CN205003349U - Zoom lens - Google Patents

Abstract

The utility model provides a zoom lens, this zoom lens includes a lens unit, dispose in thing side with for instance between the side, and has positive refractive power, the 2nd lens unit, dispose in a lens unit with for instance between the side, and has negative refractive power, the 3rd lens unit, dispose in the 2nd lens unit with for instance between the side, and has positive refractive power, and fourth lens unit, dispose in the 3rd lens unit with for instance between the side, and has positive refractive power. The utility model discloses have the angle of vision of broad and have high zoom ratio when captured images, imaging performance is good during its captured images, its compact structure, optical system keep at reasonable size, light in weight, and energy saving and environmental protection in a higher degree are provided.

Description

zoom lens

technical field

The utility model relates to a zoom lens, in particular to a zoom lens with a wide viewing angle and a high zoom ratio.

Background technique

With the development of science and technology and the improvement of people's living standards, people have more and more stringent requirements on image pickup devices, and hope that the image pickup devices can become smaller, lighter, and have better shooting performance. This requires that the imaging device not only have a higher zoom ratio, but also have a higher imaging quality when capturing images. In addition, the zoom lens needs to have a wide angle of view and a short focal length at the wide-angle end, so that even if the shooting distance of the image is short, a wide image range can be captured.

In general, in order to reduce the size of the zoom lens while achieving a high zoom ratio. The use of optical elements with materials with a higher refractive index increases the refraction ability of each lens unit in the zoom lens to reduce the number of lenses. However, if the refractive power of each lens surface increases, various aberrations will become difficult to correct. When the image is not taken, the lens units are folded to make the lens units compact. Such a structure is easy to cause assembly errors between the lens unit and the lens. If the optical sensitivity of the lens unit and the lens is high, the optical performance of the zoom lens will be reduced. decreased more significantly.

Contents of the invention

In view of the above problems, the utility model aims to provide a wide viewing angle and a high zoom ratio, and through the appropriate setting of the refractive power of the lens unit and the amount of movement of each lens unit during the zooming process within the entire zoom range, Make it have good optical performance.

A zoom lens suitable for imaging an object on the object side on an imaging surface on the image side, the zoom lens comprising:

a first lens unit, disposed between the object side and the image side, and has positive refractive power;

a second lens unit, disposed between the first lens unit and the image side, and has a negative refractive power;

a third lens unit, disposed between the second lens unit and the image side, and has positive refractive power;

and a fourth lens unit, disposed between the third lens unit and the image side, and has positive refractive power;

The first lens unit, the second lens unit, the third lens unit and the fourth lens unit are all used as moving lens units, and the zoom lens meets the following conditions:

1.8<(|Mm|+|Mt|)/fw<4.0,

0.65<f3/f4<1.0,

fm=(fw*ft) ^1/2 ,

Mm is the movement amount of the fourth lens unit, Mt is the movement amount of the fourth lens unit when zooming from the wide-angle end to the telephoto end, fw is the focal length of the zoom lens at the wide-angle end, and fm is the zoom lens at the middle zoom position The focal length is, ft is the focal length of the zoom lens at the telephoto end, f3 is the focal length of the third lens unit, and f4 is the focal length of the fourth lens unit.

The zoom lens also includes an aperture stop, the aperture stop is arranged between the second lens unit and the third lens unit, and the aperture stop is independently movable or fixed.

The first lens unit includes a cemented lens and a third lens from the object side to the image side, and the cemented lens includes a first lens and a second lens from the object side to the image side , and the first lens, the second lens and the third lens are negative, positive and positive in sequence;

The second lens unit includes a fourth lens, a fifth lens, a sixth lens and a seventh lens from the object side to the image side, and the fourth lens, the fifth lens, the sixth lens and the The seventh lens is sequentially negative, negative, negative, positive;

The third lens unit includes an eighth lens, a ninth lens, and a cemented lens from the object side to the image side, and the cemented lens includes a tenth lens from the object side to the image side and an eleventh lens, and the eighth lens, the ninth lens, the tenth lens and the eleventh lens are sequentially positive, positive, negative, and positive;

The fourth lens unit includes a twelfth lens and a thirteenth lens from the object side to the image side, and the twelfth lens and the thirteenth lens are negative and positive in sequence.

The first lens is a meniscus lens with a concave surface facing the image side, the second lens is a convex lens with a convex surface facing the object side, the third lens is a convex lens with a convex surface facing the object side, and the fourth lens is a concave lens facing the object side. The concave lens on the image side, the fifth lens is a concave-convex lens with a concave surface facing the image side, the sixth lens is a concave-convex lens with a concave surface facing the object side, the seventh lens is a convex lens with a convex surface facing the object side, and the eighth lens is a concave-convex lens with a concave surface facing the object side. The lens is a convex lens with a convex surface facing the object side, the ninth lens is a concave-convex lens with a concave surface facing the image side, the tenth lens is a concave lens with a concave surface facing the image side, and the eleventh lens is a convex lens facing the object side. The convex lens, the twelfth lens is a biconvex lens, and the thirteenth lens is a concave lens with a concave surface facing the object side.

Described zoom lens also comprises any one of optical filter, panel, crystal low-pass filter and infrared cut-off filter kind, and described optical filter, panel, crystal low-pass filter and infrared cut-off filter kind Either one is disposed between the fourth lens unit and the image side.

The utility model has the following beneficial effects:

(1) It has a wide field of view and a high zoom ratio when taking images.

(2) It has good imaging performance when taking images.

(3) Its structure is compact, the optical system is kept in a reasonable size, and the weight is light.

(4) More energy saving and environmental protection.

Description of drawings

Fig. 1 is the structural representation of the zoom lens of the present invention at the wide-angle end;

Fig. 2 is that the space frequency of zoom lens of the present invention is 1P/mm, the MTF curve diagram of short-focus state optical system;

Fig. 3 is that the space frequency of zoom lens of the present invention is 1P/mm, the MTF curve diagram of the optical system in the middle focus state;

Fig. 4 is that the utility model zoom lens space frequency is 1P/mm, the MTF curve figure of telephoto state optical system;

Fig. 5 is the distortion curve figure of short-focus state of zoom lens of the present invention;

Fig. 6 is the distortion curve diagram of the focal state of the zoom lens of the present invention;

FIG. 7 is a distortion curve diagram of the telephoto state of the zoom lens of the present invention.

Among them: 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, 6-sixth lens, 7-seventh lens, 8-eighth lens, 9-ninth lens, 10-tenth lens, 11-eleventh lens, 12-twelfth lens, 13-thirteenth lens

detailed description

Below in conjunction with accompanying drawing, the utility model is described in further detail.

As shown in Figure 1, a zoom lens is suitable for imaging an object on the object side on an imaging surface on the image side, and the lens includes:

a first lens unit, disposed between the object side and the image side, and has positive refractive power;

a second lens unit, disposed between the first lens unit and the image side, and has a negative refractive power;

a third lens unit, disposed between the second lens unit and the image side, and has positive refractive power;

and a fourth lens unit, disposed between the third lens unit and the image side, and has positive refractive power;

The first lens unit, the second lens unit, the third lens unit and the fourth lens unit are all used as moving lens units, and the zoom lens meets the following conditions:

1.8<(|Mm|+|Mt|)/fw<4.0,

0.65<f3/f4<1.0,

fm=(fw*ft) ^1/2 ,

Mm is the movement amount of the fourth lens unit, Mt is the movement amount of the fourth lens unit when zooming from the wide-angle end to the telephoto end, fw is the focal length of the zoom lens at the wide-angle end, and fm is the zoom lens at the middle zoom position The focal length is, ft is the focal length of the zoom lens at the telephoto end, f3 is the focal length of the third lens unit, and f4 is the focal length of the fourth lens unit.

In FIG. 1 , the left side is the object side (front side), and the right side is the image side (rear side). i represents the sequence number of lens units from the object side to the image side and Li represents the i-th lens unit.

L1 represents the first lens unit with positive refractive power (refractive power = reciprocal of focal length), L2 represents the second lens unit with negative refractive power, L3 represents the third lens unit with positive refractive power, and L4 represents the fourth lens unit with positive refractive power. lens unit.

SP denotes an aperture stop disposed between the second lens unit L2 and the third lens unit L3, and the aperture stop is independently movable or fixed.

G represents the corresponding optical element block such as optical filter, panel, crystal low-pass filter and infrared cut filter.

IP represents an image plane. When a zoom lens is used as an optical system for image capture, a video camera, or a digital still camera, the image plane corresponds to a solid-state image pickup element (photoelectric conversion element), such as a CCD sensor or a CMOS sensor. When a zoom lens is used as the optical system of a silver halide film camera for image capture, the image plane corresponds to the photosensitive surface of the film plane.

The lens structure of each lens unit is explained:

Since the effective lens diameter of the first lens unit L1 is relatively large, in order to reduce the size and weight of the entire system, it is necessary to reduce the number of lenses. Here, a cemented lens and a positive lens are adopted to form the first lens unit L1, and the first lens unit L1 includes a cemented lens and a third lens from the object side to the image side, and the cemented lens is formed from the object side The image side includes a first lens and a second lens, and the first lens, the second lens and the third lens are negative, positive, and positive in sequence, and the first lens is concave-convex with a concave surface facing the image side The second lens is a convex lens with a convex surface facing the object side, and the third lens is a convex lens with a convex surface facing the object side. As a result, the chromatic aberration and spherical aberration generated by the zoom lens when achieving a higher magnification are further reduced.

In the embodiment of the utility model, the second lens unit L2 is composed of four independent lenses, and the second lens unit includes a fourth lens, a fifth lens, a sixth lens and a lens from the object side to the image side. A seventh lens, and the fourth lens, the fifth lens, the sixth lens and the seventh lens are sequentially negative, negative, negative, and positive; the fourth lens is a concave lens with a concave surface facing the image side, and the fifth lens is a concave lens facing the image side For the meniscus lens on the image side, the sixth lens is a meniscus lens with a concave surface facing the object side, and the seventh lens is a convex lens with a convex surface facing the object side. Thereby, variation in aberration at the time of zooming is reduced, and both distortion at the wide-angle end and spherical aberration at the telephoto end are properly corrected.

In an embodiment of the present invention, the third lens unit includes an eighth lens, a ninth lens, and a cemented lens from the object side to the image side, and the cemented lens extends from the object side to the image side. The side includes a tenth lens and an eleventh lens, and the eighth lens, the ninth lens, the tenth lens and the eleventh lens are sequentially positive, positive, negative, and positive; the eighth lens is a convex surface facing the The convex lens on the object side, the ninth lens is a meniscus lens with a concave surface facing the image side, the tenth lens is a concave lens with a concave surface facing the image side, and the eleventh lens is a convex lens with a convex surface facing the object side. Thereby, changes in chromatic aberration generated during zooming are limited, and distortion caused by eccentricity is also limited. The third lens unit L3 has an aspherical surface therein. Thereby, aberration variation caused upon zooming is properly corrected.

In the embodiment of the present utility model, the fourth lens unit includes a twelfth lens and a thirteenth lens from the object side to the image side, and the twelfth lens and the thirteenth lens are sequentially negative , positive; the twelfth lens is a biconvex lens, and the thirteenth lens is a concave lens with a concave surface facing the object side. As a result, changing chromatic aberrations during focusing are limited and the weight of the entire zoom system is also reduced. It realizes a large image pickup angle at the wide-angle end and a high zoom ratio of a zoom lens.

In the embodiment of the present invention, when zooming from the wide-angle end to the telephoto end, each lens unit can be moved, more specifically, when zooming from the wide-angle end to the telephoto end in the embodiment, the first lens The unit L1 moves toward the object side along the dotted line of the locus, and is closer to the object than it is at the wide-angle end. In addition, the second lens unit L2 moves toward the image side, the third lens unit L3 moves toward the object side, and the fourth lens unit L4 moves along the dotted line of the locus toward the object side.

The movement of the first lens unit L1 and the third lens unit L3 at the time of zooming causes the first lens unit L1 and the third lens unit L3 to be positioned closer to the object at the telephoto end than they are at the wide-angle end, which makes it possible to obtain The case of high zoom ratio while keeping the overall length of the lens small.

In particular, in the embodiment of the present invention, the third lens unit L3 moves toward the object side during zooming, so that the third lens unit L3 and the fourth lens unit L4 jointly control the zoom ratio of the zoom lens. In addition, by moving the first lens unit L1 having positive refractive power to the object side direction within the zoom range, thereby causing the second lens unit L2 to have an influence on a large magnification change, so the first lens unit L1 and the second lens unit L2 The refractive power does not have to be very large to obtain a high zoom ratio.

The utility model adopts a rear focusing method, and realizes focusing by moving the fourth unit lens L4 along the optical axis. The utility model can realize fast focusing through the focusing method of moving the fourth lens unit L4, and makes the automatic focus detection operation and the like easier.

In the embodiment of the present utility model, by moving part or the whole third lens unit L3, the component in one direction is perpendicular to the optical axis, so that when the image is taken, the image becomes blurred due to the vibration of the optical system Ambiguity is corrected. With this method, there is no need to provide an additional lens unit for image stabilization, thereby further reducing the size of the entire optical system. The lens unit for correcting image blur is not limited to the third lens unit L3. However, since in the embodiment, the aperture stop SP is disposed close to the third lens unit L3, the outer diameter L3 of the third lens unit L3 is small, and therefore the third lens unit L3 is less expensive from the viewpoint of the weight of the drive. Preferable to use instead of other lens units.

In an embodiment of the present invention, when zooming, the aperture stop SP moves independently of the lens unit. Thus, in the region of wide-angle views, the pupil entrance is located as close as possible to the subject, so that the optional diameter of the front lens is smaller.

However, according to the preferred design, the aperture stop SP can move together with the third lens unit L3 or the aperture stop SP can be relatively fixed to the image plane IP. If the aperture stop SP moves together with the third lens unit L3, the lens is divided into lens units and moves together, and enables a reduction in the number of movable lens units, thereby tending to simplify the mechanical structure. If the aperture stop SP is fixed, it does not need to move when zooming. Therefore, the braking weight of the brakes is reduced to save power when zooming.

In the embodiment of the present invention, the focal length of the entire system at the wide-angle end is fw, the focal length at the telephoto end is ft, and the focal length of the entire system at the intermediate zoom position is fm=(fw*ft) ^1/2 . When zooming from the wide-angle end to the intermediate end, the movement amount of the fourth lens unit L4 is Mm, and the movement amount of the fourth lens unit L4 when zooming from the wide-angle end to the telephoto end is Mt. The focal lengths of the third lens unit L3 and the fourth lens unit L4 are f3 and f4, respectively.

In this case, the following conditions are met:

1.8＜(|Mm|+|Mt|)/fw＜4.0(1)

0.65<f3/f4<1.0(2)

In the embodiment, by satisfying conditional expressions (1) and (2), a zoom lens having a wide angle of view and a high zoom ratio is realized. When a zoom lens is formed to have a wide angle of view and a high zoom ratio, there is a problem that the coma aberration in the middle region (middle zoom region) varies. This problem can be solved by increasing the number of lenses so that the lens unit has a higher optical power or by using an aspheric surface.

However, increasing the number of lenses increases the size of the entire system, and in addition, aspheric surfaces are difficult to establish.

Conditional expression (1) relates to the ratio between the movement amount of the fourth lens unit L4 when zooming from the wide-angle zoom end to the telephoto end and the focal length fw of the entire system at the wide-angle end.

To correct coma aberration at the outer edge of the intermediate area, the third lens unit L3 moves toward the object side during zooming when zooming from the wide-angle end to the intermediate end, and the fourth lens unit L4 may also move toward the object side.

In addition, reducing the variation in the incident height of the incident light of the fourth lens unit L4 plays an important role in the restriction of axial chromatic flare and coma aberration in the intermediate region from the wide-angle end to the intermediate end.

If (|Mm|+|Mt|)/fw falls below the lower limit of the conditional expression (1), it will result in an insufficient amount of movement of the fourth lens unit L4 toward the object side, resulting in an off-axis phase difference variation. If (|Mm|+|Mt|)/fw exceeds the upper limit of the conditional expression (1), the movement amount of the fourth lens unit L4 becomes too large. Therefore, in the process of folding the lens unit, it is necessary to ensure that (|Mm|+|Mt|)/fw satisfies the value range of the conditional formula (1), so that the whole system becomes compact.

Conditional expression (2) expresses the ratio between the focal length of the third lens unit L3 and the focal length L4 of the fourth lens unit L4, and is used to appropriately set and change the magnification of the third lens unit L3 and the fourth lens unit L4 during zooming. rate burden.

The conditional expression (2) provides an ideal state that not only the second lens unit L2 undertakes the variation of the magnification, but also the third lens unit L3 and the fourth lens unit L4 jointly control the zoom ratio. If the ratio of f3/f4 is lower than the lower limit and the refractive power of the third lens unit L3 becomes excessively large, the change in the incident angle of the off-axis beam emitted from the third lens unit L3 with respect to the fourth lens unit L4 during zooming is considerable. Big.

Therefore, outward coma tends to occur in the intermediate focal length region (middle region). Conversely, if f3/f4 exceeds the upper limit and the refractive power of fourth lens unit L4 becomes too large, it is necessary to increase the number of lenses constituting fourth lens unit L4 in order to limit changes in coma aberration during focusing. As a result, an increase in the weight of the driving lens or an increase in the size of the entire lens unit at the time of focusing is not preferable.

This is why the numerical ranges (1) and (2) of the conditional expressions are limited. According to these expressions, the zoom lens can easily achieve a wide viewing angle and a high zoom ratio, and limit the change of aberration in the middle area.

Each optical element of the zoom lens satisfies the conditions in Table 1, Table 2 and Table 3. In Table 1 below, there are optical surface numbers numbered sequentially from the object side to the image side, R is the radius of curvature of the optical surface of each lens, D is the axial distance from the corresponding surface to the next surface, and Nd is the corresponding lens group Refractive index to light, Vd is the Abbe number of light in the corresponding lens group, B, C, D and E represent aspheric coefficients, f is the effective focal length of the zoom lens, Fnumber is the aperture number of the zoom lens, 2w is the angle of view of the zoom lens.

Table 1

surface lens surface R(mm) D(mm) Nd Vd S1 sphere 62.7127 1.5 1.8061 33.3 S2 sphere 29.9095 7 1.4970 81.5 S3 sphere 187.3046 1 S4 sphere 30.973 5.3182 1.6968 55.5 S5 sphere 136.9449 4.4 S6 sphere 12.1246 3.0048 1.8830 40.8 S7 sphere 11.5169 2.3 S8 sphere 25.5738 1.2 1.8348 42.7 S9 sphere 7.8872 3.8 S10 sphere -44.9305 1.3 1.8340 37.2 S11 sphere 21.4149 0.7 S12 sphere 14.9474 2 1.9228 18.9 S13 sphere 42.5129 27.3873 S14 aperture unlimited 1 S15 Aspherical 10.1597 0.9 1.6935 53.2 S16 sphere 12.7962 0.1 S17 sphere 7.009 3.1107 1.6580 50.9 S18 sphere 6.0843 1.5 S19 sphere 14.5258 0.4 2.0006 25.5 S20 sphere 6.3194 1.1554 1.7200 50.2 S21 sphere 109.4328 4.074 S22 sphere 13.8099 3 1.7725 49.6 S23 sphere -19.5787 0.6 1.6989 30.1 S24 sphere -420.792 5.4066

S25 sphere unlimited 0.8 1.5163 64.1 S26 sphere unlimited 0.8789 imaging surface flat unlimited 3.3643

Table II

Table three

f D5 D13 D14 D21 D24 wide-angle end 10 4.4 27.39 1 4.07 5.41 middle end 22.6 17.61 12.62 6 6.45 5.39 far end 90 23.52 0.11 1 37.59 1.86

Table four

f F number 2w(degree) wide-angle end 10 2.7 37.6 middle end 22.6 3.5 17.1 far end 90 5.6 4.3

It can be seen from Fig. 2-7, the MTF curve value and distortion curve diagram of the zoom lens in the case of short focus, medium focus and long focus when the spatial frequency is 1P/mm. It can be seen that the distortion of the full field of view is moderate and has a good The imaging quality can meet the user's image shooting requirements.

Claims (6)

1. A zoom lens is suitable for object imaging on the object side on an imaging plane on the image side, characterized in that the zoom lens includes: a first lens unit, disposed between the object side and the image side, and has positive refractive power; a second lens unit, disposed between the first lens unit and the image side, and has a negative refractive power; a third lens unit, disposed between the second lens unit and the image side, and has positive refractive power; and a fourth lens unit, disposed between the third lens unit and the image side, and has positive refractive power; The first lens unit, the second lens unit, the third lens unit and the fourth lens unit are all used as moving lens units, and the zoom lens meets the following conditions: 1.8<(|Mm|+|Mt|)/fw<4.0, 0.65<f3/f4<1.0, fm=(fw*ft) ^1/2 , Mm is the movement amount of the fourth lens unit, Mt is the movement amount of the fourth lens unit when zooming from the wide-angle end to the telephoto end, fw is the focal length of the zoom lens at the wide-angle end, and fm is the zoom lens at the middle zoom position Focal length, ft is the focal length of the zoom lens at the telephoto end, f3 is the focal length of the third lens unit, and f4 is the focal length of the fourth lens unit. 2 . The zoom lens according to claim 1 , wherein the zoom lens further comprises an aperture stop, and the aperture stop is arranged between the second lens unit and the third lens unit. 3 . 3. A zoom lens according to claim 2, wherein the aperture stop is independently movable or fixed. 4. a kind of zoom lens according to claim 1, is characterized in that, The first lens unit includes a cemented lens and a third lens from the object side to the image side, and the cemented lens includes a first lens and a second lens from the object side to the image side , and the first lens, the second lens and the third lens are negative, positive and positive in sequence; The second lens unit includes a fourth lens, a fifth lens, a sixth lens and a seventh lens from the object side to the image side, and the fourth lens, the fifth lens, the sixth lens and the The seventh lens is sequentially negative, negative, negative, positive; The third lens unit includes an eighth lens, a ninth lens, and a cemented lens from the object side to the image side, and the cemented lens includes a tenth lens from the object side to the image side and an eleventh lens, and the eighth lens, the ninth lens, the tenth lens and the eleventh lens are sequentially positive, positive, negative, and positive; The fourth lens unit includes a twelfth lens and a thirteenth lens from the object side to the image side, and the twelfth lens and the thirteenth lens are negative and positive in sequence. 5. A zoom lens according to claim 4, wherein the first lens is a concave-convex lens with a concave surface facing the image side, the second lens is a convex lens with a convex surface facing the object side, and the second lens is a convex lens with a convex surface facing the object side. The three lenses are convex lenses with a convex surface facing the object side, the fourth lens is a concave lens with a concave surface facing the image side, the fifth lens is a concave-convex lens with a concave surface facing the image side, and the sixth lens is a concave lens facing the object side. The concave-convex lens, the seventh lens is a convex lens with a convex surface facing the object side, the eighth lens is a convex lens with a convex surface facing the object side, the ninth lens is a concave-convex lens with a concave surface facing the image side, and the tenth lens is a concave lens facing the object side. The concave lens on the image side, the eleventh lens is a convex lens with a convex surface facing the object side, the twelfth lens is a biconvex lens, and the thirteenth lens is a concave lens with a concave surface facing the object side. 6. a kind of zoom lens according to claim 1, is characterized in that, described zoom lens also comprises any one of optical filter, panel, crystal low-pass filter and infrared cut-off filter kind, and described optical Any one of a filter, a panel, a crystal low-pass filter, and an infrared cut filter is disposed between the fourth lens unit and the image side.