JP6155688B2 - Imaging optics - Google Patents

Imaging optics Download PDF

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JP6155688B2
JP6155688B2 JP2013032224A JP2013032224A JP6155688B2 JP 6155688 B2 JP6155688 B2 JP 6155688B2 JP 2013032224 A JP2013032224 A JP 2013032224A JP 2013032224 A JP2013032224 A JP 2013032224A JP 6155688 B2 JP6155688 B2 JP 6155688B2
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lens
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power
image
negative
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JP2014163983A (en
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橋本 雅文
雅文 橋本
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コニカミノルタ株式会社
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  The present invention relates to an imaging optical system, for example, an imaging optical system such as an imaging optical system mounted on a camera (compact digital camera or the like) or a projection optical system mounted on a projector for image projection. is there.
  With the advent of compact digital cameras and mirrorless single-lens cameras, demand for imaging optical systems with short back focus is increasing. Further, in the projection optical system, in order to ensure brightness to every corner of the projection image, the distance from the original image (display screen, etc.) of the projection image to the lens (corresponding to the back focus of the imaging optical system). It is desired to make it shorter.
  Conventionally, a lens arrangement that has been used as an imaging optical system is generally a double Gauss type (see, for example, Patent Documents 1 to 3). However, in the double Gauss type, the back focus tends to be large, and the lens diameter increases because of the symmetrical arrangement. Further, although the aberration performance is good, there is a tendency to lack the amount of peripheral light due to vignetting. For these reasons, it is difficult to say that the lens systems described in Patent Documents 1 to 3 are optimal as a projection optical system.
  In general, the telephoto arrangement is desirable from the viewpoint of securing the peripheral light amount, but the telephoto type makes it difficult to obtain a sufficient angle of view. For this reason, even if it functions as a telephoto imaging lens, the performance as a projection optical system is insufficient (see, for example, Patent Documents 4 and 5). The lens system described in Patent Document 6 has a configuration in which the angle of view is large while being a telephoto type, and the peripheral light amount can be increased. However, since the back focus is too short, the incident angle of the light beam reaching the image plane is large. In particular, it is not suitable as a projection optical system used with a condenser lens, and it is difficult to say that it is a highly versatile optical system.
  Patent Document 7 also describes an optical system for a night vision apparatus having a relatively wide angle with a half angle of view of 20 ° and a short back focus, but the distortion is extremely large. In Patent Document 8, which discloses an optical system for solving such problems, a double Gaussian deformation is eventually used in order to suppress aberrations. Therefore, the aperture efficiency at the periphery is poor and the configuration is not suitable for a projection optical system.
Japanese Unexamined Patent Publication No. Sho 63-316815 JP-A-8-160293 Japanese Patent Laid-Open No. 62-138809 JP 2001-281538 A Japanese Patent Application Laid-Open No. 61-238011 JP 2002-6219 A JP-A-5-249371 JP-A-9-61707
  The present invention has been made in view of the above-described problems, and its purpose is to achieve a wide-angle optical performance equivalent to that of a standard lens while shortening the back focus by adopting a telephoto type power arrangement. It is an object of the present invention to provide an imaging optical system that is favorable and has a sufficient amount of peripheral light and suitable for both an imaging optical system and a projection optical system.
To achieve the above object, the imaging optical system of the first invention is an imaging optical system comprising, in order from the object side, a front group having a positive power, a stop, and a rear group having a negative power. There,
The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and satisfies the following conditional expression (5): It is characterized by.
ndP> 1.85 (1)
vdP> 28 (2)
3 <f / BF <4.3 (3)
2.0 <f1 / f3 <6.0 (5)
However,
ndP: refractive index at d-line,
vdP: Abbe number in the d-line,
f: focal length of the entire system,
BF: Back focus,
f1: focal length of the first lens,
f3: focal length of the third lens,
It is.
An imaging optical system according to a second invention is an imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. It consists of a cemented lens having four lenses and a fifth lens and having negative power, a sixth lens having negative power, and a seventh lens having positive power, and satisfies the following conditional expression (6): To do.
ndP> 1.85 (1)
vdP> 28 (2)
3 <f / BF <4.3 (3)
0.5 <f2 / f6 <4.0 (6)
However,
ndP: refractive index at d-line,
vdP: Abbe number in the d-line,
f: focal length of the entire system,
BF: Back focus,
f2: focal length of the second lens,
f6: focal length of the sixth lens,
It is.
An imaging optical system according to a third invention is an imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
The front group includes, in order from the object side, a positive lens having a convex surface facing at least the object side, a negative lens having a concave surface facing the image side, and a positive lens having a convex surface facing the object side, The rear group, in order from the object side, is a cemented lens composed of at least a negative lens and a positive lens whose convex surface is convex on the object side, a negative lens with a strong concave surface facing the object side, and a convex surface on the image surface side. It is composed of a positive lens with its characterized by Rukoto.
ndP> 1.85 (1)
vdP> 28 (2)
3 <f / BF <4.3 (3)
However,
ndP: refractive index at d-line,
vdP: Abbe number in the d-line,
f: focal length of the entire system,
BF: Back focus,
It is.
An imaging optical system according to a fourth invention is an imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and the first lens has the following conditional expression (11 ) And (12), and the second lens satisfies the following conditional expressions (13) and (14) .
ndP> 1.85 (1)
vdP> 28 (2)
3 <f / BF <4.3 (3)
1.7 <nd1 <1.8 (11)
48 <vd1 <56 (12)
1.53 <nd2 <1.7 (13)
30 <vd2 <47 (14)
However,
ndP: refractive index at d-line,
vdP: Abbe number in the d-line,
f: focal length of the entire system,
BF: Back focus,
nd1: refractive index at the d-line of the first lens,
vd1: Abbe number at the d-line of the first lens,
nd2: refractive index at the d-line of the second lens,
vd2: Abbe number at the d-line of the second lens,
It is.
An image forming optical system according to a fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects , the following conditional expression (4) is satisfied.
1 <TL / f <1.5 (4)
However,
TL: optical total length (including the image plane),
It is.
The imaging optical system according to a sixth aspect of the present invention is the imaging optical system according to any one of the first to fourth aspects, wherein the front group includes, in order from the object side, a first lens having a positive power and a second lens having a negative power. a lens, and a third lens having a positive power, and satisfies the following conditional expression (7).
| (R2B-R3A) / (R2B + R3A) | <0.6 (7)
However,
R2B: Paraxial radius of curvature of the image side surface of the second lens,
R3A: paraxial radius of curvature of the object side surface of the third lens,
It is.
An imaging optical system according to a seventh invention is the imaging optical system according to any one of the first to fourth inventions, wherein the front group has a first lens having positive power and a second power having negative power in order from the object side. a lens, and a third lens having a positive power, the rear group includes, in order from the object side, a junction lens having a negative power and a fourth lens and the fifth lens, and a sixth lens having a negative power And a seventh lens having positive power, and satisfies the following conditional expression (9).
-4.0 <(vd6-vd2) / (vd7-vd1) <0 (9)
However,
vd1: Abbe number at the d-line of the first lens,
vd2: Abbe number at the d-line of the second lens,
vd6: Abbe number of the sixth lens at the d-line,
vd7: Abbe number of the seventh lens at the d-line,
It is.
  According to the present invention, while taking a telephoto type power arrangement, the back focus is shortened, the optical performance is good at a wide angle similar to that of a standard lens, and the peripheral light quantity is sufficiently secured, and the imaging optics An imaging optical system suitable for both the system and the projection optical system can be realized. Then, by using the imaging optical system according to the present invention as an imaging optical system, a projection optical system, etc., in an optical device such as a camera or a projector, the mounted optical device has high performance, high functionality, compactness, etc. Can contribute.
The lens block diagram of 1st Embodiment (Example 1). FIG. 6 is an aberration diagram of Example 1. The lens block diagram of 2nd Embodiment (Example 2). FIG. 6 is an aberration diagram of Example 2. The lens block diagram of 3rd Embodiment (Example 3). FIG. 6 is an aberration diagram of Example 3. The lens block diagram of 4th Embodiment (Example 4). FIG. 6 is an aberration diagram of Example 4. The lens block diagram of 5th Embodiment (Example 5). FIG. 6 is an aberration diagram of Example 5. The lens block diagram of 6th Embodiment (Example 6). FIG. 10 is an aberration diagram of Example 6. The lens block diagram of 7th Embodiment (Example 7). FIG. 10 is an aberration diagram of Example 7. The lens block diagram of 8th Embodiment (Example 8). FIG. 10 is an aberration diagram of Example 8. The lens block diagram of 9th Embodiment (Example 9). FIG. 10 is an aberration diagram of Example 9. The lens block diagram of 10th Embodiment (Example 10). FIG. 10 is an aberration diagram of Example 10. The schematic diagram which shows the schematic structural example of the optical apparatus carrying an imaging optical system.
Hereinafter, the imaging optical system, the optical apparatus, etc. according to the present invention will be described. The imaging optical system according to the present invention includes, in order from the object side, a front group having positive power, a stop, and a rear group having negative power (power: an amount defined by the reciprocal of the focal length. ). The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) It is characterized by doing.
ndP> 1.85 (1)
vdP> 28 (2)
3 <f / BF <4.3 (3)
However,
ndP: refractive index at d-line,
vdP: Abbe number in the d-line,
f: focal length of the entire system,
BF: Back focus,
It is.
  By adopting the telephoto type configuration as described above, it is possible to suppress the fall of the peripheral light amount at a high image height, and to make an imaging optical system effective in both the imaging optical system and the projection optical system. Become. In addition, since at least one of the positive lenses included in the front group satisfies the conditional expressions (1) and (2), it is possible to give appropriate power to the front group while suppressing the occurrence of aberration. If the lower limit of conditional expression (1) is not reached, it is necessary to reduce the radius of curvature of the positive lens in order to obtain the same refractive power, which may deteriorate spherical aberration. On the other hand, if the lower limit of conditional expression (2) is not reached, dispersion becomes too large, and appropriate chromatic aberration correction by the negative lens cannot be performed.
  Conditional expression (3) defines a condition range relating to an appropriate back focus (the distance from the lens final surface to the paraxial image surface is a length in terms of air). By satisfying conditional expression (3), the back focus becomes an appropriate size. If the lower limit of conditional expression (3) is not reached, the back focus becomes long and it becomes difficult to secure the peripheral light amount. If the upper limit of conditional expression (3) is exceeded, the back focus becomes too short, and the sensor (imaging device) or Since there is no room to arrange the structure in front of the display, it lacks versatility.
  According to the above-mentioned characteristic configuration, the telephoto type power arrangement makes the back focus shorter, but the optical performance is good with a wide angle similar to that of a standard lens, and the amount of peripheral light is sufficiently secured. An imaging optical system suitable for both the optical system and the projection optical system can be realized. And, by using the imaging optical system as an imaging optical system, projection optical system, etc. for optical equipment such as cameras and projectors, it contributes to high performance, high functionality, compactness, etc. of the mounted optical equipment. be able to. The conditions for achieving such effects in a well-balanced manner and achieving higher optical performance, downsizing, etc. will be described below.
It is more desirable to satisfy the following conditional expression (1a).
ndP> 1.87 (1a)
The conditional expression (1a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (1). Therefore, preferably, the above-described effect can be further increased by satisfying conditional expression (1a).
It is desirable to satisfy the following conditional expression (4).
1 <TL / f <1.5 (4)
However,
TL: optical total length (including the image plane),
It is.
  Conditional expression (4) defines a preferable condition range regarding the telephoto ratio (optical total length / focal length) (the optical total length is obtained by adding the back focus to the distance from the lens front surface to the lens final surface. ). When this conditional expression (4) is satisfied, the principal point position exists inside the lens system even though it is a telephoto type, so that the lens can be arranged in a symmetrical type such as a Gaussian type. Correction can be performed appropriately. When the lower limit of conditional expression (4) is not reached, the peripheral light amount gradually decreases, and tends to be unsuitable as an imaging optical system. If the upper limit of conditional expression (4) is exceeded, it becomes difficult to handle the upper marginal ray of the entrance pupil, so that it is difficult to suppress flare and there is a risk of deteriorating imaging performance.
The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and satisfies the following conditional expression (5): Is desirable.
2.0 <f1 / f3 <6.0 (5)
However,
f1: focal length of the first lens,
f3: focal length of the third lens,
It is.
  Conditional expression (5) defines a preferable condition range regarding the positive power balance in the front group. Generation of spherical aberration can be effectively suppressed by increasing the power of the third lens in which light beams of any angle of view pass through substantially the same region as compared with the first lens. If the lower limit of conditional expression (5) is not reached, the spherical aberration in the first lens increases and the imaging performance tends to deteriorate. If the upper limit of conditional expression (5) is exceeded, the power of the first lens and the second lens will be reduced, and spherical aberration and chromatic aberration correction in the front group will not be performed properly, which may lead to performance degradation.
The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. It is desirable that the cemented lens including the fourth lens and the fifth lens and having the negative power, the sixth lens having the negative power, and the seventh lens having the positive power satisfy the following conditional expression (6). .
0.5 <f2 / f6 <4.0 (6)
However,
f2: focal length of the second lens,
f6: focal length of the sixth lens,
It is.
  Conditional expression (6) defines a preferable condition range regarding the negative power balance in the entire system. By not providing a large power difference between the second lens and the sixth lens, a negative power balance between the front group and the rear group can be obtained, and chromatic aberration can be corrected appropriately. If the lower limit of conditional expression (6) is not reached, the balance will be lost, making it difficult to design a symmetric type by placing the main plane in the vicinity of the stop, making it impossible to perform appropriate chromatic aberration correction. If the upper limit of conditional expression (6) is exceeded, the negative power of the rear group will increase, so that field curvature and distortion will tend to increase.
The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and satisfies the following conditional expression (7): Is desirable.
| (R2B-R3A) / (R2B + R3A) | <0.6 (7)
However,
R2B: Paraxial radius of curvature of the image side surface of the second lens,
R3A: paraxial radius of curvature of the object side surface of the third lens,
It is.
  Conditional expression (7) defines a preferable condition range related to the shape of the opposing surfaces of the negative lens and the positive lens in the front group. By making the curvature radii of the faces facing each other approximately the same, various aberrations occurring on each face can be canceled. In particular, the image side surface of the second lens and the object side surface of the third lens pass through a region similar to each angle of view, so that various aberration coefficients are greatly affected by changes in shape. Therefore, when the upper limit of conditional expression (7) is exceeded, spherical aberration, coma aberration, and astigmatism tend to increase particularly greatly.
The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. It is preferable that the cemented lens including the fourth lens and the fifth lens have negative power, the sixth lens having negative power, and the seventh lens having positive power, and satisfy the following conditional expression (8). .
| (| R3B |-| R4A |) / (| R3B | + | R4A |) | <0.2 (8)
However,
R3B: paraxial radius of curvature of the image side surface of the third lens,
R4A: Paraxial radius of curvature of the object side surface of the fourth lens,
It is.
  Conditional expression (8) defines a preferable range of conditions related to the shape of the facing surfaces of the front group and the rear group. By making the radii of curvature of the surfaces facing each other across the aperture the same, various aberrations occurring on each surface can be canceled. In particular, the image side surface of the third lens and the object side surface of the fourth lens pass through regions similar to each angle of view, so that various aberration coefficients are greatly affected by changes in shape. Therefore, when the upper limit of conditional expression (8) is exceeded, spherical aberration, coma aberration, and astigmatism tend to increase particularly greatly.
The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. It is preferable that the cemented lens including the four lenses and the fifth lens and having negative power, the sixth lens having negative power, and the seventh lens having positive power satisfy the following conditional expression (9). .
-4.0 <(vd6-vd2) / (vd7-vd1) <0 (9)
However,
vd1: Abbe number at the d-line of the first lens,
vd2: Abbe number at the d-line of the second lens,
vd6: Abbe number of the sixth lens at the d-line,
vd7: Abbe number of the seventh lens at the d-line,
It is.
  Conditional expression (9) defines a preferable condition range regarding the Abbe number of the first, second, sixth and seventh lenses. In the double Gaussian power arrangement composed of the first lens, the second lens, the sixth lens, and the seventh lens, the sixth lens is arranged on the rear group side where the areas of the respective surfaces through which the light flux passes at each angle of view are dispersed. By increasing the Abbe number difference with the seventh lens, it is possible to adopt a configuration in which the front group is not burdened with chromatic aberration. If the upper limit of conditional expression (9) is exceeded, the light beam passage position differs greatly for each angle of view, making it difficult to correct lateral chromatic aberration using the merit that the various aberrations are not easily affected by the lens shape. . If the lower limit of conditional expression (9) is not reached, an appropriate Abbe number difference cannot be given, and the chromatic aberration of magnification tends to increase.
  It is desirable that the lens located adjacent to the stop is a cemented lens. If the lens positioned adjacent to the stop is a cemented lens, the region through which the light flux of each angle of view passes does not differ greatly, so that it becomes easier to correct aberrations.
  It is desirable that the arrangement of the front group is a triplet type. By adopting a triplet lens arrangement in the front group that gains positive power, it is possible to make it easy to correct not only positive power but also aberration.
  In order from the object side, the front group has a positive lens (first lens) with a convex surface facing at least the object side, a negative lens (second lens) with a concave surface facing the image side, and a convex surface facing the object side. A negative lens (fourth lens) and a positive lens (fifth lens) in which at least the cemented surface is convex on the object side in order from the object side. A cemented lens composed of a lens), a negative lens (sixth lens) with a strong concave surface facing the object side, and a positive lens (seventh lens) with a convex surface facing the image surface side. .
  In the first lens and the third lens, the occurrence of spherical aberration is suppressed by directing a gentle convex surface toward the object side. Further, since there is an image-side concave surface of the second lens, there is no abrupt declination on the object side surface of the second lens. As a result, this also suppresses the occurrence of spherical aberration and chromatic aberration. Since the cemented surface is convex on the object side, the chromatic aberration is more strongly corrected with respect to ambient light, reducing the role of aberration correction in the sixth lens and the seventh lens, which is impossible and expensive. The effect of eliminating the need to use glass is obtained. The sixth lens has a strong concave surface on the object side to cancel the curvature of field (Petzbar sum) generated in the front group, and the seventh lens has a convex surface on the image side to suppress the occurrence of distortion. it can.
It is desirable to satisfy the following conditional expression (10).
−0.5 <fF / fR <−0.1 (10)
However,
fF: focal length of the front group,
fR: focal length of rear group,
It is.
  By adopting a configuration that satisfies the conditional expression (10), it is possible to arrange the main plane in the vicinity of the stop while shortening the back focus. Accordingly, a lens configuration that enables appropriate aberration correction can be obtained. If the lower limit of conditional expression (10) is not reached, both the front group and rear group powers become too strong, making it difficult to correct lateral chromatic aberration. If the upper limit of conditional expression (10) is exceeded, the principal plane is closer to the object side, so that it becomes difficult to correct the aberration of the lower marginal ray of the entrance pupil. For this reason, imaging performance deteriorates.
The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and the first lens has the following conditional expression (11 ) And (12) are satisfied, and the second lens preferably satisfies the following conditional expressions (13) and (14).
1.7 <nd1 <1.8 (11)
48 <vd1 <56 (12)
1.53 <nd2 <1.7 (13)
30 <vd2 <47 (14)
However,
nd1: refractive index at the d-line of the first lens,
vd1: Abbe number at the d-line of the first lens,
nd2: refractive index at the d-line of the second lens,
vd2: Abbe number at the d-line of the second lens,
It is.
  When the refractive index of the first lens with positive power falls below the lower limit of the conditional expression (11), or when the refractive index of the second lens with negative power exceeds the upper limit of the conditional expression (13), the load of power becomes the third lens. In the third lens, many aberrations including spherical aberration increase. Further, when the refractive index of the first lens having the positive power exceeds the upper limit of the conditional expression (11) or the refractive index of the second lens having the negative power is lower than the lower limit of the conditional expression (13), the chromatic aberration is appropriately corrected. Difficult to do.
  If the Abbe number of the first lens with positive power falls below the lower limit of the conditional expression (12) or the Abbe number of the second lens with negative power exceeds the upper limit of the conditional expression (14), a spherical surface is used to correct the dispersion. Aberrations and field curvature may be deteriorated. Conversely, when the Abbe number of the first lens with positive power exceeds the upper limit of the conditional expression (12) or the Abbe number of the second lens with negative power falls below the lower limit of the conditional expression (14), an appropriate Abbe number is obtained. It becomes difficult to obtain the difference, and chromatic aberration correction becomes difficult.
  Since the imaging optical system according to the present invention can achieve both shortening of the back focus and widening and high performance, an optical device with an image input function (compact digital camera, mirrorless single-lens camera, smartphone (high function It is suitable for both an imaging optical system for a mobile phone) and the like and a projection optical system for an optical device (projector or the like) with an image projection function. For example, in the case of an imaging optical system, an imaging optical device that optically captures an image of a subject and outputs it as an electrical signal can be configured in combination with an imaging element or the like. In the case of a projection optical system, a projection optical apparatus that enlarges and projects a display image of the image display element on a screen surface can be configured by combination with an image display element or the like. When the imaging optical system is used as a projection optical system, the screen surface originally corresponds to the image surface and the image display surface corresponds to the object surface, but the configuration of the imaging optical system itself is described in a unified manner. The projection optical system is also regarded as a reduction system, and the screen surface side (enlarged conjugate side) is the object side, and the image display surface side (reduced conjugate side) is the image side.
  The imaging optical device is an optical device that constitutes a main component of a camera used for still image shooting and moving image shooting of a subject. For example, imaging optics that forms an optical image of an object in order from the object (ie, subject) side. And an imaging device that converts an optical image formed by the imaging optical system into an electrical signal. In addition, the imaging optical system having the above-described characteristic configuration is arranged so that the optical image of the subject is formed on the light receiving surface (that is, the imaging surface) of the imaging device, thereby achieving high performance at a small size and low cost. It is possible to realize an imaging optical device having the above and a digital device including the same.
  Examples of optical equipment with an image input function include cameras such as digital cameras, video cameras, cinema cameras, surveillance cameras, security cameras, in-vehicle cameras, aircraft cameras, videophone cameras, personal computers, and mobile phones. Built in terminals (for example, mobile devices such as mobile phones, smartphones, mobile computers, etc.), peripheral devices (scanners, printers, etc.), other digital devices (drive recorders, defense equipment, etc.) An external camera can be mentioned. As can be seen from these examples, it is possible not only to configure a camera by using an imaging optical device, but also to add a camera function by mounting the imaging optical device on various devices. For example, a digital device having an image input function such as a camera-equipped mobile phone or a camera-equipped projector can be configured.
  As an example of an optical device with an image input function, FIG. 21A shows a schematic configuration example of a digital device DU in a schematic cross section. The imaging optical device LU mounted on the digital device DU shown in FIG. 21A sequentially forms an optical image system LN (AX: AX) that forms an optical image (image plane) IM of the object. An optical axis), a plane parallel plate PT (a cover glass of the image sensor SR; corresponding to an optical filter such as an optical low-pass filter and an infrared cut filter arranged as necessary), and an imaging optical system LN. And an imaging element SR that converts the optical image IM formed on the light receiving surface (imaging surface) SS into an electrical signal. When a digital device DU with an image input function is constituted by this imaging optical device LU, the imaging optical device LU is usually arranged inside the body, but when necessary to realize the camera function, a form as necessary is adopted. Is possible. For example, the unitized imaging optical device LU can be configured to be detachable or rotatable with respect to the main body of the digital device DU.
  The imaging optical system LN is a single-focus lens including, in order from the object side, a front group having positive power, a stop, and a rear group having negative power. As described above, the light receiving surface of the image sensor SR. An optical image IM is formed on the SS. As the image sensor SR, for example, a solid-state image sensor such as a CCD (Charge Coupled Device) type image sensor having a plurality of pixels or a CMOS (Complementary Metal-Oxide Semiconductor) type image sensor is used. Since the imaging optical system LN is provided so that the optical image IM of the subject is formed on the light receiving surface SS which is the photoelectric conversion unit of the image sensor SR, the optical image IM formed by the imaging optical system LN. Is converted into an electrical signal by the image sensor SR.
  The digital device DU includes a signal processing unit 1, a control unit 2, a memory 3, an operation unit 4, a display unit 5 and the like in addition to the imaging optical device LU. The signal generated by the image sensor SR is subjected to predetermined digital image processing, image compression processing, and the like in the signal processing unit 1 as necessary, and recorded as a digital video signal in the memory 3 (semiconductor memory, optical disc, etc.) In some cases, it is transmitted to other devices via a cable or converted into an infrared signal or the like (for example, a communication function of a mobile phone). The control unit 2 is composed of a microcomputer, and controls functions such as shooting functions (still image shooting function, movie shooting function, etc.) and image playback functions; focusing, lens movement mechanism control for camera shake correction, etc. Do it. For example, the control unit 2 controls the imaging optical device LU so as to perform at least one of still image shooting and moving image shooting of a subject. The display unit 5 includes a display such as a liquid crystal monitor, and performs image display using an image signal converted by the image sensor SR or image information recorded in the memory 3. The operation unit 4 is a part including operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by the operator to the control unit 2.
  As an example of an optical apparatus with an image projection function, FIG. 21B shows a schematic configuration example of a projector PJ in a schematic cross section. The projector PJ shown in FIG. 21 (B) applies the imaging optical system LN as a projection optical system, and includes a light source 12, an illumination optical system 13, an image display element 14, a control unit 15, an actuator 16, and imaging optics. A system LN, a prism PR, and the like are provided. That is, the image display element 14 that displays the image IM, the light source 12, the illumination optical system 13 that guides the light from the light source 12 to the image display element 14, and the image IM displayed on the image display element 14 are displayed on the screen surface 11. And an imaging optical system LN as a projection optical system for enlarging and projecting.
  The control unit 15 is a part that performs overall control of the projector PJ. The image display element 14 is an image modulation element (for example, a digital micromirror device) that modulates light to generate an image IM, and a cover glass CG is provided on an image display surface that displays the image IM. ing. The imaging optical system LN is a single-focus lens including, in order from the object side, a front group having positive power, a stop, and a rear group having negative power, and displays on the image display element 14 as described above. The enlarged image IM is projected onto the screen surface 11 in an enlarged manner. An actuator 16 is connected to the lens that moves for focusing or the like in the imaging optical system LN, for example, to the enlargement conjugate side or the reduction conjugate side along the optical axis AX. A controller 15 is connected to the actuator 16 in order to control the movement of the moving lens. The control unit 15 and the actuator 16 may be moved manually without using them.
  Light emitted from the light source 12 (for example, a white light source such as a xenon lamp or a laser light source) is guided to the image display element 14 by the illumination optical system 13 and the prism PR, and the image display element 14 forms image light. The prism PR is composed of, for example, a TIR prism (other color separation / combination prism or the like), and performs separation of illumination light and projection light. The image light formed by the image display element 14 is projected toward the screen surface 11 by the imaging optical system LN. That is, the image IM displayed on the image display element 14 is enlarged and projected on the screen surface 11 by the imaging optical system LN.
  1, 3, 5,..., 17, and 19 show first to tenth embodiments of the imaging optical system LN in an infinitely focused state in optical cross sections. The imaging optical system LN of the first to tenth embodiments includes, in order from the object side, a front group GrF having a positive power, a stop (aperture stop) ST, and a rear group GrR having a negative power. ing. The front group GrF is composed of, in order from the object side, a first lens L1 having positive power, a second lens L2 having negative power, and a third lens L1 having positive power. In order from the object side, a cemented lens L45 having negative power (consisting of a fourth lens L4 having negative power and a fifth lens L5 having positive power), and a sixth lens L6 having negative power. And a seventh lens L7 having positive power.
  In the first to tenth embodiments, since the front group GrF has a triplet configuration, it is possible to cover the positive power of the entire system while suppressing the occurrence of various aberrations and ensuring brightness. In the rear group GrR, it is possible to appropriately correct the lateral chromatic aberration by providing a cemented lens where the optical paths of the light flux for each angle of view are separated. Although the power balance is a telephoto type, the lens arrangement as a whole is close to orthometa, so it is possible to have good imaging performance while reducing the back focus and securing the peripheral light quantity. .
  Hereinafter, the configuration of the imaging optical system embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 10 (EX1 to 10) listed here are numerical examples corresponding to the first to tenth embodiments, respectively, and are lens configuration diagrams representing the first to tenth embodiments. (FIG. 1, FIG. 3, FIG. 5,..., FIG. 17, FIG. 19) respectively show the lens cross-sectional shape, lens arrangement, and the like of the corresponding Examples 1 to 10.
  In the construction data of each embodiment, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the axial top surface distance d (mm), the refractive index nd with respect to the d line (wavelength: 587.56 nm), The Abbe number vd regarding the d line is shown. In Table 1, as various data, the focal length of the entire system (f, mm), the focal length of the front group GrF (fF, mm), the focal length of the rear group GrR (fR, mm), and the focal length of the first lens L1. (F1, mm), focal length (f2, mm) of the second lens L2, focal length (f3, mm) of the third lens L3, focal length (f45, mm) of the cemented lens L45, focal point of the sixth lens L6 Distance (f6, mm), focal length of the seventh lens L7 (f7, mm), optical total length (TL, mm), F number (Fno), half angle of view (ω, °), maximum image height (Y ′, mm). Table 2 shows values corresponding to the conditional expressions of the respective examples. The optical total length TL is obtained by adding a back focus (a length in terms of the distance from the lens final surface to the paraxial image surface in air) to the distance from the lens front surface to the lens final surface.
  2, 4, 6,..., 18, and 20 are aberration diagrams corresponding to Examples 1 to 10 (EX 1 to 10), respectively, (A) is a spherical aberration diagram, and (B) is a non-aberration diagram. Point aberration diagram, (C) is a distortion diagram. The spherical aberration diagram shows a spherical aberration amount at a design reference wavelength of 550 nm indicated by a solid line, a spherical aberration amount at a wavelength of 450 nm indicated by a dashed line, and a spherical aberration amount at a wavelength of 650 nm indicated by a broken line, respectively, in the optical axis AX direction from the paraxial image plane. The vertical axis represents a value obtained by normalizing the incident height to the pupil by the maximum height (that is, the relative pupil height). In the astigmatism diagram, the broken line T represents the tangential image plane at the design reference wavelength of 550 nm, and the solid line S represents the sagittal image plane at the design reference wavelength of 550 nm as a deviation amount (mm) in the optical axis AX direction from the paraxial image plane. The vertical axis represents the half angle of view ω (ANGLE, °). In the distortion diagram, the horizontal axis represents the distortion (%) at the design reference wavelength 550 nm, and the vertical axis represents the half angle of view ω (ANGLE, °). Note that the maximum value of the half field angle ω corresponds to the maximum image height Y ′ on the image plane IM (half the diagonal length of the light receiving surface SS of the image sensor SR).
  In the imaging optical system LN (FIG. 1) of Example 1, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is an object. The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is located on the object side. It is a concave negative meniscus lens, and the seventh lens L7 is a biconvex positive lens.
  In the imaging optical system LN (FIG. 3) of Example 2, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is both The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is concave negative on the object side. It is a meniscus lens, and the seventh lens L7 is a biconvex positive lens.
  In the imaging optical system LN (FIG. 5) of Example 3, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is an object. The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is a biconcave lens. It is a negative lens, and the seventh lens L7 is a biconvex positive lens.
  In the imaging optical system LN (FIG. 7) of Example 4, the first lens L1 is a positive meniscus lens convex toward the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is both The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is concave negative on the object side. The seventh lens L7 is a positive meniscus lens convex to the image side.
  In the imaging optical system LN (FIG. 9) of Example 5, the first lens L1 is a biconvex positive lens, the second lens L2 is a biconcave negative lens, and the third lens L3 is a biconvex positive lens. The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is a biconcave negative lens. Seven lens L7 is a biconvex positive lens.
  In the imaging optical system LN (FIG. 11) of Example 6, the first lens L1 is a positive meniscus lens convex toward the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is both The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is concave negative on the object side. The seventh lens L7 is a positive meniscus lens convex to the image side.
  In the imaging optical system LN (FIG. 13) of the seventh embodiment, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is both The cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is concave negative on the object side. The seventh lens L7 is a positive meniscus lens convex to the image side.
  In the imaging optical system LN (FIG. 15) of Example 8, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is an object. The cemented lens L45 is a negative lens composed of a negative meniscus fourth lens L4 concave on the image side and a biconvex positive fifth lens L5, and the sixth lens L6 is a positive meniscus lens convex to the side. The negative meniscus lens is concave on the object side, and the seventh lens L7 is a positive meniscus lens convex on the image side.
  In the imaging optical system LN (FIG. 17) of Example 9, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a biconcave negative lens, and the third lens L3 is both The cemented lens L45 is a negative lens composed of a negative meniscus fourth lens L4 concave on the image side and a positive meniscus fifth lens L5 convex on the object side, and the sixth lens L6 is a convex positive lens. The negative meniscus lens is concave on the object side, and the seventh lens L7 is a positive meniscus lens convex on the image side.
  In the imaging optical system LN (FIG. 19) of Example 10, the first lens L1 is a positive meniscus lens convex on the object side, the second lens L2 is a negative meniscus lens concave on the image side, and the third lens. L3 is a positive meniscus lens convex on the object side, the cemented lens L45 is a negative lens composed of a biconcave negative fourth lens L4 and a biconvex positive fifth lens L5, and the sixth lens L6 is The negative meniscus lens is concave on the object side, and the seventh lens L7 is a positive meniscus lens convex on the image side.
  Since each of Examples 1 to 10 has the triplet configuration of the front group GrF, the generation of various aberrations is suppressed, and the positive power of the entire system is covered while ensuring the brightness. In the rear group GrR, since the cemented lens is provided where the optical path of the luminous flux for each angle of view is separated, the lateral chromatic aberration is corrected well. Further, although the power balance is a telephoto type, since the lens arrangement as a whole is an arrangement close to orthometa, good imaging performance is obtained while securing a peripheral light quantity with a short back focus.
Example 1
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 35.3449 5.2907 1.77250 49.62
2 70.6081 4.5113
3 -1043.9374 2.0000 1.54814 45.82
4 28.0619 2.9266
5 27.6194 8.3586 1.91082 35.25
6 623.9879 0.8849
7 (Aperture) ∞ 2.7746
8 -132.4832 7.5769 1.84666 23.78
9 16.9415 13.0421 1.74400 44.90
10 -85.2221 9.7353
11 -16.3737 2.0000 1.51680 64.20
12 -2271.7618 0.2000
13 1011.1371 10.7090 1.90366 31.32
14 -39.9345 19.5820
Image plane ∞ 0.0000
Example 2
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 32.9200 5.1800 1.77250 49.62
2 75.0630 4.5300
3 -138.3600 2.0000 1.54814 45.82
4 29.8270 3.0500
5 33.0860 5.1000 1.91082 35.25
6 -197.3000 0.0200
7 (Aperture) ∞ 3.2400
8 -152.2600 11.0000 1.84666 23.78
9 18.9500 13.8200 1.74400 44.90
10 -119.4690 9.7700
11 -17.9900 2.0000 1.51680 64.20
12 -3880.6000 0.3800
13 684.3600 9.9000 1.90366 31.32
14 -44.9840 19.5584
Image plane ∞ 0.0000
Example 3
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 41.6506 4.3223 1.77250 49.62
2 64.5928 5.2754
3 -186.5985 2.0000 1.54814 45.82
4 70.1255 2.6622
5 30.0538 11.0000 1.91082 35.25
6 667.9310 0.5527
7 (Aperture) ∞ 2.8573
8 -100.5697 7.1222 1.84666 23.78
9 16.8008 10.0258 1.74400 44.90
10 -75.0155 9.2895
11 -15.0927 3.7223 1.51680 64.20
12 977.3654 0.2000
13 550.6033 10.9804 1.90366 31.32
14 -39.8821 19.5849
Image plane ∞ 0.0000
Example 4
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 34.6422 5.7613 1.77250 49.62
2 95.3402 4.6884
3 -111.9316 2.0000 1.63980 34.57
4 25.5575 3.1155
5 28.3433 6.9318 1.90366 31.32
6 -127.5819 0.8216
7 (Aperture) ∞ 2.7485
8 -156.2470 8.1378 1.80518 25.46
9 15.2641 13.5251 1.74400 44.90
10 -331.6985 11.1455
11 -15.8418 2.0000 1.48749 70.45
12 -61.4038 0.2000
13 -223.6692 8.9345 1.90366 31.32
14 -41.3453 19.5838
Image plane ∞ 0.0000
Example 5
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 155.1921 3.5615 1.72916 54.67
2 -775.9872 3.3753
3 -99.7608 2.0000 1.54814 45.82
4 100.9553 0.7615
5 29.6758 11.0000 1.91082 35.25
6 -861.7677 0.4771
7 (Aperture) ∞ 3.0506
8 -70.2299 11.0000 1.84666 23.78
9 18.5221 11.0885 1.74400 44.90
10 -58.5669 9.1836
11 -15.7476 3.3116 1.51680 64.20
12 324.8119 0.2000
13 249.5775 11.0000 1.90366 31.32
14 -47.4096 19.9900
Image plane ∞ 0.0000
Example 6
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 38.5015 5.1575 1.77250 49.62
2 92.2359 4.9194
3 -95.4456 2.0000 1.54814 45.82
4 26.4720 3.0760
5 28.9077 10.2605 1.91082 35.25
6 -127.1202 -0.0759
7 (Aperture) ∞ 3.2640
8 -82.2886 2.9531 1.84666 23.78
9 21.3846 10.7062 1.74400 44.90
10 -86.4334 16.7099
11 -15.9932 2.0000 1.51680 64.20
12 -55.7454 0.2000
13 -102.7786 8.8393 1.90366 31.32
14 -35.7502 19.9900
Image plane ∞ 0.0000
Example 7
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 40.2762 4.4023 1.77250 49.62
2 79.1505 5.0246
3 -76.4616 2.0000 1.54814 45.82
4 32.7380 2.8964
5 35.3451 8.2471 1.91082 35.25
6 -78.9344 -0.4922
7 (Aperture) ∞ 3.2773
8 -49.8876 2.0440 1.84666 23.78
9 29.1169 9.4560 1.74400 44.90
10 -74.8935 24.0954
11 -18.7125 2.0000 1.51680 64.20
12 -51.6408 0.2060
13 -571.9936 6.8531 1.90366 31.32
14 -65.4153 19.9900
Image plane ∞ 0.0000
Example 8
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 33.7297 5.2448 1.77250 49.62
2 67.4782 4.7303
3 -245.8809 2.0000 1.54814 45.82
4 24.3321 3.1577
5 26.4109 8.0975 1.91082 35.25
6 341.0720 0.3002
7 (Aperture) ∞ 0.9224
8 281.7845 11.0000 1.84666 23.78
9 14.9594 11.6589 1.74400 44.90
10 -5088.6919 11.1229
11 -15.0960 2.0000 1.51680 64.20
12 -54.8397 0.2000
13 -175.8000 9.5754 1.90366 31.32
14 -37.1343 19.9900
Image plane ∞ 0.0000
Example 9
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 34.0501 6.2239 1.77250 49.62
2 89.3201 5.2302
3 -97.0020 2.0000 1.60342 38.01
4 22.5883 3.4864
5 27.4401 13.1941 1.91082 35.25
6 -103.3140 0.0130
7 (Aperture) ∞ 3.3094
8 304.1112 2.0000 1.76182 26.61
9 14.5000 11.5362 1.63854 55.45
10 109.8628 11.6098
11 -14.9028 2.0000 1.48749 70.45
12 -35.3861 0.2000
13 -106.5011 9.2071 1.90366 31.32
14 -34.4712 19.9900
Image plane ∞ 0.0000
Example 10
Unit: mm
Surface data surface number rd nd vd
Object ∞ ∞
1 31.8887 5.4441 1.77250 49.62
2 57.8337 4.3959
3 247.9907 2.0000 1.68893 31.16
4 30.8533 2.3110
5 24.2585 6.2591 1.91082 35.25
6 184.9313 2.0199
7 (Aperture) ∞ 2.9467
8 -74.1578 4.6702 1.80518 25.46
9 15.0127 8.6504 1.72342 37.99
10 -59.0282 8.9329
11 -13.9332 4.6167 1.48749 70.45
12 -89.0266 0.2000
13 -356.8415 11.0000 1.91082 35.25
14 -42.1462 19.9900
Image plane ∞ 0.0000
DU digital equipment (optical equipment)
LU imaging optical device LN imaging optical system (imaging optical system, projection optical system)
GrF Front group GrR Rear group L1 to L7 First to seventh lenses L45 Joint lens ST Aperture (aperture stop)
SR Image sensor SS Light-receiving surface (imaging surface)
IM image plane (optical image, image)
AX Optical axis 1 Signal processing unit 2 Control unit 3 Memory 4 Operation unit 5 Display unit PJ Projector (optical equipment)
11 Screen surface 12 Light source 13 Illumination optical system 14 Image display element 15 Control unit 16 Actuator PR Prism

Claims (7)

  1. An imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
    The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
    The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and satisfies the following conditional expression (5): An imaging optical system characterized by:
    ndP> 1.85 (1)
    vdP> 28 (2)
    3 <f / BF <4.3 (3)
    2.0 <f1 / f3 <6.0 (5)
    However,
    ndP: refractive index at d-line,
    vdP: Abbe number in the d-line,
    f: focal length of the entire system,
    BF: Back focus,
    f1: focal length of the first lens,
    f3: focal length of the third lens,
    It is.
  2.   An imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
      The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
      The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. It consists of a cemented lens having four lenses and a fifth lens and having negative power, a sixth lens having negative power, and a seventh lens having positive power, and satisfies the following conditional expression (6): Imaging optical system;
    ndP> 1.85 (1)
    vdP> 28 (2)
    3 <f / BF <4.3 (3)
    0.5 <f2 / f6 <4.0 (6)
      However,
    ndP: refractive index at d-line,
    vdP: Abbe number in the d-line,
    f: focal length of the entire system,
    BF: Back focus,
    f2: focal length of the second lens,
    f6: focal length of the sixth lens,
    It is.
  3.   An imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
      The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
      The front group includes, in order from the object side, a positive lens having a convex surface facing at least the object side, a negative lens having a concave surface facing the image side, and a positive lens having a convex surface facing the object side, The rear group, in order from the object side, is a cemented lens composed of at least a negative lens and a positive lens whose convex surface is convex on the object side, a negative lens with a strong concave surface facing the object side, and a convex surface on the image surface side. An imaging optical system characterized by comprising a positive lens directed toward the surface;
    ndP> 1.85 (1)
    vdP> 28 (2)
    3 <f / BF <4.3 (3)
      However,
    ndP: refractive index at d-line,
    vdP: Abbe number in the d-line,
    f: focal length of the entire system,
    BF: Back focus,
    It is.
  4.   An imaging optical system comprising, in order from the object side, a front group having positive power, a stop, and a rear group having negative power,
      The half angle of view ω is 22.5 ° or more, and at least one of the positive lenses included in the front group satisfies the following conditional expressions (1) and (2), and further satisfies the following conditional expression (3) And
      The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and the first lens has the following conditional expression (11 ) And (12), and the second lens satisfies the following conditional expressions (13) and (14):
    ndP> 1.85 (1)
    vdP> 28 (2)
    3 <f / BF <4.3 (3)
    1.7 <nd1 <1.8 (11)
    48 <vd1 <56 (12)
    1.53 <nd2 <1.7 (13)
    30 <vd2 <47 (14)
      However,
    ndP: refractive index at d-line,
    vdP: Abbe number in the d-line,
    f: focal length of the entire system,
    BF: Back focus,
    nd1: refractive index at the d-line of the first lens,
    vd1: Abbe number at the d-line of the first lens,
    nd2: refractive index at the d-line of the second lens,
    vd2: Abbe number at the d-line of the second lens,
    It is.
  5. The imaging optical system according to any one of claims 1 to 4, wherein the following conditional expression (4) is satisfied:
    1 <TL / f <1.5 (4)
    However,
    TL: optical total length (including the image plane),
    It is.
  6. The front group includes, in order from the object side, a first lens having positive power, a second lens having negative power, and a third lens having positive power, and satisfies the following conditional expression (7): The imaging optical system according to any one of claims 1 to 4, wherein
    | (R2B-R3A) / (R2B + R3A) | <0.6 (7)
    However,
    R2B: Paraxial radius of curvature of the image side surface of the second lens,
    R3A: paraxial radius of curvature of the object side surface of the third lens,
    It is.
  7. The front group includes, in order from the object side, a first lens having a positive power, a second lens having a negative power, and a third lens having a positive power. features and junction lens having a negative power consists of four lenses and a fifth lens, and a sixth lens having a negative power, composed of a seventh lens having a positive power, by satisfying the following conditional expression (9) The imaging optical system according to any one of claims 1 to 4 ;
    -4.0 <(vd6-vd2) / (vd7-vd1) <0 (9)
    However,
    vd1: Abbe number at the d-line of the first lens,
    vd2: Abbe number at the d-line of the second lens,
    vd6: Abbe number of the sixth lens at the d-line,
    vd7: Abbe number of the seventh lens at the d-line,
    It is.
JP2013032224A 2013-02-21 2013-02-21 Imaging optics Active JP6155688B2 (en)

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JPS62173417A (en) * 1986-01-27 1987-07-30 Canon Inc Switching type variable power optical system
JPH04217219A (en) * 1990-12-19 1992-08-07 Olympus Optical Co Ltd Zoom lens
JPH05173063A (en) * 1991-12-25 1993-07-13 Minolta Camera Co Ltd Photographic lens
JP2005352060A (en) * 2004-06-09 2005-12-22 Fujinon Corp Small-size wide-angle lens with large aperture and camera equipped with same
JP2007156385A (en) * 2005-06-15 2007-06-21 Olympus Imaging Corp Zoom optical system and image taking apparatus using the same
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