JP6112945B2 - Optical system and imaging apparatus having the same - Google Patents

Description

  The present invention relates to an optical system and an imaging apparatus having the optical system, and is particularly suitable for a broadcast television camera, a movie camera, a video camera, a digital still camera, a silver salt photography camera, and the like.

  Among imaging devices such as photographic cameras, movie cameras, and video cameras, the imaging optical system used for single-lens reflex cameras and movie cameras in particular has a wide angle of view, a long back focus, and a screen that covers the entire object distance. There is a demand for substantially uniform resolution from the center to the periphery of the screen. As an imaging optical system having a wide angle of view and a long back focus, a retrofocus type imaging optical system is known. Among them, a focus adjustment method using so-called floating is known in which two groups behind the optical system are moved to the object side with different amounts of movement during focus adjustment from an object at infinity to a short distance object (Patent Literature). 1, 2).

JP 63-61213 A Japanese Patent Laid-Open No. 11-211978

  The focus adjustment method using the above-described floating is relatively easy to suppress the aberration change accompanying the focus adjustment. However, it is difficult to correct simultaneously the spherical aberration and astigmatism generated by the focus adjustment only by adopting the above-described focus adjustment method using floating. Therefore, in order to achieve substantially uniform resolving power from the center of the screen to the periphery of the screen over the entire object distance, the configuration and paraxial arrangement of the first group, which is a fixed group, are appropriately set, and the first is accompanied by the focus adjustment. In particular, it is important to suppress changes in spherical aberration that occur in one group.

  An object of the present invention is to provide a single focus lens that suppresses an aberration change accompanying focus adjustment and has high optical performance over the entire object distance in the above-described focus adjustment type single focus lens using floating. Specifically, an object of the present invention is to provide a single focus lens that has an angle of view of about 65 degrees and an F number of about 1.4 and that suppresses an aberration change accompanying focus adjustment.

The single-focus lens of the present invention has, in order from the object side, a first lens unit having a negative refractive power that is fixed during focus adjustment, and a positive refractive power that moves toward the object side when focusing from an object at infinity to a short-distance object. The second group is composed of a 21st group having a positive refractive power, an aperture stop, and a 22nd group having a positive refractive power, and the 21st group and the 22nd group are mutually adjusted during focus adjustment. When moving to the object side with different moving amounts, the refractive power of the first group is φ1, the refractive power of the 21st group is φ21, and the sum of the refractive powers of the positive lenses of the first group is φ1p,
-2.80 <φ21 / φ1 <−1.64
-2.09 <φ1p / φ1 <−1. 5 0
It is characterized by satisfying.
A single focus lens according to another aspect of the present invention includes a first lens group having a fixed negative refractive power at the time of focus adjustment in order from the object side, and a positive lens that moves toward the object side when focusing from an object at infinity to a short distance object. The second group is composed of a 21st group having a positive refractive power, an aperture stop, and a 22nd group having a positive refractive power, and the 21st group and the 22nd group are When the focus is adjusted, the lens unit moves toward the object side with different amounts of movement. The refractive power of the first group is φ1, the refractive power of the 21st group is φ21, the refractive power of the 22nd group is φ22, and the positive power of the first group is positive. When the total refractive power of the lens is φ1p,
-2.80 <φ21 / φ1 <−1.64
-2.09 <φ1p / φ1 <−1.20
-4.80 <φ22 / φ1 <-2.30
1.10 <φ22 / φ21 <2.00
It is characterized by satisfying.

  According to the present invention, it is possible to obtain a single-focus lens having a high optical performance over the entire object distance and an image pickup apparatus having the same, by suppressing an aberration change accompanying focus adjustment.

It is a lens sectional view when focusing on an object at infinity of the single focus lens of Numerical Example 1 of the present invention. It is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 1. It is lens sectional drawing when focusing on the object of infinity of the single focus lens of the numerical Example 2 of this invention. FIG. 6 is a longitudinal aberration diagram when focusing on an object at infinity and (B) a close object in Numerical Example 2. It is lens sectional drawing when focusing on the object of infinity of the single focus lens of the numerical Example 3 of this invention. It is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 3. It is lens sectional drawing when focusing on the object of infinity of the single focus lens of the numerical Example 4 of this invention. FIG. 10 is a longitudinal aberration diagram when focusing on an object at infinity and (B) a close object in Numerical Example 4. It is lens sectional drawing when focusing on the object at infinity of the single focus lens of the numerical Example 5 of this invention. It is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 5. It is lens sectional drawing when focusing on the object of infinity of the single focus lens of the numerical Example 6 of this invention. It is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 6. It is lens sectional drawing when focusing on the object of infinity of the single focus lens of the numerical Example 7 of this invention. It is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 7. These are optical path diagrams when focusing on (A) an object at infinity and (B) a close object in Numerical Example 1. FIG. FIG. 4 is a schematic diagram regarding achromaticity of two colors of axial chromatic aberration and a residual secondary spectrum by a lens unit having a positive refractive power. FIG. 4 is a schematic diagram of a distribution of an Abbe number νd and a partial dispersion ratio θgF of a general glass material. These are the principal part schematic of the imaging device of this invention.

Next, features of the single focus lens of the present invention will be described.
The single-focus lens of the present invention has, in order from the object side, the first lens unit U1 having a fixed negative refractive power at the time of focus adjustment, and a positive refractive power that moves toward the object side when focusing from an object at infinity to a short distance object. The second group U2. The second group U2 includes a twenty-first group U21 having a positive refractive power, an aperture stop, and a twenty-second group U22 having a positive refractive power. The 21st group U21 and the 22nd group U22 move to the object side with different amounts of movement when focusing from an infinitely distant object to a close object.

The single focus lens of the present invention has a refractive power of the first lens unit U1 of φ1, a refractive power of the twenty-first lens unit U21 of φ21, and a sum of refractive powers of the positive lenses of the first lens unit U1 is φ1p.
-2.80 <φ21 / φ1 <−1.64 (1)
-2.09 <φ1p / φ1 <−1.20 (2)
Meet.

  FIGS. 15A and 15B are optical path diagrams when focusing on an object at infinity and a close object in Numerical Example 1 of the single focus lens of the present invention, respectively. As shown in FIGS. 15A and 15B, the incident height of the on-axis marginal ray is particularly high in the positive lens of the first lens unit U1. Further, as shown in FIG. 15B with respect to FIG. 15A, the axial marginal ray passing through the positive lens of the first unit U1 at the time of focusing the close object to the object at infinity is the object side. While the incident inclination angle to the surface becomes larger, the incident height becomes lower. Therefore, especially when the refractive power of the positive lens of the first lens unit U1 is increased and the curvature of the object-side surface is increased, spherical aberration occurs more under-focusing when the closest object is focused on the object at infinity. On the other hand, especially when the refractive power of the positive lens in the first lens unit U1 becomes weak and the curvature of the surface on the object side becomes particularly small, the spherical aberration occurs more excessively when the object close to the object at infinity is in focus. Therefore, in order to suppress the change of the spherical aberration accompanying the focus adjustment, it is particularly important to set an appropriate refractive power for the positive lens in the first lens unit U1.

Conditional expression (1) defines the ratio of the refractive powers of the first group U1 and the twenty-first group U21.
By satisfying conditional expression (1), various aberrations such as spherical aberration and coma are corrected satisfactorily.
When the upper limit of conditional expression (1) is exceeded, the refractive power of the first group U1 becomes stronger than the refractive power of the 21st group U21, and the divergence of on-axis and off-axis light beams from the first group U1 is large. It is necessary to give a strong refractive power to the 22 group U22 to converge on-axis and off-axis light beams. This makes it particularly difficult to correct spherical aberration and coma.
When the lower limit of conditional expression (1) is exceeded, the refractive power of the 21st group U21 becomes stronger than the refractive power of the first group U1, and the second group U2 in which the light beam diverged from the first group U1 has a strong refractive power. Therefore, it is difficult to correct spherical aberration and coma aberration.

More preferably, conditional expression (1) should be set as follows.
-2.50 <φ21 / φ1 <−1.70 (1a)

Conditional expression (2) defines the ratio of the sum of the refractive powers of the positive lenses of the first lens unit U1 and the first lens unit U1.
By satisfying conditional expression (2), it is possible to achieve both suppression of aberration change accompanying focus adjustment, particularly suppression of change in spherical aberration, and miniaturization.
If the upper limit of conditional expression (2) is exceeded, the sum of the refractive powers of the positive lenses of the first group U1 with respect to the refractive power of the first group U1 is insufficient. Spherical aberration occurs excessively at the time of focusing, and it becomes difficult to suppress especially the change of spherical aberration accompanying focus adjustment.
When the lower limit of conditional expression (2) is exceeded, the sum of the refractive powers of the positive lens of the first unit U1 becomes stronger than the refractive power of the first unit U1, and spherical aberration occurs under focus when the closest object is in focus. In particular, it becomes difficult to suppress a change in spherical aberration associated with focus adjustment.

More preferably, conditional expression (2) should be set as follows.
-2.08 <φ1p / φ1 <−1.50 (2a)
The single focus lens of the present invention specifies the lens configuration of the first lens unit U1 as described above, satisfies the above conditional expressions, suppresses aberration changes accompanying focus adjustment, and has high optical performance over the entire object distance. Has achieved.

As a further embodiment of the present invention, the shape of the positive lens of the first lens unit U1 is defined by conditional expression (3). The first unit U1 is composed of two negative lenses and one positive lens in order from the object side. When the radius of curvature of the object side surface of the positive lens is R1 and the radius of curvature of the image side surface is R2,
-1.5 <(R1 + R2) / (R1-R2) <-0.3 (3)
Meet.

  By satisfying the conditional expression (3), it is possible to suppress the aberration change accompanying the focus adjustment, particularly the spherical aberration, and to correct the spherical aberration and the coma aberration well. When the curvature of the positive lens of the first lens unit U1 particularly on the object side increases, spherical aberration occurs more under-focused when the closest object is focused on the object at infinity. On the other hand, particularly when the curvature of the object-side surface of the positive lens in the first lens unit U1 becomes small, spherical aberration occurs more excessively when the object close to the object at infinity is in focus. Therefore, in order to suppress the change in spherical aberration associated with focus adjustment, it is particularly important to set an appropriate shape for the positive lens in the first lens unit U1.

On the other hand, as shown in FIGS. 15A and 15B, on the image side surface of the second negative lens from the object side of the first lens unit U1, the on-axis light beam and off-axis light beam are greatly diverged, particularly spherical aberration and coma aberration. Occurs. Therefore, spherical aberration and coma aberration are favorably corrected by giving a convex shape having an appropriate curvature to the object-side surface of the positive lens of the first lens unit U1 that is one image-side surface.
Here, the object side surface of the positive lens G3 of the first lens unit U1 is defined as the R1 surface, and the image side surface is defined as the R2 surface.

If the upper limit of conditional expression (3) is exceeded, the shape of G3 will be closer to a biconvex lens shape, the positive refractive power of G3 will become stronger, and spherical aberration will occur under focus when the closest object is in focus, and focus adjustment It becomes difficult to suppress the change in aberration associated with.
If the lower limit of conditional expression (3) is exceeded, the shape of G3 becomes a convex meniscus shape with the R2 surface being concave, and the refractive power of G3 is insufficient. Spherical aberration occurs excessively, making it difficult to suppress changes in aberration associated with focus adjustment.

More preferably, the expression (3) is set as follows.
−1.3 <(R1 + R2) / (R1−R2) <− 0.4 (3a)

Here, the partial dispersion ratio and Abbe number of the material of the optical element (lens) used in this numerical example are as follows. The refractive indexes of the Fraunhofer line for g-line (435.8 nm), F-line (486.1 nm), d-line (587.6 nm), and C-line (656.3 nm) are Ng, NF, Nd, and NC, respectively. To do. The partial dispersion ratio θgF regarding the Abbe number νd, g-line, and F-line is given as follows.
νd = (Nd−1) / (NF-NC) (4)
θgF = (Ng−NF) / (NF−NC) (5)

As a further embodiment of the present invention, when the average refractive index of the positive lens of the first lens unit U1 is N1p and the average Abbe number is ν1p, the average refractive index of the positive lens of the first lens unit U1 according to the conditional expression (6) Is defined by the conditional expression (7) as the average Abbe number of the positive lens in the first lens unit U1.
1.65 <N1p <2.10 (6)
65 <ν1p <23 (7)

By satisfying conditional expression (6) and conditional expression (7), it is possible to suppress changes in aberrations associated with focus adjustment, particularly changes in spherical aberration and axial chromatic aberration.
Generally, the higher the refractive index glass material, the smaller the Abbe number, and the lower the refractive index glass material, the larger the Abbe number tends to be.
When the upper limit of conditional expression (6) and conditional expression (7) is exceeded, a high refractive index glass material can be selected for the positive lens of the first lens unit U1, and in particular, the curvature of the object side surface becomes small, and spherical aberration associated with focus adjustment. It is advantageous for suppressing the change of. However, at the same time, a glass material having a small Abbe number is selected, and it is insufficient to correct the axial chromatic aberration generated in the positive lens of the first lens unit U1 having a high incident height of the axial marginal ray in the first lens unit U1. For this reason, it is difficult to suppress a change in axial chromatic aberration particularly with focus adjustment.
If the lower limit of conditional expression (6) and conditional expression (7) is exceeded, a low refractive index glass material will be selected for the positive lens of the first lens unit U1, and therefore the surface on the object side of the positive lens of the first lens unit U1. Becomes difficult to suppress the change in spherical aberration associated with the focus adjustment.

More preferably, conditional expressions (6) and (7) should be set as follows.
1.70 <N1p <2.05 (6a)
50 <ν1p <25 (7a)

As a further embodiment of the present invention, the ratio of the refractive power of the twenty-second group U22 to the refractive power of the first group U1 according to the conditional expression (8), and the twenty-second refractive power relative to the refractive power of the twenty-first group U21 according to the conditional expression (9). The ratio of the refractive power of the group U22 is defined.
When the refractive power of the 22nd group U22 is φ22,
-4.80 <φ22 / φ1 <-2.30 (8)
1.10 <φ22 / φ21 <2.00 (9)
Meet.

By satisfying conditional expression (8), various aberrations such as spherical aberration, coma, astigmatism and distortion are corrected satisfactorily.
When the upper limit of conditional expression (8) is exceeded, the refractive power of the first group U1 becomes stronger than the refractive power of the 22nd group U22, and in particular, correction of coma, astigmatism and distortion becomes difficult.
When the lower limit of conditional expression (8) is exceeded, the refractive power of the 22nd group U22 becomes stronger than the refractive power of the 1st group U1, and the strong refractive power is given to the 22nd group U22 so Since it becomes necessary to converge, correction of spherical aberration, astigmatism, and distortion becomes difficult.

More preferably, conditional expression (8) should be set as follows.
-4.60 <φ22 / φ1 <-2.60 (8a)

By satisfying conditional expression (9), various aberrations such as spherical aberration, coma, astigmatism and distortion are corrected satisfactorily.
If the upper limit of conditional expression (9) is exceeded, the refractive power of the 22nd group U22 will be stronger than the refractive power of the 21st group U21, and it will be particularly difficult to correct spherical aberration, astigmatism and distortion.
When the lower limit of conditional expression (9) is exceeded, the refractive power of the 21st group U21 becomes stronger than the refractive power of the 22nd group U22, and in particular, it becomes difficult to correct spherical aberration, coma aberration, astigmatism, and distortion. .

More preferably, conditional expression (9) should be set as follows.
1.40 <φ22 / φ21 <1.90 (9a)

  Here, the on-axis paraxial ray and the pupil paraxial ray are rays defined as follows. An on-axis paraxial ray is a paraxial ray that is normalized with the focal length of the entire optical system set to 1, and is incident on the optical system parallel to the optical axis with an incident height of 1. A pupil paraxial ray is a paraxial ray that normalizes the focal length of the entire optical system to 1 and passes through the intersection of the entrance pupil of the optical system and the optical axis among rays incident on the maximum image height of the imaging surface. is there. It is assumed that the object is on the left side of the optical system, and light rays incident on the optical system from the object side travel from left to right.

  As shown in FIG. 17, existing optical materials are distributed in a narrow range of the partial dispersion ratio θgF with respect to νd, and θgF tends to increase as νd decreases.

Two lenses Gp having a predetermined refractive power Φ, a positive refractive power Φp, a negative refractive power Φn, an Abbe number νp, νn, an incident height h of on-axis paraxial rays, and an incident height H of pupil paraxial rays. , The axial chromatic aberration coefficient L and the lateral chromatic aberration coefficient T of the thin-walled contact system composed of Gn are:
L = h × h × (Φp / νp + Φn / νn) (10)
T = h × H × (Φp / νp + Φn / νn) (11)
It is expressed. here,
Φ = Φp + Φn (12)
And The refractive powers of the lenses in Expression (10) and Expression (11) are normalized so that Expression (12) becomes Φ = 1. The same can be considered for the case of three or more sheets. In Expressions (10) and (11), if L = 0 and T = 0, the imaging positions on the C-F line axis and on the image plane coincide.

At this time, the deviation amount of the axial chromatic aberration and the lateral chromatic aberration of the g-line with respect to the F-line when the light beam is incident with the object distance set to infinity are respectively the second-order spectral amount Δs of the axial chromatic aberration and the lateral chromatic aberration of the two. When defined as the next spectral amount Δy,
Δs = −h × h × (θp−θn) / (νp−νn) × f (13)
Δy = −h × H × (θp−θn) / (νp−νn) × Y (14)
It is represented by Here, f is the focal length of the entire lens system, and Y is the image height.

  In FIG. 16, in the achromatization with the lens unit Lp having a positive refractive power, a material having a large Abbe number νp is used as the positive lens Gp, and a material having a small νn is used as the negative lens Gn. Therefore, from equation (13), when the positive lens Gp has a small θp, the negative lens Gn has a large θn, and when the chromatic aberration is corrected by the F-line and the C-line, as shown in FIG. The point moves to the image side.

As shown in FIGS. 15A and 15B, the secondary spectrum amount Δs is remarkably generated in the second group U2 of the present embodiment in which the incident height of the on-axis marginal ray is high.
In order to achieve further improvement in optical performance at the center of the screen, it is important to correct axial chromatic aberration well.

By using a material having a larger νd for the positive lens in the 21st group and a material having a smaller νd for the negative lens and arranging them with appropriate refractive power, primary achromaticity can be satisfactorily performed.
Further, by using a material having a larger θgF for the positive lens of the 21st lens unit U21 and a material having a smaller θgF for the negative lens and arranging them with appropriate refractive power, the secondary spectrum of longitudinal chromatic aberration can be corrected well. be able to.

As a further embodiment of the present invention, the conditional expressions (15) to (17) take into account the above and positive lens and negative lens in the vicinity of the aperture stop in the 21st group U21 that can correct axial chromatic aberration more effectively. The Abbe number, the partial dispersion ratio, and the refractive power of the lens material are appropriately set.
-2.45 × 10-3 <(θp−θn) / (νp−νn) <− 0.80 × 10-3
(15)
0.50 <φp × f <1.50 (16)
−1.60 <φn × f <−0.70 (17)
Here, the twenty-first unit U21 includes a negative lens G21n and a positive lens G21p in order from the image side. The refractive powers of the positive lens G21p and the negative lens G21n are φp and φn, respectively, and the partial dispersion ratios are θp and θn, respectively. Are denoted by νp and νn, respectively, and the focal length of the entire system is denoted by f.

Conditional expression (15) defines the Abbe number and partial dispersion ratio of the materials of the positive lens G21p and the negative lens G21n in the 21st group U21.
If the upper limit of conditional expression (15) is exceeded, the difference between the Abbe numbers of the glass materials G21p and G21n becomes too small and the refractive power of both lenses becomes strong, and a low refractive index glass material is selected. As these aberrations occur, it becomes difficult to correct aberrations and perform primary achromaticity.
If the lower limit of conditional expression (15) is exceeded, the effect of correcting the secondary spectrum in the 21st group U21 will be insufficient from expression (13), making it difficult to correct axial chromatic aberration well.

More preferably, conditional expression (15) should be set as follows.
-2.42 × 10-3 <(θp−θn) / (νp−νn) <− 0.90 × 10-3
... (15a)

Conditional expression (16) defines the refractive power of the positive lens G21p.
If the upper limit of conditional expression (16) is exceeded, the refractive power of G21p will become strong and various higher-order aberrations will occur, making it difficult to correct aberrations and perform primary achromatization.
If the lower limit of conditional expression (16) is exceeded, the refractive power of G21p will be insufficient, and the secondary spectrum correction effect in the 21st group U21 will be insufficient, making it difficult to correct axial chromatic aberration well. Become.

More preferably, conditional expression (16) should be set as follows.
0.75 <φp × f <1.20 (16a)

Conditional expression (17) defines the refractive power of the negative lens G21n.
If the upper limit of conditional expression (17) is exceeded, the refractive power of G21n will be insufficient, and the secondary spectrum correction effect in the 21st group U21 will be insufficient, making it difficult to correct axial chromatic aberration well. Become.
If the lower limit of conditional expression (17) is exceeded, the refractive power of G21n becomes strong and various higher-order aberrations occur, making it difficult to correct aberrations and perform primary achromaticity.

More preferably, conditional expression (17) should be set as follows.
−1.40 <φn × f <−0.90 (17a)

[Numerical Example 1]
Numerical Example 1 of the single focus lens of the present invention is shown below. FIG. 1 is a lens cross-sectional view of a single focus lens of Numerical Example 1 when focused on an object at infinity. The single focus lens of Numerical Example 1 is a positive first lens unit U1 having a negative refractive power that is fixed during focus adjustment in order from the object side, and a positive lens that moves toward the object side when focusing from an object at infinity to a short distance object. The second group U2 of refractive power is included. The second group U2 includes, in order from the object side, a 21st group U21 having a positive refractive power, an aperture stop SP, and a 22nd group U22 having a positive refractive power. IP is an image plane, which corresponds to an imaging plane of a solid-state imaging element (photoelectric conversion element) of an imaging apparatus to which the single focus lens of the present invention is connected.

Next, the lens configuration of each group in Numerical Example 1 will be described. Hereinafter, it is assumed that the lenses are arranged in order from the object side to the image side. The first unit U1 includes two negative lenses and one positive lens. The 21st group U21 includes a positive lens and a cemented lens of a positive lens and a negative lens. The 22nd group U22 includes a cemented lens of a negative lens and a positive lens, and two positive lenses. The lens configurations described above are all the same in Numerical Examples 1 to 4.
The single focus lens of Numerical Example 1 has a focal length of 34.2 mm, a half angle of view of 32.3 degrees, and an F number of 1.45.

  FIG. 2 shows longitudinal aberration diagrams when focusing on (A) an object at infinity and (B) a close object in Numerical Example 1. FIG. The value of the focal length is a value expressed in mm. In the aberration diagrams, spherical aberration is represented by e-line and g-line. Astigmatism is represented by an e-line meridional image plane (ΔM) and an e-line sagittal image plane (ΔS). The lateral chromatic aberration is represented by the g-line. Fno is the F number, and ω is the half angle of view. In all the aberration diagrams, the spherical aberration is 0.4 mm, the astigmatism is 0.4 mm, the distortion is 5%, and the chromatic aberration of magnification is 0.05 mm. This is all the same in the following numerical examples.

[Numerical Example 2]
FIG. 3 is a lens cross-sectional view when focusing on an object at infinity of the single focus lens of Numerical Example 2. Since the basic configuration is the same as that of Numerical Example 1, the description thereof is omitted. The single focus lens of Numerical Example 2 has a focal length of 33.5 mm, a half angle of view of 32.9 degrees, and an F number of 1.45. FIG. 4 shows longitudinal aberration diagrams when focusing on (A) an object at infinity and (B) a close object in Numerical Example 2.

[Numerical Example 3]
FIG. 5 shows a lens cross-sectional view of the single focus lens of Numerical Example 3 when focused on an object at infinity. Since the basic configuration is the same as that of Numerical Example 1, the description thereof is omitted. The single focus lens of Numerical Example 3 has a focal length of 33.0 mm, a half angle of view of 33.3 degrees, and an F number of 1.45. FIG. 6 is a longitudinal aberration diagram when focusing on (A) an object at infinity and (B) a close object in Numerical Example 3.

[Numerical Example 4]
FIG. 7 shows a lens cross-sectional view when focusing on an object at infinity of the single focus lens of Numerical Example 4. Since the basic configuration is the same as that of Numerical Example 1, the description thereof is omitted. The single focus lens of Numerical Example 4 has a focal length of 34.5 mm, a half angle of view of 32.1 degrees, and an F number of 1.45. FIG. 8 shows longitudinal aberration diagrams when focusing on (A) an infinitely distant object and (B) a close object in Numerical Example 4.

[Numerical Example 5]
FIG. 9 shows a lens cross-sectional view when focusing on an object at infinity of the single focus lens of Numerical Example 5. FIG. The single focus lens of Numerical Example 5 is different from Numerical Examples 1 to 4 in that the first unit U1 is composed of two negative lenses and two positive lenses in order from the object side. However, the other configurations are all the same as those of the numerical value example 1, and the description thereof is omitted. The single focus lens of Numerical Example 5 has a focal length of 33.0 mm, a half angle of view of 33.3 degrees, and an F number of 1.45. FIG. 10 shows longitudinal aberration diagrams when focusing on (A) an object at infinity and (B) a close object in Numerical Example 5.

[Numerical Example 6]
FIG. 11 is a cross-sectional view of the lens when the single focus lens of Numerical Example 6 is focused on an object at infinity. The single focus lens of Numerical Example 6 is different from Numerical Examples 1 to 5 in that the 21st group U21 is composed of two cemented lenses of a positive lens and a negative lens. However, the other configurations are all the same as those of the numerical value example 1, and the description thereof is omitted. The single focus lens of Numerical Example 6 has a focal length of 33.3 mm, a half angle of view of 33.0 degrees, and an F number of 1.45. FIG. 12 shows longitudinal aberration diagrams when focusing on an object at (A) infinity and (B) a close object in Numerical Example 6. FIG.

[Numerical Example 7]
FIG. 13 is a lens cross-sectional view of the single focus lens of Numerical Example 7 when focused on an object at infinity. In the single focus lens of Numerical Example 7, an aspheric surface having a refractive power that weakens toward the periphery is arranged on the convex surface of the positive lens in the first group to suppress aberration change due to focus adjustment, and over the entire object distance. This is different from Numerical Examples 1 to 6 in that high optical performance is achieved. However, the other configurations are all the same as those of the numerical value example 1, and the description thereof is omitted. The single focus lens of Numerical Example 7 has a focal length of 33.0 mm, a half angle of view of 33.3 degrees, and an F number of 1.45. FIG. 14 is a longitudinal aberration diagram when focusing on (A) an infinitely distant object and (B) a close object in Numerical Example 7.

  Table 1 shows corresponding values of the conditional expressions of Numerical Examples 1 to 7. The single focus lenses of Numerical Examples 1 to 7 satisfy the conditional expressions (1) to (3), (6) to (9), and (15) to (17). Aberration change due to the lens is suppressed, and high optical performance is achieved over the entire object distance.

  Numerical data of the following numerical examples is shown. i indicates the order of the surfaces from the object side, r is the radius of curvature of the i-th surface from the object side, d is the i-th and i + 1-th spacing from the object side, and nd, νd, and θgF are the i-th surface These are the refractive index, Abbe number, and partial dispersion ratio of the optical member. The aspherical shape is the X axis in the optical axis direction, the H axis in the direction perpendicular to the optical axis, the light traveling direction is positive, R is the paraxial radius of curvature, k is the cone constant, and A4, A6, A8, and A10 are non- The spherical coefficient is given by the following equation.

又、「ｅ−Ｚ」は「×１０^-Z」を意味する。＊印は非球面であることを示す。

“E-Z” means “× 10 ^−Z ”. * Indicates an aspherical surface.

<Numerical Example 1>
Surface number rd nd vd θgF Effective diameter Focal length
1 320.116 2.80 1.51633 64.1 0.5352 51.99 -93.54
2 41.977 5.78 45.00
3 174.176 2.30 1.51823 58.9 0.5456 44.56 -97.45
4 39.095 14.53 41.15
5 83.274 4.44 1.77250 49.6 0.5521 39.37 88.98
6 -395.333 (variable) 38.88
7 57.067 5.14 1.77250 49.6 0.5521 35.63 57.75
8 -200.681 8.71 35.34
9 607.365 6.47 1.77250 49.6 0.5521 30.62 35.68
10 -28.883 1.50 1.65412 39.7 0.5737 30.02 -29.00
11 57.419 (variable) 26.96
12 (Aperture) ∞ 7.82 25.98
13 -19.812 1.60 1.80518 25.4 0.6161 24.65 -21.64
14 162.418 4.90 1.83481 42.7 0.5642 27.82 62.15
15 * -75.798 0.20 29.43
16 -470.465 6.60 1.77250 49.6 0.5521 30.27 45.14
17 -32.806 0.20 32.76
18 -154.187 6.32 1.77250 49.6 0.5521 35.98 56.91
19 -34.950 37.18
Image plane ∞

Aspheric data 15th surface
K = 4.82454e + 000 A 4 = 1.27386e-005 A 6 = 2.46580e-009 A 8 = -1.63965e-011
A10 = 1.16481e-014

Focal length 34.20
F number 1.45
Half angle of view 32.32
Statue height 21.64
Total lens length 129.16
BF 39.35

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.26 0.50
d11 4.23 3.21

Each lens group data group Start surface Focal length
1 1 -164.29
2 7 76.56
3 13 45.49

<Numerical Example 2>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 168.071 2.80 1.58913 61.1 0.5406 52.33 -95.34
2 41.959 4.84 45.64
3 101.105 2.30 1.58913 61.1 0.5406 45.20 -109.11
4 39.056 19.16 41.76
5 113.732 4.15 1.88300 40.8 0.5667 38.29 96.87
6 -347.230 (variable) 37.71
7 53.725 5.92 1.72916 54.7 0.5444 36.02 58.37
8 -199.469 6.95 35.60
9 284.925 7.67 1.77250 49.6 0.5521 31.43 35.98
10 -30.598 1.50 1.65412 39.7 0.5737 30.37 -28.27
11 48.371 (variable) 26.98
12 (Aperture) ∞ 8.17 26.11
13 -19.812 1.60 1.80518 25.4 0.6161 24.66 -21.64
14 162.418 4.90 1.83481 42.7 0.5642 27.83 62.15
15 * -75.798 0.20 29.44
16 -470.465 6.60 1.77250 49.6 0.5521 30.27 45.14
17 -32.806 0.20 32.76
18 -154.187 6.32 1.77250 49.6 0.5521 35.98 56.91
19 -34.950 37.18
Image plane ∞

Aspheric data 15th surface
K = 4.82454e + 000 A 4 = 1.27386e-005 A 6 = 2.46580e-009 A 8 = -1.63965e-011
A10 = 1.16481e-014

Focal length 33.50
F number 1.45
Half angle of view 32.85
Statue height 21.64
Total lens length 133.11
BF 39.36

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.26 0.50
d11 4.23 3.52

Each lens group data group Start surface Focal length
1 1 -187.22
2 7 81.04
3 13 45.49

<Numerical Example 3>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 138.678 2.80 1.51633 64.1 0.5352 51.75 -87.87
2 34.045 8.14 43.71
3 471.833 2.30 1.51742 52.4 0.5564 43.26 -79.65
4 37.998 15.08 39.87
5 72.980 4.33 1.83481 42.7 0.5642 38.88 84.32
6 -2286.600 (variable) 38.40
7 55.352 6.16 1.69680 55.5 0.5433 37.65 56.43
8 -131.452 7.03 37.38
9 211.651 8.86 1.56907 71.3 0.5451 32.58 38.87
10 -24.418 1.50 1.54814 45.8 0.5685 31.63 -30.23
11 53.519 (variable) 27.72
12 (Aperture) ∞ 8.51 26.83
13 -19.580 1.60 1.80518 25.4 0.6161 25.41 -24.40
14 -1624.756 3.48 1.83481 42.7 0.5642 28.74 72.36
15 * -58.607 0.20 29.90
16 -201.678 4.78 1.77250 49.6 0.5521 30.68 51.41
17 -33.656 0.20 31.43
18 -125.538 6.03 1.77250 49.6 0.5521 33.29 51.93
19 -31.155 34.55
Image plane ∞

Aspheric data 15th surface
K = 3.19091e + 000 A 4 = 1.37664e-005 A 6 = 4.83734e-009 A 8 = -1.25511e-011
A10 = 8.19810e-015

Focal length 33.00
F number 1.45
Half angle of view 33.25
Statue height 21.64
Total lens length 130.83
BF 39.35

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.26 0.50
d11 4.23 3.43

Each lens group data group Start surface Focal length
1 1 -130.50
2 7 74.94
3 13 47.34

<Numerical Example 4>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 72.833 2.80 1.51633 64.1 0.5352 52.55 -231.71
2 44.741 6.93 47.42
3 495.555 2.30 1.51633 64.1 0.5352 46.72 -68.21
4 32.946 15.21 40.84
5 73.203 3.88 1.83481 42.7 0.5642 38.13 92.69
6 1206.136 (variable) 37.56
7 69.908 4.81 1.77250 49.6 0.5521 33.57 65.84
8 -184.247 6.93 33.31
9 183.296 8.46 1.77250 49.6 0.5521 30.16 29.77
10 -25.908 1.50 1.65412 39.7 0.5737 29.21 -25.78
11 50.258 (variable) 25.93
12 (Aperture) ∞ 7.74 25.04
13 -18.324 1.60 1.80518 25.4 0.6161 23.86 -20.62
14 202.949 4.95 1.83481 42.7 0.5642 27.39 56.72
15 * -61.515 0.20 29.12
16 -224.197 6.86 1.77250 49.6 0.5521 30.70 44.55
17 -30.361 0.20 33.31
18 -169.048 6.53 1.77250 49.6 0.5521 37.12 56.54
19 -35.428 38.27

Aspheric data 15th surface
K = 3.52328e + 000 A 4 = 1.33216e-005 A 6 = 3.55802e-009 A 8 = -1.56396e-011
A10 = 1.26434e-014

Focal length 34.50
F number 1.45
Angle of View 32.09
Statue height 21.64
Total lens length 130.73
BF 39.35

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.26 0.50
d11 4.23 3.30

Each lens group data group Start surface Focal length
1 1 -193.13
2 7 80.16
3 13 43.01

<Numerical example 5>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 128.003 2.80 1.58913 61.1 0.5406 48.75 -70.18
2 31.089 8.58 41.04
3 -1434.850 2.30 1.58913 61.1 0.5406 40.66 -96.93
4 59.749 9.61 38.83
5 99.708 2.36 1.71300 53.9 0.5458 37.90 291.76
6 188.834 0.20 37.56
7 115.832 3.51 1.88300 40.8 0.5667 37.37 98.67
8 -354.793 (variable) 36.94
9 55.693 5.10 1.69680 55.5 0.5433 35.17 63.10
10 -205.133 8.16 34.92
11 135.179 6.36 1.77250 49.6 0.5521 30.94 32.82
12 -30.749 1.50 1.65412 39.7 0.5737 30.47 -28.56
13 49.273 (variable) 27.10
14 (Aperture) ∞ 8.45 26.23
15 -19.812 1.60 1.80518 25.4 0.6161 24.67 -21.64
16 162.418 4.90 1.83481 42.7 0.5642 27.85 62.15
17 * -75.798 0.20 29.46
18 -470.465 6.60 1.77250 49.6 0.5521 30.67 45.14
19 -32.806 0.20 33.09
20 -154.187 6.32 1.77250 49.6 0.5521 36.37 56.91
21 -34.950 37.53
Image plane ∞

Aspheric data 17th surface
K = 4.82454e + 000 A 4 = 1.27386e-005 A 6 = 2.46580e-009 A 8 = -1.63965e-011
A10 = 1.16481e-014

Focal length 33.00
F number 1.45
Half angle of view 33.25
Statue height 21.64
Total length of lens 128.60
BF 39.36

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 8 6.26 0.50
d13 4.23 3.57

Each lens group data group Start surface Focal length
1 1 -143.79
2 9 73.18
3 15 45.49

<Numerical Example 6>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 144.032 2.80 1.56732 42.8 0.5730 51.42 -72.47
2 31.896 7.37 43.18
3 134.427 2.30 1.69895 30.1 0.6029 42.84 -97.91
4 45.260 11.78 40.55
5 69.612 4.17 2.00069 25.5 0.6133 40.11 76.25
6 703.046 (variable) 39.63
7 65.773 7.06 1.77250 49.6 0.5521 35.48 38.40
8 -51.942 1.50 1.65412 39.7 0.5737 35.26 -105.74
9 -207.258 9.33 34.46
10 336.996 6.50 1.80400 46.6 0.5572 29.64 29.89
11 -25.793 1.50 1.72047 34.7 0.5834 29.15 -25.73
12 69.207 (variable) 26.33
13 (Aperture) ∞ 7.36 25.55
14 -18.795 1.60 1.75520 27.5 0.6103 24.45 -20.02
15 83.712 3.69 1.81600 46.6 0.5568 28.11 47.36
16 * -71.020 0.37 28.84
17 -310.370 5.67 1.77250 49.6 0.5521 29.59 44.91
18 -31.588 0.20 30.55
19 -112.941 4.94 1.77250 49.6 0.5521 32.83 57.32
20 -32.530 33.73
Image plane ∞

Aspheric data 16th surface
K = 3.09216e + 000 A 4 = 1.39545e-005 A 6 = 9.44622e-010 A 8 = -1.48017e-011
A10 = 1.54514e-015

Focal length 33.32
F number 1.45
Half angle of view 33.00
Statue height 21.64
Total lens length 126.22
BF 37.99

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.83 1.32
d12 3.26 2.26

Each lens group data group Start surface Focal length
1 1 -143.42
2 7 72.39
3 13 46.26

<Numerical Example 7>
Surface data surface number rd nd vd θgF Effective diameter Focal length
1 130.413 2.80 1.51633 64.1 0.5352 50.76 -78.78
2 30.865 9.43 42.29
3 -638.842 2.30 1.58913 61.1 0.5406 41.87 -92.75
4 60.084 10.82 39.84
5 * 84.426 4.58 1.78800 47.4 0.5559 38.60 77.00
6 -214.306 (variable) 38.18
7 57.548 5.00 1.72916 54.7 0.5444 34.99 62.34
8 -212.802 8.82 34.73
9 355.239 6.35 1.80 400 46.6 0.5572 30.60 34.70
10 -30.200 1.50 1.65412 39.7 0.5737 30.05 -30.03
11 58.273 (variable) 27.10
12 (Aperture) ∞ 8.20 26.11
13 -19.812 1.60 1.80518 25.4 0.6161 24.65 -21.64
14 162.418 4.90 1.83481 42.7 0.5642 27.82 62.15
15 * -75.798 0.20 29.43
16 -470.465 6.60 1.77250 49.6 0.5521 30.27 45.14
17 -32.806 0.20 32.76
18 -154.187 6.32 1.77250 49.6 0.5521 36.00 56.91
19 -34.950 37.18
Image plane ∞

Aspheric data 5th surface
K = -2.33085e + 000 A 4 = 2.90341e-007 A 6 = -9.23173e-011 A 8 = 1.45810e-013 A10 = -6.71605e-017

15th page
K = 4.82454e + 000 A 4 = 1.27386e-005 A 6 = 2.46580e-009 A 8 = -1.63965e-011
A10 = 1.16481e-014

Focal length 33.00
F number 1.45
Angle of view 33.25
Statue height 21.64
Total length of lens 129.44
BF 39.35

d 6 6.26
d11 4.23
d19 39.35

Focus adjustment variable interval At infinity focus At close focus (0.3m from the image plane)
d 6 6.26 0.65
d11 4.23 3.51

Each lens group data group Start surface Focal length
1 1 -155.06
2 7 75.22
3 12 45.49

FIG. 18 is a schematic view of the main part of a single-lens reflex camera. In FIG. 18, the optical system 1 is a photographing optical system of Numerical Examples 1 to 7. The photographing optical system 1 is held by a lens barrel 2 that is a holding member. Reference numeral 20 denotes a camera body. The camera body 20 includes a quick return mirror 3, a focusing screen 4, a penta roof prism 5, an eyepiece lens 6, and the like. The quick return mirror 3 reflects the light beam from the photographing optical system 10 upward. The focusing screen 4 is disposed at the image forming position of the photographing optical system 10. The penta roof prism 5 converts the reverse image formed on the focusing screen 4 into an erect image. An observer observes the erect image through the eyepiece 6. Reference numeral 7 denotes a photosensitive surface, on which a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives an image, or a silver salt film is disposed. At the time of photographing, the quick return mirror 3 is retracted from the optical path, and is formed on the photosensitive surface 7 by the photographing optical system 10 on the image side. The optical system of the present invention can be applied to broadcast television cameras, movie cameras, video cameras, digital still cameras, silver salt photography cameras, and the like.
As described above, by applying the single focus lens of the present invention to a single-lens reflex camera or a movie camera, an imaging apparatus having high optical performance is realized.

U1: First group U2: Second group U21: 21st group U22: 22nd group SP: Aperture stop 1: Shooting optical system

Claims (8)

In order from the object side, the first group of negative refractive power that is fixed at the time of focus adjustment, and the second group of positive refractive power that moves to the object side when focusing from an object at infinity to a short distance object, The second group is composed of a 21st group having a positive refractive power, an aperture stop, and a 22nd group having a positive refractive power, and the 21st group and the 22nd group move toward the object side with different amounts of movement during focus adjustment. When the refractive power of the first group is φ1, the refractive power of the 21st group is φ21, and the total refractive power of the positive lenses of the first group is φ1p,
-2.80 <φ21 / φ1 <−1.64
-2.09 <φ1p / φ1 <−1. 5 0
A single-focus lens characterized by satisfying   When the refractive power of the 22nd group is φ22,
      -4.80 <φ22 / φ1 <-2.30
        1.10 <φ22 / φ21 <2.00
The single focus lens according to claim 1, wherein:   In order from the object side, the first group of negative refractive power that is fixed at the time of focus adjustment, and the second group of positive refractive power that moves to the object side when focusing from an object at infinity to a short distance object, The second group is composed of a 21st group having a positive refractive power, an aperture stop, and a 22nd group having a positive refractive power, and the 21st group and the 22nd group move toward the object side with different amounts of movement during focus adjustment. When the refractive power of the first group is φ1, the refractive power of the 21st group is φ21, the refractive power of the 22nd group is φ22, and the sum of the refractive powers of the positive lenses of the first group is φ1p,
      -2.80 <φ21 / φ1 <−1.64
      -2.09 <φ1p / φ1 <−1.20
      -4.80 <φ22 / φ1 <-2.30
        1.10 <φ22 / φ21 <2.00
A single-focus lens characterized by satisfying The first group includes two negative lenses and one positive lens. When the radius of curvature of the object side surface of the positive lens is R1, and the radius of curvature of the image side surface is R2,
-1.5 <(R1 + R2) / (R1-R2) <-0.3
The single focus lens according to any one of claims 1 to 3, wherein: When the average refractive index of the positive lens in the first group is N1p and the average Abbe number is ν1p,
1.65 <N1p <2.10
65 <ν1p <23
Single focus lens according to any one of claims 1 to 4, characterized in that meet. It said at least one single focus lens according to any one of claims 1 to 5, characterized in that it has a non-spherical shape refractive power becomes weaker toward the periphery a convex of the first group of positive lenses. The twenty-first group includes a negative lens G21n and a positive lens G21p in order from the image side. The positive lens G21p and the negative lens G21n have refractive powers of φp and φn, partial dispersion ratios of θp and θn, respectively. When νp, νn and the focal length of the whole system are f,
-2.45 × 10 ⁻³ <(θp−θn) / (νp−νn) <− 0.80 × 10 ⁻³
0.50 <φp × f <1.50
−1.60 <φn × f <−0.70
The single focus lens according to any one of claims 1 to 6 , wherein: Imaging apparatus characterized by comprising a solid-state image sensor for receiving an image formed by the single-focus lens and the single focus lens according to any one of claims 1 to 7.

Images