JP2000206391A - Mechanism for moving lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain vibration caused by vibration or disturbance at the time of focusing/magnification adjustment. SOLUTION: Bearings 54, 56 are provided in a holding frame 20 for holding an imaging lens 42 to be connected guide shafts 22, 24 to be freely slidable. The lens 42 is movable thereby along an optical axis. When a lead screw 76 is turned, a lead nut 78 moves to an axial direction. The nut 78 is connected to the holding frame 20 via a plate spring 84, the holding frame 20 moves to the axial direction together with the nut 78, and vibration caused by disturbance is damped by spring force of the plate spring 84. A torsion coil spring 104 attached to the nut 78 presses an outer circumferential face of the frame 20 to absorb backlashes of the guide shaft 24 and the bearing 56, and generation of vibration at the time of focusing-magnification adjustment is prevented thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a lens moving mechanism provided in a scanning head or the like, which reciprocates and reads an image or writes an image.

[0002]

2. Description of the Related Art Many image recording apparatuses equipped with a digital exposure type image scanning apparatus have been developed, and some of these image scanning apparatuses move parallel to the rotation axis of an exposure drum. Some have a scanning head that scans and exposes an exposure surface.

In this scanning head, a light beam output from an LED or the like and carrying image data is condensed by an imaging lens provided with a moving mechanism, and an image is written on a photosensitive material wound around an exposure drum. It has become.

By the way, the moving mechanism guides the holding frame holding the imaging lens with a guide shaft extending in the optical axis direction, and changes the rotational force of the pulse motor to the force for moving the holding frame in the optical axis direction. It converts and adjusts the focus and magnification.

However, in such a mechanism, when adjusting the focus and magnification, vibration is generated due to backlash of a sliding portion between the holding frame and the guide shaft. On the other hand, if the play is eliminated, the holding frame does not move smoothly.

Further, when the scanning head scans, the imaging lens vibrates through the holding frame due to disturbance, and vertical stripes are generated due to density fluctuation, thereby deteriorating the image quality.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lens moving mechanism capable of suppressing vibration at the time of focus / magnification adjustment and vibration due to disturbance in consideration of the above facts.

[0008]

According to the first aspect of the present invention, the lens is held by the holding frame. The holding frame is provided with a bearing, and is slidably connected to the guide shaft. This allows the lens to move along the optical axis.

A moving means provided in parallel with the guide shaft moves along the optical axis. The moving means is provided with a connecting means for connecting the holding frame and the moving means with a spring force. The moving force of the moving means is transmitted to the holding frame by the spring force of the connecting means, the holding frame moves in the optical axis direction, and the vibration due to disturbance is attenuated by the spring force.

The moving means is provided with a biasing means. The urging means urges the holding frame to absorb backlash between the guide shaft and the bearing. For this reason, the mobility of the holding frame can be ensured, and the play can be substantially eliminated, and the occurrence of vibration at the time of focus / magnification adjustment can be prevented.

According to the second aspect of the present invention, the connecting means includes:
It is composed of a connecting piece protruding from the outer peripheral surface of the holding frame, a support plate provided on the moving means to support the connecting piece, and a leaf spring provided on the moving means and sandwiching the connecting piece with the supporting piece. .

In this configuration, the connecting piece of the holding frame is sandwiched between the support plate and the leaf spring, and the holding frame is moved together with the moving means. The vibration of the holding frame in the optical axis direction due to disturbance is attenuated by the leaf spring.

According to the third aspect of the present invention, the urging means includes:
The torsion coil spring is provided on the connecting means and presses the outer peripheral surface of the holding frame. With such a simple configuration, the play between the guide shaft and the bearing is absorbed, and the occurrence of vibration during focus adjustment is also prevented.

[0014]

FIG. 5 is a schematic diagram of a scanning head using a lens moving mechanism according to the present embodiment.

The exposure section 1 in which the scanning head 28 is disposed
At 0, both ends of the exposure drum 14 are supported by a rotatable rotating shaft 12. Two shafts 16 and 18 are provided in parallel with the rotation axis 12 of the exposure drum 14, and the scanning head 28 can slide along the shafts 16 and 18.

The upper plate 3 of the casing 30 of the scanning head 28
2, three RGB LED chips 36 that are turned on by a signal from the control unit 34 in which an image signal is stored.
Is disposed, and the light emitting surface is directed to the inside of the casing 30.

Three LED chips 36 are arranged in the main scanning direction of the scanning head 28, and each chip has a plurality of elements in the sub-scanning direction. LED chip 36
A slit plate 38 is provided on the light emitting surface side of the light emitting device to limit the spread of light.

The image forming lens 4 is provided inside the slit plate 38.
2 are arranged. The imaging lens 42 includes a plurality of lenses and an aperture, and functions to collect light from the LED chip 36 and form an image on a photosensitive material wound around the exposure drum 14. Play. In addition,
The focus and magnification are adjusted by a moving mechanism described later.

On the other hand, a connecting plate 44 is attached to the outer surface of the upper plate 32. An endless timing belt 46 is fixed to the connecting plate 44. Timing belt 46
Are wound around pulleys 48 and 50 provided near both ends of the shafts 16 and 18, respectively. The pulley 48 has a stepping motor 5 via a reduction gear.
2 is transmitted, and the scanning head 28
It reciprocates along 6,18.

The driving of the stepping motor 52 is controlled by the control unit 34, and is synchronized with the step driving of the photosensitive material. That is, with the photosensitive material stepped and stopped, the stepping motor 52 rotates forward,
The scanning head 28 moves in the width direction (main scanning direction) of the photosensitive material along the shafts 16 and 18.

After the predetermined pulse is confirmed, the stepping motor 52 is rotated in the reverse direction in a state where the photosensitive material is stepped and stopped, thereby performing reciprocal main scanning.

Next, the scanning head 2 will be described with reference to FIGS.
The lens moving mechanism of No. 8 will be described.

Two guide shafts 22 and 24 are provided in parallel with each other in a casing 30 that houses the cylindrical holding frame 20 holding the imaging lens 42. The guide shafts 22 and 24 have one end fixed to the lid 26 and the other end fixed to the top wall 30 </ b> A of the casing 30.
2 along the optical axis. Note that a transmission window 40 through which the light beam is transmitted is formed at the center of the lid 26.

On the other hand, a cylindrical bearing 54 slidably inserted into the guide shaft 22 is provided on the outer peripheral surface of the holding frame 20.
And a bearing 56 which engages the guide shaft 24 with predetermined play while sandwiching the guide shaft 24 from both sides.

As described above, the one guide shaft 24 is loosely engaged with the bearing 56 so that the holding frame 20 can be prevented from being cast even if the two guide shafts 22 and 24 are not completely parallel. Can be moved.

A coil spring 58 is disposed between the bearing 54 and the top wall 30A of the casing 30, and the coil spring 58 urges the holding frame 20 toward the lid 26, so that the holding frame 20 is moved in the optical axis direction. Absorbs backlash.

On the other hand, a projecting portion 60 projects from the casing 30, and a channel-shaped bracket 62 is attached to the projecting portion 60. On the outer surface of the bracket 62,
The stepping motor 64 is fixed, and the rotating shaft 66 reaches inside the bracket 62.

A small-diameter drive gear 68 is
Has been fixed. The driving gear 68 is a large-diameter transmission gear 70.
And are engaged. The transmission gear 70 is mounted on the bracket 6
Both ends are fixed to a lead screw 76 which is supported at both ends by bearings 72 and 74 provided in the bearing 2. Thus, the rotational force of the stepping motor 64 is reduced by the drive gear 68 and the transmission gear 70 and transmitted to the lead screw 76.

The lead screw 76 is disposed so as to be parallel to the guide shafts 22 and 24. A lead nut 78 is screwed into the lead screw 76. An arm 80 extends in the radial direction from the lead nut 78, and the tip of the arm 80 is locked by a stop bar 82 arranged in parallel with the lead screw 76.

Therefore, when the lead screw 76 turns, the lead nut 78 does not rotate but moves in the axial direction of the lead screw 76.

The boss 84 of the transmission gear 70 has a second
The tab 86 is fixed, and rotates integrally with the transmission gear 70. The tip portion 86 of the second tab 86
As A passes through the transmission-type second photointerrupter 88 attached to the overhang portion 60, the rotational position of the transmission gear 70 is detected.

Further, the boss 84 of the transmission gear 70
A coil spring 90 is mounted to absorb backlash of the lead screw 76 in the axial direction.

On the other hand, from the lead nut 78, the holding frame 2
A support plate 92 protrudes toward the 0 side. An end of a leaf spring 94 bent in a crank shape is fixed to a base of the support plate 92 with a screw 96. The support plate 92 and the leaf spring 9
4, a connecting piece 98 protruding from the outer peripheral surface of the holding frame 20 is sandwiched.

As a result, the holding frame 20 moves together with the lead nut 78, and the vibration of the holding frame 20 in the optical axis direction due to disturbance is attenuated by the spring force of the leaf spring 94.

Further, a shaft 100 is fixed to the support plate 92 with screws 102, and a core of a torsion coil spring 104 is mounted on the shaft 100. The torsion coil spring 104 does not fall off the shaft body 100 with the washer 106.

The other end of the torsion coil spring 104 is fixed to the support plate 92, and one end is in contact with the outer peripheral surface of the holding frame 20 to urge the holding frame 20 toward the axis. The play between the guide shaft 24 and the bearing 56 is absorbed by the biasing force of the torsion coil spring 104, and vibration during focus adjustment is suppressed.

A first tap 108 projects from the outer peripheral surface of the holding frame 20. This first tap 108
Passes through the transmission-type first photointerrupter 110 attached to the casing 30, so that the origin position of the holding frame 20 is detected.

An adjusting screw 112 is screwed into the screw hole 116 of the casing 30 through a washer 114, and the screwing amount of the adjusting screw 112 is adjusted to press the end of the lead screw 76. And the lead screw 76
, The relative position between the second tab 86 and the second photointerrupter 88 can be finely adjusted.

[0039]

According to the present invention having the above-described configuration, it is possible to suppress the vibration at the time of adjusting the focus of the lens and the vibration due to disturbance.

[Brief description of the drawings]

FIG. 1 is a perspective view of a scanning head provided with a lens moving mechanism according to an embodiment.

FIG. 2 is an exploded perspective view of a scanning head provided with a lens moving mechanism according to the embodiment.

FIG. 3 is a side sectional view of a scanning head provided with a lens moving mechanism according to the embodiment.

FIG. 4 is a cross-sectional view of a scanning head provided with a lens moving mechanism according to the embodiment.

FIG. 5 is a front view showing a driving mechanism of a scanning head provided with a lens moving mechanism according to the embodiment.

[Explanation of symbols]

 Reference Signs List 20 holding frame 22 guide shaft 24 guide shaft 54 bearing 56 bearing 76 lead screw (moving means) 78 lead nut (moving means) 80 arm (moving means) 82 stop bar (moving means) 92 support plate (connecting means) 94 leaf spring (Connecting means) 98 Connecting piece (Connecting means) 104 Torsion coil spring (Biasing means)

Claims (3)

[Claims] 1. A lens moving mechanism that guides a holding frame holding a lens by a guide shaft and moves the lens along an optical axis, the lens moving mechanism being provided on the holding frame and slidably connected to the guide shaft. Bearing, moving means provided in parallel with the guide shaft and moving along the optical axis, connecting means provided on the moving means for connecting the holding frame with a spring force, and the holding frame provided on the moving means And a biasing means for biasing the guide shaft and the bearing to absorb backlash. 2. The connecting means includes a connecting piece projecting from an outer peripheral surface of the holding frame, a supporting plate provided on the moving means for supporting the connecting piece, and a supporting piece provided on the moving means. 2. The lens moving mechanism according to claim 1, wherein the first and second leaf springs sandwich the connecting piece. 3. The lens moving mechanism according to claim 1, wherein said urging means is a torsion coil spring provided on said connecting means and pressing against an outer peripheral surface of said holding frame.