JP5517568B2 - Optical element and optical system having the same - Google Patents

Description

  The present invention relates to an optical element in which three or more optical elements are joined and an optical system including the optical element, and relates to an optical system such as a silver salt film camera, a digital still camera, a video camera, a telescope, a binocular, a projector, and a digital copying machine. It is suitable for an optical system used in equipment.

  In recent years, an optical system (imaging optical system) used in an imaging apparatus such as a digital camera or a video camera is required to be small and have high optical performance as the entire system is miniaturized and highly functional. ing.

  In general, in an optical system used in an imaging apparatus such as a digital camera or a video camera, various aberrations are generated as the total lens length is shortened and the entire optical system is downsized. In particular, many chromatic aberrations such as axial chromatic aberration and lateral chromatic aberration occur. As a result, the optical performance is greatly deteriorated. For example, in a telephoto type optical system in which the total lens length is shortened, the longer the focal length (the longer the length), the more chromatic aberration occurs, and the optical performance greatly decreases.

  Conventionally, as an optical system for reducing the occurrence of chromatic aberration at this time, an optical system using an optical element made of an optical material having a strong anomalous partial dispersibility, for example, a resin is known (see Patent Documents 1 and 2).

  Patent Document 1 discloses a method for reducing chromatic aberration by using an optical material having strong anomalous partial dispersibility, particularly an organic composite layer such as a resin, in an optical system. Patent Document 2 discloses a method for reducing chromatic aberration in an optical system of a retrofocus type by using an organic composite layer such as a resin having an abnormal partial dispersibility stronger on the image side than the stop. In these Patent Documents 1 and 2, the chromatic aberration of the entire system is reduced by giving refracting power to the material of the organic composite layer having strong anomalous partial dispersion and then balancing the chromatic aberration with other glass materials. .

JP 2006-145823 A JP 2006-301416 A

  Patent Documents 1 and 2 disclose optical systems in which chromatic aberration is corrected satisfactorily using an organic composite layer. Further, in order to effectively correct the chromatic aberration, it is preferable to apply a certain amount of refractive power to the organic composite layer such as resin. For this purpose, the organic composite layer needs to have a thickness corresponding to its refractive power.

  In the method of forming an organic composite layer such as a resin on the lens surface using a mold, the difficulty of forming increases as the thickness of the organic composite layer increases. This is because the amount of the organic composite layer increases, the absolute amount of cure shrinkage during molding increases, and it becomes difficult to finish the surface of the organic composite layer with high accuracy. Further, as the organic composite layer becomes thicker, the absolute amount of dimensional change of the organic composite layer with respect to temperature change increases and the influence on the optical performance increases.

  In Patent Document 1, an organic composite layer is attached on the lens surface to reduce chromatic aberration. In Patent Document 2, chromatic aberration is reduced by using an optical element in which an organic composite layer is sandwiched between lenses.

  In a junction type optical element in which an organic composite layer is sandwiched between lenses, the organic composite layer is formed on one lens surface, then the organic composite layer surface is covered with an adhesive, and the other lens is bonded together. ing. This minimizes the influence of the accuracy of the molded organic composite layer surface on the optical performance. In addition, in terms of environmental resistance, the junction type optical element is characterized in that the organic composite layer surface is regulated by an external lens sandwiching the organic composite layer, so that deformation is unlikely to occur.

  Further, in recent years, it has been demanded that junction-type optical elements satisfy the surface accuracy of the initial organic composite layer and reduce changes in performance of the optical elements under environmental resistance, particularly at high temperatures and high humidity.

  An object of the present invention is to provide an optical element having excellent optical characteristics and a correction effect of chromatic aberration, and an optical system having the same, which can reduce the change in performance of the optical element under environment resistance, particularly under high temperature and high humidity. To do.

An optical element of the present invention is an optical element in which a second optical element is bonded to an organic composite layer formed on the first optical element via an adhesive, and the optical axis of the optical element is In the included cross section, the diameter of the bonding surface bonded to the organic composite layer of the second optical element is φs, the outer diameter of the organic composite layer is φj, and the end of the bonding surface in the radial direction is at position, wherein the length along the optical axis of the organic composite layer T1 (mm), the DL1 (%) water absorption elongation is elongation at saturated water of the material of the organic composite layer, and to When
φs <φj
T1 × D L1 <0.19 (mm)
It is characterized by satisfying the following condition.
Further, the different optical element of the present invention is an optical element in which three or more optical elements are joined, and the three or more optical elements are organic composites in which two optical surfaces are in contact with other optical elements. One of the two optical surfaces of the organic composite layer is bonded to another optical element via an adhesive, and in a cross section including the optical axis of the optical element, The maximum diameter of the bonding surface of the optical element bonded to the organic composite layer via an adhesive is φs, the outer diameter of the organic composite layer is φj, and the end in the radial direction of the bonding surface having the maximum diameter φs Ti (i = 1, 2,... N) (mm), the length along the optical axis of the organic composite layer at the position of the portion, at the time of saturated water absorption of the material of the organic composite layer When the water absorption elongation, which is the elongation rate, is DLi (i = 1, 2,... N) (%),
φs <φj
Σ (Ti × DLi) <0.19 (mm)
It is characterized by satisfying the following condition.

  According to the present invention, it is possible to reduce the performance resistance of an optical element, particularly under high temperature and high humidity, and to achieve an optical element having excellent optical characteristics and a chromatic aberration correction effect, and an optical system having the optical element. be able to.

Sectional drawing of the principal part of the optical element of Example 1 of this invention The expanded sectional view of the outer periphery of the optical element of Example 1 of the present invention Sectional drawing of the principal part of the optical element of Example 2 of this invention The expanded sectional view of the outer peripheral part of the optical element of Example 2 of this invention Sectional drawing of the principal part of the optical element of Example 3 of this invention The expanded sectional view of the peripheral part of the optical element of Example 3 Sectional drawing of the principal part of the optical system using the optical element of Example 1 of this invention Sectional drawing of the principal part of the optical system using the optical element of Example 2 of this invention Sectional drawing of the principal part of the optical system using the optical element of Example 3 of this invention Schematic view of essential parts of the optical apparatus (imaging device) of the present invention

  Hereinafter, an optical element of the present invention and an optical system using the optical element will be described. In the optical element of the present invention, three or more optical elements are joined and integrated to have a predetermined refractive power (which may be 0). Of the three or more optical elements, one of the optical elements in which two optical surfaces (light incident / exit surfaces) are in contact with other optical elements is formed of an organic composite layer.

  The organic composite layer is molded on the first optical element whose one optical surface is exposed to gas. The surface of the organic composite layer opposite to the first optical element is bonded to the second optical element via an adhesive.

In the present invention, in the cross section including the optical axis of the optical element, the maximum diameter of the joint surface that does not include an object other than the adhesive among the joint surfaces joining the optical element and the optical element constituting the optical element (effective The surface diameter is φs. Further, the length (thickness) along the optical axis of the organic composite layer at the maximum diameter φs is Ti (i = 1, 2, 3,... N) (mm), and the water absorption elongation of the material of the organic composite layer ( DLi elongation) at saturated water (i = 1,2,3, ··· n) and (%). then,
Σ (Ti × DLi) <0.19 (mm) (1)
It meets the conditions.
[Example 1]
Hereinafter, with reference to FIG. 1, the optical element of Example 1 of this invention is demonstrated. FIG. 1 is a cross-sectional view of an essential part of an optical element according to Example 1 of the present invention. The optical element 11 of FIG. 1 forms an organic composite layer NL1 as a third optical element on one surface (convex surface) of the first optical element L1. The material composing the organic composite layer NL1 is an acrylic UV curable resin (Nd = 1.633, νd = 23.0, θgF = 0.68). After that, the second optical element L2 is joined through the UV curable adhesive S1 (Nd = 1.633). The first optical element L1 is made of S-FSL5 (trade name, manufactured by OHARA Corporation), and the second optical element L2 is made of S-TIH53 (trade name, manufactured by OHARA Corporation). Here, Nd, νd, and θgF are the refractive index, Abbe number, and partial dispersion ratio of the material, respectively. The same applies hereinafter.

  The outer peripheral portion of one surface of the second optical element L2 is preliminarily painted as a light-shielding agent (light-shielding portion) 2 before joining, so that flare and ghost generated from the outer periphery of the organic composite layer NL1 are generated. It is suppressed.

  In the optical element 11 of FIG. 1, the maximum diameter (inner diameter of the second optical element L2) φs of the bonding surface that does not include an adhesive other than the adhesive among the bonding surfaces obtained by bonding the optical elements to each other is 27.5 mm. is there. The outer diameter φj of the organic composite layer NL1 is 28.5 mm. In FIG. 1, 1 is the optical axis of the optical element 11.

  FIG. 2 is an enlarged view of the outer periphery of the optical element 11 of FIG. 2, the lengths T1, Tg1, and Tg2 along the optical axis of the organic composite layer NL1, the first and second optical elements L1, L2 at the maximum diameter φs are 0.295 mm, 1.863 mm, and 3. 539 mm. Moreover, the elongation DL1 at the time of saturated water absorption at 60 ° C. of the acrylic UV-cured organic composite that is the material of the organic composite layer NL1 is 0.38%, and the Young's modulus E1 is 4.3 GPa. Furthermore, the Young's moduli Eg1 and Eg2 of the first and second optical elements L1 and L2 are 62.3 GPa and 96.2 GPa, respectively.

  In the present example, the product of the length T1 along the optical axis 1 at the maximum diameter φs of the organic composite layer NL1 and the elongation DL1 at the time of saturated water absorption is made smaller than a predetermined value, so that the optical under high temperature and high humidity The deformation of the element is reduced.

In this embodiment, a plurality of organic composite layers NL1, NL2,... May be provided on the first optical element L1. The uppermost organic composite layer may be bonded to an optical element via an adhesive to constitute an optical element. The same applies to the embodiments described below.
[Example 2]
Hereinafter, with reference to FIG. 3, the optical element of Example 2 of this invention is demonstrated. FIG. 3 is a cross-sectional view of an essential part of the optical element according to Example 2 of the present invention. In the optical element 12 of FIG. 3, an organic composite layer NL1 is formed as a third optical element on one surface (concave surface) of the first optical element L1. The material composing the organic composite layer NL1 is N-polyvinylcarbazole (Nd = 1.696, νd = 17.7, θgF = 0.69). After that, the second optical element L2 is joined through the UV curable adhesive S1 (Nd = 1.633). The first optical element L1 is made of S-TIH53 (trade name, manufactured by OHARA Corporation), and the second optical element L2 is made of S-FSL5 (trade name, manufactured by OHARA Corporation).

  The light shielding member 3 is disposed on the outer peripheral portion of the second optical element L2, thereby suppressing flare and ghost generated from the outer periphery of the organic composite layer NL1.

  In the optical element 12 of FIG. 3, the maximum diameter (outer diameter of the second optical element L2) φs of the bonding surface that does not include an adhesive other than the adhesive among the bonding surfaces obtained by bonding the optical elements to each other is 11.0 mm. It is. The outer diameter φj of the organic composite layer NL1 is 11.6 mm.

  FIG. 4 is an enlarged view of the outer periphery of the optical element 12 of FIG. In FIG. 4, the lengths T1, Tg1, and Tg2 along the optical axis 1 of the organic composite layer NL1 and the first and second optical elements L1 and L2 at the maximum diameter φs are 0.161 mm, 1.702 mm, and 0, respectively. 750 mm. The elongation DL1 at the time of saturated water absorption at 60 ° C. of N-polyvinylcarbazole, which is the material of the organic composite layer NL1, is 0.03%, and the Young's modulus E1 is 1.8 GPa. Further, the Young's moduli Eg1 and Eg2 of the first and second optical elements L1 and L2 are 96.2 GPa and 62.3 GPa, respectively.

In this example, the optical element under high temperature and high humidity is obtained by making the product of the length T1 along the optical axis at the maximum diameter φs of the organic composite layer NL1 and the elongation DL1 at the time of saturated water absorption smaller than a predetermined value. The deformation is reduced.
[Example 3]
Hereinafter, with reference to FIG. 5, the optical element of Example 3 of this invention is demonstrated. FIG. 5 is a cross-sectional view of an essential part of an optical element according to Example 3 of the present invention. The optical element 13 of FIG. 5 forms an organic composite layer NL1 as a third optical element on one surface (convex surface) of the first optical element L1. The material composing the organic composite layer NL1 is an organic composite (Nd = 1.806, νd = 14.9, θgF = 0.74) in which fine particles are dispersed in a polymer. Thereafter, the second optical element L2 is joined via the UV curable adhesive S1. The material of the UV curable adhesive S1 is a polymer (refractive index Nd = 1.580, Abbe number νd = 37.2) in which TiO ₂ fine particles are dispersed at a volume ratio of 15%. The first optical element L1 is made of S-BSM14 (trade name, manufactured by OHARA Corporation), and the second optical element L2 is made of S-TIH53 (trade name, manufactured by OHARA Corporation).

  In the optical element 13 of FIG. 5, the maximum diameter (inner diameter of the second optical element L2) φs of the joint surface that does not include an adhesive other than the adhesive among the joint surfaces joined between the optical elements is 67.8 mm. is there. The outer diameter φj of the organic composite layer NL1 is 68.8 mm.

  FIG. 6 is an enlarged view of the outer peripheral portion of the optical element 13 of FIG. In FIG. 6, the lengths T1, Tg1, and Tg2 along the optical axis of the organic composite layer NL1, the first and second optical elements L1, L2 at the maximum diameter φs are 0.281 mm, 1.720 mm, and 9. 9092 mm. The elongation DL1 at the time of saturated water absorption at 60 ° C. of the organic composite that is the material of the organic composite layer NL1 is 0.61%, and the Young's modulus E1 is 2.9 GPa. Further, the Young's moduli Eg1 and Eg2 of the first and second optical elements L1 and L2 are 61.4 GPa and 96.2 GPa, respectively.

  In the present example, the product of the length T1 along the optical axis 1 at the maximum diameter φs of the organic composite layer NL1 and the elongation DL1 at the time of saturated water absorption is made smaller than a predetermined value, so that the optical under high temperature and high humidity The deformation of the element is reduced.

  Organic composites such as resins have optical properties that are not found in glass materials, and can therefore contribute to improving the performance of optical systems. However, since it is inferior in environmental resistance, especially in high temperature and high humidity, compared with glass material, measures are required.

The present inventor considered that the size (length) of the portion serving as the entrance of water vapor and the water absorption of the material of the organic composite layer NL1 when the organic composite layer NL1 in the optical element absorbs water and deforms under high temperature and high humidity. It was found that the elongation at time is related to the effect on the optical performance of the optical system. Conditional expression (1) is a relational expression obtained by such knowledge, and shows the influence on the optical performance of the optical system when the organic composite layer NL1 in the optical element absorbs water and deforms under high temperature and high humidity. It is a conditional expression for reducing.

  The technical meaning of the conditional expression (1) will be further described below. Consider the effect of high temperature and high humidity on an optical element in which three optical elements of the optical elements L1 and L2 made of glass materials on both sides and the organic composite layer NL1 sandwiched between the optical elements L1 and L2 are joined. In this case, the entrance of water vapor to the organic composite layer NL1 may be considered. In such an optical element, the entrance of water vapor to the organic composite layer NL1 is the outer peripheral portion of the organic composite layer NL1 that is not sandwiched on both sides. Water vapor gradually permeates from the outer periphery toward the inside (in the optical axis direction). Further, when the organic composite absorbs water, its volume changes and expands. When both sides are sandwiched between other optical elements L1 and L2, the optical elements L1 and L2 are pushed outward.

  Since water absorption gradually permeates into the inside from the outer peripheral portion, the organic composite layer NL1 in the optical element first extends from the outer peripheral portion and deforms the outer optical element. That is, at this time, only the outer peripheral portion of the optical element is locally deformed. When considering an optical element arranged in an optical system, it is local surface deformation that greatly affects the optical performance.

Conditional expression (1) is a conditional expression for reducing local deformation of the optical element. The length Ti in the conditional expression (1) indicates the size (length) of the portion serving as the entrance of water vapor. Further, the water absorption elongation DLi represents the elongation rate at the time of water absorption of the material of the organic composite layer NL1, and if this value is large, the outer optical elements L1 and L2 are easily expanded. The product of Ti and DLi corresponds to the force that deforms the optical element. If this is below a predetermined amount, even if a junction type optical element such as this example is used for a normal optical system, it is practically high temperature. The amount of deformation under high humidity is not a problem. Conditional expression (1) of the present embodiment is obtained based on the above knowledge, and if the upper limit of conditional expression (1) is exceeded, the deformation of the optical element increases, and the optical system is greatly affected. Absent. More preferably, the numerical range of the conditional expression (1) is set as follows.

0.0005 (mm) <Σ (Ti × DLi) <0.19 (mm) (1a)
Here, exceeding the lower limit of the conditional expression (1a) is not preferable because distortion at the time of joining and peeling and cracking at high temperatures are likely to occur.

  In this specification, an optical element is a substance having a property of changing the propagation direction of light by refraction, diffraction or the like, and in a normal optical system, a lens formed of an inorganic material such as glass or an organic material such as plastic. Is this. The organic composite layer corresponds to a cured product of a resin material or a cured product of inorganic particles dispersed in an organic material.

In the present embodiment, among the three or more optical elements constituting the optical element, the length along the optical axis at the maximum diameter φs of the two optical elements whose optical surfaces on one side are exposed to the gas, respectively. Tgn (n = 1, 2) (mm). then,
Σ (Ti × DLi) / (Tg1 + Tg2) <0.025 (2)
It meets the conditions.

  Here, the optical element whose one optical surface is exposed to gas means that the optical element is positioned on the outermost side (object side or image side) of the optical elements.

  Conditional expression (2) is a conditional expression for more reliably reducing the deformation of the optical element. In the optical element of the present embodiment, the organic composite layer NL1 tends to extend due to water absorption. However, at this time, if the thickness of the other optical elements L1 and L2 located on both sides is large, the rigidity of the optical elements L1 and L2 is increased, and the deformation amount can be reduced. Further, in order to reduce the deformation as an optical element, the sum of the thicknesses of the optical elements L1 and L2 may be considered in order to keep the deformation amount below a predetermined amount even if the force of deformation is concentrated. Conditional expression (2) is an expression when considering the deformation force generated in the organic composite layer upon water absorption and the rigidity of the outer optical element. If the upper limit of conditional expression (2) is exceeded, the deformation of the optical element increases. This is not preferable because it greatly affects the optical system. More preferably, the numerical range of the conditional expression (2) is set as follows.

0.0001 <Σ (Ti × DLi) / (Tg1 + Tg2) <0.025 (2a)
Here, exceeding the lower limit of the conditional expression (2a) is not preferable because distortion at the time of joining and peeling or cracking at the time of joining at high temperatures are likely to occur.

In this example, among three or more optical elements constituting the optical element, Young's modulus of two optical elements whose one optical surface is exposed to gas is Egn (n = 1, 2), Let the Young's modulus of the material of the organic composite layer be Ei (i = 1, 2, 3,... N). then,
Σ {(Ti × DLi) × logEi} / {Tg1 × log (Eg1) + Tg2 × log (Eg2)} <0.0090 (3)
It meets the conditions.

  Conditional expression (3) is a conditional expression for more reliably reducing the deformation of the optical element. In general, the deformation of a substance depends on the generated force and material properties such as Young's modulus. Conditional expression (3) is an expression when considering the deformation force generated in the organic composite layer upon water absorption and the rigidity of the outer optical element. If the upper limit of conditional expression (3) is exceeded, the deformation of the optical element increases. This is not preferable because it greatly affects the optical system. More preferably, the numerical range of the conditional expression (3) is set as follows.

0.00001 <Σ {(Ti × DLi) × logEi} / {Tg1 × log (Eg1) + Tg2 × log (Eg2)} <0.0090 (3a)
Here, when the lower limit of conditional expression (3a) is exceeded, the rigidity of the outer optical element is relatively increased. In this case, the deformation at the time of water absorption can be reduced, but the stress escape field at the time of molding or joining is reduced, and the stress tends to concentrate on the organic composite layer NL1. Accordingly, the birefringence of the organic composite layer is increased correspondingly, and bonding peeling and cracking are likely to occur, which is not preferable.

In the optical element of this example, the outer diameter of the organic composite layer NL1 is φj. then,
φs <φj (4)
It meets the conditions.

  Conditional expression (4) reduces the distortion of the surface of the optical element at the time of joining the optical element formed with the organic composite layer and the other optical element, and at high temperature or high temperature and high humidity. It is a conditional expression for reducing generation | occurrence | production of joining peeling. If the conditional expression (4) is satisfied, it is possible to reduce the occurrence of bonding distortion due to the distribution of the thickness of the adhesive layer. Outside the range of the conditional expression (4), it is not preferable because it causes joint distortion and joint peeling.

  Conditional expression (4) is preferably set to the following conditions, so that the occurrence of distortion and peeling of the joints can be reduced even when variations during manufacturing are taken into consideration.

φs + 0.5 <φj (4a)
In addition, the refractive indices at the d-line of the material of the organic composite layer formed on one optical element and the material of the adhesive when joining the second optical element are nr and ns, respectively. At that time, | nr-ns | <0.1 (5)
It is good to satisfy the condition.

  The degree of influence of the surface accuracy of the optical element on the optical performance is determined by the surface accuracy itself and the refractive index difference between the substances on both sides of the surface. If the refractive index difference is large, even a small change in surface accuracy can have a great influence on the optical performance. On the other hand, if the refractive index difference is small, the change in the surface accuracy hardly affects the optical performance. Therefore, especially when the molding difficulty is high, such as a thick resin, it is preferable to reduce the difference in refractive index between substances on both sides of the resin surface in order to suppress the influence of the resin surface accuracy on the optical performance.

  Conditional expression (5) is a conditional expression for reducing the influence of the surface accuracy of the molded organic composite layer NL1 on the optical performance. By satisfying this conditional expression (5), it is easy to achieve good optical performance. Can get to.

  More preferably, when the numerical range of the conditional expression (5) is set as follows, it becomes easy to obtain better optical performance.

| Nr-ns | <0.05 (5a)
More preferably, the numerical range of the conditional expression (5a) is set as follows.

| Nr-ns | <0.01 (5b)
Moreover, the same adhesive may be used when joining with the material of the organic composite layer molded on the optical element. In addition, the effect becomes more remarkable when the following conditional expression (6) is satisfied, where f is the focal length in the air of the organic composite layer formed on the optical element.

f> 0.0 (6)
Also, the anomalous partial dispersibility of the material of the organic composite layer molded on the first optical element is represented by | ΔθgFr |. then,
0.0272 <| ΔθgFr | (7)
It is better to satisfy the following conditional expression.

Here, Abbe number νd, partial dispersion ratio θgFr, and anomalous partial dispersion | ΔθgFr | are g-line (wavelength 435.8 nm), F-line (486.1 nm), d-line (587.6 nm), C-line (656 .3 nm), the refractive indices of the materials are Ng, Nd, NF, and NC in this order. At this time,
νd = (Nd−1) / (NF−NC)
θgF = (Ng−NF) / (NF−NC)
| ΔθgFr | = | θgF − (− 1.665 × 10 ⁻⁷ × νd ³ + 5.213 × 10 ⁻⁵ × νd ² −5.656 × 10 ⁻³ × νd + 7.278 × 10 ⁻¹ ) |
It is.

  Conditional expression (7) is a conditional expression related to the anomalous partial dispersibility of the organic composite. By satisfying this conditional expression (7), it becomes easy to obtain an optical element having a good ability to correct chromatic aberration.

  Conditional expression (7) can be obtained in the following numerical range to obtain better chromatic aberration correction capability.

0.0342 <| ΔθgFr | (7a)
Specific examples of the organic composite satisfying the conditional expression (7) include, for example, an acrylic UV curable resin (Nd = 1.633, νd = 23.0, θgF = 0.68) and N-polyvinylcarbazole (Nd = 1.696, νd = 17.7, θgF = 0.69). Note that the resin is not limited to these as long as it satisfies the conditional expression (7).

Moreover, as an organic composite having characteristics different from those of general glass materials, there is a mixture in which the following inorganic oxide nanoparticles are dispersed in a synthetic resin. That is, there are TiO ₂ (Nd = 2.758, νd = 9.54, θgF = 0.76), ITO (Nd = 1.857, νd = 5.69, θgF = 0.29), and the like.

Among these inorganic oxides, TiO ₂ (Nd = 2.758, νd = 9.54, θgF = 0.76) and ITO (Nd = 1.857, νd = 5.69, θgF = 0.29) fine particles Is dispersed in a synthetic resin at an appropriate volume ratio, an optical material satisfying conditional expression (7) is obtained. Note that the material is not limited to these as long as it satisfies the conditional expression (7).

TiO ₂ is a material used in various applications, and is used as an evaporation material for forming an optical thin film such as an antireflection film in the optical field. In addition, photocatalysts, white pigments and the like, and TiO ₂ fine particles are used as cosmetic materials. ITO is known as a material constituting a transparent electrode, and is usually used for liquid crystal display elements, EL (Electroluminescent) elements, and the like. Moreover, it is used for an infrared shielding element and an ultraviolet shielding element as another application.

In each example, the average diameter of the fine particles dispersed in the resin is preferably about 2 nm to 50 nm in consideration of the influence of scattering and the like, and a dispersant or the like may be added to suppress aggregation. The medium material for dispersing the fine particles is preferably a polymer, and high mass productivity can be obtained by photopolymerization molding or thermal polymerization molding using a mold or the like. The dispersion characteristic N (λ) of the mixture in which the nanoparticles are dispersed can be easily calculated by the following equation derived from the well-known Drude equation. That is, the refractive index N (λ) at the wavelength λ is
N (λ) = [1 + V {Npar (λ) ² -1} + (1-V) {Npoly (λ) ² -1}] ^1/2
It is. Here, λ is an arbitrary wavelength, Npar is the refractive index of the fine particles, Npoly is the refractive index of the polymer, and V is a fraction of the total volume of the fine particles with respect to the polymer volume.

  Hereinafter, specific numerical values of the optical elements of Numerical Examples 1 to 3 are shown in Tables 1 to 3. In each numerical example, i represents the number of the surface counted from the object side in each optical element. In each numerical example, Ri is the radius of curvature of the i-th optical surface (i-th surface), and Di is the axial distance between the i-th surface and the (i + 1) -th surface. Ndi, νdi, and θgFi respectively indicate the refractive index, Abbe number, and partial dispersion ratio of the material of the i-th optical element with respect to the d-line. The effective beam diameter of the i-th optical surface (i-th surface) is also shown. Further, the aspherical shape is such that X is the amount of displacement from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, Let C, D, E ... be the aspheric coefficients of each order,

Represented by Note that “E ± XX” in each aspheric coefficient means “× 10 ± XX”. Table 4 shows the relationship between the above-described conditional expressions and each example. Table 5 shows specific numerical values of T1, Tg1, Tg2, DL1, E1, Eg1, and Eg2 in the above-described conditional expressions.

In Numerical Example 3, an optical element composed of an organic composite layer dispersed in a UV curable resin as a host polymer by 15% by volume ratio of TiO ₂ fine particles is used. The refractive index of the TiO ₂ fine particle-dispersed material is calculated using the value calculated using the aforementioned Drude equation. Table 6 shows the optical characteristics of the materials constituting the organic composite layer used in each example. Table 7 shows the optical properties of the host polymer and TiO ₂ fine particles of the fine particle dispersed material used in Example 3.

Next, an optical system (imaging optical system) having the optical element of the present invention will be described. FIG. 7 is a lens cross-sectional view at the wide-angle end of the zoom lens having the optical element 11 according to the first embodiment of the present invention. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear). In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Bi is the i-th lens group. In the lens cross-sectional view, B1 is a first lens group having a positive refractive power (optical power = reciprocal of focal length), B2 is a second lens group having a negative refractive power, and B3 is a third lens group having a positive refractive power. , B4 is a fourth lens unit having a positive refractive power. SP is an aperture stop, which is disposed on the object side of the third lens unit B3. G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like. IP is an image plane, and when used as a photographing optical system for a video camera or a digital still camera, on the imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, Is provided with a photosensitive surface corresponding to the film surface.

  In this embodiment, each lens unit and the aperture stop SP are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end. Specifically, during zooming from the wide-angle end to the telephoto end, the first lens unit B1 moves to the image side and then moves to the object side. The second lens unit B2 moves to the object side. The third lens unit B3 moves while drawing a part of a convex locus on the object side. The fourth lens unit B4 moves along a locus convex toward the object side. The aperture stop SP moves to the object side independently of each lens group.

  The zoom lens of FIG. 7 is a zoom lens having a zoom ratio of 16 times and an F number of about 2.9 to 4.0. The optical element 11 of Example 1 is used for the first lens unit B1 of this zoom lens. As a result, the chromatic aberration can be satisfactorily corrected mainly on the telephoto side, and a zoom lens having a compact and high performance is obtained for the entire system. Furthermore, various types of zoom lenses with little fluctuation in optical performance under the environment are obtained.

  FIG. 8 is a lens cross-sectional view at the wide-angle end of the zoom lens having the optical element 12 according to the second embodiment of the present invention. The zoom type of this zoom lens is the same as the zoom lens of FIG.

  The zoom lens shown in FIG. 8 is a zoom lens having a zoom ratio of 1.5 and an F number of about 2.9 to 3.6. The optical element 12 of Example 2 is used for the fourth lens unit B4 of the zoom lens. As a result, the chromatic aberration of magnification can be favorably corrected mainly on the wide-angle side, and a zoom lens having a compact and high performance as a whole is obtained. In addition, zoom lenses having various optical performance fluctuations under the environment are obtained.

  FIG. 9 is a lens cross-sectional view of a telephoto lens (optical system) having the optical element 13 according to Embodiment 3 of the present invention. The telephoto lens in FIG. 9 is a telephoto lens including a first lens unit B1 having a positive refractive power, a second lens unit B2 having a negative refractive power, and a third lens unit B3. SP is an aperture stop, and IP is an image plane.

  When focusing from an object at infinity to a close object, the second lens unit B2 is moved to the image side as indicated by an arrow. This telephoto lens has a focal length of 300 mm and an F number of 4.0. The optical element 13 of Example 3 is used on the object side of the aperture stop SP of the telephoto lens. Thereby, chromatic aberration can be corrected satisfactorily, and a high-performance telephoto lens is obtained while achieving a compact tele ratio of 0.68. Furthermore, a telephoto lens (optical system) with little fluctuation in optical performance under various environments is obtained.

  Next, an embodiment of a digital still camera (imaging device) which is an optical apparatus of the present invention using the optical system of the present invention as a photographing optical system will be described with reference to FIG.

  In FIG. 10, 20 is a camera body, and 21 is a photographing optical system constituted by the optical system of the present invention. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image (image) formed by the photographing optical system 21 and is built in the camera body. A memory 23 records information corresponding to the subject image photoelectrically converted by the image sensor 22. Reference numeral 24 denotes a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like. Thus, by applying the optical system of the present invention to an image sensor such as a digital still camera, a small-sized image pickup apparatus having high optical performance is realized.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  NL1 organic composite layer, S1 adhesive, L1 first optical element, L2 second optical element, 11 optical element, 1 optical axis, φs maximum diameter

Claims (11)

An optical element in which a second optical element is bonded to an organic composite layer formed on the first optical element via an adhesive,
In the cross section including the optical axis of the optical element , the diameter of the bonding surface bonded to the organic composite layer of the second optical element is φs, the outer diameter of the organic composite layer is φj, and the bonding surface in at the position of the end portion in the radial direction, wherein the length along the optical axis of the organic composite layer T1 (mm), the water absorption elongation saturation is elongation at water absorption of the material of the organic composite layer DL1 (%), and the time,
φs <φj
T1 × D L1 <0.19 (mm)
An optical element characterized by satisfying the following condition. When at the position of the end portion in the radial direction of the bonding plane, the length along the optical axis of said first and second optical elements respectively Tg1, Tg2 (mm),
(T1 × D L1 ) / (Tg1 + Tg2) <0.025
The optical element according to claim 1, wherein the following condition is satisfied. When the Young's modulus of the material of the first and second optical elements is Eg1, Eg2 , respectively , and the Young's modulus of the material of the organic composite layer is E1 ,
{(T1 × D L1 ) × log E1 } / {Tg1 × log (Eg1) + Tg2 × log (Eg2)} <0.0090
The optical element according to claim 1, wherein the following condition is satisfied. 0.0005 (mm) <T1 × DL1 <0.19 (mm)
The optical element according to any one of claims 1 to 3, wherein the following condition is satisfied. The optical element according to claim 1, wherein the organic composite layer has a positive meniscus shape . When the refractive indices at the d-line of the material of the organic composite layer and the material of the adhesive are respectively nr and ns,
| Nr-ns | <0.1
The optical element according to claim 1, wherein the following condition is satisfied. When the focal length in the air of the organic composite layer is f,
f> 0.0
The optical element according to claim 1, wherein the following condition is satisfied. When the anomalous partial dispersibility of the material of the organic composite layer is | ΔθgFr |
0.0272 <| ΔθgFr |
The optical element according to claim 1, wherein the following condition is satisfied. An optical element in which three or more optical elements are joined,
  The three or more optical elements include an organic composite layer in which two optical surfaces are in contact with other optical elements, and either one of the two optical surfaces of the organic composite layer has an adhesive. Are joined to other optical elements via
  In the cross section including the optical axis of the optical element, the maximum diameter of the bonding surface of the optical element bonded to the organic composite layer via an adhesive is φs, the outer diameter of the organic composite layer is φj, Ti (i = 1, 2,... N) (mm), the length along the optical axis of the organic composite layer at the position of the end portion in the radial direction of the joint surface having the maximum diameter φs. When the water absorption elongation, which is the elongation at the time of saturated water absorption of the material of the organic composite layer, is DLi (i = 1, 2,... N) (%),
       φs <φj
       Σ (Ti × DLi) <0.19 (mm)
An optical element characterized by satisfying the following condition. Optical system comprising an optical element according to any one of claims 1 to 9. An optical apparatus comprising: the optical system according to claim 10 ; and a photoelectric conversion element that receives an image formed by the optical system.