JPH0756527B2 - Lens barrel - Google Patents

Description

The present invention relates to a lens barrel of a zoom lens suitable for use in a video camera.

[Conventional technology]

Since the zoom lens is composed of a focusing mechanism, a zooming mechanism, and an image forming mechanism and has a complicated structure, the lens barrel itself tends to be large and heavy. On the other hand, today, as video cameras become smaller and lighter, zoom lenses used therein are also required to be smaller and lighter, and in accordance therewith, simplification of structure and cost reduction are also desired. .

As a measure to meet such demands, weight reduction is achieved by using plastic molded parts for parts that were conventionally metal ground products.
It may be possible to promote integration of a plurality of parts and reduce costs.

Here, first, the structure of a conventional zoom lens will be described.

FIG. 15 is a sectional view showing an example of a conventional zoom lens, wherein 1 is a focus ring, 2 is a fixed barrel, 3 is a front lens holder,
4 is a zoom ring, 5 is a connecting cylinder, 6 is a master cylinder, 7 is a variator frame, 8 is a compensator frame, 9 is a rod, 10 is a cam ring, 11 is a cam follower, 12 is a connecting pin, 13 is a holding plate,
14 is the front lens group, 15 is the variator (magnification) lens group,
16 is a compensator (correction) lens, 17 is a master lens group, 18 is a spacing ring, 19 and 20 are helicoid screws, and 21 is a through groove.

In the figure, the zoom lens is composed of three blocks, namely, a front lens section for focusing, a zoom section for zooming, and a master section for focusing.

The front lens portion mainly includes a front lens group 14, a front lens holder 3 to which the front lens group 14 is attached, and a focus ring 1 to which the front lens holder 3 is attached. The fixed cylinder 2 is fitted inside the focus ring 1, and the helicoid screw 19 provided on the inner surface of the focus ring 1 and the helicoid screw 20 provided on the outer surface of the fixed ring 2 are meshed with each other.

Then, when the focus ring 1 is rotated, the focus ring 1 moves in the optical axis direction with respect to the fixed barrel 2, whereby the front lens group 14 is positionally adjusted in the optical axis direction to perform a focusing operation. Is performed.

The zoom section mainly includes a variator lens group 15, a compensator lens 16, and a variator frame 7, a compensator frame 8, a rod 9, a cam ring 10, a cam follower 11, a fixed cylinder 2, a holding plate 13, and a zoom ring 4 which respectively hold these. And a connecting pin 12.

The variator frame 7 and the compensator frame 8 are slidably mounted on rods 9 mounted between the fixed barrel 2 and the holding plate 13 so as to be parallel to the optical axis.
The holding plate 13 is fixed to the end of the fixed barrel 2. A cam ring 10 having two cam grooves (not shown) having a predetermined spiral shape is rotatably attached to the fixed barrel 22 inside the fixed barrel 2. A cam follower (not shown) provided on the variator frame 7 is fitted to one of the cam grooves, and a cam follower 11 provided on the compensator frame 8 is fitted to the other.

A zoom ring 4 is provided on the outer side of the fixed barrel 2 so as to be rotatable with respect to the fixed barrel 2, and an annular through groove provided in the fixed barrel 2.
The connecting pin 12 passing through the zoom ring 4 and the cam ring 10
And are connected so as to rotate together.

In this structure, when the zoom ring 4 is rotated, the cam ring 10 is also rotated integrally with this. As a result, the positions of the cam follower of the variator frame 7 and the cam follower 11 of the compensator frame 8 with respect to the cam grooves provided in the cam ring 10 change, but since these cam grooves are spiral, the variator frame 7 and the compensator frame The frame 8 moves along the rod 9 (that is, in the optical axis direction). With this, the zoom operation is performed.

The master section is mainly composed of the master cylinder 6 and the master lens group 17
Consists of. The master lens group 17 is composed of 7 to 8 lenses, and these are attached to the master cylinder 6 so that a predetermined distance is maintained by a spacing ring 18. The master cylinder 6 is provided with a flange, by which the master cylinder 6 is combined with the connecting cylinder 5, and the fixed cylinder 2 is also connected to the connecting cylinder 5. The master lens group 17 of the master unit influences the image forming performance of the zoom lens, that is, the resolution performance.

[Problems to be solved by the invention]

In the zoom lens having the structure described above, the focus ring 1, the fixed tube 2, the cam ring 12, and the master ring 6 that form the lens barrel determine the overall size of the zoom lens.
It is a large component when viewed from the entire zoom lens. Conventionally, such parts are metal ground products, but if these parts are plastic molded products, the weight of the zoom lens can be reduced, the processing cost can be reduced, and the cost can be reduced. However, if these are molded into plastics, the following problems occur.

The problems that occur in the front lens section, the zoom section, and the master section will be described below.

First, regarding the front lens portion, conventionally, the focus ring 1 and the fixed cylinder 2 are ground metal, and the precision of the helicoid screws 19 and 20 has been improved by cutting and lapping. The rattling between the helicoid screws 19 and 20 affects the focusing accuracy, and this accuracy must be very high. For this reason, the processing cost of the focus ring 1 and the fixed cylinder 2 is very high.

On the other hand, when the helicoid screw of one component is to be meshed with the other helicoid screw, the other helicoid screw is pressed against the side surface of the one helicoid screw to provide a rattling member that removes rattling between the helicoid screws. Therefore, a technique is known in which these parts are formed into plastic molded bodies (for example, Japanese Utility Model Laid-Open No. 58-102861). However, due to the backlash removing member, these helicoid screws come into line contact with each other, so that the helicoid screws are worn by repeated operations. Also,
The backlash removing member is also in contact with one helicoid screw,
Therefore, the backlash removing member also wears and loses its function. Therefore, there is a problem with their durability.

Also, if the parts are made plastic, the dimensional accuracy of the helicoid screw tends to vary due to the imbalance of shrinkage due to the molding conditions and shape. There is also a problem that the dynamic friction becomes uneven and the operation feeling deteriorates.

As described above, conventionally, plasticizing the focus ring 1 or the fixed ring 2 having the helicoid screw causes a very difficult problem.

Next, a problem that occurs in the zoom unit will be described.

In order to set the variable magnification correctly and to keep the image formation position constant regardless of the variable magnification, the variator lens group 15
It is necessary to set the position of the compensator lens 10 with high accuracy according to the magnification. Such positional accuracy is affected by rattling of the fixed barrel 2 and the cam ring 10 in the optical axis direction, and in order to maintain high accuracy, the amount of rattling must be suppressed to about 10 to 30 μm. Conventionally, this amount of backlash is measured by measuring the dimension of the cam ring containing portion of the fixed barrel 2 and the length of the cam ring 10, and assembling
It was managed by adjusting. For this reason, the assembly cost is high and the parts are expensive.

Therefore, it is conceivable to eliminate the backlash adjusting work at the time of assembling the zoom lens by plastically molding the fixed barrel 2 and the cam ring 10 with a mold, but the cam ring 10 has a cam groove of about 5 to 12 μm. It is necessary to process with high accuracy, and it is impossible to make a plastic molded body. For this reason, a metal such as aluminum must be used as the material of the cam ring 10.

On the other hand, if the fixed barrel 2 is made of plastic, as described above, a problem occurs with respect to the helicoid screw.
Since it is made of aluminum, due to the difference in thermal expansion coefficient between the fixed barrel 2 and the cam ring 10, for example, when the operating temperature range of the zoom lens is −10 ° C. to 50 ° C. A large difference occurs between the dimensional change amount a of the cam ring insertion portion and the dimensional change amount b of the cam ring 10. Now, cam ring
If the total length of 10 is about 30 mm and the amount of play between the fixed cylinder 2 and the cam cylinder 10 is 10 to 30 μm, when the operating temperature changes by 30 ° C,
| a−b | becomes about 40 μm, and the cam ring 10 may not rotate.

From this, too, the fixed cylinder 2 cannot be made plastic.

Next, a problem occurring in the master section will be described.

The maximum allowable lens eccentricity in the master lens group 17
There is a lens that must fit within 30 μm. Therefore,
If the lens outer diameter production error is 10 μm, the inner diameter error of the master cylinder 6 that houses the lens needs to be set to 20 μm. In order to obtain such accuracy, conventionally, the master cylinder 6
Is made of metal shavings, and such accuracy has been an obstacle to making the master cylinder 6 plastic. That is, when the master cylinder 6 is plastically molded, the molding accuracy such as the roundness and the concentricity of the shape accuracy is improved and each lens is accurately held so that the eccentricity of the lens is within 30 μm. It was very difficult.

As an example of lens holding in the lens barrel, for example,
These are disclosed in Japanese Utility Model Laid-Open No. 56-156010 and Japanese Utility Model Laid-Open No. 56-156011, but in both cases, when mounting a plastic lens on a lens barrel, remove the adverse effects caused by the gate and burrs of the plastic lens. However, no consideration is given to the point of holding the lens with high accuracy and without eccentricity, and the point of lens collapse due to surface deviation of the lens receiving portion of the lens barrel on the lens contact surface.

An object of the present invention is to provide a zoom lens which solves the above-mentioned problems of the prior art and ensures the lens holding accuracy and durability when compensating the range lens barrel and compensating for the deterioration of performance. There is.

[Means for solving problems]

In order to achieve this object, according to the present invention, a focus ring and a fixed cylinder are formed by plastic molding, and a helicoid screw provided on the focus cylinder and the fixed cylinder and meshing with each other is provided with a coating film having a low friction coefficient and an abrasion resistance. In addition, the cam ring is pressed against the bottom of the fixed cylinder by the pressing means, the master cylinder is made of plastic molding, and a plurality of protruding stripes are provided on the inner surface of the master cylinder. Hold each lens in the lens group.

[Action]

The wear resistance of the focus ring and the helicoid screw of the fixed barrel is high, and the durability is improved, and the rattling of the helicoid screw can be kept small enough at all times. Even if the degree of expansion and contraction differs, rattling of the cam ring is eliminated, and the concentricity of the lens in the master cylinder is improved.

〔Example〕

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

FIG. 1 is a partial sectional view of an embodiment of a lens barrel according to the present invention, in which 22 is a spacing ring, 23 is a screw, 24 is a compression spring, and 25
Is a zoom gear, 26 is a zoom motor gear, 27 is an iris,
28 is an iris motor, 29 is a zoom motor, 30 is a flange portion, 31 is a screw ring, and the same reference numerals are given to the portions corresponding to FIG.

In FIG. 1, each lens forming the front lens group 14 is attached to the front lens holder 3 by a spacing ring 22 at predetermined intervals. The front lens holder 3 is provided inside the focus ring 1 and is fixed to the focus ring 1 by a screw 23. Further, a helicoid screw 19 is provided on the inner surface of the focus ring 1, and is engaged with a helicoid screw 20 provided on the outer surface of the fixed barrel 2 inserted therein.

The above is the configuration of the front lens portion. With this configuration, when the focus ring 1 is rotated, the helicoid screws 19 and 20 mesh with each other. Then, the position of the front lens group 14 for focusing can be adjusted.

Next, the zoom unit will be described.

The fixed cylinder 2 is fixed to the connecting cylinder 5, has a bottom portion on the connecting cylinder 5 side, and has a holding plate 13 fixed to the end portion on the front lens side. Inside the fixed cylinder 2, a cam ring 1 having a length almost equal to the length thereof is rotatably provided with respect to the fixed cylinder 2, and further, a bottom portion of the fixed cylinder 2 and a holding plate 13 ( Two pairs of rods 9, though each shows only one,
9'is supported parallel to the optical axis. A variator frame 7 equipped with a variator lens group 25 is attached to one pair of rods 9 ', and a compensator frame 8 equipped with a compensator lens 16 is slidably attached to the other pair of rods 9, respectively. The rod 9 is provided with a compression spring 24 between the pressing plate 13 and the compensator frame 8. Although not shown, the cam ring 10 is provided with two spiral cam grooves, and the cam followers 11 set up in the variator frame 7 and the compensator frame 8 are fitted into the respective cam grooves. On the outside of the fixed barrel 2, the zoom ring 4 is rotatably attached to the fixed barrel 2.
The zoom ring 4 and the cam ring 10 are connected by a connecting pin 12 that penetrates through a through groove 21 provided in the fixed barrel 2.

In the above structure, when the zoom ring 4 is rotated, the cam ring 10 connected to the zoom ring 4 is rotated, and the position of the cam follower 11 with respect to the spiral cam groove provided in the cam ring 10 is changed. , The variator frame 7 and the compensator frame 8 move. As a result, the positions of the variator lens group 15 and the compensator lens 16 are adjusted so that the specified zoom magnification can be obtained.

The zoom magnification can be manually set by the user by rotating the zoom ring 4, but can also be automatically set by the zoom motor 29. To this end, the zoom ring 4 is provided with a zoom gear 25, and the zoom motor gear 26 fixed to the rotary shaft of the zoom motor 29 meshes with the zoom gear 25 so that the zoom ring 4 can be rotationally driven by the zoom motor 29. Has been done.

The zoom motor 29 is fixed to the connecting tube 5, and the iris motor 28 for driving the iris 27 provided between the zoom section and the master section is also fixed to the connecting tube 5.

Next, the master section will be described.

The master cylinder 6 has a flange 30 which is screwed to the connecting cylinder 5. Inside the master cylinder 6, each range chamber is provided, and each lens forming the master lens group 17 is attached by the interval ring 18 at a predetermined interval and fastened with a screw ring 31.

The configuration and operation of this embodiment have been described above. However, in this embodiment, there are problems caused by plasticizing the focus ring 1, the fixed barrel 2, the zoom ring 4, the master barrel 6 and the zoom gear 25. Take steps to remove it. As a plastic material for the focus ring 1 and the fixed barrel 2, a glass fiber-containing polycarbonate resin (hereinafter referred to as PC-G) is used from the viewpoint of strength.

By the way, when this PC-G is used, since the glass fiber serves as a wear promoting material, every time the focus ring 1 is rotated,
The helicoid screw 19 provided on the focus ring 1 and the helicoid screw 20 provided on the fixed barrel 2 are worn away, and their durability becomes a problem. For this reason, as shown in FIG. 2, the coating films 32, 33 of, for example, molybdenum disulfide, fluororesin, etc. having a low wear coefficient and excellent wear resistance are formed on the surfaces of the respective helicoid screws 19, 20. Apply. The thickness of these coating films 32 and 33 is about 15 to 20 μm. At this time, a gap 34 is formed between the coating films 32 and 33, and the size of the gap 34 is the amount of backlash between the helicoid screws 19 and 20. To further increase durability, grease is provided in the gap 34 between the coating films 32 and 33.

FIG. 3 shows the manufacturing process of the focus ring 1 and the fixed cylinder 2, especially the helicoid screws 19 and 20, and these are first molded by a mold (step A), but in this molded state , Molding conditions, shape effect of molded products, etc.
The shape accuracy of the helicoid screws 19 and 20 is low, and there are variations in dimensions.If they remain as they are, there will be a feeling of strangeness due to torque fluctuations when operating the zoom lens.
It is not durable and cannot be used. For this purpose, the co-sliding lap is performed to improve the shape accuracy and remove the dimensional variation and the like (step B). Then, after removing the lap material by washing (step C), the surfaces of the helicoid screws 19 and 20 are coated as shown in FIG.

The above is the front lens section, but next, the zoom section will be described.

In FIG. 1, the plastic material of the fixed barrel 2 is PC-G or the like as described above, but the material of the cam ring 10 is the one of the cam groove as described in the above-mentioned engaging technology. A metal such as aluminum is used because high precision is required. In this case, one problem is that the cam ring 10 cannot rotate due to the difference in expansion coefficient between the fixed barrel 2 and the cam ring 10. In order to prevent this, the play amount between the fixed cylinder 2 and the cam ring 10 does not disappear within the operating temperature range. For example, the material of the fixed cylinder 2 is PC-G, the material of the cam ring 10 is aluminum,
When the operating temperature range is −10 to 50 ° C., the play amount δ of the cam ring 10 is 40 to 70 μm at the center temperature of 20 ° C. and the play amount δ of the cam ring 10 is δ for the maximum temperature change of 30 ° C. Change of ±
Each dimension was set to be 30 μm. According to this, even if the temperature changes from -10 ℃ to 50 ℃, the cam ring 10
The minimum value of the backlash amount δ is +10 μm, and the cam ring 10 does not become unrotatable.

Another problem is that when the cam ring 10 rattles as described above, rattling in the optical axis direction occurs in the variator lens group 15 and the compensator lens 16, and in particular, this rattling of the compensator lens 16 causes defocusing. Optical performance is deteriorated.

In order to solve this problem, a compression spring 24 is provided between the pressing plate 18 of the rod 9 and the compensator frame 8.

That is, in FIG. 4, one end of the rod 9 is the fixed cylinder 2
Is inserted into a hole 37 provided at the bottom of the base plate, and the other end is fixed to the holding plate 13 with a screw 36 through a rod hole 35. The compensator frame 8 is slidably attached to the rod 9, and a coiled compression spring 24 is provided between the holding plate 13 and the compensator frame 8 so as to wind the rod 9. . The compensator frame 8 is urged by the compression spring 24 toward the bottom side of the fixed barrel 2 (in the direction of arrow A), and along with this, the cam followers 11 (FIG. 1) of the compensator frame B and the variator frame 7, respectively. Since it is fitted in the cam groove of the cam ring 10, the cam ring 10 and the variator frame 7 are also urged in the same arrow A direction. This compression spring 24
Even if the backlash amount δ of the cam ring 10 changes due to the expansion and contraction of the fixed cylinder 2 and the cam ring 10 due to the temperature change due to the urging force of the cam ring 10,
The 10 is pressed against the bottom surface of the fixed barrel 2 so that the cam ring 10 does not rattle. In this case, the zoom lens may be used in a downward direction, and in consideration of this, the biasing force of the compression spring 24 is adjusted so that the compensator frame 8, the compensator lens 16, the cam ring 10, the variator frame 7 and the variator lens group 15 are self-weighted. Set larger than the sum of. For example, when the total of the own weight is about 25 gr, the biasing force of the compression spring 24 is set to about 5 gr larger than this. Therefore, even if the zoom lens takes any posture, the cam ring 10
Is pressed against the bottom of the fixed barrel 2, which allows the cam ring to
The defocus 10 does not rattle, and the compensator lens 16 has no rattling, so that defocusing does not occur.

The material of the compression spring 24 is black metal (MFZn II
-Bk) is easy to apply (for example, C5191W-H),
By applying black plating to the compression spring 24, it is possible to prevent light from being reflected and prevent deterioration of image quality.

Further, the pressing plate 13 has a substantially annular shape, and is shown in FIG.
As shown in Fig.9, rod hole 35, for attaching 9,9 '
35 'are provided with protrusions and notch grooves 38 for positioning, respectively. Further, as shown in FIG. 5 (b), the notch groove is provided at the mounting portion of the holding plate 13 of the fixed cylinder 2. A protrusion 39 is provided so that the 38 can be fitted therein. Therefore, when the pressing plate 13 is attached to the fixed barrel 2, the notch groove 38 is fitted into the protrusion 39, so that the rods 9 and 9'can be prevented from being twisted around the optical axis.

Returning to FIG. 1, as described above, in order to automatically enable zooming, the zoom ring 25 is provided with the zoom gear 25, and the zoom motor gear 26 fixed to the rotary shaft of the zoom motor 29 is provided on the zoom gear 25. However, when the user rotates the zoom ring 4 during manual zooming, the reduction ratio of the reduction mechanism of the zoom motor 29 is large, so the zoom gear 25 meshed with the zoom motor gear 26 does not rotate. This is difficult and requires a great deal of force to rotate the zoom ring 4. For this reason, a predetermined coefficient of friction is provided between the zoom ring 4 and the zoom gear 25, and in the case of automatic zooming, the zoom ring 4 is rotated together with the zoom gear 25 by frictional force, and in the case of manual zooming. In the
The zoom gear 25 slides with respect to the zoom ring 4, and the zoom ring 4 rotates so that the zoom gear 25 is stopped.

As described above, the zoom gear 25 also has a clutch function. However, when the zoom ring 4 and the zoom gear 25 are made plastic, both of them wear due to friction, and the clutch function is impaired and automatic zooming cannot be performed.

Therefore, in this embodiment, as shown in detail in FIG.
A groove 40 is provided on the inner surface of the zoom gear 25 so as to extend around the circumference thereof.
Store the slip spring 41 in this groove 40, and
41 is a clutch mechanism for tightening the zoom ring 4. 7th
As shown in the figure, a stopper 42 is provided in the groove 40, and a polygonal slip spring 41 has its end abutted against the stopper 42 so as not to rotate in the groove 40. The zoom ring 4 is tightened by the slip spring 41.

In the case of automatic zooming, the slip spring 41 also rotates with the rotation of the zoom gear 25, and the tightening of the slip spring 41 causes friction between the slip spring 41 and the zoom ring 4 to rotate the zoom ring 4. On the other hand, in the case of manual zooming, even if the zoom ring 4 is rotated, a slip occurs between the zoom ring 4 and the slip spring 41, and the zoom gear 25 does not rotate. Thereby, the zoom ring 4 can be rotated with a slight turning force.

As the plastic material of the zoom gear 25, since the shape thereof is a thin annular shape with respect to the diameter, a material having a small shrinkage after molding is used. As an example thereof, there is a material in which 10% of fluorine resin powder is added to polycarbonate resin. Using this material, the clearance between the inner diameter of the zoom gear 25 and the outer diameter of the zoom ring 4 to which it is attached is set to 60 μm, and the clutch mechanism is placed in an atmosphere of 80 ° C.
After leaving for 10 hours, the temperature was returned to room temperature and the clearance was measured. The clearance amount decreased by 36 μm due to the post-shrinkage of the zoom gear 25, but no inconvenience occurred in the operation of the clutch mechanism. On the other hand, when the material of the zoom gear 25 is commonly used polyacetal resin and the clearance after post-contraction is measured under the same conditions as above, the reduction amount of the clearance is 92 μm, which is larger than the previously set clearance amount of 60 μm. However, the zoom ring 4 was integrated with the zoom ring 4 and manual zooming was disabled. Therefore, the polyacetal resin is unsuitable as a material for the zoom gear 25.

Next, a means for ensuring the lens holding accuracy in the master unit in FIG. 1 will be described.

In the figure, the master cylinder 6 needs a flange portion 30 for attaching the master lens group 17 to the connecting cylinder 5 in addition to the means for holding the master lens group 17. On the other hand, the iris motor 27 and the zoom motor 29 are also attached to the connecting tube 5, and if the area of these member mounting portions of the connecting tube 5 is increased, the zoom lens becomes large, and as shown in FIG. In addition, the notch portion 43 is provided in the flange portion 30, and in this portion,
I was able to install the iris motor 27 and the zoom motor 29. However, due to the mounting structure of these motors, the notch portion 43 needs to be formed over 1/4 to 1/3 of the flange portion 30.

As a result, in the process of cooling and solidifying after forming the master cylinder 6, the wall of the lens-entry portion (the portion in which the lens is housed) of the master cylinder 6 is pulled in the central axis direction of the master cylinder 6 to be an inner surface. The wall where the notch 43 without the flange portion 30 is located in the plane including the flange portion 30 which is perpendicular to the central axis of the master cylinder 6 although unevenness is shown is exaggerated in FIG. It is pulled more in the central axis direction of the master cylinder 6 than in other portions, and a part of the lens-entry portion becomes a concave shape, and the roundness is greatly impaired.

In this way, the lens is inserted into the master cylinder 6 in which the lens-entry portion is dented.
If you take in 44, in this dent direction (arrow A direction),
The axial deviation of each lens can be kept within an allowable range, but it may not be allowed in the direction orthogonal to this (direction of arrow B).

For this reason, in this embodiment, as shown in FIG. 10, the flange portion is equally divided into three parts, and these flange portions 30a, 30b,
30c are arranged equiangularly and cutouts 43a, 43b, 43c of equal size are provided between them. And these notches 43
The iris motor 27 and the zoom motor 29 are arranged on any of a, 43b, and 43c. As a result, the wall indentation of the master cylinder 6 in the plane including the flange portions 30a to 30c perpendicular to the central axis of the master cylinder 6 is shown in FIG.
This dent 45a-45 occurs at equiangular intervals, as shown by 45c.
The lens 44 will be held inside the circle 46 inscribed in c. Therefore, the optical axis of the lens 44 housed in this portion almost coincides with the central axis of the master cylinder 6, and the lens holding accuracy can be secured.

The above is the case where the flange portion 30 is divided into three,
Even in the case of dividing into four or more pieces, if the divided flange portions are made equal in size and arranged at equal angular intervals, it is possible to prevent the axial misalignment of the lens.

Next, the lens-entry portion of the master cylinder 6 that is deeper than the portion where the flange portion 30 is provided will be described.

In FIG. 12, the lens-entry portion (inside) of the master cylinder 6
Comprises a plurality of lens chambers having different diameters depending on the diameter of the lens to be housed, and the master cylinder 6 is provided on the wall surface of each lens chamber.
A plurality of protruding streaks 47 are provided at equal angular intervals around the central axis parallel to the central axis.

13 is a transverse sectional view taken along the line CC of FIG.
Here, it is assumed that three protruding stripes 47a, 47b, 47c are provided. In this case, as explained above,
Even if unevenness occurs on the inner wall 48 of the master cylinder 6 due to molding,
As shown in FIG. 13, the inner wall 48 of the master cylinder 6 is prevented from projecting inside the inscribed circle 46 'inscribed in the protruding stripes 47a to 47c.

The height of these protruding stripes 47a to 47c can be determined as follows.

First, the master cylinder 6 having no protruding stripes on the inner wall is formed by molding, and the roundness and the dimensional variation of the wall surface of each lens chamber are measured. Next, the height of the protruding streak is obtained based on the measurement data, and the wall surface of the full core is cut into a streak for each lens chamber so that the protruding streak is formed. As an example, the width of the protruding stripes is 0.5 to 1 mm and the height is 20 to 80 μm. At this time, in FIG. 13, the difference between the diameter of the circle 46 'inscribed in the protruding stripes 47a to 47c and the outer diameter dimension of the lens 44 to be housed is adjusted so that the axial misalignment of the lens 44 does not cause a problem. 30 ~
It was set to about 40 μm. In contrast, the protruding stripes 47a-4
The diameter of the inscribed circle 46 'of 7c is equal to or smaller than the outer diameter of the lens 44 by about 20 μm, and when the lens 44 is incorporated into the lens chamber, the lens 44 is crushed by crushing the projecting stripes 47a to 47c.
May be inserted, whereby the lens holding accuracy can be ensured.

As shown in FIG. 12, in the master cylinder 6, the lens having the smallest outer diameter is stored in the innermost part of the lens-containing portion, and the closer to the portion where the flange portion 30 is provided, The outer diameter becomes large. For this reason, the diameter of the lens chamber increases as it approaches the portion where the flange portion 30 is provided.
Therefore, at the boundary of the lens chamber, there is a stepped portion on the inner surface of the master cylinder 6, but the surface of this stepped portion serves as the lens receiving surface with which the surface of the accommodated lens abuts.

By the way, this lens receiving surface must be perpendicular to the central axis of the master cylinder 6. Otherwise, that is, if the lens receiving surface has a surface deviation, the optical axis of the housed lens inclines with respect to the central axis of the master cylinder 6, and thus the optical axis of each housed lens. Since they do not match, an accurate image cannot be obtained.

Therefore, in this embodiment, as shown in FIG. 14, a plurality of pedestals 49 are provided on the annular lens receiving surface 50 at equiangular intervals, and the plane including all the surfaces of these pedestals 49 is the center of the master cylinder 6. Try to be perpendicular to the axis. The pedestal 49 can be formed by the same method as that used for forming the protruding stripes 47a to 47c described above. In this case, even if the lens receiving surface 50 is a little
Be careful not to project from the surface of 49 to the lens chamber 51 side. The contact surface 44 'of the lens 44 with respect to the pedestal 49 is flat.

In this way, the collapse of the storage lens can be prevented.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent wear due to plasticization of each cylindrical member and rattling between the members due to temperature change, and also sufficiently secure the lens holding accuracy. It is possible to realize a great plasticization while maintaining a good optical performance and a long life, and it is possible to promote a great reduction in weight and cost.

[Brief description of drawings]

1 is a partial vertical sectional view showing an embodiment of a lens barrel according to the present invention, FIG. 2 is an enlarged sectional view showing a helicoid screw engaging portion between a focus ring and a fixed barrel in FIG. 1, and FIG. Fig. 4 is a process diagram showing a specific example of a method for manufacturing the helicoid screw portion, Fig. 4 is a sectional view showing a means for removing rattling of the cam ring in Fig. 1, and Fig. 5 (a) is a presser foot in Fig. 1. FIG. 7 (b) is a sectional view showing the clamp mechanism of the zoom section in FIG. 1, FIG. 7 (b) is a sectional view showing the holding plate mounting portion of the fixed barrel in FIG. Is a cross-sectional view showing a slip spring mounting state in the clutch mechanism, FIG. 8 is an explanatory view showing a shape of a conventional flange portion for attaching the master cylinder to the connecting cylinder, and FIG. 9 is a lens cylinder of the master cylinder due to the flange portion. Explanatory drawing showing the change in roundness of part, 1st FIG. 0 is a plan view showing a specific example of the flange part of the master cylinder in FIG. 1, FIG. 11 is an explanatory view showing the roundness of the lens-inserted part of the master cylinder by the flange, and FIG. 12 is FIG. Partial vertical cross-sectional view of the master part in
FIG. 13 is a cross-sectional view taken along the line CC of FIG.
FIG. 14 is a partially enlarged view showing the lens receiving surface in FIG. 12,
FIG. 15 is a vertical sectional view showing an example of a conventional lens barrel. 1 ... Focus ring, 2 ... Fixed tube, 4 ... Zoom ring,
6 ... Master tube, 7 ... Variator frame, 8 ... Compensator frame, 9,9 '... Rod, 10 ... Cam ring, 11 ... Cam follower, 12 ... Connecting pin, 13 ... Holding plate, 14 ... … Front lens group, 15 …… Variator lens group, 16 …… Compensator lens, 17 …… Master lens group, 19,20 …… Helicoid screw, 24 …… Compression spring, 30,30a, 30b, 30c …… Flange Part, 22,33 …… coating film, 34 …… gap, 43,43
a, 43b, 43c ...... notch, 47, 47a, 47b, 47c ...... protruding stripes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironobu Sato, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Home Appliances Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-60-243614 (JP, A) JP 52-16225 (JP, A) JP 61-5217 (JP, A) Actually opened 53-60824 (JP, U) Actually opened 57-167408 (JP, U)

Claims (1)

[Claims] 1. A focus ring to which a front lens group is attached is attached to a fixed barrel fixed to a connecting barrel via a helicoid screw so that the focus ring is movable in the optical axis direction with respect to the fixed barrel. By rotating the front lens part that performs the focusing action and the cam ring provided inside the fixed barrel, the variator lens group and the compensator lens can be moved along a rod parallel to the optical axis to perform a zooming action. In the zoom lens, the focus ring and the fixed barrel are composed of a master unit and a master unit in which a master lens group including a large number of lenses is mounted in a master barrel having a flange fixed to the connecting barrel to form an image. As a plastic molded body, a coating film having a low friction coefficient and wear resistance is provided on the surface of the helicoid screw formed on the focus ring and the fixed barrel. A pressing spring for pressing the variator lens to the bottom side of the fixed barrel is attached to the rod, and the cam ring is pressed by the pressing spring to the bottom of the fixed barrel via the variator lens, and the master barrel is plastic. As a molded body, the master cylinder has a plurality of flange portions of the same shape and at equal intervals, and these flange portions are fixed to the connecting cylinder, and the inner surface of the master cylinder has the same number of optical axes as the flange portions. Parallel protrusions are provided at equal intervals, and these protrusions serve as holding means for each lens of the master lens group, and an iris motor, a zoom motor, etc. are arranged between the flange portions on the connecting tube. A lens barrel characterized by being a part or all of the space to be filled.