JPS5837047Y2 - Zoom lens focusing lens frame straight-advancing mechanism - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a mechanism for linearly advancing a focusing lens frame of a zoom lens.

A so-called front lens rotating type zoom lens, in which the focusing lens of the zoom lens is rotated back and forth, has some disadvantages in use.

For example, if a polarizing filter is attached to a focusing lens frame, the filter will rotate together with the focusing lens, making it completely useless.

Similar problems occur with lenses called mirror lenses, adapters used to divide the screen, corner hoods, and the like.

For this reason, a so-called double helicoid system is used to move the focusing lens frame forward and backward without rotating it.

However, this double helicoid is not easy to machine, and compared to a single helicoid, if machined with the same precision, twice as much error will occur.

The play in this part causes the focusing lens and the variable magnification lens to run out and position errors, and this runout and position errors have a large effect on image formation.

If the double helicoid method improves machining accuracy and reduces backlash, it is not possible to significantly reduce backlash because a large amount of force is required for the feeding operation.

For this reason, the double helicoid system had the problem of being expensive and not very accurate.

In addition, the double helicoid system inevitably has a large external size, so it does not meet the demand for miniaturization.

An object of the present invention is to provide a focusing lens frame straight-advancing mechanism that can move the focusing lens frame straight with high precision using an extremely simple single helicoid structure.

In order to achieve the above object, the focusing lens frame linearly advancing mechanism for a zoom lens according to the present invention is a focusing lens frame linearly advancing mechanism for a zoom lens having a focusing lens, a variable power lens, a correction lens, and a mask lens. A focusing lens frame whose rotation is restricted relative to the main body and is guided to move straight, and a linear groove cam parallel to the optical axis and connected to the focusing lens frame by a helicoid so as to rotate relative to the main body. a helicoid cam having a helicoid cam, a zoom cam that is provided to rotate with respect to the main body and has a variable magnification groove cam and a correction groove cam, an operating ring that is provided to rotate and move forward and backward relative to the main body, and an operating ring A variable power transmission member that transmits the rotation of the zoom cam to the linear groove cam and the correction groove cam, and a correction transmission member that connects the linear groove cam and the correction groove cam are provided. The zoom cam is rotated by moving the lens frame straight and moving the operating ring back and forth.

According to the above structure, the object of the present invention can be completely achieved.

The mechanism according to the present invention will be explained in more detail below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of an optical system of a zoom lens to which the mechanism according to the present invention can be applied, in which 1 is a focusing lens 2 is a variable magnification lens, 3 is a correction lens, and 4 is a mask lens. .

FIG. 2 is a diagram showing an embodiment of the focusing lens frame linearly advancing mechanism according to the present invention.

Inside the focusing lens frame 5 is a focusing lens 1 shown in FIG.
is supported, and a helicoid male screw 5a is provided on the outer periphery base side (camera side) of the frame.

A pin 6 is installed in the frame 5, and this pin 6 is attached to the main body (
rotation restriction guide plate 7 fixedly provided on the
Guided by.

On the inner periphery of the front end of the cylindrical helicoid cam 8, there is provided a female helicoid thread 8a that is coupled to the male helicoid thread 5a.

In addition, the helicoid cam 8 has a straight groove cam 8b parallel to the optical axis.
is provided.

The helicoid cam 8 is provided so as to be rotatable in an angular range for focus adjustment with respect to the main body.

The zoom cam 11 is arranged inside the helicoid cam, and has a variable power groove cam 11a and a correction groove cam 11b provided on its outer periphery, and accommodates the variable power lens 2 and correction lens 3 shown in FIG. 1 inside. has been done.

The operating ring 12 is provided on the outermost periphery of the zoom lens so that it can rotate and move forward and backward relative to the main body.

The variable power transmission pin 9 provided on the operating ring 12 engages with and passes through the linear groove cam 8b of the helicoid cam, and further engages with and passes through the variable power groove cam 11a of the zoom cam 11.
It is connected to a variable magnification lens 2 provided inside the lens 1.

The correction transmission pin 10 engages with the linear groove cam 8b of the helicoid cam and the correction groove cam 11b of the zoom cam, and is connected to a correction lens within the zoom cam 11.

The mask lens 4 shown in FIG. 1 is supported by a main body base (not shown).

In the mechanism configured as described above, the operation ring 12
When the variable power transmission pin 9 moves forward and backward, the variable power transmission pin 9 moves along the linear groove cam 8b, causing the variable power lens to move forward and backward.

As a result, the zoom cam 11 rotates and the correction lens 3 is moved.

When the operating ring 12 is rotated, the helicoid cam 8 is rotated by the pin 9, and the helicoid 8a provided on the inner periphery of the front side rotates, causing the focusing lens frame coupled thereto to advance or retreat.

Since the focusing lens frame is guided by the pin 6 and the guide plate 7, it moves forward and backward without rotating.

As the operation ring 12 rotates, the helicoid cam 8 rotates, and the zoom cam similarly rotates, and the variable power lens 2 and correction lens 3 rotate, but each lens only rotates and its position on the optical axis does not change.

The helicoid cam rotates with respect to the mask lens provided on the main body, but the light flux that contributes to image formation between the lens group held by the helicoid cam and the mask lens is close to parallel light flux, so the light flux between the main bodies of the helicoid cam Even if there is play in the image, the image is rarely damaged.

As explained above, according to the present invention, it is possible to extend the focusing lens frame in a straight line using an extremely simple mechanism.

As a result, the filters, lenses, and lenses mounted on the focusing lens frame can also be moved straight forward, eliminating the conventional inconvenience.

Also, since double helicoids are not used, processing is extremely easy.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a zoom optical system to which a mechanism according to the present invention is applied, and FIG. 2 is a diagram showing an embodiment of a linear advance mechanism according to the present invention. 1... Focusing lens, 2... Variable magnification lens, 3... Correction lens, 4... Master lens, 5... Focusing lens. Focusing lens frame, 6... Focusing lens pin, 7... Rotation restriction guide plate, 8...
... Helicoid cam, 9 ... Variable power transmission pin, 10 ... Correction transmission pin, 11 ... Zoom cam (tube), 12 ... Operation ring.

Claims (1)

[Scope of utility model registration request] In a focusing lens frame straight-advancing mechanism for a zoom lens that includes a focusing lens, a variable magnification lens, a correction lens, and a mask lens, a focusing lens frame whose rotation is restricted relative to the lens body and is guided to move straight; A helicoid cam is connected to the focusing lens frame by a helicoid and is provided to rotate with respect to the main body, and has a linear groove cam parallel to the optical axis, and a variable magnification groove cam is provided to rotate with respect to the main body and has a linear groove cam parallel to the optical axis. A zoom cam having a correction groove cam, an operation ring provided to rotate and move backward with respect to the main body, a variable power transmission member that transmits rotation of the operation ring to the linear groove cam and the correction groove cam, and a linear groove. A correction transmission member connecting the cam and the correction groove cam is provided, and the focusing lens frame is moved straight without moving the zoom cam forward or backward by rotation of the operation ring, and the zoom cam is rotated by moving the operation ring forward or backward. A zoom lens focusing lens frame straight-advancing mechanism featuring: