JPH11271586A - Support structure for lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lens from having distortion even when contracting owing to changes of temperature environment by specifying the relations of the sizes and coefficients of linear expansion among the lens, a support member, and a lens frame. SOLUTION: On the internal surface of the cylindrical lens frame 10, a ring- shaped projection part 10A which supports the peripheral edge flank of one side is formed. On the opposite side from the projection part 10A, a support member 18 is arranged which consists of a spacer ring 14 and a pressure ring 16. The lens 12, support member 18, and lens frame 10 are formed satisfying A×a+B×b being about C×c. Here, A is the size of the lens 12 in a thrust direction (along the thickness of the lens) and B is the size of a part, contributing the absorption of the shrinkage of the lens 12, of the support member 18 and the size of the spacer ring 14. Further, C is the size of the part, contributing the absorption of the shrinkage of the lens 12, of the lens frame 10 and (a) to (c) are the coefficients of linear expansion of the lens 12, spacer ring 14, and lens frame 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens support structure, and more particularly to a lens support structure for preventing a decrease in optical performance due to a temperature environment in which a lens is used.

[0002]

2. Description of the Related Art In a lens device provided in a television camera or the like, a plurality of lenses are arranged along an optical axis, and each lens is supported by a cylindrical lens frame. In this case, a support member such as an interval ring or a press ring is interposed between the lens and the lens frame to fix the lens so as not to come off the lens frame.

However, when the temperature environment in which the television camera is used changes, the lens expands and contracts, so that an undue force acts on the lens, causing distortion in the lens, thereby deteriorating the optical performance. In particular, high-resolution lenses have a problem of performance degradation due to changes in the temperature environment. For this reason, conventionally, an elastic member such as rubber or a compression spring has been used as the above-mentioned support member, and the elastic member has generally absorbed the expansion and contraction of the lens.

[0004]

However, the cause of the distortion of the lens due to the change of the temperature environment is not only due to the expansion and contraction of the lens itself, but also the expansion and contraction of the lens frame and the supporting member other than the lens. Therefore, there is a drawback that a decrease in the optical performance of the lens cannot be accurately prevented by simply using the elastic member as the support member. That is, since the lens, the lens frame, and the supporting member are formed of different materials, when the temperature environment changes, the difference in the linear expansion coefficient between the members causes backlash in the supporting portion of the lens, Distortion occurs, and the optical performance is degraded. If this distortion is repeated, the distortion cannot be recovered.

Further, when an elastic member, particularly a compression spring, is used as a supporting member as in the prior art, the pressing force of the elastic member is always applied to the lens, so that the lens does not change even if the temperature environment does not change. Is distorted. Further, when a compression spring is used as the elastic member, a space for accommodating the compression spring must be ensured, and there is a problem in terms of downsizing the device.

The present invention has been made in view of such circumstances, and has as its object to provide a lens support structure that does not cause distortion in a lens even if the lens expands and contracts due to a change in temperature environment. .

[0007]

In order to achieve the above object, the present invention provides a spacing ring in which a lens is disposed in at least one of a thrust direction and a radial direction of the lens.
In a supporting structure of a lens supported on a lens frame via a supporting member such as a press ring, a dimension of the lens in a thrust direction or a radial direction is A, a coefficient of linear expansion of the lens is a, and among the supporting members, The dimension of a part contributing to the absorption of expansion and contraction of the lens is B, the linear expansion coefficient of the support member is b, and the dimension of the part of the lens frame that contributes to the absorption of expansion and contraction of the lens is C. The lens, the support member, and the lens frame are formed so as to satisfy a relationship of A × a + B × b ≒ C × c when a linear expansion coefficient of the frame is c.

According to the present invention, when the lens expands and contracts due to a change in the temperature environment, the support member and the lens frame also expand and contract so as to satisfy the relationship of A × a + B × b ≒ C × c. Nothing. Also, instead of absorbing the expansion and contraction of the lens with the elastic member as in the related art, the lens, the support member,
Since the expansion and contraction of the lens is absorbed by using the linear expansion coefficient inherent to the material used for the lens frame, the lens is not distorted by the pressing force of the elastic member as in the related art.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a lens support structure according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating a first embodiment of a lens support structure according to the present invention, and is a half cross-sectional view showing a portion above an optical axis P, and supports a lens 12 on a lens frame 10. At this time, a case is shown in which the holding ring 16 is fixed via the spacing ring 14.

As shown in FIG. 1, the inner peripheral surface of a cylindrical lens frame 10 for housing and supporting the lens 12 supports one peripheral side surface of the lens 12 when the lens 12 is inserted into the lens frame 10. A ring-shaped protrusion 10A is formed.
The optical axis P of the lens 12 and the center line of the lens frame 10 are positioned by the projection 10A. On the opposite side of the projection 10A with the lens 12 interposed therebetween, a support member 18 including a spacing ring 14 and a pressing ring 16 is arranged in contact with the peripheral edge of the lens 12. That is, the spacing ring 14 that comes into contact with the peripheral edge of the lens 12 is
The fixing ring 16 is fixed to the lens frame 10 by screwing, an adhesive or the like.

According to the present invention, in the above lens supporting structure, the following formula (1) is used.

[0012]

The lens 12, the support member 18, and the lens frame 10 are formed so as to satisfy the following expression: A × a + B × b ≒ C × c (1) Here, as shown in FIG.
Is the dimension of the lens 12 in the thrust direction (the thickness direction of the lens). B is a dimension of a portion of the support member 18 that contributes to absorption of expansion and contraction of the lens 12, and in FIG.
4 dimensions. C is the lens 12 of the lens frame 10
Is the size of the portion that contributes to the absorption of expansion and contraction. A is the linear expansion coefficient of the lens 12, b is the linear expansion coefficient of the spacing ring 14, and c is the linear expansion coefficient of the lens frame 10.

According to the lens supporting structure configured as described above, when the lens 12 expands and contracts due to a change in the temperature environment,
The support member 18 and the lens frame 10 also expand and contract so as to satisfy the relationship of A × a + B × b ≒ C × c. As a result, when the lens 12 is supported on the lens frame 10 via the support member 18, the pressing force of the support member 18 pressing the lens 12 does not change before and after the temperature change. Therefore, even if the temperature environment changes, the pressing force applied to the lens 12 is always kept constant, so that the lens 12 is not distorted. Further, in the case of the present invention, the expansion and contraction of the lens 12 is not absorbed by the elastic member as in the related art, but the lens 12 and the support member 1 are not used.
8. Since the expansion and contraction of the lens 12 is absorbed by using the linear expansion coefficient inherent to the material of all the members 10, 12, and 18 that are involved in the distortion of the lens 12 like the lens frame 10, the elastic member The lens 12 is not distorted by the pressing force. Thereby, even if the temperature environment in which the lens 12 is used changes, distortion of the lens 12 does not occur, so that the optical performance can be maintained in a highly accurate state.

FIG. 2 shows a modification of the first embodiment of the present invention, in which the supporting member 18 is constituted only by the holding ring 16. That is, the presser ring 16 is moved to the thin inner portion 16A.
And a thick outer portion 16 </ b> B so as to form an L-shaped cross section, so that the inner portion 16 </ b> A is in contact with the peripheral edge of the lens 12. The other lens support structures are the same as in the first embodiment.

In this case, since the inner portion 16A of the press ring 16 mainly contributes to the absorption of expansion and contraction of the lens 12, the size of the inner portion 16A is set to B in the above equation (1) as shown in FIG. Used as dimensions for FIG. 3 is a cross-sectional view for explaining a second embodiment of the lens supporting structure according to the present invention, and is a half cross-sectional view showing a portion above the optical axis P, in which a supporting member is provided between a plurality of lenses. The case where the spacing ring 26 is interposed is shown.

As shown in FIG. 3, ring-shaped projections 24A and 24B are formed at the front end and the rear end of a cylindrical lens frame 24 for housing and supporting the lenses 20 and 22, respectively. The convex lens 20 is arranged in contact with the projection 24A, and the cemented lens 22 in which the concave lens 22A and the convex lens 22B are joined is arranged in contact with the projection 24B at the rear end. Since the projections 24A and 24B are formed integrally with the lens frame 24, when inserting and assembling the lens, the lens may be assembled using the elastic force of the lens frame 24 or the projections 24A and 24B. This is done by crimping either one. Further, at least one of the protrusions 24A and 24B may be a separate member from the lens frame 24. Also,
A lens frame 2 is provided between the convex lens 20 and the cemented lens 22.
The spacing ring 26 incorporated with almost no gap between itself and the support member 4 is interposed as a support member. As a result, the convex lens 20 and the cemented lens 22 are sandwiched between the projections 24A and 24B at the front and rear ends and the spacing ring 26 at a predetermined interval. Then, the lenses 20, 22, the spacing ring 26, and the lens frame 24 are formed so as to satisfy the relationship of the above equation (1). In this case, as shown in FIG. 3, A in the above equation (1) is the length A ₁ of the convex lens 20 in the thrust direction and the length A ₁ of the cemented lens 22 in the thrust direction.
_It is the sum of _two . B is the width of the spacing ring 26, C
Is the length between the projection 24A on the front end side and the projection 24B on the rear end side of the lens frame 24.

Therefore, the above equation (1) becomes the following equation (2).

[0018]

(A ₁ + A ₂ ) a + B × b ≒ C × c (2) FIG. 4 shows a modification of the second embodiment, in which a lens frame 2 is provided.
4 are formed at the front end and the rear end thereof.
While holding rings 32 and 34 are provided instead of (see FIG. 3), a lens frame 24 is provided between the convex lens 20 and the cemented lens 22.
In this case, a projection 24C is formed. The shape of the projection 24C is such that the concave lens 22 side is formed in an L-shape so that the surface of the concave lens 22 is easily pressed. The shapes of the retaining rings 32 and 34 are formed in an L-shaped cross section, as described in the modification of the first embodiment.

In this case, as shown in FIG. 4, A in the above equation (1) is the length of the convex lens 20 in the thrust direction (A ₁ ) and the length of the cemented lens 22 in the thrust direction (A ₂ ). And the sum of B is a retaining ring 32, 3
4 is the sum of (B ₁ ) and (B ₂ ) which are the lengths of the portions contributing to the expansion and contraction of the lenses 20 and 22. C is the sum of (C ₁ ) and (C ₂ ), which is the length of the portion of the lens frame 24 that contributes to the expansion and contraction of the lenses 20 and 22.

Therefore, the above equation (1) becomes the following equation (3).

[0021]

## EQU3 ## (A ₁ + A ₂ ) a + (B ₁ + B ₂ ) × b ≒ (C ₁ + C ₂ ) × c (3) Also in the second embodiment of the present invention configured as described above, The same operation and effect as those of the first embodiment can be obtained. FIG. 5 shows a third embodiment of the present invention, in which the lens support structure of the present invention is applied to both the thrust direction and the radial direction of the lens 36.

As shown in FIG. 5, the support member 18 is composed of two retaining rings 16 and 38, and the retaining ring 38 is formed in a hook shape so as to be interposed between the lens 36 and the lens frame 40. It is composed of a horizontal portion 38A and a vertical portion 38B that sandwiches the peripheral edge of the lens 36 between the projection 40A of the lens frame 40. Then, the lens 36, the holding ring 38, and the lens frame 40 are formed so as to satisfy the relationship of the above expression (1). In this case, as shown in FIG. 5, how to measure the dimensions A, B, and C in the thrust direction of the lens 36 is the same as the case described with reference to FIG. On the other hand, in how to measure A, B, and C in the radial direction, A is the radius of the lens 36. B is the horizontal portion 38 of the retaining ring 38
A. C is half the length of the inner diameter of the lens frame 40.

Therefore, in this case, the above equation (1) is used in both the thrust direction and the radial direction. According to the third embodiment of the present invention, both the expansion and contraction of the lens 36 in the traverse direction and the expansion and contraction of the lens 36 in the radial direction can be accurately absorbed by the press ring 38. In each of the embodiments described above, as a method of configuring the lens support structure to satisfy the expression (1), the lenses 12, 20, 2
2, 36, spacing rings 14, 26 and holding rings 16, 32, 3
4 and 38, the supporting members 18 and the lens frames 10 and 24,
While maintaining the dimensions A, B, C of 40 constant, the linear expansion coefficient a,
When b and c are changed, or when A, B and C are changed while a, b and c are kept constant, A, B, C and a,
Both b and c may be changed.

Table 1 shows that lenses A, B, and C are constant when A, B, and C are fixed and the linear expansion coefficients a, b, and c are appropriately selected.
22, 36, support member 18, lens frame 10, 24, 40
2 is an example showing the material and the coefficient of linear expansion of the material.

[0025]

[Table 1] Then, as shown in Table 1, BK7 glass, which is a glass optical glass, is used as a lens, and an AS resin, an ABS resin, a polyacetal resin, and nylon 66 are appropriately selected as a support member, and a magnesium frame is used as a lens frame. The most satisfying combination of the above formula (1) is constituted by using a product manufactured by die-casting among aluminum, copper, and zinc products. The same applies to the case where the above equations (2) and (3) are used.

In this embodiment, the case where the supporting member 18 is constituted by a plurality of members such as the spacing ring 14 and the pressing ring 16 has been described. However, the case where the lens frame is constituted by a plurality of members is described. The same is true for In short, when the temperature environment changes, all members involved in the distortion of the lens are formed as a lens, a support member, and a lens frame, and may be applied to any of the above equations (1) to (3).

[0027]

As described above, according to the lens support structure of the present invention, the expansion and contraction of the lens is absorbed by utilizing the linear expansion coefficients inherent to the materials of the lens, the support member and the lens frame. Therefore, the lens is not distorted by the pressing force of the elastic member as in the related art. Therefore, even if the temperature environment in which the lens is used changes, distortion of the lens does not occur, so that the optical performance can be maintained in a highly accurate state.

[Brief description of the drawings]

FIG. 1 is a half cross-sectional view illustrating a first embodiment of a lens support structure according to the present invention.

FIG. 2 is a half sectional view illustrating a modification of the first embodiment.

FIG. 3 is a half sectional view illustrating a second embodiment of the lens support structure of the present invention.

FIG. 4 is a half-sectional view illustrating a modification of the second embodiment.

FIG. 5 is a half sectional view illustrating a third embodiment of the lens support structure of the present invention.

[Explanation of symbols]

 10, 24, 40 ... lens frame 12, 20, 22, 36 ... lens 14, 26 ... spacing ring 16, 32, 34, 38 ... holding ring 18 ... support member

Claims (2)

[Claims] 1. A lens support structure for supporting a lens on a lens frame via a support member such as a spacing ring or a pressing ring disposed in at least one of a thrust direction and a radial direction of the lens, The size of the lens in the thrust or radial direction is A, the coefficient of linear expansion of the lens is a, the size of the portion of the support member that contributes to absorption of expansion and contraction of the lens is B, and the coefficient of linear expansion of the support member is b, and the dimension of a portion of the lens frame that contributes to the absorption of expansion and contraction of the lens is C, and the linear expansion coefficient of the lens frame is c, and the following equation is obtained: A × a + B × b ≒ C × c Wherein the lens, the support member and the lens frame are formed so as to satisfy the following relationship. 2. The above relationship is satisfied by keeping A, B, and C constant and changing the linear expansion coefficients a, b, and c specific to the material forming the lens, the support member, and the lens frame. The lens support structure according to claim 1, wherein: