JP3243020B2 - Optical viewfinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical viewfinder for a camera, and more particularly to an optical viewfinder for realizing a clear view in the viewfinder.

[0002]

2. Description of the Related Art The structure of a conventional optical viewfinder will be described with reference to FIG. FIG. 4 shows a single-lens reflex electronic still camera having an inner focus type zoom mechanism.
It is sectional drawing cut | disconnected by the perpendicular cross section containing the optical axis P. Behind the front fixed lens group 1 disposed on the subject side, a variator lens group 2 for changing the focal length, a compensator lens 3 for adjusting the focal position, an aperture mechanism 4, a master lens group 5, a beam The splitters 6 are arranged along the same optical axis P, and the beam splitter 6 splits incident light into two optical paths.

A condensing lens 7 and a half mirror 8 are provided on one optical path side split by the beam splitter 6, and one light split by the half mirror 8 is measured by a dimming sensor 9 and is not shown. Automatically controls the flash emission,
The other light is measured by the photometric sensor 10, and the aperture 4 is automatically controlled according to the luminance of the subject.

[0004] On the other optical path side of the beam splitter 6,
A relay lens group 11, a quick return mirror 12 swingably supported by a support shaft 12a, an optical low-pass filter 13, and a two-dimensional color solid-state imaging device 14 are sequentially arranged. When the quick return mirror 12 is tilted so as to block the front surface of the optical low-pass filter 13 when the shutter release button is off as shown in the figure, the incident light is reflected toward the dummy glass 15,
When the quick return mirror 12 tilts toward the dummy glass 15 when the shutter release button is turned on, the two-dimensional color solid-state imaging device 14 is irradiated with incident light via the optical low-pass filter 13 to enable imaging. .

[0005] An optical mechanism provided behind the dummy glass 15 is an optical finder, and a screen 1 made of a glass substrate provided behind the dummy glass 15.
6, a filled lens 17, a prism 18, and an eyepiece group 19, so that the subject image reflected by the quick return mirror 15 can be viewed through a finder window 20.

Here, as shown in the figure, the distance L1 from the optical axis center Q on the reflecting surface when the quick return mirror 15 is tilted to the light receiving surface of the two-dimensional color image sensor 14, ie, the image forming surface, and the light Screen 16 from axis center Q
And the distance L2 to the entrance plane (hereinafter, referred to as a primary imaging plane) is designed to be equal. Further, the primary imaging plane of the screen 16 has a field frame for determining the field of view of the finder, a focusing state, and the like. A display pattern or the like for indicating a strobe shooting display is coated. Since such a coating is formed so that only the display pattern portion does not transmit light and the other glass substrate portion transmits the subject image, an image in which the display pattern overlaps the subject image is formed by the eyepiece lens group 19. And is projected on the finder window 20.

[0007]

However, in the optical viewfinder having such a configuration, the eyepiece group 19 enlarges only the display pattern and the subject image formed on the primary image forming surface of the screen 16. In addition to displaying on the screen, fine dust and dust adhering to the glass substrate of the screen 16 or minute scratches on the glass substrate are enlarged and displayed.

[0008] The present invention has been made in view of such a conventional problem, and has as its object to provide an optical viewfinder that realizes clear display in the viewfinder.

[0009]

In order to achieve the above object, an optical finder according to the present invention is provided with an optical system in which a subject image incident through an imaging optical system of a camera is formed behind a primary image forming surface. Place a relay lens with a magnification greater than 1,
A screen having a display pattern for display in the viewfinder is arranged on the image forming surface of the relay lens, and an eyepiece is arranged behind the screen.

[0010]

According to the present invention having such a configuration, the subject image on the primary image plane is enlarged and re-imaged on the image plane of the relay lens at a predetermined magnification, and is located on the image plane of the relay lens. The display pattern on the screen overlaps the re-imaging.
Then, the re-image having this display pattern is enlarged at a predetermined magnification by the eyepiece and appears in the finder window.
Therefore, since the magnification for the subject image is higher than the magnification for the display pattern, the image of fine dust, dust, or fine scratches attached to the screen becomes smaller and less noticeable than the subject image displayed in the viewfinder. As a result, a clear viewfinder display is realized.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. First, the configuration will be described with reference to FIG. The optical viewfinder is applied to a single-lens reflex electronic still camera having an inner focus type zoom system.

In this electronic still camera, a fixed front lens group 21 to which a subject image is incident is arranged in order along the optical axis P.
A variable variator lens group 22 provided so as to be movable forward and backward along the optical axis P, a diaphragm mechanism 23, a master lens group 24, and a focal point provided so as to be movable forward and backward along the optical axis P. An adjustment compensator lens group 25, a beam splitter 26, an optical low-pass filter 27, and a two-dimensional color solid-state imaging device 28 are provided.

Here, the aperture mechanism 23 includes a drive motor 29
A gear meshing with the gear 30 fixed to the drive shaft is formed, and the aperture amount is adjusted with the rotation of the drive shaft. The beam splitter 26 transmits the incident subject image to the two-dimensional color solid-state imaging device 28 via the optical low-pass filter 27 and, at the same time, branches the image to the optical finder.

On the branch side of the beam splitter 26, a fixed lens 31, a reflecting mirror 32,
A relay lens 33 composed of a plurality of lenses is arranged, and the relay lens 33 is located at a distance from an intersection Q between the center of the incident optical axis and the center of the branch optical axis in the beam splitter 26 to the imaging plane of the two-dimensional color solid-state imaging device 28. It is arranged at a position separated from the primary image forming surface S1 on the optical finder side at a distance L2 (= L1) equal to L1.

Further, a screen 34 is provided on an image forming surface (hereinafter, referred to as a secondary image forming surface) S2 behind the relay lens 33, and an eyepiece 3 comprising a plurality of lenses is provided behind the screen 34.
5 are provided.

As shown in FIG. 2A, the screen 34 has a pattern 36 indicating a field frame for determining the field of view of the finder, a pattern 37 indicating the focused state, and a strobe light on the surface of the transmission glass substrate. A pattern group 38 for displaying photographing and other camera operation information has a structure coated by chrome evaporation or the like, and these patterns 36 to 38 block light transmission and allow only the remaining glass portion to transmit light. It is supposed to. The pattern is not limited to chrome vapor deposition, but may be a printed pattern for blocking light transmission or other means having the same function.

Further, a light emitting unit 39 that covers only the area of the pattern group 38 from the inside is disposed. In the light emitting unit 39, the light emitting diode group 40 facing each pattern of the pattern group 38 faces the eyepiece 36 side. It is provided. Therefore, when a specific light emitting diode emits light, an image of one of the patterns in the pattern group 38 facing the light emitting diode is incident on the eyepiece 36.

According to the optical viewfinder having such a structure, the subject image split by the beam splitter 26 is formed on the primary image forming surface S1, and the subject image passes through the fixed lens 31 and is reflected by the reflecting mirror 32. Then, the image is re-imaged on the secondary image plane S2 of the relay lens 33. Then, when the subject image passes through the display pattern of the screen 34 located on the secondary imaging plane S2 as shown in FIG. 2A, the display pattern overlaps the re-formed subject image, and this display is performed. The re-imaging having the pattern is enlarged at a predetermined magnification by the eyepiece 36 and displayed on the finder window 41 as shown in FIG.

Next, the effect of the embodiment will be described by comparing the operation of the conventional optical viewfinder shown in FIG. 4 with that of the embodiment shown in FIG. In the conventional optical finder shown in FIG. 4, as shown in the principle diagram of FIG. 3A, a screen 16 on which a display pattern is formed is arranged on a primary image forming surface S1, and an eyepiece 19 is arranged behind the screen. And the focal length of the eyepiece 19 is f1,
It is assumed that the clear view distance of the finder is fm. on the other hand,
In the optical viewfinder of the embodiment shown in FIG. 1, as shown in the principle diagram of FIG. 3B, a relay lens 33 is disposed behind a primary imaging surface S1, and a secondary imaging surface S2 of the relay lens 33 is provided. A screen 34 on which a display pattern is formed is disposed, and an eyepiece 36 is further disposed behind the screen 34. The magnification of the relay lens 33 is β (> 1), the focal length of the eyepiece 35 is f2, and the viewfinder is bright. It is assumed that the visual distance is fm, which is equal to the conventional one.

First, since it is a precondition for comparison that the finder magnifications of both optical finder are equal, from the relationship of fm / f1 = β · fm / f2, f2 = β · f1 (1) Both optical viewfinders are designed to satisfy the relational expression.

Further, assuming that fine dust and the like having the same area ε are present on both the screens 19 and 34, FIG.
The area M1 of an image of dust or the like appearing in the finder window 20 of the conventional optical finder shown in FIG. 3A is as follows: M1 = ε · fm / f1 (2), and the optical finder of the embodiment shown in FIG. The area M2 of an image of dust or the like appearing in the finder window 41 is as follows: M2 = ε · fm / f2 (3) Then, when ε is eliminated from the above equations (2) and (3), the relationship of f1 · M1 = f2 · M2 (4) is obtained. When this equation (4) is substituted into the above equation (1), M1 = β · M2 (5) is obtained.

Here, the magnification of the relay lens 33 is β> 1.
Therefore, the relationship of M1> M2 always holds from the above equation (5). Therefore, the same area ε
Even if there is dust or the like, the conventional optical viewfinder is more likely to show an image of dust and the like appearing in the viewfinder window (area M1).
In the optical viewfinder of the present embodiment, the image (area M2) of dust and the like appearing in the finder window is smaller than that of the optical finder according to the present embodiment. can do.

As described above, according to this embodiment, while the subject image is enlarged to a desired magnification, the enlarged display of an image of dust or the like can be suppressed as compared with that, so that a clear viewfinder display is provided. be able to.

In this embodiment, the case where the relay lens and the eyepiece are applied has been described. However, the case where the relay lens and the eyepiece including one or more lenses are applied may be used.

Further, in this embodiment, the electronic still camera using the beam splitter 26 in the image pickup optical system is shown, but the quick return mirror 12 shown in FIG.
This can also be applied when using.

Although the case where the reflection mirror 32 is used to bend the optical axis direction has been described, the present invention can be applied to the case where the prism 18 as in the conventional example of FIG. 4 is used.

[0027]

As described above, according to the optical finder of the present invention, a relay having a magnification greater than 1 is provided behind a primary image forming surface on which a subject image incident via an imaging optical system of a camera is formed. In addition to disposing the lens, a screen having a display pattern for display in the viewfinder is arranged on the image forming surface of the relay lens, and further, an eyepiece is arranged behind the screen, so that fine Even if there is any fine dust, dust, or minute scratches, the image becomes relatively smaller than the subject image appearing in the finder window and becomes inconspicuous, so that a clear viewfinder display can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an embodiment of an optical finder according to the present invention, showing a configuration of a transmissive display substrate and a display in a finder appearing in a finder window.

FIG. 2 is a diagram illustrating a configuration of a screen and a display in a finder appearing in a finder window according to the embodiment.

FIG. 3 is a principle explanatory diagram for explaining the operation and effect of one embodiment.

FIG. 4 is a longitudinal sectional view showing a configuration of a conventional optical finder.

[Explanation of symbols]

32: reflection mirror, 33: relay lens, 34: screen, 35: eyepiece, 41: finder window, 36
... A pattern indicating a visual field frame, 37 a pattern indicating an in-focus state, 38 a pattern group for displaying operation information of a camera, S
1: Primary imaging plane, S2: Secondary imaging plane.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-6-102575 (JP, A) JP-A-5-142624 (JP, A) JP-A-5-346608 (JP, A) JP-A-1- 231013 (JP, A) Japanese Utility Model Application Showa 60-59229 (JP, U) Japanese Utility Model Application Hei 2-41241 (JP, U) Japanese Utility Model Application Utility Model 3-5142 (JP, U) (58) Field surveyed (Int. ⁷ , DB name) G03B 13/00-13/28

Claims (3)

(57) [Claims] 1. A relay lens having a magnification greater than 1 provided behind a primary image forming surface on which a subject image incident via an imaging optical system of a camera is formed as an aerial image, and an image formed by the relay lens. An optical viewfinder comprising: a screen having a display pattern for display in a viewfinder disposed on a surface; and an eyepiece disposed behind the screen. 2. An optical camera for an electronic still single-lens reflex camera.
2. The optical fiber according to claim 1, wherein
Indah. 3. The display screen, wherein the display pattern is
Be composed of a transparent glass substrate having
The optical finder according to claim 1, wherein: