KR101449039B1 - Zoom Lens - Google Patents

Abstract

A zoom lens according to an embodiment includes a first lens group including a prism lens capable of reflecting incident light; And a second lens group positioned above the first lens group and including an aspherical lens and formed of at least one lens, wherein the prism lens has a diffractive optical element (DOE) surface on the side of the object on which the incident light enters, .

A zoom lens according to an embodiment includes a first lens group including an incident surface on which light is incident, a reflection surface that reflects the incident light, and a first lens on which an exit surface from which the reflected light is emitted is formed; And a second lens unit positioned above the first lens unit and including an aspherical lens and formed of at least one or more lenses, wherein the incident surface formed on the first lens is formed of a diffractive optical element (DOE) .

Zoom lens

Description

Zoom Lens {Zoom Lens}

An embodiment relates to a zoom lens used in a camera module using a high resolution image sensor.

Recently, a camera module for a communication terminal, a digital still camera (DSC), a camcorder, a PC camera (an imaging device attached to a personal computer), and the like have been studied in connection with an image pickup system. The most important component for obtaining an image of a camera module related to such an image pickup system is a zoom lens for imaging an image.

The embodiment provides a zoom lens having an optically aberration characteristic.

A zoom lens according to an embodiment includes a first lens group including a prism lens capable of reflecting incident light; And a second lens group positioned above the first lens group and including an aspherical lens and formed of at least one lens, wherein the prism lens has a diffractive optical element (DOE) surface on the side of the object on which the incident light enters, .

A zoom lens according to an embodiment includes a first lens group including an incident surface on which light is incident, a reflection surface that reflects the incident light, and a first lens on which an exit surface from which the reflected light is emitted is formed; And a second lens unit positioned above the first lens unit and including an aspherical lens and formed of at least one or more lenses, wherein the incident surface formed on the first lens is formed of a diffractive optical element (DOE) .

The zoom lens according to the embodiment can design a zoom lens in which the slope of the zoom lens is short, by disposing a first lens, which is a prism lens having a DOE surface capable of collecting light, on the side of the object on which incident light enters have.

Further, since the direction of the incident light is changed by the first lens, and the optical path of the incident light and the optical path in the optical device are formed in the perpendicular direction, the design of the zoom lens can be designed more easily .

Further, since the zoom lens can be designed without a separate lens for collecting the light incident on the first lens, and the additional lens is not necessary on the object side of the first lens, the design of the slim zoom lens having a shorter total length It becomes possible.

Further, the first lens group including the prism lens has stronger power than the second lens group and the third lens group, and by arranging the lenses having at least one aspherical surface inflection point to realize the zoom lens, An excellent zoom lens can be realized.

Hereinafter, a zoom lens according to an embodiment will be described in detail with reference to the accompanying drawings.

1 to 3 are side cross-sectional views schematically showing an internal structure of a zoom lens according to an embodiment.

FIG. 1 is a view of a zoom lens at a wide angle, FIG. 2 is a zoom lens at a normal level, and FIG. 3 is a view of a zoom lens at a telephoto end.

1 to 3 comprises a first lens group 100, a second lens group 200, and a third lens group 300.

The first lens group 100 is located on the object side and has negative power and the second lens group 200 is located above the first lens group 100 and the positive +). ≪ / RTI >

The third lens group 300 is located above the second lens group 200 and has a positive power.

That is, the first lens group 100, the second lens group 200, and the third lens group 300 are sequentially positioned in the upper surface side direction.

The first lens group 100 includes a first lens 10, a second lens 20 and a third lens 30 and includes a first lens 10, a second lens 20 And the third lens 30 are positioned one after another.

The first lens 10 is formed of a prism lens including a DOF (Diffractive Optical Element) surface and including a reflective surface R30 capable of reflecting incident light, and the incident light is reflected by the reflective surface R30. The direction of the incident light can be changed.

The first lens 10 includes an incident surface R1 on which light is incident, a reflection surface R30 that reflects the incident light, and an exit surface R2 that emits the reflected light.

The reflecting surface R30 serves to reflect the incident light to the second lens 20 by reflecting the principal ray of the incident light at 90 degrees.

The zoom lens is designed to have a structure capable of switching the direction of the incident light by the first lens 10 to shorten the total length of the zoom lens and design a slim zoom lens, And the like.

Since the direction of the incident light is changed by the first lens 10 and the optical path of the incident light and the optical path in the optical device are formed in the vertical direction, the length of the electric field in the design of the zoom lens is not considered It can be easily designed.

At this time, the incident surface R1 of the first lens 10 may be formed as a DOE surface, and the DOE surface collects incident light incident on the first lens 10.

In addition, the DOE surface of the first lens 10 can correct the aberration of the zoom lens, and a zoom lens having excellent optical performance can be designed.

Therefore, it is possible to design a zoom lens without a separate lens for collecting the light incident on the first lens 10, and since an additional lens is not necessary on the object side of the first lens 10, A slim zoom lens can be designed.

The second lens 20 is formed of a lens having a concave surface on an upper side R4 and a negative power and the third lens 30 is formed of a lens having a positive power Lens.

The second lens group 200 includes a fourth lens 40 having positive (+) power.

The third lens group 300 includes a diaphragm 45, a fifth lens 50, a sixth lens 60, a seventh lens 70, an eighth lens 80, and a filter 90.

The diaphragm 45 is disposed between the fourth lens 40 and the fifth lens 50 and functions to adjust the focus length by selectively converging the incident light.

The fifth lens 50 and the seventh lens 70 are formed of a lens having a convex surface on the object side and having a positive power and the sixth lens 60 and the eighth lens 80 And is formed of a lens having a negative (-) power.

The filter 90 is positioned above the eighth lens 80 and may be an IR cut filter.

The infrared cut filter functions to block radiant heat emitted from external light from being transmitted to the light receiving element 400.

That is, the infrared cut filter has a structure that transmits visible light and reflects infrared light to the outside.

The image sensor may be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device. The light receiving device 95 may be an image sensor that converts an optical signal corresponding to an object image into an electrical signal. Oxide Semiconductor) sensor.

The light corresponding to the image information of the object to be captured is passed through the first lens group 100, the second lens group 200 and the third lens group 300 to be incident on the light receiving element 95 do.

The second lens group 200 and the third lens group 300 may be moved to perform a zoom function.

The first lens 10, the second lens 20, the fourth lens 40, the sixth lens 60 and the seventh lens 70 are made of glass and the third lens 30, the fifth lens 50, and the eighth lens 80 may be formed of a plastic material.

All surfaces of the third lens 30, the fifth lens 50 and the eighth lens 80 may be formed as an aspherical surface. The first lens group 100 may be formed as an aspherical surface, And the third lens group 300, and has a strong power.

The zoom lens according to the embodiment has optical characteristics as shown in Table 1 below.

Lens face Radius of curvature (mm) Thickness (mm) Material R1 ∞ 7 FDS90_HOYA R2 ∞ 0.3 R3 11.25604 1.240212 NBF2_HOYA R4 2.90675 1.2734 R5 * 8.99571 0.984738 OKP4 R6 * 21.5436 6.631579 R7 -17.2904 0.852232 FC5_HOYA R8 -6.19844 0.3 R9 ∞ 0 iris R10 * 3.04855 1.563928 E48R R11 * -7.85938 0.15 R12 -10.48576 0.65 NBFD15_HOYA R13 3.20335 0.15 R14 3.20114 1.386145 FEL6_HOYA R15 -8.92357 2.881284 R16 * -8.20682 0.65 E48R R17 * 11.79607 0.155552 R18 ∞ 0.3 filter R19 ∞ 1.55767 filter R20 ∞ -0.02674 sensor

(* Indicates an aspherical surface)

The thickness shown in Table 1 represents the distance from each lens surface to the next lens surface.

Table 2 below shows the aspherical surface coefficient values for the aspherical lens of the embodiment.

Lens face K A ₁ A ₂ A ₃ A ₄ A ₅ R5 -55.259182 0.660441 × 10 ^-2 -0.144063 × 10 ^-2 0.683798 × 10 ^-4 0.102688 × 10 ^-4 -0.633578 × 10 ^-6 R6 59.589863 -0.609127 × 10 ^-2 0.956878 × 10 ^-3 -0.544394 × 10 ^-3 0.985377 × 10 ^-4 -0.657437 × 10 ^-5 R10 -0.130196 -0.197373 x 10 ^-2 -0.176102 x 10 ^-3 -0.184458 × 10 ^-4 -0.545746 x 10 ^-5 -0.899735 × 10 ^-12 R11 -6.439951 -0.118586 × 10 ^-2 -0.391564 × 10 ^-4 -0.197214 x 10 ^-4 0.806233 × 10 ^-6 -0.351943 × 10 ^-12 R16 16.421148 -0.443366 x 10 ^-1 0.620269 × 10 ^-2 -0.358074 × 10 ^-2 0.714022 × 10 ^-3 -0.559218 × 10 ^-16 R17 -66.362452 -0.325606 x 10 ^-1 0.621201 × 10 ^-2 -0.193767 × 10 ^-2 0.341448 × 10 ^-3 0.685346 x 10 ^-17

The aspherical surface coefficient values in Table 2 for the aspherical lens of the embodiment can be obtained from the following equation (1).

Z: distance from the apex of the lens in the optical axis direction

C: Basic curvature of lens

Y: Distance in the direction perpendicular to the optical axis

K: Conic constant

A ₁ , A ₂ , A ₃ , A ₄ , A ₅ : Aspheric constant

That is, spherical aberration, coma, and astigmatism can be corrected by using the third lens 30, the fifth lens 50, and the eighth lens 80 having the above-mentioned aspheric surface coefficient values, Distortion can be corrected satisfactorily.

The focal length (f) of the entire optical system of the zoom lens according to the above-described embodiment, the focal length of each lens group, and the focal length of each lens are shown in Table 3 below.

The focal length fw at the wide end (Wide) 4 mm The focal length (fn) in the standard stage (Normal) 8 mm Focal length (ft) at telephoto (Tele) 12 mm The focal length of the first lens group -7.34 mm The focal length of the second lens group 19.31 mm The focal length of the third lens group 8.10 mm The focal length f2 of the second lens -5.521699 mm The focal length f3 of the third lens 24.639124 mm The focal length f4 of the fourth lens 19.311167 mm The focal length f5 of the fifth lens 4.355318 mm The focal length f6 of the sixth lens, -2.973660 mm The focal length f7 of the seventh lens, 4.606649 mm When the focal length f8 of the eighth lens is set to " -9.017590 mm

Since the focal length of the embodiment according to Table 3 is 4 mm at the wide angle end and 12 mm at the telephoto end, the zoom lens according to the embodiment can have a 3x zoom function.

4 is a graph of aberration at the wide-angle end according to the embodiment, Fig. 5 is a graph of aberration at the standard end, and Fig. 6 is a graph of aberration at the telephoto end.

FIGS. 4 to 6 show longitudinal spherical aberration, astigmatic field curves, and distortion aberration, respectively.

Wherein the spherical aberration is an aberration characteristic according to each wavelength and the astigmatism represents aberration characteristics of a tangential plane and a sagittal plane along a height of an upper surface, As shown in Fig.

FIG. 7 shows TV distortion at the wide-angle end according to the embodiment, FIG. 8 shows TV distortion at the standard stage, and FIG. 9 shows TV distortion at the telephoto end.

FIG. 10 is a graph showing MTF (Modulation Transfer Function) characteristics at a wide-angle end according to an embodiment, FIG. 11 is a graph showing MTF characteristics at a standard end, FIG. 12 is a graph showing MTF characteristics at a telephoto end, It is a graph.

The MTF characteristic is a graph measuring MTF characteristics of a tangential plane and a sagittal plane depending on a change of a spatial frequency (cycles / mm) of a cycle per millimeter.

The MTF value is the ratio of the difference from the image formed after passing through the lens, and the MTF value is '1'. When the MTF value is decreased, the resolution is lowered.

As shown in FIGS. 10, 11 and 12, since the MTF value is high, it can be seen that the lens module according to the embodiment has excellent optical performance.

It can be seen that the zoom lens according to the above embodiment has excellent aberration characteristics and excellent MTF characteristics, thereby realizing a high-resolution lens module.

In the zoom lens according to the above embodiment, a zoom lens having a short overall length of a zoom lens is designed by disposing a first lens, which is a prism lens having a DOE surface capable of collecting light, on the side of an object on which incident light enters .

Further, since the direction of the incident light is changed by the first lens, and the optical path of the incident light and the optical path in the optical device are formed in the perpendicular direction, the design of the zoom lens can be designed more easily .

Further, since the zoom lens can be designed without a separate lens for collecting the light incident on the first lens, and the additional lens is not necessary on the object side of the first lens, the design of the slim zoom lens having a shorter total length It becomes possible.

Further, the first lens group including the prism lens has stronger power than the second lens group and the third lens group, and by arranging the lenses having at least one aspherical surface inflection point to realize the zoom lens, An excellent zoom lens can be realized.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

1 to 3 are side cross-sectional views schematically showing an internal structure of a zoom lens according to an embodiment.

4 is a graph of aberration at the wide-angle end according to the embodiment, Fig. 5 is a graph of aberration at the standard end, and Fig. 6 is a graph of aberration at the telephoto end.

FIG. 7 shows TV distortion at the wide-angle end according to the embodiment, FIG. 8 shows TV distortion at the standard stage, and FIG. 9 shows TV distortion at the telephoto end.

FIG. 10 is a graph showing MTF (Modulation Transfer Function) characteristics at a wide-angle end according to an embodiment, FIG. 11 is a graph showing MTF characteristics at a standard end, FIG. 12 is a graph showing MTF characteristics at a telephoto end, It is a graph.

Claims (17)

A first lens group including a prism lens capable of reflecting incident light; And And a second lens group located above the first lens group and including an aspherical lens and formed of at least one or more lenses, Wherein the prism lens includes a DOE (Diffractive Optical Element) surface formed on a side surface of the object on which the incident light enters. The method according to claim 1, And the prism lens includes a reflecting surface for reflecting the incident light. The method according to claim 1, Wherein the prism lens includes the incident light path passing through the prism lens and the exit light path passing through the prism lens perpendicular to each other. The method according to claim 1, A zoom lens comprising an aspheric lens and a third lens group formed of at least one or more lenses. 5. The method of claim 4, Wherein the first lens group has a negative power, the second lens group has a positive power, and the third lens group has a positive power. 5. The method of claim 4, Wherein the first lens group has a larger power than the second lens group and the third lens group. 5. The method of claim 4, Wherein the first lens group includes a first lens, a second lens and a third lens which are prism lenses, The second lens group includes a fourth lens, And the third lens group includes a diaphragm, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a filter. 8. The method of claim 7, The first lens, the second lens, the fourth lens, the sixth lens, and the seventh lens are glass lenses, Wherein the third lens, the fifth lens, and the eighth lens are plastic lenses. 8. The method of claim 7, And the third lens, the fifth lens, and the eighth lens include at least one aspherical surface. A first lens group including an entrance surface on which light is incident, a reflection surface reflecting the incident light, and a first lens on which an exit surface from which the reflected light is emitted is formed; And And a second lens group located above the first lens group and including an aspherical lens and formed of at least one or more lenses, Wherein the incident surface formed on the first lens includes a diffractive optical element (DOE) surface. 11. The method of claim 10, Wherein the first lens includes an incident light path by the reflecting surface and an optical path reflected by the reflecting surface are perpendicular to each other. 11. The method of claim 10, A zoom lens comprising an aspheric lens and a third lens group formed of at least one or more lenses. 13. The method of claim 12, Wherein the first lens group has a negative power, the second lens group has a positive power, and the third lens group has a positive power. 13. The method of claim 12, Wherein the first lens group has a larger power than the second lens group and the third lens group. 13. The method of claim 12, Wherein the first lens group includes a first lens, a second lens and a third lens which are prism lenses, The second lens group includes a fourth lens, And the third lens group includes a diaphragm, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a filter. 16. The method of claim 15, The first lens, the second lens, the fourth lens, the sixth lens, and the seventh lens are glass lenses, Wherein the third lens, the fifth lens, and the eighth lens are plastic lenses. 16. The method of claim 15, And the third lens, the fifth lens, and the eighth lens include at least one aspherical surface.

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