JP2005215503A - Lens holding mechanism and lens unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens holding mechanism preventing excessive stress from being produced on a lens even when volume change is caused in accordance with temperature under wide environment from low temperature to high temperature. <P>SOLUTION: The lens holding mechanism is equipped with a lens holding frame having a holding hole in which a lens is housed, and the lens holding frame holds the lens through a holding member in the holding hole. In the lens holding mechanism, the lens has an outside diameter A and a thermal expansion coefficient (a), and when the thermal expansion coefficient (a) is smaller than the thermal expansion coefficient (b) of the lens holding frame, the outside diameter A and the thermal expansion coefficient (a) of the lens, the inside diameter B of the holding hole, the thermal expansion coefficient (b) of the holding member and the thermal expansion coefficient (c) of the holding member have relation c=(B×b-A×a)/(B-A). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mechanism for holding and fixing a lens, and more particularly to a lens holding frame that does not cause excessive stress and gaps in the lens regardless of changes in temperature environment.

  A conventional lens holding mechanism is disclosed in Patent Document 1. In this configuration, when the lens is stored in the lens holding frame, a holding ring is inserted between the lens and the holding frame. The holding ring has a plurality of first gaps formed in a predetermined length along the circumferential direction between the holding frame and the outer circumference of the lens. It has a shape having a second gap formed in an alternate positional relationship with the first gap, and can be deformed by radial stress. Further, the thermal expansion coefficient of the holding ring is equal to that of the lens, and the thermal expansion coefficient of the holding frame is smaller than that of the lens and the holding ring.

  A case where the lens holding mechanism of Patent Document 1 holds a lens formed of a material having a relatively large thermal expansion coefficient, such as a plastic lens, will be described. The lens, the holding ring, and the holding frame expand as the environmental temperature increases. As described above, the expansion coefficient of the lens and the holding ring are set to be the same and larger than the expansion coefficient of the holding frame.

For this reason, the retaining ring is subjected to stress in the radial direction by the retaining frame. However, since the holding ring has the first and second gaps, the holding ring is elastically deformed by the action of these gaps to absorb the stress and relieve the stress on the lens and the holding frame.
JP 7-191247 A

  Note that when the environmental temperature is lowered in the lens holding mechanism of Patent Document 1 that holds a lens having a large thermal expansion coefficient as described above, the shrinkage amount of the holding ring is larger than that of the holding frame. Accordingly, a gap is generated between the holding ring and the holding frame, and the position of the lens cannot be determined. In order to avoid this, it is necessary to assemble the holding ring that is larger than the inner diameter of the holding frame in an elastically deformed state at room temperature in advance. This assembling work requires a high level of technology, and the lens is stressed by the compressed retaining ring, which deteriorates the optical performance of the lens at room temperature.

  Further, when the lens holding mechanism of Patent Document 1 holds a lens having a small coefficient of thermal expansion, such as a quartz lens, the same problem as described above occurs when the environmental temperature rises.

  In view of the above problems, an object of the present invention is to provide a lens holding mechanism that does not cause excessive stress to a lens even when a volume change occurs in response to temperature in a wide environment from low temperature to high temperature. is there.

  In view of the above problems, the lens holding mechanism of the present invention has the following configuration.

  The lens holding mechanism of this aspect includes a lens holding frame having a holding hole that accommodates a lens, and the lens holding frame holds the lens in the holding hole via a holding member. In this lens holding mechanism, when the lens has an outer diameter A and a thermal expansion coefficient a, and the thermal expansion coefficient a is smaller than the thermal expansion coefficient b of the lens holding frame, the lens outer diameter A and the thermal expansion coefficient a. Further, the inner diameter B of the holding hole, the thermal expansion coefficient b of the holding member, and the thermal expansion coefficient c of the holding member have a relationship of c = (B · b−A · a) / (B−A).

  The present invention provides a lens holding mechanism that does not cause excessive stress to a lens even when a volume change occurs in response to a temperature in a wide environment from a low temperature to a high temperature.

The lens holding mechanism according to the embodiment of the present invention will be described below.
<First embodiment>
First, the lens holding mechanism according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view showing a lens holding mechanism according to the present embodiment. FIG. 2 is a cross-sectional view showing the lens holding mechanism of FIG.

The lens holding mechanism 1 is a holding unit that holds the lens 2, and includes a lens holding frame 3, a holding member 4, and a pressing ring 5.
The lens holding frame 3 is formed in a cylindrical shape having a holding hole 3 a for accommodating the lens 2 and the holding member 4. The lens holding frame 3 has a central axis Y as shown in FIG. In the present embodiment, the central axis of the holding hole 3a substantially coincides with the central axis Y. The lens holding frame 3 holds the lens 2 disposed in the holding hole 3 a via a plurality of holding members 4. Further, the inner peripheral surface of the holding hole 3a has a flange portion 3b for supporting the lens 2 and the holding member 4 at the central axis Y at one end (right end in FIG. 2) of the central axis Y. The other end portion is formed with a screw portion 3c for screwing the pressing ring 5. The flange portion 3b has a dimension in a direction (thrust direction) perpendicular to the central axis Y so as to be in contact with the lens 2 and the holding member 4.

  Further, the holding hole 3a has a predetermined inner radius B as shown in FIG. 1 and FIG. 1 and 2, the radius of the outer periphery of the lens 2 held by the lens holding mechanism 1 is indicated by the reference symbol A.

  The lens holding frame 3 is configured to have a predetermined thermal expansion coefficient b.

  As shown in FIG. 1, each holding member 4 has one end holding the lens 2 and the other end held by the lens holding frame 3 in the radial direction of the holding hole 3 a (radial direction of the lens 2). Accordingly, these holding members 4 are disposed between the lens 2 and the lens holding frame 3 in the radial direction. Therefore, each holding member 4 has a dimension of (radius B−radius A) in the radial direction.

  In the present embodiment, four holding members 4 are arranged in the holding hole 3a, and these holding members 4 cooperate to hold the lens 2. The lens 2 is held by the lens holding frame 3 via the four holding members 4 so that the optical axis substantially coincides with the central axis of the holding hole 3a. In the present embodiment, by this holding, the optical axis of the lens 2 is arranged so as to substantially coincide with the central axis Y. The holding member 4 is configured to have an expansion coefficient c selected by a selection method described later.

  The holding ring 5 can be screwed into the threaded portion 3c, and the dimension in the thrust direction is set so as to come into contact with the lens 2 and the holding member 4 when screwed. The presser ring 5 sandwiches the lens 2 and the holding member 4 with the flange portion 3b when screwed into the screw portion 3c. That is, the lens 2 and the holding member 4 are held between the holding ring 5 and the flange portion 3b.

  In the lens holding mechanism 1 configured as described above, each member expands or contracts due to a change in environmental temperature. That is, the volume of each member of the lens holding mechanism 1 changes according to the environmental temperature. When the environmental temperature changes in this way, in the radial direction, the distance between the lens 2 after the volume change and the lens holding frame 3 matches the dimension of the holding member 4 after the volume change. On the other hand, it is preferable in terms of achieving prevention of excessive stress and reliable support of the lens 2. When holding the lens 2 having a small expansion coefficient such as a quartz lens, if the expansion coefficient of the lens 2 is a, the expansion coefficient a of the lens 2 is smaller than the thermal expansion coefficient b of the lens holding frame 3. In order to achieve the above effect, the lens holding mechanism 1 of the present embodiment has a radius A of the lens 2 and a thermal expansion coefficient a, a radius B of the holding hole 3a, a thermal expansion coefficient b of the holding member 4, and holding. The thermal expansion coefficient c of the member 4 is configured so as to have the relationship of the following formula 1.

(B−A) c = (B · b−A · a) (Formula 1)
In order to obtain the thermal expansion coefficient c having the relationship of Equation 1, Equation 1 is transformed as Equation 2 below.

c = (B · b−A · a) / (BA) (Expression 2)
Each holding member 4 is made of a material having a coefficient of thermal expansion c that satisfies the relationship of Equation 2.

For example, a quartz lens having a thermal expansion coefficient a of 5.6 × 10 ⁻⁷ / K and a radius A of 10 mm, and an aluminum alloy having a thermal expansion coefficient b of 21.5 × 10 ⁻⁶ / K and a radius B of 13 mm. When the lens holding mechanism 1 is constituted by the holding frame, it is obtained from Equation 2. Thermal expansion coefficient c of the holding member 4 is derived from about 9 × 10 ^-5 / K, a thermal expansion coefficient of approximately 9 × ^{10 -5} / K. 66 nylon resin or polyacetal resin is used. Therefore, when the holding member 4 is formed of these materials, it is configured to have the calculated thermal expansion coefficient.

  With the above configuration, even when the holding member 4 is thermally expanded or contracted, the distance between the lens 2 and the lens holding frame 3 after the volume change can be made to substantially coincide with the dimension in the radial direction. In other words, the holding member 4 can always substantially match the distance between the lens 2 and the lens holding frame 3 in the radial direction before, during and after the volume change. Therefore, the lens holding frame 3 can always reliably hold the lens 2 via the holding member 4 without rattling, and can always prevent the lens 2 from being excessively stressed. Therefore, the lens holding mechanism 1 according to the present embodiment can hold the lens 2 without causing distortion of the lens due to stress, decentering of the lens due to play, and the like. That is, with this configuration, the lens unit having the lens 2 and the lens holding mechanism 1 can be configured to be able to cope with a wide range of environmental temperatures.

  Further, like the plastic lens, the lens 2 may be formed of a material having a relatively large thermal expansion coefficient. In this case, the thermal expansion coefficient a of the lens 2 may be larger than the thermal expansion coefficient b of the lens holding frame 3. Thus, when the thermal expansion coefficient a is larger than the thermal expansion coefficient b, the thermal expansion coefficient c of the holding member 4 is calculated based on the following Expression 3.

c = (A · a−B · b) / (BA) (Expression 3)
By configuring the holding member 4 with a material close to the thermal expansion coefficient c calculated based on Equation 3, the lens holding mechanism 1 according to the present embodiment allows the thermal expansion coefficient a to be greater than the thermal expansion coefficient b. However, it is possible to always hold the lens 2 reliably and to prevent the lens 2 from being excessively stressed.

  Further, as described above, the lens holding mechanism 1 is configured so that the lens 2 is changed by changing the expression for calculating the thermal expansion coefficient c of the holding member 4 in accordance with the relationship between the thermal expansion coefficients of the lens 2 and the lens holding frame 3. In addition, regardless of the material (thermal expansion coefficient) of the lens holding frame 3, the lens 2 can always be reliably held, and excessive stress can be prevented from being applied to the lens 2.

  In the present embodiment, the radii A and B and the thermal expansion coefficients a and b of the lens 2 and the lens holding frame 3 are fixed and the thermal expansion coefficient c of the holding member 4 is selected. It is also possible to fix the thermal expansion coefficient c and select one of the radii A and B and the thermal expansion coefficients a and b of the lens 2 and the lens holding frame 3 so as to satisfy the above-described formula 1. For example, when the expansion coefficient a, the radius A of the lens 2, the radius B of the lens holding frame 3, and the thermal expansion coefficient c of the holding member 4 are fixed, the radius B of the lens holding frame 3 satisfies the relationship of Equation 1. Is calculated as follows. The lens holding mechanism 1 configured as described above can also achieve the above-described effects. In addition, when the lens holding mechanism 1 is configured in this way, it is not necessary to change the thermal expansion coefficients a, b, and c depending on the materials of the lens 2, the lens holding frame 3, and the holding member 4. Therefore, the lens holding mechanism 1 can satisfy the relationship of the above-mentioned formula 1 only by changing the size of the lens holding frame 3 and the size of the holding member 4 correspondingly. Can be reduced. Although the dimensions of the lens 2 can be changed, it is preferable to change the shape of the lens holding frame 3 and the holding member 4 because it is easier to manufacture.

  In addition, since the lens holding mechanism 1 of the present embodiment can fix the lens 2 to the lens holding frame 3 by screwing the holding ring 5, the lens 2 can be easily fixed. In this embodiment, the pressing ring 5 is configured to press the lens 2 and the holding member 4 against the flange portion 3b. However, the lens 2 and the holding member 4 are bonded and fixed to each other to fix the lens 2. It is also possible to press only one of the holding members 4 and hold it by the flange portion 3b. In addition, it is preferable that the holding ring 5 is configured to sandwich only the holding member 4 because the possibility that unnecessary stress is applied to the lens 2 can be reduced. It is also possible to fix the lens 2 and the holding member 4 while omitting the pressing ring 5 by bonding the lens 2 to the holding member 4 and fixing the holding member 4 to the lens holding frame 3. . In this case, since the lens 2 is assembled without applying a force from the holding ring 5, the stress generated in the lens 2 can be further reduced.

<Second embodiment>
Hereinafter, a lens holding mechanism 1 according to a second embodiment of the present invention will be described with reference to FIG. In the lens holding mechanism 1 of the present embodiment, the same components as those of the first embodiment are given the same reference and the description thereof is omitted.

  FIG. 3 is a cross-sectional view showing the lens holding mechanism 1 of the present embodiment. The lens holding mechanism 1 according to the present embodiment is different from the first embodiment in the configuration of the holding member 4 '.

  As shown in FIG. 3, the holding member 4 ′ of the present embodiment has a beam portion 4 a. The beam portion 4a is connected to the beam portion 4a of the adjacent holding member 4 ', and these holding members 4' constitute an integral annular holding ring. The beam portion 4a has a gap between the outer periphery of the lens 2 and the inner periphery of the front holding hole 3a in the radial direction of the holding hole 3a. Due to this gap, the beam portion 4a can be easily deformed by a radial force on the holding member 4 '.

  The lens holding mechanism 1 of the present embodiment has the same function and effect as the first embodiment. Further, the lens holding mechanism of the present embodiment is easier to assemble because the holding member 4 'is integrally formed.

  The beam portion 4a has a gap with respect to the outer periphery of the lens 2 and the inner periphery of the lens holding frame 3, and can be easily deformed by a circumferential force applied from the holding member 4 '. With the above configuration, the holding member 4 ′ and the beam portion 4 a can prevent excessive stress from being applied to the lens 2 due to deformation of the beam portion 4 a even when the volume changes in the circumferential direction.

  In the present embodiment, the holding member 4 ′ including the beam portion 4 a is entirely made of the same material, but the beam portion 4 a is made of another flexible material so that the beam portion 4 a can be more easily deformed. It is also possible to configure with a material. In this case, the beam portion 4a can absorb the stress only by its own elastic deformation, and the gap can be omitted.

<Third embodiment>
The lens holding mechanism 1 according to the third embodiment of the present invention will be described below with reference to FIG. In the lens holding mechanism 1 of the present embodiment, the same components as those of the second embodiment are denoted by the same reference and description thereof is omitted.

The holding member 4 ″ includes a lens facing portion 4B that faces the lens 2, a holding hole facing portion 4C that faces the inner peripheral surface of the holding hole 3a, and a holding member body 4D in the radial direction of the holding hole 3a. ing.
This lens facing portion 4B has two lens contact portions 4Ba and a first gap 4Bb. Each lens contact portion 4Ba protrudes inward in the radial direction of the holding hole 3a from the holding member main body 4D and is in contact with the lens 2. In the present embodiment, the lens contact portions 4Ba are arranged at both ends of the holding member main body 4D in the circumferential direction of the holding hole 3a. The first gap 4Bb is a gap between the inner peripheral surface of the holding hole 3a and the main body of the holding member 4 ″ in the radial direction. In the present embodiment, the first gap 4Bb is the circumference of the holding hole 3a. In the direction, it is disposed between the two lens contact portions 4Ba.

  The holding hole facing portion 4C has a holding hole contact portion 4Ca and two second gaps 4Cb. The holding hole abutting portion 4Ca protrudes from the main body of the holding member 4 ″ outward in the radial direction of the holding hole 3a, and is in contact with the inner peripheral surface of the holding hole 3a. 4Ca is disposed at a position facing the first gap 4Bb in the radial direction, in other words, the holding hole contact portion 4Ca is disposed so as not to face the lens contact portion 4Ba in the radial direction. Is set.

  The second gap 4Cb is a gap between the inner peripheral surface of the holding hole 3a and the main body of the holding member 4 ″ in the radial direction. In the present embodiment, the first gap 4Bb is the circumference of the holding hole 3a. The two second gaps 4Cb are arranged at positions facing the lens contact portion 4Ba in the radial direction, respectively, in this direction. In the embodiment, each second gap 4Cb has a region in which at least a portion thereof overlaps with the first gap 4Bb in the circumferential direction. It has the area which counters in the direction.

  With the above configuration, the holding member 4 ″ can be elastically deformed in the radial direction by the first and second gaps 4Bb and 4Cb when receiving the radial force. The force is absorbed by the first and second gaps 4Bb and 4Cb, and an excessive stress can be prevented from being applied to the lens 2. As in the first embodiment, the thermal expansion coefficient c of the holding member 4 ″ is set to satisfy Expression 1. However, the thermal expansion coefficient c of the holding member 4 ″ is obtained by Expression 1. It may be difficult to select a material having a coefficient of thermal expansion that perfectly matches the ideal value. In this case, the holding member 4 ″ is formed of a material having an expansion coefficient that is an approximate value calculated by Equation 1. In this case, the amount of change in the radial direction of the gap between the lens 2 and the lens holding frame 3 is determined. And the amount of change in the radial direction of the holding member 4 ″ may not match. However, since the holding member 4 ″ of the present embodiment can be deformed in the radial direction by the first and second gaps 4Bb and 4Cb, it absorbs the difference in the deformation amount due to the error of the expansion coefficient. Thus, it is possible to prevent an excessive stress from being applied to the lens 2. With this configuration, the lens holding mechanism 1 of the present embodiment can more freely select the material of the holding member 4 ″.

  In the present embodiment, the first and second gaps 4Bb and 4Cb have portions that overlap each other in the circumferential direction. With this configuration, the holding member main body 4D serves as a beam connecting the lens contact portion 4Ba and the holding hole contact portion 4Ca. With this configuration, when the holding member 4 ″ receives the force in the radial direction, the holding member 4 ″ is elastically deformed in the direction of the second gap 4Cb so as to bend using the lens contact portion 4Ba as a fulcrum. The member 4 ″ can more reliably absorb the force applied in the radial direction and prevent the lens 2 from being excessively stressed.

  In each holding member 4 ″, the configuration of the lens facing portion 4B and the holding hole facing portion 4C is reversed, with two first gaps 4Bb, one lens contact portion 4Ba, and one second gap 4Cb. It is possible to have two locations and the holding hole contact portions 4Ca, and there is no limitation on the number of these components. In the present embodiment, each holding member 4 ″ is a beam portion. Although they are connected to each other by 4a, they can be arranged independently as in the first embodiment.

FIG. 1 is a longitudinal sectional view showing the lens holding mechanism of the first embodiment. FIG. 2 is a cross-sectional view showing the lens holding mechanism of the first embodiment. FIG. 3 is a longitudinal sectional view showing the lens holding mechanism of the second embodiment. FIG. 4 is a longitudinal sectional view showing the lens holding mechanism of the third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lens holding mechanism, 2 ... Lens, 3 ... Lens holding frame, 3a ... Holding hole, 3b ... Flange part, 3c ... Screw part, 4, 4 ', 4 "... Holding member, 4a ... Beam part, 4Ba ... Lens Contact part, 4Bb ... gap, 4C ... holding hole facing part, 4Ca ... holding hole contact part, 4Cb ... gap, 4D ... holding member body, 5 ... pressing ring.

Claims (7)

A lens holding frame having a holding hole for receiving a lens, wherein the lens holding frame holds a lens in the holding hole via a holding member;
When the lens has a radius A and a thermal expansion coefficient a, and the thermal expansion coefficient a is smaller than the thermal expansion coefficient b of the lens holding frame, the radius A of the lens, the thermal expansion coefficient a, and the holding hole The radius B, the thermal expansion coefficient b of the holding member, and the thermal expansion coefficient c of the holding member are:
c = (B · b−A · a) / (B−A)
A lens holding mechanism having the following relationship.   2. A pressing ring that is screwed into the lens holding frame is further provided, and the lens and the holding member disposed in the holding hole are clamped by the lens holding frame and the pressing ring. The lens holding mechanism described in 1.   The lens holding mechanism according to claim 1, wherein the holding member is bonded and fixed to the lens.   The lens holding mechanism according to claim 1, wherein the holding member is bonded and fixed to the lens holding frame.   The plurality of holding members are arranged between the lens and the holding hole along the circumferential direction of the holding hole, and the plurality of holding members have beam portions for connecting to adjacent holding members. Are connected to each other by the beam portion to form an annular holding ring, and the beam portion is located between the outer periphery of the lens and the inside of the holding hole in the radial direction of the holding hole. The lens holding mechanism according to any one of claims 1 to 4, wherein a gap is provided between the lens and the periphery. The holding member has, in the radial direction of the holding hole, a lens facing portion that faces the lens, and a holding hole facing portion that faces an inner peripheral surface of the holding hole,
The lens facing portion has at least one lens contact portion that contacts the lens, and at least one first gap spaced from the lens in the radial direction of the holding hole,
The holding hole facing portion includes at least one holding hole contact portion that contacts the inner peripheral surface of the holding hole, and at least one second gap spaced apart from the inner peripheral surface of the holding hole in the radial direction. And
6. The lens holding mechanism according to claim 1, wherein each holding hole contact portion is disposed at a position that does not coincide with the lens contact portion in the circumferential direction of the holding hole. A lens,
A holding mechanism for holding the lens;
A lens unit comprising:
The lens holding mechanism has a lens holding frame having a holding hole for accommodating the lens, and the lens holding frame holds the lens via a holding member in the holding hole,
When the lens has a radius A and a thermal expansion coefficient a, and the thermal expansion coefficient a is smaller than the thermal expansion coefficient b of the lens holding frame, the lens radius A, the thermal expansion coefficient a, and the holding hole radius B, the thermal expansion coefficient b of the holding member, and the thermal expansion coefficient c of the holding member are:
c = (B · b−A · a) / (B−A)
A lens unit having the relationship

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