Optical system and imaging device

Abstract

[Problem] To provide an optical system having high optical performance. [Solution] This optical system includes an optical element C. The optical element C is formed by joining a first optical element A and a second optical element B, whose optical characteristics differ from each other, via an organic material. The organic material includes a photopolymerization initiator having an absorption edge wavelength of 390 nm or greater.

Description

Optical system and imaging device

[0001] The present invention relates to an optical system suitable for imaging.

[0002] Optical systems used for imaging include those disclosed in Patent Documents 1 to 3. Patent Documents 1 and 2 disclose optical systems that correct residual chromatic aberration by using a resin optical material with high dispersion and anomalous partial dispersion in order to correct axial chromatic aberration over a wide wavelength range. Patent Document 3 discloses an optical system that corrects chromatic aberration by employing glass with an Abbe number of approximately 25 to 35 and anomalous partial dispersion.

[0003] Furthermore, Patent Document 4 discloses a method for manufacturing an optical element in which transparent substrates having a refractive index of 1.80 or more are bonded together with an adhesive.

[0004] Japanese Patent Application Laid-Open No. 2007-25653 Japanese Patent Application Laid-Open No. 2012-247451 International Publication No. WO2019 / 116563 Japanese Patent Application Laid-Open No. 2022-12297

[0005] 2. Description of the Related Art As imaging devices used for imaging have become more and more pixelated, optical systems are desired to have higher optical performance.

[0006] An optical system according to one aspect of the present invention includes an optical element. The optical element is configured by bonding a first optical element and a second optical element having different optical properties via an organic material, the organic material containing a photopolymerization initiator having an absorption edge wavelength of 390 nm or more. Note that an imaging device including the optical system also constitutes another aspect of the present invention.

[0007] According to the present invention, an optical system having high optical performance can be provided.

[0008] 1 is a cross-sectional view of an optical system of Example 1. FIG. 2 is aberration diagrams of the optical system of Example 1. FIG. 3 is a cross-sectional view of an optical system of Example 2 at the wide-angle end, a middle zoom position, and a telephoto end. FIG. 4 is a aberration diagram of the optical system of Example 2 at the wide-angle end, a middle zoom position, and a telephoto end. FIG. 5 is a cross-sectional view of an optical system of Example 3. FIG. 6 is a cross-sectional view of an optical system of Example 4 at the wide-angle end, a middle zoom position, and a telephoto end. FIG. 7 is a cross-sectional view of an optical system of Example 5 at the wide-angle end, a middle zoom position, and a telephoto end. FIG. 8 is a cross-sectional view of an optical system of Example 6 at the wide-angle end, a middle zoom position, and a telephoto end. FIG. 9 is a cross-sectional view of an optical system of Example 7. FIG. 10 is a schematic view of an imaging device including the optical systems of Examples 1 to 7. 1A and 1B are diagrams showing examples of bonding optical elements.

[0009] Embodiments of the present invention will now be described with reference to the drawings. FIGS. 1, 3, 5, 7, 9, 11, and 13 show cross sections of optical systems according to Examples 1 to 7, respectively. Note that FIGS. 3, 7, 11, and 13 show cross sections of the optical systems serving as zoom lenses according to Examples 2, 4, 5, and 6, respectively, at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end. In each figure, the arrow labeled FOCUS (and Floating) below the lens group that moves during focusing indicates the direction of movement of that lens group during focusing from infinity to a close distance.

[0010] Prior to describing specific Examples 1 to 7, we will first explain matters common to all Examples. The optical systems of each Example are used as imaging optical systems in various imaging devices, such as digital still cameras, video cameras, silver halide film cameras, broadcast cameras, and surveillance cameras. In each figure, the left side is the object side (front side), and the right side is the image side (rear side). Note that the optical systems of each Example can also be used as projection optical systems for image projection devices (projectors).

[0011] The optical system of each embodiment as an imaging optical system is composed of, arranged in order from the object side to the image side, a front group including at least one lens, an aperture stop SP, and a rear group including at least one lens. Li is the ith lens group (i = 1, 2, ...). A lens group is a group of one or more lenses that may or may not move as a unit during focusing or during zooming between the wide-angle end and the telephoto end. In other words, the spacing between adjacent lens groups changes during focusing and zooming. The wide-angle end and telephoto end respectively indicate the zoom states with the maximum angle of view (shortest focal length) and the minimum angle of view (maximum focal length) when the lens group that moves during zooming is located at both ends of the range of movement on the optical axis for mechanical or control reasons.

[0012] The aperture stop SP is provided to determine the light flux with the maximum F-number and to adjust the amount of light. FP in FIG. 13 is a flare-cut stop, which is provided to cut out unnecessary light. IP is the image plane. The image plane IP is where the imaging surface (light-receiving surface) of an imaging element such as a CCD sensor or CMOS sensor, or the film surface (photosensitive surface) of a silver halide film, is located.

[0013] In an optical system, it is desirable to not only effectively correct spherical aberration, coma aberration, and the like at a single wavelength (reference wavelength), but also to reduce chromatic aberration. When correcting chromatic aberration, it is important to effectively correct secondary spectrum in addition to primary achromatism. A common method for reducing chromatic aberration is to use an anomalous partial dispersion material as the optical material. However, when chromatic aberration is corrected by utilizing the anomalous dispersion of low-refractive-index, low-dispersion glass, the Petzval sum becomes too large on the positive side, making it difficult to correct field curvature, leading to an increase in the overall size of the optical system, and an increase in the number of lenses in the optical system.

[0014] On the other hand, when chromatic aberration is corrected using a high-refractive index, high-dispersion material as in Patent Document 1, if a material with a small dispersion and an Abbe number of about 30 is used for the positive lens, a large number of lenses are required to correct primary chromatic aberration (primary spectrum), which hinders the miniaturization of the optical system. Furthermore, if a material with an Abbe number of about 25 to 35 and anomalous partial dispersion is used for the positive lens as in Patent Document 3, the variation in spherical aberration and coma aberration for each wavelength increases when the aperture of the optical system is increased, and it becomes difficult to shorten the overall length of the optical system. The optical systems of the examples solve these exemplary problems.

[0015] The optical system of each embodiment includes an optical element C. The optical element C is a cemented optical element formed by cementing (including bonding) a first optical element A and a second optical element B, which have different optical properties, via an organic material within at least one of their optically effective range (within the effective diameter) and outside the optically effective range (outside the effective diameter). The optically effective range is the range of the optical surface of the optical element through which light rays that contribute to image formation pass. Generally, when materials with different linear expansion coefficients are cemented together, peeling can occur due to environmental changes such as temperature and humidity. Therefore, by using a low-elasticity (soft) adhesive as an organic material, the difference in expansion and contraction can be absorbed, ensuring environmental resistance.

[0016] The organic material contains a photopolymerization initiator with an absorption edge wavelength of 390 nm or longer. As described in FIG. 4 and paragraphs 0025 to 0027 of Patent Document 4, by using a phosphorus-based material having a phosphorus-containing salt, such as Irgacure 819 or Irgacure TPO, as the photopolymerization initiator, light with a wavelength of 400 nm or longer can be absorbed. As shown in Patent Document 4, the absorption edge wavelength of Irgacure 819 is 455 nm, and the absorption edge wavelength of Irgacure TPO is 425 nm.

[0017] The optical material (glass) used in the optical elements has a problem in that the higher the dispersion or refractive index, the lower the transmittance in the short wavelength range. Therefore, the longer the absorption edge wavelength, the greater the freedom in selecting the materials for optical element A and optical element B.

[0018] By setting the absorption edge wavelength to 390 nm, 400 nm, or 410 nm or more, it becomes possible to use materials with higher dispersion or higher refractive index. On the other hand, by setting the absorption edge wavelength to 390 nm, it becomes possible to bond the adhesive (photocurable resin) with less energy (i.e., in a short time). Therefore, it is preferable that the absorption edge wavelength be 390 nm or more, more preferably 400 nm or more, and even more preferably 410 nm or more.

[0019] Furthermore, the object-side or image-side optical surface of the first optical element A is in contact with air via a thin film. By forming a single-layer or multi-layer dielectric film (thin film) on the surface of the optical material for the optical surface, it is possible to prevent light reflection on the surface and improve transmittance. Furthermore, by forming a thin film, it is possible to improve the durability of the optical element.

[0020] In this way, by configuring the optical element C by cementing a first optical element A and a second optical element B having different optical properties, it is possible to improve the imaging performance of the entire optical system. Furthermore, it is possible to precisely suppress the decentering components occurring in the first optical element A and the second optical element B, thereby improving environmental resistance (particularly resistance to high temperatures and humidity and resistance to deterioration of optical performance over time). Examples of organic materials that can be used to cement the first optical element A and the second optical element B include the organic materials disclosed in Patent Document 4. Specifically, these include photocurable resins that become transparent upon curing, such as ene-thiol resin, acrylic resin, urethane acrylic resin, silicone acrylic resin, and epoxy resin, as well as phosphorus-based photopolymerization initiators containing a phosphorus-containing salt.

[0021] The optical element C is composed of only two optical elements, a first optical element A and a second optical element B. It is also possible to construct the optical element C by cementing together three or more optical elements, but this is not preferable because it requires a reduction in robustness against manufacturing errors and increases the size of the optical element C, making it difficult to obtain a sufficient aberration correction effect for the number of optical elements.

[0022] The following describes conditions that the optical system of each example preferably satisfies. Here, the refractive index of the first optical element A at the d-line is ndA, the Abbe number based on the d-line is vdA, and the partial dispersion ratios at the g-line and F-line are θgFA. The refractive index of the second optical element B at the d-line is ndB, and the Abbe number based on the d-line is vdB. The Abbe number based on the d-line vd and the partial dispersion ratios θgF at the g-line and F-line are defined as follows, where Nd, NF, NC, and Ng are the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (wavelength 435.8 nm), respectively: vd=(Nd-1) / (NF-NC) θgF=(Ng-NF) / (NF-NC)

[0023] It is preferable that the first optical element A satisfies at least one of the following expressions (1) to (3).

[0024] 1.5≦ndA≦3.9827−0.1408×νdA+0.0021×νdA ２ (1) 10≦νdA≦35 (2) −0.000003056×νdA ３ +0.0003653 × νdA ２ -0.01647 × νdA + 0.8503≦θgFA (3) The conditions of formulas (1), (2), and (3) indicate appropriate optical characteristics of the material of the first optical element A. The example of formula (1) indicates the appropriate relationship between the refractive index ndA and the Abbe number νdA of the material of the first optical element A to achieve both correction of various aberrations and Petzval sum and correction of chromatic aberration. If ndA exceeds the upper limit of formula (1), the Petzval sum becomes too large on the positive side, making it difficult to correct field curvature, which is undesirable. If ndA falls below the lower limit of formula (1), this is undesirable because it leads to the miniaturization of the optical system and insufficient correction of the secondary spectrum of axial chromatic aberration and lateral chromatic aberration.

[0025] The condition of formula (2) indicates the range of the appropriate Abbe number vdA of the material of the first optical element A. If vdA exceeds the upper limit of formula (2), the dispersion becomes too small, making it difficult to correct the primary chromatic aberration, which is undesirable. If vdA falls below the lower limit of formula (2), the optical transmittance and stability of the glass decrease, which is undesirable.

[0026] The condition of formula (3) indicates the range of an appropriate partial dispersion ratio of the first optical element A. A material that satisfies the condition of formula (3) has anomalous dispersion. If θgFA is below the lower limit of formula (3), the anomalous dispersion becomes insufficient due to the reduction of secondary spectrum, which is not preferable.

[0027] Examples of materials that satisfy the conditions of formulas (1) to (3) include J-SFH5 (product name) (nd=1.75575, vd=24.71, θgF=0.6291) manufactured by Hikari Glass Co., Ltd. and EP-5000 (product name) (nd=1.6356, vd=23.9, θgF=0.636) manufactured by Mitsubishi Gas Chemical Company, Inc.

[0028] When the material of the first optical element A is an inorganic (glass) material, it is significantly different from an optical element made of a replica layer of resin or the like in terms of environmental resistance, ease of manufacturing, and the ability to impart strong refractive power (the reciprocal of the focal length) without any restrictions on the thickness of the optical element. Because the first optical element A has excellent environmental resistance to moisture absorption, temperature, etc. and ensures sufficient hardness, it can be placed closest to the object side of the optical system. Furthermore, when the material of the first optical element A is an organic (plastic) material, it has the advantages of a low specific gravity and a high degree of freedom in shape (the shape can be determined by molding). However, because it is difficult to ensure the refractive index of the material with an organic material, it is necessary to use it in combination with an optical element made of a high refractive index material to enhance the aberration correction effect.

[0029] The second optical element B2 preferably satisfies at least one of the following expressions (4) and (5).

[0030] 1.85≦ndB (4) νdB≦36 (5) The conditions of formulas (4) and (5) indicate the appropriate optical characteristics of the material of the second optical element B for correcting field curvature while satisfactorily correcting spherical aberration and coma. Due to the characteristics of glass, as the refractive index increases, the Abbe number decreases, leading to insufficient correction of primary chromatic aberration, making it difficult to correct axial chromatic aberration and lateral chromatic aberration. Furthermore, if the refractive index of the material decreases, it becomes difficult to improve the Petzval sum, which undesirably leads to an increase in the size of the optical system in order to ensure the required optical performance.

[0031] Examples of materials that satisfy the conditions of formulas (4) and (5) include S-NPH3 (product name) (nd=1.95906, vd=17.47, θgF=0.6598) manufactured by OHARA INC. and TAFD65 (product name) (nd=2.05090, vd=26.94, θgF=0.6052) manufactured by HOYA CORPORATION.

[0032] Generally, to achieve high optical performance in optical systems with small F-numbers (i.e., bright lenses), optical systems with focal lengths in the super-telephoto range, and optical systems with focal lengths in the super-wide-angle range, it is necessary to suppress aberrations at the reference wavelength, such as spherical aberration, coma, curvature of field, and astigmatism. Furthermore, it is necessary to adequately correct chromatic aberrations (axial chromatic aberration and lateral chromatic aberration) and variations in each aberration for each wavelength. While the use of lenses made of high-refractive-index materials or aspherical lenses can effectively correct aberrations at the reference wavelength, the correction of chromatic aberrations tends to be insufficient. Therefore, by forming an optical element C by cementing first and second optical elements A and B made of materials with different optical properties so as to satisfy the above conditions, various aberrations, such as axial chromatic aberration, lateral chromatic aberration, spherical aberration, and curvature of field, can be effectively corrected, and variations in each aberration for each wavelength can be suppressed.

[0033] It is more preferable to set the numerical ranges of the formulas (1) to (5) as follows:

[0034] 1.52≦ndA≦3.950−0.1408×νdA+0.0021×νdA ２ (1a) 12≦νdA≦33 (2a) -0.000003056×νdA ３ +0.0003653 × νdA ２ −0.01647×νdA+0.8520≦θgFA≦0.70 (3a) 1.88≦ndB (4a) νdB≦35.5 (5a) It is more preferable to set the numerical ranges of the formulas (1) to (5) as follows.

[0035] 1.54≦ndA≦3.920 (or 3.900) −0.1408×νdA+0.0021×νdA ２(1b) 14 (or 16)≦νdA≦31 (2b) −0.000003056×νdA ３ +0.0003653 × νdA ２ -0.01647 × νdA + 0.8540 (or 0.8580)≦θgFA≦0.685 (or 0.670) (3b) 1.90≦ndB (4b) νdB≦35.3 (5b) Furthermore, it is preferable that the optical system of each embodiment satisfy at least one of the conditions of the following expressions (6) to (14). Here, the focal length of the first optical element A is fA, the focal length of the second optical element B is fB, the focal length of the optical element C is fC, and the focal length of the entire optical system is f. The shape factor of the first optical element A is SFA. The shape factor SFA is expressed as follows, where sgn is a sign function (+1 when the focal length fL of the first optical element A is positive, and −1 when it is negative), R1 is the radius of curvature of the object-side optical surface of the first optical element A, and R2 is the radius of curvature of the image-side optical surface of the first optical element A. Note that if the object-side or image-side optical surface of the first optical element A is aspherical, the radius of curvature is the radius of curvature of the base surface of the aspherical surface.

[0036] The distance on the optical axis from the optical surface of the optical element C closest to the aperture stop to the aperture stop SP is dSC, and the total optical length, which is the length on the optical axis from the optical surface closest to the object to the image plane IP of the optical system, is OL.

[0037] 0.25≦|fA / fB|≦4.00 (6) 0.60≦ndA / ndB≦1.40 (7) 0.40≦νdA / νdB≦1.50 (8) -2.0≦SFA≦10.0 (9) 0.02≦|fA / fC|≦3.00 (10) 1.8≦|fC / dSC|≦70.0 (11) 0.5≦|fC / f|≦25.0 (12) -0.30≦ndB-ndA≦0.50 (13) 0<dSC / OL≦0.35 (14) The condition of formula (6) indicates an appropriate relationship between the focal lengths fA and fB of the first and second optical elements A and B, and is a condition for obtaining a good chromatic aberration correction effect by the optical element C made of materials with different Abbe numbers and partial dispersion ratios. If the focal length of the first optical element A becomes too long so that |fA / fB| exceeds the upper limit of formula (6), that is, if the refractive power of the first optical element A becomes too weak, the correction of primary chromatic aberration will be insufficient, which is undesirable. If the focal length of the first optical element A becomes too short so that |fA / fB| falls below the lower limit of formula (6), the refractive power of the optical element C will be too strong, resulting in large secondary chromatic aberration. As a result, the correction effect of secondary chromatic aberration will change for each light beam and image height, making it difficult to correct chromatic aberration across the entire image, which is undesirable.

[0038] The condition of formula (7) indicates an appropriate relationship between the refractive indices ndA and ndB of the first and second optical elements A and B. By appropriately setting the refractive index ratio between the first and second optical elements A and B, which have refractive powers with opposite signs, it becomes easier to ensure different aberration correction effects from the low image height (central) region to the high image height (peripheral) region. This makes it possible to obtain a good aberration correction effect at the reference wavelength of the optical element C.

[0039] If the refractive index of the first optical element A is too high compared to the refractive power of the second optical element B, such that ndA / ndB exceeds the upper limit of formula (7), this is advantageous for correcting various aberrations, but the Abbe number will be insufficient. As a result, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration, particularly secondary spectrum correction, which is undesirable because it leads to an increase in the size of the optical system and an increase in the number of lenses in the optical system in order to ensure the required optical performance. If the refractive index of the first optical element A is too low compared to the refractive power of the second optical element B, such that ndA / ndB falls below the lower limit of formula (7), this is undesirable because it leads to insufficient correction of spherical aberration and field curvature.

[0040] The condition of formula (8) indicates an appropriate relationship between the Abbe numbers νdA and νdB of the first and second optical elements A and B, and is a condition for obtaining a good correction effect for first-order aberrations using an optical element C made of materials with different Abbe numbers and partial dispersion ratios. If the Abbe number of the first optical element A becomes too large compared to the Abbe number of the second optical element B, such that νdA / νdB exceeds the upper limit of formula (8), the Abbe number of the second optical element B must be increased proportionally, resulting in insufficient achromatic effect due to the material properties. This undesirably results in an increase in the number of lenses in the optical system. If the Abbe number of the first optical element A becomes smaller than the Abbe number of the second optical element B, such that νdA / νdB falls below the lower limit of formula (8), the achromatic effect is ensured, but the radius of curvature of the cemented or marginal surfaces of the first and second optical elements A and B becomes large. This undesirably results in insufficient correction of chromatic aberrations.

[0041] The condition of formula (9) indicates an appropriate shape factor SFA of the first optical element A, and indicates a condition for satisfactorily correcting curvature of field and ensuring high optical performance. If SFA exceeds the upper limit of formula (9), the meniscus shape of the first optical element A becomes too strong relative to the focal length of the entire optical system, making it difficult to satisfactorily correct various aberrations, such as chromatic aberration, spherical aberration, curvature of field, and coma aberration, which is undesirable. If SFA falls below the lower limit of formula (9), spherical aberration, coma aberration, and the like increase, which is undesirable.

[0042] The condition of formula (10) indicates an appropriate relationship between the focal length fA of the first optical element A and the focal length fC of the optical element C, and is a condition for obtaining a good correction effect for second-order chromatic aberration using an optical element C made of materials with different Abbe numbers and partial dispersion ratios. If the focal length of the first optical element A becomes too long so that |fA / fC| exceeds the upper limit of formula (10), that is, if the refractive power of the first optical element A becomes too weak, the correction of second-order chromatic aberration will be insufficient, which is undesirable. If the focal length of the first optical element A becomes too short so that |fA / fC| falls below the lower limit of formula (10), the refractive power of the optical element C will be too strong, resulting in large second-order chromatic aberration. As a result, the correction effect for second-order chromatic aberration will change for each light beam and image height, making it difficult to correct chromatic aberration across the entire image, which is undesirable.

[0043] The condition of equation (11) indicates an appropriate relationship between the focal length fC of optical element C and the distance dSC from optical element C to aperture stop SP, and indicates a condition for favorably correcting chromatic aberration that is likely to occur when the overall optical length is shortened. As the overall optical system is made more compact, various aberrations, particularly chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration, become larger, and optical performance deteriorates. In particular, in a telephoto optical system in which the overall optical length is shortened, chromatic aberration becomes larger as the focal length becomes longer.

[0044] If the focal length of optical element C becomes too long so that |fC / dSC| exceeds the upper limit of equation (12), that is, if the refractive power of optical element C becomes too weak, chromatic aberration correction will be insufficient, which is not preferable. If the focal length of optical element C becomes too short so that |fC / dSC| falls below the lower limit of equation (12), that is, if the refractive power of optical element C becomes too strong, the variation in chromatic aberration for each wavelength will increase. This will result in an increase in fluctuations in chromatic aberration due to zooming and focusing, which is not preferable.

[0045] The condition of formula (12) indicates an appropriate relationship between the focal length fC of optical element C and the focal length f of the entire optical system, and indicates a condition for reducing the number of lenses in the optical system. Furthermore, by satisfying the condition of formula (12), various aberrations such as coma and chromatic aberrations (axial chromatic aberration and lateral chromatic aberration) can be corrected well. If |fC / f| exceeds the upper limit of formula (12), it becomes difficult to obtain the aberration correction effect of optical element C, which is undesirable. If |fC / f| falls below the lower limit of formula (12), it becomes difficult to correct various aberrations such as coma and chromatic aberration, which is undesirable.

[0046] The condition of formula (13) indicates an appropriate difference between the refractive indices ndA and ndB of the first and second optical elements A and B. By ensuring an appropriate difference in refractive index between optical elements having refractive powers with mutually opposite signs, a high aberration correction effect can be obtained, and various aberrations such as spherical aberration, coma, and chromatic aberration (axial chromatic aberration, chromatic aberration of magnification) can be corrected well.

[0047] If the refractive index of the second optical element B becomes too high compared to the refractive index of the first optical element A, such that ndB - ndA exceeds the upper limit of formula (13), this is advantageous for correcting various aberrations, but the Abbe number becomes insufficient. As a result, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration, particularly secondary spectrum correction, and this undesirably leads to an increase in the size of the optical system and an increase in the number of lenses in the optical system in order to ensure the required optical performance. If the refractive index of the second optical element B becomes too low compared to the refractive index of the first optical element A, such that ndB - ndA falls below the lower limit of formula (13), the radius of curvature of the optical surface of the second optical element B becomes small in order to ensure the required refractive power of the second optical element B. As a result, higher-order aberrations occur, which is undesirable.

[0048] The condition of formula (14) indicates an appropriate relationship between the distance dSC from the optical element C to the aperture stop SP and the total optical length OL, and is a condition for satisfactorily correcting chromatic aberrations that tend to occur when the diameter of the optical system is increased. The larger the diameter of the optical system, the greater the variations in various aberrations, such as spherical aberration, and chromatic aberrations, such as axial chromatic aberration and lateral chromatic aberration, resulting in a deterioration in optical performance. If the distance dSC becomes too large, such that dSC / OL exceeds the upper limit of formula (14), the variations in various aberrations, such as wavelength, increase, which is undesirable. If the distance dSC becomes too small, such that dSC / OL falls below the lower limit of formula (14), the refractive power of the optical element C becomes too strong, which causes variations in coma aberration, such as wavelength, at each image height.

[0049] It is more preferable to set the numerical ranges of the formulas (6) to (14) as follows:

[0050] 0.40≦|fA / fB|≦3.70 (6a) 0.70≦ndA / ndB≦1.10 (7a) 0.45≦νdA / νdB≦1.00 (8a) −1.5≦SFA≦5.0 (9a) 0.03≦|fA / fC|≦2.80 (10a) 2.0≦|fC / dSC|≦65.0 (11a) 0.55≦|fC / f|≦20.00 (12a) −0.20≦ndB−ndA≦0.40 (13a) 0.01≦dSC / OL≦0.30 (14a) Furthermore, it is more preferable to set the numerical ranges of formulas (6) to (14) as follows.

[0051] 0.60≦|fA / fB|≦3.50 (6b) 0.80≦ndA / ndB≦1.05 (7b) 0.50≦νdA / νdB≦0.98 (8b) −1.0≦SFA≦2.5 (9b) 0.04≦|fA / fC|≦2.50 (10b) 2.3≦|fC / dSC|≦62.0 (11b) 0.60≦|fC / f|≦18.00 (12b) −0.10≦ndB−ndA≦0.37 (13b) 0.02≦dSC / OL≦0.28 (14b) Furthermore, it is desirable that the composite refractive power of the front group consisting of one or more lens groups located on the object side of the aperture stop SP be positive refractive power.

[0052] Furthermore, when the optical element C is included in the front group having positive refractive power, it is preferable that the optical element C have positive refractive power. By disposing the optical element C with positive refractive power in the front group having positive refractive power, it is possible to suppress both axial chromatic aberration and the secondary spectrum of chromatic aberration of magnification.

[0053] In a zoom lens, it is preferable to place the optical element C with negative refractive power in a lens group that moves during zooming, thereby suppressing both the axial chromatic aberration and the secondary spectrum of lateral chromatic aberration that occurs during zooming.

[0054] The optical system may also have a plurality of optical elements C. In this case, a high chromatic aberration correction effect can be obtained by selecting the optical element C having the greatest refractive power among the plurality of optical elements C and satisfying at least one of the conditions of the above expressions (1) to (14).

[0055] It is desirable that the rear group located on the image side of the aperture stop SP has at least one aspherical surface in order to reduce residual aberration (field curvature) in the meridional direction.

[0056] Furthermore, a configuration can be adopted in which all or part of any lens group in the optical system is used as an image stabilization group and moved in a direction perpendicular to the optical axis or rotated about a point on the optical axis, thereby performing image stabilization to reduce image blur caused by camera shake, etc. In a zoom lens, it is preferable that all or part of the lens group near the aperture stop SP be used as an image stabilization group.

[0057] Furthermore, focusing can also be performed by moving all or part of any lens group in the optical system as a focus group in the optical axis direction.

[0058] Examples 1 to 7 will be specifically described below. Positive and negative refractive powers will simply be referred to as positive and negative, respectively. After Example 7, Numerical Examples 1 to 7 corresponding to Examples 1 to 7, respectively, are shown.

[0059] The optical system of Example 1 (Numerical Example 1) shown in Figure 1 is composed of a positive front group, an aperture stop SP, and a positive rear group, arranged in that order from the object side to the image side, and is an optical system with a half angle of view of 24° and an aperture ratio of approximately 1.2. During focusing from infinity to a close distance, the rear group moves toward the object side.

[0060] If the i-th lens counted from the object side is the i-th lens, the sixth lens in the rear group serving as the first optical element A and the seventh lens serving as the second optical element B constitute the first optical element C (C1). The eighth lens serving as the first optical element A and the ninth lens serving as the second optical element B constitute the second optical element C (C2).

[0061] FIG. 16 shows an example of a sixth lens and a seventh lens cemented together in the optical element C1. A protrusion P located outside the effective diameter of one of the sixth and seventh lenses (the sixth lens in this example) is cemented to the outside of the effective diameter of the other lens (the seventh lens in this example) via an organic material. The sixth and seventh lenses are positioned close to each other within their effective diameters, with air between them. The sixth and seventh lenses are positioned so that their optical axes coincide. However, to optimize the optical image formed by the imaging optical system, the sixth lens may be positioned so that its optical axis is offset from the optical axis of the entire optical system. In this case, the sixth lens is cemented together with its optical axis offset from the seventh lens.

[0062] On the other hand, in optical element C2, the eighth lens and the ninth lens are cemented together via an organic material inside and outside their effective diameters. The eighth lens and the ninth lens are optical elements having a refractive index of 1.80 or more at the d-line. Optical element C2 can be cemented together by applying an adhesive as an organic material containing a photocurable resin and a photopolymerization initiator having an absorption edge wavelength of 410 nm or more to at least one of the eighth lens and the ninth lens, and then curing the adhesive by irradiating it with light having a wavelength of 400 nm or more.

[0063] In a large-diameter single focal length lens such as this embodiment, in order to correct Petzval sum, it is preferable that the refractive index of the second optical element B at the d-line be 1.85 or more and the Abbe number based on the d-line be 36 or less. If the refractive index is 1.9 or more, the effect of correcting Petzval sum can be further improved, and if the refractive index is 2.0 or more, it becomes easier to correct field curvature.

[0064] It is also preferable to place the optical element C (C1, C2) closer to the image side than the aperture stop SP, which makes it easier to suppress chromatic aberration of magnification.

[0065] Furthermore, in a large-diameter single focal length lens, it is desirable that the second optical element B has a strongly convex shape facing the image side. Furthermore, it is desirable that the shape factor be between -5 and 0, and by setting it between -2 and -0.5, it becomes easier to suppress astigmatism.

[0066] FIG. 2 shows longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the optical system of Numerical Example 1. In the spherical aberration diagram, Fno indicates the F-number, the solid line indicates spherical aberration at the d-line (wavelength 587.6 nm), and the two-dot chain line indicates spherical aberration at the g-line (wavelength 435.8 nm). The dot-dash line indicates spherical aberration at the C-line (wavelength 656.27 nm), and the dashed line indicates spherical aberration at the F-line (486.13 nm). In the astigmatism diagram, the solid line S indicates astigmatism at the sagittal image plane, and the dashed line M indicates astigmatism at the meridional image plane. The distortion diagram shows distortion at the d-line. The chromatic aberration diagram shows chromatic aberration of magnification at the g-line, C-line, and F-line. ω is the half angle of view (°). The above explanation of the aberration diagrams also applies to other numerical examples.

[0067] The optical system of Example 2 (Numerical Example 2) shown in FIG. 3 is composed of, arranged in order from the object side to the image side, a positive first lens unit L1, a negative second lens unit L2, a positive third lens unit L3 including an aperture stop SP closest to the object side, a negative fourth lens unit L4, a positive fifth lens unit L5, and a positive sixth lens unit L6. The optical system of this example is a zoom lens with a zoom ratio of 5.4 and an aperture ratio of approximately 2.9 to 5.8. The first to sixth lens units L1 to L6 move during zooming from the wide-angle end to the telephoto end. At this time, to ensure compactness and a high zoom ratio, the spacing between the lens units is changed so that the spacing between the first lens unit L1 and the second lens unit L2 is wider at the telephoto end than at the wide-angle end, and the spacing between the second lens unit L2 and the third lens unit L3 is narrower. The fourth lens unit L4 moves toward the image side during focusing from infinity to a close distance.

[0068] The negative second lens unit L2, which is the main variable magnification unit, includes an optical element C that is composed of a sixth lens as the first optical element A and a fifth lens as the second optical element B. The fifth lens and the sixth lens are cemented together via an organic material within and outside their effective diameters.

[0069] The zoom lens of this embodiment has, in order from the object side, positive, negative, and positive lens groups in order to shorten the overall optical length at the wide-angle end while providing excellent correction of aberrations throughout the entire zoom range. By having at least four lens groups, spherical aberration and coma occurring in the first lens group L1 and the second lens group L2 are effectively corrected. Furthermore, in the telephoto range, variations in spherical aberration and coma due to manufacturing errors become significant. Therefore, by using a so-called positive-lead zoom type in which the first lens group L1 is positive, the height of incidence of axial rays on each lens element on the image side of the second lens group L2 is reduced, thereby reducing the size of the optical system and improving its robustness.

[0070] The first lens unit L1 is composed of three or fewer lenses. By reducing the number of lenses constituting the first lens unit L1, which has a large lens diameter, the first lens unit L1 can be made smaller and lighter. Furthermore, the height of light rays emerging from the first lens unit L1 can be lowered, enabling off-axis aberrations such as coma and field curvature to be effectively corrected.

[0071] The second lens group L2 is composed of four lenses. Specifically, the second lens group L2 is composed of, in order from the object side, a fourth lens which is a negative single lens, an optical element C formed by cementing a fifth lens as the positive second optical element B and a sixth lens as the positive first optical element A, and a seventh lens which is a negative single lens. By using optical element C as a cemented lens, axial chromatic aberration in the telephoto range is effectively corrected, while curvature of field in the wide-angle range and spherical aberration in the telephoto range are effectively corrected, and variations in spherical aberration and coma in the telephoto range due to manufacturing errors are also suppressed.

[0072] By configuring the second lens unit L2 in this manner, the refractive power of the second lens unit L2 is increased while excellent correction is made for curvature of field in the wide-angle range and spherical aberration in the telephoto range, thereby achieving a compact overall system. Furthermore, by locating a negative lens closest to the object in the second lens unit L2, the power arrangement within the second lens unit L2 can be made retrofocus, and excellent correction is made for curvature of field and coma in the wide-angle range. Furthermore, by locating a negative lens on the image side of the optical element C, off-axis coma and curvature of field in the wide-angle range are corrected while ensuring the refractive power and magnification contribution of the second lens unit L2.

[0073] The shape factor of the sixth lens as the first optical element A is preferably set to -1.0 to 2.0. Furthermore, by setting it to -0.5 to 1.0, it becomes easier to correct spherical aberration and coma in the telephoto range.

[0074] In this embodiment, the 11th and 12th lenses are used as a vibration reduction group.

[0075] 4A, 4B, and 4C show longitudinal aberrations of the optical system of Numerical Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively.

[0076] The optical system of Example 3 (Numerical Example 3) shown in Figure 5 is composed of, arranged in order from the object side to the image side, a positive front group, an aperture stop SP, and a negative rear group, and is an optical system with a half angle of view of 3.2° and an aperture ratio of approximately 4.6. During focusing from infinity to a close distance, the eighth lens element of the rear group moves toward the image side.

[0077] The sixth lens as the first optical element A in the front group and the seventh lens as the second optical element B constitute an optical element C. The sixth lens and the seventh lens are cemented together via an organic material inside and outside their effective diameters.

[0078] The optical system of this embodiment is a telephoto type optical system whose total length is shorter than the focal length of the optical system. Generally, the longer the focal length of an optical system, the greater the amount of chromatic aberration that occurs. For this reason, it is important for telephoto type optical systems to effectively correct chromatic aberration. If the total length of the optical system is long relative to the focal length (the telephoto ratio is small), it becomes easier to correct axial chromatic aberration and lateral chromatic aberration in a balanced manner, but it becomes difficult to reduce the weight. In the optical system of this embodiment, the telephoto ratio is preferably smaller than 1.0, and more preferably smaller than 0.7.

[0079] Furthermore, as the focal length of an optical system increases, the size of the positive lens group located closer to the object than the aperture stop SP tends to increase. In a telephoto optical system, the closer the lens is to the object, the greater the axial ray height, and as a result, the larger the effective diameter. For this reason, from the perspective of chromatic aberration correction, it is preferable to use a positive lens as the first optical element A, as in this embodiment.

[0080] The shape factor of the first optical element A is preferably set to -1.0 to 2.0, and further set to -0.5 to 0.7, which makes it easier to correct spherical aberration and coma.

[0081] It is preferable that the aperture stop SP is provided on the object side of the eighth lens element that moves during focusing, thereby making it possible to reduce the diameter of the focus lens element and reduce fluctuations in the amount of aberration during focusing.

[0082] It is also preferable that the focus lens has negative refractive power, which allows the overall optical length to be shortened. It is also preferable that the focus lens is made up of a single negative lens, which allows the focus lens to be made lightweight.

[0083] In this embodiment, the tenth to twelfth lenses are used as an image stabilization group, which performs image stabilization, correction of off-axis coma aberration, and correction of spherical aberration.

[0084] FIG. 6 shows the longitudinal aberration of the optical system of Numerical Example 3.

[0085] The optical system of Example 4 (Numerical Example 4) shown in Figure 7 is composed of, arranged in order from the object side to the image side, a positive first lens unit L1, a negative second lens unit L2, a negative third lens unit L3, a positive fourth lens unit L4, a positive fifth lens unit L5 including an aperture stop SP closest to the object side, a negative sixth lens unit L6, a positive seventh lens unit L7, and a negative eighth lens unit L8. The optical system of this example is a zoom lens with a zoom ratio of 2.7 and an aperture ratio of approximately 2.9 to 2.9. The first to eighth lens units L1 to L8 move during zooming from the wide-angle end to the telephoto end. During focusing from infinity to a close distance, the sixth lens unit L6 moves toward the object side, and the seventh lens unit L7 moves toward the image side.

[0086] The positive fifth lens unit L5 in the rear group includes an optical element C that is composed of a fourteenth lens as the first optical element A and a thirteenth lens as the second optical element B. The thirteenth lens and the fourteenth lens are cemented together via an organic material within and outside their effective diameters.

[0087] In this embodiment, the optical element C is used as an image stabilization group, and performs image stabilization, correction of off-axis coma aberration, and correction of spherical aberration. The first optical element A is made of an organic material. This reduces the weight of the image stabilization group while improving the effect of correcting decentering chromatic aberration and decentering coma aberration.

[0088] When the optical element C is disposed closer to the image side than the aperture stop SP as in this embodiment, it is desirable that the refractive power of the optical element C is negative, which makes it easier to shorten the overall length of the entire optical system.

[0089] 8A, 8B, and 8C show longitudinal aberrations of the optical system of Numerical Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively.

[0090] The optical system of Example 5 (Numerical Example 5) shown in Figure 9 is composed of, arranged in order from the object side to the image side, a positive first lens unit L1, a negative second lens unit L2, a positive third lens unit L3, a positive fourth lens unit L4, an aperture stop SP, a negative fifth lens unit L5, a positive sixth lens unit L6, a negative seventh lens unit L7, and a positive eighth lens unit L8. The optical system of this example is a zoom lens with a zoom ratio of 1.4 and an aperture ratio of approximately 2.9 to 4.1. During zooming from the wide-angle end to the telephoto end, the second, fourth, and fifth lens units L2, L4, L5, and L7 move. During focusing from infinity to a close distance, the fifth lens unit L5 and the seventh lens unit L7 move toward the image side.

[0091] The negative second lens unit L2, which is a variable magnification unit in the front group, includes an optical element C that is composed of a fifth lens as the first optical element A and a sixth lens as the second optical element B. The fifth lens and the sixth lens are cemented together via an organic material within and outside their effective diameters.

[0092] As the focal length of an optical system increases, the positive lens group located closer to the object than the aperture stop SP tends to become larger. In a telephoto zoom lens with a telephoto ratio of less than 0.9 in the telephoto range, the closer the lens is to the object, the greater the height of on-axis and off-axial rays. For this reason, from the perspective of correcting chromatic aberration, it is preferable to position the positive lens closest to the object in the second lens group L2, which is a variable magnification group, as the first optical element A. This makes it possible to suppress fluctuations in chromatic aberration of magnification throughout the entire zoom range.

[0093] The first lens unit L1 is composed of five or fewer lenses. This reduces the number of lenses constituting the first lens unit L1, which has a large lens diameter, making it possible to reduce the size and weight of the first lens unit L1. Furthermore, the height of light rays emerging from the first lens unit L1 can be lowered, making it possible to effectively correct off-axis aberrations such as coma and field curvature.

[0094] The second lens unit L2 is composed of three spherical lenses. Specifically, from the object side, it is composed of a fifth lens which is a positive first optical element A, a sixth lens which is a negative second optical element B, and a negative lens. By constructing the second lens unit L2 from spherical lenses, it is possible to suppress surface shape errors (so-called astigmatism and quirk component errors) that tend to occur in aspherical lenses. This configuration enhances the refractive power of the second lens unit L2 while simultaneously correcting chromatic aberration of magnification and curvature of field in the wide-angle range and spherical aberration in the telephoto range.

[0095] 10A, 10B, and 10C show longitudinal aberrations of the optical system of Numerical Example 5 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively.

[0096] The optical system of Example 6 (Numerical Example 6) shown in Figure 11 is composed of, arranged in order from the object side to the image side, a negative first lens unit L1, a positive second lens unit L2, a negative third lens unit L3, and a positive fourth lens unit L4 including an aperture stop SP closest to the object side. The optical system of this example is a zoom lens with a zoom ratio of 1.6 and an aperture ratio of approximately 2.9 to 2.9. The first to fourth lens units L1 to L4 move during zooming from the wide-angle end to the telephoto end. The second lens unit L2 moves toward the image side during focusing from infinity to a close distance.

[0097] The second lens unit L2 in the front group is composed of a first optical element C (C1) composed of a seventh lens as the first optical element A and a sixth lens as the second optical element. The sixth lens and the seventh lens are cemented together via an organic material within and outside their effective diameters. The third lens unit L3 in the front group is composed of a second optical element C (C2) composed of an eighth lens as the first optical element A and a ninth lens as the second optical element. The optical element C1 has a positive refractive power, and the optical element C2 has a negative refractive power. The eighth lens and the ninth lens are cemented together via an organic material within and outside their effective diameters.

[0098] The optical system of this embodiment is a so-called retrofocus zoom lens. This type of lens configuration has an asymmetrical overall lens arrangement with a negative lens group closest to the object and a positive lens group closest to the object. This makes it prone to a variety of aberrations, such as distortion and lateral chromatic aberration, and makes it particularly difficult to effectively correct chromatic aberration. Therefore, in this embodiment, the second lens group L2 is configured with a second optical element B consisting of one negative lens and a first optical element A consisting of one positive lens, thereby effectively correcting spherical aberration and coma while suppressing axial chromatic aberration throughout the entire zoom range. Furthermore, the third lens group L3 is configured with a first optical element A consisting of one negative lens and a second optical element B consisting of one positive lens, thereby effectively correcting fluctuations in chromatic aberration that occur during focusing.

[0099] By providing both the positive and negative optical elements C1 and C2 as in this embodiment, it becomes easier to correct axial chromatic aberration and chromatic aberration of magnification over the entire zoom range.

[0100] 12A, 12B, and 12C show longitudinal aberrations of the optical system of Numerical Example 6 at the wide-angle end, at the intermediate zoom position, and at the telephoto end, respectively.

[0101] The optical system of Example 7 (Numerical Example 7) shown in Figure 13 is composed of, arranged in this order from the object side to the image side, a negative front group, an aperture stop SP, and a positive rear group. The entire optical system moves during focusing from infinity to a close distance.

[0102] The fourth lens as the first optical element A in the rear group and the fifth lens as the second optical element B constitute an optical element C. The fourth lens and the fifth lens are cemented together via an organic material within and outside their effective diameters.

[0103] The object-side surface of the fourth lens is aspherical. By using a UV curable resin as the organic material for forming the fourth lens, the fourth lens can be formed into a desired shape.

[0104] As in this embodiment, by arranging the optical element C closer to the image side than the aperture stop SP and adding an aspherical surface to the optical element C, it is possible to reduce the variation in spherical aberration for each wavelength and improve the balance of the aberrations.

[0105] In a compact optical system with a shortened overall length, the glass thickness relative to the overall optical length increases, making correction of chromatic aberration important. For this reason, it is advisable to set the refractive index of the second optical element B at the d-line to 1.85 or more and the Abbe number based on the d-line to 36 or less. Furthermore, if the refractive index is set to 1.9 or more, the correction effect is improved, making it easier to correct spherical aberration and coma aberration.

[0106] Moreover, by using an aspherical lens for the optical element C, good imaging performance can be ensured even if the aperture ratio of the optical system is large.

[0107] FIG. 14 shows the longitudinal aberration of the optical system of Numerical Example 7.

[0108] Numerical values ​​for Numerical Examples 1 to 7 are shown below. Surface number i indicates the order of the surface when counted from the object side. r is the radius of curvature (mm) of the ith surface from the object side, d is the lens thickness or air gap (mm) between the ith and (i+1)th surfaces, and nd is the refractive index at the d-line of the optical material between the ith and (i+1)th surfaces. νd is the Abbe number, based on the d-line, of the optical material between the ith and (i+1)th surfaces, and θgF is the partial dispersion ratio at the g-line and F-line, each defined as explained above.

[0109] The focal length (mm), F-number, and half angle of view (°) are values ​​when the optical system is focused on an object at infinity. The half angle of view indicates the angle of view determined by ray tracing.

[0110] The back focus BF is the air-equivalent distance on the optical axis from the final surface of the optical system to the paraxial image plane. The total optical length is the distance on the optical axis from the optical surface closest to the object (the foremost surface) to the optical surface closest to the image (the final surface) plus the back focus BF.

[0111] An "*" attached to a surface number means that the surface has an aspherical shape. The aspherical shape is expressed by the following formula, where X is the displacement from the vertex of the surface in the optical axis direction, H is the height from the optical axis in a direction perpendicular to the optical axis, the direction of light travel is positive, R is the paraxial radius of curvature, K is the conic constant, and A3 to A20 are aspherical coefficients. The conic constant and the aspherical coefficient "e±Z" are multiplied by 10. ±Ｚ means.

[0112]

[0113] The values ​​corresponding to the above-mentioned formulas (1) to (14) in Numerical Examples 1 to 7 are summarized in Table 1. [Numerical Example 1] Unit: mm Surface data Surface number rd nd νd θgF 1 104.5636 5.706 1.83481 42.74 0.5648 2 -1792.2944 0.400 3 29.2494 9.682 2.00100 29.13 0.5997 4 42.8366 0.740 5 52.2925 1.800 1.80809 22.76 0.6285 6 19.4401 8.373 7 -57.1986 1.300 1.75211 25.05 0.6190 8 24.1677 7.254 2.00100 29.13 0.5997 9 -114.7358 1.500 10(Aperture) ∞ 10.799 11* -82.5986 2.700 1.63560 23.90 0.6353 12* 68.4379 0.637 13 254.2639 7.868 2.00100 29.13 0.5997 14 -23.2239 0.099 15 -22.8762 1.200 1.86966 20.02 0.6434 16 13806.5379 7.652 2.00100 29.13 0.5997 17 -32.3832 24.346 Image surface ∞ Aspheric surface data Surface 11 K = 0.00000e+00 A4=-7.74963e-04 A6=-5.26808e-05 A8= 7.87969e-08 A10=-3.92578e-08 A12= 1.41217e-09 A14=-1.65137e-14 A16=-1.61433e-15 A18= 2.98085e-16 A 3= 8.04709e-04 A 5= 2.76298e-04 A 7= 2.80311e-06 A 9= 1.74560e-07 A11=-2.08835e-09 A13=-1.40347e-10 A15= 6.69420e-13 A17=-4.78815e-15 A19=-5.73648e-18 Surface 12 K = 0.00000e+00 A 4=-5.34914e-04 A 6=-1.98324e-05 A 8= 4.36415e-07 A10=-1.78659e-08 A12= A14= 1.41205e-10 A14= 1.00077e-12 A16=-9.64044e-15 A18= 5.73073e-19 A3= 6.57759e-04 A5= 1.51843e-04 A7=-8.99431e-07 A9= 2.88882e-08 A11= 1.36563e-09 A13=-2.76886e-11 A15= 9.21135e-14 A17= 2.79741e-16 A19=-1.13812e-19 Various data Focal length 48.500 F-number 1.240 Half angle of view (°) 23.859 Image height 21.635 Total optical length 92.056 BF 24.346 [Numerical example 2] Unit: mm Surface data Surface number rd nd νd θgF 1 96.0956 1.800 1.92286 20.88 0.6391 2 65.7232 7.018 1.52841 76.46 0.5396 3 -508.1873 0.250 4 56.4659 3.854 1.69680 55.53 0.5434 5 127.0580 (Variable) 6 82.1933 0.900 1.95375 32.32 0.5898 7* 16.0666 6.529 8 -48.1282 0.800 1.95375 32.32 0.5898 9 23.6250 5.099 1.92286 20.88 0.6391 10 -44.8783 1.701 11 -19.8488 0.800 1.49700 81.54 0.5375 12 -59.7634 (Variable) 13(Aperture) ∞ 0.600 14* 19.9346 4.116 1.58313 59.38 0.5423 15* -67.3192 0.250 16 26.8294 4.156 1.55200 70.70 0.5421 17 -27.6348 0.800 1.51742 52.43 0.5564 18 14.7095 1.695 19 23.9090 0.800 1.83400 37.21 0.5807 20 13.4460 4.484 1.59282 68.62 0.5458 21 -1071.4358 0.938 22 42.8667 4.248 1.61800 63.40 0.5395 23 -13.5623 0.800 1.87070 40.73 0.5686 24 -20.6436 (Variable) 25 -30.4787 0.800 1.85150 40.78 0.5695 26 19.8875 (Variable) 27* 77.4620 1.900 1.58313 59.38 0.5423 28* 148.2589 (variable) 29 219.3906 4.967 1.61800 63.40 0.5395 30 -34.3030 (variable) Image surface ∞ Aspheric data Surface 7 K = 0.00000e+00 A 4=-1.82402e-06 A 6=-2.25337e-08 A 8=7.64008e-11 Surface 14 K = 0.00000e+00 A 4=-1.25940e-05 A 6=-4.46696e-08 A 8=2.10100e-10 A10= 5.18472e-12 Surface 15 K = 0.00000e+00 A 4= 1.84772e-05 A 6=-2.11035e-08 A 8=2.72627e-10 A10= 5.23048e-12 27th side K = 0.00000e+00 A 4=-1.60614e-04 A 6=-2.70663e-07 A 8=9.87007e-10 A10=-6.79311e-11 A12= 3.14250e-13 Surface 28 K = 0.00000e+00 A 4=-1.31557e-04 A 6=-3.24603e-07 A 8=3.47339e-09 A10=-6.02937e-11 A12= 2.41181e-13 Various data Zoom ratio 5.418 Wide angle Mid-range Telephoto Focal length 15.450 31.547 83.707 F-number 2.880 4.000 5.800 Half angle of view (°) 41.664 22.768 8.842 Image height 12.750 13.660 13.660 Total optical length 111.307 124.930 143.033 BF 12.172 12.720 14.026 d 5 0.700 12.768 39.350 d12 28.386 16.543 4.515 d24 2.040 2.755 4.724 d26 7.820 7.104 5.136 d28 0.885 13.734 15.978 d30 12.172 12.720 14.026 Lens group data Group Initial surface Focal length 1 1 86.596 2 6 -14.283 3 13 17.137 4 25 -14.031 5 27 275.462 6 29 48.363 [Numerical Example 3] Unit: mm Surface data Surface number rd nd νd θgF 1 103.9187 6.279 1.61997 63.88 0.5417 2 192.0505 4.930 3 63.1548 14.438 1.43387 95.10 0.5373 4 256.9794 42.741 5 57.3097 7.571 1.43700 95.10 0.5326 6 -204.3382 1.200 1.80100 34.97 0.5864 7 30.3176 1.477 8 30.4631 7.434 1.43700 95.10 0.5326 9 147.6479 4.907 10 39.2080 8.111 1.66382 27.35 0.6319 11 -68.3462 1.500 1.90525 35.04 0.5848 12 71.5685 7.351 13 (Aperture) ∞ 2.124 14 215.9773 1.200 1.61800 63.40 0.5395 15 48.5668 29.602 16 202.9730 2.542 1.49700 81.65 0.5378 17 -218.0898 2.000 18 208.0245 2.079 1.64769 33.79 0.5938 19 -136.5324 1.100 1.59282 68.62 0.5458 20 41.0094 2.858 21 -87.4277 1.100 1.59282 68.62 0.5458 22 93.9152 2.000 23 57.0794 6.875 1.67300 38.26 0.5757 24 -26.4213 1.200 1.76385 48.49 0.5589 25 -216.5845 2.000 26 170.0424 1.300 1.94594 17.98 0.6546 27 35.4419 6.738 1.60342 38.03 0.5835 28 -326.7269 6.599 29 -78.7938 1.400 1.43700 95.10 0.5326 30 51.1374 7.545 1.68893 31.07 0.6004 31 -72.2277 55.204 Image plane ∞ Various data Focal length 388.000 F-number 4.600 Half angle of view (°) 2.729 Image height 21.635 Total optical length 243.404 BF 55.204 [Numerical example 4] Unit: mm Surface data Surface number rd nd νd θgF 1 176.1113 1.500 1.73800 32.33 0.5900 2 91.1221 9.720 1.43387 95.10 0.5373 3 -664.7077 0.200 4 80.0395 8.261 1.49700 81.54 0.5375 5 820.9590 (Variable) 6 757.4543 2.956 1.85883 30.00 0.5980 7 -346.0040 1.000 1.59282 68.62 0.5458 8 44.4586 (Variable) 9 -62.2431 1.600 1.48071 85.29 0.5355 10 55.6349 3.566 1.85451 25.16 0.6102 11 144.8503 (Variable) 12 70.0135 9.017 1.49700 81.61 0.5386 13 -45.5952 1.200 1.72342 37.99 0.5819 14 2472.6862 (Variable) 15(Aperture) ∞ 3.500 16 68.3297 6.539 1.73400 51.47 0.5486 17 -104.3688 0.200 18 247.6942 1.500 1.85478 24.80 0.6122 19 66.3038 4.320 1.80420 46.50 0.5572 20* -312.8182 1.194 21 -1616.6406 0.900 1.91082 35.25 0.5824 22 56.5188 2.638 1.68040 18.10 0.6827 23 134.9060 4.534 24 -57.9343 1.000 1.56732 42.84 0.5748 25 45.8395 7.490 1.59282 68.62 0.5458 26 -62.3319 (Variable) 27 229.6758 3.924 1.85033 42.70 0.5643 28 -80.8166 1.400 1.53775 74.70 0.5392 29 41.2366 (Variable) 30* 58.5555 8.530 1.43875 94.66 0.5340 31* -65.4493 (Variable) 32 -119.3224 1.400 1.49700 81.61 0.5386 33 109.5347 3.241 34 -196.1758 1.400 1.84666 23.84 0.6202 35 -753.0280 38.280 Image surface ∞ Aspheric surface data Surface 20 K = 0.00000e+00 A 4= 2.48914e-06 A 6= 4.74301e-11 A 8= 1.75778e-13 A10= 5.50223e-16 Surface 30 K = 0.00000e+00 A 4= 5.50327e-07 A 6=-6.47823e-10 Surface 31 K = 0.00000e+00 A 4= 1.64197e-06 A 6=-9.56154e-10 A 8= 6.22366e-14 A10= 1.27475e-16 Various data Zoom ratio 2.709 Wide angle Mid-range Telephoto Focal length 71.673 125.131 194.174 F-number 2.880 2.847 2.880 Half angle of view (°) 16.851 9.664 6.236 Image height 21.635 21.635 21.635 Total optical length 239.043 239.043 239.043 BF 38.280 38.280 38.280 d 5 2.200 34.804 55.546 d 8 31.240 17.001 10.739 d11 31.722 18.529 6.020 d14 9.615 4.444 2.473 d26 8.753 5.335 0.785 d29 11.132 16.634 30.915 d31 13.370 11.286 1.556 Lens Group Data Group Initial Surface Focal Length 1 1 141.117 2 6 -87.773 3 9 -144.770 4 12 484.144 5 15 71.047 6 27 -188.360 7 30 71.949 8 32 -83.312 Focus d26 (26-27 surfaces) / d31 (31-32 surfaces) Wide angle Medium Telephoto INF 8.753 / 13.370 5.335 / 11.286 0.785 / 1.556 1.3m 12.338 / 14.615 14.908 / 15.115 18.988 / 11.318 [Numerical Example 5] Unit: mm Surface data Face No. rd nd νd θgF 1 642.7371 7.937 1.48749 70.44 0.5303 2 -1679.4193 24.782 3 188.4549 14.514 1.43387 95.10 0.5373 4 24667.5273 65.728 5 147.9402 8.551 1.43387 95.10 0.5373 6 737.8196 1.662 7 10777.3205 2.500 1.65412 39.68 0.5737 8 172.3483 (Variable) 9 364.9638 4.612 2.00272 19.32 0.6452 10 -365.1402 1.800 1.91082 35.25 0.5834 11 132.3767 8.648 12 -128.3465 1.800 1.51680 64.20 0.5342 13 -3176.1783 (Variable) 14 313.0651 9.138 1.43387 95.10 0.5373 15 -140.6155 0.300 16 163.3222 6.664 1.49700 81.54 0.5375 17 -736.0087 0.300 18 90.2409 11.886 1.43875 94.66 0.5340 19 -212.3414 1.500 1.83400 37.34 0.5790 20 258.0913 (Variable) 21 102.0739 5.991 1.49700 81.54 0.5375 22 1490.6278 (Variable) 23 (Aperture) ∞ (Variable) 24 1376.6420 1.000 1.77250 49.60 0.5520 25 60.9123 (Variable) 26 84.1421 1.000 1.89286 20.36 0.6393 27 36.1128 6.451 1.69895 30.13 0.6030 28 -173.2369 0.951 29 -965.2698 4.120 1.66565 35.64 0.5824 30 -50.7801 1.200 1.55200 70.70 0.5421 31 45.4345 4.388 32 -96.1161 1.200 1.49700 81.54 0.5375 33 68.4079 2.310 34 41.8827 6.636 1.57501 41.50 0.5767 35 -187.4599 (Variable) 36 155.2134 1.400 1.80518 25.46 0.6156 37 53.8467 (variable) 38 52.9859 6.105 1.60342 38.03 0.5835 39 -256.0387 5.657 40 -42.2488 1.500 1.52841 76.46 0.5396 41 -77.1267 46.332 Image plane ∞ Various data Zoom ratio 1.424 Wide angle Mid-range Telephoto Focal length 408.701 505.072 581.831 F-number 2.880 3.559 4.100 Half angle of view (°) 3.016 2.439 2.116 Image height 21.635 21.635 21.635 Optical total length 475.006 475.006 475.006 BF 46.332 46.332 46.332 d 8 80.720 107.189 127.323 d13 50.108 23.638 3.504 d20 12.294 5.928 12.518 d22 4.685 11.050 4.461 d23 19.454 7.746 3.780 d25 22.066 33.774 37.740 d35 4.025 3.942 3.853 d37 13.095 13.178 13.267 Lens Group Data Group Initial Surface Focal Length 1 1 406.700 2 9 -128.623 3 14 118.377 4 21 220.163 5 23 ∞ 6 24 -82.529 7 26 257.354 8 36 -103.035 9 38 115.594 Focus d23 (23-24 surfaces) / d35 (35-36 surfaces) Wide Angle Medium Telephoto INF 19.454 / 4.025 7.746 / 3.942 3.780 / 3.853 2.8m 36.353 / 3.503 31.454 / 2.901 35.662 / 1.981 [Numerical Example 6] Unit: mm Surface data Surface number rd nd νd θgF 1* 140.7006 3.000 1.69350 53.20 0.5468 2 25.2607 8.722 3 39.2723 1.500 1.59282 68.62 0.5458 4 22.7915 8.528 5* 400.0787 2.200 1.61881 63.85 0.5418 6* 40.4392 8.473 7 -126.2503 1.000 1.59282 68.62 0.5458 8 80.7722 0.250 9 37.7868 4.429 1.85478 24.80 0.6122 10 140.2328 (Variable) 11 33.4227 0.700 2.00069 25.46 0.6136 12 17.4913 6.338 1.75575 24.71 0.6291 13 777.5780 (Variable) 14 -155.4383 0.800 1.94594 17.98 0.6546 15 35.6963 3.746 2.00100 29.13 0.5997 16 -1510.8904 (Variable) 17(Aperture) ∞ 1.250 18 65.1706 2.519 1.43700 95.10 0.5326 19 -347.6079 0.150 20 20.5596 1.100 1.72047 34.71 0.5834 21 15.3365 9.289 1.49700 81.61 0.5386 22 -42.7736 2.645 23 -45.8434 0.800 1.95375 32.32 0.5905 24 17.4719 4.777 1.92286 20.88 0.6391 25 135.1701 0.150 26 21.4400 0.800 1.88300 40.76 0.5667 27 13.4166 7.954 1.48071 85.29 0.5355 28 74.8261 1.794 29* 541.6724 2.500 1.58313 59.46 0.5418 30* -308.1924 (variable) Image surface ∞ Aspheric surface data Surface 1 K = 0.00000e+00 A4= 1.13941e-05 A6=-1.84938e-08 A8=3.62362e-11 A10=-6.46062e-14 A12= 9.30370e-17 A14=-9.60224e-20 A16=6.37947e-23 A18=-2.39147e-26 A20= 3.78519e-30 Surface 5 K = 3.96849e+02 A4=-9.15102e-07 A 6= 1.52349e-06 A8=-3.36058e-09 A10= 1.11404e-11 A12=-8.03668e-14 A14= 1.50913e-17 A16=-1.46277e-20 A18=-2.99255e-23 A20=-3.31214e-27 A 3=-5.23111e-05 A 5=-8.22002e-06 A 7=-4.67303e-08 A9= 4.79077e-11 A11= 4.85752e-13 A13= 2.06732e-15 A15=-7.29720e-19 A17= 1.13899e-21 A19= 1.48595e-25 6th side K = 1.45238e+00 A 4= 5.75658e-06 A 6= 3.70528e-07 A8=-3.29421e-08 A10=-1.87571e-11 A12=-1.63598e-14 A14=-1.67175e-16 A16= 6.59973e-19 A18=-4.91029e-23 A20=-5.09803e-25 A 3=-3.48559e-05 A 5=-4.89947e-06 A 7= 2.01642e-07 A9= 1.86446e-09 A11=-2.06229e-12 A13= 9.56881e-15 A15=-2.01957e-17 A17= 6.43253e-21 A19= 1.37261e-24 Surface 29 K = 0.00000e+00 A 4=-6.06155e-05 A 6= 3.71333e-08 A8= 8.44000e-10 A10=-4.77088e-11 A12= 7.78420e-13 A14=-7.20565e-15 A16= 4.06112e-17 A18=-1.24975e-19 A20= 1.29336e-22 30th side K = 0.00000e+00 A 4=-2.25761e-05 A 6= 1.25362e-07 A8=-3.15267e-09 A10= 5.08110e-11 A12=-4.99183e-13 A14= 2.63352e-15 A16=-5.84030e-18 A18=-8.07610e-22 A20= 5.22718e-24 Various data Zoom ratio 1.617 Wide angle Mid-range Telephoto Focal length 14.421 17.792 23.322 F-number 2.880 2.880 2.880 Half angle of view (°) 57.334 50.510 42.169 Image height 21.635 21.635 21.635 Total optical length 144.730 138.714 135.287 BF 22.236 27.199 35.059 d10 24.626 16.142 8.039 d13 4.160 4.341 4.134 d16 8.295 5.619 2.642 d30 22.236 27.199 35.059 Lens group data Group Initial surface Focal length 1 1 -21.158 2 11 65.884 3 14 -258.431 4 17 42.214 [Numerical Example 7] Unit: mm Surface data Surface number rd nd νd θgF 1 -53.1247 1.000 1.51680 64.20 0.5342 2 12.3835 2.770 3 21.9935 2.728 1.69680 55.53 0.5434 4 -319.6263 2.652 5 ∞ 4.218 6 (Aperture) ∞ 0.898 7 15.2035 2.775 1.75500 52.32 0.5475 8 -42.6161 0.799 9* -192.2595 0.200 1.63428 23.30 0.6789 10 57.5786 2.892 1.95375 32.32 0.5898 11 -28.9084 0.200 12 -335.0687 0.800 1.80809 22.76 0.6285 13 14.4244 6.494 14* -8.9783 1.900 1.83220 40.10 0.5714 15* -11.6166 0.800 16* 17.0253 6.013 1.53500 56.00 0.5625 17* 28.7232 (variable) Image plane ∞ Aspheric data Surface 9 K = 0.00000e+00 A 4=-1.46914e-04 A 6=-1.16659e-07 A 8=3.15046e-09 Surface 14 K =-6.86734e+00 A 4=-2.19272e-03 A 6=-4.03560e-04 A 8= 6.06028e-07 A10= 5.98956e-07 A12= 1.93100e-09 A 3= 2.20866e-03 A 5= 1.19801e-03 A 7= 7.07887e-05 A 9=-2.94743e-06 A11=-5.40769e-08 15th side K =-9.14754e-01 A 4=-5.61046e-04 A 6=-1.17010e-04 A 8=-3.24737e-06 A10=-7.35018e-08 A12=-1.05809e-10 A 3= 1.62778e-03 A 5= 4.12418e-04 A 7= 2.12533e-05 A 9= 5.60467e-07 A11= 4.77958e-09 Surface 16 K = 0.00000e+00 A 4=-5.36059e-04 A 6= 6.63390e-06 A 8=-4.35495e-08 A10= 1.04260e-10 Surface 17 K = 0.00000e+00 A 4=-2.78529e-04 A 6= 9.79928e-07 A 8= 7.61009e-10 A10=-1.83912e-11 Various data Focal length 19.500 F-number 2.060 Half angle of view (°) 39.456 Image height 14.400 Total optical length 44.116 BF 6.977 .

[0114]

[0115] [Imaging Device] Figure 15 shows a digital still camera 10 as an imaging device that uses the optical system of each of the above-described embodiments as its imaging optical system. Reference numeral 13 denotes a camera body, and reference numeral 11 denotes an imaging optical system configured using any of the optical systems of Examples 1 to 7. Reference numeral 12 denotes a solid-state imaging element such as a CCD sensor or CMOS sensor that is built into the camera body 13 and photoelectrically converts the optical image (subject image) formed by the imaging optical system 11, i.e., captures the subject image through the imaging optical system 11. The camera body 13 records image data generated by processing the imaging signal from the imaging element 12.

[0116] By using the optical system of each embodiment, an imaging device with high optical performance can be obtained. The imaging device may be a single-lens reflex camera with a quick-turn mirror, or a mirrorless camera without a quick-turn mirror.

[0117] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention.

Claims

1. An optical system including an optical element, wherein the optical element is configured by bonding a first optical element and a second optical element having different optical properties via an organic material, and the organic material contains a photopolymerization initiator having an absorption edge wavelength of 390 nm or more.

2. The optical system according to claim 1, wherein the first optical element and the second optical element are cemented together via the organic material within their effective optical ranges.

3. The optical system according to claim 1, wherein the first optical element and the second optical element are arranged with air between them within their effective optical ranges, and are cemented together outside their effective optical ranges.

4. The optical system according to any one of claims 1 to 3, characterized in that the object-side or image-side optical surface of the first optical element is in contact with air via a thin film.

5. When the refractive index of the first optical element at the d-line is ndA, the Abbe number based on the d-line is νdA, and the partial dispersion ratio at the g-line and the F-line is θgFA, 1.5≦ndA≦3.9827−0.1408×νdA+0.0021×νdA ２ 10≦νdA≦35 −0.000003056×νdA ３ +0.0003653 × νdA ２ 5. The optical system according to claim 1, wherein at least one of the following three conditions is satisfied: −0.01647×νdA+0.8503≦θgFA.

6. The optical system according to claim 1, characterized in that at least one of the following two conditions is satisfied: 1.85≦ndB νdB≦36, where ndB is the refractive index of the second optical element at the d-line and νdB is the Abbe number based on the d-line.

7. An optical system according to any one of claims 1 to 6, characterized in that the following condition is satisfied: 0.25≦|fA / fB|≦4.00, where fA is the focal length of the first optical element and fB is the focal length of the second optical element.

8. An optical system according to any one of claims 1 to 7, characterized in that the following condition is satisfied: 0.60≦ndA / ndB≦1.40, where ndA is the refractive index of the first optical element at the d line and ndB is the refractive index of the second optical element at the d line.

9. An optical system according to any one of claims 1 to 8, characterized in that the following condition is satisfied: 0.40≦νdA / νdB≦1.50, where νdA is the Abbe number of the first optical element referenced to the d line, and νdB is the Abbe number of the second optical element referenced to the d line.

10. An optical system according to any one of claims 1 to 9, characterized in that it satisfies the condition -2.0≦SFA≦10.0, where SFA is the shape factor of the first optical element, sgn(fL) is +1 when the focal length fL of the first optical element is positive and -1 when it is negative, R1 is the radius of curvature of the optical surface of the first optical element on the object side, and R2 is the radius of curvature of the optical surface of the first optical element on the image side, and SFA = sgn(fL) × (R2 + R1) / (R2 - R1).

11. An optical system according to any one of claims 1 to 10, characterized in that the following condition is satisfied: 0.02≦|fA / fC|≦3.00, where fA is the focal length of the first optical element and fC is the focal length of the second optical element.

12. An optical system according to any one of claims 1 to 11, characterized in that the optical system has an aperture stop, and satisfies the condition 1.8≦|fC / dSC|≦70.0, where fC is the focal length of the optical element and dSC is the distance on the optical axis from the optical surface of the optical element on the aperture stop side to the aperture stop.

13. An optical system according to any one of claims 1 to 12, characterized in that the following condition is satisfied: 0.5≦|fC / f|≦25.0, where fC is the focal length of the optical element and f is the focal length of the optical system.

14. An optical system according to any one of claims 1 to 13, characterized in that the following condition is satisfied: -0.30≦ndB−ndA≦0.50, where ndA is the refractive index of the first optical element at the d line and ndB is the refractive index of the second optical element at the d line.

15. An optical system according to any one of claims 1 to 14, characterized in that the optical system has an aperture stop, and satisfies the condition 0<dSC / OL≦0.35, where dSC is the distance on the optical axis from the optical surface of the optical element closest to the aperture stop to the aperture stop, and OL is the length on the optical axis from the optical surface of the optical system closest to the object to the image plane.

16. An optical system according to any one of claims 5 to 15, characterized in that it comprises a plurality of said optical elements, and the optical element having the greatest refractive power among said plurality of optical elements satisfies said condition.

17. An optical system according to any one of claims 1 to 15, characterized in that it is composed of a front group including at least one lens, an aperture stop, and a rear group including at least one lens, arranged in that order from the object side to the image side, and at least one of the front group and the rear group has a lens as the optical element.

18. An imaging device comprising: an optical system according to any one of claims 1 to 17; and an imaging element for capturing an image of a subject through said optical system.

Images