JP2012042791A - Optical system and optical device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system capable of easily obtaining high optical performance by preventing unnecessary stress from being added to a cemented lens when the lens is held in a lens holding frame, and reducing the occurrence of double refraction of a material due to the stress.SOLUTION: In an optical system including a cemented lens, an image side lens of the cemented lens has an outer diameter larger than that of an object side lens, and a periphery of the image side lens has a positioning part for determining a position of the cemented lens in an optical axis direction. A distance L on the optical axis from an image surface to a lens surface closest to the object side in the cemented lens and a focal distance f of the optical system are appropriately set, respectively.

Description

  The present invention relates to an optical system and an optical apparatus having the optical system, and is suitable for a photographing optical system such as a single-lens reflex camera, a digital still camera, a digital video camera, and a TV camera.

  In recent years, in an imaging apparatus such as a digital single-lens reflex camera, an increase in the number of pixels of an imaging element has progressed, and accordingly, optical performance required for a photographing optical system has become stricter. Therefore, means for further improving the optical design performance and a method for improving the lens holding accuracy and reducing the performance deterioration due to the lens position error have been studied (Patent Documents 1 and 2). Also, for lenses using resin materials, the photoelastic coefficient and Young's modulus are very large, so when holding the lens, deformation from the surface and birefringence occur due to stress from the holding mechanism, resulting in degradation of imaging performance. easy.

  For this reason, Patent Document 1 and Patent Document 2 also report a method for avoiding the application of stress in the lens effective portion when the resin lens is held. Here, attention is focused on a long focal length telephoto lens that magnifies and captures a subject at a long distance. Since a telephoto lens is required to magnify and photograph a distant subject with high definition to a finer detail, the demand for optical performance is much higher than lenses in other focal length regions. On the other hand, the telephoto lens is also strongly demanded to be small and light at the same time for convenience in carrying and photographing.

  Therefore, conventionally, as a lens type that achieves both small size and light weight and high performance, a so-called telephoto type optical system in which a first lens group having a positive refractive power and a second lens group having a negative refractive power are arranged in this order from the object side. Many systems have been reported (Patent Document 3). Patent Document 3 discloses a telephoto lens in which the tele ratio (ratio of the total length to the focal length) is smaller than 1, and the optical performance is improved to approach the diffraction limit.

Japanese Patent Laid-Open No. 10-227961 Japanese Patent Laid-Open No. 11-052108 Japanese Patent Laid-Open No. 05-027163

  In normal telephoto lenses such as Patent Document 3, in order to achieve a reduction in size and weight, the power of each lens is increased to the extent that optical performance is not deteriorated, and the total lens length and effective lens system are reduced. Therefore, the performance of such a telephoto lens is likely to deteriorate when a manufacturing error occurs, and one of the important points is how to suppress the manufacturing error in order to obtain a high-definition optical system. When the optical system is a single thin system, the axial light beam enters as a parallel light beam of f / FNO width from infinity, and convergent power is obtained by the thin system, and it is separated by the focal length of the optical system. The image is formed at the position.

  The same applies to normal thick optical systems, and divergence and convergence are repeated according to the power of each lens element, but basically a parallel light beam from infinity is reflected from the rear principal point position of the optical system. Convergence toward an image plane separated by the focal length. Therefore, as shown in FIG. 10, in a telephoto lens having a tele ratio smaller than 1 (hereinafter referred to as a telephoto type), the rear principal point position is closer to the object side than the most object side lens of the optical system. The ray height h is the largest with the most object side lens and converges toward the image plane. For this reason, most of the lens on the object side from the vicinity of the stop has a large area through which the axial luminous flux passes with respect to the effective range of the lens.

  Further, when seeking to reduce the size and weight of the entire system, the outer diameter of each lens is designed to be as small as possible while leaving a minimum lens holding portion with respect to the effective beam diameter. Partial degradation of the surface accuracy around the pupil of the lens affects the degradation of the entire screen, so if the polishing accuracy of the periphery of the lens near the stop decreases from the vicinity of the aperture, the vicinity of the most peripheral pupil of the axial luminous flux An error occurs in the image forming position of the light beam, and the entire screen becomes a flare image.

  As described above, telephoto type telephoto lenses require strict tolerance management because the surface accuracy of the peripheral portion of each lens is greatly related to the imaging performance as compared with other lens types. Here, when the present inventor demanded a higher resolution lens, the influence of surface deformation and birefringence when holding the lens, which has been a concern in the conventional plastic material, is an amount that cannot be ignored even in the glass material. I thought. The Young's modulus representing the amount of stress required to give a unit length of deformation to the material is, for example, resin material acrylic is 3.2 MPa, glass material is about 80 MPa with the trade name BK7, which is 20 times or more, It can be said that the influence of surface deformation due to stress is sufficiently negligible.

However, the photoelastic constant representing the amount of birefringence per unit stress is about 1/3, with acrylic material 6 × 10 ⁻¹² Pa ⁻¹ and glass material 2.2 × 10 ⁻¹² Pa ⁻¹ under the trade name BK7. is there. In other words, at a spatial frequency that is three times the spatial frequency range where the optical performance deteriorates due to the birefringence of the resin material, it means that the birefringence of the glass material also causes the same degree of optical performance deterioration. I thought that it was not a negligible amount for the required performance. From this point of view, the present inventor has come up with a problem that birefringence occurs that significantly deteriorates optical performance when holding a cemented lens to which two or more glasses are bonded.

  In view of this, the present invention proposes a method for reducing the deterioration of optical performance due to birefringence that occurs in an optical system including a cemented lens made of glass.

  In addition, the present invention prevents an unnecessary stress from being applied to the lens when holding the cemented lens on the lens holding frame, reduces the occurrence of birefringence of the material due to the stress, and easily obtains a high optical performance. And an optical apparatus including the same.

The optical system of the present invention is an optical system including a cemented lens, wherein the image-side lens of the cemented lens has a larger outer diameter than the object-side lens, and the outer peripheral portion of the image-side lens is in the optical axis direction of the cemented lens. When the distance on the optical axis from the image plane to the lens surface closest to the object side of the cemented lens is L, and the focal length of the optical system is f,
0.2 <L / f <1.0
It satisfies the following conditional expression.

  According to the present invention, an optical system that prevents unnecessary stress from being applied to the lens when holding the cemented lens on the lens holding frame, reduces the occurrence of birefringence of the material due to the stress, and easily obtains high optical performance. Is obtained.

Sectional view of the optical system of Example 1 Aberration diagram at infinite object distance when the optical system of Example 1 is expressed in mm. In Example 1, the shape of the cemented lens embodying the present invention and the sectional view of the lens holding mechanism Sectional drawing of the optical system of Example 2 Aberration diagram at infinite object distance when the optical system of Example 2 is expressed in mm. In Example 2, the shape of the cemented lens embodying the present invention and a sectional view of the lens holding mechanism Sectional drawing of the optical system of Example 3 (A), (B) Aberration diagrams at the infinite object distance between the wide-angle end and the telephoto end when the optical system of Example 3 is expressed in mm. In Example 3, the shape of the cemented lens embodying the present invention and a sectional view of the lens holding mechanism Explanatory drawing regarding axial luminous flux in a telephoto lens with a tele ratio smaller than 1

  The optical system of the present invention includes a cemented lens in which at least two lenses are cemented. Of the at least two lenses of the cemented lens, the image-side lens has an outer diameter larger than that of the object-side lens, and an outer peripheral portion of the image-side lens has a positioning portion that performs positioning in the optical axis direction. Two positioning portions of the image side lens are provided apart from each other in the optical axis direction, and the two positioning portions are formed of parallel plane portions. The material of the at least two lenses is glass. Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a lens cross-sectional view of the optical system according to the first embodiment of the present invention, and FIG. 2 is an aberration diagram when focusing on an object at infinity according to the first embodiment. FIG. 3 is an explanatory diagram of the lens holding mechanism in the first embodiment. The optical system of Example 1 is a telephoto lens. FIG. 4 is a lens cross-sectional view of the optical system according to the second embodiment of the present invention, and FIG. 5 is an aberration diagram when focusing on an object at infinity according to the second embodiment. FIG. 6 is an explanatory diagram of the lens holding mechanism in the second embodiment. The optical system of Example 2 is a telephoto lens. FIG. 7 is a lens cross-sectional view of the optical system according to the third embodiment of the present invention, and FIGS. 8A and 8B are aberration diagrams when focusing on an object at infinity at the wide-angle end and the telephoto end according to the third embodiment. is there. FIG. 9 is an explanatory diagram of the lens holding mechanism in the third embodiment. The optical system of Example 3 is a telephoto zoom lens.

  In each aberration diagram, spherical aberration (axial chromatic aberration), astigmatism, distortion, and lateral chromatic aberration are shown in order from the left. In the diagrams showing spherical aberration and lateral chromatic aberration, the solid line represents the d line (587.6 nm), and the broken line represents the g line (435.8 nm). In the diagram showing astigmatism, the solid line represents the sagittal direction of the d line, and the broken line represents the meridional direction of the d line. Moreover, the figure which shows distortion represents the distortion in d line | wire. Fno represents an F number, and ω represents a half angle of view. The optical system of each embodiment is a photographing lens system used in an optical apparatus such as a video camera or a digital camera. In the lens cross-sectional view, the left is the object side (front) and the right is the image side (rear). When the optical system of each embodiment is used as a projection lens such as a projector, the left side is a screen and the right side is a projected image.

  In the lens cross-sectional view, i indicates the order of the lens groups from the object side, and Li is the i-th lens group. SP is an aperture stop. The aperture stop SP is disposed on the object side of the third lens unit L3 in the first and second embodiments. In Example 3, it is disposed on the image side of the third lens unit L3, and moves together with the third lens unit L3 during zooming.

  IP is an image plane, and when used as a photographing optical system of a video camera or a digital still camera, an image of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives an image formed by the optical system. A face is placed. Further, when used as an imaging optical system of a silver salt film camera, it corresponds to a film surface.

In the optical system having the cemented lens of the present invention, L is the distance from the image plane to the object-side vertex of at least two lenses of the cemented lens, and f is the focal length of the optical system. At this time, at least two lenses of the cemented lens are 0.2 <L / f <1.0 in the optical path (1).
It is arranged at a position satisfying the following conditional expression.

  The cemented lens may be a lens in which two or more lenses are cemented. In the following, for the sake of simplicity, the principle that can reduce optical performance deterioration due to birefringence generated from a cemented lens will be described by taking a cemented lens in which two lenses made of glass are cemented in the optical system of the present invention as an example. . In a cemented lens in which a lens is bonded with an adhesive from different glass materials, the linear expansion coefficient of each material is different. For this reason, when the adhesive is cured, stress is generated in the peripheral portion of the glass. The cemented lens is indispensable in the optical system in order to reduce chromatic aberration generated from the optical system. It is known that the cemented lens generates birefringence in the lens effective portion due to stress at the time of cementing and affects the optical performance.

  In addition to the stress generated at the periphery of the lens when the adhesive is cured in the cemented lens, the inventor further increases the birefringence when the stress from the holding mechanism is applied to that portion, resulting in deterioration of the optical performance. I found.

  In particular, in a cemented lens at a position (in the optical path) that satisfies the conditional expression (1) in the optical system, the axial ray height h is 90% or more of the effective ray diameter. For this reason, when birefringence occurs at the periphery of the glass when the adhesive is cured, the imaging position of the light beam passing through the periphery of the pupil of the axial light beam tends to vary, and the optical performance is greatly deteriorated. At the position where the position of the cemented lens in the optical system deviates from the upper limit value or the lower limit value of the conditional expression (1), the light rays that determine the lens effective diameter are the underline and the upper line of the off-axis light beam, respectively. h is sufficiently on the inner peripheral side with respect to the lens outer diameter.

  Conventionally, in the holding method of the cemented lens in the lens holding frame, the both sides of the cemented lens are pressed down. Alternatively, the outer diameter of the lens on the image side having a small effective system is made smaller than the outer diameter of the lens on the object side, and the lens is pressed only by the lens on the object side. In the case of the former, stress due to the curing of the adhesive and stress from the holding mechanism are applied twice on the positive lens side where the thickness is particularly thin at the periphery of the lens, and the birefringence of the material of the positive lens is greatly generated. I understood that. In the latter case, the stress from the holding mechanism is concentrated on the lens on the object side, so that a large birefringence is generated in the material of the lens on the object side together with the stress due to the curing of the adhesive. Furthermore, since the axial ray height h of the lens on the object side is large, the influence of birefringence appears more conspicuously with respect to the pupil peripheral luminous flux.

  Therefore, in the lens holding frame of the cemented lens of each example, the outer diameter of the image side lens is made larger than the outer diameter of the object side lens, and the lens holding frame is held only by the image side lens. Thereby, the stress from the holding mechanism is concentrated on the image side lens having a small axial ray height h, and the influence of birefringence on the lens peripheral light beam (pupil peripheral light beam) is reduced. At the same time, the distance from the effective beam diameter of the image-side lens to the lens holder is increased so that the influence of birefringence due to stress does not reach the effective beam system as much as possible. By adopting such a configuration, in the optical system of each embodiment, deterioration of optical performance is reduced when stress is applied from the holding mechanism to the cemented lens in which the lenses of the glasses are cemented. More preferably, the numerical range of conditional expression (1) is set as follows.

0.25 <L / f <0.90 (1a)
As described above, according to the present invention, it is possible to reduce deterioration of optical performance due to birefringence generated in an optical system including a glass-to-glass cemented lens.

In the optical system of the present invention, it is more preferable that one or more of the following conditions are satisfied. The distance from the surface vertex on the most object side of the optical system to the image plane is defined as Ltotal. The length in the optical axis direction of the planar portions of the two positioning portions is defined as dout, and the center thickness of the cemented lens is defined as dcen. At least two lenses are composed of a positive lens and a negative lens. Of the light incident / exit surfaces of the positive lens, the smaller diameter is dea, and the thickness in the optical axis direction at the outermost periphery of the diameter of the light incident / exit surface is dcov. At this time, 0.4 <Ltotal / f <1.2 (2)
0.05 <dout / dcen <0.80 (3)
0.02 <dcov / dea <0.40 (4)
It is preferable to satisfy one or more of the following conditional expressions.

  In an optical system in which the tele ratio is in a range that satisfies the conditional expression (2) and that achieves both small size and light weight and high performance, the power of each lens element increases. As a result, the imaging position of the light beam passing through the vicinity of the pupil of the axial light beam is more likely to vary. For this reason, it is more preferable that the conditional expression (2) is satisfied in the optical system of each embodiment.

If the lower limit of conditional expression (2) is deviated, the power of each lens element becomes too strong, and it becomes difficult to obtain good optical performance.
If the upper limit value of conditional expression (2) is deviated, the power of each lens element becomes too weak, and the imaging position of the light beam passing through the periphery of the axial light beam becomes difficult to vary, and the entire system is reduced in size and weight. It becomes difficult.

  Next, in the image side lens, the holding part (positioning part) at a location (outer peripheral part) larger than the outer diameter of the object side lens is made into two parallel plane parts having a narrow width in the optical axis direction. The lens is held without increasing the glass weight. Also, by holding the image side lens so that the parallel plane part is sandwiched from both sides in the optical axis direction, the stress component in the inner diameter direction of the glass is reduced, and the occurrence of birefringence in the light beam effective part is further reduced. Yes. The width (length) of the parallel plane portion of the image side lens preferably satisfies the conditional expression (3). If the upper limit value of conditional expression (3) is deviated, the width of the parallel plane portion becomes too wide, and the glass part becomes larger and heavier. Deviating from the lower limit value of conditional expression (3) is not preferable because the width of the parallel plane portion becomes too narrow and difficult to process, and breakage easily occurs due to holding stress.

  Furthermore, in the optical system of the present invention, in the positive lens constituting the cemented lens, the thickness of the outermost periphery of the light beam effective portion is increased to such an extent that the glass weight does not increase remarkably, so that the adhesive is cured. The amount of birefringence generated due to the stress of can be reduced. This is because the amount of birefringence generated by the stress is proportional to the photoelastic coefficient and the thickness of the material, so that a larger birefringence is likely to occur in a positive lens whose thickness is reduced at the periphery of the lens. Specifically, conditional expression (4) is satisfied. If the upper limit value of conditional expression (4) is deviated, the glass part becomes heavy, which is not preferable. Further, when the lower limit value of conditional expression (4) is deviated, the amount of birefringence at the lens peripheral portion of the positive lens increases, so that the optical performance deteriorates. More preferably, the numerical ranges of the conditional expressions (2) to (4) are set as follows.

0.5 <Ltotal / f <1.0 (2a)
0.10 <dout / dcen <0.70 (3a)
0.03 <dcov / dea <0.30 (4a)
Next, in a cemented lens including a positive lens and a negative lens from the object side to the image side, the thickness of the peripheral portion of the positive lens is small and birefringence is likely to occur. In each embodiment, since the axial ray height h to the positive lens increases, it is more effective to implement the lens holding method according to the present invention on the cemented lens in the order of the positive lens and the negative lens.

  Next, in order from the object side to the image side, a telephoto type optical system having a first lens unit having a positive refractive power and a second lens unit having a negative refractive power driven by focusing is reduced in size and weight and has high performance. It is easy to balance. On the other hand, since most lenses are at positions that satisfy the conditional expression (1), variations in the imaging position of the lens's most peripheral light beam are likely to occur. Therefore, it is more effective to implement the lens holding method according to the present invention in this telephoto type optical system. In the telephoto type optical system, when focusing from an object at infinity to an object at a short distance, the second lens group having a negative power is driven to the image side, so that the spherical aberration is likely to fluctuate to the over side. Therefore, if a positive lens is disposed on the object side where the axial ray height h is larger than that of the second lens group, an underside correction effect can be obtained. For this reason, the second lens group is preferably a cemented lens of a positive lens and a negative lens from the object side to the image side.

  The cemented lens according to the present invention is not limited to the cementing of two lenses, but may be three or more cemented lenses in which one or more lenses are further cemented on the image side or the object side. A similar effect can be obtained.

  The present invention can be variously applied to an optical apparatus (for example, an imaging apparatus, an image projection apparatus, or other optical apparatus) having the above-described optical system.

[Example 1]
The optical system of Example 1 shown in FIG. 1 includes, in order from the object side to the image side, a first lens unit L1 having a positive refractive power, and a second lens unit having a negative refractive power that moves on the optical axis during focusing. This is a telephoto type telephoto lens composed of L2 and a positive third lens unit L3. In Example 1, Ltotal / f = 0.94, which satisfies the conditional expression (2), is aimed at reducing the size and weight. The cemented lens C1 constituting the second lens group L2 and the cemented lens C2 in the third lens group L3 are held by the lens holding frame by the method according to the present invention.

  The cemented lens C1 is disposed at a position of L / f = 0.57 in the optical path, and the cemented lens C2 is disposed at a position of L / f = 0.32 in the optical path, both satisfy the conditional expression (1). ing. For this reason, in each of the cemented lenses C1 and C2, the image forming position of the light beam passing through the lens peripheral portion of the axial light beam is apt to vary. As shown in FIG. 3A, the cemented lens C1 is configured by cementing a positive lens (object-side positive lens) 1 and a negative lens (image-side negative lens) 2 in order from the object side to the image side. The outer diameter of the image side negative lens 2 is larger than that of the object side positive lens 1. The cemented lens C1 is positioned outside the outer periphery of the object-side positive lens 1, and includes two plane portions 5 and 6 serving as positioning portions for positioning in the optical axis direction with a lens barrel (lens holding frame) 4 and a pressing ring 3. Is held in the optical axis direction.

  The holding of the cemented lens C1 in the radial direction by the lens barrel 4 is determined and held by abutting the outer peripheral plane portion 7 of the image side negative lens 2 against the inner peripheral surface of the lens barrel 4. As shown in FIG. 3B, the cemented lens C2 is configured by cementing a positive lens (object-side positive lens) 1 and a negative lens (image-side negative lens) 2 in order from the object side to the image side. The outer diameter of the image side negative lens 2 is larger than that of the object side positive lens 1. The cemented lens C <b> 2 abuts the object-side flat portion 5 of the negative lens 2 positioned in the optical axis direction outside the outer periphery of the object-side positive lens 1 against the abutting portion 4 a of the lens barrel 4. Then, a part of the caulking claw 8 of the lens barrel 4 is thermally deformed and applied to the flat surface portion 6 as a positioning portion on the image side of the negative lens 2 to hold in the optical axis direction.

  The holding of the cemented lens C2 in the radial direction by the lens barrel 4 is determined by abutting the outer peripheral plane portion 7 of the image side negative lens 2 against the inner peripheral surface of the lens barrel 3.

  In the present embodiment, the two flat portions 5 and 6 are separated from each other in the optical axis direction and are parallel to each other. In this embodiment, the order of the positive lens 1 and the negative lens 2 may be reversed. At this time, the outer periphery of the image side positive lens is held by the lens barrel.

  In this embodiment, as described above, the holding stress is concentrated on the image side lens having a small axial ray height h. As a result, the influence on the lens peripheral luminous flux is reduced, and at the same time, a margin is provided from the effective ray diameter of the image-side lens to the outer diameter of the lens, so that the influence of birefringence due to stress does not easily reach the effective ray diameter.

  The plane portions 5 and 6 in the cemented lens C1 and the plane portions 5 and 6 in the cemented lens C2 are parallel plane portions, and the relationship between the surface spacing and the center thickness of the cemented lens is a conditional expression ( 3) is satisfied. As a result, the stress component in the inner diameter direction of the glass (material) can be reduced, the occurrence of birefringence in the light beam effective portion can be further reduced, and at the same time, the weight of the glass (material) part is reduced. Further, in each cemented lens C1, C2, the relationship between the light incident surface diameter of the object-side positive lens and the thickness in the optical axis direction of the outermost peripheral portion of the light incident / exit surface both satisfies the conditional expression (4). As a result, the amount of birefringence due to stress is reduced and the weight of the glass material is reduced.

  Next, normally, in the telephoto type optical system, when the second lens unit L2 having a negative refractive power is driven to focus on the image side, the spherical aberration changes to the over side. On the other hand, in the cemented lens C1 of the first embodiment, a positive lens is arranged on the object side where the axial ray height h is large to enhance the underside correction effect and achieve high optical performance in the entire focus range.

[Example 2]
The optical system of Example 2 shown in FIG. 4 is the same as that of Example 1. That is, 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 negative refractive power driven to the image side by focusing, and the third lens unit L3 having a positive refractive power. It is a telephoto type telephoto lens constructed in order. In the second embodiment, Ltotal / f = 0.81 and the conditional expression (2) are satisfied, and a reduction in size and weight and an increase in performance are achieved.

  The cemented lens C1 constituting the second lens group L2 and the cemented lens C2 in the third lens group L3 are held by the lens holding frame by the method according to the present invention. The cemented lens C1 is disposed at a position of L / f = 0.48 in the optical path, and the cemented lens C2 is disposed at a position of L / f = 0.29 in the optical path, and both satisfy the conditional expression (1). . Therefore, the axial ray height h in each of the cemented lenses C1 and C2 is 90% or more of the effective ray diameter, and the imaging position of the ray passing through the lens periphery of the axial beam is easily variable. . The cemented lens C1 has the same configuration as that of the first embodiment as shown in FIG. 6A, and the effect thereof is also the same.

  The cemented lens C2 has a negative lens and a positive lens in order from the object side to the image side. As shown in FIG. 6B, the outer diameter of the image side positive lens 2 is larger than that of the negative lens 1 on the object side. Is also big. The cemented lens C2 is positioned outside the object-side negative lens 1, and a flat surface portion 5 as a positioning portion for positioning in the optical axis direction is abutted against the abutting portion 4a of the lens barrel 4. Then, some of the caulking claws 8 of the lens barrel 4 are thermally deformed and hung on the flat surface portion 6 as a positioning portion on the image side of the positive lens 2 to thereby hold the optical axis direction.

  The holding of the cemented lens C <b> 2 in the radial direction by the lens barrel 4 is determined by abutting the outer peripheral plane portion 7 of the image side positive lens 2 against the inner peripheral surface of the lens barrel 4. Thereby, the holding stress is concentrated on the image-side positive lens 2 having a small axial ray height h. As a result, the influence on the luminous flux around the lens is reduced, and at the same time, a margin is provided from the effective beam diameter of the image-side positive lens 2 to the outer diameter of the lens so that the effect of birefringence due to stress does not easily reach the effective beam diameter. . The two plane portions 5 and 6 of the image-side positive lens 2 are parallel plane portions, and the relationship between the interval and the center thickness of the cemented lens C2 satisfies the conditional expression (3). As a result, the stress component in the inner diameter direction of the glass (material) is eliminated, the occurrence of birefringence in the light beam effective portion can be further reduced, and at the same time, the weight of the glass (material) part is reduced.

  Thus, in the present embodiment, the effect of the present invention can be obtained even with a cemented lens of a negative lens and a positive lens in order from the object side to the image side.

[Example 3]
In the optical system of Example 3 shown in FIG. 7, in order from the object side to the image side, 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. The lens unit L3 includes a fourth lens unit L4 having negative refractive power. Further, the zoom lens is a seven-group telephoto zoom lens including a fifth lens unit L5 having a positive refractive power, a sixth lens unit L6 having a negative refractive power, and a seventh lens unit L7 having a positive refractive power. During zooming from the wide-angle end to the telephoto end, the first, third, and sixth lens units L1, L3, and L6 move toward the object side, and the fourth lens unit L4 moves toward the image side as indicated by an arrow. The second, fifth, and seventh lens units L2, L5, and L7 do not move for zooming.

  The optical system of the present embodiment is a telephoto zoom lens having a shooting half angle of view of 4.2 degrees at the telephoto end. In the third embodiment, Ltotal / f = 0.80 is satisfied at the zoom position at the telephoto end, which satisfies the conditional expression (2), thereby achieving a reduction in size and weight and an increase in performance. In Example 3, the cemented lens C1 in the first lens unit L1 and the cemented lens C2 in the second lens unit L2 are held by the lens holding frame by the method according to the present invention. Each cemented lens has a cemented lens C1 disposed at a position of L / f = 0.78 in the optical path and a cemented lens C2 at a position of L / f = 0.54 in the optical path at the zoom position at the telephoto end. They are arranged and both satisfy the conditional expression (1).

  For this reason, the axial ray height h at the telephoto end zoom position of each cemented lens C1, C2 is 90% or more of the effective ray diameter, and the imaging position of the ray passing through the periphery of the pupil of the axial beam is The conditions are likely to vary. The method for holding the cemented lens C1 is the same as that in the first and second embodiments as shown in FIG. 9A is different from the holding method of the cemented lens C2 in FIG. 3B only in that the method of inserting the cemented lens C2 into the lens barrel 3 is reversed. .

  9B, the cemented lens C2 abuts the flat surface portion 5 of the image-side negative lens 2 against the abutting portion 4a of the lens barrel 4, and further the negative lens 9 against the flat surface portion 6 of the negative lens 2. The image side of the negative lens 9 is pressed by the caulking claw 8 of the lens barrel 4. The plane part 5 and the plane part 6 are parallel plane parts. The cemented lens C2 is held so as to sandwich the flat portion 5 and the flat portion 6, and the same effects as those of the first and second embodiments are obtained. Thus, the effect of the present invention can be obtained even at the zoom position at the telephoto end of the zoom lens.

  As mentioned above, although the Example of the preferable optical system of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

  Next, numerical examples 1 to 3 corresponding to the respective examples will be shown. In each numerical example, i indicates the order of the optical surfaces from the object side, ri is the radius of curvature of the i-th optical surface (i-th surface), di is the distance between the i-th surface and the i + 1-th surface, ndi and νdi indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line, respectively. In addition to specs such as focal length and F-number, the angle of view is the half angle of view of the entire system, the image height is the maximum image height that determines the half angle of view, and the total lens length is the distance from the first lens surface to the final lens surface. , BF indicates the length from the final lens surface to the image plane.

In Numerical Example 3, the part where the distance d between the optical surfaces is (variable) changes during zooming, and the surface distance corresponding to the focal length is shown in the separate table.
Table 1 shows the calculation results of the conditional expressions based on the lens data of Numerical Examples 1 to 3 described below.

(Numerical example 1)

Unit mm

Surface data surface number rd nd νd Effective diameter
1 302.145 16.85 1.48749 70.2 135.31
2 -439.426 22.74 134.71
3 133.921 23.10 1.43387 95.1 118.64
4 -348.061 0.13 116.20
5 -339.367 4.30 1.65412 39.7 116.20
6 236.146 29.16 109.53
7 82.605 15.28 1.43387 95.1 94.89
8 380.565 1.00 92.78
9 65.968 6.00 1.48749 70.2 81.91
10 49.683 29.03 73.32
11 4862.721 6.72 1.80809 22.8 64.59
12 -141.662 2.60 1.80610 40.7 63.49
13 113.588 86.23 59.76
14 (Aperture) ∞ 2.04 41.39
15 137.526 8.07 1.77250 49.6 40.60
16 -67.088 2.05 1.80518 25.4 39.68
17 -308.914 5.97 38.62
18 83.839 4.48 1.84666 23.8 34.77
19 -126.211 1.71 1.72916 54.7 34.39
20 44.290 4.41 32.64
21 -183.415 1.63 1.83481 42.7 32.67
22 69.289 3.51 33.18
23 83.969 4.56 1.77250 49.6 35.51
24 -481.588 10.16 35.89
25 63.420 8.29 1.65412 39.7 39.13
26 -97.491 1.91 1.80809 22.8 38.76
27 156.214 5.29 38.40
28 ∞ 2.20 1.51633 64.1 38.70
29 ∞ 38.81

Various data

Focal length 392.39
F number 2.90
Angle of View 3.16
Statue height 21.64
Total lens length 370.71
BF 61.28

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 208.49 118.56 12.14 -81.30
2 11 -144.71 9.32 5.29 0.13
3 14 384.03 66.29 -12.42 -63.84

(Numerical example 2)

Unit mm

Surface data surface number rd nd νd Effective diameter
1 331.299 15.10 1.48749 70.2 141.97
2 -698.860 44.37 141.42
3 160.224 19.00 1.43387 95.1 122.37
4 -634.734 0.41 120.51
5 -556.300 4.50 1.65412 39.7 120.50
6 276.476 45.32 115.49
7 93.942 14.23 1.43387 95.1 98.57
8 395.355 1.00 96.70
9 82.615 5.30 1.48749 70.2 88.69
10 61.070 46.72 81.52
11 637.682 5.99 1.80809 22.8 64.41
12 -272.868 2.80 1.88300 40.8 63.29
13 146.588 97.26 60.84
14 (Aperture) ∞ 5.82 40.52
15 154.638 2.00 1.80610 33.3 38.99
16 63.649 7.03 1.59282 68.6 38.13
17 -234.143 12.76 37.53
18 87.560 3.86 1.84666 23.8 32.05
19 -444.007 1.65 1.62041 60.3 31.63
20 42.018 3.99 30.48
21 -133.996 1.60 1.81600 46.6 30.50
22 113.702 5.00 31.03
23 91.366 3.20 1.65412 39.7 33.93
24 -1021.757 10.91 34.15
25 88.375 7.49 1.72047 34.7 37.12
26 -74.187 1.91 1.80809 22.8 36.96
27 296.105 10.00 36.86
28 ∞ 2.20 1.51633 64.1 45.00
29 ∞ 45.00

Various data

Focal length 584.90
F number 4.12
Angle of View 2.12
Statue height 21.64
Total lens length 475.88
BF 94.46

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 270.91 149.24 30.00 -101.98
2 11 -200.18 8.79 5.97 1.14
3 14 1625.81 79.42 11.00 -59.54

(Numerical Example 3)

Surface data surface number rd nd νd Effective diameter
1 129.190 6.01 1.48749 70.2 53.00
2 -197.870 0.15 52.80
3 106.656 8.24 1.43875 94.9 50.39
4 -127.775 2.40 1.61340 44.3 49.08
5 262.140 (variable) 47.00
6 183.157 4.37 1.80518 25.4 25.75
7 -43.972 1.20 1.71300 53.9 24.81
8 47.602 3.12 23.31
9 -49.900 1.20 1.83481 42.7 23.26
10 212.970 (variable) 25.40
11 125.359 1.20 1.80518 25.4 25.40
12 40.994 4.46 1.60311 60.6 25.64
13 -68.824 0.15 25.74
14 47.854 3.31 1.49700 81.5 25.48
15 -237.275 1.00 25.18
16 (Aperture) ∞ (Variable) 24.60
17 -42.550 1.20 1.57135 53.0 22.40
18 47.732 2.25 1.84666 23.8 22.88
19 164.018 (variable) 22.80
20 -126.107 2.73 1.74950 35.3 24.40
21 -38.896 0.15 24.91
22 108.304 4.60 1.48749 70.2 24.91
23 -31.051 1.00 1.84666 23.8 24.82
24 -131.207 0.15 25.00
25 56.635 3.17 1.51633 64.1 25.28
26 -187.996 (variable) 25.00
27 -139.768 1.10 1.83400 37.2 25.00
28 46.843 3.69 24.17
29 77.820 5.40 1.80518 25.4 25.81
30 -39.907 4.90 26.07
31 -33.492 1.10 1.83481 42.7 24.37
32 75.079 (variable) 25.13
33 43.379 3.41 1.48749 70.2 33.40
34 116.452 33.51


Various data

Zoom ratio 4.02

Wide angle Medium telephoto focal length 72.20 134.99 289.95
F number 4.09 4.47 5.92
Angle of View 16.68 9.11 4.27
Image height 21.64 21.64 21.64
Total lens length 178.05 210.65 232.33
BF 39.65 39.65 39.65

d 5 4.01 36.49 58.01
d10 22.79 14.54 1.28
d16 3.62 17.87 43.13
d19 20.43 14.43 2.43
d26 11.60 8.78 1.23
d32 4.27 7.18 14.76

Zoom lens group data group Start surface Focal length Lens configuration length Front principal point position Rear principal point position
1 1 146.02 16.80 -1.81 -12.88
2 6 -34.23 9.89 6.03 -0.93
3 11 44.52 10.12 3.40 -3.46
4 17 -77.74 3.45 0.45 -1.52
5 20 41.25 11.80 3.57 -4.12
6 27 -34.77 16.20 8.09 -3.09
7 33 139.67 3.41 -1.34 -3.60

SP: Aperture IP: Imaging surface L1-L7: First lens group to seventh lens group Focus: A group that moves by focusing, and its moving direction C1, C2: Joint lens

Claims (10)

In an optical system including a cemented lens, the image side lens of the cemented lens has an outer diameter larger than that of the object side lens, and the outer peripheral portion of the image side lens is used to determine the position of the cemented lens in the optical axis direction. Having a positioning portion, when the distance on the optical axis from the image plane to the lens surface closest to the object side of the cemented lens is L, and the focal length of the optical system is f,
0.2 <L / f <1.0
An optical system that satisfies the following conditional expression: When the distance on the optical axis from the lens surface closest to the object side of the optical system to the image plane is Ltotal, 0.4 <Ltotal / f <1.2
The optical system according to claim 1, wherein the following conditional expression is satisfied.   3. The optical system according to claim 1, wherein two positioning portions of the image side lens are provided apart from each other in the optical axis direction, and the two positioning portions are formed of plane portions parallel to each other. 0.05 <dout / dcen <0.80 where the distance in the optical axis direction between the flat portions of the two positioning portions is dout and the center thickness of the cemented lens is dcen.
The optical system according to claim 3, wherein the following conditional expression is satisfied: The cemented lens includes a positive lens and a negative lens. Of the light incident / exit surfaces of the positive lens, the smaller diameter is dea, and the thickness in the optical axis direction at the outermost periphery of the diameter of the light incident / exit surface is dcov. 0.02 <dcov / dea <0.40
The optical system according to claim 1, wherein the following conditional expression is satisfied.   The optical system according to claim 1, wherein the cemented lens includes a positive lens and a negative lens in order from the object side to the image side.   The optical system includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power that moves on the optical axis during focusing, and a third lens group having a positive refractive power. The optical system according to claim 1, further comprising:   The optical system according to claim 7, wherein the cemented lens is included in the second lens group.   The optical system includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a negative refractive power. The zoom lens includes a lens group, a fifth lens group having a positive refractive power, a sixth lens group having a negative refractive power, and a seventh lens group having a positive refractive power. The second, fifth, and seventh lenses are used for zooming. The lens group is stationary, the first, third, fourth, and sixth lens groups move during zooming, and the cemented lens is included in the second lens group. The optical system according to any one of the above.   An optical apparatus comprising: the optical system according to claim 1; and a solid-state imaging device that receives an image formed by the optical system.