JP2003121719A - Lens barrel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens barrel capable of preventing harmful light from entering an image forming surface with simple constitution without providing a new member such as a light shielding plate. SOLUTION: This lens barrel is equipped with a 1st lens holding frame having a lens holding part, a cylinder part where a projecting cam is formed on its inside diameter and a flange part connecting the cylinder part and the lens holding part and arranged on a subject direction side, and a second lens holding frame having a cam follower engaged with the projecting cam formed on the inside diameter of the cylinder part and arranged on the image forming surface side. A notched hole is provided to have the same phase as the rotating phase of the projecting cam at the flange part of the first lens holding frame, and is covered by a photographing function means where the notched hole is arranged on the subject direction side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens barrel, and more particularly to a structure for preventing harmful light from entering a lens barrel used for a photographic lens or a video lens, which causes a ghost image.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional four-group zoom lens barrel. In the figure, reference numeral 51 is a first lens group, and 52 is a lens holding frame A for holding the first lens group, which is manually operated or driven by a motor through a known mechanical connection mechanism (cam connection, helicoid connection, etc.). It is driven in the optical axis α direction. 53 is a second lens group, 54
Is a lens holding frame B that holds the lens group, and is driven in the optical axis α direction by a manual operation or a motor drive through a known mechanical connection mechanism (cam connection, helicoid connection, etc.). Reference numeral 55 is a third lens group, 56 is a lens holding frame C for holding the third lens group, and the lens holding unit 5
6a and the cam follower 56b are integrally molded. 57
Is a fourth lens group, 58 is a lens holding frame D for holding the fourth lens group, and the lens holding portion 58a and the cylindrical portion 58b.
A convex cam 58c that engages with the cam follower 56b and a flange portion 58d that connects the lens holding portion 58a and the cylindrical portion 58b are integrally formed on the inner diameter of the cylindrical portion 58b. A diaphragm unit 59 is fixed to the lens holding frame C56 by a known method such as screwing.
It should be noted that the left direction in FIG. 3 is set as the subject direction and the right direction is set as the image forming plane direction.

Next, a mold configuration for molding the lens holding frame D58 will be described with reference to FIG. 4A is a plan view of the lens holding frame D58 as viewed from the lens subject side, and FIG. 4B is a cross-sectional view of the lens holding frame D58.
In the figure, 60 is a mold A and 61 is a mold B.
Injection molding is performed by matching the mold 60 with the mold B61 in the optical axis direction (this mold is a so-called general mold structure without front and rear punches). By the way, regarding the method of molding the convex cam 58c provided on the inner diameter of the cylindrical portion 58b of the lens holding frame D58, the convex cam 58c is formed by a mold A60.
Make one end face of the one side, and from the mold B61 to the flange part 58d
The convex cam 58c can be manufactured by inserting a part 61a of the mold B61 so as to penetrate through. That is, FIG.
As shown in (a), when there are three convex cams 58c, the state where the three notched holes 58e are opened in the flange surface 58d is the component completed state.

A zoom lens barrel having a four-group structure using the lens holding frame D58 having this structure is shown in FIG. In FIG. 3, as described above, in the lens holding frame D58, the cam follower 56b of the lens holding frame C56 engages with the convex cam 58c provided on the inner diameter of the cylindrical portion 58b, whereby the lens holding frame C56 and the lens holding frame D58. By the relative rotation of, the distance between the third lens group 55 and the fourth lens group 57 in the optical axis direction is changed to perform zoom driving.

[0005]

However, in the above-mentioned conventional example, when the harmful light A, B enters from the object direction side, it passes through the first group lens group 51, the second group lens group 53, and the third group lens group 55. Harmful lights A and B are lens holding frame D58
By reflecting the inner surface of the cylindrical portion 58b of the
A ghost image is generated by passing through e and reaching an image forming surface (not shown), or scattered light due to reflection on the inner surface of the cylindrical portion 58b reaches the image forming surface (not shown) to cause flare. There was a problem that the contrast deteriorates.
Therefore, a method of eliminating the cutout hole 58e by molding the convex cam 58c of the lens holding frame D58 with an inner diameter slide mold is conceivable, but the inner diameter slide mold configuration is complicated and the die cost is very high. There is a problem in that it is disadvantageous.

In view of the above, the present invention solves the above-mentioned problems, and a lens barrel capable of preventing harmful light from entering the image forming surface with a simple structure without providing a new member such as a light shielding plate. It is intended to provide.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a lens barrel constructed as described in (1) to (6) below. (1) A lens holding portion, a cylindrical portion having a convex cam formed on its inner diameter, a flange portion connecting the cylindrical portion and the lens holding portion, and a first lens holding frame arranged on the object direction side, A lens barrel having a second lens holding frame arranged on the image plane side and having a cam follower engaged with a convex cam formed on the inner diameter of the cylindrical portion, wherein the flange of the first lens holding frame is provided. The lens barrel is characterized in that a cutout hole is provided in the same phase as the rotational phase of the convex cam, and the cutout hole is closed by a photographing function means arranged on the object direction side. . (2) The second lens holding frame has a configuration in which a cam follower that engages with the convex cam and a lens holding portion are integrally formed with respect to a cylindrical portion that constitutes the second lens holding frame. The lens barrel described in (1) above. (3) The lens barrel according to (1) or (2), wherein the photographing function means is fixedly held by the first lens holding frame. (4) The photographing function means is arranged so as to radially overlap the cutout hole position of the first lens holding frame in the above-mentioned (1) to (3).
The lens barrel according to any one of 1. (5) The lens barrel according to (4), wherein the photographing function means arranged so as to overlap in the radial direction is an aperture unit. (6) The cutout hole provided in the flange portion of the first lens holding frame is a mold insertion hole for molding the convex cam of the cylindrical portion of the first lens holding frame. The lens barrel according to any one of (1) to (5) above.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION By applying the above configuration, a convex cam of a lens holding frame is arranged on the object side, and a notch hole for inserting a mold when molding the convex cam is arranged on the object side. By doing so, the cutout hole can be configured to be blocked by the photographing function means, whereby a means for closing the cutout hole for inserting the mold at the time of molding the convex cam can be used without providing a new member. It is possible to prevent harmful light from reaching the image forming surface only by arranging a photographing function means necessary for photographing (a light shielding plate or the like), and it is possible to provide a lens barrel which is advantageous in terms of cost. Further, since the convex cam is formed on the inner diameter portion of the lens holding frame on the object side, the lens holding frame on the image plane side can have a smaller outer diameter than the lens holding frame on the object side. Therefore, the lens holding frame on the image forming surface side can be configured to be entirely housed in the lens holding frame inner diameter portion on the object side, and the lens holding frame on the image forming surface side fits into the lens holding frame on the object side. It is possible to obtain a long length of integration, and it is possible to improve the accuracy of tilting of the lens groups. Further, by configuring the photographing function means so as to be fixedly held by the first lens holding frame, the convex cam is molded even if the lens holding frame is moved in the optical axis direction by a zoom operation or the like. A lens barrel that can always maintain a configuration that prevents harmful light from reaching the image plane because the shooting function means itself that closes the notch hole for inserting the mold at that time also moves integrally. can do. In addition, this shooting function means,
For example, the convex cam is configured by a diaphragm unit or the like, and the frame body in the unit is arranged so as to overlap at least the notch hole position of the first lens holding frame in the radial direction. Without arranging a new member as a means for closing the notch hole for inserting the mold when molding (a light shielding plate etc.), just arrange the unit so as to radially overlap the notch hole position. Therefore, it is possible to prevent harmful light from reaching the image forming surface, and it is possible to provide a lens barrel which is advantageous in terms of cost.
In addition, the cutout hole of the first lens holding frame has a simple mold configuration (a front and rear punching mold) that is usually used by adopting a structure for inserting a mold for molding the convex cam. A lens holding frame can be molded by using it, and it becomes possible to provide a lens barrel in which harmful light cannot reach the image forming surface.

[0009]

EXAMPLES Examples of the present invention will be described below.
1 is a sectional view of a zoom lens barrel having a four-group configuration according to a first exemplary embodiment of the present invention. In FIG. 1, reference numeral 1 is a first lens group, and 2 is a lens holding frame A for holding the first lens group, which is manually operated or driven by a motor through a known mechanical connection mechanism (cam connection, helicoid connection, etc.). Driven in the optical axis α direction. Reference numeral 3 denotes a second lens group, and 4 denotes a lens holding frame B for holding the lens group, which is manually operated or driven by a motor in the optical axis α direction via a known mechanical connection mechanism (cam connection, helicoid connection, etc.). Driven. Reference numeral 5 denotes a third lens group, 6 denotes a lens holding frame C for holding the third lens group, a lens holding portion 6a, a cylindrical portion 6b, a convex cam 6c on the inner diameter of the cylindrical portion 6b, and the lens holding portion 6a. And a flange portion 6 connecting the cylindrical portion 6b
d is integrally molded. 7 is a 4th lens group, 8 is the 4th lens group
A lens holding frame D for holding the lens group, and a cam follower 8b for engaging the lens holding portion 8a and the convex cam 6c.
And the cylindrical portion 8c are integrally molded. A diaphragm unit 9 is fixed to the lens holding frame C6 by a known method such as screwing. Note that the left direction in FIG. 1 is set as the subject direction, and the right direction is set as the image forming plane direction.

Next, referring to FIG. 2, description will be given of a mold structure for molding the lens holding frame D6. 2A is a plan view of the lens holding frame D6 viewed from the lens subject side, and FIG. 2B is a sectional view of the lens holding frame D6. In the figure, 10 is a mold A, 11 is a mold B, and injection molding is performed by aligning the mold A10 and the mold B11 in the optical axis direction (this mold is a so-called front-rear punch). Is a general type configuration). By the way, regarding the method of molding the convex cam 6c provided on the inner diameter of the cylindrical portion 6b of the lens holding frame D6, one end surface of the convex cam 6c is formed by the mold A10 and the flange portion 6d is penetrated from the mold B11. The convex cam 6c can be manufactured by inserting a part 11a of the mold B11 in the shape. That is, as shown in FIG. 2A, when there are three convex cams 6c, the cutout holes 6e are formed in the flange surface 6d.
The state where the three are opened is the completed state of the part.

4 using the lens holding frame D6 of this construction
The group-structure zoom lens barrel is in the state shown in FIG. In FIG. 1, as described above, the lens holding frame D6 includes the cylindrical portion 6
By engaging the cam follower 8b of the lens holding frame C8 with the convex cam 6c provided on the inner diameter of b, the relative rotation of the lens holding frame C6 and the lens holding frame D8 causes the third group lens group 5 and the fourth group lens group 7 The zoom drive is performed by changing the distance in the optical axis direction.

Next, the case where harmful light enters from the object direction side in FIG. 1 will be described. When the harmful lights A and B enter from the object direction side, the harmful lights A and B that have passed through the first lens group 1, the second lens group 3, and the third lens group 5 are the inner surface of the cylindrical portion 8c of the lens holding frame D8. However, the harmful light A, B is blocked by the lens holding portion 8a, that is, the harmful light A, B does not reach the image forming surface (not shown), which is different from the conventional case. It is possible to achieve a lens barrel in which a ghost image does not occur or flare due to scattered light due to reflection on the inner surface of the cylindrical portion 8c does not occur. As a feature of the present invention, a cutout hole for forming a convex cam for engaging the lens holding frames with each other is provided on the object side, and the cutout hole is radially overlapped by a diaphragm unit to close the cutout hole. . That is, the point different from the conventional one is that no holes through which harmful light passes are provided in the lens holding frame C6 and the lens holding frame D8. In the present invention, the diaphragm unit 9 is used as a means for closing the notch hole 6e.
However, it goes without saying that the present invention is also applicable to a configuration in which another lens holding member is provided instead of the diaphragm unit 9.

Further, according to this structure, the lens holding frame D
Since the rear part of 8 does not have a portion having an outer diameter larger than that of the lens holding frame C6, the lens holding frame D8 can be configured to be entirely housed in the inner diameter part of the lens holding frame C6.
It is possible to increase the length of fitting of the lens holding frame D8 with respect to the lens holding frame D8, and there is also an effect that it can be configured to improve the accuracy of tilting of the fourth group lens group 7 with respect to the third group lens group 5 (with the conventional configuration, in FIG. As can be seen, since it is necessary to secure a space for mounting the diaphragm unit 59 in the lens holding frame C56, the lens holding frame D58 is the lens holding frame C5.
In order to prevent the lens holding frame D58 itself from coming into contact with the diaphragm unit 59 mounting portion of the lens holding frame C56 when the lens holding frame D58 approaches 6 in the optical axis direction by a zoom operation or the like, the x dimension in FIG. 3 is secured. It is necessary to do so, that is, the fitting length is shortened by the space of the mounting portion of the diaphragm unit 59. This causes a large relative tilt of the lens group).

[0014]

According to the present invention, it is possible to realize a lens barrel capable of preventing harmful light from entering the image forming surface with a simple structure without providing a new member such as a light shielding plate. You can

[Brief description of drawings]

FIG. 1 is a sectional view of a zoom lens barrel according to an embodiment of the present invention.

FIG. 2 is a mold configuration diagram of a lens holding frame in an embodiment of the present invention.

FIG. 3 is a sectional view of a conventional zoom lens barrel.

FIG. 4 is a block diagram of a mold of a conventional lens holding frame.

[Explanation of symbols]

1: 1 group lens group 2: Lens holding frame A 3: 2 group lens group 4: Lens holding frame B 5: 3 lens group 6: Lens holding frame C (first lens holding frame) 7: 4 lens group 8: Lens holding frame D (second lens holding frame) 9: Aperture unit (shooting function means) 10, 11: Mold

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Atsushi Koyama             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F term (reference) 2H044 AD01 BD08 BD09 EE01 EF04                       EF07                 5C022 AC54 AC74

Claims (6)

[Claims] 1. A first lens holding frame having a lens holding portion, a cylindrical portion having a convex cam formed on an inner diameter thereof, and a flange portion connecting the cylindrical portion and the lens holding portion, the lens holding portion being arranged on the object direction side. A lens barrel having a cam follower that engages with a convex cam formed on the inner diameter of the cylindrical portion, and the second lens holding frame arranged on the image plane side, wherein the first lens holding frame is provided. The flange portion is provided with a cutout hole in the same phase as the rotational phase of the convex cam, and the cutout hole is configured to be closed by the photographing function means arranged on the object direction side. Lens barrel. 2. The second lens holding frame, wherein a cam follower engaging with the convex cam and a lens holding portion are integrally formed with a cylindrical portion forming the second lens holding frame. The lens barrel according to claim 1, further comprising: 3. The lens barrel according to claim 1, wherein the photographing function means is fixedly held by the first lens holding frame. 4. The photographing function means is arranged so as to radially overlap the notch hole position of the first lens holding frame.
The lens barrel according to any one of 1. 5. The lens barrel according to claim 4, wherein the photographing function means arranged so as to overlap in the radial direction is a diaphragm unit. 6. A cutout hole provided in a flange portion of the first lens holding frame is a hole for inserting a mold for molding a convex cam of a cylindrical portion of the first lens holding frame. The lens barrel according to claim 1, wherein the lens barrel is a lens barrel.