JP2008158481A - Zoom lens, image pickup apparatus, and personal digital assistant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens offering a resolution corresponding to an image element having 8 to 10 million pixels for an entire zooming range, and achieving a half field angle at a wide-angle end equal to or more than 42 degrees that can be provided at low cost. <P>SOLUTION: The zoom lens, in order from an object side, includes a first lens group I having a negative refracting power, a second lens group II having a positive refracting power and an aperture stop S. When zooming from a wide-angle end to a telephoto end, at least the first lens group and the second lens group move, so that an interval between the first lens group and the second lens group can become small and an interval between the second lens group and an image plane can become large. The second lens group II of the zoom lens has at least three positive lenses and two negative lenses and at least one of the three positive lenses is an aspheric positive lens; and an Abbe's number of the glass type, ν<SB>d</SB>and an anomalous dispersion of the glass type, and Δθ<SB>g,F</SB>satisfy conditions: (1)ν<SB>d</SB>>80.0; and (2)Δθ<SB>g,F</SB>>0.025. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a zoom lens, an imaging device, and a portable information terminal device.

  Imaging devices typified by digital cameras have become widespread, and further improvement in shooting image quality and further downsizing of the device body are required. Zoom lenses used as shooting lenses must also achieve both high performance and downsizing. It has been.

In terms of miniaturization of the zoom lens, it is first necessary to shorten the total lens length (distance from the lens surface closest to the object side to the image plane) during use. It is also important to suppress this.
Furthermore, in terms of performance enhancement, it has recently been required to have a resolving power corresponding to an image sensor with at least 8 to 10 million pixels over the entire zoom range.
There are many users who wish to widen the angle of view of the taking lens, and it is preferable that the half angle of view at the short focal end (wide angle end) of the zoom lens is 38 degrees or more. Not a few. Half angle of view: 38 degrees and 42 degrees respectively correspond to a focal length of 28 mm and 24 mm in terms of a 35 mm silver salt camera (so-called Leica version).

  A zoom lens suitable for downsizing and a zoom lens suitable for downsizing, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a positive A third lens unit having a refractive power, a stop that moves integrally with the second lens unit on the object side of the second lens unit, and the first lens unit for zooming from the wide-angle end to the telephoto end; Various zoom lenses are known in which at least the first lens group and the second lens group move so that the distance between the second lens group is reduced and the distance between the second lens group and the third lens group is increased. In such a type of zoom lens, the second lens group has at least three positive lenses and two negative lenses, and the “positive lens of the second lens group” has a low dispersion glass with an Abbe number of 80 or more. As for what was used, the thing of patent documents 1, 2, and 3 is known.

The zoom lens described in Patent Document 1 uses a low-dispersion glass having an Abbe number of 80 or more for the positive lens in the second lens group, and achieves downsizing due to the effect of an aspheric surface. The zoom lens described in Patent Document 2 uses three positive lenses and two negative lenses in the second lens group, and realizes a half angle of view of 43 degrees or more at the wide angle end. Further, in order to satisfactorily correct lateral chromatic aberration, a low dispersion glass having an Abbe number of 80 or more is used for the negative lens of the first lens group.
The “low dispersion glass having an Abbe number of 80 or more” used in Patent Documents 1 and 2 is called “special low dispersion glass” as a glass type, and is an expensive material that is effective in correcting lateral chromatic aberration. is there. In particular, in order to realize a wide angle of view at the wide angle end, it is necessary to reduce the secondary spectrum of chromatic aberration of magnification that increases with the widening of the angle of view. It is effective in such cases. However, in the zoom lens described in Patent Document 1, the special low dispersion glass is used for the second lens group, but the half angle of view at the wide angle end in a specific embodiment is less than 33 degrees. The use of glass is not fully utilized for widening the angle.

The zoom lens described in Patent Document 2 achieves a wide angle of view of 43 degrees or more, but expensive special low dispersion glass is used in the first lens group having a large lens diameter, and the size of the lens diameter is large. For this reason, the cost of the zoom lens itself becomes considerably high.
In Example 4 in which “low dispersion glass having an Abbe number of 80 or more is used for the positive lens in the second lens group” in Patent Document 3, both axial chromatic aberration and lateral chromatic aberration are corrected well, but the half angle at the wide-angle end. The angle of view is about 39 degrees, and the half angle of view: 42 degrees is not achieved.

JP 2004-102211 JP 2006-113554 A JP2005-24804

  The present invention has been made in view of the above, and can have a resolving power corresponding to an imaging element of 8 million to 10 million pixels over the entire zoom range, and also as a half angle of view at the wide angle end. It is an object of the present invention to realize a novel zoom lens that can realize a wide angle of view of 42 degrees or more and that can be realized at low cost, an imaging device that uses this zoom lens, and a portable information terminal that uses this imaging device.

  The zoom lens according to the present invention includes, in order from the object side, at least a first lens group having a negative refractive power and a second lens group having a positive refractive power, and a second lens group on the object side of the second lens group. So that the distance between the first lens group and the second lens group is reduced and the distance between the second lens group and the image plane is increased when zooming from the wide-angle end to the telephoto end. In addition, it is a “zoom lens in which at least the first lens group and the second lens group move”, and has the following characteristics (claim 1).

That is, the second lens group includes at least three positive lenses and two negative lenses, and at least one of the three positive lenses is an “aspheric positive lens”.
This “at least one aspherical positive lens” has an Abbe number of the glass type: ν _d and anomalous dispersion: Δθ _{g, F,} and the conditions are:
(1) ν _d > 80.0
(2) Δθ _{g, F} > 0.025
Satisfied.

Here, anomalous dispersion: [Delta] [theta] _{g, F} is the refractive index for the g-line glass _{types: n} g refractive index for the F _{line: n} F, the refractive index for the c line: by _{n c,} the following equation:
θ _{g, F} = (n _g −n _F ) / (n _F −n _C )
On the two-dimensional coordinate plane of the orthogonal two axes having the partial dispersion ratio: θ _{g, F} as the vertical axis and the Abbe number: v _d as the horizontal axis defined by the coordinate point (ν _d = 60. 49, θ _{g, F} = 0.5432) and the reference glass type: when the straight line connecting the coordinate point of F2 (ν _d = 36.26, θ _{g, F} = 0.5830) is the standard line, Partial dispersion ratio: defined as “deviation from standard line on two-dimensional coordinate plane” of θ _{g, F.}

Upper anomalous dispersion: Δθ _{g, F} is a “distance in a direction parallel to the vertical axis” between the coordinate point of the glass type on the two-dimensional coordinate plane and the standard line.
Partial dispersion ratio: θ _{g, F} is “physical quantity determined for each glass type”. As described above, the “standard line” represents the partial dispersion ratio of the reference glass type: K7: θ _{g, F} (K7: 0.5432) and the Abbe number: ν _d (K7: 60.49) on the two-dimensional coordinate plane. Are the vertical and horizontal coordinate points, the reference glass type: F2 partial dispersion ratio: θ _{g, F} (F2: 0.5830) and the Abbe number: ν _d (F2: 36.26), respectively. -It is a straight line connecting the coordinate points as the abscissa.

  Reference glass type: K7 is specifically “glass type name made by OHARA INC .: NSL7”, and reference glass type: F2 is specifically “glass type name made by OHARA INC .: PBM2”.

  Since the zoom lens according to claim 1 has “at least first and second lens groups” as the lens group, two groups of “first lens group and second lens group” are the minimum group configuration. Although it is possible to have a configuration, it is possible to have a “third lens group having a positive refractive power” on the image side of the second lens group having a positive refractive power, which does not contradict the miniaturization of the entire zoom lens. As long as there is a “subsequent group below the fourth lens group”.

  As a preferred aspect of the zoom lens according to claim 1, the third lens group having a positive refractive power is provided on the image side of the second lens group having a positive refractive power, and the zoom lens extends from the wide angle end to the telephoto end. At the time of zooming, at least the first lens group and the second lens group move so that the distance between the first lens group and the second lens group is decreased and the distance between the second lens group and the third lens group is increased. (Claim 2).

In the zoom lens according to claim 2, the third lens group can be “configured by one positive lens” (claim 3). In this case, one positive lens of the third lens group is not It is a spherical lens. The Abbe number of the glass type: ν _d and anomalous dispersion: Δθ _{g, F} are the conditions:
(1) ν _d > 80.0
(2) Δθ _{g, F} > 0.025
Is preferably satisfied (claim 4). In claim 3, in order to avoid confusion with the “aspheric positive lens in the second lens group” in claim 1, one positive lens forming the third lens group is referred to as “aspheric lens”.

The zoom lens according to any one of claims 1 to 4, wherein the distance on the optical axis from the stop to the most image side surface of the second lens group: dS-L, the most image side in the second lens group from the stop. The distance on the optical axis to the aspheric surface: dS-A is the condition:
(3) 0.75 <dS-A / dS-L ≦ 1.0
Is preferably satisfied (Claim 5).
The zoom lens according to any one of claims 1 to 5, wherein the focal length of the second lens group is f2, and the focal length of the aspherical lens on the image side in the second lens group is fA.
(4) 0.4 <fA / f2 <1.0
Is preferably satisfied (claim 6). In this case, when there are two or more aspherical positive lenses in the second lens group, the focal length: fA is the largest of them.

  An aspherical lens made of glass that satisfies the conditions (1) and (2) in the zoom lens according to any one of claims 1 to 6 (aspherical positive lens in the second lens group, aspherical lens in the third lens group) ) Is preferably a “hybrid aspherical lens” in which a thin resin layer is provided on at least one optical surface, and the air contact surface of the resin layer has an aspherical shape.

The hybrid aspherical lens in the zoom lens according to claim 7 has the following conditions: the center thickness of the entire hybrid aspherical lens: tA, and the center thickness of the resin layer: tR.
(5) 0.01 <tR / tA <0.1
Preferably, the hybrid aspherical lens in the zoom lens according to claim 6 or 7 has an aspherical paraxial radius of curvature: rA, a resin layer, which is an air contact surface of the resin layer. The radius of curvature of the spherical surface on which r is formed: rB is the condition:
(6) 0.5 <rB / rA <1.4
Is preferably satisfied (claim 9).

  The zoom lens according to any one of claims 1 to 9, wherein the second lens group includes at least one aspheric lens in addition to an aspheric positive lens made of a glass that satisfies the conditions (1) and (2). (Claim 10). In this case, it is preferable that one aspherical positive lens in the second lens group is disposed on the most image side of the second lens group, and one aspherical lens is disposed on the most object side of the second lens group ( Claim 11).

  The “one aspherical positive lens of the second lens group” in the zoom lens according to any one of claims 1 to 11 is disposed closest to the image side of the second lens group and adjacent to the object side. It can be cemented with a negative lens (claim 12).

  The zoom lens according to any one of claims 1 to 12, wherein the half angle of view that can be placed at the wide-angle end is 42 degrees or more and has a resolving power corresponding to an image sensor with 8 to 10 million pixels. (Claim 13).

  An image pickup apparatus according to the present invention is an image pickup apparatus having the zoom lens according to any one of claims 1 to 13 as a “shooting zoom lens” (claim 14), and an object image by the zoom lens is a “color image pickup element”. The image is formed on the light receiving surface of the image forming apparatus (claim 15).

  In the imaging device according to claim 15, by using the zoom lens according to claim 13, the number of pixels of the imaging device can be 8 million to 10 million pixels (claim 16).

  The portable information terminal device of the present invention is “a portable information terminal device including the imaging device according to claim 14, 15, or 16” (claim 17).

  To supplement the explanation, a “zoom lens having two negative and positive lens groups from the object side” such as the zoom lens of the present invention generally has a “second lens group image when zooming from the wide angle end to the telephoto end. The lens moves monotonously from the object side to the object side, and the first lens group moves so as to correct the fluctuation of the image plane position due to zooming. A "positive third lens group" can be added to keep the exit pupil away from the image plane, or for the purpose of rear focusing, but in this case as well, "the second lens group is responsible for most of the zooming function" Yes.

  In order to realize a zoom lens with low aberrations and high resolving power, it is necessary to "suppress aberration fluctuations due to zooming", and the second lens group, which is the main zooming group, is particularly good in the entire zooming range. Aberration correction is necessary, and in particular, in order to realize “a wide angle of view at the short focal end (wide angle end)”, a “secondary spectrum of lateral chromatic aberration that increases with a wide angle of view” is reduced. Therefore, the configuration of the second lens group is important for this purpose.

In general, the correction of chromatic aberrations on the axis and magnification is performed so that “the imaging positions coincide at two wavelengths in the used wavelength region”, and the inner wavelength region sandwiched between the two wavelengths and the “outside of two wavelengths” In the “wavelength region”, chromatic aberration remains, and the imaging positions do not necessarily match. "Secondary spectrum"
Such “residual chromatic aberration”.

  Human eye sensitivity (luminosity) is high at wavelengths in the green region. If the chromatic aberration is large in such a “wavelength region with high visibility”, the image will become blurred and the “visual resolution of the image” Will fall.

  The same applies to imaging with a color imaging device. In a general color imaging device having red, green, and blue mosaic filters, “50% of the total number of pixels” has a green filter to ensure resolution. ing. For this reason, the output from the “pixels in charge of the green region” is dominant in the luminance signal generated by the signal processing. If the chromatic aberration in this wavelength region is large, the resolution of the reproduced image is lowered.

  On the other hand, the majority of color image sensors have relatively high sensitivity on the short wavelength side compared to human eyes and silver halide color films, and “color blur due to chromatic aberration in the blue to purple region” appears in the reproduced image. Easy to stand out. In order to reduce such color blur, it is necessary to reduce the chromatic aberration in the blue to violet region. However, if the chromatic aberration in the blue to violet region is to be reduced without sufficiently correcting the secondary spectrum. As a result, the chromatic aberration in the green region is increased, resulting in the above-mentioned “decrease in the resolution of the reproduced image”.

  As described above, “correction of the secondary spectrum of chromatic aberration” is extremely important in securing the resolution of an image.

  As the configuration of the second lens group, there are conventionally known a configuration in which correction of spherical aberration or the like is performed using an aspheric surface, and a configuration in which correction of chromatic aberration is performed using low dispersion glass. Is characterized by the configuration of the second lens group having aberration correction capability that exceeds those of the conventional examples, and is sufficiently small and has a wide angle of view, while suppressing a rise in cost. Realized.

  That is, in the present invention, the second lens group includes “at least three positive lenses and two negative lenses”, and at least one of the positive lenses is “aspherical lens having positive refractive power ( The above-mentioned “aspherical positive lens”), and the glass type of the aspherical positive lens satisfies the conditions (1) and (2) ”.

  By using an aspherical positive lens made of an optical material (glass type) that satisfies the conditions (1) and (2) for the second lens group, “reducing both monochromatic aberration and chromatic aberration in a balanced manner”. Is possible.

  However, optical materials that satisfy the conditions (1) and (2) are generally “special low dispersion glass” and have a low refractive index, and in order to perform good aberration correction, simply use an aspherical positive lens. However, in the present invention, the second lens group as a whole has three positive lenses and two negative lenses to provide “high aberration correction capability”.

  Such a “configuration of the second lens group” is particularly effective when the half angle of view at the wide-angle end exceeds 40 degrees, and increases as the angle of view increases while sufficiently suppressing the occurrence of monochromatic aberration. It becomes possible to correct the lateral chromatic aberration and chromatic coma aberration very well. As a result, for example, a sufficiently wide angle of view can be achieved without using special low dispersion glass for the first lens group having a large lens diameter, and “cost increase as a whole” can be suppressed. .

Glass types are satisfactory condition of the aspherical positive lens used for the second lens group (1), for (2), the condition (1), the Abbe number of glass types of aspheric positive lens: [nu _d is 80.0 If it is below, the chromatic aberration of magnification cannot be sufficiently corrected. In the condition (2), when the anomalous dispersion: Δθ _{g, F} is 0.025 or less, the secondary spectrum of lateral chromatic aberration remains relatively large, and it is difficult to suppress both color blur and ensure the resolving power. Become.
As in claim 2, a positive third lens group may be added to form a negative, positive, and positive three lens group structure. By adding a positive third lens group, "ensure the exit pupil distance" is easy. “Focusing by moving the third lens group” is also possible.

  When the third lens group is arranged, it is preferable that the third lens group is composed of “a positive lens having a surface with a large curvature facing the object side” and has at least one aspherical surface. According to such a configuration, off-axis aberrations such as astigmatism can be corrected better while minimizing the thickness of the third lens group. Further, when the third lens group is composed of one positive lens, it is preferable from the viewpoint of chromatic aberration correction to use as low a dispersion glass as possible. Although the third lens group may be fixed during zooming, the “degree of freedom for aberration correction” can be increased by moving the third lens group by a small amount.

  As in the case of claim 3, when the third lens group is composed of one positive lens whose glass type satisfies the conditions (1) and (2), the positive lens is on the image plane. The closest feature is that the light beam for each angle of view is separated and passes, and the change in the light beam path due to zooming is small. Therefore, it has a function to correct chromatic aberration different from the aspherical positive lens of the second lens group. Thus, the aberration correction effect can be enhanced over the entire zooming region.

  Condition (3) is a preferable condition for better correcting the off-axis monochromatic aberration, the lateral chromatic aberration, and the chromatic coma aberration, which increase with a wide angle of view. When the aspherical positive lens is “position relatively close to the aperture stop”, that is, at a position where the parameter: dS−A / dS−L is 0.75 or less, the off-axis principal ray passes through the aspherical positive lens. Therefore, it is difficult to satisfactorily correct both “off-axis monochromatic aberrations such as astigmatism and coma” and chromatic aberrations such as lateral chromatic aberration and chromatic coma. It is obvious that “dS−A / dS−L” does not exceed 1.0.

Condition (4) parameter: If fA / f2 is 1.0 or more, the refractive power of the aspherical positive lens is not sufficient to sufficiently reduce the secondary spectrum, and sufficient chromatic aberration correction may not be performed. Conversely, if the ratio is 0.4 or less, it becomes difficult to “balance chromatic aberration correction and spherical aberration correction”.
In order to achieve a better balance between “chromatic aberration correction and spherical aberration correction” while sufficiently reducing the secondary spectrum and performing sufficient chromatic aberration correction, the parameter fA / f2 is slightly narrower than the condition (4). conditions:
(4A) 0.5 <fA / f2 <0.95
Is preferably satisfied.

Is a glass type of and "third lens County positive aspheric lens""aspheric positive lens in the second lens group", "Abbe's number: [nu _d special low dispersion lens exceeding 80.0" is very It is difficult to “manufacture by a molding method in which an aspherical mold shape is transferred to glass in a high temperature state” except for small ones. There is also a method of cutting a glass material directly into an aspherical surface, but it is very poor in mass productivity and expensive.

  Therefore, the aspherical positive lens of the second lens group and the positive aspherical lens of the third lens group that are formed of a glass that satisfies the conditions (1) and (2) are provided on at least one optical surface of the spherical lens. From the viewpoint of cost, it is effective to form a “hybrid aspherical lens” which is a “hybrid aspherical lens” formed by forming a thin resin layer to which an aspherical mold shape is transferred.

Conditions (5) and (6) are preferable conditions to be satisfied by such a hybrid aspheric lens.
Spherical lenses can be easily formed from inorganic materials such as glass, and the change in characteristics with respect to environmental fluctuations such as temperature and humidity is small, but the resin layer used for the aspherical surface is more resistant to environmental fluctuations than glass lenses. Change (expansion / contraction, refractive index change, etc.)

  Parameter (5): When tR / tA is 0.1 or more, “the resin layer is unnecessarily thick”, and the change in the optical characteristics of the entire zoom lens due to environmental fluctuations also increases, and the actual use state It becomes difficult to guarantee performance. On the other hand, if the parameter is 0.01 or less, the resin layer is too thin and it is difficult to form the “aspheric shape necessary for aberration correction”.

  Condition (6) parameter: When rB / rA is 1.4 or more, the resin layer thickness becomes thin at the periphery of the lens, and the “difference in thickness between the center and the periphery” becomes too large, resulting in an aspheric shape. Is difficult to form with high accuracy. On the other hand, if the above parameter is 0.5 or less, the thickness of the resin layer becomes thicker at the periphery of the lens, and the “difference in thickness between the center and the periphery” becomes too large, and the aspheric shape is highly accurate. It becomes difficult to form with.

  In order to make both the correction of spherical aberration and the correction of astigmatism / coma aberration compatible at a high level in the zoom lens of the present invention, as in claim 10, the second lens group includes: It is desirable to have at least one aspheric lens. By adopting such a configuration, one of the aspheric surfaces can “correct mainly spherical aberration”, and the other aspheric surface can correct “mainly astigmatism and coma”, which is a dramatic performance. Improvements can be made. By separating the aberration correction functions of the two aspherical lenses (the aspherical positive lens and the other aspherical lens), it is possible to suppress deterioration in image performance due to the eccentricity of the aspherical lenses.

  Further, as in the eleventh aspect, it is preferable that the aspheric positive lens is disposed “most image side of the second lens group” and the other aspheric lens is disposed “most object side of the second lens group”. . In order for an aspherical positive lens to be effective in “correcting chromatic aberration of magnification due to low dispersion characteristics”, it is reasonable to place it on the most image side of the second lens group. In addition, it can play a role of correcting off-axis aberrations such as astigmatism and coma. The other aspherical lenses are arranged “most close to the aperture stop”, so that the role of mainly correcting the spherical aberration can be most effectively performed.

  According to a twelfth aspect of the present invention, the aspherical positive lens is disposed closest to the image side of the second lens group, and is used in a state of being joined to the negative lens disposed adjacent to the object side. By disposing a high-dispersion negative lens on the object side of the aspherical positive lens, it becomes possible to correct magnification chromatic aberration and chromatic coma better. Further, by joining them together, the influence of manufacturing / assembly errors is suppressed, and more stable performance can be ensured.

Hereinafter, conditions for ensuring “better performance” as a zoom lens will be described.
It is preferable that the first lens group includes a negative meniscus lens having a concave surface facing the image side, a negative lens, and a positive lens in order from the object side. By disposing two negative lenses on the object side of the first lens group, the “off-axis light beam having a large incident angle” can be refracted little by little on a total of four surfaces, and the occurrence of off-axis aberrations can be further reduced. It becomes possible.

  In order to correct the monochromatic aberration better, it is preferable that the first lens group has one or more aspheric surfaces. In particular, one of the image side surfaces of the two negative lenses disposed on the object side is preferably an aspherical surface. By introducing an aspherical surface at this location, it is possible to effectively correct distortion, astigmatism, etc., particularly at the short focal end.

  It may be simplified in terms of mechanism that the aperture diameter of the aperture is “constant regardless of zooming”. However, by increasing the open diameter of the long focal end compared to the short focal end, it is possible to reduce the “F number change accompanying zooming”. When it is necessary to reduce the “light amount reaching the image plane”, the aperture may be made smaller. However, if the light amount is reduced by inserting an ND filter or the like without greatly changing the aperture diameter, the resolving power due to the diffraction phenomenon is reduced. This is preferable because it is possible to prevent a decrease in the thickness.

  As described above, according to the present invention, a novel zoom lens, imaging device, and portable information terminal device can be realized. The zoom lens according to the present invention can correct aberrations satisfactorily as shown in the examples described later, and has a zoom ratio close to 3 times while the half angle of view at the wide angle end is 42 degrees or more and is sufficiently wide. And a resolving power corresponding to an image sensor with 8 to 10 million pixels can be realized.

Embodiments of the invention will be described below.
FIG. 1 is a diagram for explaining one embodiment of a zoom lens. This figure is for Example 1 described later.
The zoom lens in FIG. 1 includes, in order from the object side (left side in the drawing), a first lens group I having negative refractive power, a second lens group II having positive refractive power, and a third lens having positive refractive power. In addition to having the lens group III, the second lens group II has an aperture S that is displaced integrally with the second lens group II on the object side, and when zooming from the wide-angle end to the telephoto end, At least the first lens group I and the second lens group II are arranged so that the distance between the first lens group I and the second lens group II decreases and the distance between the second lens group II and the third lens group III increases. A moving zoom lens. As shown in Example 1 described later, the glass type of the aspherical positive lens included in the second lens group satisfies the conditions (1) and (2).

FIG. 2 is a diagram for explaining another embodiment of the zoom lens. This figure is for Example 2 described later.
The zoom lens in FIG. 2 includes, in order from the object side (left side in the drawing), a first lens group I having a negative refractive power, a second lens group II having a positive refractive power, and a third lens having a positive refractive power. In addition to having the lens group III, the second lens group II has an aperture S that is displaced integrally with the second lens group II on the object side, and when zooming from the wide-angle end to the telephoto end, At least the first lens group I and the second lens group II are arranged so that the distance between the first lens group I and the second lens group II decreases and the distance between the second lens group II and the third lens group III increases. A moving zoom lens. As shown in Example 2 described later, the glass type of the aspherical positive lens included in the second lens group satisfies the conditions (1) and (2).

FIG. 3 is a diagram for explaining another embodiment of the zoom lens. This figure is for Example 3 described later.
The zoom lens in FIG. 3 includes, in order from the object side (left side in the figure), a first lens group I having a negative refractive power, a second lens group II having a positive refractive power, and a third lens having a positive refractive power. In addition to having the lens group III, the second lens group II has an aperture S that is displaced integrally with the second lens group II on the object side, and when zooming from the wide-angle end to the telephoto end, At least the first lens group I and the second lens group II are arranged so that the distance between the first lens group I and the second lens group II decreases and the distance between the second lens group II and the third lens group III increases. A moving zoom lens. As shown in Example 3 described later, the glass type of the aspherical positive lens included in the second lens group satisfies the conditions (1) and (2).

FIG. 4 is a diagram for explaining another embodiment of the zoom lens. This figure is for Example 4 described later.
The zoom lens in FIG. 4 includes, in order from the object side (left side in the figure), a first lens group I having a negative refractive power, a second lens group II having a positive refractive power, and a third lens having a positive refractive power. In addition to having the lens group III, the second lens group II has an aperture S that is displaced integrally with the second lens group II on the object side, and when zooming from the wide-angle end to the telephoto end, At least the first lens group I and the second lens group II are arranged so that the distance between the first lens group I and the second lens group II decreases and the distance between the second lens group II and the third lens group III increases. A moving zoom lens. As shown in Example 4 described later, the glass type of the aspherical positive lens included in the second lens group satisfies the conditions (1) and (2).
That is, in the embodiment shown in FIGS. 1 to 4, the zoom lens has a three-group structure (claim 2).

FIG. 5 is a diagram for explaining another embodiment of the zoom lens. This figure is for Example 5 described later.
The zoom lens in FIG. 5 includes, in order from the object side (left side in the drawing), a first lens group I having a negative refractive power, a second lens group II having a positive refractive power, and a second lens group II. The first lens unit I and the second lens unit II have a stop S that is displaced integrally with the second lens unit II on the object side, and, as indicated by arrows, during zooming from the wide-angle end to the telephoto end. This is a zoom lens in which the first lens group I and the second lens group II move so that the distance decreases and the distance between the second lens group II and the image plane increases. As shown in Example 5 described later, the glass type of the aspherical positive lens included in the second lens group satisfies the conditions (1) and (2).
That is, in the embodiment of FIG. 5, the zoom lens is an example in which the zoom lens according to claim 1 is implemented as a two-group configuration.
1 to 5, the parallel flat plate indicated by the symbol F is a single parallel flat plate for “various filters such as an optical low-pass filter and infrared cut filter, and a cover glass (seal glass) of a light receiving element such as a CCD sensor”. It is shown as

Before giving a specific example of a zoom lens, an embodiment of a portable information terminal device according to claim 17 will be described.
As shown in FIGS. 21 and 22, the portable information terminal device 30 includes a photographic lens 31 and a light receiving element (area sensor) 45 that is an imaging element, and receives a “photographing object image” by the photographic lens 31. An image is formed above and read by the light receiving element 45.

The imaging lens 31 and the light receiving element 45 constitute an “imaging device”. The light receiving element 45 is a “color imaging element”.
As the photographing lens 31, any one of the zoom lenses described in any one of claims 1 to 13, specifically, any one of Examples 1 to 5 described later, for example, is used. The light receiving element 45 has a pixel number of 8 to 10 million pixels, for example, a CCD area sensor having a diagonal length of the light receiving area: 9.1 mm, a pixel pitch of 2 μm, and a pixel number of about 10 million pixels. Can be used (claim 16).

  As shown in FIG. 18, the output from the light receiving element 45 is processed by the signal processing device 42 under the control of the central processing unit 40 and converted into digital information. The image information digitized by the signal processing device 42 is recorded in the semiconductor memory 44 after undergoing predetermined image processing in the image processing device 41 under the control of the central processing unit 40. The “monitored image” can be displayed on the liquid crystal monitor 38, and the “image recorded in the semiconductor memory 44” can also be displayed. The image recorded in the semiconductor memory 44 can be transmitted to the outside using the communication card 43 or the like.

  As shown in FIG. 17A, the taking lens 31 is in the “collapsed state” when the apparatus is carried. When the user operates the power switch 36 to turn on the power, as shown in FIG. It is paid out. At this time, each group of the zoom lens in the lens barrel is, for example, “arrangement of the short focal point”, and the arrangement of each group is changed by operating the zoom lever 34, and zooming to the long focal point is performed. It can be performed. At this time, the viewfinder 33 also zooms in conjunction with the change in the angle of view of the photographic lens 31.

  Focusing is performed by half-pressing the shutter button 35. When the zoom lenses of Examples 1 to 5 are used, focusing can be performed by moving the third lens group or “moving the light receiving element 45”. When the shutter button 35 is further pressed, shooting is performed, and thereafter the above-described image information processing is performed. Reference numeral 32 denotes a flash.

  When the image recorded in the semiconductor memory 44 is displayed on the liquid crystal monitor 38 or transmitted to the outside using the communication card 43 or the like, the operation button 37 is operated. The semiconductor memory 44 and the communication card 43 are inserted into dedicated or general-purpose slots 39A and 39B, respectively.

  When the photographing lens 31 is in the retracted state, the zoom lens groups do not necessarily have to be aligned on the optical axis. For example, the third lens group, the fourth lens group, and the fifth lens group have the optical axis. If the mechanism is retracted from above and “stored in parallel with other lens groups”, the portable information terminal device can be made thinner.

Four specific examples of the zoom lens according to the present invention are given below.
In all examples, the maximum image height is 4.70 mm.
The meanings of symbols in each embodiment are as follows.
f: Focal length of the entire system
F: F number ω: Half angle of view
R: radius of curvature
D: Face spacing
N _d : Refractive index ν _d : Abbe number
K: Aspheric conical constant
A ₄ : Fourth-order aspheric coefficient
A ₆ : 6th-order aspheric coefficient
A ₈ : 8th-order aspheric coefficient
A ₁₀ : 10th-order aspheric coefficient
A ₁₂ : 12th-order aspheric coefficient
A ₁₄ : 14th-order aspheric coefficient
A ₁₆ : 16th-order aspheric coefficient
A ₁₈ : 18th-order aspheric coefficient
The shape of the “aspherical surface” is the reciprocal of the paraxial radius of curvature (paraxial curvature): C, height from the optical axis: H, conic constant: K, aspheric coefficient: A ₄ , A ₆ , A _8. As well-known formula:
X = CH ² / {1 + √ (1- (1 + K) C ² H ² )}
+ A ₄・ H ⁴ + A ₆・ H ⁶ + A ₈・ H ⁸ + A ₁₀・ H ¹⁰ + A ₁₂・ H ¹² + A ₁₄・ H ¹⁴ + A ₁₆・ H ¹⁶ + A ₁₈・ H ¹⁸
It is a shape represented by.

  The optical glass used is “Ohara Co., Ltd.” or “Sumita Co., Ltd.”, and the glass type is the product name of the company.

"Example 1"
f = 5.204-14.996, F = 2.66-4.67, ω = 43.26-17.51
Surface number RDN _d ν _d Δθ _{g, F}
01 24.422 1.60 1.73310 48.89 -0.0093 OHARA L-LAM72
02 * 9.225 4.11
03 -180.153 1.20 1.77250 49.60 -0.0092 OHARA S-LAH66
04 11.584 4.10
05 20.498 3.55 1.80 100 34.97 0.0015 OHARA S-LAM66
06 -34.360 1.00 1.75700 47.82 -0.0076 OHARA S-LAM54
07 232.236 Variable (A)
08 Aperture 1.00
09 * 8.821 1.56 1.77250 49.60 -0.0092 OHARA S-LAH66
10 22.899 0.10
11 7.072 1.45 1.80440 39.59 -0.0045 OHARA S-LAH63
12 11.355 0.70 1.80 100 34.97 0.0015 OHARA S-LAM66
13 3.897 2.25 1.48749 70.24 0.0022 OHARA S-FSL5
14 6.572 0.33
15 11.142 0.60 1.74950 35.28 0.0025 OHARA S-LAM7
16 4.205 2.13 1.49700 81.54 0.0280 OHARA S-FPL51
17 * -100.000 variable (B)
18 12.952 2.50 1.43875 94.94 0.0461 OHARA S-FPL53
19 * -153.191 Variable (C)
20 ∞ 1.24 1.51680 64.20 Various filters
21 ∞.

"Aspherical surface"
Aspheric surfaces are marked with “*”. The same applies to the following embodiments.

"Second side"
K = 0.0,
A ₄ = -1.28414 × 10 ^-4 , A ₆ = -6.57446 × 10 ^-7 , A ₈ = -6.30308 × 10 ^-9 ,
A ₁₀ = -1.72874 × 10 ^-10 , A ₁₂ = -2.57252 × 10 ^-12 , A ₁₄ = 2.13910 × 10 ^-14 ,
A ₁₆ = 7.39915 × 10 ^-16 , A ₁₈ = -1.13603 × 10 ^-17
"Ninth face"
K = 0.0,
A ₄ = -7.05273 × 10 ^-5 , A ₆ = 5.04003 × 10 ^-7 , A ₈ = -6.78678 × 10 ^-8 ,
A ₁₀ = 1.47308 × 10 ^-9
“Seventeenth”
K = 0.0,
A ₄ = 4.43634 × 10 ^-5 , A ₆ = 1.20686 × 10 ^-5 , A ₈ = -4.69301 × 10 ^-6 ,
A ₁₀ = 1.28473 × 10 ^-7
"19th page"
K = 0.0,
A ₄ = 6.54212 × 10 ^-5 , A ₆ = -8.10291 × 10 ^-6 , A ₈ = 1.98320 × 10 ^-7 ,
A ₁₀ = -2.19065 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.20 f = 8.83 f = 15.00
A 21.349 7.868 1.825
B 3.669 7.448 17.837
C 4.009 4.883 2.771.

"Condition Parameter Values"
The parameters of conditions (1) and (2) are described in the above data. The same applies to the following embodiments.
dS-A / dS-L = 1.00
fA / f2 = 0.555
Since the hybrid aspherical lens is not used in Example 1, the conditions (5) and (6) do not apply.

"Example 2"
f = 5.201 to 14.992, F = 2.61 to 4.55, ω = 43.30 to 17.52
Surface number RDN _d ν _d Δθ _{g, F}
01 24.778 1.60 1.73310 48.89 -0.0093 OHARA L-LAM72
02 * 9.258 4.13
03 -135.512 0.90 1.77250 49.60 -0.0092 OHARA S-LAH66
04 11.450 3.68
05 20.052 3.62 1.80 100 34.97 0.0015 OHARA S-LAM66
06 -31.678 0.80 1.75700 47.82 -0.0076 OHARA S-LAM54
07 575.312 Variable (A)
08 Aperture 1.00
09 * 8.059 1.70 1.77250 49.60 -0.0092 OHARA S-LAH66
10 33.197 0.23
11 8.347 1.41 1.74320 49.34 -0.0085 OHARA S-LAM60
12 15.124 0.74 1.80 100 34.97 0.0015 OHARA S-LAM66
13 4.000 1.97 1.48749 70.24 0.0022 OHARA S-FSL5
14 5.836 0.81
15 11.591 0.76 1.69895 30.13 0.0103 OHARA S-TIM35
16 6.099 1.80 1.43875 94.94 0.0461 OHARA S-FPL53
17 -83.437 0.04 1.52000 52.00 Resin layer
18 * -92.525 variable (B)
19 11.393 2.77 1.43875 94.94 0.0461 OHARA S-FPL53
20 * -173.335 Variable (C)
21 ∞ 1.24 1.51680 64.20 Various filters
22 ∞.

"Aspherical surface"
"Second side"
K = 0.0,
A ₄ = -1.35800 × 10 ^-4 , A ₆ = -6.92172 × 10 ^-7 , A ₈ = -6.14443 × 10 ^-9 ,
A ₁₀ = -1.43503 × 10 ^-10
A ₁₂ = -3.48101 × 10 ^-12 , A ₁₄ = 2.10 140 × 10 ^-14 , A ₁₆ = 9.10457 × 10 ^-16 ,
A ₁₈ = -1.22550 × 10 ^-17
"Ninth face"
K = 0.0,
A ₄ = -1.07511 × 10 ^-4 , A ₆ = -2.17978 × 10 ^-7 , A ₈ = -6.37972 × 10 ^-8 ,
A ₁₀ = 9.25387 × 10 ^-10
“18th page”
K = 0.0,
A ₄ = 9.82250 × 10 ^-5 , A ₆ = 2.14093 × 10 ^-5 , A ₈ = -4.33536 × 10 ^-6 ,
A ₁₀ = 2.17218 × 10 ^-7
"20th page"
K = 0.0,
A ₄ = 1.17631 × 10 ^-4 , A ₆ = -9.65391 × 10 ^-6 , A ₈ = 2.41593 × 10 ^-7 ,
A ₁₀ = -2.63773 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.20 f = 8.83 f = 14.99
A 21.522 8.000 1.810
B 3.665 7.592 17.621
C 3.514 4.348 2.830.

"Condition Parameter Values"
dS-A / dS-L = 1.00
fA / f2 = 0.484
tR / tA = 0.0217
rB / rA = 0.902.

"Example 3"
f = 5.204-15.004, F = 2.64-4.66, ω = 43.27-17.52
Surface number RDN _d ν _d Δθ _{g, F}
01 25.388 1.60 1.73310 48.89 -0.0093 OHARA L-LAM72
02 * 9.192 4.03
03 -284.803 0.90 1.77250 49.60 -0.0092 OHARA S-LAH66
04 11.799 4.27
05 20.868 3.43 1.80100 34.97 0.0015 OHARA S-LAM66
06 -34.927 0.80 1.75700 47.82 -0.0076 OHARA S-LAM54
07 206.277 Variable (A)
08 Aperture 1.00
09 * 8.032 1.65 1.79952 42.22 -0.0060 OHARA S-LAH52
10 22.923 0.57
11 7.349 1.69 1.78470 26.29 0.0146 OHARA S-TIH23
12 3.790 1.74 1.48749 70.24 0.0022 OHARA S-FSL5
13 6.487 0.44
14 15.189 0.75 1.74950 35.28 0.0025 OHARA S-LAM7
15 6.168 0.16
16 * 6.977 0.12 1.52000 52.00 Resin layer
17 6.589 1.50 1.43875 94.94 0.0461 OHARA S-FPL53
18 -22.660 Variable (B)
19 12.659 2.72 1.43875 94.94 0.0461 OHARA S-FPL53
20 * -112.732 Variable (C)
21 ∞ 1.24 1.51680 64.20 Various filters
21 ∞.

"Aspherical surface"
"Second side"
K = 0.0,
A ₄ = -1.36863 × 10 ^-4 , A ₆ = -6.47708 × 10 ^-7 , A ₈ = -7.35880 × 10 ^-9 ,
A ₁₀ = -1.35479 × 10 ^-10 , A ₁₂ = -3.38913 × 10 ^-12 , A ₁₄ = 2.21060 × 10 ^-14 ,
A ₁₆ = 9.07422 × 10 ^-16 , A ₁₈ = -1.29112 × 10 ^-17
"Ninth face"
K = 0.0,
A ₄ = -9.88713 × 10 ^-5 , A ₆ = -2.55374 × 10 ^-7 , A ₈ = -7.80472 × 10 ^-8 ,
A ₁₀ = 1.69652 × 10 ^-9
"Sixteenth"
K = 0.0,
A ₄ = -4.0.962 × 10 ^-5 , A ₆ = 5.78224 × 10 ^-6 , A ₈ = 1.51452 × 10 ^-6 ,
A ₁₀ = -1.25 128 × 10 ^-8
"20th page"
K = 0.0,
A ₄ = 3.98967 × 10 ^-5 , A ₆ = -5.16113 × 10 ^-6 , A ₈ = 1.10338 × 10 ^-7 ,
A ₁₀ = -1.01513 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.20 f = 8.84 f = 15.00
A 21.350 7.748 1.828
B 4.087 8.347 19.430
C 4.321 5.093 2.815.

"Condition Parameter Values"
dS-A / dS-L = 0.833
fA / f2 = 0.811
tR / tA = 0.0741
rB / rA = 0.944.

Example 4
f = 5.206-15.006, F = 2.58-4.49, ω = 43.27-17.47
Surface number RDN _d ν _d Δθ _{g, F}
01 24.439 1.60 1.73310 48.89 -0.0093 OHARA L-LAM72
02 * 9.047 4.04
03 -208.323 0.90 1.74400 44.79 -0.0035 OHARA S-LAM2
04 12.228 4.35
05 22.021 2.42 1.80518 25.42 0.0158 OHARA S-TIH6
06 250.000 Variable (A)
07 Aperture 1.00
08 * 7.935 1.64 1.79952 42.22 -0.0060 OHARA S-LAH52
09 25.546 0.28
10 7.796 1.54 1.80610 40.93 -0.0052 OHARA S-LAH53
11 -205.340 0.50 1.85000 32.40 0.0039 SUMITA K-LaSFn21
12 4.000 1.95 1.48749 70.24 0.0022 OHARA S-FSL5
13 5.774 0.39
14 10.938 1.17 1.68893 31.07 0.0092 OHARA S-TIM28
15 6.023 1.80 1.43875 94.94 0.0461 OHARA S-FPL53
16 -56.695 0.08 1.52000 52.00 Resin layer
17 * -59.395 Variable (B)
18 11.698 2.64 1.43875 94.94 0.0461 OHARA S-FPL53
19 * -225.859 Variable (C)
20 ∞ 1.24 1.51680 64.20 Various filters
21 ∞.

"Aspherical surface"
"Second side"
K = 0.0,
A ₄ = -1.30875 × 10 ^-4 , A ₆ = -6.16199 × 10 ^-7 , A ₈ = -9.33434 × 10 ^-9 ,
A ₁₀ = -1.13135 × 10 ^-10 , A ₁₂ = -3.64254 × 10 ^-12 , A ₁₄ = 2.18018 × 10 ^-14 ,
A ₁₆ = 9.66843 × 10 ^-16 , A ₁₈ = -1.47933 × 10 ^-17
"Eighth side"
K = 0.0,
A ₄ = -9.42018 × 10 ^-5 , A ₆ = 1.48563 × 10 ^-7 , A ₈ = -9.08707 × 10 ^-8 ,
A ₁₀ = 2.14 140 × 10 ^-9
“Seventeenth”
K = 0.0,
A ₄ = 1.48391 × 10 ^-4 , A ₆ = 2.15451 × 10 ^-5 , A ₈ = -4.41154 × 10 ^-6 ,
A ₁₀ = 2.28669 × 10 ^-7
"19th page"
K = 0.0,
A ₄ = 1.35253 × 10 ^-4 , A ₆ = -8.89107 × 10 ^-6 , A ₈ = 1.65638 × 10 ^-7 ,
A ₁₀ = -1.21325 × 10 ^-9 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.21 f = 8.84 f = 15.01
A 21.161 7.897 1.822
B 3.661 7.342 17.177
C 3.498 4.405 2.848.

"Condition Parameter Values"
dS-A / dS-L = 1.00
fA / f2 = 0.877
tR / tA = 0.0444
rB / rA = 0.955.

"Example 5"
f = 5.200-12.492, F = 2.84-3.96, ω = 43.22-20.63
Surface number RDN _d ν _d Δθ _{g, F}
01 27.986 1.60 1.73310 48.89 -0.0093 OHARA L-LAM72
02 * 9.245 2.67
03 47.734 0.90 1.77250 49.60 -0.0092 OHARA S-LAH66
04 8.311 3.60
05 16.509 2.79 1.71736 29.52 0.0110 OHARA S-TIH1
06 * 250.000 Variable (A)
07 Aperture 1.00
08 * 7.987 1.54 1.79952 42.22 -0.0060 OHARA S-LAH52
09 35.368 0.16
10 10.446 1.57 1.77250 49.60 -0.0092 OHARA S-LAH66
11 -13.557 0.96 1.83400 37.16 -0.0037 OHARA S-LAH60
12 4.260 3.53 1.49700 81.54 0.0280 OHARA S-FPL51
13 7.834 0.59
14 6.809 0.50 1.73400 51.47 -0.0096 OHARA S-LAL59
15 4.128 3.24 1.43875 94.94 0.0461 OHARA S-FPL53
16 -19.373 0.04 1.52000 52.00 Resin layer
17 * -19.770 Variable (B)
18 ∞ 1.24 1.51680 64.20 Various filters
19 ∞.

"Aspherical surface"
"Second side"
K = 0.0,
A ₄ = -1.23905 × 10 ^-4 , A ₆ = -2.67726 × 10 ^-6 , A ₈ = 1.13346 × 10 ^-8 ,
A ₁₀ = -7.07042 × 10 ^-11 , A ₁₂ = -4.31642 × 10 ^-12 , A ₁₄ = 1.17946 × 10 ^-14 ,
A ₁₆ = 9.29475 × 10 ^-16 , A ₁₈ = -1.19738 × 10 ^-17
"Sixth page"
K = 0.0,
A ₄ = -3.05548 × 10 ^-5 , A ₆ = 1.71370 × 10 ^-7 , A ₈ = -2.16113 × 10 ^-8 ,
A ₁₀ = 9.03382 × 10 ^-11
"Eighth side"
K = 0.0,
A ₄ = -9.07935 × 10 ^-5 , A ₆ = 2.92706 × 10 ^-7 , A ₈ = -1.23507 × 10 ^-7 ,
A ₁₀ = 5.11168 × 10 ^-9
“Seventeenth”
K = 0.0,
A ₄ = 2.07163 × 10 ^-4 , A ₆ = 4.32738 × 10 ^-6 , A ₈ = -1.9072 × 10 ^-6 ,
A ₁₀ = 1.13689 × 10 ^-8 .

"Variable amount"
Short focal end Intermediate focal length Long focal end
f = 5.20 f = 8.06 f = 12.49
A 21.075 9.408 1.879
B 6.431 8.997 12.976.

"Condition Parameter Values"
dS-A / dS-L = 1.00
fA / f2 = 0.656
tR / tA = 0.0122
rB / rA = 1.020.

Aberration diagrams relating to Example 1 are shown in FIGS. 6 is an aberration diagram at the “short focal end (wide angle end)”, FIG. 7 is an “intermediate focal length”, and FIG. 8 is an aberration diagram at the “long focal end (telephoto end)”. The broken line in the spherical aberration diagram represents the sine condition. In the figure of astigmatism, the solid line represents “sagittal” and the broken line represents “meridional”. The same applies to the aberration diagrams of the other examples.
Aberration diagrams relating to Example 2 are shown in FIGS. FIG. 9 is an aberration diagram at a “short focal end (wide angle end)”, FIG. 10 is an “intermediate focal length”, and FIG. 11 is an aberration diagram at a “long focal end (telephoto end)”.
Aberration diagrams relating to Example 3 are shown in FIGS. 11 is an aberration diagram at a “short focal end (wide angle end)”, FIG. 13 is an “intermediate focal length”, and FIG. 14 is an aberration diagram at a “long focal end (telephoto end)”.
Aberration diagrams relating to Example 4 are shown in FIGS. 15 is an aberration diagram at the “short focal end (wide angle end)”, FIG. 16 is an “intermediate focal length”, and FIG. 17 is an aberration diagram at the “long focal end (telephoto end)”.
Aberration diagrams relating to Example 5 are shown in FIGS. 18 is an aberration diagram at the “short focal end (wide angle end)”, FIG. 19 is an “intermediate focal length”, and FIG. 20 is an aberration diagram at the “long focal end (telephoto end)”.
In each embodiment, the aberration is sufficiently corrected, and it is possible to cope with a light receiving element of 8 to 10 million pixels.

FIG. 3 is a diagram illustrating a configuration of a zoom lens according to Embodiment 1 and displacement accompanying zooming. FIG. 6 is a diagram illustrating a configuration of a zoom lens according to Example 2 and displacement accompanying zooming. FIG. 6 is a diagram illustrating a configuration of a zoom lens according to Example 3 and displacements associated with zooming. FIG. 6 is a diagram illustrating a configuration of a zoom lens according to Example 4 and displacement accompanying zooming. FIG. 10 is a diagram illustrating a configuration of a zoom lens according to Example 5 and displacement accompanying zooming. FIG. 6 is an aberration diagram at the short focal end for Example 1. FIG. 6 is an aberration diagram at the intermediate focal length related to Example 1. FIG. 6 is an aberration diagram at the long focal end for Example 1. FIG. 6 is an aberration diagram at the short focal end for Example 2. FIG. 6 is an aberration diagram at an intermediate focal length for Example 2. FIG. 6 is an aberration diagram at the long focal end for Example 2. FIG. 10 is an aberration diagram at the short focal end for Example 3. FIG. 6 is an aberration diagram for Example 3 at the intermediate focal length. FIG. 6 is an aberration diagram at the long focal end for Example 3. FIG. 6 is an aberration diagram at the short focal end for Example 4. FIG. 10 is an aberration diagram at an intermediate focal length according to Example 4. FIG. 6 is an aberration diagram at the long focal end for Example 4. FIG. 9 is an aberration diagram at a short focal end for Example 5. FIG. 6 is an aberration diagram at an intermediate focal length for Example 5. FIG. 10 is an aberration diagram at the long focal end for Example 5. It is a figure for demonstrating one Embodiment of a portable information terminal device. It is a figure for demonstrating the system of the apparatus of FIG.

Explanation of symbols

I First lens group
II Second lens group
III Third lens group
S Aperture

Claims (17)

In order from the object side, there is at least a first lens group having a negative refractive power and a second lens group having a positive refractive power, and a diaphragm that moves integrally with the second lens group on the object side of the second lens group. And at the time of zooming from the wide-angle end to the telephoto end, at least the first lens group so that the distance between the first lens group and the second lens group is reduced and the distance between the second lens group and the image plane is increased. In the zoom lens in which the second lens group moves,
The second lens group has at least three positive lenses and two negative lenses, and at least one of the three positive lenses is an aspherical positive lens.
Refractive index for g line: n _g , Refractive index for F line: n _F , Refractive index for c line: n _c
θ _{g, F} = (n _g −n _F ) / (n _F −n _C )
On the two-dimensional coordinate plane of the orthogonal two axes having the partial dispersion ratio: θ _{g, F} as the vertical axis and the Abbe number: v _d as the horizontal axis defined by the coordinate point (ν _d = 60. 49, θ _{g, F} = 0.5432) and the reference glass type: a straight line connecting the coordinate point of F2 (ν _d = 36.26, θ _{g, F} = 0.5830) as a standard line, and partial dispersion of the glass type When the deviation of the ratio: θ _{g, F} from the standard line on the two-dimensional coordinate plane is the anomalous dispersion of the glass type: Δθ _{g, F} ,
For the glass type of at least one aspherical positive lens in the second lens group, its Abbe number: ν _d and anomalous dispersion: Δθ _{g, F} are:
(1) ν _d > 80.0
(2) Δθ _{g, F} > 0.025
A zoom lens characterized by satisfying The zoom lens according to claim 1.
A third lens group having a positive refractive power on the image side of the second lens group having a positive refractive power;
At the time of zooming from the wide-angle end to the telephoto end, at least the first lens group and the first lens group are arranged so that the distance between the first lens group and the second lens group becomes small and the distance between the second lens group and the third lens group becomes large. A zoom lens characterized in that two lens groups move. The zoom lens according to claim 2.
A zoom lens, wherein the third lens group is composed of one positive lens. The zoom lens according to claim 3.
One positive lens in the third lens group is an aspherical lens, and its condition is that the glass type has an Abbe number: ν _d and anomalous dispersion: Δθ _{g, F.}
(1) ν _d > 80.0
(2) Δθ _{g, F} > 0.025
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 4,
The distance on the optical axis from the stop to the most image side surface of the second lens group: dS-L, and the distance on the optical axis from the stop to the most aspheric surface on the image side in the second lens group: dS-A. ,conditions:
(3) 0.75 <dS-A / dS-L ≦ 1.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 5,
The focal length of the second lens group is f2, and the focal length of the aspherical lens on the image side in the second lens group is fA.
(4) 0.4 <fA / f2 <1.0
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 6,
The aspherical lens made of glass that satisfies the conditions (1) and (2) is a hybrid aspherical lens in which a thin resin layer is provided on at least one optical surface, and the air contact surface of the resin layer has an aspherical shape. A zoom lens characterized by that. The zoom lens according to claim 7.
The center thickness of the entire hybrid aspheric lens: tA, the center thickness of the resin layer: tR, the conditions:
(5) 0.01 <tR / tA <0.1
A zoom lens characterized by satisfying The zoom lens according to claim 6 or 7,
In the hybrid aspheric lens, the paraxial curvature radius of the aspheric surface, which is the air contact surface of the resin layer, is rA, and the curvature radius of the spherical surface on which the resin layer is formed is rB.
(6) 0.5 <rB / rA <1.4
A zoom lens characterized by satisfying The zoom lens according to any one of claims 1 to 9,
A zoom lens characterized in that the second lens group has at least one aspheric lens in addition to an aspheric positive lens made of a glass that satisfies the conditions (1) and (2). The zoom lens according to claim 10.
One aspherical positive lens in the second lens group is disposed closest to the image side of the second lens group, and one aspherical lens is disposed closest to the object side of the second lens group. . The zoom lens according to any one of claims 1 to 11,
A zoom lens, wherein one aspherical positive lens of the second lens group is disposed closest to the image side of the second lens group and is joined to a negative lens disposed adjacent to the object side. The zoom lens according to any one of claims 1 to 12,
A zoom lens having a half field angle at a wide-angle end of 42 degrees or more and having a resolving power corresponding to an image sensor having 8 to 10 million pixels.   An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 13 as a zoom lens for photographing. The imaging device according to claim 14.
An object image formed by a zoom lens is formed on a light receiving surface of a color image sensor. The imaging device according to claim 15, wherein
An image pickup apparatus using the zoom lens according to claim 13, wherein the number of pixels of the image pickup element is 8 million to 10 million pixels or more.   A portable information terminal device comprising the imaging device according to claim 14, 15 or 16.

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