JPS58194005A - Automatic focusing zoom lens device - Google Patents

Abstract

PURPOSE:To prevent an image surface moving speed from varying with focal length, by providing a driving controller which varies the driving speed of a focusing lens driving means by the output of a zooming information detecting means. CONSTITUTION:A zoom lens 1 consists of a focusing lens 4, variable power lens group 5, compensating lens group 6, and fixed lens group 7. Incident light L is observed through the mirror 8, etc., in a camera body 2. Light passed through a semitransparent part 8' reaches a photoelectric element 13 for focus detection. The motor 18 for the zoom lens is driven through a contact 16 by a signal from a focus detecting circuit 14 to move the lens group 4 and a barrel 20. When a zoom operation ring 22 is rotated, a brush 28 slides on a resistor 29 and zoom ratio information is detected from its resistance value to vary the rotating speed of the motor 18 by a lens driving control circuit 17 on the basis of the zoom ratio information.

Description

[Detailed description of the invention] The present invention relates to an autofocus zoom lens.

In the zoom lens optical system, a focusing lens group for focus adjustment and a zooming lens group for zooming are provided separately and independently.
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An example of such a lens is the curved lens focus m type no-sumres/z, in other words, Taigu's zoo lens fully automatic focusing, which adjusts the focus by moving the first group by attaching a 4f number to the lens group on the incident line of light. When using fC as a zoom lens, there are drawbacks as described below.

In such a zoom lens, the moving distance of the focusing lens group to focus on a subject at a predetermined close distance from infinity is always constant regardless of the focal length set by the zooming operation. When the focusing lens group is moved with respect to an object at a distance of , the corresponding movement of the image plane varies greatly depending on the focal length. The movement type of the image plane changes approximately in proportion to the ratio of a predetermined focal length to another set focal length (hereinafter referred to as the direct zoom ratio). be. Urge ゛rTL
A focus detection device that detects the focus of the image plane or a secondary image plane with a negative valence of -8 detects the focus shift and moves the entire focusing lens group to perform automatic focusing, so the apparent focus is Therefore, the driving movement of the focusing lens group should be determined so that the moving speed of the image plane due to the movement of the focusing lens group on the telephoto side is appropriate. On the wide-angle side, the apparent focus tracking speed becomes too slow, and on the other hand, if you set the force single lens/lens group drive speed so that it is appropriate on the wide-angle side, the image plane will fall behind the telescope. moves too quickly, and if the non-focal lens 110 is stopped during focusing, a hunting phenomenon will occur and a small portion 41 will occur.

However, despite these drawbacks, it is an object of the present invention to provide an eye-movement focusing zoom lens that can always optimize the apparent focus tracking speed for a set focal length.

The first problem can be seen in the figure showing the embodiment of the book @ Ming.

2 in Figure 1, IF, I eye movement focusing zoom lens.
'l'!, attached to camera body 2 equipped with force-type automatic focus detection function with lens 1 and 5. Zoom lens 1
The original 4 systems have a focusing lens group 4, a variable magnification lens group 5, a correction lens group 6, and a fixed lens group 7 in the original incident direction.
It consists of

The element f incident on the object side passes through the lens groups 4 to 4 and reaches the main mirror 8 in the camera body 2. The light reflected by the main mirror 8 is guided onto a finder screen 9, and is directed to the photographer through a venta grism 10 and an eyepiece 11. On the other hand, IJJ, which passes through the semi-transparent part 8° of the main mirror 8, is reflected by the rear sub-mirror 12 and reaches an element 16 in the focus detection circuit 'f' provided at the bottom of the camera body 2. In this embodiment, the photoelectric element 16 and the black dot &9 are provided on a surface conjugate to the film surface F. The output of the photoelectric element 16 is inputted to the focus detection circuit 14 to determine whether the focus is in the form of a focal point or not. 15 is this ninth power supply. From the focus detection circuit 14, there is a contact 16 provided with a mounted zjasvc. A lens advance signal, a lens I/retraction signal, a lens stop signal, and a power signal are sent to the lens drive control circuit 17 provided in the zoom lens 1. The V lens drive circuit 17 rotates the seventh gear 18 in response to the L signal.
Gear 19 attached to motor shaft 18° is barrel 2
Rotate the inner am 20' set at 0 completely. barrel 2
0 is provided with a helicoid screw 201, the focusing lens group 4 and barrel 20 move forward or backward while rotating relative to the fixed FI cylinder 24, so that the subject image is not formed on the frame surface F. Focus all the way. Is motor 18 and both sides 19.20° the driving means for focusing lens group 4? It is *X to form. As shown in C, the eye movements can be focused.

Perform the steps as described below. When the zooming operation ring 22 is rotated by -f movement, the cam barrel 26 is also rotated by ν. Cam tube 25
A zooming cam groove 23a2b is formed in the lens 1, a bin 25 is installed in the barrel 24 that holds the variable magnification lens group 5, and a barrel 26 is installed in the barrel 26 that holds the correction lens #6. The bottle 27 is installed on the fixed mirror dog 21 and is passed through the straight guide r421'1ic.
, 21K (-; t'L) are aligned. By rotating the cam cylinder 26, the variable magnification lens group 5 and the correction lens group 6 are moved in the original axial direction, and the bluff 28 is moved 17 on the resistor 29. , the detected resistance value changes.This resistance value is used as the zoom ratio @ 1 in each state of this zoom lens.Here, the zoom ratio er, the focal length set in the valley state and γ When ftrrtn is ftrrtn and the shortest focal length is f, then r=ftnm/f, 1un-W.As mentioned above, the moving surface of the image plane at each focal length is equal to the shortest focal length. In this case, if all standards are used, then the rotation speed will be significantly lower than the zoom ratio information, so the lens drive control circuit 17 changes the rotational speed of the motor 18 using this zoom ratio information.

Specifically, when the focal length is short, the rotational speed of the aperture motor 18 is stopped and the four focus lens groups are moved faster. By doing this, the moving speed of the image plane at the valley focal length? Therefore, the apparent focusing speed (i.e., when the photographer is observing 1 under
The speed at which the corresponding bits coalesce (1r) can be kept almost constant regardless of the set focal length.

Note that as a method for controlling the rotational speed of the rotor by IC, commonly known means such as changing the driving wJ11I pressure or changing the duty in pulse driving may be used.

! Up to now, we have described the case where the zoom ratio 1 is adopted as the zooming information, but it is also possible to use the focal length p,*e set by the zooming operation ring 22 as is as this zooming information. However, the focus tracking speed can be kept almost constant regardless of the set focal length.

Furthermore, the case where the above-described zoom lens 1 in the first row is of an interchangeable lens type is assumed. However, the present invention may be applied to a case where the zoom lens 1 is provided in a solid state on the camera body 2.

As mentioned above, the inventive lens is equipped with an automatic focusing zoom lens that can maintain an almost constant focusing speed no matter what the focal length is. be able to.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a pupil according to the present invention. Applicant: Nippon Kogaku Kogyo Co., Ltd. Agent 61 Takashi Bebe

Claims (1)

[Claims] Can be used for an ITTL type focus detection device,
A focusing lens group zoom lens device for focus adjustment, comprising: a zooming information detection means for detecting zooming information in conjunction with a previous zooming operation member; a focusing lens driving means for moving the focusing lens; An automatic focusing x-lens device comprising: a drive control device that completely changes the drive speed of the focus lens group drive means based on the output of the zooming information detection means. 2. In the automatic focusing zoom lens device according to claim 1, the zooming information detection means detects a ratio of a set focal length value to a predetermined focal length value. Device.