JP4928297B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

  The present invention relates to a zoom lens and an image pickup apparatus having the same, and is suitable for broadcasting television cameras, video cameras, digital still cameras, silver salt photography cameras, and the like.

  2. Description of the Related Art In recent years, zoom lenses having a high zoom ratio and high optical performance have been demanded for imaging devices such as television cameras, silver salt film cameras, digital cameras, and video cameras.

  Among these, in an imaging apparatus such as a color television camera for broadcasting, since a color separation optical system and various filters are arranged in front of the imaging means (object side), a zoom lens having a long back focus is desired. Yes.

  As a zoom lens having a high zoom ratio and a long back focus, a positive lead type four-group zoom lens in which a lens group having a positive refractive power is disposed closest to the object side is known.

  The four-group zoom lens includes a first lens group having a positive refractive power including a focusing lens group in order from the object side to the image side, a second lens group having a negative refractive power for zooming, and an image accompanying zooming. The third lens group has a positive or negative refractive power for correcting surface fluctuations, and the fourth lens group has a positive refractive power for imaging.

  In this positive type four-group zoom lens, zoom lenses are known in which a diffractive optical element is arranged in an optical system to correct chromatic aberration to achieve high performance (Patent Documents 1 to 4).

  Patent Document 1 discloses a zoom lens having a zoom ratio of about 5 using a diffractive optical element in the first lens group.

  Patent Document 2 discloses a zoom lens having a zoom ratio of about 21 using a diffractive optical element in the first lens group.

  Patent Document 3 discloses a zoom lens having a zoom ratio of about 10 times in which chromatic aberration is reduced by using a diffractive optical element in the second lens group or the third lens group.

Patent Document 4 discloses a zoom lens using a diffractive optical element for the third lens group and having a zoom ratio of about 10 times.
JP 2000-221402 A JP 2003-287678 A US Pat. No. 5,268,790 Japanese Patent Application Laid-Open No. 11-311743

  When a diffractive optical element is used as a part of the zoom lens, chromatic aberration can be easily corrected, and it becomes easy to obtain a zoom lens having a high zoom ratio and high optical performance.

  However, even if a diffractive optical element is simply provided in the lens system, a zoom lens with high optical performance that corrects chromatic aberration well can be obtained unless the position, power, and lens configuration of the lens group including the diffractive optical element are appropriately set. Difficult to get.

  For example, in the positive lead type four-group zoom lens described above, various aberrations such as spherical aberration and chromatic aberration occur from the first lens group at the telephoto end as the zoom ratio becomes higher.

  For this reason, in order to obtain high optical performance while achieving a high zoom ratio, it is important to appropriately set the lens configuration of the first lens group and to properly correct various aberrations such as chromatic aberration and spherical aberration on the telephoto side. It becomes.

  In particular, if the lens configuration of the first lens group is not appropriate, even if a diffractive optical element is used, fluctuations in aberrations due to zooming, such as chromatic aberration, spherical aberration, halocoma aberration, and chromatic differences in spherical aberration, are reduced, resulting in a high zoom ratio. Therefore, it is difficult to obtain a high-performance zoom lens.

  An object of the present invention is to provide a zoom lens having a high zoom ratio and excellently correcting chromatic aberration over the entire zoom range from the wide-angle end to the telephoto end, and having a high optical performance in the entire zoom range, and an image pickup apparatus having the same.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power , and a positive lens having a positive refractive power. The first lens group includes at least one diffractive optical element. The focal length of the diffractive portion of the diffractive optical element is f _DOE , and the focal length at the telephoto end of the entire system is When the average value of the Abbe number of the material of the positive lens included in the first lens group is ν _{G1 + av} , f _T
0.02 <f _T / f _DOE <0.2
30 <ν _{G1 + av} <80
It satisfies the following conditional expression.

  According to the present invention, it is possible to obtain a zoom lens having high optical performance in the entire zoom range and an imaging apparatus having the same.

  Embodiments of the zoom lens of the present invention and an image pickup apparatus having the same will be described below.

  The zoom lens of the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a rear lens group. is doing.

The first lens group is a fixed lens group during zooming.

  The first lens group has at least one diffractive optical element.

  The first lens group has a fixed 1a lens group for focusing and a 1b lens group that moves to the object side for focusing from an object at infinity to a close object.

  The second lens group is a lens group that moves monotonously to the image side during zooming from the wide-angle end (short focal length end) to the telephoto end (long focal length end). The third lens group is a lens group that moves to the object side and corrects image plane fluctuations accompanying zooming. The rear lens group includes a fourth lens group having a positive refractive power that has a fixed imaging function during zooming.

  FIG. 1 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the first exemplary embodiment of the present invention.

  2, 3, and 4 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end when the zoom lens of Example 1 is an object at infinity, respectively.

  Example 1 is a zoom lens having a zoom ratio of 35 with a field angle of 58 ° at the wide-angle end and a field angle of 1.8 ° at the telephoto end.

  FIG. 5 is a lens cross-sectional view at the wide-angle end of the zoom lens according to the second embodiment of the present invention.

  6, 7, and 8 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, when the zoom lens of Example 2 is an object at infinity.

  The second embodiment is a zoom lens having a zoom ratio of 46 with a field angle of 63.4 ° at the wide-angle end and a field angle of 1.54 ° at the telephoto end.

  FIG. 9 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Example 3 of the present invention.

  10, 11, and 12 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, when the zoom lens of Example 3 is an object at infinity.

  Example 3 is a zoom lens having an angle of view of 60.2 ° at the wide-angle end, an angle of view of 3.4 ° at the telephoto end, and a zoom ratio of 19.5.

  FIG. 13 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Example 4 of the present invention.

  FIGS. 14, 15, and 16 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, when the zoom lens of Example 4 is an object at infinity.

  Example 4 is a zoom lens having a field angle of 20.8 ° at the wide-angle end, a field angle of 1.4 ° at the telephoto end, and a zoom ratio of 15.

  FIG. 17 is a lens cross-sectional view at the wide-angle end of the zoom lens according to Example 5 of the present invention.

  FIGS. 18, 19 and 20 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, when the zoom lens of Example 5 is an object at infinity.

  The fifth exemplary embodiment is a zoom lens in which the angle of view at the wide-angle end is 20.8 °, the angle of view at the telephoto end is 1.06 °, and the zoom ratio is 20.

  FIG. 21 is a lens cross-sectional view at the wide-angle end of a zoom lens as a conventional reference example 1.

  FIGS. 22, 23, and 24 are longitudinal aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end when the zoom lens of the conventional reference example 1 is an object at infinity.

  FIG. 25 is an explanatory diagram of a diffractive optical element according to the present invention.

  FIG. 26 is an explanatory diagram of wavelength-dependent characteristics of the diffractive optical element according to the present invention.

  FIG. 27 is an explanatory diagram of a diffractive optical element according to the present invention.

  FIG. 28 is an explanatory diagram of the wavelength dependence characteristics of the diffractive optical element according to the present invention.

  FIG. 29 is an explanatory diagram of a diffractive optical element according to the present invention.

  FIG. 30 is a schematic diagram of a main part of the imaging apparatus of the present invention.

  In the lens cross-sectional view, L1 is a first lens unit having a positive refractive power that is fixed during zooming. L2 is a second lens group (variator lens group) having negative refractive power that is movable during zooming. L3 is a third lens group (conventional sweater lens group) having a positive refractive power that is movable during zooming and corrects a change in image plane position due to zooming.

  SP is an aperture stop, which is disposed on the image side of the third lens unit L3. L4 is a rear lens group (relay lens group) for image formation. P is a color separation prism or optical filter, and is shown as a glass block. IP is an image plane and corresponds to the imaging plane of a solid-state imaging device (photoelectric conversion device). A is a diffraction part.

  In the aberration diagrams, e, g, F, and C are, in order, e-line, g-line, F-line, and C-line. M and S are meridional image surfaces, sagittal image surfaces, and lateral chromatic aberration is represented by g-line, C-line, and F-line. fno is an F number, and ω is a half angle of view.

  In all the aberration diagrams, the spherical aberration is drawn on a scale of 0.4 mm, the astigmatism is 0.4 mm, the distortion is 5%, and the lateral aberration is drawn on a scale of 0.05 mm.

  In the following embodiments, the wide-angle end and the telephoto end refer to zoom positions when the second lens unit L2 for zooming is positioned at both ends of a range in which the mechanism can move on the optical axis.

  Next, features of each embodiment will be described.

  During zooming from the wide-angle end to the telephoto end, the first lens unit L1 and the fourth lens unit L4 are fixed (non-moving). The second lens unit L2 moves toward the image side to perform main zooming, and the third lens unit L3 reciprocates along a convex locus on the object side to correct image point movement accompanying zooming. is doing.

  The first lens unit L1 performs focusing by moving some lens units having refractive power.

  In Examples 1 to 3, the first lens unit L1 includes a 1a lens unit L1a and a 1b lens unit L1b. When the subject distance moves from an object at infinity to a close object, the first-a lens unit L1a does not move, and the first-b lens unit L1b is moved out toward the object side to perform focusing.

  In Examples 4 and 5, the first lens unit L1 includes a 1a lens unit L1a, a 1b lens unit L1b, and a 1c lens unit L1C. When the subject distance moves from an infinite object to a close object, the 1a lens unit L1a and the 1c lens unit L1c do not move, and focusing is performed by extending the 1b lens unit L1b to the object side.

  In general, in such a four-group zoom lens, when the focal length at the telephoto end is increased to increase the aperture, the effective diameter of the first lens unit L1 increases significantly. This is because the incident height of the axial ray increases, and this causes an increase in the amount of various aberrations including spherical aberration and chromatic aberration during zooming and focusing. Generally, if the number of lenses in each lens group is increased to increase the degree of design freedom in order to satisfactorily correct various aberrations at this time, the entire lens system becomes larger and heavier.

  Therefore, in each embodiment, the diffractive optical element is arranged in the first lens unit L1 in which the incident height of the axial ray is highest as described above. Thereby, various aberrations generated in the first lens unit L1, particularly chromatic aberration, are corrected well. Further, the chromatic aberration correction generated in the first lens unit L1 is used so that the effect of the diffractive optical element is increased. This increases the degree of freedom in the glass material used for the positive lens in the first lens unit L1, and allows the selection of a glass material with a low specific gravity so that various aberrations are corrected well.

  The lens configuration of the first lens unit L1 provided with the diffractive portion is as follows.

  In Example 1 of FIG. 1, the first-a lens unit L1a includes a negative lens and a positive lens, and a diffractive portion is formed on the image side surface of the negative lens. The 1b lens unit L1b is composed of three positive lenses.

  In Example 2 of FIG. 5, the first-a lens unit L1a includes a negative lens and a positive lens. The 1b lens group L1b is composed of three positive lenses.

  Among these, the diffraction part is formed on the image side surface of the first positive lens from the object side.

  In Example 3 of FIG. 9, the first-a lens unit L1a is composed of a cemented lens of a negative lens and a positive lens. The 1b lens unit L1b is composed of two positive lenses.

  Among these, the diffraction part is formed on the image side surface of the first positive lens from the object side.

  In Example 4 of FIG. 13, the first-a lens unit L1a includes a positive lens, and a cemented lens of a negative lens and a positive lens. The 1b lens unit L1b is composed of two positive lenses. The first c lens unit L1c includes one negative lens, and a diffractive portion is formed on the object side surface of the negative lens.

  In Example 5 of FIG. 17, the first-a lens unit L1a is composed of a positive lens and a cemented lens of a negative lens and a positive lens. The 1b lens unit L1b includes a positive lens and a cemented lens of a positive lens and a negative lens. A diffractive portion is formed on the object side surface of the object side positive lens. The first c lens unit L1c includes a cemented lens of a positive lens and a negative lens.

In each embodiment, the focal length of the diffractive portion of the diffractive optical element is defined as f _DOE . Let f _T be the focal length at the telephoto end of the entire system. The average value of the Abbe number of the material of the positive lens included in the first lens unit L1 is ν _{G1 + av} . At this time,
0.02 <f _T / f _DOE <0.2 (1)
30 <ν _{G1 + av} <80 (2)
The following conditional expression is satisfied.

  In each embodiment, the diffractive portion refers to one or more diffraction gratings provided on a substrate (a flat plate or a lens). A diffractive optical element refers to an element in which a diffractive portion composed of one or more diffraction gratings is provided on a substrate (flat plate or lens).

  The refractive power (power = reciprocal of focal length) φD of the diffractive portion is obtained as follows.

The shape of the diffraction grating of the diffractive portion is defined such that the reference wavelength (e-line) is λ ₀ , the distance from the optical axis is H, and the phase is φ (H).
φ (H) = (2π · m / λ ₀ ) · (C ₂ · H ² + C ₄ · H ⁴ + ·· C _2i · H ²ⁱ )
... (a)
From the coefficient C _{2 of the} secondary term, the refractive power φD is
φD = -2 · C ₂
It becomes.

That is,
f _DOE = -1 / (2 · C ₂ )
It is represented by

  Conditional expression (1) is for maintaining good correction of various aberrations and the overall size of the optical system in a well-balanced manner in the above-described four-group zoom lens.

  If the upper limit value of conditional expression (1) is exceeded, the power of the diffraction part becomes too strong, and chromatic aberration is overcorrected. On the other hand, if the lower limit value of conditional expression (1) is exceeded, the power of the diffractive portion becomes too weak, and it becomes difficult to correct chromatic aberration at the telephoto end only by the diffractive portion. For this reason, a glass material with high anomalous dispersion such as fluorite is required for correcting chromatic aberration, which is not good.

  In each embodiment, it is preferable to set the numerical range of conditional expression (1) as follows in order to further improve the optical performance.

0.02 <f _T / f _DOE <0.15 (1a)
In order to further improve the optical performance, it is preferable that the numerical range of the conditional expression (1a) is as follows.

0.02 <f _T / f _DOE <0.1 (1b)
Conditional expression (2) relates to the average value of the Abbe number of the material of the positive lens in the first lens unit L1.

  If the upper limit of conditional expression (2) is exceeded, a glass material with high anomalous dispersion is used, so that a glass material with a large specific gravity is required and the weight increases. In addition, since these glass materials are generally glass materials having a low refractive index, it is difficult to correct spherical aberration.

  On the other hand, if the lower limit value of conditional expression (2) is exceeded, only a highly dispersed material is used, and it becomes difficult to maintain the balance of chromatic aberration that can be corrected by the diffraction section. Therefore, it becomes difficult to effectively use the diffraction part for correcting chromatic aberration.

  In order to further improve the optical performance, it is preferable that the numerical range of the conditional expression (2) is as follows.

40 <ν _{G1 + av} <71 (2a)
In order to further improve the optical performance, the numerical range of the conditional expression (2a) is preferably set as follows.

50 <ν _{G1 + av} <71 (2b)
According to each embodiment, by specifying each component as described above, it is possible to obtain a high-quality image with good chromatic aberration correction over the entire zoom range while having a high zoom ratio.

  In particular, by using a diffractive optical element for the first lens unit L1, it is possible to maintain good optical performance and to effectively correct fluctuations in axial chromatic aberration that occur during zooming.

  Further, by satisfying the conditional expressions (1) and (2), the diffractive optical element is effectively responsible for correcting chromatic aberration that occurs during zooming. Accordingly, good optical characteristics can be maintained without using an anomalous dispersive glass material such as fluorite, the use of a low specific gravity glass material and the number of lenses can be reduced, and the overall weight can be easily reduced.

  In the zoom lens of each embodiment, in order to obtain good optical performance at a higher zoom ratio, it is more preferable to satisfy the following conditional expression. According to this, an effect corresponding to the conditional expression can be obtained.

The focal length of the first lens unit L1 and _{f 1.} At this time,
_{0.1 <f 1 / f T <} 0.5 ··· (3)
The following conditional expression is satisfied.

  The first lens unit L1 greatly affects aberration fluctuations on the telephoto end side. For this reason, if the refractive power of the first lens unit L1 becomes too strong beyond the lower limit value of conditional expression (3), it is advantageous for shortening the total length, but spherical aberration and chromatic aberration become worse at the telephoto end. . On the other hand, if the upper limit is exceeded, the amount of movement of the second lens unit L2 necessary to ensure a high zoom ratio becomes too large, making it difficult to downsize the entire system.

More preferably, the numerical range of the conditional expression (3) is 0.15 <f ₁ / f _T <0.45 (3a)
This facilitates further downsizing and higher performance of the entire system.

  An aperture stop SP is provided between the third lens unit L3 and the rear lens unit L4.

  This is because it is easy to keep the exit pupil position at a constant position far away from the zooming by placing the aperture stop SP on the image side of the lens group that performs a large zooming action.

  Therefore, for example, when the imaging unit is used in a color separation system represented by a three-plate prism, or a color camera using a CCD or CMOS whose characteristics change depending on the incident angle, the image quality is deteriorated due to color shading. It becomes difficult.

  The diffraction part itself may have an aspherical effect. In the phase equation (a) of the diffraction part of each embodiment, this is done by giving a value to the higher-order terms after the coefficient C4 of the fourth power term of the distance h from the optical axis.

  As a result, in addition to the aspherical effects other than chromatic aberration described above, the aspherical effect due to the diffraction grating varies depending on the wavelength, so that it becomes easy to correct the chromatic difference variation of the spherical aberration, particularly on the telephoto side.

  Here, the configuration of the diffractive optical element used in the zoom lens of each embodiment will be described.

  The diffractive portion constituting the diffractive optical element disposed in the first lens unit L1 is composed of a diffraction grating that is rotationally symmetric with respect to the optical axis.

  FIG. 25 is a partially enlarged cross-sectional view of the diffractive portion of the diffractive optical element 1, and a diffraction grating (diffractive portion) 3 composed of one layer is provided on a substrate (transparent substrate) 2. FIG. 26 is a diagram showing the characteristics of the diffraction efficiency of the diffractive optical element 1. In FIG. 26, the horizontal axis represents the wavelength, and the vertical axis represents the diffraction efficiency. Note that the diffraction efficiency is the ratio of the amount of diffracted light to the total transmitted light beam, and the reflected light at the lattice boundary is not considered here because the explanation is complicated.

  The optical material of the diffraction grating 3 is an ultraviolet curable resin (refractive index nd = 1.513, Abbe number νd = 51.0), the grating thickness d1 is set to 1.03 μm, the wavelength is 530 nm, and the + 1st order diffracted light. The diffraction efficiency is made the highest. That is, the design order is + 1st order and the design wavelength is 530 nm. In FIG. 26, the diffraction efficiency of the + 1st order diffracted light is indicated by a solid line.

  Further, in FIG. 26, diffraction efficiency of diffraction orders near the design order (+ 1st order ± 1st order, 0th order and + 2nd order) is also shown. As can be seen from the figure, the diffraction efficiency at the design order is highest near the design wavelength, and gradually decreases at other wavelengths.

  The decrease in diffraction efficiency at this design order becomes diffracted light of other orders, which causes flare. Further, when the diffractive optical element is used at a plurality of locations in the optical system, a decrease in diffraction efficiency at a wavelength other than the design wavelength leads to a decrease in transmittance.

  Next, a laminated diffractive optical element in which a plurality of diffraction gratings made of different materials are laminated will be described. FIG. 27 is a partially enlarged cross-sectional view of a laminated diffractive optical element, and FIG. 28 is a diagram showing the wavelength dependence of the diffraction efficiency of + 1st order diffracted light of the diffractive optical element shown in FIG. In the diffractive optical element of FIG. 27, a first diffraction grating 104 made of an ultraviolet curable resin (refractive index nd = 1.499, Abbe number νd = 54) is formed on a substrate 102. Further, a second diffraction grating 105 (refractive index nd = 1.598, Abbe number νd = 28) is formed thereon. In this combination of materials, the grating thickness d1 of the first diffraction grating 104 is d1 = 13.8 μm, and the grating thickness d2 of the second diffraction grating 105 is d2 = 10.5 μm.

  As can be seen from FIG. 28, by using a diffractive optical element provided with a diffraction grating having a laminated structure, a high diffraction efficiency of 95% or more is obtained in the entire range of wavelengths used (in this case, the visible region) in the diffracted light of the designed order. Yes.

  The diffractive optical element having the above-described laminated structure is not limited to the material that constitutes the diffraction grating, but other plastic materials may be used. Depending on the substrate, the first layer may be directly You may form in a base material. In addition, the lattice thicknesses are not necessarily different, and the lattice thicknesses of the two layers 104 and 105 may be equal depending on the combination of materials as shown in FIG. In this case, since the lattice shape is not formed on the surface, it is excellent in dust resistance and can improve the assembling workability of the diffractive optical element. Furthermore, the two diffraction gratings 104 and 105 are not necessarily in close contact with each other, and two diffraction grating layers may be arranged with an air layer therebetween.

  Although the diffractive portion is provided on the optical surface, the base thereof may be spherical, flat, or aspheric. Moreover, you may create by what is called a replica aspherical surface which is the method of attaching films | membranes, such as a plastics, to those optical surfaces as a diffraction part (diffraction surface).

  Since the diffractive part has a large anomalous dispersion, by providing the diffractive part on the surface of the first lens unit L1 in this way, it is possible to effectively correct axial chromatic aberration and lateral chromatic aberration on the telephoto side.

As for the shape of the diffraction grating, the phase φ (H) at the distance H from the optical axis is expressed by the following equation (a) as described above, where C _2i is the phase coefficient of the 2i-order term. Where m is the diffraction order and λ ₀ is the reference wavelength.

  In general, the Abbe number (dispersion value) νd of the refractive optical system is expressed by the following equation when the refractive powers at the wavelengths of d, C, and F lines are Nd, NC, and NF.

νd = (Nd−1) / (NF-NC)> 0 (5)
On the other hand, when the Abbe number νd of the diffractive portion is set to λd, λC, and λF for the wavelengths of d, C, and F lines,
νd = λd / (λF−λC) (6)
And νd = −3.45.

  Thereby, it is shown that the dispersibility at an arbitrary wavelength has a reverse action with respect to the refractive optical system.

Further, the refractive power φ of the paraxial temporary diffracted light (m = 1) at the reference wavelength of the diffractive portion is φ = when the coefficient of the second-order term is C2 from the previous equation (a) representing the phase of the diffractive portion. represented as -2 · _{C 2.}

Further, when the arbitrary wavelength is λ and the reference wavelength is λ ₀ , the refractive power change with respect to the reference wavelength of the arbitrary wavelength is expressed by the following equation.

φ ′ = (λ / λ ₀ ) × (−2 · C ₂ ) (7)
Thereby, it can be understood that, as a characteristic of the diffraction part, by changing the phase coefficient C2 of the previous equation (a), a large dispersibility can be obtained with a weak change in the paraxial refractive power.
This means that chromatic aberration is corrected without greatly affecting various aberrations other than chromatic aberration.

With respect to the higher order coefficients of the phase coefficient C ₄ and later, the refractive power changes to the light incident height of the change in the diffraction unit can obtain the effect similar to aspheric. At the same time, it is possible to change the refractive power at an arbitrary wavelength with respect to the reference wavelength according to the change in the incident light height. Therefore, it is effective for correcting lateral chromatic aberration.

  FIG. 21 is a lens cross-sectional view at the wide-angle end of a conventional zoom lens that is the same as the zoom type according to the first embodiment of the present invention and does not have a diffractive optical element.

  FIGS. 22, 23, and 24 are longitudinal aberration diagrams of the conventional zoom lens at the wide-angle end, the intermediate zoom position, and the telephoto end.

  The aberration diagrams of FIGS. 22 to 24 and the aberration diagrams of FIGS. 2 to 4 of Example 1 are compared. The axial chromatic aberration at the telephoto end is improved to the same or more in the case of Example 1 in which the diffractive optical element is used for chromatic aberration correction, even though no anomalous dispersion glass material such as fluorite is used. I understand that.

  Numerical examples 1 to 5 of the present invention are shown below. In each numerical example, i indicates the order of the surfaces from the object side, Ri is the radius of curvature of the i-th surface from the object side, Di is the i-th and i + 1-th distance from the object side, Ni and νi Are the refractive index and Abbe number of the i-th optical member. f, fno, and 2ω represent the focal length, F number, and angle of view of the entire system when focusing on an object at infinity, respectively.

  The last three surfaces are glass blocks such as filters.

  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 eccentricity, and A, B, C, D, E are each When the aspheric coefficient is used,

It is expressed by the following formula.

  The diffraction part (diffraction surface) is represented by giving the phase coefficient of the phase function of the above-mentioned formula (a).

Table 6 shows the relationship between the conditional expressions described above and the numerical values in the numerical examples.
(Numerical example 1)
f = 10.0 to 350.0 fno = 2.0 to 3.8 2ω = 57.6 ° to 1.8 °
r1 = 1464.477 d1 = 5.45 n1 = 1.84666 ν1 = 23.78
Diffractive optical element r2 = 238.976 d2 = 4.84
r3 = 510.756 d3 = 7.29 n2 = 1.48749 ν2 = 70.23
r4 = -841.863 d4 = 9.50
r5 = 214.098 d5 = 10.64 n3 = 1.51633 ν3 = 64.14
r6 = -429.990 d6 = 0.25
r7 = 146.162 d7 = 8.38 n4 = 1.51633 ν4 = 64.14
r8 = 499.284 d8 = 0.25
r9 = 81.255 d9 = 8.04 n5 = 1.57099 ν5 = 50.80
r10 = 104.145 d10 = (variable)
Aspherical surface r11 = 137.067 d11 = 1.30 n6 = 1.81600 ν6 = 46.62
r12 = 16.216 d12 = 6.87
r13 = -60.616 d13 = 6.58 n7 = 1.80518 ν7 = 25.42
r14 = -18.000 d14 = 1.10 n8 = 1.81600 ν8 = 46.62
r15 = -331.167 d15 = 0.25
Aspherical surface r16 = 193.362 d16 = 7.73 n9 = 1.66998 ν9 = 39.30
r17 = -27.677 d17 = 3.31 n10 = 1.88300 ν10 = 40.76
r18 = -109.202 d18 = (variable)
r19 = -45.102 d19 = 2.82 n11 = 1.79952 ν11 = 42.22
r20 = 111.214 d20 = 3.73 n12 = 1.92286 ν12 = 18.90
r21 = -506.063 d21 = (variable)
r22 = 0.000 d22 = 1.32
r23 = 253.440 d23 = 6.00 n13 = 1.51633 ν13 = 64.14
r24 = -48.158 d24 = 0.20
r25 = 128.686 d25 = 3.91 n14 = 1.51823 ν14 = 58.90
r26 = -109.638 d26 = 0.20
r27 = 43.959 d27 = 9.30 n15 = 1.51633 ν15 = 64.14
r28 = -59.382 d28 = 1.85 n16 = 1.88300 ν16 = 40.76
r29 = 77.789 d29 = 43.65
r30 = 86.878 d30 = 5.87 n17 = 1.51823 ν17 = 58.90
r31 = -63.675 d31 = 0.62
r32 = 170.425 d32 = 1.65 n18 = 1.79952 ν18 = 42.22
r33 = 24.626 d33 = 6.72 n19 = 1.51823 ν19 = 58.90
r34 = 438.673 d34 = 0.82
r35 = 30.405 d35 = 8.03 n20 = 1.51633 ν20 = 64.14
r36 = -75.712 d36 = 1.33 n21 = 1.78590 ν21 = 44.20
r37 = 94.992 d37 = 2.41
r38 = 653.143 d38 = 1.76 n22 = 1.51823 ν22 = 58.90
r39 = -472.700 d39 = 5.16
r40 = ∞ d40 = 37.50 n23 = 1.60342 ν23 = 38.03
r41 = ∞ d41 = 20.25 n24 = 1.51633 ν24 = 64.14
r42 = ∞

Aspheric coefficient
11 side K = 12.86298 A = 0 B = -4.32030 × 10 ^-6
C = -1.69771 × 10 ^-8 D = 6.49 100 × 10 ^-11 E = -1.31 100 × 10 ^-18
16 sides K = -3.76277 A = 0 B = 1.162499 × 10 ^-5
C = 3.89743 × 10 ^-8 D = -9.43000 × 10 ^-11 E = 3.74400 × 10 ^-18
Phase coefficient
2 sides C ₂ = -4.18426 × 10 ^-5 C ₄ = 8.353765 × 10 ^-10
C ₆ = -1.06146 × 10 ^-13 C ₈ = 0

(Numerical example 2)
f = 8.9 to 410.0 fno = 2.0 to 3.8 2ω = 63.4 ° to 1.54 °
r1 = 596.741 d1 = 6.17 n1 = 1.83400 ν1 = 37.16
r2 = 139.043 d2 = 1.42
r3 = 141.047 d3 = 17.00 n2 = 1.48749 ν2 = 70.23
r4 = -1035.398 d4 = 12.37
r5 = 190.258 d5 = 9.00 n3 = 1.48749 ν3 = 70.23
Diffractive optical element r6 = 724.127 d6 = 0.12
r7 = 171.110 d7 = 9.00 n4 = 1.48749 ν4 = 70.23
r8 = 498.733 d8 = 0.12
r9 = 168.400 d9 = 10.00 n5 = 1.51633 ν5 = 64.14
r10 = 1401.582 d10 = (variable)
Aspherical surface r11 = -353.976 d11 = 1.80 n6 = 1.88300 ν6 = 40.76
r12 = 27.239 d12 = 8.50
r13 = -67.583 d13 = 5.42 n7 = 1.92286 ν7 = 21.29
r14 = -27.160 d14 = 1.50 n8 = 1.80400 ν8 = 46.57
r15 = 100.543 d15 = 0.12
r16 = 47.753 d16 = 5.61 n9 = 1.72342 ν9 = 37.95
r17 = -228.222 d17 = 1.50 n10 = 1.88300 ν10 = 40.76
r18 = 188.878 d18 = (variable)
r19 = -43.394 d19 = 5.98 n11 = 1.84666 ν11 = 23.78
r20 = -28.784 d20 = 1.50 n12 = 1.72916 ν12 = 54.68
r21 = -137.232 d21 = 1.32
r22 = -64.459 d22 = 1.60 n13 = 1.72916 ν13 = 54.68
r23 = -642.122 d23 = (variable)
r24 = (Aperture) d24 = 1.99
r25 = 4587.238 d25 = 4.72 n14 = 1.60300 ν14 = 65.44
r26 = -65.557 d26 = 0.12
r27 = 99.677 d27 = 8.19 n15 = 1.48749 ν15 = 70.23
r28 = -71.758 d28 = 0.66
r29 = 145.422 d29 = 4.04 n16 = 1.69680 ν16 = 55.53
r30 = -186.666 d30 = 2.00
r31 = 82.169 d31 = 5.97 n17 = 1.48749 ν17 = 70.23
r32 = -61.421 d32 = 1.85 n18 = 1.80518 ν18 = 25.42
r33 = -400.086 d33 = 4.83
r34 = -87.259 d34 = 1.65 n19 = 1.88300 ν19 = 40.76
r35 = 192.396 d35 = 41.52
r36 = 82.172 d36 = 3.98 n20 = 1.75500 ν20 = 52.32
r37 = -144.276 d37 = 0.78
r38 = 49.793 d38 = 6.29 n21 = 1.84666 ν21 = 23.78
r39 = -76.111 d39 = 1.45 n22 = 1.80610 ν22 = 33.27
r40 = 23.771 d40 = 1.50
r41 = 31.332 d41 = 10.67 n23 = 1.48749 ν23 = 70.23
r42 = -28.121 d42 = 1.72 n24 = 1.80610 ν24 = 33.27
r43 = 99.045 d43 = 1.11
r44 = 113.940 d44 = 7.04 n25 = 1.48749 ν25 = 70.23
r45 = -33.773 d45 = 0.50
r46 = ∞ d46 = 33.00 n26 = 1.61340 ν26 = 44.30
r47 = ∞ d47 = 13.20 n27 = 1.51633 ν27 = 64.14
r48 = ∞

Aspheric coefficient
11 sides K = -1.05555 × 10 ^-5 A = 0 B = 6.47916 × 10 ^-7
C = 0 D = 0 E = 0
Phase coefficient
6 sides C ₂ = -3.04767 × 10 ^-5 C ₄ = 6.56060 × 10 ^-11
C ₆ = -4.19036 × 10 ^-14 C ₈ = 0

(Numerical example 3)
f = 9.5 to 185.3 fno = 1.85 to 2.85 2ω = 60.2 ° to 3.4 °
r1 = 567.528 d1 = 3.60 n1 = 1.80518 ν1 = 25.42
r2 = 96.245 d2 = 10.78 n2 = 1.51633 ν2 = 64.14
r3 = -518.076 d3 = 7.12
r4 = 132.845 d4 = 6.84 n3 = 1.61800 ν3 = 63.33
Diffractive optical element r5 = -482.834 d5 = 0.05
r6 = 58.604 d6 = 6.56 n4 = 1.69350 ν4 = 50.80
r7 = 150.000 d7 = (variable)
r8 = -1003.352 d8 = 1.25 n5 = 1.88300 ν5 = 40.76
r9 = 18.776 d9 = 4.87
r10 = -61.579 d10 = 1.00 n6 = 1.81600 ν6 = 46.62
r11 = 32.913 d11 = 1.99
r12 = 28.829 d12 = 5.64 n7 = 1.80518 ν7 = 25.42
r13 = -34.163 d13 = 1.31 n8 = 1.78800 ν8 = 47.37
r14 = 76.628 d14 = (variable)
r15 = -28.304 d15 = 1.05 n9 = 1.74320 ν9 = 49.34
r16 = 34.514 d16 = 3.65 n10 = 1.80810 ν10 = 22.76
r17 = 1305.509 d17 = (variable)
r18 = (aperture) d18 = 1.73
r19 = -454.502 d19 = 3.65 n11 = 1.72342 ν11 = 37.95
r20 = -51.478 d20 = 0.18
r21 = 154.116 d21 = 3.66 n12 = 1.52249 ν12 = 59.84
r22 = -63.366 d22 = 0.40
r23 = 36.390 d23 = 8.07 n13 = 1.48749 ν13 = 70.23
r24 = -34.524 d24 = 1.62 n14 = 1.83400 ν14 = 37.16
r25 = 186.891 d25 = 21.94
r26 = 97.137 d26 = 5.83 n15 = 1.51823 ν15 = 58.90
r27 = -43.827 d27 = 0.23
r28 = 70.596 d28 = 1.50 n16 = 1.83400 ν16 = 37.16
r29 = 21.654 d29 = 7.16 n17 = 1.51823 ν17 = 58.90
r30 = 477.952 d30 = 0.20
r31 = 67.728 d31 = 7.59 n18 = 1.51633 ν18 = 64.14
r32 = -23.556 d32 = 1.30 n19 = 1.80400 ν19 = 46.57
r33 = 74.724 d33 = 0.31
r34 = 38.089 d34 = 6.92 n20 = 1.51823 ν20 = 58.90
r35 = -53.056 d35 = 5.00
r36 = ∞ d36 = 30.00 n21 = 1.60342 ν21 = 38.03
r37 = ∞ d37 = 16.20 n22 = 1.51633 ν22 = 64.14
r38 = ∞

Phase coefficient
5 sides C ₂ = -5.83943 × 10 ^-5 C ₄ = 3.74402 × 10 ^-9
C ₆ = 0 C ₈ = 0

(Numerical example 4)
f = 30 to 450 fno = 2.8 to 5.0 2ω = 20.8 ° to 1.4 °
r1 = 113.637 d1 = 11.25 n1 = 1.51633 ν1 = 64.14
r2 = 417.586 d2 = 0.15
r3 = 131.046 d3 = 4.00 n2 = 1.74950 ν2 = 35.33
r4 = 82.652 d4 = 16.98 n3 = 1.48749 ν3 = 70.23
r5 = 1035.600 d5 = 10.00
r6 = 93.683 d6 = 8.10 n4 = 1.48749 ν4 = 70.23
r7 = 364.092 d7 = 0.42
r8 = 145.631 d8 = 8.53 n5 = 1.84666 ν5 = 23.78
r9 = 184.518 d9 = 9.50
Diffractive optical element r10 = -64320.670 d10 = 4.05 n6 = 1.92286 ν6 = 21.29
r11 = 200.083 d11 = (variable)
r12 = 34.442 d12 = 1.00 n7 = 1.88300 ν7 = 40.76
r13 = 19.562 d13 = 3.19
r14 = -749.572 d14 = 4.59 n8 = 1.84666 ν8 = 23.78
r15 = -17.733 d15 = 0.90 n9 = 1.88300 ν9 = 40.76
r16 = 55.535 d16 = 0.17
r17 = 24.438 d17 = 4.48 n10 = 1.84666 ν10 = 23.78
r18 = 27.988 d18 = 8.11
r19 = -25.168 d19 = 0.90 n11 = 1.88300 ν11 = 40.76
r20 = -51.712 d20 = (variable)
r21 = -41.860 d21 = 0.90 n12 = 1.71700 ν12 = 47.92
r22 = 77.672 d22 = 1.86 n13 = 1.84666 ν13 = 23.78
r23 = -2875.064 d23 = (variable)
r24 = (Aperture) d24 = 0.74
r25 = 71.450 d25 = 4.95 n14 = 1.60311 ν14 = 60.64
r26 = -46.436 d26 = 0.15
r27 = 98.053 d27 = 5.46 n15 = 1.62041 ν15 = 60.29
r28 = -888.571 d28 = 0.15
r29 = 60.279 d29 = 7.24 n16 = 1.48749 ν16 = 70.23
r30 = -39.608 d30 = 1.00 n17 = 1.80 100 ν17 = 34.97
r31 = -266.405 d31 = 9.14
r32 = -41.886 d32 = 1.00 n18 = 1.75520 ν18 = 27.51
r33 = -143.407 d33 = 38.00
r34 = 180.865 d34 = 3.08 n19 = 1.48749 ν19 = 70.23
r35 = -35.735 d35 = 2.65
r36 = 47.355 d36 = 5.13 n20 = 1.48749 ν20 = 70.23
r37 = -27.941 d37 = 0.80 n21 = 1.88300 ν21 = 40.76
r38 = -859.131 d38 = 2.50
r39 = -76.546 d39 = 0.80 n22 = 1.83481 ν22 = 42.72
r40 = 34.012 d40 = 2.04 n23 = 1.48749 ν23 = 70.23
r41 = 57.738 d41 = 1.50
r42 = 42.009 d42 = 6.12 n24 = 1.69895 ν24 = 30.13
r43 = -28.285 d43 = 1.00 n25 = 1.80610 ν25 = 40.92
r44 = -50.808 d44 = 5.00
r45 = ∞ d45 = 33.00 n26 = 1.60859 ν26 = 46.44
r46 = ∞ d46 = 13.20 n27 = 1.51680 ν27 = 64.17
r47 = ∞ d47 =

Phase coefficient
10 faces C ₂ = -9.22558 × 10 ^-5 C ₄ = 9.88283 × 10 ^-9
C ₆ = -3.21136 × 10 ^-12 C ₈ = 0

(Numerical example 5)
f = 30 to 600 fno = 2.8 to 5.0 2ω = 20.8 ° to 1.06 °
r1 = 129.531 d1 = 12.04 n1 = 1.48749 ν1 = 70.23
r2 = 199.653 d2 = 0.15
r3 = 135.666 d3 = 4.00 n2 = 1.84666 ν2 = 23.78
r4 = 95.801 d4 = 21.13 n3 = 1.48749 ν3 = 70.23
r5 = 4674.080 d5 = 10.00
Diffractive optical element r6 = 132.315 d6 = 9.38 n4 = 1.48749 ν4 = 70.23
r7 = 379.593 d7 = 0.42
r8 = 82.832 d8 = 16.81 n5 = 1.48749 ν5 = 70.23
r9 = 1636.317 d9 = 2.43 n6 = 1.72047 ν6 = 34.70
r10 = 339.484 d10 = 7.77
r11 = 5178.571 d11 = 4.74 n7 = 1.92286 ν7 = 21.29
r12 = -245.720 d12 = 2.20 n8 = 1.72047 ν8 = 34.70
r13 = 171.961 d13 = (variable)
Aspheric surface r14 = 25.345 d14 = 1.50 n9 = 1.88300 ν9 = 40.76
r15 = 14.543 d15 = 5.50
r16 = -125.389 d16 = 4.16 n10 = 1.92286 ν10 = 21.29
r17 = -20.114 d17 = 0.90 n11 = 1.88300 ν11 = 40.76
r18 = 45.415 d18 = 0.17
r19 = 23.054 d19 = 3.96 n12 = 1.92286 ν12 = 21.29
r20 = 31.043 d20 = 4.27
r21 = -21.550 d21 = 1.20 n13 = 1.88300 ν13 = 40.76
r22 = -50.342 d22 = (variable)
r23 = -43.932 d23 = 1.50 n14 = 1.71700 ν14 = 47.92
r24 = 61.947 d24 = 2.32 n15 = 1.84666 ν15 = 23.78
r25 = 528.648 d25 = (variable)
r26 = (aperture) d26 = 0.74
r27 = 82.201 d27 = 5.90 n16 = 1.60311 ν16 = 60.64
r28 = -49.990 d28 = 0.15
r29 = 70.827 d29 = 5.09 n17 = 1.62041 ν17 = 60.29
r30 = -147.728 d30 = 0.15
r31 = 49.683 d31 = 6.99 n18 = 1.48749 ν18 = 70.23
r32 = -47.260 d32 = 1.30 n19 = 1.80100 ν19 = 34.97
r33 = 245.471 d33 = 8.70
r34 = -56.437 d34 = 1.20 n20 = 1.75520 ν20 = 27.51
r35 = -490.165 d35 = 38.00
r36 = 180.865 d36 = 4.28 n21 = 1.48749 ν21 = 70.23
r37 = -35.735 d37 = 2.00
r38 = 47.355 d38 = 5.01 n22 = 1.48749 ν22 = 70.23
r39 = -27.941 d39 = 1.00 n23 = 1.88300 ν23 = 40.76
r40 = -859.131 d40 = 2.50
r41 = -76.546 d41 = 1.00 n23 = 1.83481 ν23 = 42.72
r42 = 34.012 d42 = 2.04 n24 = 1.48749 ν24 = 70.23
r43 = 57.738 d43 = 1.50
r44 = 42.009 d44 = 4.54 n25 = 1.69895 ν25 = 30.13
r45 = -28.285 d45 = 1.00 n26 = 1.80610 ν26 = 40.92
r46 = -72.551 d46 = 5.00
r47 = ∞ d47 = 33.00 n27 = 1.60859 ν27 = 46.44
r48 = ∞ d48 = 13.20 n28 = 1.51680 ν28 = 64.17
r49 = ∞

Aspheric coefficient
14 sides K = 5.97571 × 10 ^-7 A = 0 B = 7.60584 × 10 ^-8
C = 6.08753 × 10 ^-12 D = 0 E = 0
Phase coefficient
6 sides C ₂ = -4.33312 × 10 ^-5 C ₄ = -5.63727 × 10 ^-10
C ₆ = -1.35271 × 10 ^-13 C ₈ = 0

  Next, an embodiment of a photographing apparatus (television camera system) using the zoom lenses of Numerical Examples 1 to 5 as a photographing optical system will be described with reference to FIG.

  In FIG. 30, reference numeral 206 denotes a photographing apparatus main body including a zoom lens, 201 denotes a photographing optical system constituted by the zoom lenses of Numerical Examples 1 to 5, and 202 denotes a glass block corresponding to a filter or a color separation prism.

  Reference numeral 203 denotes a solid-state image sensor such as a CCD that receives a subject image formed by the photographing optical system 201, and 204 and 205 denote CPUs that control the photographing apparatus main body 206 and the zoom lens 201.

  Thus, by applying the zoom lenses of Numerical Examples 1 to 5 to a television camera or the like, it is possible to realize a photographing apparatus having high optical performance.

Lens sectional view at the wide-angle end when the object distance is infinite in Numerical Example 1 Longitudinal aberration diagram at the wide-angle end when the object distance in Numerical Example 1 is infinite Longitudinal aberration diagram at the intermediate zoom position when the object distance in Numerical Example 1 is infinite Longitudinal aberration diagram at the telephoto end when the object distance in Numerical Example 1 is infinity Lens sectional view at the wide-angle end when the object distance is infinite in Numerical Example 2 Longitudinal aberration diagram at the wide-angle end when the object distance in Numerical Example 2 is infinity Longitudinal aberration diagram at intermediate zoom position when the object distance in Numerical Example 2 is infinite Longitudinal aberration diagram at the telephoto end when the object distance in Numerical Example 2 is infinity Lens sectional view at the wide-angle end when the object distance is infinite in Numerical Example 3 Longitudinal aberration diagram at the wide-angle end when the object distance in Numerical Example 3 is infinity Longitudinal aberration diagram at intermediate zoom position when the object distance in Numerical Example 3 is infinity Longitudinal aberration diagram at the telephoto end when the object distance in Numerical Example 3 is infinity Lens sectional view at the wide-angle end when the object distance is infinite in Numerical Example 4 Longitudinal aberration diagram at the wide-angle end when the object distance in Numerical Example 4 is infinity Longitudinal aberration diagram at the intermediate zoom position when the object distance in Numerical Example 4 is infinite Longitudinal aberration diagram at the telephoto end when the object distance in Numerical Example 4 is infinity Lens cross-sectional view at the wide-angle end when the object distance is infinite in Numerical Example 5 Longitudinal aberration diagram at the wide-angle end when the object distance in Numerical Example 5 is infinity Longitudinal aberration diagram at the intermediate zoom position when the object distance in Numerical Example 5 is infinity Longitudinal aberration diagram at the telephoto end when the object distance in Numerical Example 5 is infinity Lens cross-sectional view at the wide-angle end when the object distance is infinity in Reference Example 1 Longitudinal aberration diagram at the wide-angle end when the object distance in Reference Example 1 is infinite Longitudinal aberration diagram at intermediate zoom position when the object distance is infinity in Reference Example 1 Longitudinal aberration diagram at the telephoto end when the object distance is infinity in Reference Example 1 Cross section of diffractive optical element with single layer structure Illustration of diffraction efficiency of a diffractive optical element with a single layer structure Cross-sectional view of a laminated diffractive optical element Illustration of diffraction efficiency of diffractive optical element with structure Cross section of diffractive optical element with structure Explanatory drawing of the imaging device of the present invention

Explanation of symbols

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group SP Aperture stop P Color separation prism and optical filter IP Image surface S Sagittal image surface M Meridional image surface g g line e e line F F line C C line ω Half angle of view

Claims (6)

In order from the object side to the image side, the lens unit includes a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power. The first lens group includes at least one diffractive optical element, the focal length of the diffractive portion of the diffractive optical element is f _DOE , the focal length at the telephoto end of the entire system is f _T , and the first lens When the average value of the Abbe number of the material of the positive lens included in the group is ν _{G1 + av} ,
0.02 <f _T / f _DOE <0.2
30 <ν _{G1 + av} <80
A zoom lens satisfying the following conditional expression:   The first lens group is a lens group that is fixed during zooming, and the second lens group is a lens group that monotonously moves to the image side during zooming from the wide-angle end to the telephoto end, and the third lens group 2. The zoom lens according to claim 1, wherein the zoom lens is a lens group that moves toward the object side and corrects image plane fluctuations accompanying zooming. The zoom lens according to claim 1, wherein an aperture stop is provided between the third lens group and the fourth lens group.   The first lens group includes a 1a lens group that is fixed during focusing and a 1b lens group that moves toward the object side during focusing from an object at infinity to a close object. The zoom lens according to item. When the focal length of the first lens group and f _1,
0.1 <f ₁ / f _T <0.5
The zoom lens according to claim 1, wherein the following conditional expression is satisfied.   6. An image pickup apparatus comprising: the zoom lens according to claim 1; and a solid-state image pickup device that receives an image formed by the zoom lens.

Images