JP2012173366A - Lens holding structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens holding structure capable of holding a lens without damaging the surface of a lens.SOLUTION: A lens holding structure holds a lens by putting the outer peripheral region of a lens into a lens support frame having an opening that can dispose the lens having a curved surface inside thereof. A pressing ring is provided for supporting the lens by being made to engaged with the lens support frame and made to contact with the outer periphery area of a lens face. The pressing ring includes a lens contact surface having an inclined shape in conformity with the shape of the surface of the lens face outer periphery area of the lens. The lens is held by making the pressing ring engaged with the lens support frame under the condition in which the lens contact surface of the pressing ring is made to contact with the outer periphery of the lens.

Description

  The present invention relates to a lens holding mechanism that holds a lens in a frame body such as a lens barrel.

  As shown in FIG. 5, the lens used in the imaging apparatus has a plurality of lenses 101 and 102 fitted in a frame body 100 such as a lens barrel, and uses a pressing ring 103 that is an elastic material such as a leaf spring or an annular frame body. A method of sealing the lenses 101 and 102 by pressing them in a predetermined direction is employed.

  For example, Patent Document 1 discloses a lens barrel in which a plurality of lens groups are provided inside a lens support frame that is a cylindrical member and integrally includes a radially inward inner flange. In the lens barrel of Patent Document 1, the outer peripheral edge of the first group lens is in contact with the front surface (subject side) of the inner flange, and an annular member that is concentric with the first group lens immediately before the first group lens. It is disclosed that a male screw formed on the outer peripheral surface of the pressing ring is fused with a female screw formed on the inner peripheral surface of the lens support frame using a certain pressing ring.

  By the way, an infrared camera is used in applications such as a security camera, a disaster prevention camera, and a vehicle-mounted camera. Since lenses for infrared cameras are made of germanium or silicon capable of transmitting infrared light, the hardness thereof is lower than that of lenses made of optical glass or the like used in the visible light region. Therefore, in the conventional lens barrel as disclosed in Patent Document 1 and the like, the corner of the inner peripheral end of the pressing ring comes into contact with the R surface of the lens, and when the R surface of the lens is pressed with the pressing ring in this state, Damage to the abutting portion affects the performance of the lens.

  Therefore, in Patent Document 2, in order to prevent the lens contact portion from being crushed even when the lens is pressed against the lens contact portion, the lens support frame is formed as a ring-shaped conical surface including a tangent to the curved surface of the lens. A technique is disclosed in which the lens abutting portion is configured so that the lens abutting portion abuts on the outer peripheral surface of the lens.

  In the imaging device disclosed in Patent Document 3, the first lens is disposed on the subject side of the lens barrel, and the lens is pressed and sealed in a substantially optical axis direction by a screw-type pressing member that is fitted to the outer peripheral portion of the lens barrel. In the lens assembly, a configuration is disclosed in which an O-ring is disposed in the gap between the first lens and the pressing member or in the gap between the pressing member and the lens barrel. In Patent Document 3, by adopting such a configuration, in addition to effects such as prevention of change in lens position and waterproofing in the environment where the imaging apparatus is used, such as water immersion, temperature, vibration, etc., the inner wall surface of the holding member and the lens barrel It is disclosed that contact with a large frictional force can be avoided between the front end portion of each of the two.

JP 2010-186157 A JP-A-6-317734 JP 2005-17951 A

  In the technique disclosed in Patent Document 2, since the lens support frame is provided with a ring-shaped conical surface of the lens abutting portion, the lens that abuts on the lens supports the support frame so as to be along the ring-shaped conical surface. It is easy to tilt and it is difficult to align the lens when attaching the lens to the lens support frame.

  In addition, since the lens assembly disclosed in Patent Document 3 is configured to avoid contact with the pressing member and the lens surface via the O-ring with frictional force, there is a slight shift in the position of the first lens in the optical axis direction. As a result, the imaging performance is likely to be affected. In addition, replacement is required when the O-ring deteriorates due to use.

  Therefore, an object of the present invention is to provide a lens holding structure that can hold a lens without damaging the lens surface.

  As a result of intensive studies, the present inventors have achieved the above-mentioned problem by employing the following lens holding structure.

  The lens holding structure according to the present invention is a lens holding structure for holding the lens by fitting the outer periphery of the lens to a lens support frame having an opening on which a lens having a curved surface can be arranged inside, and is associated with the lens support frame. A holding ring that supports the lens by contacting the outer peripheral area of the lens surface, and the holding ring includes a lens contacting surface that is inclined according to the surface shape of the outer peripheral area of the lens surface of the lens. The lens is held by engaging the pressing ring with the lens support frame in a state where the lens contact surface of the pressing ring is in contact with the outer peripheral portion of the lens.

  In the lens holding structure according to the present invention, it is more preferable that the lens contact surface of the pressing ring has a shape inclined at an angle substantially equal to a tangent to the curved surface of the lens.

  In the lens holding structure according to the present invention, it is also preferable that the lens contact surface of the pressing ring has a curved and inclined shape in accordance with the shape of the outer peripheral region of the lens surface.

  In the lens holding structure according to the present invention, it is more preferable that a tolerance between the curved surface of the lens and the lens contact surface of the pressing ring is within ± 2%.

  In the lens holding structure according to the present invention, it is more preferable that a clearance is provided between the press ring and the lens surface on the inner side of the inner end of the lens contact surface.

  In the lens holding structure according to the present invention, more preferably, a protective member is disposed between the pressing ring and the lens.

  In the lens holding structure according to the present invention, more preferably, the lens is a lens used for an infrared camera.

  In the lens holding structure according to the present invention, it is preferable that the lens is a spherical lens or an aspheric lens.

  The lens holding structure according to the present invention is provided with a lens abutting surface having a shape that is inclined in accordance with the shape of the outer peripheral area of the lens surface having a curved surface, on the holding ring that engages with the lens holding frame, Since the lens is supported by contacting the outer peripheral area of the lens, the optical axis is aligned by placing the lens on the lens support frame, and the holding ring is engaged with the lens support frame while maintaining this state. It is easy to align the optical axis of the lens at a desired position, and the lens can be held at a preferred position. Further, it is possible to prevent the surface of the lens from being scratched or chipped when the pressing ring is attached to the lens support frame. In particular, it can be suitably used when an infrared camera lens is used as the lens.

It is a fragmentary sectional view showing a 1st embodiment of a lens holding structure concerning the present invention. It is sectional drawing of the contact part of the lens surface of FIG. 1, and the lens contact surface of a pressing ring. It is a fragmentary sectional view which shows 2nd Embodiment of the lens holding structure which concerns on this invention. It is a fragmentary sectional view showing the example which provided the protection member in the lens holding structure concerning the present invention. It is sectional drawing which shows the conventional lens holding structure.

  A preferred embodiment of the lens holding structure according to the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment, which is an example in which the lens holding structure according to the present invention is used to fix a lens to a lens barrel, and is a cross-sectional view showing a part of the lens barrel on the subject side It is.

  In the lens holding structure 1 according to the present invention, an outer peripheral portion 21 of the lens 2 is fitted to an inner periphery of the lens support frame 3 in a lens support frame 3 having an opening in which the lens 2 can be disposed. The holding ring 4 that can be engaged with the inner periphery of the opening is brought into contact with the lens surface 21 to hold the lens 2 in a predetermined position. In the lens holding structure 1 according to the present invention, the holding ring 4 is provided with a lens contact surface 41 having a shape inclined in accordance with the surface shape of the outer peripheral region of the lens surface of the lens 2, and the lens contact surface 41 is provided. The lens 2 is held by engaging the holding ring 4 with the lens support frame 3 in a state where the lens 2 is in contact with the outer periphery of the lens surface.

  The lens holding structure 1 according to the present invention is effective when holding a lens having a curved surface. The lens having a curved surface is a spherical lens or aspherical lens such as a biconvex lens, a plano-convex lens, or a meniscus lens. The lens 2 can be applied to a lens for an infrared camera in addition to a lens for a visible light region. It is particularly suitable for supporting a lens for an infrared camera used in the mid-infrared or far-infrared band. Infrared camera Lenses for infrared cameras may be made of germanium, silicon, chalcogenite, zinc sulfite (ZnS), and zinc selenium. This infrared camera lens is a lens capable of imaging infrared light, but has low hardness and is easily physically damaged. Therefore, by adopting the lens holding structure 1 according to the present invention, it is possible to stably hold the lens for the infrared camera.

  The lens support frame 3 is substantially cylindrical and constitutes a lens barrel. On the inner periphery of the lens support frame 3, a step 31 for reducing the inner peripheral diameter of the lens support frame 3 is provided at a predetermined position where the lens is fitted, and the step 31 and the outer peripheral end 23 of the lens 2 are connected. The lens 2 is fitted into the lens support frame 3 in contact. At this time, the fitted lens 2 is likely to be displaced in the optical axis direction and is not stable. Therefore, it is necessary to press the outer peripheral ends of both surfaces of the lens 2 in the optical axis direction. Therefore, a step 32 may be further provided, or the pressing ring 4 may be used. The lens holding structure 1 according to the present invention has a configuration in which the pressing ring 4 is used on at least one surface side of the lens 2, and can also be used when the pressing rings are arranged on both sides of a lens having curved surfaces on both sides. .

  The holding ring 4 is a substantially annular member that can be engaged with the lens support frame 3. In the present embodiment shown in FIG. 1, the presser ring 4 is screwed by screw threads 34 and 42 formed on the outer peripheral surface of the base 44 of the presser ring 4 and the inner periphery of the lens support frame 3, respectively. The presser ring 4 is engaged with the support frame 3 by pushing in the optical axis direction L from the outside. The method of engaging the holding ring 4 and the lens support frame 3 in the lens holding structure 1 according to the present invention is not limited to the method of screwing the screw thread. Further, the configuration is not limited to the configuration in which the outer periphery of the presser ring 4 is engaged with the inner periphery of the lens support frame 4, and the outer peripheral surface of the lens support frame 4 may be provided with an engaging portion with the presser ring 4.

  Furthermore, the holding ring 4 has a base portion 44 that engages with the lens support frame 3, and a pressing portion 43 that has a smaller inner peripheral diameter than the base portion 44 and presses the lens 2 toward the optical axis direction L. As shown in FIG. 1, the thickness in the radial direction of the holding ring 4 is such that the base portion 44 has a larger inner peripheral diameter than the pressing portion 43 so as not to disturb the incident light to the lens 2. To do.

  As shown in FIG. 2, the pressing portion 43 of the pressing ring 4 has a lens contact surface 41 that contacts the lens surface 22. The lens contact surface 41 has a shape inclined according to the surface shape of the outer peripheral region of the lens surface of the lens, and the circumference of the inner peripheral side end 41 b of the lens contact surface 41 is larger than the outer periphery of the lens 2. It is smaller and larger than the outer periphery of the effective surface of the lens 2.

  In order to smoothly press the pressing ring 4 in the direction of the lens 2 with respect to the lens support frame 3, the pressing ring 4 is often pressed while being rotated. Therefore, the press ring 4 is rotated in a state in which the lens 2 and the lens contact surface 41 of the press ring 4 are in contact with each other, and friction generated between the lens surface 22 and the lens contact surface 41 is caused on the lens surface 22. Cause damage. Accordingly, in the lens holding structure 1 according to the present invention, the lens surface 22 and the lens contact surface 41 are formed by using the lens contact surface 41 having a shape that is inclined in accordance with the surface shape of the outer peripheral region of the lens surface of the lens 2. Can be prevented from becoming point contact, and the lens surface 22 can be prevented from being scratched.

  If the lens contact surface 41 of the press ring 4 is inclined at an angle substantially equal to the tangent to the curved surface of the lens 2, the surface of the lens 2 can be stably supported by the press ring 4. That is, the lens contact surface 41 of the presser ring 4 is inclined in a taper shape from the outer peripheral side end portion 41 a toward the inner peripheral side end portion 41 b, and this inclined surface has an angle substantially equal to the tangent to the curved surface of the lens 2. . When the aspherical lens is held, the lens contact surface 41 of the presser ring 4 is an inclined surface having an angle substantially equal to the tangent to the curved surface of the aspherical lens at the contact position with the lens contact surface 41 of the presser ring 4. And

  Further, the lens contact surface 41 may be curved and inclined in accordance with the curved shape of the outer peripheral region of the lens surface 22. In this case, since the holding ring 4 is an annular member, the lens contact surface 41 is inclined in an annular shape from the outer peripheral side end 41a toward the inner peripheral side end 41b while curving in a bowl shape and having a small opening diameter. It becomes the shape.

  Further, when the tolerance between the curved surface of the lens 2 (lens surface 22) and the lens contact surface 41 of the pressing ring 4 is within ± 2%, the lens 2 can be prevented from being displaced and stably held. . When the tolerance exceeds ± 2%, an excessive gap is generated between the lens contact surface 41 and the lens surface 22, and the lens contact surface when the presser ring 4 is rotated and fitted to the lens support frame 3. Since the contact surface between 41 and the lens surface 22 rattles and the frictional force concentrates in one place, there is a high possibility that the lens surface 22 will be damaged. Further, the optical axis of the lens 2 may be shifted, which is not preferable.

  The lens contact surface 41 is inclined according to the surface shape of the lens 2, but may be any shape that is inclined at least according to the surface shape of the lens 2 at a position where the lens contact surface 41 contacts the lens contact surface 41. For example, in the present embodiment, an example of the lens 2 in which the curved surface from the lens surface 22 to the outer peripheral end has an arc shape with one point as a virtual center is shown. In the case of a lens that does not have an arc shape centered on one point, the lens may be inclined in accordance with the shape of the lens surface 22 at a position where the lens abutment surface 41 abuts.

  Further, as shown in FIG. 2, by providing a clearance S <b> 1 between the outer peripheral side end portion 41 a of the lens contact surface 41 of the pressing ring 4 and the outer peripheral end portion 22 a of the lens surface 22, The force acting toward 2 prevents the outer peripheral end 22a of the lens 2 from being chipped. As a method of providing the clearance S1, any one or both of the outer peripheral end portion 22a of the lens surface 22 and the pressing portion 43 of the pressing ring 4 may be chamfered.

  The material constituting the presser ring 4 is such that at least the lens contact surface 41 is made of a metal such as aluminum or brass, or a plastic such as polycarbonate or polybutylene terephthalate. It is preferable because scratches are unlikely to occur on the lens surface 22 due to friction between them. In particular, in the case where the lens 2 is a lens for an infrared camera such as germanium, silicon, chalcogenite, zinc sulfite (ZnS), zinc selenium, etc., the lens is fragile and easily damaged. By forming with the said material, generation | occurrence | production of the damage | wound of the lens 2 can be suppressed.

  Next, FIG. 3 is a partial cross-sectional view showing a contact portion between the holding ring 4 and the lens surface 22 according to the second embodiment of the lens holding structure 1 according to the present invention. As described above, when the presser ring 4 is rotated and fitted to the inner periphery of the lens support frame 3, friction is generated between the lens surface 22 and the lens contact surface 41. It is preferable to keep it to the minimum necessary. On the other hand, when it is desired to take a large area for restricting the incident range of light to the lens 2 by the press ring 4, as shown in FIG. A configuration in which a clearance S2 is provided between the pressing ring 4 and the lens surface 22 on the inner side of the inner peripheral side end portion 41b may be adopted. As described above, when the clearance S <b> 2 is provided, it is possible to prevent the vicinity of the effective surface of the lens surface 22 from being damaged by the force acting from the pressing ring 4 toward the lens 2.

  Further, the lens holding structure according to the present invention may have a configuration in which a protective member 6 is disposed between the pressing ring 4 and the lens 2 as shown in FIGS. 3 and 4. As described above, the protective member 6 is disposed between the pressing ring 4 and the lens 2, thereby causing the contact between the lens contact surface 41 of the pressing ring 4 and the lens surface 22 when the pressing ring 4 is attached. Damage to the lens surface 22 can be prevented. Specifically, the protection member 6 may be disposed between at least a part of the lens contact surface 41 and the lens surface 22. The protective member may be a shock absorbing member such as urethane, elastomer, sorbo (registered trademark), or O-ring, with a thickness of 0.1 mm to 1.5 mm. When the protective member 6 is disposed, the pressing ring 4 and the lens 2 do not directly rub, so that the material constituting the pressing ring 4 is not restricted from the viewpoint of preventing wear of the lens 2 and a wide range of options. On the other hand, when the protection member 6 is not used, the presser ring 4 can be prevented from being scratched or chipped on the surface of the lens 2 by using a material made of a material having some elasticity such as plastic. preferable. In the present embodiment, a germanium lens is used as the lens 2, and the press ring 4 is made of aluminum. In the present embodiment, the protective member 6 is a sorbo sheet manufactured by Sanshin Kosan Co., Ltd. having a thickness of 0.5 mm and has a ring shape smaller than the area of the lens contact surface 41.

  Since the lens holding structure according to the present invention can stably hold a lens having a curved surface while preventing damage to the lens surface, it can be suitably used for a lens holding structure for an infrared camera. In addition, since the lens holding structure according to the present invention has a simple configuration and can stably hold a lens having a curved surface, it can be mass-produced when employed as a lens holding structure for an imaging device in the visible light range. It is possible to contribute to the provision of an imaging device that is excellent in.

DESCRIPTION OF SYMBOLS 1 ... Lens holding structure 2 ... Lens 3 ... Lens support frame 4 ... Holding ring 6 ... Protection member 21 ... Outer peripheral part 22 ... Lens surface 41 ... Lens contact Surface 42 ... inner peripheral side end

Claims (8)

A lens holding structure for holding the lens by fitting the outer periphery of the lens to a lens support frame having an opening on which a lens having a curved surface can be arranged,
Engage with the lens support frame, and have a pressing ring that supports the lens by contacting the outer peripheral area of the lens surface,
The press ring includes a lens contact surface having a shape inclined according to the surface shape of the lens surface outer peripheral region of the lens,
A lens holding structure for holding a lens by engaging the holding ring with a lens support frame in a state where the lens contact surface of the holding ring is in contact with the outer peripheral portion of the lens. The lens holding structure according to claim 1, wherein the lens contact surface of the pressing ring is inclined at an angle substantially equal to a tangent to the curved surface of the lens. The lens holding structure according to claim 1, wherein the lens contact surface of the pressing ring has a curved and inclined shape in accordance with the shape of the outer peripheral region of the lens surface. The lens holding structure according to any one of claims 1 to 3, wherein a tolerance between the curved surface of the lens and a lens contact surface of the pressing ring is within ± 2%. The lens holding structure according to any one of claims 1 to 4, wherein a clearance is provided between the pressing ring and the lens surface on the inner side of the inner peripheral side end portion of the lens contact surface. The lens holding structure according to any one of claims 1 to 5, wherein a protective member is disposed between the pressing ring and the lens. The lens holding structure according to claim 1, wherein the lens is a lens used for an infrared camera. The lens holding structure according to any one of claims 1 to 7, wherein the lens is a spherical lens or an aspheric lens.

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