JPH0323890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a zoom lens that performs focusing using a lens group including at least one lens other than the first lens group on the object side. The present invention relates to a zoom lens barrel that automatically corrects the amount.

Conventionally, in a zoom lens, the role of each group is determined, such as a lens group for zooming and a lens group for focusing, and the first group lens on the object side is usually used for focusing. . This is because even if the lens moves due to zooming, the position of the object's joint point with respect to the image-side principal point of the first lens group remains almost unchanged, so once focusing is performed, even when zooming. This is because the focused state remains unchanged.

However, using only a specific lens group for focusing in this way not only increases the amount of lens movement when trying to focus at close range, but also increases the amount of peripheral light in zoom lenses, including wide-angle lenses. In order to prevent a decrease in the lens diameter, the diameter of the first group lens must be increased, making it difficult to make the lens compact and improve operability.

In contrast, if the role of each lens group is not fixed as in the past, but if the lens group that has the role of zooming is also used for focusing at the same time, even zoom lenses with the same configuration can be used for zooming. While the number of lens groups that can be used has increased and the zoom ratio can be increased, the number of lens groups that can be used for focusing has also increased, creating a new type of zoom lens that allows focusing up to close distances without increasing the amount of movement. It has been developed.

However, with this type of zoom lens, the optical conditions such as the composite focal length of the focusing lens system and the position of the yoke point change as the lens zooms, and even if the focus is achieved once, the zooming will not continue. Accordingly, the in-focus state cannot be maintained unless the lens is further moved for focusing. Moreover, since this amount of movement changes depending on changes in two variables: the distance to the object and the focal length of the zoom lens, a two-dimensional cam is generally required, and such a camera is used in small portable lenses. It was virtually impossible to incorporate a moving mechanism.

On the other hand, when the object point distance is constant, the lens movement amount curve associated with zooming becomes a curve similar to a logarithmic curve. It has become clear that this can be achieved by moving the focusing lens using different parts of the curved cam.
(Refer to Patent Application No. 77124 of 1982) In other words, the relationship x-f ² /U approximately holds between the lens extension amount x, focal length f, and object point distance U, and x= It can be expressed as e ^{(21og f+log1/U)} .

Therefore, in this case, when an exponential curve cam is prepared for focusing, the relationship between the zoom position and the object point distance is the sum of each, and the change in lens extension amount due to zooming and the object point distance on a single focus curve cam. Changes in the amount of lens extension due to changes in distance can be reacted to by adding angles. At this time, the distance scale is
1og1/U.

The present invention relates to such a special zoom lens barrel. A detailed explanation will be given below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a lens barrel embodying the present invention. In this example, for simplicity, a first group lens and a second group lens are used as focusing lenses. Therefore, in this example, the first group lens and the second group lens move separately in the case of zooming, and move as one unit in the case of focusing.

The fixed barrel 1, which has a substantially U-shaped cross section, has a helicoid threaded portion 1-1 on the inner surface and an escape hole 1- on the outer shell.
2, 1-3, the inner barrel has a guide groove 1-4 in the optical axis direction and a relief hole 1-5, and stop pins 1-5 for the zoom ring and focus ring are installed at appropriate positions on the outer barrel.
6, 1-8 are provided. Note that one end of the escape hole 1-3 forms a focusing member 1-7 on the short distance side, as will be explained later.

A double helicoid is arranged between the inner and outer shells of the fixed barrel 1, and the female helicoid 2 has a helicoid screw portion 2- on the outer surface that engages with the helicoid screw 1-1.
1 and a threaded part 2-2 on the inner surface, and a second threaded part at the tip.
A guide groove 2-3 in the optical axis direction that engages with the pin 8-1 of the group lens frame 8, and a pin 9- of the third group and fifth group lens frame 9.
1 and the cam groove 2-4 that engages with the fourth group lens frame 1
A cam groove 2-5 that engages with the pin 10-1 of 0 is provided. Further, on the outer surface, there is a pin 2-6 that engages with the zoom ring as described later through the relief hole 1-2.
is firmly planted.

Helicoid male 3 has helicoid screw 2-2 on the outside.
Helicoid screw part 3-1 and pin 9- that engage with
Relief hole 3-2 for 1, 10-1, pin 8-1
A guide groove 3-4 in the optical axis direction that engages with a focus pin 4-1 to be described later is provided, and rotation with the fixed barrel is prohibited by a key located at a position not shown. It is said that it can only be moved forward and backward.

A focus sliding barrel 4 that is slidably fitted inside the male helicoid 3 has a first group lens fixed thereto and a cam 4-2 that engages with a pin 8-1.
A pin 4-1 that engages with a guide groove 3-4 of the male helicoid 3 and a focus cam 5-1, which will be described later, is fixed on the outer surface, and only forward and backward movement is allowed by the guide groove 3-4.

The focus control ring 5 is rotatably held by the male helicoid 3 and has a focus cam 5-1 that engages with the focus slide barrel pin 4-1. This focus cam directly regulates the amount of movement of the lens for focusing. Further, a transmission pin 5-2 is fixedly provided on the outer surface.

The focus ring 6 is held rotatably by the fixed cylinder 1, and is provided with a focus correction cam 6-1 and an abutting portion 6-2. The focus correction cam 6-1 engages with the aforementioned transmission pin 5-2, and corrects the amount of lens movement by rotating the focus control ring 5 and slightly rotating the focus cam 5-1 during zooming. . The ∽ abutting portion is for stopping further rotation of the focus ring at the ∞ focusing position.

The curve of the focus cam 5-1 corresponds to the above x=e ^{(21og f+log1/U)} , and the focus correction cam 6-1 corresponds to the exponential term 21ogf in the previous equation.

The zoom ring 7 is rotatably held by the fixed barrel 1, has a guide groove 7-1 in the optical axis direction, and engages with the aforementioned zoom transmission pin 2-6. Further, the rotation angle of the zoom lens 7 is limited by the engagement between the notch 7-2 and the limiting pin 1-8.

The state of engagement between each of the above-mentioned pins and a movement regulating member such as a cam is shown in developed views in FIGS. 2 to 4, excluding escape holes.

Focusing and zooming of a zoom lens having such a lens barrel are performed as follows.

FIG. 2 shows that the ∽ abutting portion 6-2 of the focus ring 6 is in contact with the stop pin 1-6, and the ∽ is in focus.

In order to focus on a nearby object, when the focus ring 6 is extended in the direction of the arrow, the focus correction cam 6-1 rotates as shown in the dotted line along with the transmission pin 5-2, and the focus control ring 5 , therefore, the focus cam 5-1 also moves as indicated by the dotted line. As a result, the focus pin 4-1 moves forward according to the guide groove 3-4, the focus sliding cylinder 4 moves forward, and the first group lens moves forward, and the cam 4-2 moves forward to enter the guide groove 2-3. When the pin 8-1 moves straight, the second group lens moves forward. That is, by the rotation of the focus ring 6, the first group lens and the second group lens move forward as one, and focusing is performed.

Zooming is performed by rotating the zoom ring 7, whose notch 7-2 engages with the stop pin 1-8 to limit its rotational angle, as shown in FIG. By rotating the zoom ring 7, the helicoid female 2
moves forward while being rotated by the helicoid screws 1-1, 2-1, and along with this, the cam grooves 2-4, 2-5 also rotate while moving forward. As a result, the third group, the fifth group lens, and the fourth group lens are connected to pins 9-1 and 10.
-1 moves in the guide groove 1-4. On the other hand, due to the rotation of the female helicoid 2, the male helicoid 3, which is not allowed to rotate, moves straight along with the focus sliding barrel 4 and the focus control ring 5 by the helicoid screws 2-2 and 3-1, and the first group lens also move forward. On the other hand, since the pin 8-1 of the second group lens frame 8 is engaged with the cam groove 4-2 and at the same time with the guide groove 2-3 of the helicoid female 2, it is rotated by the rotation of the helicoid female. The cam 4-2 moves by a combined amount of the forward movement of the cam 4-2 and the backward movement determined by the inclination of the cam 4-2 and the rotation angle of the guide groove 2-3.

Changes in these cam positions as the zoom ring 7 rotates in the direction of the arrow are shown by dotted lines in FIGS. 3 and 4.

A feature of this invention is that the amount of movement of the lens for focusing changes with zooming even for the same object point distance. This amount of movement can be corrected as follows with reference to FIG. It will be done.

At the wide-angle end shown by the solid line in FIG.
and the range where the pin 5-2 contacts the close distance limiting member 1-7, and the range where the upper pin 4-1 of the focus cam 5-1 engages and slides is the range shown by W. Become. Due to zooming, the helicoid male 3 moves forward, and the focus control ring 5
When the pin 5-2 moves forward along with this movement, the pin 5-2 slides forward in the correction cam 6-1, so the control ring 5 rotates slightly as shown by the dotted line in response to this, and the focus cam 5-2 moves forward. The sliding range of pin 4-1 on pin 1 changes to the range shown by T in the figure. As a result, changes in the amount of lens extension for focusing on the same object point due to zooming are automatically corrected, and the same scale can be used. Note that the closest distance at which focusing is possible is determined by the position of the limiting member 1-7, so by selecting the shape of the limiting member 1-7, the closest distance at each focal length can be freely selected.

When zooming is performed while focusing on a fixed object point, the focus ring 6 is not rotated once focusing is performed. When the zoom ring 7 is rotated in this state, each lens group moves according to a movement regulating member such as a cam, as described above, and the combined focal length of the lens system changes. Along with this, helicoid male 3 moves forward and backward,
At the same time, the focus control ring 5 also moves back and forth, and the transmission pin 5-2 slides within the correction cam 6-1 over a range V, causing the focus control ring 5 to rotate.
This rotation of the control ring 5 is controlled by the focus cam 5-1.
By rotating over the range V, the pin 4-1 can be moved back and forth in the guide groove 3-4, and the amount of movement of the lens can be corrected.

In this way, the zoom lens barrel of this invention is
As a movement regulating member for the lens group, a member that moves when the focus operation is performed and a correction member that moves when the zooming operation is provided are provided, and the position of each lens group is determined by both movement regulating members. Even with zoom lenses in which the amount of movement of the lens for focusing changes with zooming, a common distance scale can be used for each focal length, and once an object is in focus, it can be freely zoomed. Even when the lens is moved, the amount of lens movement is automatically corrected and the in-focus state can be maintained at all times.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of one embodiment of a lens barrel having a focusing mechanism according to the present invention, FIG.
4 and 5 are explanatory diagrams of the operation of each cam, and the reference numerals in the figures indicate the following, respectively. 1: Fixed body, 1-1: Helicoid screw part, 1-
2, 1-3, 1-5: escape hole, 1-4: guide groove,
1-6, 1-8: Stop pin, 1-7: Close range limiting member, 2: Female helicoid, 2-1, 2-
2: Helicoid screw part, 2-3: Guide groove, 2-
4, 2-5: Cam groove, 2-6: Pin, 3: Helicoid male, 3-1: Helicoid screw part, 3-2, 3
-3: Relief hole, 3-4: Guide groove, 4: Focus sliding barrel, 4-1: Pin, 4-2: Cam groove, 5: Focus control ring, 5-1: Focus cam,
5-2: Transmission pin, 6: Focus ring, 6-
1: Focus correction cam, 6-2: ∞ abutment, 7: Zoom ring, 7-1: Guide groove, 7-
2: Notch, 8: Second group lens frame, 8-1: Pin, 9: Third and fifth group lens frames, 9-1: Pin, 10: Fourth group lens frame, 10-1: Pin .

Claims (1)

[Claims] 1. In a zoom lens barrel having a plurality of movable lens groups, a helicoid female 2 is screwed to the fixed barrel 1 so as to be rotatable and movable in the optical axis direction in conjunction with the rotation of the zoom ring 7. and a male helicoid 3 screwed into the female helicoid 2 and guided straight to the fixed body 1.
a focus ring 6 which is rotatably fitted to the fixed barrel 1 and has a focus correction cam 6-1 bored in the optical axis direction; and a focus ring 6 which is rotatably fitted to the helicoid male 3; Focus cam 5 in the circumferential direction
-1 is bored and the transmission pin 5-2 is fitted into the focus correction cam 6-1 of the focus ring.
A pin 4-1 is fitted into the male helicoid 3 and fitted into the linear guide groove 3-4 of the male helicoid and the focus cam 5-1 of the focus control ring. A focus sliding barrel 4 carrying a first group lens, a circumferential cam groove 4-2 of the focus sliding barrel fitted in the focus sliding barrel 4, and an optical axis guide groove 2 of the female helicoid. Pin 8 that fits into -3
The focus control ring 5 rotates in conjunction with the rotation of the focus correction cam 6-1 of the focus ring 6 during focusing. Rotation is applied to the focus cam 5-1 by the rotational direction displacement amount of the focus correction cam 6-1 via a transmission pin that slides forward within the correction cam 6-1 of the focus ring in conjunction with zooming. A focus mechanism for a zoom lens, characterized in that the focus movable lens corrects the position on the optical axis.