Patent Application
20220291489
The present invention relates to an optical system, an optical apparatus and a method for manufacturing the optical system.
In recent years, the image resolutions of imaging elements included in imaging apparatuses, such as digital cameras and video cameras, have been improved. It is desired that a photographing lens provided in an imaging apparatus including such an imaging element be a lens of which not only the reference aberrations (aberrations for single-wavelength aberrations), such as the spherical aberration and the coma aberration, be favorably corrected, but also chromatic aberrations be favorably corrected so as not to cause color bleeding for a white light source, and which have a high resolution. In particular, for correction of the chromatic aberrations, it is desirable that not only primary achromatism be achieved but also secondary spectrum be favorably corrected. As means for correcting the chromatic aberrations, for example, a method of using a resin material having anomalous dispersion characteristics (for example, see Patent literature 1) has been known. As described above, accompanied by the recent improvement in imaging element resolution, a photographing lens with various aberrations being favorably corrected has been desired.
A first optical system according to the present invention comprises: an aperture stop; and a negative lens that is disposed closer to an image than the aperture stop, wherein the negative lens satisfies the following conditional expressions:
−0.010<ndN2−(2.015−0.0068×νdN2),
50.00<νdN2<65.00,
0.545<θgFN2,
−0.010<θgFN2−(0.6418−0.00168×νdN2)
where ndN2: a refractive index of the negative lens for d-line,
νdN2: an Abbe number of the negative lens with reference to d-line,
θgFN2: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN2, a refractive index of the negative lens for F-line is nFN2, and a refractive index of the negative lens for C-line is nCN2:
θgFN2=(ngN2−nFN2)/(nFN2−nCN2).
A second optical system according to the present invention comprises: a plurality of lens groups that include lens groups having negative refractive powers, wherein upon zooming or focusing, a distance between the lens groups adjacent to each other changes, and an image-side negative lens group disposed closest to an image among the lens groups having the negative refractive powers includes a negative lens that satisfies the following conditional expressions:
−0.010<ndN4−(2.015−0.0068×νdN4),
50.00<νdN4<65.00,
0.545<θgFN4,
−0.010<θgFN4−(0.6418−0.00168×νdN4)
where ndN4: a refractive index of the negative lens for d-line,
νdN4: an Abbe number of the negative lens with reference to d-line, and
θgFN4: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN4, a refractive index of the negative lens for F-line is nFN4, and a refractive index of the negative lens for C-line is nCN4:
θgFN4=(ngN4−nFN4)/(nFN4−nCN4).
An optical apparatus according to the present invention comprises the optical system described above.
A first method for manufacturing an optical system according to the present invention arranges each lens in a lens barrel so that the optical system comprises: an aperture stop; and a negative lens that is disposed closer to an image than the aperture stop, the negative lens satisfying the following conditional expressions:
−0.010<ndN2−(2.015−0.0068×νdN2),
50.00<νdN2<65.00,
0.545<θgFN2,
−0.010<θgFN2−(0.6418−0.00168×νdN2)
where ndN2: a refractive index of the negative lens for d-line,
νdN2: an Abbe number of the negative lens with reference to d-line, and
θgFN2: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN2, a refractive index of the negative lens for F-line is nFN2, and a refractive index of the negative lens for C-line is nCN2:
θgFN2=(ngN2−nFN2)/(nFN2−nCN2).
A second method for manufacturing an optical system according to the present invention that includes a plurality of lens groups including lens groups having negative refractive powers, the method arranging each lens in a lens barrel so that upon zooming or focusing, a distance between the lens groups adjacent to each other changes, and an image-side negative lens group disposed closest to an image among the lens groups having the negative refractive powers includes a negative lens that satisfies the following conditional expressions:
−0.010<ndN4−(2.015−0.0068×νdN4),
50.00<νdN4<65.00,
0.545<θgFN4,
−0.010<θgFN4−(0.6418−0.00168×νdN4)
where ndN4: a refractive index of the negative lens for d-line,
νdN4: an Abbe number of the negative lens with reference to d-line, and
θgFN4: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN4, a refractive index of the negative lens for F-line is nFN4, and a refractive index of the negative lens for C-line is nCN4:
θgFN4=(ngN4−nFN4)/(nFN4−nCN4).
Hereinafter, preferable embodiments according to the present invention are described. First, a camera (optical apparatus) that includes an optical system according to each embodiment is described with reference to
Next, the optical system according to a first embodiment is described. As shown in
−0.010<ndN2−(2.015−0.0068×νdN2), (1),
50.00<νdN2<65.00 (2),
0.545<θgFN2 (3),
−0.010<θgFN2−(0.6418−0.00168×νdN2) (4)
where ndN2: a refractive index of the negative lens for d-line,
νdN2: an Abbe number of the negative lens with reference to d-line, and
θgFN2: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN2, a refractive index of the negative lens for F-line is nFN2, and a refractive index of the negative lens for C-line is nCN2:
θgFN2=(ngN2−nFN2)/(nFN2−nCN2).
Note that the Abbe number νdN2 of the negative lens with reference to d-line is defined by the following expression:
νdN2=(ndN2−1)/(nFN2−nCN2).
According to this embodiment, the optical system where for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum is favorably corrected, and the optical apparatus that includes this optical system can be achieved. The optical system LS according to the first embodiment may be an optical system LS(2) shown in
The conditional expression (1) defines an appropriate relationship between the refractive index of the negative lens for d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (1), correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration can be favorably performed.
If the corresponding value of the conditional expression (1) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (1) to −0.005, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (1) may be set to −0.001, 0.000, 0.003, 0.005 or 0.007, or further to 0.008.
Note that the upper limit value of the conditional expression (1) may be set to less than 0.150. Accordingly, correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed. In this case, by setting the upper limit value of the conditional expression (1) to 0.100, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (1) may be set to 0.080, 0.060 or 0.050, or further to 0.045.
The conditional expression (2) defines an appropriate range of the Abbe number of the negative lens with reference to d-line. By satisfying the conditional expression (2), correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed.
If the corresponding value of the conditional expression (2) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (2) to 50.50, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (2) may be set to 51.00, 51.50 or 52.00, or further to 52.40.
By setting the upper limit value of the conditional expression (2) to 64.00, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (2) may be set to 63.00, 62.50, 62.00, 61.50, 61.00 or 60.00, or further to 59.50.
The conditional expression (3) appropriately defines the anomalous dispersion characteristics of the negative lens. By satisfying the conditional expression (3), for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum can be favorably corrected.
If the corresponding value of the conditional expression (3) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (3) to 0.547, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (3) may be set to 0.548 or 0.549, or further to 0.550.
The conditional expression (4) appropriately defines the anomalous dispersion characteristics of the negative lens. By satisfying the conditional expression (4), for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum can be favorably corrected.
If the corresponding value of the conditional expression (4) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (4) to −0.005, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (4) may be set to −0.001.
Note that the upper limit value of the conditional expression (4) may be set to less than 0.040. Accordingly, correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed. In this case, by setting the upper limit value of the conditional expression (4) to 0.030, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (4) may be set to 0.025, or further to 0.020.
Preferably, the optical system LS according to the first embodiment consists of: the aperture stop S; a front group GF disposed closer to the object than the aperture stop S; and a rear group GR disposed closer to an image than the aperture stop S, wherein the rear group GR includes the negative lens, and satisfies the following conditional expression (5):
−10.00<(−fN2)/fR<10.00 (5)
where fN2: the focal length of the negative lens, and
fR: a focal length of the rear group GR; in a case where the optical system LS is a zoom optical system, the focal length of the rear group GR in the wide angle end state.
The conditional expression (5) defines an appropriate relationship between the focal length of the negative lens and the focal length of the rear group GR. By satisfying the conditional expression (5), the reference aberrations, such as the spherical aberration and the coma aberration, can be favorably corrected.
If the corresponding value of the conditional expression (5) falls outside of the range, the correction of the reference aberrations, such as the spherical aberration and the coma aberration, becomes difficult. By setting the lower limit value of the conditional expression (5) to −9.50, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (5) may be set to −9.00, −8.50, −8.00, −7.00, −5.00, −3.00, −1.50, −0.05 or 0.05, or further to 0.10.
By setting the upper limit value of the conditional expression (5) to 8.50, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (5) may be set to 7.50, 6.50, 5.00 or 4.00, or further to 3.00.
In the optical system LS according to the first embodiment, preferably, the negative lens satisfies the following conditional expression (6),
0.10<(−fN2)/f<15.00 (6)
where fN2: the focal length of the negative lens, and
f: a focal length of the optical system; the focal length of the optical system LS in the wide angle end state in a case where the optical system LS is a zoom optical system.
The conditional expression (6) defines an appropriate relationship between the focal length of the negative lens and the focal length of the optical system LS. By satisfying the conditional expression (6), the reference aberrations, such as the spherical aberration and the coma aberration, can be favorably corrected.
If the corresponding value of the conditional expression (6) falls outside of the range, the correction of the reference aberrations, such as the spherical aberration and the coma aberration, becomes difficult. By setting the lower limit value of the conditional expression (6) to 0.20, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (6) may be set to 0.30, 0.40 or 0.45, or further to 0.50.
By setting the upper limit value of the conditional expression (6) to 14.20, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (6) may be set to 12.00, 10.00 or 8.50, or further to 7.50.
In the optical system LS according to the first embodiment, the negative lens may satisfy the following conditional expression (3-1),
0.555<θgFN2. (3-1)
The conditional expression (3-1) is an expression similar to the conditional expression (3), and can exert advantageous effects similar to those of the conditional expression (3). By setting the lower limit value of the conditional expression (3-1) to 0.556, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, it is preferable to set the lower limit value of the conditional expression (3-1) to 0.557.
In the optical system LS according to the first embodiment, the negative lens may satisfy the following conditional expression (4-1),
0.010<θgFN2−(0.6418−0.00168×νdN2). (4-1)
The conditional expression (4-1) is an expression similar to the conditional expression (4), and can exert advantageous effects similar to those of the conditional expression (4). By setting the lower limit value of the conditional expression (4-1) to 0.011, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, it is preferable to set the lower limit value of the conditional expression (4-1) to 0.012.
Note that the upper limit value of the conditional expression (4-1) may be set to less than 0.030. Accordingly, advantageous effects similar to those of the conditional expression (4) can be achieved. In this case, by setting the upper limit value of the conditional expression (4-1) to 0.028, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (4-1) may be set to 0.025 or 0.023, or further to 0.020.
In the optical system LS according to the first embodiment, preferably, the negative lens satisfies the following conditional expression (7),
DN2>0.400 [mm] (7)
where DN2: a thickness of the negative lens on an optical axis.
The conditional expression (7) appropriately defines the thickness of the negative lens on the optical axis. By satisfying the conditional expression (7), the various aberrations, such as the coma aberration, the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected.
If the corresponding value of the conditional expression (7) falls outside of the range, the correction of the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), becomes difficult. By setting the lower limit value of the conditional expression (7) to 0.450 [mm], the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (7) may be set to 0.490 [mm], 0.550 [mm], 0.580 [mm], 0.650 [mm], 0.680 [mm], 0.750 [mm], 0.800 [mm], 0.850 [mm], 0.880 [mm], 0.950 [mm], 0.980 [mm], 1.050 [mm], 1.100 [mm], 1.140 [mm], 1.250 [mm], or further to 1.350 [mm].
In the optical system LS according to the first embodiment, preferably, the negative lens is a single lens, or one lens of two lenses of a cemented lens consisting of the two lenses cemented to each other. Use of glass as the material of the lens has smaller variation in optical characteristics due to temperature than that of resin. In this embodiment, glass can be used as a material of the negative lens. Accordingly, even in the case where the negative lens has a lens surface in contact with air (i.e., a single lens, or one lens of two lenses of a cemented lens consisting of the two lenses cemented to each other), it is preferable because variation in optical characteristics due to temperature is small.
In the optical system LS according to the first embodiment, it is desirable that at least one lens surface of an object-side lens surface and an image-side lens surface of the negative lens be in contact with air. Use of glass as the material of the lens has smaller variation in optical characteristics due to temperature than that of resin. In this embodiment, glass can be used as a material of the negative lens. Accordingly, even in a case where a lens surface of the negative lens is in contact with air, it is preferable because the variation in optical characteristics due to temperature is small.
In the optical system LS according to the first embodiment, it is desirable that the negative lens be a glass lens. The secular change of the negative lens that is a glass lens is smaller than that of a resin lens. Accordingly, it is preferable because the variation in optical characteristics due to temperature is small.
Subsequently, referring to
Next, the optical system according to a second embodiment is described. As shown in
−0.010<ndN4−(2.015−0.0068×νdN4), (11)
50.00<νdN4<65.00, (12)
0.545<θgFN4, (13)
−0.010<θgFN4−(0.6418−0.00168×νdN4), (14)
where ndN4: a refractive index of the negative lens for d-line,
νdN4: an Abbe number of the negative lens with reference to d-line, and
θgFN4: a partial dispersion ratio of the negative lens, defined by a following expression when a refractive index of the negative lens for g-line is ngN4, a refractive index of the negative lens for F-line is nFN4, and a refractive index of the negative lens for C-line is nCN4:
θgFN4=(ngN4−nFN4)/(nFN4−nCN4).
Note that the Abbe number νdN4 of the negative lens with reference to d-line is defined by the following expression:
νdN4=(ndN4−1)/(nFN4−nCN4).
According to this embodiment, the optical system where for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum is favorably corrected, and the optical apparatus that includes this optical system can be achieved. The optical system LS according to the second embodiment may be an optical system LS(2) shown in
The conditional expression (11) defines an appropriate relationship between the refractive index of the negative lens for d-line and the Abbe number with reference to d-line. By satisfying the conditional expression (11), correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed.
If the corresponding value of the conditional expression (11) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (11) to −0.005, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (11) may be set to −0.001, 0.000, 0.003, 0.005 or 0.007, or further to 0.008.
Note that the upper limit value of the conditional expression (11) may be set to less than 0.150. Accordingly, correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed. In this case, by setting the upper limit value of the conditional expression (11) to 0.100, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (11) may be set to 0.080, 0.060 or 0.050, or further to 0.045.
The conditional expression (12) defines an appropriate range of the Abbe number of the negative lens with reference to d-line. By satisfying the conditional expression (12), correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed.
If the corresponding value of the conditional expression (12) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (12) to 50.50, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (12) may be set to 51.00, 51.50 or 52.00, or further to 52.40.
By setting the upper limit value of the conditional expression (12) to 64.00, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (12) may be set to 63.00, 62.50, 62.00, 61.50, 61.00 or 60.00, or further to 59.50.
The conditional expression (13) appropriately defines the anomalous dispersion characteristics of the negative lens. By satisfying the conditional expression (13), for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum can be favorably corrected.
If the corresponding value of the conditional expression (13) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (13) to 0.547, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (13) may be set to 0.548 or 0.549, or further to 0.550.
The conditional expression (14) appropriately defines the anomalous dispersion characteristics of the negative lens. By satisfying the conditional expression (14), for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum can be favorably corrected.
If the corresponding value of the conditional expression (14) falls outside of the range, the correction of the chromatic aberrations becomes difficult. By setting the lower limit value of the conditional expression (14) to −0.005, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (14) may be set to −0.001.
Note that the upper limit value of the conditional expression (14) may be set to less than 0.040. Accordingly, correction of the reference aberrations, such as the spherical aberration and the coma aberration, and correction of the primary chromatic aberration (achromatization) can be favorably performed. In this case, by setting the upper limit value of the conditional expression (14) to 0.030, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (14) may be set to 0.025, or further to 0.020.
In the optical system LS according to the second embodiment, preferably, the negative lens satisfies the following conditional expression (15):
0.02<fN4/fGb<3.00 (15)
where fN4: the focal length of the negative lens, and
fGb: a focal length of the image-side negative lens group.
The conditional expression (15) defines an appropriate relationship between the focal length of the negative lens and the focal length of the image-side negative lens group. By satisfying the conditional expression (15), the reference aberrations, such as the spherical aberration and the coma aberration, can be favorably corrected.
If the corresponding value of the conditional expression (15) falls outside of the range, the correction of the reference aberrations, such as the spherical aberration and the coma aberration, becomes difficult. By setting the lower limit value of the conditional expression (15) to 0.03, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (15) may be set to 0.04, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 or 0.40, or further to 0.42.
By setting the upper limit value of the conditional expression (15) to 2.80, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (15) may be set to 2.50, 2.30, 2.20, 2.00, 1.75 or 1.50, or further to 1.30.
In the optical system LS according to the second embodiment, preferably, the image-side negative lens group satisfies the following conditional expression (16):
0.50<(−fGb)/f<100.00 (16)
where fGb: a focal length of the image-side negative lens group, and
f: a focal length of the optical system; in a case where the optical system LS is a zoom optical system, the focal length of the optical system LS in the wide angle end state.
The conditional expression (16) defines an appropriate relationship between the focal length of the image-side negative lens group and the focal length of the optical system LS. By satisfying the conditional expression (16), the reference aberrations, such as the spherical aberration and the coma aberration, can be favorably corrected.
If the corresponding value of the conditional expression (16) falls outside of the range, the correction of the reference aberrations, such as the spherical aberration and the coma aberration, becomes difficult. By setting the lower limit value of the conditional expression (16) to 0.60, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (16) may be set to 0.70, 0.80 or 0.90, or further to 0.95.
By setting the upper limit value of the conditional expression (16) to 85.00, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (16) may be set to 70.00, 50.00, 35.00, 20.00, 10.00, 5.00, 3.50 or 2.80, or further to 2.20.
In the optical system LS according to the second embodiment, the negative lens may satisfy the following conditional expression (13-1),
0.555<θgFN4. (13-1)
The conditional expression (13-1) is an expression similar to the conditional expression (13), and can exert advantageous effects similar to those of the conditional expression (13). By setting the lower limit value of the conditional expression (13-1) to 0.556, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, it is preferable to set the lower limit value of the conditional expression (13-1) to 0.557.
In the optical system LS according to the second embodiment, the negative lens may satisfy the following conditional expression (14-1),
0.010<θgFN4−(0.6418−0.00168×νdN4). (14-1)
The conditional expression (14-1) is an expression similar to the conditional expression (14), and can exert advantageous effects similar to those of the conditional expression (14). By setting the lower limit value of the conditional expression (14-1) to 0.011, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, it is preferable to set the lower limit value of the conditional expression (14-1) to 0.012.
Note that the upper limit value of the conditional expression (14-1) may be set to less than 0.030. Accordingly, advantageous effects similar to those of the conditional expression (14) can be achieved. In this case, by setting the upper limit value of the conditional expression (14-1) to 0.028, the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the upper limit value of the conditional expression (14-1) may be set to 0.025 or 0.023, or further to 0.020.
In the optical system LS according to the second embodiment, preferably, the negative lens satisfies the following conditional expression (17),
DN4>0.400 [mm] (17)
where DN4: a thickness of the negative lens on an optical axis.
The conditional expression (17) appropriately defines the thickness of the negative lens on the optical axis. By satisfying the conditional expression (17), the various aberrations, such as the coma aberration, the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), can be favorably corrected.
If the corresponding value of the conditional expression (17) falls outside of the range, the correction of the various aberrations, such as the coma aberration and the chromatic aberrations (the longitudinal chromatic aberration and the chromatic aberration of magnification), becomes difficult. By setting the lower limit value of the conditional expression (17) to 0.450 [mm], the advantageous effects of this embodiment can be further secured. To further secure the advantageous effects of this embodiment, the lower limit value of the conditional expression (17) may be set to 0.490 [mm], 0.550 [mm], 0.580 [mm], 0.650 [mm], 0.680 [mm], 0.750 [mm], 0.800 [mm], 0.850 [mm], 0.880 [mm], 0.950 [mm], 0.980 [mm], 1.050 [mm], 1.100 [mm], 1.140 [mm] or 1.250 [mm], or further to 1.350 [mm].
In the optical system LS according to the second embodiment, preferably, the negative lens is a single lens, or one lens of two lenses of a cemented lens consisting of the two lenses cemented to each other. Use of glass as the material of the lens has smaller variation in optical characteristics due to temperature than that of resin. In this embodiment, glass can be used as a material of the negative lens. Accordingly, even in the case where the negative lens has a lens surface in contact with air (i.e., a single lens, or one lens of two lenses of a cemented lens consisting of the two lenses cemented to each other), it is preferable because variation in optical characteristics due to temperature is small.
In the optical system LS according to the second embodiment, at least one lens surface of an object-side lens surface and an image-side lens surface of the negative lens is in contact with air. Use of glass as the material of the lens has smaller variation in optical characteristics due to temperature than that of resin. In this embodiment, glass can be used as a material of the negative lens. Accordingly, even in a case where a lens surface of the negative lens is in contact with air, it is preferable because the variation in optical characteristics due to temperature is small.
In the optical system LS according to the second embodiment, it is desirable that the negative lens be a glass lens. The secular change of the negative lens that is a glass lens is smaller than that of a resin lens. Accordingly, it is preferable because the variation in optical characteristics due to temperature is small.
Subsequently, referring to
Optical systems LS according to Examples of each embodiment are described with reference to the drawings.
In
Tables 1 to 7 are shown below. Among the drawings, Table 1 is a table showing each data item in First Example, Table 2 is that in Second Example, Table 3 is that in Third Example, Table 4 is that in Fourth Example, Table 5 is that in Fifth Example, Table 6 is that in Sixth Example, and Table 7 is that in Seventh Example. In each Example, as targets of calculation of aberration characteristics, d-line (wavelength λ=587.6 nm), g-line (wavelength λ=435.8 nm), C-line (wavelength λ=656.3 nm), and F-line (wavelength λ=486.1 nm) are selected.
In the table of [General Data], f indicates the focal length of the entire lens system, FNO indicates the f-number, 2ω indicates the angle of view (the unit is ° (degrees), and co is the half angle of view), and Y indicates the image height. TL indicates a distance obtained by adding BF to the distance from the lens foremost surface to the lens last surface on the optical axis upon focusing on infinity. BF indicates the distance (back focus) from the lens last surface to the image surface I on the optical axis upon focusing on infinity. fF indicates the focal length of the front group, and fR indicates the focal length of the rear group. Note that in a case where the optical system is a zoom optical system, these values are indicated for each of zoom states at the wide-angle end (W), the intermediate focal length (M) and the telephoto end (T).
In the table of [Lens Data], Surface Number indicates the order of the optical surface from the object side along the direction in which the ray travels, R indicates the radius of curvature (the surface whose center of curvature resides on the image side is regarded to have a positive value) of each optical surface, D indicates the surface distance which is the distance to the next lens surface (or the image surface) from each optical surface on the optical axis, nd is the refractive index of the material of the optical member for d-line, νd indicates the Abbe number of the material of the optical member with respect to d-line, and θgF indicates the partial dispersion ratio of the material of the optical member. The radius of curvature “∞” indicates a plane or an opening. (Aperture Stop S) indicates an aperture stop S. The description of the air refractive index nd=1.00000 is omitted. In a case where the optical surface is an aspherical surface, the surface number is assigned * symbol, and the field of the radius of curvature R indicates the paraxial radius of curvature.
The refractive index of the optical member for g-line (wavelength λ=435.8 nm) is indicated by ng. The refractive index of the optical member for F-line (wavelength λ=486.1 nm) is indicated by nF. The refractive index of the optical member for C-line (wavelength λ=656.3 nm) is indicated by nC. Here, the partial dispersion ratio θgF of the material of the optical member is defined by the following expression (A).
θgF=(ng−nF)/(nF−nC). (A)
In the table of [Aspherical Surface Data], the shape of the aspherical surface indicated in [Lens Data] is indicated by the following expression (B). X(y) indicates the distance (sag amount) from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at the height y along the optical axis direction. R indicates the radius of curvature (paraxial radius of curvature) of the reference spherical surface. κ indicates the conic constant. Ai indicates the i-th aspherical coefficient. “E−n” indicates “×10−n”. For example, 1.234E−05=1.234×10−5. Note that the second-order aspherical coefficient A2 is zero, and the description thereof is omitted.
X(y)=(y2/R)/{1+(1−κ×y2/R2)1/2}+A4×y4+A6×y6+A8×y8+A10×y10+A12×y12. (B)
In a case where the optical system is not a zoom optical system, f indicates the focal length of the entire lens system, and β indicates the photographing magnification, as [Variable Distance Data on Short-Distance Photographing]. The table of [Variable Distance Data on Short-Distance Photographing] indicates the surface distance at the surface number where the surface distance is “Variable” in [Lens Data] corresponding to each focal length and photographing magnification.
In the case where the optical system is the zoom optical system, the surface distance at the surface number where the surface distance is “Variable” in [Lens Data] corresponding to each of zooming states at the wide angle end (W), the intermediate focal length (M) and the telephoto end (T) are indicated as [Variable Distance Data on Zoom Photographing].
The table of [Lens Group Data] shows the first surface (the surface closest to the object) and the focal length of each lens group.
The table of [Conditional Expression Corresponding Value] shows the value corresponding to each conditional expression.
Hereinafter, at all the data values, the listed focal length f, the radius of curvature R, the surface distance D, other lengths and the like are represented with “mm” if not otherwise specified. However, even after subjected to proportional scaling in or out, the optical system can achieve equivalent optical performance. Accordingly, the representation is not limited thereto.
The descriptions of the tables so far are common to all the Examples. Redundant descriptions are hereinafter omitted.
First Example is described with reference to
The first lens group G1 consists of, in order from the object: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a positive meniscus lens L12 having a convex surface facing the object; and a positive meniscus lens L13 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a negative meniscus lens L21 having a convex surface facing the object; a biconcave negative lens L22; a biconvex positive lens L23; and a negative meniscus lens L24 having a concave surface facing the object. The negative meniscus lens L21 has an object-side lens surface that is an aspherical surface.
The third lens group G3 consists of, in order from the object: a positive meniscus lens L31 having a convex surface facing the object; and a biconvex positive lens L32. The aperture stop S is disposed adjacent to the object side of the positive meniscus lens L31, and moves with the third lens group G3 upon zooming. The positive meniscus lens L31 has an object-side lens surface that is an aspherical surface.
The fourth lens group G4 consists of, in order from the object, a cemented lens consisting of a negative meniscus lens L41 having a convex surface facing the object, and a biconvex positive lens L42.
The fifth lens group G5 consists of, in order from the object: a negative meniscus lens L51 having a concave surface facing the object; and a biconvex positive lens L52. Upon focusing from the infinity object to the short-distant (finite distant) object, the fifth lens group G5 and the sixth lens group G6 move toward the object along the optical axis by different amounts of movement.
The sixth lens group G6 consists of a positive meniscus lens L61 having a concave surface facing the object. The positive meniscus lens L61 has an image-side lens surface that is an aspherical surface.
The seventh lens group G7 consists of, in order from the object: a positive meniscus lens L71 having a concave surface facing the object; a biconcave negative lens L72; and a negative meniscus lens L73 having a concave surface facing the object. An image surface I is disposed on the image side of the seventh lens group G7. In this Example, the negative meniscus lens L73 of the seventh lens group G7 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the seventh lens group G7 corresponds to an image-side negative lens group, and the negative meniscus lens L73 of the seventh lens group G7 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like. The negative lens L72 has an object-side lens surface that is an aspherical surface.
In this Example, the cemented lens consisting of the negative meniscus lens L11 and the positive meniscus lens L12, the positive meniscus lens L13, the negative meniscus lens L21, the negative lens L22, the positive lens L23, and the negative meniscus lens L24 constitute the front group GF disposed closer to the object than the aperture stop S. The positive meniscus lens L31, the positive lens L32, the cemented lens consisting of the negative meniscus lens L41 and the biconvex positive lens L42, the negative meniscus lens L51, the biconvex positive lens L52, the positive meniscus lens L61, the positive meniscus lens L71, the negative lens L72, and the negative meniscus lens L73 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 1 lists values of data on the optical system according to First Example.
The various aberration graphs show that the optical system according to First Example has favorably corrected various aberrations, and exerts excellent imaging performance.
Second Example is described with reference to
The first lens group G1 consists of, in order from the object: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a biconvex positive lens L12; and a positive meniscus lens L13 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a negative meniscus lens L21 having a convex surface facing the object; biconcave negative lens L22; a biconvex positive lens L23; and a negative meniscus lens L24 having a concave surface facing the object. Upon focusing from the infinity object to the short-distant (finite distant) object, the second lens group G2 moves toward the object along the optical axis. The negative meniscus lens L21 has an object-side lens surface that is an aspherical surface. The negative meniscus lens L24 has an image-side lens surface that is an aspherical surface.
The third lens group G3 consists of, in order from the object: a biconvex positive lens L31; a cemented lens consisting of a negative meniscus lens L32 having a convex surface facing the object, and a biconvex positive lens L33; and a biconvex positive lens L34. An aperture stop S is disposed between the positive lens L31 and the negative meniscus lens L32 (of the cemented lens) of the third lens group G3.
The fourth lens group G4 consists of, in order from the object: a cemented lens consisting of a positive meniscus lens L41 having a concave surface facing the object, and a negative meniscus lens L42 having a concave surface facing the object; and a biconcave negative lens L43. In this Example, the negative lens L43 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the fourth lens group G4 corresponds to an image-side negative lens group, and the negative lens L43 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like.
The fifth lens group G5 consists of, in order from the object: a biconvex positive lens L51; and a cemented lens consisting of a biconvex positive lens L52, and a biconcave negative lens L53. An image surface I is disposed on the image side of the fifth lens group G5. The positive lens L51 has an object-side lens surface that is an aspherical surface.
In this Example, the cemented lens consisting of the negative meniscus lens L11 and the positive lens L12, the positive meniscus lens L13, the negative meniscus lens L21, the negative lens L22, the positive lens L23, the negative meniscus lens L24, and the positive lens L31 constitute the front group GF disposed closer to the object than the aperture stop S. The cemented lens consisting of the negative meniscus lens L32 and the positive lens L33, the positive lens L34, the cemented lens consisting of the positive meniscus lens L41 and the negative meniscus lens L42, the negative lens L43, the positive lens L51, and the cemented lens consisting of the positive lens L52 and the negative lens L53 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 2 lists values of data on the optical system according to Second Example.
Third Example is described with reference to
The first lens group G1 consists of, in order from the object: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a biconvex positive lens L12; and a plano-convex positive lens L13 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a positive meniscus lens L21 having a convex surface facing the object; a cemented lens consisting of biconvex positive lens L22, and a biconcave negative lens L23; a cemented lens consisting of a biconcave negative lens L24, and a positive meniscus lens L25 having a convex surface facing the object; and a negative meniscus lens L26 having a concave surface facing the object.
The third lens group G3 consists of, in order from the object: a biconvex positive lens L31; a biconvex positive lens L32; a biconcave negative lens L33; and a biconvex positive lens L34.
The fourth lens group G4 consists of, in order from the object: a plano-convex positive lens L41 having a convex surface facing the image; and a cemented lens consisting of the biconvex positive lens L42, and a biconcave negative lens L43. Upon focusing from the infinity object to the short-distant (finite distant) object, the fourth lens group G4 moves toward the object along the optical axis.
The fifth lens group G5 consists of, in order from the object: a biconcave negative lens L51; a biconvex positive lens L52; a negative meniscus lens L53 having a convex surface facing the object; a cemented lens consisting of a positive meniscus lens L54 having a concave surface facing the object, and a biconcave negative lens L55; a biconvex positive lens L56; a cemented lens consisting of a negative meniscus lens L57 having a convex surface facing the object, and a biconvex positive lens L58; and a biconcave negative lens L59. An image surface I is disposed on the image side of the fifth lens group G5. An aperture stop S is disposed between the negative lens L51 and the positive lens L52 of the fifth lens group G5. In this Example, the negative lens L55 of the fifth lens group G5 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the fifth lens group G5 corresponds to an image-side negative lens group, and the negative lens L55 of the fifth lens group G5 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like. Note that a fixed aperture stop (flare cut stop) Sa is disposed between the negative lens L55 (of the cemented lens) and the positive lens L56.
In this Example, the cemented lens consisting of the negative meniscus lens L11 and the positive lens L12, the positive lens L13, the positive meniscus lens L21, the cemented lens consisting of the positive lens L22 and the negative lens L23, the cemented lens consisting of the negative lens L24 and the positive meniscus lens L25, the negative meniscus lens L26, the positive lens L31, the positive lens L32, the negative lens L33, the positive lens L34, the positive lens L41, the cemented lens consisting of the positive lens L42 and the negative lens L43, and the negative lens L51 constitute the front group GF disposed closer to the object than the aperture stop S. The positive lens L52, the negative meniscus lens L53, the cemented lens consisting of the positive meniscus lens L54 and the negative lens L55, the positive lens L56, the cemented lens consisting of the negative meniscus lens L57 and the positive lens L58, and the negative lens L59 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 3 lists values of data on the optical system according to Third Example.
Fourth Example is described with reference to
The first lens group G1 consists of, in order from the object: a negative meniscus lens L11 having a convex surface facing the object; a biconvex positive lens L12; and a positive meniscus lens L13 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a negative meniscus lens L21 having a convex surface facing the object; biconcave negative lens L22; a biconvex positive lens L23; and a negative meniscus lens L24 having a concave surface facing the object.
The third lens group G3 consists of, in order from the object: a biconvex positive lens L31; a cemented lens consisting of a negative meniscus lens L32 having a convex surface facing the object, and a biconvex positive lens L33; and a negative meniscus lens L34 having a concave surface facing the object. The aperture stop S is disposed adjacent to the object side of the positive lens L31, and moves with the third lens group G3 upon zooming. The cemented lens consisting of the negative meniscus lens L32 and the positive lens L33 of the third lens group G3 constitutes a vibration-proof lens group (partial group) that is movable in a direction perpendicular to the optical axis, and corrects variation in imaging position due to a camera shake and the like (image blur on the image surface I).
The fourth lens group G4 consists of, in order from the object: a cemented lens consisting of a biconvex positive lens L41, and a negative meniscus lens L42 having a concave surface facing the object; and a cemented lens consisting of a negative meniscus lens L43 having a convex surface facing the object, and a biconvex positive lens L44. The positive lens L44 has an image-side lens surface that is an aspherical surface.
The fifth lens group G5 consists of, in order from the object: a cemented lens consisting of a biconvex positive lens L51, and a biconcave negative lens L52. Upon focusing from the infinity object to the short-distant (finite distant) object, the fifth lens group G5 moves toward the image along the optical axis. The negative lens L52 has an image-side lens surface that is an aspherical surface.
The sixth lens group G6 consists of, in order from the object: a negative meniscus lens L61 having a concave surface facing the object; and a biconvex positive lens L62. An image surface I is disposed on the image side of the sixth lens group G6. In this Example, the negative meniscus lens L61 of the sixth lens group G6 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the sixth lens group G6 corresponds to an image-side negative lens group, and the negative meniscus lens L61 of the sixth lens group G6 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like. The negative meniscus lens L61 has an image-side lens surface that is an aspherical surface.
In this Example, the negative meniscus lens L11, the positive lens L12, the positive meniscus lens L13, the negative meniscus lens L21, the negative lens L22, the positive lens L23, and the negative meniscus lens L24 constitute the front group GF disposed closer to the object than the aperture stop S. The positive lens L31, the cemented lens consisting of the negative meniscus lens L32 and the positive lens L33, the negative meniscus lens L34, the cemented lens consisting of the positive lens L41 and the negative meniscus lens L42, the cemented lens consisting of the negative meniscus lens L43 and the positive lens L44, the cemented lens consisting of the positive lens L51 and the negative lens L52, the negative meniscus lens L61, and the positive lens L62 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 4 lists values of data on the optical system according to Fourth Example.
Fifth Example is described with reference to
The first lens group G1 consists of, in order from the object: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a biconvex positive lens L12; and a positive meniscus lens L13 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a negative meniscus lens L21 having a convex surface facing the object; a biconcave negative lens L22; a biconvex positive lens L23; and a cemented lens consisting of a biconcave negative lens L24 and a biconvex positive lens L25. Upon focusing from the infinity object to the short-distant (finite distant) object, the second lens group G2 moves toward the object along the optical axis. The negative meniscus lens L21 is a hybrid type lens that includes a lens main body made of glass, and a resin layer provided on the object-side surface of the lens main body. The object-side surface of the resin layer is an aspherical surface. The negative meniscus lens L21 is a composite type aspherical surface lens. In [Lens Data] described later, the surface number 6 indicates the object-side surface of the resin layer, the surface number 7 indicates the image-side surface of the resin layer and the object-side surface of the lens main body (a surface on which both the elements are in contact), and the surface number 8 indicates the image-side surface of the lens main body.
The third lens group G3 consists of, in order from the object: a biconvex positive lens L31; a biconvex positive lens L32; and a cemented lens consisting of a biconvex positive lens L33 and a negative meniscus lens L34 having a concave surface facing the object. The aperture stop S is disposed adjacent to the object side of the positive lens L31, and moves with the third lens group G3 upon zooming.
The fourth lens group G4 consists of, in order from the object: a cemented lens consisting of a biconcave negative lens L41 and a positive meniscus lens L42 having a convex surface facing the object; and a negative meniscus lens L43 having a concave surface facing the object. The cemented lens consisting of the negative lens L41 and the positive meniscus lens L42 of the fourth lens group G4 constitute a vibration-proof lens group (partial group) that is movable in a direction perpendicular to the optical axis, and corrects variation in imaging position due to a camera shake and the like (image blur on the image surface I). In this Example, the negative lens L41 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the fourth lens group G4 corresponds to an image-side negative lens group, and the negative lens L41 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like. The negative lens L41 is a hybrid type lens that includes a lens main body made of glass, and a resin layer provided on the object-side surface of the lens main body. The object-side surface of the resin layer is an aspherical surface. The negative lens L41 is a composite type aspherical surface lens. In [Lens Data] described later, the surface number 24 indicates the object-side surface of the resin layer, the surface number 25 indicates the image-side surface of the resin layer and the object-side surface of the lens main body (a surface on which both the elements are in contact), and the surface number 26 indicates the image-side surface of the lens main body and the object-side surface of the positive meniscus lens L42 (a surface on which both the elements are in contact).
The fifth lens group G5 consists of, in order from the object: a positive meniscus lens L51 having a concave surface facing the object; a biconvex positive lens L52; and a cemented lens consisting of a biconcave negative lens L53 and a biconvex positive lens L54. An image surface I is disposed on the image side of the fifth lens group G5. The negative lens L53 has an object-side lens surface that is an aspherical surface.
In this Example, the cemented lens consisting of the negative meniscus lens L11 and the positive lens L12, the positive meniscus lens L13, the negative meniscus lens L21, the negative lens L22, the positive lens L23, the cemented lens consisting of the negative lens L24 and the positive lens L25 constitute the front group GF disposed closer to the object than the aperture stop S. The positive lens L31, the positive lens L32, the cemented lens consisting of the positive lens L33 and the negative meniscus lens L34, the cemented lens consisting of the negative lens L41 and the positive meniscus lens L42, the negative meniscus lens L43, the positive meniscus lens L51, the positive lens L52, and the cemented lens consisting of the negative lens L53 and the positive lens L54 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 5 lists values of data on the optical system according to Fifth Example.
Sixth Example is described with reference to
The first lens group G1 consists of, in order from the object: a biconcave negative lens L11; a biconvex positive lens L12; a cemented lens consisting of a biconvex positive lens L13 and a biconcave negative lens L14; and a negative meniscus lens L15 having a convex surface facing the object. The aperture stop S is disposed adjacent to the image side of the negative meniscus lens L15, and moves with the first lens group G1 upon focusing. The negative lens L11 has an image-side lens surface that is an aspherical surface.
The second lens group G2 consists of, in order from the object: a biconvex positive lens L21; and a negative meniscus lens L22 having a convex surface facing the object.
The third lens group G3 consists of, in order from the object: a positive meniscus lens L31 having a convex surface facing the object; a negative meniscus lens L32 having a concave surface facing the object; and a biconvex positive lens L33. An image surface I is disposed on the image side of the third lens group G3. In this Example, the negative meniscus lens L32 of the third lens group G3 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the third lens group G3 corresponds to an image-side negative lens group, and the negative meniscus lens L32 of the third lens group G3 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like. The positive meniscus lens L31 has an image-side lens surface that is an aspherical surface. A cover glass CV is disposed between the third lens group G3 and the image surface I.
In this Example, the negative lens L11, the positive lens L12, the cemented lens consisting of the positive lens L13 and the negative lens L14, and the negative lens L15 constitute the front group GF disposed closer to the object than the aperture stop S. The positive lens L21, the negative meniscus lens L22, the positive meniscus lens L31, the negative meniscus lens L32, and the positive lens L33 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 6 lists values of data on the optical system according to Sixth Example.
Seventh Example is described with reference to
The first lens group G1 consists of, in order from the object: a cemented lens consisting of a negative meniscus lens L11 having a convex surface facing the object, and a biconvex positive lens L12; a positive meniscus lens L13 having a convex surface facing the object; and a positive meniscus lens L14 having a convex surface facing the object.
The second lens group G2 consists of, in order from the object: a negative meniscus lens L21 having a convex surface facing the object; a biconcave negative lens L22; and a cemented lens consisting of a biconvex positive lens L23, and a biconcave negative lens L24.
The third lens group G3 consists of, in order from the object: a biconvex positive lens L31; a cemented lens consisting of a positive meniscus lens L32 having a convex surface facing the object, and a negative meniscus lens L33 having a convex surface facing the object; and a biconvex positive lens L34. The aperture stop S is disposed adjacent to the object side of the positive lens L31, and moves with the third lens group G3 upon zooming. The third lens group G3 constitutes a vibration-proof lens group (partial group) that is movable in a direction perpendicular to the optical axis, and corrects variation in imaging position due to a camera shake and the like (image blur on the image surface I). The positive lens L31 has opposite lens surfaces that are aspherical surfaces.
The fourth lens group G4 consists of, in order from the object: a cemented lens consisting of a biconvex positive lens L41, and a biconcave negative lens L42. In this Example, the negative lens L42 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (1) to (4) and the like. In this Example, the fourth lens group G4 corresponds to an image-side negative lens group, and the negative lens L42 of the fourth lens group G4 corresponds to a negative lens that satisfies the conditional expressions (11) to (14) and the like.
The fifth lens group G5 consists of, in order from the object: a cemented lens consisting of biconvex positive lens L51, and a negative meniscus lens L52 having a concave surface facing the object. An image surface I is disposed on the image side of the fifth lens group G5. Upon focusing from the infinity object to the short-distant (finite distant) object, the fifth lens group G5 moves toward the image along the optical axis. The positive lens L51 has an object-side lens surface that is an aspherical surface. An optical filter FL is disposed between the fifth lens group G5 and the image surface I. The optical filter FL may be, for example, an NC filter (neutral color filter), a color filter, a polarizing filter, an ND filter (neutral density filter), an IR filter (infrared cutoff filter) or the like.
In this Example, the cemented lens consisting of the negative meniscus lens L11 and the positive lens L22, the positive meniscus lens L13, the positive meniscus lens L14, the negative meniscus lens L21, the negative lens L22, the cemented lens consisting of the positive lens L23 and the negative lens L24 constitute the front group GF disposed closer to the object than the aperture stop S. The positive lens L31, the cemented lens consisting of the positive meniscus lens L32 and the negative meniscus lens L33, the positive lens L34, the cemented lens consisting of positive lens L41 and the negative lens L42, and the cemented lens consisting of the positive lens L51 and the negative meniscus lens L52 constitute the rear group GR disposed closer to the image than the aperture stop S.
The following Table 7 lists values of data on the optical system according to Seventh Example.
According to each Example, the optical system where for correction of chromatic aberrations, in addition to primary achromatization, the secondary spectrum is favorably corrected can be achieved.
Here, Examples described above show specific examples of the invention of the present application. The invention of the present application is not limited to these Examples.
Note that the following content can be adopted in a range without impairing the optical performance of the optical system of this embodiment.
The focusing lens group is assumed to indicate a portion that includes at least one lens separated by air distances changing upon focusing. That is, a focusing lens group may be adopted that moves a single or multiple lens groups, or a partial lens group in the optical axis direction to achieve focusing from the infinity object to the short-distant object. The focusing lens group is also applicable to autofocusing, and is suitable also for motor drive for autofocusing (using an ultrasonic motor).
In Fourth, Fifth, and Seventh Examples, the configurations having the vibration-proof function are described. However, the present application is not limited thereto, and may adopt a configuration having no vibration-proof function. The other Examples having no vibration-proof function may have a configuration having the vibration-proof function.
The lens surface may be made of a spherical surface or a planar surface, or an aspherical surface. A case where the lens surface is a spherical surface or a planar surface is preferable because lens processing, and assembling and adjustment are facilitated, and the optical performance degradation due to errors caused by processing and assembling and adjustment can be prevented. Furthermore, it is preferable because the degradation in representation performance even with the image surface being misaligned is small.
In a case where the lens surface is an aspherical surface, the aspherical surface may be any of an aspherical surface made by a grinding process, a glass mold aspherical surface made by forming glass into an aspherical shape with a mold, and a composite type aspherical surface made by forming a resin on a surface of glass into an aspherical shape. The lens surface may be a diffractive surface. The lens may be a gradient-index lens (GRIN lens), or a plastic lens.
An antireflection film having a high transmissivity in a wide wavelength region may be applied onto each lens surface in order to reduce flares and ghosts and achieve optical performances having a high contrast. Accordingly, flares and ghosts can be reduced, and high optical performances having a high contrast can be achieved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-157741 | Aug 2019 | JP | national |
| 2019-157744 | Aug 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/032106 | 8/26/2020 | WO |
