JP2009223251A - Image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image pickup apparatus equipped with a small photographic optical system particularly suiting a wide field-of-view system without generating large negative distortion. <P>SOLUTION: The image pickup apparatus has the photographic optical system, and an electronic image pickup element, and it satisfies an equation 1 of -1.73<IH/EXP<-0.65, and an equation 2 of 0.50<TH/TC<1 wherein EXP is a position P of an exit pupil of the photographic optical system, IH is half of a diagonal length of the image pickup element, TH is collection efficiency with respect to a main beam from a center of the image pickup element to a position of IH, and TC is collection efficiency with respect to vertical incident light on an optical axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus.

Conventionally, in a photographic lens compatible with a silver salt film camera, it is effective to reduce the incident angle of the off-axis light flux on the film in order to reduce the size of the wide-angle lens. It is also known that negative distortion is generated in order to compensate for the insufficient light quantity due to the COS (cosine) fourth law. Furthermore, the device corresponding to the electronic image sensor is required to make the incident angle of the off-axis light beam on the imaging surface close to vertical. For this reason, a method has been proposed in which negative distortion is generated, the lens is made small, and the distortion is corrected by image processing. In addition, regarding the downsizing of the taking lens without taking the image sensor into consideration, many proposals have been made without taking the image sensor into consideration.
On the other hand, regarding an image sensor, a proposal has been made to use a gradient index lens for an on-chip lens.
As an image processing method, it has been proposed to improve the sensitivity by adding outputs of adjacent pixels, that is, to increase the sensitivity.

JP 2006-351972 A JP 2005-266129 A JP 2006-54526 A JP 2006-330675 A "A MOS Image Sensor with Microlenses Built by Sub-Wavelength Patterning", ISSCC 2007 / SESSION 28 / IMAGE SENSORS / 28.8

  By combining the photographing optical system and the electronic image sensor, it is possible to combine the light collecting action of the photographing optical system and the image processing for reproducing the image of the subject. Further, in order to promote downsizing particularly in a photographing optical system having a wide angle of view, it is effective to bring the position of the exit pupil closer to the imaging surface. However, if the position of the exit pupil is brought close to the image plane, there is a problem in that the peripheral light amount is insufficient in the peripheral portion of the imaging surface and the image quality is deteriorated.

  Conventionally, negative distortion (distortion aberration) is generated, the peripheral light amount is increased, and the distortion aberration is corrected by image processing. In this case, there has been a problem that the resolution of the peripheral portion for correcting distortion of the shape of the subject is reduced. In addition, there is an inefficiency that a part of the image data projected on the image sensor cannot be used. There is also a problem that the exit pupil position cannot be brought close enough to the image plane in order to generate negative distortion.

  The present invention has been made in view of the above, and an object of the present invention is to provide an imaging apparatus including a small photographic optical system particularly suitable for a wide-angle system without generating a large negative distortion. More specifically, an object of the present invention is to provide an image pickup apparatus including a small photographic optical system that does not assume correction of distortion with respect to peripheral light quantity. Alternatively, an object of the present invention is to provide an imaging apparatus including a small imaging optical system that generates positive distortion and secures peripheral resolution.

In order to solve the above-described problems and achieve the object, an imaging apparatus according to the present invention includes an imaging optical system and an electronic imaging device, and satisfies the following conditional expression.
-1.73 <IH / EXP <-0.65 (1)
0.50 <TH / TC <1 (2)
here,
EXP is the position of the exit pupil of the photographic optical system,
IH is half the diagonal length of the image sensor,
TH The light collection efficiency for the chief ray at the IH position from the center of the image sensor,
TC is the light collection efficiency for vertically incident light on the optical axis,
It is.

In the above imaging apparatus, the imaging element satisfies the following conditional expression.
5000 <N × FN <45000 (3)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
FN is Fno of the photographic optical system,
It is.

  In the imaging apparatus, the on-chip lens of the imaging element is a refractive index distribution type lens, and the refractive index distribution lens has a structure divided by a line width that is approximately equal to or shorter than the wavelength of incident light. It is configured.

  In the imaging apparatus, the on-chip lens of the imaging element is sufficiently larger than the wavelength of incident light, is macroscopically substantially planar, and the entire imaging surface is a single plane or curved surface. To do.

In the above imaging apparatus, only air is provided between the imaging optical system and the imaging element, and an interval between the imaging optical system and the imaging element satisfies the following conditions.
0.1 <(fb / IH) / FN <0.3 (4)
here,
fb is back focus,
IH is half the diagonal length of the image sensor,
FN is Fno of the photographic optical system,
It is.

  In the imaging apparatus, a surface treatment having an infrared cut function is applied to a lens group having a convex surface directed toward the image surface on the image side from the stop of the photographing optical system.

  In the imaging apparatus described above, a surface treatment having an infrared cut function is applied to a lens group having a concave surface directed toward the object-side image surface from the stop of the photographing optical system.

  In the above imaging device, an infrared cut filter function is provided between the on-chip lens and the photoelectric conversion surface of the imaging element.

  In the imaging apparatus, the photographing optical system has a low-pass filter function.

In the above imaging apparatus, the image side surface of the imaging optical system and the on-chip lens surface of the imaging element are adjacent to each other, and satisfy the following conditional expression.
2300 <N (5)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
It is.

In the imaging apparatus, the shape of the final surface of the photographing optical system through which the light beam incident on the maximum image height of the photographing optical system passes is a part of a convex surface with respect to the image surface, and satisfies the following conditional expression: It is characterized by doing.
-1.5 <IH / PR <-0.1 (6)
here,
IH is half the diagonal length of the image sensor,
PR is the local curvature radius of the surface normal at any position incident on the maximum image height of the final surface of the imaging optical system.

In the above imaging apparatus, the photographing optical system includes, in order from the subject side, a positive front group, a diaphragm, and a rear group having a lens having a positive power. The shape of the final surface of the photographing optical system that passes through is a part of the convex surface with respect to the image surface, and satisfies the following conditional expression.
-1.5 <IH / PR <-0.1 (6)
0.8 <(1 / (fall + EXP) -1 / fr) <6 (7)
here,
IH is half the diagonal length of the image sensor,
PR is the local curvature radius of the surface normal at any position incident on the maximum image height of the final surface of the imaging optical system,
fall is the overall focal length of the photographic optical system,
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the rear group,
It is.

In the above imaging apparatus, the photographing optical system includes at least an aperture and a rear group in order from the subject side, and satisfies the following conditional expression.
-3.5 <fall / EXP <-0.5 (8)
-2 <fr / ff <10 (9)
-1.2 <rsf / rsr <4 (10)
-3 <fall / rsr <2.5 (11)
here,
fall is the focal length of the entire system
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the front group,
ff is the focal length of the lens group on the subject side of the aperture,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is. When the lens group exists on the subject side from the stop, the front group is set. When the lens group does not exist on the subject side from the stop, 1 / ff = 0 and 1 / rsf = 0.

In the above imaging device, the following conditional expression is satisfied.
-0.6 <rsf / rsr <4 (10 ')
here,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is.

  According to the present invention, it is possible to provide an imaging apparatus including a small photographic optical system particularly suitable for a wide-angle system without generating a large negative distortion. More specifically, it is possible to provide an image pickup apparatus including a small photographic optical system that does not presuppose correction for distortion with respect to the amount of peripheral light. Alternatively, it is possible to provide an imaging apparatus including a small imaging optical system that generates positive distortion, ensures peripheral resolution, and improves image quality by a method such as pixel addition as necessary.

An imaging apparatus according to an embodiment will be described. The imaging apparatus according to the present embodiment includes an imaging optical system and an electronic imaging element, and satisfies the following conditional expression.
-1.73 <IH / EXP <-0.65 (1)
0.50 <TH / TC <1 (2)
here,
EXP is the position of the exit pupil of the photographic optical system,
IH is half the diagonal length of the image sensor,
TH The light collection efficiency for the chief ray at the IH position from the center of the image sensor,
TC is the light collection efficiency for vertically incident light on the optical axis,
It is.

Conditional expression (1) relates to the exit pupil position. If the lower limit of conditional expression (1) is not reached, the value of the cosine fourth power becomes larger than 0.5. For this reason, when image processing is assumed, the optical system cannot be sufficiently reduced in view of the balance between the small size and the light quantity. Moreover, if it exceeds the upper limit of conditional expression (1), the value of the cosine fourth power exceeds 2 ⁻⁴ . For this reason, even if image processing is performed, sufficient image quality cannot be reproduced. Furthermore, if the upper limit and lower limit of conditional expression (2) are exceeded, it is not preferable because a sufficient luminous flux cannot be guided to the pixels of the image sensor without causing a large negative distortion.

The cosine fourth law indicates the relationship between the incident angle and the illuminance. When the incident angle of light incident on the lens is θ with respect to the optical axis, the illuminance satisfies the following relationship: Say.
I = I ₀ cos ⁴ θ
here,
I ₀ is the illuminance of the light before incidence,
I is the illuminance of light after incidence.

Moreover, according to a preferable aspect of the present embodiment, it is desirable that the image sensor satisfies the following conditional expression.
5000 <N × FN <45000 (3)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
FN is Fno of the photographic optical system,
It is.

  When the number of pixels on the long side is increased, the quality of image processing in consideration of pixel addition and peripheral pixel information is improved by illuminance. When the F-number is small, a large amount of light is obtained, and it is less susceptible to diffraction. For this reason, good imaging performance can be obtained. If the lower limit of conditional expression (3) is not reached, it is difficult to ensure peripheral performance even for VGA class images. Exceeding the upper limit of conditional expression (3) is not preferable because the photographic lens itself becomes large and the burden of image processing increases. On the other hand, it is not preferable because the effect of improving the image quality of the displayed image on the printed matter or display of the photographed image becomes relatively small.

  According to a preferred aspect of the present embodiment, the on-chip lens of the image sensor is preferably a gradient index lens. The refractive index distribution lens is preferably constituted by a structure divided by a line width that is approximately the same as the wavelength of incident light or shorter than the wavelength.

  In order to satisfy the conditional expressions (1) and (2) with a general on-chip lens, it is required to dramatically improve the accuracy of individual lens positions in the peripheral portion. In addition, the incident angle of the light beam to the lens chip is tighter (larger) than the principal ray angle, and the surface reflectance is increased. Further, the convex surface of each on-chip lens is configured to be perpendicular to the imaging surface. For this reason, the light receiving efficiency decreases.

  Here, there is also a method of combining an on-chip lens and a condenser lens that can be easily produced. However, disposing a lens near the imaging surface causes unnecessary flare and ghost. In the present embodiment, by using a gradient index lens proposed in Japanese Patent Application Laid-Open No. 2006-351972 and Non-Patent Document 1 described above, the incident surface can be made close to a plane, and the light receiving efficiency can be increased. Since it does not depend on the so-called refraction phenomenon, the occurrence of flare is reduced.

  In addition, when it falls below the lower limit of conditional expression (1), it is easier and more preferable to configure with a general on-chip lens. Further, it is preferable to match the characteristics of the on-chip lens of each pixel in accordance with the oblique incidence characteristics from the photographing optical system. In addition, in order to prevent a sudden decrease in the amount of light at the periphery of the image, the main light incident on the image sensor near 80% of the image height is changed rather than the change in the chief ray angle incident on the image sensor near 50% of the image height. It is desirable that the light beam angle change gradually.

  Further, according to a preferred aspect of the present embodiment, the on-chip lens of the image sensor is sufficiently larger than the wavelength of the incident light, is macroscopically substantially planar, and the entire imaging surface is a single plane or curved surface. Is desirable.

  If each pixel is formed of a convex surface, when an off-axis light beam that satisfies the conditional expression (1) is incident, the chance of image quality degradation increases due to a decrease in light receiving efficiency or a phenomenon such as pixel mixing. For this reason, the on-chip lens is a gradient index lens, the incident surface to the imaging element is substantially flat, and the entire imaging surface is a single plane or curved surface. Thereby, it is possible to prevent image quality deterioration such as light receiving efficiency. In particular, manufacturing efficiency can be improved by making the entire imaging surface one plane. In particular, the light receiving efficiency can be further increased by using a concave surface as a whole. Here, when each pixel is macroscopically substantially flat, it means that the entire imaging surface is a part of a single surface. If the whole is a plane, it is desirable that each pixel is also a plane.

Further, according to a preferred aspect of the present embodiment, it is desirable that only the air is provided between the photographic optical system and the image sensor, and the distance between the photographic optical system and the image sensor satisfies the following conditions.
0.1 <(fb / IH) / Fn <0.3 (4)
here,
fb is back focus,
IH is half the diagonal length of the image sensor,
FN is Fno of the photographic optical system,
It is.

  When the incident angle to the photographic optical system is large, it is not preferable to dispose a low-pass filter or an infrared cut filter between the photographic optical system and the image sensor because of the surface reflectance of the filter and the filter characteristics. That is, it is desirable to provide these filter functions in the photographing optical system or in the image sensor. Furthermore, satisfying conditional expression (4) is preferable because flare and ghost occurring between the image sensor and the photographing optical system can be reduced.

  That is, if fb is increased, the energy at which unnecessary light re-enters the imaging optical system can be reduced. However, the optical system becomes large. Further, when FN is reduced, flare light can be dispersed, and the amount of light per unit area for normal imaging can be reduced. However, the depth of field becomes shallow and the optical system becomes complicated.

Further, according to a preferred aspect of the present embodiment, it is desirable that the lens group having a convex surface facing the image surface on the image side from the stop of the photographing optical system is subjected to surface treatment having an infrared cut function.
Further, according to a preferable aspect of the present embodiment, it is desirable that the lens group having the concave surface directed toward the object-side image surface from the stop of the photographing optical system is subjected to a surface treatment having an infrared cut function.

  In an optical system that satisfies the conditional expression (1), when an infrared cut filter is disposed between the photographing optical system and the image sensor, when the filter is an interference filter type, the spectral reflection transmittance characteristic depending on the incident angle changes. It is not preferable. In addition, when the filter is an absorption filter type, the optical path length difference passing through the filter changes greatly, and the reflectance characteristics also change, which is not preferable. On the other hand, in the thin optical system that satisfies the conditional expression (1), the positive / negative relationship between the angle of the light beam and the optical axis hardly changes. And it is effective to give the surface treatment (coating) which has an infrared cut function with the structure of this aspect. Moreover, this coating may satisfy | fill the function of an infrared cut filter combining several surfaces.

  Moreover, according to the preferable aspect of this embodiment, it is desirable to have an infrared cut filter function between the on-chip lens of the image sensor and the photoelectric conversion surface.

  The light beam that has passed through the on-chip lens is substantially parallel to the optical axis. For this reason, if an infrared cut filter function is disposed between the on-chip lens and the photoelectric conversion surface, it is easy to obtain good characteristics. Note that it is preferable to use an interference filter type because it is not necessary to increase the distance between the on-chip lens and the photoelectric conversion surface.

Further, according to a preferred aspect of the present embodiment, it is desirable that the photographing optical system has a low-pass filter function.
By providing the imaging optical system with a low-pass filter function, it is not necessary to arrange a filter between the imaging optical system and the image sensor. The low-pass filter in the photographing optical system may be any of a phase type, an aberration type, and a wedge prism type. With this configuration, it is possible to configure a photographic optical system that does not generate moire even in the case of an image sensor with a small number of pixels.

Further, according to a preferred aspect of the present embodiment, it is desirable that the image-side surface of the photographing optical system and the on-chip lens surface of the image sensor are adjacent to each other and satisfy the following conditional expression.
2300 <N (5)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
It is.

  When the conditional expression (5) is satisfied, the Nyquist frequency becomes higher than the frequency on the subject side, and a good image quality can be obtained without arranging a low-pass filter. In addition, you may combine the filter made to low-pass only in a specific direction. Such filters can often be made thin.

Further, according to a preferable aspect of the present embodiment, the shape of the final surface of the photographing optical system through which the light beam incident on the maximum image height of the photographing optical system passes is a part of a convex surface with respect to the image surface. It is desirable to satisfy the equation.
-1.5 <IH / PR <-0.1 (6)
here,
IH is half the diagonal length of the image sensor,
PR is the local curvature radius of the surface normal at any position incident on the maximum image height of the final surface of the imaging optical system.

  It is desirable to satisfy conditional expression (6) after satisfying conditional expressions (1) and (2). If the lower limit of conditional expression (6) is not reached, the outer diameter of the lens system will increase and the burden on the optical system will increase. Further, off-axis aberrations such as distortion and astigmatism are deteriorated and the balance is lost, which is not preferable. In addition, it is not preferable because an opportunity of image quality degradation due to re-incident light described below increases. If the lower limit of conditional expression (6) is not reached, the change to the image sensor due to the image height increases. For this reason, the tolerance of the eccentricity accuracy of the lens and the image sensor and the tolerance of the on-chip lens are undesirably small.

  Next, image quality deterioration due to the above-described re-incident light will be described. Here, the combination of conditional expression (4) and conditional expression (6) is also significant. That is, if fb is shortened with respect to IH, the reflected light from the image sensor is reflected by the final surface and the image quality is deteriorated due to re-incident on the image sensor. In the vicinity of the optical axis, such re-incident light flux is also conspicuous because it gathers around the optical axis. On the other hand, in the periphery, the normal incident position and the re-incident position may be different, and image quality is likely to deteriorate.

  In particular, when the conditional expression (1) is satisfied, this position is likely to be different. As a method and configuration for solving this problem, a configuration in which the re-incidence position is outside the effective screen, and a configuration in which the re-incident light is diffused to reduce energy per unit area and become inconspicuous can be considered. The former configuration is not preferable because it is difficult to realize in a short fb state. In conditional expression (6), it is desirable that PR be a local radius of curvature of the normal of the surface at the passing position of the principal ray incident on the maximum image height of the final surface of the photographing optical system.

Further, according to a preferred aspect of the present embodiment, the photographing optical system includes, in order from the subject side, a positive front group, a diaphragm, and a rear group having a lens having a positive power.
The shape of the final surface of the photographing optical system through which the light beam incident on the maximum image height passes is a part of the convex surface with respect to the image surface,
It is desirable to satisfy the following conditional expression.
-1.5 <IH / PR <-0.1 (6)
0.8 <(1 / (fall + exp) -1 / fr) <6 (7)
here,
IH is half the diagonal length of the image sensor,
PR is the local curvature radius of the surface normal at any position incident on the maximum image height of the final surface of the imaging optical system,
fall is the overall focal length of the photographic optical system,
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the rear group,
It is.

  In addition, it is desirable to satisfy the conditional expressions (1) and (2) and then satisfy the conditional expressions (6) and (7). If the lower limit of conditional expression (7) is not reached, it is difficult to dispose a lens between the stop and the imaging surface. If the upper limit of conditional expression (7) is exceeded, the position of the stop is separated from the image plane, which is contrary to miniaturization. In particular, when the combination with conditional expression (7) is below the lower limit of conditional expression (6), the off-axis aberration generated between the stop and the final surface tends to increase, which is not preferable.

Further, according to a preferable aspect of the present embodiment, it is desirable that the photographing optical system includes at least a stop and a rear group in order from the subject side, and satisfies the following conditional expression.
-3.5 <fall / exp <-0.5 (8)
-2 <fr / ff <10 (9)
-1.2 <rsf / rsr <4 (10)
-3 <fall / rsr <2.5 (11)
here,
fall is the focal length of the entire system
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the front group,
ff is the focal length of the lens group on the subject side of the aperture,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is. When the lens group exists on the subject side from the stop, the front group is set. When the lens group does not exist on the subject side from the stop, 1 / ff = 0 and 1 / rsf = 0.

  Conditional expression (8) defines a range suitable for preventing a large negative distortion in the wide-angle lens. By satisfying conditional expression (8), it is possible to reduce the angle of the incident light beam and the angle difference of the emitted light beam. Furthermore, by satisfying conditional expression (9), a symmetrical system before and after the diaphragm can be secured, and the occurrence of large negative distortion can be reduced. Further, when the conditional expression (10) is satisfied, spherical aberration and coma aberration can be corrected satisfactorily. That is, since the angle of the off-axis light beam is steep and the separation of the light beam proceeds rapidly, it is necessary to properly correct spherical aberration and coma aberration on this surface near the stop. By satisfying conditional expression (11), a small size and a sufficient space for aberration correction can be secured. Here, the negative large distortion means a level exceeding -7% and requiring correction by image processing or the like.

Moreover, according to a preferable aspect of the present embodiment, it is desirable that the following conditional expression is satisfied.
-0.6 <rsf / rsr <4 (10 ')
here,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is.

  By satisfying conditional expression (10 '), an optical system suitable for reducing distortion can be obtained. If the lower limit of conditional expression (10 ') is not reached, it becomes difficult to achieve a correction balance of chief rays on the surfaces before and after the stop. In particular, the burden of correction on the off-axis light beam on the final surface increases. As a result, the tendency to generate positive distortion becomes stronger. A photographing optical system in which no lens element is disposed on the subject side from the stop is also possible. In this case, it is desirable that three or more lens surfaces have a convex surface in a direction different from the optical axis in the lens cross-sectional view.

  In the photographing optical system according to the present embodiment, the focusing function may be configured by moving all or some of the lenses. However, it is preferable that the main focusing function is on the subject side with respect to the aperture. That is, the change in the angle of view due to focusing can be reduced.

Hereinafter, an embodiment of an imaging apparatus will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
FIG. 29 shows the relationship between the incident angle and the light receiving efficiency of the gradient index on-chip lens. This is estimated from Non-Patent Document 1 described above. Each example of the present embodiment will be described on the basis of this, but is not limited to this within the scope of the claims. In each embodiment, the pixel size is 2.2 μm × 2.2 μm and the aspect ratio is 4: 3. In addition, it is not restricted to this in the range included in a claim. In particular, it is preferable to further reduce the pixel size to increase the number of pixels and to reduce the focal length and maximum image height of the photographing lens.
30 and 31 show the structure of an imaging device having a refractive index distribution type on-chip lens disclosed in the above-mentioned literature.

  Example 1 of the present invention will be described. FIG. 1 is a cross-sectional view of a photographing optical system included in the imaging apparatus according to the first embodiment. FIG. 2 is an aberration diagram of Example 1, and shows spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when an object at infinity is focused. FIG. 3 shows the relationship between the image height and the light receiving efficiency, and FIG. 4 shows the relationship between the angle at which the chief ray is incident on the image sensor and the image height.

  In this embodiment, as shown in FIG. 1, in order from the subject side, a positive meniscus lens L1 having a convex surface facing the subject side, an aperture S (r3 surface), a positive meniscus lens L2 having a convex surface facing the image side, biconcave It is composed of a negative lens L3. The sensor surface is indicated by I.

  The aspherical surfaces are used on six surfaces including both surfaces of a positive meniscus lens L1 having a convex surface facing the subject, both surfaces of a positive meniscus lens L2 having a convex surface facing the image side, and both surfaces of a biconcave negative lens L3.

  Distortion is within ± 7%. The infrared cut function can be dealt with by applying a coating having a low infrared transmittance on one or a plurality of surfaces of the positive meniscus lens L1 and the positive meniscus lens L2. The low-pass function may be arranged in the vicinity of the diaphragm S (r3 surface). Although close to the sensor surface I, a filter group having an infrared cut function and a low-pass filter function may be disposed between the lens L3 and the sensor surface I. At this time, it is desirable to add a reflectance reduction function by SWS (fine structure below wavelength) or the like to the filter.

  Next, Example 2 will be described. 5, 6, 7, and 8 are respectively a cross-sectional view, an aberration diagram, a relationship between image height and light receiving efficiency, an angle of incident light on the image sensor and an image of the principal ray, as in the first embodiment. It shows a high relationship.

  In this embodiment, as shown in FIG. 5, in order from the subject side, a cemented lens including a plano-convex positive lens L1 having a strong convex surface facing the subject side and a plano-concave negative lens L2 having a strong concave surface facing the image side; A filter having an aperture S (r4 surface), a cemented lens composed of a plano-concave negative lens L3 having a strong concave surface facing the object side and a plano-convex positive lens L4 having a strong convex surface facing the image side, and a filter having an infrared cut function and a low-pass filter function It consists of a group L5 and a sensor surface I.

  An aspherical surface is a subject side surface of a plano-convex positive lens L1 with a strong convex surface facing the object side, an image side surface of a plano-concave negative lens L2 with a strong concave surface facing the image side, and a plano-concave surface with a strong concave surface facing the subject side. It is used on the four surfaces of the image side surface of the negative lens L3 and the image side surface of the planoconvex positive lens L4 with a strong convex surface facing the image side.

  The present embodiment secures a space for arranging the filter while realizing miniaturization. Also, it has a large positive distortion and considers securing peripheral resolution.

  Next, Example 3 will be described. 9, 10, 11, and 12 are respectively a cross-sectional view, an aberration diagram, a relationship between image height and light receiving efficiency, an angle of incident light on an image sensor and an image of a principal ray, as in the first embodiment. It shows a high relationship.

  In this embodiment, as shown in FIG. 9, in order from the subject side, a positive meniscus lens L1 having a convex surface facing the subject side, an aperture S (r3 surface), and a positive meniscus lens L2 having a convex surface on the image side are configured. Is done. The sensor surface is I.

  The aspherical surfaces are used on the four surfaces of the positive meniscus lens L1 having a convex surface facing the subject and both surfaces of the positive meniscus lens L2 having a convex surface facing the image side.

  Although this embodiment has a simple configuration of two sheets, it has a large positive distortion, and other aberrations are well corrected in consideration of securing of peripheral resolution. The diaphragm S may be formed on the image side surface of the meniscus lens L1. The low-pass function may be arranged on the image plane side surface of the meniscus lens L1. The infrared cut function may be supported by applying a coating with low infrared transmittance on any one or a plurality of lens surfaces.

  Although close to the sensor surface I, a filter group having an infrared cut function and a low-pass filter function may be disposed between the lens L2 and the sensor surface I. At this time, it is desirable to add a reflectance reduction function such as SWS to the filter.

  Next, Example 4 will be described. 13, 14, 15, and 16 are respectively a cross-sectional view, an aberration diagram, a relationship between the image height and the light receiving efficiency, an angle of the principal ray incident on the image sensor, and an image as in the first embodiment. It shows a high relationship.

  In this embodiment, as shown in FIG. 13, in order from the subject side, a negative meniscus lens L1 having a concave surface facing the subject side, an aperture S (r3 surface), a biconvex positive lens L2, and a negative surface having a concave surface facing the subject side. It is composed of a meniscus lens L3 and a negative meniscus lens L4 having a concave surface facing the subject. The sensor surface is I.

  The aspherical surface includes both sides of a negative meniscus lens L1 having a concave surface facing the subject, both surfaces of a biconvex positive lens L2, both surfaces of a negative meniscus lens L3 having a concave surface facing the subject side, and a negative meniscus lens having a concave surface facing the subject side. It is used on 8 sides with both sides of L4.

  In this example, the maximum off-axis chief ray sensor incident angle is set to about 50 degrees, and while achieving a reduction in size, distortion (distortion) is realized at ± 0.5% or less, and it is possible to shoot without distortion without image processing. Yes. In addition, other aberrations are also well constructed. The diaphragm S may be configured on the subject side surface of the biconvex positive lens L2. Further, the low-pass function may be arranged on the object side surface of the biconvex positive lens L2. The infrared cut function may be dealt with, for example, by applying a coating having a low infrared transmittance on the object-side lens surface of the negative meniscus lens L5. Further, an infrared cut function may be added to a color filter or the like in the sensor. Although close to the sensor surface, a filter group having an infrared cut function and a low-pass filter function may be disposed between the negative meniscus lens L5 and the sensor surface I. At this time, it is desirable to add a reflectance reduction function such as SWS to the filter.

  Next, Example 5 will be described. 17, 18, 19, and 20 are respectively a cross-sectional view, an aberration diagram, a relationship between image height and light receiving efficiency, an angle of incident light on the image sensor and an image of the principal ray, similarly to the first embodiment. It shows a high relationship.

  In this embodiment, as shown in FIG. 17, in order from the subject side, an aperture S (r1 surface), a biconvex positive lens L1, and a negative meniscus lens having a concave surface facing the subject side, a lens cross-sectional view, an image side axis A lens L2 having a concave surface on the outside, a negative meniscus lens having a concave surface facing the image side, a lens L3 having a convex surface portion on the image side outside the lens surfaces on both sides of the lens cross-sectional view, an infrared cut function and a low-pass filter function It has a filter group L4 and a sensor surface I.

  The aspherical surfaces are used on six surfaces including both surfaces of the biconvex positive lens L1, both surfaces of the negative meniscus lens L2 having a concave surface facing the object side, and both surfaces of the negative meniscus lens L3 having a concave surface facing the image side.

  With such a configuration, it is possible to shoot without distortion without image processing, with a small size and a distortion aberration (distortion) of ± 2% or less despite the pre-aperture type. Aberrations are also well constructed. In addition, a sufficient space for filters is secured.

  Next, Example 6 will be described. 21, 22, 23, and 24 are respectively a cross-sectional view, an aberration diagram, a relationship between image height and light receiving efficiency, an angle of incident light on the image sensor and an image of the principal ray, as in the first embodiment. It shows a high relationship.

  In this example, as shown in FIG. 21, in order from the subject side, a plano-concave negative lens L1 having a concave surface facing the image surface side, a negative meniscus lens L2 having a convex surface facing the subject side, and a biconvex positive lens L3. The lens includes a cemented lens, a stop S (r6 surface), a positive meniscus lens L4 having a concave surface facing the subject, a positive meniscus lens L5 having a concave surface facing the subject, and a sensor surface I.

  An aspherical surface is an image side surface of a plano-concave negative lens L1 with the concave surface facing the image surface side, an image side surface of the biconvex positive lens L3, both surfaces of the positive meniscus lens L4 with a concave surface facing the subject side, the subject side The positive meniscus lens L5 having a concave surface facing the object side is used for five surfaces.

  Next, Example 7 will be described. 25, FIG. 26, FIG. 27, and FIG. 28 are respectively a cross-sectional view, an aberration diagram, a relationship between image height and light receiving efficiency, an angle of incident light on the image sensor and an image of the chief ray as in the first embodiment. It shows a high relationship.

  In this embodiment, as shown in FIG. 25, in order from the subject side, a negative meniscus lens L1 having a convex surface facing the subject side, a positive meniscus lens L2 having a convex surface facing the subject side, and a negative meniscus having a convex surface facing the subject side. A cemented lens of a lens L3 and a biconvex positive lens L4, an aperture S (r8 surface), a negative meniscus lens L5 having a concave surface facing the subject, a positive meniscus lens L6 having a concave surface facing the subject, and a concave surface facing the subject. And a negative meniscus lens L7 directed to the sensor surface I.

  The aspherical surface has a subject side surface of a positive meniscus lens L2 having a convex surface facing the subject side, a cemented lens of a negative meniscus lens L3 having a convex surface facing the subject side and a biconvex positive lens L4, and a concave surface facing the subject side. It is used for two surfaces of the negative meniscus lens L5 and the surface on the subject side.

  Next, numerical data of each of the above embodiments will be listed. Symbols are the above, r1, r2... Curvature radius of each lens surface, d1, d2... Spacing between lens surfaces, nd1, nd2..., Refractive index of d-line of each lens, .nu.d1, .nu.d2. It is the Abbe number of the lens.

  The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A4 y ⁴ + A6 y ⁶ + A8 y ⁸ + A10y ¹⁰ + A12y ¹²
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A4, A6, A8, A10, and A12 are fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients. In the aspheric coefficient, “E−n” (n is an integer) indicates “10 ⁻ⁿ ”. Moreover, the value which is not described in the aspheric coefficient is zero.

  Further, the surface number is marked with * on the aspheric surface. The unit is mm.

Numerical example 1

Surface number rd nd νd Effective diameter object surface ∞ ∞
1 * 2.1718 0.626 1.52559 56.45 1.9
2 * 12.9262 0.21 1.39
3 (Aperture) ∞ 0.327 1.03
4 * -2.9343 1.085 1.52559 56.45 1.39
5 * -1.1431 0.241 2.15
6 * -19.2395 1.253 1.58393 30.21 2.62
7 * 1.8828 1.214 4.27
Image plane ∞

Single lens data
Lens Start surface Focal length
L1 1 4.87
L2 4 2.948
L3 6 -2.871


Aspheric data 1st surface
K = -2.0704, A2 = 0, A4 = 2.3738E-02, A6 = 1.0747E-02
Second side
K = 127.5681, A2 = 0, A4 = 6.8204E-03
4th page
K = -37.2316, A2 = 0, A4 = -2.5507E-01, A6 = 2.1522E-02
5th page
K = -0.7297, A2 = 0, A4 = -6.6339E-02, A6 = -1.0620E-02
6th page
K = 196.0254, A2 = 0, A4 = -1.5353E-01, A6 = 4.2527E-02
7th page
K = -8.9067, A2 = 0, A4 = -2.7429E-02, A6 = 1.8190E-03

Numerical example 2


Surface number rd nd νd Effective diameter object surface ∞ ∞
1 * 1.9369 0.752 1.83481 42.71 1.95
2 ∞ 0.199 1.58393 30.21 1.32
3 * 2.1252 0.084 0.91
4 (Aperture) ∞ 0.317 0.8
5 * -1.572 0.198 1.58393 30.21 1.1
6 ∞ 0.627 1.83481 42.71 1.48
7 * -1.9229 1 1.9
8 ∞ 0.5 1.51633 64.14 3.58
9 ∞ 1.259 3.98
Image plane ∞

Single lens Data lens Start surface Focal length
L1 1 2.32
L2 2 -3.689
L3 5 -2.692
L 6 2.303

Joint lens Data lens Start surface Focal length
L1, L2 1 4.554
L3, L4 5 7.248

Aspheric data 1st surface
K = 0, A2 = 0, A4 = 8.9185E-03, A6 = 4.9032E-03
Third side
K = 0, A2 = 0, A4 = 7.7033E-02, A6 = -1.1908E-01
5th page
K = 0, A2 = 0, A4 = -1.2021E-02, A6 = -4.8359E-03
7th page
K = 0, A2 = 0, A4 = 8.6867E-03, A6 = 1.4758E-02

Numerical Example 3

Surface number rd nd νd Effective diameter object surface ∞ ∞
1 * 1.4081 1.1436 1.52559 56.45 1.8
2 * 6.2963 0.0237 0.9
3 (Aperture) ∞ 0.4013 0.78
4 * -5.4766 2.0974 1.52559 56.45 1.36
5 * -4.253 0.1994 4.1
6 ∞ 0.5 1.51633 64.14 5.01
7 ∞ 0.3 5.38
Image plane ∞

Single lens Data lens Start surface Focal length
L1 1 3.193
L2 4 22.771

Aspheric data 1st surface
K = -4.7059, A2 = 0, A4 = 2.6221E-02, A6 = 2.2300E-03, A8 = -1.5356E-03, A10 = 1.6984E-04
Second side
K = 0, A2 = 0, A4 = 6.5372E-02, A6 = -3.9544E-03, A8 = 7.5934E-03, A10 = -2.1773E-06,
A12 = -2.5634E-03, A14 = 1.0325E-03
4th page
K = -0.5805, A2 = 0, A4 = 2.0148E-03.A6 = 1.3550E-03, A8 = 3.8538E-03, A10 = -4.8816E-03
5th page
K = 0, A2 = 0, A4 = 5.2276E-02, A6 = -2.9145E-03, A8 = -2.3567E-02
6th page
K = -5.3767, A2 = 0, A4 = 5.7845E-02, A6 = -3.1126E-03, A8 = -3.5389E-02
7th page
K = 0, A2 = 0, A4 = 7.3307E-02, A6 = -8.4035E-03, A8 = 4.9403E-03, A10 = -3.4278E-03, A12 = 9.7300E-04
8th page
K = 1.0328, A2 = 0, A4 = -1.0364E-02, A6 = -1.4788E-03
9th page
K = 0, A2 = 0, A4 = -1.6068E-02, A6 = 7.4698E-04, A8 = -5.8444E-05

Numerical example 4

Surface number rd nd vd Effective diameter object surface ∞ ∞
1 * -2.6456 0.4 1.52542 55.78 2.89
2 * -5.0632 0.873 2.38
3 (Aperture) ∞ -0.2 1.94
4 * 2.5143 1.247 1.6935 53.21 1.94
5 * -2.4404 0.063 1.82
6 * -2.1394 0.818 1.60687 27.03 1.76
7 * -9.4751 1.699 2.18
8 * -2.4138 0.4 1.52542 55.78 3.13
9 * -29.9695 1.338 4.49
Image plane ∞

Single lens Data lens Start surface Focal length
L1 1 -11.182
L2 4 1.991
L3 6 -4.754
L4 8 -5.022

Aspheric data 2nd surface
K = 1.5419, A2 = 0, A4 = -7.5136E-02, A6 = -6.6120E-02, A8 = -1.1726E-01
Third side
K = -3.1883, A2 = 0, A4 = -3.3532E-01, A6 = 2.7435E-01, A8 = -1.5698E-01
4th page
K = -0.9547, A2 = 0, A4 = 4.8369E-01, A6 = -9.9110E-02, A8 = 1.8389E-02
5th page
K = -0.1148, A2 = 0, A4 = 4.0560E-01, A6 = -6.1849E-02, A8 = 4.2315E-02
6th page
K = -2.9112, A2 = 0, A4 = -7.1142E-02, A6 = -1.3183E-02
7th page
K = -5, A2 = 0, A4 = -6.1704E-03, A6 = -3.9079E-02, A8 = 1.2513E-02, A10 = -1.8260E-03

Numerical Example 5

Surface number rd nd vd Effective diameter object surface ∞ ∞
1 (Aperture) ∞ 0.2 1.14
2 * 2.1304 1.054 1.53296 55.69 1.62
3 * -1.2576 0.2 2.01
4 * -0.6 0.537 1.58856 30.21 2.04
5 * -1.2071 0.362 2.29
6 * 1.3884 0.53 1.53296 55.69 2.98
7 * 1.201 0.667 3.62
8 ∞ 0.2 4.27
9 ∞ 0.5 1.51825 64.14 4.5
10 ∞ 0.3 4.85
Image plane ∞

Single lens Data lens Start surface Focal length
L1 2 1.664
L2 4 -3.015
L3 6 -1000.02

Aspheric data 2nd surface
K = 17.1045, A2 = 0, A4 = 1.7277E-03, A6 = 2.3593E-04, A8 = -6.4699E-06
5th page
K = 0, A2 = 0, A4 = 2.2485E-04, A6 = -3.6442E-05, A8 = -4.3487E-06
7th page
K = -2.4849, A2 = 0, A4 = 3.4700E-03, A6 = 2.0632E-04, A8 = -1.3696E-04
8th page
K = -2.8354, A2 = 0, A4 = 9.1116E-03, A6 = -1.8289E-03, A8 = -2.5761E-05
9th page
K = 0.0347, A2 = 0, A4 = 1.4367E-02, A6 = -4.5744E-03, A8 = 3.1799E-04
10th page
K = 19.4581, A2 = 0, A4 = -1.2173E-03, A6 = -1.3403E-03, A8 = 1.6211E-04, A10 = -6.1856E-06

Numerical Example 6

Surface number rd nd vd Effective diameter object surface ∞ ∞
1 ∞ 0.5 1.7432 49.34 4
2 * 10.3794 0.869 3.68
3 9.4771 1.64 2.0033 28.27 3.52
4 3.6338 2.535 1.7432 49.34 3
5 * -4.2061 0.1 2.6
6 (Aperture) ∞ 3.51 2.3
7 * -10.3339 1.294 1.58423 30.49 4.6
8 * -3.4759 0.715 5.04
9 * -3.5527 0.6 1.83481 42.71 4.96
10 $ 15.9619 1.768 6.45
Image plane ∞

Single lens Data lens Start surface Focal length
L1 1 -13.969
L2 3 -6.84
L3 4 3.043
L4 7 8.381
L5 9 -3.433

Joint lens Data lens Start surface Focal length
L2, L3 3 5.224

Aspheric data 2nd surface
K = 17.1045, A2 = 0, A4 = 1.7277E-03, A6 = 2.3593E-04, A8 = -6.4699E-06
5th page
K = 0, A2 = 0, A4 = 2.2485E-04, A6 = -3.6442E-05, A8-4.3487E-06
7th page
K = -2.4849, A2 = 0, A4 = 3.4700E-03, A6 = 2.0632E-04, A8 = 1.3696E-04
8th page
K = -2.8354, A2 = 0, A4 = 9.1116E-03, A6 = -1.8289E-03, A8 = -2.5761E-05
9th page
K = 0.0347, A2 = 0, A4 = 1.4367E-02, A6 = -4.5744E-03, A8 = 3.1799E-04
10th page
K = 19.4581, A2 = 0, A4 = -1.2173E-03, A6 = -1.3403E-03, A8 = 1.6211E-04, A10 = -6.1856E-06

Numerical Example 7

Surface number rd nd vd Effective diameter object surface ∞ ∞
1 23.1442 0.337 1.71999 50.23 3.56
2 7.165 0.157 3.56
3 * 5.5974 0.449 1.49241 57.66 3.52
4 7.2912 1.067 3.38
5 13.6301 0.516 1.64769 33.79 3.18
6 3.6139 1.581 1.5725 57.74 3.01
7 -3.6139 0.225 2.83
8 (Aperture) ∞ 3.666 2.3
9 * -9.0802 0.045 1.52288 52.5 4.49
10 -12.3547 0.763 1.57501 41.49 4.47
11 -5.7464 1.156 4.63
12 -2.6576 0.359 1.6968 55.53 4.64
13 -11.06 1.916 6.13
Image plane ∞

Single lens Data lens Start surface Focal length
L1 1 -14.542
L2 3 44.996
L3 4 -7.75
L4 5 3.429
L5 9 -65.831
L6 10 17.928
L7 12 -5.11

Joint lens Data lens Start surface Focal length
L3, L4 5 5.594
L5, L6 9 24.143

Aspheric data 2nd surface
K = -0.1663, A2 = 0, A4 = -6.8994E-03, A6 = -8.0553E-04, A8 = -1.2259E-04, A10 = 1.1496E-05
9th page
K = 0, A2 = 0, A4 = 3.8612E-03, A6 = 1.8043E-04, A8 = 1.0677E-04, A10 = -9.5103E-06

Next, the values of the conditional expressions in each example are listed. In addition, BF (back focus) represents the distance from the lens final surface to the paraxial image surface in terms of air. In addition, ex01 to ex07 indicate Examples 1 to 7.

Various data
ex01 ex02 ex03 ex04 ex05 ex06 ex07
Focal length 3.56 3.716 3.5 4.751 3.252 8.107 8.826
F number 3 3.503 3.255 2.84 2.85 3.78 3.78
Angle of view (ω) ° 38.7 37.5 39.2 30.9 38.6 30.9 28.8
Image height 2.85 2.85 2.85 2.8412 2.6 4.85 4.85
Total lens length 4.956 4.767 4.485 6.6281 4.396 13.519 12.237
BF 1.214 2.5898 0.819 1.3281 1.513 1.768 1.916

Entrance pupil position 0.728 0.841 1.087 0.9836 0 3.259 3.055
Exit pupil position -2.718 -3.702 -3.08 -2.2087 -3.144 -2.874 -3.141
Front principal point position -0.374 0.828 0.598 -8.8323 -0.005 -2.79 -3.5229
Rear principal point position -2.3454 -1.1264 -2.681 -3.4224 -1.7393 -6.338 -6.91

fr 17.04 7.25 22.77 3.23 3.25 -6.31 -6.59
RP -10 -2.096 -2.73 -4.211 -2.191 -26.54 -11.06
mcl 2.04 0.76 1.98 2.12 2.42 2.89 2.65
rsf 12.926 2.125 6.296 -5.063 1E + 08 -4.2061 -3.6139
rsr -2.9343 -1.572 -5.4766 2.5143 2.1304 -10.334 -9.0802
ff 4.8691 4.5535 3.1934 -11.182 1E + 08 6.3526 6.6853
TH 71 73 74 60 80 62 65
TC 100 100 100 100 100 100 100

Conditional expression
ex01 ex02 ex03 ex04 ex05 ex06 ex07
IH / EXP -1.048 -0.814 -0.925 -1.285 -0.827 -1.705 -1.544
TH / TC 0.71 0.73 0.74 0.6 0.8 0.62 0.65
N × FN 6219 7256 6748.44 8330.4 5389.35 13346.2 13346.2
(Fb / IH) / Fn 0.142 0.26 0.088 0.116 0.204 0.096 0.104
N 2073 2073 2073 2932 1891 3527 3527
IH / PR -0.285 -1.359 -1.044 -0.957 -1.187 -0.183 -0.439
(1 / (fall + exp) -1 / fr)
1.133 4.538 2.339 0.31 8.931 0.3486 0.328
fall / EXP -1.309 -1.061 -1.136 -1.514 -1.034 -2.85 -2.81
fr / ff 3.5 1.592 7.131 -0.289 0 -0.993 -0.986
rsf / rsr -0.227 -0.74 -0.87 -0.497 0 2.457 2.513
fall / rsr -1.213 -2.364 -0.639 1.889 1.526 -0.784 -0.972

  The imaging optical system of the present invention as described above is a photographing apparatus for photographing an image of an object with an electronic image sensor such as a CCD or CMOS, in particular, a digital camera, a video camera, a personal computer or an example of an information processing apparatus, a telephone. It can be used for portable terminals, especially mobile phones that are convenient to carry. The embodiment is illustrated below.

  FIGS. 32 to 34 are conceptual diagrams of a configuration in which the imaging optical system according to the present invention is incorporated in a photographing optical system 41 of a digital camera. 32 is a front perspective view showing the appearance of the digital camera 40, FIG. 33 is a rear perspective view thereof, and FIG. 34 is a cross-sectional view showing an optical configuration of the digital camera 40.

  In this example, the digital 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. Then, when the photographer presses the shutter 45 disposed on the upper portion of the camera 40, photographing is performed through the photographing optical system 41, for example, the lens 48 of the first embodiment in conjunction therewith.

  The object image formed by the photographing optical system 41 is formed on the image pickup surface of the CCD 49. 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 image processing means 51. Further, the image processing means 51 is provided with a memory or the like, and can record a captured electronic image. This memory may be provided separately from the image processing means 51, or may be configured to perform recording and writing electronically using a flexible disk, memory card, MO, or the like.

  Further, a finder objective optical system 53 is disposed on the finder optical path 44. The finder objective optical system 53 includes a cover lens 54, a first prism 10, an aperture stop 2, a second prism 20, and a focusing lens 66. An object image is formed on the imaging surface 67 by the finder objective optical system 53. This object image is formed on the field frame 57 of the Porro prism 55 which is an image erecting member. Behind the Porro prism 55, an eyepiece optical system 59 for guiding an erect image to the observer eyeball E is disposed.

  According to the digital camera 40 configured in this way, an electronic imaging device having a small and thin lens with a reduced number of components of the photographing optical system 41 can be realized. The present invention is not limited to the above-described retractable digital camera, but can also be applied to a folding digital camera that employs a bending optical system.

  Next, a personal computer which is an example of an information processing apparatus in which the imaging optical system of the present invention is incorporated as an objective optical system is shown in FIGS. 35 is a front perspective view of the personal computer 300 with the cover open, FIG. 36 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 37 is a side view of FIG. As shown in FIGS. 35 to 37, the personal computer 300 includes a keyboard 301, information processing means and recording means, a monitor 302, and a photographing optical system 303.

  Here, the keyboard 301 is for an operator to input information from the outside. The information processing means and recording means are not shown. The monitor 302 is for displaying information to the operator. The photographing optical system 303 is for photographing an image of the operator himself or a surrounding area. The monitor 302 may be a liquid crystal display element, a CRT display, or the like. As the liquid crystal display element, there are a transmissive liquid crystal display element that is illuminated from the back by a backlight (not shown), and a reflective liquid crystal display element that reflects and displays light from the front. In the drawing, the photographic optical system 303 is built in the upper right of the monitor 302, but is not limited to that location, and may be anywhere around the monitor 302 or the keyboard 301.

  The photographing optical system 303 includes, on the photographing optical path 304, the objective optical system 100 including, for example, the lens of Example 1, and an electronic image sensor chip 162 that receives an image. These are built in the personal computer 300.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic image sensor chip 162 is input to the processing means of the personal computer 300 via the terminal 166. Finally, the object image is displayed on the monitor 302 as an electronic image. FIG. 35 shows an image 305 taken by the operator as an example. The image 305 can also be displayed on a communication partner's personal computer from a remote location via the processing means. The Internet and telephone are used for image transmission to remote places.

  Next, FIG. 38 shows a telephone which is an example of an information processing apparatus in which the imaging optical system of the present invention is incorporated as a photographing optical system, particularly a portable telephone which is convenient to carry. 38A is a front view of the mobile phone 400, FIG. 38B is a side view, and FIG. 38C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 38A to 38C, the mobile phone 400 includes a microphone unit 401, a speaker unit 402, an input dial 403, a monitor 404, a photographing optical system 405, an antenna 406, and processing. Means.

  Here, the microphone unit 401 is for inputting an operator's voice as information. The speaker unit 402 is for outputting the voice of the other party. An input dial 403 is used by an operator to input information. The monitor 404 is for displaying information such as a photographed image of the operator himself or the other party, a telephone number, and the like. The antenna 406 is for transmitting and receiving communication radio waves. The processing means (not shown) is for processing image information, communication information, input signals, and the like.

  Here, the monitor 404 is a liquid crystal display element. Further, in the drawing, the arrangement positions of the respective components, in particular, are not limited thereto. The photographing optical system 405 includes an objective optical system 100 disposed on a photographing optical path 407 and an electronic image sensor chip 162 that receives an object image. As the objective optical system 100, for example, the lens of Example 1 is used. These are built in the mobile phone 400.

A cover glass 102 for protecting the objective optical system 100 is disposed at the tip of the mirror frame.
The object image received by the electronic imaging element chip 162 is input to an image processing unit (not shown) via the terminal 166. Finally, the object image is displayed as an electronic image on the monitor 404, the monitor of the communication partner, or both. The processing means includes a signal processing function. When transmitting an image to a communication partner, this function converts information on the object image received by the electronic image sensor chip 162 into a signal that can be transmitted.

  The present invention can take various modifications without departing from the spirit of the present invention.

FIG. 3 is a lens cross-sectional view of the first embodiment of the present invention when focusing on a subject at infinity. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 1, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 1, and image height. It is a lens sectional view at the time of focusing on an infinite distance subject of Example 2 of the present invention. FIG. 6 is an aberration diagram for Example 2 upon focusing on an infinite object. It is a figure which shows the relationship between the image height of Example 2, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 2, and image height. It is a lens sectional view at the time of focusing on an infinite distance object of Example 3 of the present invention. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 3, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 3, and image height. FIG. 6 is a lens cross-sectional view of Example 4 of the present invention when focusing on a subject at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 4, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 4, and image height. FIG. 10 is a lens cross-sectional view of Example 5 of the present invention when focusing on a subject at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 5, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 5, and image height. It is lens sectional drawing at the time of an infinite object focusing of Example 6 of this invention. FIG. 10 is an aberration diagram for Example 6 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 6, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 6, and image height. It is lens sectional drawing at the time of an infinite distance object focus of Example 7 of this invention. FIG. 10 is an aberration diagram for Example 7 upon focusing on an object at infinity. It is a figure which shows the relationship between the image height of Example 7, and light reception efficiency. It is a figure which shows the relationship between the angle which injects into the image pick-up element of the chief ray of Example 7, and image height. It is a figure which shows the relationship between the incident angle and light reception efficiency by a refractive index distribution type on-chip lens. It is a figure which shows the structure of the image pick-up element which has a gradient index type on-chip lens. It is another figure which shows the structure of the image pick-up element which has a refractive index distribution type on-chip lens. It is a front perspective view which shows the external appearance of the digital camera 40 incorporating the optical system by this invention. 2 is a rear perspective view of the digital camera 40. FIG. 2 is a cross-sectional view showing an optical configuration of a digital camera 40. FIG. 1 is a front perspective view of a state in which a cover of a personal computer 300 that is an example of an information processing apparatus in which an optical system of the present invention is incorporated as an objective optical system is opened. FIG. 2 is a cross-sectional view of a photographing optical system 303 of a personal computer 300. FIG. 2 is a side view of a personal computer 300. FIG. 1A and 1B are diagrams showing a mobile phone that is an example of an information processing apparatus in which the optical system of the present invention is incorporated as a photographing optical system. FIG. 3A is a front view of the mobile phone 400, FIG. 2 is a cross-sectional view of a photographing optical system 405. FIG.

Explanation of symbols

L1 lens L2 lens L3 lens L4 lens L5 lens, filter I sensor surface E observer eye 40 digital camera 41 photographing optical system 42 photographing optical path 43 finder optical system 44 finder optical path 45 shutter 46 flash 47 liquid crystal display monitor 48 lens 49 CCD
DESCRIPTION OF SYMBOLS 50 Image pick-up surface 51 Processing means 53 Finder objective optical system 55 Porro prism 57 Field frame 59 Eyepiece optical system 66 Focusing lens 67 Imaging surface 100 Objective optical system 102 Cover glass 162 Electronic image pick-up element chip | tip 166 Terminal 300 Personal computer 301 Keyboard 302 Monitor 303 Imaging Optical System 304 Imaging Optical Path 305 Image 400 Mobile Phone 401 Microphone Unit 402 Speaker Unit 403 Input Dial 404 Monitor 405 Imaging Optical System 406 Antenna 407 Imaging Optical Path

Claims (14)

Photographic optics,
An image pickup apparatus having an electronic image pickup element and satisfying the following conditional expression:
-1.73 <IH / EXP <-0.65 (1)
0.50 <TH / TC <1 (2)
here,
EXP is the position P of the exit pupil of the photographing optical system,
IH is half the diagonal length of the image sensor,
TH is the condensing efficiency for the principal ray at the position of IH from the center of the image sensor,
TC is the light collection efficiency for vertically incident light on the optical axis,
It is. The imaging apparatus according to claim 1, wherein the imaging element satisfies the following conditional expression.
5000 <N × FN <45000 (3)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
FN is Fno of the photographic optical system,
It is. The on-chip lens of the image sensor is a gradient index lens,
The imaging apparatus according to claim 1, wherein the refractive index distribution lens is configured by a structure divided by a line width that is approximately equal to or shorter than the wavelength of incident light.   The imaging device according to claim 3, wherein the on-chip lens of the imaging device is sufficiently larger than the wavelength of incident light, is macroscopically substantially flat, and the entire imaging surface is a single plane or curved surface. apparatus. Only the air between the imaging optical system and the image sensor,
The imaging apparatus according to claim 1, wherein an interval between the imaging optical system and the imaging element satisfies the following condition.
0.1 <(fb / IH) / FN <0.3 (4)
here,
fb is back focus,
IH is half the diagonal length of the image sensor,
FN is Fno of the photographic optical system,
It is.   6. The imaging according to claim 1, wherein a surface treatment having an infrared cut function is applied to a lens group having a convex surface facing an image surface on the image side from the stop of the photographing optical system. apparatus.   The imaging according to any one of claims 1 to 6, wherein a surface group having an infrared cut function is applied to a lens group having a concave surface directed toward the object-side image surface from the stop of the photographing optical system. apparatus.   The imaging apparatus according to claim 1, further comprising an infrared cut filter function between an on-chip lens and a photoelectric conversion surface of the imaging element.   The imaging apparatus according to claim 1, wherein the photographing optical system has a low-pass filter function. The image-side surface of the photographing optical system and the on-chip lens surface of the imaging device are surfaces adjacent to each other, and satisfy the following conditional expression: The imaging device described.
2300 <N (5)
here,
N is the number of pixels on the long side of the image sensor (number of horizontal pixels),
It is. The shape of the final surface of the photographing optical system through which a light beam incident on the maximum image height of the photographing optical system passes is a part of a convex surface with respect to the image surface, and satisfies the following conditional expression: The imaging device according to any one of 1 to 10.
-1.5 <IH / PR <-0.1 (6)
here,
IH is half the diagonal length of the image sensor,
PR is the local radius of curvature of the surface normal at any position incident on the maximum image height of the final surface of the photographic optical system,
It is. The photographing optical system is composed of, in order from the subject side, a positive front group, a diaphragm, and a rear group having a lens having a positive power,
The shape of the final surface of the photographing optical system through which the light beam incident on the maximum image height passes is a part of a convex surface with respect to the image surface,
The imaging apparatus according to claim 11, wherein the following conditional expression is satisfied.
-1.5 <IH / PR <-0.1 (6)
0.8 <(1 / (fall + EXP) -1 / fr) <6 (7)
here,
IH is half the diagonal length of the image sensor,
PR is the local curvature radius of the surface normal at any position incident on the maximum image height of the final surface of the imaging optical system,
fall is the overall focal length of the photographic optical system,
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the rear group,
It is. The photographing optical system is composed of at least an aperture and a rear group in order from the subject side,
The imaging apparatus according to claim 1, wherein the following conditional expression is satisfied.
-3.5 <fall / EXP <-0.5 (8)
-2 <fr / ff <10 (9)
-1.2 <rsf / rsr <4 (10)
-3 <fall / rsr <2.5 (11)
here,
fall is the focal length of the entire system
EXP is the position of the exit pupil of the photographic optical system,
fr is the focal length of the front group,
ff is the focal length of the lens group on the subject side of the aperture,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is. When the lens group exists on the subject side from the stop, the front group is set. When the lens group does not exist on the subject side from the stop, 1 / ff = 0 and 1 / rsf = 0. The imaging apparatus according to claim 13, wherein the following conditional expression is satisfied.
-0.6 <rsf / rsr <4 (10 ')
here,
rsf is the radius of curvature of the lens adjacent to the subject side of the aperture,
rsr is the radius of curvature of the lens adjacent to the image side of the aperture,
It is.

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