JP2000206386A - Lens presser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a lens from being cracked or broken even under a condition where a severe temperature change is generated. SOLUTION: This presser is provided with a presser ring for pressing a lens to a lens-barrel to be fixed, and an annular elastic member 4 arranged between the presser ring and the lens. The elastic member 4 has a contact part 5 for contacting with the lens in a lens side and a noncontact part 6 not contacting with the lens in the side, it has also a contact part 7 for contacting with the presser ring and a noncontact part 8 not contacting with the ring in a presser ring side, and the contact part 5 in the lens side and the contact part 7 in the presser ring side are arranged to be prevented from being overlapped in view of an optical axis direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens holding device for stably fixing a lens to a lens barrel even in the vicinity of a high heat source or in an environment where temperature changes are severe.

[0002]

2. Description of the Related Art Conventionally, special optical glasses such as fluorite and low dispersion glass have been used for super-telephoto interchangeable lenses such as single-lens reflex cameras. Improving performance. However, such an optical glass has a feature that it is brittle and easily broken as compared with a normal optical glass material.

[0003]

It is known that the following problems occur when fluorite or low-dispersion glass is used as a large-diameter lens. When such a lens is fixed to a lens barrel, usually, FIGS. 6A and 6B
As shown in FIG. 3, a metal press ring 3 is inserted into a lens barrel 2 made of metal (aluminum, magnesium, or the like) to hold the lens 1 in the optical axis direction.
In such a fixed state, when a severe temperature change is given to the external environment, under a certain condition, an excessive load stress may be applied to the lens due to a difference between a linear expansion coefficient of the metal lens barrel and a linear expansion coefficient of the glass material. is there.

[0004] For example, as shown in FIG.
8), a rapid cooling (−30 ° C.) from the steady state is performed, and as shown in FIG. 8, the lens 1 is loaded with the load Fr due to radial contraction of the lens barrel 2 on the outer diameter side and the holding ring. Loads Fz and Fz ′ in the optical axis direction due to the narrowing of the distance between the lens barrel 3 and the lens barrel 2 in the optical axis direction are received. Due to these loads, a large stress distribution occurs inside the lens 1,
As a result, the lens 1 may be cracked,
It is known that cracks occur in the steel. Such extreme temperature changes are almost impossible in everyday shooting conditions, but accidentally changing the lens placed near a heater or the like in a hurry to cool down by changing the location will cause it to be placed under severe conditions. When dislodged, the low dispersion lens cracks,
May break.

An object of the present invention is to provide a lens holding device capable of preventing a lens from being cracked or broken even when subjected to a severe temperature change in view of the problems of the prior art. Is to do.

[0006]

According to the present invention, there is provided a press ring for pressing a lens against a lens barrel to fix the lens, and a ring disposed between the lens and the press ring. The elastic member has a non-contact portion on the lens side that does not contact a contact portion that contacts the lens, and a non-contact portion that does not contact the contact portion that contacts the press ring on the holding ring side. The contact portion on the lens side and the contact portion on the press ring are arranged so as not to overlap when viewed in the optical axis direction.

[0007] According to this, since the pressing force of the pressing ring against the lens is applied to the lens via the elastically deformed elastic member, even if the lens is subjected to a severe temperature change, the lens may be cracked or broken. Is prevented from occurring.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described through examples.

[0009]

FIG. 2 is an enlarged sectional view of a lens holding device of a super-telephoto single-lens reflex interchangeable lens according to an embodiment of the present invention. As shown in FIG. 1, the lens holding device includes a holding ring 3 for pressing the lens 1 against the lens barrel 2 and fixing the lens 1, and an annular ring disposed between the lens 1 and the holding ring 3. Elastic member 4. The lens 1 is made of low dispersion glass, and the holding ring 3 and the lens barrel 2 are made of metal.
The lens 1 is composed of a holding ring 3 and a lens barrel 2 and a lens 1 and an elastic member 4.
And are fixed by sandwiching them. The lens 1 made of low-dispersion glass has the property of being brittle in strength and fragile as compared with those of other lens glass materials. In FIG. 2, the outer diameter of the lens 1 is fitted to the inner diameter of the lens barrel 2,
It is fixed in the optical axis direction by an elastic member 4 between the holding ring 3 and the lens 1. Pressing ring 3 with respect to lens barrel 2
The screwing is performed by engaging both screw portions, and as a result, the lens 1 is held by the lens barrel 2 by pressing the elastic member 4 in the optical axis direction.

FIG. 1 is a perspective view showing the shape of an elastic member 4 interposed between the holding ring 3 and the lens 1. FIG. As shown in the figure, a portion 5 that contacts the lens 1 and a portion 6 that is spaced from the lens 1 so as not to contact the lens 1 are provided on the lens side of the elastic member 4. Further, on the presser ring side, there are provided a portion 7 which comes into contact with the presser ring 3 and a portion 8 which has a gap so as not to contact the presser ring 3. In addition, the lens contact portion 5 and the press ring contact portion 7 are arranged at appropriate intervals so as not to overlap in the circumferential direction of the lens (as viewed in the optical axis direction).

FIG. 3 is a developed view showing a state in which the elastic member 4 comes into contact with the press ring 3 and the lens 1, and schematically shows a state of deformation of the elastic member 4. FIG. 3A shows a deformed state of the elastic member 4 before the holding ring 3 is tightened. Presser ring 3
By tightening, as shown in FIG.
The gap between the elastic members 4 is appropriately deformed within the elastic deformation limit, and the elastic force can press the lens 1. The initial control of the amount of deformation is as follows:
By providing a contact portion where the lens and the lens barrel 2 abut, accurate management can be achieved. Further, as the initial deformation amount, it is preferable to apply a deformation approximately in the middle of the elastic deformation region of the elastic member 4.

FIG. 3D shows a case where the distance between the lens 1 and the holding ring 3 is at room temperature. When a stress is applied to the elastic member 4 when the entire lens barrel suddenly changes from a high temperature state to a low temperature state, as shown in FIG. No load stress is applied. If the temperature of the entire lens barrel suddenly rises from low to high,
The elastic member 4 can be elastically deformed as shown in FIG. 3C to prevent the lens 1 from being subjected to an excessive load.

FIG. 4 is a perspective view showing a lens pressing device according to another embodiment of the present invention. As shown in the figure, in this case, the press ring 3 has a convex portion 10 and the elastic member 4 has a concave portion 11 in which the convex portion 10 fits as a contact portion on the press ring side.
With this configuration, the same effect as in the above-described embodiment can be obtained.

In the case of the present embodiment, the elastic member 4 and the press ring 3 are in contact with each other via the projection 10. Therefore, the gap between the elastic member 4 and the press ring 3 is provided by providing the concave portion 12 which is dented on the press ring 3 side. The convex portion 10 of the press ring 3 is fitted into the concave portion 11 of the elastic member 4 so that the position in the circumferential direction is determined.

FIG. 5 is a developed view showing the state of the elastic deformation of the elastic member 4. FIG. 5B shows a case where the distance between the lens 1 and the press ring 3 is at room temperature. When stress is applied to the elastic member 4 when the entire lens barrel suddenly changes from a high temperature state to a low temperature state, elastic deformation occurs in the elastic member 4 as shown in FIG. No load stress is applied. When the temperature of the entire lens barrel suddenly rises from a low temperature to a high temperature, the elastic member 4 is elastically deformed as shown in FIG.
Can be prevented from generating an excessive load. In this way, it is possible to reduce an excessive load on the lens 1 caused by a rapid temperature change, and it is possible to stably hold the lens 1.

[0016]

As described above, according to the present invention, even when a sudden temperature change occurs, it is possible to reduce the stress applied to the lens in the optical axis direction due to the contraction of the lens barrel and the holding ring. Therefore, it is possible to prevent the lens from being destroyed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a shape of an elastic member of the lens pressing device of FIG. 2;

FIG. 2 is an enlarged cross-sectional view of a lens pressing device portion of the super-telephoto single-lens reflex interchangeable lens according to one embodiment of the present invention.

FIG. 3 is a developed view showing a state of deformation of the elastic member of FIG.

FIG. 4 is a perspective view showing a lens holding device according to another embodiment of the present invention.

5 is a development view showing a state of deformation of an elastic member of the device of FIG.

FIG. 6 is a diagram showing a configuration for holding a conventional lens.

FIG. 7 is a diagram showing a state of a rapid change in environment over time.

8 is a diagram showing a state of external stress applied to a lens in the conventional configuration of FIG.

[Explanation of symbols]

1: lens, 2: lens barrel, 3: press ring, 4: elastic member, 5: part that contacts the lens, 6: part that does not contact the lens, 7: part that contacts the press ring, 8: the press ring Non-contact portion, 10: convex portion of press ring, 11: concave portion of elastic member, 12: concave portion of press ring.

Claims (2)

[Claims] 1. A pressing ring for pressing and fixing a lens against a lens barrel, and an annular elastic member disposed between the lens and the pressing ring, wherein the elastic member is provided on the lens side. It has a non-contact portion that does not come into contact with the contact portion that comes into contact with the lens, and has a non-contact portion that does not come into contact with the contact portion that comes into contact with the press ring on the press ring side, and the contact portion on the lens side and the contact between the press ring side. The lens pressing device, wherein the portions are arranged so as not to overlap when viewed in the optical axis direction. 2. The lens presser according to claim 1, wherein the presser ring has a convex portion, and the elastic member has a concave portion in which the convex portion fits as a contact portion on the presser ring side. apparatus.