JPH0623014U - Varifocal lens barrel - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a varifocal lens barrel that can reduce the focus movement associated with zooming and does not require a helicoid screw as a mechanism for moving the focus lens group. In a varifocal lens barrel having at least a focus lens group, a moving lens group, and a master lens group, a fixed lens barrel supporting the master lens group is rotatably provided with a variable magnification ring. In addition to supporting the lens, the movable lens group can be moved in the optical axis direction to support a rectilinear ring, and a focus lens frame that supports the focus lens group can be screwed onto this rectilinear ring. Not only the varifocal lens barrel, but also the rectilinear ring is provided with a cam mechanism that moves the lens along a predetermined trajectory in a direction that changes the magnification and that compensates the focus movement that accompanies the magnification change.

Description

[Detailed description of the device]

[0001]

【Technical field】

 The present invention relates to a varifocal lens barrel.

[0002]

[Prior art and its problems]

 As is well known, the varifocal lens is a lens in which the focal point shifts with zooming. In this lens, conventionally, a variable magnification ring is used to move the movable lens group to a predetermined position along the optical axis, and then the focus lens group is moved in order to compensate for the focus movement and focus. It is taken. However, the general property of the varifocal lens is that if only the moving lens group is moved during zooming, the focus will be greatly changed due to the movement of the focal point. Therefore, a large amount of movement of the focus lens is required to refocus. As a result, in the conventional structure, a helicoid (multi-row) screw was indispensable to secure the amount of movement of the focus lens. However, the helicoid screw has a problem in that it is difficult to miniaturize the helicoid screw because the machining cost is high and a certain screwing length is required to maintain accuracy.

[0003]

[The purpose of the device]

 The present invention is based on the above-mentioned awareness of the conventional varifocal lens barrel, and can reduce the focus movement associated with zooming. Therefore, a varifocal lens that does not require a helicoid screw as a moving mechanism of the focus lens group. The aim is to get a lens barrel.

[0004]

[Outline of the device]

 The present invention is a varifocal lens barrel having at least a focus lens group, a moving lens group, and a master lens group, and a variably movable lens barrel that supports the master lens group. In addition to supporting the zoom ring, it is movable in the optical axis direction to support the moving lens frame and the rectilinear ring, and the focus lens frame that supports the focus lens group is screwed into this rectilinear ring. A feature is that a cam mechanism is provided to move not only the moving lens group but also the rectilinear ring by rotation, so as to move along a predetermined locus in a direction that compensates for the focal point movement accompanying zooming.

According to this lens barrel, when the zoom ring is rotated, zooming occurs by the moving lens group, and at the same time, the focus movement by the focus lens group can be compensated to some extent. It is possible to reduce the focus shift due to zooming, and therefore the movement amount of the focus lens frame can be small, so that an inexpensive lead (single thread) screw can be used without using a helicoid screw.

[0006]

[Example of device]

 The present invention will be described below with reference to illustrated embodiments. In this embodiment, the present invention is applied to a lens for a surveillance camera, and includes a focus lens unit L1, a moving lens unit L2, and a master lens unit L3 from the object side. The master lens group L3 is fixed to the master lens frame 11, and the master lens frame 11 is fixed to the fixed lens barrel 12. The movable lens group L2 is fixed to the movable lens frame 13, and the focus lens group L1 is fixed to the focus lens frame 14.

A diaphragm setting ring 15 and a magnification changing ring 16 are rotatably fitted on the outer circumference of the fixed lens barrel 12, and the diaphragm setting ring 15 and the magnification changing ring 16 are respectively arranged on the inner circumference. A diaphragm opening / closing ring 17 and a cam ring 18 which rotate in the same manner are rotatably fitted. That is, the radial interlocking pins 17a and 18a planted in the opening and closing ring 17 and the cam ring 18 pass through the circumferential grooves 17b and 18b formed in the fixed lens barrel 12 respectively, and the outside of the fixed lens barrel 12 The protruding portions are fitted in the connecting grooves 15a and 16a formed in the aperture setting ring 15 and the variable power ring 16 in parallel with the optical axis.

Therefore, when the aperture setting ring 15 and the variable power ring 16 are rotated, the aperture opening / closing ring 17 and the cam ring 18 are integrally rotated. As is well known, when the diaphragm opening / closing ring 17 is rotated, the size of the diaphragm opening is changed. The position of the variable magnification ring 16 in the optical axis direction is movably fitted in the circumferential groove 12b of the fixed lens barrel 12, and the position regulation block 19 and the variable magnification ring 16 are fixed by a fixing screw 19a. Are regulated.

A rear portion of the rectilinear ring 20 is further rotatably fitted to the inner circumference of the cam ring 18, and the front portion of the rectilinear ring 20 is connected to the front end surface of the fixed barrel 12 and the variable magnification ring 16. Extends between the inner circumference of the. The movable lens frame 13 is fitted to the inner periphery of the rear portion of the rectilinear ring 20, and the follower pins 21 in the radial direction embedded in the rectilinear ring 20 are provided with a rectilinear guide groove 20a parallel to the optical axis formed in the rectilinear ring 20 and a cam. The cam groove (lead groove) 18c formed in the ring 18 and the linear guide groove 12a formed in the fixed lens barrel 12 parallel to the optical axis are simultaneously fitted. Therefore, both the moving lens frame 13 and the rectilinear ring 20 can only rectilinearly move in the optical axis direction.

A compression coil spring 23 is inserted between the front end surface of the fixed barrel 12 and the front portion of the rectilinear ring 20, so that the rectilinear ring 20 is always urged to move forward. An end face cam is provided between the variable power ring 16 and the rectilinear ring 20 on the opposing surface that is constantly in contact with the urging force. In this embodiment, as developed and shown in FIG. 3, an end face cam 24 is formed on the variable magnification ring 16 side, and a follower portion 25 that abuts against this end face cam 24 is integrally provided on the rectilinear ring 20 side. ing.

The focus lens frame 14 is screwed onto the inner peripheral surface of the front part of the rectilinear ring 20 via a lead (single thread) screw 26. Therefore, the focus lens group L1 moves linearly in the optical axis direction according to the shape of the end face cam 24 when the variable magnification ring 16 is rotated, and when the focus lens frame 14 is rotated according to the lead screw 26, the lead screw 26 Follow the lead of, and move in the direction of the optical axis while rotating. The rotation range of the focus lens frame 14 with respect to the rectilinear ring 20 is restricted by a rotation range restriction groove 27 in the circumferential direction and a restriction protrusion 28 fitted into the rotation range restriction groove 27.

The shape of the end face cam 24 is set so as to roughly move the focus lens unit L1 in a direction that compensates the focus movement that inevitably occurs when the magnification changing ring 16 is rotated to change the magnification. . That is, the surveillance camera lens of the illustrated embodiment shows a short focal length state of about 4 mm in FIG. 1 and a long focal length state of about 8 mm in FIG. The transition from the short focal length to the long focal length occurs by moving the moving lens unit L2 backward, as shown in FIG. It has been found that the focus movement at that time is compensated by moving the focus lens unit L1 forward by an appropriate amount. Therefore, in this embodiment, the end surface cam 24 is determined to roughly move the focus lens unit L1 forward with the transition from the short focal length to the long focal length. Of course, since it is a varifocal lens, it is not possible to completely compensate for the focus movement due to zooming only by the shape of the end face cam 24. The final focusing is performed by rotating the focus lens frame 14 according to the lead screw 26.

That is, in the present varifocal lens barrel having the above-described configuration, when the variable power ring 16 is rotated, the movable lens group L2 moves linearly in the optical axis direction according to the cam groove 18c of the cam ring 18, and at the same time, the end surface cam 24 Accordingly, the focus lens unit L1 moves straight in the optical axis direction. This coarse movement of the focus lens unit L1 is a direction for compensating for the focus movement due to the magnification change, so the focus shift due to the magnification change is suppressed to be smaller than that of the conventional device in which only the movement lens unit L2 is moved. be able to. Therefore, focusing performed by rotating the focus lens frame 14 only needs to cover the amount of focus movement that could not be compensated by the end face cam 24, so the amount of movement can be small, and therefore the helicoid screw should be used. However, the use of the lead screw 26 is sufficient.

The end face cam 24 thus has a function of roughly moving the focus lens unit L1 to roughly compensate the focus movement associated with zooming. Therefore, there is flexibility in its shape. 5 and 6 show another example of the shape, FIG. 5 shows an example of the linear lead surface 24A, and FIG. 6 shows an example of the step end surface cam 24B in which the flat surface portion 24a and the inclined portion 24b are combined.

[0015]

[Effect of device]

 As described above, according to the varifocal lens barrel of the present invention, when performing the magnification change by moving the movable lens group, the focus lens is coarsely moved in a direction to compensate the focus movement that is inevitably caused by the magnification change. It can be moved. Therefore, it is possible to suppress the focus shift due to the magnification change and to use an inexpensive single-start screw as a screw mechanism for finely adjusting the focus lens group without using an expensive helicoid screw. Therefore, the processing cost can be reduced and the size can be reduced.

[Brief description of drawings]

FIG. 1 is an upper half cross-sectional view showing a varifocal lens barrel according to an embodiment of the present invention in a short focal length state.

FIG. 2 is an upper half sectional view of the lens barrel of FIG. 1 in a long focal length state.

FIG. 3 is a development view taken in the direction of arrow A in FIG. 1, showing an example of the shape of an end face cam.

FIG. 4 is a locus diagram showing an example of a movement locus of a lens group of the lens system of FIGS. 1 and 2.

5 is a development view similar to FIG. 3, showing another example of the shape of the end face cam.

FIG. 6 is a development view similar to FIG. 3, showing another example of the shape of the end face cam.

[Explanation of symbols]

 L1 Focus lens group L2 Moving lens group L3 Master lens group 11 Master lens frame 12 Fixed lens barrel 12a Straight-ahead guide groove 13 Moving lens frame 14 Focus lens frame 15 Aperture setting ring 16 Variable magnification ring 17 Aperture opening / closing ring 18 Cam ring 18c Cam groove 20 rectilinear ring 20a rectilinear guide groove 21 follower pin 23 compression coil spring 24 24A 24B end face cam 25 follower part 26 lead screw

Claims (2)

[Scope of utility model registration request] 1. A varifocal lens barrel having at least a focus lens group, a moving lens group, and a master lens group, and a fixed lens barrel supporting the master lens group; A variable magnification ring rotatably supported; a movable lens frame supporting the movable lens group and a rectilinear ring movably supported on the fixed lens barrel in the optical axis direction; supporting the focus lens group Then, the focus lens frame screwed to the rectilinear ring is rotated in advance in a direction in which both the moving lens group and the rectilinear ring are magnified by the rotation of the magnifying ring and the focus movement accompanying the magnification is compensated in advance. A varifocal lens barrel, comprising: a cam mechanism that moves along a predetermined trajectory. 2. The cam mechanism according to claim 1, wherein the cam mechanism has a cam groove for the movable lens group, which is provided on a cam ring that rotates integrally with the variable magnification ring; and a spring unit that biases the rectilinear ring forward. A varifocal lens barrel composed of an end face cam provided on the facing surface of the variable power ring and the rectilinear ring, which is always in contact by the biasing means.