JPH04102811A - Zoom lens barrel - Google Patents

Abstract

PURPOSE:To make a zoom lens simple and small in size by driving a cam member and moving a shaft back in the direction of the optical axis, rotating a lead screw and moving a 1st and 2nd lens frame back, and thus prescribing the positions of the 1st and 2nd lens groups. CONSTITUTION:A front group lens 15 and a rear group lens 21 are incorporated in the front group lens frame 23 and rear group lens frame 24, provided in parallel to the direction of the optical axis, and fitted to a fixed shaft 27 so that it can move freely forward and backward through leg parts 23a and 24b. A spiral cam member 38 is rotated to move the rear group lens frame 24 toward the front lens side 15 through a steel ball 52 engaging a cam groove 51, thereby varying the photographic magnification. At the same time, the front group lens frame 23 is moved along a transition curve through a steel ball 42 which engages a cam groove 41 to correct a shift in focus position with the photographic magnification.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zoom lens barrel used in electronic still cameras, video cameras, and the like.

[Conventional technology]

A two-group zoom type zoom lens consists of two lens groups, a front group and a rear group, and by changing the relative distance between them, the photographic magnification is changed and the focal plane is kept constant. This is what I did. With this zoom lens, it is necessary to change the relative position of each lens group in a complicated manner depending on the imaging magnification, so a cam tube with cam grooves for moving each lens group in the optical axis direction is used. The position of each lens group was determined by rotating this cam barrel by zooming.

[Problem to be solved by the invention]

Incidentally, since the processing accuracy of the cam barrel greatly affects the positional accuracy of each lens group, it is necessary to process the cam barrel with high precision, which is one of the factors that makes zoom lenses expensive. Furthermore, in addition to the cam barrel, the zoom lens includes a fixed barrel, etc., in which a linear groove is formed to serve as a guide when the frame of each lens group is moved, and these are fitted together with high precision. Therefore, there was a problem that the mechanism was complicated and miniaturization was difficult.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a zoom lens barrel that can simplify the mechanism of a zoom lens and contribute to miniaturization and cost reduction.

[Means to solve the problem]

In order to achieve the above object, the zoom lens barrel of the present invention includes a cam member having a cam surface that is displaced in the optical axis direction during zooming, and one end of which is in contact with the cam surface. a shaft that moves forward and backward in the optical axis direction in response to displacement, and a first lens frame that holds a first lens group, engages with the shaft, and moves in the optical axis direction in response to the movement of the shaft A spiral cam groove is provided on the circumferential surface of the shaft, and is rotatable in response to the displacement of the cam surface, and is engaged with the second lens frame holding the second lens group. The second lens frame and the second lens group are driven according to a predetermined cam diagram.

Further, the lead screw is driven by the rotation of the cam member via a gear supported in parallel with the optical axis direction.

Further, the first lens frame has a spiral cam groove that is engaged with the cam groove formed on the circumferential surface thereof, and the shaft is connected to the first lens frame through a cylindrical second cam groove that is pivotally supported by the jaw 71-. It is designed to be moved in the optical axis direction in response to advances and retreats.

Further, by rotating the second lead screw, the first lens frame is moved forward and backward in the optical axis direction to adjust the focus.

Further, a gear is fixed to the shaft so that the rotational phase thereof can be freely adjusted with respect to the lead screw, and a gear is pivotally supported for transmitting the rotation of the cam member to the lead screw.

Further, a magnification change information detecting means for detecting the rotational position of the cam member and obtaining magnification change information of the zoom lens is provided on the surface of the cam member opposite to the cam surface.

Further, the gear is a helical gear.

[Effect]

According to the above configuration, when the cam member is driven, the shaft is moved back and forth in the optical axis direction according to the displacement of the cam surface, and the lead screw is rotated.

The first lens frame is advanced or retreated by advancing and retracting the shaft, and the second lens frame is advanced or retreated by rotation of the lead screw.
The respective positions of the first lens group and the second lens group are defined according to the desired imaging magnification.

Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

In FIG. 1A showing the wide-angle side position of the zoom lens barrel according to the embodiment of the present invention, the zoom lens using the zoom lens barrel has a front group lens 15 composed of lenses 12, 13, and 14. This is a two-group zoom system consisting of a rear group lens 21 consisting of lenses 16, 17, and 18, and 19. Front group lens 15. The rear group lens 21 is connected to the front group lens frame 23 . These are incorporated into the rear group lens frame 24, and are attached to the fixed shirt 1 27, which is provided parallel to the optical axis direction and fixed between the lens barrel front frame 25 and the lens barrel middle frame 26.
They are attached via leg portions 23a and 24a so that they can move forward and backward, respectively.

A gear 28 rotatably provided on the fixed shirt 1-27 in close proximity to the leg portion 23a of the front group lens frame 23 meshes with a gear 29 in the same figure (B) showing the telephoto side position of the zoom lens barrel. As shown in FIG. 2, the front group lead screw 32 is rotated by the rotational driving force of the drive morph 31 transmitted through the gear train 30.

The gear 29 and the front group lead screw 32 are fixed to a shaft 33, and this shaft 33 is connected to the lens barrel front frame 2.
5 and the lens barrel middle frame 26 so as to be able to move forward and backward in the optical axis direction, and is urged in a direction away from the lens barrel front frame 25 by a coil spring 35. The end portion 33a of the shaft 33 is connected to the helical cam member 3 via a rotatable steel ball 36.
A helical force 1 formed at the edge of one end surface of 8 is in contact with surface 38a. With this, the front group lead screw 3
The position in the optical axis direction of No. 2 is defined by the inclination of the cam surface 38a, and the transition curve α is determined by the rotation of the helical cam member 38.
It moves forward and backward in the optical axis direction as shown in . A stopper 39 (see also FIG. 3) for regulating the range of movement of the shaft 33 is provided at the highest portion of the cam surface 38a.

A spiral cam groove 41 is formed on the circumferential surface of the front group lead screw 32 , and the front group lens frame 23 is engaged with this via a steel ball 42 .
As the front group lens frame 23 is rotated, the front group lens frame 23 is moved back and forth along the fixed shaft 27. The steel ball 42 is urged toward the cam groove 41 by a leaf spring 43 installed inside the front group lens frame 23.

A rear group lead screw 45. is connected between the gear 29 of the shaft 33 and the lens barrel middle frame 26 through a tube 44, one end of which is fixed to the lens barrel middle frame 26 and through which the shaft 33 is rotatably passed. A helical gear 46 is rotatably attached. One end of this helical gear 46 has a convex portion 46 in the axial direction.
a is provided, and this convex portion 46a fits into a concave portion 45a of the rear group lead screw 45. Then, by tightening the set screw 47 provided at the end of the rear group lead screw 45, the tip of the set screw 47 enters the 7-shaped groove 46b of the convex portion 46a, and the rear group lead screw 4
5 and the helical gear 46 are tightly fixed.

A stopper 48 is fixed to the end of the cylinder 44 on the gear 29 side, and a coil spring 49 is set between this and the rear group lead screw 45, and a helical gear 46 is inserted through the rear group lead screw 45. It is pushed toward the lens barrel middle frame 26 side. This eliminates backlash between the helical gear 46 and a later-described helical gear that meshes with the helical gear 46, and prevents out-of-focus during zooming.

A spiral cam groove 51 is formed on the circumferential surface of the rear group lead screw 45, and the rear group lens frame 24 is engaged with this via a steel ball 52, and the rear group lead screw 45 is rotated. As the rear group lens frame 24 is rotated, the fixed shaft 27
It advances and retreats along the

The steel ball 52 is urged toward the cam groove 51 by a plate spring 53 installed inside the rear group lens frame 24.

Note that the relative rotational positional relationship between the rear group lead screw 45 and the helical gear 46 can be adjusted simply by retightening the setscrew 47, so the front group lens 15. The relative positional relationship of the rear group lens 21 can be easily adjusted,
Front lens group 15. during tracking adjustment. Rear group lens 21
There is no need to move the entire lens barrel, and the length of the lens barrel does not change.

The spiral cam member 38 is connected to the lens barrel middle frame 26 and the lens barrel rear frame 56.
It is rotatably attached to a fixed shaft 58 fixed between
1 is formed. A gear 63 that is rotationally driven by a drive motor 62 (see FIG. 3) for variable magnification is meshed with this gear portion 61. Further, a gear portion 64 formed on the circumferential surface of the lens barrel middle frame 26 of the spiral cam member 38 meshes with a gear 67 rotatably attached to a shaft 66 fixed to a metal fitting 65. This gear 67 has a bearing portion 68
A helical gear 69 is integrally formed with the helical gear 69 interposed therebetween, and this helical gear 69 meshes with the helical gear 46. Although the metal fittings 65 are not shown, the metal fittings 65 are attached to the lens barrel middle frame 26.
is fixed.

A circular chamber 7I is formed at the end of the spiral cam member 38 on the side of the lens barrel rear frame 56, and a microbrush 7I is formed at the bottom of the circular chamber 7I.
A disk-shaped sliding resistance substrate 73 on which the microbrush 72 slides is fixed to the rear frame 56 of the lens barrel. The rotational position of the spiral cam member 38 is detected by the change in the contact position between the microbrush 72 and the sliding resistance substrate 73, and the output signal from the sliding resistance substrate 73 is digitized and the zoom lens mirror of this embodiment is It is powered by a microcomputer that controls, for example, an electronic still camera mounted on the body. In this way, since the variable power information is obtained by detecting the rotational position of the helical cam member 38, it does not take up much space compared to detecting the position of the rear group lead screw 45.
This can contribute to downsizing of the zoom lens barrel.

In order to change the photographing magnification of a zoom lens using the zoom lens barrel of the present invention configured as described above from, for example, the telephoto side to the wide-angle side, the drive motor 62 is rotated counterclockwise in the drawing "2" of FIG. drive it. As a result, the helical cam member 38 is rotated counterclockwise via the gear 63 and the gear section 61, and the helical cam member 38 is rotated counterclockwise via the gear section 64 and the gear 67.
is rotated clockwise, and the rear group screw 45 is rotated counterclockwise via the helical gear 46. Therefore, the rear group lens frame 24 is moved toward the front group lens 15 (in the opposite direction of the arrow β shown in FIG. 1(B)) via the steel ball 52 engaged with the cam groove 51, and the photographing magnification is changed. It will be done.

At the same time, the cam surface 38a in contact with the steel ball 36 is moved lower, so the shaft 33 is urged by the coil spring 35 and moved toward the helical cam member 38. As a result, the front group lead screw 32 is moved, so that the front group lens frame 23 is moved through the steel ball 42 engaged with the cam groove 41.
is moved toward the rear group lens 21 along the transition curve α, and the movement of the focus position due to the change in photographic magnification is corrected, and the focus plane is maintained constant. On the other hand, to change from the wide-angle side to the telephoto side, the drive motor 62 may be driven in the reverse direction.

Further, as the helical cam member 38 is rotated, the microbrush 72 moves on the sliding resistance board 73, and the accurate rotational position of the helical cam member 38 is input to the microcomputer in real time. The microcomputer changes the aperture aperture, for example, based on the rotational position of the helical cam member 38, that is, the magnification change information, to prevent fluctuations in the amount of incident light due to magnification change.

To perform focus adjustment, the drive motor 31 is driven and the gear train 30. The shaft 33 is rotated via gears 28,29. As a result, the front group lead screw 32 fixed to the shaft 33 is rotated, and the front group lens frame 23 is moved back and forth in the optical axis direction via the steel ball 42 engaged with the cam groove 41, thereby performing pin i adjustment. be exposed. Note that, of course, this focus adjustment may be automatically performed based on distance measurement information from an autofocus mechanism (not shown).

〔Effect of the invention〕

As described above, according to the zoom lens barrel of the present invention, a cam member having a cam surface that is displaced in the optical axis direction is used, and the shaft is moved forward and backward in the optical axis direction in accordance with the displacement of the cam surface.
As the lens frame moves forward and backward, the lead screw, which is pivotally supported on the shaft, is rotated to move the second lens frame forward and backward, eliminating the need for the costly conventional cam barrel, and making it easier to use zoom lenses. This simplifies the mechanism and contributes to the miniaturization of zoom lenses and the use of low-angle lenses.

Further, since the lead screw is driven by the rotation of the cam member via a gear supported in parallel with the optical axis direction, it is possible to contribute to downsizing and cost reduction of the zoom lens.

Further, a spiral cam groove is formed on the circumferential surface of the first lens frame to be engaged with the first lens frame, and a spiral cam groove is formed on the circumferential surface of the first lens frame, and a spiral cam groove is formed on the circumferential surface of the first lens frame, and a spiral cam groove is formed on the circumferential surface of the first lens frame. Since it is moved in the axial direction, it can also be used as a shaft, contributing to miniaturization and cost reduction of the zoom lens.

Further, by rotating the second lead screw, the first lens frame is moved back and forth in the optical axis direction to adjust the focus, which contributes to downsizing of the zoom lens.

Further, since the shaft is fixed to the lead screw so that the rotational phase thereof can be freely adjusted, and a gear that transmits the rotation of the cam member to the lead screw is pivotally supported, tracking adjustment can be performed extremely easily, and the lens There is no need to adjust the entire group, and the length of the lens barrel does not change.

Further, since a magnification change information detecting means for detecting the rotational position of the cam member and obtaining magnification change information of the zoom lens is provided on the surface of the cam member opposite to the cam surface, This eliminates the need to correct the magnification information even when the zoom lens is changed, and contributes to the conversion of zoom lenses to zoom lenses and higher precision.

In addition, since the gear is a helical gear, it is possible to remove the hack run between the cam member and the lead screw, and easily prevent focus shift during zooming, which contributes to higher performance of the zoom lens. can.

[Brief explanation of drawings]

FIG. 1(A) is a side sectional view showing a wide-angle photographing state of an embodiment of the present invention. FIG. 1(B) is a side sectional view showing a telephoto shooting state of an embodiment of the present invention. FIG. 2 is a plan view schematically showing the focus adjustment mechanism according to the embodiment shown in FIG. 1 from the front. FIG. 3 is a plan view showing a part of the variable power mechanism according to the embodiment shown in FIG. 1 from the front. 23 ・ 24 ・ 32 ・ 33 ・ 38 ・ 45 ・ 46° 47 ・ Front group lens frame Rear group lens frame Front group lead screw shaft Spiral cam member Rear group lead screw Helical gear set screw.

Claims (7)

[Claims] (1) In a zoom lens barrel having at least two movable lens groups, a cam member is provided with a cam surface that is displaced in the optical axis direction during zooming, and one end of the cam member is in contact with the cam surface. a shaft that moves forward and backward in the optical axis direction in response to displacement; and a first lens frame that holds a first lens group, engages with the shaft, and moves in the optical axis direction in response to the movement of the shaft. A spiral cam groove is provided on the circumferential surface of the shaft, and is rotatable in response to the displacement of the cam surface, and is engaged with the second lens frame holding the second lens group. 1. A zoom lens barrel comprising a cylindrical lead screw formed in a cylindrical lead screw, the first lens group and the second lens group being driven according to a predetermined cam diagram. (2) The zoom lens barrel according to claim 1, wherein the lead screw is driven by the rotation of the cam member via a gear supported in parallel with the optical axis direction. . (3) The first lens frame has a spiral cam groove formed on its circumferential surface that is engaged with the first lens frame, and is controlled by the movement of the shaft through a cylindrical second lead screw pivotally supported by the shaft. The zoom lens barrel according to claim 1, wherein the zoom lens barrel is moved in the optical axis direction in response. (4) The zoom lens barrel according to claim 3, wherein focus adjustment is performed by moving the first lens frame forward and backward in the optical axis direction by rotating the second lead screw. (5) The shaft is fixed to the lead screw so that its rotational phase can be freely adjusted, and a gear for transmitting the rotation of the cam member to the lead screw is pivotally supported. zoom lens barrel. (6) A patent claim characterized in that a magnification change information detection means for detecting the rotational position of the cam member and obtaining magnification change information of the zoom lens is provided on the surface of the cam member opposite to the cam surface. The zoom lens barrel according to item 1. (7) The zoom lens barrel according to claim 5, wherein the gear is a helical gear.