JPH11109447A - Zoom finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom finder using a disk cam whose outside diameter is small and whose pressure angle with a cam follower is small. SOLUTION: First and second lenses 20 and 30 guided along an optical axis 80, a reflection mirror 60, a condenser lens 62, a Porro prism 64 and an eyepiece 66 are arranged at the inside of a box type base plate 12 in order from an object side to an eyepiece side along the optical axis 80. The disk cam 50 is freely rotatably supported by a machine screw 59 extending upward in a direction perpendicular to the optical axis 80 at the lower part of the base plate 12. Cam follower pins 25 and 35 projectingly provided at the first and second lenses 20 and 30 are respectively engaged with first and second spiral cam grooves 52 and 54 at both sides respectively formed over the range of 360 deg. on the upper surface of the disk cam 50 by holding the rotary shaft of the disk cam 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom finder, and more particularly, to a zoom finder driven by a disk cam.

[0002]

2. Description of the Related Art Conventionally, in a zoom finder in which a finder lens is driven by a cam member interlocked with a zoom drive of a photographing lens barrel to change the magnification, for example, as shown in FIG. In order to reduce the cost, a two-lens objective optical system including a -lens G1 having -power and a + lens G2 having + power was adopted, and an image was formed in the vicinity of the side of the Porro prism 4 of the condenser lens 2. There is a configuration in which a real image is magnified and observed with an eyepiece 5. In this zoom finder 1, as a cam member, for example, as shown in FIG.
Disc cams 6, 6a, 6b having cam grooves 7, 8; 7a, 8a; 7b, 8b extending substantially in an arc shape or a spiral shape with which cam follower pins P1, P2 of the -lens G1 and the + lens G2 engage. Having. This zoom finder 1
Are the U-turn type zoom solutions Z1, Z as shown in FIG.
2, each disk cam 6, 6a, 6b has a cam groove 7, 8; 7a, 8a; 7b, 8b with a diameter as small as possible.
Are rotated so that they do not intersect.
0 degrees. Specifically, the disc cam 6 in FIG.
Cam follower pin P for lens G1 and + lens G2
This is an example in which the pressure angle is reduced by shifting 1, P2, and the disc cam 6a in FIG. 2B shifts only the cam follower pin P2 of the + lens G2 to reduce the pressure angle. The disk cam 6b in FIG. 2C is a cam follower pin P1 of the minus lens G1 and the plus lens G2.
This is an example in which P2 is not shifted.

In general, when the U-turn type zoom solutions Z1 and Z2 are used, the diopter of the viewfinder greatly varies with a slight stop position error of the lens G1, and the variation of diopter becomes large. Therefore, when the position error sensitivity relating to the diopter of the objective optical system having the structure of-+ 2 is suppressed low and the optical design is performed so that the diopter does not vary, specifically,
-If the power of the lens G1 is substantially equal to the power of the objective optical system at the time of telephoto (telephoto), the zoom solution necessarily has a C-shape. However, in the C-shaped zoom solution, the pressure angle of the zoom drive cam at the wide end (wide-angle end) becomes large, which causes zoom operation failure, image skipping during zoom operation, variation in zoom magnification, and the like. .

In order to reduce the pressure angle of the zoom drive cam, as shown in FIG. 3, if the cam grooves 7s and 8s are configured to drive the-+ lenses G1 and G2 by the long flat slide cam 6s, the flat slide can be achieved. The evacuation space of the cam 6s becomes too large, and the entire width of the viewfinder 1s becomes large. In order to reduce the pressure angle of the zoom drive cam, as shown in FIG. 4, when the cam surfaces 7x and 8x are configured to drive the-+ lenses G1 and G2 with the long cylindrical cam 6x, the cylindrical cam 6x has The diameter becomes too large, and the overall height of the viewfinder 1x increases. On the other hand, the conventional disk cam has a smaller volume and does not require a large space as compared with the cylindrical cam 6x or the flat plate slide cam 6s, so that the entire finder can be reduced in size. In particular, the pressure angle near the wide end is
The length can be reduced by lengthening the cam groove near the outer periphery.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a zoom finder using a disk cam having a small outer diameter and a small pressure angle with a cam follower.

[0006]

In order to solve the above technical problems, the present invention provides a zoom finder having the following configuration.

The zoom finder has at least two movable lens groups movably supported along the optical axis, and is arranged near the movable lens group and rotates about a rotation axis perpendicular to the optical axis. And at least two cam protrusions or cam grooves are respectively engaged with the respective cam protrusions or cam grooves of the disk cam, the disk cams extending substantially in an arc or spiral around the rotation axis, In addition, at least two cam followers are respectively coupled to the moving lens groups, and each of the moving lens groups moves along the optical axis when the disk cam is rotated. When each of the moving lens groups moves most in the direction in which they approach each other, the cam followers that engage with the cam projections or the cam grooves of the disk cam are respectively disposed on both sides of the rotating shaft. Each of the cam protrusions or cam grooves of the disc cam is provided over a range of more than 180 ° about the rotation axis.

In the above arrangement, when the disk cam rotates, the cam follower engaged with the cam projection or the cam groove (including the case formed on the outer peripheral surface of the disk cam) of the disk cam moves. Moves. That is, the zoom finder is driven to zoom. When each moving lens group moves most in the direction approaching each other, each cam follower engaging with each cam projection or cam groove of the disk cam is arranged on both sides of the rotating shaft, so that each cam follower performs zoom drive. However, they are always arranged on both sides of the rotating shaft, and the radius of the disk cam can be minimized. The cam projections or cam grooves of the disc cam are arranged in a range exceeding 180 ° and are long in the circumferential direction. Therefore, the circumferential displacement with respect to the radial displacement is increased, and the pressure angle between the cam protrusion or the cam groove and the cam follower is increased. Can be reduced.

Therefore, the outer diameter of the disk cam is small, and the pressure angle with the cam follower can be reduced.

Preferably, of the two moving lens groups, the moving distance in the optical axis direction of the moving lens group on the subject side is A,
When the moving distance in the optical axis direction of the moving lens group on the eyepiece side is B, 2/3 <A / B <4/3 is satisfied.

According to the above configuration, since the sizes of A and B do not extremely differ from each other, the cam projections or the cam grooves can be arranged within a range exceeding 180 ° without intersecting.

Preferably, the two moving lens groups constitute an objective optical system, the moving lens group on the object side has a negative power P1, and the moving lens group on the eyepiece side has a positive power P1.
-1.2 × P2 ≦ P1 ≦ −0.8
× P2 is satisfied.

In the above configuration, when P1 <−1 × P2, a U-turn occurs near the telephoto end of the −lens. However, if P1 ≧ −1.2 × P2, the U-turn for the lens is very small, and it is possible to design a disk cam having the above configuration. On the other hand, P1 ≧ −1 ×
At the time of P2, the U-turn becomes zero, and a C-shaped zoom solution is obtained in which the tele end side of the minus lens approaches the tele end side of the plus lens. At this time, if P1 ≦ −0.8 × P2, the approach of the − + lens at the telephoto end is allowable.

Preferably, the cam projection or the cam groove of the disk cam is a projection or a groove with a bottom.

According to the above configuration, the disk cam body has no penetrating portion, so that the strength of the cam can be improved.

[0016] More preferably, the disk cam is arranged below the finder unit.

In the above arrangement, by extending the disc cam having no penetrating portion through which light leaks in the horizontal direction, the overall height of the finder can be reduced and light leakage can be prevented.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The zoom finder according to each embodiment of the present invention shown in FIGS. 5 to 12 will be described below in detail.

First, the zoom finder 10 according to the first embodiment will be described.

As shown in the optical system configuration diagram of FIG. 11, the zoom finder 10 has a two-lens objective optical system including a first lens 20 having negative power and a second lens 30 having positive power. The real image formed near the surface of the condenser lens 62 on the Porro prism 64 side is enlarged and observed by the eyepiece 66. The first and second lenses 20 and 30 are driven to zoom in conjunction with zooming of the taking lens. The first and second lenses 20, 30 have zoom curves indicated by reference numerals 82, 84.

More specifically, the zoom finder 10 is disposed above the camera body (not shown), and is an exploded perspective view of FIG.
As shown in the assembled perspective views of FIGS. 6 and 7, the first lens 20, the second lens 30, and the reflection mirror 6 are sequentially arranged along the optical axis 80 from the object side to the eyepiece side in the box-shaped base plate 12.
0, a condenser lens 62, a porro prism 64, and an eyepiece 66 are arranged.
0 is arranged.

The first and second lenses 20 and 30 are provided on both sides of the lens body with guide sleeves 24 and 34 and engaging projections 2.
2 and 32, and are guided in the optical axis direction. That is, the guide sleeves 24 and 34 have the optical axis 8
The lens guide shaft 18, which is arranged parallel to the base plate 12 and is fixed to the base plate 12, is inserted therethrough. It comes into sliding contact with.

The guide sleeves 24 and 34 have spring engaging projections 26 and 36 projecting from their upper parts, respectively, and cam follower pins 25 and 35 projecting from their lower parts. The ends of the tension springs 28 are locked at the tips of the spring locking projections 26 and 36, respectively, so that the first and second lenses 20 and 30 are urged in directions approaching each other. The cam follower pins 25 and 35 are
, And extends downward from the opening 15 of the bottom plate 14 of the base plate 12.

The disk cam 50 is rotatably supported on the lower surface of the bottom plate 14 of the base plate 12 by a screw 59 extending vertically upward with respect to the optical axis 80. The disk cam 50 has first and second spiral cam grooves 52 and 54 on the upper surface thereof.
The cam follower pins 25 and 35 of the first and second lenses 20 and 30 are engaged with each other. When the cam follower pins 25 and 35 come closest to each other, the screw 59, that is, the rotating shaft of the disc cam 50, is arranged almost in the middle thereof, so that the outer diameter of the disc cam 50 can be reduced. I have. Since the first and second cam grooves 52 and 54 are bottomed grooves formed so as not to penetrate the disk cam 50, the strength of the cam can be improved and light shielding can be achieved.

The first and second cam grooves 52 and 54 correspond to FIG.
As shown in the plan view of FIG. 2 (b), the disk cam 50 is formed in a substantially arc shape or a spiral shape, more specifically, in a spiral shape gradually moving away from the center axis of the disk cam 50 according to clockwise rotation. The first and second cam grooves 52 and 54 are formed over a range of 360 °, and the first and second lenses 20 and 30 are driven to zoom by rotating the disc cam 50 by 360 °. ing. FIG.
As shown in FIG. 2 (a), when zooming is performed by rotating the disc cam 50x by 270 °, the pressure angle between the cam grooves 52x and 54x and the cam follower pins 25 and 35 increases.
If the zoom drive is performed by 360 ° rotation as shown in FIG. 12B, the pressure angle is reduced, and the zoom drive can be performed more smoothly.

The disk cam 50 is rotated by a driving member 70 in conjunction with the zooming of the taking lens. That is, as shown in FIG. 6, when the disc cam 50 rotates in the counterclockwise direction indicated by the arrow 90, the first and second lenses 20, 30 are separated from each other and are in a wide state. On the other hand, as shown in FIG. 7, when the disk cam 50 rotates clockwise as indicated by the arrow 92, the first and second lenses 20, 3 are rotated.
Zeros approach each other and enter a telephoto state. The first and second lenses 20, 30 are cam-coupled without backlash by the urging of the tension spring 28, and are driven for zooming. The cam follower pins 25 and 35 are always disposed on both sides of the rotating shaft of the disk cam 50 even when the zoom drive is performed. Therefore, the radius of the disc cam 50 can be minimized.

Next, a description will be given of a zoom finder 10a according to a second embodiment in which the biasing directions of the springs are different, with reference to the perspective view of FIG. This zoom finder 10
Since a is substantially the same as that of the first embodiment, the following description focuses on the differences, and the same reference numerals are used for the same components.

In this zoom finder 10a, the second
The spring engagement projection 36a of the lens 30 is
It protrudes from the side. One end of each of the tension springs 28a, 38a is separately locked to each of the spring locking projections 26, 36a of the first and second lenses 20, 30, and the other end of each of the tension springs 28a, 38a is a base plate. Locked to 12,
The first and second lenses 20, 30 are both biased toward the eyepiece side in the optical axis direction.

Next, a zoom finder 10b according to a third embodiment will be described.

As shown in the perspective view of FIG. 9, the zoom finder 10b is substantially the same as the zoom finder 10 of the first embodiment, but has a third lens in front of the first lens 20, that is, on the object side. The difference from the first embodiment is that a lens 40 is further provided.

More specifically, the third lens 40 includes, on the side of the lens body, an engagement protrusion 42 that slides on the upper edge 17 of the side plate 16 of the base plate 12 and a guide sleeve 44 through which the lens guide shaft 18 is inserted. Having. A compression spring 48 is inserted through the lens guide shaft 18 in front of the guide sleeve 44 of the third lens 40, so that the third lens 40 is biased toward the eyepiece in the optical axis direction. A cam follower pin 45 protrudes downward from the guide sleeve 44 of the third lens 40 in a direction perpendicular to the optical axis 80.

FIG. 12C shows the disk cam 50b.
As shown in FIG. 7, in addition to the first and second cam grooves 52 and 54, a third groove 56 with which the cam follower pin 45 of the third lens 40 engages is formed. That is, the zoom finder 10b has an objective optical system having a three-element configuration.

Next, a zoom finder 10c according to a fourth embodiment will be described.

The zoom finder 10c is shown in FIG.
As shown in the perspective view of FIG. 10, the disk cam 50 is configured in a substantially similar manner to the zoom finder 10b of the third embodiment.
The configuration of c is different from that of the third embodiment. That is, FIG.
As shown in (d), the disc cam 50c is
Instead of 6, the outer peripheral surface 58 comes into contact with the cam follower pin 45 of the third lens 40.

In the zoom finders 10, 10a, 10b, and 10c of the embodiments described above, the disk cam 5
0, 50b, 50c have small outer diameters and the cams 52, 5
4, 56, 58 and cam follower pins 25, 35, 45
And pressure angle is small.

It should be noted that the present invention is not limited to the above embodiment, but can be embodied in various other modes.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system of a conventional zoom finder.

FIG. 2 is a plan view of a disk cam of the zoom finder of FIG. 1;

FIG. 3 is a perspective view of a zoom finder using a conventional flat plate slide cam.

FIG. 4 is a perspective view of a conventional zoom finder using a cylindrical cam.

FIG. 5 is an exploded perspective view of the zoom finder according to the first embodiment of the present invention.

FIG. 6 is an assembled perspective view of the zoom finder of FIG. 5; Indicates the wide end state.

FIG. 7 is an assembled perspective view of the zoom finder of FIG. 5; Shows the tele end state.

FIG. 8 is an assembled perspective view of a zoom finder according to a second embodiment of the present invention.

FIG. 9 is an assembled perspective view of a zoom finder according to a third embodiment of the present invention.

FIG. 10 is an assembled perspective view of a zoom finder according to a fourth embodiment of the present invention.

FIG. 11 is a configuration diagram of an optical system of a zoom finder.

FIG. 12 is a plan view of a disk cam of the zoom finder.

[Explanation of symbols]

 10, 10a, 10b, 10c Zoom finder 12 Base plate 14 Bottom plate 15 Opening 16 Side plate 17 Upper edge 18 Lens guide shaft 20 First lens (movable lens group) 22 Engagement projection 24 Guide sleeve (cam follower) 25 Cam follower pin (Cam follower) 26 Spring locking projection 28a Tension spring 30 Second lens (moving lens group) 32 Engagement projection (Cam follower) 34 Guide sleeve (Cam follower) 35 Cam follower pin 36, 36a Spring locking projection 38a Tension spring 40 third lens (moving lens group) 42 engagement protrusion 44 guide sleeve (cam follower) 45 cam follower pin (cam follower) 48 compression spring 50, 50b, 50c, 50x disk cam 52, 52x first cam groove 54, 54x Second cam groove 56 Third cam groove 8 the outer peripheral surface 59 bis 60 reflecting mirror 62 the condenser lens 64 Porro prism 66 eyepiece 70 the drive member 80 the optical axis 90 and 92 arrows

Claims (5)

[Claims] 1. At least two moving lens groups movably supported along an optical axis, and are arranged near the moving lens group and rotate around a rotation axis perpendicular to the optical axis,
And at least two cam protrusions or cam grooves are respectively engaged with the respective cam protrusions or cam grooves of the disk cam, the disk cams extending substantially in an arc or spiral around the rotation axis, A zoom finder comprising: at least two cam followers respectively coupled to the moving lens groups, wherein each of the moving lens groups moves along an optical axis when the disc cam is rotated. When the moving lens groups move most in the direction in which they approach each other, the cam followers that engage with the cam protrusions or the cam grooves of the disk cam are arranged on both sides of the rotating shaft, respectively. A zoom finder, wherein each cam projection or cam groove is provided over a range of more than 180 ° about the rotation axis. 2. When the moving distance in the optical axis direction of the moving lens group on the subject side is A, and the moving distance in the optical axis direction of the moving lens group on the eyepiece side is B in the two moving lens groups, 2/3.
The zoom finder according to claim 1, wherein <A / B <4/3 is satisfied. 3. An objective optical system is constituted by the two moving lens groups. The moving lens group on the subject side has a negative power P1, and the moving lens group on the eyepiece side has a positive power P.
2. The zoom finder according to claim 1, wherein the zoom finder satisfies -1.2 × P2 ≦ P1 ≦ −0.8 × P2. 4. The disk cam according to claim 1, wherein the cam projection or the cam groove is a projection or a bottomed groove.
The described zoom finder. 5. The zoom finder according to claim 4, wherein said disk cam is disposed below a finder unit.