JP2010139724A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact zoom lens which holds satisfactory optical performance and has less performance degradation associated with a manufacture error and an assembly error even when power of a second lens group is made strong. <P>SOLUTION: The zoom lens includes, in order from an object side, a first positive lens group G1, a second negative lens group G2 which moves to perform variable power, a diaphragm, a third positive lens group G3, and a fourth positive lens group G4 which performs correction of an image plane position associated with the variable power and focusing. The second lens group G2 includes, in order from the object side, a first negative lens L21, a meniscus lens L22 turning its convex surface to the object side, a second negative lens L23, and a positive lens L24. When a focal length of the meniscus lens L22 is denoted as f22, and a focal length of the second lens group G2 is denoted as f2, a conditional expression (1)¾f22/f2¾>5.0 is satisfied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a zoom lens and an imaging apparatus, and more particularly to a zoom lens that can be suitably used for a video camera, an electronic still camera, a surveillance camera, and the like, and an imaging apparatus including the zoom lens.

Conventionally, many zoom lenses of the 4-group type and 5-group type have been proposed as zoom lenses used for consumer video cameras, surveillance video cameras, and the like. For example, Patent Documents 1 and 2 disclose zoom lenses having a zoom ratio of about 10 times and an F number of about 1.8. In this type, regardless of single plate type or three plate type, the first lens group consists of three lenses, a negative lens, a positive lens, and a positive lens, and the second lens group consists of three lenses, a negative lens, a negative lens, and a positive lens. The structure consisting of has been commonly used in many zoom lenses.
JP 2006-221208 A JP 2006-113257 A

  By the way, in the zoom lens as described above, in order to reduce the amount of movement of the second lens unit due to zooming and to reduce the size of the optical system, strong negative power is often given to the second lens unit. Because of this, the power of each lens has increased. In that case, there has been a problem that the performance deterioration due to the manufacturing error and the assembly error tends to increase.

  The present invention has been made in view of the above circumstances. Even when the second lens group has a strong power, performance deterioration due to manufacturing errors and assembly errors is small, and good optical performance is maintained. An object of the present invention is to provide a zoom lens that can be used and an image pickup apparatus including the zoom lens.

The zoom lens of the present invention has, in order from the object side, a first lens group having a positive refractive power and fixed at the time of zooming, a negative refractive power, and moving along the optical axis. A second lens group that performs zooming, a stop, a third lens group that has positive refractive power and is fixed at the time of zooming, and has a positive refractive power, and the position of the image plane associated with zooming A fourth lens group that performs correction and focusing, the second lens group in order from the object side, a first negative lens, a meniscus lens having a convex surface facing the object side, a second negative lens, When the focal length of the meniscus lens is f22 and the focal length of the second lens group is f2, the following conditional expression (1) is satisfied.
| F22 / f2 |> 5.0 (1)

  Here, the above-mentioned “meniscus lens having a convex surface facing the object side” means a meniscus lens having a convex surface facing the object side in the paraxial region. Further, f22 in the conditional expression (1) is in the paraxial region.

  In the present invention, each “lens group” includes not only a plurality of lenses but also a lens group.

  In the zoom lens according to the present invention, the first negative lens and the first negative lens are arranged so that the second lens group can have a strong power without increasing the power of the first negative lens and the second negative lens of the second lens group. A configuration is adopted in which the interval between the two negative lenses is widened and a meniscus lens is disposed between the two negative lenses so as to make effective use of the interval. This meniscus lens can advantageously correct distortion and astigmatism. In the zoom lens of the present invention, by satisfying conditional expression (1), the power of the meniscus lens is made weak, and good aberration correction is performed without greatly changing the power arrangement in the second lens group. Is possible.

In the zoom lens of the present invention, it is preferable that the following conditional expressions (2) and (3) are satisfied, where the Abbe number and refractive index at the d-line of the second negative lens are ν23 and N23, respectively.
ν23> 58.0 (2)
N23 <1.55 (3)

  In the zoom lens of the present invention, it is preferable that the meniscus lens has at least one aspheric surface.

  In the zoom lens of the present invention, it is preferable that the meniscus lens is made of a plastic material.

In the zoom lens according to the present invention, it is preferable that the following conditional expression (4) is satisfied, where fw is the focal length of the entire system at the wide-angle end.
1.5 <| f2 / fw | <2.0 (4)

In the zoom lens of the present invention, it is preferable that the following conditional expression (5) is satisfied, where f1 is the focal length of the first lens group.
5.0 <| f1 / f2 | <5.8 (5)

  The values of the conditional expressions are those at the reference wavelength of the zoom lens unless otherwise specified.

  An image pickup apparatus according to the present invention includes the zoom lens according to the present invention described above.

  According to the present invention, the first lens group and the third lens group are fixed groups, and the second lens group is moved along the optical axis to perform zooming, thereby correcting and focusing the image plane position. In the zoom lens of the type in which the fourth lens group is moved, the configuration of the second lens group is suitably set so as to satisfy the conditional expression (1), so that the second lens group can be reduced while downsizing. Even when the lens has a strong power, it is possible to provide a zoom lens that retains good optical performance with little degradation in performance due to manufacturing errors and assembly errors, and an imaging device including the zoom lens.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a configuration example of a zoom lens according to an embodiment of the present invention, and corresponds to a zoom lens of Example 1 described later. 2 to 6 are cross-sectional views showing other configuration examples according to the embodiment of the present invention, and correspond to zoom lenses of Examples 2 to 6 described later, respectively. The basic configurations of the examples shown in FIGS. 1 to 6 are the same, and the illustration method of each figure is also the same, so here, with reference mainly to FIG. 1, the zoom lens according to the embodiment of the present invention will be described. explain.

  The zoom lens according to the embodiment of the present invention includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and an aperture in order from the object side along the optical axis Z. A stop St, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are provided.

  When zooming from the wide-angle end to the telephoto end, the zoom lens fixes the first lens group G1 and the third lens group G3 on the optical axis Z, and the second lens group G2 on the optical axis Z. In addition to performing zooming by moving the lens along the image side, correction and focusing of the image plane position accompanying zooming are performed by moving the fourth lens group G4 along the optical axis Z. ing.

  In FIG. 1, the left side is the object side, the right side is the image side, the upper stage shows the lens arrangement at the wide-angle end, the lower stage shows the lens arrangement at the telephoto end, and each lens group when zooming from the wide-angle end to the telephoto end The general movement trajectory is indicated by arrows. Note that the aperture stop St shown in FIG. 1 does not necessarily indicate the size or shape, but indicates the position on the optical axis Z.

  In FIG. 1, the image plane is shown as Sim. For example, when this zoom lens is applied to an image pickup apparatus equipped with an image pickup device, the zoom lens is arranged so that the image pickup surface of the image pickup device is positioned on the image plane Sim.

  When applying a zoom lens to an imaging device, depending on the configuration of the camera side on which the lens is mounted, a cover glass, prism, infrared cut filter, low-pass filter, etc. are provided between the lens closest to the image side and the imaging surface. Various filters and the like are preferably arranged, and FIG. 1 shows an example in which a parallel plate-shaped optical member PP assuming these is arranged between the lens group closest to the image side and the image plane Sim.

  The zoom lens according to the present embodiment mainly has a characteristic configuration in the second lens group G2. As in the example shown in FIG. 1, the second lens group G2 includes, in order from the object side, a negative lens L21, a meniscus lens L22 having a convex surface facing the object side, a negative lens L23, and a positive lens L24. Configured.

  The meniscus lens L22 may have either a positive power or a negative power in the paraxial region as long as the meniscus shape has a convex surface facing the object side in the paraxial region.

  For example, the second lens group G2 of the zoom lens of the example shown in FIG. 1 includes, in order from the object side, a meniscus negative lens L21, a meniscus lens L22 having aspherical surfaces on both sides, and a biconcave shape. This is a three-group four-lens configuration including a negative lens L23 and a cemented lens of a meniscus positive lens L24.

  As described in the section of the problem, in a zoom lens having four groups as in the present embodiment, in general, in order to reduce the amount of movement of the second lens group accompanying zooming and reduce the size of the optical system, In many cases, strong power is given to the two lens groups. However, if the power of each lens in the second lens group is increased in order to give the second lens group strong power, the tolerance of manufacturing error and assembly error tends to be reduced, and the performance deterioration due to these tends to be large. Prone.

  Therefore, in this zoom lens, the arrangement of the two negative lenses L21 and L23 included in the second lens group G2 is considered. Since the combined power increases as the air space between the two negative lenses L21 and L23 increases, the power of the individual negative lenses in the second lens group can be reduced without changing the power of the second lens group. What is necessary is just to widen these air space | intervals.

  That is, this zoom lens has a configuration in which the interval between the two negative lenses L21 and L23 is widened. As a result, while ensuring the strong power necessary for the second lens group, the power of the two negative lenses L21 and L23 can be reduced, the tolerance of manufacturing errors and assembly errors can be increased, and the performance associated therewith. Deterioration can be suppressed.

  In addition to the above configuration, this zoom lens employs a configuration in which a meniscus lens L22 having low power is disposed in this space in order to effectively use the space between the two negative lenses L21 and L23. By disposing such a weak meniscus lens L22, distortion and astigmatism can be corrected more advantageously without greatly changing the power arrangement in the second lens group G2.

The power of the meniscus lens L22 is defined by configuring the zoom lens so as to satisfy the following conditional expression (1). Here, f22 is the focal length of the meniscus lens L22 in the paraxial region, and f2 is the focal length of the second lens group G2.
| F22 / f2 |> 5.0 (1)

  Conditional expression (1) defines the relationship between the focal lengths of the meniscus lens L22 and the second lens group G2, and so to speak, defines the ratio of the power of the meniscus lens L22 to the power of the second lens group G2. When the meniscus lens L22 is a negative lens, it becomes very difficult to correct distortion and astigmatism with a good balance if the lower limit of conditional expression (1) is reached. When the meniscus lens L22 is a positive lens, the power of the second lens group G2 is weakened if the lower limit of the conditional expression (1) is not reached, so that the amount of movement of the second lens group G2 during zooming increases and the lens system Will become larger.

  Since the meniscus lens L22 is set so that its power becomes weak, it is preferable that the meniscus lens L22 is made of a plastic material. Plastic lenses are more susceptible to temperature changes than glass lenses, but when the power is weak, the effects of temperature changes are small. By forming the lens with a plastic material, it is possible to reduce the cost and weight, which is advantageous.

  The meniscus lens L22 preferably has at least one aspheric surface. By providing an aspheric surface in the second lens group G2, it is possible to satisfactorily suppress aberration fluctuations and distortion. It is not preferable to provide an aspherical surface for a high-power lens, because performance degradation due to manufacturing errors and assembly errors tends to increase. However, if the meniscus lens L22 has low power, performance degradation due to manufacturing errors and assembly errors is small. The meniscus lens L22 is preferably provided with an aspherical surface. The lens provided with the aspherical surface is preferably a lens made of a plastic material from the viewpoint of cost and workability.

  Furthermore, it is preferable to provide an aspheric surface on the meniscus lens L22 from the viewpoint of correcting chromatic aberration. In the second lens group G2, the meniscus lens L22 does not significantly affect chromatic aberration, but other lenses in the second lens group G2 have a large influence on chromatic aberration. If an aspheric surface is provided on another lens of the second lens group G2, it is preferable to use an aspheric plastic lens made of a plastic material as described above. However, plastic has a lower material selectivity than glass. In this case, it is difficult to correct chromatic aberration well. On the other hand, when the meniscus lens L22 is an aspheric plastic lens, it can be said that the meniscus lens L22 does not greatly affect the chromatic aberration, and therefore does not cause a great disadvantage in correcting the chromatic aberration.

  Note that the configuration of the second lens group G2 is not limited to the example shown in FIG. Although it is conceivable that the second lens group G2 is composed of five or more lenses, when importance is attached to downsizing, the second lens group G2 includes the negative lens L21, the meniscus lens L22, and the negative lens L23 described above. And four lenses including the positive lens L24.

  The configuration of the first lens group G1 of the zoom lens may be configured by one negative lens and three positive lenses. In a zoom lens having a high magnification of about 20 times, in order to satisfactorily correct chromatic aberration on the telephoto side, the first lens group G1 is preferably composed of at least four lenses.

  For example, the zoom lens of the example shown in FIG. 1 includes, in order from the object side, a cemented lens of a meniscus negative lens L11 and a meniscus positive lens L12, a meniscus positive lens L13, and a meniscus positive lens L14. It consists of 3 groups and 4 sheets.

  As the configuration of the third lens group G3, for example, as in the example shown in FIG. 1, a meniscus positive lens L31 in a paraxial region with a double-sided aspheric surface, a meniscus positive lens L32, and a meniscus negative lens L33. A two-group three-lens configuration including a cemented lens may be used.

  As the configuration of the fourth lens group G4, as in the example shown in FIG. 1, for example, two groups of two lenses including a biconvex positive lens L41 and a meniscus negative lens L42 in a paraxial region with both aspheric surfaces. It is good also as a structure. Alternatively, as the configuration of the fourth lens group G4, for example, as in the example shown in FIG. 2, a cemented lens of a biconvex positive lens L41 and a meniscus negative lens L42 and a double-sided aspherical surface in the paraxial region. A two-group three-lens configuration including the convex positive lens L43 may be employed.

  The zoom lens according to the embodiment of the present invention is preferably configured to further satisfy the following conditional expression. In addition, as a preferable aspect, any one of the following conditional expressions may be satisfied, or any combination may be satisfied. Below, the conditional expression regarding a preferable aspect and its effect are described.

When the Abbe number and the refractive index of the negative lens L23 of the second lens group G2 at the d-line are ν23 and N23, respectively, it is preferable that the following conditional expressions (2) and (3) are satisfied.
ν23> 58.0 (2)
N23 <1.55 (3)

  Conditional expression (2) defines the Abbe number of the negative lens L23 and is a condition for performing good chromatic aberration correction. If the lower limit of conditional expression (2) is not reached, the chromatic aberration of magnification becomes large, and the variation of chromatic aberration associated with zooming becomes large, which is not preferable.

  Conditional expression (3) prescribes the refractive index of the negative lens L23, and if it exceeds the upper limit of conditional expression (3), it is advantageous when configuring the length of the second lens group G2 in the optical axis direction to be short. However, it becomes difficult to correct the coma aberration well.

When the focal length of the second lens group G2 is f2, and the focal length of the entire system at the wide angle end is fw, it is preferable to satisfy the following conditional expression (4).
1.5 <| f2 / fw | <2.0 (4)

  Conditional expression (4) defines the relationship between the focal length of the second lens group G2 and the focal length of the entire system at the wide-angle end. If the power of the second lens group G2 is increased as the lower limit of conditional expression (4) is reached, the power of each lens becomes too strong, and it becomes difficult to obtain good image surface characteristics. Moreover, the curvature of the lens becomes large, and as described above, the performance deterioration due to aberration fluctuations and manufacturing errors becomes large, which is not preferable. Alternatively, when the power of the second lens group G2 is increased so that the lower limit of conditional expression (4) is not reached, it is necessary to increase the distance between the two negative lenses L21 and L23 in order to prevent the lens curvature from becoming too large. This increases the size of the second lens group G2 and the size of the entire optical system, which is not preferable. If the upper limit of conditional expression (4) is exceeded, the power of the second lens group G2 becomes weak, the amount of movement of the second lens group G2 during zooming increases, and the lens system becomes large.

When the focal length of the first lens group is f1, and the focal length of the second lens group G2 is f2, it is preferable that the following conditional expression (5) is satisfied.
5.0 <| f1 / f2 | <5.8 (5)

  Conditional expression (5) defines the relationship between the focal lengths of the first lens group G1 and the second lens group G2, and is a condition for obtaining compact and good optical performance while being highly variable. . As the lower limit of conditional expression (5) is reached, the focal length of the second lens unit increases, and when the focal length of the first lens unit decreases, the amount of movement of the second lens unit associated with zooming increases and the total lens length increases. It is difficult to reduce the size of the front lens (the lens closest to the object). In addition, the amount of movement of the fourth lens group on the telephoto side increases, and aberration fluctuation during zooming increases. On the other hand, if the upper limit of conditional expression (5) is exceeded, it becomes difficult to satisfactorily correct various aberrations such as distortion.

The zoom lens according to the embodiment of the present invention further includes any or all of the following conditional expressions (1-1), (2-1), (3-1), (4-1), and (5-1). Is more preferable. Conditional expressions (1-1), (2-1), (2-1), (3-1), (4-1), (5-1) are satisfied to satisfy conditional expressions (1), (2), (3). , (4) and (5), the effects obtained by satisfying each can be further enhanced. Regarding conditional expression (2-1), satisfying the upper limit of (2-1) is further advantageous for correcting lateral chromatic aberration.
| F22 / f2 |> 6.0 (1-1)
60.0 <ν23 <83.0 (2-1)
N23 <1.52 (3-1)
1.6 <| f2 / fw | <1.90 (4-1)
5.1 <| f1 / f2 | <5.7 (5-1)

  In addition, when this zoom lens is used in harsh environments such as outdoors, the lens placed closest to the object is resistant to surface deterioration due to wind and rain, temperature changes due to direct sunlight, and oils and detergents. It is preferable to use a material resistant to chemicals, that is, a material having high water resistance, weather resistance, acid resistance, chemical resistance, and the like, and further, a material that is hard and difficult to break. From the above, as the material arranged closest to the object side, specifically, glass is preferably used, or transparent ceramics may be used.

  When the zoom lens is used in a harsh environment, a protective multilayer coating is preferably applied. In addition to the protective coat, an antireflection coating film for reducing ghost light during use may be applied.

  In the example shown in FIG. 1, an example in which the optical member PP is arranged between the lens system and the image plane Sim is shown, but instead of arranging a low-pass filter, various filters that cut a specific wavelength range, or the like, These various filters may be disposed between the lenses, or a coating having the same action as the various filters may be applied to the lens surface of any lens.

  As described above, according to the zoom lens of the present embodiment, the above-described preferable configuration is appropriately adopted according to required specifications and the like, so that the power of the second lens group is increased while reducing the size. Even in this case, it is possible to reduce the performance deterioration due to the manufacturing error and the assembly error, and to maintain the good optical performance.

  Next, numerical examples of the zoom lens according to the present invention will be described. The lens sectional views of the zoom lenses of Examples 1 to 6 are those shown in FIGS.

  Table 1 shows basic lens data of the zoom lens according to Example 1, Table 2 shows data relating to zooming (magnification), and Table 3 shows aspherical data. Similarly, basic lens data, zoom-related data, and aspherical data of the zoom lenses according to Examples 2 to 6 are shown in Tables 4 to 18. In the following, the meaning of the symbols in the table will be described using Example 1 as an example, but the same applies to Examples 2 to 6.

  In the basic lens data of Table 1, Si indicates the i-th (i = 1, 2, 3,...) Surface number that increases sequentially toward the image side with the most object-side component surface being first. Indicates the radius of curvature of the i-th surface, and Di indicates the surface interval on the optical axis Z between the i-th surface and the i + 1-th surface. The sign of the radius of curvature is positive when convex on the object side and negative when convex on the image side, and the numerical value in the bottom column of the surface interval is the surface interval between the last surface in the table and the image surface Sim. Is shown.

  In the basic lens data, Ndj is the d-line (wavelength: 587.6 nm) of the j-th (j = 1, 2, 3,...) Optical element that sequentially increases toward the image side with the most object-side lens as the first lens. ), And νdj represents the Abbe number of the j-th optical element with respect to the d-line. The basic lens data includes the aperture stop St and the optical member PP. The surface number column of the surface corresponding to the aperture stop St includes the word “aperture stop” together with the surface number. Yes.

  In the basic lens data of Table 1, the symbols D7, D14, D20, and D24 are described in the column of the surface interval in which the interval changes at the time of zooming, and (variable) is described after each symbol. Similarly, in the embodiments described later, the corresponding code and the word (variable) are described in the space interval column where the interval changes at the time of zooming.

  The zoom-related data in Table 2 includes the focal length f of the entire system at the wide-angle end and the telephoto end, the F number Fno. , The total field angle 2ω, and the values of the surface spacings D7, D14, D20, and D24 that change with zooming.

In the basic lens data in Table 1, the surface number of the aspheric surface is marked with *, and the paraxial radius of curvature is shown as the radius of curvature of the aspheric surface. The aspherical data in Table 3 shows the sign of a lens that is an aspherical lens, the surface number of the aspherical surface, and the aspherical coefficient for each aspherical surface. The numerical value “E-0n” (n: integer) of the aspheric data in Table 3 means “× 10 ⁻ⁿ ”. The aspheric coefficient is a value of each coefficient KA, RA _m (m = 3, 4, 5,... 10) in the aspheric expression expressed by the following expression (A).

Zd = C · h ² / {1+ (1−KA · C ² · h ² ) ^1/2 } + ΣRA _m · h ^m (A)
However,
Zd: Depth of aspheric surface (length of perpendicular drawn from a point on the aspherical surface of height h to a plane perpendicular to the optical axis where the aspherical vertex contacts)
h: Height (distance from the optical axis to the lens surface)
C: Reciprocal number of paraxial radius of curvature KA, RA _m : aspheric coefficient (m = 3, 4, 5,... 10)

  Here, as an example, “mm” is used as the unit of length in Tables 1 to 3, “degree” is used as the unit of angle, and “mm” is used as the unit of Zd and h in the formula (A). ing. However, since the same optical performance can be obtained even if the optical system is proportionally enlarged or reduced, the unit is not limited to “mm”, and other appropriate units can also be used.

  Table 19 shows values corresponding to the conditional expressions (1) to (5) in Examples 1 to 6. As can be seen from Table 19, all of Examples 1 to 6 satisfy the conditional expressions (1) to (5).

  7A to 7H show respective aberration diagrams of spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration at the wide-angle end and the telephoto end of the zoom lens of Example 1. FIG. Each aberration diagram shows the aberration with the d-line (wavelength 587.6 nm) as the reference wavelength, while the spherical aberration diagram and the magnification chromatic aberration diagram also show the aberrations for the wavelength 460.0 nm and the wavelength 615.0 nm. Fno. Of spherical aberration diagram. Means F number, and ω in other aberration diagrams means half angle of view.

  Similarly, FIG. 8 (A) to FIG. 8 (H), FIG. 9 (A) to FIG. 9 (H), FIG. 10 (A) to FIG. 10 (H), FIG. 11 (A) to FIG. FIGS. 12A to 12H are graphs showing spherical aberration, astigmatism, distortion (distortion aberration), and lateral chromatic aberration at the wide-angle end and the telephoto end of the zoom lenses of Examples 2 to 6, respectively. Show.

  From the above data, the zoom lenses of Examples 1 to 6 have a high magnification of about 20 times, and are designed to be downsized. The total angle of view at the wide angle end is about 63 to 68 degrees, and the F-number is 1. It can be seen that it is as small as 9 and each aberration is corrected well, and both the wide-angle end and the telephoto end have high optical performance in the visible range. These zoom lenses can be suitably used for imaging devices such as surveillance cameras, video cameras, and electronic still cameras.

  FIG. 13 shows a configuration diagram of a video camera 10 configured using the zoom lens 1 according to the embodiment of the present invention as an example of the imaging apparatus of the embodiment of the present invention. In FIG. 13, the positive first lens group G1, the negative second lens group G2, the aperture stop St, the positive third lens group G3, and the positive fourth lens group G4 included in the zoom lens 1 are schematically illustrated. A double-headed arrow is provided on the second lens group G2 and the fourth lens group G4 that move during zooming.

  The video camera 10 includes a zoom lens 1, a filter 2 having functions such as a low-pass filter and an infrared cut filter disposed on the image side of the zoom lens 1, an image pickup device 4 disposed on the image side of the filter 2, and a signal. And a processing circuit 5. The image sensor 4 converts an optical image formed by the zoom lens 1 into an electric signal. For example, the image sensor 4 may be a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like. it can. The image sensor 4 is arranged such that its image plane coincides with the image plane of the zoom lens 1.

  An image picked up by the zoom lens 1 is formed on the image pickup surface of the image pickup device 4, an output signal from the image pickup device 4 relating to the image is subjected to arithmetic processing by the signal processing circuit 5, and the image is displayed on the display device 6. The

  Note that FIG. 13 shows a so-called single-plate type imaging apparatus using one imaging element 4, but the imaging apparatus of the present invention has an R (red) between the zoom lens 1 and the imaging element 4. ), G (green), B (blue), or the like, and a so-called three-plate type using three image sensors corresponding to the respective colors may be inserted.

  Since the zoom lens according to the embodiment of the present invention has the above-described advantages, the imaging apparatus of the present embodiment has high productivity, can be configured in a small size, and can obtain a high-quality image.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, the values of the radius of curvature, the surface spacing, the refractive index, the Abbe number, etc. of each lens component are not limited to the values shown in the above numerical examples, but can take other values.

Sectional drawing which shows the lens structure of the zoom lens concerning Example 1 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 2 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 3 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 4 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 5 of this invention. Sectional drawing which shows the lens structure of the zoom lens concerning Example 6 of this invention. FIGS. 7A to 7H are graphs showing aberrations of the zoom lens according to Example 1 of the present invention. 8A to 8H are aberration diagrams of the zoom lens according to Example 2 of the present invention. 9A to 9H are aberration diagrams of the zoom lens according to Example 3 of the present invention. 10A to 10H are aberration diagrams of the zoom lens according to Example 4 of the present invention. FIGS. 11A to 11H are graphs showing aberrations of the zoom lens according to Example 5 of the present invention. FIGS. 12A to 12H are graphs showing aberrations of the zoom lens according to Example 6 of the present invention. 1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Zoom lens 2 Filter 4 Image pick-up element 5 Signal processing circuit 6 Display apparatus 10 Video camera G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group PP Optical member St Aperture stop Z Optical axis

Claims (7)

In order from the object side, a first lens group having positive refractive power and fixed at the time of zooming, and a second lens having negative refractive power and zooming by moving along the optical axis A third lens group having a positive refracting power and fixed at the time of zooming, a first lens having a positive refracting power, and correcting and focusing the image plane position accompanying the zooming. With 4 lens groups,
The second lens group includes, in order from the object side, a first negative lens, a meniscus lens having a convex surface facing the object side, a second negative lens, and a positive lens.
A zoom lens satisfying the following conditional expression (1) when a focal length of the meniscus lens is f22 and a focal length of the second lens group is f2.
| F22 / f2 |> 5.0 (1) 2. The zoom lens according to claim 1, wherein the following conditional expressions (2) and (3) are satisfied when an Abbe number and a refractive index at the d-line of the second negative lens are ν23 and N23, respectively.
ν23> 58.0 (2)
N23 <1.55 (3)   The zoom lens according to claim 1, wherein the meniscus lens has at least one aspheric surface.   The zoom lens according to claim 1, wherein the meniscus lens is made of a plastic material. 5. The zoom lens according to claim 1, wherein the following conditional expression (4) is satisfied, where fw is the focal length of the entire system at the wide-angle end.
1.5 <| f2 / fw | <2.0 (4) 6. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied when a focal length of the first lens unit is f <b> 1.
5.0 <| f1 / f2 | <5.8 (5)   An imaging apparatus comprising the zoom lens according to claim 1.

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