JPS6117110A - Lens holding device - Google Patents

Abstract

PURPOSE:To eliminate the stress-strain of a lens due to the variation of environments, to prevent the degradation of the capacity and to compensate the variation of back focus by engaging a mirror frame and the lenw with each other by a projection and a recess which can be slid and pressing and holding them elastically and including properly the bottom face of the recess as the engaging part. CONSTITUTION:Three or more projections 5 are arranged on a circle with the axis of a lens 3 as the center ona lens engaging step part 2 of a mirror frame 1, and recesses 6 are provided in positions corresponding to projections 5 on the lens 3. Each recess 6 has a circular arcuate shape, which passes the center of the lens and has radius R, and the recess 6 is longer in the peripheral direction. A bottom face 7 of the recess 6 is inclined, and the upper face of the projection 5 is inclined similarly, and the height of the projection 5 is larger than the depth of the recess 6, and therefore, a gap 8 is generated between the mirror frame 1 and the lens 3. Meanwhile, a proper number of notches are provided in a lens retaining ring 9 in the peripheral direction to form a cantilever elastic piece 10 is brought into contact with the lens 3 to retain the lens 3, and a gap 8' is generated between the retaining ring 9 and the lens 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a lens holding device, particularly to a plastic lens holding device.

(Prior art) Methods for fixing the lens to the lens frame include crimping,
There are methods such as using a spring ring, but the most common method is the 5th method.
As shown in the figure, in this method, a lens 3 is dropped into a step 2 provided on a lens frame 1, and a presser ring 4 is screwed into a threaded portion provided on the inner surface of the lens frame 1 to fix it.

In recent years, lenses have come to be made of plastic, and the lenses themselves expand and contract due to changes in temperature and humidity.
Distortion occurs due to stress generation, and thickness, curvature, etc. change,
(2) The back focus of the lens changes due to changes in the refractive index, and (2) problems such as eccentricity increase due to changes in the outer diameter have arisen.

To deal with this, rather than tightening and fixing the lens to the lens frame, efforts have been made to engage the lens with a cantilevered holding piece that has elasticity in the radial direction to reduce the effects of heat, etc. Suggestions have been made. (For example, JP-A-58-87
(No. 508) However, since this method also strongly suppresses and fixes the lens in the optical axis direction, it is not possible to compensate for changes in back focus, and in order to allow movement in the radial direction,
The contact surface with the lens must be made of a friction-reducing material such as Teflon.

(Problems to be solved by this invention) This invention aims to provide a lens holding device with a simple structure that compensates for distortion caused by environmental changes, changes in pack focus, eccentricity, etc., which are specific to plastic lenses. It is.

Structure of the Invention (Means for Solving the Problems) In this invention, each of the lens and the lens frame has three or more recesses concentrically fitted into the recesses, and the recesses are smaller in size in the radial direction than the depth of the recesses. A protrusion having a large height is provided to fit the above-mentioned projections and depressions, and the lens is suppressed and held by a presser ring that applies a pressing force in the optical axis direction.

(Embodiment) FIGS. 1 and 2 are a front view and a sectional view of an embodiment of the lens holding device of the present invention.

Three or more protrusions 5 are arranged on the lens holding step 2 of the lens frame 1 along the circumference centered on the center of the lens, and the lens 3 is provided with a recess 6 at a corresponding position. .

As shown in FIG. 1, this recess 6 has a circular arc shape with a radius R passing through the center of the lens, and is elongated in the radial direction. As the enlarged partial cross section is shown in FIG. 4, the bottom surface 1 of the recess 6 is inclined, and the upper surface of the protrusion 5 has the same slope, and its height is greater than the depth of the recess 6. Therefore, a gap 8 is created between the lens frame 1 and the lens frame 1.

On the other hand, the lens holding ring 9 is provided with an appropriate number of notches in its circumferential direction to form a cantilevered elastic piece 10, and this elastic piece 10 is brought into contact with the lens 2 to hold the lens 2 down. A gap 8' is also formed between the ring 9 and the ring 9.

(Function) When the lens 2 expands or contracts due to environmental changes such as temperature or humidity, the curvature and thickness of the lens 2 change, and the outer diameter also changes.

At this time, there is a gap g18'' between the lens outer diameter and the lens barrel inner diameter, and a gap 8.8' between the lens holding step 2 and the presser ring 9.
The lens 2 can be freely deformed without stress distortion.

However, since the protrusion 5 and the recess 6 are engaged and pressed by the elastic piece 10, a change in lens diameter causes slippage between the protrusion 5 and the recess 6, causing the lens to rotate. As a result, the depth of the recess 6 with which the protrusion 5 comes into contact changes, so that the lens 2 moves in the optical axis direction. Therefore, by appropriately selecting the slope of the bottom surface of the recess 6, it is possible to cancel out the deviation of the pack focus due to changes in the curvature, thickness, and refractive index of the lens 2.

Many design changes are possible, such as reversing the above-mentioned irregularities between the lens and the lens frame, and making the elastic member of the retainer ring have a different shape.

Effects of the Invention As described above, in this invention, the lens frame and the lens are engaged with each other by sliding protrusions and recesses, and are elastically pressed and held, and the other parts are the lens frame and the holding ring. Since the lens is not in direct contact with the lens, the lens is free to deform due to environmental changes, does not cause stress distortion, and can prevent performance deterioration.

Furthermore, by properly slanting the bottom of the recess, which is the retaining portion, the lens can be caused to move back and forth through sliding, thereby compensating for changes in pack focus.

[Brief explanation of the drawing]

1 and 2 are front views of the lens holding device of the present invention,
3 and 4 are partial sectional views of the retaining portion of the recessed protrusion and the presser ring, and FIG. 5 is a sectional view of a conventional example. 1...Mirror frame, 3...Lens, 4,9...
Holding ring, 5... Protrusion, 6... Recess, 8... Gap, 10... Elastic piece Patent applicant Konishi Roku Photo Industry Co., Ltd. Applicant's agent Patent attorney Fumi Sato (and 1 other person) )

Claims (1)

[Claims] Each of the lens and the lens frame is provided with three or more recesses on a concentric circle, and a convex part that is small in the radial direction and has a dimension higher than the depth of the recess, which fits into the recesses, and the concave and convex parts are fitted together, A lens holding device characterized by applying a pressing force elastically in the optical axis direction.