JP2010072032A - Imaging lens and camera module - Google Patents

Abstract

An imaging lens and a camera module that enable downsizing of an imaging apparatus are provided.
At least one of an object side surface (12A) and an image side surface (12B) has a plurality of regions (first region (12C), second region (12D), first region (12E), concentric circles having different sizes around the optical axis. The second region 12F) is divided into a plurality of regions (first region 12C, second region 12D, first region 12E, second region 12F), each having a different aspherical shape. The focal lengths of the plurality of regions (the first region 12C, the second region 12D, the first region 12E, and the second region 12F) are different from each other.
[Selection] Figure 2

Description

  The present invention relates to an imaging lens and a camera module, and more particularly to an imaging lens and a camera module mounted on an imaging device such as a surveillance camera.

  Conventionally, surveillance cameras are equipped with a wide-angle lens with a low magnification and a standard lens (a telephoto lens) with a high magnification as an imaging lens. Then, an image of the entire range (monitoring range) to be monitored is captured by the wide-angle lens, and a part of the monitoring range is captured at a high magnification by the standard lens. Further, the standard lens is mounted so as to be drivable so that a desired portion within the monitoring range can be imaged. Then, by driving the standard lens, it is possible to track and image a target that moves within the monitoring range. Further, surveillance cameras that use imaging lenses having two or more different angles of view are also known.

  However, if a plurality of imaging lenses are used, the imaging device becomes larger accordingly. In recent years, an imaging apparatus has been mounted on a mobile phone or the like, and it is desired to reduce the size of the imaging apparatus. Also in the field of surveillance cameras, downsizing of imaging devices is desired with the diversification of installation locations and downsizing of onboard equipment.

Therefore, Patent Document 1 describes a surveillance camera using a wide-angle lens that progressively distributes focal lengths as an imaging lens. And the surveillance camera of patent document 1 images the wide visual field at a short distance by one wide angle lens. Specifically, the surveillance camera described in Patent Document 1 corrects distortion occurring in a wide-angle lens by progressively distributing the focal length.
Japanese Patent Laid-Open No. 06-088939

  However, the technique described in Patent Literature 1 cannot capture a desired portion within the monitoring range at a high magnification.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an imaging lens and a camera module that enable downsizing of the imaging apparatus.

  In the imaging lens according to the first aspect of the present invention, at least one of the object-side surface and the image-side surface is divided into a plurality of regions by concentric circles having different sizes around the optical axis, and the plurality of regions Have different aspherical shapes, and the focal lengths of the plurality of regions are different from each other.

  In the first aspect of the present invention, at least one of the object-side surface and the image-side surface is divided into a plurality of regions having different aspherical shapes. Further, since the focal lengths of the respective regions are different, the angles of view of the respective regions are different. Thereby, it is possible to capture images in different ranges with one imaging lens. In other words, the role of both the wide-angle lens and the standard lens can be performed by a single imaging lens. For this reason, it is possible to capture images in different ranges simply by providing one imaging lens in the imaging device, and the imaging device can be miniaturized.

  Further, since the focal lengths of the respective regions are different, the magnifications of the respective regions are different. Thereby, a magnification can be changed for every range which each area picturizes. Therefore, it is possible to take an image while changing the magnification within the imaging range of one imaging lens.

Moreover, it is preferable that the light shielding material is affixed to the boundary part of the said area | region.
Since the surface shape of each region is different, the surface shape of the boundary portion of each region changes greatly. Therefore, there is a high possibility that light incident on the boundary portion will be scattered. Then, the scattered light captures a white area in the captured image, and an image near the area becomes unclear. However, the effect of scattered light can be prevented by attaching a light shielding material to the boundary portion.

  In the imaging lens according to the second aspect of the present invention, at least one of the object-side surface and the image-side surface has a first region, and a second region located outside the first region. Is divided into a central part and a peripheral part, and the first area and the second area have different aspheric shapes, and the focal length of the central part is It is larger than the focal length of the peripheral part.

  In the second aspect of the present invention, at least one of the object-side surface and the image-side surface is divided into a first region and a second region, so that the center portion and the peripheral portion are divided. . Further, since the first region and the second region have different aspherical shapes, the focal lengths of the central portion and the peripheral portion are different. For this reason, the angles of view of the central portion and the peripheral portion are different. Thereby, it is possible to capture images in different ranges with one imaging lens. In other words, the role of both the wide-angle lens and the standard lens can be performed by a single imaging lens. For this reason, it is possible to capture images in different ranges simply by providing one imaging lens in the imaging device, and the imaging device can be miniaturized.

  Further, since the focal lengths of the central portion and the peripheral portion are different, the magnifications of the central portion and the peripheral portion are different. Thereby, it is possible to change the magnification within the imaging range of one imaging lens.

In particular, since the focal length at the center is larger than the focal length at the periphery, the angle of view at the center is smaller than the angle of view at the periphery. Thereby, the central part of the imaging range becomes the central part of the captured image, and the peripheral part of the imaging range becomes the peripheral part of the captured image. Therefore, a natural captured image can be obtained.
Further, since the focal length of the central portion is larger than the focal length of the peripheral portion, the magnification of the central portion is higher than the magnification of the peripheral portion. Thereby, the image of the center part of the imaging range can be taken at a high magnification. Therefore, the central part of the imaging range can be observed in more detail.

Further, it is more preferable that a light shielding material is attached to a boundary portion between the first region and the second region.
Since the surface shapes of the first region and the second region are different, the surface shape of the boundary portion between the first region and the second region changes greatly. Therefore, there is a high possibility that light incident on the boundary portion will be scattered. Then, the scattered light captures a white area in the captured image, and an image near the area becomes unclear. However, the effect of scattered light can be prevented by attaching a light shielding material to the boundary portion.

  A camera module according to the present invention has the above-described imaging lens. With the imaging lens described above, it is possible to capture images in different ranges with a single imaging lens. In addition, since the magnification of each region is different, the magnification can be changed for each range captured by each region. In other words, the role of both the wide-angle lens and the standard lens (telephoto lens) can be performed by a single imaging lens. For this reason, it is possible to capture images in different ranges simply by providing one imaging lens in the imaging device, and the imaging device can be miniaturized.

  Moreover, since the surface shape of each area | region differs, the surface shape of the boundary part of each area | region changes a lot. Therefore, there is a high possibility that light incident on the boundary portion will be scattered. Then, the scattered light captures a white area in the captured image, and an image near the area becomes unclear. However, the effect of scattered light can be prevented by attaching a light shielding material to the boundary portion.

  According to the present invention, it is possible to provide an imaging lens and a camera module that enable downsizing of the imaging device.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments.
FIG. 1 shows an example of a camera module 100 according to an embodiment of the present invention. The camera module 100 includes an entrance diaphragm 11, an imaging lens 12, and the like.
Further, the entrance stop 11, the imaging lens 12, and the imaging element 13 are arranged in this order from the object side to the imaging side.

The distance between the entrance stop 11 and the imaging lens 12 is 0.3 to 0.5 times the effective diameter of the imaging lens 12. Further, the distance between the entrance stop 11 and the imaging lens 12 is preferably 0.4 times the effective diameter of the imaging lens 12.
The image sensor 13 includes a cover glass 13A, a solid-state image sensor 13B, and the like. The cover glass 13A has an IRCF (infrared cut filter) function or the like so that light rays other than visible light do not enter the solid-state imaging device 13B.
The solid-state imaging device 13B is configured by a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like.

FIG. 2 is a ray diagram of the camera module 100 according to the embodiment of the present invention.
A surface 12A on the object side of the imaging lens 12 (hereinafter referred to as an object side surface 12A) is formed in an aspheric shape. Further, the object side surface 12A of the imaging lens 12 is divided into a plurality of regions by concentric circles having different sizes around the optical axis.
Specifically, the object side surface 12A of the imaging lens 12 is divided into a first region 12C in the central region and a second region D that is a peripheral region located outside the first region 12C.

An image side surface 12B (hereinafter referred to as an image side surface 12B) of the imaging lens 12 is formed in an aspherical shape. Further, the image side surface 12B of the imaging lens is divided into a plurality of regions by concentric circles having different sizes around the optical axis.
Specifically, the image side surface 12B of the imaging lens 12 is divided into a first region 12E in the central region and a second region 12F that is a peripheral region located outside the first region 12E.

  The boundary position between the first region 12C and the second region 12D on the object side surface 12A is substantially the same as the boundary position between the first region 12E and the second region 12F on the imaging surface 12B. Specifically, the boundary position on the object side surface 12 </ b> A and the boundary position on the imaging surface 12 </ b> B may be positions that are 20% to 40% of the effective diameter of the imaging lens 12. Furthermore, the boundary position on the object side surface 12 </ b> A and the boundary position on the imaging surface 12 </ b> B are more preferably 30% of the effective diameter of the imaging lens 12.

In the object side surface 12A, the first region 12C and the second region 12D have different aspheric shapes. Thereby, the object side surface 12A is divided into a first region 12C and a second region 12D.
On the image side surface 12B, the first region 12E and the second region 12F have different aspheric shapes. Thus, the image side surface 12B is divided into a first region 12E and a second region 12F.
The imaging lens 12 is obtained by dividing the object side surface 12A into a first region 12C and a second region 12D and dividing the image side surface 12B into a first region 12E and a second region 12F. Is divided into a central part and a peripheral part.

In addition, the first region 12C and the second region 12D have different aspheric shapes, and the first region 12E and the second region 12F have different aspheric shapes, whereby the imaging lens 12 The lens power at the center of the lens is different from the lens power at the outside. Specifically, the focal length of the central portion of the imaging lens 12 is larger than the focal length of the peripheral portion.
More specifically, the focal length of the central portion of the imaging lens 12 is preferably 2 to 3 times the effective diameter. Furthermore, the focal length of the central portion of the imaging lens 12 is more preferably 2.3 times the effective diameter. Moreover, it is preferable that the focal distance of the peripheral part of the imaging lens 12 is 0.8 to 0.9 times the effective diameter. Furthermore, the focal length of the periphery of the imaging lens 12 is more preferably 0.85 times the effective diameter.

  Further, it is preferable that a light shielding material is attached to a boundary portion between the first region 12E and the second region 12F on the image side surface 12B. As the light shielding material, an optical shield can be used. For example, a ring-shaped cut filter can be used.

  According to the imaging lens 12 and the camera module 100 according to the present embodiment described above, the object side surface 12A is divided into the first region 12C and the second region 12D. Further, the image side surface 12B is divided into a first region 12E and a second region 12F. Thereby, the imaging lens 12 is divided | segmented into the center part and the peripheral part. In addition, since the first region 12C and the second region 12D have different aspherical shapes, and the first region 12E and the second region 12F have different aspherical shapes, the central portion and the peripheral portion The focal length is different. For this reason, the angles of view of the central portion and the peripheral portion are different. As a result, it is possible to capture images in different ranges with the single imaging lens 12. In other words, the role of both the wide-angle lens and the standard lens can be performed by the single imaging lens 12. Therefore, it is possible to pick up images in different ranges simply by providing one image pickup lens 12 in the image pickup device, and the image pickup device can be miniaturized.

  Further, since the focal lengths of the central portion and the peripheral portion are different, the magnifications of the central portion and the peripheral portion are different. As a result, it is possible to take an image while changing the magnification within the imaging range of one imaging lens 12.

In particular, since the focal length at the center is larger than the focal length at the periphery, the angle of view at the center is smaller than the angle of view at the periphery. Thereby, the central part of the imaging range becomes the central part of the captured image, and the peripheral part of the imaging range becomes the peripheral part of the captured image. Therefore, a natural captured image can be obtained.
Further, since the focal length of the central portion is larger than the focal length of the peripheral portion, the magnification of the central portion is higher than the magnification of the peripheral portion. Thereby, the image of the center part of the imaging range can be taken at a high magnification. Therefore, the central part of the imaging range can be observed in more detail.

  Further, a light shielding material is attached to the boundary portion between the first region 12E and the second region 12F. Since the surface shapes of the first region 12E and the second region 12F are different, the surface shape of the boundary portion between the first region 12E and the second region 12F changes greatly. Therefore, there is a high possibility that light incident on the boundary portion will be scattered. Then, the scattered light captures a white area in the captured image, and an image near the area becomes unclear. However, the effect of scattered light can be prevented by attaching a light shielding material to the boundary portion.

Example 1
Next, Example 1 of the present invention will be described. The table shown in FIG. 3 shows lens data of the camera module 100 according to the first embodiment.
3 shows the respective surfaces of the camera module 100 according to the first embodiment (the surface of the entrance stop 11, the first surface (the object side surface 12A), the second surface (the image side surface 12B), and the cover glass surface (the cover glass). 13A, the radius of curvature, the thickness, the CONIC coefficient, and the aspherical coefficient on the imaging surface (the surface of the imaging element 13B)).

  In the camera module 100 according to the first embodiment, the glass material of the imaging lens 12 is resin. The imaging lens 12 has a refractive index of 1.51 and a dispersion value of 70.3. In the camera module 100 according to the first embodiment, the cover glass 13A is made of glass. The cover glass 13A has a refractive index of 1.52 and a dispersion value of 64.2.

  As shown in the table of FIG. 3, the curvature radius of the central portion of the imaging lens 12 and the curvature radius of the peripheral portion are greatly different in both the object side surface 12A and the image side surface 12B.

数式（１）において、ｈは光線高さ、Ｙ（ｈ）は光線高さｈにおけるサグ量、ＫはＣＯＮＩＣ係数、ｃは曲率、Ａ_４は４次の非球面係数である。ここで、ｃ＝１／Ｒ、Ｒは曲率半径である。 Further, the surface shape of the object side surface 12A of the imaging lens 12 is defined by the radius of curvature, the CONIC coefficient, the aspheric coefficient of the first surface in the table shown in FIG. Similarly, the surface shape of the image side surface 12B of the imaging lens 12 is defined by the radius of curvature, the CONIC coefficient, the aspheric coefficient of the second surface in the table shown in FIG.

In Equation (1), h is the height of rays, Y (h) is the sag of the ray height h, K is CONIC coefficient, c is curvature, _{A 4} are aspherical coefficients of fourth order. Here, c = 1 / R and R is a radius of curvature.

In the object side surface 12A of the imaging lens 12 according to the first example, the range of the first region 12C is a range from the optical axis to 0.35 mm in the radial direction. The range of the second region D is a range from the outer edge of the first region 12C to 1.02 mm.
Further, in the image side surface 12B of the imaging lens 12 according to the first example, the range of the first region 12E is a range from the optical axis to 0.38 mm in the radial direction. The range of the second region F is a range from the outer edge of the first region E to 1.14 mm.

  Further, as shown in FIG. 2, the central portion of the imaging lens 12 has a lens shape convex toward the object side. On the other hand, the peripheral portion of the imaging lens 12 has a lens shape convex toward the image side. In addition, on the image side surface 12B, the surface shape of the boundary portion between the first region 12E and the second region 12F changes greatly. Specifically, a step is formed at the boundary between the first region 12E and the second region 12F.

  And by having the above structures, the focal distance of the center part of the imaging lens 12 concerning Example 1 can be 5.26 mm, and the focal distance of a peripheral part can be 2.16 mm. Further, the magnification of the central portion of the imaging lens 12 according to the first embodiment can be 0.673 times, and the magnification of the peripheral portion can be 0.633 times. In other words, the central portion of the imaging lens 12 can be used as a telephoto lens (standard lens), and the peripheral portion of the imaging lens 12 can be used as a wide-angle lens.

FIG. 4 shows distortion occurring in the imaging lens 12 according to the first example.
As shown in FIG. 4, in the imaging lens 12 according to the example 1, pincushion distortion occurs at an image height of 0 mm to about 0.4 mm, and a barrel at an image height of about 0.7 mm to about 1.3 mm. Mold distortion has occurred. Therefore, it can be seen that the central portion of the imaging lens 12 has a function as a telephoto lens, and the peripheral portion has a function as a wide-angle lens.

In addition, measurement of distortion is not possible at an image height of about 0.4 to about 0.7. This is because the surface shape of the imaging lens 12 changes greatly at the boundary position between the central portion and the peripheral portion of the imaging lens 12. That is, since the scattered light is generated at the portion where the surface shape changes greatly, the distortion aberration cannot be measured.
When such scattered light is incident on the image sensor 13B, a white-lighted area is captured in the captured image, and an image near the area becomes unclear. Therefore, it is preferable that a light shielding material is attached to a boundary portion between the central portion and the peripheral portion of the imaging lens 12.

  In the imaging lens 12 according to the first embodiment, the width of the second region 12D and the second region 12F is 0.5 mm or more, and a step formed between the first region 12E and the second region 12F. Is 0.1 mm or more. In other words, both the width of each region and the step between the regions can be designed large. Therefore, as the glass material of the imaging lens 12, not only a resin but also a difficult material such as glass can be used.

It is a disassembled perspective view which shows schematic structure of the camera module concerning embodiment of this invention. It is a light ray diagram of the camera module concerning an embodiment of the invention. It is a table | surface which shows the lens data of the camera module concerning Example 1 of this invention. 3 is a graph showing distortion aberration generated in the image sensor according to Example 1 of the present invention.

Explanation of symbols

12 imaging lens 12A object side surface (object side surface)
12B Image side (image side surface)
12C First region (region)
12D second region (region)
12E First region (region)
12F Second region (region)
100 camera module

Claims (5)

At least one of the object side surface and the image side surface is divided into a plurality of regions by concentric circles having different sizes around the optical axis,
Each of the plurality of regions has a different aspheric shape,
The imaging lenses having different focal lengths in the plurality of regions.   The imaging lens according to claim 1, wherein a light shielding material is affixed to a boundary portion of the region. At least one of the object-side surface and the image-side surface is divided into a first region and a second region located outside the first region, so that a central portion and a peripheral portion are divided. And
The first region and the second region have different aspheric shapes,
An imaging lens in which a focal length of the central portion is larger than a focal length of the peripheral portion.   The imaging lens according to claim 3, wherein a light shielding material is affixed to a boundary portion between the first region and the second region.   The camera module which has an imaging lens as described in any one of Claims 1 thru | or 4.

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