JP4671635B2 - Zoom lens - Google Patents

Description

  The present invention relates to a compact and lightweight zoom lens that supports mega-order high-quality images used in in-vehicle cameras, surveillance cameras, digital cameras, mobile phone cameras, and the like using light receiving elements such as CCDs and CMOSs. is there.

  As light receiving elements such as CCDs and CMOSs, 1/3 and 1/4 inch sizes have been put into practical use, and along with this, the cameras themselves have been miniaturized. Inevitably, there is an increasing demand for downsizing and downsizing. Furthermore, light receiving elements such as CCDs have become higher in the order of mega pixels, contrary to the miniaturization of CCDs. A zoom lens used in a camera using such a high-pixel light-receiving element must inevitably exhibit high optical performance. Conventionally, zoom lenses of this type have been corrected for aberrations using a large number of lenses in order to exhibit high optical performance.

Examples of the two-group zoom lens include those described in Patent Documents 1 and 2. Each of these two-group zoom lenses has a method of moving to the object side while reducing the air gap between the first lens group and the second lens group when zooming from the wide side to the tele side. The optical total length at the end is considerably longer than that at the wide end. Also, what is described in Patent Document 3 is a three-group zoom lens composed of negative and positive, and the total length of the wide end and the total length of the tele end are substantially the same. However, since the second group of second lenses is thick, the optical total length is relatively long.
JP-A-8-129133 Japanese Patent Laid-Open No. 9-184979 JP 2003-222798 A

  An object of the present invention is to propose a zoom lens suitable for mounting on a mobile phone or the like.

  That is, the object of the present invention is to make the total length of the lens system as short as possible, and at the same time, the total length from the object side lens surface of the first group lens to the imaging surface at wide time and the object side of the first group lens at tele time. The object is to propose a zoom lens in which the overall length from the lens surface to the imaging surface can be made substantially the same.

  Another object of the present invention is to enable super macro photography (super close-up photography) by extending the first lens group to the tele or wide position at the intermediate focal length between the tele end and the wide end. The object is to propose a small, lightweight, high-power zoom lens with a small number of lenses that can handle fine pixels.

  In order to solve the above problems, the zoom lens of the present invention is a two-group zoom lens in which the entire optical system is composed of three to four lenses, and the focal length of the first lens group and the focal point of the second lens group. The optical total length at the wide end and the optical total length at the tele end are made substantially the same by the ratio distribution of distances. In addition, the first lens group has an action of correcting fluctuations in the image plane position caused by zooming, and has a distance adjustment function as necessary. The focal length of the second lens group changes from wide to telephoto by narrowing the spatial distance formed with the first lens group along the optical axis. Furthermore, the optical performance is advantageous by making at least one lens surface out of the lens surfaces of the lenses constituting the first lens group and the second lens group.

  Each lens can be either a plastic lens or a glass lens, but using a plastic lens is very convenient for processing. The present invention is not limited to a zoom lens having a two-group three-lens configuration, and the first lens group has a two-group four-lens configuration including two lenses, or the front lens of the second lens group has two lenses. The present invention can be similarly applied to a zoom lens having two groups and four lenses.

More specifically, the present invention
A zoom lens having a two-group configuration in which a first lens group having a negative power and a second lens group having a positive power are arranged in this order from the object side toward the imaging side ,
The first lens group is composed of a single concave lens with a large curvature lens surface facing the object side ,
The second lens group has a configuration in which a front lens made up of a single convex lens and a rear lens made up of a single convex lens are arranged in a state of maintaining a constant distance via a diaphragm. ,
Of the lens surfaces of the lenses constituting the first lens group and the second lens group, at least one lens surface is an aspheric surface,
The following conditional expressions (1) to (7) are satisfied.
0.5 <dm / fW <3.0 (1)
2.0 <ΣdW / fW <8.0 (2)
0.5 <| f1 / f23 | <2.0 (3)
1.0 <f3 / f2 <10.0 (4)
| R8 / R7 | <1.0 (5)
0.05 <H / fW / ΣdW <0.1 (6)
1.0 / fW <dn <3.5 / fW (7)
However, fW: Composite focal length at the wide end of the entire lens system f1: Focal length of the first lens group f2: Focal length of the front lens of the second lens group f3: Focal length of the rear lens of the second lens group f23: Focal length of second lens group R7: Curvature of object side lens surface of rear lens of second lens group R8: Curvature of imaging side lens surface of rear lens of second lens group dm: Front side of second lens group Distance from the object-side lens surface of the lens to the imaging-side lens surface of the rear lens dn: Distance on the optical axis from the object-side lens surface of the front lens to the image-side lens surface in the second lens group ΣdW : Distance on the optical axis from the object side lens surface to the imaging plane at the wide end H: Maximum image height on the imaging plane

  In conditional expression (1), if the lower limit of 0.5 is not reached, the off-axis chromatic aberration will be undercorrected, and at each zoom position, coma and spherical aberration will remain stable while maintaining a large aperture. I can't. Next, when the upper limit of 3.0 is exceeded, it becomes difficult to ensure the amount of peripheral light, and at the same time, it is difficult to achieve downsizing.

  Conditional expression (2) defines the size of the optical system. If the lower limit of 2.0 is not reached, the power of each lens group becomes strong, making it difficult to correct aberrations and processing the lens. Become. If the upper limit of 8.0 is exceeded, the power of each lens group becomes weak, which is advantageous for aberration correction and lens workability, but is not suitable for the original size reduction.

  Conditional expression (3) is a condition for keeping the entire length of the lens system constant in the wide position and the tele position, and is also a condition for stabilizing the optical performance of the wide and tele.

  That is, when the lower limit is less than 0.5, the tele-side length is shortened with respect to the wide-side length, and the power of the first lens group is increased, making it difficult to balance the correction of each aberration. When the upper limit of 2.0 is exceeded, the total length on the wide side becomes shorter than the total length on the telephoto side, and at the same time, the power of the second lens group becomes strong, making it difficult to balance each aberration. Therefore, if this conditional expression (3) exceeds the range of the lower limit and the upper limit, the full length of the wide end and the tele end cannot be matched.

  Conditional expression (4) is a condition for keeping the balance of each aberration stable. If the lower limit of 1.0 is not reached, it is difficult to correct off-axis chromatic aberration and it is difficult to reduce the size. If the upper limit of 10.0 is exceeded, the power of the front lens of the second lens group will become strong and it will be difficult to stably correct each aberration. In particular, chromatic aberration at off-axis magnification will be overcorrected. .

  Conditional expression (5) is a condition for balancing the curvature of field and the spherical aberration at each zoom position. If this range is exceeded, the surrounding image surface is curved toward the object side, and the balance with the spherical aberration is satisfied. Can not be removed. That is, the image surface is curved in the (−) direction, and the spherical aberration is inclined in the (+) direction.

  In conditional expression (6), if the lower limit of 0.05 is not reached, the entire lens system becomes large, making it impossible to achieve the original size reduction and making it difficult to widen the zoom system. If the upper limit is exceeded, the lens system can be reduced in size, but the power of each lens group becomes too strong, and stable aberrations cannot be secured.

  In conditional expression (7), if the upper limit of 3.5 / fW is exceeded, the total length becomes longer, and the original size reduction cannot be achieved. In addition, in the state where the full length is maintained, since the power of the second group is reduced, the distortion is increased, and the image surface on the wide side is over, and the imaging performance is not satisfied. If the lower limit of 1 / fW is not reached, the edge thickness of the front lens of the second lens group becomes thin, making production difficult.

Next, according to the present invention, a first lens group having a negative power and a second lens group having a positive power are arranged in this order from the object side toward the imaging surface. becomes a large lens surface curvature from the two concave lenses toward the object side, the second lens group, a front lens made of a single convex lens, and the side lens after made from a single convex lens, a diaphragm And at least one of the lens surfaces of the lenses constituting the first lens group and the second lens group is an aspherical surface. The present invention can also be applied to a zoom lens having a two-group configuration .

Further, according to the present invention, a first lens group having a negative power and a second lens group having a positive power are arranged in this order from the object side toward the imaging surface, and the first lens group includes: becomes a large lens surface curvature from one concave toward the object side, the second lens group, a front lens comprising two convex lenses, the rear lens after made from a single convex lens, through the aperture And at least one of the lens surfaces of the lenses constituting the first lens group and the second lens group is an aspherical surface. The present invention can also be applied to a two-group zoom lens.

  In the zoom lens of the present invention, the distance from the imaging surface at the wide end and the tele end in zooming in the first lens group can be made substantially the same, and the distance from the imaging surface at the standard position is The distance can be shorter than the distance at the wide end and the tele end. Further, the second lens group can be moved along the optical axis so that the distance from the first lens group becomes narrower from the wide end toward the tele end.

  In addition, super close-up photography can be performed by setting the first lens group at the tele end or the wide end at the standard position in zooming.

  Further, if the lenses constituting the first lens group and the second lens group are made of the same material, particularly plastic, there is an advantage that the processing is simplified.

  As described above, the zoom lens of the present invention is a lens having a two-group three-element configuration or a two-group four-element configuration, and has a high zoom ratio of 2 to 3 times despite the fact that the total length of the optical system is as small as 10 mm or less. It is possible to support high pixels equivalent to mega orders. Therefore, according to the present invention, it is possible to realize a high-power zoom lens that is small and supports high-order megapixels.

  Embodiments of a zoom lens to which the present invention is applied will be described below with reference to the drawings. The zoom lenses of Examples 1 to 3 are examples of double zoom lenses, and the zoom lenses of Examples 4 to 6 are examples of high magnification zoom lenses of 3 times. In each of the embodiments, examples in which all the optical materials are made of plastic, which is the same material, and different optical materials, for example, plastic and glass are included. However, all the optical materials may be glass, and in each embodiment, an optical material different from the material used can be used.

  FIG. 1A is a configuration diagram illustrating the zoom lens according to the first exemplary embodiment. The zoom lens 10 </ b> A of this example has a configuration in which the first lens group I and the second lens group II are arranged in this order from the object side toward the image plane 11. The first lens group I is composed of a single concave lens 1, and the second lens group II is composed of a front lens 2 and a rear lens 3. A diaphragm 4 is disposed in the vicinity of the rear lens 3 on the object side, and a cover glass 10 is disposed between the rear lens 3 and the imaging surface 11.

  The first lens 1 is a concave lens provided with a lens surface 1a having a large curvature on the object side. The front lens 2 of the second lens group II consists of a single convex lens 2, and the rear lens 3 also consists of a single convex lens. These two convex lenses 2 and 3 are arranged in a state of maintaining a constant interval. That is, it is configured to move in the optical axis direction while maintaining a constant interval during zooming. The lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2 of the second lens group II, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are aspherical. Yes.

  FIG. 1B shows the movement locus of the first lens group I and the second lens group II during zooming of the zoom lens 10A. The first lens group I has substantially the same distance from the image plane 11 at the wide end W and the tele end T, and is shorter at the intermediate focal length (standard) position S. The first lens group I corrects movement of the focal plane due to zooming by drawing a curved movement locus Ia connecting these points. On the other hand, the second lens group II draws a linear movement trajectory IIa so that the distance from the first lens group I decreases from the wide end W toward the telephoto end T, thereby changing the magnification. Is going.

  In addition, the first lens group I has a distance adjusting function. In this example, by using a 50 cm finite set, in general, ∞ to 12 cm at the wide end, ∞ to 18 cm at the standard, and tele end. Has realized ∞ to 22cm.

  Further, at the standard position S, the first lens group I is extended to the position at the time of the wide end W or the tele end T, so that the close-up photographing (macro photographing) of 23 mm from the lens surface 1a on the object side of the concave lens 1 is performed. Is possible.

The lens data of the entire optical system of the zoom lens 10A is as follows.
Wide end Standard Tele end F-number: 3.37 4.40 5.40
Focal length: 2.25mm 3.40mm 4.50mm
f1: -3.19 mm
f2: 3.125 mm
f3: 8.39 mm
f23: 2.70 mm
dm: 2.5 mm
ΣdW: 9.0165 mm

  Table 1A shows lens data of each lens surface of the zoom lens 10A, and Table 1B shows aspheric coefficients for defining the aspherical shape of the aspherical lens surface. In Table 1A, i represents the order of the lens surfaces counted from the object side, R represents the curvature of the lens surfaces, d represents the distance of the lens surfaces, Nd represents the refractive index of each lens, and νd represents each lens. Represents the Abbe number. In addition, a lens surface with a star mark attached to the number i indicates an aspherical surface.

  The aspherical shape adopted for the lens surface is as follows, where the axis in the optical axis direction is X, the height in the direction perpendicular to the optical axis is H, the conical coefficient is K, and the aspherical coefficients are A, B, C, and D. It can be expressed by a formula.

  The meaning of each symbol and the expression representing the aspherical shape are the same in Examples 2 to 6 described later.

The zoom lens 10A satisfies the conditional expressions (1) to (7).
0.5 <dm / fW <3.0 (1)
2.0 <ΣdW / fW <8.0 (2)
0.5 <| f1 / f23 | <2.0 (3)
1.0 <f3 / f2 <10.0 (4)
| R8 / R7 | <1.0 (5)
0.05 <H / fW / ΣdW <0.1 (6)
1.0 / fW <dn <3.5 / fW (7)

That is, dm / fW = 1.11, ΣdW / fW = 4.0, | f1 / f23 | = 1.16 , f3 / f2 = 2.69 , | R8 / R7 | = 0.19 , H / fW / ΣdW = 0.092, 0.44 <dn = 0.8 <1.56, which satisfies the conditional expressions (1) to (7). Note that H is 1.867 mm.

  FIG. 6 is an aberration diagram showing various aberrations in the zoom lens 10A. SA represents spherical aberration, AS represents astigmatism, T represents tangential, S represents sagittal image plane, and DIST represents distortion. The meanings of these symbols are the same in aberration diagrams showing various aberrations for Examples 2 to 6 described later.

  Since the configuration of the zoom lens 20 of the second embodiment is basically the same as that of the first embodiment, FIG. In the zoom lens 20, the first lens group I and the second lens group II are arranged in this order from the object side toward the imaging plane 11. The first lens group I consists of a single concave lens 1. The second lens group II has a configuration in which a front lens 2 and a rear lens 3 are arranged via a diaphragm 4, and the diaphragm 4 is disposed in the vicinity of the object side of the rear lens 3. A cover glass 10 is disposed between the rear lens 3 and the imaging plane 11.

  The first lens 1 is a concave lens provided with a lens surface 1a having a large curvature on the object side. The front lens 2 of the second lens group II consists of a single convex lens 2, and the rear lens 3 also consists of a single convex lens. These two convex lenses 2 and 3 are arranged in a state of maintaining a constant interval. That is, it is configured to move in the optical axis direction while maintaining a constant interval during zooming. The lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2 of the second lens group II, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are aspherical. Yes.

  The zoom method, distance adjustment method, and super close-up photographing method (macro photographing method) in the zoom lens 20 are the same as those of the zoom lens 10A of the first embodiment.

The lens data of the entire optical system of the zoom lens 20 is as follows.
Wide end Standard Tele end F-number: 3.46 4.4 5.3
Focal length: 2.25mm 3.40mm 4.50mm
f1: -3.19 mm
f2: 3.21 mm
f3: 8.127 mm
f23: 2.75 mm
dm: 2.40 mm
ΣdW: 9.0754 mm

  Table 2A shows lens data of each lens surface of the zoom lens 20, and Table 2B shows aspherical coefficients for defining the aspherical shape of the aspherical lens surface.

In the zoom lens 20, dm / fW = 1.07, ΣdW / fW = 4.0, | f1 / f23 | = 1.16, f3 / f2 = 2.53 , | R8 / R7 | = 0.003, Since H / fW / ΣdW = 0.09 and 0.45 <dn = 0.8 <1.56, the above-described conditional expressions (1) to (7) are satisfied. H is 1.835 mm.

  FIG. 7 is an aberration diagram showing various aberrations in the zoom lens 20 of the second embodiment.

  FIG. 2A is a configuration diagram of the zoom lens 30 according to the third embodiment. The zoom lens 30 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I is composed of a single concave lens 1, and this concave lens 1 is a meniscus lens having a convex surface facing the object side. The second lens group II includes a front lens 2 and a rear lens 3 and a diaphragm 4 disposed therebetween. The front lens 2 is composed of a single convex lens, and the rear lens 3 is also composed of a single convex lens. These convex lenses are arranged in a state where a constant interval is maintained.

  In this example, the lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are all aspherical.

  The zoom method, distance adjustment method, and macro photography method in the zoom lens 30 are the same as those in the zoom lens 10A of Example 1 as shown in FIG.

The lens data of the entire optical system of the zoom lens 30 is as follows.
Wide end Standard Tele end F-number: 3.0 3.9 4.8
Focal length: 2.14mm 3.24mm 4.28mm
f1: −3.058 mm
f2: 2.71 mm
f23: 2.706 mm
f3: 8.224 mm
dm: 2.45 mm
ΣdW: 8.4565mm

  Table 3A shows lens data of each lens surface of the zoom lens 30, and Table 3B shows aspheric coefficients for defining the aspherical shape of the aspheric lens surface.

In the zoom lens 30, dm / fW = 1.15 , ΣdW / fW = 3.95, | f1 / f23 | = 1.13, f3 / f2 = 3.0, | R8 / R7 | = 0.79, H / fW / ΣdW = 0.07, 0.47 <dn = 0.8 <1.64, which satisfies the above-described conditional expressions (1) to (7). Note that H is 1.267 mm.

  FIG. 8 is an aberration diagram showing various aberrations of the zoom lens 30.

  Since the basic configuration of the zoom lens 40 according to the fourth embodiment is the same as that of the zoom lens 30 according to the third embodiment, FIG. The zoom lens 40 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I is composed of a single concave lens 1, and this concave lens 1 is a meniscus lens having a convex surface facing the object side. The second lens group II includes a front lens 2 and a rear lens 3 and a diaphragm 4 disposed therebetween. The front lens 2 is composed of a single convex lens, and the rear lens 3 is also composed of a single convex lens. These convex lenses are arranged in a state where a constant interval is maintained.

  In this example, the lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are all aspherical.

  The zoom method, distance adjustment method, and macro photography method in the zoom lens 40 are the same as those in the zoom lens 10A of the first embodiment.

The lens data of the entire optical system of the zoom lens 40 is as follows.
Wide end Standard Tele end F-number: 3.0 4.6 6.3
Focal length: 1.54mm 3.0mm 4.62mm
f1: -2.67 mm
f2: 2.66 mm
f3: 7.81 mm
f23: 2.71 mm
dm: 2.59 mm
ΣdW: 9.176 mm

  Table 4A shows lens data of each lens surface of the zoom lens 40, and Table 4B shows aspheric coefficients for defining the aspherical shape of the aspherical lens surface.

In the zoom lens 40, dm / fW = 1.68, ΣdW / fW = 5.96 , | f1 / f23 | = 0.98, f3 / f2 = 2.94, | R8 / R7 | = 0.78, H /FW/ΣdW=0.09 and 0.65 <dn = 0.75 <2.27, which satisfy the above-described conditional expressions (1) to (7). Note that H is 1.272 mm.

  FIG. 9 is an aberration diagram showing various aberrations of the zoom lens 40.

  FIG. 3A is a configuration diagram illustrating a zoom lens according to the fifth embodiment. The zoom lens 50 of Example 5 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I is composed of a single concave lens. The concave lens 1 is a meniscus lens having a convex surface facing the object side. The second lens group II includes a front lens 2 and a rear lens 3 and a diaphragm 4 disposed therebetween. The front lens 2 is composed of a single convex lens, and the rear lens 3 is also composed of a single convex lens. These second lens groups II are arranged in a state of maintaining a constant interval.

  In this example, the lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are all aspherical.

  The zoom method, distance adjustment method, and macro photography method in the zoom lens 50 are the same as in the zoom lens 10A of Example 1 as shown in FIG.

The lens data of the entire optical system of the zoom lens 50 is as follows.
Wide end Standard Tele end F-number: 3.0 4.4 6.4
Focal length: 1.503mm 2.63mm 4.47mm
f1: -2.60mm
f2: 2.466 mm
f3: 9.39 mm
f23: 2.65 mm
dm: 2.514 mm
ΣdW: 9.289 mm

  Table 5A shows lens data of each lens surface of the zoom lens 50, and Table 5B shows aspheric coefficients for defining the aspheric shape of the aspheric lens surface.

In the zoom lens 50, dm / fW = 1.67 , ΣdW / fW = 6.18 , | f1 / f23 | = 0.98, f3 / f2 = 3.81 , | R8 / R7 | = 0.90, H /FW/ΣdW=0.093 and 0.67 <dn = 0.95 < 2.33 , which satisfy the above-described conditional expressions (1) to (7). Note that H is 1.298 mm.

  FIG. 10 is an aberration diagram showing various aberrations of the zoom lens 50.

  Since the basic configuration of the zoom lens 60 according to the sixth embodiment is substantially the same as the configuration of the zoom lens 50 according to the fifth embodiment, FIG. The zoom lens 60 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I is composed of a single concave lens 1, and this concave lens 1 is a meniscus lens having a convex surface facing the object side. The second lens group II includes a front lens 2 and a rear lens 3 and a diaphragm 4 disposed therebetween. The front lens 2 is composed of a single convex lens, and the rear lens 3 is also composed of a single convex lens. The second lens group II is arranged with a constant interval.

  In this example, the lens surfaces 1a and 1b on both sides of the concave lens 1, the lens surfaces 2a and 2b on both sides of the front lens 2, and the lens surfaces 3a and 3b on both sides of the rear lens 3 are all aspherical. The zoom method, distance adjustment method, and macro photography method in the zoom lens 60 are the same as those in the zoom lens 10A of the first embodiment.

The lens data of the entire optical system of the zoom lens 60 is as follows.
Wide end Standard Tele end F-number: 2.8 3.8 5.8
Focal length: 1.565mm 2.63mm 4.67mm
f1 (1a + 1b): -2.705 mm
f2: 2.42 mm
f3: 10.27 mm
f23: 2.63 mm
dm: 2.514 mm
ΣdW: 9.209 mm

  Table 6A shows lens data of each lens surface of the zoom lens 60, and Table 6B shows aspheric coefficients for defining the aspherical shape of the aspherical lens surface.

In the zoom lens 60, dm / fW = 1.61 , ΣdW / fW = 5.88 , | f1 / f23 | = 1.03, f3 / f2 = 4.24, | R8 / R7 | = 0.93, H /FW/ΣdW=0.07, 0.64 <dn = 0.95 < 2.24 , which satisfies the above-described conditional expressions (1) to (7). H is 1.09 mm.

  FIG. 11 is an aberration diagram showing various aberrations of the zoom lens 60.

  FIG. 4A is a configuration diagram illustrating a zoom lens according to the seventh embodiment. The zoom lens 70 according to the seventh exemplary embodiment is a zoom lens having a triple magnification by dividing the power of the concave lens of the first lens group I into two.

  The zoom lens 70 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I includes two concave lenses 101 and 102, and these concave lenses 101 and 102 are meniscus lenses having a convex surface facing the object side. The second lens group II includes a front lens 2 and a rear lens 3 having positive power, and a diaphragm 4 is disposed between these lenses 2 and 3. The front lens 2 is composed of a single convex lens, the rear lens 3 is also composed of a single convex lens, and these convex lenses 2 and 3 are configured to maintain a constant interval. The lens surface 101a on the object side of the concave lens 101 of the first lens group I, the lens surfaces 102a and 102b on both sides of the concave lens 102 of the first lens group I, and the lenses on both sides of the front lens 2 of the second lens group II. The surfaces 2a and 2b and the lens surfaces 3a and 3b on both sides of the rear lens 3 are aspheric.

  The zoom method, distance adjustment method, and macro photography method of the zoom lens 70 are the same as those of the zoom lens 10A of Example 1 as shown in FIG.

The lens data of the entire optical system of the zoom lens 70 is as follows.
Wide end Standard Tele end F-number: 2.8 4.0 5.6
Focal length: 1.54mm 2.98mm 4.62mm
f1 (1a + 1b): -2.66 mm
f2: 2.58 mm
f3: 13.155 mm
f23: 2.72 mm
dm: 2.84 mm
ΣdW: 10.34 mm

  Table 7A shows lens data of each lens surface of the zoom lens 50, and Table 7B shows aspheric coefficients for defining the aspherical shape of the aspherical lens surface.

In the zoom lens 70, dm / fW = 1.85 , ΣdW / fW = 6.72 , | f1 / f23 | = 0.98, f3 / f2 = 5.1, | R8 / R7 | = 0.8, H /FW/ΣdW=0.08, 0.65 <dn = 0.9 <2.27, which satisfies the above-described conditional expressions (1) to (7). Note that H is 1.273 mm.

  FIG. 12 is an aberration diagram showing various aberrations of the zoom lens 70.

  FIG. 5A is a configuration diagram of a zoom lens according to Example 8. In the zoom lens 80 of Example 8, the front lens of the second lens group is divided into two to form a two-group four-lens configuration and a three-times zoom lens.

  The zoom lens 80 has a configuration in which the first lens group I, the second lens group II, and the cover glass 10 are arranged in this order from the object side toward the image plane 11. The first lens group I includes a single concave lens 1 and is a meniscus lens having a convex surface facing the object side. The second lens group II has a front lens 2 and a rear lens 3, and a diaphragm 4 disposed in the vicinity of the rear lens 3 is located between them. The front lens 2 includes two convex lenses 201 and 202, and the rear lens 3 includes a single convex lens. In this example, the lens surfaces 1a and 1b on both sides of the concave lens 1 of the first lens group I, the lens surfaces 201a and 201b on both sides of the convex lens 201 of the front lens 2 of the second lens group II, and the convex lens 202 of the front lens 2 are used. The lens surface 202a on the object side and the lens surfaces 3a and 3b on both sides of the rear lens 3 are aspheric.

  The zoom method, distance adjustment method, and macro photography method of the zoom lens 80 are also the same as those of the zoom lens 10A of Example 1 as shown in FIG.

The lens data of the entire optical system for the zoom lens 80 is as follows.
Wide end Standard Tele end F-number: 2.8 3.9 5.4
Focal length: 1.543mm 3.0mm 4.65mm
f1: -2.69 mm
f2 (2a + 2b): 2.54 mm
f3: 8.03 mm
f23: 2.69 mm
dm: 2.79 mm
ΣdW: 9.166 mm

  Table 8A shows lens data of each lens surface of the zoom lens 80, and Table 8B shows aspheric coefficients for defining the aspherical shape of the aspheric lens surface.

In the zoom lens 80, dm / fW = 1.81, ΣdW / fW = 5.94 , | f1 / f23 | = 1.0, f3 / f2 = 3.16, | R8 / R7 | = 0.83 , H /FW/ΣdW=0.09 and 0.65 <dn = 1.35 <2.27, which satisfy the conditional expressions (1) to (7). Note that H is 1.273 mm.

  FIG. 13 is an aberration diagram showing various aberrations of the zoom lens 80.

FIG. 2 is a configuration diagram of zoom lenses of Embodiments 1 and 2 of the present invention, and an explanatory diagram showing movement trajectories of a first lens group and a second lens group. FIG. 4 is a configuration diagram of a zoom lens according to Embodiments 3 and 4 of the present invention, and an explanatory diagram illustrating movement trajectories of a first lens group and a second lens group. FIG. 6 is a configuration diagram of zoom lenses according to embodiments 5 and 6 of the present invention, and an explanatory diagram showing movement trajectories of a first lens group and a second lens group. FIG. 10 is a configuration diagram of a zoom lens according to Example 7 of the present invention, and an explanatory diagram showing movement trajectories of a first lens group and a second lens group. FIG. 10 is a configuration diagram of a zoom lens according to Example 8 of the present invention, and an explanatory diagram showing movement trajectories of a first lens group and a second lens group. FIG. 4 is an aberration diagram of the zoom lens 10A according to the first embodiment of the present invention. It is an aberration diagram of the zoom lens 20 of Example 2 of the present invention. It is an aberration diagram of the zoom lens 30 of Example 3 of the present invention. It is an aberration diagram of the zoom lens 40 of Example 4 of the present invention. FIG. 10 is an aberration diagram of the zoom lens 50 according to the fifth embodiment of the present invention. It is an aberration diagram of the zoom lens 60 of Example 6 of the present invention. It is an aberration diagram of the zoom lens 70 of Example 7 of the present invention. It is an aberration diagram of the zoom lens 80 of Example 8 of the present invention.

Explanation of symbols

10A, 20, 30, 40, 50, 60, 70, 80 Zoom lens I First lens group
II Second lens group 1, 101, 102 Concave lens 2 Front lens 201, 202 Convex lens 3 Rear lens 4 Diaphragm 10 Cover glass 11 Imaging surface R1, R2, R3, R4, R5, R6, R7, R8 Curvature d1, d3, d5, d7 Thickness of each lens d2, d4, d6 Air spacing between each lens

Claims (5)

A zoom lens having a two-group configuration in which a first lens group having a negative power and a second lens group having a positive power are arranged in this order from the object side toward the imaging side ,
The first lens group is composed of a single concave lens with a large curvature lens surface facing the object side ,
The second lens group has a configuration in which a front lens made up of a single convex lens and a rear lens made up of a single convex lens are arranged in a state of maintaining a constant distance through a diaphragm. ,
Of the lens surfaces of the lenses constituting the first lens group and the second lens group, at least one lens surface is an aspheric surface,
The focal length of the first lens group is f1, the focal length of the front lens is f2, the focal length of the rear lens is f3, and the focal length of the second lens group is f23. The curvature of the lens surface is R7, the curvature of the lens surface on the imaging side is R8, the thickness of the front lens is dn, and the lens surface on the object side of the front lens to the lens surface on the imaging side of the rear lens Is the distance dm, the combined focal length at the wide end is fW, the distance on the optical axis from the object-side lens surface of the first lens group to the imaging surface at the time of wide is ΣdW, and the maximum image height is H. When the zoom lens satisfies the following conditional expression.
0.5 <dm / fW <3.0 (1)
2.0 <ΣdW / fW <8.0 (2)
0.5 <| f1 / f23 | <2.0 (3)
1.0 <f3 / f2 <10.0 (4)
| R8 / R7 | <1.0 (5)
0.05 <H / fW / ΣdW <0.1 (6)
1.0 / fW <dn <3.5 / fW (7) A zoom lens having a two-group configuration in which a first lens group having a negative power and a second lens group having a positive power from the object side toward the imaging surface are arranged in this order ,
The first lens group is composed of two concave lenses having a lens surface with a large curvature facing the object side ,
The second lens group has a configuration in which a front lens made up of a single convex lens and a rear lens made up of a single convex lens are arranged in a state of maintaining a constant distance through a diaphragm. ,
Of the lens surfaces of the lenses constituting the first lens group and the second lens group, at least one surface is an aspheric surface,
The focal length of the first lens group is f1, the focal length of the front lens is f2, the focal length of the rear lens is f3, and the focal length of the second lens group is f23. The curvature of the lens surface is R7, the curvature of the lens surface on the imaging side is R8, the thickness of the front lens is dn, and the lens surface on the object side of the front lens to the lens surface on the imaging side of the rear lens Is the distance dm, the combined focal length at the wide end is fW, the distance on the optical axis from the object-side lens surface of the first lens group to the imaging surface at the time of wide is ΣdW, and the maximum image height is H. When the zoom lens satisfies the following conditional expression.
0.5 <dm / fW <3.0 (1)
2.0 <ΣdW / fW <8.0 (2)
0.5 <| f1 / f23 | <2.0 (3)
1.0 <f3 / f2 <10.0 (4)
| R8 / R7 | <1.0 (5)
0.05 <H / fW / ΣdW <0.1 (6)
1.0 / fW <dn <3.5 / fW (7) A zoom lens having a two-group configuration in which a first lens group having a negative power and a second lens group having a positive power from the object side toward the imaging surface are arranged in this order ,
The first lens group is composed of a single concave lens with a large curvature lens surface facing the object side ,
The second lens group has a configuration in which a front lens made up of two convex lenses and a rear lens made up of a single convex lens are arranged in a state of maintaining a constant distance through a diaphragm. ,
Of the lens surfaces of the lenses constituting the first lens group and the second lens group, at least one surface is an aspheric surface,
The focal length of the first lens group is f1, the focal length of the front lens is f2, the focal length of the rear lens is f3, and the focal length of the second lens group is f23. The curvature of the lens surface is R7, and the curvature of the lens surface on the imaging side is R8. On the image surface side of the convex lens located on the image surface side from the object side lens surface of the convex lens located on the object side of the front lens. The distance on the optical axis to the lens surface is dn, the distance from the object-side lens surface of the front lens to the image-side lens surface of the rear lens is dm, and the combined focal length at the wide end is fW. A zoom lens satisfying the following conditional expression, where ΣdW is the distance on the optical axis from the object-side lens surface of the first lens group to the imaging surface and H is the maximum image height.
0.5 <dm / fW <3.0 (1)
2.0 <ΣdW / fW <8.0 (2)
0.5 <| f1 / f23 | <2.0 (3)
1.0 <f3 / f2 <10.0 (4)
| R8 / R7 | <1.0 (5)
0.05 <H / fW / ΣdW <0.1 (6)
1.0 / fW <dn <3.5 / fW (7) In any one of claims 1 to 3,
The first lens group has substantially the same distance from the imaging surface at the wide end and the tele end in zooming, and the distance from the imaging surface at the standard position is the distance between the wide end and the tele end. Shorter than
The zoom lens is configured such that the distance between the second lens group and the first lens group decreases from the wide end toward the tele end. In any one of claims 1 to 4,
A zoom lens in which the first lens group is at a tele end or a wide end at the standard position for zooming in order to perform super close-up photography.

Images