JP2013011831A - Optical system, imaging apparatus having optical system, and manufacturing method of optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high performance optical system with little coma aberration and spherical aberration, which is capable of reducing ghost images or flares, an imaging apparatus having the optical system, and a manufacturing method of the optical system.SOLUTION: The optical system includes a front group GF and a rear group GR having a positive refractive power from the object side in order along an optical axis. The front group includes from the object side in order: a first lens element LFP having a positive refractive power; a second lens element LFN1 having a convex surface at the object side, and a negative refractive power; and a third lens element LFN2 having a negative refractive power. The rear group includes from the object side in order: a first lens element LRN in which a negative lens L21 and a positive L22 are joined with each other, and which has a concave surface at the object side; a second lens element LRP1 having a concave surface at the image side, and a positive refractive power; and a third lens element LRP2 having a positive refractive power. At least one of the optical surfaces of the front group and the rear group has an antireflection film including at least one layer formed using a wet processing.

Description

  The present invention relates to an optical system, an imaging apparatus having the optical system, and a method for manufacturing the optical system.

  Conventionally, many so-called modified Gaussian lenses have been proposed (see, for example, Patent Document 1). In recent years, not only aberration performance but also ghost and flare requirements, which are one of the factors that impair optical performance, have become increasingly demanding for such optical systems. Higher performance is required for the prevention film, and multilayer film design technology and multilayer film formation technology continue to advance to meet the demand (see, for example, Patent Document 2).

JP 2009-251398 A JP 2000-356704 A

  However, the conventional Gaussian lens has insufficient correction of coma, and it has been particularly difficult to improve sagittal coma. At the same time, the optical surface in such an optical system also has a problem that reflected light that becomes ghost or flare is easily generated.

  The present invention has been made in view of such problems, and is an optical system that is small in size, has a small number of components, has reduced ghosts and flares, has high performance, and has low coma, particularly sagittal coma and spherical aberration. An object of the present invention is to provide an imaging device having this optical system and a method for manufacturing the optical system.

In order to solve the above problems, an optical system according to the present invention includes, in order from the object side along the optical axis, a front group and a rear group having a positive refractive power. The first lens component having a positive refractive power, the second lens component having a negative refractive power and having a convex surface facing the object side, and the third lens component having a negative refractive power are sequentially provided. In the rear group, in order from the object side, a negative lens and a positive lens are cemented, a first lens component having a concave surface directed toward the object side, a first lens component having a positive refractive power, and a concave surface directed toward the image side. Two lens components and a third lens component having a positive refractive power, and an antireflection film is provided on at least one of the optical surfaces in the front group and the rear group, and the antireflection film is a wet process It is configured to include at least one layer formed using And butterflies.
0.000 <nRNP-nRNN <0.350
−2.00 <(rp2−rp1) / (rp2 + rp1) <− 0.00
However,
nRNP: Refractive index with respect to d-line of medium of positive lens in first lens component in rear group nRNN: Refractive index with respect to d-line of medium of negative lens in first lens component in rear group rp1: In rear group Radius of curvature of the surface closest to the object side of the second lens component rp2: radius of curvature of the surface closest to the image side of the second lens component in the rear group

  In addition, an imaging apparatus according to the present invention includes any one of the above-described optical systems.

Further, the present invention is a method of manufacturing an optical system having a front group and a rear group having a positive refractive power in order from the object side along the optical axis. A first lens component having a positive refractive power, a second lens component having a negative refractive power and having a convex surface directed toward the object side, and a third lens component having a negative refractive power are disposed. As a group, in order from the object side, a negative lens and a positive lens are cemented, a first lens component having a concave surface facing the object side, and a second lens component having a positive refractive power and having a concave surface facing the image side And a third lens component having a positive refractive power, and an antireflection film is provided on at least one of the optical surfaces in the front group and the rear group, and the antireflection film is formed using a wet process. It is configured to include at least one formed layer and satisfies the following conditional expression To provide a manufacturing method of an optical system characterized by and.
0.000 <nRNP-nRNN <0.350
−2.00 <(rp2−rp1) / (rp2 + rp1) <− 0.00
However,
nRNP: Refractive index with respect to d-line of medium of positive lens in first lens component in rear group nRNN: Refractive index with respect to d-line of medium of negative lens in first lens component in rear group rp1: In rear group Radius of curvature of the surface closest to the object side of the second lens component rp2: radius of curvature of the surface closest to the image side of the second lens component in the rear group

  According to the present invention, an optical system that is small in size, has a small number of components, has reduced ghosts and flares, has high performance, has high performance, and has low coma, particularly sagittal coma and spherical aberration, an image pickup apparatus having the optical system, and An optical system manufacturing method can be provided.

It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 1st Example. FIG. 6 is a diagram illustrating various aberrations of the optical system according to Example 1 in an infinitely focused state. It is sectional drawing which shows the lens structure of the optical system which concerns on 1st Example, Comprising: The figure explaining an example of a mode that the incident light ray reflects in the 1st reflected light generation surface and the 2nd reflected light generation surface It is. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 2nd Example. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 2 in a focused state at infinity. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 3rd Example. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 3 in an infinitely focused state. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 4th Example. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 4 in the infinitely focused state. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 5th Example. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 5 in a focused state at infinity. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 6th Example. It is various aberrational figures in the infinite point focusing state of the optical system which concerns on 6th Example. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 7th Example. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 7 in a focused state at infinity. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 8th Example. It is various aberrational figures in the infinite point focusing state of the optical system which concerns on 8th Example. A sectional view of a single-lens reflex camera equipped with an optical system is shown. It is a flowchart for demonstrating the manufacturing method of an optical system. It is explanatory drawing which shows an example of the layer structure of an antireflection film. It is a graph which shows the spectral characteristic of an antireflection film. It is a graph which shows the spectral characteristics of the antireflection film concerning a modification. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film concerning a modification. It is a graph which shows the spectral characteristics of the anti-reflective film produced with the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the anti-reflective film produced with the prior art.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical system OS according to the present embodiment includes a front group GF and a rear group GR having a positive refractive power in order from the object side along the optical axis. . The front group GF includes, in order from the object side, a first lens component LFP having a positive refractive power, a second lens component LFN1 having a negative refractive power and having a convex surface facing the object side, and negative refraction. The rear lens group GR has a first lens component LRN in which a negative lens L21 and a positive lens L22 are cemented in order from the object side, and a concave surface is directed to the object side. The lens includes a second lens component LRP1 having a positive refractive power and a concave surface facing the image side, and a third lens component LRP2 having a positive refractive power. In the following description, “lens component” refers to a single lens (lens element) or a cemented lens in which two or more single lenses (lens elements) are cemented.

  The optical system OS according to the present embodiment has coma aberration, particularly sagittal coma aberration, which is a defect of so-called Gaussian type and xenota type optical systems, which are basically represented by positive, negative, positive, negative, chromatic aberration, curvature of field and non-existence. This is an improvement without deteriorating the point aberration. Hereinafter, conditions for configuring such an optical system OS will be described.

  The optical system OS according to the present embodiment desirably satisfies the following conditional expression (1).

0.000 <nRNP-nRNN <0.350 (1)
However,
nRNP: refractive index with respect to the d-line of the medium of the positive lens L22 in the first lens component LRN in the rear group GR nRNN: refractive index with respect to the d-line of the medium of the negative lens L21 in the first lens component LRN in the rear group GR

  Conditional expression (1) is a condition that regulates the difference in refractive index between the positive lens L22 and the negative lens L21 constituting the first lens component LRN in the rear group GR at the d-line (wavelength λ = 587.6 nm). If this condition is not met, the setting of the optimum value for the Petzval sum will be impaired, resulting in a worsening of field curvature.

  If the upper limit value of the conditional expression (1) is exceeded, it means that the refractive index difference is remarkably increased. Even in this case, the Petzval sum is deteriorated from the optimum value, and as a result, the correction of the field curvature is deteriorated. In addition, the ability to correct spherical aberration also decreases, which makes it impossible to select a glass material for optimal chromatic aberration. If the upper limit value of conditional expression (1) is set to 0.300, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (1) is set to 0.200, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (1) to 0.130, the effect of the present application can be maximized.

  If the lower limit of conditional expression (1) is not reached, the difference in refractive index becomes remarkably small, and finally the refractive index of the negative lens L21 becomes larger than the refractive index of the positive lens L22. In this case, the positive and negative refractive indexes are reversed, and it is difficult to keep the Petzval sum small. Accordingly, the Petzval sum deviates greatly from the optimum value, and as a result, correction of curvature of field and correction of astigmatism are deteriorated, which is not preferable. If the lower limit value of conditional expression (1) is set to 0.020, it is advantageous for correction of various aberrations such as field curvature and astigmatism. Setting the lower limit of conditional expression (1) to 0.035 is advantageous for correcting various aberrations such as field curvature and astigmatism. Further, by setting the lower limit value of conditional expression (1) to 0.05, the effect of the present application can be maximized.

  Moreover, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (2).

−2.00 <(rp2-rp1) / (rp2 + rp1) <− 0.00 (2)
However,
rp1: radius of curvature of the most object side surface of the second lens component LRP1 in the rear group GR rp2: radius of curvature of the most image side surface of the second lens component LRP1 in the rear group GR

  Conditional expression (2) is a condition that defines the reciprocal of the form factor of the entire second lens component LRP1 having a positive refractive power with the concave surface facing the image side in the rear group GR. This condition is greatly related to correction of spherical aberration and sagittal coma. The fact that the value set in the conditional expression (2) is negative means that the entire shape of the second lens component LRP1 with the concave surface facing the image side in the rear group GR is a positive lens component. However, it shows a negative meniscus shape. Due to the presence of the air lens formed between this shape and the positive lens component (third lens component LRP2) located on the image side, it is possible to satisfactorily correct sagittal coma, meridional coma, and spherical aberration.

  When the upper limit value of conditional expression (2) is exceeded, the second lens component LRP1 changes its shape greatly from the negative meniscus shape and is a positive meniscus shape with a convex surface facing the object side, or a negative meniscus with a concave surface facing the object side Become a shape. Regardless of which shape is reached, the correction of sagittal coma and meridional coma is deteriorated, and correction of spherical aberration is also undesirably deteriorated when trying to correct it satisfactorily. If the upper limit value of conditional expression (2) is set to -0.01, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (2) is set to -0.03, it becomes more advantageous to correct the above-mentioned various aberrations. In addition, the effect of the present application can be maximized by setting the upper limit value of conditional expression (2) to -0.05.

  When the lower limit value of conditional expression (2) is not reached, the second lens component LRP1 is greatly changed from a negative meniscus shape to a biconvex shape or a biconcave shape. For this reason, the air lens described above does not exist, and the characteristics from the negative meniscus shape are not maintained, so that sagittal coma aberration, meridional coma aberration correction, and spherical aberration correction are deteriorated, which is not preferable. If the lower limit value of conditional expression (2) is set to -1.00, it is advantageous for correcting the above-mentioned various aberrations. Setting the lower limit of conditional expression (2) to −0.60 is advantageous for correcting the above-mentioned various aberrations. Moreover, the effect of the present application can be maximized by setting the lower limit value of conditional expression (2) to −0.40.

  Further, in the optical system OS according to this embodiment, an antireflection film is provided on at least one of the optical surfaces in the front group GF and the rear group GR, and this antireflection film is a layer formed by using a wet process. Contains at least one layer. With this configuration, the optical system OS according to the present embodiment can further reduce ghosts and flares caused by reflection of light from an object on an optical surface, and achieve high imaging performance. it can.

  In the optical system OS according to this embodiment, the antireflection film is preferably a multilayer film, and the layer formed by the wet process is preferably the outermost layer among the layers constituting the multilayer film. In this way, since the difference in refractive index with air can be reduced, the reflection of light can be further reduced, and ghosts and flares can be further reduced.

  In the optical system OS according to this embodiment, the refractive index nd is preferably 1.30 or less, where nd is the refractive index of the layer formed using the wet process. In this way, since the difference in refractive index with air can be reduced, the reflection of light can be further reduced, and ghosts and flares can be further reduced.

  In the optical system OS according to the present embodiment, the optical surface provided with the antireflection film among the optical surfaces in the front group GF and the rear group GR is preferably a concave lens surface as viewed from the aperture stop. . Of the optical surfaces in the front group GF and rear group GR, reflected light is likely to be generated on a concave lens surface as viewed from the aperture stop. Therefore, an anti-reflection film is formed on such an optical surface, so that ghost and flare are effective. Can be reduced.

  In the optical system OS according to the present embodiment, it is preferable that the concave lens surface viewed from the aperture stop provided with the antireflection film in the front group GF and the rear group GR is a lens surface on the object side. . Of the optical surfaces in the front group GF and rear group GR, reflected light is likely to be generated on a concave lens surface as viewed from the aperture stop. Therefore, an anti-reflection film is formed on such an optical surface, so that ghost and flare are effective. Can be reduced.

  In the optical system OS according to the present embodiment, the concave lens surface as viewed from the aperture stop provided with the antireflection film in the front group GF and the rear group GR is a lens surface on the image plane side. preferable. Of the optical surfaces in the front group GF and rear group GR, reflected light is likely to be generated on a concave lens surface as viewed from the aperture stop. Therefore, an anti-reflection film is formed on such an optical surface, so that ghost and flare are effective. Can be reduced.

  In the optical system OS according to the present embodiment, the optical surface provided with the antireflection film among the optical surfaces in the front group GF is preferably a concave lens surface when viewed from the object side. In this way, reflected light is likely to be generated on the concave lens surface when viewed from the object side among the optical surfaces in the front group GF. Therefore, by forming an antireflection film on such an optical surface, ghost and flare are formed. Can be effectively reduced.

  Further, in the optical system OS according to the present embodiment, the concave lens surface as viewed from the object side provided with the antireflection film among the optical surfaces in the front group GF is the lens closest to the image plane of the front group GF. The object side lens surface is preferable. Since reflected light is likely to be generated on a concave lens surface when viewed from the object side among the optical surfaces in the front group GF, ghosts and flares are effectively reduced by forming an antireflection film on such an optical surface. be able to.

  Further, in the optical system OS according to the present embodiment, the concave lens surface as viewed from the object side provided with the antireflection film among the optical surfaces in the front group GF is the lens closest to the image plane of the front group GF. The image surface side lens surface is preferable. Since reflected light is likely to be generated on a concave lens surface when viewed from the object side among the optical surfaces in the front group GF, ghosts and flares are effectively reduced by forming an antireflection film on such an optical surface. be able to.

  In the optical system OS according to the present embodiment, the optical surface provided with the antireflection film among the optical surfaces in the rear group GR is preferably a concave lens surface as viewed from the image plane side. In this way, reflected light is likely to be generated on a concave lens surface as viewed from the image plane side among the optical surfaces in the rear group GR. Therefore, by forming an antireflection film on such an optical surface, ghost and Flares can be effectively reduced.

  Further, in the optical system OS according to the present embodiment, the concave lens surface provided with the antireflection film among the optical surfaces in the rear group GR and the concave lens surface when viewed from the image side is the most image side of the rear group GR. It is preferably the object side lens surface of the lens. Reflective light is likely to be generated on the concave lens surface when viewed from the image plane side among the optical surfaces in the rear group GR. By forming an antireflection film on such an optical surface, ghosts and flares are effectively reduced. Can be made.

  Further, in the optical system OS according to the present embodiment, the concave lens surface provided with the antireflection film among the optical surfaces in the rear group GR and the concave lens surface when viewed from the image side is the most image side of the rear group GR. It is preferable that the second lens surface on the object side from the lens is the image surface side lens surface. Reflective light is likely to be generated on the concave lens surface when viewed from the image plane side among the optical surfaces in the rear group GR. By forming an antireflection film on such an optical surface, ghosts and flares are effectively reduced. Can be made.

  In the optical system OS according to the present embodiment, the antireflection film is not limited to the wet process, and may be formed by a dry process or the like. At this time, it is preferable that the antireflection film includes at least one layer having a refractive index of 1.30 or less. By making the antireflection film include at least one layer having a refractive index of 1.30 or less, even if the antireflection film is formed by a dry process or the like, the same effect as that obtained by using a wet process can be obtained. Can be obtained. At this time, the layer having a refractive index of 1.30 or less is preferably the most surface layer among the layers constituting the multilayer film.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (3).

0.00 <(− fFN1) / f0 <20.00 (3)
However,
fFN1: focal length of the second lens component LFN1 in the front group GF f0: focal length of the entire system when focusing on infinity

  Conditional expression (3) is a condition that defines the combined focal length of the negative lens component (second lens component LFN1) with the convex surface facing the object side of the front group GF. The front group GF of the optical system OS according to the present embodiment has a positive and negative configuration, and defines the optimum refractive power of the negative lens component (second lens component LFN1) at the intermediate portion.

  When the upper limit value of the conditional expression (3) is exceeded, it means that the negative refractive power of the negative lens component (second lens component LFN1) becomes weak. In this case, correction of field curvature and astigmatism deteriorates, which is not preferable. When the upper limit value of conditional expression (3) is set to 15.00, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (3) is set to 12.00, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (3) to 10.00, the effects of the present application can be maximized.

  Further, when the lower limit value of conditional expression (3) is not reached, it means that the negative refractive power of the negative lens component (second lens component LFN1) becomes strong. In that case, correction of coma aberration, spherical aberration, and distortion is deteriorated as a result, which is not preferable. If the lower limit value of conditional expression (3) is set to 0.30, it is advantageous for correction of various aberrations such as spherical aberration. Setting the lower limit value of conditional expression (3) to 0.59 is advantageous for correcting various aberrations such as spherical aberration. In addition, by setting the lower limit value of conditional expression (3) to 1.00, the effects of the present application can be maximized.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (4).

0.20 <(− fFN2) / f0 <15.00 (4)
However,
fFN2: focal length of the third lens component LFN2 in the front group GF f0: focal length of the entire system when focusing on infinity

  Conditional expression (4) is a condition that defines the magnitude of the focal length of the negative lens component (third lens component LFN2) on the image side of the front group GF, in other words, the magnitude of the negative refractive power.

  When the upper limit value of the conditional expression (4) is exceeded, it means that the negative refractive power of the negative lens component (third lens component LFN2) on the image side of the front group GF is reduced. In this case, the balance of correction for spherical aberration and coma is lost, which is not preferable. When the upper limit value of conditional expression (4) is set to 10.00, the above-described correction of various aberrations is advantageous. If the upper limit value of conditional expression (4) is set to 8.00, the above-described correction of various aberrations is advantageous. Further, by setting the upper limit value of conditional expression (4) to 7.00, the effect of the present application can be maximized.

  Further, when the lower limit value of conditional expression (4) is not reached, it means that the negative refractive power of the negative lens component (third lens component LFN2) on the image side of the front group GF is increased. This is not preferable because sagittal coma and distortion are particularly deteriorated. If the lower limit value of conditional expression (4) is set to 0.30, the above-mentioned various aberrations can be corrected more favorably. If the lower limit value of conditional expression (4) is set to 0.50, the above-mentioned various aberrations can be corrected more favorably. If the lower limit value of conditional expression (4) is set to 0.80, the above-mentioned various aberrations can be corrected more favorably. Further, by setting the lower limit value of conditional expression (4) to 0.86, the effect of the present application can be maximized.

  In the optical system OS according to the present embodiment, the second lens component LRP1 of the rear group GR is a cemented lens in which the positive lens L23 and the negative lens L24 are cemented, and satisfies the following conditional expression (5): It is desirable to do.

0.000 <nRPP-nRPN <0.500 (5)
However,
nRPP: refractive index of the second lens component LRP1 in the rear group GR with respect to the d-line of the medium of the positive lens L23 nRPN: refractive index of the medium of the negative lens L24 of the second lens component LRP1 in the rear group GR with respect to the d-line

  Conditional expression (5) is a condition that defines the relationship between the refractive indexes of the positive lens L23 and the negative lens L24 in the positive lens component (second lens component LRP1) in the rear group GR. Basically, the positive lens L23 has a higher refractive index than the negative lens L24, and the Petzval sum is suppressed to a small value.

  If the upper limit value of the conditional expression (5) is exceeded, the difference in refractive index between the positive lens L23 and the negative lens L24 becomes remarkably large, so that a dispersion difference cannot be secured with the currently existing glass material, and the correction of chromatic aberration deteriorates. If the upper limit value of conditional expression (5) is set to 0.400, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (5) is set to 0.300, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit of conditional expression (5) to 0.250, the effect of the present application can be maximized.

  When the lower limit of conditional expression (5) is not reached, the difference in refractive index between the positive lens L23 and the negative lens L24 becomes smaller, and the height is finally reversed. Since the refractive index of the negative lens L24 is higher than that of the positive lens L23, it becomes difficult to set an optimal value for the Petzval sum, and as a result, field curvature and astigmatism are deteriorated. If the lower limit value of conditional expression (5) is set to 0.100, it is advantageous for correcting the above-mentioned various aberrations. Setting the lower limit of conditional expression (5) to 0.130 is advantageous for correcting the above-mentioned various aberrations. Further, by setting the lower limit value of conditional expression (5) to 0.145, the effect of the present application can be maximized.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (6).

1.00 <fRP / f0 <12.00 (6)
However,
fRP: focal length of the second lens component LRP1 in the rear group GR f0: focal length of the entire system when focusing on infinity

  Conditional expression (6) is a condition that defines the combined focal length of the positive lens component (second lens component LRP1) with the concave surface facing the image side in the rear group GR. In the optical system OS according to the present embodiment, the rear group GR has a negative positive or positive configuration, and a positive lens component (second lens) disposed at the intermediate portion and having a concave surface facing the image side. It defines the optimum refractive power of the component LRP1).

  When exceeding the upper limit value of the conditional expression (6), it means that the focal length of the positive lens component (second lens component LRP1) is remarkably increased and the positive refractive power is weakened. In this case, the correction of sagittal coma, meridional coma, field curvature, and astigmatism deteriorates, which is not preferable. When the upper limit value of conditional expression (6) is set to 10.00, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (6) is set to 9.00, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (6) to 8.00, the effect of the present application can be maximized.

  On the other hand, if the lower limit value of conditional expression (6) is not reached, it means that the focal length of the positive lens component (second lens component LRP1) is remarkably shortened and the positive refractive power is remarkably increased. In this case, the correction of spherical aberration, sagittal coma aberration, and meridional coma aberration deteriorates as a result, which is not preferable. Also, the sensitivity to eccentricity increases, which is not preferable. If the lower limit value of conditional expression (6) is set to 1.50, it is advantageous for correction of various aberrations such as spherical aberration. Setting the lower limit of conditional expression (6) to 1.92 is advantageous for correcting various aberrations such as spherical aberration. Further, by setting the lower limit value of conditional expression (6) to 2.75, the effect of the present application can be maximized.

  Moreover, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (7).

0.1 <fRP2 / f0 <3.0 (7)
However,
fRP2: focal length of the third lens component LRP2 in the rear group GR f0: focal length of the entire system when focusing on infinity

  Conditional expression (7) is a condition that defines the focal length of the positive lens component (third lens component LRP2) located on the image side in the rear group GR. In the optical system OS according to the present embodiment, the rear group GR has a negative positive or positive configuration, and an optimum refractive power of the positive lens component (third lens component LRP2) disposed on the image side. It prescribes.

  When the upper limit value of the conditional expression (7) is exceeded, it means that the focal length of the positive lens component (third lens component LRP2) is remarkably increased and the positive refractive power is weakened. In this case, the correction capability of spherical aberration and coma aberration is lowered, which is not preferable. If the upper limit value of conditional expression (7) is set to 2.5, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (7) is set to 2.0, the above-described correction of various aberrations becomes more advantageous. In addition, the effect of the present application can be maximized by setting the upper limit value of conditional expression (7) to 1.5.

  If the lower limit value of conditional expression (7) is not reached, it means that the focal length of the positive lens component (third lens component LRP2) is remarkably shortened and the positive refractive power is remarkably increased. In this case, the correction of spherical aberration, sagittal coma aberration, and meridional coma aberration deteriorates as a result, which is not preferable. Also, the sensitivity to eccentricity increases, which is not preferable. If the lower limit value of conditional expression (7) is set to 0.2, it is advantageous for correction of various aberrations such as spherical aberration. Setting the lower limit of conditional expression (7) to 0.4 is advantageous for correcting various aberrations such as spherical aberration. Further, by setting the lower limit value of conditional expression (7) to 0.6, the effect of the present application can be maximized.

  The front group GF preferably has at least one aspheric surface, which is advantageous for correcting spherical aberration and coma corresponding to a large aperture. In addition, it is desirable that the rear group GR described above also has at least one aspheric surface. Similarly, the rear group GR is advantageous for correcting spherical aberration and coma corresponding to a large aperture. It should be noted that having one aspherical surface before and after the aperture stop S is effective in correcting aberrations caused by a large aperture such as spherical aberration, sagittal coma and meridional coma.

  The positive lens component (third lens component LRP2) disposed on the image side in the rear group GR is preferably a positive lens having a convex surface directed toward the object side. Combined with the positive lens component (second lens component LRP1) with the concave surface facing the image side in the rear group GR just before, a convex air lens can be made, which is advantageous for correcting spherical aberration and sagittal coma aberration. .

  In addition, an aperture stop S between the front group GF and the rear group GR is preferable for correcting lateral chromatic aberration and distortion.

  In the optical system OS according to the present embodiment, the first to third lens components LFP, LFN1, and LFN2 constituting the front group GF and the third lens component LRP2 constituting the rear group GR are shown in FIG. Although it is composed of a single lens, it may be composed of a cemented lens in which two or more single lenses are cemented.

  FIG. 18 is a schematic cross-sectional view of a single-lens reflex camera 1 (hereinafter simply referred to as a camera) as an imaging apparatus including the optical system OS described above. In this camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 (optical system OS) and focused on the focusing screen 4 via the quick return mirror-3. The light imaged on the focusing screen 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 6.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and the light of the object (subject) (not shown) condensed by the taking lens 2 is captured by the image sensor 7. A subject image is formed on the top. Thereby, the light from the object (subject) is captured by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can shoot an object (subject) with the camera 1. The camera 1 shown in FIG. 18 may be one that holds the photographic lens 2 in a detachable manner or may be molded integrally with the photographic lens 2. The camera 1 may be a so-called single-lens reflex camera, or a compact camera or a mirrorless camera that does not have a quick return mirror or the like.

  Here, by mounting the above-described optical system OS as the photographing lens 2 on the camera 1, a large-aperture lens with less spherical aberration, sagittal coma flare, field curvature, and coma is realized by its characteristic lens configuration. doing. As a result, the camera 1 can realize an image pickup apparatus that has a large aperture and is capable of wide-angle shooting with less spherical aberration, sagittal coma aberration, field curvature, and meridional coma aberration.

  In addition, the contents described below can be appropriately adopted as long as the optical performance is not impaired.

  In the present embodiment, the optical system OS having the two-group configuration is shown, but the above-described configuration conditions and the like can be applied to other group configurations such as the third group, the fourth group, and the like. Further, a configuration in which a lens or a lens group is added closest to the object side, a configuration in which a lens or a lens group is added closest to the image side, or a configuration in which a lens group is added between the lens groups may be used. The lens group is a portion having at least one lens separated by the aperture stop S as described above, or at least one piece separated by an air interval that changes at the time of zooming or focusing. The part which has a lens is shown.

  In this embodiment, the entire (all groups) feed is used to focus on an object at a short distance from an object at infinity. A focusing lens group that performs focusing from an object to a short-distance object may be used. That is, a method using the front group GF or a rear focus using the rear group GR may be used. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like).

  Also, by moving the lens group or partial lens group so that it has a component in the direction perpendicular to the optical axis, or rotating (swinging) in the in-plane direction including the optical axis, image blur caused by camera shake is corrected. An anti-vibration lens group may be used. In particular, it is preferable that at least one of the rear group GR is an anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment is prevented. Further, even when the image plane is shifted in the optical axis direction, it is preferable because there is little deterioration in the drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin on the glass surface. Any of the aspherical surfaces may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  The aperture stop S is preferably arranged near the center of the optical system OS. However, the role of the aperture stop may be substituted by a lens frame without providing a member as an aperture stop.

  Further, each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength range in order to reduce flare and ghost and achieve high optical performance with high contrast.

  Hereinafter, an outline of a method for manufacturing the optical system OS according to the present embodiment will be described with reference to FIG. In the manufacturing method of the optical system OS according to the present embodiment, the front group GF and the rear group GR having a positive refractive power are arranged in order from the object side along the optical axis. Further, an antireflection film, which will be described later, is provided on at least one of the optical surfaces in the front group GF and the rear group GR, and the antireflection film includes at least one layer formed by using a wet process. Yes.

  Specifically, in the present embodiment, for example, as the front group GF, in order from the object side, a biconvex aspherical positive lens L11 (first positive lens component LFP), a negative refractive power, and on the object side A negative meniscus lens L12 (second lens component LFN1) having a convex surface and a biconcave negative lens L13 (third lens component LFN2) are arranged (step S100), and the rear group GR is sequentially arranged from the object side. A biconcave negative lens L21 and a biconvex positive lens L22 are cemented, and a first lens component LRN having a concave surface directed toward the object side, a biconvex positive lens L23, and a biconcave negative lens L24. A second lens component LRP1 which is cemented and has a positive refractive power as a whole and has a concave surface facing the image side, and a biconvex aspherical positive lens L25 having a positive refractive power (third lens component LRP2) (Step S200). At this time, the first lens component LRN and the second lens component LRP1 constituting the rear group GR satisfy the above-described conditional expressions (1) and (2).

  As described above, according to the optical system OS according to the present embodiment, ghosts and flares, which are suitable for an imaging device such as a camera, a printing lens, and a copying lens, are further reduced, and a small and high imaging performance is achieved. It is possible to provide a lens having the same and an imaging apparatus using the lens.

  Hereinafter, examples of the optical system OS according to the present embodiment will be described with reference to the drawings. 1, 4, 6, 8, 10, 12, 14, and 16 illustrate the configuration of the optical system OS (OS1 to OS8) according to each embodiment.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and An is the nth-order aspherical coefficient, and is expressed by the following equation (a). . In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.

S (y) = (y ² / r) / [1+ {1−κ (y ² / r ² )} ^1/2 ]
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰ (a)

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the right side of the surface number.

[First embodiment]
FIG. 1 is a cross-sectional view illustrating a lens configuration of an optical system OS1 according to the first example. The optical system OS1 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a biconvex aspherical positive lens L11, a second lens component LFN1 including a negative meniscus lens L12 having a convex surface facing the object side, and biconcave. The third lens component LFN2 is formed of a negative lens L13 having a shape.

  In the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a first lens component LRN having a concave surface facing the object side, and a biconvex positive The lens L23 and the biconcave negative lens L24 are cemented, and from the second lens component LRP1 having a positive refractive power as a whole and having a concave surface facing the image side, and the biconvex aspherical positive lens L25 The third lens component LRP2 is formed. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS1 and the image plane I.

  The optical system OS1 according to the first example includes the image side lens surface (surface number 6) of the biconcave negative lens L13 of the front group GF and the object side of the biconcave negative lens L21 of the rear group GR. An antireflection film described later is formed on the lens surface (surface number 8).

  Table 1 below lists values of specifications of the optical system OS1 according to the first example. In the overall specifications of Table 1, f is the focal length, FNO is the F number, ω is the half angle of view (unit: degree), Y is the image height, TL is the total length of the optical system OS1, and Bf is the back focus. Represents each. The total length TL indicates the distance on the optical axis from the most object side lens surface (first surface) of the optical system OS1 to the image plane I, and the air conversion back focus Bf is obtained when the dummy glass FL is removed. The distance on the optical axis from the most image side lens surface (fifteenth surface) of the optical system OS1 to the image surface I is shown. In the lens data, the first column m indicates the order (surface number) of the optical surfaces from the object side along the traveling direction of the light beam, the second column r indicates the curvature radius of each optical surface, The column d shows the distance (surface interval) on the optical axis from each optical surface to the next optical surface, and the fourth column νd and the fifth column nd show the Ab for the d-line (wavelength λ = 587.6 nm), respectively. Number and refractive index are shown. The surface numbers 1 to 17 shown in Table 1 correspond to the numbers 1 to 17 shown in FIG. Further, “∞” of the curvature radius of the object surface and the image surface, “0.0000” of the curvature radius of the aperture stop and the lens surface respectively indicate a plane. Further, the refractive index of air of 1.0000 is omitted. Further, the surface interval of the final surface (the 17th surface) is a distance on the optical axis to the image surface I. The lens group focal length indicates the surface number (starting surface) where each lens group starts and the focal length of each lens group.

  Here, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1) First Example [Overall Specifications]
f = 58.0220
FNO = F1.210
ω = 20.81 °
Y = 21.6
TL = 108.8935
Air equivalent Bf = 38.0120

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 65.8839 7.0000 49.53 1.744430
2 -497.8249 0.1000
3 31.8477 8.0000 63.88 1.516800
4 25.3357 7.5000
5 -1352.9378 1.5000 31.16 1.688930
6 45.3369 5.5000
7 0.0000 8.5000 Aperture stop S
8 -26.2017 1.7000 29.57 1.717360
9 140.0354 9.8000 46.59 1.816000
10 -37.7310 0.1000
11 40.8209 10.0000 49.62 1.772500
12 -155.3245 1.3000 41.51 1.575010
13 32.9483 2.7000
14 54.6222 6.5000 49.53 1.744430
15 * -117.5302 36.0000
16 0.0000 2.0000 63.88 1.516800
17 0.0000 0.6935
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 1452.0656
Rear group 8 41.4561

  In the optical system OS1 according to the first example, each lens surface of the first surface and the fifteenth surface is formed in an aspherical shape. Table 2 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A6. The aspheric constants (A8 to A10) that are not displayed are zero. The description of these symbols is the same in the following embodiments.

(Table 2)
κ A4 A6
First side -0.4179 6.27748E-08 -9.11068E-11
15th 3.6628 2.28024E-06 7.37001E-10

  Table 3 below shows values corresponding to the conditional expressions for the optical system OS1 according to the first example. In Table 3, nRNP is the refractive index with respect to the d-line of the medium of the positive lens L22 in the first lens component LRN in the rear group GR, and nRNN is the negative lens L21 in the first lens component LRN in the rear group GR. Rp1 is the radius of curvature of the most object side surface of the second lens component LRP1 in the rear group GR, and rp2 is the most image side surface of the second lens component LRP1 in the rear group GR. The radius of curvature, fFN1 is the focal length of the second lens component LFN1 in the front group GF, fFN2 is the focal length of the third lens component LFN2 in the front group GF, and nRPP is the positive lens of the second lens component LRP1 in the rear group GR. The refractive index with respect to the d-line of the medium of L23, nRPN: is the refractive index of the second lens component LRP1 in the group GR with respect to the d-line of the medium of the negative lens L24, and fRP is the second lens component LRP in the rear group GR. The focal length of, FRP third lens focal length components LRP2 in the rear group GR is, f0 is the focal length of the entire system when focused on an object at infinity, respectively. The description of these symbols is the same in the following embodiments.

(Table 3)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1067
(3) (-fFN1) /f0=7.1072
(4) (−fFN2) /f0=1.0970
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 3.6208
(7) fRP2 / f0 = 0.8775

  Thus, the optical system OS1 according to the first example satisfies all the conditional expressions (1) to (7).

  FIG. 2 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS1 according to the first example. In each aberration diagram, FNO represents an F number, Y represents an image height, and ω represents a half angle of view [unit: degree]. In each aberration diagram, d represents the aberration with respect to the d-line (wavelength λ = 587.6 nm), and g represents the aberration with respect to the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, at each half angle of view ω, the solid line represents the meridional coma aberration with respect to the d-line and the g-line, and the broken line on the left side from the origin represents the sagittal coma aberration generated in the meridional direction with respect to the d-line. The broken line represents the sagittal coma generated in the sagittal direction with respect to the d line. The description of this aberration diagram is the same in the following examples.

  As is apparent from the respective aberration diagrams shown in FIG. 2, in the optical system OS1 according to the first example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

  FIG. 3 shows an optical system OS1 having the same configuration as that of the first embodiment, and incident light rays are reflected by the first reflecting surface and the second reflecting surface to cause ghost and flare on the image surface I. It is a figure which shows an example of a mode that it forms.

  In FIG. 3, when a light beam BM from the object side enters the optical system OS1 as shown in the figure, the object-side lens surface (the first reflected light generation surface, whose surface number is the surface number) in the biconcave negative lens L21. 8), and the reflected light is reflected again on the image surface I by the lens surface on the image surface side (the second reflected light generation surface, whose surface number is 6) in the biconcave negative lens L13. Reach and cause ghosts and flares. The first reflected light generation surface 8 is a concave lens surface when viewed from the aperture stop, and the second reflected light generation surface 6 is a concave lens surface when viewed from the aperture stop. By forming an antireflection film corresponding to a wide incident angle in a wider wavelength range on such a surface, ghosts and flares can be effectively reduced.

[Second Embodiment]
FIG. 4 is a cross-sectional view showing the lens configuration of the optical system OS2 according to the second example. The optical system OS2 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a biconvex aspherical positive lens L11, a positive meniscus lens L12 having a convex surface facing the object side, and a negative meniscus lens L13 having a convex surface facing the object side. And a second lens component LFN1 having a negative meniscus lens shape as a whole and a third lens component LFN2 including a negative lens L14 having a biconcave shape.

  In the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a first lens component LRN having a concave surface facing the object side, and a biconvex positive The lens L23 and the biconcave negative lens L24 are cemented, and from the second lens component LRP1 having a positive refractive power as a whole and having a concave surface facing the image side, and the biconvex aspherical positive lens L25 The third lens component LRP2 is formed. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS2 and the image plane I.

  The optical system OS2 according to the second example includes the image side lens surface (surface number 14) of the biconcave negative lens L24 of the rear group GR and the object side of the biconvex positive lens L25 of the rear group GR. An antireflection film described later is formed on the lens surface (surface number 15).

  Table 4 below lists values of specifications of the optical system OS2 according to the second example. In addition, the surface numbers 1-18 shown in this Table 4 respond | correspond to the numbers 1-18 shown in FIG.

(Table 4) Second Example [Overall Specifications]
f = 58.0216
FNO = F1.210
ω = 21.03 °
Y = 21.6
TL = 111.4017
Air conversion Bf = 38.0203

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 48.5419 9.0000 49.53 1.744430
2 -4006.7159 0.1000
3 41.2667 6.5000 82.57 1.497820
4 60.0000 1.5000 63.88 1.516800
5 24.7856 7.5000
6 -11889.5204 1.5000 31.16 1.688930
7 45.6954 5.5000
8 0.0000 8.5000 Aperture stop S
9 -26.7890 1.7000 29.57 1.717360
10 95.9330 9.8000 46.59 1.816000
11 -40.5577 0.1000
12 40.7407 10.0000 49.62 1.772500
13 -352.6242 1.3000 41.51 1.575010
14 32.8034 2.7000
15 51.7528 7.0000 49.53 1.744430
16 * -90.7205 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 0.7017
Image plane ∞
[Lens focal length]
Lens group Start surface Focal length Front group 1 4379.4722
Rear group 9 40.0599

  In the optical system OS2 according to the second example, the first and sixteenth lens surfaces are formed in an aspherical shape. Table 5 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A6.

(Table 5)
κ A4 A6
1st surface -0.0458 2.67968E-07 -1.70729E-10
16th 1.9662 2.63114E-06 1.81677E-10

  Table 6 below shows values corresponding to the conditional expressions for the optical system OS2 according to the second example.

(Table 6)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1079
(3) (-fFN1) /f0=2.4136
(4) (−fFN2) /f0=1.1388
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 4.2148
(7) fRP2 / f0 = 0.7793

  Thus, the optical system OS2 according to the second example satisfies all the conditional expressions (1) to (7).

  FIG. 5 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS2 according to the second example. As is apparent from the aberration diagrams shown in FIG. 5, in the optical system OS2 according to the second example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Third embodiment]
FIG. 6 is a cross-sectional view showing the lens configuration of the optical system OS3 according to the third example. The optical system OS3 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a biconvex aspherical positive lens L11, a second lens component LFN1 including a negative meniscus lens L12 having a convex surface facing the object side, and the object side. The third lens component LFN2 is composed of a negative meniscus lens L13 having a convex surface facing the surface.

  Further, in the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a first lens component LRN having a concave surface on the object side, and a convex surface on the object side. A positive meniscus lens L23 directed to a negative meniscus lens L24 having a convex surface facing the object side is cemented, a second lens component LRP1 having a positive refractive power as a whole and a concave surface facing the image side, and biconvex It is composed of a third lens component LRP2 composed of an aspherical positive lens L25 having a shape. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS3 and the image plane I.

  The optical system OS3 according to the third example includes an object side lens surface (surface number 3) of the negative meniscus lens L12 of the front group GF and an image surface side lens surface (surface number 4) of the negative meniscus lens L12 of the front group GF. ) Is formed with an antireflection film to be described later.

  Table 7 below provides values of specifications of the optical system OS3 according to the third example. The surface numbers 1 to 17 shown in Table 7 correspond to the numbers 1 to 17 shown in FIG.

(Table 7) Third Example [Overall Specifications]
f = 58.0216
FNO = F1.212
ω = 20.67 °
Y = 21.6
TL = 111.7529
Air equivalent Bf = 38.0715

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 42.9001 9.0000 49.53 1.744430
2 -759.7809 0.1000
3 39.3381 5.0000 63.88 1.516800
4 23.0671 7.0000
5 109.0084 1.5000 31.16 1.688930
6 30.0146 7.5000
7 0.0000 8.5000 Aperture stop S
8 -29.9941 1.7000 29.57 1.717360
9 53.7056 12.0000 46.59 1.816000
10 -39.1782 0.1000
11 35.1890 7.0000 52.34 1.755000
12 141.3160 1.3000 45.51 1.548140
13 28.5039 4.8000
14 72.7463 7.5000 49.53 1.744430
15 * -87.9348 36.0000
16 0.0000 2.0000 63.88 1.516800
17 0.0000 0.7529
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 2966.21728
Rear group 8 41.35903

  In the optical system OS3 according to the third example, each lens surface of the first surface and the fifteenth surface is formed in an aspherical shape. Table 8 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A6.

(Table 8)
κ A4 A6
First side -0.2253 1.10855E-07 -5.77849E-10
15th 3.8248 1.40952E-06 -1.06066E-10

  Table 9 below shows values corresponding to the conditional expressions for the optical system OS3 according to the third example.

(Table 9)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1050
(3) (−fFN1) /f0=2.0774
(4) (−fFN2) /f0=1.0443
(5) nRPP-nRPN = 0.2069
(6) fRP / f0 = 6.0322
(7) fRP2 / f0 = 0.9405

  Thus, the optical system OS3 according to the third example satisfies all the conditional expressions (1) to (7).

  FIG. 7 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS3 according to the third example. As is apparent from the respective aberration diagrams shown in FIG. 7, in the optical system OS3 according to the third example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Fourth embodiment]
FIG. 8 is a cross-sectional view showing the lens configuration of the optical system OS4 according to the fourth example. The optical system OS4 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a biconvex aspherical positive lens L11, a second lens component LFN1 including a negative meniscus lens L12 having a convex surface facing the object side, and the object side. The third lens component LFN2 is composed of a negative meniscus lens L13 having a convex surface facing the surface.

  Further, in the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a first lens component LRN having a concave surface on the object side, and a convex surface on the object side. A positive meniscus lens L23 directed to a negative meniscus lens L24 having a convex surface facing the object side is cemented, a second lens component LRP1 having a positive refractive power as a whole and a concave surface facing the image side, and biconvex It is composed of a third lens component LRP2 composed of an aspherical positive lens L25 having a shape. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS4 and the image plane I.

  In the optical system OS4 according to the fourth example, an antireflection film described later is formed on the object side lens surface (surface number 5) of the negative meniscus lens L13 of the front group GF.

  Table 10 below lists values of specifications of the optical system OS4 according to the fourth example. The surface numbers 1 to 17 shown in Table 10 correspond to the numbers 1 to 17 shown in FIG.

(Table 10) Fourth Example [Overall Specifications]
f = 58.0216
FNO = F1.2075
ω = 20.71 °
Y = 21.6
TL = 115.1080
Air conversion Bf = 38.2266

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 42.3307 11.0000 49.53 1.744430
2 -1195.5447 0.1000
3 38.4586 3.0000 63.88 1.516800
4 22.9860 9.0000
5 100.1795 1.5000 31.16 1.688930
6 30.4674 7.0000
7 0.0000 8.5000 Aperture stop S
8 -28.6498 1.7000 29.57 1.717360
9 56.2750 13.0000 46.59 1.816000
10 -38.4062 0.1000
11 36.0036 8.5000 49.62 1.772500
12 147.7696 1.3000 41.51 1.575010
13 28.8771 5.0000
14 65.3476 6.5000 49.53 1.744430
15 * -98.9846 36.0000
16 0.0000 2.0000 63.88 1.516800
17 0.0000 0.9080
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 2657.53882
Rear group 8 41.38318

  In the optical system OS4 according to the fourth example, each lens surface of the first surface and the fifteenth surface is formed in an aspherical shape. Table 11 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A6.

(Table 11)
κ A4 A6
1st surface -0.2144 3.20826E-07 -5.21258E-10
Surface 15 1.9946 1.02179E-06 -1.79192E-10

  Table 12 below shows values corresponding to the conditional expressions for the optical system OS4 according to the fourth example.

(Table 12)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1098
(3) (-fFN1) /f0=2.0402
(4) (-fFN2) /f0=1.1050
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 6.3210
(7) fRP2 / f0 = 0.9270

  As described above, the optical system OS4 according to the fourth example satisfies all the conditional expressions (1) to (7).

  FIG. 9 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS4 according to the fourth example. As is apparent from the respective aberration diagrams shown in FIG. 9, in the optical system OS4 according to the fourth example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Fifth embodiment]
FIG. 10 is a cross-sectional view showing a lens configuration of an optical system OS5 according to the fifth example. The optical system OS5 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a biconvex aspherical positive lens L11, a positive meniscus lens L12 having a convex surface facing the object side, and a negative meniscus lens L13 having a convex surface facing the object side. And a second lens component LFN1 having a negative meniscus lens shape as a whole, and a third lens component LFN2 including a negative meniscus lens L14 having a convex surface facing the object side.

  Further, in the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a first lens component LRN having a concave surface on the object side, and a convex surface on the object side. A positive meniscus lens L23 directed to a negative meniscus lens L24 having a convex surface facing the object side is cemented, a second lens component LRP1 having a positive refractive power as a whole and a concave surface facing the image side, and biconvex It is composed of a third lens component LRP2 composed of an aspherical positive lens L25 having a shape. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS5 and the image plane I.

  In the optical system OS5 according to the fifth example, an antireflection film described later is formed on the image surface side lens surface (surface number 7) of the negative meniscus lens L14 of the front group GF.

  Table 13 below provides values of specifications of the optical system OS5 according to the fifth example. In addition, the surface numbers 1-18 shown in this Table 13 respond | correspond to the numbers 1-18 shown in FIG.

(Table 13) 5th Example [whole specification]
f = 58.0216
FNO = F1.210
ω = 20.81 °
Y = 21.6
TL = 110.39748
Air conversion Bf = 38.01604

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 49.8688 9.0000 49.53 1.744430
2 -518.0363 0.1000
3 40.2883 5.5000 52.20 1.517420
4 60.0000 1.5000 63.88 1.516800
5 27.9254 6.0000
6 168.7999 1.5000 31.16 1.688930
7 30.2735 7.5000
8 0.0000 8.5000 Aperture stop S
9 -28.8341 1.7000 29.57 1.717360
10 78.5900 10.5000 46.59 1.816000
11 -40.5395 0.1000
12 37.3064 7.5000 49.62 1.772500
13 396.2828 1.3000 41.51 1.575010
14 30.5026 4.0000
15 62.3814 7.0000 49.53 1.744430
16 * -82.5179 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 0.6975
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 2115.41898
Rear group 9 40.65448

  In the optical system OS5 according to the fifth example, the lens surfaces of the first surface and the sixteenth surface are formed in an aspherical shape. Table 14 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A6.

(Table 14)
κ A4 A6
1st surface -0.2362 3.22585E-08 -4.00333E-10
16th 2.6137 1.95398E-06 -1.27860E-10

  Table 15 below shows values corresponding to the conditional expressions for the optical system OS5 according to the fifth example.

(Table 15)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1003
(3) (-fFN1) /f0=3.7656
(4) (−fFN2) /f0=0.9270
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 5.1177
(7) fRP2 / f0 = 0.8398

  Thus, the optical system OS5 according to the fifth example satisfies all the conditional expressions (1) to (7).

  FIG. 11 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS5 according to the fifth example. As is apparent from the respective aberration diagrams shown in FIG. 11, in the optical system OS5 according to the fifth example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Sixth embodiment]
FIG. 12 is a cross-sectional view illustrating a lens configuration of an optical system OS6 according to the sixth example. The optical system OS6 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a positive meniscus aspherical positive lens L11 with a convex surface facing the object side, a biconvex positive lens L12, and a biconcave negative lens L13. And a third lens component LFN2 including a negative meniscus lens L14 having a negative meniscus lens shape as a whole and a negative meniscus lens L14 having a concave surface facing the object side.

  In the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, and have a negative refractive power as a whole, with the concave surface facing the object side. 1 lens component LRN, a biconvex positive lens L23 and a biconcave negative lens L24 are cemented together, a second lens component LRP1 having a positive refractive power as a whole and having a concave surface facing the image side, and The third lens component LRP2 is composed of a biconvex aspherical positive lens L25. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS6 and the image plane I.

  In the optical system OS6 according to the sixth example, an antireflection film described later is formed on the image surface side lens surface (surface number 7) of the negative meniscus lens L14 of the front group GF.

  Table 16 below provides values of specifications of the optical system OS6 according to the sixth example. In addition, the surface numbers 1-18 shown in this Table 16 respond | correspond to the numbers 1-18 shown in FIG.

(Table 16) Sixth Example [Overall specifications]
f = 58.0216
FNO = F1.229
ω = 20.82 °
Y = 21.6
TL = 122.05004
Air conversion Bf = 38.01861

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 41.8098 11.0500 49.53 1.744430
2 * 2652.8412 1.0000
3 117.6517 5.4000 82.57 1.497820
4 -257.3631 1.5000 48.78 1.531720
5 22.4645 11.0000
6 -55.6445 2.0000 70.31 1.487490
7 -96.0152 3.0000
8 0.0000 10.0000 Aperture stop S
9 -29.5135 1.7000 28.38 1.728250
10 109.6394 11.0000 46.59 1.816000
11 -40.5171 0.1000
12 44.9154 14.5000 49.62 1.772500
13 -50.7224 1.6000 41.51 1.575010
14 33.7818 2.5000
15 54.2656 7.0000 49.53 1.744430
16 * -233.5493 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 0.7000
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 6928.27452
Rear group 9 43.40473

  In the optical system OS6 according to the sixth example, the lens surfaces of the first surface, the second surface, and the sixteenth surface are formed in an aspherical shape. Table 17 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 17)
κ A4 A6 A8 A10
First side -1.3241 3.10229E-06 -7.79759E-10 3.01550E-13 -7.29996E-16
2nd surface -0.1653E + 05 -7.21606E-08 7.08003E-11 -3.55610E-13 1.07080E-17
16th surface -16.7337 1.90857E-06 4.23655E-09 -1.20892E-11 2.56021E-14

  Table 18 below shows values corresponding to the conditional expressions for the optical system OS6 according to the sixth example.

(Table 18)
(1) nRNP-nRNN = 0.08775
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1415
(3) (−fFN1) /f0=0.9018
(4) (−fFN2) /f0=4.7562
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 2.7473
(7) fRP2 / f0 = 1.0302

  As described above, the optical system OS6 according to the sixth example satisfies all the conditional expressions (1) to (7).

  FIG. 13 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, chromatic aberration of magnification, and coma aberration in the infinitely focused state of the optical system OS6 according to the sixth example. As is apparent from the aberration diagrams shown in FIG. 13, in the optical system OS6 according to the sixth example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Seventh embodiment]

  FIG. 14 is a cross-sectional view showing a lens configuration of an optical system OS7 according to the seventh example. The optical system OS7 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a positive meniscus aspherical positive lens L11 with a convex surface facing the object side, a biconvex positive lens L12, and a biconcave negative lens L13. And a third lens component LFN2 including a negative meniscus lens L14 having a negative meniscus lens shape as a whole and a negative meniscus lens L14 having a concave surface facing the object side.

  In the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, and have a negative refractive power as a whole, with the concave surface facing the object side. 1 lens component LRN, a biconvex positive lens L23 and a biconcave negative lens L24 are cemented together, a second lens component LRP1 having a positive refractive power as a whole and having a concave surface facing the image side, and The third lens component LRP2 is composed of a biconvex aspherical positive lens L25. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS7 and the image plane I.

  The optical system OS7 according to the seventh example includes an object side lens surface (surface number 6) of the negative meniscus lens L14 of the front group GF and an image surface side lens surface (surface number 7) of the negative meniscus lens L14 of the front group GF. ) Is formed with an antireflection film to be described later.

  Table 19 below provides values of specifications of the optical system OS7 according to the seventh example. The surface numbers 1 to 18 shown in Table 19 correspond to the numbers 1 to 18 shown in FIG.

(Table 19) Seventh Example [Overall specifications]
f = 58.0216
FNO = F1.2300
ω = 20.83 °
Y = 21.6
TL = 121.55017
Air conversion Bf = 38.01873

[Lens data]
m rd νd nd
Object ∞ ∞
1 * 42.3882 11.0500 49.53 1.744430
2 * 2167.3376 1.0000
3 113.8826 5.4000 82.57 1.497820
4 -622.3931 1.5000 48.78 1.531720
5 22.7071 11.0000
6 -60.3750 2.0000 52.20 1.517420
7 -96.0594 3.0000
8 0.0000 10.0000 Aperture stop S
9 -28.9264 1.7000 28.38 1.728250
10 129.6692 11.0000 46.59 1.816000
11 -39.3334 0.1000
12 46.0594 14.0000 49.62 1.772500
13 -50.2692 1.6000 41.51 1.575010
14 34.3180 2.5000
15 55.6965 7.0000 49.53 1.744430
16 * -232.9169 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 0.7002
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 1869.98022
Rear group 9 43.86208

  In the optical system OS7 according to the seventh example, the lens surfaces of the first surface, the second surface, and the sixteenth surface are formed in an aspherical shape. Table 20 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 20)
κ A4 A6 A8 A10
1st surface -1.3412 2.99857E-06 -8.24891E-10 2.35245E-13 -4.91290E-16
2nd surface -0.3444E + 04 -8.68033E-08 4.62357E-11 -2.08722E-13 -2.01437E-17
16th surface -8.6128 1.92924E-06 2.40259E-09 -6.72709E-12 1.77887E-14

  Table 21 below shows values corresponding to the conditional expressions for the optical system OS7 according to the seventh example.

(Table 21)
(1) nRNP-nRNN = 0.08775
(2) (rp2-rp1) / (rp2 + rp1) =-0.1461
(3) (−fFN1) /f0=0.9251
(4) (−fFN2) /f0=5.5192
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 2.8784
(7) fRP2 / f0 = 1.0515

  As described above, the optical system OS7 according to the seventh example satisfies all the conditional expressions (1) to (7).

  FIG. 15 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, chromatic aberration of magnification, and coma aberration in the infinitely focused state of the optical system OS7 according to the seventh example. As is apparent from the aberration diagrams shown in FIG. 15, in the optical system OS7 according to the seventh example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Eighth embodiment]
FIG. 16 is a cross-sectional view showing a lens configuration of an optical system OS8 according to the eighth example. The optical system OS8 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power.

  The front group GF includes, in order from the object side, a first lens component LFP including a positive meniscus aspherical positive lens L11 with a convex surface facing the object side, a biconvex positive lens L12, and a biconcave negative lens L13. And a third lens component LFN2 including a negative meniscus lens L14 having a negative meniscus lens shape as a whole and a negative meniscus lens L14 having a concave surface facing the object side.

  In the rear group GR, in order from the object side, a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, and have a positive refractive power as a whole, with the concave surface facing the object side. 1 lens component LRN, a biconvex positive lens L23 and a biconcave negative lens L24 are cemented together, a second lens component LRP1 having a positive refractive power as a whole and having a concave surface facing the image side, and The third lens component LRP2 is composed of a biconvex aspherical positive lens L25. A dummy glass FL corresponding to an optical low-pass filter is disposed between the rear group GR of the optical system OS8 and the image plane I.

  The optical system OS8 according to the eighth example includes the image side lens surface (surface number 7) of the negative meniscus lens L14 of the front group GF and the object side lens surface of the biconcave negative lens L21 of the rear group GR (surface number 7). An antireflection film described later is formed on the surface number 9).

  Table 22 below presents values of specifications of the optical system OS8 according to the eighth example. In addition, the surface numbers 1-18 shown in this Table 22 respond | correspond to the numbers 1-18 shown in FIG.

(Table 22) Eighth Example [Overall Specifications]
f = 58.0216
FNO = F1.2300
ω = 20.82 °
Y = 21.6
TL = 118.89463
Air equivalent Bf = 38.01320

[Lens data]
m rd νd nd
Object ∞
1 * 39.7073 11.0000 49.53 1.744430
2 * 2526.2002 0.1000
3 102.0678 6.5000 82.57 1.497820
4 -84.0848 1.5000 52.20 1.517420
5 21.4694 11.0000
6 -62.0246 2.0000 31.16 1.688930
7 -97.3881 3.0000
8 0.0000 10.0000 Aperture stop S
9 -26.3978 1.7000 29.57 1.717360
10 72.7424 12.0000 46.59 1.816000
11 -37.7187 0.1000
12 45.2189 10.0000 49.62 1.772500
13 -117.8426 1.3000 41.51 1.575010
14 33.4623 3.0000
15 56.4087 7.0000 49.53 1.744430
16 * -132.4054 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 0.6946
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length Front group 1 678.80939
Rear group 9 42.58204

  In the optical system OS8 according to the eighth example, the lens surfaces of the first surface, the second surface, and the sixteenth surface are formed in an aspherical shape. Table 23 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A10.

(Table 23)
κ A4 A6 A8 A10
First side -0.8567 3.05299E-06 -6.59016E-10 6.97421E-13 -4.05702E-16
2nd surface 0.5931E + 04 6.03268E-08 7.20986E-11 -2.17040E-13 8.89735E-17
16th surface 1.4374 1.57765E-06 -1.04169E-09 1.88087E-12 -4.58581E-16

  Table 24 below shows values corresponding to the conditional expressions for the optical system OS8 according to the eighth example.

(Table 24)
(1) nRNP-nRNN = 0.09864
(2) (rp2-rp1) / (rp2 + rp1) = − 0.1494
(3) (−fFN1) /f0=0.9153
(4) (−fFN2) /f0=4.3742
(5) nRPP-nRPN = 0.1975
(6) fRP / f0 = 5.1695
(7) fRP2 / f0 = 0.9306

  As described above, the optical system OS8 according to the eighth example satisfies all the conditional expressions (1) to (7).

  FIG. 17 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS8 according to the eighth example. As is apparent from the respective aberration diagrams shown in FIG. 17, in the optical system OS8 according to the eighth example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

  Here, an antireflection film (also referred to as a multilayer broadband antireflection film) used in the optical system OS according to the embodiment of the present application will be described. FIG. 20 is a diagram illustrating an example of a film configuration of the antireflection film. The antireflection film 101 is composed of seven layers and is formed on the optical surface of the optical member 102 such as a lens. The first layer 101a is formed of aluminum oxide deposited by a vacuum deposition method. Further, a second layer 101b made of a mixture of titanium oxide and zirconium oxide deposited by a vacuum deposition method is further formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide deposited by a vacuum deposition method is formed on the second layer 101b, and titanium oxide and zirconium oxide deposited by a vacuum deposition method are formed on the third layer 101c. A fourth layer 101d made of the mixture is formed. Furthermore, a fifth layer 101e made of aluminum oxide deposited by vacuum deposition is formed on the fourth layer 101d, and titanium oxide and zirconium oxide deposited by vacuum deposition on the fifth layer 101e. A sixth layer 101f made of the mixture is formed.

  Then, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed on the sixth layer 101f formed in this way by a wet process, and the antireflection film 101 of this embodiment is formed. For the formation of the seventh layer 101g, a sol-gel method which is a kind of wet process is used. The sol-gel method is a method in which a sol obtained by mixing raw materials is made into a non-flowable gel by hydrolysis / polycondensation reaction, etc., and this gel is heated and decomposed to obtain a product, In the production of an optical thin film, a film can be formed by applying an optical thin film material sol on the optical surface of an optical member and forming a gel film by drying and solidifying. The wet process is not limited to the sol-gel method, and a method of obtaining a solid film without going through a gel state may be used.

  Thus, the first layer 101a to the sixth layer 101f of the antireflection film 101 are formed by electron beam evaporation which is a dry process, and the seventh layer 101g which is the uppermost layer is prepared by a hydrofluoric acid / magnesium acetate method. It is formed by the following procedure by a wet process using the prepared sol solution. First, an aluminum oxide layer to be the first layer 101a, a titanium oxide-zirconium oxide mixed layer to be the second layer 101b, a third layer on the lens film formation surface (the optical surface of the optical member 102 described above) in advance using a vacuum deposition apparatus, An aluminum oxide layer to be the layer 101c, a titanium oxide-zirconium oxide mixed layer to be the fourth layer 101d, an aluminum oxide layer to be the fifth layer 101e, and a titanium oxide-zirconium oxide mixed layer to be the sixth layer 101f are formed in this order. And after taking out the optical member 102 from a vapor deposition apparatus, the thing which added the silicon alkoxide to the sol liquid prepared by the hydrofluoric acid / magnesium acetate method is apply | coated by the spin coat method, The magnesium fluoride used as the 7th layer 101g A layer made of a mixture of silica and silica is formed. The reaction formula when prepared by the hydrofluoric acid / magnesium acetate method is shown in the following formula (b).

2HF + Mg (CH3COO) 2 → MgF2 + 2CH3COOH (b)

  The sol solution used for the film formation is used for film formation after mixing raw materials and subjecting to an autoclave at 140 ° C. for 24 hours at a high temperature and pressure. The optical member 102 is completed by heat treatment at 160 ° C. for 1 hour in the air after the seventh layer 101g is formed. By using such a sol-gel method, the seventh layer 101g is formed by depositing particles having a size of several nm to several tens of nm leaving a void.

  The optical performance of the optical member having the antireflection film 101 formed as described above will be described with reference to spectral characteristics shown in FIG.

  The optical member (lens) having the antireflection film according to this embodiment is formed under the conditions shown in Table 25 below. Here, in Table 25, the reference wavelength is λ, and the layers 101a (first layer) to 101g (seventh layer) of the antireflection film 101 when the refractive index (optical member) of the substrate is 1.62, 1.74, and 1.85. The optical film thickness of each layer is determined. In Table 25, aluminum oxide is represented by Al2O3, a mixture of titanium oxide and zirconium oxide is represented by ZrO2 + TiO2, and a mixture of magnesium fluoride and silica is represented by MgF2 + SiO2.

(Table 25)
Substance Refractive index Optical film thickness Optical film thickness Optical film thickness
Medium air 1
7th layer MgF2 + SiO2 1.26 0.268λ 0.271λ 0.269λ
6th layer ZrO2 + TiO2 2.12 0.057λ 0.054λ 0.059λ
5th layer Al2O3 1.65 0.171λ 0.178λ 0.162λ
4th layer ZrO2 + TiO2 2.12 0.127λ 0.13λ 0.158λ
3rd layer Al2O3 1.65 0.122λ 0.107λ 0.08λ
Second layer ZrO2 + TiO2 2.12 0.059λ 0.075λ 0.105λ
1st layer Al2O3 1.65 0.257λ 0.03λ 0.03λ
Refractive index of substrate 1.62 1.74 1.85

  FIG. 21 shows spectral characteristics when light rays are perpendicularly incident on an optical member in which the reference wavelength λ is set to 550 nm in Table 25 and the optical film thickness of each layer of the antireflection film 101 is designed.

  From FIG. 21, it can be seen that the optical member having the antireflection film 101 designed with the reference wavelength λ of 550 nm can suppress the reflectance to 0.2% or less over the entire wavelength range of 420 nm to 720 nm. Further, even in the optical member having the antireflection film 101 in which each optical film thickness is designed with the reference wavelength λ as d line (wavelength 587.6 nm) in Table 25, the spectral characteristics are hardly affected, and the reference shown in FIG. Spectral characteristics substantially equivalent to those when the wavelength λ is 550 nm.

  Next, a modified example of the antireflection film will be described. This antireflection film consists of five layers, and similarly to Table 25, the optical film thickness of each layer with respect to the reference wavelength λ is designed under the conditions shown in Table 26 below. In this modification, the above-described sol-gel method is used for forming the fifth layer.

(Table 26)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1
5th layer MgF2 + SiO2 1.26 0.275λ 0.269λ
4th layer ZrO2 + TiO2 2.12 0.045λ 0.043λ
3rd layer Al2O3 1.65 0.212λ 0.217λ
Second layer ZrO2 + TiO2 2.12 0.077λ 0.066λ
1st layer Al2O3 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

  FIG. 22 shows the spectral characteristics in Table 26 when light rays are perpendicularly incident on an optical member having an antireflection film whose optical film thickness is designed with a refractive index of the substrate of 1.52 and a reference wavelength λ of 550 nm. Yes. It can be seen from FIG. 22 that the antireflection film of the present modification has a reflectivity of 0.2% or less over the entire wavelength range of 420 nm to 720 nm. In Table 26, even an optical member having an antireflection film whose optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) hardly affects the spectral characteristics, and the spectral characteristics shown in FIG. Has almost the same characteristics.

  FIG. 23 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 22 are 30, 45, and 60 degrees, respectively. 22 and 23 do not show the spectral characteristics of the optical member having the antireflection film whose refractive index is 1.46 shown in Table 26, but the refractive index of the substrate is almost equal to 1.52. Needless to say, it has the following spectral characteristics.

  For comparison, FIG. 24 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum deposition method. FIG. 24 shows the spectral characteristics when a light beam is perpendicularly incident on an optical member designed with an antireflection film having the refractive index of 1.52 of the same substrate as in Table 26 and the conditions shown in Table 27 below. FIG. 25 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 24 are 30, 45, and 60 degrees, respectively.

(Table 27)
Material Refractive index Optical film thickness Medium Air 1
7th layer MgF2 1.39 0.243λ
6th layer ZrO2 + TiO2 2.12 0.119λ
5th layer Al2O3 1.65 0.057λ
4th layer ZrO2 + TiO2 2.12 0.220λ
3rd layer Al2O3 1.65 0.064λ
Second layer ZrO2 + TiO2 2.12 0.057λ
1st layer Al2O3 1.65 0.193λ
Refractive index of substrate 1.52

  When the spectral characteristics of the optical member having the antireflection film according to this embodiment shown in FIGS. 21 to 23 are compared with the spectral characteristics of the conventional example shown in FIGS. 24 and 25, the antireflection film according to this embodiment is compared. It can be seen that has a lower reflectivity at any angle of incidence and a lower reflectivity over a wider band.

  Next, an example in which the antireflection film shown in Table 25 and Table 26 is applied to the first to eighth embodiments of the present application will be described.

  In the optical system OS1 of the first example, the refractive index of the biconcave negative lens L13 of the front group GF is nd = 1.688930, as shown in Table 1, and the biconcave shape of the rear group GR. Since the refractive index of the negative lens L21 is nd = 1.717360, the antireflection film 101 (Table 25) has a refractive index of 1.74 corresponding to the refractive index of the substrate on the image surface side lens surface of the negative biconcave lens L13. And an antireflection film (see Table 25) corresponding to a refractive index of the substrate of 1.74 is used on the object-side lens surface of the biconcave negative lens L21, and the reflected light from each lens surface , And ghost and flare can be reduced.

  In the optical system OS2 of the second example, the refractive index of the biconcave negative lens L24 of the rear group GR is nd = 1.575010 as shown in Table 4, and the biconvex shape of the rear group GR is Since the refractive index of the aspherical positive lens L25 is nd = 1.744430, the antireflective film 101 (with a refractive index of the substrate corresponding to 1.62 on the image surface side lens surface of the biconcave negative lens L24) ( Each lens surface is obtained by using an antireflection film (see Table 25) corresponding to a refractive index of the substrate of 1.74 on the object-side lens surface of the biconvex aspherical positive lens L25. The amount of reflected light can be reduced, and ghost and flare can be reduced.

  In the optical system OS3 of the third example, since the refractive index of the negative meniscus lens L12 of the front group GF is nd = 1.516800 as shown in Table 7, the object-side lens surface of the negative meniscus lens L12 In addition, an antireflection film 101 (see Table 26) corresponding to a refractive index of the substrate of 1.52 is used for the lens surface on the image plane side of the negative meniscus lens L12, and the antireflection of the substrate corresponding to a refractive index of 1.52 is used. By using a film (see Table 26), the reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the optical system OS4 of the fourth example, since the refractive index of the negative meniscus lens L13 of the front group GF is nd = 1.688930 as shown in Table 10, the object-side lens surface of the negative meniscus lens L13 In addition, by using an antireflection film (see Table 25) corresponding to a refractive index of the substrate of 1.74, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the optical system OS5 of the fifth example, since the refractive index of the negative meniscus lens L14 of the front group GF is nd = 1.688930 as shown in Table 13, the lens on the image plane side in the negative meniscus lens L14 By using an antireflection film (see Table 25) having a substrate refractive index of 1.74 on the surface, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the optical system OS6 of the sixth example, since the refractive index of the negative meniscus lens L14 of the front group GF is nd = 1.487490 as shown in Table 16, the lens on the image plane side in the negative meniscus lens L14 By using an antireflection film (see Table 26) corresponding to a refractive index of the substrate of 1.46 on the surface, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the optical system OS7 of the seventh example, since the refractive index of the negative meniscus lens L14 of the front group GF is nd = 1.517420 as shown in Table 19, the object-side lens surface of the negative meniscus lens L14 The antireflective film 101 (see Table 26) corresponding to the refractive index of the substrate of 1.52 is used for the lens surface on the image plane side of the negative meniscus lens L14, and the antireflective property of the substrate corresponding to the refractive index of 1.52 is used. By using a film (see Table 26), the reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the optical system OS8 of the eighth example, the refractive index of the negative meniscus lens L14 of the front group GF is nd = 1.688930 as shown in Table 22, and the biconcave negative lens L21 of the rear group GR Since the refractive index of nd is 1.717360, the antireflective film 101 (see Table 25) corresponding to the refractive index of the substrate of 1.74 is used for the lens surface on the image surface side of the negative meniscus lens L14. By using an antireflection film (see Table 25) whose refractive index of the substrate corresponds to 1.74 on the object-side lens surface of the concave negative lens L21, reflected light from each lens surface can be reduced. Flare can be reduced.

  According to each of the above-described embodiments, it has a comprehensive angle of about 2ω = 41.6 °, further has a large aperture of F1.2, further reduces ghosts and flares, and has high performance with spherical aberration and sagittal coma. An optical system OS in which aberrations, field curvature, and meridional coma are corrected well can be realized. In addition, a small optical system OS can be realized with a small number of lenses.

  Needless to say, the above-described effects can be obtained by mounting the optical systems OS1 to OS8 shown in the above embodiments in the camera 1 described above. Moreover, each said Example has shown the specific example of this invention, and this invention is not limited to these.

OS (OS1-OS8) Optical system GF Front group
LFP Front lens first lens component LFN1 Front lens second lens component
LFN2 Front lens third lens component GR Rear lens LRN Rear lens first lens component
L21 negative lens
L22 Positive lens LRP1 Second lens component in the rear group
L23 positive lens
L24 Negative lens LRP2 Rear lens third lens component
S aperture stop I image plane 1 single-lens reflex camera
101 Antireflection film 101a 1st layer 101b 2nd layer 101c 3rd layer 101d 4th layer 101e 5th layer 101f 6th layer 101g 7th layer 102 Optical member

Claims (23)

In order from the object side along the optical axis,
The front group,
A rear group having a positive refractive power,
The front group is in order from the object side,
A first lens component having a positive refractive power;
A second lens component having negative refractive power and having a convex surface facing the object side;
A third lens component having negative refractive power,
The rear group is in order from the object side,
A first lens component in which a negative lens and a positive lens are cemented and having a concave surface facing the object side;
A second lens component having a positive refractive power and having a concave surface facing the image side;
A third lens component having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces in the front group and the rear group, and the antireflection film is configured to include at least one layer formed using a wet process,
An optical system satisfying the following conditional expression:
0.000 <nRNP-nRNN <0.350
−2.00 <(rp2−rp1) / (rp2 + rp1) <− 0.00
However,
nRNP: Refractive index for the d-line of the medium of the positive lens in the first lens component in the rear group nRNN: Refractive index for the d-line of the medium of the negative lens in the first lens component in the rear group rp1: radius of curvature of the surface closest to the object side of the second lens component in the rear group rp2: radius of curvature of the surface closest to the image side of the second lens component in the rear group The antireflection film is a multilayer film,
The optical system according to claim 1, wherein the layer formed by the wet process is a layer on a most surface side among layers constituting the multilayer film.   3. The optical system according to claim 1, wherein nd is 1.30 or less, where nd is a refractive index of a layer formed by using the wet process.   4. The optical system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from an aperture stop.   The optical system according to claim 4, wherein the concave lens surface when viewed from the aperture stop is an object-side lens surface.   5. The optical system according to claim 4, wherein the concave lens surface as viewed from the aperture stop is a lens surface on the image plane side.   4. The optical system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the object side.   The optical system according to claim 7, wherein the lens surface having a concave shape when viewed from the object side is an object side lens surface of the most image side lens in the front group.   The optical system according to claim 7, wherein the lens surface having a concave shape when viewed from the object side is an image surface side lens surface of the most image surface side lens of the front group.   4. The optical system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the image surface side.   11. The optical system according to claim 10, wherein the lens surface having a concave shape when viewed from the image surface side is an object-side lens surface of the lens in the rear group that is closest to the image surface.   11. The concave lens surface as viewed from the image surface side is an image surface side lens surface of the second lens from the most image surface side lens in the rear group to the object side. The optical system described in 1. The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.00 <(− fFN1) / f0 <20.00
However,
fFN1: focal length of the second lens component in the front group f0: focal length of the entire system when focusing on infinity The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.20 <(-fFN2) / f0 <15.00
However,
fFN2: focal length of the third lens component in the front group f0: focal length of the entire system when focusing on infinity The second lens component in the rear group is a cemented lens in which a positive lens and a negative lens are cemented, and satisfies the following conditional expression: 15. The optical system described in 1.
0.000 <nRPP-nRPN <0.500
However,
nRPP: refractive index of the second lens component in the rear group with respect to the d-line of the medium of the positive lens nRPN: refractive index of the second lens component in the rear group with respect to the d-line of the medium of the negative lens The optical system according to claim 1, wherein the following conditional expression is satisfied.
1.00 <fRP / f0 <12.00
However,
fRP: focal length of the second lens component in the rear group f0: focal length of the entire system when focusing on infinity The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.1 <fRP2 / f0 <3.0
However,
fRP2: focal length of the third lens component in the rear group f0: focal length of the entire system when focusing on infinity   The optical system according to any one of claims 1 to 17, wherein the front group has at least one aspherical surface.   The optical system according to claim 1, wherein the rear group has at least one aspheric surface.   The optical system according to claim 1, wherein the third lens component in the rear group is a positive lens having a convex surface directed toward the object side.   21. The optical system according to claim 1, further comprising an aperture stop between the front group and the rear group.   An imaging apparatus comprising the optical system according to any one of claims 1 to 21. In order from the object side along the optical axis, a manufacturing method of an optical system having a front group and a rear group having a positive refractive power,
As the front group, in order from the object side, a first lens component having a positive refractive power, a second lens component having a negative refractive power and having a convex surface facing the object side, and a first lens component having a negative refractive power. And three lens components,
As the rear group, in order from the object side, a negative lens and a positive lens are cemented, a first lens component having a concave surface facing the object side, a second lens having a positive refractive power and a concave surface facing the image side. A lens component and a third lens component having a positive refractive power,
An antireflection film is provided on at least one of the optical surfaces in the front group and the rear group, and the antireflection film is configured to include at least one layer formed using a wet process,
An optical system manufacturing method satisfying the following conditional expression:
0.000 <nRNP-nRNN <0.350
−2.00 <(rp2−rp1) / (rp2 + rp1) <− 0.00
However,
nRNP: Refractive index for the d-line of the medium of the positive lens in the first lens component in the rear group nRNN: Refractive index for the d-line of the medium of the negative lens in the first lens component in the rear group rp1: radius of curvature of the surface closest to the object side of the second lens component in the rear group rp2: radius of curvature of the surface closest to the image side of the second lens component in the rear group

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