JPH1115046A - Viewfinder optical system for digital cameras - Google Patents

Abstract

(57) [Problem] In a digital camera that captures a subject image formed by a photographic optical system by a CCD, an error occurs in a mounting position of the CCD, causing a shift between an actual imaging range and a view range of a finder. Camera quality is degraded. SOLUTION: A subject image formed by a photographing optical system 2 is converted to CC.
An image is captured by D7, and the imaging range is set to the finder optical system 3.
In a digital camera configured to be visually confirmed by a user, the position of a field mask 33 provided in the finder optical system 3 for setting a shooting range can be adjusted on a plane perpendicular to the optical axis of the finder optical system 3. Therefore, even if the position of the CCD 7 is shifted with respect to the photographing optical system 2, the position of the field
Can be matched with the set photographing range of the field mask 33, the deviation between the screen actually photographed and the view range of the finder can be eliminated, and the photographing quality can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a viewfinder optical system for a digital camera, and more particularly to a viewfinder optical system for preventing an actual photographing range from being shifted from a view range of the viewfinder.

[0002]

2. Description of the Related Art In recent years, various so-called digital cameras have been proposed in which a subject image formed by a photographing optical system is picked up by a CCD element and the picked-up image is recorded. In this type of camera, it is possible to visually recognize a photographing screen by displaying an image captured by a CCD element on a monitor device. However, when the monitor device is constantly driven, current consumption increases and battery life is short. Becomes In view of the above, in a digital camera that is reduced in size and weight, a finder using an optical system that does not cause a problem of power consumption is provided. However, since a finder using this optical system is configured as an optical system independent of a photographic optical system for performing imaging with a CCD element, it is necessary to design the finder so that the visible range and the imaging range in the finder match. Even if it is performed, the range actually picked up by the CCD element and the field of view range in the finder optical system may not match due to a manufacturing error or an assembly error when actually manufacturing the digital camera. In particular, CC
Since the image pickup surface of the D element is very small, due to the mounting position error of the CCD element when assembling the digital camera,
The mounting position of the shooting optical system with respect to the optical axis has changed,
This causes a large change in the photographing range.

On the other hand, since the finder optical system used in this type of camera uses the finder optical system of a conventional camera using a silver halide film as it is, it does not have a mechanism for adjusting the field of view. There are many things.
This is because, in a silver halide film camera, an exposure range for a film, that is, a photographing screen is determined by an aperture provided in a camera body, and a photographing optical system is assembled to the camera body. Since the size is larger than that of the image pickup surface, slight displacement of the photographing screen hardly causes a problem. Therefore, the finder optical system is not provided with a mechanism for adjusting the field of view in particular. For this reason, when the finder optical system of the camera based on the silver halide film is applied as it is to the finder optical system of the digital camera, the positional shift on the CCD element side is directly generated as a shift of the actual shooting range with respect to the visual field range in the finder optical system. Will be.

[0004]

As described above, the conventional digital camera does not have a mechanism for adjusting the field of view of the finder optical system. Therefore, when the shooting range is set based on the view range of the finder optical system, there is a gap between the actual shooting range and the screen range, which directly lowers the performance quality of the digital camera. There is a problem of being connected.

It is an object of the present invention to provide a viewfinder optical system of a digital camera which eliminates a difference between a screen range actually photographed and a view range of a viewfinder, thereby improving camera quality. is there.

[0006]

A finder optical system according to the present invention is a digital camera having a configuration in which an image pickup element is used to pick up an image and an image pickup range is visually recognized by the finder optical system. A field mask for setting a range is provided, and the position of the field mask is adjustable on a plane perpendicular to the optical axis of the finder optical system. The field mask is formed in a shape and a size that allows the same range as the imaging range of the imaging device to be visually recognized. The visual field mask includes, for example, a visual field frame that allows the same range as the imaging range of the image sensor to be visually recognized, and a mounting plate that supports the visual field frame and is supported by a camera body of a digital camera. Is mounted on the mounting plate so as to be adjustable in one direction on a plane perpendicular to the optical axis, and the mounting plate is perpendicular to the one direction on the plane perpendicular to the optical axis with respect to the camera body. It is configured to be supported so that the position can be adjusted in various directions.

[0007]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an embodiment in which the present invention is applied to a small and thin digital still camera having a zoom configuration. FIG. 1 (a) is a diagram viewed from the front, and FIG. 1 (b) is a diagram viewed from the rear. FIG. Camera body 1
Is formed in a thin rectangular housing shape having a depth dimension D smaller than the width dimension W and the height dimension H, and the photographing optical system 2 is disposed on the front surface at the upper right position toward the front surface. The objective window 31 of the finder optical system 3 is arranged at a position adjacent to the photographing optical system 2. An eyepiece window 32 of the finder optical system 3 is arranged on the rear surface of the camera body 1 at an upper left position toward the rear surface, and an LCD for monitoring a captured image is provided on a lower area on the right side.
(Liquid crystal display device) 4 is arranged. A release button 5 and other switches 6 are arranged on the upper surface of the camera body 1.

FIG. 2 is a schematic perspective view showing the arrangement of each part in the camera body 1 of the digital still camera. The photographing optical system 2 is configured as a zoom lens and constitutes the photographing optical system 2. Of multiple lenses,
The lenses 21 and 22 are moved in the main optical axis direction by feed mechanisms 25 and 26 driven by the small motors 23 and 24, respectively, so that the focal length, that is, the zoom magnification can be changed and adjusted. Further, a CCD 7 is arranged at an image forming position of the photographing optical system 2, captures a subject image formed by the photographing optical system 2, and outputs an image pickup signal. Since the configuration and operation principle of the CCD 7 are already known technologies, a detailed description thereof will be omitted here.
The imaging surface 7 is set to a required size in advance.

On the other hand, the finder optical system 3 also has a zoom configuration in which the finder magnification is variable. As will be described later in detail, an optical path L extending from the objective window 31 to the eyepiece window 32 is bent, and along the optical path L Four lenses 34a
To 34d, four reflection mirrors 35a to 35d, and a visual field mask 33 are arranged. And
A circuit board 81 on which a processing circuit for processing an image signal output from the CCD 7 is mounted in an internal area of the camera body 1 which does not interfere with the optical path L of the finder optical system 3, and a drive for driving the LCD 4 A circuit board 82 on which a circuit is mounted, a small motor 23 of the photographing optical system 2,
Circuit board 8 on which a drive circuit for driving 24 is mounted
3. A circuit board 84, a battery 85, a recording card 86 for recording photographed image data, a backlight 87 for the LCD 4, and the like are mounted inside a central processing circuit for comprehensively controlling the circuits. ing.

FIG. 3 is a schematic perspective view showing the configuration of the finder optical system 3. As shown in FIG. A first reflecting surface is directed downward at an angle of 45 degrees with respect to the optical axis of the objective window 31 oriented parallel to the main optical axis of the photographing optical system 2, that is, the main optical axis Om of the finder optical system. A second reflecting mirror 35b disposed at a position directly below the first reflecting mirror 35a and having a reflecting surface directed rightward in the drawing at an angle of 45 degrees; and a second reflecting mirror 35b. A third reflection mirror 35c disposed at the right side in the horizontal direction of 35b and having a reflection surface directed upward at an angle of 45 degrees; and a position immediately above the third reflection mirror 35c and opposed to the eyepiece window 32 And a fourth reflection mirror 35d disposed at a position, the reflection surface of which is directed rearward at an angle of 45 degrees. As a result, the main optical axis Om is reflected by the first reflection mirror 35a and bent downward at a right angle, reflected by the second reflection mirror 35b and bent horizontally rightward, and is reflected by the third reflection mirror 35c.
And is bent vertically upward, and further reflected by the fourth reflecting mirror 35d and directed in a direction parallel to the main optical axis Om. As a result, the digital camera has a concave shape when viewed from the front side. Thus, an optical path is formed.

Also, on the optical path L, a first lens 34a fixed between the objective window 31 and the first reflection mirror 35a, the first reflection mirror 35a and the second reflection mirror 35b The second lens 34b and the third lens 34c, which are respectively movable in the optical axis direction, are disposed between the fourth reflection mirror 35d and the eyepiece window 32, and are minute in the optical axis direction. A movable fourth lens (eyepiece lens) 34d is arranged. A field mask 33 is disposed between the third reflection mirror 35c and the fourth reflection mirror 35d. And the second lens 3
4b and the third lens 34c are respectively a small motor 36,
It is configured to be moved while being linked in the optical axis direction by feed mechanisms 38 and 39 having a drive source 37. As the feed mechanism, a known screw mechanism is used, but a detailed description thereof is omitted here. The rotation of the small motors 36 and 37 is controlled by a drive circuit mounted on the circuit board 83 so as to be driven in a predetermined relationship with the small motors 23 and 24 of the photographing optical system 2.

In the finder optical system having this configuration, a real image of a subject is formed by the first lens 34a, the second lens 34b, and the third lens 34c at a position on the optical axis where the field mask 33 is disposed. You. At this time, since the light is reflected by the first to third reflection mirrors 35a to 35c,
At the position of the field mask 33, an image is formed as a real image of an inverted normal image. The visual field mask 33 sets the visual field area of the real image, and the real image is reflected by the fourth reflecting mirror 35d and is observed by the photographer through the fourth lens 34d. At this time, the image is observed as an erect image by the reflection of the fourth reflection mirror 35d and the image formation of the fourth lens 34d. At this time, the diopter can be adjusted by adjusting the optical axis position of the fourth lens 34d by a diopter adjustment mechanism not shown.

The field mask 33 is shown in an exploded perspective view in FIG. 4 and a plan view in an assembled state in FIG. 5, respectively.
A field frame 41 formed as a rectangular frame-shaped member having an opening window 41a having a screen size corresponding to a shooting screen captured by the CCD 7, and the field frame 41 is attached to and supported by the part 11 in the camera body 1. The view frame 41 is supported by the mounting plate 42, and the mounting plate 42 is supported by the part 11 of the camera body. The mounting plate 42 and the field frame 41 are arranged on a plane perpendicular to the optical axis L of the finder optical system 3. The visual field frame 41 has tabs 43 protruding in one direction on a plane perpendicular to the optical axis L, in this case, in the direction of arrow UD which is the vertical direction of the subject image formed at the visual field mask position. These tabs 43 are formed with elongated holes 44 whose longitudinal direction is oriented in the vertical direction. The tabs 43 are supported on the mounting plate 42 by vertical position adjusting screws 45 inserted into the elongated holes 44. Is done. The mounting plate 42 is formed as a plate-shaped frame member having an adjustment window 42a having an opening dimension slightly larger in vertical and horizontal dimensions than the opening window 41a of the field frame 41, and is arranged in one direction on a plane perpendicular to the optical axis L. Notch holes 46 whose longitudinal direction is also directed to the left and right directions are formed on both sides in the direction perpendicular to the direction, here the arrow LR direction which is the left and right direction of the subject image, respectively.
Left and right position adjusting screw 47 inserted into this notch hole 46
Accordingly, the camera body 1 is supported by a pair of visual field mask support portions 12 provided at locations corresponding to the portions 11 of the camera body 1, respectively.

Therefore, in the field mask 33, the vertical position adjusting screw 45 is loosened and the field frame 41 is moved in the longitudinal direction of the elongated hole 44 with respect to the mounting plate 42 as shown by the arrow UD in FIG. By adjusting the position, it is possible to change the vertical viewing range of the subject image on the optical path. Also, loosen the left / right position adjustment screw 47, as shown in FIG.
As shown by the arrow LR, the mounting plate 42 is moved in the notch direction of the notch hole 46 with respect to the field mask support portion 12 to adjust the position thereof, so that the field of view of the subject image on the optical path in the left and right direction is obtained. The range can be changed. This makes it possible to adjust the vertical and horizontal positions with respect to the subject image and adjust the visual field range of the subject image. The actual adjustment of this visual field range is performed by the photographing optical system 2 and C
The monitor image of the subject actually captured by the CD 7 is displayed on the LCD 4.
The confirmation is made so that the monitor range of the LCD 4 matches the view range of the finder optical system 3.

Thus, even when the CCD 7 has a small imaging area and is displaced in a direction perpendicular to the optical axis of the photographing optical system 2 when assembled with the photographing optical system 2, the finder optical system 3 By adjusting the position of the visual field mask 33, the photographing range of the CCD 7 and the visual field range of the finder optical system 3 can be almost completely matched. And
In this case, since the size of the field of view of the field mask 33 is much larger than the size of the imaging range of the CCD 7, the position adjustment sensitivity of the field mask 33 is extremely lower than the position adjustment sensitivity of the CCD 7, and Can easily adjust the visual field range. This allows
It is possible to eliminate the shift between the screen actually shot and the field of view of the finder, and to obtain a digital still camera with high performance quality.

In this embodiment, in the finder optical system 3, the optical axes of the second lens 34b and the third lens 34c are maintained in a predetermined relationship by controlling the rotation of the small motors 36 and 37, respectively. By performing the change control, the size of the real image formed at the position of the field mask 33 is changed, and further, the size of the image observed by the fourth lens 34d,
That is, the finder magnification is changed. That is, the second
By changing the optical axis positions of the lens 34b and the third lens 34c, the real image size is changed, and the finder magnification is changed. Since the finder magnification is linked to the zoom magnification in the photographing optical system 2, it is possible to confirm the subject at a magnification corresponding to the photographing magnification, and to reduce the photographing range by the CCD and the visual field range by the viewfinder optical system. Can always be matched.

Here, the elongated hole provided in the visual field frame of the embodiment may be formed as a notch hole, or the notch hole provided in the mounting plate may be formed as an elongated hole. It is possible to In the above embodiment,
The field mask allows the position of the field frame and the mounting plate to be adjusted by tightening and adjusting screws, but the position is adjusted by linearly moving the field frame and the mounting plate in each direction using an eccentric cam. It may be configured. Further, the field frame may be configured such that a frame line is engraved on a transparent plate member, and the field range is set using the frame line. Further, in the above embodiment, the finder optical system has a porro-mirror configuration using four reflecting mirrors, but may be an optical system using a prism or an optical system using a pentaprism.

[0018]

As described above, according to the present invention, the position of the field mask provided in the viewfinder optical system for setting the photographing range can be adjusted on a plane perpendicular to the optical axis of the viewfinder optical system. With this configuration, even if the CCD is misaligned with respect to the imaging optical system, by adjusting the position of the field mask, the imaging range of the CCD and the set imaging range of the field mask can be matched. Eliminates the gap between the screen actually shot and the view range of the viewfinder,
The performance quality of the digital camera is improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a digital still camera equipped with a finder optical system according to an embodiment of the present invention in a front direction and a rear direction.

FIG. 2 is a schematic perspective view showing the entire configuration of the digital still camera according to the first embodiment of the present invention.

FIG. 3 is a schematic perspective view of a finder optical system of the digital still camera in FIG. 2;

FIG. 4 is a partially exploded perspective view of a visual field mask.

FIG. 5 is a plan view of a field mask.

[Description of Signs] 1 Camera body 2 Photographing optical system 3 Finder optical system 4 LCD 5 Release button 7 CCD 31 Object window 32 Eyepiece window 33 Field mask 34a-34d Lens 35a-35e Reflection mirror 41 Field frame 42 Mounting plate 44 Slot 45 Vertical position adjustment screw 46 Notch hole 47 Left / right position adjustment screw

Claims (5)

[Claims] An imaging optical system for forming an image of a subject;
An image sensor for capturing an optical image of the subject formed by the photographing optical system, and a digital camera including a finder optical system for visually recognizing a photographing range of the subject, wherein the finder optical system includes: A finder optical system for a digital camera, wherein a field mask for setting an imaging range is provided, and the position of the field mask is adjustable on a plane perpendicular to the optical axis of the finder optical system. . 2. The finder optical system of a digital camera according to claim 1, wherein the field mask is formed in a shape and a size that allows a same range as an imaging range of the imaging device to be visually recognized. 3. The field mask includes a field frame that allows the same range as a shooting range of the image sensor to be viewed, and a mounting plate that supports the field frame and is supported by a camera body of a digital camera. The viewing frame is supported so as to be position-adjustable in one direction on a plane perpendicular to the optical axis with respect to the mounting plate, and the mounting plate is positioned on the plane perpendicular to the optical axis with respect to the camera body. 3. The finder optical system for a digital camera according to claim 2, wherein the finder optical system is supported so as to be adjustable in a direction perpendicular to the direction. 4. The field frame is fixedly supported on the mounting plate by first fastening means in a slot or notch directed in the one direction, and the mounting plate is oriented in a direction perpendicular to the one direction. The frame and the mounting plate are fixedly supported by the camera body by the second fastening means in the elongated holes or cutouts, and by releasing the fastening of the first and second fastening means, the view frame and the mounting plate are respectively moved in the one direction or 4. The finder optical system of a digital camera according to claim 3, wherein the position can be adjusted in a direction perpendicular to the direction. 5. The finder optical system includes an optical system for forming an image of the subject at an optical axis position where the field mask is disposed, and an optical system for enlarging the formed subject image. A viewfinder optical system for a digital camera according to claim 1.