JP2015129869A - Imaging optical system, imaging apparatus, and portable terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact imaging optical system which achieves excellently corrected chromatic aberration during both long range imaging and short range imaging, an imaging apparatus including the imaging optical system, and a portable terminal including the imaging apparatus.SOLUTION: An imaging optical system 10 comprises a plurality of lenses including a first lens L1 arranged closest to the object side. During short range imaging in which the distance from the imaging optical system 10 to a subject is less than a predetermined value, a first aperture stop AP1 arranged on the object side of the first lens functions as an aperture stop, and during long range imaging in which the distance from the imaging optical system 10 to the subject is equal to or larger than the predetermined value, a second aperture stop AP2 arranged between lenses functions as an aperture stop. The imaging optical system satisfies the following conditional expressions: φF>φN...(1), and L/2Y<1.1...(2), where φN is the aperture diameter (mm) of the first aperture stop during short range imaging, φF is the aperture diameter (mm) of the second aperture stop, L is the distance (mm) from the vertex of the object side surface of the first lens to an imaging plane during long range imaging, and Y is the maximum image height (mm) during long range imaging.

Description

  The present invention relates to an imaging optical system, and more particularly, to a small and high-resolution imaging optical system using a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, and an imaging apparatus and a portable terminal including the imaging optical system.

  In recent years, portable terminals equipped with an imaging device using a solid-state imaging device such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor have become widespread. In such an imaging apparatus mounted on a portable terminal, an apparatus using an imaging element having a high pixel number has been supplied to the market so that a higher quality image can be obtained. Conventional image pickup devices having a large number of pixels have been accompanied by an increase in size, but in recent years, pixels have become increasingly thinner, and image pickup devices have become smaller and higher in density.

  An imaging optical system that forms a subject image on such a high-definition imaging device is required to have high optical performance. On the other hand, as a small and high-performance optical system, the aberration correction function is higher than that of a three- or four-lens imaging optical system and high performance is possible. A system has been proposed. On the other hand, in order to use it for an imaging device for a portable terminal, even in the case of an imaging optical system having a configuration of five or six sheets, it is necessary to reduce the overall length and reduce the height as in the past. In addition, there is also a demand for securing a bright F number in order to improve resolution and to capture a low-luminance subject.

  By the way, in the case of a low-profile imaging optical system having a bright F-number, if aberrations are corrected optimally when imaging a subject at a long distance, deterioration of aberrations when imaging a subject at a short distance cannot be sufficiently suppressed. There are challenges. On the other hand, in imaging optical systems used for general digital cameras and video cameras, a technique for suppressing aberration degradation by displacing a part of the imaging optical system in the optical axis direction in order to reduce aberration degradation. It has been known. However, an imaging apparatus mounted on a portable terminal or the like is required to be disposed in a limited space, and there are many restrictions on the degree of freedom such as the size of the imaging optical system and the amount of movement of the optical system. On the other hand, there are attempts to improve not only the aberration at the time of long-distance imaging but also the aberration at the time of short-distance imaging by different methods.

JP 2012-185345 A JP 2011-102871 A JP 2010-96820 A

  In the zoom optical system for digital cameras and video cameras disclosed in Patent Document 1, the aperture stop is displaced in the optical axis direction at the telephoto end and the wide-angle end, and the aperture diameter is variable, but the number of lenses is large. In addition, since the lens movement amount is too large, it is difficult to mount the lens in an imaging device for a portable terminal as it is. Also, in the rear focus type retro-focus type wide-angle zoom lens for a camera disclosed in Patent Document 2, two groups including a diaphragm are moved toward the object side at the time of short-distance imaging. Since it is large and the amount of movement of the lens is too large, it is difficult to mount it on an imaging device for a portable terminal as it is.

  On the other hand, the imaging optical system disclosed in Patent Document 3 is low in height so that it can be mounted on an imaging device for a portable terminal, and is disposed on the object side of the lens and has an open F number, and a first aperture It has a second aperture which is arranged closer to the object side and has a small aperture F-number, and this makes it possible to effectively cut marginal peripheral rays having a relatively large aberration while having a simple configuration. However, the imaging optical system disclosed in Patent Document 3 is slightly insufficient to improve the performance at close-up shooting when the height is lowered, and both the first and second apertures are used. The configuration arranged on the object side of the lens hinders a reduction in height because a space is required on the object side.

  The present invention has been made in view of the above-described problems, and various aberrations are favorably corrected at both long-distance imaging and short-distance imaging while having a low profile with a short overall optical system length. Another object of the present invention is to provide a small-sized imaging optical system, an imaging device including the imaging optical system, and a portable terminal including the imaging device.

The imaging optical system according to claim 1 is an imaging optical system including a plurality of lenses including a first lens arranged closest to the object side,
During short-distance imaging in which the distance from the imaging optical system to the subject is less than a predetermined value, the first diaphragm disposed on the object side of the first lens functions as an aperture diaphragm,
During long-distance imaging in which the distance from the imaging optical system to the subject is a predetermined value or more, the second diaphragm disposed between the lenses functions as an aperture diaphragm and satisfies the following conditional expression.
φF> φN (1)
L / 2Y <1.1 (2)
However,
φN: Aperture diameter (mm) of the first diaphragm during short-distance imaging
φF: aperture diameter of the second diaphragm (mm)
L: Distance (mm) from the object side surface vertex of the first lens to the imaging surface during long-distance imaging
Y: Maximum image height (mm) during long-distance imaging

  According to the present invention, by satisfying the expression (1), it is possible to perform favorable imaging using the second diaphragm at the time of long-distance imaging, and the first aperture having a smaller aperture diameter than that of the second diaphragm at the time of short-distance imaging. With the stop, it is possible to suppress the marginal peripheral light beam from contributing to the image formation and to suppress the deterioration of the aberration. In addition, the depth of focus can be increased. Furthermore, by arranging the first stop closer to the object side than the second stop, the marginal peripheral light beam is more easily cut, and the light beam emitted from the final surface of the optical system and imaged on the image pickup surface is directed to the image pickup surface. Since the incident angle becomes small, the problem of shading can be alleviated. However, if the second diaphragm is provided closer to the object side than the lens on the most object side, when the first diaphragm is moved away from the second diaphragm, the length in the optical axis direction of the imaging optical system becomes long, and the low-profile imaging optical system Cannot be secured. In addition, the peripheral aperture is excessively kicked by the first diaphragm, and the periphery becomes dark. Therefore, in the present invention, by disposing the second diaphragm between the lenses, it is possible to correct various aberrations regardless of the subject distance even in a low-profile imaging optical system that satisfies Equation (2). Therefore, shading can be reduced by securing a sufficient telecentric characteristic. In the case where the shape of the diaphragm is a non-circular shape (including a rectangle or an ellipse), the “aperture diameter” refers to the diameter of the aperture area converted to a perfect circle. In addition, “functioning as an aperture stop” means a state in which the light beam focused on the optical axis of the imaging plane (such as the imaging plane of the solid-state imaging device) is substantially limited, that is, a plurality of normal imaging optical systems. This indicates a state in which a stop is arranged but functions as a stop for determining a marginal ray of a light beam that forms an image on the optical axis.

The imaging optical system according to claim 2 is characterized in that, in the invention according to claim 1, the following conditional expression is satisfied.
1.1 <φF / φN <2.0 (3)

If the value of equation (3) exceeds the lower limit, good imaging is possible even in an imaging environment where a sufficient amount of light cannot be obtained. On the other hand, if the value of equation (3) is less than the upper limit, sufficient marginal peripheral luminous flux is obtained. In this way, it is possible to obtain an image in which various aberrations are satisfactorily corrected even when imaging a short-distance subject. More preferably, the following expression is satisfied.
1.5 <φF / φN <2.0 (3 ′)

  According to a third aspect of the present invention, there is provided the imaging optical system according to the first or second aspect, wherein the first diaphragm has a constant aperture diameter and is inserted into the optical axis, and the optical axis. It is characterized in that a retreat position for retreating can be selectively taken.

  The configuration in which the first aperture with a fixed aperture diameter is inserted into the optical path or removed from the optical path can use, for example, a conventional simple rotation mechanism, and is relatively small and simple. Therefore, for example, it can be easily mounted on an imaging device for a portable terminal. A plurality of paths may be taken as a method of moving between the aperture position and the retracted position. For example, when the first diaphragm is located on the object side of the first lens in the optical axis direction and is located on the image side from the vertex of the first lens, it is shifted to the object side parallel to the optical axis and then retracted to the retracted position. You can do it.

  According to a fourth aspect of the present invention, there is provided the imaging optical system according to the first or second aspect, wherein the first aperture has a variable aperture diameter.

  With such a configuration, it is not necessary to retract the first diaphragm from the optical path, so that a retreat space is not necessary, and a smaller imaging device can be realized. Specifically, at the time of long-distance imaging, the diameter of the first diaphragm is made larger than that at the time of short-distance imaging so that the second diaphragm having a fixed aperture diameter can function as an aperture diaphragm. On the other hand, at the time of short-distance imaging, the diameter of the first diaphragm can be made smaller than that at the time of long-distance imaging, so that the first diaphragm can function as an aperture diaphragm. In addition, as a 1st aperture_diaphragm | restriction, what changed the aperture diameter by driving several aperture blades, and what changed an aperture diameter using a liquid crystal can be used. In the case of a diaphragm using liquid crystal, due to the characteristics of the liquid crystal, light may leak outside the aperture diameter that should be shielded from light, and the outer transmittance may not become zero. In such a case, in consideration of leaking light, the substantial aperture diameter may be set assuming that the aperture diameter increases accordingly.

  The imaging optical system according to claim 5 is the invention according to any one of claims 1 to 4, wherein the F-number during long-distance imaging is less than 2.0, and the number of lenses is 5 or 6. It is characterized by that.

  In general, when the F-number is decreased, the aberration deterioration at the time of short-distance imaging tends to increase. However, in combination with the present invention, it is possible to perform imaging at lower luminance while achieving good image quality even at a short distance. Can be imaged.

  The imaging optical system according to a sixth aspect is the invention according to any one of the first to fifth aspects, wherein the imaging optical system as a whole is displaced toward the object side during short-distance imaging with respect to long-distance imaging. And

  By displacing the entire imaging optical system to the object side, the relative positional relationship between the lenses does not change, so that it is possible to prevent the mutual shift and tilt of the lenses in the optical system. In combination with the present invention, good optical characteristics are obtained. be able to.

  The imaging optical system according to a seventh aspect is the invention according to any one of the first to fifth aspects, wherein the imaging optical system includes a first lens group and a second lens group in order from the object side. At the time of short-distance imaging with respect to distance imaging, only the first lens group or only the second lens is displaced in the optical axis direction.

  By displacing only the first lens group or only the second lens group in the optical axis direction, a small actuator with a smaller driving force can be used, and focusing on a subject at a short distance can be performed with power saving. In combination with the present invention, good optical characteristics can be obtained.

The imaging optical system according to claim 8 is the invention according to any one of claims 1 to 5, wherein the imaging optical system is composed of a first lens group and a second lens group in order from the object side. The first lens group and the second lens group are displaced toward the object side during short-distance imaging as compared with distance imaging, and satisfy the following conditional expression.
T1> T2 (4)
However,
T1: Amount of displacement (mm) in the optical axis direction during short-distance imaging with respect to long-distance imaging with the first lens group
T2: optical axis direction displacement amount (mm) at the time of short-distance imaging with respect to long-distance imaging with the second lens group

  By displacing the first lens group to the object side more than the second lens group, it is possible to suppress an increase in field curvature when focusing on a subject at a short distance. Performance degradation can be further suppressed, and in combination with the present invention, there are effects such as suppressing the amount of movement of the lens group and preventing the aperture diameter of the diaphragm from being made too small. Can brighten the F number.

  The imaging optical system according to a ninth aspect is the invention according to any one of the first to eighth aspects, wherein the second diaphragm is disposed between the first lens and the third lens. And

  As a result, even in a low-profile imaging optical system, the distance between the first diaphragm and the second diaphragm can be appropriately secured, and various aberrations can be corrected satisfactorily even in imaging at a short distance. The incident angle can be reduced and shading can be reduced.

  The imaging optical system according to a tenth aspect is the invention according to any one of the first to ninth aspects, wherein the predetermined value is any distance within a range of 80 to 500 mm.

  As a result, it is possible to image a short-distance subject with good image quality.

  An imaging apparatus according to an eleventh aspect includes the imaging optical system according to any one of the first to tenth aspects and a solid-state imaging element.

  A portable terminal according to a twelfth aspect includes the imaging device according to the eleventh aspect and a display device, and displays an image captured by the imaging device on the display device. By using the imaging device of the present invention, a portable terminal capable of obtaining a smaller and higher performance image can be obtained.

  According to the present invention, there is provided a compact imaging optical system in which various aberrations are favorably corrected both at the time of long-distance imaging and at the time of short-distance imaging while having a low profile with a short overall optical system length. An imaging apparatus including the system and a portable terminal including the imaging apparatus can be provided.

It is a perspective view of the imaging device 50 concerning this Embodiment. 3 is a diagram schematically showing a cross section along the optical axis of an imaging optical system of the imaging apparatus 50. FIG. It is the front view (a) of the smart phone as a portable terminal to which an imaging device is applied, and the back view (b) of the smart phone to which the imaging device is applied. It is a control block diagram of the smart phone of FIG. 2 is a cross-sectional view in the optical axis direction of the imaging optical system in the 1-A state of Embodiment 1. FIG. FIG. 4 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) in the 1-A state of Example 1. 3 is a graph showing MTF (Modulation Transfer Function) values of the imaging optical system in the 1-A state of Example 1. FIG. 6 is a graph showing the MTF value of the imaging optical system in the 1-B state of Example 1. FIG. 6 is a graph showing the MTF value of the imaging optical system in the 1-C state of Example 1. FIG. FIG. 6 is a cross-sectional view in the optical axis direction of the imaging optical system in the 2-A state according to the second embodiment. FIG. 6 is an aberration diagram (spherical aberration (a), astigmatism (b), distortion (c)) in the 2-A state of Example 2. 6 is a graph showing an MTF (Modulation Transfer Function) value of the imaging optical system in the 2-A state of Example 2. 10 is a graph showing the MTF value of the imaging optical system in the 2-B state of Example 2. 10 is a graph showing the MTF value of the imaging optical system in the 2-C state of Example 2.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an imaging apparatus 50 according to the present embodiment, and FIG. 2 is a diagram schematically showing a cross section along the optical axis of the imaging optical system of the imaging apparatus 50. Specifically, FIG. 1 is a cross-sectional view of a lens with a barrel corresponding to Example 1. FIG.

  As shown in FIGS. 1 and 2, the imaging device 50 captures a subject image on a CMOS type imaging device 51 as a solid-state imaging device having a photoelectric conversion unit 51 a and a photoelectric conversion unit (imaging surface) 51 a of the imaging device 51. An imaging optical system 10 to be performed, a lens barrel 53 that holds the imaging optical system 10, a parallel plate-like optical filter 54 that is supported by a sensor cover (not shown) and disposed between the imaging optical system 10 and the imaging element 51, An actuator 55 that drives the imaging optical system 10 in the optical axis direction, a substrate 52 on which the imaging element 51 is mounted, and a housing 56 that is disposed on the substrate 52 and covers the imaging optical system 10.

  As shown in FIG. 2, the imaging element 51 has a photoelectric conversion part 51 a as a light receiving part in which pixels (photoelectric conversion elements) are two-dimensionally arranged at the center of the plane on the light receiving side. A signal processing circuit (not shown) is formed around the periphery. Such a signal processing circuit includes a drive circuit unit that sequentially drives each pixel to obtain a signal charge, an A / D conversion unit that converts each signal charge into a digital signal, and a signal that forms an image signal output using the digital signal. It consists of a processing unit and the like. In addition, a large number of pads (not shown) are arranged in the vicinity of the outer edge of the plane on the light receiving side of the image sensor 51, and are connected to the substrate 52 via wires 51b. The image sensor 51 converts the signal charge from the photoelectric conversion unit 51a into an image signal such as a digital YUV signal and outputs the image signal to a predetermined circuit on the substrate 52 through the wire 51b. Here, Y is a luminance signal, U (= R−Y) is a color difference signal between red and the luminance signal, and V (= BY) is a color difference signal between blue and the luminance signal. Note that the image sensor is not limited to the above CMOS image sensor, and other devices such as a CCD may be used.

  The imaging optical system 10 disposed in the lens barrel 53 includes, in order from the object side, the first aperture AP1, the first lens L1, the second aperture AP2, the second lens L2, the third lens L3, the fourth lens L4, 5 lenses L5. The first diaphragm AP1 is a variable diaphragm whose opening diameter is variable by opening and closing a plurality of diaphragm blades 57a by an actuator 57, and the second diaphragm AP2 is a fixed diaphragm having a constant opening diameter. The first stop AP1 may be a type in which an aperture having a fixed aperture diameter is inserted into and removed from the optical axis AX by an actuator 57, or a liquid crystal stop.

During short-distance imaging, the first aperture AP1 disposed on the object side of the first lens L1 functions as an aperture stop, and during long-distance imaging, the second aperture AP2 functions as an aperture stop, which satisfies the following conditional expression.
φF> φN (1)
L / 2Y <1.1 (2)
However,
φN: Aperture diameter (mm) of the first aperture stop AP1 during short-distance imaging
φF: Opening diameter of the second aperture AP2 (mm)
L: Distance (mm) from the object side surface vertex of the first lens L1 to the imaging surface during long-distance imaging
Y: Maximum image height (mm) during long-distance imaging

  The operation of the imaging device 50 described above will be described. FIG. 3 is a diagram illustrating a state in which the imaging device 50 is mounted on a smartphone 100 as a mobile terminal. FIG. 4 is a control block diagram of the smartphone 100.

  In the imaging device 50, for example, the object-side end surface of the housing 56 is provided on the back surface of the smartphone 100 (see FIG. 3B), and is disposed at a position corresponding to the back side of the touch panel 70.

  The imaging device 50 is connected to the control unit 101 of the smartphone 100 and outputs an image signal such as a luminance signal or a color difference signal to the control unit 101 side.

  On the other hand, as shown in FIG. 4, the smartphone 100 performs overall control of each unit, and also inputs a control unit (CPU) 101 that executes a program corresponding to each process, and inputs a number and the like with a key. Unit 60, a liquid crystal display unit 70 for displaying captured images in addition to predetermined data, a wireless communication unit 80 for realizing various information communication with an external server, a system program for mobile phone 100, Obtained by a storage unit (ROM) 91 storing various processing programs and necessary data such as a terminal ID, and various processing programs and data executed by the control unit 101, or processing data, or the imaging device 50 And a temporary storage unit (RAM) 92 that is used as a work area for temporarily storing imaging data and the like.

  The smartphone 100 operates by operating the input key unit 60 and can touch the icon 71 displayed on the touch panel (display unit) 70 to operate the imaging device 50 to perform imaging. Here, at the time of long-distance imaging, the aperture diameter of the first aperture stop AP1 is increased by driving the actuator 57 in the direction to open the aperture blade 57a. Therefore, the second aperture AP2 functions as an aperture stop, and a subject image is formed on the photoelectric conversion unit 51a.

  On the other hand, at the time of short-distance imaging, by driving the actuator 55, the imaging optical system 10 can be extended to the object side as a whole, and focusing on a short-distance subject can be performed. At this time, when the actuator 57 is driven in the direction to close the aperture blade 57a, the aperture diameter of the first aperture AP1 is reduced, the first aperture AP1 functions as the aperture aperture, and the subject image is formed on the photoelectric conversion unit 51a. To do. The image signal input from the imaging device 50 according to the release performed at an appropriate timing is subjected to image processing described later in the control unit 101, and is stored in the storage unit 92 by the control system of the smartphone 100, Alternatively, it is displayed on the touch panel 70, and further transmitted to the outside as video information via the wireless communication unit 80.

  Note that although the entire imaging optical system 10 is moved during short-distance imaging, the imaging optical system 10 is divided into a first lens group and a second lens group, and the second lens group is always fixed, Only the first lens group may be moved during distance imaging, or the first lens group may be always fixed, and only the second lens group may be moved during short-distance imaging. In addition, the first lens group and the second lens group are extended to the object side during short-distance imaging, but the extension amount (T1) of the first lens group may be larger than the extension amount (T2) of the second lens group.

[Example]
Examples of the imaging optical system according to the present invention will be described below. Symbols used in each example are as follows.
f: Focal length of the entire imaging optical system fB: Back focus F: F number 2Y: Diagonal length of imaging surface of solid-state imaging device
ENTP: Entrance pupil position (distance from first surface to entrance pupil position)
EXTP: Exit pupil position (distance from imaging surface to exit pupil position)
H1: Front principal point position (distance from the first surface to the front principal point position)
H2: Rear principal point position (distance from the final surface to the rear principal point position)
R: radius of curvature D: axial distance Nd: refractive index of lens material with respect to d-line νd: Abbe number of lens material with respect to d-line

  In each embodiment, the surface described with “*” after each surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and the X axis in the optical axis direction. (The image side is plus), and the height in the direction perpendicular to the optical axis is h, and is expressed by the following “Equation 1”.

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数

However,
Ai: i-order aspheric coefficient R: radius of curvature K: conic constant

  Regarding the meaning of the paraxial radius of curvature described in the claims and the examples, in the actual lens measurement scene, in the vicinity of the center of the lens (specifically, the central region within 10% of the lens outer diameter) ) Can be regarded as the paraxial curvature radius when fitting the shape measurement value in the least square method. For example, when a secondary aspherical coefficient is used, a radius of curvature that takes into account the secondary aspherical coefficient in the reference curvature radius of the aspherical definition formula can be regarded as the paraxial curvature radius. (For example, refer to P41-42 of “Lens Design Method” written by Yoshiya Matsui (Kyoritsu Publishing Co., Ltd.) as a reference)

Example 1
FIG. 5 is a cross-sectional view of the imaging optical system of Example 1 during long-distance imaging. In the figure, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, and L5 is a fifth lens having an extreme value on the image side surface. S1 is a first diaphragm disposed on the object side of the first lens L1, S2 is a second diaphragm disposed between the first lens L1 and the second lens L2, and IM represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like.

In the imaging optical system of Example 1, Table 1 shows lens data in a state (1-A state) in which the second diaphragm functions as an aperture diaphragm during long-distance imaging (subject distance ∞). Table 2 shows that at the time of short-distance imaging (subject distance: 100 mm), the first diaphragm functions as an aperture stop, and the entire imaging optical system is displaced toward the object side by 0.142 mm with respect to long-distance imaging. FIG. 3 shows lens data in the state (1-B state), and Table 3 shows the first lens L <b> 1 to L <b> 1 at the time of short-distance imaging (subject distance: 100 mm). The fourth lens L4 is the first group and the fifth lens L5 is the second group, and the first group and the second group are independently displaced toward the object side during long-distance imaging, but the displacement amount of the first group is In a state larger than the displacement of the second group (referred to as 1-C state) It shows lens data. Note that the aspheric coefficients and single lens data in Table 2 (1-B state) and Table 3 (1-C state) are the same as in Table 1 (1-A state), and are therefore omitted. Further, in this specification (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).

[Table 1]
Example 1-A

f = 3.62mm fB = 0.275mm F = 1.85 2Y = 5.842mm
ENTP = 0.27mm EXTP = -2.03mm H1 = -1.8mm H2 = -3.35mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.050 1.00
2 ∞ 0.000 1.00
3 * 1.690 0.670 1.54470 56.2 0.99
4 * -17.129 0.005 0.92
5 (Aperture) ∞ 0.045 0.90
6 * 7.652 0.170 1.63470 23.9 0.90
7 * 2.146 0.423 0.93
8 * 9.575 0.535 1.54470 56.2 1.11
9 * ∞ 0.460 1.24
10 * 17.437 0.745 1.54470 56.2 1.41
11 * -1.380 0.300 1.70
12 * -4.526 0.342 1.54470 56.2 2.25
13 * 1.244 0.450 2.51
14 ∞ 0.110 1.51630 64.1 3.30
15 ∞ 0.275 3.30

Aspheric coefficient

3rd side 9th side
K = -0.16099E + 01 K = 0.00000E + 00
A4 = 0.42509E-01 A4 = -0.94188E-01
A6 = -0.24907E-01 A6 = 0.52351E-03
A8 = 0.96714E-01 A8 = -0.32026E-01
A10 = -0.20014E + 00 A10 = 0.65498E-01
A12 = 0.18931E + 00 A12 = -0.60565E-01
A14 = -0.76314E-01 A14 = 0.22566E-01

4th page 10th page
K = -0.50000E + 02 K = 0.50000E + 02
A3 = 0.00000E + 00 A3 = -0.42649E-01
A4 = -0.80097E-01 A4 = 0.48067E-01
A5 = 0.00000E + 00 A5 = -0.10040E + 00
A6 = 0.34510E + 00 A6 = 0.14611E-01
A8 = -0.59251E + 00 A8 = 0.10093E-01
A10 = 0.43589E + 00 A10 = -0.10196E-01
A12 = -0.13901E + 00 A12 = 0.10353E-02

6th 11th
K = 0.38417E + 02 K = -0.76240E + 01
A3 = 0.00000E + 00 A3 = -0.11300E + 00
A4 = -0.25522E + 00 A4 = 0.10455E-01
A5 = 0.00000E + 00 A5 = 0.32856E-02
A6 = 0.79024E + 00 A6 = 0.30690E-02
A8 = -0.12284E + 01 A8 = 0.37157E-03
A10 = 0.94293E + 00 A10 = -0.20447E-02
A12 = -0.30120E + 00 A12 = 0.12798E-02
A14 = 0.00000E + 00 A14 = -0.22925E-03

Surface 7 Surface 12
K = -0.14022E + 02 K = 0.79050E + 00
A3 = 0.00000E + 00 A3 = -0.24413E + 00
A4 = -0.19126E-01 A4 = 0.46216E-01
A5 = 0.00000E + 00 A5 = 0.35437E-01
A6 = 0.34238E + 00 A6 = 0.29272E-02
A8 = -0.52334E + 00 A8 = -0.13992E-02
A10 = 0.44676E + 00 A10 = -0.10781E-03
A12 = -0.15009E + 00 A12 = 0.75523E-05
A14 = 0.00000E + 00 A14 = 0.18354E-05

8th 13th
K = 0.21484E + 02 K = -0.85142E + 01
A3 = 0.00000E + 00 A3 = -0.15196E + 00
A4 = -0.87540E-01 A4 = 0.74618E-01
A5 = 0.00000E + 00 A5 = -0.15556E-01
A6 = -0.97850E-01 A6 = 0.28003E-03
A8 = 0.36161E + 00 A8 = -0.30821E-03
A10 = -0.57724E + 00 A10 = -0.44514E-05
A12 = 0.44668E + 00 A12 = 0.34227E-05
A14 = -0.12141E + 00 A14 = 0.17208E-06

Single lens data

Lens Start surface Focal length (mm)
1 3 2.860
2 6 -4.755
3 8 17.578
4 10 2.380
5 12 -1.755

[Table 2]
Example 1-B

f = 3.62mm fB = 0.417mm F = 3.99 2Y = 5.842mm
ENTP = 0.27mm EXTP = -2.03mm H1 = -1.8mm H2 = -3.35mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.050 0.48
2 (Aperture) ∞ 0.000 0.48
3 * 1.690 0.670 1.54470 56.2 0.99
4 * -17.129 0.005 0.92
5 * ∞ 0.045 0.90
6 * 7.652 0.170 1.63470 23.9 0.90
7 * 2.146 0.423 0.93
8 * 9.575 0.535 1.54470 56.2 1.11
9 * ∞ 0.460 1.24
10 * 17.437 0.745 1.54470 56.2 1.41
11 * -1.380 0.300 1.70
12 * -4.526 0.342 1.54470 56.2 2.25
13 * 1.244 0.450 2.51
14 ∞ 0.110 1.51630 64.1 3.30
15 ∞ 0.417 3.30

[Table 3]
Example 1-C

f = 3.6mm fB = 0.406mm F = 3.96 2Y = 5.842mm
ENTP = 0.27mm EXTP = -2.02mm H1 = -1.79mm H2 = -3.33mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 ∞ 0.050 0.48
2 (Aperture) ∞ 0.000 0.48
3 * 1.690 0.670 1.54470 56.2 0.99
4 * -17.129 0.005 0.92
5 * ∞ 0.045 0.90
6 * 7.652 0.170 1.63470 23.9 0.90
7 * 2.146 0.423 0.93
8 * 9.575 0.535 1.54470 56.2 1.11
9 * ∞ 0.460 1.24
10 * 17.437 0.745 1.54470 56.2 1.41
11 * -1.380 0.307 1.70
12 * -4.526 0.342 1.54470 56.2 2.25
13 * 1.244 0.443 2.51
14 ∞ 0.110 1.51630 64.1 3.30
15 ∞ 0.406 3.30

  FIG. 6 shows aberration diagrams (spherical aberration (a), astigmatism (b), distortion aberration (c)) of Example 1 during long-distance imaging (1-A state). In the following aberration diagrams, in the spherical aberration diagram, the solid line represents the d-line and the dotted line represents the g-line, and in the astigmatism diagram, the solid line S represents the sagittal image plane, and the dotted line M represents the meridional image plane.

  7 is a graph showing the MTF (Modulation Transfer Function) value of the imaging optical system in the 1-A state, and FIG. 8 is a graph showing the MTF value of the imaging optical system in the 1-B state. 9 is a graph showing the MTF value of the imaging optical system in the 1-C state. 7 to 9, the vertical axis represents the MTF value, the horizontal axis represents the position in the optical axis direction with the best position on the axis being 0, O is on the axis, 3S is the position of the 30% image height in the sagittal direction, 3M is the position of 30% image height in the meridional direction, 5S is the position of 50% image height in the sagittal direction, 5M is the position of 50% image height in the meridional direction, 7S is the position of 70% image height in the sagittal direction, and 7M is It means the position of 70% image height in the meridional direction (hereinafter the same). According to FIGS. 7 to 9, it can be seen that the MTF value is maximized even at each image height in the vicinity of the best position on the axis regardless of the long-distance imaging or the short-distance imaging, and it is possible to focus on almost the entire screen. .

  Table 4 shows incident angles of light rays emitted from the final surface that forms an image at each position of the imaging surface in the 1-A state (represented by a distance from the imaging surface center (Y = 0)). The incident angle of the light beam emitted from the final surface imaged at each position of the imaging surface in the -B state is shown. Table 6 shows the incident angle of the light beam emitted from the final surface imaged at each position of the imaging surface in the 1-C state. Indicates the angle of incidence. Upper and Lower are the outermost rays among the rays to be imaged, and Chief is the principal ray (the same applies hereinafter). According to Tables 4 to 6, it can be seen that the incident angle CRA (Chief Ray Angle) of the principal ray imaged on the periphery of the imaging surface can be reduced during short-distance imaging.

(Example 2)
FIG. 10 is a cross-sectional view of the imaging optical system of Example 2 during long-distance imaging. In the figure, L1 is a first lens, L2 is a second lens, L3 is a third lens, L4 is a fourth lens, L5 is a fifth lens, and L6 is a sixth lens having an extreme value on the image side surface. S1 is a first diaphragm disposed on the object side of the first lens L1, S2 is a second diaphragm disposed between the first lens L1 and the second lens L2, and IM represents an imaging surface. Further, F is a parallel plate assuming an optical low-pass filter, an IR cut filter, a seal glass of a solid-state image sensor, or the like.

  In the imaging optical system of the second embodiment, Table 7 shows lens data in a long distance imaging state (subject distance ∞) in a state where the second diaphragm functions as an aperture diaphragm (a 2-A state). Table 8 shows that at the time of short-distance imaging (subject distance: 100 mm), the first diaphragm functions as an aperture stop, and the entire imaging optical system is displaced to the object side by 0.156 mm with respect to long-distance imaging. Table 9 shows lens data in the state (2-B state), and Table 9 shows a short distance imaging (object distance: 100 mm), the first diaphragm functions as an aperture stop, and the first lens L1 to the first lens. The fifth lens L5 is the first group and the sixth lens L6 is the second group, and the first group and the second group are independently displaced toward the object side during long-distance imaging, but the displacement amount of the first group is In a state larger than the displacement of the second group (2-C state) It shows lens data. Note that the aspherical coefficients and single lens data in Table 8 (2-B state) and Table 9 (2-C state) are the same as in Table 7 (2-A state), and are therefore omitted.

[Table 7]
Example 2-A

f = 3.74mm fB = 0.180mm F = 1.85 2Y = 5.842mm
ENTP = 0mm EXTP = -2.13mm H1 = -2.33mm H2 = -3.57mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 * 1.599 0.550 1.54470 56.2 1.03
2 * -649.379 0.060 0.98
3 (Aperture) ∞ 0.000 0.92
4 * 5.699 0.170 1.63470 23.9 0.92
5 * 2.094 0.491 0.92
6 * 20.962 0.398 1.54470 56.2 1.06
7 * -7.179 0.080 1.14
8 * -8.404 0.250 1.63470 23.9 1.16
9 * ∞ 0.416 1.30
10 * 5.495 0.548 1.54470 56.2 1.50
11 * -2.413 0.494 1.78
12 * -3.790 0.322 1.54470 56.2 2.25
13 * 1.776 0.450 2.40
14 ∞ 0.000 2.83
15 ∞ 0.110 1.51630 64.1 3.30
16 ∞ 0.180 3.30

Aspheric coefficient

1st side 8th side
K = -0.10392E + 01 K = 0.49507E + 02
A3 = 0.00000E + 00 A3 = 0.35638E-02
A4 = 0.40456E-01 A4 = -0.52225E-01
A5 = 0.00000E + 00 A5 = -0.15538E-01
A6 = -0.14174E-01 A6 = -0.16086E-02
A8 = 0.80395E-01 A8 = -0.15709E-02
A10 = -0.13977E + 00 A10 = 0.14030E-03
A12 = 0.12330E + 00 A12 = 0.20030E-02
A14 = -0.41967E-01 A14 = 0.00000E + 00

2nd side 9th side
K = -0.50000E + 02 K = 0.00000E + 00
A4 = -0.41753E-01 A4 = -0.37038E + 00
A6 = 0.18492E + 00 A6 = 0.39587E + 00
A8 = -0.27987E + 00 A8 = -0.63206E + 00
A10 = 0.22395E + 00 A10 = 0.79439E + 00
A12 = -0.75565E-01 A12 = -0.62751E + 00
A14 = 0.00000E + 00 A14 = 0.23464E + 00

4th page 10th page
K = 0.27562E + 02 K = 0.95975E + 01
A3 = 0.00000E + 00 A3 = -0.47379E-01
A4 = -0.17419E + 00 A4 = 0.26749E-01
A5 = 0.00000E + 00 A5 = -0.76708E-01
A6 = 0.37501E + 00 A6 = 0.13991E-01
A8 = -0.48527E + 00 A8 = 0.70859E-02
A10 = 0.36207E + 00 A10 = -0.92400E-02
A12 = -0.12262E + 00 A12 = 0.15262E-02

5th surface 11th surface
K = -0.11708E + 02 K = -0.30589E + 02
A3 = 0.00000E + 00 A3 = -0.13955E + 00
A4 = 0.86610E-03 A4 = 0.44605E-01
A5 = 0.00000E + 00 A5 = 0.10408E-01
A6 = 0.15149E + 00 A6 = -0.49845E-03
A8 = -0.16857E + 00 A8 = -0.12120E-02
A10 = 0.13108E + 00 A10 = -0.22153E-02
A12 = -0.31985E-01 A12 = 0.12969E-02
A14 = 0.00000E + 00 A14 = -0.19310E-03

6th page 12th page
K = 0.21484E + 02 K = -0.16113E + 01
A3 = 0.00000E + 00 A3 = -0.25332E + 00
A4 = -0.10647E + 00 A4 = 0.39398E-01
A5 = 0.00000E + 00 A5 = 0.40885E-01
A6 = -0.34385E + 00 A6 = 0.42280E-02
A8 = 0.81173E + 00 A8 = -0.15708E-02
A10 = -0.12200E + 01 A10 = -0.14857E-03
A12 = 0.83765E + 00 A12 = 0.49192E-05
A14 = -0.48015E-01 A14 = 0.25161E-05

7th 13th
K = 0.30276E + 02 K = -0.18260E + 02
A3 = 0.27147E-01 A3 = -0.13148E + 00
A4 = -0.32265E-01 A4 = 0.65014E-01
A5 = -0.53399E-01 A5 = -0.19520E-01
A6 = -0.35395E-01 A6 = 0.26579E-02
A8 = 0.14988E-02 A8 = -0.12921E-03
A10 = 0.59713E-02 A10 = -0.75259E-04
A12 = -0.76625E-04 A12 = -0.46408E-05
A14 = 0.00000E + 00 A14 = 0.20410E-05

Single lens data

Lens Start surface Focal length (mm)
1 1 2.929
2 4 -5.313
3 6 9.867
4 8 -13.241
5 10 3.156
6 12 -2.176

[Table 8]
Example 2-B

f = 3.74mm fB = 0.336mm F = 3.99 2Y = 5.842mm
ENTP = 0mm EXTP = -2.13mm H1 = -2.33mm H2 = -3.57mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ 0.000 0.50
2 * 1.599 0.550 1.54470 56.2 0.64
3 * -649.379 0.060 0.45
4 * 5.699 0.170 1.63470 23.9 0.92
5 * 2.094 0.491 0.53
6 * 20.962 0.398 1.54470 56.2 0.86
7 * -7.179 0.080 1.01
8 * -8.404 0.250 1.63470 23.9 1.05
9 * ∞ 0.416 1.19
10 * 5.495 0.548 1.54470 56.2 1.42
11 * -2.413 0.494 1.63
12 * -3.790 0.322 1.54470 56.2 2.25
13 * 1.776 0.450 2.29
14 ∞ 0.000 2.73
15 ∞ 0.110 1.51630 64.1 3.30
16 ∞ 0.336 3.30

[Table 9]
Example 2-C

f = 3.71mm fB = 0.318mm F = 3.95 2Y = 5.842mm
ENTP = 0mm EXTP = -2.12mm H1 = -2.32mm H2 = -3.55mm

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
1 (Aperture) ∞ 0.000 0.50
2 * 1.599 0.550 1.54470 56.2 0.64
3 * -649.379 0.060 0.45
4 * 5.699 0.170 1.63470 23.9 0.92
5 * 2.094 0.491 0.53
6 * 20.962 0.398 1.54470 56.2 0.87
7 * -7.179 0.080 1.01
8 * -8.404 0.250 1.63470 23.9 1.06
9 * ∞ 0.416 1.20
10 * 5.495 0.548 1.54470 56.2 1.43
11 * -2.413 0.510 1.65
12 * -3.790 0.322 1.54470 56.2 2.25
13 * 1.776 0.450 2.31
14 ∞ -0.016 2.75
15 ∞ 0.110 1.51630 64.1 3.30
16 ∞ 0.318 3.30

  FIG. 11 is an aberration diagram of Example 2 (spherical aberration (a), astigmatism (b), distortion aberration (c)) at the time of long-distance imaging (2-A state).

  FIG. 12 is a graph showing the MTF (Modulation Transfer Function) value of the imaging optical system in the 2-A state, and FIG. 13 is a graph showing the MTF value of the imaging optical system in the 2-B state. 14 is a graph showing the MTF value of the imaging optical system in the 2-C state. 12 to 14, the vertical axis represents the MTF value, and the horizontal axis represents the position in the optical axis direction with the best position on the axis being zero. According to FIGS. 12 to 14, it can be seen that the MTF value is maximized even at each image height near the best position on the axis regardless of the long-distance imaging or the short-distance imaging, and it is possible to focus on almost the entire screen. .

  Table 10 shows incident angles of light rays emitted from the final surface that forms an image at each position of the imaging surface in the 2-A state (represented by a distance from the center of the imaging surface (Y = 0)). The incident angle of the light beam emitted from the final surface imaged at each position on the imaging surface in the -B state is shown. Table 12 shows the incident angles from the final surface imaged at each position on the imaging surface of the imaging optical system in the 2-C state. The incident angle of the emitted light is shown. According to Tables 10 to 12, it can be seen that the incident angle CRA (Chief Ray Angle) of the chief ray imaged on the periphery of the imaging surface can be reduced at the time of short-distance imaging.

  Table 13 shows values of the respective examples corresponding to the respective conditional expressions.

  Further, the present invention is not limited to the embodiments described in the specification, and it is understood that other embodiments and modifications are included in the art from the embodiments and ideas described in the present specification. It is obvious to For example, even when a dummy lens having substantially no refractive power is further provided, it is within the scope of application of the present invention. In the above embodiment, the second diaphragm is described as being disposed between the first lens and the second lens. However, the same effect can be obtained even when the second diaphragm is disposed between the second lens and the third lens. Can be obtained. In addition, although the example at the time of short-distance imaging has been described with the subject distance being 100 mm, the present invention is not limited to this, and the same effect can be obtained by switching the function as the aperture stop at a distance in the range of 80 mm to 500 mm. Can be obtained.

  The present invention can provide an imaging optical system suitable for a small portable terminal.

DESCRIPTION OF SYMBOLS 10 Image pick-up optical system 50 Image pick-up device 51 Solid image pick-up element 51a Photoelectric conversion part 51b Wire 52 Substrate 53 Optical tube 55 Actuator 56 Case 57 Actuator 57a Diaphragm blade 60 Input part 60 Input key part 70 Touch panel 71 Icon 80 Wireless communication part 92 storage unit 100 smartphone 101 control unit L1-L6 lens AP1 first aperture AP2 second aperture F IR cut filter

Claims (12)

An imaging optical system comprising a plurality of lenses, including a first lens arranged closest to the object side,
During short-distance imaging in which the distance from the imaging optical system to the subject is less than a predetermined value, the first diaphragm disposed on the object side of the first lens functions as an aperture diaphragm,
In long-distance imaging in which the distance from the imaging optical system to the subject is a predetermined value or more, the second diaphragm arranged between the lenses functions as an aperture diaphragm, and satisfies the following conditional expression: .
φF> φN (1)
L / 2Y <1.1 (2)
However,
φN: Aperture diameter (mm) of the first diaphragm during short-distance imaging
φF: aperture diameter of the second diaphragm (mm)
L: Distance (mm) from the object side surface vertex of the first lens to the imaging surface during long-distance imaging
Y: Maximum image height (mm) during long-distance imaging The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
1.1 <φF / φN <2.0 (3)   The first diaphragm has a constant opening diameter, and can selectively take an insertion position into the optical axis and a retreat position to retreat from the optical axis. Item 3. The imaging optical system according to Item 1 or 2.   The imaging optical system according to claim 1, wherein an aperture diameter of the first diaphragm is variable.   5. The imaging optical system according to claim 1, wherein the F-number at the time of long-distance imaging is less than 2.0, and the number of lenses is five or six.   6. The imaging optical system according to claim 1, wherein the entire imaging optical system is displaced toward the object side during short-distance imaging with respect to long-distance imaging.   The imaging optical system is composed of a first lens group and a second lens group in order from the object side, and only the first lens group or only the second lens group emits light during short-distance imaging compared to long-distance imaging. The imaging optical system according to claim 1, wherein the imaging optical system is displaced in an axial direction. The imaging optical system is composed of a first lens group and a second lens group in order from the object side, and the first lens group and the second lens group are located on the object side during short-distance imaging compared to long-distance imaging. 6. The imaging optical system according to claim 1, wherein the imaging optical system is displaced and satisfies the following conditional expression.
T1> T2 (4)
However,
T1: Amount of displacement (mm) in the optical axis direction during short-distance imaging with respect to long-distance imaging with the first lens group
T2: optical axis direction displacement amount (mm) at the time of short-distance imaging with respect to long-distance imaging with the second lens group   The imaging optical system according to claim 1, wherein the second diaphragm is disposed between the first lens and the third lens.   The imaging optical system according to claim 1, wherein the predetermined value is any distance within a range of 80 to 500 mm.   An imaging apparatus comprising the imaging optical system according to claim 1 and a solid-state imaging device.   12. A portable terminal comprising the imaging device according to claim 11 and a display device, and displaying an image captured by the imaging device on the display device.

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