KR101564418B1 - Zoom lens and imaging optical device having the same - Google Patents

Abstract

A zoom lens and an optical imaging apparatus having the zoom lens are disclosed.

The zoom lens system according to claim 1, wherein the zoom lens is arranged in order from the object side to the image side, and includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, Wherein the first lens group, the second lens group, the third lens group, and the fourth lens group move when zooming from the wide angle end to the telephoto end, The distance between the second lens group and the second lens group is increased, the distance between the second lens group and the third lens group is reduced, the distance between the third lens group and the fourth lens group is increased, When the zooming from the end to the end of the telephoto end is performed.

Description

[0001] The present invention relates to a zoom lens and an imaging optical device having the zoom lens.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a zoom lens of a wide angle having a small size and a high zoom magnification, and an image pickup apparatus employing the zoom lens.

2. Description of the Related Art Recently, digital cameras and video cameras having solid-state image pickup devices such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor) have been widely used. Particularly, the demand for mega pixel camera modules is increasing, and in the entry level digital cameras, more than 5 million pixels and high quality performance are emerging. An imaging optical device such as a digital camera or a mobile phone camera using an image pickup device such as a CCD or a CMOS is required to be downsized, lightweight, and low in cost. Furthermore, there is an increasing demand for a wide angle range to capture a wider range of subjects.

The present invention provides a wide-angle zoom lens having a short overall length, a high resolution, and a large zoom magnification.

The present invention provides an optical imaging apparatus employing a wide-angle zoom lens having a short overall length, a high resolution, and a large zoom magnification.

A zoom lens according to an embodiment of the present invention includes: a first lens group having a positive refractive power; a second lens group having a negative refractive power; and a second lens group having a positive refractive power, A third lens group, and a fourth lens group having positive refractive power,

Wherein the first lens group, the second lens group, the third lens group, and the fourth lens group move when zooming from the wide-angle end to the telephoto end, and the distance between the first lens group and the second lens group The distance between the third lens group and the fourth lens group is increased and the distance between the third lens group and the fourth lens group is increased and the first lens group is moved from the wide angle end to the telephoto end, And the following equation is satisfied.

<Expression>

4 &lt; ft / fw &lt; 7

35 ° ≤ωw

0.8 <Da / fw * tan (? W) <1.2

Here, fw is the total focal length at the wide-angle end, ft is the total focal length at the telephoto end,? W is the half angle of view at the wide-angle end, Da is the total Lt; / RTI &gt;

According to another embodiment of the present invention, the zoom lens may satisfy the following expression.

<Expression>

1.6 &lt; f1 / ft &lt; 2.3

-0.3 &lt; f2 / ft &lt; -0.4

0.3 &lt; f3 / ft &lt; 0.4

Here, f1 represents the focal length of the first lens unit, f2 represents the focal length of the second lens unit, f3 represents the focal length of the third lens unit, and ft represents the total focal length at the telephoto end.

According to another embodiment of the present invention, the first lens group includes a cemented lens of a negative lens and both lenses, the second lens group includes a negative lens and both lenses, And a cemented lens of both lenses and the negative lens, and the fourth lens unit may include both lenses.

According to another embodiment of the present invention, the negative lens of the second lens group may have a double-sided aspheric surface.

According to another embodiment of the present invention, both of the lenses on the most object side of the third lens group may have at least one aspherical surface.

According to another embodiment of the present invention, the fourth lens group may have at least one aspheric surface.

According to another embodiment of the present invention, the third lens group moves in a direction perpendicular to the optical axis to perform vibration correction by camera shake.

According to an embodiment of the present invention, there is provided a zoom lens comprising a zoom lens and an imaging sensor for receiving an image formed by the zoom lens,

Wherein the zoom lens is arranged in order from the object side to the image side and includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, And a fourth lens group having refractive power of &lt; RTI ID = 0.0 &gt;

Wherein the first lens group, the second lens group, the third lens group, and the fourth lens group move when zooming from the wide-angle end to the telephoto end, and the distance between the first lens group and the second lens group The distance between the third lens group and the fourth lens group is increased and the distance between the third lens group and the fourth lens group is increased and the first lens group is moved from the wide angle end to the telephoto end, And moving in a locus of a convex shape with respect to the optical axis of the optical system, and satisfying the following expression.

<Expression>

4 &lt; ft / fw &lt; 7

35 ° ≤ωw

0.8 <Da / fw * tan (? W) <1.2

Here, fw is the total focal length at the wide-angle end, ft is the total focal length at the telephoto end,? W is the half angle of view at the wide-angle end, Da is the total Lt; / RTI &gt;

1, a zoom lens according to an embodiment of the present invention includes a first lens group G1 having positive refractive power and a second lens group G2 having positive refractive power, which are arranged in order from the object side O to the image side I, A second lens group G2 having a refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power.

The first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 all move when zooming from the wide-angle end to the telephoto end, The distance between the first lens group G1 and the second lens group G2 is increased and the interval between the second lens group G2 and the third lens group G3 is reduced and the distance between the third lens group G3 ) And the fourth lens group G4 is increased. The first lens group G1 moves in a convex locus with respect to the image I at the time of zooming from the wide angle end to the telephoto end. Here, the convex trajectory indicates that the first lens group G1 moves from the wide-angle end to the telephoto end in the zooming to the image side I and then to the object side (O).

The zoom lens according to the embodiment of the present invention may have a zoom magnification of 4-7 as follows.

4 < ft / fw < 7

The zoom lens according to the embodiment of the present invention satisfies the following condition.

35 ° ≤ωw

Here, ft represents the total focal length at the telephoto end, fw represents the total focal length at the wide-angle end, and w represents the half angle of view at the wide-angle end. If the zoom magnification exceeds the upper limit of the expression (1), the amount of movement of the lens group is large and the total length of the zoom lens becomes large, making miniaturization difficult. If the zoom magnification is smaller than the lower limit of the expression (1), miniaturization is easy, but a high photographing angle of view can not be ensured. The zoom lens according to the present invention has an angle of view of 70 degrees or more at a wide angle end, and allows a wide range of subjects to be photographed at the time of wide angle photographing. The zoom lens according to the present invention can be suitably applied to a video camera, an electronic still camera, a compact digital camera, a mobile phone camera or the like using a solid-state image pickup device such as a CCD or a CMOS. It is necessary to effectively apply the zooming action to each lens group and to correct the aberration well in all the zooming regions in order to have a high zoom magnification while maintaining the optical performance. Therefore, in the present invention, all of the first to fourth lens groups are moved when zooming.

Meanwhile, the zoom lens according to the embodiment of the present invention may be configured to satisfy the following expression.

0.8 <Da / fw * tan (? W) <1.2

Here, fw represents the total focal length at the wide-angle end, and Da represents the total thickness on the optical axis of the first lens group and the second lens group. If the upper limit of the expression (3) is exceeded, the total thickness of the first lens group and the second lens group becomes large, and it becomes difficult to miniaturize the lens. If the value is smaller than the lower limit of the expression (3), the aberration can not be corrected well and the power of the second lens group can not be ensured and the off-axis aberration is deteriorated

The zoom lens of the present invention can satisfy the following expression.

1.6 &lt; f1 / ft &lt; 2.3

-0.3 &lt; f2 / ft &lt; -0.4

0.3 &lt; f3 / ft &lt; 0.4

Here, f1 represents the focal length of the first lens unit, f2 represents the focal length of the second lens unit, f3 represents the focal length of the third lens unit, and ft represents the total focal length at the telephoto end.

If the upper limit of the expression (4) is exceeded, the power of the first lens group becomes too small, so that the overall length of the zoom lens becomes long, making miniaturization difficult. If the value is smaller than the lower limit of the expression (4), the power of the first lens group becomes too strong, and spherical aberration and coma aberration at the telephoto end become large, and it is difficult to secure good optical performance.

When the upper limit of the expression (5) is exceeded, the power of the second lens group becomes too weak, and therefore, the amount of movement for zooming becomes large, making miniaturization difficult. If the value is smaller than the lower limit value of the expression (5), the paraxial imaging magnification of the second lens group becomes small, the amount of movement for zooming becomes large, and aberration correction becomes difficult.

When the upper limit of the expression (6) is exceeded, the power of the third lens group becomes too weak, and therefore the amount of movement for zooming becomes large. If the value is smaller than the lower limit of the expression (6), the paraxial imaging magnification of the third lens group is reduced, the amount of movement for zooming becomes large, and aberration correction becomes difficult.

FIG. 1 shows a zoom lens according to a first embodiment. The first lens group G1 includes a first lens L11 and a second lens L12 in order from the object side O , The second lens group G2 includes a third lens L21 and a fourth lens L22 and the third lens group G3 includes a fifth lens L31, a sixth lens L32, Lens L33, and the fourth lens group G4 includes an eighth lens L41. For example, the first lens L11 may be a negative lens, the second lens L12 may be a positive lens, and the negative lens and both lenses may be a cemented lens. Wherein the third lens L21 is a negative lens, the fourth lens L22 is a positive lens, the fifth lens L31 is a positive lens, the sixth lens L32 is a positive lens, The third lens L33 may be a negative lens, and the sixth lens and the seventh lens may be a cemented lens. The eighth lens L41 may be a positive lens.

In order to miniaturize the lens barrel, the thickness of the entire lens system at the time of lens penetration must be reduced. In order to do so, the total number of lenses of the zoom lens must be reduced as much as possible in consideration of the optical performance. The zoom lens shown in Fig. 1 includes a total of eight lenses to achieve miniaturization. Further, by including the cemented lens in the first lens group and the third lens group to reduce the interval between the lenses, the zoom lens can be further downsized.

In the first lens group G1 and the second lens group G2, since the height of the off-axial ray from the optical axis is high, the thickness of the edge portion of the lens is required to some extent in order to secure the light quantity of the off-axial rays. However, if the thickness of the edge portion of the lens is increased, the thickness of the axial lens of the lens tends to be thick. When the number of lenses of the first lens group and the second lens group is increased, the entrance pupil position becomes farther from the object side (O), so that the height of the off-axis rays passing through the first lens group and the second lens group becomes higher, The thickness of the axial lens for securing the edge thickness becomes thicker. As described above, when the number of lenses is increased, the axial thickness of the lens is also increased. Therefore, as the number of lenses increases, the size of the lens group in the radial direction or the thickness of the lens on the optical axis becomes thicker than necessary, which makes miniaturization of the zoom lens difficult. Therefore, the zoom lens can be downsized by constituting the first lens group G1 and the second lens group G2 with two lenses, respectively.

Further, by moving the first lens group G1 in a convex locus with respect to the image side at the time of zooming from the wide-angle end to the telephoto end, the magnitude of the off-axis light at the intermediate position is almost equal to the magnitude of the off- The sufficient amount of light can be ensured and the diameter of the first lens group G1 can be reduced.

The negative lens of the second lens group G2 may have an aspherical surface on both sides. When the zoom magnification is secured while suppressing the entire length of the zoom lens, the change of the light incident position on the second lens group tends to increase. Here, if the negative lens of the second lens group G2 is constituted of aspheric surfaces on both sides, it is advantageous to correct the off-axis aberration at the wide-angle end.

Further, the third lens group is composed of three lenses, and the fourth lens group is composed of one lens, thereby miniaturizing the zoom lens. Both lenses on the most object side (O) of the third lens group (G3) have at least one aspherical surface. Thereby, not only the spherical aberration and coma generated in the third lens group G3 can be corrected better, but also the refractive power of the entire third lens group G3 can be increased, thereby realizing the miniaturization of the entire zoom lens .

On the other hand, the third lens group moves in a direction perpendicular to the optical axis to perform vibration correction by camera shake.

The fourth lens group G4 may have at least one aspherical surface. For example, the eighth lens L41 may have at least one aspheric surface. Thus, the astigmatism that can not be corrected by the first lens group G1, the second lens group G2 and the third lens group G3 can be effectively corrected.

The definitions of aspherical surfaces in the embodiment of the present invention are as follows.

The aspherical shape of the zoom lens according to the present invention is characterized in that the direction of light propagation is positive, z is the amount of displacement from the vertex in the optical axis direction, h is the size from the optical axis in the direction perpendicular to the optical axis, c is the curvature, k is the conic constant, When A, B, C, and D are aspheric coefficients, the sag (z) of the aspherical surface is defined by the following equation.

Hereinafter, embodiments according to various designs of the present invention will be described.

The straight line on the rightmost side in each drawing shows the position of the upper surface IM and an IR (infrared) cutoff filter P1 or a cover glass P2 of the imaging element is provided on the object side O thereof. Ri represents the radius of curvature of the lens surface, Di represents the distance between the i-th surface and the (i + 1) th surface, Ni and vdi represent the distance from the d-line A refractive index and an Abbe number.

&Lt; Embodiment 1 >

1 shows the zoom lens of the first embodiment. 2A, 2B, and 2C are aberration diagrams at the wide-angle end, middle end, and telephoto end of the first embodiment.

The focal length f, FNo, the angle of view 2ω, the overall length L of the zoom lens, and the inter-lens variable distance (in the case of lens data, aspherical surface data, and image pickup distance of infinity of the zoom lens of the first embodiment) D3, D7, D12, D14).

-

&Lt; Embodiment 2 >

3 shows the zoom lens of the second embodiment, and design data according to the second embodiment will be described below.

&Lt; Third Embodiment >

5 shows the zoom lens of the third embodiment, and design data according to the third embodiment will be described below.

<Fourth Embodiment>

Fig. 7 shows the zoom lens of the fourth embodiment, and design data according to the fourth embodiment will be described below.

In the spherical aberration diagrams of the respective embodiments, the vertical axis represents FNo, the vertical axis represents the maximum image height IH, the solid line represents the sagittal field curvature S, and the dotted line represents the tangential field curvature. The vertical axis in the distortion diagram represents the maximum image height (IH).

The following shows that the above-described first to fourth embodiments satisfy the condition of each expression described above.

  Equation  First Embodiment Second Embodiment Third Embodiment Fourth Embodiment Da / fw * tan (? W) 1.06 1.04 1.07 1.06  f1 / ft 1.80 1.84 1.94 1.95 f2 / ft -0.37 -0.38 -0.38 -0.38 f3 / ft 0.37 0.37 0.37 0.37

The zoom lens according to the embodiment of the present invention has a high aspect ratio and realizes miniaturization while securing a wide-angle view angle at a wide angle end. By realizing such wide angle, it is possible to photograph a subject in a wider range. The zoom lens according to the embodiment of the present invention can be suitably used in an imaging optical apparatus such as a digital still camera, a video camera, and a portable terminal using a solid-state image pickup device such as a CCD or CMOS.

9 shows an image-forming optical apparatus having a zoom lens according to an embodiment of the present invention. The imaging optical apparatus includes a zoom lens 11 described in the foregoing embodiment and an imaging sensor 12 for receiving light image-formed by the zoom lens 11. The imaging optical apparatus includes recording means 13 recording information corresponding to an object photoelectrically converted from the imaging sensor 12, and a finder 14 for observing a subject image. A liquid crystal display panel 15 may be provided to display a subject image. The imaging optical system shown in Fig. 9 is only an example, and the present invention is not limited thereto, but may be applied to various optical apparatuses other than a camera. As described above, by applying the zoom lens of the present invention to an imaging optical apparatus such as a digital camera, an optical apparatus capable of taking a subject at a wide angle with a small size and a high zoom magnification is realized.

 The above-described embodiments are merely illustrative, and various modifications and equivalent other embodiments are possible without departing from the scope of the present invention. Therefore, the scope of the true technical protection according to the embodiment of the present invention should be determined by the technical idea of the invention described in the following claims.

1 is a configuration diagram of a zoom lens according to a first embodiment of the present invention.

2A shows an aberration diagram at a wide angle end of a zoom lens according to a first embodiment of the present invention.

FIG. 2B is an aberration diagram at the middle end of the zoom lens according to the first embodiment of the present invention.

FIG. 2C is an aberration diagram at the telephoto end of the zoom lens according to the first embodiment of the present invention.

2 is a configuration diagram of a zoom lens according to a second embodiment of the present invention.

4A is an aberration diagram of the zoom lens according to the second embodiment of the present invention at a wide angle end.

FIG. 4B shows an aberration diagram at the middle end of the zoom lens according to the second embodiment of the present invention.

4C shows an aberration diagram at the telephoto end of the zoom lens according to the second embodiment of the present invention.

5 is a configuration diagram of a zoom lens according to a third embodiment of the present invention.

6A is an aberration diagram of the zoom lens according to the third embodiment of the present invention at a wide angle end.

6B is an aberration diagram at the middle end of the zoom lens according to the third embodiment of the present invention.

6C shows an aberration diagram at the telephoto end of the zoom lens according to the third embodiment of the present invention.

7 is a configuration diagram of a zoom lens according to a fourth embodiment of the present invention.

8A shows an aberration diagram of the zoom lens according to the fourth embodiment of the present invention at a wide angle end.

8B shows an aberration diagram at the middle end of the zoom lens according to the fourth embodiment of the present invention.

8C shows an aberration diagram at the telephoto end of the zoom lens according to the fourth embodiment of the present invention.

9 shows an optical imaging apparatus according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

G1 ... first lens group, G2 ... second lens group

G3 third lens group, G4 fourth lens group

Claims (9)

A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side to the image side, 4 &lt; / RTI &gt; lens group, Wherein the first lens group, the second lens group, the third lens group, and the fourth lens group move when zooming from the wide-angle end to the telephoto end, and the distance between the first lens group and the second lens group The distance between the third lens group and the fourth lens group is increased and the distance between the third lens group and the fourth lens group is increased and the first lens group is moved from the wide angle end to the telephoto end, And the zoom lens satisfies the following expression. <Expression> 4 &lt; ft / fw &lt; 7 35 ° ≤ωw 0.8 <Da / fw * tan (? W) <1.2 Here, fw is the total focal length at the wide-angle end, ft is the total focal length at the telephoto end,? W is the half angle of view at the wide-angle end, Da is the total Lt; / RTI &gt; The method according to claim 1, A zoom lens satisfying the following expression. <Expression> 1.6 &lt; f1 / ft &lt; 2.3 -0.3 &lt; f2 / ft &lt; -0.4 0.3 &lt; f3 / ft &lt; 0.4 Here, f1 represents the focal length of the first lens unit, f2 represents the focal length of the second lens unit, f3 represents the focal length of the third lens unit, and ft represents the total focal length at the telephoto end. 3. The method according to claim 1 or 2, Wherein the first lens group includes a cemented lens of a negative lens and both lenses, the second lens group includes a negative lens and both positive lenses, the third lens group includes both positive lenses, Wherein the fourth lens group includes both lenses. 3. The method according to claim 1 or 2, And the negative lens of the second lens group has a double-sided aspherical surface. 3. The method according to claim 1 or 2, And both lenses on the most object side of said third lens group have at least one aspherical surface. 3. The method according to claim 1 or 2, And the fourth lens group has at least one aspherical surface. 3. The method according to claim 1 or 2, And the third lens group moves in a direction perpendicular to the optical axis to perform vibration correction by camera shake. A zoom lens according to claim 1 or 2; And And an imaging sensor for receiving the image formed by the zoom lens. 9. The method of claim 8, Wherein the first lens group includes a cemented lens of a negative lens and both lenses, the second lens group includes a negative lens and both positive lenses, the third lens group includes both positive lenses, And the fourth lens group includes both lenses.

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