JPH03287146A - Finder optical system - Google Patents

Abstract

PURPOSE:To vary power in accordance with pseudo zooming and to correctly display the frame of visual field corresponding to a printed image plane by providing a relay lens which forms a primary image into a secondary image by varying the power in accordance with the magnification of the pseudo zooming, an ocular which magnifies the secondary image and a frame showing an actuated object range by an AF device. CONSTITUTION:The primary image is formed on a primary image plane 12 by the photographing lens 10 of a camera and formed into the secondary image by the relay lens 15. Since the power of the lens 15 can be varied, the power is varied corresponding to the magnification of the pseudo zooming of the camera. The secondary image is magnified by the ocular 18 and observed by a photographer 19. The range of the visual field (reference visual field) being the object on which focus is detected by the AF device is confirmed in a finder by the frame 27 (AF frame) provided on the plane 12. Since the AF from 27 on the plane 12 is magnified by the lens 15 corresponding to the pseudo zooming, the display of the AF frame in the finder where the pseudo zooming is reflected becomes correct.

Description

[Detailed Description of the Invention] 1. The present invention provides pseudo zooming (electronic zoom) by trimming.
The present invention relates to a finder optical system for an SLR camera with functions.

Currently, both SLR and LS cameras are equipped with zoom lenses, but zoom lenses have more lenses than single-focal-length lenses, making it difficult to increase their size. I can't do it. Therefore, a pseudo zoom function has been proposed as something that can be included in compact cameras (
For example, JP-A-54-26721, etc.).

As shown in Figure 10(b), the pseudo-zoom function means that printing is done by enlarging a portion of the film surface (trimmed screen) 120 than the standard size (as shown in Figure 10(a)) during processing. , to obtain an enlarged photographic image. Information 122 regarding the size of this trimming screen (portion to be printed) is imprinted on the outside of the photographing surface of the film by the camera at the time of photographing.

In this way, the pseudo zoom function is realized by a system that integrates the photographing process using the camera and the printing process. Therefore, at the time of shooting with a camera,
Only the standard (that is, the photographic lens) magnification image is projected on the film surface, and if you use a conventional viewfinder, you cannot visually check what the screen will look like when it is printed. Can not.

Therefore, in the case of an SLR camera, a movable field frame 101 is provided at the position of the focus plate 100, as shown in FIG. By making the image narrower as shown in Figure (c), the frame of the screen at the time of printing is shown in the viewfinder.

However, simply narrowing the field frame 101 will also narrow the field of view in the finder, so in order to bring the field of view in the finder closer to the finished state, the eyepiece 104 of the finder optical system is zoomed to match the pseudo zoom. It is also being considered to expand the field of view narrowed by the frame 101 to the size of a standard field of view within the finder.

Many SLR cameras with
11, but the focus detection is usually performed using the photographing lens 1.
This is done using light that has passed through 06. At this time, the light going to the finder optical system and the light going to the AF device 111 pass through the same optical system up to the photographing lens 106, so there is no problem during normal shooting, but the finder optical system zooms according to the pseudo zoom. A problem arises when performing (variable magnification). In other words, in the case of pseudo zoom, the light entering the AF device 111 does not change in any way, but the image observed through the viewfinder is magnified, so the range of the field of view targeted for AF can be confirmed from the viewfinder. There are cases where it becomes difficult to do so.

Another problem is with the in-finder display. In recent cameras, as shown in FIG. 9(b), the line of sight in the viewfinder is VI! It is essential to display a display (infinder display) 110 regarding photographing information such as shutter speed and aperture value on the outside of 1109 to inform the photographer. This infinder display 11
0 is achieved by providing an infinder optical system 105 at the focusing plate 100, as shown in FIG.

However, in the case of such a conventional configuration, the field frame 101 is narrowed by performing pseudo zoom, and the eyepiece lens 10 is narrowed by that amount.
When the image of the focus plate 100 is enlarged by 4, the image shown in FIG.
As shown, the field of view 109' and the infinder display 11
0, and if you try to fully show the field of view, there is a possibility that the infinder display 110 will be vignetted.

Furthermore, if pseudo zooming is performed in a system that measures light using the light that has passed through the photographic lens 106, the photometry range will remain constant, but only the burn-in range will become narrower, resulting in the inconvenience of metering outside the screen after printing. It comes out.

4- It is an object of the present invention to provide a finder for an SLR camera that can correct these problems and display the field frame corresponding to the printed screen by changing the magnification according to the pseudo zoom.

In order to achieve the above object, the present invention provides a TTL finder for an SLR camera with a pseudo zoom function, which is equipped with an AF device that performs focus detection using light that has passed through the photographic lens. A relay lens that changes the magnification of the primary image formed on the image plane according to the magnification of the pseudo zoom and forms it into a secondary image, an eyepiece lens that magnifies this secondary image, and is provided on the primary image plane. and a frame representing the operating range of the AF device.

In addition to the above configuration, it is desirable to arrange an infinder display system near the surface on which the secondary image is formed. Furthermore, it is desirable to further include a photometry device that performs photometry using a portion of the light that forms the secondary image.

In the finder optical system, the image of the subject enters the photographer's eye in the following manner. First, a primary image is formed on a primary image plane by a photographing lens of a camera. This primary image is formed into a secondary image by a relay lens.

This relay lens is variable in magnification, and the magnification is changed in accordance with the pseudo zoom magnification of the camera. This secondary image is magnified by an eyepiece and observed by the photographer. As a result, the finished screen when burn-in is always displayed at the same size (inside the viewfinder - on the cup) depending on the pseudo zoom.

On the other hand, the AF device performs focus detection using light that has passed through the photographic lens (separate from the light that goes to the finder system after the relay lens). The range of the field of view (reference field of view) that is subject to focus detection with this AF device is the frame (
You can confirm this in the viewfinder using the AF frame.

Since there is only a photographing lens in front of the primary image plane where the AF device and AF frame are installed, if you match the size of the AF point with the reference field of the AF device in advance, you can easily determine what kind of photographic lens you are using. Even if they are used, the two will always match. Also, even if magnification is changed using pseudo zoom,
Although the absolute size of the FF irradiation field remains constant, the AFF irradiation field expands in relation to the extent of burn-in on the film surface. In the present invention, the AF frame on the primary image plane is also enlarged by the relay lens in response to the pseudo zoom, so that the AF quality display in the finder is correct, reflecting the pseudo zoom.

As stated in the second claim, by arranging the in-finder display system near the secondary image plane, the in-finder display is always arranged near the image field after being magnified by the relay lens. Become.

Therefore, regardless of the pseudo zoom, the in-finder display is always displayed at the same position within the finder.

Furthermore, as described in the third claim, by performing photometry using a portion of the light that has reached the secondary image plane, photometry can be performed within a predetermined field frame cut out from the image after being magnified by the relay lens. It will be done.

This allows the cropped screen (
Since photometry can be performed within the burn-in range), appropriate photometry that matches the screen will be performed even during pseudo zoom.

Figure 1 is a perspective view showing a schematic configuration of an optical system according to a first embodiment of the present invention. The light that has passed through the photographing lens 10 of the camera is bent upward by the reflecting mirror 11 and forms an object image (primary image) on the focus plate 12. The focus plate 12 has an AF frame frame 7
This frame 27 is drawn so as to coincide with the reference range in which the AFF device 6 performs focus detection, as will be explained later in FIG. The primary image formed on the focus plate is once bent toward the pupil side by the first reflecting mirror 13 of the finder optical system, and then further bent toward the object side by the second reflecting mirror 14 and also bent at a predetermined angle with respect to the vertical plane. and is imaged on a secondary image plane by the relay lens 15.

A fixed field frame 16 is provided on the secondary image plane, and the secondary image within this field frame 16 is reflected back toward the pupil by the third reflecting mirror 17 and magnified by the eyepiece 18.
leading to. Note that the film surface is arranged behind the reflecting mirror 11, as in the conventional SLR camera.

FIG. 2 shows the arrangement of this optical system when looking down from above the focus plate 12. In the standard shooting condition (without pseudo zoom), the shooting range of the entire film surface is the focus plate 12.
However, when pseudo-zoom photography is performed, the photographic field of view (burn-in range) is within the frame 26 shown by the dotted line.

However, as will be described later, as the relay lens 15 performs a magnification change operation in accordance with the pseudo zoom, the field frame 1
In the secondary image plane formed at location 6, the range 26 is expanded to the same size as during standard photographing.

Therefore, as long as the object is observed through the eyepiece lens 18, even if pseudo zooming is performed, the photographic field of view (printed area) will always be represented in the finder at the same size (screen-glass).

FIG. 3 shows the lens configuration of the finder optical system.

The relay lens 15 includes, from the object side, a lens group consisting of only a second lens L2 having positive power, a second lens L2 having positive power, and a third lens group having negative power.
It is composed of a lens L3 and a second lens group that is positive as a whole. Here, the 1077th group (Luns L)
The focal length f1 of lens l) is set to be shorter than the focal length f2 of the second lens group (fl<f2). The basic idea of this optical system 15 is as follows. Correct the whole thing
It has a configuration of two positive groups, and the positive power of the 1077th group (Ll) in front is increased, and the magnification is changed by moving this. Then, the rear positive second lens group (A2, A3) corrects the conjugate length to be constant. The second lens group has a positive/negative configuration, and the rear negative lens (A3) makes it possible to increase the distance 31 (the distance from the primary image plane to the relay lens 15).

The magnification of the entire finder optical system, including the taking lens as an objective lens, is approximately [focal length of taking lens] x [magnification of relay lens]/
[Focal length of eyepiece] In a conventional SLR camera, when the focal length of the photographing lens is 50 mm, the magnification of the entire finder optical system is approximately 0.75 to 0.9 times, but in this example, the magnification of the entire finder optical system is approximately 0.75 to 0.9 times. The goal was to achieve a magnification of 0.7 times or more.

If the magnification of the relay lens is decreased, the secondary image becomes smaller, but if the overall magnification is to be kept constant at this time, it is necessary to shorten the focal length f1 of the eyepiece lens. However, if the focal length f1 of the lens is shortened, its square (fl
Aberrations worsen in proportion to 2), making it difficult to correct them.

On the other hand, if the magnification of the relay lens is increased, this difficulty can be avoided, but the secondary image plane must be increased and Sl must be shortened. As in this embodiment, there are two reflecting mirrors 1 from the primary image plane 12 to the relay lens 15.
In an optical system in which 3.14 mm must be placed, it is difficult to shorten Sl. Considering the above, in this embodiment, the magnification of the relay lens 15 is set to 0 during standard shooting.
．． 3 to 0.5 times (0.6 to 1.
0x), the focal length of the photographic lens is 50
It was possible to increase the magnification of the finder optical system up to 0.70 times when the lens was mm.

Table 1 shows each lens data of the relay lens 15. In the same table (and Table 2 described later), rl represents the radius of curvature of the i-th surface counting from the object 1 side, "surface spacing" represents the axial surface spacing, and "refractive index" represents the refractive index for the d-line.

The magnification of the relay lens 15 is -0.36 in standard shooting conditions.
It is possible to change the magnification up to -0°70 times in correspondence with pseudo zoom, and its magnification ratio is about 2 times. At this time, the 1077th group (Ll) is on the object side (62,
72-43,96=)18.76mm, and the second lens group (A2.A3) as a whole moves toward the object side (13,49
-12,01=) 1.48mm movement.

In Figure 3, the field of view range at the primary image plane 12 at -0.36x is A1, and the field of view range at -0.70x is A1.
It was expressed as 2. All of these visual field ranges are imaged to the same size on the secondary image plane 30 by the relay lens 15. Aberration diagrams at each magnification are shown in FIGS. 4(a) and 4(b). In each of the figures (a) and (b), in the left figure, the solid line d indicates the spherical aberration with respect to the d-line, and the dotted line SC indicates the sine condition. In the central figure, the dotted line DM represents the meridional plane.
A solid line DS indicates astigmatism on the sagittal plane.

The figure on the right shows the distortion rate.

As shown in FIG. 2, when the relay lens 15 is magnified to around the maximum magnification of 2 (-0.70x), the lens L1 is extended to a position where it interferes with the field of view 25 in the standard photographing state. However, in this case, since pseudo zooming is performed according to the magnification, the actual field of view where printing is performed is within the range 26 shown by the dotted line.
The 1st Runs Ll does not change the field of view. Naturally, as the pseudo zoom magnification decreases, the burn-in area 26 expands, but
The second lens L1 also retreats in a direction out of the field of view, and the two always do not interfere.

In this way, in this embodiment, the relay lens 15 is connected to the focusing plate 1.
By placing it as close as possible to 2,
The finder optical system has become more compact, which in turn has made it possible to reduce the overall size of the camera.

A field frame 16 is provided at the position of the secondary image plane 30 to indicate the field of view range. As mentioned above, this field frame 16
displays the viewing range (burn-in range) correctly even during pseudo zoom. A condenser lens 23 is provided immediately in front of the object side of the secondary image plane 30 (field frame 16) in order to narrow down the light beam at the relay lens position. Further, the eyepiece lens 18 is composed of two fixed lenses each having negative and positive powers.

As shown in FIG. 2, an infinder optical system 21 is provided at one end of the condenser lens 23 just in front of the field frame 16 (ie, the secondary image plane 30). Here, an image of an in-finder display device 22 (including display of shutter speed, aperture value, etc.) provided outside the field of view is displayed by a prism of an in-finder optical system 21 in a field frame 1.
The image passes through an infinder display frame provided outside one side of the camera 6 and is projected onto a secondary image plane, and is magnified together with the object image by the eyepiece lens 18. Therefore, even if the relay lens 15 zooms (enlarges) according to the pseudo zoom,
The in-finder display is never obscured from the field of view and is always displayed at a fixed position within the viewfinder field of view.

The second reflecting mirror 17 is a half mirror, and a photometric device 20 is arranged behind it. This photometric device 20
In this case, since the light after being imaged on the secondary image plane 30 is photometered, even when a pseudo zoom is performed, the photometry of the visual field range after the zoom can be performed. Therefore, for example, even if there is a bright object such as the sun within the entire field of view, but the bright object is not included in the trimmed field of view after pseudo zooming, the photometry device of this embodiment can be used. By using this, correct photometry (and exposure) can be performed within the field of view where printing is performed.

The AF (automatic focus adjustment) system in this embodiment is the same as that in the third embodiment (FIG. 8), which will be described later.

FIGS. 5 and 6 show the configuration of the second embodiment.

In this embodiment, between the primary image plane 12 and a zoom lens 15' (consisting of Ll, L2, and L3) similar to that used in the first embodiment (more specifically, the first reflecting mirror 13 and the second A fixed lens L4 having positive power is provided between the reflecting mirrors 14), and four lenses L4 to L7 constitute a relay lens. Lens data of this example is shown in Table 2.

In this embodiment, by inserting the lens L4 having positive power in front of the zoom lens 15'', the zoom lens 1
5" focal length f1 is made longer, making it easier to correct aberrations. The aberration diagram in this example is shown in Figure 7.
As shown in the figure. In addition, this makes it possible to lengthen the distance S1 between the lens L5 of the zoom lens 15' and the primary image plane 12, which is advantageous when the pseudo zoom magnification is low and the field of view cropping range is small. Become.

The configuration of a third embodiment of the present invention is shown in FIG. In this embodiment, a relay lens 15 similar to that in the first embodiment is arranged after the first reflecting mirror 31 directly above the focus plate 12, and the secondary image resulting from the relay lens 15 is reflected toward the object side by the second reflecting mirror 33. I am trying to form an image later. This secondary image is further reflected toward the pupil by the third reflecting mirror 34 and observed by the eyepiece 18. In addition, the photographing lens 10, the relay lens 15,
The optical axes of the eyepieces 18 are all in the same vertical plane, so the eyepieces 18 are arranged just behind the film plane 37. By adopting such an arrangement, the overall length of the finder optical system can be shortened, and a sufficient lens movement distance for zooming of the relay lens 15 can be taken. It will also be compatible with zoom.

Here, the operation of the AF device will be explained.

A portion of the light incident from the photographing lens 10 passes through the flip-up mirror 11 and is guided to the AFF device 6 by the reflecting mirror 38. The AFF device 6 measures the distance to an object using various methods such as phase difference detection, and at this time, the range (AFF illumination field) to be subjected to focus detection is determined in advance. Therefore, a frame (AF frame) 27 is drawn on the focusing plate 12 in an area corresponding to the AFF illumination field. By doing so, the photographer can know which part of the finder is targeted by AF, and can take appropriate measures if the desired subject is not targeted.

When pseudo zooming is performed and the screen is cropped, this AFF illumination field does not change on the film plane 37. However, on the printed screen, the AFF illumination field expands relative to the entire screen. By drawing the AF frame frame 7 on the primary image plane 12 as in this embodiment, these relationships are correctly displayed in the finder. That is, by changing the magnification of the relay lens 15 in response to the pseudo zoom, the relative enlargement of the AF reference field of view with respect to the screen is correctly displayed in the viewfinder. Thereby, the photographer can know the accurate AF reference field of view even during pseudo-zoom photography, and can take appropriate measures if correction of the AF operation is required.

Note that the AF related device 36°37 explained in the third embodiment
, 38 are similarly provided in the first and second embodiments. Further, in each embodiment, the photographing lens 10
may be a normal zoom lens, and in this case as well, the pseudo zoom operation and the corresponding zoom operation of the finder optical system are not affected at all.

(Left below) Table 1 *r, , r are aspheric surfaces. The surface shape is x (y) of the following equation
It is expressed as

(However, in this case, +ΣA1y y: arbitrary optical axis vertical height, r: reference radius of curvature of aspherical surface, ε: quadratic surface parameter, A, 1 aspherical surface coefficient, Σ is the sum when i≧2 ) r, : ε=-4,04,r4: ε=-5,56°9- Table 2 *r3. r6 is an aspherical surface. The surface shape is x (y) of the following equation
It is expressed as

(However, in this case, y: height in the vertical direction of the arbitrary optical axis, r: reference radius of curvature of the aspherical surface, ε: quadratic surface parameter, AI=aspherical surface coefficient, Σ is the sum when i≧2) r3 :ε=-4,03,r6:ε=-5,58゜0- From JL! DU14 As explained above, in the present invention, the TTL viewfinder optical system zooms in response to the pseudo zoom of the SLR camera, so even during pseudo zoom, the printed screen is always the same in the viewfinder, just like during normal zoom. It will be displayed in size (in the viewfinder - on the cup). And A
By placing the F frame on the primary image plane, the AF frame is magnified in the viewfinder according to the pseudo zoom, and the relationship between the shooting field of view (burn-in is on the screen) during pseudo zoom and the reference field of the AF device is correct. It will be represented in the finder.

Furthermore, by arranging the in-finder display system near the secondary image plane, the dopa in-finder display will not be vignetted outside the viewfinder's field of view, and will always appear at a fixed position within the finder. Furthermore, by performing photometry based on the light on the secondary image plane, exposure during pseudo zooming can be performed correctly.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of the first embodiment of the present invention, FIG. 2 is a plan view of the optical configuration of the first embodiment viewed from above the focus plate, and FIG.
4 is an aberration diagram of the optical system of the first embodiment. FIG. 5 is a plan view of the optical configuration of the second embodiment viewed from above the focus plate. Fig. 6 is a configuration diagram of the optical system of the second embodiment, Fig. 7 is an aberration diagram of the optical system of the second embodiment, and Fig. 8 is a diagram of the aberration of the optical system of the second embodiment.
The figure is a side view of the optical configuration of the third embodiment viewed from the side, and FIG. ), (d
), FIG. 10 is an explanatory diagram of pseudo zoom.

Claims (3)

[Claims] (1) Focus detection is performed using light that has passed through the photographic lens A
In a TTL finder for an SLR camera equipped with an F device and having a pseudo zoom function, a primary image formed on a primary image plane by a photographing lens is magnified according to the magnification of the pseudo zoom and is formed into a secondary image. A finder optical system comprising: a relay lens; an eyepiece lens that magnifies the secondary image; and a frame provided on the primary image plane and representing an operating range of the AF device. (2) The finder optical system according to claim 1, further comprising an in-finder display system disposed near the surface on which the secondary image is formed. (3) The finder optical system according to claim 1 or 2, further comprising a photometry device that performs photometry using a portion of the light that forms the secondary image.