JP2021060621A - 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 imaging device.

In recent years, imaging 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 a particularly small image pickup device installed outdoors. In a high temperature or low temperature environment, the lens spacing changes from the design value due to thermal expansion or contraction due to temperature change, and if 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 adjustment function such as a focus lens, it is difficult to correct the deterioration of image quality caused by the shift of the focus position due to the temperature change.

In the image pickup apparatus described in Patent Document 1, a plurality of lenses are independently held in different mirror frames, and the plurality of mirror frames are formed 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 deviation of the focus position due to a temperature change.

In the image pickup apparatus described in Patent Document 2, the distance between the lens unit and the image pickup element is changed so as to compensate the focus position by arranging an expansion / contraction member that expands and contracts according to the temperature on the back surface of the image pickup element.

Japanese Unexamined Patent Publication No. 2003-262777 Japanese Unexamined Patent Publication No. 2004-147188

In the image pickup apparatus described in Patent Document 1, since a plurality of lenses are independently held in different mirror frames, the structure becomes complicated and the cost becomes high. Further, since each mirror frame must be formed of a material having a different linear expansion and a combination of materials that reduces the focus shift due to a temperature change must be selected, there is a problem that it is difficult to select the material of the mirror 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 image pickup apparatus capable of suppressing focus shift due to thermal expansion or contraction with a simple structure.

The lens unit according to the present invention is
A lens unit in which three or more lenses including a set of lenses having different power codes arranged next to each other are held inside.
When the temperature fluctuates, the lens arranged on the image side of the set of lenses having different power codes 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.
When the temperature drops, it is preferable that the lens arranged on the image side moves in a direction closer to the lens arranged on the object side.

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

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

The imaging device according to the present invention is
A lens unit in which three or more lenses including a set of lenses having different power codes arranged adjacent to each other are held inside, and among the sets of lenses 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 and
To be equipped.

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 contraction with a simple structure.

It is sectional drawing which shows the structure of the lens unit which concerns on Embodiment 1. FIG. It is sectional drawing which shows the structure of the modification of the lens unit which concerns on Embodiment 1. FIG. It is sectional drawing which shows the structure of the lens unit which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the modification of the lens unit which concerns on Embodiment 2. FIG. It is sectional drawing which shows the structure of the camera module which concerns on Embodiment 1. FIG. It is sectional drawing which shows an example of the lens unit of 3 elements composition which concerns on other embodiment. It is sectional drawing which shows another example of the three-element lens unit 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 mirror frame 13, and a second mirror frame 12. It has an intermediate ring 14 and. The image pickup lens system held inside the lens unit 10 is composed of a first lens 16, a second lens 17, a third lens 18, and a fourth lens 19. In FIG. 1, the left side in the drawing of the lens unit 10 is the object side, and the right side in the drawing is the image side. The lens unit 10 forms an image of the incident light rays on the image plane IMG.

The first lens 16 is a meniscus lens that is concave on the image side and has a negative power. The second lens 17 is a meniscus lens that is concave on the image side and has a negative power. The third lens 18 is a lens that is convex toward the object and has a 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 arranged next to each other and having different power codes. The second lens 17 and the third lens 18 can be considered as a set of lenses arranged adjacent to each other and having different power codes.

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

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

The names of the first mirror frame 13 and the second mirror frame 12 are merely names for convenience, and therefore do not prevent the use of other names. For example, the first mirror frame 13 may be referred to as a moving lens holding frame, and the second mirror frame 12 may be referred to as a lens barrel or a barrel.

The intermediate ring 14 is an annular member arranged between the first mirror 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 formed of a material having a coefficient of linear expansion smaller than that of the material of the first mirror frame 13. The intermediate ring 14 may be formed of a material having a coefficient of linear expansion smaller than that of the material of the second mirror frame 12, or may be formed of a material having a coefficient of linear expansion larger than that of the material of the second mirror frame 12. Good.

The fourth lens 19 is fitted and fixed to the fourth inner peripheral surface P14, and movement toward the image side in the optical axis direction is restricted by the aperture wall 12b formed at the image side end of the second mirror 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 19a of the fourth lens 19. The first mirror frame 13 is fitted and fixed to the second inner peripheral surface P12. The image side surface of the flange 13a of the first mirror 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 stepped portion between the first inner peripheral surface P11 and the second inner peripheral surface P12 and the object-side end surface of the first mirror 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. A notch portion 16b is provided at the object side edge portion of the first lens 16, and the movement of the first lens 16 toward the object side in the optical axis direction is restricted by caulking the object side end portion of the second mirror frame 12. ing. A step portion is provided on the image side edge portion 16a of the first lens 16, and a sealing member 15 such as an O-ring is arranged on 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 (second lens 17 and third lens 18) are fixed to the same lens barrel (second lens frame 12). It refers to movement that is greater 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 for example, the reference temperature is 25 ° C.

That is, when the temperature becomes higher than the reference temperature, the first mirror frame 13 expands toward the image side with reference to the surface abutted by the second lens 17, so that the third lens 18 is arranged on the object side. Move away from the lens. Therefore, the amount of expansion of the distance between the second lens 17 and the third lens 18 is compared with the amount of expansion 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. Will grow. As a result, the lens unit 10 can cancel the rearward shift of the focus position caused by the expansion of the lens spacing when the temperature rises.

On the other hand, when the temperature becomes lower than the reference temperature, the first mirror frame 13 contracts toward the object side with respect to the surface abutted by the second lens 17, so that the third lens 18 is arranged on the object side. Move in the direction closer to. Therefore, the amount of contraction of the distance between the second lens 17 and the third lens 18 is compared with the amount of contraction 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. As a result, the lens unit 10 can cancel the forward shift of the focus position caused by the contraction of the lens interval when the temperature drops.

As described above, according to the present embodiment, it is possible to provide a lens unit 10 capable of suppressing focus shift due to thermal expansion or 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 an imaging device according to the present embodiment. The camera module 200 includes an upper case (camera case) 201 which is an exterior component, a mount (pedestal) 202 for holding the lens unit 10, a seal member 203, an image sensor (image sensor) 204, a sensor substrate 205, and the like. 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 provided with an opening for exposing the end portion of the lens unit 10 on the object side and covering the other portion. The mount 202 is arranged inside the upper case 201, and has a female screw on the inner peripheral surface for screwing with a male screw formed on the outer peripheral surface of the second mirror frame 12 of the lens unit 10. The seal member 203 is a member inserted between the flange 12a of the second mirror 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 pickup sensor 204 is arranged inside the upper case 201 and at a focal position formed by the lens unit 10. Further, 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 the light focused by the lens unit 10 into an electric signal. The electric signal obtained by the image pickup sensor 204 is converted into digital data which is a component of the image data.

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

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

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

By sandwiching the first mirror frame 13 between the stepped 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 does not use the intermediate ring 14. The outer circumference of the flange 13a of the frame 13 can be fixed to the second inner peripheral surface P22 of the second mirror frame 22. Since the number of parts can be reduced by the above configuration, the manufacturing cost of the lens unit can be reduced.

[Embodiment 2]
The lens unit 30 according to the second embodiment of the present invention will be described with reference to FIG. The lens unit 30 has an image pickup lens system different from the image pickup 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 mirror frame 33, and a second mirror frame 32. It has an intermediate ring 34 and.

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

The second mirror 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 (first inner peripheral surface P31, second inner peripheral surface P32, third inner peripheral surface P33, and fourth inner peripheral surface P34) having different diameters are formed on the inner wall of the second mirror 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 and fixed to the fourth inner peripheral surface P34, and is moved toward the image side in the optical axis direction by the diaphragm wall 32b formed at the image side end of the second mirror 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 stepped 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 mirror frame 33 are fitted and fixed to the first inner peripheral surface P31. The image side surface of the flange 33a of the first mirror frame 33 is in contact with the stepped 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 mirror frame 33. A notch 36b is provided at the object side edge of the flange 36a of the first lens 36, and the first lens 36 moves toward the object in the optical axis direction by caulking the object side end of the second mirror frame 32. Is regulated.

(Modified Example of Embodiment 2)
As shown in FIG. 4, the lens unit according to the second embodiment can be realized by a configuration that does not use the intermediate ring 34. The difference between the lens unit 40 and the lens unit 30 according to the modified example of the second embodiment will be described.

The second mirror frame 42 is a cylindrical member, and a flange 42a 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 P41, second inner peripheral surface P42, third inner peripheral surface P43, and fourth inner peripheral surface P44) are formed on the inner wall of the second mirror 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 a step portion formed at the image side end portion of the fourth inner peripheral surface P44, and the positioning member 45 regulates the movement of the fourth lens 49 toward the optical axis direction image side. There is.

The flange 38a of the third lens 38 is sandwiched and fixed between the stepped 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. The image side surface of the flange 33a of the first mirror frame 33 is in contact with the stepped portion between the first inner peripheral surface P41 and the second inner peripheral surface P42, and the step between the first inner peripheral surface P41 and the second inner peripheral surface P42. The movement of the first mirror frame 33 toward the image side in the optical axis direction is restricted by the portion.

By sandwiching the first mirror frame 33 between the stepped portion between the first inner peripheral surface P41 and the second inner peripheral surface P42 of the second mirror frame 42 and the flange 36a of the first lens 36, the intermediate ring 34 is formed. Without using it, the outer circumference of the flange 33a of the first mirror frame 33 can be fixed to the first inner peripheral surface P41 of the second mirror frame 42. 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 embodiment, and can be appropriately modified without departing from the spirit.

In the first and second embodiments, the lens supported by the first mirror frame is supported by the second mirror frame by using materials having different linear expansion coefficients for the first mirror frame and the second mirror frame. It is moved with respect to the lens located on the side. The lens unit and the image pickup apparatus according to the present invention are not limited to the above-described configuration. For example, the ambient temperature is detected by a temperature sensor, and the power is determined based on the difference between the detected temperature and the reference temperature. A lens arranged on the image side of the set of lenses having different symbols may be moved with respect to the lens arranged on the object side by 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, 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 that is concave on the image side and has a negative power. The second lens 72 is a lens that is convex toward the object 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 mirror frame 74 made of a material having a large coefficient of linear expansion. The first lens 71 and the third lens 73 are supported by a second mirror frame (not shown) having a coefficient of linear expansion smaller than that of the first mirror frame 74. By moving the second lens 72 supported by the first mirror frame 74 with respect to the first lens 71 located on the object side, it is possible to suppress the out-of-focus caused by thermal expansion or 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, 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 lens having a biconcave shape and having a negative power. The third lens 83 is a biconvex lens having a positive power.

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

Further, when the number of lenses of the lens unit according to the present invention is 5 or more, it is preferable to change the lens spacing of a set of lenses having different power codes located on the object side of the diaphragm. At this time, the number of lenses located on the image side of the aperture is not limited. For example, in the case of a wide-angle lens, the optical system on the object side of the aperture is approximately the focal system. Therefore, by moving the lens of the present invention in the optical system on the object side of the aperture, the focal length of the entire lens system can be increased. Because it can be changed.

10, 20, 30, 40 Lens unit 12, 22, 32, 42 Second mirror frame 12b, 32b Aperture wall 13, 33 First mirror 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 1st inner peripheral surface P12, P22, P32, P42 2nd inner peripheral surface P13, P23, P33, P43 3rd inner peripheral surface P14, P24, P34, P44 4th inner peripheral surface

Claims (5)

3 includes at least a set of lenses composed of 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 more than one lens in the lens barrel.
The first lens and the second lens are lenses having different power codes from each other.
The first lens and the third lens are held in the lens barrel.
The second lens is independently held by a holding frame and is held by a holding frame.
The coefficient of linear expansion differs between the holding frame and the lens barrel.
A lens unit characterized in that the second lens is arranged between the first lens and the third lens so as to be movable with respect to the first lens held in the lens barrel when the temperature changes. .. 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, wherein the first lens and the second lens are located on the object side of the diaphragm. An image pickup apparatus comprising any of the lens units according to claim 1 and an image pickup device so that an image is formed on the image pickup element via the lens unit.

Images