JP4385319B2 - Zoom lens - Google Patents

Description

  The present invention relates to a zoom lens used for a video camera, a still camera, or the like.

Many video cameras and still cameras are equipped with a so-called zoom lens that has a function capable of changing magnification while focusing.
In order to improve the portability of these cameras, it is desired to make the camera body small and light, and accordingly, the zoom lens is also required to be small and light while improving performance. Yes.

In general, a lens constituting the zoom lens is composed of a front lens, a variable power lens, an iris, a fixed master lens, and a focusing lens in order from the subject side.
The front lens and the fixed master lens are fixed, and the variable power lens and the focusing lens are movable in the optical axis direction.
Further, on the inner surface of the lens barrel of the zoom lens, an antireflection rib that continuously protrudes in a pleat shape is provided to prevent irregular reflection of incident light that adversely affects a captured image.
Normally, the lens barrel has a complicated shape, and is formed by injection molding a thermoplastic resin such as polycarbonate for the purpose of mass productivity and low cost.

By the way, conventionally, as a zoom lens and its lens barrel structure, various structural forms have been proposed in order to realize the above-described reduction in size and weight.
For example, there is a lens barrel described in Patent Document 1 filed by the present applicant.
The lens barrel is divided into a front lens barrel holding a front lens and a rear lens barrel behind the front lens barrel, and each movable lens supported and moved by two shafts from the front-rear direction of the rear lens barrel. The (frame) is inserted and assembled together with a shaft that slidably supports them.
As another structural form, there is a zoom lens barrel described in Patent Document 2.
This zoom lens barrel is composed of a box having one side wall opened along the optical axis and a lid member covering the opening.
JP 2002-258139 A JP-A-5-232369

However, in the zoom lens having the lens barrel described in Patent Document 1, it is possible to stably support the movable lens by further increasing the number of shafts, but the rear barrel is substantially cylindrical. In the case of forming the antireflection rib by injection molding, there is a problem in that it is undercut with respect to the drawing direction from the mold, but because it is cylindrical, it is difficult to adopt the inner slide structure and molding is difficult. .
In addition, when trying to obtain the antireflection function by a method other than molding, it is necessary to keep the inner wall of the lens barrel away from the optical axis or to arrange another part having an antireflection function, which increases the size of the entire lens or the number of parts. There was a problem that the cost would be increased.

On the other hand, the zoom lens having the lens barrel described in Patent Document 2 has an advantage that the antireflection rib can be formed by so-called punching in the injection molding.
However, since the guide shaft is arranged and fixed from the direction orthogonal to the axis, the number of the shafts is increased (for example, 4) in order to improve the slidability and movement accuracy of the movable lens supported by the guide shaft. If it is going to be a book, there existed a problem that arrangement design was difficult and many restrictions produced and it was difficult to reduce the whole.
Accordingly, there is a problem in a device equipped with this zoom lens that the resolution of the image is remarkably reduced and the imaging performance such as image shake is liable to deteriorate.
SUMMARY OF THE INVENTION The present invention provides a zoom lens that can be reduced in size without degrading imaging performance and is inexpensive.

In order to solve the above problems, the present invention has the following configurations 1) and 2).
1) In a zoom lens having a variable power lens, a fixed master lens, and a focusing lens,
The lens barrel,
Four shafts arranged parallel to each other along the optical axis inside the lens barrel, arranged in parallel on one side with the zoom lens, fixed master lens, and focusing lens in between First and fourth shafts and second and third shafts arranged in parallel on the other side ;
A first engaging portion that holds the zoom lens and engages the first shaft so that movement in a direction orthogonal to the optical axis is restricted, and the optical axis with respect to the second shaft a zooming lens frame having a second engagement portion, the movement of only a single direction that Jo Tokoro to orthogonal engaged to be acceptable,
A third engagement portion that holds the focusing lens and is engaged with the third shaft so that movement in a direction orthogonal to the optical axis is restricted; and the optical axis with respect to the fourth shaft a focusing lens frame having a fourth engaging portion, the movement of only a single direction that Jo Tokoro to orthogonal engaged to be acceptable,
The fixed master lens holds, comprising a front Symbol fixed lens frame having a fifth engaging portion moving direction is engaged to be restricted to perpendicular to the fourth shaft to said optical axis, a,
The lens barrel is divided in the optical axis direction, and is connected to at least a first wall surface substantially orthogonal to the optical axis and the first wall surface, and extends in the optical axis direction to form an antireflection rib portion. A first lens barrel and a second lens barrel having a second wall surface and at least one surface along the optical axis that is substantially open.
The zoom lens is characterized in that the first to fourth shafts are supported by the first and second lens barrels from both ends.
2) The position of the fixed lens frame in the optical axis direction is determined by the first and second lens barrels being substantially in contact with the fifth engaging portion from both directions of the optical axis. a zoom lens according to 1) and.

  According to the present invention, there is an effect of obtaining a small and inexpensive zoom lens that does not deteriorate in resolution and does not cause image shaking.

The preferred embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is an external perspective view of an embodiment of a zoom lens according to the present invention.
FIG. 2 is an assembly diagram illustrating an embodiment of the zoom lens according to the present invention.
FIG. 3 is a first perspective view for explaining a main part in the embodiment of the zoom lens of the present invention.
FIG. 4 is a second perspective view for explaining a main part in the embodiment of the zoom lens of the present invention.
FIG. 5 is a front view for explaining a main part in the embodiment of the zoom lens of the present invention.
FIG. 6 is a bottom view for explaining a main part in the embodiment of the zoom lens of the present invention,
FIG. 7 is a side view for explaining a main part in the embodiment of the zoom lens of the present invention.

An external perspective view of an embodiment of the zoom lens 100 of the present invention is shown in FIG. FIG. 2 shows an assembly diagram of the zoom lens 100. As shown in FIG.
As shown in the drawings, the zoom lens 100 includes a front lens barrel 1, a rear lens barrel 2, a lens block 4, an iris block 5, a drive unit 6, and an actuator 50.
The front lens barrel 1 and the rear lens barrel 2 are lens housings that are roughly divided forward and backward along the optical axis CL, and are fastened with screws 3 and integrated as a lens barrel.
Details of each member will be described below. Note that the directions of up, down, front, back, left, and right are unified as shown in FIG.

<About the front lens barrel 1>
Before barrel 1, the rear side and the right which has three walls of the left wall 1b and the upper wall 1c extending along the front wall 1a and connecting to the optical axis to the front wall 1 a generally perpendicular to the optical axis A casing having an open side is formed by injection molding of polycarbonate (PC).
Therefore, the mold for molding the mold has a slide mold that slides in the front-rear direction of the optical axis and is opened in the vertical direction, and the front lens barrel 1 is formed by the mold having this structure.
A lens frame 1d having a circular opening is formed on the front wall 1a, and the front lens 7 is fixed to the lens frame 1d.
Four shaft holes 1e for fitting and supporting four guide shafts 8 to be described later are formed in the rear side surface of the front wall 1a.
The upper wall 1c is formed with a lower hole 1f for fastening a drive unit 6 described later in detail with a screw.
An antireflection rib 1g that prevents reflection of light incident from the front lens 7 is formed on the lower surface of the upper wall 1c. The antireflection rib 1g is the same as that formed on the rear lens barrel 2, and details will be described later.

<About the rear lens barrel 2>
The rear lens barrel 2 has three walls, a rear wall 2a substantially orthogonal to the optical axis, and a right wall 2b and a lower wall 2c that are connected to the rear wall 2a and extend along the optical axis. It is a housing opened on the side, and is formed by injection molding a PC.
Accordingly, the mold for molding the mold has a slide mold that slides in the front-rear direction of the optical axis and is opened in the vertical direction, and the rear lens barrel 2 is molded by the mold having this structure.
An image sensor mounting portion 2d having a substantially rectangular opening is formed on the rear wall 2a, and the low pass filter 9A and the image sensor 9 are mounted. As the imaging device 9 to be used, there is, for example, a CCD (Charge-Coupled Device).
Four guide shaft holes 2e for fitting and supporting the above-described four guide shafts are formed on the front surface of the rear wall 2a.

A pilot hole 2f for fastening the drive block 6 with the screw 3 is formed at the upper end of the rear wall 2a.
Two protrusions 2h are formed at the upper end of the right wall 2b to engage with the drive block 6 in order to position it.
Antireflection ribs 2g are formed on the inner surface of the lower wall 2c. This is a plurality of arc-shaped ribs having a ridge line in a direction substantially perpendicular to the optical axis and formed at a predetermined interval in the optical axis direction, and effectively prevents internal reflection of light. As described above, the antireflection rib is formed on the front lens barrel 1 in the same manner.

<About the lens block 5>
Next, the lens block 5 will be described with reference to FIGS.
FIG. 3 is a perspective view of the lens block 5, and FIG. 6 is a view of the block as viewed from below.

This lens block 5 includes a variable magnification lens frame 11 to which a variable magnification lens 10 is fixed, a fixed lens frame 13 to which a fixed master lens 12 is fixed, a focusing lens frame 15 to which a focusing lens 14 is fixed, and these lenses. Four guide shafts 8 inserted into and supported by the guide shaft holes of the frame, and a lead screw 6a of a drive unit 6 fixed to the zoom lens frame 11 and slidable with respect to the guide shaft. And a coil 17 that is fixed to the focusing lens frame 15 and is loosely fitted to a U-shaped yoke 50a of an actuator 50 for sliding the frame with respect to the guide shaft 8. Yes.
Each of the lens frames 11, 13, and 15 is formed by injection molding PC, the guide shaft 8 is formed of SUS material, and the holder portion 16 is formed by injection molding of polyacetal (POM).

The zoom lens frame 11 includes first and second arm portions 11a and 11b extending in the left-right direction. The first arm portion 11a is formed with a U-shaped cutout portion 11a1 that opens downward. The U-shaped cutout portion 11a1 is slidable with respect to the guide shaft 8A so that there is no backlash in the left-right direction. Is fitted.
A reference position detection projection 11e that operates a position sensor 51 (see FIG. 1) arranged to detect a reference position of the variable magnification lens frame 11 in the optical axis direction is provided on the upper surface of the first arm portion 11a. Is formed.
A connecting arm portion 11c that is bent in the rearward direction of the optical axis and is connected and has a length L1 is formed at the distal end portion of the second arm portion 11b. In addition, a through hole 11c1 is formed in the connecting arm portion 11c, and the through hole 11c1 is slidably fitted to the guide shaft 8C without play.
On the upper surface of the second arm portion 11b, a clamping portion 11d having a slit 11d1 for clamping and holding the pin 16a of the holder portion 16 is formed.

The fixed lens frame 13 has first and second arm portions 13a and 13b extending in the left-right direction. The first arm portion 13a is formed with a U-shaped cutout portion 13a1 that opens to the outside. The U-shaped cutout portion 13a1 is slidably fitted to the guide shaft 8A without any vertical play. ing.
A connecting arm portion 13c that is bent in the forward direction of the optical axis and connected to the tip end portion of the second arm portion 13b and having a length L2 is formed. Further, a through hole 13c1 is formed in the connecting arm portion 13c, and the through hole 13c1 is slidably fitted to the guide shaft 8D without play.

The focusing lens frame 15 has first and second arm portions 15a and 15b extending in the left-right direction. The first arm 1 5 a, the through hole 15a1 of larger diameter than the diameter of the shaft 8A is formed, is inserted as the shaft 8A does not contact.
In addition, a connecting arm portion 15c that is bent in the forward direction of the optical axis and is connected and has a length L3 (see FIG. 6) is formed. A through hole 15c1 is formed in the connecting arm portion 15c, and the through hole 15c1 is slidably fitted to the guide shaft 8B without play. Further, the intermediate portion 15c2 of the connecting arm portion 15c is partially cut away from the wall, and the shaft 8B is exposed. Further, a coil 17 is fixed to the connecting arm portion 15c.
On the other hand, the second arm portion 15b is formed with a rectangular hole 15b1 in which the distance between the upper and lower opposing sides is substantially the same as that of the guide shaft, and the guide shaft 8D is slidably fitted in the vertical direction without play. is doing.

The holder portion 16 includes a plate-like base portion 16a erected in the vertical direction and a tongue-like engagement portion 16b erected opposite to the base portion 16a with a predetermined interval.
An inclined portion 16a1 is formed on the inner surface at the front end of the base portion 16a and the engaging portion 16b, which serves as an invitation when a lead screw 16a described later is attached.
Further, the engaging portion 16b has flexibility and can be bent outward.

When the drive unit 6 is mounted from above the lens block 4, the lead screw 6a is inserted between the base portion 16a and the engaging portion 16b.
Since the interval between the base portion 16a and the engaging portion 16b is set to be narrower than that of the lead screw 6a, the engaging portion 16b engages with the screw lead while energizing the lead of the screw, and according to the rotation of the lead screw 6a. And move in the front-rear direction of the optical axis (see FIG. 7).
Thereby, the variable magnification lens frame 11 slides on the guide shafts 8A and 8B in the optical axis direction.
The lead screw 6a is driven by a pulse motor 16c. Since the zoom lens is driven only when zoom operation is necessary, it is preferable to use the pulse motor 16c. In this case, the moving distance of the zoom lens frame is determined using the number of drive pulses. be able to.

As shown in FIGS. 5 and 6, the actuator 50 fixed to the rear lens barrel 2 includes a U-shaped yoke 50a, a magnet 50b attached to the inner surface of the yoke 50a, and the focusing lens frame 15. And a coil 17 that is loosely fitted to one arm of the yoke 50a.
By controlling the value of the current flowing through the coil 17 and its direction, the focusing lens frame 15 integrated with the coil 17 is slid on the guide shafts 8B and 8D at an arbitrary speed in the front-rear direction of the optical axis. Can do.
Since the focusing lens frame 15 is related to a focusing operation that is always used, and the drive source is always energized, it is preferable to use an actuator having the above-described configuration with low power consumption.
Further, in order to determine the moving distance (position) of the focusing lens frame 15, a position magnet 18 magnetized with a predetermined NS pattern is attached to the outside of the first arm 15a, and a magnetic sensor (not shown) is attached to this. The moving distance (position) in the optical axis direction can be determined.

Iris block 4, the iris unit 4 a and drives it and a iris motor 4 b to obtain a predetermined aperture. The iris portion 4 a is disposed between the variable magnification lens 10 and the fixed master lens 12.

<About assembly>
The assembly procedure of the zoom lens having the above-described configuration will be described below with reference to FIG.
The lens block 5 is sandwiched between the front lens barrel 1 and the rear lens barrel 2 so that the guide shaft 8 and the shaft hole 1e of the front lens barrel 1 and the shaft hole 2e of the rear lens barrel 2 are engaged from the front and rear directions. The front lens barrel 1 and the rear lens barrel 2 are fastened and integrated with screws 3a and 3b.
The iris block 4 and the drive block 6 are mounted from above and fastened to the front lens barrel 1 and the rear lens barrel 2 with screws 3c and 3e, respectively, and integrated.
Therefore, this zoom lens is inexpensive because an exclusive member for holding the guide shaft 8 is not required in assembling the lens block 5, and can be assembled simply by moving the front and rear lens barrels 1 and 2 in the optical axis direction. So it can be assembled very easily.

As described above, the fixed lens frame 13 is slidable on the guide shaft 8, but is provided in the front lens barrel 1 when it is sandwiched between the front lens barrel 1 and the rear lens barrel 2 in the assembly process. The fixed lens frame abutting portion 1j and the fixed lens frame abutting portion 2j provided on the rear lens barrel 2 are substantially on the optical axis direction end surface of the protruding portion 13c2 provided at the tip of the connecting arm portion 13c of the fixed lens frame 13, respectively. The position of the fixed lens frame 13 in the optical axis direction is fixed by abutting and sandwiching the protruding portion 13c2 without play (see the broken line arrow in FIG. 2 ).

In the zoom lens having the above-described configuration, the zoom lens frame 11 is independently moved by the drive unit, and the focusing lens frame 15 is independently moved by the actuator 50 in the optical axis direction. FIG. 3 shows the state in which these are farthest (WIDE side), and FIG. 4 shows the state in which they are closest (TELE side).
The guide shafts that support the variable magnification lens frame 11 and the focusing lens frame 15 that are the two moving lens frames are different from each other.
That is, the zoom lens frame 11 is supported by the guide shafts 8A and 8C, and the focusing lens frame 15 is supported by the guide shafts 8B and 8D.
Therefore, even when the two lens frames 11 and 15 are closest, the arm portions and the connecting arm portions do not interfere with each other and can be configured to overlap each other (the connecting arms in FIG. 4). Part 11c and second arm part 15b, and first arm part 11a and articulated arm part 15c).

The shaft that supports the fixed lens frame 13 is supported by guide shafts 8A and 8D that support the second arm portions 11b and 15b that are not the connecting arm portions 11c and 15c of the variable magnification lens frame and the focusing lens frame. is doing.
Accordingly, the lengths L1 and L3 of the connecting arm portions 11c and 15c of the variable magnification lens frame 11 and the focusing lens frame 15 can be made as long as possible on the guide shaft 8, so The focal lens frame 15 can slide with extremely stable accuracy.
Further, since the connecting arm portion 13C of the fixed lens frame 13 having a long axial length is supported by the same guide shaft 8D as the second arm portion 15b of the focusing lens frame 15 having a short axial length, the shaft The length in the optical axis direction of the portion to be fitted can be very short, and the entire length of the zoom lens in the optical axis direction can be shortened.
Further, the connecting arm portion 13c of the fixed lens frame 13 covers the guide shaft 8D in the range of the length L2, and prevents unnecessary reflection of the guide shaft 8D in this range.

  The antireflection ribs 1g and 2g are provided on the inner surface of the upper wall 1c of the front lens barrel 1 and the inner surface of the lower wall 2c of the rear lens barrel 2, and this is not undercut in the mold opening direction. The lens barrels 1 and 2 can be easily formed integrally, and can be freely formed in a desired range on these surfaces.

According to the embodiment detailed above,
(1) Since four shafts are employed and portions where a plurality of lens frames are fitted to these shafts are combined so that they do not interfere with each other even during movement, the overall length of the zoom lens can be made extremely short.
(2) Since the fitting portion can be lengthened by the configuration of (1), the zoom lens frame and the focusing lens frame can be moved stably and accurately. Therefore, high image pickup performance can be exhibited without causing resolution degradation or image shake.
(3) Since the antireflection rib in the lens barrel can be easily formed, it can be provided at an optimum position to prevent internal reflection extremely effectively. Therefore, high-quality imaging with high contrast without flare and ghost can be obtained.

The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.
The front lens 7, the fixed master lens 12, and the focusing lens 14 may be a single lens or a lens group including a plurality of lenses.
Further, the drive unit 6 and the actuator 50 are not limited to the above-described structure, and may be another known drive method.

1 is an external perspective view of an embodiment of a zoom lens according to the present invention. It is an assembly drawing explaining the Example of the zoom lens of this invention. It is a 1st perspective view explaining the principal part in the Example of the zoom lens of this invention. It is a 2nd perspective view explaining the principal part in the Example of the zoom lens of this invention. It is a front view explaining the principal part in the Example of the zoom lens of this invention. It is a bottom view explaining the principal part in the Example of the zoom lens of this invention. It is a side view explaining the principal part in the Example of the zoom lens of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Front lens barrel 1a Front wall 1b Left wall 1c Upper wall 1d Lens frame 1e Shaft hole 1f Lower hole 1g Antireflection rib 1h Projection 1j Lens frame contact part 2 Rear lens barrel 2a Rear wall 2b Right wall 2c Lower wall 2d Image sensor Mounting portion 2e Shaft hole 2g Antireflection rib 2h Protrusion 2j Lens frame abutting portion 3 Screw 4 Iris block 5 Lens block 6 Drive unit 6a Lead screw 7 Front lens 8 (8A to 8D) Guide shaft 9 Imaging element 9A Low pass filter 10 Variable lens 11 Variable lens frame 11a, 11b First and second arm portion 11a1 U-shaped notch portion 11c Articulated arm portion 11e Reference position detection projection 12 Fixed master lens 13 Fixed lens frame 13a, 13b First and second Arm part 13a1 U-shaped notch part 13c Articulating arm part 13c1 Through hole 13c2 Lens frame stopper 14 Focus lens 15 Focus lens Frame 15a, 15b first, second arm portion 15a1 through hole 15b1 square holes 15c connecting arms 16 the holder portion 16a base portion 17 coil 18 position the magnet 50 actuator 50a yoke 50b magnet 51 position sensor 100 zoom lens CL light axis

Claims (2)

In a zoom lens with a variable power lens, a fixed master lens, and a focusing lens,
The lens barrel,
Four shafts arranged parallel to each other along the optical axis inside the lens barrel, arranged in parallel on one side with the zoom lens, fixed master lens, and focusing lens in between First and fourth shafts and second and third shafts arranged in parallel on the other side ;
A first engaging portion that holds the zoom lens and engages the first shaft so that movement in a direction orthogonal to the optical axis is restricted, and the optical axis with respect to the second shaft a zooming lens frame having a second engagement portion, the movement of only a single direction that Jo Tokoro to orthogonal engaged to be acceptable,
A third engagement portion that holds the focusing lens and is engaged with the third shaft so that movement in a direction orthogonal to the optical axis is restricted; and the optical axis with respect to the fourth shaft a focusing lens frame having a fourth engaging portion, the movement of only a single direction that Jo Tokoro to orthogonal engaged to be acceptable,
The fixed master lens holds, comprising a front Symbol fixed lens frame having a fifth engaging portion moving direction is engaged to be restricted to perpendicular to the fourth shaft to said optical axis, a,
The lens barrel is divided in the optical axis direction, and is connected to at least a first wall surface substantially orthogonal to the optical axis and the first wall surface, and extends in the optical axis direction to form an antireflection rib portion. A first lens barrel and a second lens barrel having a second wall surface and at least one surface along the optical axis that is substantially open.
The zoom lens, wherein the first to fourth shafts are supported by the first and second lens barrels from both ends. Wherein the fifth and the first and second lens barrel in the engagement portion of the are is determined the position in the optical axis direction of the fixed lens frame and almost abut each from both directions of the optical axis The zoom lens according to claim 1.

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