TWI504925B - Camera optics, camera and digital machines - Google Patents

Description

Camera optics, camera and digital machine

The present invention relates to an imaging optical system in which an optical image of a subject is formed on a predetermined surface. Then, the present invention relates to an image pickup apparatus and a digital apparatus using the imaging optical system.

In recent years, there has been an improvement in the performance and miniaturization of an imaging device using a solid-state imaging device such as a CCD (Charged Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor. Digital devices such as mobile phones or portable information terminals equipped with such imaging devices have also become popular. Such a digital machine has a tendency to become thinner and thinner due to the convenience of carrying it. In particular, so-called smart phones have a tendency to be significantly thinner. Therefore, the imaging device mounted thereon is also increasingly required to be thinner, and the optical total length of the imaging optical system used in the imaging device has been shortened.

In order to respond to the demand for shortening the total length of the optical lens, for example, in Patent Document 1, a predetermined lens among a plurality of lenses constituting the imaging lens is formed by a glass member that absorbs infrared rays. Use solid The imaging device of the bulk imaging device generally includes an infrared ray cut filter due to the light receiving wavelength characteristic of the solid-state imaging device. However, the imaging lens disclosed in Patent Document 1 can be omitted by the above configuration. This infrared cutoff filter can achieve a reduction in the total optical length.

By the way, in the imaging lens disclosed in the above-mentioned Patent Document 1, in order to form a lens that absorbs infrared rays, an infrared absorbing material of an inorganic substance is mixed into the glass member. Therefore, in order to obtain the desired amount of infrared absorption, the glass member (lens) in which the infrared absorbing material is mixed must be thick, which is disadvantageous for shortening the total optical length. In particular, an imaging optical system used in an imaging device mounted in a mobile phone such as a smart phone has an optical total length of only several mm, so that the lens is as thin as possible, and this problem is significant.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2007-225642

The present invention has been made in view of the above circumstances, and an object thereof is to provide an imaging optical system which can reduce a lens having an infrared absorbing function.

The imaging optical system, the imaging device, and the digital device according to the present invention include a plurality of lenses arranged in order from the object side, and the lens disposed on the most object side of the plurality of lenses has a positive refractive At least one of the plurality of lenses is an aspherical lens made of a resin material containing an infrared ray absorbing material that absorbs infrared rays. Therefore, such an imaging optical system, an imaging device, and a digital device can make a lens having an infrared absorbing function thinner.

The above, as well as other objects, features and advantages of the present invention will be apparent from the description and appended claims.

1A~1G‧‧‧Video Optics

3‧‧‧Digital machines

5‧‧‧Mobile phone

21‧‧‧ camera

30‧‧‧Photography Department

31‧‧‧Image Generation Department

32‧‧‧Image data buffer

33‧‧‧Image Processing Department

34‧‧‧ Drive Department

35‧‧‧Control Department

36‧‧‧Memory Department

37‧‧‧ face

51‧‧‧Display Department

52‧‧‧Input Operation Department

100‧‧‧Photographic Optics

111‧‧‧1st lens

112‧‧‧2nd lens

113‧‧‧3rd lens

114‧‧‧4th lens

115‧‧‧5th lens

116‧‧‧Filter

117‧‧‧Photographic components

118‧‧‧Optical aperture

200‧‧‧Video Optics

211‧‧‧1st lens

212‧‧‧2nd lens

213‧‧‧3rd lens

214‧‧‧4th lens

215‧‧‧5th lens

216‧‧‧Filter

217‧‧‧Photographic components

218‧‧‧Optical aperture

300‧‧‧Photographic Optics

311‧‧‧1st lens

312‧‧‧2nd lens

313‧‧‧3rd lens

314‧‧‧4th lens

315‧‧‧5th lens

316‧‧‧Filter

317‧‧‧Photographic components

318‧‧‧Optical aperture

AR‧‧‧ concave and convex structure

AX‧‧‧ optical axis

HS‧‧‧ frame

IS‧‧‧Photographic components

L1‧‧‧1st lens

L2‧‧‧2nd lens

L3‧‧‧3rd lens

L4‧‧‧4th lens

L5‧‧‧5th lens

R1~r15‧‧‧ lens surface

Fig. 1 is a cross-sectional view showing a configuration of a schematic configuration of an imaging optical system according to a first embodiment.

[Fig. 2] A schematic diagram showing the definition of the incident angle of the image plane of the chief ray.

Fig. 3 is a cross-sectional view showing a configuration of a schematic configuration of an imaging optical system in a second embodiment.

Fig. 4 is a cross-sectional view showing a configuration of a schematic configuration of an imaging optical system in a third embodiment.

[Fig. 5] An explanatory view of a concave-convex structure for preventing reflection formed on an infrared absorbing lens in the imaging optical system according to the first to third embodiments.

Fig. 6 is a block diagram showing the configuration of a digital device in the fourth embodiment.

Fig. 7 is a view showing an external configuration of a camera-equipped mobile phone according to an embodiment of a digital device.

Fig. 8 is a cross-sectional view showing an arrangement of lenses in the imaging optical system of the first embodiment.

Fig. 9 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the second embodiment.

Fig. 10 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the third embodiment.

Fig. 11 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the fourth embodiment.

Fig. 12 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the fifth embodiment.

Fig. 13 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the sixth embodiment.

Fig. 14 is a cross-sectional view showing the arrangement of lenses in the imaging optical system of the seventh embodiment.

Hereinafter, an embodiment of the implementation of the present invention will be described based on the drawings. In addition, the same code|symbol is attached|subjected in the figure, and the structure is the same, and is ab Further, in the present specification, the general term is denoted by the component symbol omitting the suffix, and the individual configuration is indicated by the component symbol of the additional suffix.

<Description of main terms>

The terms used in the following description are as defined in the present specification.

(a) The refractive index is relative to the wavelength of the d line (587.56 nm) Refractive index.

(b) The Abbe number is such that the refractive indices of the d line, the F line (wavelength 486.13 nm), and the C line (wavelength 656.28 nm) are nd, nF, and nC, respectively, and the Abbe number is νd. Νd=(nd-1)/(nF-nC) The Abbe number νd obtained by this definition.

(c) When the expression "concave", "convex" or "crescent" is used for the lens, these are lens shapes indicating the vicinity of the optical axis (near the center of the lens).

(d) The expression of the refractive power (reciprocal of the optical power and the focal length) of each of the single lenses constituting the cemented lens is the power when the lens surfaces of the single lens are air on both sides.

(e) The resin material used in the composite aspherical lens is only an additive function of the substrate glass material, and therefore is not considered to be a separate optical member, and is considered to be equivalent to the case where the substrate glass material has an aspherical surface. The number of pieces is also considered as one. Moreover, the refractive index of the lens is also the refractive index of the glass material of the substrate. The composite aspherical lens is formed by coating a thin resin material on a glass material of a substrate to form an aspherical lens.

(f) The number of lenses in the cemented lens is not the total number of the cemented lenses, but is represented by the number of single lenses constituting the cemented lens.

<Description of an imaging optical system in one embodiment>

The imaging optical system according to the present embodiment includes a plurality of lenses arranged in order from the object side toward the image side; wherein the plurality of lenses are disposed in the plurality of lenses The lens on the most object side has a positive refractive power, and at least one of the plurality of lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays. Such an imaging optical system can make a lens having an infrared absorbing function thinner. Then, such an imaging optical system is suitable for use in an imaging device or a digital device. Hereinafter, such an imaging optical system, an imaging device, and a digital device will be specifically described.

<Description of Imaging Optical System of First Embodiment>

Fig. 1 is a cross-sectional view showing a configuration of a schematic diagram of an imaging optical system in the first embodiment. Fig. 2 is a schematic view showing the definition of the incident angle of the image plane of the chief ray. In addition, in the following description, the incident angle of the image plane of the chief ray is as shown in FIG. 2, which is the chief ray of the maximum angle of incidence among the incident rays incident on the imaging surface, with respect to the angle perpendicular to the perpendicular of the image plane. (deg, degree) α, the image plane incident angle α , is the chief ray angle when the exit pupil is located closer to the object side than the image plane, and is regarded as the positive direction.

In FIG. 1, the imaging optical system 100 is formed by imaging an optical image of an object (subject) on a light receiving surface of an image sensor 117 that converts an optical image into an electrical signal, and is formed from the object side toward the image side. An optical system consisting of a plurality of lenses. In the example shown in FIG. 1, the imaging optical system 100 is formed by five lenses of the first to fifth lenses 111 to 115. The imaging element 117 is disposed such that its light receiving surface substantially matches the image plane of the imaging optical system 100 (image surface = imaging surface).

Then, in the imaging optical system 100, the first to fifth lenses 111 to 115 are moved in the optical axis direction to perform pairing. focal.

In the imaging optical system 100, the lens disposed on the most object side of the plurality of lenses has a positive refractive power, and at least one of the plurality of lenses is an infrared absorbing material containing infrared absorbing material. Aspherical lens made of resin material.

More specifically, in the example shown in FIG. 1, the first lens 111 has a positive refractive power, both sides are convex double convex positive lenses, the second lens 112 has a negative refractive power, and the image side is concave. The negative crescent lens, the third lens 113 has a positive refractive power, the object side is a convex positive crescent lens, the fourth lens 114 has a positive refractive power, and the image side is a convex positive crescent lens Then, the fifth lens 115 has a negative refractive power, and the image side is a concave negative crescent lens. In such an imaging optical system 100, the refractive powers of the first to fifth lenses 111 to 115 are positive and negative positive and negative.

Each of the first to fifth lenses 111 to 115 is a non-spherical surface on both sides, and is a lens made of a resin material such as a plastic material, more specifically, a resin material such as polycarbonate or a cyclic olefin resin. Further, when the optical path length of the 80% image height in the aspherical lens made of the resin material is OPp, and the optical path length on the optical axis in the aspherical lens made of the resin material is OPc, these resin material lenses are used. Among the first to fifth lenses 111 to 115, the lens that satisfies the conditional expression of (A1) below is provided with a function of absorbing infrared rays.

0.5<OPp/OPc<1.5. . . (A1) In the example shown in FIG. 1, the values of OPp/OPc in the first to fifth lenses 111 to 115 are sequentially 1.05, 1.10, 1.05, 0.60, 1.67. Therefore, in the imaging optical system 100 shown in FIG. 1, one of the first to fourth lenses 111 to 114 or the plurality of lenses is an infrared absorption lens having a function of absorbing infrared rays. In order to make the optical path length more uniform, it is preferable to provide a lens for providing an infrared absorbing function in the order that the value of OPp/OPc is close to 1. In this example, the first to fourth lenses 111 to 114 are selected as infrared absorbing lenses in the order of the first and third lenses 111 and 113, the second lens 112, and the fourth lens 114.

The infrared absorbing lens is a lens to which an infrared absorbing material is added, and the infrared absorbing function is applied by adding a predetermined infrared absorbing material to the resin material. Examples of the infrared ray absorbing material specified above include, for example, Lumogen IR765 and Lumogen IR788 manufactured by BASF, ABS643 manufactured by Exciton, ABS654, ABS667, ABS670T, IRA693N, and IRA735, and SDA3598, SDA6075, SDA8030, SDA8303, and SDA8470 manufactured by HWSANDS. , SDA3039, SDA3040, SDA3922 and SDA7257, TAP-15 and IR-706 manufactured by Yamada Chemical Industry, CIR-1080 and CIR-1081 manufactured by Japan Carlit., YKR-3080 and YKR-3081 manufactured by Yamamoto Chemical Co., Ltd., and Japanese catalyst Ex-color IR-10, IR-12 and IR-14, SIR-128, SIR-130, SIR-159, PA-1001, PA-1005, etc. manufactured by Mitsui Chemicals FINE. In general, a lens in which an infrared ray absorbing material is not added is used in an infrared field having a wavelength of 800 nm to 1000 nm, and an average value of transmittance in a vertical direction is 70% or more, and a lens to which an infrared absorbing material is added is used at a wavelength of 800 nm to 1000 nm. In the infrared field, the average value of the transmittance in the vertical direction is 20% or less.

Further, in the example shown in FIG. 1, the first to fifth lenses 111 to 115 are all lenses made of a resin material, but the fifth lens 115 which cannot provide an infrared absorbing function may be, for example, a glass mold lens. .

Then, the incident angle of the light corresponding to the chief ray of the maximum image height of the image plane is α (deg), the maximum image height is Y, and when the optical full length of the infinity object is TTL, the imaging optical system 100 is also The conditional expressions of the following (A2) and (A3) are satisfied.

26< α ≦45. . . (A2)

0.55≦Y/TTL. . . (A3)

In the imaging optical system 100, for example, the optical aperture 118 such as an aperture stop is disposed between the first lens 111 and the second lens 112 (on the image side of the first lens 111), and the imaging optical system 100 is internal. Aperture type.

Then, an imaging element 117 is disposed on the image side of the imaging optical system 100, that is, on the image side of the fifth lens 115. The imaging element 117 is photoelectrically converted into image signals of respective components of R (red), G (green), and B (blue) in accordance with the amount of light of the optical image of the subject imaged by the imaging optical system 100. The component that is output to a predetermined image processing circuit (not shown). The imaging element 117 is a solid-state imaging element such as a CCD type image sensor or a CMOS type image sensor. By this, the optical image of the object on the object side is guided to the light receiving surface of the image sensor 117 at a predetermined magnification along the optical axis AX by the imaging optical system 100, and the image is detected by the image sensor 117. The optical image of the subject. Further, between the fifth lens 115 and the imaging element 117, as shown in FIG. A filter 116 is also disposed. In other words, the optical image of the subject may be incident on the imaging element 117 via the filter 116. This filter 116 is a parallel plate-shaped optical element, and schematically shows various optical filters or cover glass (protective glass) of the image sensor 117. The use, the imaging element 117, the configuration of the camera, and the like can be appropriately arranged.

In the imaging optical system 100, a resin material is used for forming a nitrate material to which an infrared absorption lens having an infrared absorbing function is applied, and an infrared absorbing material of an organic material can be used, and a glass material can be used for the nitrate material. The infrared absorbing lens is formed to be thinner.

Further, in the short-back imaging optical system, the incident angle α of the light at the periphery of the image plane of the image sensor is usually only about 30 degrees. Therefore, when a reflection type infrared cut filter having an incident angle dependency on the amount of incident infrared rays is used in an image pickup apparatus, the amount of infrared cutoff on the periphery of the image plane is insufficient, which causes so-called color unevenness of the image. . In particular, the imaging optical system 100 of the present embodiment satisfies the conditional expressions (A2) and (A3) as described above, and satisfies the conditions of the stricter incident angle of light or the optical total length, so that it is easy to follow the light. A bad condition occurs when the incident angle occurs. The countermeasure is considered to be that the absorption type infrared cut filter is not used, and the absorption type infrared cut filter is used instead. In this case, the above-described problem occurs when a glass material is used. However, in the imaging optical system 100 of the present embodiment, the above-mentioned problem with the incident angle of light can be solved by using a resin material. In the absorption-type infrared cut filter, the infrared absorption amount is proportional to the optical path length. However, in the imaging optical system 100 of the present embodiment, the effective field of the lens can be obtained by satisfying the conditional expression (A1). The optical path length in the whole domain is slightly uniform, and a substantially uniform infrared absorption amount can be obtained in the entire effective field of the lens. As a result, a good image with reduced color unevenness or no color unevenness can be obtained. That is, in the case where the value is lower than the lower limit value of the conditional expression (A1) or higher than the upper limit value, the optical path length becomes uneven and is not desirable in the effective field of the lens.

From this point of view, the conditional expression (A1) is ideal as the following conditional expression (A1A), and the preferred condition is the following conditional expression (A1B).

0.7<OPp/OPc<1.3. . . (A1A)

0.8<OPp/OPc<1.2. . . (A1B)

According to this point of view, the conditional expression (A2) is more effectively the following conditional expression (A2A), and more effectively, the following conditional expression (A2B).

26< α ≦40. . . (A2A)

26< α ≦35. . . (A2B)

From this point of view, the conditional expression (A3) is more effectively the following conditional expression (A3A), and more effectively, the following conditional expression (A3B).

0.6≦Y/TTL. . . (A3A)

0.65≦Y/TTL. . . (A3B)

Further, as a countermeasure against such color unevenness, the imaging lens disclosed in Patent Document 1 is formed by a glass member that absorbs infrared rays, and has an optical path length on a light axis that passes through the light beams of the respective lenses and is imaged at the center of the screen (lens). The thickness of the main beam of the light beam imaged at the peripheral portion of the screen passes through the lens having a difference in optical path length within the lens of ±15% or less. however, The imaging optical system 100 of the present embodiment differs from the above-described Patent Document 1 in that the color unevenness is solved by the conditional expression (A1) described above.

Further, in the imaging optical system 100, when the F value is FN and the half-angle angle is w (deg), the conditional expressions of the following (A4) and (A5) are satisfied.

FN≦3. . . (A4)

25≦w≦100. . . (A5)

In such an imaging optical system 100, by satisfying the conditional expression (A4), it is possible to avoid an increase in noise or a deterioration in darkness which is likely to occur in a dark imaging optical system. Further, when an infrared absorbing lens is used in a dark imaging optical system, the infrared absorbing material is limited and the cost is increased. However, by satisfying the conditional expression (A4), it is easy to avoid high cost. Further, such an imaging optical system 100 can effectively obtain such an effect by satisfying the conditional expression (A5).

From this point of view, the conditional expression (A4) is ideal as the following conditional expression (A4A), and is preferably the following conditional expression (A4B).

FN≦2.8. . . (A4A)

FN≦2.4. . . (A4B)

From this point of view, the conditional expression (A5) is more effectively the following conditional expression (A5A), and more effectively, the following conditional expression (A5B).

30≦w≦60. . . (A5A)

30≦w≦50. . . (A5B)

Further, this imaging optical system 100 is the largest aspherical lens (infrared absorption lens) made of a resin material containing an infrared absorbing material. When the minimum thickness of the aspherical lens (infrared absorption lens) made of the resin material containing the infrared absorbing material is TDmin, the thickness is TDmax, and at least one of the aspherical lenses made of the resin material containing the infrared absorbing material is at least one. Satisfy the conditional expression of the following (A6). Further, the aforementioned thickness is a length parallel to the direction of the optical axis.

1≦TDmax/TDmin<2.3. . . (A6)

This TDmax/TDmin is an index indicating the difference in thickness in the aspherical lens. Such an imaging optical system 100 can exceed the lower limit of the conditional expression (A6), and can allow thickness difference in each part of the lens, thereby increasing the degree of freedom of the lens shape and achieving an improvement in performance. Then, such an imaging optical system is lower than the upper limit value of the conditional expression (A6) without impairing the formability, so that the lens shape can be designed with a large degree of freedom, and performance can be improved. .

From this point of view, the conditional expression (A6) is ideal as the following conditional expression (A6A), and is preferably the following conditional expression (A6B).

1.3<TDmax/TDmin<2.2. . . (A6A)

1.5<TDmax/TDmin<2.1. . . (A6B)

In addition, in the imaging optical system 100, the focal length of the entire imaging optical system 100 is f, and when the focal length of the aspherical lens (infrared absorption lens) made of the infrared absorbing resin material is fir, the resin material containing the infrared absorbing material is made of a resin material. At least one of the aspherical lenses satisfies the conditional expression of the following (A7).

0≦|f/fir|<1.5. . . (A7)

This |f/fir| indicates the ratio of the refractive power that the infrared absorbing lens bears with respect to the refractive power of the entire imaging optical system 100. this Since the imaging optical system 100 satisfies the conditional expression (A7), the infrared absorbing lens is not given an excessive refractive power. Therefore, even if the manufacturing difficulty of the infrared absorbing lens is high, the manufacturing error can be suppressed. The performance of aberration deterioration or the like deteriorates.

From this point of view, the conditional expression (A7) is ideal as the following conditional expression (A7A), and is preferably the following conditional expression (A7B), and more preferably the following conditional expression (A7C).

0.05<|f/fir|<1.5. . . (A7A)

0.1<|f/fir|<1.45. . . (A7B)

0.2<|f/fir|<1.4. . . (A7C)

Further, the imaging optical system 100 is composed of five first to fifth lenses 111 to 115, and at least two of the five lenses have positive refractive power, and at least two of the five lenses are Has a negative refractive power. Further, the imaging optical system 100 is not limited thereto, and the plurality of lenses may be any one of four, five, and six, as long as at least two of the plurality of lenses have a positive refractive power, and the plurality of lenses At least two of the lens systems may have a negative refractive power.

In such an imaging optical system 100, by providing at least two positive lenses having a positive refractive power and negative lenses having a negative refractive power, the burden of the refractive power of each lens can be dispersed. Therefore, in the imaging optical system 100, even when the ease of manufacture of the infrared absorbing lens is high, performance deterioration such as aberration deterioration due to manufacturing errors can be suppressed.

Further, in the imaging optical system 100 as described above, the filter 116 can be omitted (may be optional). Since the imaging optical system 100 of the present embodiment uses an infrared absorbing lens, it can be deleted previously. The infrared cut-off filter can reduce the cost.

Further, although the imaging optical system 100 described above has five configurations, the present invention is not limited thereto, and may be configured in three configurations, four configurations, or six configurations. In the case of the four configurations, the refractive powers of the first to fourth lenses are preferably positive, negative, positive and negative, and in the case of six configurations, the refractive powers of the first to sixth lenses are sequentially positive. (arbitrary) Negative (arbitrary) positive and negative is ideal. By thus arranging the positive lens and the negative lens in this way, the aberration occurring on the positive lens can be effectively corrected by the negative lens. According to this point of view, in the case of five configurations, the refractive power of the first to fifth lenses is preferably positive or negative (arbitrary) positive and negative, and the first to fifth lenses 111 in the imaging optical system 100 described above are preferable. The refractive power of ~115 is positive and negative positive and negative. Further, the number of the plurality of lenses is preferably five or more. With this configuration, various aberrations can be corrected, and high pixelation and bright F values can be achieved.

Further, in the imaging optical system 100 described above, the lens disposed on the most image side of the plurality of lenses is the fifth lens 115 in the example shown in FIG. 1, for example, even in focus (focus) It is still fixed at the time, which is ideal. In the imaging optical system 100, since the lens on the most image side is fixed, the imaging element 117 can be sealed by the fixed lens. Therefore, it is possible to reduce the sealing member of the imaging element 117 required to prevent dust from adhering, for example. Cover glass). Therefore, such an imaging optical system 100 can easily achieve a low profile.

<Description of Imaging Optical System of Second Embodiment>

Fig. 3 is a view for explaining the imaging optical system in the second embodiment; A schematic sectional view of the lens is shown. In FIG. 3, the imaging optical system 200 is formed by imaging an optical image of an object (subject) on a light receiving surface of an image sensor 217 that converts an optical image into an electrical signal, and is formed from the object side toward the image side. An optical system consisting of a plurality of lenses. In the example shown in FIG. 3, the imaging optical system 200 is formed by five lenses of the first to fifth lenses 211 to 215. The imaging element 217 is disposed such that the light receiving surface thereof substantially matches the image plane of the imaging optical system 200 (image surface = imaging surface).

Then, in the imaging optical system 200, the first to fifth lenses 211 to 215 are moved in the optical axis direction to perform focusing.

In the imaging optical system 200, the first lens 211 has a positive refractive power, and the second lens 212 has a negative refractive power. At least one of the first and second lenses 211 and 212 is included. An aspherical lens made of a resin material that absorbs infrared ray infrared absorbing material.

More specifically, in the example shown in FIG. 3, the first lens 211 has a positive refractive power, the both surfaces are convex double convex positive lenses, the second lens 212 has a negative refractive power, and the image side is concave. The negative crescent lens, the third lens 213 has a positive refractive power, the object side is a convex positive crescent lens, the fourth lens 214 has a positive refractive power, and the image side is a convex positive crescent lens. Then, the fifth lens 215 has a negative refractive power, and the image side is a concave negative crescent lens. In such an imaging optical system 200, the refractive powers of the first to fifth lenses 211 to 215 are positive and negative positive and negative.

Each of the first to fifth lenses 211 to 215 is aspherical on both sides, and is then, for example, a plastic, more specifically a polycarbonate or a ring. A lens made of a resin material formed of a resin material such as an olefin-based resin. In addition, the infrared absorbing lens is a lens to which an infrared absorbing material is added, and the infrared absorbing function is provided by adding a predetermined infrared absorbing material to the resin material. The above-mentioned infrared absorbing material is exemplified by the above-mentioned materials. In general, a lens in which an infrared ray absorbing material is not added is used in an infrared field having a wavelength of 800 nm to 1000 nm, and an average value of transmittance in a vertical direction is 70% or more, and a lens to which an infrared absorbing material is added is used at a wavelength of 800 nm to 1000 nm. In the infrared field, the average value of the transmittance in the vertical direction is 20% or less.

In addition, in the example shown in FIG. 3, the first to fifth lenses 211 to 215 are lenses made of a resin material, but the third to fifth lenses 213 to 215 which cannot provide the infrared absorbing function may be For example, a glass molded lens.

In the imaging optical system 200, for example, the optical aperture 218 such as an aperture stop is disposed between the first lens 211 and the second lens 212 (on the image side of the first lens 211), and the imaging optical system 200 is an internal aperture type. .

Then, the focal length of the entire imaging optical system 200 is f, and the focal length of the aspherical lens made of the infrared absorbing resin material is fir, so that the aspherical lens made of the resin material that absorbs infrared rays is used from the aperture of the opening. The optical path length on the optical axis of the object is Dir, and the optical full length of the infinity object is TTL, so that the F value is FN, and the half angle is w (deg), and then the image surface corresponds to the maximum. When the incident angle of the light of the main light of the image is α (deg), the imaging optical system 200 is at least one of the lenses including the infrared absorbing material, and satisfies the conditional expressions of the following (B1) to (B5). .

0.5≦|f/fir|<1.5. . . (B1)

0≦|Dir/TTL|<0.2. . . (B2)

FN≦3. . . (B3)

25≦w≦100. . . (B4)

25< α ≦45. . . (B5)

Then, an imaging element 217 is disposed on the image side of the imaging optical system 200, that is, on the image side of the fifth lens 215. The imaging element 217 is photoelectrically converted into image signals of respective components of R (red), G (green), and B (blue) in accordance with the amount of light of the optical image of the subject imaged by the imaging optical system 200, and then The component that is output to a predetermined image processing circuit (not shown). The imaging element 217 is a solid-state imaging element such as a CCD type image sensor or a CMOS type image sensor. By this, the optical image of the object on the object side is guided to the light receiving surface of the image sensor 217 at a predetermined magnification along the optical axis AX by the imaging optical system 200, and the image is detected by the image sensor 217. The optical image of the subject. Further, between the fifth lens 215 and the imaging element 217, a filter 216 may be further disposed as shown in FIG. In other words, the optical image of the subject may be incident on the imaging element 217 via the filter 216. This filter 216 is a parallel plate-shaped optical element, and schematically shows various optical filters or cover glass (protective glass) of the image sensor 217. The use, the imaging element 217, the configuration of the camera, and the like can be appropriately arranged.

Such an imaging optical system 200 uses a resin material in a nitrate material that forms an infrared absorption lens to which an infrared absorption function is applied. Further, the infrared absorbing material of the organic substance can be used, and the infrared absorbing lens can be formed thinner than the case where the glass material is used in the above-mentioned nitrate material.

Further, by providing the first lens 211 with a positive refractive power and the second lens 212 having a negative refractive power, the entire length can be shortened, and various aberrations can be satisfactorily corrected. In such a low-back imaging optical system, the incident angle (CRA) of the light incident on the image surface of the imaging element is usually only about 30 degrees. Therefore, when a reflection type infrared cut filter having an incident angle dependency on the amount of incident infrared rays is used in an image pickup apparatus, the amount of infrared cutoff on the periphery of the image plane is insufficient, which causes so-called color unevenness of the image. . In particular, the imaging optical system 200 according to the present embodiment satisfies the conditional expressions (B4) and (B5), and satisfies the conditions such as a relatively severe incident angle of light, and thus it is easy to cause a problem with the incident angle of light. situation. Further, if an infrared absorbing lens is used in a dark imaging optical system, the infrared absorbing material is limited, resulting in a high cost, and an increase in noise or deterioration in darkness. In the imaging optical system 200 of the present embodiment, the five lens configurations that can achieve high performance even with a large aperture can be placed in the vicinity of the aperture and the axis by satisfying the conditional expression (B2). At least one of the first and second lenses having the same beam diameter as that of the off-axis light becomes an infrared absorption lens, so that the total amount of light can be ensured while avoiding the above-mentioned problem due to the incident angle of the light. Then, the imaging optical system 200 can avoid high cost by satisfying the conditional expression (B3), and avoids an increase in noise or deterioration in darkness which is likely to occur in the dark imaging optical system. Then, by arranging the infrared absorbing lens at a position close to the optical aperture, the optical path difference of the entire image on the image plane can be made. Generally, the lens can be given a relatively large refractive power (optical power). Then, in the imaging optical system 200, by exceeding the lower limit value of the conditional expression (B1), the refractive power of the infrared absorbing lens is not too weak, and the total optical length of the entire system can be shortened. On the other hand, by lowering the upper limit value of the conditional expression (B1), it is possible to prevent an excessive refractive power from being applied to the infrared absorbing lens, and it is possible to prevent deterioration of optical performance due to various aberrations due to excessive refractive power. .

From this point of view, the conditional expression (B1) is ideal as the following conditional expression (B1A), and the ideal condition is the following conditional expression (B1B).

0.7<|f/fir|<1.45. . . (B1A)

0.8<|f/fir|<1.4. . . (B1B)

From this point of view, the conditional expression (B2) is ideal as the following conditional expression (B2A), and the ideal condition is the following conditional expression (B2B).

0≦|Dir/TTL|<0.15. . . (B2A)

0≦|Dir/TTL|<0.14. . . (B2B)

From this point of view, the conditional expression (B3) is ideal as the following conditional expression (B3A), and is preferably the following conditional expression (B3B).

FN≦2.8. . . (B3A)

FN≦2.4. . . (B3B)

According to this point of view, the conditional expression (B4) is more effectively the following conditional expression (B4A), and more effectively, the following conditional expression (B4B).

30≦w≦60. . . (B4A)

30≦w≦50. . . (B4B)

According to this point of view, conditional formula (B5), more effective The conditional expression (B5A) is as follows, and more effectively, it is the conditional expression (B5B) below.

25< α ≦40. . . (B5A)

25< α ≦35. . . (B5B)

Further, as an anti-color unevenness measure, the imaging lens disclosed in Patent Document 1 is formed by a glass member that absorbs infrared rays, and has an optical path length on a light axis that passes through the light beams of the respective lenses and is imaged at the center of the screen (lens) The thickness of the main beam of the light beam imaged at the peripheral portion of the screen passes through the lens having a difference in optical path length within the lens of ±15% or less. However, the imaging optical system 200 of the present embodiment differs from the above-described Patent Document 1 in that the color unevenness is mainly solved by the conditional expression (B2) described above.

In addition, the imaging optical system 200 is such that the maximum thickness of the aspherical lens (infrared absorption lens) made of a resin material containing an infrared ray absorbing material is TDmax, and the aspherical lens (infrared absorbing lens) made of a resin material containing the infrared absorbing material is used. When the minimum thickness is TDmin, at least one of the aspherical lenses made of the resin material containing the infrared absorbing material satisfies the conditional expression of the following (B6). Further, the aforementioned thickness is a length parallel to the direction of the optical axis.

1≦TDmax/TDmin<2.3. . . (B6)

This TDmax/TDmin is an index indicating the difference in thickness in the aspherical lens. Such an imaging optical system 200 can exceed the lower limit of the conditional expression (B6), and can allow thickness difference in each part of the lens, thereby increasing the degree of freedom of the lens shape and achieving an improvement in performance. Then, such an imaging optical system can reduce the formability by lowering the upper limit value of the conditional expression (B6), so that the lens shape can be designed with a large degree of freedom. Can improve performance.

From this point of view, the conditional expression (B6) is ideal as the following conditional expression (B6A), and the preferred condition is the following conditional expression (B6B).

1.3<TDmax/TDmin<2.2. . . (B6A)

1.5<TDmax/TDmin<2.1. . . (B6B)

In the imaging optical system 200, the optical path length of the 80% image height in the aspherical lens made of the resin material containing the infrared absorbing material is OPp, and the aspherical lens made of a resin material containing the infrared absorbing material is used. When the optical path length on the optical axis is OPc, the conditional expression of the following (B7) is satisfied.

0.7<OPp/OPc<1.3. . . (B7)

In the absorption type infrared cut filter, the infrared absorption amount is proportional to the optical path length. However, in the imaging optical system 200, by satisfying the conditional expression (B7), the optical path length in the effective field of the lens can be made larger. Uniform, a roughly uniform infrared absorption can be obtained in the entire field of the effective field of the lens. As a result, a good image with reduced color unevenness or no color unevenness can be obtained. That is, in the case where the value is lower than the lower limit value of the conditional expression (B7) or higher than the upper limit value, the optical path length becomes uneven in the effective field of the lens, which is not preferable.

From this point of view, the conditional expression (B7) is ideal as the following conditional expression (B7A), and the preferred condition is the following conditional expression (B7B).

0.9<OPp/OPc<1.2. . . (B7A)

1<OPp/OPc<1.2. . . (B7B)

In addition, in order to make the optical path length more uniform, the lens that gives the infrared absorption function is in the order that the value of OPp/OPc is close to 1. Selected, ideal. In the example shown in FIG. 3, the values of OPp/OPc in the first and second lenses 211 and 212 are 1.05 and 1.10, respectively. Therefore, in this example, the first and second lenses 211 and 212 are selected as an infrared absorption lens in the order of the first lens 211 and the second lens 212.

Further, the imaging optical system 200 is composed of five of the first to fifth lenses 211 to 215, and at least two of the five lenses have positive refractive power, and at least two of the five lenses are Has a negative refractive power.

In the imaging optical system 200, by providing two positive lenses having positive refractive power and negative lenses having negative refractive power, the burden of the refractive power of each lens can be dispersed. Therefore, in the imaging optical system 200, even when the ease of manufacture of the infrared absorbing lens is high, performance deterioration such as aberration deterioration due to manufacturing errors can be suppressed.

Further, in the imaging optical system 200, as described above, the filter 216 as the infrared cut filter can be omitted (may be optional). When the imaging optical system 200 includes the filter 216, the filter 216 is, for example, a parallel flat plate that covers the glass of the imaging element 217. Since the imaging optical system 200 of the present embodiment uses an infrared absorbing lens, the infrared ray cut filter previously used can be deleted, and the cost can be reduced.

Further, in the above-described imaging optical system 200, the aspherical lens made of a resin material containing the infrared ray absorbing material is preferably one. If more than two lenses are designed to absorb infrared rays In the case of the mirror, if the relative position between the infrared absorbing lenses deviates from the design, the infrared absorbing characteristics desired in the design cannot be obtained, and the amount of infrared absorbing is uneven (deviated from the design value). Therefore, since the imaging optical system 200 has only one infrared absorbing lens, the ease of manufacture can be reduced.

Further, in the above-described imaging optical system, when the average transmittance (%) in the visible light band (wavelength: 400 nm to 700 nm) is Tr, the conditional expression of the following (B8) is satisfied. In the imaging optical system, the above-described effects of the conditional expressions (B1) to (B5) can be effectively obtained by satisfying the conditional expression (B8).

80<Tr<90. . . (B8)

Further, in the imaging optical system 200 described above, the lens disposed on the most image side of the plurality of lenses is the fifth lens 215 in the example shown in FIG. 1, for example, even in focus (focus) It is still fixed at the time, which is ideal. In the imaging optical system 200, since the lens on the most image side is fixed, the imaging element 217 can be sealed by the fixed lens. Therefore, it is possible to reduce the sealing member of the imaging element 217 required to prevent dust from adhering, for example. Cover glass). Therefore, such an imaging optical system 200 can easily achieve a low profile.

<Description of Imaging Optical System of Third Embodiment>

Fig. 4 is a cross-sectional view showing a configuration of a schematic diagram of the imaging optical system in the third embodiment. In FIG. 4, the imaging optical system 300 receives light from an imaging element 317 that converts an optical image into an electrical signal. On the surface, an optical system composed of a plurality of lenses is formed by imaging an optical image of an object (subject) from the object side to the image side. In the example shown in FIG. 4, the imaging optical system 300 is formed by five lenses of the first to fifth lenses 311 to 315. The imaging element 317 is disposed such that the light receiving surface thereof substantially matches the image plane of the imaging optical system 300 (image surface = imaging surface).

Then, in the imaging optical system 300, the first to fifth lenses 311 to 315 are moved in the optical axis direction to perform focusing.

In the imaging optical system 300, the first lens 311 has a positive refractive power, the second lens 312 has a negative refractive power, and at least one of the third to fifth lenses 313 to 315 has absorption. An aspherical lens made of a resin material of an infrared infrared absorbing material.

More specifically, in the example shown in FIG. 4, the first lens 311 has a positive refractive power, the both surfaces are convex double convex positive lenses, the second lens 312 has a negative refractive power, and the image side is concave. a negative crescent lens, the third lens 313 has a positive refractive power, the object side is a convex positive crescent lens, the fourth lens 314 has a positive refractive power, and the image side is a convex positive crescent lens Then, the fifth lens 315 has a negative refractive power, and the image side is a concave negative crescent lens. In the imaging optical system 300, the refractive powers of the first to fifth lenses 311 to 315 are positive and negative positive and negative.

Each of the first to fifth lenses 311 to 315 is a non-spherical surface, and is a lens made of a resin material such as a plastic material, more specifically, a polycarbonate or a cyclic olefin resin. Moreover, the infrared absorbing lens means that an infrared absorbing material is added. The lens and the infrared absorbing function are provided by adding a predetermined infrared absorbing material to the resin material. The above-mentioned infrared absorbing material is exemplified by the above-mentioned materials. In general, a lens in which an infrared ray absorbing material is not added is used in an infrared field having a wavelength of 800 nm to 1000 nm, and an average value of transmittance in a vertical direction is 70% or more, and a lens to which an infrared absorbing material is added is used at a wavelength of 800 nm to 1000 nm. In the infrared field, the average value of the transmittance in the vertical direction is 20% or less.

In addition, in the example shown in FIG. 4, the first to fifth lenses 311 to 315 are all lenses made of a resin material, but the first and second lenses 311 and 312 which cannot provide the infrared absorbing function may be For example, a glass molded lens.

In the imaging optical system 300, for example, the optical aperture 318 such as an aperture stop is disposed between the first lens 311 and the second lens 312 (on the image side of the first lens 311), and the imaging optical system 300 is an internal aperture type. .

Then, the focal length of the entire imaging optical system 300 is f, so that the focal length of the aspherical lens made of the infrared absorbing resin material is fir, the F value is FN, and the half angle is w (deg), and then When the incident angle of the light rays corresponding to the chief ray of the maximum image height is α (deg), at least one of the lenses including the infrared absorbing material that absorbs infrared rays in the imaging optical system 300 satisfies the following ( Each conditional formula of C1) to (C4).

0≦|f/fir|<0.5. . . (C1)

FN≦3. . . (C2)

25≦w≦100. . . (C3)

25< α ≦45. . . (C4)

Then, an imaging element 317 is disposed on the image side of the imaging optical system 300, that is, on the image side of the fifth lens 315. The imaging element 317 is photoelectrically converted into image signals of respective components of R (red), G (green), and B (blue) in accordance with the amount of light of the optical image of the subject imaged by the imaging optical system 300, and then The component that is output to a predetermined image processing circuit (not shown). The imaging element 317 is a solid-state imaging element such as a CCD type image sensor or a CMOS type image sensor. By this, the optical image of the object on the object side is guided to the light receiving surface of the image sensor 317 at a predetermined magnification along the optical axis AX by the imaging optical system 300, and the image is detected by the image sensor 317. The optical image of the subject. Further, between the fifth lens 315 and the image sensor 317, a filter 316 may be disposed as shown in FIG. In other words, the optical image of the subject may be incident on the imaging element 317 via the filter 316. This filter 316 is a parallel plate-shaped optical element, and schematically shows various optical filters or cover glass (protective glass) of the image sensor 317. The use, the imaging element 317, the configuration of the camera, and the like can be appropriately arranged.

In the imaging optical system 300, a resin material is used for forming a nitrate material which is provided with an infrared absorption lens having an infrared absorbing function, and an infrared absorbing material of an organic material can be used, and a glass material can be used for the above-mentioned nitrate material. The infrared absorbing lens is formed to be thinner.

Further, by providing the first lens 311 with a positive refractive power and the second lens 312 having a negative refractive power, the entire length can be shortened, and various aberrations can be satisfactorily corrected. In such a low-profile imaging optical system, an imaging element The angle of incidence of light (CRA) around the image plane is usually only about 30 degrees. Therefore, when a reflection type infrared cut filter having an incident angle dependency on the amount of incident infrared rays is used in an image pickup apparatus, the amount of infrared cutoff on the periphery of the image plane is insufficient, which causes so-called color unevenness of the image. . In particular, the imaging optical system 300 according to the present embodiment satisfies the conditional expressions (C3) and (C4), satisfies the conditions of a relatively severe incident angle of light, and the like, and thus it is easy to cause a problem with the incident angle of light. . Further, if an infrared absorbing lens is used in a dark imaging optical system, the infrared absorbing material is limited, resulting in a high cost, and an increase in noise or deterioration in darkness. Therefore, in the imaging optical system 300 of the present embodiment, in the configuration of five lenses which can achieve high performance even in a large diameter, by satisfying the conditional expression (C1), the thickness can be made small, and the on-axis light can be made. At least one of the third and fifth lenses 313 to 315 having the same optical path length as the off-axis light becomes an infrared absorbing lens. Therefore, it is possible to avoid the above-mentioned problem due to the incident angle of the light while ensuring the total amount of light. Then, such an imaging optical system 300 can avoid high cost by satisfying the conditional expression (C2), and avoids an increase in noise or deterioration in darkness which is likely to occur in a dark imaging optical system.

From this point of view, the conditional expression (C1) is ideal as the following conditional expression (C1A), and the preferred condition is the following conditional expression (C1B).

0.05<|f/fir|<0.4. . . (C1A)

0.1<|f/fir|<0.35. . . (C1B)

From this point of view, the conditional expression (C2) is ideal as the following conditional expression (C2A), and the ideal condition is the following conditional expression (C2B).

FN≦2.8. . . (C2A)

FN≦2.4. . . (C2B)

According to this point of view, the conditional expression (C3) is more effectively the following conditional formula (C3A), and more effectively, the following conditional expression (C3B).

30≦w≦60. . . (C3A)

30≦w≦50. . . (C3B)

According to this point of view, the conditional expression (C4) is, more effectively, the conditional expression (C4A) below, and more effectively, the conditional expression (C4B) below.

25< α ≦40. . . (C4A)

25< α ≦35. . . (C4B)

Further, as an anti-color unevenness measure, the imaging lens disclosed in Patent Document 1 is formed by a glass member that absorbs infrared rays, and has an optical path length on a light axis that passes through the light beams of the respective lenses and is imaged at the center of the screen (lens) The thickness of the main beam of the light beam imaged at the peripheral portion of the screen passes through the lens having a difference in optical path length within the lens of ±15% or less. However, the imaging optical system 300 of the present embodiment differs from the above-described Patent Document 1 in that the color unevenness is mainly solved by the conditional expression (C1) described above.

In addition, the imaging optical system 300 is such that the maximum thickness of the aspherical lens (infrared absorption lens) made of a resin material containing an infrared absorbing material is TDmax, and an aspherical lens made of a resin material containing an infrared absorbing material (infrared absorbing lens) When the minimum thickness is TDmin, at least one of the aspherical lenses made of the resin material containing the infrared absorbing material satisfies the conditional expression of the following (C5). In addition, the aforementioned thickness is It is the length parallel to the direction of the optical axis.

1<TDmax/TDmin<1.75. . . (C5)

This TDmax/TDmin is an index indicating the difference in thickness in the aspherical lens. Such an imaging optical system 300 can exceed the lower limit of the conditional expression (C5), and can allow thickness difference in each part of the lens, thereby increasing the degree of freedom of the lens shape and achieving an improvement in performance. Then, the imaging optical system 300 is lower than the upper limit of the conditional expression (C5) without impairing the formability, so that the lens shape can be designed with a large degree of freedom, and performance can be achieved. Upgrade.

From this point of view, the conditional expression (C5) is ideal as the following conditional expression (C5A), and the preferred condition is the following conditional expression (C5B).

1<TDmax/TDmin<1.72. . . (C5A)

1<TDmax/TDmin<1.5. . . (C5B)

In addition, the imaging optical system 300 is such that the optical path length of the 80% image height in the aspherical lens made of the resin material containing the infrared absorbing material is OPp, and the aspherical lens made of a resin material containing the infrared absorbing material is used. When the optical path length on the optical axis is OPc, the conditional expression of the following (C6) is satisfied.

0.7<OPp/OPc<1.3. . . (C6)

In the absorption type infrared cut filter, the infrared absorption amount is proportional to the optical path length. However, in the imaging optical system 300, by satisfying the conditional expression (C6), the optical path length in the effective field of the lens can be made slightly larger. Uniform, a roughly uniform infrared absorption can be obtained in the entire field of the effective field of the lens. As a result, a good image with reduced color unevenness or no color unevenness can be obtained. That is, below the conditional expression (C6) In the case of the limit value or higher than the upper limit value, the optical path length becomes uneven and is not ideal in the effective field of the lens.

From this point of view, the conditional expression (C6) is ideal as the following conditional expression (C6A), and the preferred condition is the following conditional expression (C6B).

0.8<OPp/OPc<1.2. . . (C6A)

0.9<OPp/OPc<1.1. . . (C6B)

Further, in order to make the optical path length more uniform, it is preferable to provide a lens for providing an infrared absorbing function in the order that the value of OPp/OPc is close to one. In the imaging optical system 1B of the second embodiment to be described later, the values of OPp/OPc in the third to fifth lenses L3 to L5 are 1.00, 1.16, and 1.28, respectively. Therefore, in this example, the third to fifth lenses L3 to L5 are selected as the infrared absorption lens in the order of the third lens L3, the fourth lens L4, and the fifth lens L5.

Further, the imaging optical system 300 is composed of five first to fifth lenses 311 to 315, and at least two of the five lenses have a positive refractive power, and at least two of the five lenses are at least two lenses. Has a negative refractive power.

In such an imaging optical system 300, by providing two positive lenses having positive refractive power and negative lenses having negative refractive power, the burden of the refractive power of each lens can be dispersed. Therefore, in such an imaging optical system 300, even when the ease of manufacture of the infrared absorbing lens is high, performance deterioration such as aberration deterioration due to a manufacturing error can be suppressed.

Further, the imaging optical system 300 is as described above, and the filter 316 can be omitted (may be optional). When the imaging optical system 300 includes the filter 316, the filter 316 is, for example, an imaging element. A parallel plate of 317 covering glass. Since the imaging optical system 300 of the present embodiment uses an infrared absorbing lens, the infrared ray cut filter previously used can be deleted, and the cost can be reduced.

Further, in the above-described imaging optical system 300, it is preferable that the third lens 313 has a concave shape on the image side in the field of being in the effective field and outside the one half of the effective field. Generally, the incident angle of the light is larger at the peripheral portion of the image plane of the image sensor 317 than at the center of the screen. In the imaging optical system 300, in the field in which the third lens 313 is in the effective field and is outside from one of the effective fields, the third lens 313 has a concave shape on the image side, so that the thickness of the portion can be made. It is thinner in the center. Therefore, in such an imaging optical system 300, even if the incident angle of light is large, the optical path length can be made substantially uniform in the entire screen.

Further, in the above-described imaging optical system, when the average transmittance (%) in the visible light band (wavelength: 400 nm to 700 nm) is Tr, the conditional expression of the following (C7) is also satisfied. In such an imaging optical system, the above-described effects of the conditional expressions (C1) to (C4) can be effectively obtained by satisfying the conditional expression (C7).

80<Tr<90. . . (C7)

In the above-described imaging optical system 300, the aspherical lens made of a resin material containing the infrared ray absorbing material is preferably one. When two or more lenses are designed as infrared absorbing lenses, if the relative position between these infrared absorbing lenses deviates from the design, the desired infrared absorbing characteristics cannot be obtained, and the infrared absorbing amount will not be generated. Evenly (deviation from the design value). therefore, In such an imaging optical system 300, since only one infrared absorption lens is used, the ease of manufacture can be reduced.

Further, in the imaging optical system 300 described above, the lens disposed on the most image side of the plurality of lenses is the fifth lens 315 in the example shown in FIG. 1, for example, even in focus (focus) It is still fixed at the time, which is ideal. In the imaging optical system 300, since the lens on the image side is fixed, the image sensor 317 can be sealed by the fixed lens. Therefore, it is possible to reduce the sealing member of the image sensor 317 required to prevent dust from adhering, for example. Cover glass). Therefore, such an imaging optical system 300 can easily achieve a low profile.

Further, in the above-described first to third imaging optical systems 100, 200, and 300 (including the above-described respective modifications), at least one of the plurality of lenses is formed on the lens surface. It is preferable to suppress a plating layer having a wavelength band of 400 nm or less and a transmittance of each wavelength band of 700 nm or more. In the imaging optical systems 100, 200, and 300, when the infrared ray intercepting characteristics (infrared cutoff amount at each wavelength) cannot be obtained by the infrared absorbing lens, the infrared ray breaking characteristics can be compensated by the plating layer. The insufficient portion can obtain the desired infrared cutoff characteristics in the imaging optical systems 100, 200, and 300.

Further, in the above-described first to third imaging optical systems 100, 200, and 300 (including the above-described respective modifications), the infrared absorbing lens may have a surface to be formed as shown in FIG. A fine concavo-convex structure AR for preventing reflection. If you add infrared absorption The material sometimes reduces the adhesion of the anti-reflection film. In this case, since the antireflection film is easily peeled off, the reliability thereof is lowered. Therefore, as shown in FIG. 5, by forming fine concavo-convex structures on the optical surface of the infrared absorbing lens, a concave-convex structure AR is formed on the surface of the lens, whereby the imaging optical systems 100, 200, and 300 can simultaneously Take into account the reflection prevention function and reliability. Further, the depth of the uneven shape of the anti-reflection structure is preferably about 50 nm or more and about 1000 nm or less. Further, the method for producing the anti-reflection structure includes, for example, a patterning process in which a mask pattern is formed on a lens surface that has been formed, and an etching process is performed by etching an ion beam on the lens surface. It is preferable to form the reflection preventing structure.

<Description of a digital machine equipped with an imaging optical system>

Next, a digital device in which an imaging optical system is incorporated will be described. In the digital device, the above-described first imaging optical system 100 may be incorporated, or the above-described second imaging optical system 200 may be incorporated, or the above-described third imaging optical system 300 may be incorporated.

Fig. 6 is a block diagram showing the configuration of a digital device in the fourth embodiment. For example, as shown in FIG. 6, the digital device 3 includes an imaging unit 30, a video generation unit 31, a video data buffer 32, an image processing unit 33, a drive unit 34, a control unit 35, and a memory unit. 36 and the face (I/F part) 37. Examples of the digital device 3 include a portable camera such as a digital still camera, a video camera, a surveillance camera (monitor camera), a mobile phone, or a portable information terminal (PDA). Terminals, personal computers, and portable computers can also include peripheral devices such as mice, scanners, and printers. In particular, the imaging optical systems 100, 200, and 300 of the first to third embodiments are sufficiently compact and short-cut to be mounted on a portable terminal such as a mobile phone or a portable information terminal (PDA). Therefore, it is suitable to be mounted in the portable terminal.

The imaging unit 30 is an example of the imaging device 21, and includes an imaging optical system 100 and an imaging element 117 as shown in FIG. 1 as a function of the imaging lens, and is included in the imaging optical system 1 in the optical axis direction. A lens driving device (not shown) that drives a lens required for focusing is configured to perform focusing. The imaging unit 30 may be replaced with the imaging optical system 200 as shown in FIG. 2 as a function of the imaging lens, or may be replaced by the imaging optical system 100 instead of the imaging unit 100. The imaging optical system 300 shown in FIG. 3 functions as an imaging lens. In the following, the case where the imaging optical system 100 is included in the imaging unit 30 is representatively described. However, even if the imaging optical system 200 is replaced instead of the imaging optical system 100, the same is true. The same is true in the case where the system 100 is replaced with the imaging optical system 300. The light from the subject is imaged on the light receiving surface of the image sensor 117 by the imaging optical system 100, and becomes an optical image of the subject.

As described above, the imaging element 117 converts the optical image of the subject imaged by the imaging optical system 100 into an electrical signal (image signal) of the color components of R, G, and B, and becomes an R, G, and B color. Video The number is output to the image generating unit 31. The imaging device 117 controls the imaging operation of either of the still video or the animation by the control unit 35 or the reading of the output signals (horizontal synchronization, vertical synchronization, transmission) of each pixel in the imaging device 117. . Further, the imaging element 117 may be a so-called back-illuminated solid-state imaging element. In the back-illuminated solid-state imaging device, the light-receiving portion (the portion where the photoelectric conversion is performed by PN bonding or the like) is disposed on the side closer to the imaging lens than the wiring layer, and therefore the substantial amount of light reaching the light-receiving portion is Since the solid-state imaging element having the above-described structure is more increased, the effect of improving the low-luminance sensitivity or the effect of suppressing the decrease in the amount of peripheral light due to oblique incidence is extremely large.

The image generating unit 31 performs an amplification process, a digital conversion process, and the like on the analog output signal from the image sensor 117, and determines the black level of the image, the gamma correction, the white balance adjustment (WB adjustment), and the contour. Correct image processing such as correction and color unevenness correction, and image data generation from image signals. The image data generated by the image generating unit 31 is output to the video data buffer 32.

The video data buffer 32 is a memory for temporarily storing the video data, and is used as a work area required for the image data to be described later by the image processing unit 33, for example, a volatile memory element. RAM (Random Access Memory) and the like.

The image processing unit 33 is a circuit that performs predetermined image processing such as resolution conversion on the image data of the image data buffer 32.

Moreover, the image processing unit 33 can also be configured as needed. In the known distortion correction processing such as distortion correction of the optical image of the subject formed on the light receiving surface of the imaging element 117, the aberration that cannot be completely corrected in the imaging optical system 100 is corrected. The distortion correction is an image in which the distortion is caused by the aberration, and it is corrected to a natural image similar to the shape of the naked eye and substantially free of distortion. According to this configuration, even if distortion is generated in the optical image of the subject guided by the imaging optical system 100 to the imaging element 117, a natural image that is substantially undistorted can be generated. Further, in the configuration in which the distortion is corrected by the image processing by the information processing, in particular, it is only necessary to consider various aberrations other than the distortion aberration, and thus the design freedom of the imaging optical system 100 is increased. Design will become easier. Further, in the configuration in which the distortion is corrected by the image processing by the information processing, in particular, the burden of the aberration shared by the lens close to the image plane can be reduced, so that the control of the position of the exit pupil can be easily performed. The lens shape can be designed into a shape with good workability.

In addition, the image processing unit 33 may include a peripheral illuminance reduction correction process for correcting the peripheral illuminance of the optical image of the subject formed on the light receiving surface of the image sensor 117, if necessary. In the imaging optical system 100 of the present embodiment, the difference between the incident angle at the center of the imaging element 117 and the incident angle around the imaging element 117 is small, and the peripheral illumination is reduced, but the digital device 3 is also provided. Such a peripheral illumination is reduced and corrected, and a better image can be obtained. Peripheral illuminance correction (shadow correction) is used to correct the correction data required for peripheral illuminance reduction in advance, and the correction is performed by multiplying the corrected image (pixel) by the image. The peripheral illumination is mainly due to the imaging element 117. Since the sensitivity of the incident angle dependence, the lens aperture erosion, and the cosine four-time method are generated, the correction data is set to a predetermined value that can correct the illuminance caused by these factors. According to this configuration, even if the peripheral illuminance is lowered in the optical image of the subject guided by the imaging optical system 100 to the imaging element 117, it is possible to generate an image having sufficient illuminance to the periphery.

The drive unit 34 operates the lens driving device (not shown) based on the control signal output from the control unit 35, thereby driving the focus lens in the imaging optical system 100 to perform desired focusing.

The control unit 35 includes, for example, a microprocessor and its peripheral circuits, and the imaging unit 30, the video generation unit 31, the video data buffer 32, the video processing unit 33, the drive unit 34, the memory unit 36, and the I/F unit. The actions of the various parts of 37 are controlled according to their functions. In other words, by the control unit 35, the imaging device 21 is controlled to perform at least one of still image shooting and animation shooting of the subject.

The memory unit 36 is a memory circuit that memorizes image data generated by still image shooting or moving photography of a subject, for example, a ROM (Read Only Memory) having a non-volatile memory element, or a rewritable non-volatile memory. It is composed of an EEPROM (Electrically Erasable Programmable Read Only Memory) or a RAM. In other words, the memory unit 36 has a function of a memory for still images and animation.

The I/F unit 37 is an interface for receiving image data with an external device, for example, according to USB (Universal Serial Bus) or Interface of specifications such as IEEE1394.

The imaging operation of the digital device 3 having such a configuration will be described below.

When the still image is captured, the control unit 35 controls the imaging unit 30 (the imaging device 21) to take a still image, and transmits the lens driving device of the imaging unit 30 through the driving unit 34. Move the full lens to focus. As a result, the optical image of the focus image is periodically over-imaged on the light-receiving surface of the image sensor 117, and is converted into image signals of the color components of R, G, and B, and then output to the image generating unit 31. The image signal is temporarily stored in the image data buffer 32, and after being processed by the image processing unit 33, the image based on the image signal is displayed on a display (not shown). Then, by referring to the aforementioned display, the photographer can adjust so that the main subject is accommodated at a desired position in the screen. In this state, by pressing a so-called shutter button (not shown), the image data is stored in the memory unit 36 as a still image memory to obtain a still image.

Further, when the animation is performed, the control unit 35 controls the imaging unit 30 to perform an animation. Thereafter, in the same manner as in the case of still image shooting, the photographer can adjust the image of the subject obtained by the imaging unit 30 to be placed at a desired position on the screen by referring to the display (not shown). The animation photography is started by pressing the aforementioned shutter button (not shown). Then, during the animation shooting, the control unit 35 controls the imaging unit 30 to perform an animation, and transmits the lens driving device of the imaging unit 30 through the driving unit 34 to perform focusing. borrow As a result, the optical image of the focus image is periodically over-imaged on the light-receiving surface of the image sensor 117, and converted into image signals of the color components of R, G, and B, and then output to the image generating unit 31. The image signal is temporarily stored in the image data buffer 32, and after being processed by the image processing unit 33, the image based on the image signal is displayed on a display (not shown). Then, by pressing the shutter button (not shown) once, the animation photography ends. The moving image to be photographed is stored in the memory unit 36 of the memory for animation and stored.

In the digital device 3 or the imaging device 21 (the imaging unit 30), the imaging optical system 100 (200, 300) that can easily supply the infrared absorbing function to the lens is used. Therefore, the infrared ray cutting filter can be omitted, and the imaging device can be omitted. For the low back. That is, a thin digital machine 3 or an image pickup device 21 can be provided. Therefore, it is suitable for mobile phones that are moving toward thinning, especially so-called smart phones. As an example, a case where the imaging device 21 is mounted on a mobile phone will be described below.

Fig. 7 is a view showing the external configuration of a camera-equipped mobile phone according to an embodiment of a digital device. Fig. 7A shows the operation surface of the mobile phone, and Fig. 7B shows the reverse side of the operation surface, that is, the back side.

For example, as shown in FIG. 7, the mobile phone 5 includes a display unit 51 that displays predetermined information, an input operation unit 52 that accepts input of a predetermined instruction, and a communication unit that performs communication using a mobile phone network to realize a telephone function. 53. Each of the portions 30 to 37 shown in FIG. 6 and a thin plate-shaped frame HS in which the respective portions 51 to 53 and 30 to 37 are housed. In the one main surface (surface) of the casing HS, a rectangular display of the display portion 51 is attached. The input operation unit 52 is provided on one side (lower side) of the display surface. The display surface of the display unit 51 includes a touch panel that accepts input by touching the display surface with a fingertip or a pen tip, and an input of an instruction that the input operation unit 52 cannot input is by the touch panel and the display unit 51. The information displayed above is combined to achieve. For example, the display unit 51 displays a start button of the image capturing mode, a video shooting button and a shutter button for switching between still image shooting and movie shooting, and the button is touched by the display surface of the displayed button position. The indicated indication is input to the mobile phone 5. Further, the touch panel described above may be a well-known method such as a so-called capacitive type. Then, the imaging unit 30 (imaging device 21) is attached to the other main surface (back surface) of the casing HS.

In the mobile phone 5, when the start button of the video shooting mode is operated, the control signal indicating the operation content is output to the control unit 35, and the control unit 35 activates the function of the image capturing. When the photography button is operated, the control signal indicating the operation content thereof is output to the control unit 35, and the control unit 35 performs activation and execution of the still picture shooting mode, or activation, execution, and the like of the animation shooting mode, corresponding to the operation content. The action. Then, when the shutter button is operated, the control signal indicating the operation content thereof is output to the control unit 35, and the control unit 35 performs an operation corresponding to the operation content such as still image shooting or animation shooting.

<Description of a more specific embodiment of the imaging optical system>

Hereinafter, one side of the drawing will be described with reference to the drawings. The specific configuration of the imaging optical systems 100, 200, and 300. In addition, the imaging optical systems 1A to 1G shown below are provided in the digital device 3 and the imaging device 21 mounted in the mobile phone 5 shown in FIGS. 6 and 7 respectively.

<Description of each embodiment>

8 to 14 are cross-sectional views showing the arrangement of lenses in the imaging optical systems of the first to seventh embodiments.

In the imaging optical systems 1A to 1G of the first to seventh embodiments, as shown in FIG. 8 to FIG. 14 , roughly, the plurality of lenses Ln are arranged in order from the object side to the image side, and the focus is focused. When the plural lenses Ln are all moved, they move integrally in the optical axis direction AX. Then, in the imaging optical systems 1A to 1G of the first to seventh embodiments, the lens L1 disposed on the most object side of the plurality of lenses Ln has a positive refractive power, and at least one of the plurality of lenses Ln It is an aspherical lens made of a resin material that absorbs infrared rays.

In the imaging optical systems 1A to 1G of the first to seventh embodiments, the imaging optical systems 1A to 1D of the first to fourth embodiments are composed of five first to fifth lenses L1 to L5. Then, in the imaging optical systems 1A, 1C, and 1D of the first, third, and fourth embodiments, the refractive powers of the first to fifth lenses L1 to L5 are positive and negative positive and negative, and in the second embodiment, In the imaging optical system 1B, the refractive power of the first to fifth lenses L1 to L5 is positive and negative, positive and negative. In the imaging optical system 1A of the first embodiment, the optical aperture ST is disposed between the first lens L1 and the second lens L2. (Image side of the first lens L1), the imaging optical system 1A of the first embodiment is of an internal aperture type, and in the imaging optical systems 1B to 1D of the second to fourth embodiments, the optical aperture ST is disposed. On the object side of the first lens L1, the imaging optical systems 1B to 1D of the second to fourth embodiments are of a front aperture type.

With respect to the imaging optical systems 1A to 1D of the first to fourth embodiments, the imaging optical system 1E of the fifth embodiment is composed of three first to third lenses L1 to L3. Then, in the imaging optical system 1E of the fifth embodiment, the refractive powers of the first to third lenses L1 to L3 are positive and negative. In the imaging optical system 1E of the fifth embodiment, the optical aperture ST is disposed between the first lens L1 and the second lens L2, and the imaging optical system 1E of the fifth embodiment is of an internal aperture type.

In addition, the imaging optical system 1F of the sixth embodiment is composed of four first to fourth lenses L1 to L4 with respect to the imaging optical systems 1A to 1D of the above-described first to fourth embodiments. Then, in the imaging optical system 1F of the sixth embodiment, the refractive powers of the first to fourth lenses L1 to L4 are positive and negative. In the imaging optical system 1F of the sixth embodiment, the optical aperture ST is disposed on the object side of the first lens L1, and the imaging optical system 1F of the sixth embodiment is a front aperture type.

Then, with respect to the imaging optical systems 1A to 1D of the above-described first to fourth embodiments, the imaging optical system 1G of the seventh embodiment is composed of six first to sixth lenses L1 to L6. Then, in the imaging optical system 1G of the seventh embodiment, the refractive powers of the first to sixth lenses L1 to L6 are positive and negative, positive and negative. In the imaging optical system 1G of the seventh embodiment, the optical aperture ST is disposed between the first lens L1 and the second lens L2, and the seventh embodiment The imaging optical system 1G is an internal aperture type.

More specifically, in the imaging optical systems 1A to 1G of the first to seventh embodiments, the complex lenses Ln are arranged in order from the object side to the image side, and are configured as follows.

First, the imaging optical system 1A of the first embodiment will be described. The first lens L1 is a biconvex positive lens having a positive refractive power, and the second lens L2 is a negative crescent lens having a negative refractive power and a concave side on the image side. The third lens L3 is a positive crescent lens having a positive refractive power and a convex side on the object side, and the fourth lens L4 is a positive crescent lens having a positive refractive power and a convex side on the image side, and then the fifth lens L5 A negative crescent lens having a negative refractive power and a concave side on the image side.

The imaging optical system 1B of the second embodiment will be described. The first lens L1 has a positive refractive lens with a positive refractive power and a convex side on the object side, and the second lens L2 has a negative refractive power and the image side has a concave new color. The lunar lens, the third lens L3 is a biconvex positive lens having a positive refractive power, and the fourth lens L4 is a biconcave negative lens having a negative refractive power, and then the fifth lens L5 has a negative refractive power and the image side A negative crescent lens for the recess.

The imaging optical system 1C of the third embodiment will be described. The first lens L1 is a biconvex positive lens having a positive refractive power, the second lens L2 is a negative crescent lens having a negative refractive power and the image side is concave, and the third lens L3 is used. The lens L3 is a positive single lens having a positive refractive power and the object side is convex, the fourth lens L4 is a biconvex positive lens having a positive refractive power, and then the fifth lens L5 is a biconcave having a negative refractive power. Negative lens.

The imaging optical system 1D of the fourth embodiment will be described, first to fourth The lenses L1 to L4 are the same as the first to fourth lenses L1 to L4 in the imaging optical system 1A of the first embodiment, and the fifth lens L5 is a double concave negative lens having a negative refractive power.

In the imaging optical systems 1A to 1D of the first to fourth embodiments, in the first, second, and fourth embodiments, all of the first to fifth lenses L1 to L5 are lenses made of a resin material. In the imaging optical systems 1A and 1D of the first and fourth embodiments, one of the first to fourth lenses L1 to L4 or the plurality of lenses is an infrared absorbing lens having a function of absorbing infrared rays. In the imaging optical system 1B, at least one of the first and second lenses L1 and L2 is an infrared absorbing lens having a function of absorbing infrared rays. On the other hand, in the third embodiment, the first lens L1 is a glass lens, and the second to fifth lenses L2 to L5 are lenses made of a resin material. Then, one of the second to fourth lenses L1 to L4 or the plurality of lenses is an infrared absorbing lens having a function of absorbing infrared rays.

On the other hand, the imaging optical system 1E of the fifth embodiment will be described. The first lens L1 has a positive refractive index and the object side is a convex positive crescent lens, and the second lens L2 has a positive refractive power and the image side is convex. A positive crescent lens is produced, and then the third lens L3 has a negative refractive lens and the image side is a concave negative crescent lens. All of the first to third lenses L1 to L3 are lenses made of a resin material, and one of the first to third lenses L1 to L3 or a plurality of lenses is an infrared absorption lens having a function of absorbing infrared rays.

Further, the imaging optical system 1F of the sixth embodiment will be described. The mirror L1 is a biconvex positive lens having a positive refractive power, the second lens L2 is a biconcave negative lens having a negative refractive power, the third lens L3 has a positive refractive power, and the image side is a convex positive crescent The lens, then, the fourth lens L4 is a double concave negative lens having a negative refractive power. All of the first to fourth lenses L1 to L4 are lenses made of a resin material, and one of the first to third lenses L1 to L3 or a plurality of lenses is an infrared absorption lens having a function of absorbing infrared rays.

Next, the imaging optical system 1G of the seventh embodiment will be described. The first lens L1 is a biconvex positive lens having a positive refractive power, and the second lens L2 is a negative crescent lens having a negative refractive power and a concave side on the image side. The third lens L3 is a negative crescent lens having a negative refractive power and the image side is concave, the fourth lens L4 is a positive crescent lens having a positive refractive power and a convex side on the object side, and the fifth lens L5 has a positive lens. A biconvex positive lens of positive refractive power, and then the sixth lens L6 is a biconcave negative lens having a negative refractive power. All of the first to sixth lenses L1 to L6 are lenses made of a resin material, and one of the first to fourth lenses L1 to L4 or a plurality of lenses is an infrared absorption lens having a function of absorbing infrared rays.

The optical aperture ST may be an aperture stop or a mechanical shutter or an iris diaphragm in the case of each of the first to seventh embodiments.

In the case of each of the first to seventh embodiments, the light receiving surface of the image sensor IS is disposed on the image side of the lens L disposed on the most image side. Further, between the lens L disposed on the most image side and the image sensor IS, a parallel flat plate FT may be disposed. In other words, the image side of the lens L disposed on the most image side is disposed with the parallel flat plate FT. The light receiving surface of the image sensor IS is placed. The parallel flat plate FT is a cover glass of the image sensor IS or the like.

In each of Figs. 8 to 14, the number ri (i = 1, 2, 3, ‧ ‧) indicated by each lens surface indicates the i-th lens surface when counting from the object side (where The joint surface of the lens is counted as one surface, and the surface with the "*" mark attached to ri indicates that it is an aspherical surface. Further, the surface of the optical aperture ST and the both sides of the parallel flat plate FT are also counted as one surface. The meaning of such symbols is the same in all embodiments. However, this does not mean the same meaning. For example, as shown in the respective drawings of the respective embodiments, the same symbol (r1) is attached to the lens surface disposed on the most object side, but structural data as will be described later. As shown, their curvatures and the like are not the same across the respective embodiments 1 to 7.

With this configuration, in the imaging optical system 1A of the first embodiment, the light incident from the object side sequentially passes through the optical aperture ST, the first lens L1, the second lens L2, and the third along the optical axis AX. The lens L3, the fourth lens L4, and the fifth lens L5 form an optical image of the object on the light receiving surface of the image sensor IS. In the imaging optical systems 1B to 1D of the second to fourth embodiments, the light rays incident from the object side sequentially pass through the first lens L1, the optical aperture ST, the second lens L2, and the third lens L3 along the optical axis AX. The fourth lens L4 and the fifth lens L5 form an optical image of the object on the light receiving surface of the image sensor IS. In the imaging optical system 1E of the fifth embodiment, the light incident from the object side passes through the first lens L1, the optical aperture ST, the second lens L2, and the third lens L3 sequentially along the optical axis AX. The light receiving surface of the IS forms an optical image of the object. Photographed in Example 6 In the optical system 1F, the light incident from the object side sequentially passes through the optical aperture ST, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 along the optical axis AX, in the imaging element. The light receiving surface of the IS forms an optical image of the object. In the imaging optical system 1G of the seventh embodiment, the light incident from the object side sequentially passes through the first lens L1, the optical aperture ST, the second lens L2, the third lens L3, and the fourth lens along the optical axis AX. L4, the fifth lens L5, and the sixth lens L6 form an optical image of the object on the light receiving surface of the image sensor IS.

Then, in the imaging optical systems 1A to 1G of the first to seventh embodiments, the optical image system is converted into an electrical signal in the imaging element IS. The electrical signal is subjected to digital image processing as required, and is recorded as a digital image signal to be stored in a memory of a digital device such as a digital camera or transmitted through a wired or wireless communication interface through a interface. To other digital machines and so on.

The structural data of each lens in the imaging optical systems 1A to 1G of the first to seventh embodiments is as follows.

First, the structural data of each lens in the imaging optical system 1A of the first embodiment is as follows.

Numerical Example 1

Aspheric data

First side

K=-0.28388E+00, A4=-0.11429E-01, A6=0.58394E-02, A8=-0.30635E-01, A10=0.25844E-01, A12=-0.11762E-01, A14=-0.24890 E-02

Second side

K=0.29247E+02, A4=-0.24343E-01, A6=0.16540E+00, A8=-0.35209E+00, A10=0.38420E+00, A12=-0.26046E+00, A14=0.77919E- 01

Fourth side

K=-0.29353E+02, A4=-0.58267E-01, A6=0.27269E+00, A8=-0.39392E+00, A10=0.22595E+00, A12=-0.42192E-01, A14=-0.51043 E-03

Fifth side

K=-0.55718E+01, A4=-0.71904E-02, A6=0.15580E+00, A8=-0.14089E+00, A10=0.28229E-01, A12=-0.32553E-01, A14=0.38484E -01

Sixth side

K=0.22272E+02, A4=-0.10217E+00, A6=-0.13167E-01, A8=0.99700E-01, A10=-0.14042E+00, A12=0.12255E+00, A14=-0.50937E -01

Side 7

K=-0.95653E+02, A4=-0.61924E-01, A6=0.13566E-01, A8=-0.35274E-01, A10=0.20141E-01, A12=0.64892E-02, A14=-0.31555E -02

8th side

K=0.10552E+02, A4=0.14950E-01, A6=0.82129E-02, A8=-0.12281E-01, A10=-0.26695E-02, A12=0.44153E-02, A14=-0.68681E- 03

Ninth face

K=-0.39323E+01, A4=-0.70567E-01, A6=0.49341E-01, A8=-0.42386E-02, A10=-0.20788E-04, A12=-0.91338E-03, A14=0.18678 E-03

10th side

K=0.79799E+01, A4=-0.11271E+00, A6=0.35926E-01, A8=-0.81251E-03, A10=-0.12071E-02, A12=0.18687E-03, A14=-0.80839E -05

11th side

K=-0.60657E+01, A4=-0.62302E-01, A6=0.18921E-01, A8=-0.44435E-02, A10=0.53983E-03, A12=-0.23945E-04, A14=-0.61553 E-07

Various data

Focal length of each lens (mm)

Next, the structural data of each lens in the imaging optical system 1B of the second embodiment is as follows.

Numerical Example 2

Aspheric data

Second side

K=-0.30565E+00, A4=0.21285E-01, A6=0.75751E-01, A8=-0.32279E+00, A10=0.68260E+00, A12=-0.28318E+00, A14=-0.10821E +01

Third side

K=0.35574E+02, A4=-0.27169E+00, A6=0.34491E+00, A8=-0.64675E+00, A10=0.68427E-01, A12=-0.50424E-01, A14=0.13037E+ 00

Fourth side

K=-0.70000E+02, A4=-0.27305E+00, A6=0.38254E+00, A8=0.31528E-01, A10=-0.15770E+01, A12=0.16835E+01, A14=0.56100E+ 00

Fifth side

K=-0.52576E+02, A4=0.23852E+00, A6=-0.28857E+00, A8=0.66639E+00, A10=0.14364E+01, A12=-0.56913E+01, A14=0.70700E+ 01

Sixth side

K=0.70000E+02, A4=-0.15742E+00, A6=-0.48731E-01, A8=0.29234E+00, A10=-0.77692E-01, A12=-0.17529E+00, A14=0.93057E +00

Side 7

K=-0.70000E+02, A4=-0.13749E+00, A6=-0.15531E+00, A8=0.24223E+00, A10=0.89280E-01, A12=-0.25665E+00, A14=0.43377E +00

8th side

K=0.41981E+02, A4=0.16810E+00, A6=-0.75297E+00, A8=0.56261E+00, A10=-0.38464E+00, A12=0.87706E-01, A14=-0.62914E- 01

Ninth face

K=0.70000E+02, A4=0.12832E-01, A6=-0.27040E+00, A8=0.11692E+00, A10=0.19738E-02, A12=-0.18302E-01, A14=0.67674E-02

10th side

K=-0.24796E+02, A4=-0.29698E+00, A6=0.74264E-01, A8=0.11234E-01, A10=-0.40120E-03, A12=-0.57008E-03, A14=-0.20397 E-03

11th side

K=-0.96609E+01, A4=-0.12306E+00, A6=0.24225E-01, A8=-0.32605E-03, A10=-0.77368E-03, A12=-0.18265E-03, A14=0.57268 E-04

Various data

Focal length of each lens (mm)

Next, the structural data of each lens in the imaging optical system 1C of the third embodiment is as follows.

Numerical Example 3

Aspheric data

Second side

K=-0.75937E+00, A4=-0.16351E-01, A6=-0.73565E-02, A8=-0.13596E+00, A10=0.20267E+00, A12=-0.18185E+00

Third side

K=0.51562E+01, A4=-0.37204E-01, A6=0.50106E-01, A8=-0.24971E+00, A10=0.15743E+00

Fourth side

K=0.25290E+01, A4=-0.59955E-01, A6=0.24177E+00, A8=-0.42185E+00, A10=0.28532E+00

Fifth side

K=-0.98038E+01, A4=0.87620E-01, A6=0.48244E-01, A8=-0.90951E-04, A10=-0.11025E+00, A12=0.11245E+00

Sixth side

K=-0.30000E+02, A4=-0.11177E+00, A6=0.54701E-01, A8=-0.39017E-01, A10=0.46976E-01, A12=0.66356E-01, A14=-0.44595E -01

Side 7

A4=-0.13715E+00, A6=0.15085E-01, A8=-0.15361E-01, A10=0.10194E-01, A12=0.10842E-01, A14=0.13234E-01, A16=-0.11126E- 02

8th side

K=0.30000E+02, A4=-0.10518E+00, A6=0.85872E-02, A8=0.12970E-02, A10=-0.25995E-01, A12=0.48414E-02, A14=0.82281E-02 , A16=-0.25504E-02

Ninth face

K=-0.45195E+01, A4=-0.80796E-01, A6=0.76110E-01, A8=-0.15132E-01, A10=-0.14302E-02, A12=0.40993E-03, A14=0.16150E -03, A16=-0.52241E-04

10th side

K=-0.60133E+01, A4=-0.72425E-01, A6=0.31292E-01, A8=0.11232E-02, A10=-0.11042E-02, A12=-0.11145E-03, A14=0.32643E -04, A16=0.41277E-06

11th side

K=-0.18062E+02, A4=-0.36300E-01, A6=0.73573E-02, A8=-0.30389E-02, A10=0.55223E-03, A12=-0.27217E-04, A14=-0.76948 E-05, A16=0.10957E-05

Various data

Focal length of each lens (mm)

Next, the structural data of each lens in the imaging optical system 1D of the fourth embodiment is as follows.

Numerical Example 4

Aspheric data

Second side

K=-0.22999E+00, A4=-0.69407E-02, A6=-0.81920E-02, A8=-0.49145E-01, A10=0.22519E-01, A12=0.13169E-01, A14=-0.80208 E-01

Third side

K=-0.30000E+02, A4=0.30733E-02, A6=-0.91942E-01, A8=0.42997E-01, A10=-0.47026E-01, A12=-0.57654E-01, A14=0.51295E -01

Fourth side

K=-0.29971E+02, A4=0.20317E-01, A6=0.69346E-01, A8=-0.12202E+00, A10=0.31089E-01, A12=0.91194E-01, A14=-0.29017E- 01

Fifth side

K=-0.11151E+02, A4=0.81743E-01, A6=0.73249E-01, A8=-0.18483E-01, A10=-0.13073E-01, A12=0.11421E-01, A14=0.43182E- 01

Sixth side

K=-0.15621E+01, A4=-0.16700E+00, A6=0.43170E-01, A8=0.18122E-01, A10=-0.44573E-01, A12=0.52331E-01, A14=-0.34923E -01

Side 7

K=-0.27058E+02, A4=-0.63600E-01, A6=-0.33041E-01, A8=0.16808E-01, A10=0.15799E-01, A12=0.13649E-02, A14=-0.37117E -02

8th side

K=0.29963E+02, A4=-0.17740E-01, A6=0.40560E-01, A8=-0.38689E-01, A10=-0.23572E-02, A12=0.11047E-01, A14=-0.24298E -02

Ninth face

K=-0.30056E+01, A4=-0.88146E-03, A6=0.57319E-01, A8=-0.20755E-01, A10=-0.92344E-03, A12=0.13487E-02, A14=-0.15172 E-03

10th side

K=-0.92913E+01, A4=-0.54865E-01, A6=0.18251E-01, A8=0.26096E-03, A10=-0.44267E-03, A12=-0.92970E-05, A14=0.69479E -05

11th side

K=-0.11000E+02, A4=-0.66617E-01, A6=0.19615E-01, A8=-0.43680E-02, A10=0.37738E-03, A12=-0.12828E-04, A14=0.13564E -05

Various data

Focal length of each lens (mm)

Next, the structural data of each lens in the imaging optical system 1E of the fifth embodiment is as follows.

Numerical Example 5

Aspheric data

First side

K=-0.35138E+00, A4=0.43728E-01, A6=0.15900E-01, A8=0.91842E-01, A10=-0.14196E+00, A12=0.24812E+00, A14=-0.32812E+ 00, A16=0.63433E-01

Second side

K=0.20670E+02, A4=-0.13714E+00, A6=0.93091E+00, A8=-0.89056E+01, A10=0.30763E+02, A12=-0.48851E+02, A14=0.26954E+ 02, A16=-0.13712E+02

Fourth side

K=0.10971E+01, A4=-0.80353E-01, A6=0.77670E+00, A8=-0.32124E+01, A10=0.19476E+02, A12=-0.50013E+02, A14=0.48694E+ 02, A16=-0.13234E+02

Fifth side

K=-0.93617E+00, A4=0.45641E-01, A6=-0.72231E-01, A8=0.40401E+00, A10=0.25557E+00, A12=-0.18152E+00, A14=-0.43306E +00, A16=0.21991E+00

Sixth side

K=-0.55658E+00, A4=0.10605E+00, A6=-0.18789E-01, A8=0.33491E-02, A10=0.66911E-04, A12=-0.14977E-03, A14=0.21222E- 04, A16=-0.13217E-06

Side 7

K=-0.30000E+02, A4=-0.53487E-01, A6=0.12475E-01, A8=-0.40252E-02, A10=0.31844E-03, A12=0.14448E-03, A14=-0.23171E -04, A16=0.25766E-05

Various data

Focal length of each lens (mm)

Next, the structural data of each lens in the imaging optical system 1F of the sixth embodiment is as follows.

Numerical Example 6

Unit mm

Surface data

Aspheric data

Second side

K=-0.19948E+00, A4=-0.12995E-01, A6=-0.14293E+00, A8=0.23654E+00, A10=-0.39195E+00

Third side

K=-0.90000E+02, A4=-0.15510E+00, A6=0.85783E-01, A8=0.20108E+00, A10=-0.42579E+00

Fourth side

K=0.90000E+02, A4=0.19041E-02, A6=-0.17371E+00, A8=0.99022E+00, A10=-0.90213E+00, A12=0.94446E-01

Fifth side

K=-0.16060E-01, A4=0.12057E+00, A6=-0.23375E-01, A8=-0.26848E+00, A10=0.12017E+01, A12=-0.95442E+00

Sixth side

K=-0.41312E+02, A4=-0.17561E-01, A6=-0.15266E+00, A8=0.29806E+00, A10=-0.31964E+00, A12=0.13248E+00

Side 7

K=-0.48643E+01, A4=-0.30483E+00, A6=0.50026E+00, A8=-0.61291E+00, A10=0.43873E+00, A12=-0.11189E+00

8th side

K=-0.14108E+00, A4=-0.20400E+00, A6=0.42329E-01, A8=0.26399E-01, A10=-0.61184E-02, A12=-0.16013E-02, A14=0.41103E -03

Ninth face

K=-0.61585E+01, A4=-0.14631E+00, A6=0.76525E-01, A8=-0.34041E-01, A10=0.97871E-02, A12=-0.17089E-02, A14=0.13459E -03

Various data

Focal length of each lens (mm)

Next, each lens in the imaging optical system 1G of the seventh embodiment The structure data is as follows.

Numerical Example 7

Aspheric data

First side

K=-0.35266E+00, A4=0.17876E-02, A6=0.25122E-02, A8=-0.11691E-01, A10=0.68717E-02, A12=-0.37756E-02

Second side

K=-0.50000E+02, A4=-0.24060E-02, A6=0.93964E-02, A8=-0.20026E-01, A10=0.71184E-02, A12=-0.15635E-02

Fourth side

K=-0.33812E+02, A4=-0.31977E-01, A6=0.26673E-01, A8=-0.69083E-02, A10=0.26725E-02, A12=0.12675E-02

Fifth side

K=-0.86937E+01, A4=-0.19768E-01, A6=0.35609E-02, A8=-0.67704E-03, A10=0.40106E-03, A12=-0.17523E-02

Sixth side

K=0.15291E+02, A4=-0.10498E+00, A6=0.77244E-02, A8=-0.36729E-01, A10=-0.65175E-02, A12=0.11747E-01

Side 7

K=-0.15003E+03, A4=-0.46838E-01, A6=-0.13609E-01, A8=-0.53287E-03, A10=-0.59168E-03, A12=0.32180E-02

8th side

K=-0.15573E+02, A4=-0.16242E-01, A6=0.54973E-02, A8=-0.16158E-02, A10=0.74709E-03, A12=-0.11447E-03

Ninth face

K=-0.17837E+02, A4=-0.34995E-01, A6=0.50616E-03, A8=-0.12060E-02, A10=0.91768E-04, A12=0.19897E-03

10th side

K=-0.22297E+02, A4=-0.30142E-01, A6=0.11288E-01, A8=-0.38607E-02, A10=-0.53681E-03, A12=0.23041E-03

11th side

K=-0.48430E+01, A4=-0.48149E-01, A6=0.26459E-01, A8=-0.40246E-02, A10=0.50919E-03, A12=-0.77910E-04, A14=-0.81821 E-05, A16=0.19237E-05

12th side

K=0.46873E+02, A4=-0.67404E-01, A6=0.15586E-01, A8=-0.78561E-04, A10=-0.14079E-03, A12=-0.58505E-05, A14=0.15409E -05

13th face

K=-0.60707E+01, A4=-0.43812E-01, A6=0.11297E-01, A8=-0.20994E-02, A10=0.18653E-03, A12=-0.23108E-05, A14=-0.33756 E-06

Various data

Focal length of each lens (mm)

Here, the total length of the lens (TTL) of the various data is the total length of the lens when the object is infinity (the distance from the side of the first lens object to the imaging surface), and the parallel plate is calculated as the air conversion length. ENTP is the distance from the entrance pupil to the first surface, and is 0 when the entrance pupil = aperture. The distance from the final surface of the EXTP (covering the image side of the glass) to the exit pupil, H1 is the distance from the first surface to the main point on the object side, and H2 is the final surface (covering the glass image side) to the image side main The distance to the point.

In the surface data of the above, the surface number corresponds to the number i of the symbol ri (i = 1, 2, 3, ...) indicated by each lens surface shown in Figs. 8 to 14 . The number i has a surface to which * is attached, and indicates an aspherical surface (a refractive optical surface of an aspherical shape or a surface having a refractive effect equivalent to an aspherical surface).

Further, "r" indicates the radius of curvature of each surface (unit: mm), and "d" indicates the interval between the lens faces on the optical axis in the infinity in-focus state (the focus state in the wireless range) (axis) The upper interval, unit: mm), "nd" indicates the refractive index of each lens with respect to the d line (wavelength 587.56 nm), "νd" indicates the Abbe number, and then "ER" indicates the effective radius (unit: Mm). Further, since the respective faces of the optical aperture ST and the light receiving surface of the imaging element SI are flat, the radius of curvature of these is ∞ (infinity). Further, both sides of the parallel flat plate FT which are arranged as needed have a radius of curvature of ∞ (infinity).

The aspherical data described above indicates the secondary surface parameter (cone coefficient K) and the aspherical coefficient Ai (i=4, 6, 8) of the surface designed to be aspherical (the surface in which the number i is appended * in the surface data). , 10, 12, 14, 16).

In each of the embodiments, the aspherical surface has the surface apex as the origin, and the optical axis direction is the X axis, and when the height of the optical axis in the vertical direction is h, it is defined by the following formula.

X=(h ² /R)/[1+(1-(1+K)h ² /R ² ) ^1/2 ]+Σ A _i ‧h ⁱ where Ai is the aspheric coefficient of the power of i, R is the reference radius of curvature, and K is the conic constant.

Further, regarding the request term, the embodiment, and the paraxial radius of curvature (r) described in each of the embodiments, in the actual lens measurement, the vicinity of the center of the lens (more specifically, the outer diameter of the lens) The shape measurement value at the central region within 10% is approximated by the least square method, and the approximate radius of curvature at this time is regarded as the paraxial radius of curvature. Further, for example, when the aspherical coefficient of the second time is used, the radius of curvature obtained by considering the aspherical coefficient of the aspherical defined radius of the aspherical surface is considered to be a paraxial radius of curvature (for example, as a reference, For example, P41~P42 of the "Lens Design Method" (Kyoritsu Publishing Co., Ltd.) can be referred to.

Then, in the above aspherical data, "En" means "10 nth power". For example, "E+001" means "10 to the power of +1", and "E-003" means "10 to the power of -3".

In the imaging optical systems 1A to 1G of the first to seventh embodiments listed above, the numerical values when the conditional expressions (A1) to (A7) are satisfied are shown in Table 1.

Further, in the imaging optical systems 1A to 1D of the first to fourth embodiments listed above, the numerical values when the conditional expressions (B1) to (B7) are satisfied are shown in Table 2.

Further, in the imaging optical systems 1A to 1D of the first to fourth embodiments listed above, the numerical values when the conditional expressions (C1) to (C6) are satisfied are shown in Table 3.

As described above, the imaging optical systems 1A to 1G in the above-described first to seventh embodiments are three to six lens configurations, and as a result of satisfying the above various conditions, it is possible to satisfactorily correct various aberrations while having various aberrations. The lens of the infrared absorbing material is thinned to shorten the optical total length. Then, the imaging optical systems 1A to 1G in the above-described first to seventh embodiments are mounted on the imaging device 21 and the digital device 3, and are particularly mounted on the mobile phone 5, and the total optical length can be sufficiently shortened.

This specification discloses various techniques as described above, but the main techniques are summarized as follows.

The imaging optical system according to the aspect of the invention includes a plurality of lenses arranged in order from the object side toward the image side; wherein the plurality of lenses disposed on the most object side have positive refractive power; and the plurality of lenses At least one of the lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays.

In such an imaging optical system, at least one of the plurality of lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays, so that a lens having an infrared absorbing function can be made thinner.

In another aspect, the imaging optical system includes a plurality of lenses arranged in order from the object side toward the image side, and a lens disposed on the most object side of the plurality of lenses has a positive refractive power; At least one of the lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays, and satisfies the following conditional expressions (A1) to (A3).

0.5<OPp/OPc<1.5. . . (A1)

26< α ≦45. . . (A2)

0.55≦Y/TTL. . . (A3) The OPp is an optical path length of an 80% image height of an aspherical lens made of a resin material containing an infrared ray absorbing material that absorbs infrared rays, and the OPc is made of a resin material containing an infrared ray absorbing material that absorbs infrared rays. The optical path length on the optical axis of the aspherical lens, α is the incident angle (deg) of the ray corresponding to the chief ray of the maximum image height toward the image plane, Y is the maximum image height, and the TTL is the optical at infinity object. full length.

In such an imaging optical system, a resin material is used for forming a nitrate material having a lens (infrared absorption lens) having an infrared absorbing function, and an infrared absorbing material of an organic material can be used, compared to a case where a glass material is used in the above-mentioned nitrate material. The infrared absorbing lens can be formed to be thinner.

In another aspect, in the imaging optical system described above, the plurality of lenses are any one of four, five, and six; and at least two of the plurality of lenses have positive refraction. The force, at least two of the plurality of lenses have a negative refractive power.

In such an imaging optical system, even when the ease of manufacture of the infrared absorbing lens is high, performance deterioration such as aberration deterioration due to manufacturing errors can be suppressed. In addition, from the viewpoint of correcting various aberrations and achieving high pixelation and bright F value, the number of the plurality of lenses is preferably five or more.

In another aspect, in the above-described imaging optical systems, the conditional expressions of the following (A4) and (A5) are also satisfied.

FN≦3. . . (A4)

25≦w≦100. . . (A5) Among them, FN is an F value, and w is a half angle (deg).

By satisfying the conditional expression (A4), such an imaging optical system can avoid an increase in noise or deterioration in darkness which is likely to occur in a dark imaging optical system, and can easily avoid high cost. Further, such an imaging optical system can effectively obtain such an effect by satisfying the conditional expression (A5).

In the above-described imaging optical system, at least one of the aspherical lenses made of a resin material containing the infrared ray absorbing material satisfies the conditional expression of the following (A6).

1≦TDmax/TDmin<2.3. . . (A6) The TDmax is a maximum thickness of an aspherical lens made of a resin material containing the infrared absorbing material, and TDmin is a minimum thickness of an aspherical lens made of a resin material containing the infrared ray absorbing material. Further, the aforementioned thickness is a length parallel to the direction of the optical axis.

Such an imaging optical system can improve its performance by satisfying the conditional expression (A6).

In another aspect of the invention, at least one of the aspherical lenses made of a resin material containing the infrared ray absorbing material is in a conditional expression of the following (A7).

0≦|f/fir|<1.5. . . (A7) wherein f is a focal length of the entire imaging optical system, and fir is a focal length of the aspherical lens made of the infrared absorbing resin material.

Such a camera optical system is satisfied by the conditional expression (A7), even when the ease of manufacture of the infrared absorbing lens is high, performance deterioration such as aberration deterioration due to manufacturing errors can be suppressed.

In another aspect of the invention, in the imaging optical system described above, a lens disposed on the most image side of the plurality of lenses is fixed.

In such an imaging optical system, since the lens on the most image side is fixed, the fixed lens can be used as a sealing member as an imaging element. Therefore, such an imaging optical system can reduce the so-called cover glass, and thus it is easier to achieve a short profile.

In another aspect of the invention, in the imaging optical system, at least one of the plurality of lenses is formed on a lens surface, and suppresses a wavelength band of 400 nm or less and a wavelength band of 700 nm or more. The coating layer of each transmittance.

Such an imaging optical system can compensate for the insufficiency of the infrared cutoff characteristics by the plating layer as needed, and can obtain the desired infrared cutoff characteristics in the imaging optical system.

In another aspect, the imaging optical system includes five lenses from the object side to the image side in order from the first lens to the fifth lens, and the first lens system has a positive refractive power; The lens system has a negative refractive power; at least one of the first and second lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays, and at least one of the lenses including the infrared absorbing material. The pieces satisfy the conditional expressions of the following (B1) to (B5).

0.5≦|f/fir|<1.5. . . (B1)

0≦|Dir/TTL|<0.2. . . (B2)

FN≦3. . . (B3)

25≦w≦100. . . (B4)

25< α ≦45. . . (B5) wherein f is a focal length of the entire imaging optical system, and fir is a focal length of an aspherical lens made of a resin material containing the infrared absorbing material, and Dir is from an aperture stop to the infrared absorbing material. The optical path length on the optical axis of the object surface of the aspherical lens made of a resin material, and the TTL is the optical total length when the object is an infinity object, the FN is the F value, and the w is the half angle (deg), and then α It is the ray incident angle (deg) of the chief ray corresponding to the maximum image height of the image plane.

In such an imaging optical system, a resin material is used for forming a nitrate material having a lens (infrared absorption lens) having an infrared absorbing function, and an infrared absorbing material of an organic material can be used, compared to a case where a glass material is used in the above-mentioned nitrate material. The infrared absorbing lens can be formed to be thinner.

In another aspect, in the imaging optical system described above, at least one of the aspherical lenses made of the resin material containing the infrared ray absorbing material satisfies the conditional expression of the following (B6).

1≦TDmax/TDmin<2.3. . . (B6) wherein TDmax is the maximum thickness of the aspherical lens made of the resin material containing the infrared ray absorbing material, and TDmin is the minimum thickness of the aspherical lens made of the resin material containing the infrared ray absorbing material. Further, the aforementioned thickness is a length parallel to the direction of the optical axis.

Such an imaging optical system can improve performance by satisfying conditional expression (B6).

In another aspect, in the above-described imaging optical system, the conditional expression of the following (B7) is also satisfied.

0.7<OPp/OPc<1.3. . . (B7) The OPp is an optical path length of 80% of the height of the aspherical lens made of the resin material containing the infrared absorbing material, and then OPc is an aspherical lens made of a resin material containing the infrared absorbing material. The optical path on the optical axis is long.

In the absorption type infrared cut filter, the infrared absorption amount is proportional to the optical path length. However, in the above-mentioned imaging optical system, by satisfying the conditional expression (B7), the optical path length in the effective field of the lens can be slightly uniform. A substantially uniform amount of infrared absorption can be obtained in the entire field of the effective field of the lens. As a result, a good image with reduced color unevenness or no color unevenness can be obtained. That is, in the case where the value is lower than the lower limit value of the conditional expression (B7) or higher than the upper limit value, the optical path length becomes uneven in the effective field of the lens, which is not preferable.

In another aspect, in the above-described imaging optical system, the aspherical lens made of a resin material containing the infrared ray absorbing material is one.

In such an imaging optical system, since only one infrared absorbing lens is used, the ease of manufacture can be reduced.

In another aspect, in the above-described imaging optical system, the conditional expression of the following (B8) is also satisfied.

80<Tr<90. . . (B8) wherein Tr is an average transmittance (%) in a visible light band (wavelength: 400 nm to 700 nm).

In the imaging optical system, the above-described effects of the conditional expressions (B1) to (B5) can be effectively obtained by satisfying the conditional expression (B8).

In another aspect, the imaging optical system includes five lenses from the object side to the image side in order from the first lens to the fifth lens, and the first lens system has a positive refractive power; The lens system has a negative refractive power; at least one of the third to fifth lenses is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays, and the lens containing the infrared absorbing material that absorbs infrared rays At least one of them satisfies the conditional expressions of the following (C1) to (C4).

0≦|f/fir|<0.5. . . (C1)

FN≦3. . . (C2)

25≦w≦100. . . (C3)

25< α ≦45. . . (C4) wherein f is a focal length of the entire imaging optical system, and fir is a focal length of an aspherical lens made of a resin material containing the infrared absorbing infrared absorbing material, FN is an F value, and w is a half shot. The angle (deg), then, α is the incident angle (deg) of the ray of the chief ray corresponding to the maximum image height toward the image plane.

In such an imaging optical system, an infrared absorbing material of an organic substance can be used by using a resin material in a nitrate material that forms a lens (infrared absorbing lens) to which an infrared absorbing function is applied, compared to the above-mentioned nitrate material. In the case where a glass material is used, the infrared absorbing lens can be formed to be thinner.

In another aspect, at least one of the aspherical lenses made of the resin material containing the infrared absorbing material is in the above-described imaging optical system, and the conditional expression of the following (C5) is satisfied.

1<TDmax/TDmin<1.75. . . (C5) wherein TDmax is the maximum thickness of the aspherical lens made of the resin material containing the infrared ray absorbing material, and TDmin is the minimum thickness of the aspherical lens made of the resin material containing the infrared ray absorbing material. Further, the aforementioned thickness is a length parallel to the direction of the optical axis.

Such an imaging optical system can improve performance by satisfying the conditional expression (C5).

In another aspect, in the above-described imaging optical system, the conditional expression of the following (C6) is also satisfied.

0.7<OPp/OPc<1.3. . . (C6) The OPp is an optical path length of 80% of the image height in the aspherical lens made of the resin material containing the infrared absorbing material, and then OPc is an aspherical lens made of a resin material containing the infrared absorbing material. The optical path on the optical axis is long.

In the absorption type infrared cut filter, the infrared absorption amount is proportional to the optical path length. However, in the above-mentioned imaging optical system, by satisfying the conditional expression (C6), the optical path length in the effective field of the lens can be slightly uniform. A substantially uniform amount of infrared absorption can be obtained in the entire field of the effective field of the lens. As a result, it is possible to reduce the unevenness of the color or the color is not A well-balanced image. That is, in the case where the value is lower than the lower limit value of the conditional expression (C6) or higher than the upper limit value, the optical path length becomes uneven and is not desirable in the effective field of the lens.

In another aspect of the invention, in the imaging optical system described above, the third lens is concave on the image side in an effective field and is located outside the center of the effective field. shape.

In such an imaging optical system, even if the incident angle of light is large, the optical path length can be made substantially uniform in the entire screen.

In another aspect, it is characterized in that the above-described imaging optical system further satisfies the conditional expression of the following (C7).

80<Tr<90. . . (C7) wherein Tr is an average transmittance (%) in a visible light band (wavelength: 400 nm to 700 nm).

In such an imaging optical system, the above-described effects of the conditional expressions (C1) to (C4) can be effectively obtained by satisfying the conditional expression (C7).

In another aspect, in the above-described imaging optical system, the aspherical lens made of a resin material containing the infrared ray absorbing material is one.

In such an imaging optical system, since only one infrared absorbing lens is used, the ease of manufacture can be reduced.

Further, in another aspect, the image pickup apparatus includes: any one of the above-described imaging optical systems, and converting the optical image An imaging element that generates an electrical signal; and the imaging optical system forms an optical image of the object on a light receiving surface of the imaging element.

In such an image pickup apparatus, since the infrared absorbing lens can be made thin, it is possible to easily achieve a short profile. That is, a thin type of image pickup device can be provided.

Further, the digital device according to another aspect of the invention includes the image pickup device and the control unit, wherein the image pickup device performs at least one of still image shooting and animation shooting of the object; The imaging optical system of the imaging device is mounted such that an optical image of the subject can be formed on an imaging surface of the imaging element. Then, ideally, the digital machine is made up of a portable terminal.

Such a digital machine or a portable terminal is relatively easy to achieve a low profile because the infrared absorbing lens can be made thin. That is, a thin digital machine or a portable terminal can be provided.

This application is based on Japanese Patent Application No. 2012-255158, filed on November 21, 2012, and Japanese Patent Application No. 2012-255159, filed on November 21, 2012, and November 21, 2012. Japanese Patent Application No. 2012-255160, filed on August 5, 2013, and Japanese Patent Application No. 2013-161961, filed on August 5, 2013, and Japanese Patent Application No. 2013-161962, filed on August 5, 2013 The Japanese Patent Application No. 2013-161963, filed on August 5, 2013, is hereby incorporated by reference.

In order to demonstrate the present invention, the present invention will be appropriately described and described in the above embodiments with reference to the drawings, but It should be appreciated by those skilled in the art that the above-described embodiments are susceptible to alterations and/or improvements. Therefore, as long as the change form or the modified form implemented by the practitioner is beyond the scope of the scope of the claims contained in the scope of the patent application, the change form or the modified form is interpreted as being included in the request. In the scope of the rights of the item.

[Possibility of industrial use]

According to the present invention, an imaging optical system, an imaging device, and a digital device can be provided.

100‧‧‧Photographic Optics

111‧‧‧1st lens

112‧‧‧2nd lens

113‧‧‧3rd lens

114‧‧‧4th lens

115‧‧‧5th lens

116‧‧‧Filter

117‧‧‧Photographic components

118‧‧‧Optical aperture

AX‧‧‧ optical axis

Claims (21)

An imaging optical system comprising: a plurality of lenses arranged in order from the object side toward the image side; wherein the lens disposed on the most object side of the plurality of lenses has a positive refractive power; wherein the plurality of lenses At least one lens is an aspherical lens made of a resin material containing an infrared absorbing material that absorbs infrared rays; and also satisfies the following conditional formulas of (A4) and (A5): FN≦3. . . (A4) 25≦w≦100. . . (A5) wherein, FN: F value w: half angle (deg). The imaging optical system according to claim 1, wherein the conditional expressions of the following (A1) to (A3) are satisfied: 0.5 < OPp / OPc < 1.5. . . (A1) 26< α ≦45. . . (A2) 0.55≦Y/TTL. . . (A3) The optical path length OPc of the chief ray of the 80% image-high main beam in the aspherical lens made of the resin material containing the infrared ray absorbing material: an aspherical lens made of a resin material containing the infrared ray absorbing material The optical path length α of the chief ray of the on-axis beam: the incident angle (deg) of the ray corresponding to the chief ray of the maximum image height Y: Maximum image height TTL: The optical total length of the object at infinity. The imaging optical system according to claim 1 or claim 2, wherein the plurality of lenses are any one of four, five, and six; and at least two of the plurality of lenses have Positive refractive power; at least two of the plurality of lenses have a negative refractive power. The imaging optical system according to claim 1 or claim 2, wherein at least one of the aspherical lenses made of a resin material containing the infrared ray absorbing material satisfies the conditional expression of the following (A6): 1 ≦ TDmax /TDmin<2.3. . . (A6) wherein TDmax: the maximum thickness TDmin of the aspherical lens made of the resin material containing the infrared absorbing material: the minimum thickness of the aspherical lens made of the resin material containing the infrared absorbing material, and the thickness is parallel to The length of the direction of the optical axis. The imaging optical system described in claim 1 or claim 2, wherein At least one of the aspherical lenses made of the resin material containing the infrared ray absorbing material satisfies the conditional expression of the following (A7): 0 ≦ | f / fir | < 1.5. . . (A7) wherein: f: a focal length fir of the entire imaging optical system: a focal length of the aspherical lens made of the infrared absorbing resin material. The imaging optical system according to claim 1 or claim 2, wherein the lens of the plurality of lenses disposed on the most image side is fixed. The imaging optical system according to claim 1 or claim 2, wherein at least one of the plurality of lenses is formed on a lens surface, and a wavelength band of 400 nm or less and a wavelength band of 700 nm or more are suppressed. The coating layer of each transmittance. The imaging optical system according to claim 1, wherein the plurality of lenses are five first to fifth lenses, the second lens has a negative refractive power, and the resin material containing the infrared absorbing infrared absorbing material The aspherical lens is at least one of the first and second lenses, and at least one of the aspherical lenses made of a resin material containing the infrared absorbing material satisfies the following (B1) to (B5). Each conditional formula: 0.5≦|f/fir|<1.5. . . (B1) 0≦|Dir/TTL<0.2. . . (B2) FN≦3. . . (B3) 25≦w≦100. . . (B4) 25< α ≦45. . . (B5) wherein: f: a focal length fir of the entire imaging optical system: a focal length Dir of the aspherical lens made of the resin material containing the infrared absorbing infrared absorbing material: from the aperture stop to the infrared absorption containing the infrared absorbing absorption Optical path length on the optical axis from the side of the object of the aspherical lens made of resin material TTL: optical total length FN when the object is infinity: F value w: half angle of observation (deg) α : corresponding to the maximum of the image plane The angle of incidence of light (deg) as the chief ray of the high light. The imaging optical system according to claim 8, wherein at least one of the aspherical lenses made of a resin material containing the infrared absorbing material further satisfies the conditional expression of the following (B6): 1 ≦ < TDmax / TDmin <2.3. . . (B6) wherein TDmax: a non-resin material containing the infrared ray absorbing material The maximum thickness TDmin of the spherical lens: the minimum thickness of the aspherical lens made of the resin material containing the infrared ray absorbing material, and the thickness is a length parallel to the optical axis. The imaging optical system described in claim 8 or claim 9, wherein the conditional expression of the following (B7) is also satisfied: 0.7 < OPp / OPc < 1.3. . . (B7) OPp: optical path length OPc of the chief ray of 80% of the image main beam in the aspherical lens made of the resin material containing the infrared ray absorbing material: axis in the aspherical lens made of the resin material containing the infrared ray absorbing material The optical path of the chief ray of the upper beam is long. The imaging optical system according to claim 8 or claim 9, wherein the aspherical lens made of a resin material containing the infrared absorbing material is one. The imaging optical system according to claim 8 or claim 9, wherein the conditional expression of the following (B8) is satisfied: 80<Tr<90. . . (B8) wherein, Tr: average transmittance (%) in the visible light band (wavelength: 400 nm to 700 nm). The imaging optical system according to claim 1, wherein the plurality of lenses are five first to fifth lenses, the second lens has a negative refractive power, and the resin material containing the infrared absorbing infrared absorbing material The aspherical lens is at least one of the third to fifth lenses, and at least one of the aspherical lenses made of a resin material containing the infrared absorbing material satisfies the following (C1) to Each conditional expression of (C4): 0≦|f/fir|<0.5. . . (C1) FN≦3. . . (C2) 25≦w≦100. . . (C3) 25< α ≦45. . . (C4) wherein f: a focal length fir of the entire imaging optical system: a focal length FN of an aspherical lens made of a resin material containing the infrared absorbing infrared absorbing material: F value w: half angle (deg) α : The incident angle (deg) of the ray of the image plane corresponding to the chief ray of the maximum image height. The imaging optical system according to claim 13, wherein at least one of the aspherical lenses made of a resin material containing the infrared absorbing material further satisfies the conditional expression of (C5) below: 1<TDmax/TDmin<1.75. . . (C5) wherein TDmax: the maximum thickness TDmin of the aspherical lens made of the resin material containing the infrared absorbing material: the minimum thickness of the aspherical lens made of the resin material containing the infrared absorbing material, and the thickness is parallel to The length of the direction of the optical axis. The imaging optical system described in claim 13 or claim 14, wherein the conditional expression of the following (C6) is also satisfied: 0.7 < OPp / OPc < 1.3. . . (C6) OPp: the optical path length OPc of the chief ray of the 80% image main beam in the aspherical lens made of the resin material containing the infrared absorbing material: the axis in the aspherical lens made of the resin material containing the infrared absorbing material The optical path of the chief ray of the upper beam is long. The imaging optical system according to claim 13 or claim 14, wherein the third lens is concave on the image side in a field in which the third lens is outside the effective field and is outside the one of the effective fields. shape. The imaging optical system described in claim 13 or claim 14, wherein the conditional expression of the following (C7) is also satisfied: 80<Tr<90. . . (C7) wherein, Tr: average transmittance (%) in the visible light band (wavelength: 400 nm to 700 nm). The imaging optical system according to claim 13 or claim 14, wherein the aspherical lens made of a resin material containing the infrared ray absorbing material is one. An imaging device comprising: an imaging optical system described in any one of the request item 1, the request item 8 and the request item 13; and an imaging element that converts the optical image into an electrical signal; the imaging optical system The optical image of the object can be formed on the light receiving surface of the imaging element. A digital device comprising: an imaging device according to claim 19; and a control unit for causing the imaging device to perform at least one of still image shooting and animation shooting of the subject; and the imaging device The imaging optical system is mounted such that an optical image of the subject can be formed on an imaging surface of the imaging element. The digital device as recited in claim 20, wherein the digital device is formed by a portable terminal.