JPH05341393A - Zoom lens driving device - Google Patents

Abstract

PURPOSE:To highly accurately attain a power varying operation by moving two front and back groups of lenses which function as a zoom lens in the optical axis direction, and a focal distance adjustment by adjusting the distance between two groups of lenses by an inexpensive mechanism having a small number of parts and a simple constitution. CONSTITUTION:A lens barrel for holding two groups of lenses and which is connected with a driving mechanism 28 in the optical axis direction is provided with a reference block 13 for holding one group of lenses and which is connected with the driving mechanism 28, and a movable block for holding the other group of lenses and which is held so as to be moved in the optical axis direction of the reference block 13, and a focal distance adjusting gear 39 supported by a shaft is installed on the reference block 13 and a member for moving the same body, and the focal distance adjusting gear 39 is directly engaged with a rack 37 installed along the optical axis, or engaged with the rack through a different gear 40, a cam groove is installed around the rotary shaft of the focal distance adjusting gear 39, and a cam follower installed on the movable block is made to slide in contact with the cam groove.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens driving device, for example, a zoom lens driving device for changing the projection magnification by moving two lens groups, front and rear, between a document and a photoconductor of a copying machine in the optical axis direction. It relates to the device.

[0002]

2. Description of the Related Art A zoom lens driving device of this type is known from Japanese Utility Model Laid-Open No. 59-7441.

This is because when the zoom lens is moved in the optical axis direction to change the magnification, the two lens groups in front of and behind the zoom lens are adjusted in space to adjust the focal length. The distance between the two lens groups is adjusted by using the movement of.

Specifically, a wire stretched along the optical axis is wound around the wire along the guide of two idle pulleys, and is rotated when the zoom lens moves in the optical axis direction. Drive pulley, and a focal length adjustment cam that presses against a cam follower provided in the movable part of the zoom lens,
And a connecting shaft that is supported on the side of the moving base that supports the zoom lens and that connects the drive pulley and the focal length adjusting cam.

According to this, when the zoom lens is moved in the optical axis direction to change the magnification, the drive pulley is rotated by the movement and is transmitted to the focal length adjusting cam by the connecting shaft, and the focal length adjusting cam is moved. It is possible to adjust the focal length by moving the movable part of the zoom lens in the optical axis direction via the cam follower.

[0006]

However, in the above-mentioned conventional structure, the motion transmitting mechanism for converting the movement of the zoom lens in the optical axis direction into the adjusting operation of the distance between the two lens groups in front of and behind the zoom lens has a large number of parts. It's complicated, so it's expensive.

Further, as is known from Japanese Patent Laid-Open Nos. 60-12537 and 1-94331, a type of projection in which the zoom lens moves in a direction perpendicular to the optical axis as the zoom lens moves in the optical axis direction In the optical system, the guide structure of the zoom lens and the drive mechanism are complicated and have a large number of parts, which is expensive. In addition, due to the large number of parts, due to the relationship between mutual position accuracy and operation transmissibility, etc., the movement of the zoom lens in the optical axis direction, or the optical axis direction and the direction perpendicular to the optical axis, and the movement of the zoom lens It is difficult to obtain high accuracy in adjusting the distance between the front and rear two lens groups.

Therefore, it is an object of the present invention to provide a zoom lens driving device capable of solving the above-mentioned conventional problems by improving the driving method of the zoom lens.

[0009]

In order to achieve the above-mentioned object, the present invention provides a zoom lens driving device which changes a projection magnification by moving two lens groups, a front lens and a rear lens, in the optical axis direction. A reference block which holds the lens group and is connected to the drive mechanism, and a movable block which holds the other lens group and is held by the reference block so as to be movable in the optical axis direction, A focal length adjusting gear is pivotally supported on the reference block or a member moving the same as the reference block, and the focal length adjusting gear is meshed with a rack provided along the optical axis directly or via another gear, and the focal length adjusting gear is attached. Is provided with a cam groove around its own rotation axis, and a cam follower provided on the movable block is brought into sliding contact with this cam groove.

Further, the rack is provided on a guide member for guiding the movement of the zoom lens in the optical axis direction, and the guide member is installed between the free ends of the pair of parallel levers, and the drive mechanism moves the zoom lens along the guide member. The lever can be rotated with the movement of the zoom lens.

[0011]

According to the above configuration of the present invention, when the reference block is driven by the connection with the drive mechanism, the reference block is moved in the optical axis direction together with the movable block held by the reference block to change the magnification. At this time, the focal length adjusting gear pivotally supported by the reference block or its movable member is rotated by an amount corresponding to the movement of the reference block in the optical axis direction due to meshing with a rack provided along the optical axis. The movable block is moved in the optical axis direction with respect to the reference block via the cam groove around the rotation axis of the lens itself and the cam follower on the movable block that is in sliding contact with the zoom groove, and the two front and rear lens groups held by them are zoomed. Since the distance is set according to the position of the lens in the optical axis direction, the influence of mutual positional accuracy is small due to the small number of members, and the zooming due to the movement of the zoom lens in the optical axis direction and the accompanying two lens groups before and after it Focal length adjustment by spacing adjustment can be achieved.

Further, when the rack is provided on the guide member for guiding the movement of the zoom lens in the optical axis direction, no special member for the rack is required, and the guide member is provided between the free ends of the pair of parallel levers. When the drive mechanism moves the zoom lens along the guide member and rotates the lever in accordance with the movement of the zoom lens, the zoom lens moves at the same time in the optical axis direction along the guide member, By rotating the pair of parallel levers, the guide member is moved in the direction perpendicular to the optical axis together with the zoom lens guided by the pair of parallel levers. The zoom lens utilizes the movement in the optical axis direction due to the engagement between the rack and the focal length adjusting gear. It can also be achieved the focal length adjustment by adjusting the distance of the two lens groups after.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a zoom lens 1 to which the present invention is applied.
1 shows a schematic configuration of a copying machine having a variable power optical system including a.

The zoom lens 1 is provided between a platen glass 2 on which an original is placed and a photosensitive drum 3 which exposes an image on the original to form an image. The zoom lens 1 can change the projection magnification by moving in the optical axis direction, and can project the image of the document on the photosensitive drum 3 at the same size or reduced or enlarged.

As described above, when the zoom lens 1 moves in the optical axis direction to change the projection magnification, the zoom lens 1 moves forward and backward.
The focal length is adjusted by changing the distance between the two lens groups 5 and 6 so that the conjugate length of the projection optical system becomes constant.

The image of the original on the platen glass 2 is
Scanning is performed by moving the light source 61 and the first mirror 7 at a speed V proportional to the peripheral speed of the photosensitive drum 3. The image at each time point to be scanned is imaged on the photosensitive drum 3 via the second and third mirrors 8 and 9, the zoom lens 1 and the fourth mirror 10, and the second and third mirrors 8 and 9 are V / 1st at a speed of 2
By moving in the same direction as the mirror 7, the conjugate length is kept constant.

The zoom lens 1, as shown in FIGS.
A reference block 13 as a lens frame for holding the front lens group 5 of the front and rear two lens groups 5 and 6, and the rear lens group 1
A lens barrel 15 is formed by a movable block 14 as a lens frame for holding 2.

The movable block 14 is covered over the reference block 13 from above, and the lenses of the movable block 14 are alternately inserted so that the movable block 14 is slidably received by the reference block 13 in the optical axis direction. However, the specific configuration of the lens group is not limited to this.

The movable block 14 has a guide pin 21 projecting downward on the bottom surface on the front end side fitted into an elongated hole 22 in the optical axis direction provided on the bottom wall of the reference block 13, and on the upper surface on the rear end side. A guide pin 23 protruding upward is fitted into a long hole 24 provided in the upper wall of the reference block 13 in the optical axis direction. As a result, the movable block 14 is guided so as to move stably on the reference block 13 in the optical axis direction.

As shown in FIG. 5, the reference block 13 has a mounting base portion 13a extending to one side of the bottom portion, and the mounting base portion 13a is provided on one side of the optical axis substantially along the optical axis. It is slidably fitted in the guide member 24 and is guided so as to be movable in the optical axis direction.

The guide member 62 is installed between the free ends of a pair of parallel levers 26, 26 whose base ends are pivotally supported by a shaft 25, connected by a pin 30, and each parallel lever 26 centered on the shaft 25. , 26 by the rotation of the zoom lens 1
Since the lens is moved in parallel with, the zoom lens 1 can also be moved in a direction perpendicular to the optical axis.

A shaft 2 for pivotally attaching the parallel levers 26, 26.
5, 25 and the shafts 27, 27 provided near the free ends of the parallel levers 26, 26, the pulleys 31 to 34 are rotatably mounted, and the drive wires 28 are attached to the pulleys 31 to 34.
Has been passed over.

A part of one side of the drive wire 28 along the guide member 62 is fixed to the mounting base 13a of the reference block 13 with a pin 35, and the other side is wound around a drive pulley 36. It is turning.

A stepping motor (not shown) is connected to the drive pulley 36 so that the drive wire 28 can be driven in either forward or reverse directions via the drive pulley 36.

When the drive wire 28 is driven in the forward or reverse direction, the reference block 13 follows this along with the movable block 14, and the entire zoom lens 1 is stabilized in the optical axis direction while being guided by the guide member 62. Then, it can be moved forward or backward and positioned at any position along the optical axis. This gives the required projection magnification.

A rack 37 is formed on the guide member 62, and a focal length adjusting gear 39 pivotally supported by a shaft 38 on the bottom surface of the reference block 13 is meshed with the rack 37 via a pinion gear 40. Pinion gear 40
Is pivotally supported on the reference block 13 by an axis 50.

Although the focal length adjusting gear 39 may be directly meshed with the rack 37, the required diameter of the focal length adjusting gear 39 can be reduced by interposing the pinion gear 40.

A cam groove 41 around the shaft 38 is formed in the focal length adjusting gear 39, and the guide pin 21 of the movable block 14 is fitted in the cam groove 41.

As a result, when the zoom lens 1 is moved in the optical axis direction, the focal length adjusting gear 39 moves relative to the rack 37 together with the pinion gear 40 so that the zoom lens 1 moves in the optical axis direction and the amount of movement. Is rotated in response to the movement of the movable block 14 in the optical axis direction with respect to the reference block 13 via the cam groove 41 and the guide pin 21,
The position in the optical axis direction of the lens group 6 held by the movable block 14 with respect to the lens group 4 held by the reference block 13 is set to a position corresponding to the magnification change, and the necessary focal length adjustment is achieved.

In short, the reference block 13 forming the half of the lens barrel 15 is the drive wire 28 which is the drive mechanism.
It is directly connected to the movable block 14 which is driven by the optical axis direction without any special support base and can move in the optical axis direction together with the movable block 14 held by itself. During this movement in the optical axis direction, the focal length adjusting gear 42 pivotally supported by the reference block 13 rotates via the pinion gear 40 with the rack 37 using the guide member 62 provided along the optical axis. Since it receives, the power transmission structure is simplified.

Transmission of an operation for adjusting the distance between the front and rear two lens groups 5 and 6 of the zoom lens 1 by moving the zoom lens 1 in the optical axis direction is performed by the focal length adjusting gear 39 and the pinion gear 40 on the reference block 13. This is achieved by the rotation without requiring any other member, the mounting positional relationship of the motion transmitting member is uniquely determined, and a highly accurate focal length adjusting function can be achieved with a simple mechanism.

The optical axis of the zoom lens 1 is connected to one of the shafts 32 of the pair of parallel levers 26 by being connected to the drive system of the stepping motor at a predetermined rotation ratio or by connecting another stepping motor (not shown). Interlocking with zooming operation and focal length adjusting operation by driving in the direction,
The pair of parallel levers 26, 26 is rotated.

As a result, the parallel levers 26, 26 are rotated together with the guide member 62 to move the zoom lens 1 in the direction perpendicular to the optical axis. The projection position can be set so as to match the predetermined end portion of the zoom lens 1 for this purpose.
The support and driving force transmission mechanism of is simplified.

Actually, the movement of the zoom lens 1 in the optical axis direction and in the direction perpendicular to the optical axis is substantially the same as the movement of the zoom lens 1 on the guide member 62 along the optical axis, and the parallel lever 2
6 and 26 and the parallel movement of the guide member 62.

Further, a lens position correcting cam 51 is provided between the optical axis and the guide member 62, and a cam surface 51a of the lens position correcting cam 51 is provided.
In addition, a spring 52 is applied to the pair of parallel levers 26, 26 so that the shaft 38 slides as a cam follower and urges it in a fixed direction.

As a result, when the zoom lens 1 is moved in the optical axis direction and the direction perpendicular thereto, the position of each zoom position of the zoom lens 1 in the direction perpendicular to the optical axis is
The correction is appropriately performed with the rotation of the pair of parallel levers 26, 26.

The cam groove 41 of the focal length adjusting gear 39
The same effect can be obtained by replacing the cam groove with a concave line or a convex line formed on one surface of the focal length adjusting gear 39,
It can also be formed as a mere step. in this case,
In the cam groove on one side formed by the ridge or the stepped portion, it is necessary to apply an urging means such as a spring to the movable block 14 side in order to slide the guide pin 21 into the cam groove.

Further, by providing a plurality of cam grooves of the focal length adjusting gear 39 or various cam grooves instead of them, the same can be applied to the case where the zoom lens 1 has three or more lens structures.

Further, although the focal length adjusting gear 39 and the pinion gear 40 are directly provided on the reference block 13, they may be provided on the reference block 13 as long as they are the same members as the reference block 13.

[0041]

According to the present invention, when the lens reference block is driven by the connection with the driving mechanism and is moved in the optical axis direction together with the movable block held by itself, the reference block or the reference block is moved. The focal length adjusting gear pivotally supported by a shaft on the same moving member as is rotated by an amount corresponding to the movement of the reference block in the optical axis direction by meshing with a rack provided along the optical axis, Before and after the movable block is moved in the optical axis direction with respect to the reference block through the cam groove provided around the axis of itself and the cam follower on the movable block which is slidably contacted with the cam groove, and 2
Since the two lens groups are set at intervals according to the position of the zoom lens in the optical axis direction, the influence of mutual positional accuracy is small due to a small number of members, and the zooming due to the movement of the zoom lens in the optical axis direction and the accompanying 2 It is possible to achieve focal length adjustment by adjusting the distance between two lens groups, which makes the structure simple and inexpensive, and improves the mutual position accuracy and motion transmissibility due to the small number of parts. Is achieved with high precision.

Further, when the rack is provided on the guide member for guiding the movement of the zoom lens in the optical axis direction, a special member for the rack is not required, and this guide member is provided between the free ends of the pair of parallel levers. When the drive mechanism moves the zoom lens along the guide member and rotates the lever in accordance with the movement of the zoom lens, the zoom lens moves at the same time in the optical axis direction along the guide member, By rotating the pair of parallel levers, the guide member is moved in the direction perpendicular to the optical axis together with the zoom lens guided by the pair of parallel levers. The zoom lens utilizes the movement in the optical axis direction due to the engagement between the rack and the focal length adjusting gear. It is also possible to achieve focal length adjustment by adjusting the distance between two lens groups, and it is easy to adjust the focal length when the zoom lens is moved in the direction perpendicular to the optical axis along with the movement of the optical axis. Moreover, it can be achieved with high accuracy by using an inexpensive structure.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine including a zoom lens to which the present invention is applied.

FIG. 2 is a cross-sectional view of the zoom lens of FIG.

FIG. 3 is a cross-sectional view of the zoom lens of FIG. 2 with the direction changed.

FIG. 4 is a bottom view of the zoom lens of FIG.

5 is a plan view showing an entire drive mechanism of the zoom lens of FIG. 2. FIG.

[Explanation of symbols]

 1 Zoom lens 5 and 6 Lens group 13 Reference block 14 Movable block 15 Lens barrel 21, 23 Guide pin 22, 24 Long hole 62 Guide member 28 Drive wire 36 Drive pulley 37 Rack 39 Focal length adjustment gear 40 Pinion gear 41 Cam groove

Claims (2)

[Claims] 1. A drive device for a zoom lens that changes a projection magnification by moving two front and rear lens groups in an optical axis direction, a reference block that holds the one lens group and is connected to the drive mechanism, A movable block which holds the other lens group and is held by the reference block so as to be movable in the optical axis direction, and a focal length adjusting gear is pivotally supported on the reference block or a member moving therewith. , The focal length adjusting gear is meshed with a rack provided along the optical axis directly or via another gear, and the focal length adjusting gear is provided with a cam groove around its rotation axis, and the movable groove is provided in the cam groove. A zoom lens driving device characterized in that a cam follower provided on a block is brought into sliding contact with the block. 2. The rack is provided on a guide member for guiding the movement of the zoom lens in the optical axis direction, the guide member is installed between free ends of a pair of parallel levers, and the drive mechanism moves the zoom lens along the guide member. 2. The zoom lens driving device according to claim 1, wherein the lever is rotated in accordance with the movement of the zoom lens.