JP2020060795A - Lens unit and imaging apparatus - Google Patents

Abstract

To provide a lens unit capable of preventing out-of-focus due to thermal expansion or thermal contraction with a simple structure, and to provide an imaging apparatus.SOLUTION: A lens unit 10 in an embodiment is a lens unit having three or more lenses therein including a set of lenses each having a power sign different from each other disposed being neighboring to each other. When temperature changes, a lens (third lens 18) which is disposed at the image side in the lens set each having a power sign different from moves with respect to a lens (second lens 17) disposed at the object side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lens unit and an image pickup device.

  2. Description of the Related Art In recent years, image pickup devices installed outdoors, such as in-vehicle cameras and surveillance cameras, have become widespread. A fixed-focus lens unit called a pan-focus type is often used for an especially small-sized image pickup apparatus installed outdoors. In a high-temperature or low-temperature environment, the lens interval changes from the design value due to thermal expansion or contraction due to temperature change, and when the amount of change is large, the focus position may deviate from the design value. Since the fixed focus lens unit does not have a focus adjusting function such as a focus lens, it is difficult to correct the deterioration of the image quality caused by the shift of the focus position due to the temperature change.

  In the imaging device described in Patent Document 1, a plurality of lenses are individually held by different lens frames, and the plurality of lens frames are made of materials having different linear expansion coefficients. The image pickup apparatus described in Patent Document 1 holds a plurality of lenses independently and adjusts the linear expansion coefficient of each lens frame to suppress the shift of the focus position due to the temperature change.

  In the image pickup apparatus described in Japanese Patent Laid-Open No. 2004-242242, an expansion / contraction member that expands / contracts according to temperature is arranged on the back surface of the image pickup element to change the distance between the lens unit and the image pickup element so as to compensate the focus position.

JP, 2003-262777, A JP 2004-147188 A

  In the image pickup device described in Patent Document 1, since a plurality of lenses are individually held by different lens frames, the structure becomes complicated and the cost becomes high. In addition, since the respective lens frames must be formed of materials having different linear expansions and a combination of materials that reduce the focus shift due to temperature change must be selected, there is a problem that it is difficult to select the material of the lens frame. Further, in the image pickup apparatus described in Patent Document 2, there is a problem that the total length of the lens system changes because the distance between the image pickup element and the lens unit changes.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a lens unit and an imaging device capable of suppressing a focus shift due to thermal expansion or thermal contraction with a simple structure.

The lens unit according to the present invention is
A lens unit that internally holds three or more lenses including a set of lenses that are adjacently arranged and have different power signs,
When the temperature fluctuates, the lens arranged on the image side of the group of lenses having different signs of power moves with respect to the lens arranged on the object side.

In the present invention,
When the temperature rises, the lens arranged on the image side moves in a direction away from the lens arranged on the object side,
It is preferable that, when the temperature decreases, the lens arranged on the image side moves in a direction approaching the lens arranged on the object side.

In the present invention,
The lens arranged on the image side is independently held by the first lens frame,
The remaining plurality of lenses including the lens disposed on the object side are held by the second lens frame,
The first lens frame is
It is made of a material having a larger linear expansion coefficient than the material of the second lens frame,
It is preferable that the second lens frame expands toward the image side when the temperature rises and contracts toward the object side when the temperature falls.

In the present invention,
The lens arranged on the image side is preferably a lens other than the lens arranged on the most image side among the lenses forming the lens unit.

The imaging device according to the present invention,
A lens unit that internally holds three or more lenses, including a group of lenses having different power signs arranged adjacent to each other, wherein among the lens groups having different power signs when the temperature fluctuates. A lens unit in which the lens arranged on the image side moves with respect to the lens arranged on the object side,
An image sensor arranged at the focal position of the lens unit,
Is provided.

  According to the present invention, it is possible to provide a lens unit and an imaging device capable of suppressing focus shift due to thermal expansion or thermal contraction with a simple structure.

3 is a cross-sectional view showing the configuration of the lens unit according to Embodiment 1. FIG. FIG. 6 is a cross-sectional view showing a configuration of a modified example of the lens unit according to the first embodiment. 5 is a cross-sectional view showing the configuration of a lens unit according to Embodiment 2. FIG. FIG. 9 is a cross-sectional view showing a configuration of a modified example of the lens unit according to the second embodiment. 3 is a cross-sectional view showing the configuration of the camera module according to Embodiment 1. FIG. It is sectional drawing which shows an example of the lens unit of a 3 sheet structure which concerns on other embodiment. It is sectional drawing which shows another example of the lens unit of a 3 sheet structure which concerns on other embodiment.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the lens unit 10 includes a first lens 16, a second lens 17, a third lens 18, a fourth lens 19, a first lens frame 13, a second lens frame 12, And an intermediate ring 14. The imaging lens system held inside the lens unit 10 includes a first lens 16, a second lens 17, a third lens 18, and a fourth lens 19. In FIG. 1, the left side of the lens unit 10 in the figure is the object side, and the right side in the figure is the image side. The lens unit 10 forms an incident light ray on the image plane IMG.

  The first lens 16 is a meniscus lens having a concave shape on the image side and having negative power. The second lens 17 is a meniscus lens having a concave shape on the image side and having negative power. The third lens 18 is a lens that is convex toward the object side and has positive power. The fourth lens 19 is a lens having a convex shape on the image side and having a positive power.

  As shown in FIG. 1, a first lens 16, a second lens 17, a third lens 18, and a fourth lens 19 are held inside the lens unit 10. That is, the lens unit 10 stores four lenses including a set of lenses that are adjacently arranged and have different power signs. The second lens 17 and the third lens 18 can be considered as a set of lenses that are arranged adjacent to each other and have different power signs.

  The second lens frame 12 is a cylindrical member, and a flange 12a is formed near the center of the outer peripheral surface in the direction along the optical axis Z. A plurality of inner peripheral surfaces having different diameters (first inner peripheral surface P11, second inner peripheral surface P12, third inner peripheral surface P13, and fourth inner peripheral surface P14) are formed on the inner wall of the second lens frame 12. ing. The inner diameter increases in the order of the fourth inner peripheral surface P14, the third inner peripheral surface P13, the second inner peripheral surface P12, and the first inner peripheral surface P11.

  The first lens frame 13 is a cylindrical member, and a flange 13a is formed at the end of the outer peripheral surface on the object side. The first lens frame 13 is fixed by fitting the outer peripheral surface of the flange 13a into the second inner peripheral surface P12 of the second lens frame 12. The third lens 18 is fitted and fixed to the inner peripheral surface of the first lens frame 13. That is, the first lens frame 13 holds the third lens 18 alone.

  The first lens frame 13 is made of a material having a larger linear expansion coefficient than the material of the second lens frame 12. For example, the material of the second lens frame 12 is preferably aluminum or stainless steel, and the material of the first lens frame 13 is preferably plastic such as polycarbonate (PC). The first lens frame 13 expands toward the image side with respect to the second lens frame 12 when the temperature becomes higher than the reference temperature, and contracts toward the object side with respect to the second lens frame 12 when the temperature becomes lower than the reference temperature.

  It should be noted that the names of the first lens frame 13 and the second lens frame 12 are merely named for the sake of convenience, and thus it does not prevent the use of other names. For example, the first lens frame 13 may be referred to as a moving lens holding frame, and the second lens frame 12 may be referred to as a lens barrel or barrel.

  The intermediate ring 14 is an annular member arranged between the first lens frame 13 and the fourth lens 19. The intermediate ring 14 is fitted and fixed to the third inner peripheral surface P13. The intermediate ring 14 is preferably made of a material having a smaller linear expansion coefficient than the material of the first lens frame 13. The intermediate ring 14 may be formed of a material having a linear expansion coefficient smaller than that of the second lens frame 12, or may be formed of a material having a linear expansion coefficient larger than that of the second lens frame 12. Good.

  The fourth lens 19 is fitted into and fixed to the fourth inner peripheral surface P14, and its movement toward the image side in the optical axis direction is restricted by the diaphragm wall 12b formed at the image side end of the second lens frame 12. Has been done. The image side end surface of the intermediate ring 14 is in contact with the object side surface of the flange 19 a of the fourth lens 19. The first lens frame 13 is fitted and fixed to the second inner peripheral surface P12. The image side surface of the flange 13 a of the first lens frame 13 is in contact with the object side end surface of the intermediate ring 14.

  The first lens 16 and the second lens 17 are fitted and fixed to the first inner peripheral surface P11. The image side surface of the flange 17a of the second lens 17 is in contact with the step portion between the first inner peripheral surface P11 and the second inner peripheral surface P12 and the object side end surface of the first lens frame 13. The image side edge portion 16a of the first lens 16 is in contact with the object side surface of the flange 17a of the second lens 17. The object side edge of the first lens 16 is provided with a notch 16b, and the caulking of the object side end of the second lens frame 12 restricts the movement of the first lens 16 toward the object side in the optical axis direction. ing. A step portion is provided on the image side edge portion 16a of the first lens 16, and a seal member 15 such as an O-ring is arranged in the step portion.

  In the lens unit 10, when the temperature fluctuates with respect to the reference temperature, the third lens 18 moves with respect to the second lens 17 arranged on the object side. Here, the movement of the lens means the thermal expansion of the lens barrel itself when the two lenses (the second lens 17 and the third lens 18) are fixed to the same lens barrel (the second lens frame 12). It means more than movement due to heat shrinkage. The reference temperature is a temperature used as a reference when designing the structure of the lens unit 10, and the reference temperature is 25 ° C., for example.

  That is, when the temperature becomes higher than the reference temperature, the first lens frame 13 expands toward the image side with respect to the surface abutted against the second lens 17, so that the third lens 18 is placed on the object side. Move away from. Therefore, the expansion amount of the space between the second lens 17 and the third lens 18 is compared with the expansion amount of the space between the first lens 16 and the second lens 17 and the space between the third lens 18 and the fourth lens 19. Grows. Accordingly, the lens unit 10 can cancel the backward shift of the focus position caused by the expansion of the lens interval when the temperature rises.

  On the other hand, when the temperature becomes lower than the reference temperature, the first lens frame 13 contracts toward the object side with the surface abutted against the second lens 17 as a reference, so that the third lens 18 becomes the second lens 17 arranged on the object side. Move closer to. Therefore, the contraction amount of the distance between the second lens 17 and the third lens 18 is compared with the contraction amount of the distance between the first lens 16 and the second lens 17 and the distance between the third lens 18 and the fourth lens 19. Is big. Accordingly, the lens unit 10 can cancel the forward shift of the focus position caused by the contraction of the lens interval when the temperature decreases.

  As described above, according to the present embodiment, it is possible to provide the lens unit 10 capable of suppressing the focus shift due to the thermal expansion or the thermal contraction with a simple structure.

  FIG. 5 is a schematic configuration diagram showing the configuration of the camera module 200. The camera module 200 is the imaging device according to the present embodiment. The camera module 200 includes an upper case (camera case) 201 that is an exterior component, a mount (pedestal) 202 that holds the lens unit 10, a seal member 203, an image sensor (image sensor) 204, and a sensor substrate 205. have. The image sensor 204 is arranged at the focal position (image plane IMG) of the lens unit 10.

  The upper case 201 is a member that is provided with an opening for exposing the end of the lens unit 10 on the object side and covers other portions. The mount 202 is arranged inside the upper case 201, and has a female screw on its inner peripheral surface for screwing with a male screw formed on the outer peripheral surface of the second lens frame 12 of the lens unit 10. The seal member 203 is a member inserted between the flange 12 a of the second lens frame 12 and the inner surface of the upper case 201, and is a member for maintaining the airtightness inside the upper case 201.

  The image sensor 204 is arranged inside the upper case 201, and is also arranged at a focal position where an image is formed by the lens unit 10. The image sensor 204 is, for example, a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, or the like, and converts light collected by the lens unit 10 into an electric signal. The electric signal obtained by the image sensor 204 is converted into digital data which is a constituent element of image data.

  According to the camera module 200 according to the present embodiment, by having the lens unit 10 described above, it is possible to provide an imaging device capable of suppressing the focus shift due to thermal expansion or thermal contraction with a simple structure.

(Modification of Embodiment 1)
As shown in FIG. 2, the lens unit according to Embodiment 1 can also be realized by a configuration that does not use the intermediate ring 14. Differences of the lens unit 20 according to the modification of the first embodiment will be described.

  The second lens frame 22 is a cylindrical member, and a flange 22a is formed near the center of the outer peripheral surface in the direction along the optical axis Z. A plurality of inner peripheral surfaces (first inner peripheral surface P21, second inner peripheral surface P22, third inner peripheral surface P23, and fourth inner peripheral surface P24) having different diameters are formed on the inner wall of the second lens frame 22. ing. The inner diameter increases in the order of the fourth inner peripheral surface P24, the third inner peripheral surface P23, the second inner peripheral surface P22, and the first inner peripheral surface P21. Further, a protrusion P25 is provided between the third inner peripheral surface P23 and the fourth inner peripheral surface P24.

  The fourth lens 29 is fitted and fixed to the fourth inner peripheral surface P24, and its movement toward the object side in the optical axis direction is restricted by the protrusion P25. The first lens frame 13 is fitted and fixed to the second inner peripheral surface P22. An image side surface of the flange 13a of the first lens frame 13 is in contact with a step portion between the second inner peripheral surface P22 and the third inner peripheral surface P23, and a step difference between the second inner peripheral surface P22 and the third inner peripheral surface P23. The portion restricts the movement of the first lens frame 13 toward the image side in the optical axis direction.

  By sandwiching the first lens frame 13 between the step portion between the second inner peripheral surface P22 and the third inner peripheral surface P23 and the flange 17a of the second lens 17, the first mirror can be formed without using the intermediate ring 14. The outer periphery of the flange 13a of the frame 13 can be fixed to the second inner peripheral surface P22 of the second lens frame 22. Since the number of parts can be reduced by the above configuration, the manufacturing cost of the lens unit can be reduced.

[Second Embodiment]
The lens unit 30 according to Embodiment 2 of the present invention will be described with reference to FIG. The lens unit 30 has an imaging lens system different from the imaging lens system according to the first embodiment.

  As shown in FIG. 3, the lens unit 30 includes a first lens 36, a second lens 37, a third lens 38, a fourth lens 39, a first lens frame 33, a second lens frame 32, and And an intermediate ring 34.

  The first lens 36 is a biconvex lens having a positive power. The second lens 37 is a meniscus lens having a concave shape on the image side and having negative power. The third lens 38 is a meniscus lens having a convex shape on the image side and having a positive power. The fourth lens 39 is a lens having a convex shape on the object side and having negative power. The first lens 36 and the second lens 37 can be considered as a set of lenses that are arranged adjacent to each other and have different power signs.

  The second lens frame 32 is a cylindrical member, and a flange 32a is formed near the center of the outer peripheral surface in the direction along the optical axis Z. A plurality of inner peripheral surfaces having different diameters (first inner peripheral surface P31, second inner peripheral surface P32, third inner peripheral surface P33 and fourth inner peripheral surface P34) are formed on the inner wall of the second lens frame 32. ing. The inner diameter increases in the order of the fourth inner peripheral surface P34, the third inner peripheral surface P33, the second inner peripheral surface P32, and the first inner peripheral surface P31.

  The fourth lens 39 is fitted into and fixed to the fourth inner peripheral surface P34, and can be moved toward the image side in the optical axis direction by the diaphragm wall 32b formed at the image side end of the second lens frame 32. It is regulated. The third lens 38 is fitted and fixed to the third inner peripheral surface P33. The image side surface of the flange 38a of the third lens 38 is in contact with the object side surface of the flange 39a of the fourth lens 39. The intermediate ring 34 is fitted and fixed to the second inner peripheral surface P32. The image-side end surface of the intermediate ring 34 is in contact with the step portion between the second inner peripheral surface P32 and the third inner peripheral surface P33 and the object side surface of the flange 38a of the third lens 38.

  The first lens 36 and the first lens frame 33 are fitted and fixed to the first inner peripheral surface P31. The image side surface of the flange 33a of the first lens frame 33 is in contact with the step portion between the first inner peripheral surface P31 and the second inner peripheral surface P32 and the object side end surface of the intermediate ring 34. The image side surface of the flange 36a of the first lens 36 is in contact with the object side surface of the flange 33a of the first lens frame 33. A notch 36b is provided on the object side edge of the flange 36a of the first lens 36, and the first lens 36 is moved to the object side in the optical axis direction by caulking the object side end of the second lens frame 32. Is regulated.

(Modification of Embodiment 2)
As shown in FIG. 4, the lens unit according to Embodiment 2 can also be realized by a configuration that does not use the intermediate ring 34. Differences between the lens unit 40 according to the modification of the second embodiment and the lens unit 30 will be described.

  The second lens frame 42 is a cylindrical member, and has a flange 42a formed near the center of the outer peripheral surface in the direction along the optical axis Z. A plurality of inner peripheral surfaces (first inner peripheral surface P41, second inner peripheral surface P42, third inner peripheral surface P43, and fourth inner peripheral surface P44) having different diameters are formed on the inner wall of the second lens frame 42. ing. The inner diameter increases in the order of the second inner peripheral surface P42, the third inner peripheral surface P43, the first inner peripheral surface P41, and the fourth inner peripheral surface P44. The second inner peripheral surface P42 projects from between the first inner peripheral surface P41 and the third inner peripheral surface P43.

  The fourth lens 49 is fitted and fixed to the fourth inner peripheral surface P44. A positioning member 45 is fixed to the stepped portion formed at the image-side end of the fourth inner peripheral surface P44, and the positioning member 45 restricts the movement of the fourth lens 49 toward the image side in the optical axis direction. There is.

  The flange 38a of the third lens 38 is fixed by being sandwiched between the step portion between the second inner peripheral surface P42 and the third inner peripheral surface P43 and the object side surface of the flange 49a of the fourth lens 49. An image side surface of the flange 33a of the first lens frame 33 is in contact with a step portion between the first inner peripheral surface P41 and the second inner peripheral surface P42, and a step between the first inner peripheral surface P41 and the second inner peripheral surface P42. The part regulates the movement of the first lens frame 33 toward the image side in the optical axis direction.

  By sandwiching the first lens frame 33 between the step portion between the first inner peripheral surface P41 and the second inner peripheral surface P42 of the second lens frame 42 and the flange 36a of the first lens 36, the intermediate ring 34 is formed. The outer circumference of the flange 33a of the first lens frame 33 can be fixed to the first inner peripheral surface P41 of the second lens frame 42 without using it. Since the number of parts can be reduced by the above configuration, the manufacturing cost of the lens unit can be reduced.

[Other Embodiments]
The present invention is not limited to the above-mentioned embodiments, but can be modified as appropriate without departing from the spirit of the present invention.

  In the first and second embodiments, by using materials having different linear expansion coefficients for the first lens frame and the second lens frame, an object in which the lens supported by the first lens frame is supported by the second lens frame It is moved with respect to the lens located on the side. The lens unit and the imaging device according to the present invention are not limited to the above-described configuration, for example, the ambient temperature is detected by the temperature sensor, and the power of the power is calculated based on the difference between the detected temperature and the reference temperature. The configuration may be such that the lens arranged on the image side of the group of lenses having different signs is moved with respect to the lens arranged on the object side using a stepping motor.

  Further, the number of lenses held by the lens unit according to the present invention is not limited to four, and the present invention can be applied to a lens unit having three or more lenses.

  As shown in FIG. 6, the present invention also relates to a lens unit 70 having an imaging lens system including an aperture stop STOP, a first lens 71, a second lens 72, and a third lens 73 in order from the object side. Can be applied. The first lens 71 is a meniscus lens having a concave shape on the image side and having negative power. The second lens 72 is a lens that is convex on the object side and has positive power. The third lens 73 is a lens having a convex shape on the image side and having a positive power.

  The second lens 72 is supported by a first lens frame 74 formed of a material having a large linear expansion coefficient. The first lens 71 and the third lens 73 are supported by a second lens frame (not shown) having a smaller linear expansion coefficient than the first lens frame 74. By moving the second lens 72 supported by the first lens frame 74 with respect to the first lens 71 located on the object side, it is possible to suppress focus shift due to thermal expansion or thermal contraction.

  As shown in FIG. 7, the present invention also relates to a lens unit 80 having an imaging lens system including an aperture stop STOP, a first lens 81, a second lens 82, and a third lens 83 in order from the object side. Can be applied. The first lens 81 is a biconvex lens having a positive power. The second lens 82 is a biconcave lens having negative power. The third lens 83 is a biconvex lens having a positive power.

  The second lens 82 is supported by the first lens frame 84 formed of a material having a large linear expansion coefficient. The first lens 81 and the third lens 83 are supported by a second lens frame (not shown) having a smaller linear expansion coefficient than the first lens frame 84. By moving the second lens 82 supported by the first lens frame 84 with respect to the first lens 81 located on the object side, it is possible to suppress focus shift due to thermal expansion or thermal contraction.

  Further, when the number of lenses of the lens unit according to the present invention is five or more, it is preferable to change the lens interval of a set of lenses having different power signs located closer to the object than the diaphragm. At this time, the number of lenses located on the image side of the diaphragm is not limited. For example, in the case of a wide-angle lens, since the optical system on the object side of the diaphragm is a focal system, the focal length of the entire lens system can be changed by moving the lens that is the subject of the present invention in the optical system on the object side of the diaphragm. Because it can be changed.

10, 20, 30, 40 Lens unit 12, 22, 32, 42 Second lens frame 12b, 32b Aperture wall 13, 33 First lens frame 13a, 33a Flange 14, 34 Intermediate ring 16, 36, 71, 81 First Lens 17, 37, 72, 82 Second lens 18, 38, 73, 83 Third lens 19, 29, 39, 49 Fourth lens 200 Camera module 201 Upper case 202 Mount 203 Seal member 204 Imaging sensor 205 Sensor substrate P11, P21, P31, P41 First inner peripheral surface P12, P22, P32, P42 Second inner peripheral surface P13, P23, P33, P43 Third inner peripheral surface P14, P24, P34, P44 Fourth inner peripheral surface

Claims (5)

3 including at least a set of lenses including a first lens on the object side and a second lens on the image side arranged adjacent to each other, and a third lens arranged adjacent to the image side of the set of lenses A lens unit that holds one or more lenses in a first lens frame or a second lens frame,
The first lens and the second lens are lenses having different power signs,
The second lens frame holds the first lens and the third lens,
The first lens frame holds the second lens independently on the image side, and is made of a material having a linear expansion coefficient larger than that of the material of the second lens frame. Is arranged between the first lens and the first lens so as to be movable with respect to the first lens held by the first lens frame;
When the temperature rises, the second lens moves in a direction away from the first lens and moves in a direction closer to the third lens,
The lens unit, wherein when the temperature decreases, the second lens moves toward the first lens and moves away from the third lens.   The lens unit according to claim 1, wherein the first lens has a negative power, the second lens has a positive power, and the third lens has a positive power.   The lens unit according to claim 1, wherein the first lens has a positive power, the second lens has a negative power, and the third lens has a positive power.   The lens unit according to claim 1, comprising five or more lenses and a diaphragm, wherein the first lens and the second lens are located closer to the object side than the diaphragm.   An image pickup apparatus comprising: the lens unit according to claim 1; and an image pickup element, wherein an image is formed on the image pickup element via the lens unit.

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