JP2012118404A - Lens barrel and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of an image by changing a distance between a resin lens and an imaging element in response to the change in a focal length of the resin lens due to the change in the environmental temperature without providing a complicated mechanism.SOLUTION: On the image side of a lens unit 120 made of a material having a first linear expansion coefficient, a mounting reference surface 120a which extends in a direction perpendicular to an optical axis 111 of a lens group 110 is formed. A plurality of boss parts 123 are projected from the mounting reference surface 120a toward the image side in parallel to the optical axis 111. An extension part 131 which extends in parallel to the optical axis 111 is provided on an imaging element holding frame 130 made of a material having a second linear expansion coefficient. Mounting stators 132 provided on the side face of the extension part 131 are externally fitted to the boss parts 123 of the lens unit 120 from the image side, and screw members 150 are screwed to female screws 123a of the boss parts 123 through disc springs 140.

Description

  The present invention relates to a lens barrel that avoids degradation of an image caused by a change in the focal length of a resin lens caused by a change in environmental temperature, and an imaging apparatus including the lens barrel.

  In an image pickup apparatus equipped with an image pickup device, since the image pickup device is generally attached to a lens barrel directly or via a substrate, the positional relationship between the lens and the image pickup device remains unchanged. In recent years, since processing is easy, it is excellent in cost reduction and lightweight, so resin lenses are increasingly used in imaging devices. This resin lens is more susceptible to changes in environmental temperature than a glass lens. That is, the resin lens has a property that the refractive index changes due to a change in environmental temperature and the focal length changes. Even if the amount of change in the focal length of a single lens is small, the imaging device usually includes a lens group composed of a plurality of lenses. Changes, the amount of change in the focal length of each lens group constituting the lens group cannot be ignored. Since the change in the focal length of the lens causes image deterioration, it is difficult to ensure a wide operating temperature range of the image pickup apparatus on which the resin lens is mounted.

  In order to solve such a problem, the distance between the lens and the image sensor may be changed in response to a change in the focal length of the lens due to a change in environmental temperature. However, changing the distance between the lens and the image sensor by providing a mechanism such as a cam in the lens barrel not only increases the manufacturing cost due to the complexity of the lens barrel mechanism, but also increases the weight of the lens barrel. It is not preferable because it goes forward. Although it is ideal to adopt a technique for changing the distance between the lens and the image pickup element without adding a complicated mechanism to the lens barrel, there is no technique that employs such a technique in the lens barrel at present. A technique for avoiding blurring of an image caused by a change in the focal length of a lens in a projection display device instead of a lens barrel has been proposed (see, for example, Patent Document 1).

JP 2005-55801 A

  The technique described in Patent Document 1 uses a correction member formed of a material having a predetermined thermal expansion coefficient, and even if the back focus value of the projection lens changes due to a change in environmental temperature, the projection is performed according to the change. This is a projection type display device that avoids blurring of the projected image by arranging a light valve near the back focus position of the lens. As described above, the technique disclosed in Patent Document 1 avoids blurring of an image caused by a change in the focal length of a resin lens only in a projection display device. Therefore, with this technique, in a lens barrel mounted on an imaging device such as a digital camera, it is possible to change the distance between the lens and the imaging element in response to a change in the focal length of the resin lens due to a change in the environmental temperature. It was not possible to avoid image quality degradation.

  In order to eliminate the above-described problems caused by the conventional technology, the present invention provides a resin lens, an image sensor, and an imaging device in response to a change in the focal length of the resin lens caused by a change in the environmental temperature without providing a complicated mechanism. It is an object of the present invention to provide a lens barrel that can change the distance of the lens and avoid image degradation. It is also an object of the present invention to provide an imaging device provided with such a lens barrel.

  In order to solve the above-described problems and achieve the object, a lens barrel according to the present invention is formed of a lens group including at least one resin lens and a material having a first linear expansion coefficient. A lens unit that holds the lens group; and an imaging element holding frame that holds the imaging element and is made of a material having a second linear expansion coefficient larger than the first linear expansion coefficient. On the image side, an attachment reference surface is formed as a reference for attaching the image sensor holding frame in a direction extending perpendicularly to the optical axis of the lens group, and further, the attachment is parallel to the optical axis. A boss portion is provided so as to protrude from the reference surface to the image side, the imaging element holding frame is provided with an extending portion extending in parallel to the optical axis, and the side surface of the extending portion is further Front from image side parallel to optical axis A sleeve-shaped mounting stator for externally fitting the boss portion to attach the image sensor holding frame to the lens unit is provided. The mounting stator is externally fitted to the boss portion, and further via an urging member. By screwing the screw member into the boss portion, the object side end of the image sensor holding frame is urged to come into contact with the attachment reference surface, and the change of the environmental temperature causes the attachment reference surface as a reference. The extending portion extends and contracts in a direction parallel to the optical axis.

The lens barrel according to the present invention satisfies the following conditional expression.
(Α2−α1) × ΔT × L = Δf
Where α1 is the linear expansion coefficient of the material forming the lens unit, α2 is the linear expansion coefficient of the material forming the image sensor holding frame, ΔT is the amount of change in environmental temperature, and L is the extension of the image sensor holding frame. The length of the portion in the direction parallel to the optical axis, Δf, indicates the amount of change in the focal length of the lens group when the amount of change in environmental temperature ΔT.

  Further, in the lens barrel according to the present invention, the extending portion has a hollow rectangular parallelepiped shape surrounding the four side surfaces of the image pickup device, and the substrate on which the image pickup device is attached is connected to the image side of the extending portion. The image pickup device is shielded by being attached to the end portion.

  Further, in the lens barrel according to the present invention, a convex portion having an opening at the tip is formed in the vicinity of the boss portion so as to protrude from the attachment reference plane to the image side in parallel to the optical axis A flange extending in a direction perpendicular to the optical axis from the image side end of the mounting stator is formed along the side surface of the extending portion, and the object side surface of the flange is parallel to the optical axis. A protrusion projecting toward the object side, and the protrusion is fitted into the opening to position the image sensor holding frame in a direction perpendicular to the optical axis. .

  In the lens barrel according to the present invention, the height of the convex portion is lower than the height of the boss portion, the height of the protruding portion is lower than the height of the mounting stator, and the opening portion. In the state in which the protrusion is fitted to the flange, a gap is generated between the tip of the convex portion and the object side surface of the flange, and the extension portion does not hinder expansion and contraction in a direction parallel to the optical axis. It is characterized by that.

  An imaging apparatus according to the present invention includes the lens barrel.

  According to the present invention, without providing a complicated mechanism, the distance between the resin lens and the image sensor is changed in response to the change in the focal length of the resin lens due to the change in the environmental temperature, and the image is deteriorated. There is an effect that it is possible to provide a lens barrel that can be avoided. In addition, it is possible to provide an imaging apparatus including such a lens barrel.

It is sectional drawing which follows the optical axis which shows the structure of the lens-barrel concerning embodiment of this invention. FIG. 6 is a perspective view showing a state where an image sensor 160 is attached to a substrate 170. FIG. 6 is a diagram for explaining an assembly procedure of the lens barrel 100. FIG. 6 is a diagram for explaining an assembly procedure of the lens barrel 100. 3 is an external view of an image sensor holding frame 130. FIG. It is sectional drawing which follows the BB line of FIG. It is sectional drawing which follows the CC line of FIG. It is an enlarged view of the A section shown in FIG. It is a figure for demonstrating the change of the focal distance of the lens group 110 by the change of environmental temperature.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view along the optical axis showing the configuration of a lens barrel according to an embodiment of the present invention. FIG. 1 shows a cross section taken along the line DD of FIG. 4 to be described later. A lens barrel 100 according to this embodiment includes a lens group 110, a lens unit 120 formed of a material having a first linear expansion coefficient, and an image sensor holding frame formed of a material having a second linear expansion coefficient. 130. Note that the second linear expansion coefficient is larger than the first linear expansion coefficient.

  The lens group 110 includes at least one resin lens. The lens unit 120 is configured in a cylindrical shape, and a lens frame 121 that holds the lens group 110 from the object (not shown) side to the image side is provided therein. Further, on the image side of the lens unit 120, an attachment reference surface 120a for attaching the image sensor holding frame 130 extending in a direction perpendicular to the optical axis 111 of the lens group 110 is formed. Further, a plurality (three or more) of bosses 123 projecting toward the image side in parallel with the optical axis 111 from the attachment reference surface 120a are provided. The boss portion 123 has a sleeve shape, and a female screw 123a is formed inside the sleeve.

  The image sensor holding frame 130 is provided with an extending portion 131 that extends in parallel to the optical axis 111. A plurality of sleeve-shaped mounting stators 132 (the same number as the boss portions 123) are provided on the side surface of the extending portion 131 so as to extend parallel to the optical axis 111. The attachment stator 132 is for attaching the image sensor holding frame 130 to the lens unit 120 by fitting the boss portion 123 from the image side. In addition, female screws 131a for attaching a substrate to be described later are formed at diagonal positions inside the extending portion 131. The boss portion 123 is externally fitted to the mounting stator 132 and is further screwed by a screw member 150 via a disc spring 140. The image sensor 160 is attached to the substrate 170. And the board | substrate 170 is attached to the extension part 131 with the screw member 150 through the screw hole 170a each formed in the diagonal position.

  Next, the assembly procedure of the lens barrel according to this embodiment will be described in detail. FIG. 2 is a perspective view showing a state in which the image sensor 160 is attached to the substrate 170. FIGS. 3A and 3B are diagrams for explaining the assembly procedure of the lens barrel 100. FIGS. 3A and 3B are views of the lens barrel 100 viewed from the image side to the object side, but FIG. 3A is a state viewed from the upper side of the optical axis 111 shown in FIG. FIG. 3-2 shows a state viewed from below the optical axis 111. Further, members on the object side from the mounting reference surface 120a of the lens unit 120 are omitted.

  First, as shown in FIG. 2, the image sensor 160 is attached to the central portion of the substrate 170. Screw holes 170 a are formed at diagonal positions of the substrate 170. Next, as shown in FIGS. 3A and 3B, the mounting reference surface 120a of the lens unit 120 is provided with three boss portions 123 protruding toward the image side in parallel to the optical axis 111. It has been. The boss portion 123 has a sleeve shape, and a female screw 123a is formed inside the sleeve. In addition, a convex portion 124 for positioning in the direction perpendicular to the optical axis 111 of the image sensor holding frame 130 is formed in the vicinity of the two boss portions 123. The height of the convex portion 124 is lower than the height of the boss portion 123. An opening 124 a is formed at the tip of the convex portion 124.

  The image sensor holding frame 130 is provided with an extending portion 131 that extends in parallel to the optical axis 111. The extending portion 131 is provided so as to surround the four side surfaces of the image sensor 160 and has a hollow rectangular parallelepiped shape. On the side surface of the extended portion 131, sleeve-shaped mounting stators 132 extending in parallel to the optical axis 111 are provided at three locations. Further, a flange 133 is formed in a direction perpendicular to the optical axis 111 along the side surface of the extending portion 131 from the image side end portions of the two mounting stators 132. A protrusion 133 a that protrudes toward the object side in parallel to the optical axis 111 is provided on the object side surface of the flange 133. The height of the protrusion 133a is lower than the height of the mounting stator 132. In addition, female screws 131a for attaching the substrate 170 are formed at diagonal positions inside the extending portion 131, respectively.

  When the lens barrel 100 is assembled, first, the mounting stator 132 of the image sensor holding frame 130 is externally fitted from the image side to the boss portion 123 of the lens unit 120 in which the lens group 110 is accommodated. At this time, the protrusion 133a provided on the flange 133 is also fitted into the opening 124a of the projection 124 provided on the attachment reference surface 120a. As described above, since the height of the convex portion 124 is lower than the height of the boss portion 123 and the height of the protruding portion 133a is lower than the height of the mounting stator 132, the protruding portion 133a is When fitted into the opening 124 a, a gap is generated between the object side surface of the flange 133 and the tip of the convex portion 124. Further, the imaging element holding frame 130 is attached to the lens unit 120 by screwing the screw member 150 with the female screw 123 a of the boss portion 123 via the disc spring 140.

  Thus, by using the disc spring 140, the object side end portion of the image sensor holding frame 130 is constantly biased with respect to the attachment reference surface 120a. Finally, the board 170 is attached to the image sensor holding frame 130 by screwing the screw member 150 into the female screw 131a of the extending portion 131 through screw holes 170a formed at diagonal positions of the board 170. By doing in this way, the image pick-up element 160 is shielded and it can prevent adhesion of dust and dust.

  FIG. 4 is an external view of the image sensor holding frame 130. 4A is a rear view of the image sensor holding frame 130, FIG. 4B is a top view of the image sensor holding frame 130, and FIG. 4C is a bottom view of the image sensor holding frame 130. FIG. 5 is a cross-sectional view taken along line BB in FIG. 6 is a cross-sectional view taken along the line CC in FIG.

  As shown in FIGS. 5 and 6, the mounting stator 132 of the image sensor holding frame 130 is externally fitted from the image side to the boss portion 123 protruding from the mounting reference surface 120 a, and the screw member is further interposed via the disc spring 140. The lens unit 120 is attached to the image sensor holding frame 130 by screwing 150 into the female screw 123 a of the boss portion 123. For this reason, the object side end of the image sensor holding frame 130 is always urged by the disc spring 140 toward the attachment reference surface 120a.

  Therefore, when the image sensor holding frame 130 expands and contracts due to a change in the environmental temperature, the image sensor holding frame 130 expands and contracts in a direction parallel to the optical axis 111 with respect to the attachment reference surface 120a, and the lens unit 120 and the image capturing device. There is no gap between the element holding frame 130 and the element holding frame 130. Further, since the disc spring 140 also serves as a cushioning material between the boss portion 123 and the mounting stator 132 by using the disc spring 140, the lens unit 120 and the image sensor holding frame 130 due to an increase in environmental temperature. Does not hinder the extension in the direction parallel to the optical axis 111. Further, when the protrusion 133a provided on the flange 133 is fitted into the opening 124a of the convex portion 124 provided on the attachment reference surface 120a, the object side surface of the flange 133 and the tip of the convex portion 124 do not contact each other. , Play has occurred. Accordingly, the expansion and contraction of the lens unit 120 and the image sensor holding frame 130 in the direction parallel to the optical axis 111 (thrust direction) is not affected. The protrusions 124 and the protrusions 133a are for preventing displacement in the direction (radical direction) perpendicular to the optical axis 111 of the image sensor holding frame 130.

  As described above, the lens barrel 100 according to this embodiment holds the lens group 110 even when the focal length varies due to the change in the refractive index of the lens group 110 due to the change in the environmental temperature. The distance between the lens group 110 and the image sensor 160 can be adjusted to the change in the focal length of the lens group 110 by greatly expanding and contracting the image sensor holding frame 130 that holds the image sensor 160 with respect to the lens unit 120 to be Image degradation can be avoided.

In general, the lens unit 120 is made of a material having a linear expansion coefficient of about 10 × 10 ^{−6 to} 20 × 10 ⁻⁶ . The image sensor holding frame 130 is made of a material having a linear expansion coefficient of about 60 × 10 ⁻⁶ . And the temperature range of the use environment generally assumed is -20 degreeC-+60 degreeC.

  FIG. 7 is an enlarged view of a portion A shown in FIG. As shown in FIG. 7, the length (L) in the direction parallel to the optical axis 111 in the extending part 131 of the lens unit 120, which is generally a design value, is 6 mm to 8 mm.

  FIG. 8 is a diagram for explaining a change in the focal length of the lens group 110 due to a change in the environmental temperature. For convenience of explanation, the focal positions before and after the environmental temperature change are indicated by a solid line and a two-dot chain line from the image side surface of the lens group 110 to the image sensor 160, respectively. When the temperature range of the usage environment is −20 ° C. to + 60 ° C., the amount of change (Δf) in the focal length of the lens group 110 formed of a general resin lens is about 0.019 mm to 0.032 mm. Therefore, it is necessary to correct the distance between the lens group 110 and the image sensor 160 in accordance with the amount of change (Δf).

Therefore, in order to accurately correct the distance between the lens group 110 and the image sensor 160 in accordance with the change in the focal length of the lens group 110, it is preferable that the following conditional expression (1) is satisfied.
(Α2−α1) × ΔT × L = Δf (1)
Where α1 is the linear expansion coefficient of the material forming the lens unit 120, α2 is the linear expansion coefficient of the material forming the image sensor holding frame 130, ΔT is the amount of change in environmental temperature, and L is the extension of the image sensor holding frame 130 The length of the part 131 in the direction parallel to the optical axis 111, Δf, indicates the amount of change in the focal length of the lens group 110 when the amount of change in environmental temperature ΔT.

For example, the lens unit 120 is formed of a material having a linear expansion coefficient (α1) of 10 × 10 ⁻⁶ , and the image sensor holding frame 130 is formed of a material having a linear expansion coefficient (α2) of 60 × 10 ⁻⁶ . Consider a case where the length (L) of the extending portion 131 of the lens unit 120 is 6.5 mm. When the temperature of the usage environment changes from −20 ° C. to + 60 ° C. (ΔT = 80), the change amount Δf (mm) of the focal length of the lens group 110 is
Δf = (60 × 10 ⁻⁶ −10 × 10 ⁻⁶ ) × 80 × 6.5 = 0.026
It becomes.

  As described above, the lens barrel 100 according to this embodiment includes the lens unit 120 that houses the lens group 110 and the image sensor holding frame 130 that holds the image sensor 160 with a material that expands and contracts according to changes in the environmental temperature. In addition, the linear expansion coefficient of the material of the image sensor holding frame 130 is made larger than the linear expansion coefficient of the material of the lens unit 120. Further, the image sensor holding frame 130 is attached to the lens unit 120 so that expansion and contraction of the lens unit 120 and the image sensor holding frame 130 in the direction parallel to the optical axis 111 is not hindered.

  As a result, when the refractive index of the lens group 110 changes due to a change in the environmental temperature and the focal length varies, the image sensor holding frame 130 that holds the image sensor 160 with respect to the lens unit 120 that holds the lens group 110. Thus, the distance between the lens group 110 and the image sensor 160 can be adjusted to the change in the focal length of the lens group 110, and deterioration of the image can be avoided. In particular, when the conditional expression (1) is satisfied, the distance between the lens group 110 and the image sensor 160 can be adjusted to the change in the focal length of the lens group 110 with higher accuracy.

  Further, as shown in this embodiment, a mechanism for connecting the lens unit 120 and the image sensor holding frame 130 is provided on the outer periphery of the lens barrel 100, so that the lens unit 120 has a small outer shape, Even when the distance between the lens group 110 and the image sensor 160 is narrow, a configuration that does not hinder the expansion and contraction of the lens unit 120 and the image sensor holding frame 130 can be realized. Furthermore, in the example shown in this embodiment, the lens unit 120 does not include filters or cover glass. However, if the lens unit 120 needs to include filters or cover glass, the extension portion The dimension in the direction parallel to the optical axis 111 of 131 may be adjusted. In addition, by adjusting the dimension of the extending portion 131 in the direction parallel to the optical axis 111, it is possible to use the imaging elements 160 having different thicknesses. Furthermore, by mounting the lens barrel 100 shown in this embodiment on an imaging apparatus, an imaging apparatus that can be used even in an environment with a large temperature change can be realized.

  As described above, the lens barrel according to the present invention is excellent in avoiding image degradation due to a change in the focal length of a resin lens caused by a change in the environmental temperature, and particularly used in an environment where the temperature change is large. Suitable for equipment.

DESCRIPTION OF SYMBOLS 100 Lens barrel 110 Lens group 111 Optical axis 120 Lens unit 120a Mounting reference surface 121 Lens frame 123 Boss part 123a, 131a Female thread 124 Convex part 124a Opening part 130 Imaging element holding frame 131 Extension part 132 Mounting stator 133 Flange 133a Protrusion Part 140 disc spring (biasing member)
150 Screw member 160 Image sensor 170 Substrate 170a Screw hole

Claims (6)

A lens group configured to include at least one resin lens;
A lens unit formed of a material having a first linear expansion coefficient and holding the lens group;
An imaging element holding frame for holding an imaging element, formed of a material having a second linear expansion coefficient larger than the first linear expansion coefficient;
With
On the image side of the lens unit, an attachment reference surface serving as a reference for attaching the image sensor holding frame in a direction extending perpendicularly to the optical axis of the lens group is formed, and is further parallel to the optical axis. A boss portion is provided so as to protrude from the mounting reference surface to the image side,
The image sensor holding frame is provided with an extending portion extending in parallel with the optical axis, and the boss portion is fitted on the side surface of the extending portion from the image side in parallel with the optical axis. A sleeve-shaped mounting stator for mounting the imaging element holding frame to the lens unit is provided,
The mounting stator is externally fitted to the boss portion, and a screw member is screwed to the boss portion via an urging member, so that the object side end of the image sensor holding frame abuts the mounting reference surface. Energized to touch,
A lens barrel characterized in that the extending portion expands and contracts in a direction parallel to the optical axis with respect to the mounting reference plane as a result of changes in environmental temperature. The lens barrel according to claim 1, wherein the following conditional expression is satisfied.
(Α2−α1) × ΔT × L = Δf
Where α1 is the linear expansion coefficient of the material forming the lens unit, α2 is the linear expansion coefficient of the material forming the image sensor holding frame, ΔT is the amount of change in environmental temperature, and L is the extension of the image sensor holding frame. The length of the portion in the direction parallel to the optical axis, Δf, indicates the amount of change in the focal length of the lens group when the amount of change in environmental temperature ΔT.   The extending portion has a hollow rectangular parallelepiped shape surrounding the four side surfaces of the image pickup device, and the image pickup device is attached by attaching a substrate to which the image pickup device is attached to an image side end portion of the extension portion. The lens barrel according to claim 1, wherein the lens barrel is shielded. In the vicinity of the boss portion, a convex portion having an opening at the tip is formed so as to protrude from the mounting reference plane to the image side in parallel to the optical axis,
A flange extending in a direction perpendicular to the optical axis from the image side end of the mounting stator is formed along the side surface of the extending portion, and the object side surface of the flange is parallel to the optical axis. Is provided with a protrusion protruding to the object side,
4. The positioning of the imaging element holding frame in a direction perpendicular to the optical axis is performed by fitting the protrusion into the opening. 5. Lens barrel. The height of the convex portion is lower than the height of the boss portion, and the height of the protruding portion is lower than the height of the mounting stator,
In a state where the protrusion is fitted in the opening, a gap is generated between the tip of the convex portion and the object side surface of the flange, and the extension portion extends and contracts in a direction parallel to the optical axis. The lens barrel according to claim 4, wherein the lens barrel is not disturbed.   An imaging apparatus comprising the lens barrel according to claim 1.

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