JPS58158615A - Lens holding mechanism - Google Patents

Abstract

PURPOSE:To hold lens in a state of less aberration by beveling the circumferential edge of the 2nd concave surface of a lens on the opposite side to an object and allowing the annular contacting part of the 2nd surface to abut on a body- attached surface in a lens barrel. CONSTITUTION:The 2nd surface 10r is a concave surface, so the boundary part between the 2nd surface 10r and beveled part 11 is formed into an annular and linear contacting part 14 for contacting the body-attached surface 13 of the lens barrel 12. This surface 13 for contacting and holding the lens 10 is formed nearly at right angles to an optical axis O and said linear contacting part 14 of the lens 10 contacts the surface uniformly. Consequently, if the lens 10 moves, it becomes parallel to the body-attached surface 13 crossing the optical axis O at right angles, so the 1st surface 10f is concave and even parallel eccentricity due to movement less causes a circumferential out-of-focus state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens holding mechanism in a photographic optical system.

Conventionally, a lens for a camera or the like is often held by having one surface abut against a barrel surface of a lens barrel and pressing the other surface with a retaining ring, a spacer, or the like. For example, as shown in FIG. 1, the second surface 1r of the lens 1 on the side opposite to the object is
There is a means for abutting against an annular protrusion 4 provided on the holder and holding it down with a holding ring 5. However, this mechanism
If 1r is a concave surface and there is a fitting gap in the lens barrel 2, the lens 1 will rarely move in a direction perpendicular to its tip axis O, but as shown by the dotted line in FIG. becomes easier to move in an arc shape along the second surface 1r. When the first surface 1f on the object side is a convex surface, this arcuate movement has relatively little influence on aberrations and the like. However, the first page 1f
When is a concave surface, the first surface 1f is inclined due to this movement, which has a large effect on aberrations, and there is an extremely large possibility that one-sided blurring will occur.

In recent years, as cameras have become more compact, photographic optical systems with strict manufacturing precision are required, and it is especially necessary to prevent the above-mentioned phenomenon.

Here, the object of the present invention is to provide a lens holding mechanism that solves the problems mentioned in -1- above and holds the lens in a state with little aberration. When holding a lens whose second surface is a concave surface in a lens barrel, by providing a chamfer on the peripheral edge of the second surface of the lens that is inclined or perpendicular to the optical axis, the second surface of the lens can be The lens is characterized in that an annular contact portion is formed, and the contact portion of the lens abuts against a barrel mounting surface that is provided within the lens barrel and is substantially perpendicular to the optical axis.

The present invention will be explained in detail based on the embodiment shown in FIG.

In FIG. 2, reference numeral 10 denotes a lens whose first surface 10f and second surface 10r are both concave. A chamfered portion 11 having an inclination angle of approximately 1° is provided. Since the second surface 10r is a concave surface, the second surface 10r
The boundary between r and the chamfered portion 11 is formed into an annular line contact portion 14 that contacts the barrel mounting surface 13 of the lens barrel 12 . The barrel mounting surface 13 that contacts and holds the lens 10 is formed in a direction substantially perpendicular to the optical axis 0, and the linear contact portion 14 of the lens 10 uniformly abuts thereon. In addition, 15
indicates a presser ring that presses the lens 10 from the first surface 1f side.

Since the embodiment of the present invention has the above-described configuration, the lens 10
does not move in an arc shape as shown by the dotted line in FIG.
The direction is parallel to Therefore, even if the first surface 10f is a concave surface and parallel eccentricity occurs due to movement, it is unlikely to cause one-sided blur.

In the above-described embodiment, the chamfered portion 11 is provided at an angle with respect to the optical axis O, but it may be formed so as to be orthogonal to the optical axis O.

As explained above, the lens whose second surface is held by the lens holding mechanism according to the present invention has no risk of moving in an arcuate manner as would occur with conventional mounting means, and even if it moves, the optical axis Since it only moves in the direction perpendicular to
In particular, a lens whose first surface is a concave surface has the advantage of having a large holding effect and extremely little aberration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional lens holding mechanism, and FIG. 2 is a block diagram showing an embodiment of the lens holding mechanism according to the present invention. Reference numeral 10 is an L/7 lens, lof is a first surface, 10r is a second surface, 11 is a chamfered portion, 12 is a lens barrel, 13 is a barrel mounting surface, and 14 is a line contact portion. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. When a lens whose second surface opposite to the object is a concave surface is held in a lens barrel, a surface inclined or perpendicular to the optical axis is provided at the peripheral edge of the second surface of the lens. By providing the recess, an annular contact portion is formed on the second surface of the lens, and the contact portion of the lens is brought into abutment against a barrel mounting surface that is installed in the lens barrel and is substantially perpendicular to the optical axis. A lens holding mechanism characterized by: 2. The lens holding mechanism according to claim 1, characterized by a first surface on the object side.