, a user sees an image obtained by superimposing the image, which is displayed on the display screen, upon the optical image of the subject. If correct focusing is achieved, the optical image of the subject and the image coincide. Since a video representing a portion of the image of the subject is read out of the image sensing device, the image is displayed without delay.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a Continuation of PCT International Application No. PCT JP2013/065370 filed on Jun. 3, 2013, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2012-163891 filed Jul. 24, 2012. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a camera and to a method of controlling the operation thereof.
2. Description of the Related Art
There is a digital camera equipped with a device having both optical and electronic finders (Patent Document 1). The fine optical image of a subject can be seen by using the optical finder, and the image of a subject identical with the captured image of the subject can be seen by using the electronic finder.
Further, there is a camera in which a partial image clipped from a subordinate image obtained from the image sensor of a subordinate imaging unit is superimposed upon a main image obtained from the image sensor of a main imaging unit (Patent Document 2), as well as a camera in which the operation of a conventional image coincidence optical rangefinder is performed by superimposing images from two image sensing devices (Patent Document 3). Furthermore, there is a camera in which pixels to be used in a parallax calculation are selected suitably upon taking into consideration processing time relating to the parallax calculation (Patent Document 4), and a camera in which it is possible to set shooting conditions in accordance with a cropping area (Patent Document 4).
Patent Document 1: Japanese Patent Application Laid-Open No. 2012-65294
Patent Document 2: Japanese Patent Application Laid-Open No. 2011-135490
Patent Document 3: Japanese Patent Application Laid-Open No. 2007-163724
Patent Document 4: Japanese Patent Application Laid-Open No. 2012-18013
Patent Document 5: Japanese Patent Application Laid-Open No. 2007-201779
Cameras heretofore referred to as high-performance cameras are equipped with a double-image coincidence rangefinder which, when the user performs focusing while looking at the finder device, is such that the image of the subject becomes a pair of offset images if the image of the subject is out of focus, although such offset vanishes when the image of the subject is brought into focus. Hence there is a need to arrange it so that the double-image coincidence system can be applied also to a camera having both the optical and electronic finders mentioned above. However, none of Patent Documents 1 to 5 give any consideration whatsoever to the application of the double-image coincidence system to such an optical/electronic viewfinder. In a case where the double-image coincidence system is applied, a conceivable arrangement is to superimpose the image of a subject that is the result of optical formation and an image that lies within an AF target area displayed on a display screen, where the image in the AF target area is from within the image of the subject obtained by imaging using a solid-state electronic image sensing device. In a case where the double-image coincidence system is applied to a camera having both the optical and electronic finders mentioned above, the time needed to display an image on the display unit is delayed by the length of time needed for a readout from the solid-state electronic image sensing device. If the subject or the camera is moving, the optical image of the subject and the AF target image being displayed on the display unit will not coincide. As a result, not only does the user experience a sense of discomfort but the user may also judge that the subject is out of focus even though the subject is in focus.
SUMMARY OF THE INVENTION
As object of the present invention is to eliminate a delay in displaying an AF target image on a display unit in a case where the double-image coincidence system is applied to an optical/electronic hybrid finder having both optical and electronic finder functions.
According to the present invention, there is provided a camera comprising: a lens barrel, which is provided on its periphery with a focusing ring being freely rotatable and incorporates a focusing lens, for adjusting the position of the focusing lens in accordance with rotation of the focusing ring; a setting device (setting means) for setting either an optical/electronic hybrid viewfinder function or an electronic viewfinder function; a finder unit formed on the front of the camera and having an objective window facing a subject and an eyepiece window for looking at an optical image of the subject seen through the objective window; a shutter device (shutter means) for opening and closing a shutter so as to block light incident from the objective window of the finder unit in response to setting of the electronic viewfinder function by the setting device, and so as to pass light incident from the objective window of the finder unit in response to setting of the optical/electronic hybrid viewfinder function by the setting device; a solid-state electronic image sensing device responsive to setting of the electronic viewfinder function by the setting device for capturing the image of the subject formed by the lens barrel and outputting subject-image data representing the captured image of the subject, and responsive to setting of the optical/electronic hybrid viewfinder function by the setting device for capturing the image of the subject formed by the lens barrel and outputting AF-target image data representing the image within a desired AF target area, which image is a portion of the captured image of the subject; a display unit responsive to setting of the electronic viewfinder function by the setting device for displaying the image of the subject, which is represented by the subject-image data that is output from the solid-state electronic image sensing device, on a display screen, and responsive to setting of the optical/electronic hybrid viewfinder function by the setting device for displaying the AF target image, which is represented by the AF target image data that is output from the solid-state electronic image sensing device, on the display screen; a deflecting unit, which is provided between the objective window and the eyepiece window, for introducing the AF target image or image of the subject, which is being displayed on the display screen of the display unit, to the eyepiece window; and a display control device (display control means) responsive to setting of the optical/electronic hybrid viewfinder function by the setting device for controlling the display unit so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.
The present invention also provides an operation control method suited to the above-described camera. Specifically, the present invention provides a method of controlling operation of a camera having a lens barrel, which is provided on its periphery with a focusing ring being freely rotatable and incorporates a focusing lens, for adjusting the position of the focusing lens in accordance with rotation of the focusing ring, and a finder unit formed on the front of the camera and having an objective window facing a subject and an eyepiece window for looking at an optical image of the subject seen through the objective window, the method comprising steps of: a setting device setting either an optical/electronic hybrid viewfinder function or an electronic viewfinder function; a shutter device opening and closing a shutter so as to block light incident from the objective window of the finder unit in response to setting of the electronic viewfinder function by the setting device, and so as to pass light incident from the objective window of the finder unit in response to setting of the optical/electronic hybrid viewfinder function by the setting device; a solid-state electronic image sensing device capturing the image of the subject formed by the lens barrel and outputting subject-image data representing the captured image of the subject in response to setting of the electronic viewfinder function by the setting device, and capturing the image of the subject formed by the lens barrel and outputting AF-target image data representing the image within a desired AF target area, which image is a portion of the captured image of the subject, in response to setting of the optical/electronic hybrid viewfinder function by the setting device; a display unit displaying the image of the subject, which is represented by the subject-image data that is output from the solid-state electronic image sensing device, on a display screen in response to setting of the electronic viewfinder function by the setting device, and displaying the AF target image, which is represented by the AF target image data that is output from the solid-state electronic image sensing device, on the display screen in response to setting of the optical/electronic hybrid viewfinder function by the setting device; a deflecting unit, which is provided between the objective window and the eyepiece window, introducing the AF target image or image of the subject, which is being displayed on the display screen of the display unit, to the eyepiece window; and in response to setting of the optical/electronic hybrid viewfinder function by the setting device, a display control device controlling the display unit so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.
In accordance with the present invention, either an optical/electronic hybrid viewfinder function or electronic viewfinder function can be set. If the camera is set to the optical/electronic hybrid viewfinder, an optical image of a subject is obtained because the shutter opens. The image within an AF target area is displayed on the display screen of a display unit in the image of the subject obtained by imaging. The user sees an image that is the result of superimposing the displayed image within the AF target area upon the optical image of the subject. If the image within the AF target area is not in focus, an offset develops between the two superimposed images. If the image within the AF target area is in focus, no offset develops between the two superimposed images. Thus a so-called double-image coincidence finder can be realized. If the camera is set to the electronic viewfinder, the shutter closes and the user sees the image of the subject displayed on the display unit. The user performs focusing while viewing this image of the subject.
In particular, in this embodiment, when the optical/electronic hybrid viewfinder has been set, the AF target image data that is output from the solid-state electronic image sensing device represents not the entire captured image of the subject but is AF target image data that is a portion of the entire image. Subject-image data representing the entire image of the subject is not output from the solid-state electronic image sensing device; AF target image data that is a portion of the image data is output from the solid-state electronic image sensing device. This means that readout can be performed comparatively quickly. The AF target image data thus read out is applied to the display unit and the AF target image is displayed on the display screen of the display unit. The AF target image is introduced to the eyepiece window of the finder unit by the deflecting unit and is superimposed upon the optical image of the subject. If the image within the AF target area is not in focus, an offset develops between the optical image of the subject and the image within the AF target area. If the image within the AF target area is in focus, the image within the AF target area is displayed upon the display screen of the display unit in such a manner that the optical image of the subject and the image within the AF target area will not be offset from each other but will coincide. Thus a so-called double-image coincidence finder unit can be realized.
The display control device may include a rotation-amount detection device for detecting amount of rotation of the focusing ring. In this case, the display control device would control the display unit, based upon amount of rotation detected by the rotation-amount detection device, so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other in at least the transverse direction, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.
The display control device may for example control the display unit, based upon amount of rotation detected by the rotation-amount detection device, so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other on an axis connecting optical axis of the lens barrel and optical axis of the finder unit, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.
The display control device may control the display unit so as to cause the image within the AF target area to move along at least the transverse direction in accordance with rotation of the focusing ring, and so as to display the image within the AF target area on the display screen in such a manner that, in a case where in-focus position of the focusing lens coincides with distance to the subject, the optical image of the subject seen through the objective window and the image within the AF target area will coincide. Further, the display control device may include: a rotation-amount detection device (rotation-amount detection means) for detecting amount of rotation of the focusing ring; and a distance calculation device (distance calculation device) for calculating, based upon the amount of rotation detected by the rotation-amount detection device, at what distance in front of the camera a subject at this distance is in focus; the first display control device causing the optical image of a subject seen through the objective window of the finder unit, where this subject is at the distance calculated by the distance calculation device, to coincide with the image within the AF target area being displayed on the display screen of the display unit owing to imaging of this subject by the solid-state electronic image sensing device.
By way of example, the display control device displays the image within the AF target area on the display screen upon correcting an offset between the optical image of the subject seen through the objective window and the image within the AF target area, the offset being ascribable to an offset between optical axis of the solid-state electronic image sensing device and optical axis of the finder unit.
The control display device displays the image within the AF target area on the display screen upon correcting, by a correction quantity that conforms to the distance calculated by the distance calculation device, an offset between the optical image of the subject seen through the objective window and the image within the AF target area, the offset being ascribable to an offset between optical axis of the solid-state electronic image sensing device and optical axis of the finder unit.
The camera may further comprise a first AF target area setting device (first AF target area setting means) for setting at least one among position, size and number of the AF target area(s).
The camera may further comprise a second AF target area setting device (second AF target area setting means) for setting at least one of brightness and density of the image within the AF target area.
The camera may further comprise: a face detection device (face detection means) for detecting the area of a face included in the image of a subject captured by the solid-state electronic image sensing device; and a third AF target area setting device (third AF target area setting means) for setting the area of the face, which has been detected by the face detection device, to the AF target area.
The solid-state electronic image sensing device may capture the image of the subject formed by the lens barrel and outputting subject-image data representing the captured image of the subject responsive to setting of the electronic viewfinder function by the setting device, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for capturing the image of the subject formed by the lens barrel and outputting AF-target image data, which is a portion of the captured image of the subject, and the display unit may display the image of the subject, which is represented by the subject-image data that is output from the solid-state electronic image sensing device, on a display screen responsive to setting of the electronic viewfinder function by the setting device, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for displaying the AF target image, which is represented by the AF target image data that is output from the solid-state electronic image sensing device, on the display screen.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a digital camera;
FIG. 2 is a back view of the digital camera;
FIG. 3 is a perspective view of the digital camera when viewed from the back;
FIG. 4 is a block diagram illustrating the electrical configuration of the digital camera;
FIG. 5 illustrates offset between the optical axis of a lens barrel and the optical axis of a finder unit;
FIG. 6 illustrates parallax between the lens barrel and the finder unit;
FIG. 7 is a plane view of the finder unit and a perspective view of the finder unit;
FIG. 8 illustrates the relationship between distance from a digital camera to a subject and parallax angle;
FIGS. 9 and 10 illustrate the manner in which a signal is read out of a solid-state electronic image sensing device;
FIG. 11 is an example of the optical image of a subject;
FIG. 12 is an example of an electronic viewfinder image displayed in an electronic viewfinder;
FIG. 13 illustrates an optical image of a subject and an electronic viewfinder image in superimposed form;
FIG. 14 is a flowchart illustrating processing executed by the digital camera;
FIG. 15 is an example of an image for setting the frame of an AF target area;
FIG. 16 is an example of an image for setting the density of an AF target area;
FIG. 17 is an example of an electronic viewfinder image; and
FIG. 18 is an example of the image of a subject in which a face has been detected.



DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 to 3, which illustrate an embodiment of the present invention, show the external appearance of a digital camera 1. FIG. 1 is a front view, FIG. 2 a back view and FIG. 3 a perspective view when viewed from the back.
With reference to FIG. 1, a lens barrel 2 projects forwardly from the approximate center of the front side of the digital camera 1. A finder unit is constructed at the upper right of the digital camera 1 and is formed to include an objective window 3 facing a subject. A flash device 4 is provided on the left side of the objective window 3. As will be described later in greater detail, the finder unit of this embodiment is capable of being switched between an optical/electronic hybrid viewfinder function and an electronic viewfinder function. The optical/electronic hybrid viewfinder function has a function for superimposing information, which is displayed in an electronic viewfinder, upon the optical image of the subject obtained by an optical viewfinder. A switching lever 19 for switching between the optical/electronic hybrid viewfinder function and the electronic viewfinder function is provided on the left side of the flash device 4. If the switching lever 19 is tilted leftward when viewed from the front, the finder unit is set to the optical viewfinder function. If the switching lever 19 tilted rightward when viewed from the front, the finder unit is set to the electronic viewfinder function.
A shutter-speed dial 6, a power lever 7, a shutter-release button 8 and an exposure dial 9 are provided on the top of the digital camera 1 on the left side thereof when viewed from the front. The shutter-speed dial 6 is a circular dial that is free to rotate. By rotating the shutter-speed dial 6, the user can set a desired shutter speed. The power lever 7 can be moved through a prescribed angle rightward and leftward as viewed from the front. By moving the power lever 7 through the prescribed angle, the user can turn the power supply of the digital camera 1 on and off. The power lever 7 has the shape of a ring with an interior space when viewed from the top (see FIG. 3), and the shutter-release button 8 is provided within the space. The exposure dial 9 also is a circular dial that is free to rotate. By turning the exposure dial 9, the user can correct the exposure.
With reference to FIGS. 2 and 3, a display screen 12 of a liquid crystal display device is formed substantially over the entirety of the back side of the digital camera 1. An eyepiece window 11 constituting a finder unit is formed on the back side of the digital camera 1 at the upper left thereof. A command lever 10 movable to the left and right is provided on the back side of the digital camera 1 at the upper right thereof. By manipulating the command lever 10, the user can supply the digital camera 1 with a command such as an aperture adjustment command in steps of 1⁄3 EV when the camera is in the manual exposure mode.
Provided below the command lever 10 are an AF (autofocus)/AE (autoexposure) lock button 13, a command dial 14, a menu/OK button 15, a back button 16 and a RAW button 17, etc.
With reference primarily to FIG. 3, the shutter-speed dial 6, the power lever 7, the shutter-release button 8 and the exposure dial 9 are provided on the top of the digital camera 1 on the right side thereof (the right side when viewed from the back), as mentioned above. The power lever 7 is formed to have a projection 7A projecting toward the front side. The power supply of the digital camera 1 can be turned on and off by grasping the projection 7A and moving it to the right or left.
By bringing an eye close to the eyepiece window 11 of the finder unit and looking at the eyepiece window 11, the user can view a subject through the objective window 3 and the eyepiece window 11 and can decide the camera angle.
FIG. 4 is a block diagram illustrating the electrical configuration of the digital camera 1.
The overall operation of the digital camera 1 is controlled by a CPU 47.
The digital camera 1 includes a solid-state electronic image sensing device 41. A focusing lens group 31 incorporated in the lens barrel 2 is positioned in front of the solid-state electronic image sensing device 41. A freely rotatable focusing ring 32 is provided on the periphery of the lens barrel 2. The focusing lens group 31 is positioned in accordance with user manipulation of the focusing ring 32.
When a subject is imaged by the solid-state electronic image sensing device 41, a video signal representing the image of the subject is output from the solid-state electronic image sensing device 41. The video signal is input to an analog/digital conversion circuit 43 via a sample/hold circuit 42. The video signal is converted to digital image data by the analog/digital conversion circuit 43. A signal processing circuit 44 subjects the digital image data obtained by the conversion to predetermined signal processing such as a white balance adjustment and gamma correction.
The digital image data that has been output from the signal processing circuit 44 is applied to an LCD (Liquid Crystal Display) driver 48 via a memory 46. The liquid crystal display device 12 (the same reference characters are used to denote the display screen) is controlled by the LCD driver 48 and the image of the subject captured by the solid-state electronic image sensing device 41 is displayed on the display screen of the liquid crystal display device 12.
When the shutter-release button 8 is pressed, the image data that has been input to the memory 46, as mentioned above, is recorded on a memory card 50 under the control of a memory card controller 49.
The image data that has been output from the signal processing circuit 44 as described above is applied to a digital/analog conversion circuit 45. The image data is restored to an analog video signal in the digital/analog conversion circuit 45 and the analog video signal is applied to an image shifting circuit 35.
When the focusing ring 32 provided on the periphery of the lens barrel 2 as described above is rotated, the amount of rotation of the focusing ring 32 is detected by an encoder 33. A signal indicating the amount of rotation detected is input to a distance calculation circuit 34. Based upon the entered signal indicating amount of rotation, the distance calculation circuit 34 calculates a distance (in-focus distance) indicating at what distance in front of the camera a subject at this distance comes into focus (this represents manual focusing). Data indicating the distance calculated is input to the image shifting circuit 35.
As mentioned above, the video signal indicating the image of the subject also is being input to the image shifting circuit 35. As will be described later in greater detail, processing by which the image of the subject is shifted in accordance with the calculated distance is executed in the image shifting circuit 35. The video signal that is output from the image shifting circuit 35 is applied to an electronic viewfinder 65 of the finder unit 60 by an LCD driver 36. The electronic viewfinder 65 is a liquid crystal display device. Thus it becomes possible to display the image of the subject, which has been obtained by imaging, on the display screen of the electronic viewfinder 65.
The finder unit 60 is equipped with an eyepiece lens 66 provided in front of the eyepiece window 11. A prism 63 formed to have a half-mirror 64 is provided in front of the eyepiece lens 66. The half-mirror 64 is formed so as to have a 45-degree angle of incidence with respect to optical axis C3 of the optical viewfinder 60. An OVF (optical viewfinder) shutter (which may be a mechanical shutter or a liquid crystal shutter) 62 and an objective lens 61 are provided in front of the prism 63.
When the OVF shutter 62 is open, the image of a subject OB formed by the objective lens 61 and the eyepiece lens 66 can be seen through the eyepiece window 11. Further, when the image of the subject obtained by imaging is displayed on the display screen of the electronic viewfinder 65 when the OVF shutter 62 is open, light rays representing the image of the subject are reflected by the half-mirror 64 so that the user can see the image of the subject being displayed on the display screen of the electronic viewfinder 65. The image of the subject displayed on the display screen of the electronic viewfinder 65 can be seen superimposed upon the optical image of the subject formed by the objective lens 61, etc.
Let C2 represent the optical axis of the lens barrel 2 (the optical axis of the lens barrel 2 and the optical axis of the solid-state electronic image sensing device 41 are the same) and let C3 represent the optical axis of the finder unit 60. The optical axes C2 and C3 do not coincide. As a consequence, parallax having a parallax angle θ is produced between the subject OB when viewed through the finder unit 60 and the subject OB imaged utilizing the lens barrel 2. In a case where the image of the subject displayed on the display screen of the electronic viewfinder 65 is viewed superimposed upon the optical image of the subject seen through the finder unit 60, as described above, the optical image of the subject seen through the finder unit 60 and the image of the subject displayed on the electronic viewfinder 65 are offset from each other due to parallax despite the fact that the user is viewing the same subject OB. In this embodiment, the image of the subject is shifted in the image shifting circuit 35 so as to correct for parallax. In a case where the focusing lens group 31 has been positioned by the focusing ring 32 so as to bring the subject OB into focus, the optical image of the subject seen through the eyepiece window 11 of the finder unit 60 and the image of the subject displayed in the electronic viewfinder 65 will coincide. If the subject OB is not in focus, the optical image of the subject seen through the eyepiece window 11 of the finder unit 60 and the image of the subject displayed in the electronic viewfinder 65 will not coincide. Thus a so-called image coincidence finder unit can be realized with the digital camera 1 according to this embodiment.
FIG. 5 illustrates the relationship between the lens barrel 2 and the objective window 3 when the digital camera 1 is viewed from the front.
The optical axis C2 of the lens barrel 2 and the optical axis C3 of the optical finder 60 (objective window 3) have a distance d apart and parallax exists between them. Consequently, in a case where a subject does not exist at a position regarded as infinity, an offset develops between the image of the subject seen through the eyepiece window 3 and the image of the subject captured by the lens barrel 2. As described above, when the image of a subject captured by the solid-state electronic image sensing device 34 is displayed in the electronic viewfinder 65 and this is superimposed upon the optical image of the subject formed via the objective window 3, there are instances where, owing to the aforesaid parallax, the portion of the image of the subject displayed in the electronic viewfinder 65 and the optical image of the subject will not coincide even if the focusing lens group 31 has been positioned so as to bring the subject into focus.
FIG. 6 illustrates a case where the subject OB is seen (imaged) via the lens barrel 2 and how the subject OB is seen through the eyepiece window 3 of the finder unit 60.
As mentioned above, the distance between the optical axis C2 of the lens barrel 2 and the optical axis C3 of the eyepiece window 3 is d. Let D represent the distance from the lens barrel 2 to the subject OB. Accordingly, a parallax angle θ defined by a line from the lens barrel 2 to the object OB and a line from the eyepiece window 3 to the object OB is θ=arc tan(d/D). That is, in a case where the subject OB is viewed through the lens barrel 2, the subject OB that appears in front is seen offset by the parallax angle θ from the eyepiece window 3 (finder unit 60). [The subject OB is offset from the lens barrel 2 (solid-state electronic image sensing device 41) by the parallax angle θ also in a case where the subject OB is viewed through the eyepiece window 3).]
FIG. 7 illustrates the structure of the finder unit 60. The diagram at the top of FIG. 7 illustrates the finder unit 60 in a planar view in a manner similar to FIG. 4, and the diagram at the bottom of FIG. 7 illustrates the finder unit 60 in three dimensions. Components in FIG. 7 identical with those shown in FIG. 4 are designated by like reference characters.
As shown in FIGS. 4 and 6, when the subject OB is viewed through the eyepiece window 3, it appears offset from the optical axis of the optical viewfinder 60 by the parallax angle θ. (In a case where the camera angle is decided by looking through the eyepiece window 3, it is conceivable that the subject OB will reside on the optical axis C3 of the finder unit 60. Even in such case, however, the subject OB will be offset by the parallax angle θ from the optical axis C2 of the lens barrel 2.) Therefore, in order to make the portion of the image of the subject displayed in the electronic viewfinder 65 coincide with the optical image of the subject formed through the eyepiece window 3, the portion of the image of the subject need only be displayed upon being shifted by the parallax angle θ. It goes without saying that the direction in which the portion of the image of the subject is shifted through the above-mentioned angle is decided in accordance with the positional relationship between the positions where the eyepiece window 3 and lens barrel 2 are placed and the position where the finder unit 60 is placed.
FIG. 8 illustrates the positional relationship among the digital camera 1 and principal subjects OB1, OB2 and OB3 when viewed in a plane.
If the principal subject OB1 is at a position (having a distance D1) comparatively far from the digital camera 1, then a parallax angle formed with the optical axis of the eyepiece window 3 will be θ1 in a case where the principal subject OB1 is viewed from the eyepiece window 3. Similarly, if the principal subject OB2 is at an intermediate position (having a distance D2) that is neither far from nor close to the digital camera 1, then a parallax angle formed with the optical axis of the eyepiece window 3 will be θ2 in a case where the principal subject OB2 is viewed from the eyepiece window 3. Furthermore, if the principal subject OB3 is at a position (having a distance D3) close to the digital camera 1, then a parallax angle formed with the optical axis of the eyepiece window 3 will be θ3. These parallax angles θ1, θ2 and θ3 are related as follows: θ1<θ2<θ3. In a case where the subject is located at a position so far away that it can be regarded as infinity, the parallax angle is almost negligible. In such case there will be almost no offset between the optical image of the subject seen through the eyepiece window 3 and the image of the subject displayed in the electronic viewfinder 65. This means that the above-mentioned parallax correction need not necessarily be applied in a case where the user views a subject at a great distance from the digital camera 1.
FIG. 9 illustrates a method of reading out signal charge that has accumulated in opto-electronic transducers formed on a photoreceptor surface 41A of the solid-state electronic image sensing device 41.
If the camera has been set to the optical/electronic hybrid viewfinder function, an image within an AF target area (the image will be referred to as an “AF target image”) is displayed on the display screen of the electronic viewfinder 65, as will be described in detail later. In this embodiment, if the optical/electronic hybrid viewfinder function has been set, signal charge that has accumulated in the opto-electronic transducers formed on the photoreceptor surface is not read out as a video signal; rather, signal charge that has accumulated in opto-electronic transducers contained in a photoreceptor region 51 that corresponds to the AF target area is read out as the video signal. Since the scope of the readout zone is thus reduced, the time needed to read out the video signal is shortened. For example, if the region 51 corresponding to the AF target area is on the order, of 1/10 of the entire photoreceptor surface, then readout can be accomplished in 1/10 the time in comparison with the case where the video signal of the entire photoreceptor surface is read out.
It may be arranged so that, in the case where the image shift is performed in the image shifting circuit 35 as described above, the signal charge that is read out as the video signal is signal charge that has accumulated in opto-electronic transducers contained in a region 51A larger than the region 51 corresponding to the AF target area but smaller than the photoreceptor surface. The reason for doing this is that there are occasions where, owing to the fact that the image represented by the video signal obtained from the region 51 is shifted, the image no longer represents the image within the AF target area.
In a case where signal charge is read out from the opto-electronic transducers in a portion of the photoreceptor surface 41A as shown in FIG. 9, CMOS (Complementary Metal-Oxide Semiconductor) can be utilized as the solid-state electronic image sensing device.
FIG. 10 also illustrates a method of reading out signal charge that has accumulated in opto-electronic transducers formed on the photoreceptor surface 41A of the solid-state electronic image sensing device 41.
If the camera has been set to the electronic viewfinder function, the OVF shutter 62 closes and the user sees the image of the subject displayed on the display screen of the memory card 50, as described above. It is necessary that the entire image of the subject captured by the solid-state electronic image sensing device 41 be displayed on the display screen of the electronic viewfinder 65. In order to achieve this, signal charge that has accumulated in the opto-electronic transducers on the entirety of the photoreceptor surface is read out as the video signal.
FIG. 11 is an example of an optical image 70 of the subject seen through the objective window 3 of the finder unit 60.
An image 72 of a principal subject, which is to be brought into focus, is positioned at the approximate center of the image 70 of the subject.
FIG. 12 is an example of an electronic viewfinder image 80 displayed on the display screen of the electronic viewfinder 65.
One AF target area 81 has been formed at the approximate center of the electronic viewfinder image 80. An image 82 of the subject captured by the solid-state electronic image sensing device 41 is being displayed in the AF target area 81. (The image 82 is illustrated by chain lines in FIG. 10 so as to indicate that this image has been obtained by electronic imaging.) The image of the subject 82 being displayed at the AF target area 81 was shifted by the image shift circuit 35 as mentioned above. The region surrounding the slide groove 82 is a mask region 85. In the image of the subject captured by the solid-state electronic image sensing device 41, the mask region 85 masks the image that is not being displayed in the AF target area 81. Further, brackets of a visual-field frame 83 indicating a picture-taking zone are being displayed at the four corners of the electronic viewfinder image 80. Data indicating the mask region 85 and visual-field frame 83 has been stored in memory 46. These items of data are read out of the memory 46 and applied to the LCD driver 36 by the CPU 47, whereby the mask region 85 and visual-field frame 83 are displayed.
FIG. 13 is an example of a finder image seen through the eyepiece window 11.
When the optical/electronic hybrid viewfinder function is set, the OVF shutter 62 opens. When the OVF shutter 62 is open, an image obtained by superimposing the electronic viewfinder image 80, which is shown in FIG. 12, upon the optical image 70 of the subject shown in FIG. 11 can be seen through the eyepiece window 11.
Although parallax develops between the optical axis C2 of the lens barrel 2 and the optical axis C3 of the finder unit 60 as mentioned above, the position at which the electronic viewfinder 65 is displayed is shifted by the image shifting circuit 35 in such a manner that a parallax correction is applied to the image 82 of the subject displayed in the electronic viewfinder 65. As a result, if the image 82 of the subject within the AF target area 81 is in focus, then the image 82 of the subject that is being superimposed upon the optical image 72 of the subject will coincide with it. If the image 82 of the subject within the AF target area 81 is not in focus, then an offset will develop between the optical image 72 of the subject and the image 82 of the subject that is being superimposed upon it. Focusing by way of manual focusing can be achieved by rotating the focusing ring 32 in accordance with the offset between the optical image 72 of the subject and the electronically captured image 82 of the subject. In particular, in this embodiment, if the optical/electronic hybrid viewfinder function is set, signal charge is not read out, as a video signal, from all of the opto-electronic transducers on the photoreceptor surface of the solid-state electronic image sensing device 41 but is instead read out, as a video signal, from the opto-electronic transducers contained in the region corresponding to the AF target area 81 (or in a region one size larger than said region). Readout time is shortened, therefore, and delay time until a display is presented in the electronic viewfinder 65 can be shortened. Even if the subject or the camera itself is moving, the AF target image can be displayed on the display screen of the electronic viewfinder 65 rapidly and focusing can be achieved.
FIG. 14 is a flowchart illustrating focusing processing by way of manual focusing.
First, it is determined whether the camera has been set to the optical/electronic hybrid viewfinder function (step 91).
If the optical/electronic hybrid viewfinder function has been set (“YES” at step 91), the image within the AF target area being displayed in the electronic viewfinder 65 is superimposed upon the optical image 72 of the subject as shown in FIG. 13 and the OVF shutter 62, therefore, opens (step 92). The optical image of the subject can be seen through the finder unit 60. In order to achieve rapid readout from the solid-state electronic image sensing device 41, as shown in FIG. 9, the video signal is read out from the region 51 corresponding to the AF target area (or from a region one size larger than said region) (step 93).
The user looks through the eyepiece window 11 of the finder unit 60 and turns the focusing ring 32 while viewing the optical image of the subject (step 94). The amount of rotation of the focusing ring 32 is detected by the encoder 33 (step 95) and the distance from the digital camera 1 to the subject brought into focus by the focusing lens group 31 is calculated (step 96). The relationship between the amount of rotation of the focusing ring 32 and the distance from the digital camera 1 to the subject brought into focus by the focusing lens group 31 is detected beforehand at the manufacturing stage of the digital camera 1. Data indicating this relationship is stored in a memory (not shown) within the distance calculation circuit 34. By utilizing the data indicating this relationship, and based upon the amount of rotation of the focusing lens group 31, the distance calculation circuit 34 calculates the distance from the digital camera 1 to the subject brought into focus by the focusing lens group 31.
The amount of image shift for effecting the parallax correction is calculated in accordance with the calculated distance (step 97). It goes without saying that, with regard to the relationship between the amount of shift and the distance from the digital camera 1 to the subject brought into focus by the focusing lens group 31, the relationship is calculated beforehand and stored at the manufacturing stage of the digital camera.
The image within the AF target area 81, which has been shifted by the amount of the image shift calculated in accordance with the amount of rotation of the focusing lens group 31, is displayed on the display screen of the electronic viewfinder 65 (step 98). As mentioned above, if the image 82 of the subject within the AF target area 81 is not in focus, an offset will develop relative to the optical image 72 of the subject (an offset along the transverse direction, an offset along the horizontal direction, an offset on the axis connecting the optical axis of the lens barrel 2 and the optical axis of the finder unit 60). If the image 82 of the subject within the AF target area 81 is in focus, then it will coincide with the optical image 72 of the subject. Thus, the finder unit 60 is of the so-called double-image coincidence type. For example, with reference to FIG. 8, assume that, even though a subject is the subject OB2 at the distance D2, the user has rotated the focusing ring 32 so as to bring into focus the subject OB1 at the distance D1 or the subject OB3 at the distance D3. In such case the user looking through the finder unit 60 will see a double image of the subject, namely two images with an offset between them. If the focusing ring 32 is rotated so as to bring into focus the subject OB2 at the distance D2, the user looking through the finder unit 60 will see an image of the subject that is devoid of image offset. Recognizing that correct focusing has been achieved, the user presses the shutter-release button (“YES” at step 99 in FIG. 14), whereby the image of the subject is captured. Image data representing the captured image of the subject is recorded on the memory card 50.
When the electronic viewfinder function is set and not the optical/electronic hybrid viewfinder function (“NO” at step 91), the OVF shutter 62 closes (step 100). The optical image of the subject acquired via the objective window 3 can no longer be seen through the eyepiece window 11.
The subject is imaged by the solid-state electronic image sensing device 41 and the video signal representing the entire image of the subject is read out (step 101). The focus of the image of the subject is adjusted by the user in accordance with user operation of the focusing ring 32 (step 102). The entire image of the subject the focus of which has been adjusted is displayed in the electronic viewfinder 65 (step 103). The user adjusts the focus by turning the focusing ring 32 while viewing the image of the subject displayed in the electronic viewfinder 65. By pressing the shutter-release button (“YES” at step 99), the image data representing the image of the subject is recorded on the memory card 50.
FIG. 15, which illustrates a modification, is an example of an image for setting the size of the AF target frame.
If a menu display screen is selected utilizing the menu/OK button 15 among the buttons of the digital camera 1, it becomes possible to select a menu for setting the size of the AF target frame. When the menu for setting the size of the AF target frame is selected, an image for setting the size of the AF target frame shown in FIG. 15 is displayed on the liquid crystal display screen 12.
A size setting bar 105 extending in the transverse direction is formed below the image for setting the size of the AF target frame. A slider 106 freely slidable in the transverse direction along the size setting bar 105 also is formed. When the menu for setting the size of the AF target frame is selected, the user moves the slide 106 left or right along the size setting bar 105 by operating a prescribed button among the buttons of the digital camera 1. The size of the AF target area 81 decreases as the slider 106 is moved left and, as indicated by the chain lines, increases as the slider 106 is moved right. The AF target area 81 can thus be set to a desired size.
FIG. 16, which illustrates a further modification, is an image for setting the density of the AF target.
If the menu display screen is selected utilizing the menu/OK button 15 among the buttons of the digital camera 1, in a manner similar to the setting of the AF target frame described above, it becomes possible to select a menu for setting the density of the AF target frame. When the menu for setting the density of the AF target frame is selected, an image for setting the density of the AF target frame shown in FIG. 16 is displayed on the liquid crystal display screen 12.
A density setting bar 108 extending in the transverse direction is formed below the image for setting the density of the AF target frame. A slider 107 freely slidable in the transverse direction along the density setting bar 108 also is formed. When the menu for setting the density of the AF target frame is selected, the user moves the slider 107 left or right along the density setting bar 108 by operating a prescribed button among the buttons of the digital camera 1. The image 82 of the subject displayed within the AF target area 81 becomes lighter as the slider 107 is moved left and becomes darker as the slider 102 is moved right. The density of the image of the subject displayed within the AF target area 81 can thus be set.
FIG. 17, which illustrates yet another modification, is an example of an electronic viewfinder image 80A displayed on the display screen of the electronic viewfinder 65. This corresponds to the electronic viewfinder image 80 shown in FIG. 12.
In the example shown in FIG. 12, the single AF target area 81 is set approximately at the center. In the example shown in FIG. 17, however, the signal AF target area 81 is set approximately at the center but, in addition, four AF target areas 111 to 114 are set around the AF target area 81.
By thus setting the plurality of AF target areas 81 and 111 to 114, a subject within a desired target frame can be brought into focus.
In a case where the plurality of AF target areas 81 and 111 to 114 are set, the menu display screen is set and the menu for setting the AF target area is selected in a manner similar to that described above. When this is done, the number of AF targets to be set can be entered and so can the positions at which the AF target areas are to be set. If necessary, the display screen 12 may be provided with a touch-sensitive panel or the like and the positions of the AF target areas may be specified on the touch-sensitive panel. Naturally, it may be arranged beforehand so that either the five AF target areas 81 and 111 to 114 can be set as shown in FIG. 17 or the single AF target area 81 as shown in FIG. 12, and so that the user may make either selection. It goes without saying that the corresponding image portions from within the image of the subject captured by the solid-state electronic image sensing device 41 would be displayed within these multiple AF target areas 81 and 111 to 114.
Even in the case where the multiple target areas 81, 111 to 114 have thus been set, it goes without saying that, if the optical/electronic hybrid viewfinder function is set, the signal charge read out as the video signal is the signal charge from the opto-electronic transducers contained in regions corresponding to respective ones of the target areas 81, 111 to 114 from among the electronic transducers formed on the photoreceptor surface of the solid-state electronic image sensing device 41.
FIG. 18, which illustrates yet another modification, is an example of the captured image of a subject.
A face image 121 is detected by imaging a subject. The area of the detected face image 121 is set in the AF target area 81. It will suffice if face detection is executed by the CPU 47. The face portion of the image will be brought into focus.
Thus, even if the camera has been set to the optical/electronic hybrid viewfinder function in a case where the area of the detected face image 121 is set to the AF target area 81, a video signal representing the entire image of the subject is read out of the solid-state electronic image sensing device 41 one time and the area of the face image 121 is detected from within the entire image of the subject represented by this video signal. The video signal corresponding to the area of the detected face image 121 (or to a region one size larger than this area) is read out of the solid-state electronic image sensing device 41 and is displayed on the display screen of the electronic viewfinder 65 in the manner described above.
As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

## Claims

1. A camera comprising:
a lens barrel, which is provided on its periphery with a focusing ring being freely rotatable and incorporates a focusing lens, for adjusting the position of the focusing lens in accordance with rotation of the focusing ring;
a setting device for setting either an optical/electronic hybrid viewfinder function or an electronic viewfinder function;
a finder unit formed on the front of the camera and having an objective window facing a subject and an eyepiece window for looking at an optical image of the subject seen through the objective window;
a shutter device for opening and closing a shutter so as to block light incident from the objective window of said finder unit in response to setting of the electronic viewfinder function by said setting device, and so as to pass light incident from the objective window of the finder unit in response to setting of the optical/electronic hybrid viewfinder function by said setting device;
a solid-state electronic image sensing device responsive to setting of the electronic viewfinder function by said setting device for capturing the image of the subject formed by said lens barrel and outputting subject-image data representing the captured image of the subject, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for capturing the image of the subject formed by said lens barrel and outputting AF-target image data representing the image within a desired AF target area, which image is a portion of the captured image of the subject;
a display unit responsive to setting of the electronic viewfinder function by said setting device for displaying the image of the subject, which is represented by the subject-image data that is output from said solid-state electronic image sensing device, on a display screen, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for displaying the AF target image, which is represented by the AF target image data that is output from said solid-state electronic image sensing device, on the display screen;
a deflecting unit, which is provided between the objective window and the eyepiece window, for introducing the AF target image or image of the subject, which is being displayed on the display screen of said display unit, to the eyepiece window; and
a display control device responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for controlling said display unit so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.

2. The camera according to claim 1, wherein said display control device includes a rotation-amount detection device for detecting amount of rotation of the focusing ring;
said display control device controlling said display unit, based upon amount of rotation detected by said rotation-amount detection device, so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other in at least the transverse direction, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.

3. The camera according to claim 2, wherein said display control device controls said display unit, based upon amount of rotation detected by said rotation-amount detection device, so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other on an axis connecting optical axis of said lens barrel and optical axis of said finder unit, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.

4. The camera according to claim 1, wherein said display control device controls said display unit so as to cause the image within the AF target area to move along at least the transverse direction in accordance with rotation of the focusing ring, and so as to display the image within the AF target area on the display screen in such a manner that, in a case where in-focus position of the focusing lens coincides with distance to the subject, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.

5. The camera according to claim 1, wherein said display control device further includes:
a rotation-amount detection device for detecting amount of rotation of the focusing ring; and
a distance calculation device for calculating, based upon the amount of rotation detected by said rotation-amount calculation device, at what distance in front of the camera a subject at this distance is in focus;
said display control device causing the optical image of a subject seen through the objective window of said finder unit, where this subject is at the distance calculated by said distance calculation device, to coincide with the image within the AF target area being displayed on the display screen of said display unit owing to imaging of this subject by said solid-state electronic image sensing device.

6. The camera according to claim 1, wherein said display control device displays the image within the AF target area on the display screen upon correcting an offset between the optical image of the subject seen through the objective window and the image within the AF target area, the offset being ascribable to an offset between optical axis of said solid-state electronic image sensing device and optical axis of said finder unit.

7. The camera according to claim 6, wherein said display control device displays the image within the AF target area on the display screen upon correcting, by a correction quantity that conforms to the distance calculated by said distance calculation device, an offset between the optical image of the subject seen through the objective window and the image within the AF target area, the offset being ascribable to an offset between optical axis of said solid-state electronic image sensing device and optical axis of said finder unit.

8. The camera according to claim 1, further comprising a first AF target area setting device for setting at least one among position, size and number of the AF target area(s).

9. The camera according to claim 1, further comprising a second AF target area setting device for setting at least one of brightness and density of the image within the AF target area.

10. The camera according to claim 1, further comprising:
a face detection device for detecting the area of a face included in the image of a subject captured by said solid-state electronic image sensing device; and
a third AF target area setting device for setting the area of the face, which has been detected by said face detection device, to the AF target area.

11. The camera according to claim 1, wherein said solid-state electronic image sensing device captures the image of the subject formed by the lens barrel and outputting subject-image data representing the captured image of the subject responsive to setting of the electronic viewfinder function by the setting device, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for capturing the image of the subject formed by the lens barrel and outputting AF-target image data, which is a portion of the captured image of the subject; and said display unit displays the image of the subject, which is represented by the subject-image data that is output from the solid-state electronic image sensing device, on a display screen responsive to setting of the electronic viewfinder function by the setting device, and responsive to setting of the optical/electronic hybrid viewfinder function by said setting device for displaying the AF target image, which is represented by the AF target image data that is output from the solid-state electronic image sensing device, on the display screen.

12. A method of controlling operation of a camera having a lens barrel, which is provided on its periphery with a focusing ring being freely rotatable and incorporates a focusing lens, for adjusting the position of the focusing lens in accordance with rotation of the focusing ring, and a finder unit formed on the front of the camera and having an objective window facing a subject and an eyepiece window for looking at an optical image of the subject seen through the objective window, said method comprising steps of:
a setting device setting either an optical/electronic hybrid viewfinder function or an electronic viewfinder function;
a shutter device opening and closing a shutter so as to block light incident from the objective window of the finder unit in response to setting of the electronic viewfinder function by the setting device, and so as to pass light incident from the objective window of the finder unit in response to setting of the optical/electronic hybrid viewfinder function by the setting device;
a solid-state electronic image sensing device capturing the image of the subject formed by the lens barrel and outputting subject-image data representing the captured image of the subject in response to setting of the electronic viewfinder function by the setting device, and capturing the image of the subject formed by the lens barrel and outputting AF-target image data representing the image within a desired AF target area, which image is a portion of the captured image of the subject, in response to setting of the optical/electronic hybrid viewfinder function by the setting device;
a display unit displaying the image of the subject, which is represented by the subject-image data that is output from the solid-state electronic image sensing device, on a display screen in response to setting of the electronic viewfinder function by the setting device, and displaying the AF target image, which is represented by the AF target image data that is output from the solid-state electronic image sensing device, on the display screen in response to setting of the optical/electronic hybrid viewfinder function by the setting device;
a deflecting unit, which is provided between the objective window and the eyepiece window, introducing the AF target image or image of the subject, which is being displayed on the display screen of the display unit, to the eyepiece window; and
in response to setting of the optical/electronic hybrid viewfinder function by the setting device, a display control device controlling the display unit so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is out of focus, the optical image of the subject seen through the objective window and the image within the AF target area will be offset from each other, and so as to display the image within the AF target area on the display screen in such a manner that, if the image within the AF target area is in focus, the optical image of the subject seen through the objective window and the image within the AF target area will coincide.