JPS6138447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zoom lens structure.

Conventionally, zoom lenses used in small cameras, etc. generally consist of four groups: a focusing lens, a variable power lens, a correction lens, and a fixed relay lens.The focusing lens is displaced in the optical axis direction by a helicoid mechanism, etc. Variable magnification lenses and correction lenses were designed to move relative to each other in a fixed relationship using a cam groove provided in a cam ring linked to a zoom ring, etc., but the mechanism was complicated, the lens barrel became large, and There were problems such as extremely high precision was required for machining the cam grooves, etc., and manufacturing costs were also high.

The present invention has a four-group structure similar to the conventional one, in which the first group lens is moved for focusing and correction of focal plane movement during zooming, the second group lens is moved for zooming, and the third group and Using a zoom lens optical system with only two movable lens groups, the fourth lens group is fixed,
The purpose is to provide a zoom lens body with simple structure and high precision.

The present invention will be explained below with reference to the drawings.

FIG. 1 explains the configuration of a known zoom lens to which the present invention is applied, in which _L1 is the first group lens that performs focusing and zoom correction, _L2 is the second group lens that performs magnification change, and L2 is the second group lens that performs zooming. ₃ is the third lens group and is fixed.
_L4 indicates a relay lens, which receives parallel light rays coming out of the afocal system composed of _L1 to _L3 , converges the light, and forms an image. A in the figure shows a wide-angle state in which the second lens group _L2 , which is the variable power system, is located in the front, and B in the figure shows a telephoto state in which _L2 is located in the rear. The second group lens L ₂ is continuously displaced as shown by the solid line from A to B in the figure, and at this time, the first group lens L ₁ is displaced by the arc shown from A to B in the figure. It moves as shown by the solid line and performs a zoom correction effect. The first group lens _L1 performs a focusing action by moving forward and backward in the optical axis direction, as shown by the broken line.

FIG. 2 is a perspective view showing an embodiment in which the present invention is applied to a cine camera, and FIG. 3 is a sectional view of a zoom lens barrel.

In the figure, 1 is a cine camera main body, 2 is a lens base plate fixed to the main body 1, and a holding tube 2a of a third group lens _L3 and a fixed lens barrel 3 are attached thereto. 6
is a front base plate fixed to the front end of the lens barrel. 4 is a cam ring having a zoom operation lever 4c, which is rotatably fitted into the fixed lens barrel 3, and which is connected to both the base plates 3,
6 prevents movement in the optical axis direction.
5 is a movable ring that holds the variable magnification lens L ₂ , and the main plate 3
The pin 5a is guided straight in the optical axis direction by guide bars 7a and 7b supported by guide bars 7a and 6, and a pin 5a planted thereon fits into the cam groove 4a of the cam ring 4. Reference numeral 10 denotes a guide tube in which straight bars 10a and 10b are fixedly fitted into guide holes provided in the base plates 3 and 6, and a holding tube 9 holding a focusing lens _L1 is rotatably fitted on the inner periphery. The rear end 10a' of the straight bar 10a is biased rearward by the spring 14 so as to come into contact with a focusing cam 25b, which will be described later.

As shown in the sectional view in FIG. 4, three holes 10c are provided on the outer periphery of the guide tube 10, three cam grooves 9c having a V-shaped cross section are provided in the holding tube 9, and the holes 10c are provided in the holding tube 9. The steel ball 11 that fits into the cam groove comes into contact with the slope of the cam groove and is held down by the flexible portion 12a of the spring ring 12 that fits around the outer periphery of the lens barrel 10.

Reference numeral 13 denotes a ring that fits around the outer periphery of the spring ring 12 to prevent excessive deformation of the flexible portion.

At the rear end of the holding cylinder 9 are straight keys 9a, 9 that engage with key grooves 4e, 4f provided on the inner circumference of the cam ring 4.
b is fixedly installed, and as the cam ring 4 rotates, the holding cylinder 9
At this time, the cam groove 9c also moves in the optical axis direction. 16 is a drive motor that rotates a shaft 21b with gears 17 and 18, and drives a gear 20 and a worm 2 through a clutch 19.
4 is selectively driven. The gear 20 includes a known shutter blade, a film feed claw, and an integrated shaft 21a.
A take-up shaft inside the cartridge c is driven via a worm 22 and a worm wheel 23. Further, the worm 24 meshes with a worm wheel 25a, and rotates a focusing cam 25b provided integrally with the worm wheel 25a around a fixed shaft 26. The rear end 10a' of the straight bar of the guide tube is in contact with the cam 25b, and as the cam rotates, the guide tube 10 moves straight back and forth against the force of the spring 14 or due to its pressing force. It seems to be moving.

When performing focusing operations, warm up the clutch 2.
By switching to the 4 side, the cam plate 25b is rotated by the power of the motor 16, and the guide cylinder 10 is moved forward and backward as described above. At this time, the holding tube 9 of the first group lens is securely held in the guide tube 10 by the frictional force between its V-shaped groove 9c and the steel ball 11, and moves together with the guide tube to move the lens group _L1 to the light beam. Displace it in the axial direction. By confirming the in-focus state and disengaging the clutch, the lens _L1 stops at that position and maintains the in-focus state.

Next, when adjusting the focal length for zooming,
The magnification change operation lever 4c of the cam ring 4 is rotated in the circumferential direction. The movable ring 5 that holds the second group lens _L2 is moved along the cam groove 4a by rotation of the cam ring 4 because the pin 5a implanted thereon is fitted into the cam groove 4c of the cam ring. Move straight in the direction of the optical axis.

In FIG. 4, the portion above the optical axis shows the variable magnification lens _L2 at the telephoto end, the bottom portion shows the state at the wide end, and the bottom portion shows the state at the wide end.

The first group lens holding cylinder 9 is connected to the straight key 9 as described above.
a and 9b are slidably fitted into key grooves 4e and 4f of the cam ring 4, and rotate integrally when the cam ring 4 rotates. The guide tube 10 has two straight bars 10
Since rotation is prevented by a and 10b,
The holding cylinder 9 is displaced in the optical axis direction by the action of the cam groove 9c and the steel ball 11, and the lens _L1 is moved to a position corresponding to the focal length along the arc-shaped line explained in FIG. Correct focal plane movement. As mentioned above, the cam groove 9c has a V-shaped cross section, and the steel ball is brought into elastic contact with the slope of the cam groove 9c as a guide piece.
Even if there is some error in the depth of the groove, there is no backlash unlike with conventional cam grooves and guide pins, and the operation is smooth.

Furthermore, since the groove is V-shaped as described above, the holding cylinder 9 can be molded from synthetic resin, and the spring ring 12 can also be made from synthetic resin, so it can be manufactured at low cost. .

The present invention has an extremely simple structure due to the above-described configuration, and has the advantage of being able to provide a highly accurate zoom lens at a low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a zoom lens optical system to which the present invention is applied, FIG. 2 is a perspective view showing an embodiment, and FIG.
The figure is a sectional view showing a part of the same embodiment, and FIG.
FIG. 3 is a cross-sectional view taken along line A-A in the figure. L ₁ : 1st group lens, L ₂ : 2nd group lens, L ₃ :
3rd group lens, L ₄ : Relay lens, 3: Fixed lens barrel, 4: Variable magnification operation means, 5: 2nd group lens moving ring, 9: 1st group lens holding tube, 9c: Cam groove, 1
0: First group lens guide means, 11: Guide piece, 1
2: Spring ring.

Claims (1)

[Scope of Claims] 1. A holding tube 9 that holds a lens _L1 that performs focusing and zooming functions is provided with a cam groove 9c for moving the lens _L1 to change magnification, and a guide tube is provided in the holding tube 9. 10 and spring ring 12
the guide ball 11 into the cam groove 9c.
Fit the guide ball 11 into the spring ring 1
2, and has linear keys 9a and 9b that engage with key grooves 4e and 4f of a cam ring 4 extending parallel to the optical axis in the holding cylinder 9 and provided with a cam groove for variable magnification; 4
The lens is moved by the variable magnification cam groove.
L ₂ is fitted, and the straight bar 10 is inserted into the guide tube 10.
a, 10b are fixedly installed, and the straight bars 10a, 10
b is a cam member 25 rotated by the driving means 16;
b, and focusing adjustment is performed by engaging the cam of the cam member 25b and the straight bars 10a, 10b.
0 and the holding cylinder 9, and magnification adjustment is performed by moving the lenses L ₁ and L ₂ by the cam groove of the cam ring and the cam groove 9c of the guide cylinder by rotation of the cam ring 4. A zoom lens structure characterized by: