JPH0687091B2 - Lens holding device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens holding device used for a photographing lens of a video camera.

(Prior Art) With the widespread use of video cameras in recent years, demand for taking lenses has increased rapidly, and demands for smaller size, lighter weight, and lower prices have become stronger. Also in the lens holding device, it has been attempted to improve productivity and adjustment accuracy by simplifying the lens barrel structure for fixing the lens group and facilitating optical adjustment.

A conventional lens holding device of this type will be described with reference to FIGS. 3 and 4.

FIG. 3 is a cross-sectional view showing a part of a conventional lens holding device by cutting it out, and is used for fixing a master lens group for back focus adjustment used in a zoom lens.

A female screw formed on the rear end of the lens barrel 1 by sequentially loading three lenses 5, 6 and 7 whose intervals are regulated by three annular spacers 2, 3 and 4 inside the lens barrel 1. An annular cap screw 8 is fitted to and is tightened to fix the above-mentioned lenses 5, 6 and 7. The above-mentioned lens barrel 1 is formed with an annular guide portion 1a at the front and rear and a circumferential groove 1b for position adjustment at substantially the center.

Such a lens barrel 1 has an outer frame 9 having a guide collar on the outer periphery of the rear portion.
After being roughly slidably fitted to the inner periphery of the guide portion 1a by using the guide portion 1a, and the circumferential groove 1b is brought to the position of the adjusting circular hole 9a provided in the outer frame 9, The frame 9 is fixed by a fixing small screw 10 arranged so as to face the center thereof.

The back focus adjustment of the lens holding device thus configured will be described.

First, the fixing small screw 10 is loosened so that the lens barrel 1 can freely slide in the outer frame 9. Next, as shown in FIG. 4, the adjusting rod 11 having the eccentric pin 11a formed at its tip is inserted into the adjusting circular hole 9a of the outer frame 9, and the eccentric pin 11a is inserted into the adjusting circumferential groove 1 of the lens barrel 1.
engage b. When the adjusting rod 11 is rotated in this state, the eccentric pin 11a moves the lens barrel 1 back and forth with respect to the outer frame 9 through the adjusting circumferential groove 1b. Tighten the fixing small screw 10 at the position where the back focus is adjusted to fix it.

After adjusting the back focus, the adjusting rod 11 is removed from the adjusting round hole 9a.

(Problems to be Solved by the Invention) However, in the above configuration, when the back focus is adjusted, the lens barrel 1 relative to the rotation angle of the adjustment rod 11 and the outer frame 9 is adjusted.
There is a problem in that the amount of movement is a sine curve as shown in the relationship diagram between the two shown in FIG. 5, and is not in a direct proportional relationship. In FIG. 5, the horizontal axis represents the rotation angle of the adjusting rod 11, and the vertical axis represents the amount of movement of the lens barrel 1. Therefore, the eccentric pin 11
There was a problem that the amount of movement was not constant depending on the position of a, and fine adjustment was difficult. Further, if the fixing small screw 10 is tightened at the time when the adjustment is finished, the lens barrel 1 may slightly move, which causes a problem that the adjustment error is large.
Also, as the adjusting rod 11 is rotated in one direction, it reverses from the middle and the rotation direction and movement direction are reversed, so the eccentric pin
Depending on the engagement position of 11a, the rotation direction of the adjusting rod 11 and the lens barrel 1
There was a problem that the workability was not good because the moving direction of was not constant.

Furthermore, since a plurality of lenses 5, 6 and 7 are inserted into the lens barrel 1 in an overlapping manner with the spacers 2, 3 and 4, respectively, it is difficult to align the optical axes and there is a problem that the number of assembling steps is large. It was

The present invention solves the above problems, and provides a lens holding device which is excellent in workability, has a significantly reduced number of assembling steps, is easy to adjust the back focus, and has high accuracy.

(Means for Solving Problems) In order to solve the above problems, according to the present invention, a plurality of holding grooves for fixing a plurality of lenses respectively are formed on the inner circumference and an even number of male threads are formed on the outer circumference. Then, a split lens barrel divided into two in a plane including the optical axis, a coupling means for fixing the split lens barrel in a state of facing each other, a gear positioned on the outer peripheral portion of the split lens barrel, the above An outer frame having an adjusting window in which an even number of female threads fitted to the male thread and a guide portion for slidably holding the lens barrel are formed on the inner circumference, and a part of the circumference of the gear is exposed. A lens holding device is constituted by the spring means for urging the above-mentioned split lens barrel in the optical axis direction with respect to the outer frame.

(Operation) According to the above configuration, the gear of the lens barrel fitted into the outer frame is driven by rotating the adjustment shaft having the small gear that meshes with the gear, and the rotation of the even-numbered threads causes the mirror to move against the outer frame. Since the rotation angle of the adjustment rod and the amount of movement of the lens barrel are not directly proportional to move the barrel in the optical axis direction, the direction is always constant,
The workability is good, and the optimum position of the back focus can be found very easily. Further, since the male and female screws are in contact with each other due to the urging force of the spring device, they are fixed as they are at the adjustment position, so there is no slight movement of the lens barrel after adjustment, and the adjustment accuracy is improved.

Further, since the moving screw formed on the outer periphery of the two-divided lens barrel is an even number thread, it can be formed with the same mold, so that the precision is good and the cost is low. Further, since the lenses can be individually inserted from the direction perpendicular to the optical axis, the assembling becomes easy and the number of assembling steps can be significantly reduced.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a cross-sectional view showing a lens holding device according to the present invention with a part cut away, showing a plane including the optical axis 12 and perpendicular to the plane of the drawing.
The split lens barrels 13 and 14 of the same shape, which are split and made of a synthetic resin material, have five lenses 15, 16, 17, 18 on the inner peripheral surface.
Lens holding grooves 20,21,22,2 in which and 19 are fixed respectively
3 and 24 are fitted on the front and back on the outer peripheral surface Cylindrical surfaces 25 and 2
6. Two male threads 27 and spur gear 28 are formed in the central portion. Since the lens holding grooves 20, 21, 22, 23, and 24 have the same configuration, the lens holding groove denoted by the reference numeral 20 will be described as a representative. Cylindrical surface 20 with its central axis aligned with the optical axis 12
a, the body-attached surface 20b that provides a right angle with the optical axis 12, and the body-attached surface 20
It is composed of an elastic piece 20c for bringing the lens 15 into close contact with b.

To assemble the lens barrel, use the lens holding grooves 20, 2 of the split lens barrel 13 on one side.
1, 22, 23 and 24, after sequentially inserting lenses 15, 16, 17, 18, and 19 from the radial direction, cover the remaining split lens barrel 14,
When the adhesive tape 29 is wound around the outer circumference and fixed, the thread of the two-thread male screw 27 formed on the outer circumference of each of the split lens barrels 13 and 14 (the two-thread male screw of the split lens barrel 14 is not drawn) is connected. Will be one double-threaded male screw.

The outer frame 30 having a guide flange on the outer periphery of the rear end that accommodates the split lens barrels 13 and 14 to which the above lens groups are fixed is fitted with the fitting cylindrical surfaces 25 and 26 of the split lens barrels 13 and 14 on the inner peripheral surface, respectively. The guide portions 31 and 32 that mate with each other, the double-threaded female thread 33 into which the double-threaded male thread 27 is fitted, and the adjustment square hole 34 through which the spur gear 28 is exposed are formed in the substantially central portion.

In addition, the front guide portion 31 of the outer frame 30 and the split lens barrels 13 and 14
A corrugated spring washer 35 is inserted between the opposing surfaces of the spur gear 28 of the above, and the split lens barrels 13 and 14 are biased rearward in parallel with the optical axis 12 and the two-thread male screw 27 and the two-thread female screw 33. It is pressed so that it always comes into close contact with pressure.

The operation of the lens holding device configured as described above at the time of adjusting the back focus will be described.

In the adjustment square hole 34 of the outer frame 30, the spur gears of the split lens barrels 13 and 14 are provided.
When an adjusting jig (not shown) having a small gear that meshes with 28 is attached and the spur gear 28 is driven, the split lens barrels 13 and 14 rotate with respect to the outer frame 30, and two threaded male and female threads 33 are fitted. By the functions of and 27, the split lens barrels 13 and 14 move in the direction of the optical axis 12 with respect to the outer frame 30, and the back focus is adjusted.

FIG. 2 is a relationship diagram in which the horizontal axis represents the rotation angle of the adjustment shaft (not shown) and the vertical axis represents the amount of movement of the lens barrel in the optical axis direction, and both are in direct proportion. Moreover, since the rotation direction and the movement direction are always constant, workability is good.

Furthermore, since the wave spring washer 35 exerts an urging force in the optical axis direction and a frictional force is constantly exerted between the two-thread male and female threads 33 and 27, the position remains as it is when the adjustment jig is removed. Is fixed and does not move due to vibration during use of the camera.

In this embodiment, the male and female screws 33 and 27 are two threads, but if the threads are even, such as four threads and six threads, the threads are continuous at the time of assembly, so the split lens barrels 13 and 14 have the same mold. It can be molded.

(Effects of the Invention) As described above, according to the present invention, the amount of movement of the lens barrel in the optical axis direction is directly proportional to the rotation angle of the adjustment axis and the direction is constant during back focus adjustment. Workability is good and adjustment is easy. Further, since it is not necessary to fix the lens barrel with the fixing small screw after the adjustment is completed, the adjustment accuracy is improved.

Further, since the split lens barrel can be molded with the same mold by using even-numbered threads, there is no inclination caused by the dimensional difference between the set of split lens barrels, and the deterioration of optical performance is small. Furthermore, since the lens can be inserted from the radial direction, the assembling is easy and the number of assembling steps is significantly reduced.

Therefore, it is possible to obtain an inexpensive lens holding device having an excellent optical property and having a small number of assembling steps.

[Brief description of drawings]

FIG. 1 is a sectional view of a lens holding device according to the present invention, FIG. 2 is a relationship diagram of a rotation angle of an adjusting shaft and a lens barrel moving amount at the time of back focus adjustment of the present invention, and FIG. 3 is a conventional lens holding device. FIG. 4 is a cross-sectional view, FIG. 4 is a perspective view of the adjustment rod, and FIG. 5 is a relationship diagram between the rotation angle of the adjustment rod and the lens barrel movement amount during the conventional back focus adjustment. 1 ... Lens barrel, 1a, 31, 32 ... Guide part, 1b ... Circumferential groove for adjustment, 2, 3, 4 ... Spacer, 5,6,7,15,16,17,18,19 ... … Lens, 8 …… Pressing screw, 9,30 …… Outer frame, 9a …… Round hole for adjustment, 10 …… Screw for fixing, 11 …… Adjusting rod, 11a …… Eccentric pin, 12 …… Optical axis , 13,14 …… Split barrel, 20,21,22,23,2
4 …… Lens holding groove, 20a …… Cylinder surface, 20b …… Body mounting surface, 2
0c …… Elastic piece, 25,26 …… Mating cylindrical surface, 27 …… Double male thread, 28 …… Spur gear, 29 …… Adhesive tape, 33 …… Double female thread, 34 …… Adjusting square hole, 35 …… Wavy spring washer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-187808 (JP, A) Actual development: S.A. 51-92137 (JP, U) JP-B 5-74050 (JP, B2)

Claims (1)

[Claims] 1. A split lens barrel having a plurality of holding grooves for fixing a plurality of lenses respectively on the inner circumference and an even number of male threads formed on the outer circumference, and divided into two parts in a plane including the optical axis. The connecting means for fixing the split lens barrels in a state of facing each other, the gear located on the outer peripheral portion of the split lens barrel, the even-numbered female screws fitted to the male screws and the lens barrel are slidable. An outer frame having a guide part for holding is formed on the inner periphery and an adjusting window exposing a part of the circumference of the gear, and the split lens barrel are urged in the optical axis direction with respect to the outer frame. A lens holding device comprising: