JPS6160407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lens holding mechanism for an optical device such as a camera lens, and particularly to a lens holding mechanism suitable for use with a plastic lens having relatively low temperature resistance.

Generally, a lens holding mechanism for an optical system such as a camera lens is constructed as shown in FIG. To briefly explain each part, numeral 4 is a lens mounting part, and a lens fitting part 5 is formed inside this barrel mounting part 4 . When assembling the parts, first, for example, the convex lens 7 is fitted into the fitting part 5, and then the presser ring 1 that is screwed into the threaded part 3 formed on the inner wall of the lens frame 2 is screwed in, thereby tightening the inner diameter part of the presser ring 1. is brought into contact with the peripheral edge of the lens 7 to hold the lens.

By the way, in such a lens holding mechanism, when parts assembled at room temperature are placed under high temperature or low temperature conditions, the following disadvantages arise due to differences in linear expansion coefficients of each part. That is, since the coefficient of linear expansion of the material forming the lens 7 is larger than that of the material forming the lens frame 2 and the presser ring 1, for example, under high temperature conditions, the increase in the volume of the lens 7 causes the lens frame 2 and the presser ring 1 to expand. This will exceed the same increase in Ring 1. On the other hand, since the lens holding mechanism is originally constructed for the purpose of fixing the lens 7, it is already assembled to the design clearance under normal temperature conditions as described above, and as a result, under high temperature conditions, it cannot be directly attached to the lens. This will affect the surface shape. In particular, this effect is most noticeable at the peripheral edge contact portion of the lens 7 with the presser ring 1, and is also significant in plastic lenses where the hardness of the material forming the lens is relatively low. FIG. 2 shows a partially enlarged configuration diagram of the abutting portion (dotted chain line circle A section in FIG. 1). As is clear from the figure, the stress due to the expansion of the lens 7 is concentrated at the abutting portion 8 between the lens 7 and the presser ring 1, causing a dent in the surface of the lens 7.

To explain this state in more detail, the lens 7
tends to expand in the radial direction as the temperature increases, but as described above, the peripheral edge of the lens 7 is restricted by the retainer ring 1, so that expansion in the radial direction is prevented. Also, due to this regulation, thermal stress is generated inside the lens, but the unregulated lens expands in the optical axis direction to cancel this thermal stress, and as a result, as shown in Figure 3. Although the spherical surface on the optical axis of the lens is at position P under normal temperature conditions, it expands to position P ₁ under high temperature conditions, and the radius of curvature of the lens changes from r=OP to r=
_{1 1} , and the radius of curvature of the lens becomes smaller. In this case, if the length of the arc that is the spherical surface of the lens is l ₀ at room temperature, l ₁ is when the temperature is t°C higher than room temperature, and α is the linear expansion coefficient of the lens, then l ₁ ≒l ₀・(1+αt) It can be approximated by

On the other hand, even under low temperature conditions, the situation is similar to that under high temperature conditions, but the phenomenon is opposite. In other words, the coefficient of linear expansion of the material forming the lens 7 is larger than that of the materials forming the lens frame 2 and the retainer ring 1, so as the temperature decreases, the lens frame 2 and the retainer ring 1 contract. The lens 7 tries to contract, but since the peripheral edge of the lens 7 is restricted by the presser ring 1, the lens 7 cannot be contracted more than the contraction of the presser ring 1. In this case, thermal stress is generated inside the lens 7, and the lens contracts in the optical axis direction to cancel this thermal stress.
As a result, as shown in Fig. 4, the spherical surface on the optical axis of lens 7, which was at position P under normal temperature conditions, shifts to position P ₂ under low temperature conditions, and the radius of curvature of lens 7 is r = From OP, r ₂ = _{2 2} , and a phenomenon that increases, which is completely opposite to the case under the above-mentioned high temperature condition, occurs. In this case, if the arc length of the lens is l ₀ at room temperature, l ₂ when the temperature is t℃ lower than room temperature, and the linear expansion coefficient of the lens is α, then it is approximated by l ₂ ≧l ₀・(1−αt) can do.

In such conventional lens holding mechanisms, the radius of curvature of the lens changes due to temperature changes, and even if the parts are assembled accurately at room temperature, the focal position of the lens may shift significantly depending on the temperature at which it is used. This has been a cause of deterioration of optical characteristics such as aberrations. This problem is particularly severe in plastic lenses, which have relatively low temperature resistance.

The present invention eliminates such disadvantages, and constitutes a lens holding mechanism with strong temperature resistance that is unaffected by temperature changes even when the plastic lens has relatively low temperature resistance, thereby expanding the operating temperature range of the plastic lens. The purpose is to Another object of the present invention is to prevent the retainer ring 1 from loosening, which occurs due to stress relaxation in the plastic lens, and to eliminate rattling of the lens. When holding the lens on the lens barrel part with a holding ring, a cantilever-shaped lens holding part having elasticity in the lens radial direction is continuously or The lens is provided intermittently and is characterized in that the lens is provided with an engaging portion that engages with the lens holding portion.

Hereinafter, various embodiments applied to the present invention will be described in detail with reference to the drawings.

FIG. 5 shows a first embodiment of the present invention, and FIG. 5a is a side sectional view including the optical axis of the lens holding mechanism. In the figure, 9 is a lens frame, 10 is a lens barrel attachment part,
According to the present invention, a lens holding section 12 is formed on the lens holding side of this barrel mounting section 10. This lens holding part 12 is fixed to or integrally formed with the lens mounting part 10, and has a cantilever shape as shown in FIG. 5a. In addition, the lens holding part 12 is intermittently moved along the circumferential surface of the lens barrel attachment part 10 as shown in FIG. It is formed by an outer lens holding plate 12a and an inner lens holding plate 12b in the form of thin plates. On the other hand, the lens holder 12 is attached to the peripheral edge 13a of the lens 13.
An engaging portion 13b, which is a concave portion into which the tip of the lens engages, preferably fits, is bored, and is held and fixed to the lens holding portion 12. A holding ring 14 having a thread formed on the outer periphery is screwed into the threaded portion 11 to hold the lens 13. Note that this presser ring 14
As the forming material, metals, synthetic resins, and Teflon (tetrafluoroethylene) materials, which are friction damping members, can be used. In addition, the structure of the lens holding part may be provided intermittently along the circumferential surface of the lens barrel mounting part as described above, or it may be provided continuously. However, as shown in FIG.
As shown in Fig. d, the cross-sectional shape can be formed into a V-shape, but the point is that it is sufficient that it is formed into a cantilever shape to hold the lens 13, and the shape of the lens holding part is according to the present invention. It is not limited to. For example, although not shown, the cross-sectional shape is an inverted V-shape, a U-shape, etc.
Various shapes such as letter shapes do not depart from the scope of the present invention, and any size or shape can be used to engage the engaging portion provided on the lens 13 within tolerances that do not affect the optical characteristics. Bye. Note that FIGS. 5c and 5d are partially enlarged views of the chain line circle B shown in FIG. 5a. According to this embodiment, the position of the lens to be held in the optical axis direction is determined by the lens holding part and the holding ring at room temperature, and the engaging part provided on the lens and the lens holding part The radial position is determined by being engaged and fixed. On the other hand, under high temperature conditions, the lens 13 uniformly expands in the radial direction as shown by the two-dot chain line in FIG. Because of this, the lens can be displaced to the position 13a, and therefore the expansion of the lens is not restricted as in the conventional case. It should be noted that it is easy to understand that the same effect can be obtained even under low temperature conditions.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 6a is a side sectional view including the optical axis of the lens holding mechanism. The difference from the first embodiment is that a cantilever-shaped lens holding portion is provided on the holding ring. First, in the figure, 9 is a lens frame, 10 is a lens barrel mounting portion, and 10a is a lens barrel mounting surface. lens 1
3 is held by a presser ring 17 from the lens frame 9 side with its peripheral edge 13a in contact with this lens barrel mounting surface.
According to the present invention, this presser ring 17 is provided with a cantilever-shaped lens holding portion 19 on the peripheral surface on the lens contact side, and is preferably fitted with a cantilever-shaped lens holding portion 19 formed on the peripheral edge of the lens. Engagement part 1 which is a formed recess
It is held and fixed at 3c. In this case, the method of assembling the presser ring 17 is different from the first embodiment in that the locking piece 18 formed on the outer periphery of the presser ring 17 is locked and fixed to the locking portion 20 undercut in the lens frame 9. (See Figure 6 a or b). Therefore, no threaded portion is formed on the inner wall of the lens frame 9, and the outer diameter of the retaining ring 17 is made larger than the inner diameter of the lens frame 9, and is press-fitted when assembling the parts. Therefore, the presser ring is made of a material with a large elastic modulus, such as resin. Note that the method of assembling the retaining ring can of course be carried out by screwing as in the first embodiment, and the shape or construction method of the lens holding part 13 can be carried out in the same manner as in the first embodiment. can be implemented. FIG. 6b shows an embodiment in which the lens 21 is attached with the front and back sides reversed from those shown in FIG. 6a.

Note that FIG. 6b is a partially enlarged view of the chain line circle D shown in FIG. 6a. Therefore, in the second embodiment as well, the same effects as in the first embodiment can be obtained due to the action of the lens holding portion provided on the holding ring and having elasticity in the lens radial direction.

As described above, each of the above-mentioned embodiments is applicable to cases in which a cantilever-shaped lens holding part having elasticity in the lens radial direction is continuously or intermittently provided on the circumferential surface of the lens barrel mounting part and/or the holding ring, and This shows an exemplary configuration method in the case of providing a lens holding part and an engaging part, and it can be similarly implemented with various other shape and configuration modifications.

Thus, according to the present invention, since the lens is held by the cantilever-shaped lens holding portion having elasticity in the lens radial direction, expansion and contraction of the lens due to temperature changes is absorbed, and the radius of curvature of the lens is As a result, in any of the embodiments of the various embodiments, it is possible to prevent the focus position from shifting due to changes in the radius of curvature of the lens or from worsening of various aberrations. Even if the plastic lens has weak properties, the temperature range in which it can be used can be expanded.

Furthermore, in the present invention, it is possible to prevent the lens from shaking in the lens holding mechanism due to temperature changes, vibrations, etc. of conventional plastic lenses. In this way, the lens holding mechanism according to the present invention can prevent the deterioration of various optical properties as described above, and specifically, it is possible to prevent the lens from deteriorating due to thermal expansion or contraction.
The NR was improved from 10 or more in the conventional system (see Figure 1) to 2 to 3 in the present invention, and furthermore, the NR was improved from 10 or more in the conventional system (see Figure 1) to 2 to 3 in the present invention. Various technical effects have been achieved, such as preventing deterioration of optical characteristics due to "distortion" and other aberrations.

[Brief explanation of the drawing]

Fig. 1 is a side cross-sectional view including the optical axis showing an example of the conventional lower lens holding mechanism, Fig. 2 is a partial enlarged view of the dashed-dotted line circle A section in Fig. 1, and Fig. 3 is the conventional lower lens holding mechanism. FIG. 4 is an explanatory diagram showing the disadvantages of the lens holding mechanism at high temperatures; FIG. 4 is an explanatory diagram showing the disadvantages of the conventional lens holding mechanism at low temperatures;
FIG. 5 shows a first embodiment according to the present invention, and FIG.
is a side sectional view including the optical axis of the lens holding mechanism, b is a configuration diagram of the lens holding part taken along the line B-B' in a of the same figure, and c and d are the dashed line circle B shown in the figure a. Partially enlarged view of the section. FIG. 6 shows a second embodiment of the present invention, in which FIG. 6a is a side sectional view including the optical axis of the lens holding mechanism, and FIG. . 12, 15, 16, 19... Lens holding part, 12
a...Outer lens holding plate, 12b...Inner lens holding plate, 13, 21, 22... Lens, 13a, 21a
... Lens peripheral edge portion, 13b, 13c, 21b... Engaging portion, 17... Holding ring, 18... Locking piece, 20... Locking portion.

Claims (1)

[Claims] 1. In a lens holding mechanism in which a lens is held by a holding ring on a lens mounting part in a lens frame, the lens has elasticity in the radial direction of the lens provided on the circumferential surface of the lens mounting part and/or the holding ring, and is elastic in the optical axis direction. a lens holder protruding from the lens, and an engagement hole into which the lens holder fits into the lens, and when the lens is displaced in a direction perpendicular to the optical axis, the elastic lens holder is bent. A lens holding mechanism characterized by absorbing the displacement.