KR100647555B1 - optical system for high resolving power - Google Patents

Abstract

The high-resolution optical system includes a first lens group having negative refractive power; It consists of a second lens group having a positive refractive power, and includes at least one aspherical lens. The first lens group includes a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, and the second lens group includes a fourth lens having negative refractive power and positive refractive power. And a fifth lens having a positive refractive power, and a sixth lens having positive refractive power, and an aperture is positioned between the first lens group and the second lens group. The optical system for high resolution is -0.17 <f / f1 <-0.16, 0.09 <r3 / Vd1 <0.15, 3.5 <f1 / f12 <4.0, 0.19 <d6 / dI <0.2 (where f is the focal length of the whole optical system, f1: Focal length of the first lens, r3: Radius of curvature of the object-side surface of the first lens, Vd1: Abbe number of the first lens, f12: Composite focal length of the first lens and the second lens, d6: Of the third lens Center distance between the image side surface and the iris, dI: the center distance between the first lens and the iris. Therefore, a high resolution of about 1.5 million pixels or more can be realized by using the minimum number of lenses, and an optical system having a brightness Fno of 2.8 or more is provided.

CCD, Aspheric Lens, Spherical Lens

Description

Optical system for high resolving power

1 is a structural diagram of an optical system for high resolution according to a first embodiment of the present invention.

2 is a structural diagram of an optical system for high resolution according to a second embodiment of the present invention.

3 is an aberration diagram of an optical system for high resolution according to the first and second embodiments of the present invention.

4 is a structural diagram of an optical system for high resolution according to a third embodiment of the present invention.

5 is a structural diagram of an optical system for high resolution according to a fourth embodiment of the present invention.

6 is aberration diagrams of the optical system for high resolution according to the third and fourth embodiments of the present invention.

The present invention relates to an optical system for high resolution, and more particularly, to an optical system applicable to imaging of a subject of a charge coupled device (CCD).

As CCD technology is developed, it is possible to realize high resolution, and accordingly, a high resolution lens for image forming of a high resolution CCD is required. Cameras to which such a CCD is applied have a uniform specification of a lens unit and a mount unit combined with the lens, and thus, interchangeable lenses can be mounted. Examples of the interchangeable lenses include standard lenses, telephoto lenses, and wide-angle lenses. As a representative type of such an interchangeable lens, a retro-focus type lens is mainly used.

Conventionally, an optical system that can be applied to a CCD having a high resolution of about 1.5 million pixels is developed and used, but according to the development of technology, a CCD having 1.5 million or more 2 million pixels is realized, and thus suitable for a CCD of 2 million pixels. An optical system is required.

Therefore, an object of the present invention is to provide an optical system for high resolution suitable for a CCD of 1.5 million pixels or more.

Moreover, the objective of this invention is to implement | achieve a high resolution with minimum number of sheets, and to provide the optical system whose lens brightness F is 2.8 or more.

For this purpose, the high resolution optical system according to the present invention comprises a first lens group having negative refractive power and a second lens group having positive refractive power, and includes at least one aspherical lens.

The first lens group includes a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, and the second lens group includes a fourth lens having negative refractive power and positive refractive power. And a fifth lens having a positive refractive power, and a sixth lens having positive refractive power, and an aperture is positioned between the first lens group and the second lens group.                     

The optical system for high resolution of this invention satisfies -0.17 <f / f1 <-0.16, 0.09 <r3 / Vd1 <0.15, 3.5 <f1 / f12 <4.0, 0.19 <d6 / dI <0.2, where f is Is the focal length of the entire optical system, f1 is the focal length of the first lens, r3 is the radius of curvature of the object-side surface of the first lens, Vd1 is the Abbe's number of the first lens, and f12 is the distance between the first and second lenses. It is the composite focal length, d6 is the center distance between the image side surface of the third lens and the aperture, and dI is the center distance from the first lens to the aperture.

In addition, in order to achieve the above object, in the high-resolution optical system according to the present invention, both the first and second lens groups may be made of spherical lenses, where -0.95 <f / fN <-0.85, nd3> 1.80 (where , fN: composite focal length of the first lens and the second lens, and nd3: refractive index of the third lens.

Then, with reference to the accompanying drawings will be described in detail with reference to the accompanying drawings the most preferred embodiment that can be easily carried out by those of ordinary skill in the art.

1 shows a structure of an optical system for high resolution according to a first embodiment of the present invention, and FIG. 2 shows a structure of an optical system for high resolution according to a second embodiment of the present invention.

First, the optical system for high resolution according to the first and second embodiments of the present invention will be described with reference to FIGS. 1 and 2.

As shown in Figs. 1 and 2, the high-resolution optical system according to the first and the embodiments of the present invention includes a first lens group 10 having negative refractive power which is sequentially arranged from the object side on the same optical axis. And a second lens group 20 having positive refractive power.

The first lens group 10 is a meniscus-type first lens 101 having a negative refractive power and a convex object side surface sequentially from an object side, and a meniscus type having a negative refractive power and a convex object side surface. 2nd lens 102 and the 3rd lens 103 which has positive refractive power, and the object side is convex.

The second lens group 20 includes a fourth lens 201 having negative refractive power and concave on both sides, a fifth lens 202 having positive refractive power and convex on both sides, and a sixth lens 203 having positive refractive power and on both sides. )

An aperture A is provided between the first lens group 10 and the second lens group 20, and the optical low pass filter F1 is disposed on an image side of the sixth lens 203 of the second lens group 20. Is installed.

In the high resolution optical system according to the first and second embodiments, the first lens 101 has a negative refractive power to widen the angle of view, and the second lens 102 minimizes the negative refractive power generated by the first lens 101. In order to have negative refractive power, the negative refractive power of the first lens group 10 was divided. In addition, the third lens 103 has a positive refractive power in order to minimize aberrations caused by the first and second lenses 101 and 102.

The fourth lens 201 and the fifth lens 202 of the second lens group 20 are designed to have negative refractive power and positive refractive power to cancel the aberration remaining in the first first lens group 10, and The lens 203 corrects the aberration of the entire optical system and corrects the distortion aberration.                     

At this time, the third lens 103 of the first lens group 10 is made of a low dispersion material having a strong positive refractive power in order to correct the aberration generated in the preceding lenses 101 and 102.

The optical system for high resolution according to the first and second embodiments of the present invention having such a structure satisfies the following conditions.

-0.17 <f / f1 <-0.16

0.09 <r3 / Vd1 <0.15

3.5 <f1 / f12 <4.0

0.19 <d6 / dI <0.2

4.0 <d6 + d7 <5.0

0.6 <fB / Exi <0.67

0.4 <f / dT <0.6

108 <r9 / d9 <110

f: focal length of the whole optical system,

f1: focal length of the first lens 101,

r3: radius of curvature of the object-side surface of the first lens 101,

Vd1: Abbe's number of the first lens 101,

f12: composite focal length of the first lens 101 and the second lens 102,

d6: center distance between the image side surface of the third lens 103 and the aperture A,

dI: center distance between the first lens 101 and the aperture A. FIG.

d7: center distance between the aperture A and the object-side surface of the fourth lens 201,

fB: back focal length of optical system,

Exi: the exit pupil position of the optical system,

dT: center distance from the iris to the top,

r6: radius of curvature of the image-side surface of the fourth lens 201,

d9: center distance between the fourth lens 201 and the fifth lens 202.

Equation 3 relates to the radius of curvature of the image side surface of the first lens 101, which is the first from the object side, among the lenses having negative refractive power of the first lens group 10. The first lens group 10 forms negative refractive power only when it is positioned within the range set by.

Equations 5 and 6 are provided to minimize the space in which the shutter can be inserted by installing the aperture A between the first lens group 10 and the second lens group 20. When the lower limit values of the equations (5) and (6) are exceeded, the aberration correction becomes easy and the performance is improved, but the aperture A cannot be provided.

Example values of the high resolution optical system of the first and second embodiments of the present invention that satisfy the above-described Equations 1 to 8 are as follows.

In the following, ri (i = 1-15) denotes the radius of curvature of the lens surface, di (i = 1-15) denotes the thickness of the lens or the distance between the lenses, and N denotes the refractive index of d-lime. The unit of the value corresponding to the distance is millimeters (mm).

 Aspheric formulas are generally widely used formulas, and thus detailed descriptions of the formulas are omitted.

The focal length of the high-resolution optical system according to the first embodiment is 7.9, the post focal length is 8.5 (in air), the angle of view is 30 degrees, and the Fno is 2.1.

Face number Radius of curvature (r) Thickness and spacing (d) Refractive index (N) Dispersion value (ν) *One 6.66140 1.982787 1.65844 50.85 2 4.80936 2.500000 3 10.35138 1.233561 1.51680 64.20 4 4.53068 2.500000 5 7.96513 2.000000 1.83400 37.34 6 24.17505 2.509657 7 (aperture) ∞ 2.000000 8 -16.38805 0.700000 1.80518 25.46 9 10.90840 0.103378 10 13.70588 1.800000 1.58913 61.25 11 -6.52345 0.100000 12 11.33549 2.220467 1.69680 55.46 13 -25.97247 0.000000 14 0.1E + 11 4.500000 1.51680 64.20 15 0.1E + 11 5.499873 Top ∞ 0.000000

* Denotes an aspherical surface, and aspheric coefficients are shown in Table 2 below.                     

Aspheric coefficient of the first side  K 0.168232  A -0.271564E-03  B  0.216965E-04  C -0.655734E-06  D  0.803419E-08

The focal length of the optical system for high resolution according to the second embodiment of the present invention is 8.0, the focal length is 7.7 (in air), the angle of view is 29 DEG, the Fno is 2.1, and the embodiment values are shown in Table 3 below.

Face number Radius of curvature (r) Thickness and spacing (d) Refractive index (N) Dispersion value (ν) *One 6.74035 1.997890 1.65844 50.85 2 4.87097 3.000000 3 11.87318 1.322819 1.5168 64.20 4 5.15508 1.998348 5 8.88600 2.338025 1.8340 37.34 6 44.77473 3.000000 7 (aperture) ∞ 1.500000 8 -18.15775 1.901379 1.80518 25.46 9 11.04598 0.108045 10 13.96080 2.300000 1.65844 50.85 11 -6.79965 0.500000 12 11.82019 2.800000 1.69680 55.46 13 -26.02515 0.000000 14 0.1E + 11 4.500000 1.51680 64.20 15 0.1E + 11 4.733482 Top ∞ 0.000000

* Denotes an aspherical surface, and aspheric coefficients are shown in Table 4 below.

Aspheric coefficient of the first side K 0.168960 A -0.313800E-03 B  0.233747E-04 C -0.662217E-06 D  0.765151E-08

Fig. 3 shows astigmatism, spherical aberration and distortion aberration of the high resolution optical system according to the first and second embodiments of the present invention, respectively.

Next, a high resolution optical system according to the third and fourth embodiments of the present invention will be described.

4 is a high resolution optical system according to a third embodiment of the present invention, and FIG. 5 is a high resolution optical system according to a fourth embodiment of the present invention.

4 and 5, the optical system for high resolution according to the third and fourth embodiments of the present invention has a first lens 101 'having the same structure as that of the first and second embodiments described above. ), A first lens group 10 'including a second lens 102' and a third lens 103 ', a fourth lens 201', a fifth lens 202 'and a sixth lens ( And a second lens group 20 'including 203'.

The high resolution optical system according to the third and fourth embodiments of the present invention does not include an aspherical lens, and the first to sixth lenses 101 'to 103' and 201 'to 203' are made of spherical lenses.

The optical system for high resolution according to the third and fourth embodiments of the present invention, unlike the first and second embodiments, satisfies the following conditions.

-0.95 <f / fN <-0.85

nd3 ＞ 1.80

4.67 <r2 <4.75

0.1 <FB / Vd6 <0.16

-0.173 <d7 / fg45 <-0.16

d6 + d7> 3.85

0.85 <ΦG6 x Ymax / Vd6 <0.93

0.1 <Ymax / TD <0.2

fN: composite focal length of the first lens 101 'and the second lens 102'

nd3: refractive index of the third lens 103 '

r2: radius of curvature of the image-side surface of the first lens 101 ′

FB: post focal length

Vd6: Abbe number of the sixth lens 203 '

fg45: composite focal length of the fourth lens 201 ′ and the fifth lens 202 ′

d7: center distance between the aperture A and the fourth lens 201 '

d6: center distance between the third lens 103 'and the aperture A                     

ΦG6: refractive power of the sixth lens 203 '

Vd6: Abbe number of the sixth lens 203 '

Ymax: height of height

TD: center distance from the object side to the first lens plane

Equation (9) shows the refractive power configuration of the result of correcting the overall optical performance by the ratio of the refractive power of the entire optical system and the refractive power of the first lens composed of the surface to which the aspherical surface is applied to correct the aberration.

Equation 10 shows the relation with the refractive power of the second lens with an Abbe number, which is a dispersion value for the first lens, to limit the material of the lens.

Equations 12 and 13 are equations for securing a space between the aperture and the lens, and when the lower limit values of Equations 12 and 13 are exceeded, sufficient space for installing the shutter cannot be secured.

Equation (14) represents an angle incident on the upper surface, and to secure telecentric characteristics, color bleeding occurs when the lower limit of Equation 14 is exceeded, and aberration correction when the upper limit of Equation 14 is exceeded. This becomes difficult and degrades performance.

Equation (15) is an expression representing a lens length (distance from the object side to the image surface) and a focus representing the characteristics of the optical system.

Equation 16 is a formula relating to the configuration of the fourth lens 201 'and the fifth lens 202' of the second lens group 20.                     

Example values of the optical system for high resolution according to the third and fourth embodiments of the present invention that satisfy the above-described Equations 9 to 16 are as follows.

In the high-resolution optical system according to the third embodiment of the present invention, the focal length is 7.5, the post focal length is 7.9 (in air), the angle of view is 31 °, the Fno is 2.8, and the exemplary values are shown in Table 5 below.

Face number Radius of curvature (r) Thickness and spacing (d) Refractive index (N) Dispersion value (ν) One 11.23349 0.800000 1.58913 61.25 2 4.72199 6.432417 3 8.24751 1.000000 1.75520 27.53 4 5.08443 1.499413 5 8.29610 1.800000 1.80420 46.50 6 -9.89217 1.300000 7 (aperture) ∞ 2.547127 8 -6.14569 1.500000 1.84666 23.78 9 12.87116 0.345152 10 -27.51786 1.800000 1.58913 61.25 11 -5.62046 0.100000 12 16.74828 2.945595 1.69680 55.46 13 -12.99825 7.930296 Top ∞ 0.000000

In the optical system for high resolution according to the fourth embodiment of the present invention, the focal length is 7.5, the rear focal length is 8.5 (in air), the angle of view is 31 DEG, the Fno is 2.8, and the exemplary values are shown in Table 6 below.

Face number Radius of curvature (r) Thickness and spacing (d) Refractive index (N) Dispersion value (ν) One 12.30461 0.800000 1.51680 64.20 2 5.55510 0.911181 3 13.48143 0.800000 1.51680 64.20 4 6.33651 4.000000 5 10.91437 1.967970 1.80420 46.50 6 -17.36882 1.300000 7 (aperture) ∞ 3.000000 8 -6.07371 1.300000 1.80518 25.46 9 11.56739 0.194650 10 -111,12351 1.500000 1.77250 49.62 11 -6.27984 0.100000 12 17.45086 2.600000 1.69680 55.46 13 -13.89425 8.491253 Top ∞ 0.000000

Fig. 6 shows astigmatism, spherical aberration and distortion aberration of the high resolution optical system according to the third and fourth embodiments of the present invention, respectively.

As described above, according to the exemplary embodiment of the present invention, an optical system having a high resolution applicable to a CCD of about 1.5 million pixels or more using a minimum number of lenses can be provided.

In addition, an optical system having a brightness Fno of 2.8 can be provided.

Claims (3)

From the object side sequentially, A first lens group comprising a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, and having a negative refractive power as a whole; A fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having positive refractive power, and a second lens group having a positive refractive power as a whole. An optical system for high resolution, characterized in that an aperture is located between lens groups, the lens comprises at least one aspherical lens, and satisfies the following conditions. -0.17 <f / f1 <-0.16 0.09 <r3 / Vd1 <0.15 3.5 <f1 / f12 <4.0 0.19 <d6 / dI <0.2 4.0 <d6 + d7 <5.0 0.6 <fB / Exi <0.67 0.4 <f / dT <0.6 108 <r9 / d9 <110 f: focal length of the whole optical system f1: Focal length of the first lens r3: radius of curvature of the object-side surface of the first lens Vd1: Abbe number of the first lens f12: Composite focal length of the first lens and the second lens d6: distance between the image side surface of the third lens and the aperture dI: distance from the first lens to the aperture d9: center distance from the iris to the object-side surface of the fourth lens fB: back focal length of optical system Exi: Location of exit pupil of optical system dT: distance from the iris to the top r9: radius of curvature of the image-side surface of the fourth lens d9: center distance between the fourth lens and the fifth lens From the object side sequentially, A first lens group including a first lens having negative refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, and having a negative refractive power as a whole; A fourth lens having negative refractive power, a fifth lens having positive refractive power, and a sixth lens having positive refractive power, and a second lens group having a positive refractive power as a whole. An optical system for high resolution, characterized in that an aperture is located between lens groups, and satisfies the following conditions. -0.95 <f / fN <-0.85 nd3 ＞ 1.80 4.67 <r2 <4.75 0.1 <FB / Vd6 <0.16 -0.173 <d7 / fg45 <-0.16 d6 + d7> 3.85 fN: Composite focal length of the first lens and the second lens nd3: refractive index of the third lens r2: radius of curvature of the image-side surface of the first lens FB: post focal length Vd6: Abbe number of the sixth lens fg45: composite focal length of fourth lens and fifth lens, d7: center distance between the iris and the fourth lens d6: center distance between the image side surface of the third lens and the iris The optical system for high resolution according to claim 2, further comprising the following conditions. 0.85 <ΦG6 x Ymax / Vd6 <0.93 0.1 <Ymax / TD <0.2 ΦG6: refractive power of the sixth lens, Vd6: Abbe number of the sixth lens Ymax: height of height TD: center distance from the object side to the image plane of the first lens Ymax: height of height

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