JP2006330675A - Zoom optical system and electronic equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom optical system which reduces a burden of distortion correction imposed on an optical system, realizes a wide angle of view while retaining a suitable high zooming ratio, is small-sized and secures a high image-quality performance, and to provide electronic equipment provided with the zoom optical system. <P>SOLUTION: The zoom optical system comprises: a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; and a third lens unit having a positive refractive power which are arranged in order from an object side, an interval between the lens units being changed to vary magnification, wherein distortion of the zoom optical system satisfies the following condition: -35≤DTmin≤-10% wherein DTmin is a minimum value (%) of distortion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a variable magnification optical system and an electronic apparatus equipped with the variable magnification optical system, and in particular, an electronic apparatus including a compact variable magnification optical system and a compact variable magnification optical system (for example, a digital camera, a video camera, and a digital video unit). , Personal computer, mobile computer, mobile phone, portable information terminal, etc.).

In recent years, portable information terminals and mobile phones called PDAs have exploded, and built-in compact digital cameras and digital video units using CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) sensors in the image sensor. Things are also increasing. Furthermore, recently, an image sensor having a relatively small size and a high pixel (megapixel) has been developed, and a small and high-performance optical system has been required. As such an optical system, for example, as one of small optical systems, there is a variable magnification optical system having a negative-positive-positive three-lens group configuration (see Patent Document 1).
JP 2003-177315 A

  By the way, a retrofocus type optical system preceding the negative lens group is usually configured such that distortion and coma can be corrected in a balanced manner by the first lens group having negative refractive power. However, if both of these aberrations are corrected simultaneously by the first lens group, there arises a problem that the lens burden for aberration correction particularly at the wide angle end increases. For this reason, in order to correct both aberrations in a well-balanced manner, the number of lenses in the first lens group must be increased to complicate the lens configuration, the overall length of the optical system should be lengthened, and the specifications should not be so high. It was necessary.

  However, the variable power optical system as disclosed in Patent Document 1 has a small number of lenses constituting the optical system, such as four, but the zoom ratio is relatively small at 2.4 times and the angle of view is also small. However, there is a problem that it is impossible to widen the angle of view while securing the image quality.

  The present invention has been made in view of such problems, and can reduce the burden on aberration correction of the optical system, and can realize a wide angle of view while maintaining an appropriate zoom ratio. An object of the present invention is to provide a variable magnification optical system that secures performance and an electronic apparatus equipped with the same.

In order to achieve the above object, a variable magnification optical system according to the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens having a positive refractive power. A variable power optical system that includes lens groups and performs zooming by changing the interval between the lens groups, wherein the distortion satisfies the following condition (1).
−35 (%) ≦ DTmin ≦ −10 (%) (1)
However, DTmin is the minimum distortion aberration amount (%).

  In the zoom optical system according to the present invention, it is preferable that the first lens group is composed of one negative lens.

In the zoom optical system according to the present invention, it is preferable that the first lens group is composed of one negative lens, and the negative lens satisfies the following condition (2).
−4.5 <r1 / fw <−1.0 (2)
Here, r1 is the radius of curvature of the most object-side surface of the negative lens constituting the first lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

In the zoom optical system according to the present invention, it is preferable that the first lens group is one negative lens, the second lens group is one positive lens and one negative lens in order from the object side, and the third lens. Each group consists of one positive lens and satisfies the following condition (3).
-5.0 <(r5 + r6) / (r5-r6) <2.0 (3)
Here, r5 is the radius of curvature of the positive lens of the second lens group on the image side, and r6 is the radius of curvature of the negative lens of the second lens group on the object side.

In the zoom optical system according to the present invention, it is preferable that the first lens group is one negative lens, the second lens group is one positive lens and one negative lens in order from the object side, and the third lens. The group is composed of one positive lens, and the negative lens located on the image side of the second lens group satisfies the following condition (4).
−0.1 <(r6 + r7) / (r6-r7) <5.0 (4)
Here, r6 is the radius of curvature of the negative lens of the second lens group on the object side, and r7 is the radius of curvature of the negative lens of the second lens group on the image side.

  In the zoom optical system according to the present invention, it is preferable that the first lens group is one negative lens, the second lens group is one positive lens and one negative lens in order from the object side, and the third lens. Each group is composed of one positive lens, and satisfies the conditional expressions (3) and (4) at the same time.

In the zoom optical system according to the present invention, it is preferable that a positive lens constituting the second lens group satisfies the following condition (5).
0.53 ≦ r4 / fw <1.2 (5)
Here, r4 is the radius of curvature of the most object side surface of the positive lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

In the zoom optical system according to the present invention, it is preferable that the negative lens constituting the second lens group satisfies the following condition (6).
0.1 <r7 / fw ≦ 1.1 (6)
Here, r7 is the radius of curvature of the surface closest to the image side of the negative lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

The variable magnification optical system according to the present invention is preferably characterized in that the Abbe number νd1 of the negative lens constituting the first lens group satisfies the following condition (7).
50 <νd1 (7)

In the zoom optical system according to the present invention, it is preferable that the Abbe number νd2 of the positive lens constituting the second lens group satisfies the following condition (8).
50 <νd2 (8)

In the zoom optical system according to the present invention, preferably, the refractive index N2P of the positive lens constituting the second lens group satisfies the following condition (9).
1.5 <N2P (9)

  The variable magnification optical system according to the present invention preferably uses at least one plastic lens.

  The variable magnification optical system according to the present invention is preferably characterized in that the positive lens constituting the third lens group is coated with an infrared cut function.

  In the zoom optical system according to the present invention, it is preferable that the third lens group is composed of one glass lens.

  In the zoom optical system according to the present invention, it is preferable that each of the first lens group and the second lens group has at least one glass lens.

  In the zoom optical system according to the present invention, it is preferable that the positive lens of the second lens group is a glass lens.

In the zoom optical system according to the present invention, it is preferable that the positive lens of the third lens group satisfies the following condition (10).
0.3 <(r8 + r9) / (r8-r9) <3.0 (10)
Where r8 is the radius of curvature of the object side surface of the positive lens of the third lens group, and r9 is the radius of curvature of the image side surface of the positive lens of the third lens group.

In the zoom optical system according to the present invention, it is preferable that the second lens group satisfies the following condition (11).
0.8 <f2 / fw <1.6 (11)
Here, f2 is the focal length of the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

In the zoom optical system according to the present invention, it is preferable that the third lens group satisfies the following condition (12).
1.3 <f3 / fw <4.0 (12)
Here, f3 is the focal length of the third lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  The variable magnification optical system according to the present invention is preferably characterized in that focusing is performed by moving the negative lens of the first lens group.

  In the zoom optical system according to the present invention, it is preferable that focusing is performed by moving the third lens group.

  An electronic imaging apparatus according to the present invention electrically connects any one of the variable magnification optical systems, an electronic imaging element disposed on the image side of the variable magnification optical system, and image data captured by the electronic imaging element. An image processing unit that changes the shape by processing.

The electronic imaging apparatus according to the present invention preferably includes any one of the variable magnification optical systems and an electronic imaging element disposed on the image side of the variable magnification optical system, and constitutes the second lens group. The total thickness G2L of the lens satisfies the following condition.
0.6 <(G2L) / Y ′ <1.16 (13)
However, Y ′ is half the diagonal length of the effective imaging region in the electronic imaging device.

  According to the present invention, it is possible to reduce the burden on the aberration correction of the optical system, realize a wide angle of view while maintaining an appropriate zoom ratio, and is equipped with a zoom optical system that is small in size and ensures high image quality performance and the same. An electronic device can be provided.

  Prior to the description of the embodiments of the present invention, the operational effects of the present invention will be described.

Since an optical system mounted on an electronic device such as a mobile phone requires a relatively long back focus, a negative lead retrofocus configuration is optimal. To realize a compact and high-magnification optical system, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power It is desirable that the zoom optical system perform zooming by changing the interval between the lens groups, and that the distortion satisfies the following conditional expression (1).
−35 (%) ≦ DTmin ≦ −10 (%) (1)
However, DTmin is the minimum distortion aberration amount (%).

  That is, by disposing negative refractive power in the first lens group, it is possible to obtain an advantageous configuration for obtaining a wide angle and a relatively long back focus. Further, a positive refractive power is arranged in the third lens group so that the position of the exit pupil is away from the image plane. On the other hand, there are distortion aberration and coma aberration as elements that are difficult to correct by widening the angle. By generating distortion aberration to the extent that satisfies the conditional expression (1), the lens shape and material of the first lens group can be changed. It is possible to cope with correction of coma aberration, and it is possible to widen the angle while reducing the burden of aberration correction. At this time, by generating a negative distortion at the wide-angle end, it is possible to concentrate the burden on the optical system on the correction of aberrations outside the distortion, and it is possible to achieve a configuration that can correct coma aberration and the like satisfactorily. The above configuration is particularly effective when the distortion aberration is electrically corrected. When the distortion aberration is electrically corrected by satisfying the conditional expression (1), a wide angle of view can be realized with good image quality.

  If the upper limit of conditional expression (1) is exceeded, the negative distortion that occurs mainly at wide-angle will be reduced simultaneously with coma, the number of lens components will increase, and the optical system will become larger (the total length during shooting). Will be long). On the other hand, if the value is below the lower limit, the enlargement magnification at the outermost periphery of the image becomes large, and the image after the distortion aberration is electrically corrected becomes rough, which is not preferable. The electrical correction may be performed by an apparatus having an image processing process arranged integrally with the zoom optical system, or may be performed by another apparatus.

  Further, it is preferable that the first lens group is composed of one negative lens.

  That is, by reducing the number of lenses constituting the first lens group, it is possible to reduce the total number of components of the entire optical system while ensuring imaging performance, and to shorten the total length. The size of the lens group can be kept small.

Further, it is preferable that one negative lens constituting the first lens group satisfies the following conditional expression (2).
−4.5 <r1 / fw <−1.0 (2)
Here, r1 is the radius of curvature of the most object-side surface of the negative lens constituting the first lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  That is, especially when the angle is increased and the size is reduced, if the upper limit of the conditional expression (2) is exceeded, it is difficult to correct specific off-axis coma aberration. Below the lower limit, the refractive power of the first lens group becomes weak, and the optical system becomes large. It is not preferable to maintain the refractive power because the amount of aberration generated on the image side surface of the negative lens increases, and it becomes difficult to correct field curvature aberration and coma aberration.

  If it becomes possible to electrically correct distortion, it is not necessary to suppress distortion generated particularly in the negative lens, and further downsizing (shortening of the total length during photographing) can be achieved.

The first lens group is composed of one negative lens, the second lens group is composed of one positive lens and one negative lens in order from the object side, and the third lens group is composed of one positive lens. It is preferable to satisfy (3).
-5.0 <(r5 + r6) / (r5-r6) <2.0 (3)
Where r5 is the radius of curvature of the positive lens in the second lens group on the image side, and r6 is the radius of curvature of the negative lens in the second lens group on the object side.

  That is, by disposing negative refractive power in the first lens group, it is possible to obtain an advantageous configuration for obtaining a wide angle and a relatively long back focus. In addition, the overall length can be further shortened by configuring the first lens group with a single lens. Furthermore, the second lens group has a positive refractive power as a whole, and by making a positive and negative lens configuration in order from the object side, various aberrations can be effectively corrected despite being small. In particular, field curvature aberration and chromatic aberration can be effectively corrected. Further, by arranging a positive refractive power in the third lens group so that the position of the exit pupil is away from the image plane, and the third lens group has a single lens configuration, the overall length can be further shortened.

  Conditional expression (3) is a condition for correcting field curvature aberration and coma with a good balance. In addition to the above-described configuration, by setting the shaping factor of the air lens in the second lens group within the range of the conditional expression (3), various aberrations generated in the second lens group, particularly field curvature aberration and coma Aberration can be corrected satisfactorily, and high image quality (megapixel) compatible performance can be ensured. Further, by satisfying this condition, it is possible to make the second lens group have a relatively strong power, and it is possible to realize high zooming even with the same group interval. If the upper limit of conditional expression (3) is exceeded, the amount of aberration generated on the object-side surface of the negative lens in the second lens group is large, which makes correction of field curvature aberration difficult, which is not preferable. Below the lower limit, correction of field curvature aberration and coma becomes difficult, which is not preferable.

In the present invention, it is more preferable that the following condition (3-1) is satisfied.
-3.8 <(r5 + r6) / (r5-r6) <0 (3-1)

The first lens group includes one negative lens, the second lens group includes one positive lens and one negative lens in order from the object side, and the third lens group includes one positive lens. It is preferable that the negative lens located on the image side of the lens group satisfies the following conditional expression (4).
−0.1 <(r6 + r7) / (r6-r7) <5.0 (4)
Here, r6 is the radius of curvature of the negative lens of the second lens group on the object side, and r7 is the radius of curvature of the negative lens of the second lens group on the image side.

  That is, by disposing negative refractive power in the first lens group, it is possible to obtain an advantageous configuration for obtaining a wide angle and a relatively long back focus. In addition, the overall length can be further shortened by configuring the first lens group with a single lens. Furthermore, the second lens group has a positive refractive power as a whole, and by making a positive and negative lens configuration in order from the object side, various aberrations can be effectively corrected despite being small. In particular, field curvature aberration and chromatic aberration can be effectively corrected. Further, by arranging a positive refractive power in the third lens group so that the position of the exit pupil is away from the image plane, and the third lens group has a single lens configuration, the overall length can be further shortened.

  Conditional expression (4) is a condition for contributing to miniaturization while correcting various aberrations. In addition to the above-described configuration, by satisfying conditional expression (4), the principal point position of the second lens group can be arranged closer to the object side, which is advantageous for downsizing. If the upper limit of conditional expression (4) is exceeded, fluctuations in off-axis aberrations that occur on the image side surface of the negative lens located on the image side of the second lens group become large, which is not preferable for aberration correction. Below the lower limit, the distance between principal points in the second lens group becomes large, the total length of the second lens group becomes long, and the total length of the optical system becomes long.

In the present invention, it is more preferable that the following condition (4-1) is satisfied.
0.1 <(r6 + r7) / (r6-r7) <1.81 (4-1)

  The first lens group includes one negative lens, the second lens group includes one positive lens and one negative lens in order from the object side, and the third lens group includes one positive lens. It is preferable that the conditional expressions (3) or (3-1) and (4) or (4-1) are satisfied simultaneously.

  That is, by satisfying the conditional expressions (3) or (3-1) and (4) or (4-1) at the same time, an optical device that achieves both high performance and miniaturization while maintaining an appropriate zoom ratio. A system can be constructed.

In addition, it is preferable that the positive lens constituting the second lens group satisfies the following conditional expression (5).
0.53 ≦ r4 / fw <1.2 (5)
Here, r4 is the radius of curvature of the most object side surface of the positive lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  That is, conditional expression (5) is a condition for contributing to miniaturization while correcting spherical aberration. If the upper limit of conditional expression (5) is exceeded, the refractive power of the positive lens constituting the second lens group will be weak, which will contribute to an increase in the size of the optical system. Below the lower limit, the amount of spherical aberration generated on the most object-side surface of the positive lens constituting the second lens group increases, and it is impossible to ensure the performance of ensuring high image quality.

In the present invention, it is more preferable that the following condition (5-1) is satisfied.
0.55 ≦ r4 / fw <0.95 (5-1)

In addition, it is preferable that the negative lens constituting the second lens group satisfies the following conditional expression (6).
0.1 <r7 / fw ≦ 1.1 (6)
Here, r7 is the radius of curvature of the surface closest to the image side of the negative lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  That is, conditional expression (6) is a condition for correcting coma aberration and spherical aberration with good balance. If the upper limit of conditional expression (6) is exceeded, the negative component aberration on the surface closest to the image side of the negative lens constituting the second lens group becomes too small, and positive spherical aberration that occurs in other lens elements. This is not preferable because it cannot be corrected. Below the lower limit, the amount of coma aberration generated on the surface increases, which contributes to deterioration of the performance of the peripheral portion.

In the present invention, it is more preferable that the following condition (6-1) is satisfied.
0.23 <r7 / fw ≦ 1.0 (6-1)

Moreover, it is preferable that the Abbe number νd1 of the negative lens constituting the first lens group satisfies the following conditional expression (7).
50 <νd1 (7)

  That is, chromatic aberration can be improved by satisfying conditional expression (7). The value of νd1 is determined by the manufacturing limit of the material forming the lens. When the lens is formed of a glass material, it is preferable to use a low-dispersion anomalous dispersion glass material, which makes it possible to suppress the variation in axial chromatic aberration due to zooming. If the lower limit of conditional expression (7) is not reached, it will be difficult to correct chromatic aberration in the entire optical system.

In the present invention, it is more preferable that the following condition (7-1) is satisfied.
50 <νd1 <100 (7-1)

Further, it is preferable that the Abbe number νd2 of the positive lens constituting the second lens group satisfies the following conditional expression (8).
50 <νd2 (8)

  That is, chromatic aberration can be improved by satisfying conditional expression (8). Note that the value of νd2 is determined by the manufacturing limit of the material forming the lens. When the lens is formed of a glass material, it is preferable to use a low-dispersion anomalous dispersion glass material, which makes it possible to suppress the variation in axial chromatic aberration due to zooming.

In the present invention, it is more preferable that the following condition (8-1) is satisfied.
50 <νd2 <100 (8-1)

Further, it is preferable that the refractive index N2P of the positive lens constituting the second lens group satisfies the following conditional expression (9): 1.5 <N2P (9)

  That is, by selecting a glass material having a high refractive index exceeding 1.5 as a material for forming the positive lens constituting the second lens group, the Petzval sum generated in the lens can be reduced. The upper limit of conditional expression (9) is determined by the production limit of the glass material forming the lens. By selecting a glass material having an appropriate Abbe number as a material for forming the positive lens constituting the second lens group, it is possible to reduce the axial chromatic aberration that becomes large especially at the time of telephoto.

  Moreover, it is preferable to use at least one plastic lens.

  That is, by using a plastic lens, it is possible to reduce the weight of the optical system at low cost.

  Further, it is preferable that the positive lens constituting the third lens group is coated with an infrared cut function.

  That is, since the positive lens constituting the third lens group is coated with an infrared cut function, an infrared cut filter is not required, and the optical system can be further miniaturized. In particular, in an optical system in which the exit pupil is separated to some extent due to the characteristics of an electronic imaging device such as a CCD, a stable infrared cut effect can be easily obtained by coating the lens close to the image plane with an infrared cut function. . Further, the lens for coating having an infrared cut function may be a plastic material or a glass material. When a plastic lens is used, the weight can be reduced more easily, whereas when a glass lens is used, manufacturing is easy. That is, since the glass material is hardly deformed by heat and hardly absorbs moisture, the number of coating layers can be easily increased, and coating having an infrared cut function can be performed relatively easily.

  Moreover, it is preferable that the third lens group is composed of one glass lens.

  That is, by configuring at least one lens of the third lens group with a glass lens, off-axis aberrations, particularly field curvature aberrations can be corrected more satisfactorily. That is, the refractive index and Abbe number can be freely selected. In addition, the glass lens can be constructed with a higher precision on the lens surface and a thinner rim than the resin lens. Therefore, the glass lens can be made thinner while ensuring the necessary lens power. This can contribute to the miniaturization of the system.

  Moreover, it is preferable that each of the first lens group and the second lens group has at least one glass lens.

  That is, by selecting at least one glass material having a high refractive index as the glass lenses constituting the first lens group and the second lens group, it is possible to reduce the Petzval sum generated in the lenses. Further, by using the at least two lenses as a glass lens, it is possible to suppress the amount of aberration fluctuation at the time of zooming, and in particular to keep axial chromatic aberration better.

  Furthermore, it is preferable that the positive lens of the second lens group is made of a glass lens.

  That is, by using a glass lens with negative and positive refractive powers different from each other, it is possible to further suppress image plane deviation due to temperature change.

Moreover, it is preferable that the positive lens of the third lens group satisfies the following conditional expression (10).
0.3 <(r8 + r9) / (r8-r9) <3.0 (10)
Where r8 is the radius of curvature of the object side surface of the positive lens of the third lens group, and r9 is the radius of curvature of the image side surface of the positive lens of the third lens group.

  That is, conditional expression (10) is a condition for providing an optical system with a short overall length without increasing the exit angle of the off-axis light beam. If the upper limit of conditional expression (10) is exceeded, the exit angle of the off-axis light beam becomes too large, which contributes to a shortage of light in the peripheral portion. In addition, the deterioration of off-axis aberrations, particularly coma, cannot be corrected satisfactorily. Below the lower limit, the total length of the optical system tends to be long, which is disadvantageous for miniaturization.

In addition, it is preferable that the second lens group satisfies the following conditional expression (11).
0.8 <f2 / fw <1.6 (11)
Here, f2 is the focal length of the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  That is, when the upper limit of conditional expression (11) is exceeded, the refractive power of the second lens group becomes weak, and the optical system becomes large when trying to realize a zoom lens with a high zoom ratio. If the value is below the lower limit, it is advantageous for downsizing, but the amount of aberration generated in the second lens group increases, which is not preferable for off-axis aberration correction.

Further, it is preferable that the third lens group satisfies the following conditional expression (12).
1.3 <f3 / fw <4.0 (12)
Here, f3 is the focal length of the third lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.

  That is, if the upper limit of conditional expression (12) is exceeded, it is advantageous for securing the back focus and correcting the aberration, but the total length of the optical system becomes long, which is disadvantageous for miniaturization. Below the lower limit, off-axis aberrations are worsened, and in particular, coma cannot be corrected.

  Further, it is preferable to perform focusing by moving the negative lens of the first lens group.

  In other words, if the focusing is performed by moving the negative lens that is the first lens group, it is possible to reduce the aberration fluctuation with respect to the distance change.

  Alternatively, focusing is preferably performed by moving the third lens group.

  That is, when focusing is performed by moving the third lens group, it is possible to obtain driving superiority.

  In the optical system of the present invention, by fixing the third lens group, the movable group can be reduced and the frame mechanism can be simplified. It is advantageous for correcting external aberrations, particularly field curvature aberration, and it is possible to improve the peripheral image quality. These are preferably selected as appropriate according to the required characteristics.

  When an electronic imaging device is configured using any of the above-described variable-power optical systems, in addition to the variable-power optical system, an electronic image-capturing device disposed on the image side of the variable-power optical system, and the electronic image-capturing device It is desirable to have an image processing unit that electrically processes the image data picked up in step 1 and changes its shape.

  If image data in which distortion is corrected can be output by the image processing unit, a good image can be obtained even using a printer or display that does not have an image processing unit that is electrically processed to change its shape.

Further, the electronic imaging device includes any one of the variable magnification optical systems and an electronic imaging element disposed on the image side of the variable magnification optical system, and has a thickness of a lens constituting the second lens group. The total G2L preferably satisfies the following conditional expression.
0.6 <(G2L) / Y ′ <1.16 (13)
However, Y ′ is half the diagonal length of the effective imaging region in the electronic imaging device.

  That is, if the upper limit of conditional expression (13) is exceeded, the total length of the second lens group becomes longer, which contributes to an increase in the size of the entire optical system. If the value is below the lower limit, the lens becomes thin with respect to the diameter and is likely to be damaged, which is not desirable for processing and assembly.

  Next, a basic concept for digitally correcting image distortion will be described.

For example, as shown in FIG. 1, the magnification on the circumference (image height) of the radius R inscribed in the short side of the effective imaging surface around the intersection of the optical axis and the imaging surface is fixed, and this circumference is The standard for correction. Then, correction is performed by moving each point on the circumference (image height) of any other radius r (ω) substantially in the radial direction and concentrically so as to have the radius r ′ (ω). To do. For example, in FIG. 1, a point P ₁ on the circumference of an arbitrary radius r ₁ (ω) located inside the circle of radius R is a radius r ₁ ′ (ω) circle to be corrected toward the center of the circle. Move to point P ₂ on the circumference. A point Q ₁ on the circumference of an arbitrary radius r ₂ (ω) located outside the circle of radius R is a circle of radius r ₂ ′ (ω) to be corrected in a direction away from the center of the circle. Move to point Q ₂ on the circumference. Here, r ′ (ω) can be expressed as follows.
r ′ (ω) = αf tan ω (0 ≦ α ≦ 1)
However, ω is a subject half angle of view, and f is a focal length of an imaging optical system (a zoom optical system in the present invention).
Here, if the ideal image height corresponding to the circle (image height) of the radius R is Y,
α = R / Y = R / ftanω
It becomes.

  The optical system is ideally rotationally symmetric with respect to the optical axis, that is, distortion is also generated rotationally symmetric with respect to the optical axis. Therefore, as described above, when the optically generated distortion aberration is electrically corrected, the radius inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface on the reproduced image. The magnification on the circumference of the circle of R (image height) is fixed, and the other points on the circumference of the circle (image height) of radius r (ω) are moved substantially in the radial direction to obtain radius r ′ ( If correction can be performed by moving the concentric circles so that ω), it is considered advantageous in terms of data amount and calculation amount.

  In the electronic imaging apparatus of the present invention, in order to calculate the correction amount r ′ (ω) −r (ω), r (ω), that is, the relationship between the half angle of view and the image height, or the real image height r and the ideal image height. The relationship with r ′ / α may be recorded on a recording medium built in the electronic imaging apparatus.

The focal length section that needs to be corrected is corrected by dividing it into several focal zones. Then, in the vicinity of the telephoto end in the divided focal zone, approximately r ′ (ω) = αf tan ω
You may correct | amend with the same correction amount as the case where the correction result which satisfies is obtained. However, in that case, some barrel distortion remains at the wide-angle end in the divided focal zone. Further, if the number of divided zones is increased, it becomes unnecessary to store extraneous data necessary for correction on the recording medium, which is not preferable. Therefore, one or several coefficients related to each focal length in the divided focal zone are calculated in advance. This coefficient may be determined based on a simulation or an actual operation. In the vicinity of the telephoto end in the divided zone, approximately r ′ (ω) = αf tan ω
It is also possible to calculate a correction amount when a correction result satisfying the above is obtained, and uniformly multiply the correction amount for each focal distance to obtain a final correction amount.

By the way, if there is no distortion in the image obtained by imaging an object at infinity,
f = y / tan ω
Is established.
Where y is the height of the image point from the optical axis (image height), f is the focal length of the imaging system (in the present invention, the zoom optical system), and ω is the image connected from the center on the imaging surface to the y position. This is an angle (subject half field angle) with respect to the optical axis in the object direction corresponding to the point.
If the imaging system has barrel distortion,
f> y / tan ω
It becomes.
That is, if the focal length f and the image height y of the imaging system are constant, the value of ω increases.

The following conditional expression defines the degree of barrel distortion at the wide-angle end of the zoom optical system.
0.85 <y ₀₇ / (fw · tan ω _07w ) <0.97
Where fw is the focal length of the entire zoom optical system at the wide-angle end, and y ₀₇ is the distance (maximum image height) from the center to the farthest point in the effective imaging plane (in the plane where imaging is possible) of the electronic imaging element. _The image height represented by 0.7y ₁₀ when ₁₀ is assumed, and ω _0.7w is the light in the object direction corresponding to the image point connected to the position of y ₀₇ from the center on the effective image pickup surface of the electronic image pickup device at the wide angle end. The angle with respect to the axis. More specifically, as shown in FIG. 2, ω _0.7w is an angle on the object side formed by the principal ray passing through the position of the image height y ₀₇ and the optical axis, and from the object side to the front side principal of the zoom optical system. This is the angle formed by the principal ray toward the point position and the optical axis.

  If this conditional expression is satisfied, an image can be captured as an image over a wide viewing angle while keeping the size of the optical system small, and image processing by the signal processing system built in the electronic imaging device described above Thus, the image distortion due to the distortion of the optical system can be corrected without increasing the enlargement ratio in the radial direction of the peripheral portion of the image and without conspicuous the deterioration of the sharpness of the peripheral portion of the image.

  In the present invention, the purpose of deliberately generating distortion aberration in the optical system and correcting the distortion by electrically processing the image after taking an image with the electronic image pickup device is the downsizing and wide angle of the optical system. This is because of satisfying the increase in magnification and zooming. Therefore, in the present invention, it is also important to select an optical system so that the size of the optical system itself is not wasted.

  Hereinafter, the present invention will be described in detail based on illustrated embodiments.

In the following examples, R is the radius of curvature of each lens surface, D is the thickness or spacing of each lens, Nd is the refractive index of each lens at the d-line, Vd is the Abbe number of each lens at the d-line, K is the conic coefficient, A ₄ , A ₆ and A ₈ are aspheric coefficients, f is the focal length of the entire system, and Fno. Indicates the F number, 2ω indicates the total angle of view, and D1 and D2 indicate variable intervals.
Each aspheric shape is expressed by the following equation using each aspheric coefficient. However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + K) · (Y / r) ² } ^1/2 ]
+ A ₄ Y ⁴ + A ₆ Y ⁶ + A ₈ Y ⁸
In the aspheric coefficient, for example, the value of A _{4 in} the aspheric surface 2 of Example 1, −4.4963E-3, can be displayed as −4.4963 × 10 ^−3, but in this numerical data, All are displayed in the former format.

  3A and 3B are cross-sectional views along the optical axis showing the configuration of the photographing optical system according to the present embodiment, where FIG. 3A shows a state at the wide-angle end, FIG. 3B shows an intermediate state, and FIG. 3C shows a state at the telephoto end. ing. FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral coma when the zoom lens according to the present embodiment is focused on an object point at infinity. b) shows the state at the middle, and (c) shows the state at the telephoto end.

As shown in FIGS. 3A to 3C, the variable magnification optical system of the present embodiment includes a first lens group G ₁ having a negative refractive power and a second lens group G ₂ having a positive refractive power. And a third lens group G ₃ having a positive refractive power.

The first lens group G ₁ is composed only of a biconcave negative lens L _{1 having} both aspheric surfaces. The second lens group G ₂ includes, in order from the object side, both surfaces of a biconvex positive lens L ₂₁ which is a non-spherical surface, the image side surface is composed of a biconcave negative lens L ₂₂ which is a non-spherical surface. The third lens group G ₃ is composed only of a biconvex positive lens L ₃ having an object-side surface with an infrared cut coat (not shown) and an image-side surface that is an aspherical surface. Further, S indicates a diaphragm, and CG indicates a cover glass.

In the thus configured variable power optical system of this embodiment, from the wide-angle end in the optical axis Lc when zooming to the telephoto end, the back object side after the first lens group G ₁ is moved to the image side The second lens group G ₂ moves toward the object side, and the third lens group G ₃ is fixed.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Focal length 3.2mm-8.5mm
Fno. 2.8 to 4.8
Angle of view (2ω) 76.2 ° to 28.8 °
Effective imaging area (diagonal length) 4.5mm

Surface RD Nd Vd
1 * -7.898 0.67 1.52542 55.78 (Plastic lens)
2 * 6.245 D1
3 (Aperture) ∞ 0.75
4 * 2.581 1.40 1.52542 55.78 (plastic lens)
5 * -3.679 1.02
6 -8.795 0.99 1.60687 27.03 (plastic lens)
7 * 3.222 D2
8 19.576 0.88 1.52542 55.78 (Plastic lens)
9 -7.913 1.40
10 ∞ 0.50 1.51633 64.14
11 ∞ 0.50
12 (Shooting surface)
*: Aspherical surface

Aspheric coefficient surface R k A ₄ A ₆ A ₈
1 -7.898 0 -4.4963E-3 1.1928E-3 -6.1456E-5
2 6.245 0 -5.9954E-3 1.8182E-3 5.4713E-6
4 2.581 -1.9920 6.8196E-3 -4.6381E-4
5 -3.679 0 1.1181E-2 -1.2020E-3 8.4288E-5
7 3.222 3.1471 -1.3938E-2 4.6177E-3 -1.5879E-3
9 -7.913 -0.7915 6.5630E-3 -1.1630E-5 7.0550E-5

Zoom data Zoom status Wide-angle end Medium telephoto end f 3.2 5.1 8.5
Fno. 2.8 3.5 4.8
D1 5.83 3.30 1.53
D2 0.65 2.25 5.20

In addition, each numerical data related to each conditional expression is shown below.
Conditional expression (1): DTmin = -20.94
Conditional expression (2): r1 / fw = −2.45
Conditional expression (3): (r5 + r6) / (r5-r6) = − 2.44
Conditional expression (4): (r6 + r7) / (r6-r7) = 0.46
Conditional expression (5): r4 / fw = 0.80
Conditional expression (6): r7 / fw = 1.00
Conditional expression (7): νd1 = 55.78
Conditional expression (8): νd2 = 55.78
Conditional expression (9): N2P = 1.53
Conditional expression (10): (r8 + r9) / (r8-r9) = 0.42
Conditional expression (11): f2 / fw = 1.36
Conditional expression (12): f3 / fw = 3.37
Conditional expression (13): (G2L) /Y′=1.06

  FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the photographing optical system according to the present embodiment, where (a) shows a state at the wide angle end, (b) shows an intermediate state, and (c) shows a state at the telephoto end. ing. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral coma aberration when the zoom lens according to the present embodiment is focused on an object point at infinity, and FIG. b) shows the state at the middle, and (c) shows the state at the telephoto end.

As shown in FIGS. 5A to 5C, the variable magnification optical system of the present embodiment includes a first lens group G ₁ having a negative refractive power and a second lens group G ₂ having a positive refractive power. And a third lens group G ₃ having a positive refractive power.

The first lens group G ₁ is composed only of a biconcave negative lens L _{1 having} both aspheric surfaces. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having two aspheric surfaces, a negative meniscus lens L ₂₂ having a convex surface facing the object side, and an image-side surface being aspheric. It is comprised by. The third lens group G ₃ is constituted only by a positive meniscus lens L ₃ having an infrared cut coat (not shown) on the object side surface and a convex surface facing the image side, and the image side surface being an aspherical surface. ing. Further, S indicates a diaphragm, and CG indicates a cover glass.

In the thus configured variable power optical system of this embodiment, from the wide-angle end in the optical axis Lc when zooming to the telephoto end, the back object side after the first lens group G ₁ is moved to the image side The second lens group G ₂ moves toward the object side, and the third lens group G ₃ is fixed.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Focal length 3.2mm-8.5mm
Fno. 2.8 to 5.2
Angle of view (2ω) 76.2 ° -30.0 °
Effective imaging area (diagonal length) 4.5mm

Surface RD Nd Vd
1 * -6.323 0.44 1.49700 81.54
2 * 4.922 D1
3 (Aperture) ∞ 0.27
4 * 1.844 0.90 1.51633 64.14
5 * -2.442 0.39
6 40.886 0.71 1.60687 27.03 (Plastic lens)
7 * 1.550 D2
8 -15.137 1.10 1.52542 55.78 (Plastic lens)
9 * -2.831 0.20
10 ∞ 0.50 1.51633 64.14
11 ∞ 0.50
12 (Shooting surface)
*: Aspherical surface

Aspheric coefficient surface R k A ₄ A ₆ A ₈
1 -6.323 3.5169 -2.1335E-2 6.3053E-3 -5.4714E-4
2 4.922 2.9441 -3.0890E-2 8.0850E-3 -7.3810E-4
4 1.844 -1.4468 4.3351E-3 1.0293E-3 -1.9064E-4
5 -2.442 -0.1228 4.7204E-2 -1.5997E-2 2.8091E-3
7 1.550 -0.6647 -3.2923E-2 7.3056E-2 -2.9607E-2
9 -2.831 -2.1618 2.1542E-2 -6.3161E-3 4.5745E-4

Zoom data Zoom status Wide-angle end Medium telephoto end f 3.2 5.0 8.5
Fno. 2.8 3.6 5.2
D1 3.95 2.10 0.78
D2 2.01 3.35 5.88

In addition, each numerical data related to each conditional expression is shown below.
Conditional expression (1): DTmin = −29.90
Conditional expression (2): r1 / fw = -1.97
Conditional expression (3): (r5 + r6) / (r5-r6) = − 0.89
Conditional expression (4): (r6 + r7) / (r6-r7) = 1.08
Conditional expression (5): r4 / fw = 0.57
Conditional expression (6): r7 / fw = 0.48
Conditional expression (7): νd1 = 81.54
Conditional expression (8): νd2 = 64.14
Conditional expression (9): N2P = 1.52
Conditional expression (10): (r8 + r9) / (r8-r9) = 1.46
Conditional expression (11): f2 / fw = 1.07
Conditional expression (12): f3 / fw = 2.00
Conditional expression (13): (G2L) /Y′=0.71

  FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the photographing optical system according to the present embodiment, where (a) shows the state at the wide angle end, (b) shows the middle, and (c) shows the state at the telephoto end. ing. FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral coma when the zoom lens according to the present embodiment is focused on an object point at infinity. b) shows the state at the middle, and (c) shows the state at the telephoto end.

As shown in FIGS. 7A to 7C, the variable magnification optical system of the present embodiment includes a first lens group G ₁ having a negative refractive power and a second lens group G ₂ having a positive refractive power. And a third lens group G ₃ having a positive refractive power.

The first lens group G ₁ is composed only of a biconcave negative lens L _{1 having} both aspheric surfaces. The second lens group G ₂ includes, in order from the object side, both surfaces of a biconvex positive lens L ₂₁ which is a non-spherical surface, the image side surface is composed of a biconcave negative lens L ₂₂ which is a non-spherical surface. The third lens group G ₃ is composed only of a biconvex positive lens L ₃ having an object-side surface with an infrared cut coat (not shown) and an image-side surface that is an aspherical surface. Further, S indicates a diaphragm, and CG indicates a cover glass.

In the thus configured variable power optical system of this embodiment, from the wide-angle end in the optical axis Lc when zooming to the telephoto end, the back object side after the first lens group G ₁ is moved to the image side The second lens group G ₂ moves toward the object side, and the third lens group G ₃ is fixed.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Focal length 3.2mm-8.5mm
Fno. 2.8 to 4.8
Angle of view (2ω) 76.2 ° to 28.8 °
Effective imaging area (diagonal length) 4.5mm

Surface RD Nd Vd
1 * -7.898 0.67 1.52542 55.78 (Plastic lens)
2 * 6.245 D1
3 (Aperture) ∞ 0.75
4 * 2.581 1.40 1.52542 55.78 (plastic lens)
5 * -3.679 1.02
6 -8.795 0.99 1.60687 27.03 (plastic lens)
7 * 3.222 D2
8 19.576 0.88 1.52542 55.78 (Plastic lens)
9 -7.913 1.40
10 ∞ 0.50 1.51633 64.14
11 ∞ 0.50
12 (Shooting surface)
*: Aspherical surface

Aspheric coefficient surface R k A ₄ A ₆ A ₈
1 -7.898 0 -4.4963E-3 1.1928E-3 -6.1456E-5
2 6.245 0 -5.9954E-3 1.8182E-3 5.4713E-6
4 2.581 -1.9920 6.8196E-3 -4.6381E-4
5 -3.679 0 1.1181E-2 -1.2020E-3 8.4288E-5
7 3.222 3.1471 -1.3938E-2 4.6177E-3 -1.5879E-3
9 -7.913 -0.7915 6.5630E-3 -1.1630E-3 7.0550E-5

Zoom data Zoom status Wide-angle end Medium telephoto end f 3.2 5.1 8.5
Fno. 2.8 3.5 4.8
D1 5.83 3.30 1.53
D2 0.65 2.25 5.20

In addition, each numerical data related to each conditional expression is shown below.
Conditional expression (1): DTmin = -20.94
Conditional expression (2): r1 / fw = −2.45
Conditional expression (3): (r5 + r6) / (r5-r6) = − 2.44
Conditional expression (4): (r6 + r7) / (r6-r7) = 0.46
Conditional expression (5): r4 / fw = 0.80
Conditional expression (6): r7 / fw = 1.00
Conditional expression (7): νd1 = 55.78
Conditional expression (8): νd2 = 55.78
Conditional expression (9): N2P = 1.53
Conditional expression (10): (r8 + r9) / (r8-r9) = 0.42
Conditional expression (11): f2 / fw = 1.36
Conditional expression (12): f3 / fw = 3.37
Conditional expression (13): (G2L) /Y′=1.06

  FIG. 9 is a cross-sectional view along the optical axis showing the configuration of the photographing optical system according to the present embodiment, where (a) shows the state at the wide angle end, (b) shows the middle, and (c) shows the state at the telephoto end. ing. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral coma aberration when the zoom lens according to the present embodiment is focused on an object point at infinity, and FIG. b) shows the state at the middle, and (c) shows the state at the telephoto end.

As shown in FIGS. 9A to 9C, the variable magnification optical system of the present embodiment includes a first lens group G ₁ having a negative refractive power and a second lens group G ₂ having a positive refractive power. And a third lens group G ₃ having a positive refractive power.

The first lens group G ₁ is composed only of a biconcave negative lens L _{1 having} both aspheric surfaces. The second lens group G ₂ includes, in order from the object side, a biconvex positive lens L ₂₁ having two aspheric surfaces, a negative meniscus lens L ₂₂ having a convex surface facing the object side, and an image-side surface being aspheric. It is comprised by. The third lens group G ₃ is constituted only by a positive meniscus lens L ₃ having an infrared cut coat (not shown) on the object side surface and a convex surface facing the image side, and the image side surface being an aspherical surface. ing. Further, S indicates a diaphragm, and CG indicates a cover glass.

In the thus configured variable power optical system of this embodiment, from the wide-angle end in the optical axis Lc when zooming to the telephoto end, the back object side after the first lens group G ₁ is moved to the image side The second lens group G ₂ moves toward the object side, and the third lens group G ₃ is fixed.

  Next, numerical data of lenses constituting the photographing optical system according to the present example are shown.

Focal length 3.2mm-8.5mm
Fno. 2.8 to 5.2
Angle of view (2ω) 76.2 ° -30.0 °
Effective imaging area (diagonal length) 4.5mm

Surface RD Nd Vd
1 * -6.323 0.44 1.49700 81.54
2 * 4.922 D1
3 (Aperture) ∞ 0.27
4 * 1.844 0.90 1.51633 64.14
5 * -2.442 0.39
6 40.886 0.71 1.60687 27.03 (Plastic lens)
7 * 1.550 D2
8 -15.137 1.10 1.52542 55.78 (Plastic lens)
9 * -2.831 0.20
10 ∞ 0.50 1.51633 64.14
11 ∞ 0.50
12 (Shooting surface)
*: Aspherical surface

Aspheric coefficient surface R k A ₄ A ₆ A ₈
1 -6.323 3.5169 -2.1335E-2 6.3053E-3 -5.4714E-4
2 4.922 2.9441 -3.0890E-2 8.0850E-3 -7.3810E-4
4 1.844 -1.4468 4.3351E-3 1.0293E-3 -1.9064E-3
5 -2.442 -0.1228 4.7204E-2 -1.5997E-2 2.8091E-3
7 1.550 -0.6647 -3.2923E-2 7.3056E-2 -2.9607E-2
9 -2.831 -2.1618 2.1542E-2 -6.3161E-3 4.5745E-4

Zoom data Zoom status Wide-angle end Medium telephoto end f 3.2 5.0 8.5
Fno. 2.8 3.6 5.2
D1 3.95 2.10 0.78
D2 2.01 3.35 5.88

In addition, each numerical data related to each conditional expression is shown below.
Conditional expression (1): DTmin = −29.90
Conditional expression (2): r1 / fw = -1.97
Conditional expression (3): (r5 + r6) / (r5-r6) = − 0.89
Conditional expression (4): (r6 + r7) / (r6-r7) = 1.08
Conditional expression (5): r4 / fw = 0.57
Conditional expression (6): r7 / fw = 0.48
Conditional expression (7): νd1 = 81.54
Conditional expression (8): νd2 = 64.14
Conditional expression (9): N2P = 1.52
Conditional expression (10): (r8 + r9) / (r8-r9) = 1.46
Conditional expression (11): f2 / fw = 1.07
Conditional expression (12): f3 / fw = 2.00
Conditional expression (13): (G2L) /Y′=0.71

  The variable magnification optical system of the present invention described above can be incorporated in an electronic device such as a digital camera, a video camera, a digital video unit, a personal computer, a mobile computer, a mobile phone, and an information portable terminal. For example, the variable magnification optical system of the present invention can be suitably used in an imaging apparatus that forms an object image and receives the image on a solid-state imaging device such as a CCD, and in particular, an imaging optical system for a mobile phone. The embodiment is illustrated below.

FIG. 11 shows an example in which the variable magnification optical system of the present invention is incorporated in a mobile phone that is convenient to carry.
11A is a front view of the mobile phone 400, FIG. 11B is a side view, and FIG. 11C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 11A to 11C, a mobile phone 400 includes a microphone unit 401 that inputs an operator's voice as information, a speaker unit 402 that outputs a voice of a call partner, and an operator who receives information. An input dial 403 for inputting information, a monitor 404 for displaying information such as a photographed image and a telephone number of the operator and the other party, a photographing optical system 405, an antenna 406 for transmitting and receiving communication radio waves, and an image And processing means (not shown) for processing information, communication information, input signals, and the like. Here, the monitor 404 is a liquid crystal display element. In the drawing, the arrangement positions of the respective components are not particularly limited to these. The photographing optical system 405 includes an objective optical system 100 that is a variable power optical system of the present invention disposed on a photographing optical path 407 and an image pickup element chip 162 that receives an image. These are built in the mobile phone 400.

  Here, since the imaging element chip 162 can be attached by being fitted to the rear end of the lens frame 101 of the objective optical system 100 with a single touch, the centering of the objective optical system 100 and the imaging element chip 162 and the distance between the surfaces can be adjusted. No adjustment is required and assembly is simple. Further, a cover glass 102 for protecting the objective optical system 100 is disposed at the tip (not shown) of the lens frame 101. The zoom lens driving mechanism in the lens frame 101 is not shown.

  The object image received by the imaging element chip 162 is input to the processing means (not shown) via the terminal 166 and displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. . Further, when transmitting an image to a communication partner, the processing means includes a signal processing function for converting information of an object image received by the image sensor chip 162 into a signal that can be transmitted.

  Next, FIG. 12 to FIG. 14 are conceptual diagrams showing a configuration in which the optical system of the present invention is built in a personal computer which is another example of the information processing apparatus.

12 is a front perspective view with the cover of the personal computer 300 opened, FIG. 13 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 14 is a side view of the state of FIG. As shown in FIGS. 12 to 14, the personal computer 300 includes a keyboard 301 for a writer to input information from the outside, information processing means and recording means not shown, and a monitor for displaying information to the operator. 302 and a photographing optical system 303 for photographing the operator himself and surrounding images. Here, the monitor 302 may be a transmissive liquid crystal display element that is illuminated from the back by a backlight (not shown), a reflective liquid crystal display element that reflects and displays light from the front, a CRT display, or the like. Further, in the drawing, the photographing optical system 303 is built in the upper right of the monitor 302. However, the imaging optical system 303 is not limited to the place, and may be anywhere around the monitor 302 or the keyboard 301.
The photographing optical system 303 has an objective optical system 100 including a variable magnification optical system according to the present invention and an image pickup element chip 162 that receives an image on a photographing optical path 304. These are built in the personal computer 300.

  Here, since the imaging element chip 162 can be attached by being fitted to the rear end of the lens frame 101 of the objective optical system 100 with a single touch, the centering of the objective optical system 100 and the imaging element chip 162 and the distance between the surfaces can be adjusted. No adjustment is required and assembly is simple. Further, a cover glass 102 for protecting the objective optical system 100 is disposed at the tip (not shown) of the lens frame 101. The zoom lens driving mechanism in the lens frame 101 is not shown.

  The object image received by the image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166 and displayed on the monitor 302 as an electronic image. FIG. A rendered image 305 is shown. The image 305 can also be displayed on the personal computer of the communication partner from a remote location via the processing means, the Internet, or the telephone.

  15 to 17 are conceptual diagrams of a configuration in which the variable magnification optical system of the present invention is incorporated in the photographing optical system 41 of the electronic camera. 15 is a front perspective view showing the appearance of the electronic camera 40, FIG. 16 is a rear perspective view thereof, and FIG. 17 is a cross-sectional view showing the configuration of the electronic camera 40. In this example, the electronic camera 40 includes a photographing optical system 41 having a photographing optical path 42, a finder optical system 43 having a finder optical path 44, a shutter 45, a flash 46, a liquid crystal display monitor 47, and the like. When the shutter 45 disposed in the position is pressed, photographing is performed through the photographing optical system 41 in conjunction therewith. An object image formed by the photographing optical system 41 is formed on the imaging surface 50 of the CCD 49 through a filter 51 such as a low-pass filter. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera via the processing means 52. In addition, the processing means 52 is provided with a memory or the like, and can record a captured electronic image. This memory may be provided separately from the processing means 52, or may be configured to perform recording and writing electronically using a floppy (registered trademark) disk or the like.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The object image formed on the imaging surface 67 formed by the finder objective optical system 53 is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. The field frame 57 separates the first reflecting surface 56 and the second reflecting surface 58 of the Porro prism 55 and is disposed therebetween. Behind this polyprism 55 is an eyepiece optical system 59 that guides the erect image to the observer eyeball E. Note that cover members 54 are disposed on the entrance surface of the photographing optical system 41 and the objective optical system 53 for the finder and the exit surface of the eyepiece optical system 59, respectively.

  In the camera 40 configured in this manner, since the photographing optical system 41 is a variable magnification optical system having a high zoom ratio and good aberration, high performance can be realized, and the photographing optical system 41 can be reduced in number of optical members. Therefore, downsizing and cost reduction can be realized.

  In the configuration of FIG. 17, a parallel plane plate is arranged as the cover member 54, but a lens having power may be used.

  Next, FIG. 18 shows a conceptual diagram of a configuration in which the variable magnification optical system of the present invention is incorporated in the objective optical system 48 of the photographing unit of the electronic camera 40. In this case, the variable power optical system according to the present invention is used for the photographing objective optical system 48 disposed on the photographing optical path 42. The object image formed by the photographing objective optical system 48 is formed on the imaging surface 50 of the CCD 49 through a filter 51 such as a low-pass filter. The object image received by the CCD 49 is displayed as an electronic image on a liquid crystal display element (LCD) 60 via the processing means 52. The processing means 52 also controls the recording means 61 that records the object image taken by the CCD 49 as electronic information. The image displayed on the LCD 60 is guided to the observer eyeball E through the eyepiece optical system 59. The eyepiece optical system 59 is composed of a decentered prism. In this example, the eyepiece optical system 59 is composed of three surfaces: an incident surface 62, a reflecting surface 63, and a combined reflecting / refracting surface 64. In addition, at least one of the two reflecting surfaces 63 and 64, preferably both surfaces, provides power to the light beam and has a single symmetry plane that corrects decentration aberrations. It consists of a curved surface.

  The camera 40 configured in this manner is a variable magnification optical system having a high variable magnification ratio and a good aberration ratio, so that high performance can be realized, and the objective optical system 48 for photographing is realized. Therefore, it is possible to realize downsizing and cost reduction.

  In this example, a plane-parallel plate is disposed as the cover member 65 of the photographing objective optical system 48, but a lens having power may be used as in the previous example.

  Here, without providing the cover member, the surface disposed closest to the object side in the optical system of the present invention can also be used as the cover member. In this example, the most object side surface is the entrance surface of the first lens group G1.

  FIG. 19 is a configuration block diagram of an internal circuit of a main part of the electronic device 11 such as the mobile phone, the personal computer, or the electronic camera. In the following description, the imaging element chip 162 and the CCD 49 are composed of, for example, the imaging element 23, and the processing means 52 is composed of, for example, the CDS / ADC section 24, the temporary storage memory 17, the image processing section 18, and the like. Consists of, for example, the storage medium unit 19 and the like.

  As shown in FIG. 19, the electronic device 11 includes an operation unit 12, a control unit 13 connected to the operation unit 12, and an imaging drive connected to the control signal output port of the control unit 13 via buses 14 and 15. The circuit 16 includes a temporary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21.

  The temporary storage memory 17, the image processing unit 18, the storage medium unit 19, the display unit 20, and the setting information storage memory unit 21 are configured to be able to input or output data with each other via the bus 22. The imaging drive circuit 16 is connected with an imaging device 23 and a CDS / ADC unit 24.

  The operation unit 12 includes various input buttons and switches, and is a circuit that notifies the control unit of event information input from the outside (electronic device user) via these input buttons and switches. The control unit 13 is a central processing unit composed of, for example, a CPU, and has a built-in program memory (not shown). The control unit 13 is input by a camera user via the operation unit 12 according to a program stored in the program memory. This is a circuit that controls the entire electronic device 11 in response to an instruction command.

  The image sensor 23 receives an object image formed via the variable magnification optical system 22 according to the present invention. The image pickup device 23 is an image pickup device that is driven and controlled by the image pickup drive circuit 16 and converts the light amount of each pixel of the object image into an electric signal and outputs the electric signal to the CDS / ADC unit 24.

  The CDS / ADC unit 24 amplifies an electrical signal input from the image sensor 23 and performs analog / digital conversion, and then performs raw video data (Bayer data, hereinafter referred to as RAW data) obtained by performing the amplification and digital conversion. This is a circuit for outputting to the temporary storage memory 17.

  The temporary storage memory 17 is a buffer made of, for example, SDRAM or the like, and is a memory device that temporarily stores the RAW data output from the CDS / ADC unit 24. The image processing unit 18 reads out the RAW data stored in the temporary storage memory 17 or the RAW data stored in the storage medium unit 19, and performs various corrections including distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs image processing electrically.

  The recording medium unit 19 detachably mounts a card-type or stick-type recording medium made of, for example, a flash memory, and the RAW data transferred from the temporary storage memory 17 to the card-type or stick-type flash memory. It is a control circuit of an apparatus that records and holds image data processed by the image processing unit 18.

  The display unit 20 includes a liquid crystal display monitor 47 and is a circuit that displays an image, an operation menu, and the like on the liquid crystal display monitor 47. The setting information storage memory unit 21 stores a ROM unit in which various image quality parameters are stored in advance, and an image quality parameter selected by an input operation of the operation unit 12 among the image quality parameters read from the ROM unit. RAM section is provided. The setting information storage memory unit 21 is a circuit for controlling input / output to / from these memories.

  As mentioned above, although the Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation is possible in the range which does not deviate from the summary of invention. For example, in the above embodiment, the infrared cut coat is applied to the object side surface of the positive lens constituting the third lens group. However, the present invention is not limited to such a configuration, and an infrared cut coat may be applied to other lens surfaces and filters such as a low-pass filter. Or it is good also as a structure which provides an infrared cut filter separately.

It is a figure for demonstrating the basic concept for carrying out the digital correction of the distortion of an image. It is a figure for showing the relation between the incident angle of light with respect to an optical axis, and image height. 1 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to a first embodiment of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. Yes. FIG. 4A is an aberration curve diagram of the zoom lens according to the first example of the present invention. FIG. 5A illustrates a state at the wide-angle end, FIG. 5B illustrates an intermediate state, and FIG. FIG. 4 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to a second embodiment of the present invention, where (a) shows the state at the wide-angle end, (b) shows the state at the middle, and (c) shows the state at the telephoto end. Yes. FIG. 5A is an aberration curve diagram of a zoom lens according to a second example of the present invention, where FIG. 5A illustrates a state at a wide-angle end, FIG. 5B illustrates an intermediate state, and FIG. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to a third embodiment of the present invention, where (a) shows the state at the wide-angle end, (b) shows the middle, and (c) shows the state at the telephoto end. Yes. FIG. 6A is an aberration curve diagram of a zoom lens according to a third example of the present invention, where FIG. 5A illustrates a state at a wide angle end, FIG. 5B illustrates an intermediate state, and FIG. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a zoom lens according to a fourth embodiment of the present invention, where (a) shows a state at a wide angle end, (b) shows an intermediate state, and (c) shows a state at a telephoto end. Yes. FIG. 6A is an aberration curve diagram of a zoom lens according to a fourth example of the present invention. FIG. 5A illustrates a state at a wide angle end, FIG. 5B illustrates an intermediate state, and FIG. It is a figure which shows the mobile phone incorporating the optical system of this invention, (a) is a front view of an external appearance, (b) is a side view of an external appearance, (c) is sectional drawing of the built-in imaging optical system. It is a front perspective view which shows the external appearance of the personal computer incorporating the optical system of this invention. It is sectional drawing of the imaging optical system incorporated in the personal computer of FIG. It is a side view which shows the external appearance of the personal computer of FIG. It is a front perspective view which shows the external appearance of the electronic camera to which the optical system of this invention is applied. FIG. 16 is a rear perspective view of the electronic camera of FIG. 15. It is sectional drawing which shows the structure of the electronic camera of FIG. It is a conceptual diagram of another electronic camera to which the optical system of the present invention is applied. It is a block diagram of the internal circuit of the main part of an electronic device such as a mobile phone, a personal computer, and an electronic camera.

Explanation of symbols

G ₁ First lens group G ₂ Second lens group G ₃ Third lens group S Aperture CG Cover glass Lc Optical axis 100 Objective optical system 101 Mirror frame 160 Imaging unit 162 Imaging element chip 166 Terminal 180 Infrared cut filter 400 Mobile phone 401 Microphone unit 402 Speaker unit 403 Input dial 404 Monitor 405 Imaging optics System 406 antenna 407 imaging optical path 300 personal computer 301 keyboard 302 monitor 303 imaging optical system 304 imaging optical path 305 image 40 camera 41 imaging optical system 42 imaging optical path 43 finder optical system 44 finder optical path 45 shutter 46 flash 47 liquid crystal display monitor 48 objective optical Series 49 CCD
DESCRIPTION OF SYMBOLS 50 Imaging surface 51 Filter 52 Processing means 53 Finder objective optical system 54 Cover member 55 Porro prism 56 1st reflective surface 57 Field frame 58 2nd reflective surface 59 Eyepiece optical system 60 Liquid crystal display element (LCD)
61 Recording means 62 Incident surface 63 Reflecting surface 64 Combined reflection and refraction surface 65 Cover member 67 Imaging surface E Observer eyeball 11 Electronic device 12 Operation unit 13 Control unit 14, 15, 22 Bus 16 Imaging drive circuit 17 Temporary storage memory DESCRIPTION OF SYMBOLS 18 Image processing part 19 Storage medium part 20 Display part 21 Setting information storage memory part 22 Variable magnification optical system 23 Image sensor 24 CDS / ADC part

Claims (23)

In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and by changing the interval between the lens groups. A variable magnification optical system for performing variable magnification, wherein the distortion satisfies the following condition.
−35 (%) ≦ DTmin ≦ −10 (%)
However, DTmin is the minimum distortion aberration amount (%).   The variable power optical system according to claim 1, wherein the first lens group includes one negative lens. 3. The zoom optical system according to claim 1, wherein the first lens group includes one negative lens, and the negative lens satisfies the following condition.
−4.5 <r1 / fw <−1.0
Here, r1 is the radius of curvature of the most object-side surface of the negative lens constituting the first lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end. The first lens group includes one negative lens, the second lens group includes one positive lens and one negative lens in order from the object side, and the third lens group includes one positive lens. The zoom optical system according to any one of claims 1 to 3, wherein a condition is satisfied.
-5.0 <(r5 + r6) / (r5-r6) <2.0
Where r5 is the radius of curvature of the positive lens in the second lens group on the image side, and r6 is the radius of curvature of the negative lens in the second lens group on the object side. The first lens group includes one negative lens, the second lens group includes one positive lens and one negative lens in order from the object side, and the third lens group includes one positive lens. 4. The variable magnification optical system according to claim 1, wherein the negative lens positioned on the image side of the second lens group satisfies the following condition.
−0.1 <(r6 + r7) / (r6-r7) <5.0
Here, r6 is the radius of curvature of the negative lens of the second lens group on the object side, and r7 is the radius of curvature of the negative lens of the second lens group on the image side. The first lens group includes one negative lens, the second lens group includes one positive lens and one negative lens in order from the object side, and the third lens group includes one positive lens. 6. The variable magnification optical system according to claim 1, wherein both conditions are satisfied.
-5.0 <(r5 + r6) / (r5-r6) <2.0
−0.1 <(r6 + r7) / (r6-r7) <5.0
Where r5 is the radius of curvature of the positive lens in the second lens group on the image side, r6 is the radius of curvature of the negative lens in the second lens group on the object side, and r7 is the radius of curvature of the negative lens in the second lens group on the image side. is there. The variable magnification optical system according to claim 4, wherein the positive lens constituting the second lens group satisfies the following condition.
0.53 ≦ r4 / fw <1.2
Here, r4 is the radius of curvature of the most object side surface of the positive lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end. The variable power optical system according to any one of claims 4 to 7, wherein the negative lens constituting the second lens group satisfies the following condition.
0.1 <r7 / fw ≦ 1.1
Here, r7 is the radius of curvature of the surface closest to the image side of the negative lens constituting the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end. 9. The variable magnification optical system according to claim 1, wherein an Abbe number νd <b> 1 of the negative lens constituting the first lens group satisfies the following condition.
50 <νd1 10. The variable magnification optical system according to claim 1, wherein an Abbe number νd <b> 2 of the positive lens constituting the second lens group satisfies the following condition.
50 <νd2 The variable power optical system according to any one of claims 1 to 10, wherein a refractive index N2P of a positive lens constituting the second lens group satisfies the following condition.
1.5 <N2P   9. The variable magnification optical system according to claim 1, wherein at least one plastic lens is used.   The variable magnification optical system according to any one of claims 1 to 12, wherein the positive lens constituting the third lens group is coated with an infrared cut function.   The zoom optical system according to any one of claims 1 to 13, wherein the third lens group includes one glass lens.   15. The variable magnification optical system according to claim 1, wherein each of the first lens group and the second lens group has at least one glass lens.   16. The variable magnification optical system according to claim 15, wherein the positive lens of the second lens group is made of a glass lens. The variable magnification optical system according to claim 4, wherein the positive lens of the third lens group satisfies the following condition.
0.3 <(r8 + r9) / (r8-r9) <3.0
Where r8 is the radius of curvature of the object side surface of the positive lens of the third lens group, and r9 is the radius of curvature of the image side surface of the positive lens of the third lens group. The variable power optical system according to claim 1, wherein the second lens group satisfies the following condition.
0.8 <f2 / fw <1.6
Here, f2 is the focal length of the second lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end. The variable magnification optical system according to claim 1, wherein the third lens group satisfies the following condition.
1.3 <f3 / fw <4.0
Here, f3 is the focal length of the third lens group, and fw is the focal length of the entire variable magnification optical system at the wide angle end.   The variable power optical system according to claim 1, wherein focusing is performed by moving a negative lens of the first lens group.   The variable magnification optical system according to claim 1, wherein focusing is performed by moving the third lens group.   22. A zoom optical system according to claim 1, an electronic imaging device disposed on an image side of the zoom optical system, and image data captured by the electronic imaging device are electrically processed. An electronic imaging device having an image processing unit that changes its shape. A lens thickness comprising the variable magnification optical system according to any one of claims 1 to 21 and an electronic imaging device disposed on an image side of the variable magnification optical system, and constituting the second lens group. An electronic imaging device characterized in that the sum G2L satisfies the following condition.
0.6 <(G2L) / Y ′ <1.16
However, Y ′ is half the diagonal length of the effective imaging area in the imaging device.

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