JP2013109374A - Imaging optical system and imaging apparatus with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small, high performance imaging optical system and an imaging device with the small, high performance imaging optical system.SOLUTION: The imaging optical system according to the invention comprises five lenses, which are, in order from an object side, an aperture stop S, a first lens L1 of positive refractive power, a second lens L2 of negative refractive power, a third lens L3 of positive refractive power, a fourth lens L4 of positive refractive power, and a fifth les L5 of negative refractive power. The imaging apparatus has the imaging optical system.

Description

  The present invention relates to a compact and high-performance imaging optical system and an imaging apparatus including the same.

In recent years, with the thinning of mobile phones, there has been a demand for camera modules in which the length of the optical system in the optical axis direction is made as thin as possible.
In addition, with the recent increase in the size and the number of pixels of an image sensor, a lens having a high resolution is required. In order to meet this demand, for example, Patent Document 1 and Patent Document 2 propose a single-focus optical system composed of about 3 to 5 aspheric lenses.

JP 2007-264180 A JP 2007-298572 A

  However, the example proposed in Patent Document 1 is a positive / negative / positive / negative type in order to ensure high performance and telecentricity. In this type, the fourth lens is a negative lens. For this reason, from the viewpoints of shortening the optical length and correcting field curvature, it is still insufficient and there is room for improvement.

  In the example proposed in Patent Document 2, the first lens and the second lens are cemented from the viewpoint of chromatic aberration. When such a cemented lens is used, the surface shape of the cemented surface is restricted, which is still insufficient in terms of shortening the optical length and correcting various aberrations, and there is room for improvement.

  The present invention has been made in view of the above, and an object thereof is to provide a small and high-performance imaging optical system and an imaging apparatus including the same.

In order to solve the above-described problems and achieve the object, the imaging optical system of the present invention includes:
From the object side,
An aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
A fifth lens having negative refractive power;
5 lenses.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
0.36 <f4 / f <3.88 (1)
here,
f4 is the focal length of the fourth lens,
f is the focal length of the entire imaging optical system,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
0.81 <f3 / f4 <3.25 (2)
here,
f3 is the focal length of the third lens,
f4 is the focal length of the fourth lens,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
0.28 <f1 / f <1.23 (3)
However,
f1 is the focal length of the first lens,
f is the focal length of the entire imaging optical system,
It is.

  According to a preferred aspect of the present invention, it is desirable that the image plane side surface of the second lens is concave on the image plane side.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
0.57 <f3 / f <6.31 (4)
here,
f3 is the focal length of the third lens,
f is the focal length of the entire imaging optical system,
It is.

Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
0 <| (SAG4AS-SAG4AA) / 4AR | <0.147 (5)
And 0 <| (SAG4BS-SAG4BA) / 4BR | <0.395 (6)
here,
SAG4AS is the amount of sag at a position where the effective diameter is 60% when the object side surface of the fourth lens is a spherical surface.
SAG4AA is the amount of sag at the position of the effective diameter 60% of the object side surface of the fourth lens,
SAG4BS is the amount of sag at the position of 60% effective diameter when the imaging surface side surface of the fourth lens is a spherical surface,
SAG4BA is the amount of sag at the position of the effective diameter 60% of the surface on the imaging surface side of the fourth lens,
4AR is the paraxial radius of curvature of the object side surface of the fourth lens,
4BR is the paraxial radius of curvature of the imaging surface side of the fourth lens,
It is.

  According to a preferred aspect of the present invention, it is desirable that the object side surface of the fifth lens has a concave shape on the object side.

  According to a preferred aspect of the present invention, it is desirable that the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are formed of resin.

In the imaging device of the present invention,
The imaging optical system described above;
An imaging device comprising an electronic imaging device having an imaging surface,
The following conditional expression is satisfied.
15 ° <αi <30 ° (7)
Here, αi is the incident angle of the principal ray on the imaging surface at the maximum image height.

  According to a preferred aspect of the present invention, it is further desirable to have a shutter mechanism on the most object side of the imaging optical system.

  According to a preferred aspect of the present invention, it is desirable that the imaging optical system has an autofocus mechanism.

  According to a preferred aspect of the present invention, it is desirable to integrate the imaging optical system and the electronic imaging element.

  According to the present invention, it is possible to provide a small and high-performance imaging optical system and an imaging apparatus including the imaging optical system.

It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 1 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 1. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 2 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 2. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 3 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 3. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 4 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 4. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 5 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 5. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 6 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 6. FIG. It is sectional drawing which follows the optical axis which shows the optical structure at the time of infinity object point focusing of the imaging optical system concerning Example 7 of this invention. It is a figure which shows the spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration (CC) at the time of an infinite object point focusing of the imaging optical system concerning Example 7. It is a front perspective view which shows the external appearance of the digital camera 40 incorporating the zoom 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 which is an example of an information processing apparatus in which an imaging optical system of the present invention is built as an objective optical system is opened. 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 as an example of an information processing apparatus in which an imaging optical system of the present invention is built in as a photographic optical system, where FIG. 3A is a front view of the mobile phone 400, FIG. FIG. 6 is a cross-sectional view of the photographing optical system 405. It is a figure explaining the amount of sag.

  Prior to the description of the examples, the effects of the imaging optical system of the present embodiment will be described.

The imaging optical system of this embodiment is
From the object side,
An aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
A fifth lens having negative refractive power;
5 lenses.

In the imaging optical system of the present embodiment, the aperture stop is disposed closest to the object side. For this reason, the exit pupil can be separated from the image plane. Thereby, the angle of the light ray incident on the peripheral portion can be reduced at the imaging position (the imaging surface of the electronic imaging device). Therefore, it is possible to avoid shortening the optical length and lowering the sensitivity of the periphery of the image sensor.
In addition, since the position of the principal point can be arranged closer to the object side of the optical system, the total length can be sufficiently reduced with respect to the focal length. Thereby, shortening of the full length of an optical system is realizable.
In addition, by arranging a third lens having a positive refractive power and a five-lens configuration in which the fourth lens is positive, correction of lateral chromatic aberration of magnification in the peripheral portion compared to a conventional four-lens imaging lens is possible. Is advantageous. Furthermore, since the fourth lens has a positive refractive power, it is advantageous for shortening the overall length of the optical system.

In addition, it is desirable that the imaging optical system of the present embodiment satisfies the following conditional expression.
0.36 <f4 / f <3.88 (1)
here,
f4 is the focal length of the fourth lens,
f is the focal length of the entire imaging optical system,
It is.

Conditional expression (1) defines the distribution of refractive power between the fourth lens and the entire imaging optical system. By satisfying conditional expression (2), it is possible to shorten the optical length and correct aberrations.
When the upper limit of conditional expression (1) is exceeded, the refractive power of the fourth lens becomes small. As a result, when the shortening of the total length of the optical system is promoted, it is not preferable because it becomes difficult to ensure telecentricity.
If the lower limit value of conditional expression (1) is not reached, the refractive power of the fourth lens becomes too large. For this reason, axial chromatic aberration increases, and aberration correction becomes difficult.

Instead of conditional expression (1), the following conditional expression (1 ′) should be satisfied.
0.47 <f4 / f <2.91 (1 ')
It is more preferable that the following conditional expression (1 ″) is satisfied instead of conditional expression (1).
0.55 <f4 / f <2.52 (1 ")

In addition, it is desirable that the imaging optical system of the present embodiment satisfies the following conditional expression.
0.81 <f3 / f4 <3.25 (2)
here,
f3 is the focal length of the third lens,
f4 is the focal length of the fourth lens,
It is.

Conditional expression (2) defines the distribution of refractive power of the third lens and the fourth lens. Satisfying the conditional expression (2) can alleviate the deterioration of the decentration sensitivity accompanying the shortening of the optical length and correct the curvature of field well.
When the upper limit of conditional expression (2) is exceeded, the refractive power of the fourth lens is significantly greater than that of the third lens. For this reason, since the decentration sensitivity of a 4th lens becomes high, it is not preferable.
When the lower limit of conditional expression (2) is not reached, the refractive power of the third lens is significantly greater than that of the fourth lens. For this reason, the decentering sensitivity of the third lens is increased, which is not preferable.
Further, it is not preferable to deviate from the range of the conditional expression (2) because it is difficult to correct the Petzval sum, that is, the field curvature.

Instead of conditional expression (2), the following conditional expression (2 ′) should be satisfied.
1.07 <f3 / f4 <2.44 (2 ')
It is more preferable that the following conditional expression (2 ″) is satisfied instead of conditional expression (2).
1.24 <f3 / f4 <2.11 (2 ")

In addition, it is desirable that the imaging optical system of the present embodiment satisfies the following conditional expression.
0.28 <f1 / f <1.23 (3)
here,
f1 is the focal length of the first lens,
f is the focal length of the entire imaging optical system,
It is.

Conditional expression (3) defines the distribution of refractive power between the first lens and the entire imaging optical system. By satisfying conditional expression (3), the total length of the optical system can be shortened and good aberration correction can be performed.
When the value of conditional expression (3) falls below the lower limit value, the refractive power of the first lens becomes strong. In this case, various aberrations increase and it becomes difficult to correct the aberrations. Moreover, since manufacturing sensitivity becomes low, it is not preferable.
When the value of conditional expression (3) exceeds the upper limit value, the refractive power of the first lens becomes weak. In this case, since it becomes difficult to shorten the total length of the optical system, it is not preferable.

Instead of conditional expression (3), the following conditional expression (3 ′) should be satisfied.
0.51 <f1 / f <0.77 (3 ′)
It is more preferable that the following conditional expression (3 ″) is satisfied instead of conditional expression (3).
0.52 <f1 / f <0.64 (3 ")

  In the imaging optical system of the present embodiment, it is desirable that the image side surface of the second lens has a concave meniscus shape on the image side.

  By making the image surface side of the second lens concave on the image surface side and making it have a negative refractive power, the light emission angle is increased, telecentricity is ensured, and the total length of the optical system is shortened. Is possible.

In the imaging optical system of the embodiment, it is desirable that the object side surface of the third lens is concave or convex on the object side. By making the object side surface of the third lens concave on the object side, it is possible to suppress image plane fluctuation due to lens position shift during manufacturing, and manufacturing sensitivity is lowered.
Further, it is advantageous to correct lateral chromatic aberration by making the object side surface of the third lens convex toward the object side.

In the imaging optical system of the present embodiment, it is desirable that the following conditional expression is satisfied.
0.57 <f3 / f <6.31 (4)
here,
f3 is the focal length of the third lens,
f is the focal length of the entire imaging optical system,
It is.

Conditional expression (4) defines the refractive power distribution of the third lens and the entire imaging optical system. If conditional expression (4) is satisfied, good aberration correction can be performed. More specifically, in the third lens, an increase in axial chromatic aberration can be suppressed by appropriately suppressing the paraxial refractive power, and the field curvature can be favorably corrected.
If the lower limit of conditional expression (4) is not reached, the refractive power of the third lens will become strong. In this case, the longitudinal chromatic aberration increases and it becomes difficult to correct the aberration.
If the upper limit of conditional expression (4) is exceeded, the refractive power of the third lens will be weak. In this case, the total length of the optical system becomes long.

Instead of conditional expression (4), the following conditional expression (4 ′) should be satisfied.
1.68 <f3 / f <4.73 (4 ′)
It is more preferable that the following conditional expression (4 ″) is satisfied instead of conditional expression (4).
1.78 <f3 / f <4.06 (4 ")

  In the imaging optical system of the embodiment, it is desirable that the fourth lens has a meniscus shape that is concave on the object side and convex on the image side. Correction of coma aberration while maintaining concentricity without losing concentricity by making the fourth lens concave on the object side and convex meniscus on the image side Is advantageous.

In addition, it is desirable that the imaging optical system of the present embodiment satisfies the following conditional expression.
0 <| (SAG4AS-SAG4AA) / 4AR | <0.147 (5)
And 0 <| (SAG4BS-SAG4BA) / 4BR | <0.395 (6)
here,
SAG4AS is the amount of sag at a position where the effective diameter is 60% when the object side surface of the fourth lens is a spherical surface.
SAG4AA is the amount of sag at the position of the effective diameter 60% of the object side surface of the fourth lens,
SAG4BS is the amount of sag at the position of 60% effective diameter when the imaging surface side surface of the fourth lens is a spherical surface,
SAG4BA is the amount of sag at the position of the effective diameter 60% of the surface on the imaging surface side of the fourth lens,
4AR is the paraxial radius of curvature of the object side surface of the fourth lens,
4BR is the paraxial radius of curvature of the imaging surface side surface of the fourth lens,
It is.

Here, the sag amount will be described with reference to FIG. “The amount of sag at an effective diameter of 60% when the lens surface is a spherical surface” is indicated by a dotted line in a direction along the direction parallel to the optical axis at an effective diameter of 60% (height). This is the distance SAGs between the reference spherical surface and the plane P passing through the top V.
“The amount of sag at the position where the effective diameter of the lens surface is 60%” means that the lens surface and surface indicated by the solid line in the direction along the direction parallel to the optical axis at the position (height) where the effective diameter is 60%. This is the distance SAGa to the plane P passing through the top V.

Conditional expressions (5) and (6) define preferable conditions for suppressing fluctuations in field curvature due to fluctuations in object distance.
Exceeding the upper limit values of conditional expressions (5) and (6) is not preferable because a large difference occurs between the on-axis and off-axis refractive power, and the variation in field curvature due to the variation in object distance becomes significant.

Instead of conditional expressions (5) and (6), the following conditional expressions (5 ′) and (6 ′) may be satisfied.
0 <| (SAG4AS−SAG4AA) / 4AR | <0.091 (5 ′)
0 <| (SAG4BS−SAG4BA) / 4BR | <0.197 (6 ′)
It is more preferable to satisfy the following conditional expressions (5 ″) and (6 ″) instead of the conditional expressions (5) and (6).
0 <| (SAG4AS-SAG4AA) / 4AR | <0.074 (5 ")
0 <| (SAG4BS-SAG4BA) / 4BR | <0.059 (6 ")

  In the imaging optical system of the present embodiment, it is desirable that the object side surface of the fifth lens has a concave shape on the object side.

  By making the object side surface of the fifth lens concave on the object side, correction of curvature of field and distortion can be advantageously performed while the light beam on the exit side has the optical axis parallel.

  In the imaging optical system of the present embodiment, it is desirable that the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are formed of resin.

  An inexpensive imaging optical system can be provided by using a resin as the lens material.

In addition, the imaging apparatus of the present embodiment
The imaging optical system described above;
An imaging device comprising an electronic imaging device having an imaging surface,
The following conditional expression is satisfied.
15 ° <αi <30 ° (7)
Here, αi is the incident angle of the principal ray on the imaging surface at the maximum image height.

When a CCD or the like is used for the electronic image pickup device, the brightness of the image changes between the central portion and the peripheral portion of the image when an off-axis light beam emitted from the optical system is incident on the image pickup surface at a large angle. If the incident angle on the imaging surface is small, the problem of this change in brightness is solved, but the total length of the optical system becomes long.
When the conditional expression (7) is satisfied, it is possible to suppress the nonuniformity of the brightness of the image at the central portion and the peripheral portion of the image while suppressing an increase in the total length of the optical system.

In the imaging apparatus of this embodiment, it is desirable to have a shutter mechanism on the most object side of the imaging optical system.
By disposing the shutter closest to the object side of the imaging optical system, the entire optical system and the shutter mechanism can be configured separately. Therefore, the assembly of the imaging module is facilitated, and it is advantageous for downsizing the imaging module. Further, by disposing near the aperture stop, the influence of shutter shading can be reduced.

In the imaging apparatus of this embodiment, it is desirable that the imaging optical system has an autofocus mechanism.
By mounting an autofocus mechanism, it is possible to focus at any subject distance.

In the imaging apparatus of the present embodiment, it is desirable to integrate the imaging optical system and the electronic imaging element.
By integrating the electronic image pickup element, an optical image obtained by the image pickup optical system can be converted into an electric signal. In addition, a small and high-performance imaging device can be provided by selecting an electronic imaging device that can reduce the change in brightness of the image at the central portion and the peripheral portion due to αi.

In the imaging optical system of the present embodiment, it is desirable that both surfaces of the first lens are aspheric surfaces. This is advantageous for correcting various aberrations. In particular, it is advantageous for correction of spherical aberration, coma aberration, and astigmatism.
Furthermore, in the imaging optical system of the present embodiment, it is desirable that both surfaces of the second lens are aspherical surfaces. This is advantageous for correcting various aberrations. In particular, it is advantageous for correction of spherical aberration, coma aberration, and astigmatism.
In the imaging optical system of the present embodiment, it is desirable that both surfaces of the fourth lens are aspherical surfaces. This is advantageous for correcting various aberrations. In particular, it is advantageous for correction of curvature aberration and distortion aberration.
In the imaging optical system of the present embodiment, it is desirable that both surfaces of the fifth lens are aspherical surfaces. This is advantageous for correcting various aberrations. In particular, it is advantageous for correcting curvature of field and distortion. Further, it is advantageous for securing the so-called telecentricity in a state where the light beam on the emission side is parallel to the optical axis.

  Hereinafter, examples of the imaging optical system and the electronic imaging apparatus of the present embodiment will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  Next, the image pickup optical system according to the first embodiment will be described. FIG. 1 is a cross-sectional view along the optical axis showing the optical configuration of the imaging optical system according to the first embodiment when focusing on an object point at infinity.

  FIG. 2 is a diagram illustrating spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) when the imaging optical system according to the example 1 is focused on an object point at infinity. FIY represents the image height. The symbols in the aberration diagrams are the same in the examples described later.

  As shown in FIG. 1, the imaging optical system according to the first embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power. In all the following examples, in the lens cross-sectional views, CG represents a cover glass, and I represents an image pickup surface of an electronic image pickup element.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a biconcave negative lens. The third lens L3 is a positive meniscus lens having a convex surface facing the object side. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a biconcave negative lens.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 3, the imaging optical system according to the second embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a positive meniscus lens having a convex surface facing the image surface side. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a negative meniscus lens having a convex surface facing the image surface side.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 5, the imaging optical system according to the third embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a positive meniscus lens having a convex surface facing the image surface side. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a negative meniscus lens having a convex surface facing the image surface side.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 7, the imaging optical system according to the fourth embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a biconvex positive lens. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a negative meniscus lens having a convex surface facing the image surface side.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 9, the imaging optical system according to the fifth embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a positive meniscus lens having a convex surface facing the image surface side. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a negative meniscus lens having a convex surface facing the image surface side.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 11, the imaging optical system according to the sixth embodiment includes, in order from the object side, an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a biconvex positive lens. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a biconcave negative lens.

  The aspheric surfaces are provided on both surfaces of all of the first lens L1 to the fifth lens L5.

  As shown in FIG. 13, the imaging optical system according to the seventh embodiment has an aperture stop S, a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, and a positive refractive power in order from the object side. It has a third lens L3, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power.

  The first lens L1 is a biconvex positive lens. The second lens L2 is a negative meniscus lens having a convex surface facing the object side. The third lens L3 is a positive meniscus lens having a convex surface facing the image surface side. The fourth lens L4 is a positive meniscus lens having a convex surface facing the image plane side. The fifth lens L5 is a biconcave negative lens.

  The aspheric surfaces are provided on both surfaces of the first lens L1, the second lens L2, the fourth lens L4, and the fifth lens L5, and the image side surface of the third lens L3.

  Next, numerical data of optical members constituting the imaging optical system of each of the above embodiments will be listed. In the numerical data of each embodiment, r1, r2,... Are the curvature radii of the lens surfaces, d1, d2,... Are the thickness or air spacing of each lens, and nd1, nd2,. Are the Abbe number of each lens, Fno. Indicates the F number, f indicates the focal length of the entire system, and * indicates an aspherical surface.

The aspherical shape is expressed by the following equation when the optical axis direction is z, the direction orthogonal to the optical axis is y, the conical coefficient is K, and the aspherical coefficients are A4, A6, A8, and A10. .
z = (y ² / r) / [1+ {1− (1 + K) (y / r) ² } ^1/2 ]
+ A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰
E represents a power of 10. The symbols of these specification values are common to the numerical data of the examples described later.

Numerical example 1
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.16
2 * 1.514 0.61 1.53071 55.71
3 * -8.512 0.06
4 * -77.883 0.30 1.63260 23.28
5 * 2.165 0.39
6 * 2.008 0.31 1.58393 30.22
7 * 2.362 0.64
8 * -5.337 0.56 1.53071 55.71
9 * -1.247 0.47
10 * -1.175 0.55 1.53071 55.71
11 * 52.979 0.25
12 ∞ 0.20 1.51633 64.14
13 ∞ 0.32
Image plane ∞

Aspheric data 2nd surface
k = 0.437
A4 = -1.52719e-02, A6 = -2.10431e-02
Third side
k = 7.266
A4 = 1.32557e-01, A6 = -1.59129e-02
4th page
k = 1.079
A4 = 1.22858e-01, A6 = 4.14234e-02, A8 = -2.33656e-02
5th page
k = 3.268
A4 = -5.43689e-02, A6 = 1.07848e-01, A8 = -5.00662e-02
6th page
k = -11.164
A4 = 5.89647e-03, A6 = -4.95146e-02, A8 = 3.70178e-02, A10 = -1.95327e-02
7th page
k = 0.009
A4 = -9.63662e-02, A6 = 2.41469e-02, A8 = -1.08413e-02
8th page
k = 0.562
A4 = -8.57895e-02, A6 = 3.88476e-02, A8 = -2.04390e-02
9th page
k = -1.040
A4 = -2.78432e-03, A6 = 2.26031e-02, A8 = 3.85116e-03, A10 = -2.11278e-03
10th page
k = -1.147
A4 = 7.76084e-02, A6 = -7.56962e-03, A8 = 1.86176e-04, A10 = 5.78786e-07
11th page
k = -99.772
A4 = -2.96309e-02, A6 = 7.64446e-04, A8 = -2.13386e-04, A10 = 3.93374e-07

fb (in air) 0.71
Total length (in air) 4.59

Total focal length 4.23

Numerical example 2
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.15
2 * 1.562 0.62 1.54454 55.93
3 * -5.723 0.04
4 * 5.330 0.33 1.63494 23.91
5 * 1.462 0.29
6 * -41.633 0.34 1.60352 28.21
7 * -6.459 0.51
8 * -2.971 0.33 1.60352 28.21
9 * -1.697 0.58
10 * -1.453 0.81 1.54454 55.93
11 * -7.483 0.25
12 ∞ 0.20 1.51633 64.14
13 ∞ 0.31
Image plane ∞

Aspheric data 2nd surface
k = -0.251
A4 = -6.57688e-03, A6 = -1.08256e-02, A8-2.88799e-02, A10 = -5.91158e-03
Third side
k = 5.554
A4 = 6.34805e-02, A6 = -1.12391e-01, A8 = 1.01639e-01, A10 = -5.33485e-02
4th page
k = -171.109
A4 = 5.52591e-02, A6 = -5.59237e-02, A8 = 1.30568e-01, A10 = -5.13041e-02
5th page
k = -0.238
A4 = -1.73099e-01, A6 = 2.88831e-01, A8 = -2.17465e-01, A10 = 1.23197e-01
6th page
k = 43.598
A4 = -8.87746e-02, A6 = -7.59662e-02, A8 = 2.87338e-01, A10 = -1.19189e-01
7th page
k = 25.501
A4 = -5.60907e-02, A6 = -6.79959e-02, A8 = 1.24828e-01, A10 = 3.11344e-02
8th page
k = 0.363
A4 = -4.35137e-02, A6 = -4.64459e-02, A8 = -8.27315e-03, A10 = 1.12264e-03
9th page
k = 0.173
A4 = 6.74807e-02, A6 = 1.99499e-02, A8 = -6.40927e-03, A10 = 1.56685e-03
10th page
k = -1.578
A4 = 5.99798e-02, A6 = -8.31077e-03, A8 = 7.03202e-04, A10 = -5.05168e-05
11th page
k = -200.000
A4 = -2.41208e-02, A6 = -7.90557e-04, A8 = -3.92103e-04, A10 = 4.61755e-05

fb (in air) 0.69
Total length (in air) 4.54

Total focal length 4.28

Numerical Example 3
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.10
2 * 1.618 0.62 1.53071 55.71
3 * -4.961 0.05
4 * 5.710 0.33 1.63494 23.91
5 * 1.563 0.39
6 * -3.756 0.39 1.53071 55.71
7 * -2.061 0.42
8 * -1.845 0.50 1.60352 28.21
9 * -1.580 0.73
10 * -1.614 0.67 1.53071 55.71
11 * -7.980 0.25
12 ∞ 0.20 1.51633 64.14
13 ∞ 0.31
Image plane ∞

Aspheric data 2nd surface
k = -0.170
A4 = -1.00356e-02, A6 = -3.81996e-03, A8 = 5.51225e-03, A10 = -2.99796e-03
Third side
k = 7.114
A4 = 7.85575e-02, A6 = 1.21370e-02, A8 = 5.33615e-03, A10 = 1.31206e-02
4th page
k = -113.321
A4 = 6.01996e-02, A6 = 4.26326e-03, A8 = 1.30646e-01, A10 = -9.05304e-02
5th page
k = 0.790
A4 = -1.32069e-01, A6 = 1.44559e-01, A8 = -6.94869e-02, A10 = 2.98790e-02
6th page
k = -22.022
A4 = -1.85512e-02, A6 = 6.79936e-02, A8 = 8.52940e-04, A10 = 4.87794e-04
7th page
k = -5.915
A4 = 1.50114e-02, A6 = 6.95824e-02, A8 = -5.46294e-04, A10 = -2.72286e-03
8th page
k = -2.318
A4 = 1.39851e-02, A6 = 9.33341e-02, A8 = -1.01201e-01, A10 = 3.11984e-02, A12 = -2.96310e-03
9th page
k = -0.109
A4 = 4.90824e-02, A6 = 8.55630e-02, A8 = -4.72267e-02, A10 = 8.61669e-03, A12 = 1.97114e-04
10th page
k = -1.005
A4 = 5.28628e-02, A6 = -5.86815e-03, A8 = 8.46175e-04, A10 = -8.07449e-05, A12 = 3.71532e-07
11th page
k = -445.082
A4 = -2.58354e-02, A6 = 1.51787e-03, A8 = -3.84860e-04, A10 = 2.54376e-05, A12 = 9.34150e-08

fb (in air) 0.71
Total length (in air) 4.82

Total focal length 4.47

Numerical Example 4
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.18
2 * 1.449 0.55 1.53071 55.71
3 * -6.171 0.06
4 * 5.948 0.33 1.63494 23.91
5 * 1.443 0.28
6 * 19.919 0.34 1.60352 28.21
7 * -19.991 0.43
8 * -2.719 0.34 1.60352 28.21
9 * -1.699 0.70
10 * -1.722 0.81 1.53071 55.71
11 * -11.154 0.25
12 ∞ 0.20 1.51633 64.14
13 ∞ 0.33
Image plane ∞

Aspheric data 2nd surface
k = -0.117
A4 = -1.18556e-03, A6 = -6.58231e-03, A8 = -2.32639e-02, A10 = 3.01692e-02
Third side
k = -11.751
A4 = 7.53795e-02, A6 = -9.31862e-02, A8 = 1.10250e-01, A10 = 4.78478e-03
4th page
k = -174.630
A4 = 4.88256e-02, A6 = -5.68098e-02, A8 = 1.46920e-01, A10 = -3.82802e-02
5th page
k = -0.092
A4 = -1.63449e-01, A6 = 2.78687e-01, A8 = -2.54070e-01, A10 = 1.68844e-01
6th page
k = 41.914
A4 = -7.82489e-02, A6 = -5.97126e-02, A8 = 2.95170e-01, A10 = -1.61574e-01
7th page
k = 101.771
A4 = -6.86789e-02, A6 = -8.41227e-02, A8 = 1.10130e-01, A10 = 3.83175e-02
8th page
k = 0.915
A4 = -4.70200e-02, A6 = -6.88395e-02, A8 = -2.66452e-03, A10 = -2.39501e-02
9th page
k = 0.332
A4 = 6.15674e-02, A6 = 2.48501e-02, A8 = -4.90039e-03, A10 = 2.29803e-03
10th page
k = -1.112
A4 = 5.82775e-02, A6 = -7.14819e-03, A8 = 6.34866e-04, A10 = -4.04834e-05
11th page
k = -636.320
A4 = -2.12631e-02, A6 = -1.50144e-03, A8 = -4.38711e-04, A10 = 6.36103e-05

fb (in air) 0.71
Total length (in air) 4.55

Total focal length 4.37

Numerical Example 5
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.10
2 * 1.566 0.55 1.54454 55.93
3 * -13.551 0.06
4 * 6.440 0.33 1.63494 23.91
5 * 1.754 0.33
6 -10.574 0.47 1.53071 55.71
7 * -3.536 0.43
8 * -2.442 0.57 1.54454 55.93
9 * -1.247 0.70
10 * -1.071 0.41 1.54454 55.93
11 * -4.779 0.30
12 ∞ 0.20 1.51633 64.14
13 ∞ 0.30
Image plane ∞

Aspheric data 2nd surface
k = 0.118
A4 = 3.51981e-03, A6 = 3.15415e-04, A8 = 2.85742e-02
Third side
k = -49.163
A4 = 9.91226e-02, A6 = -1.01062e-01, A8 = 1.87672e-01
4th page
k = 6.287
A4 = 4.22317e-02, A6 = -1.42760e-01, A8 = 2.38264e-01, A10 = -3.19567e-02
5th page
k = 1.391
A4 = -6.20887e-02, A6 = 2.25292e-02, A8 = -9.94067e-02, A10 = 1.30287e-01
7th page
k = -3.816
A4 = 1.98999e-02, A6 = -5.49857e-02, A8 = 2.73220e-02, A10 = 1.14483e-02
8th page
k = 1.870
A4 = -5.96485e-02, A6 = 1.39147e-01, A8 = -1.30303e-01, A10 = 4.49195e-02
9th page
k = -0.461
A4 = -2.79628e-03, A6 = 1.03908e-01, A8 = -3.66048e-02, A10 = 6.17661e-03
10th page
k = -1.885
A4 = 5.81773e-02, A6 = -6.68551e-03, A8 = 1.30080e-04, A10 = 8.02451e-06, A12 = 8.92094e-07
11th page
k = -150.548
A4 = -1.68889e-02, A6 = 5.444836e-04, A8 = -5.25831e-04, A10 = 1.26296e-04, A12 = -1.02406e-05

fb (in air) 0.76
Total length (in air) 4.61

Total focal length 4.09

Numerical Example 6
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.10
2 * 1.895 0.70 1.54454 55.93
3 * -35.770 0.05
4 * 4.541 0.34 1.63494 23.91
5 * 1.763 0.36
6 * 554.313 0.49 1.53071 55.71
7 * -4.923 0.49
8 * -2.316 0.77 1.54454 55.93
9 * -1.132 0.57
10 * -3.874 0.44 1.54454 55.93
11 * 2.329 0.46
12 ∞ 0.30 1.51633 64.14
13 ∞ 0.40
Image plane ∞

Aspheric data 2nd surface
k = -0.417
A4 = 2.30722e-02, A6 = -1.57621e-02, A8 = 2.42845e-02
Third side
k = 0.027
A4 = 8.14577e-04, A6 = 3.23114e-02, A8 = 1.84596e-02
4th page
k = -41.241
A4 = -5.43173e-02, A6 = 6.47387e-02, A8 = -9.99442e-03, A10 = -6.30963e-03
5th page
k = 0.803
A4 = -1.26827e-01, A6 = 8.91246e-02, A8 = -5.28834e-02, A10 = 6.13521e-03
6th page
k = -1.264
A4 = -3.67651e-02, A6 = 4.83340e-04, A8 = 2.45824e-02, A10 = -7.23457e-03
7th page
k = -3.287
A4 = -5.22028e-02, A6 = 3.97193e-02, A8 = -3.88474e-02, A10 = 1.79400e-02
8th page
k = 1.102
A4 = -9.69947e-02, A6 = 1.27478e-01, A8 = -5.71162e-02, A10 = 1.24910e-02
9th page
k = -0.868
A4 = 3.03167e-02, A6 = 5.02812e-03, A8 = 9.35928e-03, A10 = -2.37338e-03
10th page
k = -0.243
A4 = 6.13107e-03, A6 = 2.18227e-04, A8 = 2.20085e-04, A10 = -2.21650e-05
11th page
k = -9.257
A4 = -3.71806e-02, A6 = 6.26959e-03, A8 = -8.14906e-04, A10 = 4.31811e-05

fb (in air) 1.06
Total length (in air) 5.28

Total focal length 4.32

Numerical Example 7
Unit: mm

Surface data surface number rd nd νd
Object ∞ ∞
1 (Aperture) ∞ -0.10
2 * 2.100 0.85 1.53071 55.71
3 * -10.000 0.05
4 * 9.391 0.40 1.63494 23.91
5 * 2.428 0.76
6 * -3.409 0.66 1.53071 55.71
7 * -1.539 0.38
8 * -1.402 0.83 1.53071 55.71
9 * -1.300 0.66
10 * -1.908 0.50 1.53071 55.71
11 * 47.477 0.60
12 ∞ 0.30 1.51633 64.14
13 ∞ 0.45
Image plane ∞

Aspheric data 2nd surface
k = -1.154
A4 = 1.46019e-02, A6 = 8.67027e-04, A8 = -1.00000e-03
Third side
k = -5.000
A4 = 7.83820e-03, A6 = 2.24308e-04, A8 = -1.09538e-04
4th page
k = 3.593
A4 = -1.93960e-02, A6 = 1.25120e-02, A8 = 5.66178e-04
5th page
k = 1.505
A4 = -3.04522e-02, A6 = 1.15182e-02, A8 = 1.85302e-04
6th page
k = 1.351
A4 = -1.00000e-02, A6 = 1.30000e-03
7th page
k = -1.575
A4 = 2.33107e-02, A6 = -5.69157e-03
8th page
k = -0.869
A4 = 5.99547e-02, A6 = -6.95207e-03, A8 = -4.49331e-04
9th page
k = -1.259
A4 = 1.00000e-02, A6 = 1.00000e-03
10th page
k = -0.818
A4 = 4.38227e-02, A6 = -4.00871e-03, A8 = -2.87456e-05, A10 = 1.78791e-05
11th page
k = 15.000
A4 = -8.66144e-03, A6 = 1.01133e-03, A8 = -1.84966e-04, A10 = 5.56796e-06

fb (in air) 1.25
Total length (in air) 6.35

Total focal length 5.43

Next, the values of the conditional expressions in each example are listed.

Formula (1) f4 / f
Formula (2) f3 / f4
Formula (3) f1 / f
Formula (4) f3 / f
Formula (5) | (SAG4AS-SAG4AA) / 4AR |
Formula (6) | (SAG4BS-SAG4BA) / 4BR |
Formula (7) αi

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
f 4.23 4.28 4.47 4.37 4.09 4.32 5.43
f1 2.46 2.31 2.37 2.26 2.60 3.31 3.34
f2 -3.28 -3.25 -3.47 -3.06 -3.86 -4.72 -5.23
f3 17.13 12.52 7.94 16.45 9.74 9.16 4.68
f4 2.91 5.93 10.54 6.61 3.99 3.29 8.77
f5 -2.15 -3.46 -3.94 -3.94 -2.63 -2.59 -3.43
F NO 2.80 2.80 2.94 2.94 2.94 2.80 2.89
Formula (1) 0.58 0.54 0.53 0.52 0.64 0.77 0.61
Formula (2) 0.69 1.38 2.36 1.51 0.98 0.76 1.62
Formula (3) 5.89 2.11 0.75 2.49 2.44 2.78 0.53
Formula (4) 4.06 2.92 1.78 3.76 2.38 2.12 0.86
Formula (5) 0.005 0.004 0.013 0.004 0.004 0.010 0.074
Formula (6) 0.062 0.021 0.040 0.014 0.059 0.182 0.197
Formula (7) 26 26 24 25 25 24 24

  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 a CMOS, especially 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. 15 to 17 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. 15 is a front perspective view showing the appearance of the digital camera 40, FIG. 16 is a rear perspective view thereof, and FIG. 17 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 part of the camera 40, photographing is performed through the photographing optical system 41, for example, the imaging optical system 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 the image formed into an erect image to the observer eyeball E is disposed.

  According to the digital camera 40 configured as described above, an electronic imaging device having a compact and thin zoom lens in which the number of components of the photographing optical system 41 is reduced can be realized. The imaging optical system of the retractable digital camera is different from the lens cross-sectional configuration of each numerical example, but includes the imaging optical system of each example as described above.

  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. 18 is a front perspective view of the personal computer 300 with the cover open, FIG. 19 is a sectional view of the photographing optical system 303 of the personal computer 300, and FIG. 20 is a side view of FIG. As shown in FIGS. 18 to 20, 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. Examples of the liquid crystal display element include a transmissive liquid crystal display element that illuminates from the back with a backlight (not shown), and a reflective liquid crystal display element that reflects and displays light from the front. Further, in the drawing, the photographing optical system 303 is built in the upper right of the monitor 302. However, the imaging optical system 303 is not limited to the place, and may be anywhere around the monitor 302 or the keyboard 301.

The photographic optical system 303 includes, on the photographic optical path 304, the objective optical system 100 including, for example, the imaging optical system according to the first embodiment, and the electronic imaging element chip 162 that receives an image. These are built in the personal computer 300.
The imaging optical system of this personal computer is different from the lens cross-sectional configuration of each numerical example described above, but includes the imaging optical system of each of the above examples as described above.

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. 18 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. 21 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 that is convenient to carry. 21A is a front view of the mobile phone 400, FIG. 21B is a side view, and FIG. 21C is a cross-sectional view of the photographing optical system 405. As shown in FIGS. 21A to 21C, 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 the objective optical system 100 disposed on the 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 zoom 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 imaging optical system of the information processing apparatus is different from the lens cross-sectional configuration of each numerical example, but includes the imaging optical system of each example as described above.

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

  As described above, the present invention is useful for a compact and high-performance imaging optical system.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens CG Cover glass I Imaging surface E Eyeball of observer 40 Digital camera 41 Imaging optical system 42 Optical path for imaging 43 Viewfinder optical system 44 Optical path for viewfinder 45 Shutter 46 Flash 47 Liquid crystal display monitor 48 Imaging optical system 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

In order to solve the above-described problems and achieve the object, the imaging optical system of the present invention includes:
From the object side,
An aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
A fifth lens having negative refractive power;
Ri name than five lenses of,
The object side surface of the third lens is convex to the object side;
At least one surface of the fifth lens is aspheric and has at least one inflection point;
Distance between the adjacent lenses are all characterized by fixing der Rukoto.

According to a preferred aspect of the present invention, it is desirable that the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are formed of resin.
According to a preferred aspect of the present invention, it is desirable that the second lens has a meniscus shape having a concave image side surface.
According to a preferred aspect of the present invention, it is desirable that the object side surface of the first lens is convex toward the object side.
According to a preferred aspect of the present invention, it is desirable that the first lens is biconvex.
According to a preferred aspect of the present invention, it is desirable that the fourth lens has a meniscus shape with a concave object side surface.
Moreover, according to the preferable aspect of this invention, it is desirable to satisfy the following conditional expressions.
1.68 <f3 / f <6.31 (4 ''')
here,
f3 is the focal length of the third lens,
f is the focal length of the entire imaging optical system,
It is.
According to a preferred aspect of the present invention, it is desirable that both the first lens surface and the second lens surface are both aspherical.
According to a preferred aspect of the present invention, it is desirable that both surfaces of the fourth lens and both surfaces of the fifth lens are aspheric surfaces.
Further, according to a preferred aspect of the present invention, the aperture stop is disposed on the image side from the top position of the object side surface of the first lens and closer to the object side than the most peripheral portion of the object side surface of the first lens. It is desirable that
According to a preferred aspect of the present invention, it is desirable that there is an air space between the second lens and the third lens.
According to a preferred aspect of the present invention, it is desirable that the fifth lens is configured to have the largest diameter.

The imaging equipment of the present invention,
The imaging optical system described above;
And an electronic imaging device having an imaging surface .
Moreover, it is desirable that the image pickup apparatus of the present invention satisfies the following conditional expression.
15 ° <αi <30 ° (7)
Here, αi is the incident angle of the principal ray on the imaging surface at the maximum image height.

Prior to the description of the examples, the effects of the imaging optical system of the present embodiment will be described. In the following description, the imaging optical system is appropriately referred to as an imaging optical system.

In the imaging optical system of the present embodiment, the aperture stop is disposed closest to the object side. For this reason, the exit pupil can be separated from the image plane. Thereby, the angle of the light ray incident on the peripheral portion can be reduced at the imaging position (the imaging surface of the electronic imaging device). Therefore, it is possible to avoid shortening the optical length and lowering the sensitivity of the periphery of the image sensor.
In addition, since the position of the principal point can be arranged closer to the object side of the optical system, the total length can be sufficiently reduced with respect to the focal length. Thereby, shortening of the full length of an optical system is realizable.
In addition, by arranging a third lens having a positive refractive power and a five-lens configuration in which the fourth lens is positive, correction of lateral chromatic aberration of magnification in the peripheral portion compared to a conventional four-lens imaging lens is possible. Is advantageous. Furthermore, since the fourth lens has a positive refractive power, it is advantageous for shortening the overall length of the optical system.
In addition, in the imaging optical system of the present embodiment, the object side surface of the third lens is convex toward the object side, at least one surface of the fifth lens is aspherical, and has at least one inflection point, The intervals between adjacent lenses are all fixed.

In the imaging apparatus of the reference example , it is desirable to have a shutter mechanism on the most object side of the imaging optical system.
By disposing the shutter closest to the object side of the imaging optical system, the entire optical system and the shutter mechanism can be configured separately. Therefore, the assembly of the imaging module is facilitated, and it is advantageous for downsizing the imaging module. Further, by disposing near the aperture stop, the influence of shutter shading can be reduced.

Hereinafter, examples of the imaging optical system and the electronic imaging apparatus of the present embodiment will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Examples 2, 3, 5 and 7 are reference examples.

Next, the values of the conditional expressions in each example are listed.

Formula (1) f4 / f
Formula (2) f3 / f4
Formula (3) f1 / f
Formula (4) f3 / f
Formula (5) | (SAG4AS-SAG4AA) / 4AR |
Formula (6) | (SAG4BS-SAG4BA) / 4BR |
Formula (7) αi

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7
f 4.23 4.28 4.47 4.37 4.09 4.32 5.43
f1 2.46 2.31 2.37 2.26 2.60 3.31 3.34
f2 -3.28 -3.25 -3.47 -3.06 -3.86 -4.72 -5.23
f3 17.13 12.52 7.94 16.45 9.74 9.16 4.68
f4 2.91 5.93 10.54 6.61 3.99 3.29 8.77
f5 -2.15 -3.46 -3.94 -3.94 -2.63 -2.59 -3.43
F NO 2.80 2.80 2.94 2.94 2.94 2.80 2.89
Formula (1) 0.69 1.38 2.36 1.51 0.98 0.76 1.62
Formula (2) 5.89 2.11 0.75 2.49 2.44 2.78 0.53
Formula (3) 0.58 0.54 0.53 0.52 0.64 0.77 0.61
Formula (4) 4.06 2.92 1.78 3.76 2.38 2.12 0.86
Formula (5) 0.005 0.004 0.013 0.004 0.004 0.010 0.074
Formula (6) 0.062 0.021 0.040 0.014 0.059 0.182 0.197
Formula (7) 26 26 24 25 25 24 24

Claims (13)

From the object side,
An aperture stop,
A first lens having a positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power;
A fourth lens having a positive refractive power;
A fifth lens having negative refractive power;
An imaging optical system comprising the five lenses. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0.36 <f4 / f <3.88 (1)
here,
f4 is the focal length of the fourth lens,
f is the focal length of the entire imaging optical system,
Is The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0.81 <f3 / f4 <3.25 (2)
here,
f3 is the focal length of the third lens,
f4 is the focal length of the fourth lens,
It is. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0.28 <f1 / f <1.23 (3)
However,
f1 is the focal length of the first lens,
f is the focal length of the entire imaging optical system,
It is.   5. The imaging optical system according to claim 1, wherein a surface on the image plane side of the second lens has a concave shape on the image plane side. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied. 0.57 <f3 / f <6.31 (4)
here,
f3 is the focal length of the third lens,
f is the focal length of the entire imaging optical system,
It is. The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
0 <| (SAG4AS-SAG4AA) / 4AR | <0.147 (5)
And 0 <| (SAG4BS-SAG4BA) / 4BR | <0.395 (6)
here,
SAG4AS is the amount of sag at the position where the effective diameter is 60% when the object side surface of the fourth lens is a spherical surface.
SAG4AA is the amount of sag at the position of 60% effective diameter of the object side surface of the fourth lens,
SAG4BS is the amount of sag at the position of 60% effective diameter when the imaging surface side surface of the fourth lens is a spherical surface.
SAG4BA is the amount of sag at the position of the effective diameter of 60% of the surface on the imaging surface side of the fourth lens,
4AR is the paraxial radius of curvature of the object side surface of the fourth lens,
4BR is the paraxial radius of curvature of the imaging surface side surface of the fourth lens,
It is.   The imaging optical system according to claim 1, wherein the object side surface of the fifth lens is a concave lens.   The said 1st lens, the said 2nd lens, the said 3rd lens, the said 4th lens, and the said 5th lens are formed with resin, The Claim 1 characterized by the above-mentioned. Imaging optical system. The imaging optical system according to any one of claims 1 to 9,
An imaging device comprising an electronic imaging device having an imaging surface,
An image pickup apparatus satisfying the following conditional expression:
15 ° <αi <30 ° (7)
Here, αi is the incident angle of the principal ray on the imaging surface at the maximum image height.   The imaging apparatus according to claim 10, further comprising a shutter mechanism closest to the object side of the imaging optical system.   The imaging apparatus according to claim 10, wherein the imaging optical system includes an autofocus mechanism.   The image pickup apparatus according to claim 10, 11 or 12, wherein the image pickup optical system and an electronic image pickup element are integrated.

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