JP7152445B2 - Extender Lenses, Optics, and Imagers - Google Patents

Description

The technology of the present disclosure relates to an extender lens, an optical system, and an imaging device.

Conventionally, in the field of broadcast cameras, etc., the lens is detachably placed inside a master lens for imaging, and the focal length of the entire lens system after insertion is changed to the longer focal length side than the focal length of the master lens. Extender lenses are known.

For example, Patent Document 1 below describes a first lens group with positive refractive power that does not move for zooming and a second lens group with negative refractive power that moves during zooming, in order from the object side to the image side. , a zoom lens that includes an aperture diaphragm and is composed of a front relay lens group having positive refractive power, an extender lens group that can be inserted into and removed from the optical path, and a rear relay lens group that does not move for zooming. there is

Patent Document 2 below discloses a zoom lens body composed of four or more lens groups, and a focal length conversion lens group which is arranged in a space on the optical axis in front of or behind the lens groups of the zoom lens body so as to be able to move in and out. A zoom lens is described comprising:

Patent Document 3 below describes, in order from the object side to the image side, a focus lens group that moves during focusing, a variable magnification lens group that is composed of two or more lens groups that move during zooming, an aperture stop, A zoom lens is described that includes an extender lens group that is detachably mounted in the optical path, and a relay lens group that does not move for zooming.

JP 2016-045310 A JP-A-2000-275521 JP 2017-181577 A

An object of the technique of the present disclosure is to provide an extender lens with good optical performance, an optical system including this extender lens, and an imaging apparatus including this extender lens.

One aspect of the technology of the present disclosure is an extender lens that changes the focal length of the entire lens system after replacement to a longer focal length side than the focal length of the master lens by replacing a part of the master lens, The extender lens consists of a first lens group and a second lens group having negative refractive power as a whole in order from the object side to the image side, and one lens component is one single lens or one cemented lens. In this case, the first lens group is a lens group having a positive refractive power as a whole and a minimum focal length among lens groups consisting of one lens component or a plurality of lens components arranged in series, If the distance on the optical axis from the surface of the extender lens closest to the object side to the surface closest to the image side of the extender lens is TLex, and the focal length of the first lens group is f1, the following conditional expression (1) is satisfied.
0.1<TLex/f1<0.36 (1)

It is preferable that the extender lens of the above aspect further satisfies the following conditional expression (1-1).
0.15<TLex/f1<0.33 (1-1)

When the focal length of the second lens group is f2 and the focal length of the extender lens is fex, it is preferable to satisfy the following conditional expression (2), and more preferably to satisfy the following conditional expression (2-1).
0.23<f2/fex<0.5 (2)
0.24<f2/fex<0.46 (2-1)

When the focal length of the first lens group is f1 and the focal length of the extender lens is fex, it is preferable to satisfy the following conditional expression (3), and more preferably to satisfy the following conditional expression (3-1).
-1<f1/fex<-0.25 (3)
-1<f1/fex<-0.35 (3-1)

For at least one negative lens in the second lens group, the following conditional expressions (4) and (5) are satisfied, where νn is the d-line reference Abbe number and θgFn is the partial dispersion ratio between the g-line and the F-line. preferably. Moreover, it is more preferable to satisfy at least one of the following conditional expressions (4-1) and (5-1) in addition to satisfying the conditional expressions (4) and (5).
60<νn (4)
0.64<θgFn+0.001625×νn<0.7 (5)
60<νn<86 (4-1)
0.64<θgFn+0.001625×νn<0.68 (5-1)

If f2 is the focal length of the second lens group and f2n is the focal length of at least one negative lens in the second lens group that satisfies the above conditional expressions (4) and (5), then the following conditional expression (6) is satisfied. is preferably satisfied, and more preferably conditional expression (6-1) below is satisfied.
0.1<f2/f2n<1.5 (6)
0.15<f2/f2n<1 (6-1)

dN is the temperature coefficient of the relative refractive index for the d-line in the range from 20° C. to 40° C. of at least one negative lens in the second lens group that satisfies the above conditional expressions (4), (5), and (6); /dT, it is preferable to satisfy the following conditional expression (7). The unit of dN/dT is °C ^-1 .
−7×10 ⁻⁶ <dN/dT<−2×10 ⁻⁶ (7)

The first lens group includes a lens having a convex surface on the object side, and for at least one lens having a convex surface on the object side in the first lens group, the radius of curvature of the surface on the object side is Rf, and the radius of curvature of the surface on the image side is Rf. When the radius of curvature of the surface is Rr, it is preferable to satisfy the following conditional expression (8), and more preferably to satisfy the following conditional expression (8-1).
-0.08<(Rf−Rr)/(Rf+Rr)<0.05 (8)
-0.07<(Rf−Rr)/(Rf+Rr)<0.03 (8-1)

The first lens group preferably includes, in addition to a lens having a convex object-side surface that satisfies conditional expression (8), a cemented lens in which a negative lens and a positive lens are cemented together.

The first lens group includes a cemented lens in which a negative lens having a convex surface on the object side and a positive lens are cemented in order from the object side, continuously from the most object side to the image side, and the above conditional expression (8) and a lens having a convex object-side surface that satisfies:

Another aspect of the technology of the present disclosure is an optical system that includes a master lens that is a zoom lens and the extender lens of the aspect described above.

Yet another aspect of the technology of the present disclosure is an imaging device provided with the extender lens of the aspect described above.

In addition, "consisting of" and "consisting of" in this specification refer to lenses that have substantially no refractive power, and lenses such as diaphragms, filters, and cover glasses, in addition to the listed components. It is intended that other optical elements, lens flanges, lens barrels, imaging elements, and mechanical parts such as image stabilization mechanisms may be included.

In this specification, "a lens having a positive refractive power" and "a positive lens" are synonymous. The terms “lens having negative refractive power” and “negative lens” are synonymous. The "-lens group" is not limited to a structure consisting of a plurality of lenses, and may be a structure consisting of only one lens.

"single lens" means a single lens that is not cemented; However, a compound aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally formed to function as a single aspherical lens as a whole) is not a cemented lens. are treated as a single lens. The sign of refractive power, surface shape, and radius of curvature of a lens including an aspherical surface are considered in the paraxial region unless otherwise specified. Regarding the sign of the radius of curvature, the sign of the radius of curvature of the surface convex to the object side is positive, and the sign of the radius of curvature of the surface convex to the image side is negative.

The "focal length" used in the conditional expression is the paraxial focal length. The values used in the conditional expressions, other than the partial dispersion ratio, are values when the d-line is used as a reference when an object at infinity is focused. The partial dispersion ratio θgF between the g-line and the F-line of a certain lens is given by θgF=(Ng− NF)/(NF-NC). The "d-line", "C-line", "F-line", and "g-line" described herein are emission lines, the wavelength of the d-line is 587.56 nm (nanometers), and the wavelength of the C-line is 656 nm. .27 nm (nanometers), the wavelength of the F line is 486.13 nm (nanometers), and the wavelength of the g line is 435.83 nm (nanometers).

1 is a cross-sectional view showing a configuration of an optical system according to an embodiment of the present disclosure, corresponding to a master lens and an extender lens of Example 1 of the present disclosure, and a diagram showing a movement locus; FIG. 1 is a sectional view of the configuration of an extender lens of Example 1. FIG. 3 is a diagram showing the configuration and light fluxes at the wide-angle end and the telephoto end of the entire lens system after replacement with the extender lens of Example 1. FIG. 4A and 4B are aberration diagrams of the master lens of Example 1. FIG. 4A and 4B are aberration diagrams of the entire lens system after replacement with the extender lens of Example 1. FIG. FIG. 11 is a cross-sectional view of the configuration of the extender lens of Example 2; FIG. 10 is an aberration diagram of the entire lens system after replacement with the extender lens of Example 2; FIG. 12 is a cross-sectional view showing the configuration of the master lens and the extender lens of Example 3, and a diagram showing movement trajectories. FIG. 11 is a cross-sectional view of the configuration of the extender lens of Example 3; FIG. 10 is a diagram showing the configuration and light flux at the wide-angle end and the telephoto end of the entire lens system after replacement with the extender lens of Example 3; 4A to 4C are aberration diagrams of the master lens of Example 3. FIG. 10A and 10B are aberration diagrams of the entire lens system after replacement with the extender lens of Example 3. FIG. FIG. 11 is a cross-sectional view of the configuration of the extender lens of Example 4; FIG. 10 is a diagram of each aberration of the entire lens system after replacement with the extender lens of Example 4; 1 is a schematic configuration diagram of an imaging device according to an embodiment of the present disclosure; FIG.

An example of an embodiment according to the technology of the present disclosure will be described below with reference to the drawings. An optical system according to the technology of the present disclosure includes a master lens ML and an extender lens EX that can replace a part of the master lens ML. The master lens ML is, for example, an imaging lens system that can be applied to an imaging apparatus such as a broadcast camera.

The extender lens EX can be inserted into and removed from the optical path, and by replacing a part of the master lens ML, the focal length of the entire lens system after replacement can be changed to that of the master lens ML while maintaining the imaging position constant. to the longer focal length side than the focal length of . Here, the "whole lens system after replacement" is a lens system obtained by synthesizing all other parts of the master lens ML (the parts of the master lens ML that are not replaced with the extender lens EX) and the extender lens EX. Further, the above-mentioned "keeping the imaging position constant" is not limited to the case of perfect match, but allows some error. For example, the permissible error can be ±(δ×AFN), where δ is the permissible circle of confusion diameter and AFN is the F-number of the entire lens system after replacement.

FIG. 1 shows a configuration cross-sectional view of a master lens ML and an extender lens EX according to an embodiment of the present disclosure. As an example, the master lens ML shown in FIG. 1 is a zoom lens composed of, in order from the object side to the image side, a focusing portion F, a variable magnification portion V, an aperture stop St, and an imaging portion RL.

When applying the lens system to an imaging device, it is preferable to include various filters, prisms, and/or cover glass, etc. according to the specifications of the imaging device. An example of arrangement between the imaging unit RL and the image plane Sim is shown. Various filters include, for example, a low-pass filter and an infrared cut filter. The optical member PP is a member having a parallel incident surface and a parallel output surface and does not have refractive power, and a configuration in which the optical member PP is omitted is also possible.

The focusing section F includes a lens group that moves along the optical axis Z during focusing. The zooming section V includes a lens group that moves along the optical axis Z during zooming. As an example, the variable power unit V in FIG. 1 is composed of a V1 lens group V1, a V2 lens group V2, and a V3 lens group V3 in order from the object side to the image side. It moves along the optical axis Z while changing the distance between adjacent lens groups. In FIG. 1, below these three lens groups, arrows schematically indicate the locus of movement of each lens group during zooming from the wide-angle end to the telephoto end. In the example of FIG. 1, the focusing section F and the imaging section RL are fixed with respect to the image plane Sim during zooming.

The imaging unit RL is composed of, in order from the object side to the image side, an RL1 lens group RL1, an RL2 lens group RL2, and an RL3 lens group RL3. The RL2 lens group RL2 can be inserted into and removed from the optical path, and is configured to be replaceable with the extender lens EX. In the following description with reference to the example of FIG. 1, a lens system consisting of a focusing section F, a variable magnification section V, an aperture stop St, an RL1 lens group RL1, an extender lens EX, and an RL3 lens group RL3 will be described. It will be referred to as "the entire lens system after replacement".

FIG. 2 shows a structural sectional view of an example of the extender lens EX. The example shown in FIG. 2 corresponds to Example 1 described later. FIG. 3 shows the configuration and luminous flux at the wide-angle end and the telephoto end of the entire lens system after replacement. In FIG. 3, the upper part labeled "WIDE" shows the wide-angle end state, and the lower part labeled "TELE" shows the telephoto end state. FIG. 3 shows, as the light fluxes, the axial light flux wa and the maximum angle of view light flux wb in the wide-angle end state, and the axial light flux ta and the maximum angle of view light flux tb in the telephoto end state. 1, 2 and 3, the left side is the object side and the right side is the image side.

The extender lens EX consists of, in order from the object side to the image side, a first lens group G1 having positive refractive power as a whole, and a second lens separated from the first lens group G1 by an air gap and having negative refractive power as a whole. and the group G2. The first lens group G1 is a lens group having positive refractive power as a whole and having the shortest focal length among lens groups composed of one lens component or a plurality of continuously arranged lens components. Here, a "lens component" is a lens that has only two air contact surfaces on the optical axis, an object-side surface and an image-side surface. is the lens. By adopting the telephoto type configuration as described above, the extender lens EX can easily have the effect of increasing the focal length.

The definition of the first lens group G1 will be described in detail with reference to FIG. The extender lens EX in the example of FIG. 2 includes, in order from the object side to the image side, a cemented lens in which a lens L11 and a lens L12 are cemented, a single lens L13, and a cemented lens in which a lens L14 and a lens L15 are cemented. , a cemented lens in which a lens L21 and a lens L22 are cemented together, and a lens L23, which is a single lens. When the extender lens EX in the example of FIG. 2 is divided into two lens groups with an air gap as a boundary, the lens closest to the object side of the extender lens EX is included, and is composed of one lens component or a plurality of continuously arranged lens components. The lens groups include a lens group consisting of lenses L11 and L12, a lens group consisting of lenses L11, L12 and L13, a lens group consisting of lenses L11, L12, L13, L14 and L15, and a lens group consisting of lenses L11, L12, L13 and L14. , L15, L21, and L22. When the focal length of each of these four lens groups is obtained in the example of FIG. A lens group consisting of L11 to L15. Therefore, in the example of FIG. 2, the lenses L11 to L15 constitute the first lens group G1, and the remaining lenses L21 to L23 constitute the second lens group G2.

When the focal length of the first lens group G1 is f1, and the distance on the optical axis from the most object side surface of the extender lens EX to the most image side surface of the extender lens EX is TLex, the extender lens EX is determined by the following conditional expression. It is configured to satisfy (1). By ensuring that the lower limit of conditional expression (1) is not exceeded, the refractive power of the first lens group G1 does not become too weak, so that it becomes easy to increase the focal length. Alternatively, since the total length of the extender lens EX does not become too short, good aberration correction is facilitated. By not exceeding the upper limit of conditional expression (1), the refractive power of the first lens group G1 does not become too strong, so that the refractive power of the second lens group G2 does not become too strong. Favorable aberration correction is facilitated. Alternatively, since the total length of the extender lens EX does not become too long, the extender lens EX can be accommodated within a prescribed range within the master lens. Furthermore, if the structure satisfies the following conditional expression (1-1), better characteristics can be obtained.
0.1<TLex/f1<0.36 (1)
0.15<TLex/f1<0.33 (1-1)

Next, a preferred configuration of the extender lens EX will be described. Assuming that the focal length of the second lens group G2 is f2 and the focal length of the extender lens EX is fex, it is preferable to satisfy the following conditional expression (2). By ensuring that the lower limit of conditional expression (2) is not exceeded, the focal length of the second lens group G2 does not become too short, so it is possible to prevent the image-side principal point position of the extender lens EX from becoming further toward the object side. Therefore, it is possible to prevent the image forming position of the entire lens system after the replacement from being more likely to move toward the object side than the image forming position of the master lens ML before the replacement. By not exceeding the upper limit of conditional expression (2), the focal length of the second lens group G2 does not become too long, so the position of the image-side principal point of the extender lens EX is suppressed from being located further on the image side. As a result, it is possible to prevent the image forming position of the entire lens system after replacement from being more likely to move toward the image side than the image forming position of the master lens ML before replacement. By satisfying conditional expression (2), it becomes easier to match the imaging position of the entire lens system after replacement with the imaging position of the master lens ML. Further, if the structure satisfies the following conditional expression (2-1), better characteristics can be obtained.
0.23<f2/fex<0.5 (2)
0.24<f2/fex<0.46 (2-1)

Assuming that the focal length of the first lens group G1 is f1 and the focal length of the extender lens EX is fex, it is preferable to satisfy the following conditional expression (3). By ensuring that the lower limit of conditional expression (3) is not exceeded, the refractive power of the first lens group G1 does not become too strong, thereby suppressing overcorrection of spherical aberration, axial chromatic aberration, and curvature of field. can. By ensuring that the upper limit of conditional expression (3) is not exceeded, the refractive power of the first lens group G1 does not become too weak, thereby suppressing insufficient correction of spherical aberration, axial chromatic aberration, and curvature of field. can. By satisfying the conditional expression (3), the image forming position of the entire lens system after the replacement can be matched with the image forming position of the master lens ML while being advantageous for correction of spherical aberration, longitudinal chromatic aberration, and curvature of field. easier. Further, if the structure satisfies the following conditional expression (3-1), better characteristics can be obtained.
-1<f1/fex<-0.25 (3)
-1<f1/fex<-0.35 (3-1)

The first lens group G1 includes a lens whose object-side surface is convex. For at least one lens whose object-side surface is convex in the first lens group G1, Rf is the radius of curvature of the object-side surface, and Rf is the radius of curvature of the object-side surface. When the radius of curvature of the side surface is Rr, it is preferable to satisfy the following conditional expression (8). A lens whose object-side surface is convex and which satisfies −0.08<(Rf−Rr)/(Rf+Rr)<0 is a positive lens. A lens whose object-side surface is convex and which satisfies 0<(Rf−Rr)/(Rf+Rr)<0.05 is a negative lens. Abiding by the lower limit of conditional expression (8) makes it possible to suppress the tendency of astigmatism to become under-corrected, which is advantageous for ensuring good optical performance. If the upper limit of conditional expression (8) is not exceeded, the negative refractive power does not become too strong, so overcorrection of spherical aberration can be suppressed, and correction of marginal rays is particularly facilitated. Satisfying conditional expression (8) is advantageous for correction of the tangential image plane. Further, if the structure satisfies the following conditional expression (8-1), better characteristics can be obtained.
-0.08<(Rf−Rr)/(Rf+Rr)<0.05 (8)
-0.07<(Rf−Rr)/(Rf+Rr)<0.03 (8-1)

The first lens group G1 preferably includes, in addition to a lens having a convex object-side surface that satisfies conditional expression (8), a cemented lens in which a negative lens and a positive lens are cemented together. In general, the extender lens EX is often arranged in the imaging section RL of the master lens ML including the focusing section F, the variable magnification section V, and the imaging section RL as described above. The diameter of the light beam inside the extender lens EX tends to be larger on the object side than on the image side. That is, the luminous flux diameter in the first lens group G1 tends to be larger than the luminous flux diameter in the second lens group G2. By arranging the above-mentioned cemented lens and a lens having a convex surface on the object side that satisfies conditional expression (8) on the object side of the extender lens EX, which has a larger luminous flux diameter, spherical aberration, axial chromatic aberration, non-uniform This is advantageous for correcting astigmatism and curvature of field.

More specifically, the first lens group G1 is a cemented lens in which a negative lens having a convex surface on the object side and a positive lens are cemented in order from the object side, continuously from the most object side to the image side, and the condition and a lens having a convex object-side surface that satisfies equation (8). By making the lens surface closest to the object side of the first lens group G1 convex, it is possible to obtain the effect of lowering the light rays, thereby facilitating correction of spherical aberration in the first lens group G1. Further, by using a negative meniscus lens having a convex surface on the object side as the lens closest to the object side in the first lens group G1, it is possible to correct axial chromatic aberration at the cemented surface. Furthermore, by arranging a lens having a convex object-side surface that satisfies conditional expression (8) at a position that is continuous with the image side of the cemented lens and has a relatively large luminous flux diameter, spherical aberration and astigmatism , and curvature of field can be easily corrected.

The second lens group G2 is configured to include a negative lens. It is preferable that at least one negative lens in the second lens group G2 satisfies the following conditional expression (4), where νn is the d-line reference Abbe number. Satisfying conditional expression (4) is advantageous for correction of first-order axial chromatic aberration. It is preferable that at least one negative lens in the second lens group G2 further satisfies the following conditional expression (4-1). By not exceeding the upper limit of conditional expression (4-1), it is possible to prevent the refractive index of the negative lens in the second lens group G2 from becoming too low, which is advantageous for correcting aberrations.
60<νn (4)
60<νn<86 (4-1)

It is preferable that at least one negative lens in the second lens group G2 satisfies the following conditional expression (5), where θgFn is the partial dispersion ratio between the g-line and the F-line. Satisfying conditional expression (5) is advantageous for correction of secondary axial chromatic aberration. Further, if the structure satisfies the following conditional expression (5-1), better characteristics can be obtained.
0.64<θgFn+0.001625×νn<0.7 (5)
0.64<θgFn+0.001625×νn<0.68 (5-1)

It is preferable that at least one negative lens in the second lens group G2 satisfies the conditional expressions (4) and (5). ) and (5-1) are more preferably satisfied.

Further, when the focal length of the second lens group G2 is f2, and the focal length of the negative lens in the second lens group G2 that satisfies the conditional expressions (4) and (5) is f2n, at least one negative lens is: It is preferable to satisfy conditional expression (6). A negative lens that satisfies conditional expressions (4) and (5) and satisfies conditional expression (6) is more advantageous for correction of longitudinal chromatic aberration. Further, if the structure satisfies the following conditional expression (6-1), better characteristics can be obtained.
0.1<f2/f2n<1.5 (6)
0.15<f2/f2n<1 (6-1)

Furthermore, the temperature coefficient of the relative refractive index for the d-line in the range from 20° C. to 40° C. of the negative lens in the second lens group G2 that satisfies the conditional expressions (4), (5), and (6) is dN/dT , it is preferable that at least one negative lens satisfies the following conditional expression (7). Since the negative lens satisfying conditional expressions (4), (5), and (6) satisfies conditional expression (7), it is possible to correct the in-focus position of the entire lens system after replacement when the temperature changes. be advantageous. The unit of dN/dT is °C ^-1 .
−7×10 ⁻⁶ <dN/dT<−2×10 ⁻⁶ (7)

In the example of FIG. 2, the first lens group G1 consists of five lenses, and the second lens group G2 consists of three lenses. may be different from the number shown in FIG. Also, the number of lens groups of the master lens ML that move during zooming may be different from the number in the example of FIG. Furthermore, the master lens ML may be a zoom lens having a configuration different from the example of FIG. If the master lens ML is a zoom lens, the configuration is highly versatile, but the master lens ML may be a variable focal lens or a fixed focus optical system.

The preferred and possible configurations described above can be arbitrarily combined, and are preferably selectively employed as appropriate according to required specifications.

Numerical examples of the extender lens EX and the master lens ML according to the technique of the present disclosure will now be described. The master lens ML of Examples 1 and 2 described below is common, and the master lens ML of Examples 3 and 4 is common.

[Example 1]
[Master lens]
The block diagram of the master lens ML of Example 1 is indicated by the symbol ML in FIG. 1, and the method of illustration and the structure are as described above, so redundant description is partially omitted here. The master lens ML of Example 1 is a zoom lens, and includes, in order from the object side to the image side, a focusing portion F, a variable magnification portion V, an aperture stop St, and an imaging portion RL. The focusing unit F includes, in order from the object side to the image side, two lenses that are fixed with respect to the image plane Sim during focusing, two lenses that move during focusing, and a focusing lens. It consists of one lens that moves when moving, and adopts the floating focus method. The zooming section V consists of a V1 lens group V1, a V2 lens group V2, and a V3 lens group V3 in order from the object side to the image side. move by changing the interval between The imaging unit RL is composed of, in order from the object side to the image side, an RL1 lens group RL1, an RL2 lens group RL2, and an RL3 lens group RL3. The RL2 lens group RL2 is configured to be replaceable with the extender lens EX. The above is the outline of the master lens ML of the first embodiment.

For the master lens ML of Example 1, Tables 1A and 1B show basic lens data, Table 2 shows specifications, Table 3 shows variable surface distances, and Table 4 shows aspheric coefficients. Here, the basic lens data are divided into two tables, Table 1A and Table 1B, and displayed in order to avoid making one table too long. Table 1A shows the focusing portion F and the variable magnification portion V, and Table 1B shows the aperture stop St, imaging portion RL, and optical member PP. In Table 1B, a column labeled "RL2" is added to the left of the surface numbers corresponding to the RL2 lens group RL2.

In Tables 1A and 1B, the column of Sn shows the surface number when the surface closest to the object side is the first surface and the number is increased by one toward the image side, and the column of R shows the surface number of each surface. The radius of curvature is shown, and the column D shows the distance between each surface and the surface adjacent to the image side on the optical axis. The column of Nd shows the refractive index for the d-line of each component, the column of νd shows the Abbe number of each component based on the d-line, and the column of θgF shows the distance between the g-line and the F-line of each component. shows the partial dispersion ratio of

In Tables 1A and 1B, the sign of the radius of curvature of the surface with the convex surface facing the object side is positive, and the sign of the radius of curvature of the surface with the convex surface facing the image side is negative. In Table 1B, the surface number and the phrase (St) are described in the surface number column of the surface corresponding to the aperture stop St. In Tables 1A and 1B, the symbol DD [ ] is used for the variable surface distance during zooming. .

Table 2 shows zoom magnification Zr, focal length f, F number FNo. , and the maximum total angle of view 2ω on the basis of the d-line. (°) in the column of 2ω means that the unit is degrees. Table 3 shows the variable surface distance at the time of zooming on the basis of the d-line. In Tables 2 and 3, the values for the wide-angle end state and the telephoto end state are shown in the columns labeled WIDE and TELE, respectively.

In the basic lens data, the surface numbers of the aspherical surfaces are marked with an asterisk (*), and the paraxial radius of curvature is described in the column for the radius of curvature of the aspherical surfaces. In Table 4, the Sn column indicates the surface number of the aspherical surface, and the KA and Am columns indicate the numerical value of the aspherical surface coefficient for each aspherical surface. "E±n" (n: integer) in the numerical values of the aspheric coefficients in Table 4 means "×10 ^±n ". KA and Am are aspherical coefficients in the aspherical formula given below. m is an integer greater than or equal to 3, and differs depending on the surface. For example, m=3, 4, 5, .
Zd=C×h ² /{1+(1−KA×C ² ×h ² ) ^1/2 }+ΣAm×h ^m
however,
Zd: Depth of aspherical surface (length of the perpendicular drawn from a point on the aspherical surface with height h to a plane perpendicular to the optical axis where the aspherical vertex is in contact)
h: height (distance from optical axis to lens surface)
C: Reciprocal of paraxial radius of curvature KA, Am: Aspherical surface coefficient, Σ in the aspherical expression means the summation with respect to m.

In the data in each table, degrees are used as units of angles and mm (millimeters) are used as units of length. Units can also be used. Also, in each table shown below, numerical values rounded to predetermined digits are described.

FIG. 4 shows aberration diagrams of the master lens ML of Example 1 when focused on an object at infinity. FIG. 4 shows spherical aberration, astigmatism, distortion, and chromatic aberration of magnification in order from the left. In FIG. 4, the upper part labeled "WIDE" shows the aberration in the wide-angle end state, and the lower part labeled "TELE" shows the aberration in the telephoto end state. In spherical aberration diagrams, aberrations at the d-line, C-line, and F-line are indicated by solid lines, long dashed lines, and short dashed lines, respectively. In the astigmatism diagrams, the solid line indicates the aberration at the d-line in the sagittal direction, and the short dashed line indicates the aberration at the d-line in the tangential direction. In the distortion diagrams, the solid line indicates the aberration at the d-line. In the diagram of chromatic aberration of magnification, aberrations at C-line and F-line are indicated by long dashed lines and short dashed lines, respectively. FNo. in the spherical aberration diagram. means the F-number, and ω in other aberration diagrams means the half angle of view.

Unless otherwise specified, the symbols, meanings, description methods, and illustration methods of each data described above are the same in the following examples, and redundant description will be omitted below.

[Entire lens system after replacement with extender lens]
The extender lens EX of Example 1 is configured to be replaceable with the RL2 lens group RL2 of the master lens ML. FIG. 2 shows the configuration of the extender lens EX of Example 1. As shown in FIG. FIG. 3 shows the configuration and luminous flux at the wide-angle end and the telephoto end of the entire lens system in which the RL2 lens group RL2 is replaced with the extender lens EX. 2 and 3 are the same as described above, so redundant description will be partially omitted here. The extender lens EX of Example 1 comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power as a whole and a second lens group G2 having negative refractive power as a whole. The first lens group G1 consists of lenses L11 to L15, and the second lens group G2 consists of lenses L21 to L23.

Tables 5A and 5B show basic lens data, Table 6 shows specifications, and FIG. 5 shows aberration diagrams for the entire lens system after replacement with the extender lens EX. Table 5A shows the focusing portion F and the variable magnification portion V, and Table 5B shows the aperture stop St, RL1 lens group RL1, extender lens EX, RL3 lens group RL3, and optical member PP. In Table 5B, a column labeled "EX" is attached to the left of the surface number corresponding to the extender lens EX, and this notation is the same in the following examples. The data in Table 5A are identical to the data in Table 1A. The variable surface distance and the aspheric coefficient of the aspheric surface for the data in Table 5A are the same as those shown in Tables 3 and 4, respectively, and are omitted here.

[Example 2]
[Master lens]
Since the master lens ML of Example 2 is common to the master lens ML of Example 1, redundant description of data is omitted.

[Entire lens system after replacement with extender lens]
The extender lens EX of Example 2 is configured to be replaceable with the RL2 lens group RL2 of the master lens ML. FIG. 6 shows the configuration of the extender lens EX of Example 2. As shown in FIG. The extender lens EX of Example 2 comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power as a whole and a second lens group G2 having negative refractive power as a whole. The first lens group G1 consists of lenses L11 to L14, and the second lens group G2 consists of lenses L21 to L22.

Tables 7A and 7B show basic lens data, Table 8 shows specifications, and FIG. 7 shows aberration diagrams of the entire lens system after replacement with the extender lens EX. Table 7A shows the focusing portion F and the variable magnification portion V, and Table 7B shows the aperture stop St, RL1 lens group RL1, extender lens EX, RL3 lens group RL3, and optical member PP. The data in Table 7A are identical to the data in Table 1A. The variable surface distance and the aspheric coefficient of the aspheric surface for the data in Table 7A are the same as those shown in Tables 3 and 4, respectively, and are omitted here.

[Example 3]
[Master lens]
FIG. 8 shows a block diagram of the master lens ML of Example 3 with the symbol ML attached. The master lens ML of Example 3 has the same configuration as the master lens ML of Example 1, except that the number of lenses that are fixed during focusing of the focusing unit F is three.

Regarding the master lens ML of Example 3, basic lens data are shown in Tables 9A and 9B, specifications are shown in Table 10, variable surface spacing is shown in Table 11, aspheric coefficients are shown in Table 12, and aberration diagrams are shown in FIG. show. Table 9A shows the focusing portion F and the variable magnification portion V, and Table 9B shows the aperture stop St, imaging portion RL, and optical member PP.

[Entire lens system after replacement with extender lens]
The extender lens EX of Example 3 is configured to be replaceable with the RL2 lens group RL2 of the master lens ML. FIG. 9 shows the configuration of the extender lens EX of Example 3. As shown in FIG. FIG. 10 shows the configuration and light beams at the wide-angle end and the telephoto end of the entire lens system in which the RL2 lens group RL2 is replaced with the extender lens EX. The extender lens EX of Example 3 comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power as a whole and a second lens group G2 having negative refractive power as a whole. The first lens group G1 consists of lenses L11 to L17, and the second lens group G2 consists of lens L21.

Tables 13A and 13B show basic lens data, Table 14 shows specifications, and FIG. 12 shows aberration diagrams for the entire lens system after replacement with the extender lens EX. Table 13A shows the focusing portion F and the variable magnification portion V, and Table 13B shows the aperture stop St, RL1 lens group RL1, extender lens EX, RL3 lens group RL3, and optical member PP. The data in Table 13A are identical to the data in Table 9A. The variable surface distance and the aspheric coefficient of the aspheric surface for the data in Table 13A are the same as those shown in Tables 11 and 12, respectively, and are omitted here.

[Example 4]
[Master lens]
Since the master lens ML of Example 4 is common to the master lens ML of Example 3, redundant description of data is omitted.

[Entire lens system after replacement with extender lens]
The extender lens EX of Example 4 is configured to be replaceable with the RL2 lens group RL2 of the master lens ML. FIG. 13 shows the configuration of the extender lens EX of Example 4. As shown in FIG. The extender lens EX of Example 4 comprises, in order from the object side to the image side, a first lens group G1 having positive refractive power as a whole and a second lens group G2 having negative refractive power as a whole. The first lens group G1 consists of lenses L11 to L13, and the second lens group G2 consists of lenses L21 to L25.

Tables 15A and 15B show basic lens data, Table 16 shows specifications, and FIG. 14 shows aberration diagrams for the entire lens system after replacement with the extender lens EX. Table 15A shows the focusing portion F and the variable magnification portion V, and Table 15B shows the aperture stop St, RL1 lens group RL1, extender lens EX, RL3 lens group RL3, and optical member PP. The data in Table 15A are identical to the data in Table 9A. The variable surface distance and the aspheric coefficient of the aspheric surface for the data in Table 15A are the same as those shown in Tables 11 and 12, respectively, and are omitted here.

Table 17 shows the corresponding values of the conditional expressions (1) to (8) of the extender lenses EX of Examples 1 to 4. The unit of the corresponding value in conditional expression (7) is °C ^-1 . The lenses of the second lens group G2 that satisfy conditional expressions (4), (5), and (6) are the lens L23 in Example 1, the lens L22 in Example 2, the lens L21 in Example 3, and the lens L21 in Example 4. Now let's look at the lens L25. In the column under the column related to conditional expression (7) in Table 17, the material name is given for each of the lens L23 of Example 1, the lens L22 of Example 2, the lens L21 of Example 3, and the lens L25 of Example 4. and a brief manufacturer name. In Table 17, "Hikari Glass" means Hikari Glass Co., Ltd., "OHARA" means OHARA Co., Ltd., and "HOYA" means HOYA Co., Ltd. The lens whose object-side surface in the first lens group G1 is convex and which satisfies the conditional expression (8) is the lens L13 in all of the first to fourth embodiments.

As can be seen from the data described above, the extender lenses EX of Examples 1 to 4 are replaced with a part of the master lens ML, so that the focal length of the entire lens system after replacement is 1 of the focal length of the master lens ML. 0.4 times, more specifically, 1.37 times or more and 1.4 times or less. Moreover, both the master lens ML of Examples 1 to 4 and the entire lens system after replacement maintain good optical performance.

Conventionally, the magnification of an extender lens attached to a zoom lens used in a broadcast camera or the like was mainly 2 times. Zoom lenses tend to have a larger f-number on the telephoto side as the magnification increases. In addition, if a 2x extender lens is used, the f-number will be doubled. In order to reduce the f-number on the telephoto side, it is necessary to increase the diameter of the lens closest to the object side of the lens system. I can't proceed. Due to these circumstances, the demand for extender lenses with a magnification of about 1.4 is increasing. The above Examples 1 to 4 are lens systems that meet this demand.

Next, an imaging device according to an embodiment of the present disclosure will be described. FIG. 15 shows a schematic configuration diagram of an imaging device 10 using the optical system 1 according to the embodiment of the present disclosure as an example of the imaging device of the embodiment of the present disclosure. Examples of the imaging device 10 include a broadcast camera, a movie camera, a video camera, a digital camera, and a surveillance camera.

The imaging device 10 includes an optical system 1 , an optical member 2 arranged on the image side of the optical system 1 , and an imaging device 3 arranged on the image side of the optical member 2 . Optical member 2 is a filter and/or a prism. The optical system 1 includes a master lens ML and an extender lens EX. In FIG. 15, the focusing portion F, the variable magnification portion V, the aperture stop St, the imaging portion RL, the RL1 lens group RL1, the RL2 lens group RL2, the RL3 lens group RL3, and the extender lens EX included in the optical system 1 are Schematically illustrated.

The imaging device 3 converts an optical image formed by the optical system 1 into an electrical signal, and may be, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The imaging element 3 is arranged so that its imaging plane coincides with the image plane of the optical system 1 . Although only one imaging device 3 is shown in FIG. 15, the imaging device 10 may be a so-called three-plate imaging device having three imaging devices.

The imaging apparatus 10 also includes a signal processing unit 4 that performs arithmetic processing on an output signal from the imaging device 3, a variable power control unit 5 that controls variable power of the optical system 1, and a focus control unit that controls focusing of the optical system 1. a part 6; The zoom control unit 5 replaces the RL2 lens group RL2 with the extender lens EX.

Although the technology of the present disclosure has been described above with reference to the embodiments and examples, the technology of the present disclosure is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspheric coefficient, and the like of each lens are not limited to the values shown in the above numerical examples, and may take other values.

1 optical system 2 optical member 3 imaging device 4 signal processing unit 5 magnification control unit 6 focus control unit 10 imaging device EX extender lens F focusing unit G1 first lens group G2 second lens group L11 to L17, L21 to L25 lens ML Master lens PP Optical member RL Imaging unit RL1 RL1 lens group RL2 RL2 lens group RL3 RL3 lens group Sim Image plane St Aperture diaphragm ta, wa On-axis light beams tb, wb Light beams at maximum angle of view V Magnifying unit V1 V1 lens group V2 V2 lens group V3 V3 lens group Z Optical axis

Claims (17)

An extender lens that replaces a part of a master lens to change the focal length of the entire lens system after replacement to a longer focal length side than the focal length of the master lens,
The extender lens comprises, in order from the object side to the image side, a first lens group and a second lens group having a negative refractive power as a whole,
When one lens component is one single lens or one cemented lens, the first lens group is a lens group consisting of one lens component or a plurality of continuously arranged lens components, and has positive refraction as a whole. A lens group having a power and a minimum focal length,
The first lens group includes a lens having a convex surface on the object side,
TLex the distance on the optical axis from the most object-side surface of the extender lens to the most image-side surface of the extender lens,
The focal length of the first lens group is f1 ,
For at least one lens having a convex object-side surface in the first lens group, when the radius of curvature of the object-side surface is Rf and the radius of curvature of the image-side surface is Rr ,
0.1<TLex/f1<0.36 (1)
-0.08<(Rf−Rr)/(Rf+Rr)<0.05 (8)
An extender lens that satisfies conditional expressions (1) and (8) represented by: the focal length of the second lens group is f2;
When the focal length of the extender lens is fex,
0.23<f2/fex<0.5 (2)
The extender lens according to claim 1, which satisfies conditional expression (2) represented by: When the focal length of the extender lens is fex,
-1<f1/fex<-0.25 (3)
3. The extender lens according to claim 1, which satisfies conditional expression (3) represented by: For at least one negative lens in the second lens group, when the d-line reference Abbe number is νn and the partial dispersion ratio between the g-line and the F-line is θgFn,
60<νn (4)
0.64<θgFn+0.001625×νn<0.7 (5)
The extender lens according to any one of claims 1 to 3, which satisfies conditional expressions (4) and (5) represented by the following. the focal length of the second lens group is f2;
When the focal length of at least one negative lens in the second lens group that satisfies the conditional expressions (4) and (5) is f2n,
0.1<f2/f2n<1.5 (6)
5. The extender lens according to claim 4, which satisfies conditional expression (6) represented by: The temperature coefficient of the relative refractive index for the d-line in the range from 20° C. to 40° C. of at least one negative lens in the second lens group that satisfies the conditional expressions (4), (5), and (6) When the unit of dN/dT and dN/dT is ℃ ^-1 ,
−7×10 ⁻⁶ <dN/dT<−2×10 ⁻⁶ (7)
6. The extender lens according to claim 5, which satisfies the conditional expression (7) represented by the following. The extender lens according to claim 1 , wherein the first lens group further includes a cemented lens in which a negative lens and a positive lens are cemented together. The first lens group includes a cemented lens in which a negative lens having a convex surface on the object side and a positive lens are cemented in order from the object side, and the conditional expression (8 2. The extender lens according to claim 1 , wherein the lens has a convex object-side surface that satisfies ). 0.15<TLex/f1<0.33 (1-1)
The extender lens according to claim 1, which satisfies conditional expression (1-1) represented by: 0.24<f2/fex<0.46 (2-1)
3. The extender lens according to claim 2, which satisfies conditional expression (2-1) represented by: -1<f1/fex<-0.35 (3-1)
4. The extender lens according to claim 3, which satisfies conditional expression (3-1) represented by: 60<νn<86 (4-1)
5. The extender lens according to claim 4, which satisfies conditional expression (4-1) represented by: 0.64<θgFn+0.001625×νn<0.68 (5-1)
5. The extender lens according to claim 4, which satisfies conditional expression (5-1) represented by: 0.15<f2/f2n<1 (6-1)
6. The extender lens according to claim 5, which satisfies conditional expression (6-1) represented by: -0.07<(Rf−Rr)/(Rf+Rr)<0.03 (8-1)
The extender lens according to claim 1 , which satisfies conditional expression (8-1) represented by: the master lens, which is a zoom lens;
An optical system comprising an extender lens according to any one of claims 1 to 15 . An imaging device comprising the extender lens according to any one of claims 1 to 15 .

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