KR101994286B1 - Fish-eye lens system - Google Patents

Abstract

The present invention provides a zoom lens comprising, in order from an object side to an image side, a first lens unit having a total negative refracting power and including four lenses, and a second lens unit having an overall positive refracting power and including at least three lenses And a fisheye lens system satisfying the following conditions is provided.
0.3 <| FL / FF | <0.5
Here, FF denotes the focal length of the first lens unit, and FL denotes the focal length of the second lens unit.

Description

Fish-eye lens system

The present invention relates to a fish-eye lens system.

The lens system of an electronic image pickup device such as a digital still camera, a video camera, a surveillance camera, a mobile phone camera and the like which implements an image by using an image pickup device such as a CCD or a CMOS, Various forms have been adopted. With the miniaturization and high quality of the electronic image pickup device, the demand for a lens system that can cope with mega pixels of a small size and a high resolution is steadily increasing.

Particularly, in an electronic image pickup apparatus such as a surveillance camera, a fish-eye lens system is sometimes used as a lens system in order to secure a wide field of view. The lens system must be well corrected to the aberrations occurring in the periphery of the screen in order to clearly record even the small information that the subject has. However, in order to achieve high performance, it is difficult to achieve miniaturization, and in order to miniaturize it, it is accompanied with an increase in manufacturing cost, so it is difficult to satisfy high optical performance such as high power and high resolving power and manufacturing cost.

An embodiment of the present invention relates to a small-sized fish-eye lens system including a relatively small number of lenses and having high resolving power in the center and the periphery.

According to an aspect of the present invention, there is provided a zoom lens comprising, in order from an object side to an image side, a first lens group having negative refracting power as a whole; And a second lens group having a positive refracting power as a whole and including at least three lenses, wherein the second lens group satisfies the following conditions.

<Condition>

0.3 <| FL / FF | <0.5

Here, FF denotes the focal length of the first lens unit, and FL denotes the focal length of the second lens unit.

According to one aspect of the present invention, the first lens group includes three lenses having a negative refractive power and one lens having a positive refractive power, wherein the second lens group has a negative refracting power A first lens, a second lens having a positive refractive power, and a third lens having a positive refractive power, wherein the first lens and the second lens are bonded to each other to form a cemented lens.

According to another aspect of the present invention, the first lens group may include a lens having at least one aspherical surface and having a positive refractive power.

According to another aspect of the present invention, the second lens group may include at least one aspherical surface and a lens having a positive refractive power.

According to still another aspect of the present invention, the second lens group may include a lens disposed closest to the image side and having a positive refractive power and satisfying the following conditions.

<Condition>

Nd < 1.52

Here, the refractive index at the d line of the lens disposed closest to the image side of the second lens unit and having a positive refractive power is shown.

According to another aspect of the present invention, there is provided an image processing apparatus comprising:

A first lens group having a total negative refracting power and including four lenses; And

And a second lens group having a positive refractive power as a whole and including three lenses,

Wherein the first lens group includes an aspheric surface, the lens disposed closest to the image side,

And a lens disposed closest to the image side of the second lens group satisfies the following conditions.

<Condition>

Nd < 1.52

Here, Nd represents the refractive index at the d line of the lens disposed on the image side closest to the image side of the second lens group.

According to the embodiment of the present invention as described above, it is possible to provide a fish-eye lens system that is compact and can sufficiently secure the resolution of not only the center but also the peripheral portion.

FIG. 1 schematically shows a configuration of a fish-eye lens system according to an embodiment of the present invention.
2 schematically shows the configuration of a fish-eye lens system according to the first embodiment of the present invention.
Fig. 3 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism and distortion of the fish-eye lens system shown in Fig. 2. Fig.
Fig. 4 shows an aberration diagram of the coma aberration of the fish-eye lens system shown in Fig. 2. Fig.
5 schematically shows a configuration of a fish-eye lens system according to a second embodiment of the present invention.
Fig. 6 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism and distortion of the fish-eye lens system shown in Fig. 5. Fig.
Fig. 7 shows an aberration diagram relating to coma aberration of the fish-eye lens system shown in Fig. 5. Fig.
8 schematically shows the configuration of a fish-eye lens system according to the third embodiment of the present invention.
Fig. 9 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism, and distortion of the fish-eye lens system shown in Fig. 8. Fig.
Fig. 10 shows an aberration diagram relating to coma aberration of the fish-eye lens system shown in Fig.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and particular embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another. The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, Should not be construed to preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof. In the following description, "/" may be interpreted as "and "

FIG. 1 schematically shows a configuration of a fish-eye lens system according to an embodiment of the present invention.

In the fish-eye lens system according to the embodiment of the present invention, the optical performance can be ensured by the second lens group G2 while securing a sufficient field of view, that is, an angle of view, by the first lens group G1. The fisheye lens system includes, in order from the object side to the image side, a first lens group G1, a stop ST, and a second lens group G2 having a positive refractive power as a whole, all of which have negative refractive power. An optical block OB equivalent to an optical filter, a face plate or the like may be disposed between the second lens group G2 and the image plane IP.

The fish-eye lens system according to the embodiment of the present invention can satisfy the following conditions.

<Condition 1>

0.3 <| FL / FF | <0.5

Here, FF denotes the focal length of the first lens group G1 and FL denotes the focal length of the second lens group G2.

Condition 1 defines the ratio of the focal length of the second lens group G2 to the focal length of the first lens group G1 and is set so that the refractive power of the first lens group G1 and the second lens group G2 is regulated It is. By satisfying the condition 1, the generation of aberration can be suppressed while securing an angle of view of about 180 degrees. On the other hand, when the value of condition 1 deviates from the upper limit, a larger angle of view can be obtained, but the aberration correction of the peripheral part is difficult and the optical performance deteriorates. If the value of condition 1 deviates from the lower limit, the aberration correction may be good, Is difficult to secure.

The first lens group G1 may include four lenses. For example, the first lens group G1 includes a first lens 11 having a negative refractive power, a second lens 12 having a negative refractive power, a third lens 13 having a negative refractive power, and a fourth lens having a positive refractive power And a lens 14. In this case, the first to fourth lenses 11, 12, 13, and 14 may be independent lenses. In the present specification, the independent lens means a single lens that does not constitute a cemented lens.

The first lens group G1 may include at least one aspherical surface. For example, the fourth lens disposed closest to the object side among the lenses belonging to the first lens group G1 may include at least one aspherical surface, and astigmatism can be effectively removed through such a configuration.

The second lens group G2 may include three or more lenses. In one embodiment, the second lens group G2 may include a fifth lens 15 having a negative refracting power, a sixth lens 16 having a positive refracting power, and a seventh lens having a positive refracting power. At this time, the fifth lens 15 and the sixth lens may constitute a cemented lens, and the seventh lens may be an independent lens. The second lens group G2 can correct the chromatic aberration of the fish-eye lens system through the cemented lens.

A lens disposed at the most image side among the lenses included in the second lens group G2, for example, the seventh lens may satisfy the following conditions.

<Condition 2>

Nd < 1.52

Here, Nd represents the refractive index at the d line of the seventh lens disposed closest to the image side among the lenses included in the second lens group G2.

Condition 2 defines the refractive index at the d line of the seventh lens disposed closest to the image side among the lenses included in the second lens group G2. When the condition 2 is exceeded, it becomes difficult to control the coma aberration.

The second lens group G2 may include a lens having a positive refractive power and having at least one aspherical surface, and thus the number of lenses can be reduced and the curvature aberration can be eliminated as a whole. For example, the seventh lens, which is the lens disposed closest to the object side among the second lens group G2, may have at least one aspherical surface.

The fish-eye lens system as described above can obtain an image of a high resolution even at a small size and at a peripheral portion. Therefore, it can be very usefully used in an electronic image pickup apparatus such as a surveillance camera which requires a high quality image while securing a wide field of view.

The definitions of the aspheric surface in the embodiment of the present invention are as follows.

The aspheric surface shape of the zoom lens according to the embodiment of the present invention can be expressed by the following expression with the direction of the light ray as a positive when the direction of the optical axis is the x axis and the direction perpendicular to the optical axis direction is the y axis have. Where x is the distance from the vertex of the lens to the optical axis direction, y is the distance in the direction perpendicular to the optical axis, k is a conic constant, A, B, C and D are aspheric coefficients, and c represents the inverse number (1 / R) of the radius of curvature at the apex of the lens.

In the following description, f denotes the focal length, F # denotes the F number, Rn denotes the radius of curvature, and Dn denotes the distance between the lens surface and the lens surface on the optical axis. Dn represents the thickness of the lens or the distance between the lens and the lens. And, nd is the refractive index of the material, and vd is the Abbe number of the material.

&Lt; Embodiment 1 >

Table 1 shows design data of a fish-eye lens system according to the first embodiment of the present invention shown in Fig.

f: 1.076 mm

F #: 2.4797

S Rn Dn nd vd One 13.41021 0.800000 1.804200 46.5025 2 8.97426 2.633144 3 10.58614 1.600000 1.804200 46.5025 4 3.61683 3.380942 5 181.86286 0.800000 1.804200 46.5025 6 3.76880 2.462854 7 -10.67649 1.600000 1.922860 20.8814 8 -5.14622 3.556771 9 (ST) Infinity 0.600000 10 6.14821 1.320050 1.740770 27.7605 11 2.02282 1.146239 1.496997 81.6084 12 -22.50381 0.100000 13 7.68964 1.700000 1.497103 81.5596 14 -2.61441 0.847909 15 Infinity 1.200000 1.516798 64.1983 16 Infinity 2.252076 IP Infinity

Table 2 shows the aspherical surface coefficients in the zoom lens system shown in Fig.

S K A B C D 7 0 5.375099E-03 -2.398125E-04 6.878614E-06 1.192746E-06 8 0 4.140647E-03 -1.888026E-04 1.252336E-06 1.126409E-06 13 0 -7.007768E-03 9.721653E-04 -5.589134E-04 8.937037E-05 14 0 5.058978E-03 -8.429543E-04 1.963392E-04 -4.160351E-05

Fig. 3 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism and distortion of the fish-eye lens system shown in Fig. 2, and Fig. 4 shows an aberration diagram relating to coma aberration of the fish- .

3, the longitudinal spherical aberration is shown for light having wavelengths of 656.28 (nm), 587.56 (nm), 546.07 (nm), 486.13 (nm), and 435.83 (nm), respectively, Tangential field curvature (S) and sagittal field curvature (S) with respect to light with a wavelength of 546.07 (nm).

&Lt; Embodiment 2 >

Table 3 shows design data of the fish-eye lens system according to the second embodiment of the present invention shown in Fig.

f: 1.0935 mm

F #: 2.4708

S Rn Dn nd vd One 13.33420 0.800000 1.804200 46.5025 2 9.00000 2.495934 3 10.18615 1.468411 1.804200 46.5025 4 3.66466 3.517754 5 133.55519 0.800000 1.804200 46.5025 6 3.98878 2.675220 7 -9.61814 1.600000 1.922860 20.8814 8 -4.96460 3.571044 9 (ST) Infinity 0.600000 10 7.13634 1.238249 1.740770 27.7605 11 2.09788 1.187239 1.496997 81.6084 12 -10.93557 0.100000 13 8.48604 1.646149 1.497103 81.5596 14 -2.77662 0.847872 15 Infinity 1.200000 1.516798 64.1983 16 Infinity 2.252127 IP Infinity

Table 4 shows the aspherical surface coefficients in the zoom lens system shown in Fig.

S K A B C D 7 0 3.830008E-03 -1.211471E-04  5.539868E-06  8.045927E-07 8 0 3.557185E-03 -1.452776E-04  6.720989E-06  5.079923E-07 13 0 -6.759729E-03 6.412241E-04 -4.810219E-04  8.463281E-05 14 0 2.709631E-03 -7.854109E-04  1.043544E-04 -2.878036E-05

Fig. 6 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism and distortion of the fish-eye lens system shown in Fig. 5, and Fig. 7 shows an aberration diagram relating to coma aberration of the fish- .

6, the longitudinal spherical aberration is shown for light having wavelengths of 656.28 nm, 587.56 nm, 546.07 nm, 486.13 nm and 435.83 nm, respectively, and the surface curvature is 546.07 nm Tangential field curvature (S) and sagittal field curvature (S) with respect to light with a wavelength of 546.07 (nm).

&Lt; Third Embodiment >

Table 5 shows design data of a fish-eye lens system according to the third embodiment of the present invention shown in Fig.

f: 1.0918 mm

F #: 2.5548

S Rn Dn nd vd One 13.34563 0.800000 1.804200 46.5025 2 9.00000 2.529599 3 10.20996 1.517224 1.804200 46.5025 4 3.67344 3.524585 5 165.10426 0.800000 1.804200 46.5025 6 4.02904 2.854560 7 -9.47315 1.600818 1.922860 20.8814 8 -4.90047 3.243902 9 (ST) Infinity 0.600000 10 7.75820 1.300000 1.740770 27.7605 11 1.98862 1.117158 1.496997 81.6084 12 -12.07153 0.100799 13 9.18657 1.584950 1.497103 81.5596 14 -2.56932 0.847509 15 Infinity 1.200000 1.516798 64.1983 16 Infinity 2.378971 IP Infinity

Table 6 shows the aspherical surface coefficients in the zoom lens system shown in Fig.

S K A B C D 7 0 3.975983E-03 -1.170791E-04  6.601930E-06  4.961538E-07 8 0 3.726579E-03 -1.203842E-04  6.570969E-06  2.939155E-07 13 0 -7.067047E-03 3.242890E-04 -3.229535E-04  8.235251E-05 14 0 3.801788E-03 -1.215295E-03  2.608991E-04 -4.893262E-05

Fig. 9 shows aberration diagrams relating to longitudinal spherical aberration, astigmatism and distortion of the fish-eye lens system shown in Fig. 8, and Fig. 10 shows aberration diagrams relating to coma aberration of the fish- .

9, the longitudinal spherical aberration is shown for light having wavelengths of 656.28 (nm), 587.56 (nm), 546.07 (nm), 486.13 (nm), and 435.83 (nm), respectively, Tangential field curvature (S) and sagittal field curvature (S) with respect to light with a wavelength of 546.07 (nm).

Table 7 below shows that the fish-eye lens system of each embodiment of the present invention satisfies the above condition.

Example 1 Example 2 Example 3 Condition 1 0.498211 0.412097 0.349276 Condition 2 1.497103 1.497103 1.497103

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications and variations without departing from the spirit and scope of the invention. Accordingly, it is intended that the appended claims cover all such modifications and variations as fall within the true spirit of the invention.

G1: first lens group G2: second lens group
11: first lens 12: second lens
13: third lens 14: fourth lens
14: fifth lens 15: sixth lens
17: seventh lens OB: optical block

Claims (6)

In order from the object side to the image side,
A first lens group including three lenses having a negative refractive power as a whole and having a negative refractive power and a single lens having a positive refractive power; And
And a second lens group having a positive refractive power as a whole and including at least three lenses, and satisfies the following conditions.
<Condition>
0.3 <| FL / FF | <0.5
Here, FF denotes the focal length of the first lens unit, and FL denotes the focal length of the second lens unit. The method according to claim 1,
Wherein the second lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, and a third lens having a positive refractive power from the object side, wherein the first lens and the second lens are bonded to each other, Forming, fisheye lens system. The method according to claim 1,
Wherein said first lens group comprises a lens having at least one aspherical surface and having a positive refractive power. The method according to claim 1,
Wherein the second lens group includes at least one aspherical surface and includes a lens having a positive refractive power. ◈ Claim 5 is abandoned due to the registration fee. The method according to claim 1,
Wherein said second lens group comprises a lens disposed closest to the image side and having a positive refractive power and satisfying the following conditions.
<Condition>
Nd < 1.52
Here, the refractive index at the d line of the lens disposed closest to the image side of the second lens unit and having a positive refractive power is shown. In order from the object side to the image side,
A first lens group having a total negative refracting power and including four lenses; And
And a second lens group having a positive refractive power as a whole and including three lenses,
Wherein the first lens group includes an aspheric surface, the lens disposed closest to the image side,
Wherein the lens disposed closest to the image side among the second lens groups satisfies the following condition.
<Condition>
Nd < 1.52
Here, Nd represents the refractive index at the d line of the lens disposed on the image side closest to the image side of the second lens group.

Images