JPH03287107A - Finder optical system - Google Patents

Abstract

PURPOSE:To perform power variation corresponding to artificial zooming of relatively high magnification by providing a relay lens which forms a secondary image by varying the magnification of a primary image according to the magnification of the artificial zooming and an ocular which magnifies the secondary image. CONSTITUTION:The primary image formed on a focus plate 12 is reflected once by a 1st reflecting mirror 13 toward a pupil, reflected by a 2nd reflecting mirror 14 toward an object, and further reflected by a specific angle to a perpendicular plane to appear on the secondary image plane through a relay lens 15. A fixed visual field frame 16 is provided on the secondary image plane and the secondary image in this visual field frame 16 is reflected again by a 3rd reflecting mirror 17 toward the pupil and enlarged by the ocular 18 to reach the pupil plane. This relay lens 15 shortens the focal length of a 1st lens group L1 on the object side, the 1st lens group 1 which has large positive power is moved to increase the power variation ratio, and 2nd positive lens groups L2 and L3 are moved with the 1st lens group L1 to correct the conjugation length into a constant value. Consequently, the primary image is varied in magnification with the magnification corresponding to the artificial zooming of high magnification and formed as the secondary image.

Description

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

At present, both SLR and LS cameras are equipped with zoom lenses, but zoom lenses have more lenses than single-focal-length lenses and are inevitably larger. . 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 it narrower as shown in Figure (C), the screen frame at the time of printing is shown in the finder.

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.

In a conventional SLR camera with a high
04, the focal length of the eyepiece 104 cannot be shortened, and the zoom range (variable magnification ratio) of the eyepiece 104 is limited, and in reality, the magnification can only be varied to about 10%. There is a problem.

The present invention solves these problems and provides an SLR that can sufficiently handle relatively high magnification pseudo zoom and perform magnification changes.
The purpose is to provide a finder for cameras.

In order to achieve the above object, the present invention provides a TTL finder for an SLR camera having a pseudo zoom function.
The first lens group and the 2
A relay lens that changes the magnification of the primary image formed on the primary image plane by the photographing lens according to the magnification of the pseudo zoom by moving the lens group and forms it into a secondary image, and a relay lens that magnifies this secondary image. It is characterized by comprising an eyepiece lens.

Note that the second lens group can be composed of two lenses, one positive and one negative from the object side.

Further, a positive fixed lens may be arranged closer to the object than the first lens group.

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 secondary image is formed into a secondary image by a relay lens.

This relay lens is composed of two lens groups, positive and positive, but the focal length of the first lens group on the object side is shortened, and the lens group with strong positive power (first lens group) is moved. By doing so, it is possible to increase the variable power ratio. The positive second lens group on the pupil side moves with the movement of the first lens group, and performs correction so that the conjugate length is constant. As a result, the -order image is magnified at a magnification corresponding to the pseudo zoom and formed into a secondary image. This secondary image is magnified by a fixed eyepiece and observed by the photographer.

As described in the second claim, this second lens group is
If we use a negative two-lens configuration, the rear negative lens will produce 8
1 (distance from the -th image plane to the first lens group) can be made longer, making it possible to increase the variable power ratio.

As described in the third claim, by arranging a positive fixed lens closer to the object side than the first lens group, the focal lengths of the first and second lens groups can be made longer, and their aberrations can be corrected. It can be easily done. Moreover, the distance S1 between the −th order image plane and the electron lens group can be further increased.

The drawing 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 (minus 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 placed behind the reflection @11, similar to a 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 state (state N where pseudo zoom is not performed), the shooting range of the entire film surface corresponds to the outer frame 25 of the focusing plate 12, but when pseudo zoom shooting is performed, the shooting field ( Burn-in range) is
It falls within a frame 26 indicated by a 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 first lens group consisting of only a second lens L2 having positive power;
The second lens L2 has a positive power and the third lens L3 has a negative power.
It consists of a lens group. Here, the focal length f1 of the first lens group (second lens L2) is the focal length f2 of the second lens group.
The optical system 15 is set to be shorter than (f 1 (f 2)).The basic concept of the optical system 15 is as follows.

The entire structure has two groups, positive and positive, with the front first lens group (Ll
) by increasing its positive power and moving it to change the magnification. And the rear positive second lens group (L2.L3)
Correct so that the conjugate length is constant. The second lens group has a positive/negative configuration, and the rear negative lens (L3)
(distance from the -th image plane to the relay lens 15) can be made longer.

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 (f1
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 reflective lenses 11 from the primary image plane 12 to the relay lens 15.
In an optical system where 13 and 14 must be arranged, Sl.
is difficult to shorten. Considering the above,
In this embodiment, the magnification of the relay lens 15 is set to 0.3 to 0.5 times during standard shooting (0.6 to 1 when using 2 times pseudo zoom).
．． 0x), the focal length of the photographic lens becomes 5
I was able to increase the magnification of the finder optical system up to 0.70 times when it was 0 mm.

Table 1 shows each lens data of the relay lens 15. In the same table (and Table 2 described below), ri represents the radius of curvature of the first surface counted from the object 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 10.36 times in the standard shooting state, and the maximum is -0 in correspondence with the pseudo zoom.

The magnification can be changed up to 70 times, and the magnification ratio is approximately 2 times. At this time, the first lens group (Ll) moves toward the object side by (62,72-43,96=)18.76 mm, and the second lens group (L2.L3) as a whole moves toward the object side by (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 3o 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 indicates the astigmatism of the meridional plane, and the solid line DS indicates the astigmatism of the sagittal plane.

The figure on the right shows the distortion rate.

As shown in FIG. 2, the relay lens 15 has the maximum magnification (-
When the magnification is changed to around 0.70x), the first 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 in which printing is performed is within the range 26 shown by the dotted line, and the first
Lens L1 does not interfere with the field of view. Naturally, as the pseudo zoom magnification decreases, the image burning range 26 expands, but the first lens L1 also retreats in a direction outside the field of view, so that the two do not always 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, a 1-in-finder 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, the infinder display device 22 provided outside the field of view
An image (including display of shutter speed, aperture value, etc.) is passed through the in-finder display frame provided outside one side of the field frame 16 by the prism of the in-finder optical system 21, and Imprinted on the next image plane, the eyepiece 18
is magnified together with the object image. Therefore, even if the relay lens 15 zooms (enlarges) in accordance with the pseudo zoom, the in-finder display is not eclipsed 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 2, 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, the space between the -order image plane 12 and a zoom lens (consisting of LL, L2, and L3) 15'' similar to that used in the first embodiment (more specifically, the first reflecting mirror 13 and A fixed lens L4 having positive power is provided between the two reflecting mirrors 14), and four lenses L4 to L7 constitute a relay lens.The 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
The focal length f1 of 5° is increased to facilitate correction of aberrations. FIG. 7 shows an aberration diagram in this example.

In addition, as a result, the first lens L of the zoom lens 15゜
Since the distance S1 between the primary image plane 1 and the primary image plane 12 can be increased, this is advantageous when the magnification of the pseudo zoom is low and the trimming range of the field of view is small.

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, and it can also be used for high-magnification pseudo zooming. It becomes possible to respond.

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

A portion of the light incident from the photographic lens 10 passes through the flip-up mirror 11 and is reflected by the reflecting mirror 38 in an AFFFF position 65-. The distance to an object is measured using various methods such as AFFFF positioning 6 phase difference detection, and 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.

While the pseudo zoom is performed and the screen is trimmed, this AFF illumination field does not change on the film surface 37. However, on the printed screen, the AFF illumination field expands relative to the entire screen. As in this example, -
By drawing the AF frame frame 7 on the next image plane 12, 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 AFF illumination field with respect to the screen is correctly displayed in the viewfinder. Thereby, the photographer can know the accurate A1F 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 AFF link 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 *rl + r4 is an aspherical surface. The shape of the surface is x (
y).

+ΣA + y (where y: arbitrary optical axis vertical height, r: reference radius of curvature of aspherical surface, ε: quadratic surface parameter, AI=aspherical surface coefficient, Σ is the sum when i≧2) In the case, rl:ε=-4,04, r4:ε=-5,5
6゜Table 2 *r,, r6 is an aspherical surface. The surface shape is x (y) of the following equation
It is expressed as

+ΣA + '1 (where y: height in the vertical direction of the arbitrary optical axis, r: standard radius of curvature of the aspherical surface, ε: quadratic surface parameter, Al2 aspherical coefficient, Σ is the sum of i≧2) Now In the case of r3:ε--4,03,r6:ε=-5,5
8゜9-丑''70[14 As explained above, in the present invention, the TTL finder optical system is zoomed in response to the pseudo zoom of the SLR camera, so during the pseudo zoom, as well as during the normal zoom, Once baked, the screen will be displayed at a fixed size in the viewfinder (in the viewfinder - on the glass). In addition, the finder optical system uses a relay lens that performs a zoom function between the photographing lens (objective lens) and the fixed eyepiece lens, and its configuration is divided into positive (short focal length) and positive (long focal length) lenses. By using two groups, a relatively large magnification ratio can be achieved even under the constraints of the TTL viewfinder of an SLR camera, and it is possible to sufficiently cope with a wide range of pseudo-zooming.

[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.
The figure is a configuration diagram of the optical system of the first embodiment, Figure 4 is an aberration diagram of the optical system of the first embodiment, and Figure 5 is a plane view of the optical configuration of the 0-2nd embodiment viewed from above the focus plate. Figure 6 is a configuration diagram of the optical system of the second embodiment, Figure 7 is an aberration diagram of the optical system of the second embodiment, and Figure 8 is a side view of the optical configuration of the third embodiment as seen from the side. , Figure 9 is a side view (a), (c) of the optical system of the camera and views (b), (d) of the viewfinder display to explain the pseudo zoom, and Figure 10 is an explanatory diagram of the pseudo zoom. be.

Claims (3)

[Claims] (1) TTL for SLR cameras with pseudo zoom function
In the finder, the first lens group is composed of a first lens group on the object side that has positive power, and a second lens group on the pupil side that also has positive power and has a longer focal length than the first lens group. group and second
A relay lens that changes the magnification of the primary image formed on the primary image plane by the photographing lens according to the magnification of the pseudo zoom by moving the lens group to form a secondary image, and a relay lens that magnifies this secondary image. A finder optical system characterized by comprising an eyepiece lens. (2) The finder optical system according to claim 1, wherein the second lens group is composed of two lenses, a positive lens and a negative lens from the object side. (3) The finder optical system according to claim 1 or 2, further comprising a fixed lens having positive power disposed closer to the object than the first lens group.