JPS63314511A - Internal focusing type zoom lens - Google Patents

Abstract

PURPOSE:To obtain an internal focusing type zoom lens which is miniaturized and lightweight, and can control automatic focusing with high accuracy, by varying a moving range of a focusing lens and a position of an objective lens by allowing them to interlock with an adjustment of a zooming operating member. CONSTITUTION:An internal focusing type zoom lens for moving a variator lens L2 and a compensator lens L3 by adjusting a zooming operating member is constituted so that a moving range of a focusing lens L4 and a position of an objective lens L1 are varied by allowing them to interlock with an adjustment of the zooming operating member. That is, when a cam cylinder 2 turns, the variator lens L2 and the compensator lens L3 move and zooming is executed. Simultaneously, the focusing relay lens L4 also moves back and forth. In such a way, a focused state is not varied by zooming, and also, a moving lens for focusing is miniaturized and lightweight, and by a small torque automatic focusing mechanism, a focusing control can be executed at a high speed and with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Prior Art) In conventional zoom lenses for still cameras, video cameras, etc., a first group including an objective lens is moved to adjust the focus. When automatically focusing a zoom lens using this method, there is a problem that the lens driven by a motor has a large inertial mass, making it difficult to drive at high speed and requiring a long operating time. This is more noticeable with longer focal length lenses. Furthermore, the drive motor used for automatic focus adjustment is required to be as small, lightweight, and consume as little power as possible, and - in order to increase the blade drive torque, the drive speed must be lowered by adjusting the gear ratio, etc. . In order to satisfy the above requirements, it is sufficient to use an internal focusing zoom lens with a small inertial mass and configure the lightweight focusing lens to move, which enables high-speed drive and shortens the operating time until focusing. .

However, when focusing a zoom lens using an internal focus method, the amount of movement of the focusing lens changes depending on each focal length. That is, there is a characteristic that the amount is small on the short focal length side and large on the long focal length side. Therefore, with conventional focus adjustment devices, the focus position moves every time you zoom.
There was a problem in that the characteristics as a zoom lens were lost. In other words, when photographing the same subject from the same position, if you zoom while the camera is in focus, the camera will become out of focus (out of focus) and you will have to refocus, which is an annoying problem. .

(Objective of the Invention) The present invention was made in view of the above-mentioned problems regarding focusing of conventional zoom lenses, and an object of the present invention is to provide an internal focusing zoom lens whose focusing state does not change even when zooming. .

The present invention further provides an internal focusing zoom lens in which the movable lens for focusing is small and lightweight, the drive torque required for the automatic focus adjustment mechanism is small, and the automatic focus adjustment can be controlled with high precision. The purpose is to

(Structure of the Invention) An internal focusing zoom lens according to the present invention that achieves the above-mentioned object is an internal focusing zoom lens in which a variator lens and a compensator lens are moved by adjusting a zooming operating member, which has the following features: The present invention is characterized in that it is configured to change the movement range of the focusing lens and the position of the objective lens.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a cross-sectional explanatory diagram showing a simplified configuration of an embodiment of the present invention, which has a four-group lens configuration and is applied to a rotary zooming zoom lens. The first group of objective lenses L r on the object side (left side in the figure) is fixed to the lens barrel 1 . Variator lens L2 of the second group and third group
The compensator lens L3 of the group is mounted on the lens barrel 1 so as to be movable in the optical axis direction. The focus lens of the fourth group is the focus relay lens L4 and the fixed relay L.
,' The focusing relay lens L is movably attached to the lens barrel 1, and the fixed relays L and I are fixed to the lens barrel 1.

Inside the lens barrel 1, a cam barrel 2 is connected to a guide pin 6 and a guide groove 1.
0, it is fitted so as to be rotatable around the optical axis, and rotates together with the zoom operation ff14.

As shown in FIGS. 1 and 2, cam grooves 11.12 are formed in the cam cylinder 2, and pins 7.8 fixed to the variator lens L2 and the compensator lens L3 are formed in these cam grooves 11.12. is inserted. Therefore, when the cam cylinder 2 rotates, the variator lens L2 and the compensator lens L move toward and away from each other along the cam grooves 11 and 12. It is well known that zooming is performed by this movement. A focus cam groove 13 is further formed in the cam cylinder 2, and a pin 9 fixed to the holding frame of the focus relay lens L is fitted into a cam groove 17 formed at a distance L13 from the cam groove 13. . Therefore, the focus relay lens L
, are moved back and forth along the cam groove 13 by rotation of the focus operation ring 3.

The relationship between the cam groove of the cam barrel 2 and the pin that engages with it will be explained in more detail with reference to FIG. 2(a) showing the short focus adjustment state and FIG. 2(b) showing the long focus adjustment state. do.

In FIG. 2(a), the cam cylinder 2 is formed with a cam groove 11 for moving the variator, a cam groove 12 for moving the compensator, a cam groove 13 for moving the focus relay, and a cam groove 10 for guiding the cam cylinder 2. The cam groove 17 rotates in the direction of arrow M by the rotation of operation 1l13, and the pin 9 fixed to the focus movement ring moves from the infinity side to the near distance side (9' side in the figure) along the focus cam groove 13. I will have to move. Δd is the focusing relay L when the focusing operation is performed to a distance shorter than infinity while zoomed to a short focal point.

is the amount of movement.

FIG. 2(b) shows a state in which the pin 18 fixed to the cam barrel is rotated by the rotation of the zoom operation i14, and the cam barrel 2 is rotated toward the long focal point side for zooming. Variator lens L
2 and compensator L3 are each lens barrel 30.32
It is guided to a predetermined position by the groove 14.15 of the lens barrel 1 and 11.12 of the cam barrel 2 based on the amount of displacement of the pin 7.8 fixed to the lens barrel 1.

Guide a10 and focus cam a formed in the cam cylinder 2
To further explain the relationship between 13 and 13, the focus cam groove 13 approximately changes the amount of movement of the focusing relay lens L from the short focus side to the long focus side from infinity side focusing to close distance side focusing. This is a corrected high-order cam curve, where Δd is the amount of movement on the short focus side, and Δd' is the amount of movement on the long focus side. It is clear that the amount of movement at the intermediate focal length becomes Δdi depending on the use position within the focus cam groove forming range depending on the zoom position.

In addition, the guide groove 10 is the same as the cam curve formed in the focus cam groove 13 from a short focus to a long focus in an infinity state, so that the amount of displacement of the pin 9 with respect to the pin 6 in an infinity focus state is zero. It is displaced along the guide groove 10 by rotation of the cam cylinder 2 with a cam curve that should be formed as follows. That is, the focus cam groove 13 is also displaced together with the guide groove 10, and the amount of displacement of the pin 9 is reduced to zero due to the displacement of the pin 9. Therefore, in the infinity focusing state, the focusing relay lens L is not displaced by zooming, but in other cases, the amount of displacement is changed depending on the use position of the focus cam groove 13, and the lens is moved to a predetermined position.

In addition, since the cam cylinder 2 is rotationally displaced by the pin 18,
Cam groove 11 for variator and male groove 1 for compensator
2 also rotates, that is, the variator lens L2 and the compensator lens L3 are corrected in accordance with the displacement of the cam cylinder 2.

These movement methods make it possible to maintain a focused state at all times regardless of zooming operations.

Although one embodiment has been described above, it goes without saying that the present invention is not limited to this embodiment. However, the present invention is not limited to this mechanism, and various known mechanisms may be employed without departing from the technical idea of the present invention, such as arranging the focus operation ring closer to the camera body than the zoom operation ring.

(Effects of the Invention) According to the present invention, the focus state does not change due to zooming, the movable lens for focusing is small and lightweight, and the focus is controlled quickly and with high precision using a small torque automatic focus adjustment mechanism. An internal focusing zoom lens can be constructed.

[Brief explanation of drawings]

Fig. 1 is an explanatory cross-sectional view of an internal focusing zoom lens according to an embodiment of the present invention, Fig. 2 is an explanatory view showing the relationship between a cam cylinder and a pin that engages with it, and Fig. FIG. 2(b) shows a state in which the lens is zoomed to a focal point, and FIG. 2(b) shows a state in which it is zoomed to a long focal point. 1-... Lens barrel 2... Cam barrel 3... Focus operation ring Ll... Objective lens

Claims (2)

[Claims] (1) In an internal focusing zoom lens that moves the variator lens and compensator lens by adjusting the zooming operation member, the lens is configured to change the movement range of the focusing lens and the position of the objective lens in conjunction with the adjustment of the zooming operation member. An internal focusing zoom lens. (2) The movement range of the focusing lens is determined by selecting a specific area of one guide groove cam in relation to the adjustment amount of the zooming operation member. ) The internal focusing zoom lens described in item 1.