JP2016194609A - Optical element and optical apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element constituted of plural optical components which are joined with each other superior in environment resistance, particularly in heat tolerance, to provide an optical system having the same and an optical apparatus.SOLUTION: An optical element 1 includes: a first optical component 11; a second optical component 12 which is formed of an organic material and is joined with the first optical component 11; and a third optical component 13 which is joined with the second optical component 12. Defining the minimum diameter of the first optical component 11 in a cross section including the optical axis as φh; the diameter in a junction area with the minimum diameter in the junction areas of the first to third optical components as φc; and the maximum diameter of the second optical component 12 as φr, a condition formula of φh<φc≤φr is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical element in which a plurality of optical elements are joined, and an optical system having the optical element.

  In recent years, an optical system (photographing optical system) used for an optical apparatus such as a camera or a video camera is required to be small and light and have high optical performance. Patent Document 1 describes an optical system that can satisfactorily correct chromatic aberration while achieving downsizing by employing an optical element in which an optical element made of inorganic glass and an optical element made of resin are joined. Has been.

JP 2010-117472 A

  However, in the optical element described in Patent Document 1, since the linear expansion coefficients of the inorganic glass and the resin are greatly different from each other, when the environmental temperature changes, a large stress is generated at the joint surface between the optical elements, and peeling or cracking occurs. May occur.

  It is an object of the present invention to provide an optical element that is configured by bonding a plurality of optical elements and has excellent environmental resistance, an optical system having the optical element, and an optical apparatus.

  In order to achieve the above object, an optical element according to one aspect of the present invention includes a first optical element, a second optical element composed of an organic substance bonded to the first optical element, and the second optical element. A third optical element bonded to the optical element, wherein a minimum diameter of the first optical element is φh in a cross section including the optical axis, and each of the bonding surfaces of the first to third optical elements is When the diameter of the joining surface with the smallest diameter is φc and the maximum diameter of the second optical element is φr, the conditional expression φh <φc ≦ φr is satisfied.

  ADVANTAGE OF THE INVENTION According to this invention, the optical element comprised by joining the some optical element and excellent in environmental resistance, especially heat resistance, an optical system and optical apparatus which has it can be provided.

Sectional drawing of the principal part of the optical element which concerns on Example 1 of this invention. Sectional drawing of the principal part of the optical element which concerns on a comparative example The figure which shows the stress which arises in the optical element which concerns on Example 1 and a comparative example Sectional drawing in the focused state to the object of infinity of the optical system which concerns on Example 2 of this invention Sectional drawing of the principal part of the optical element which concerns on Example 3 of this invention. Sectional drawing in the focusing state to the infinite object of the optical system which concerns on Example 4 of this invention Sectional drawing of the principal part of the optical element which concerns on Example 5 of this invention. Sectional drawing in the focused state to the object of infinity of the optical system which concerns on Example 6 of this invention Sectional drawing of the principal part of the optical element which concerns on Example 7 of this invention. Sectional drawing of the principal part of the optical element which concerns on Example 8 of this invention. The perspective view of the optical apparatus which concerns on embodiment of this invention

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Each drawing may be drawn on a different scale for convenience. Moreover, in each drawing, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 1A is a main part schematic diagram (main part cross-sectional view) in a cross section including the optical axis of the optical element 1 according to the present embodiment, and FIG. 1B is an end part of the optical element 1 ( It is the enlarged view to which the peripheral part) was expanded.

The optical element 1 according to the present embodiment is configured by bonding (integrating) three optical elements. Specifically, the optical element 1 includes a first optical element 11, a second optical element 12 made of an organic material bonded to the first optical element 11, and a third bonded to the second optical element 12. The optical element 13 is included. In the cross section including the optical axis, the optical element 1 has a minimum diameter of the first optical element 11 of φh, a diameter of the bonding surface having the smallest diameter among the bonding surfaces (minimum diameter of the bonding surface) φc, When the maximum diameter of the second optical element 12 is φr, the following conditional expression (1) is satisfied.
φh <φc ≦ φr (1)

  The optical element 1 which concerns on this embodiment is equipped with the outstanding environment resistance, implement | achieving size reduction and favorable optical performance by said structure. The optical element 1 will be described in detail below.

  The optical element in the present embodiment is an optical member made of an inorganic material such as glass or an organic material such as plastic (resin) and having a refractive action. In the present embodiment, those having substantially no refractive power, such as an adhesive layer (joining means) for joining the optical elements, a thin film and a coating material for preventing reflection and improving adhesiveness, etc. It is not included in the optical element concerning. The optical element 1 shown in FIG. 1 has a configuration including three optical elements. However, if three or more optical elements including the first to third optical elements are bonded, the optical element 1 The number of is not limited to this.

  The organic material in the present embodiment includes a material obtained by curing a resin material and a material obtained by dispersing and curing inorganic fine particles in an organic material (organic composite). For example, as the organic substance, acrylic, polycarbonate, polyvinyl carbazole, a mixture thereof, or a mixture of them with other organic substance or inorganic substance can be adopted. The second optical element 12 may be composed of a plurality of optical members made of different organic substances.

  The optical element 1 includes a step of forming the first optical element 11 and the third optical element 13, a step of forming the second optical element 12 on the optical surface of the first optical element 11, and a second The optical surfaces of the optical element 12 and the third optical element 13 can be bonded to each other. At this time, the 2nd optical element 12 and the 3rd optical element 13 are joined via a joining member (adhesive etc.) not shown if needed. It should be noted that the second optical element 12 is formed on the optical surface of the third optical element 13 and then bonded to the first optical element 11, or the first optical element 12 is formed in advance after the first optical element 12 is formed. A method of bonding to each of the optical element 11 and the third optical element 13 may be employed.

  The “optical surface” in the present embodiment indicates a portion having a continuous curved surface (a spherical surface having a constant curvature radius or an aspheric surface defined by the same definition formula) in each optical element. In the present embodiment, the optical surfaces of the optical elements are all mirror surfaces. That is, a non-mirror surface for holding each optical element or an end surface in a direction (radial direction) perpendicular to the optical axis in a cross section including the optical axis is a non-optical surface not included in the optical surface. .

  The “diameter of the optical element” in the present embodiment indicates the distance (width) between the end portions of each optical element or the position of the end portion in the radial direction within the cross section including the optical axis. That is, the minimum diameter φh of the first optical element 11 indicates the minimum value of the distance between the end portions in the radial direction of the first optical element 11. In the present embodiment, the value of the diameter of each optical element is equal to or greater than the value of the diameter of the optical surface. In addition, the “bonding surface” in the present embodiment indicates a surface bonded to another optical element in each optical element regardless of the presence or absence of a bonding member.

  In the optical element 1 according to the present embodiment, it is possible to achieve miniaturization and good optical performance by appropriately setting the shape and material of each optical element. However, in general, organic substances are easily deformed due to environmental fluctuations as compared with inorganic materials such as glass. For example, in a high and low temperature environment where the temperature of the atmosphere (air, etc.) has changed significantly with respect to room temperature, an optical element made of an organic material expands or contracts, and its optical characteristics such as its refractive index change. In a high humidity environment, the surface shape of the optical element made of an organic material is deformed by water absorption, and the optical characteristics thereof change.

  At this time, by reducing the thickness of the optical element made of an organic material, the area of the surface exposed to the atmosphere can be reduced to reduce the influence of environmental fluctuations. However, since the organic material has a lower mechanical strength than inorganic glass or the like, there is a concern that when the optical element made of the organic material is made thin, it is deformed when it is held by a lens barrel or the like.

  Therefore, the optical element 1 according to the present embodiment has a configuration in which both of the two optical surfaces (incident surface and outgoing surface) of the second optical element 12 made of an organic material are joined to the optical surfaces of other optical elements. Adopted. Thereby, the optical surface of the second optical element 12 can be prevented from being exposed to the atmosphere, deformation due to environmental fluctuations can be suppressed, and the mechanical strength of the second optical element 12 can be maintained. .

  However, since the linear expansion coefficients of the inorganic glass and the organic substance are greatly different from each other, the second optical element 12 and other optical elements expand and contract unevenly in a high humidity environment. As a result, a large stress is generated at an interface (bonding surface) where the optical elements are bonded to each other, and peeling or cracking of the optical elements occurs. At this time, the stress generated at each joint surface with a change in the environmental temperature is larger as the difference in the linear expansion coefficient between the optical elements is larger, and is generated remarkably at the end of each optical element.

  Therefore, the optical element 1 according to the present embodiment employs a configuration in which a notch portion (recessed portion) 14 is provided in the edge portion of the first optical element 11 in which the optical surface on one side is exposed to the atmosphere. . By providing the notch portion 14 in the first optical element 11, the diameter of the first optical element 11 becomes non-uniform in the optical axis direction, and the maximum diameter and the minimum diameter of the first optical element 11 are different values. become. Thereby, the rigidity of the edge part of the 1st optical element 11 can be made small, and it becomes possible to suppress generation | occurrence | production of the stress in a joint surface.

  As the cutout portion provided as necessary, a shape having an apex with an internal angle θ exceeding 90 ° can be adopted in the cross section including the optical axis, except for an angle formed by the optical surface and the edge portion. For example, a stepped shape provided in the edge portion as shown in FIG. 1, a groove shape including a groove or a depression (concave portion), a chamfered shape, a tapered shape, or the like can be adopted. However, the present invention is not limited to these shapes, and a chamfered shape having a curved end may be employed.

  In addition, when manufacturing the optical element 1 according to the present embodiment, it is necessary to perform alignment (alignment) in the optical axis direction of each optical element. Further, in order to hold the optical element with high accuracy during alignment, it is desirable that the edge portion has a surface substantially parallel to the optical axis. Therefore, when providing the notch 14 in the optical element 1, it is desirable to form a region substantially parallel to the optical axis.

  In this embodiment, the left side of the conditional expression (1) is satisfied by providing the notch 14 at the end of the first optical element 11. Thereby, in the optical element 1, since the thickness (rigidity) of the edge part of each optical element bonded can be reduced, the generation of stress on each bonded surface in a high and low temperature environment is suppressed. It becomes possible. On the other hand, when the left side of the conditional expression (1) is not satisfied, the thickness of the end of the portion where each optical element is joined is substantially the same as when the notch portion 14 is not provided. Can't get.

  Further, the optical element 1 according to this embodiment satisfies the right side of the conditional expression (1) by adopting a configuration in which the end of the second optical element 12 protrudes from between the first and third optical elements. ing. Thereby, since it can comprise so that the joint surface of each optical element may become a continuous curved surface, it becomes possible to suppress that stress concentrates on a part of joint surface at the time of environmental temperature change. On the other hand, when the right side of the conditional expression (1) is not satisfied, the first and third optical elements whose one optical surface is exposed to the atmosphere are outside the diameter φr in the radial direction (outer peripheral part). Are joined to each other. For this reason, the joint surfaces of the first and third optical elements are discontinuous at the diameter φr, and a large stress is generated at that portion.

  Note that the maximum diameter φr of the second optical element 12 may coincide with the outer diameter of the first optical element 11 (maximum diameter including a non-optical surface). In addition, when the diameter φr is larger than the outer diameter of the first or third optical element, the diameter of the bonding surface having the largest diameter among the bonding surfaces (the maximum diameter of the bonding surface) is the first or third. May be equal to the outer diameter of the optical element. The minimum diameter φh of the first optical element 11 is, for example, the distance between the steps closest to the optical axis in the stepped shape as shown in FIG. 1, and the distance between the bottoms (vertices) of the grooves in the groove shape. In the taper shape, the distance between vertices existing at positions closest to the optical axis is shown.

Here, it is desirable that the optical element 1 according to the present embodiment satisfies the following conditional expression (2).
0.5 <φh / φr <0.98 (2)

  In order to prevent the edge of the first optical element 11 from being chipped or from damaging other members at the time of contact, a method of performing a fine chamfering on the edge portion or the like can be considered. However, the chamfered shape provided for such a purpose cannot sufficiently obtain the above-described stress reduction effect. Therefore, it is desirable to reduce the value of the diameter φh to some extent with respect to the diameter φr so as to satisfy the right side of the conditional expression (2). On the other hand, if the value of the diameter φh is too small, it is necessary to enlarge each optical element in the radial direction in order to secure an effective region through which an effective light beam contributing to image formation passes. It is desirable to satisfy the left side of (2).

Furthermore, it is more preferable to satisfy the following conditional expressions (2a) to (2d) in order.
0.6 <φh / φr <0.96 (2a)
0.65 <φh / φr <0.94 (2b)
0.7 <φh / φr <0.93 (2c)
0.75 <φh / φr <0.92 (2d)

The optical element 1 according to the present embodiment has the following conditional expression (3) or (3) when the thicknesses of the second optical element 12 on the optical axis and in the optical axis direction at the diameter φc are trc and tre, respectively. It is desirable to satisfy either one of 4).
0.0005 <tre / trc <0.95 (3)
1.05 <tre / trc <10000 (4)

  Under high and low temperature environments, the greater the amount of change in the radial direction of the thickness of the second optical element 12 in the optical axis direction, the greater the stress generated at each joint surface. Conditional expression (3) is satisfied when the second optical element 12 has a positive refractive power, and conditional expression (4) is satisfied when the second optical element 12 has a negative refractive power. Since the stress is significantly generated at each joint surface, the effect of reducing the stress by satisfying conditional expression (1) is increased.

Furthermore, it is more preferable to satisfy the following conditional expressions (3a) or (4a) to (3d) or (4d) in order.
0.001 <tre / trc <0.90 (3a)
1.2 <tre / trc <2000 (4a)
0.004 <tre / trc <0.80 (3b)
1.5 <tre / trc <1600 (4b)
0.008 <tre / trc <0.60 (3c)
1.8 <tre / trc <1200 (4c)
0.01 <tre / trc <0.50 (3d)
2.0 <tre / trc <1000 (4d)

As described above, since a large stress is likely to be generated at the end portion of each joint surface in a high and low temperature environment, the first optical element is provided by providing the notch portion 14 in order to suppress the generation of the stress. It is desirable to reduce the thickness (rigidity) at the end portion (maximum diameter) 11. On the other hand, if the thickness at the end of the first optical element 11 is made too small, the rigidity at the end of the first optical element 11 becomes weak, and there is a concern that deformation, cracking, and the like may occur. Therefore, when the thickness in the optical axis direction at the maximum diameter and the diameter φh of the first optical element 11 is te and th0, the notch portion 14 is provided so as to satisfy the following conditional expression (5). desirable.
0.005 <te / th0 <0.9 (5)

Furthermore, it is more preferable to satisfy the following conditional expressions (5a) to (5d) in order.
0.01 <te / th0 <0.8 (5a)
0.05 <te / th0 <0.7 (5b)
0.1 <te / th0 <0.6 (5c)
0.15 <te / th0 <0.5 (5d)

Further, in the optical element 1 according to the present embodiment, when the distance in the optical axis direction between the apex (the position of the diameter φh) at which the inner angle of the notch portion 14 exceeds 90 ° and the second optical element 12 is defined as th, It is desirable to satisfy the following conditional expression (6).
0.005 <th / th0 <0.9 (6)

  If the lower limit of conditional expression (6) is not reached, the rigidity at the end of the first optical element 11 provided with the notch portion 14 becomes too small, and deformation or cracking may occur, which is not preferable. . When the upper limit of conditional expression (6) is exceeded, the rigidity at the end of the first optical element 11 provided with the notch 14 becomes too large, and the stress is released due to the distortion of the first optical element 11. Becomes difficult.

Furthermore, it is more preferable to satisfy the following conditional expressions (6a) to (6d) in order.
0.01 <th / th0 <0.8 (6a)
0.05 <th / th0 <0.7 (6b)
0.1 <th / th0 <0.6 (6c)
0.15 <th / th0 <0.5 (6d)

In order to suppress the generation of stress under high and low temperature environments, it is desirable to appropriately set the degree of expansion and contraction of each optical element due to temperature changes. Here, the degree of expansion and contraction of each optical element due to temperature change correlates with the product of the thickness of each optical element in the optical axis direction and the Young's modulus of the material constituting each optical element. Therefore, it is desirable that the optical element 1 according to this embodiment satisfies the following conditional expression (7) when the Young's moduli of the materials constituting the first and second optical elements are Eh and E2, respectively.
0.01 <tre × logE2 / (te × logEh) <10 (7)

  If the lower limit of conditional expression (7) is not reached, the expansion and contraction of the first optical element 11 due to the temperature change at the end of the optical element 1 become too small relative to the expansion and contraction of the second optical element 12. Therefore, it becomes difficult to suppress the stress at the joint surfaces. If the upper limit of conditional expression (7) is exceeded, the expansion and contraction of the first optical element 11 due to the temperature change at the end of the optical element 1 become too large relative to the expansion and contraction of the second optical element 12. Therefore, since there is a concern that the first optical element 11 may be cracked, it is not preferable.

Furthermore, it is more preferable to satisfy the following conditional expressions (7a) to (7c) in order.
0.03 <tre × logE2 / (te × logEh) <6 (7a)
0.04 <tre × logE2 / (te × logEh) <5 (7b)
0.04 <tre × logE2 / (te × logEh) <4 (7c)

The degree of expansion and contraction of each optical element due to temperature change is also correlated with the product of the thickness of each optical element in the optical axis direction and the linear expansion coefficient of the material constituting each optical element. It can be considered by replacing the Young's modulus with the linear expansion coefficient. That is, it is desirable that the optical element 1 according to the present embodiment satisfies the following conditional expression (8) when the linear expansion coefficients of the materials constituting the first and second optical elements are αh and α2, respectively. .
0.01 <tre × logα2 / (te × logαh) <10 (8)

Furthermore, it is more preferable to satisfy the following conditional expressions (8a) to (8c) in order.
0.03 <tre × logα2 / (te × logαh) <6 (8a)
0.04 <tre × logα2 / (te × logαh) <5 (8b)
0.04 <tre × logα2 / (te × logαh) <4 (8c)

In the present embodiment, the notch portion 14 is provided only in the first optical element 11, but the notch portion is provided only in the third optical element 13 as necessary, or the first and first optical elements 11 may be provided. Notch portions may be provided in both of the three optical elements. When the third optical element 13 is provided with a notch, the following conditional expression (1a) may be satisfied when the minimum diameter of the third optical element 13 is φh ′.
φh ′ <φc ≦ φr (1a)

  That is, the effect of the present invention can be obtained as long as at least one of the first and third optical elements is provided with a notch and satisfies at least one of conditional expressions (1) and (1a). Can do. Here, in the optical element having a negative refractive power, the thickness at the end is larger than the thickness on the optical axis, and therefore the rigidity at the end is relatively increased. Therefore, in order to suppress the occurrence of stress on the joint surface, it is desirable to provide a notch in the optical element having negative refractive power as in this embodiment.

  As described above, according to the optical element 1 according to the present embodiment, environmental resistance, downsizing, and good optical performance can be realized. Next, examples of the optical element 1 will be described in detail.

[Example 1]
Hereinafter, the optical element 1 according to Example 1 of the present invention will be described in detail. The configuration of the optical element 1 according to the present example is the same as the configuration according to the above-described embodiment.

  In the present embodiment, the first optical element 11 and the third optical element 13 are optical elements made of inorganic glass and having refractive powers having different signs. The first optical element 11 is made of OHARA S-TIH10 and has negative refractive power. The third optical element 13 is made of OHARA S-BSM 14 and has a positive refractive power. The second optical element 12 is a meniscus optical element made of UV curable resin and having a positive refractive power. The thickness of the second optical element 12 in the optical axis direction decreases from the optical axis toward the end.

  The first optical element 11 and the second optical element 12 are joined in a region within the maximum diameter of the first optical element 11, and the first optical element 11 and the second optical element 12 are connected to each other. The diameter of the first joining surface coincides with the maximum diameter of the first optical element 11. Further, the second optical element 12 and the third optical element 13 are joined in a region within the maximum diameter φr of the second optical element 12, and the second optical element 12 and the third optical element 13 are joined. The diameter of the second joint surface is equal to the maximum diameter φr of the second optical element 12.

  At this time, since the maximum diameter of the first optical element 11 is smaller than the maximum diameter φr of the second optical element 12, the minimum diameter φc of the bonding surface is the diameter of the first bonding surface. In this way, by configuring so that the condition of φc <φr is satisfied, each joint surface becomes a continuous curved surface, so that light is refracted, reflected, and scattered at the end of the second optical element 12 and unnecessary light. Can be suppressed.

  Furthermore, in this embodiment, a step is provided as a notch 14 at the end of the first optical element 11 having a negative refractive power, so that the minimum diameter φh of the first optical element 11 is equal to the bonding surface. It is configured to be smaller than the minimum diameter φc. As described above, by configuring so as to satisfy the condition of φh <φc, the rigidity of the end portion of the first optical element 11 can be relatively reduced, and the stress at each joint surface in a high and low temperature environment Can be suppressed. In addition, holding | maintenance at the time of the alignment of the 1st optical element 11 can be made easy by making the extreme end surface of the 1st optical element 11 into a surface parallel to an optical axis.

  Here, in order to explain the effect of the optical element 1 according to the present embodiment, consider an optical element C1 according to a comparative example as shown in FIG. The optical element C1 according to the comparative example has the same configuration as that of the optical element 1 according to the present example except that the first optical element C11 is not provided with a notch. As shown in FIG. 2, since the minimum diameter φh of the first optical element C11 is equal to the minimum diameter φc of the joint surface, the optical element C1 according to the comparative example does not satisfy the conditional expression (1).

  FIG. 3 shows a bonding surface between the first optical element 11 and the second optical element 12 according to the present embodiment and a bonding surface between the first optical element C11 and the second optical element C12 according to the comparative example. It is a figure which shows the relationship between the stress of an optical axis direction, and the position of radial direction. Here, the stress generated when a temperature change from room temperature to + 40 ° C. is calculated using the finite element method. In FIG. 3, the solid line corresponds to the present example, and the broken line corresponds to the comparative example. When the stress takes a positive value, it indicates a tensile stress, and when the stress takes a negative value, it indicates a compressive stress. .

  As shown in FIG. 3, the stress value according to the present example suddenly changes before and after the minimum diameter φh of the first optical element 11, and the stress according to the comparative example is observed at the minimum diameter φc of the joint surface. It is 41% smaller than the value. From this, it can be seen that by providing the first optical element 11 with the notch 14, it is possible to suppress the generation of stress on the joint surface.

[Example 2]
FIG. 4 is a cross-sectional view of a main part of the optical system 2 according to the second embodiment that includes the optical element 1 according to the first embodiment. In FIG. 4, IP indicates an image plane, OA indicates an optical axis, SP indicates an aperture stop, and an arrow indicates the direction of the optical axis of each lens unit and the aperture stop SP during focusing from infinity to a short distance. The movement trajectory is shown.

  The optical system 2 according to this embodiment includes a first lens unit (lens group) L1 having a positive refractive power, a second lens unit L2 having a positive refractive power, and a positive refraction, which are arranged in order from the object side to the image side. A third lens unit L3 of force. The second lens unit L2 includes the optical element 1 according to Example 1, and the optical element 1 is disposed so that the convex surface of the second optical element 12 faces the image side. In the optical system 2, the interval between the lens units changes during focusing.

  In the optical element 1, the second optical element 12 made of UV curable resin has an abnormal partial dispersion, and the partial dispersion ratio θgF with respect to the g-line and F-line is larger than that of a general glass material. The optical system 2 can correct axial chromatic aberration and lateral chromatic aberration satisfactorily by employing the optical element 1 having such anomalous partial dispersion.

  In the optical element 1, the maximum diameter of the third optical element 13 is larger than the maximum diameters of the second optical element 12 and the first optical element 11. Therefore, in the optical system 2, when the optical element 1 is held (fixed) by holding means such as a lens barrel, the optical element 1 can be held only through the third optical element 13. It is possible to suppress distortion of the optical surface when it expands and contracts.

  In this embodiment, the optical element 1 is held only through the third optical element 13, but is held via at least one of the first optical element 11 and the third optical element 13. However, the configuration is not limited to this. The optical system 2 according to the present embodiment is a coaxial system in which the center of curvature of each optical surface and the center position of the image surface are arranged on the optical axis, but the optical system 2 is a non-coaxial system as necessary. Also good. In addition, the optical system 2 according to the present embodiment employs a configuration having only one optical element 1, but is not limited thereto, and may have a configuration having a plurality of optical elements 1. At this time, any optical element that satisfies the conditional expression (1) may be used instead of the optical element 1.

[Example 3]
FIG. 5A is a cross-sectional view of the main part of the optical element 3 according to Example 3 of the present invention, and FIG. 5B is an enlarged view in which the end of the optical element 3 is enlarged. The optical element 3 according to the present embodiment is configured by joining three optical elements in the same manner as the optical element 1 according to the first embodiment. However, the material and shape of each optical element are different from those of the optical element 1.

  In the present embodiment, the first optical element 31 is a negative meniscus optical element made of S-TIH1 manufactured by OHARA and having a concave surface facing the object side. The third optical element 33 is made of S-LAL7 manufactured by OHARA, and is a biconvex optical element having a positive refractive power. The second optical element 32 is a biconcave optical element having a negative refractive power and made of a mixture in which ITO (Indium-Tin-Oxide) fine particles are dispersed in PMMA at a volume ratio of 15%. The thickness of the second optical element 32 in the optical axis direction increases from the optical axis toward the end.

  Also in the present embodiment, as in the first embodiment, a notch 34 is provided at the end of the first optical element 31 having a negative refractive power. In the present embodiment, the cutout portion 34 is formed by combining the stepped shape and the groove shape as shown in the first embodiment. Since the optical element 3 according to the present example satisfies the conditional expression (1) similarly to the optical element 1 according to the first example, it is possible to suppress the generation of stress at the joint surface. Yes.

[Example 4]
FIG. 6 is a cross-sectional view of a main part of the optical system 4 according to the fourth embodiment having the optical element 3 according to the third embodiment. The arrows in FIG. 6 indicate the movement trajectory of each lens unit and aperture stop SP in the optical axis direction during focusing from infinity to a short distance. In the optical system 4 according to this example, the description of the same configuration as that of the optical system 2 according to Example 2 is omitted.

  The optical system 2 according to the present embodiment is arranged in order from the object side to the image side, the first lens unit L1 having a positive refractive power, the second lens unit L2 having a positive refractive power, and a third lens having a positive refractive power. The lens unit L3. The third lens unit L3 includes the optical element 3 according to the third embodiment. In the optical system 4, the distance between the lens units changes during focusing.

  In the optical element 3, the second optical element 32 made of a mixture of PMMA and ITO fine particles has an anomalous partial dispersion, and the partial dispersion ratio θgF with respect to the g-line and F-line is compared with a general glass material. And small. The optical system 4 can correct axial chromatic aberration and lateral chromatic aberration satisfactorily by adopting the optical element 3 having such anomalous partial dispersion.

[Example 5]
FIG. 7A is a cross-sectional view of the main part of the optical element 5 according to the fifth embodiment of the present invention, and FIG. 7B is an enlarged view of an end portion of the optical element 5. Unlike the optical elements 1 and 3 according to the first and third embodiments, the optical element 5 according to the present embodiment employs a configuration in which the second optical element 52 made of an organic material includes two optical members.

  In this embodiment, the first optical element 51 is a negative meniscus optical element made of S-TIH 53 of OHARA and having a convex surface facing the object side. The third optical element 53 is made of OHARA S-FSL5, and is a biconvex optical element having positive refractive power. The second optical element 52 includes a first optical member 52a made of a UV curable resin and a second optical member 52b made of a mixture in which ITO fine particles are dispersed in PMMA at a volume ratio of 10%. Consists of two optical members.

  The first optical member 52a is a positive meniscus optical member having a convex surface facing the object side, and its thickness in the optical axis direction decreases from the optical axis toward the end. The second optical member 52b is a negative meniscus optical member having a convex surface facing the object side, and its thickness in the optical axis direction increases from the optical axis toward the end.

  Also in the present embodiment, as in the first and third embodiments, a notch 54 is provided at the end of the first optical element 51 having a negative refractive power. In the present embodiment, as in the third embodiment, a shape in which a stepped shape and a groove shape are combined is adopted as the notch portion 54. And since the optical element 5 which concerns on a present Example satisfy | fills conditional expression (1), it is possible to suppress generation | occurrence | production of the stress in a joint surface.

  In the present embodiment, the second optical element 52 is configured by two optical members. However, the second optical element 52 is configured by three or more optical members as necessary. It may be adopted. Moreover, you may form a diffraction grating in the interface of the optical members which comprise the 2nd optical element 52 as needed.

[Example 6]
FIG. 8 is a cross-sectional view of a main part of the optical system 6 according to the sixth embodiment having the optical element 5 according to the fifth embodiment. In FIG. 8, FC indicates a flare cut stop. The arrows in FIG. 8 indicate the movement trajectory of each lens unit in the optical axis direction during zooming from the wide-angle end to the telephoto end. In the optical system 6 according to the present embodiment, the description of the same configuration as that of the optical systems 2 and 4 according to the second and fourth embodiments will be omitted.

  The optical system 6 according to this embodiment includes a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side to the image side. The unit L3 includes a fourth lens unit L4 having a positive refractive power. The first lens unit L1 includes the optical element 5 according to the fifth embodiment. In the optical system 6, when zooming, the interval between the lens units changes, and when performing focusing, the position of the fourth lens unit L4 in the optical axis direction changes.

  In the optical element 5, the second optical element 52 has anomalous partial dispersion. The partial dispersion ratio θgF regarding the g-line and the F-line of the first optical member 52a made of the UV curable resin is larger than that of a general glass material. The partial dispersion ratio θgF regarding the g-line and the F-line of the second optical member 52b made of a mixture of PMMA and ITO fine particles is smaller than that of a general glass material. The optical system 6 can correct axial chromatic aberration and lateral chromatic aberration satisfactorily by employing the optical element 5 having such anomalous partial dispersion.

  In the optical element 5, the maximum diameter of the first optical element 51 is larger than the maximum diameters of the second optical element 52 and the third optical element 53. Therefore, in the optical system 6, when the optical element 5 is held by holding means such as a lens barrel, the optical element 5 can be held only through the first optical element 51, so that each optical element expands and contracts due to a temperature change. It becomes possible to suppress distortion of the optical surface at the time. In this embodiment, the optical element 5 is held only through the first optical element 51, but is held via at least one of the first optical element 51 and the third optical element 53. However, the configuration is not limited to this.

[Example 7]
FIG. 9A is a main part sectional view of the optical element 7 according to Example 7 of the present invention, and FIG. 9B is an enlarged view of an end part of the optical element 7. The optical element 7 according to the present embodiment is configured by joining three optical elements in the same manner as the optical element 1 according to the first embodiment. However, the material and shape of each optical element are different from those of the optical element 1.

  In the present embodiment, the first optical element 71 is a biconcave optical element made of S-TIH10 manufactured by OHARA and having negative refractive power. The third optical element 73 is a biconvex optical element made of S-BSM14 manufactured by OHARA and having a positive refractive power. The second optical element 72 is a meniscus optical element made of UV curable resin and having a positive refractive power with a concave surface facing the object side. The thickness of the second optical element 72 in the optical axis direction decreases from the optical axis toward the end.

  Also in the present embodiment, as in the first embodiment, a notch 74 is provided at the end of the first optical element 71 having a negative refractive power. In this embodiment, unlike the first embodiment, a V-groove is provided as the notch 74. And since the optical element 7 which concerns on a present Example satisfy | fills conditional expression (1) similarly to the optical element 1 which concerns on Example 1, it becomes possible to suppress generation | occurrence | production of the stress in a joint surface. Yes.

[Example 8]
FIG. 10A is a cross-sectional view of the main part of the optical element 8 according to Example 8 of the present invention, and FIG. 10B is an enlarged view of an end portion of the optical element 8. The optical element 8 according to the present embodiment is configured by bonding three optical elements in the same manner as the optical element 1 according to the first embodiment. However, the material and shape of each optical element are different from those of the optical element 1.

  In this embodiment, the first optical element 81 is a biconcave optical element made of S-TIH10 manufactured by OHARA and having negative refractive power. The third optical element 83 is made of S-BSM14 manufactured by OHARA, and is a biconvex optical element having a positive refractive power. The second optical element 82 is a meniscus optical element made of UV curable resin and having a positive refractive power with a concave surface facing the object side. The thickness of the second optical element 82 in the optical axis direction decreases from the optical axis toward the end.

  Also in the present embodiment, as in the first embodiment, a notch 84 is provided at the end of the first optical element 81 having a negative refractive power. In this embodiment, unlike the first embodiment, a tapered shape is adopted as the notch portion 84. In the present embodiment, the taper angle (angle formed with the optical axis) of the tapered shape is set to 21 degrees. And since the optical element 8 which concerns on a present Example satisfy | fills conditional expression (1) similarly to the optical element 1 which concerns on Example 1, it becomes possible to suppress generation | occurrence | production of the stress in a joint surface. Yes.

In each of the embodiments described above, when a material obtained by mixing fine particles of an inorganic oxide (such as TiO ₂ or ITO) with a solid material is used as the material of the second optical element, light is emitted by the fine particles of the inorganic oxide. It is necessary to suppress the scattering. For this purpose, it is preferable to set the particle diameter of the fine particles within a range of 2 nm to 50 nm. Further, a dispersant or the like may be added in order to suppress aggregation when the inorganic oxide fine particles are mixed with the solid material.

  Here, in a mixture in which fine particles are dispersed in a solid material (base material), the refractive index n (λ) with respect to the wavelength λ can be derived from a relational expression based on Maxwell-Garnet theory. Specifically, the refractive index n (λ) is expressed as follows when the relative permittivity of the solid material is εm, the relative permittivity of the fine particles is εp, and the fraction of the total volume of the fine particles with respect to the volume of the solid material is η. Based on the relative dielectric constant εav of the mixture defined by the equation (9), it is expressed as the following equation (10).

  Table 1 shows numerical values and values of the middle sides of the conditional expressions (1) to (8) for the optical elements according to the above-described embodiments.

  Table 2 shows physical property values of the second optical element according to each example.

Next, specific numerical data will be shown in numerical examples 1 to 8 corresponding to the first to eighth embodiments described above. In each numerical example, m represents the number of the surface counted from the light incident side, rm represents the radius of curvature of the mth optical surface (mth surface), and dm represents the mth surface and (m + 1) th. ) An on-axis distance (distance on the optical axis) between the surfaces. Each of ndm and νdm represents the refractive index and Abbe number of the m-th optical member with respect to the d-line. Here, the refractive indices for the F line (486.1 nm), d line (587.6 nm), and C line (656.3 nm) of the Fraunhofer line are NF, Nd, and NC, respectively, and the Abbe number νd for the d line is as follows: The following equation (11) is defined.
νd = (Nd−1) / (NF-NC) (11)

In each numerical example, an aspherical optical surface is given an asterisk (*) after the surface number. In addition, “e ± XX” in each aspheric coefficient means “× 10 ^{± XX} ”. The aspherical shape of the optical surface is such that the amount of displacement from the surface vertex in the optical axis direction is X, the height from the optical axis in the direction perpendicular to the optical axis direction is h, the paraxial radius of curvature is r, the conic constant is k, When the aspheric coefficients are B, C, D, E,...

(Numerical example 1)
Surface number rd nd vd Effective diameter on object side Effective diameter on image side
1 333.607 4.76 1.60311 60.6-38.00
2 -61.478 1.00 1.63556 22.4 38.00 35.80
3 -45.844 1.59 1.72825 28.5 35.80 35.00
4 32.360 28.40-

(Numerical example 2)
Surface number rd nd vd Effective diameter
1 72.080 2.65 1.58313 59.4 50.00
2 * 25.512 13.45 41.33
3 -96.609 2.50 1.48749 70.2 40.75
4 66.944 3.13 39.59
5 175.419 5.63 1.91082 35.3 39.68
6 -77.862 3.86 39.54
7 -44.606 2.30 1.69895 30.1 38.10
8 -178.782 0.15 38.34
9 62.257 8.11 1.59522 67.7 38.01
10 -59.637 (variable) 37.40
11 48.797 4.61 2.00100 29.1 35.03
12 9939.838 1.32 34.39
13 333.607 4.76 1.60311 60.6 32.67
14 -61.478 1.00 0.00000 0.0 31.18
15 -45.844 1.59 1.72825 28.5 30.99
16 32.360 (variable) 27.20
17 (Aperture) ∞ 7.17 26.60
18 -21.286 1.40 1.69895 30.1 25.93
19 177.619 4.21 1.59522 67.7 28.93
20 -52.749 0.15 29.70
21 97.355 7.19 1.59522 67.7 31.37
22 -35.549 0.15 32.12
23 * -158.409 4.26 1.85400 40.4 33.44
24 -43.693 (variable) 34.50
Image plane ∞
Aspheric data 2nd surface
K = 0.00000e + 000 B = -1.26283e-006 C = -4.27073e-009 D = 5.04254e-012 E = -1.12945e-014
23rd page
K = 0.00000e + 000 B = -6.35905e-006 C = -4.47403e-010 D = -4.21764e-012 E = 2.36025e-015
Various data focal length 34.30
F number 1.45
Angle of View 32.24
Statue height 21.64
Total lens length 131.15
BF 39.00
Object distance infinity 1750 300
d10 7.06 6.32 0.80
d18 5.50 5.50 5.50
d26 39.00 39.74 45.26

(Numerical Example 3)
Surface number rd nd vd Effective diameter on object side Effective diameter on image side
1 -20.859 1.40 1.71736 29.5-26.90
2 -526.799 0.05 1.54402 19.7 31.50 33.00
3 150.060 5.37 1.69680 55.5 33.00 35.00
4 -49.018 35.00

(Numerical example 4)
Surface number rd nd vd Effective diameter
1 55.052 1.39 1.58313 59.4 50.00
2 * 25.148 13.72 42.43
3 -106.406 2.03 1.51633 64.1 42.14
4 50.816 3.68 40.61
5 113.354 6.23 1.91082 35.3 40.83
6 -89.012 7.06 40.66
7 -44.957 2.03 1.69895 30.1 37.20
8 -336.413 0.17 37.42
9 69.607 8.37 1.59522 67.7 37.46
10 -50.652 (variable) 37.88
11 43.189 5.19 2.00100 29.1 35.48
12 1039.705 0.14 34.68
13 78.829 5.45 1.59522 67.7 32.76
14 -62.807 1.54 1.85026 32.3 31.30
15 28.545 (variable) 27.08
16 (Aperture) ∞ 7.24 26.48
17 -20.859 1.40 1.71736 29.5 25.82
18 -526.799 0.05 1.54402 19.6 28.63
19 150.060 5.37 1.69680 55.5 29.15
20 -49.018 0.15 30.23
21 122.455 6.57 1.65160 58.5 31.49
22 -37.407 0.19 32.50
23 * -82.464 3.70 1.85400 40.4 33.20
24 -40.578 (variable) 34.31
Image plane ∞
Aspheric data 2nd surface
K = 0.00000e + 000 B = -1.17609e-006 C = -3.67097e-009 D = 4.77220e-012 E = -1.15057e-014
24th page
K = 0.00000e + 000 B = -6.57816e-006 C = -1.77654e-010 D = -5.21093e-012 E = 4.55629e-015
Various data focal length 34.30
F number 1.45
Angle of View 32.24
Statue height 21.64
Total lens length 133.69
BF 39.00
Object distance infinity 1750 300
d10 7.10 6.36 0.80
d15 5.92 5.92 5.92
d24 39.00 39.74 45.30

(Numerical example 5)
Surface number rd nd vd Effective diameter on object side Effective diameter on image side
1 64.220 1.75 1.84666 23.8-32.50
2 29.865 0.01 1.52144 46.6 34.50 30.90
3 29.865 0.94 1.63556 22.8 30.90 31.50
4 35.779 0.05 1.52651 24.8 31.50 31.50
5 32.261 5.30 1.48749 70.2 31.50 33.00
6 -1189.473 0.10 33.00-

(Numerical example 6)
Surface number rd nd vd Effective diameter
1 64.220 1.75 1.84666 23.8 32.00
2 29.865 0.01 1.52144 46.6 29.84
3 29.865 0.94 1.63556 22.8 29.84
4 35.779 0.05 1.52651 24.8 29.78
5 32.261 5.30 1.48749 70.2 29.66
6 -1189.473 0.10 29.22
7 32.482 3.23 1.77250 49.6 28.20
8 140.080 (variable) 27.86
9 51.133 0.90 1.88300 40.8 16.81
10 8.275 3.81 12.93
11 -38.963 0.75 1.60738 56.8 12.89
12 21.403 1.00 12.75
13 15.132 1.84 1.92286 18.9 13.20
14 36.354 (variable) 12.92
15 (Aperture) ∞ (Variable) 6.29
16 * 7.801 2.27 1.55880 62.5 7.38
17 268.502 2.06 7.12
18 20.932 0.70 1.80610 33.3 6.94
19 7.517 0.62 6.71
20 34.492 1.46 1.56873 63.1 6.71
21 -61.306 (variable) 6.99
22 ∞ (variable) 7.85
23 16.816 2.59 1.72916 54.7 9.33
24 -10.631 0.80 1.73800 32.3 9.16
25 1995.188 (variable) 9.00
Image plane ∞
Aspheric data 16th surface
K = -4.19230e-001 B = -5.01477e-005 C = -1.48975e-006 D = 1.05713e-007 E = -3.27034e-009
Various data zoom ratio 11.59
Wide angle Medium telephoto focal length 6.15 20.45 71.28
F number 2.88 3.62 3.44
Angle of view 30.09 9.89 2.86
Statue height 3.56 3.56 3.56
Total lens length 81.87 85.95 87.02
BF 12.65 16.24 11.72
d 8 1.68 18.58 31.68
d14 26.21 12.62 1.42
d15 7.07 2.00 2.00
d21 1.10 2.77 4.09
d22 2.99 3.56 5.93
d25 12.65 16.24 11.72

(Numerical example 7)
Surface number rd nd vd Effective diameter on object side Effective diameter on image side
1 333.607 4.76 1.60311 60.6-38.00
2 -61.478 1.00 1.63556 22.4 38.00 35.80
3 -45.844 1.59 1.72825 28.5 35.80 35.00
4 32.360 28.40-

(Numerical example 8)
Surface number rd nd vd Effective diameter on object side Effective diameter on image side
1 333.607 4.76 1.60311 60.6-38.00
2 -61.478 1.00 1.63556 22.4 38.00 35.80
3 -45.844 1.59 1.72825 28.5 35.80 35.00
4 32.360 28.40-

[Optical equipment]
FIG. 11 is a main part schematic diagram of an imaging device (digital still camera) as an optical apparatus according to an embodiment of the present invention. The imaging apparatus according to the present embodiment receives the light from the camera main body 90, the photographing optical system 91 including the optical element according to any of the above-described embodiments, and the photographing optical system 91, and the photographing optical system 91 A light receiving element (imaging element) 92 that photoelectrically converts the formed subject image.

  According to the imaging apparatus according to the present embodiment, by employing the optical element according to any of the above-described examples, high optical performance can be obtained, and a high-quality image can be acquired. . As the light receiving element 92, a solid-state imaging device (electronic imaging device) such as a CCD sensor or a CMOS sensor can be used. At this time, it is possible to improve the image quality of the output image by electrically correcting various aberrations such as distortion and chromatic aberration of the image acquired by the light receiving element 92.

  The optical elements according to the above-described embodiments are not limited to the digital still camera shown in FIG. 11, but are used in various optical devices such as a silver salt film camera, a video camera, a telescope, binoculars, a projector, and a digital copying machine. Can be applied.

  The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes can be made within the scope of the gist.

DESCRIPTION OF SYMBOLS 1 Optical element 11 1st optical element 12 2nd optical element 13 3rd optical element

The present invention relates to an optical element in which a plurality of optical elements are joined and an optical apparatus having the optical element.

The present invention aims at providing yet structure in which a plurality of optical elements are bonded, excellent optical element environmental resistance, optical science instruments that have a it.

According to the present invention, it is possible to provide yet structure in which a plurality of optical elements are bonded, excellent optical element environmental resistance, optical science instruments that have a it.

The organic material in the present embodiment includes a material obtained by curing a resin material and a material obtained by dispersing and curing inorganic fine particles in an organic material (organic composite). For example, as the organic substance, acrylic, polycarbonate, polyvinyl carbazole, a mixture thereof, or a mixture of them with other organic substance or inorganic substance can be adopted. The second optical element 12 may be composed of a plurality of optical members made of different organic substances from each other.

However, since the linear expansion coefficients of the inorganic glass and the organic material are greatly different from each other, the second optical element 12 and other optical elements expand and contract unevenly in a high and low temperature environment. As a result, a large stress is generated at an interface (bonding surface) where the optical elements are bonded to each other, and peeling or cracking of the optical elements occurs. At this time, the stress generated at each joint surface with a change in the environmental temperature is larger as the difference in the linear expansion coefficient between the optical elements is larger, and is generated remarkably at the end of each optical element.

The optical system 6 according to this embodiment includes a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side to the image side. The lens unit L3 and the fourth lens unit L4 having a positive refractive power are configured. The first lens unit L1 includes the optical element 5 according to the fifth embodiment. In the optical system 6, when zooming, the interval between the lens units changes, and when performing focusing, the position of the fourth lens unit L4 in the optical axis direction changes.

Next, specific numerical data will be shown in numerical examples 1 to 8 corresponding to the first to eighth embodiments described above. In each numerical example, m represents the number of the surface counted from the light incident side, rm represents the radius of curvature of the mth optical surface (mth surface), and dm represents the mth surface and (m + 1) th. ) An on-axis distance (distance on the optical axis) between the surfaces. Each of ndm and νdm indicates the refractive index and Abbe number of the medium between the m-th surface and the (m + 1) -th surface with respect to the d-line. Here, the refractive indices for the F line (486.1 nm), d line (587.6 nm), and C line (656.3 nm) of the Fraunhofer line are NF, Nd, and NC, respectively, and the Abbe number νd for the d line is as follows: defined as in equation (11) of.

Claims (18)

A first optical element, a second optical element made of an organic material bonded to the first optical element, and a third optical element bonded to the second optical element,
In the cross section including the optical axis, the minimum diameter of the first optical element is φh, the diameter of the bonding surface having the smallest diameter among the bonding surfaces of the first to third optical elements is φc, and the second When the maximum diameter of the optical element is φr,
φh <φc ≦ φr
An optical element that satisfies the following conditional expression: 0.5 <φh / φr <0.98
The optical element according to claim 1, wherein the following conditional expression is satisfied. When the thicknesses on the optical axis of the second optical element and in the optical axis direction at the diameter φc are trc and tre, respectively,
0.0005 <tre / trc <0.95
The optical element according to claim 1, wherein the following conditional expression is satisfied. When the thicknesses on the optical axis of the second optical element and in the optical axis direction at the diameter φc are trc and tre, respectively,
1.05 <tre / trc <10000
The optical element according to claim 1, wherein the following conditional expression is satisfied. When the maximum diameter of the first optical element and the thickness in the optical axis direction at the diameter φh are te and th0, respectively.
0.005 <te / th0 <0.9
The optical element according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.   The at least one of the first and third optical elements has an apex having an inner angle exceeding 90 ° except for an angle formed by an optical surface and an end portion in a radial direction in the cross section. The optical element according to any one of 1 to 5.   The optical element according to claim 6, wherein the apex exists at a position of the diameter φh in the radial direction. When the distance in the optical axis direction between the second optical element and the apex is th, and the thickness in the optical axis direction at the diameter φh of the first optical element is th0,
0.005 <th / th0 <0.9
The optical element according to claim 6, wherein the following conditional expression is satisfied. The thickness in the optical axis direction at the maximum diameter of the first optical element is te, the thickness in the optical axis direction at the diameter φc of the second optical element is tre, and the first and second optical elements are configured. When the Young's modulus of the material to be performed is Eh and E2, respectively,
0.01 <tre × logE2 / (te × logEh) <10
The optical element according to claim 1, wherein the following conditional expression is satisfied. The thickness in the optical axis direction at the maximum diameter of the first optical element is te, the thickness in the optical axis direction at the diameter φc of the second optical element is tre, and the first and second optical elements are configured. When the linear expansion coefficients of the materials to be made are αh and α2, respectively,
0.01 <tre × logα2 / (te × logαh) <10
The optical element according to claim 1, wherein the following conditional expression is satisfied.   The optical element according to claim 10, wherein each joint surface is a continuous curved surface. When the minimum diameter of the third optical element is φh ′,
φh ′ <φc ≦ φr
The optical element according to claim 1, wherein the following conditional expression is satisfied.   The optical element according to claim 1, wherein a maximum diameter of the first optical element is the same as the diameter φc.   14. The optical element according to claim 1, wherein a maximum diameter of the first optical element is smaller than the diameter φr.   The optical element according to claim 1, wherein the first optical element has a negative refractive power.   The optical element according to any one of claims 1 to 15, wherein the first optical element and the third optical element have refractive powers having different signs.   An optical system comprising: the optical element according to claim 1; and an aperture stop disposed on the object side or the image side of the optical element.   An optical apparatus comprising: the optical system according to claim 17; and a light receiving element that receives light from the optical system.

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