JP2006317800A - Variable power optical system, imaging lens device, and digital equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable power optical system which is compact, has high optical performance, capable of fully correcting various aberrations, and is adaptable even to a high pixel imaging element. <P>SOLUTION: Successively starting from an object side, the variable power optical system 100 comprises a first lens group 101 which comprises one negative single lens L1, a second lens group 102 which comprises a positive single lens L2 and a negative single lens L3 and has positive optical power and a third lens group 103 which comprises one negative single lens L4. The variable power optical system 100 is configured, so that if the radius of curvature of the object side surface of the negative single lens L1 is R1 and the radius of curvature of its image side surface is R2, the relation -2.0<(R1+R2)/(R1-R2)<0.85 is satisfied; and if the refractive index of the negative single lens L3 in the second lens group 102 is N3 and its dispersion is ν3, the conditional expressions 1.65<N3<2.4 and 15<ν3<35 are satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a variable magnification optical system that includes a plurality of lens groups and performs zooming by changing the interval between the lens groups in the optical axis direction, an imaging lens device including the zooming optical system, and the imaging lens device. In particular, the present invention relates to a variable magnification optical system suitable for miniaturization.

  In recent years, mobile phones and personal digital assistants (PDAs) have become widespread, and specifications for incorporating compact digital still camera units and digital video units into these devices have become common. Since these devices are severely limited in size and cost, they have a small image sensor with a small number of pixels and a single-focus optical system consisting of about 1 to 3 plastic lenses compared to a digital still camera that is an independent product. An imaging lens device provided is generally used.

  However, since the magnification of the single focus optical system is about the same as that of visual observation, the object that can be photographed is limited to that near the photographer. In this regard, with the rapid increase in the number of pixels and functionality of image pickup devices, this is a compact device that can be mounted on a mobile phone or the like that can support high-pixel image pickup devices and can shoot subjects away from the photographer. A variable magnification optical system is required.

  Conventionally, a variable magnification optical system corresponding to a high-pixel imaging device having 1 million pixels or more generally uses 5 or more lenses, and it is difficult to achieve a sufficiently compact size due to the influence of the lens thickness and the like. It was. In addition, a variable magnification optical system configured with four or less lenses is currently only capable of handling up to about VGA (300,000 pixels).

  Further, for example, in Patent Document 1, in order from the object side, a first lens group having a negative optical power, a second lens group having a positive optical power, and a third lens having a positive optical power. In a so-called negative positive / positive three component variable magnification optical system comprising a group, the first lens group and the third lens group are constituted by a single lens, and the second lens group is constituted by two positive and negative single lenses. A variable power optical system composed of four lenses is disclosed. However, in this variable magnification optical system, since the refractive index of the negative lens in the second lens group is low and the dispersion is low, it is difficult to correct curvature of field aberration and the like, and sufficient performance cannot be achieved. There is.

  Similarly, in Patent Document 2, in a variable-magnification optical system with negative positive and positive three components, the first lens group and the third lens group are constituted by a single lens, and the second lens group is constituted by two single lenses. A variable power optical system composed of four lenses is disclosed. In this variable power optical system, the positive lens in the second lens group is made of a glass material having a high refractive index and a high dispersion. However, the second lens group is composed of two positive lenses, which is insufficient in terms of correcting chromatic aberration and the like.

Further, Patent Document 3 discloses a variable magnification optical system having a similar four-lens configuration and a negative positive / positive three component. However, in this variable magnification optical system, the setting of the curvature radii of the front and rear surfaces of the negative single lens constituting the first lens group is not appropriate, and it becomes difficult to correct curvature of field aberration and the like. There is a problem that performance cannot be achieved.
JP 2003-177315 A JP 2002-82284 A (Example 6) Japanese Patent Laying-Open No. 2005-77771

  The present invention has been made in view of the above problems, and provides a compact variable power optical system that can be mounted on a digital device such as a cellular phone by optimizing the number of lenses constituting the variable power optical system. It is an object of the present invention to provide a variable magnification optical system, an imaging lens device, and a digital device that have high optical performance capable of sufficiently correcting various aberrations, and that can be applied to a high-pixel imaging device having 1 million pixels or more. And

The present invention provides a variable magnification optical system having the following configuration in order to solve the above technical problem. Note that the terms used in the following description are defined in the present specification as follows.
(A) A refractive index is a refractive index with respect to the wavelength (587.56 nm) of d line | wire.
(B) Abbe number is determined when the refractive index for d line, F line (486.13 nm) and C line (656.28 nm) is nd, nF, nC and Abbe number is νd, respectively.
νd = (nd−1) / (nF−nC)
The Abbe number νd obtained by the definition formula
(C) The notation regarding the surface shape is a notation based on the paraxial curvature.
(D) When the notation “concave”, “convex” or “meniscus” is used for the lens, these represent the lens shape near the optical axis (near the center of the lens) (based on the paraxial curvature) Notation).

The zoom optical system according to claim 1 of the present invention includes, in order from the object side, a first lens group having a negative optical power, a second lens group having a positive optical power, and a positive optical power. A variable-power optical system that performs zooming by moving two or more of these lens groups,
The first lens group and the third lens group are each composed of a single lens, and the second lens group is composed of two lenses of a positive single lens and a negative single lens in order from the object side,
The single lens constituting the first lens group has a concave surface on the object side and satisfies the following conditional expression (1), and the second lens group satisfies the following conditional expressions (2) and (3). It is characterized by that.
-2.0 <(R1 + R2) / (R1-R2) <0.85 (1)
However, R1: radius of curvature of object side surface of single lens constituting first lens group (image side is positive)
R2: radius of curvature of image side surface of single lens constituting first lens group (image side is positive)
1.65 <N3 <2.4 (2)
15 <ν3 <35 (3)
N3: refractive index of the negative lens in the second lens group
ν3: Dispersion of the negative lens in the second lens group

  According to this configuration, the first lens group located closest to the object side is a so-called negative lead optical system having negative optical power. For this reason, light rays incident at a large angle from the object side can be quickly relaxed by the negative optical power of the first lens group, which is advantageous in terms of reducing the overall optical length and the size of the front lens diameter. Become. In addition, since the variable magnification optical system of negative / positive / positive three components is composed of four lenses, it is possible to suppress the increase in thickness due to the large number of lenses. Further, since the second lens group is composed of two positive and negative single lenses, it is advantageous in correcting chromatic aberration and spherical aberration. Accordingly, it is possible to achieve compactness of the entire optical system while ensuring good optical performance.

  In addition to this, the radius of curvature of the single lens constituting the first lens group and the refractive index and dispersion (Abbe number) of the negative lens in the second lens group are as in the above conditional expressions (1) to (3). Therefore, it has good optical performance. That is, when the curvature radius of the negative single lens having a concave surface on the object side constituting the first lens group is less than the lower limit of the conditional expression (1), the concave surface on the object side surface of the single lens becomes too tight. The tendency to make it difficult to correct the curvature of field aberration occurring in the image becomes remarkable. When the upper limit of conditional expression (1) is exceeded, the concave surface of the image side surface of the single lens becomes too tight, and the tendency that it becomes difficult to correct curvature of field aberration occurring on this surface becomes significant.

  On the other hand, when the refractive index of the negative lens in the second lens group falls below the lower limit of conditional expression (2), the Petzval sum of the second lens group becomes negative and the tendency of the field curvature to become too large becomes significant. . Moreover, when the upper limit of conditional expression (2) is exceeded, it becomes necessary to use a special glass material, and the difficulty in mass productivity increases.

  Further, regarding the dispersion of the negative lens in the second lens group, if it falls below the lower limit of the conditional expression (3), it is necessary to use a special glass material, which increases the difficulty in mass productivity. When the upper limit of conditional expression (3) is exceeded, it is necessary to increase the power of the negative lens of the second lens group in order to correct chromatic aberration, and as a result, the tendency that field curvature correction becomes difficult becomes remarkable.

The zoom optical system according to claim 2 of the present invention includes, in order from the object side, a first lens group having a negative optical power, a second lens group having a positive optical power, and a positive optical power. A variable power optical system that performs zooming by moving two or more of these lens groups, wherein the first lens group and the third lens group include: The second lens group is composed of two lenses, a positive single lens and a negative single lens, in order from the object side. Each of the second lens groups includes the following conditions (4) and (5): It is characterized by satisfying the formula.
1.78 <N3 <2.4 (4)
15 <ν3 <27 (5)

  According to this configuration, since it is also a negative lead optical system, it is advantageous in terms of downsizing the overall optical length and the size of the front lens diameter. Since it is composed of a single lens, it is possible to suppress the increase in thickness due to the large number of lenses. Furthermore, since the second lens group is composed of two positive and negative single lenses, it is advantageous in terms of correcting chromatic aberration and spherical aberration, ensuring good optical performance, and compacting the entire optical system. Can be achieved.

  In addition, since the refractive index and dispersion (Abbe number) of the negative lens in the second lens group are set according to the conditional expressions (4) and (5) above, field curvature correction and chromatic aberration correction This makes it possible to construct a variable magnification optical system that is advantageous not only in this respect but also in terms of error sensitivity. That is, if the refractive index of the negative lens in the second lens group is below the lower limit of conditional expression (4), the negative lens in the second lens group must be given a relatively tight surface shape to correct chromatic aberration. The required power cannot be provided, and as a result, the tendency for the error sensitivity to increase becomes apparent. If the upper limit of conditional expression (4) is exceeded, it becomes difficult to make the surface aspheric by a glass mold using a glass material, so it is difficult to make the total lens length compact using an aspheric surface. The tendency to become remarkable.

  Further, regarding the dispersion of the negative lens in the second lens group, if the lower limit of the conditional expression (5) is not reached, it is necessary to use a special glass material, which increases the difficulty in mass productivity. If the upper limit of conditional expression (5) is exceeded, it is necessary to increase the power of the negative lens of the second lens group for chromatic aberration correction, resulting in high error sensitivity and difficulty in maintaining performance during mass production. The tendency to become remarkable.

According to a third aspect of the present invention, the variable magnification optical system according to the second aspect is characterized in that the single lens constituting the first lens group has a concave surface on the object side and satisfies the following conditional expression (6).
-2.0 <(R1 + R2) / (R1-R2) <0.85 (6)

  Regarding the radius of curvature of a negative single lens having a concave surface on the object side constituting the first lens group, if the lower limit of conditional expression (6) is not reached, the concave surface of the object side surface of the single lens becomes too tight and occurs on this surface. The tendency that it becomes difficult to correct the curvature of field aberration becomes remarkable. When the upper limit of conditional expression (6) is exceeded, the concave surface of the image side surface of the single lens becomes too tight, and the tendency that correction of field curvature aberration generated on this surface becomes difficult becomes remarkable.

A variable power optical system according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the following conditional expression (7) is satisfied.
0.8 <f3 / (fw · ft) ^1/2 <1.45 (7)
Where f3: focal length of the third lens group
fw: Total focal length at the wide end
ft: Total focal length at the telephoto end

  According to this configuration, the optical characteristics of the variable magnification optical system can be further optimized. If the lower limit of conditional expression (7) is not reached, the positive power of the third lens group becomes too strong, and the tendency that it becomes difficult to correct curvature of field and distortion occurring in the third lens group becomes significant. If the upper limit of conditional expression (7) is exceeded, the power of the third lens group becomes too small, and the incident angle of the light beam to the periphery of the imaging element when the imaging element is arranged on the image plane of the variable magnification optical system. And the problem of lowering the amount of peripheral light due to the increase in the vignetting of the light beam by the image sensor of the ambient light becomes obvious.

  An imaging lens apparatus according to a fifth aspect of the present invention uses the variable magnification optical system according to any one of the first to fourth aspects, and the variable magnification optical system displays an optical image of a subject on a predetermined imaging surface. It is characterized in that it can be formed. According to this configuration, it is possible to realize an imaging lens device that is compact and can be mounted on a mobile phone, a portable information terminal, and the like, has excellent optical performance, and can be changed in magnification.

  According to a sixth aspect of the present invention, there is provided a digital device according to the fifth aspect, the imaging lens device according to the fifth aspect, an imaging device that converts an optical image into an electrical signal, and still image shooting of a subject in the imaging lens device and the imaging device. And a control unit that performs shooting of at least one of moving image shooting, and the variable magnification optical system of the imaging lens device is assembled so that an optical image of a subject can be formed on the light receiving surface of the imaging device. It is characterized by. According to these configurations, it is possible to realize a digital device equipped with an imaging lens device capable of zooming while maintaining high definition.

  According to the first aspect of the present invention, the variable-power optical system is made compact by using four lenses, and the first lens group is configured as in the conditional expressions (1) to (3). By setting the radius of curvature of the negative lens and the refractive index and dispersion (Abbe number) of the negative lens included in the second lens group, it is possible to construct a variable magnification optical system in which aberrations are well corrected over the entire variable magnification range. It becomes like this. Therefore, there is an effect that it is possible to provide a variable magnification optical system that is small and has excellent optical performance compatible with a high-pixel imaging device.

  According to the second aspect of the present invention, the zoom lens system is made compact by using four lenses, and is included in the second lens group as in the conditional expressions (4) and (5). By setting the refractive index and dispersion (Abbe number) of the negative lens, it is possible to construct a variable magnification optical system in which aberrations are favorably corrected over the entire variable magnification region. Therefore, there is an effect that it is possible to provide a variable magnification optical system that is small and has excellent optical performance compatible with a high-pixel imaging device.

  According to the third aspect of the present invention, the curvature radius of the negative lens constituting the first lens group in the second aspect of the invention is further satisfied by the conditional expression (6). It becomes possible to provide a variable magnification optical system capable of performing correction satisfactorily.

  According to the fourth aspect of the present invention, it is possible to provide a variable magnification optical system in which field curvature and distortion are corrected more satisfactorily and the problem that the peripheral light amount of the image pickup device is reduced does not become obvious. It becomes like this.

  According to the fifth aspect of the present invention, it is possible to realize a compact imaging lens device that can be changed in magnification and can be mounted on a mobile phone, a portable information terminal, and the like, and has excellent optical performance.

  According to the invention described in claim 6, it is possible to realize a digital device such as a mobile phone or a portable information terminal capable of zooming in still image shooting or moving image shooting of a subject while maintaining high definition.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Description of configuration of variable magnification optical system>
FIG. 1 is an optical path diagram (optical path diagram at the wide angle end) showing a configuration example of a variable magnification optical system 100 according to the present invention. The variable magnification optical system 100 forms an optical image of the subject H on the light receiving surface of the image sensor 105 that converts an optical image into an electrical signal, and has negative optical power in order from the object side. A first lens group 101 having a positive optical power, a third lens group 103 having a positive optical power, and a third lens group 103 having a positive optical power are arranged, and the first lens at the time of zooming from the wide-angle end to the telephoto end This is a variable magnification optical system in which the distance between the group 101 and the second lens group 102 is narrow.

  Here, the first lens group 101 and the third lens group 103 are respectively composed of a negative single lens and a positive single lens, and the second lens group 102 is a positive single lens and a negative single lens in order from the object side. This example is composed of two lenses, and is composed of four lenses as a whole. Specifically, the first lens group 101 is composed of only a first lens L1 made of a biconcave negative lens, and the second lens group 102 is convex to the object side with a second lens L2 made of a biconvex positive lens. In this example, the third lens L3 is composed of a negative meniscus lens, and the third lens group 103 is composed of only a fourth lens L4 composed of a positive meniscus lens convex on the image side. An optical diaphragm 104 is disposed on the object side of the second lens group 102. On the image side of such a variable magnification optical system 100, an image sensor 105 is disposed via a low-pass filter 106, whereby an optical image of a subject is appropriately changed along the optical axis AX by the variable magnification optical system 100. The zoom lens is guided to the light receiving surface of the image sensor 105 at a zoom ratio, and an optical image of the subject is captured by the image sensor 105.

In the present invention, in the variable magnification optical system 100 configured as described above, with respect to the first lens L1 (a negative single lens having a concave surface on the object side constituting the first lens group 101), its radius of curvature is When the range of the conditional expressions (1) and (6), that is, the radius of curvature of the object side surface of the first lens L1 is R1, and the radius of curvature of the image side surface is R2,
-2.0 <(R1 + R2) / (R1-R2) <0.85
Is set to satisfy the relationship. In order to improve the correction of the field curvature aberration, it is desirable to satisfy the following conditional expression (8).
-1.6 <(R1 + R2) / (R1-R2) <0.45 (8)

Further, from the viewpoint of an actual preferable optical path design, it is desirable that the radius of curvature of the first lens L1 satisfies the following conditional expression (9).
-1.0 <(R1 + R2) / (R1-R2) <0.3 (9)
If the lower limit of conditional expression (9) is not reached, the principal point position of the first lens L1 moves to the object side, and the first lens L1 is disposed on the image side with respect to the image side principal point position of the first lens L1. Therefore, the tendency that it becomes difficult to ensure a sufficient air space between the first lens group 101 and the second lens group 102 at the wide end becomes remarkable. If the upper limit of conditional expression (9) is exceeded, the principal point position of the first lens L1 moves too far to the image plane side, so the first surface (object side of the first lens L1) with respect to the object side principal point position. ) Moves toward the object side, and the tendency for the total optical length to increase becomes remarkable.

  Next, regarding the second lens group 102 of the variable magnification optical system 100, as shown in FIG. 1, in order from the object side, there are a second lens L2 made of a positive single lens and a third lens L3 made of a negative single lens. It is set as the structure arrange | positioned in order. Accordingly, the light beam expanded by the first lens group 101 having negative optical power can be converged by the second lens L2, and the height of the light beam in the second lens group 102 can be suppressed low. become. Accordingly, it is possible to reduce aberration and error sensitivity. Further, by making the second lens group 102 have two positive and negative lenses, chromatic aberration correction can be performed in the second lens group 102.

Regarding the refractive index of the third lens L3 (negative lens in the second lens group 102), the range of the conditional expressions (2) and (3), that is, the refractive index of the third lens L3 is N3, and dispersion (Abbe). When the number is ν3,
1.65 <N3 <2.4
15 <ν3 <35
Is set to satisfy the relationship. This makes it possible to provide a variable magnification optical system 100 that can correct field curvature aberration and chromatic aberration satisfactorily and that is excellent in mass productivity. Further, in order to obtain a variable magnification optical system 100 that is also advantageous in error sensitivity, the range of the conditional expressions (4) and (5), that is,
1.78 <N3 <2.4
15 <ν3 <27
It is desirable to set the refractive index and the like of the third lens L3 so as to satisfy this relationship.

Further, regarding the optical path setting of the variable magnification optical system 100, the range of the conditional expression (7), that is, the focal length of the third lens group 103 is f3, the total focal length at the wide end is fw, and the total focal point at the tele end. When the distance is ft,
0.8 <f3 / (fw · ft) ^1/2 <1.45
It is desirable to satisfy this relationship. As a result, the optical power of the third lens group 103 can be optimized, the field curvature and distortion can be corrected more satisfactorily, and the decrease in the peripheral light amount of the image sensor 105 can be prevented from becoming apparent. .

Further, from the viewpoint of optimizing the optical power of the first lens group 101, it is desirable to configure so as to satisfy the following conditional expression (10).
−1.5 <f1 / (fw · ft) ^1/2 <−0.9 (10)
However, f1: focal length of the first lens group 101 If the lower limit of the conditional expression (10) is not reached, the power of the first lens group 101 becomes too weak, and the amount of movement of the first lens group 101 during zooming is large. Therefore, as a result, the tendency that the overall length of the variable magnification optical system 100 becomes large becomes remarkable. If the upper limit of the conditional expression (10) is exceeded, the power of the first lens group 101 becomes too strong, and it tends to be difficult to correct curvature of field aberration and lateral chromatic aberration generated in the first lens group 101. become.

Similarly, from the viewpoint of optimizing the optical power of the second lens group 102, it is desirable to configure so as to satisfy the following conditional expression (11).
0.4 <f2 / (fw · ft) ^1/2 <0.8 (11)
However, f2: focal length of the second lens group 102 If the lower limit of the conditional expression (11) is not reached, the power of the second lens group 102 becomes too strong, and spherical aberration and field curvature generated in the second lens group 102 The tendency for the correction of aberrations to become difficult becomes remarkable. If the upper limit of conditional expression (11) is exceeded, the power of the second lens group 102 becomes too weak, and the amount of movement of the second lens group 102 at the time of zooming becomes large. The tendency that the total length of 100 becomes large becomes remarkable.

Further, it is desirable that the third lens L3 included in the second lens group 102 is configured to satisfy the following conditional expression (12).
−0.7 <fL3 / (fw · ft) ^1/2 <−0.3 (12)
However, fL3: focal length of the third lens L3 If the lower limit of the conditional expression (12) is not reached, the negative power of the third lens L3 becomes too weak, and it is difficult to correct axial chromatic aberration in the second lens group 102. The tendency to become remarkable. If the upper limit of the conditional expression (12) is exceeded, the negative power of the third lens L3 becomes too strong, and it tends to be difficult to correct spherical aberration and field curvature aberration generated in the third lens L3. Become prominent.

In addition, it is desirable that the second lens group 102 be configured to satisfy the following conditional expression (13) with respect to the movement amount at the time of zooming.
0.35 <i2 / (fw · ft) ^1/2 <0.55 (13)
However, i2: Amount of movement of the second lens group 102 from wide to telephoto If the lower limit of the conditional expression (13) is not reached, the amount of movement of the second lens group 102 becomes small. However, it is necessary to increase the power of the first lens group 101 and the second lens group 102, which makes it difficult to correct field curvature and spherical aberration generated in the first and second lens groups 101 and 102. Becomes prominent. When the upper limit of the conditional expression (13) is exceeded, the movement amount of the second lens group 102 becomes too large, and as a result, the total length of the variable magnification optical system 100 tends to become large.

Further, regarding the dispersion (Abbe number) of the first lens L1, it is desirable to configure so as to satisfy the following conditional expression (14).
52 <ν1 (14)
However, ν1: dispersion of the first lens L1 If the value falls below the lower limit of the conditional expression (14), the tendency that the chromatic aberration generated in the first lens L1 becomes excessive becomes remarkable.

More preferably, regarding the dispersion of the first lens L1, it is desirable to configure so as to satisfy the following conditional expression (15).
65 <ν1 <90 (15)
If the lower limit of the conditional expression (15) is not reached, the chromatic aberration generated in the first lens L1 is large, so that the compatibility with the image sensor 105 having a high pixel tends to be inferior. Moreover, when the upper limit of the conditional expression (15) is exceeded, it is necessary to use a special glass material, and mass productivity tends to decrease.

  It is desirable to provide an aspherical surface on at least one surface of the first lens L1 constituting the first lens group 101. Thereby, even when the first lens group 101 is composed of one single lens, it is possible to satisfactorily correct field curvature and distortion.

  In addition, it is desirable to provide aspheric surfaces on a plurality of surfaces of the lenses (second lens L2 and third lens L3) included in the second lens group 102. Thereby, spherical aberration and curvature of field can be corrected satisfactorily, and the configuration of the second lens group 102 is the minimum number of lenses necessary for correcting chromatic aberration, ie, a positive single lens and a negative single lens. This can be achieved with a single lens and contributes to the compactness of the variable magnification optical system 100. In particular, if all surfaces of the second lens L2 and the third lens L3 are aspherical surfaces, it becomes possible to control not only curvature of field and spherical aberration correction but also error sensitivity of the lenses in the second lens group 102. This is particularly preferable because it eliminates the trouble of adjusting the lens position.

  Similarly, it is desirable to provide an aspherical surface on at least one surface of the fourth lens L4 constituting the third lens group 103. Thereby, even when the third lens group 103 is constituted by one single lens, it is possible to satisfactorily correct field curvature and distortion.

  As shown in the variable magnification optical system 100 of FIG. 1, it is desirable to dispose an optical aperture 104 (or a mechanical shutter described later) on the object side of the second lens group 102. Thereby, the lens diameter of the first lens group 101 can be reduced, and the exit pupil position can be further distant. Therefore, the incident angle of the light beam around the image sensor 105 can be reduced, and a decrease in peripheral light amount due to light vignetting at the image sensor 105 can be reduced.

  Next, regarding the manufacturing method of the variable magnification optical system 100, there is no restriction | limiting in particular about the material of each lens which comprises the said 1st-3rd lens groups 101-103, The optical material which can satisfy | fill the requirements of the said refractive index and Abbe number Any glass material or resin (plastic) material can be used. However, if a resin material is used, it is lightweight and can be mass-produced by an injection mold or the like. Therefore, compared with the case of manufacturing with a glass material, cost reduction and weight reduction of the variable magnification optical system 100 are achieved. Is advantageous.

  In the variable magnification optical system 100, when an aspheric glass lens is used, the aspheric glass lens may be molded by a mold, or may of course be a composite type of a glass material and a resin material. The mold type is suitable for mass production, but the glass material is limited. On the other hand, the composite type has the advantage that there are many glass materials that can be used as a substrate and the degree of freedom in design is high. Since an aspherical lens using a high refractive material is generally difficult to mold, in the case of a single-sided aspherical surface, the advantages of the composite type can be maximized.

  In the variable magnification optical system 100, a mechanical shutter having a function of shielding light from the image sensor 105 may be disposed instead of the optical aperture 104. Such a mechanical shutter is effective in preventing smear when, for example, a CCD (Charge Coupled Device) type is used as the image sensor 105.

  A conventionally known cam mechanism or stepping motor can be used as a drive source for driving each lens group, diaphragm, shutter, etc. provided in the variable magnification optical system 100. In addition, when the amount of movement is small or the weight of the drive group is light, it is possible to drive each group independently while suppressing the increase in volume and power consumption of the drive unit by using an ultra-small piezoelectric actuator. Thus, the imaging lens device including the variable magnification optical system 100 can be further downsized.

  The image sensor 105 photoelectrically converts the image signals of the R, G, and B components according to the light amount of the light image of the subject H formed by the variable magnification optical system 100 and outputs the image signal to a predetermined image processing circuit. Is. For example, as the image sensor 105, color filters of R (red), G (green), and B (blue) are pasted in a checkered pattern on the surface of each CCD of an area sensor in which the CCD is two-dimensionally arranged. In addition, it is possible to use a so-called Bayer type single-chip color area sensor. In addition to such a CCD image sensor, a CMOS image sensor, a VMIS image sensor, or the like can also be used.

  The low-pass filter 106 is a parallel plate-shaped optical component that is disposed on the imaging surface of the imaging element 105 and removes noise components. As this low-pass filter 106, for example, a birefringence low-pass filter made of quartz or the like whose predetermined crystal axis direction is adjusted, a phase-type low-pass filter that realizes a required optical cutoff frequency characteristic by a diffraction effect, etc. Is applicable. Note that the low-pass filter 106 is not necessarily provided, and an infrared cut filter may be used in order to reduce noise included in the image signal of the image sensor 105 instead of the optical low-pass filter 106 described above. Good. Further, an infrared reflection coating may be applied to the surface of the optical low-pass filter 106 to realize both filter functions by one.

<Description of digital equipment incorporating variable magnification optical system>
Next, a digital apparatus incorporating the variable magnification optical system 100 as described above will be described. FIG. 2 is an external configuration diagram of a camera-equipped mobile phone 200 showing an embodiment of a digital device according to the present invention. In the present invention, the digital device includes a digital still camera, a video camera, a digital video unit, a personal digital assistant (PDA), a personal computer, a mobile computer, or peripheral devices (mouse, scanner, printer). Etc.). Digital still cameras and digital video cameras optically capture an image of a subject, then convert the image into an electrical signal using a semiconductor element (imaging device), and store it as a digital data in a storage medium such as a flash memory. It is an imaging lens device. Furthermore, in the present invention, a mobile phone, a personal digital assistant, a personal computer, a mobile computer, or a peripheral device having a specification that incorporates a compact imaging lens device that optically captures a still or moving image of a subject. Contains.

  2A shows the operation surface of the mobile phone 200, and FIG. 2B shows the back surface of the operation surface, that is, the back surface. The mobile phone 200 has an antenna 201 on the top, a rectangular display 202 on the operation surface, an image switching button 203 for starting an image shooting mode and switching between still image and moving image shooting, and a variable for controlling zooming. A double button 204, a shutter button 205, and a dial button 206 are provided. The enlargement / reduction button 204 is printed with “T” representing telephoto at the upper end and “W” representing wide angle at the lower end, and each enlargement operation is instructed by pressing the print position. It consists of possible two-contact type switches. Further, the mobile phone 200 incorporates an imaging lens device 207 configured by the variable magnification optical system 100 described above.

  FIG. 3 is a functional block diagram showing an electrical functional configuration relating to imaging of the mobile phone 200. The cellular phone 200 includes an imaging unit 10, an image generation unit 11, an image data buffer 12, an image processing unit 13, a driving unit 14, a control unit 15, a storage unit 16, and an I / F unit 17 for an imaging function. It is prepared for.

  The imaging unit 10 includes an imaging lens device 207 and an imaging element 105. The imaging lens device 207 includes a variable magnification optical system 100 as shown in FIG. 1 and a lens driving device (not shown) for driving the lens in the optical axis direction to perform variable magnification and focusing. . The light beam from the subject is imaged on the light receiving surface of the image sensor 105 by the variable magnification optical system 100 and becomes an optical image of the subject.

  The image sensor 105 converts the optical image of the subject formed by the variable magnification optical system 100 into electrical signals (image signals) of R (red), G (green), and B (blue) color components. It outputs to the image generation part 11 as an image signal of each color of G and B. The imaging device 105 controls imaging operations such as imaging of either a still image or a moving image or reading of output signals of each pixel (horizontal synchronization, vertical synchronization, transfer) in the imaging device 105 under the control of the control unit 15. Is done.

  The image generation unit 11 performs amplification processing, digital conversion processing, and the like on the analog output signal from the image sensor 105, and determines an appropriate black level, γ correction, and white balance adjustment (WB adjustment) for the entire image. Then, well-known image processing such as contour correction and color unevenness correction is performed to generate image data of each pixel from the image signal. The image data generated by the image generation unit 11 is output to the image data buffer 12.

  The image data buffer 12 is a memory that temporarily stores image data and is used as a work area for performing processing described later on the image data by the image processing unit 13. For example, a RAM (Random Access Memory) Etc.

  The image processing unit 13 is a circuit that performs image processing such as resolution conversion on the image data in the image data buffer 12. Further, it is possible to configure the image processing unit 13 to correct aberrations that cannot be corrected by the variable magnification optical system 100 as necessary. The drive unit 14 drives a plurality of lens groups of the variable magnification optical system 100 so as to perform desired variable magnification and focusing by a control signal output from the control unit 15.

  The control unit 15 includes, for example, a microprocessor and the like. The control unit 15 includes an imaging unit 10, an image generation unit 11, an image data buffer 12, an image processing unit 13, a drive unit 14, a storage unit 16, and an I / F unit 17. Control the behavior. That is, the control unit 15 controls the imaging lens device 207 and the imaging element 105 to perform at least one of the still image shooting and the moving image shooting of the subject.

  The storage unit 16 is a storage circuit that stores image data generated by still image shooting or moving image shooting of a subject, and includes, for example, a ROM (Read Only Memory) and a RAM. That is, the storage unit 16 has a function as a memory for still images and moving images. The I / F unit 17 is an interface that transmits / receives image data to / from an external device. For example, the I / F unit 17 is an interface that conforms to a standard such as USB or IEEE1394.

  An imaging operation of the mobile phone 200 configured as described above will be described. When shooting a still image, first, the image switching mode 203 is activated to activate the image shooting mode. Here, the still image shooting mode is activated by pressing the image switching button 203 once, and the moving image shooting mode is switched by pressing the image switching button 203 again in this state. That is, the control unit 15 of the mobile phone body 200 that has received an instruction from the image switching button 203 causes the imaging lens device 207 and the imaging element 105 to perform at least one of still image shooting and moving image shooting of the object on the object side. .

  When the still image shooting mode is activated, the control unit 15 controls the imaging lens device 207 and the imaging element 105 to take a still image, and drives a lens driving device (not shown) of the imaging lens device 207, Perform focusing. As a result, the focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 105, converted into R, G, and B color component image signals, and then output to the image generation unit 11. . The image signal is temporarily stored in the image data buffer 12, subjected to image processing by the image processing unit 13, transferred to a display memory (not shown), and guided to the display 202. Then, the photographer can adjust the main subject to fit in a desired position in the screen by looking at the display 202. By pressing the shutter button 205 in this state, a still image can be obtained, that is, image data is stored in the storage unit 16 serving as a still image memory.

  At this time, when zoom shooting is performed because the subject is at a position away from the photographer or a close subject is desired to be magnified, the state is detected by pressing the printing portion of the upper end “T” of the scaling button 204, The control unit 15 performs lens driving for zooming according to the pressing time, and causes the zooming optical system 100 to perform zooming continuously. Further, when it is desired to reduce the enlargement ratio of the subject, such as when zooming is excessive, the state is detected by pressing the lower end “W” of the magnification button 204, and the control unit 15 performs the magnification optical. By controlling the system 100, scaling is continuously performed according to the pressing time. In this way, the enlargement ratio can be adjusted using the zoom button 204 even for a subject away from the photographer. Then, as in normal normal shooting, an enlarged still image can be obtained by adjusting the main subject so that it falls within a desired position on the screen and pressing the shutter button 205.

  In addition, when performing moving image shooting, the still image shooting mode is activated by pressing the image switching button 203 once, and then the image switching button 203 is pressed again to switch to the moving image shooting mode. As a result, the control unit 15 controls the imaging lens device 207 and the imaging element 105 to take a moving image. After that, as in the case of still image shooting, the photographer looks into the display 202 and adjusts so that the image of the subject obtained through the imaging lens device 207 falls within a desired position on the screen. At this time, similarly to the still image shooting, the enlargement ratio of the subject image can be adjusted by using the zoom button 204. By pressing the shutter button 205 in this state, moving image shooting is started. During this shooting, the enlargement ratio of the subject can be changed at any time by the zoom button 204.

  At the time of moving image shooting, the control unit 15 controls the imaging lens device 207 and the image sensor 105 to take a moving image, and drives a lens driving device (not shown) of the imaging lens device 207 to perform focusing. As a result, a focused optical image is periodically and repeatedly formed on the light receiving surface of the image sensor 105 such as a CCD, converted into image signals of R, G, and B color components, and then transmitted to the image generator 11. Is output. The image signal is temporarily stored in the image data buffer 12, subjected to image processing by the image processing unit 13, transferred to the display memory, and guided to the display 202. Here, when the shutter button 205 is pressed again, the moving image shooting ends. The captured moving image is guided to and stored in the storage unit 16 serving as a moving image memory.

<Description of More Specific Embodiment of Variable-Magnification Optical System>
Hereinafter, a specific configuration of the variable power optical system 100 as shown in FIG. 1, that is, the variable power optical system 100 constituting the imaging lens device 207 mounted in the camera-equipped mobile phone 200 as shown in FIG. This will be described with reference to the drawings.

  FIG. 4 is a cross-sectional view (optical path diagram) in which the optical axis (AX) is cut longitudinally and shows the arrangement of lens groups in the variable magnification optical system 100A of Example 1. 4 and the optical path diagrams of FIGS. 5 to 13 shown below show the lens arrangement at the wide angle end (W). Through Example 1 and Examples 2 to 10 shown below, these lens groups are arranged in order from the object side (left side in FIG. 4) in the figure, the first lens group (Gr1) having negative optical power, as a whole. The second lens group (Gr2) having positive optical power and the third lens group (Gr3) having positive optical power are included. In other words, the first lens group located closest to the object side has a negative optical power so-called negative lead configuration.

  In Example 1 and Examples 2 to 10 described below, the first lens group (Gr1) is composed of only the first lens L1 made of a negative single lens, and the second lens group (Gr2) is from the object side. The second lens L2 is composed of a positive single lens and the third lens L3 is composed of a negative single lens. The third lens group (Gr3) is a fourth lens L4 composed of a positive single lens. It is common in that it consists of only.

  The specific lens configuration in the variable magnification optical system 100A according to the first example is as follows in order from the object side. The first lens group (Gr1) has negative optical power and is composed of a biconcave negative lens (L1). The second lens group (Gr2) has a positive optical power as a whole, and is composed of two lenses, a biconvex positive lens (L2) and a negative meniscus lens (L3) convex toward the object side. The third lens group (Gr3) has a positive optical power, and includes a positive meniscus lens (L4) convex toward the image side. On the object side of the second lens group (Gr2), an optical stop (ST) that moves together with the first lens group (Gr1) and the second lens group (Gr2) at the time of zooming is provided. In addition, on the image side of the third lens group (Gr3), a light receiving surface of the image sensor (SR) is disposed via a parallel plate (FT). The parallel plate (FT) corresponds to an optical low-pass filter, an infrared cut filter, a cover glass of an image sensor, or the like.

  A mechanical shutter may be arranged in place of the optical aperture (ST). Although FIG. 4 shows a continuous variable power optical system, a bifocal switching variable power optical system having the same optical configuration may be used for further compactness. In particular, during zooming from the wide-angle end to the telephoto end, the movement locus of the first lens group (Gr1) makes a U-turn (moves so as to draw a convex locus on the image side), and as a result, the total optical length at the wide-angle end and the telephoto end. Are substantially the same, the bifocal switching variable magnification optical system allows the first lens group (Gr1) to be fixed at the time of variable magnification, so the unit size including the drive mechanism can be reduced. Has a great effect. These points are the same in Examples 2 to 10 described below (the description is omitted below).

  In FIG. 4, the number ri (i = 1, 2, 3,...) Given to each lens surface is the i-th lens surface when counted from the object side. Throughout Example 1 and Examples 2 to 10 described below, the lens surfaces r1 to r9 are all aspherical surfaces. The optical diaphragm (ST), both surfaces of the parallel plate (FT), and the light receiving surface of the image sensor (SR) are also handled as one surface. Such a treatment is the same in the optical path diagrams (FIGS. 5 to 13) for other embodiments to be described later, and the meanings of the reference numerals in the drawings are basically the same as those in FIG. However, it does not mean that they are exactly the same. For example, the lens surface closest to the object is denoted by the same reference numeral (r1) throughout the drawings, but these curvatures are the same throughout the embodiments. It does not mean that.

  Under such a configuration, light incident from the object side sequentially passes through the first, second, and third lens groups (Gr1, Gr2, Gr3) and the parallel plate (FT) along the optical axis AX, An optical image of the object is formed on the light receiving surface of the image sensor (SR). In the image sensor (SR), the optical image corrected in the parallel plate (FT) is converted into an electrical signal. This electric signal is subjected to predetermined digital image processing, image compression processing, and the like as necessary, and is recorded as a digital video signal in a memory of a mobile phone, a portable information terminal, or other digital device by wire or wirelessly Or transmitted to.

  FIG. 24 is a schematic diagram showing the moving direction of these lens groups during zooming. In FIG. 24, not only the first embodiment but also the moving directions of the lens units in the second and later embodiments which will be described later are also shown. Also in FIG. 24, the left side is the object side as before, and the first lens group (Gr1), the second lens group (Gr2), and the third lens group (Gr3) are arranged in this order from the object side. Yes. In this figure, the symbol W indicates the wide angle end with the shortest focal length, that is, the largest angle of view, and the symbol T indicates the telephoto end with the longest focal length, that is, the smallest angle of view. The symbol M represents the middle of the focal length between the wide-angle end (W) and the telephoto end (T) (hereinafter referred to as an intermediate point). The actual lens group is moved on a straight line along the optical axis. In this figure, the positions of the lens group at the wide-angle end (W), the intermediate point (M), and the telephoto end (T) are It is shown in the form of arranging from the bottom.

  As shown in FIG. 24, in Example 1, the first lens group (Gr1) and the second lens group (Gr2) are movable during zooming, and the third lens group (Gr3) is fixed during zooming. Yes. Specifically, at the time of zooming from the wide-angle end (W) to the telephoto end (T), the position of the second lens group (Gr2) is linearly moved in the direction approaching the object, while the first lens group (Gr1) ) Is moved (U-turn movement) so as to draw a convex trajectory on the image side. However, including the following embodiments, the direction and amount of movement of these lens groups can vary depending on the optical power of the lens group, the lens configuration, and the like. For example, in FIG. 24, even if the lens is drawn so as to move linearly like the second lens group (Gr2), it includes a case where it is a convex curve on the object side or the image side. This includes the case of a U-turn shape.

  Tables 1 and 2 show construction data of each lens in the variable magnification optical system 100A of Example 1.

  Table 1 shows, in order from the left, the number of each lens surface, the radius of curvature of each surface (unit: mm), the wide angle end (W), the midpoint (M), and the telephoto end (T) at infinity. The distance between the lens surfaces on the optical axis AX in the focused state (axis upper surface distance; unit is mm), the refractive index of each lens, and the Abbe number (dispersion). The blanks for the axial top surface spacings M and T indicate that they are the same as the values in the left W column. Further, the axial upper surface interval is a distance converted assuming that the medium existing in the region between a pair of opposing surfaces (including the optical surface and the imaging surface) is air. Here, the number ri (i = 1, 2, 3,...) Of each optical surface is the i-th optical surface counted from the object side on the optical path, as shown in FIG. In addition, since each surface of the optical diaphragm (ST), both surfaces of the plane parallel plate (FT), and the light receiving surface of the image sensor (SR) are flat surfaces, their curvature radii are ∞.

  The aspherical shape of the optical surface is defined by the following mathematical formula using a local orthogonal coordinate system (x, y, z) in which the surface vertex is the origin and the direction from the object toward the image sensor is the positive z-axis direction. .

Where z is the amount of displacement in the z-axis direction at the height h (based on the surface vertex)
h: Height in the direction perpendicular to the z-axis (h ² = x ² + y ² )
c: Paraxial curvature (= 1 / radius of curvature)
A to J: 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th and 20th order aspherical coefficients, respectively
k: Conical coefficient

  As can be seen from the above equation (16), the radius of curvature for the aspherical lens shown in Table 1 indicates a value near the surface vertex of the lens. Table 2 shows the conical coefficient k and the values of the aspheric coefficients A, B, C, and D, respectively, for the aspheric surfaces (all surfaces r1 to r9).

  From the left side of FIG. 14, spherical aberration (LONGITUDINAL SPHERICAL ABERRATION), astigmatism (ASTIGMATISM), and distortion (DISTORTION) of the entire optical system in Example 1 under the lens arrangement and configuration as described above are shown. Shown in order. In this figure, the upper part represents the aberration at the wide-angle end (W), the middle part represents the aberration at the intermediate point (M), and the lower part represents the aberration at the telephoto end (T). In addition, the horizontal axis of spherical aberration and astigmatism represents the focal position shift in mm, and the horizontal axis of distortion aberration represents the amount of distortion as a percentage (%) of the total. The vertical axis of spherical aberration is indicated by a value normalized by the incident height, while the vertical axis of astigmatism and distortion is indicated by the height of the image (image height) (unit: mm).

  Further, the spherical aberration diagram shows three different wavelengths: red (dashed wavelength 656.28 nm) with a dashed line, yellow (so-called d-line; wavelength 587.56 nm) with a solid line, and blue (wavelength 435.84 nm) with a broken line. The aberrations when using light are shown respectively. In the figure of astigmatism, symbols s and t represent results on the sagittal (radial) plane and the tangential (meridional) plane, respectively. Further, the diagrams of astigmatism and distortion are the results when the yellow line (d line) is used. As can be seen from FIG. 14, the lens group of Example 1 has excellent optical characteristics with distortion within approximately 5% at any of the wide-angle end (W), intermediate point (M), and telephoto end (T). Is shown. In addition, Tables 21 and 22 show focal lengths (unit: mm) and F values at the wide angle end (W), the intermediate point (M), and the telephoto end (T) in Example 1, respectively. From these tables, it can be seen that in the present invention, a bright optical system with a short focus can be realized.

  FIG. 5 is a cross-sectional view of the arrangement of lens groups in the variable magnification optical system 100B of Example 2 along the optical axis (AX). The variable magnification optical system 100B of Example 2 includes a biconvex negative lens (L1) as a first lens group (Gr1) and a biconvex positive lens as a second lens group (Gr2) in order from the object side. (L2), a convex meniscus lens (L3) on the object side, and a positive meniscus lens (L4) convex on the image side as the third lens group (Gr3).

  In the zoom optical system 100B according to the second embodiment having such a lens configuration, as shown in FIG. 24, the first lens group (Gr1) is zoomed from the wide-angle end (W) to the telephoto end (T). ) Is moved so as to draw a convex trajectory on the image side, and the position of the second lens group (Gr2) is linearly moved in the direction approaching the object. On the other hand, the third lens group (Gr3) is fixed during zooming. However, unlike the first embodiment, the relationship is the full length at the wide-angle end> the total length at the telephoto end.

  Tables 3 and 4 show construction data of each lens in the variable magnification optical system 100B according to Example 2.

  FIG. 6 is a cross-sectional view of the lens group in the variable magnification optical system 100C according to the third embodiment, taken along the optical axis (AX). The variable magnification optical system 100C of Example 3 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a positive meniscus lens (L4) convex on the image side as the third lens group (Gr3).

  In the zoom optical system 100C according to the third embodiment having such a lens configuration, as shown in FIG. 24, the first lens group (Gr1) is zoomed from the wide-angle end (W) to the telephoto end (T). ) Is moved so as to draw a convex trajectory on the image side, and the position of the second lens group (Gr2) is linearly moved in the direction approaching the object. On the other hand, the third lens group (Gr3) is fixed during zooming. However, unlike the first and second embodiments, the wide-angle end total length is equal to the telephoto end total length.

  Tables 5 and 6 show construction data of each lens in the variable magnification optical system 100C according to Example 3.

  FIG. 7 is a cross-sectional view of the lens group in the variable magnification optical system 100D according to the fourth embodiment, taken along the optical axis (AX). The variable magnification optical system 100D of Example 4 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a positive meniscus lens (L4) convex on the image side as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that of the third embodiment as shown in FIG.

  Tables 7 and 8 show construction data of each lens in the variable magnification optical system 100D according to Example 4.

  FIG. 8 is a cross-sectional view of the lens group in the variable magnification optical system 100E according to the fifth embodiment, taken along the optical axis (AX). The variable magnification optical system 100E of Example 5 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a biconvex positive lens (L4) as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that in the first embodiment as shown in FIG.

  Table 9 and Table 10 show construction data of each lens in the variable magnification optical system 100E according to Example 5.

  FIG. 9 is a cross-sectional view of the lens group in the variable magnification optical system 100F of Example 6 taken along the optical axis (AX). The variable magnification optical system 100F of Example 6 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a biconvex positive lens (L4) as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that in the first embodiment as shown in FIG.

  Tables 11 and 12 show construction data of each lens in the variable magnification optical system 100F according to the sixth example.

  FIG. 10 is a cross-sectional view of the lens group in the variable magnification optical system 100G of Example 7 with the optical axis (AX) cut longitudinally. The variable magnification optical system 100G of Example 7 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a positive meniscus lens (L4) convex on the image side as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that of the second embodiment as shown in FIG.

  Tables 13 and 14 show construction data of each lens in the variable magnification optical system 100G according to Example 7.

  FIG. 11 is a cross-sectional view of the lens group in the variable magnification optical system 100H of Example 8 taken along the optical axis (AX). The variable magnification optical system 100H of Example 8 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a biconvex positive lens (L4) as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that in the first embodiment as shown in FIG.

  Tables 15 and 16 show construction data of each lens in the variable magnification optical system 100H according to the eighth example.

  FIG. 12 is a cross-sectional view of the lens group in the variable magnification optical system 100I according to the ninth example, taken along the optical axis (AX). The variable magnification optical system 100I of Example 9 includes, in order from the object side, a biconcave negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2). (L2), a convex meniscus lens (L3) on the object side, and a biconvex positive lens (L4) as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that in the first embodiment as shown in FIG.

  Tables 17 and 18 show construction data of each lens in the variable magnification optical system 100I according to the ninth example.

  FIG. 13 is a cross-sectional view of the lens group in the variable magnification optical system 100J of Example 10 taken along the optical axis (AX). The variable magnification optical system 100J of Example 10 includes a biconvex negative lens (L1) as the first lens group (Gr1) and a biconvex positive lens as the second lens group (Gr2) in order from the object side. (L2), a convex meniscus lens (L3) on the object side, and a biconvex positive lens (L4) as the third lens group (Gr3). The operation at the time of zooming from the wide-angle end (W) to the telephoto end (T) is the same as that in the first embodiment as shown in FIG.

  Table 19 and Table 20 show construction data of each lens in the variable magnification optical system 100J according to Example 10.

  FIGS. 15 to 23 show the spherical aberration, astigmatism, and distortion of the all optical systems of Examples 2 to 10, respectively, under the lens arrangement and configuration as described above. In these figures, the spherical aberration diagrams show the aberrations when three lights having different wavelengths are used, as in FIG. 14, red with a dashed line, yellow with a solid line, and blue with a broken line. . The lens groups in any of the examples show excellent optical characteristics with distortion within approximately 5% at any of the wide-angle end (W), the midpoint (M), and the telephoto end (T).

  Tables 21 and 22 show focal lengths (unit: mm) and F values at the wide-angle end (W), the intermediate point (M), and the telephoto end (T) in the variable magnification optical systems of Examples 2 to 16, respectively. Respectively. From these tables, it can be seen that, similarly to Example 1, a bright optical system with a short focal point can be realized.

  Further, Table 23 shows respective numerical values when the conditional expressions (1) to (15) described above are applied to the variable magnification optical systems of Examples 1 to 10, respectively. Table 23 also includes parameters that are not used in the conditional expressions (1) to (15). FL2 is the focal length of the second lens L2, tw is the full-angle end total length, and tt is the telephoto end total length. Each is shown. R1 and R2 correspond to the values of r1 and r2 in Tables 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19.

  As described above, the variable power optical systems 100A to 100J according to the first to tenth embodiments have a variable power range while configuring the variable power optical system with four lenses that are advantageous for achieving compactness. It can be said that this is a variable magnification optical system in which various aberrations are well corrected over the entire area, and the usefulness of the present invention has been demonstrated.

It is a figure which shows typically the structure of the variable magnification optical system concerning this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external appearance block diagram of the camera-equipped mobile telephone which mounts the variable magnification optical system based on this invention, Comprising: (a) is an external appearance block diagram which shows the operation surface, (b) is an external appearance structure which shows the back surface of an operation surface. FIG. It is a functional block diagram which shows the structure of the function part which concerns on the imaging of the mobile telephone as an example of the digital apparatus which comprises the variable magnification optical system which concerns on this invention. It is sectional drawing which shows the wide angle end optical path figure of the variable magnification optical system which concerns on Example 1 of this invention. 6 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 2. FIG. 7 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 3. FIG. 6 is a cross-sectional view showing a wide-angle end optical path diagram of a variable magnification optical system according to Example 4. FIG. 10 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 5. FIG. 10 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 6. FIG. 10 is a cross-sectional view showing a wide-angle end optical path diagram of a variable magnification optical system according to Example 7. FIG. 10 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 8. FIG. 10 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 9. FIG. FIG. 12 is a cross-sectional view illustrating a wide-angle end optical path diagram of a variable magnification optical system according to Example 10. FIG. 3 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion of the lens group in Example 1. FIG. 7 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 2. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 3. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 4. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 5. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 6. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 7. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 8. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 9. FIG. 12 is an aberration diagram showing spherical aberration, astigmatism, and distortion of the lens group in Example 10. It is a schematic diagram which shows the moving direction of the lens group in each Example of the variable magnification optical system which concerns on this invention.

Explanation of symbols

100, 100A to 100J Variable magnification optical system 101, Gr1 first lens group 102, Gr2 second lens group 103, Gr3 third lens group 104, ST optical aperture 105, SR imaging device 200 mobile phone (digital equipment)
207 Imaging Lens Device AX Optical Axis L1 First Lens L2 Second Lens L3 Third Lens L4 Fourth Lens

Claims (6)

In order from the object side, a first lens group having negative optical power, a second lens group having positive optical power, and a third lens group having positive optical power, A variable power optical system that performs zooming by moving two or more lens groups,
The first lens group and the third lens group are each composed of a single lens, and the second lens group is composed of two lenses of a positive single lens and a negative single lens in order from the object side,
The single lens constituting the first lens group has a concave surface on the object side and satisfies the following conditional expression (1), and the second lens group satisfies the following conditional expressions (2) and (3). A variable magnification optical system characterized by that.
-2.0 <(R1 + R2) / (R1-R2) <0.85 (1)
However, R1: radius of curvature of object side surface of single lens constituting first lens group (image side is positive)
R2: radius of curvature of image side surface of single lens constituting first lens group (image side is positive)
1.65 <N3 <2.4 (2)
15 <ν3 <35 (3)
N3: refractive index of the negative lens in the second lens group
ν3: Dispersion of the negative lens in the second lens group In order from the object side, a first lens group having negative optical power, a second lens group having positive optical power, and a third lens group having positive optical power, A variable power optical system that performs zooming by moving two or more lens groups,
The first lens group and the third lens group are each composed of a single lens, and the second lens group is composed of two lenses of a positive single lens and a negative single lens in order from the object side,
The variable power optical system, wherein the second lens group satisfies the following conditional expressions (4) and (5).
1.78 <N3 <2.4 (4)
15 <ν3 <27 (5) 3. The variable magnification optical system according to claim 2, wherein the single lens constituting the first lens group has a concave surface on the object side and satisfies the following conditional expression (6).
-2.0 <(R1 + R2) / (R1-R2) <0.85 (6) The variable power optical system according to claim 1, wherein the following conditional expression (7) is satisfied.
0.8 <f3 / (fw · ft) ^1/2 <1.45 (7)
Where f3: focal length of the third lens group
fw: Total focal length at the wide end
ft: Total focal length at the telephoto end   5. The variable magnification optical system according to claim 1, wherein the variable magnification optical system is configured to be able to form an optical image of a subject on a predetermined imaging surface. Imaging lens device. 6. The imaging lens device according to claim 5, an imaging device that converts an optical image into an electrical signal, and control that causes the imaging lens device and the imaging device to perform at least one of shooting a still image and moving image shooting of a subject. And comprising
A digital apparatus, wherein the variable magnification optical system of the imaging lens device is assembled so that an optical image of a subject can be formed on a light receiving surface of the imaging element.

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