JP2015060140A - Lens unit and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens unit and imaging device that enable suppression of a variation of a focusing position even when an environment temperature change occurs, even with a simple configuration.SOLUTION: A linear expansion coefficient α1 of a plastic forming a first array lens AL1 is larger than a linear expansion coefficient α2 of a lens frame LF, and when the linear expansion occurs in the first array lens AL1 when the environment temperature increases and the array lens extends in a direction orthogonal to an optical axis, an amount of linear expansion of the lens frame LF is smaller than that of the first array lens at the same temperature, and thus, an inclined plane FL1a is raised along an inclined plane LFa as shown by a chain line in Figure 3. Thus, the first array lens AL1 moves to an object side relatively to the lens frame LF, thereby a change in refractive index occurs in lenses L1a, L1b, L2a and L2b and even when a lens back is longer, a variation of a focusing position can be suppressed.

Description

  The present invention relates to a lens unit and an imaging apparatus suitable for a compound eye camera module.

  2. Description of the Related Art In recent years, mobile terminals with a thin camera module typified by smartphones and tablet personal computers are rapidly spreading. Here, an imaging apparatus mounted on a thin portable terminal is required to be thin and compact while having high resolution. In order to meet such demands, we have improved the manufacturing accuracy in response to the shortening of the overall length by the optical design of the imaging lens and the accompanying increase in error sensitivity. There is a limit to the configuration in which an image is obtained by a combination of an imaging lens and an imaging element, and development of an optical system that is different from the conventional one is expected.

  On the other hand, a compound-eye optical system that divides the imaging region of the imaging device, arranges lenses (hereinafter referred to as single-eye optical systems), and processes the obtained images to perform final image output An optical system called “A” is attracting attention in order to meet the demand for thinning. Patent Document 1 discloses a compound eye camera module capable of reconstructing one image from a plurality of images captured by a plurality of imaging regions using disparity information of each image.

JP 2007-180653 A

  By the way, there is an attempt to configure the compound eye optical system from an array lens in which a plurality of lenses are integrated. When plastic is used to mold such an array lens, mass production becomes possible by mold molding, but the focus position changes due to changes in refractive index or deformation caused by temperature changes in the array lens. The image quality of the image is reduced, which is not preferable. On the other hand, an actuator that moves the array lens in the optical axis direction may be provided to move the array lens in accordance with the change in focal length when the temperature changes, but this increases the cost and increases the size of the lens unit. There is a problem of inviting.

  The present invention has been made in view of the problems of the related art, and provides a lens unit and an imaging apparatus that can suppress a change in the focal position even when an environmental temperature change occurs even with a simple configuration. With the goal.

The lens unit according to claim 1, wherein the lens unit is formed of plastic, and includes an array lens having a plurality of lens portions arranged in parallel to each other and a flange portion around the lens portion, and holds the array lens. A lens unit having a lens frame,
The flange portion of the array lens has a first inclined surface that goes outward in the optical axis orthogonal direction toward the object side in the optical axis direction,
The lens frame has a second slope that contacts the first slope so as to face the first slope,
Biasing means for biasing the first slope toward the second slope is provided;
The linear expansion coefficient of the plastic of the array lens is larger than the linear expansion coefficient of the lens frame.

  According to the present invention, since the linear expansion coefficient of the plastic of the array lens is larger than the linear expansion coefficient of the lens frame, thermal expansion occurs in the array lens when the environmental temperature rises, and the optical axis is perpendicular to the optical axis. When spread, since the thermal expansion amount of the lens frame is smaller at the same temperature, the first slope rises along the second slope. As a result, since the array lens moves to the object side with respect to the lens frame, a change in the refractive index occurs in the lens portion due to a temperature change, thereby suppressing a change in the focal position even when the lens back becomes long. it can. Note that when the environmental temperature is lowered, an operation opposite to that described above occurs, and the first inclined surface is lowered along the second inclined surface.

  A lens unit according to a second aspect of the present invention is the lens unit according to the first aspect, wherein the biasing means is an elastic body.

  This avoids the first slope and the second slope from being separated. The biasing means is not limited to an elastic body and may generate a magnetic force.

  The lens unit according to claim 3 is the invention according to claim 1 or 2, wherein the lens unit is formed by laminating a plurality of array lenses.

  As a result, the lens unit can be configured accurately at low cost.

  An imaging apparatus according to a third aspect includes the lens unit according to the first or second aspect.

  According to the present invention, it is possible to provide a lens unit and an imaging apparatus that have a simple configuration and can suppress a change in focal position even when an environmental temperature change occurs.

It is a schematic diagram of the camera module concerning this Embodiment. It is sectional drawing of imaging unit LU. It is a partially enlarged view of the imaging unit LU.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

  First, a compound eye camera module using a lens unit as a compound eye optical system will be described. A compound eye optical system is an optical system in which a plurality of lens systems are arranged in an array for one image sensor, and each lens system has a different field of view and a super-resolution type in which each lens system images the same field of view. Usually, it is divided into a field division type that performs imaging of the above. Here, a super-resolution type compound eye camera module that performs a plurality of images with different fields of view in order to connect a plurality of images with different fields of view and output one composite image will be described.

  FIG. 1 schematically shows an imaging apparatus according to the present embodiment. As shown in FIG. 1, the imaging device DU includes an imaging unit LU, an image processing unit 1, a calculation unit 2, a memory 3, and the like. The imaging unit LU includes one imaging element SR and a lens unit LH that performs a plurality of imaging with different fields of view on the imaging element SR. As the image sensor SR, for example, a solid-state image sensor such as a CCD image sensor or a CMOS image sensor having a plurality of pixels is used. Since the lens unit LH is provided on the light receiving surface SS which is a photoelectric conversion unit of the image sensor SR so that an optical image of the subject is formed, the optical image formed by the lens unit LH is the image sensor SR. Is converted into an electrical signal.

  FIG. 2 is a cross-sectional view illustrating the imaging unit according to the present embodiment. In the present embodiment, a so-called array lens in which a plurality of lenses are integrally formed is stacked and used as the lens unit LH. More specifically, the first array lens AL1 integrally formed from plastic includes a resin-made first object side lens L1a formed on the object side surface of the first flat flange portion FL1 and a first flange portion. A first image-side lens L1b made of resin formed on the image side surface of FL1. The lenses L1a and L1b are arranged in a 4 × 4 matrix.

  The second array lens AL2 integrally formed of plastic includes a resin-made second object-side lens L2a formed on the object side surface of the square flat plate-like second flange portion FL2, and an image side surface of the second flange portion FL2. And a second image-side lens L2b made of resin. The lenses L2a and L2b are arranged in a matrix of 4 × 4 corresponding to the lenses L1a and L1b. A black film (not shown) that suppresses stray light is formed on the surfaces of the flange portions FL1 and FL2 other than the lens. Note that three or more array lenses may be laminated.

  The number of lenses L1a, L1b, L2a, and L2b is equal to the number of object images (referred to as single-eye images) formed on the imaging surface SS of the image sensor SR (here, 4 × 4). That is, the light beams that have passed through the lenses L1a, L1b, L2a, and L2b stacked in the optical axis direction form one image (single-eye image) on the imaging surface SS.

  In FIG. 2, a frame-like or block-like spacer SP bonded to the periphery is interposed between the first flange portion FL1 and the second flange portion FL2, and the distance between the two is maintained at a predetermined value. Yes.

  On the other hand, the black lens frame LF has a rectangular frame shape, surrounds the periphery of the lens unit LH, and has a tapered flat inclined surface (second surface) toward the outer side in the optical axis toward the upper inner periphery at the upper end. (Slope) Four LFa are formed. A step portion LFb is formed on the inner periphery near the lower end of the lens frame LF, and a parallel plate-shaped IR cut filter F is attached. The lower end of the lens frame LF is in contact with the upper surface of the substrate ST on which the imaging element SR is placed.

  The first flange portion FL1 of the first array lens AL1 constituting the lens unit LH is in contact with the inclined surface LFa of the lens frame LF so as to face the outer side in the optical axis orthogonal direction toward the object side in the optical axis direction. Four tapered flat slopes (first slopes) FL1a are provided. One end of a spring plate SPG as an elastic body is attached to the upper end of the lens frame LF, and the other end is in contact with the upper surface of the first flange portion FL1 to urge the lens unit LH toward the image side. The linear expansion coefficient α1 of the plastic forming the first array lens AL1 is larger than the linear expansion coefficient α2 of the lens frame LF.

  FIG. 3 is an enlarged view of an arrow II part of FIG. The inclination angle θ of the inclined surface LFa of the lens frame LF and the inclined surface FL1a of the first array lens AL1 with respect to the optical axis orthogonal surface is 42 ° to 72 °. Considering the slip of the slope, if the friction angle θ ′ and the friction coefficient μ are μ = tan θ ′, that is, if the angle is larger than the friction angle, the slip occurs. Considering the friction coefficient μ of various materials, the maximum is about 0.9, and the friction angle θ ′ at that time is 42 °. On the other hand, increasing the tilt angle θ leads to an increase in the size of the imaging unit, so the upper limit value of the tilt angle θ is limited by the size of the imaging unit. Assuming that the size of the imaging unit is a minimum of about 8 mm, the upper limit value of the inclination angle θ at that time is 72 °.

  According to this embodiment, since the linear expansion coefficient α1 of the plastic forming the first array lens AL1 is larger than the linear expansion coefficient α2 of the lens frame LF, the first array lens AL1 is heated when the environmental temperature rises. When the expansion occurs and spreads in the direction perpendicular to the optical axis, the thermal expansion amount of the lens frame LF is smaller at the same temperature, so that the inclined surface FL1a rises along the inclined surface LFa as shown by a one-dot chain line in FIG. Become. At this time, since the spring plate SPG urges the first array lens AL1 from above, the inclined surface LFa of the lens frame LF and the inclined surface FL1a of the first array lens AL1 are not separated from each other.

  As described above, since the first array lens AL1 moves parallel to the object side with respect to the lens frame LF, the refractive index change occurs in the lenses L1a, L1b, L2a, and L2b due to the temperature change, and the lens back becomes longer due to this. However, the fluctuation of the focal position can be suppressed. Note that when the environmental temperature is lowered, an action opposite to the above occurs, and the slope FL1a is lowered to the image side along the slope LFa, and the first array lens AL1 is moved in parallel to the image side. Can be suppressed.

The examination results of the present inventors will be described. In the lens unit LH in which the width of the slope portion of the first array lens AL1 is 14 mm, it is assumed that the lens back lengthens by +15 μm when the temperature rises by + 30 ° C. Here, the array lens material is plastic with a linear expansion coefficient α1 = 60 × 10 ⁻⁶ / ° C., and the lens frame material is aluminum with a linear expansion coefficient α2 = 23.6 × 10 ⁻⁶ / ° C. When the height of the inclined surface of the lens frame is 2.5 mm, when the temperature rises by + 30 ° C., the inclined surface moves 1.8 μm to the + object side due to the expansion of the lens frame itself. Due to the temperature increase of + 30 ° C., the linear expansion difference between the array lens material and the lens frame is generated at 15.3 μm at both ends of the slope portion. That is, if it is on one side of the slope, the expansion difference is 7.65 μm. By setting the inclination angle θ = 59.9 °, the remaining +13.2 μm remaining on the object side can be extended, and when the temperature rises by + 30 ° C. together with the expansion of the lens frame itself, the lens unit LH can be moved. It can be moved +15 μm to the object side, and the focal position variation of the lens can be canceled.

Further, under the same conditions, when the array lens material is a plastic having a linear expansion coefficient α1 = 60 × 10 ⁻⁶ / ° C. and the lens frame material is a stainless steel having a linear expansion coefficient α2 = 17.3 × 10 ⁻⁶ / ° C., By setting the inclination angle θ = 56.8 °, the lens unit LH can be moved +15 μm to the object side when the temperature rises by + 30 ° C., and the focal position variation of the lens can be canceled.

Furthermore, under the same conditions, when the array lens material is a plastic having a linear expansion coefficient α1 = 60 × 10 ⁻⁶ / ° C. and the lens frame material is a ceramic having a linear expansion coefficient α2 = 2.6 × 10 ⁻⁶ / ° C., By setting the inclination angle θ = 50.8 °, the lens unit LH can be moved +15 μm toward the object side when the temperature rises by + 30 ° C., and the focal position variation of the lens can be canceled.

  The operation of the imaging apparatus according to the present embodiment will be described. As shown in FIG. 1, the image processing unit 1 includes an image composition unit 1a, an image correction unit 1b, and an output image processing unit 1c. . The image synthesizing unit 1a synthesizes image signals from the plurality of imaging regions SS formed by the lens unit LH, and outputs one synthesized image ML. At that time, the image correction unit 1b performs inversion processing, distortion processing, shading processing, composition processing, and the like. Further, distortion correction is performed as necessary. The output composite image ML is stored in the memory 3.

DESCRIPTION OF SYMBOLS 1 Image processing part 1a Image composition part 1b Image correction part 1c Output image processing part 2, Operation part 3 Memory AL1 1st array lens AL2 2nd array lens DU Imaging device F IR cut filter FL1 1st flange part FL1a Slope FL2 2nd Flange part HLD Mirror frame L1a Lens L1a Object side lens L1b Image side lens L2a Object side lens L2b Image side lens LF Mirror frame LFa Slope LFb Step part LH Lens unit LU Imaging unit ML Composite image SP Spacer SPG Spring plate SR Imaging element SS Imaging Surface ST substrate

Claims (4)

A lens unit having an array lens having a plurality of lens portions formed of plastic and having optical axes arranged in parallel to each other and a flange portion around the lens portion, and a lens frame for holding the array lens. And
The flange portion of the array lens has a first inclined surface that goes outward in the optical axis orthogonal direction toward the object side in the optical axis direction,
The lens frame has a second slope that contacts the first slope so as to face the first slope,
Biasing means for biasing the first slope toward the second slope is provided;
The lens unit according to claim 1, wherein a linear expansion coefficient of the plastic of the array lens is larger than a linear expansion coefficient of the lens frame.   The lens unit according to claim 1, wherein the urging unit is an elastic body.   The lens unit according to claim 1, wherein the lens unit is formed by stacking a plurality of array lenses.   An imaging apparatus comprising the lens unit according to claim 1.

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